Volume 62 (2010)
List of Contents
Volume 62, Issue 1
- Molecular dynamic modeling (MD) in designing radioactive waste vitrification
- Strony: 3-13
Molecular dynamic (MD) modeling was applied for determination of the changes in the structure and properties of borosilicate nuclear waste glass, resulting from the incorporation of Ca and Cs, which are the components of hospital waste incineration ash. Results of the modeling, including diffusion coeffi cients and diffusion activation energy of the components in the glass structure, correspond well to the actual knowledge of the borosilicate glass structure and correlate accurately with experimental data on their thermal properties and crystallization. Results of the MD modeling are accurate enough to use them for the interpretation of the results of an experimental investigation of waste glass and predict the effect of incorporation of the components of waste for their immobilization.
- Synthesis of Portland cement clinker with wastelimestone-clay material
- Strony: 14-19
The applicability of waste material from the karst process, accompanying raw deposits, for the Portland cement clinker production was investigated. The sinterability of the raw meal, as well as the phase composition and microstructure of synthetic clinker were determined. The calculations based upon the free CaO contents, following the procedure proposed by Musikas. The sinterability values were very similar, the best factor was found for the clinker sample at 8% waste material replacement. The scanning electron microscopy and backscattered electrons studies, supported by the EDS revealed the high alite contents and the fairly good, complete synthesis of cement clinker in the presence of supplementary material from karst weathering.
- Metallic and ceramic composites for application in medicine
- Strony: 20-23
Demand for new materials in medicine is on the increase. Long-lasting implants (joint prostheses, dentistry implants) made typically of metals and their alloys are characterized with high mechanical properties, however their corrosion resistance and biocompatibility is relatively low. One of the methods of ensuring particular functional properties is to employ composite implants, combining improved mechanical properties of metallic material with biocompatibility of ceramic materials. The work aimed to develop and analyse properties of metallic/ceramic composites made of the mixture of austenitic steel (316LHD) and ceramic (hydroxyapatite) powders.
- Influence of glass structure on the positrons lifetime
- Strony: 24-27
The oxyfluoride glass from the SiO2-Al2O3-Na2O-LaF3-NaF–Yb2O3 system is characterized. The DTA/DSC method is used to determine thermal stability of glass and crystalline phases formed upon heat treatment. It has been found that the nanocrystalline phases of LaF3 are formed upon the heat treatment of the oxyfluoride glasses in the ceramming temperature range. The kind of crystallizing phases was determined by XRD and SEM methods. A systematic study of positron annihilation in an amorphous glass and glass ceramic has been carried out. The experimental setup for the positron lifetime measurements consisted of a 22Na positron source. Results thus favour the idea that the lifetime (τ3) and intensity (I3) are indicators of the free volume in glass and glass-ceramic materials. The longer component lifetime (τ3) and its intensity (I3) are found to vary with the crystallinity of the sample. The size of free volume is estimated by Tao-Eldrup formula.
- Influence of the PZT ceramics microstructure on dielectric and piezoelectric properties
- Strony: 28-31
The aim of this work was to show the infl uence of the microstructure on dielectric and piezoelectric properties of the PZT ceramics. The analysis of the microstructure of PZT type ceramics containing cadmium and tungsten was presented. The studied material was obtained by the solid state synthesis. The pressureless sintering and hot pressing methods were used to sinter the samples. The SEM micrographs were delivered by the Hitachi S-4700 microscope. It was a base to analyze the microstructures. The VISILOG 4 system was applied to calculate average grain sizes and homogeneity of grain size distributions. The results of measurements of dielectric parameters (dielectric permittivity, loss tangent) and piezoelectric parameters (electromechanical coupling coeffi cient, piezoelectric modulus) are presented. The resonance-antiresonance method was used to calculate piezoelectric properties. The infl uence of density, porosity, grains size and homogeneity of grain size distribution on dielectric and piezoelectric parameters is shown.
- Production and testing of the 54/46 PZT ceramics admixed with barium and niobium
- Strony: 34-36
Multicomponent PZT ceramics of the 54/46 type with the Pb0,84Ba0,16(Zr0,54Ti0,46)0,975Nb0,025O3 composition was obtained by a free sintering method. Both the X-ray and microstructure examinations and the temperature measurements of dielectric parameters and an electric hysteresis loop were performed. The electrophysical parameters of the obtained ceramics show that it may be used for biomorphic and ignition transducers and for building piezoelectric low frequency transducers (high values of permittivity).
- Structure and physical properties of 54/46 PZT ceramics modified with strontium, chromium and neodymium
- Strony: 37-41
A technology of producing the multicomponent PZT type ceramics with the composition of Pb0,94Sr0,06(Zr0,46Ti0,54)0,99Cr0,01O3 was developed and basic physical properties of the materials were examined. An influence of the neodymium admixture added to the base composition on dielectric properties of the material was also presented. The multicomponent ceramics of the PZT type was obtained by the solid state reaction of a mixture of simple oxides at a high temperature, enabling the powders to be synthesized, which were compacted and further consolidated by the free sintering method. A set of electrophysical parameters of the obtained ceramics shows that it may be used in electronics as a material for building electric filters.
- Manufacturing PLZT electro-optical fibres by the thermoplastic extrusion method
- Strony: 42-45
Lanthanum-modifi ed lead zirconate titanate (PLZT) ceramics are known to exhibit a range of interesting electro-optical properties. The advantages of PLZT ceramics include high optical transparency, desirable electrooptic properties, and fast response.
Piezoelectric fibers present many advantages comparing to conventional piezoelectric bulk materials ie. higher anisotropy, excellent flexibility and higher strength, but processing methods and conditions of manufacturing are still actively studied because they affect significantly the final fibres properties.
The aim of this study was to develop PLZT powder for the production of transparent or translucent thin fibers. The infl uence of different sintering parameters on the resultant microstructure and phase composition of the fi bres was checked. The main goal of the experiments was to determine a sintering atmosphere suitable to achieve proper density, porosity and microstructure of the fibres.
- Preparation of antireflection coatings by the sol-gel method
- Strony: 46-50
Preparation of antirefl ection coatings by a sol-gel method was the subject of this study. In particular, long-term stability was the main concern. The infl uence of aging on antirefl ection parameters and porosity was also studied. Refractive index, porosity and thickness of the layers were estimated on the base of ellipsometric measurements. It was found that the refractive index lowers with time of aging making worse antirefl ection properties of the coatings. Porosity increases from 26% for the freshly prepared sol up to about 50% after 185 days of aging. The sol of studied composition is technologically stabile within 30 days.
- TCP bioceramics (αTCP, βTCP, BCP) for orthopaedic and stomatological applications – preparation and in vitro evaluation
- Strony: 51-55
In the present work, monophase βTCP or αTCP as well as biphasic BTCP ceramics (βTCP + αTCP) were biologically evaluated using the in vitro test. The chemical stability of above materials, indicating their susceptibility to corrosion and biodegradation, was estimated. The obtained results allowed the bioactive potential of investigated materials to be determined.
- Properties of thermoelectric materials prepared by directional crystallization
- Strony: 56-59
The aim of this work was to prepare single crystals of AgSbSe2, Ag0,9Sb1,1Se2 and BiSbTe3 by the Bridgman method. Materials were prepared by means of two variants of this method, differing in temperature gradients in the area of the crystallization front. Microstructural and chemical analysis were done using Scanning Electron Microscope (SEM) with Energy-Dispersive X-ray Spectroscopy (EDS) and Atomic Emission Spectroscopy (AES). Analysis of homogeneity of thermoelectric properties was carried out using the Seebeck microprobe at room temperature.
It was found that the Seebeck coefficient for AgSbSe2 changed monotonically in the range from 250 to 1000 μVK-1. For Ag0.9Sb1.1Se2, the Seebeck coefficient is in range from -500 to -750 μVK-1. Single crystals of BiSbTe3 exhibit small changes of the Seebeck coefficient in the range from 200 to 280 μVK-1.
- Manufacturing and properties of CoSb3 doped with Ag
- Strony: 60-64
The aim of this work was to examine the influence of Ag additive on thermoelectric figure of merit, ZT, of cobalt triantimonide CoSb3. A series of samples with nominal composition of AgxCo8Sb24, (x = 0-0,5) was prepared. Structural properties and phase composition was analyzed by XRD diffraction method. The influence of Ag content on electrical conductivity, Seebeck coefficient, thermal conductivity and crystal structure parameter was investigated. The temperature dependence of thermoelectric figure of merit, ZT, was determined using measured thermal and electrical parameters.
- CoSb3/Cu junctions with diffusive barriers obtained by the magnetron sputtering technique
- Strony: 65-69
The goal of the present work was to develop the junctions between CoSb3 semiconducting thermoelectric material and a copper electrode,as well as the selection of appropriate protective layers, which inhibit diffusion processes at a junctions area.
The CoSb3/Cu junctions were formed by resistance soldering technique in the protective atmosphere of 90% Ar + 10% H2, using Ag-Cu based solders. Diffusion layers (Ni, Mo, Cr80Si20) were prepared by magnetron sputtering technique and deposited on polycrystalline element made of CoSb3. The microstructural properties and chemical compositions of the junction area were analyzed by a scanning electron microscope (SEM) equipped with energy-dispersive X-ray analyzer (EDX). Measurements of electrical properties of the junctions such as resistance and current–voltage characteristics were performed on an apparatus designed especially for this purpose. Thermal expansion coefficients of the thermoelectric material and the solder were also characterized.
- Preparation of Sr0.7Ba0.3Nb2O6 for textured composites by the sol-gel method
- Strony: 70-73
Strontium barium niobate SrxBa1-xNb2O6 (SBN) in the range of 0.25<x<0.75 is a ferroelectric material with the tetragonal tungsten bronze type structure. In this work, ceramic powders obtained by a sol-gel method were used to obtain Sr0.7Ba0.3Nb2O6-PVDF (SBN70-PVDF) textured composites. The powders of strontium barium niobate Sr0.7Ba0.3Nb2O6 (SBN70) were prepared using strontium acetate, barium acetate and niobium ethoxide as precursors. The powders were dispersed in a polyvinylidene fluoride (PVDF) matrix, providing a composite with 0-3 connectivity. Composite surface images were obtained by AFM tapping mode (NT-MDT Solver P47) in air at room temperature.
The textured SBN70-PVDF composite has a high potential to be used as piezo- and pyroelectric elements. The pyroelectric current of composites was measured using the Keithley 6517A electrometer.
- New construction of active optical fibres for fibre laser application
- Strony: 74-80
The present paper shows possibility of applying a new construction of rare–earth doped optical fibres fabricated by the authors as an active material for constructing high-power fibre lasers. Double-clad multicore active optical fibres enable a high-intensity and low-divergence laser beam (supermod) in the far-field diffraction region to be attained. A helical-core optical fibre is the second type of active optical fibres shown in the paper. Due to specifi c shape of the core, such a fibre is characterized by the effective absorption of pump radiation. Moreover, optimization of material and geometrical optical fibre properties makes it possible to increase volume of active material (core diameter) while the single mode operation is preserved. Strong luminescence of both types of manufactured optical fibres doped with Nd3+ ions creates conditoins to their application in optical fibre lasers.
- Categorization of fly ash against the properties of cement-fly ash composites
- Strony: 81-86
Fly ashes have been put into categories according to the current standard PN-EN 450:1:2009 Fly ash for concrete. Definition, requirements and quality control. The aim of the categorization process is to differentiate the quality of fly ashes on the basis of content of ignition loss (categories A, B, C) and fineness (categories N and S). During tests, it was stated that fly ashes of the particular categories differ in the phase composition, pozzolana activity and water demand, and they influence the performance of commonly used chemical admixtures such as plasticizers and superplasticizers. These properties are essential for the durability of cement-fly ash composites, and the command of them will make possible the effective use of particular categories of fly ashes in the cement and concrete production.
- Polished and rectified tiles as an example of highly processed ceramic tiles
- Strony: 87-92
The polished and rectified tiles are an example of highly processed tiles, which have received an excellent welcome from the Clients and still win a great number of supporters. A room designed in an interesting manner, where these tiles were used, is much more attractive than in the case of application of traditional tiles. Their main advantage is an ideal finishing of the surface and edges as well as the effect of mirror surface and uniform wall, giving an impression of laying the tiles without a joint.
The paper presents a method of manufacturing the polished and rectified tiles, demonstrates differences between these and traditional tiles, and provides practical clues in regard to assembly and further use of the polished and rectified tiles.
- Influence of inorganic and organic modifiers on viscosity of sols, structure and properties of coloured hybrid coatings
- Strony: 93-101
Coating glasses with coats of various functionalities is an issue of modern glass industry at present, because it allows us to obtain a product with modified properties, which are adequate to the purpose. One of the possible modification of glass is to apply thin colour layers that adhere to the substrate perfectly, having various intensive colours and being mechanically and chemically resistant. The ORMOCER type inorganic-organic hybrid coatings have such properties. A matrix of these coatings is made of the silica network often containing also other elements (Al, Ti, Zr) substituting silicon; organic groups bound with silicon via the Si–C bond are the main modifiers of such a network.
Colour of the coatings is mostly given by organic dyes, for which the organically modified silica network is a very good compatible matrix. Solutions used for application of the thin layers are received from adequate organic compounds. The coatings are mostly applied on the glass products by two alternative methods: dipping or spraying. Viscosity of the initial solution used for the glass coating is the parameter, which determines the quality of the coating, and also the layer thickness and colour intensity. Furthermore, the sol viscosity depends on the composition of the initial solution, particularly, on the type of inorganic and organic modifiers used in the silica network and the dilution grade of the solution. From the point of view of colour properties of hybrid coatings, a good solution is to use matrices that composition is based on two compounds, namely TEOS and GPTMS. Since, the addition of other elements, e.g. titanium and zirconium, to such organic compound matrices influences the quality and properties of the coatings, a study of the influence of Ti and Zr containing compounds on the viscosity of sols, the structure of gels and the optical UV/VIS characteristics of colour coatings has been carried out. In the study, tetraethyl ortho-titaniate C8H20O4Ti and tetrapropyl ortho-zirconate Zr(OC3H7)4 were used as precursors for Ti and Zr. In order to obtain colours, ORASOL type dyes (Red BL, Blue GN or Black RLI) were dissolved in alcohol, and added to the initial solution. The measurements of viscosity as a function of time were carried out for each initial solution, and were accompanied by a parallel application of thin layers, using solutions with known viscosity. The films were applied by dipping on surfaces of flat glasses and glass products. Both the visual quality estimation of the applied layers and the spectrophotometric UV/VIS characterization were made. Spectroscopic examinations, i.e. FTIR and 29Si MAS NMR, were used to investigate the structure of the gels, obtained from the initial solutions. It has been found, that the type of the modifier, which was used in a form of organic compound containing Ti and Zr, strongly affected the sol viscosity. Thus, it determines the conditions of thin layer application.
- Building ceramics in Poland – History and the present day
- Strony: 102-110
Building ceramics is manufactured for 800 years in the Polish lands. During that time, it was always marked by modernity and rich tradition. The earliest bricks were shaped manually, and fired in the mielerzowy kilns. The contemporary brick production is signifi cantly automated. The most modern technologies has been introduced to the production practice. The new technique allows the effective and relatively fast brick production to be combined with pro-ecological actions, that result in substantial reductions in eclectic and thermal energies, and the decreased harmfulness of working conditions.
The oldest brick buildings are dated on the twelfth century, which exist till the present day in the Polish terrain. Those are sacred structures partially built with bricks and partially with stone. A church in Kołbacz near Szczecin is the oldest building made from bricks completely. Its building was commenced in 1210. Large popularity and durability of the bricks as a building material caused that the rich and varied examples of brick architecture can be admired today in the Polish lands.
During many years, products manufactured by building ceramic industry were subjected to the peculiar evolution. Solid bricks were mainly manufactured initially, somewhat later, roofing tiles were commenced to produce. At the moment, very diverse assortments of structural clay tiles, clinker bricks, roofing tiles and special products are produced. The development of production technologies made possible to produce the structural clay tiles of large dimensions and specific properties. The structural tiles made from porous ceramics gained the special popularity due to usefulness for making monolayer walls with no additional warming up. The ground structural tiles with a high dimensional precision of the supporting surfaces are a novelty on the Polish market. Such tiles make possibility to build by means of using thin joints, including polyurethane mortars.
- Strony: 111-111
List of Contents
Volume 62, Issue 2
- Dielectric and dynamic mechanical properties of BST/PVDT ceramic-polymer composite
- Strony: 115-120
In this paper, we report the results of a study of microstructure and dielectric and dynamic mechanical properties of ceramic-polymer composites composed of barium strontium titanate Ba0.6Sr0.4TiO4 (BST60/40) and polyvinylidene fluoride (PVDF). The composite BST60/40//PVDF was obtained by the hot pressing method for volume fraction of BST60/40 ceramic powder cv = 50%. The morphology of BST60/40//PVDF composites powder was observed by transmission electron microscopy and scanning electron microscopy. Temperature dependence of dielectric permittivity of BST60/40//PVDF composites was measured in a frequency range of f = 10·103-1·106Hz. Dynamic
mechanical properties of BST60/40//PVDF composites were measured by the internal friction method and by the dynamic mechanical thermal analysis DMTA.
- Synthesis, crystal structure and dielectric behaviour of 0.7BiFeO3–0.3BaTiO3 ceramics
- Strony: 121-125
The solid solutions of (1-x)BiFeO3–xBaTiO3 were synthesized with x=0.3 (0.7BF–0.3BT). Adopting optimum conditions of the solid state sintering route, dense ceramics with a pure perovskite phase, and homogeneous microstructure have been obtained. All precursors were thoroughly mixed and ceramics was synthesized at temperatures in the range of T=750-850°C. Simultaneous thermal analysis (STA), in which both thermal analysis (DTA) and mass change effects (TG and DTG) are measured concurrently on the same sample, was used to investigate synthesis effects in the powdered 0.7BF–0.3BT ceramics. The measurements were obtained with Netzsch STA409 thermal analyzer. Microstructure was investigated by a scanning electron microscope whereas the chemical composition was studied by an energy dispersive spectrometer (EDS). The crystal structure and phase composition of bulk ceramics were studied by the X-ray diffraction method at room temperature. Dielectric properties of (1-x)BiFeO3–(x)BaTiO3 ceramics were studied by impedance spectroscopy (IS).
- Dielectric and magnetic properties of Bi5Ti3FeO15 multiferroic ceramics
- Strony: 126-133
In the present paper, the results of studies devoted to fabrication and characterization of Bi5Ti3FeO15 (BTFO) multiferroic ceramics exhibiting Aurivillius - type structure are reported. By means of simultaneous thermal and X-ray diffraction analysis, the process of synthesis of BTFO ceramics has been studied. Mixed oxide method followed by free sintering was used for ceramics preparation. Dielectric and magnetic properties has been studied by impedance spectroscopy and Mössbauer spectroscopy, respectively. It has been found that BTFO ceramics exhibited orthorhombic symmetry with Cmc21 (36) space group. Room-temperature Mössbauer spectra of BTFO revealed its paramagnetic properties as well as confirmed fabrication of a single phase ceramic material. Application of impedance spectroscopy makes it possible to determine frequencies of relaxation phenomena present in BFTO ceramics within the temperature range DT = RT – 500°C.
- Ce0.8Gd0.2O2 ceramic electrolites for components of SOFCs
- Strony: 134-142
The paper presents the results of selected studies of electrolytic properties of the sintered Ce0.8Gd0.2O2 (20GDC) solid solution used as electrolyte in IT-SOFC. It also presents the selected results of research carried out to clarify the mechanism of oxygen reduction in the 20GDC electrolyte when metallic Au, Ag and Pt point electrodes were used. Single-phase 20GDC solid solution powders were obtained by coprecipitation-calcination (A) and hydrothermal (B) methods. The 20GDC samples produced from the (A) and (B) powders were sintered respectively for 4 hrs at 1270°C and at 1600°C for 2 hrs in air. The sintered gas-tight 20GDCs were tested for long-term exposure to such factors as temperature, composition of a gaseous reactive atmosphere and current load of the cell. As a result of the research, it has been found that the long-term operation of 20GDC sinters under current load in oxidizing atmospheres did not lead to any noticeable structural or microstructural changes of the electrolyte. On the other hand, on the basis of the studies on electrochemical reduction of oxygen
at the metal-20GDC interface, using a point electrode, it can be concluded that the mechanism of the oxygen electrode is very complicated, and it is affected not only by the catalytic properties of the electrode material, but also it depends upon the type of transport of oxygen to the place where the reaction occurs.
- Factors improving efficiency of direct carbon fuel cell
- Strony: 143-148
The paper examines the influence of ionic conductivity of solid oxide electrolytes (ZrO2-Y2O3) on efficiency of a planar solid oxide fuel cell with direct oxidation of carbon (DC-SOFC), operating at temperatures from 600 to 850°C. The ZrO2 solid solutions contained from 3 to 12 mol% Y2O3. The highest current densities were obtained for DC-SOFC with 8 mol% Y2O3 in ZrO2 (8YSZ) used as electrolyte. The performance efficiency of that fuel cell increases also as a result of reducing the thickness of the electrolyte, which results in a decrease of ohmic polarization. Also, preliminary studies were performed, focusing on the effectiveness of conversion of different types of coal to electricity in DC-SOFC.
During research, it was showed that adding 8YSZ ionic oxide conductor to the powdered coal fuel in the amount not exceeding 10% of its weight results in an increase of current densities as opposed to the current densities obtained from pure carbon fuel cells. The measurements were carried out in the planar and tubular oxide fuel cells.
- Utilization of chrysotile asbestos for sintering ceramics production
- Strony: 149-155
The paper reports the possibility of detoxifi cation of asbestos through low temperature heating and grinding treatment. It has been found that chrysotile can be transformed to a mixture of non hazardous silicate phases as a result of thermal treatment at the temperatures higher than 600°C. Calcinated chrysotile asbestos is easily milled to the pulverulent shape material by mechanical milling. The material prepared in such a way acted as a substitute of quartz sand, which is widely used as a leaning agent in ceramic masses to be formed into stoneware. The parameters of the samples pressed with water and then sintered were collated with the samples with the addition of NaH2PO4. The laboratory scale investigations showed that the calcinated chrysotile asbestos can be used as one of raw materials for the sintered ceramics.
- Durability of concretes containing fly ash from co-combustion of wood biomass and bituminous coal
- Strony: 156-160
The results of a frost resistance test of concrete with fly ash formed during co-combustion of the fuel mix containing 80% of biomass and 20% of bituminous coal were presented. The changes of concrete resistance to the chloride penetration were also discussed. Because of significant differences between fly ash tested and conventional fly ash, the ways of its application cannot be indicated without the risk of decrease in concrete durability during freezing and thawing. The frost resistance was evaluated based on the mass of material scaled from the concrete surface subjected to 112 cycles of freezing and thawing in the presence of 3% NaCl solution. The chloride ion penetration into the concrete was determined by means of a rapid method in non-steady-state condition, after 28, 90 and 180 days of storage. The analysis of test results indicates that the introduction to concrete up to 25% of ground fly ash derived from the co-combustion of biomass and coal may have beneficial effect on the concrete properties responsible for durability of the structures when sufficient amount of the air-entraining agent is added and the proper curing conditions applied.
- Thermoelectric properties of lightweight mortars with waste graphite additive
- Strony: 161-165
This paper presents the results of investigation of physical and thermoelectric properties of lightweight cement mortars with cenospheres from coal ash and waste graphite powder additive. Quartz sand was replaced by the aluminosilicate cenospheres up to 60% of mass. The sand replacement led to the significant reduction of bulk density and thermal conductivity of the cement mortars. The waste graphite powder obtained during mechanical treatment of electrodes for the metallurgical industry was used as a conductive filler. It was added up to 35% of cement mass. The main physical properties i.e. bulk density, thermal conductivity, and bending strength were investigated. In case of the mortars with the 35% replacement of cement by graphite, the Seebeck voltage was measured. Addition of the graphite powder to mortars led to the moderate deterioration of main properties but the cement mortars received possibility of thermoelectric reaction due to the temperature changes. The Seebeck coefficients calculated for all investigated mortars were similar (in the error range) and, in each case, weak dependence of temperature gradient was visible. But in typical application, the thickness of used mortars was very small (about 1-2 cm) and the changes were too small to induce measurable level of the thermoelectric force. The point is that in case of lightweight mortars the low thermal conductivity caused much higher temperature gradient and as a consequence the Seebeck voltage increased.
Lightweight cement mortars with conductive particles originated from the graphite powder are the multifunctional materials and may be used to monitor the temperature of building walls.
- Assessment of fly ash from co-combustion of biomass and coal as a component of cement composites
- Strony: 166-170
The increasing application of the fossil fuels-biomass co-combustion causes the increased interest in fly ashes produced in this process. The tests were carried out for ashes originated from combustion of the mixtures of wood chips and coal in a conventional boiler of the industrial plant. When combusting, biomass accounted for 40% (ash I) and 80% (ash II) of fuel mass. The chemical composition, morphology, pozzolana activity and other physical properties of the ash were examined. The effect of ashes on the hydration process of binders was evaluated on the basis of the kinetics of hydration heat emission. The test results of the effects of fly ashes on concrete compressive strength were presented. Cement composites tested contained from 0 to 25% ash related to cement mass. The results indicate that the analyzed fly ashes, derived from co-combustion of wood biomass and coal can be used as the active component of cement concrete, although their application should be correlated with the quality parameters, related to the fuel mixture composition. As in case of conventional ash, the applicability of these mineral additives must be tested for each of their application.
- The chemical extraction and rietveld methods in investigations of glass content in siliceous fly ashes
- Strony: 171-175
In this paper, a glass content in siliceous fly ashes was investigated by chemical treatment with the 1% HF solution, and the Rietvield quantitative analysis. The glass content in fly ashes determined with the Rietvield analysis was 71-85%, whereas the chemical method indicated 41-73%. The HF solution dissolves glass partially from fly ashes. Treatment with the 1% HF solution removes also the crystalline phases such as mullite and β-quartz. After chemical treatment, the 0-16 μm fly ashes indicated lower amount of β-quartz in comparison to the initial samples. It is attributed to the presence mainly of amorphous silicon dioxide in these fly ashes. The increase of mullite content in the fly ash samples after treatment with the 1% HF solution is connected with the smallest solubility of mullite in comparison to crystalline quartz and glass. The results confirm variable structure and properties of glass included within the fly ashes, agreeing with the early investigations.
- Optical fibre doped with Yb3+ and Tm3+ ions
- Strony: 176-181
Yb3+/Tm3+-doped tellurite-germanium glasses were fabricated and characterized. Strong blue emission at 477 nm corresponding to the 1G4→3H6 transition in thulium ions was investigated under the excitation with a 976 nm diode laser. The dependence of up-conversion emission intensity upon thulium ions concentration was analyzed. The most effective energy transfer Yb3+ → Tm3+ occurs in the matrix when the molar ratio of Yb3+ to Tm3+ is 1:0.1. A crucible method was used to fabricate double-clad fibre with the active tellurite-germanium core. As a result of the excitation of fibre with the 976 nm diode laser, the ultraviolet emission at 351 nm (1D2 ® 3H6) was measured. Based on the three- and four-photon absorption processes, the up-conversion mechanisms were evaluated by the proper rate of model equation.
- Modification of the float glass surface by low-temperature plasma
- Strony: 182-183
The surface of flat glass was treated by a low-temperature plasma. An influence of plasma processing on the glass surface composition was analysed by means of ion scattering spectroscopy (ISS). The observed changes of the surface composition were explained basing on the thermal and electric fields created by the plasma.
- Glass–ceramics for waste immobilization
- Strony: 184-190
Vitrification is the most effective method for nuclear waste immobilization. Toxic elements are incorporated into the glass structure. Glasses from the P2O5–Al2O3–R2O and P2O5-Al2O3-Fe2O3-R2O systems were studied for the immobilization of salt waste. As a method of immobilization, sintering of glass–waste mixtures was chosen.
CaCl2 was used to simulate the waste. The immobilization process of calcium ions was studied during sintering with glasses containing above 50wt.% P2O5.
Properties of the glasses and glass–ceramic materials were determined. Thermal analysis showed that all glasses demonstrated the ability to crystallize. Intensity of this process depended on the chemical composition. The addition of Fe2O3 to glass increased this process. Thermal treatment caused high degree of crystallization of the studied glasses. According to the results of hydrolytic resistance tests, the glass sinters containing Fe2O3 are the most efficient for waste immobilization. Vitrification process of all the glasses reduced leachibility of waste components to a minimum.
The studies showed that CaCl2 being a simulated waste was permanently encapsulated in the glass–ceramic materials, making possible their effective immobilization.
- The influence of nano-scaled Al2O3 and TiO2 on properties of high alumina refractories
- Strony: 191-196
Refractories of high alumina contents are very popular for using in many applications. They show a very high mechanical strength at low temperatures. At high temperatures, of above 1300°C, a strong decreasing of the material strength can often be observed, particularly in case of materials containing refractory clay or reactive alumina. This phenomenon can be attributed to the migration of alkali oxides towards the grain boundary. In this zone in reaction with Al2O3 and SiO2, a liquid phase of low viscosity is formed.
In the paper, the influence of the nano-scaled aluminium oxide (Alu-C) and TiO2 (P25) on the hot crushing strength of both shaped materials and alumina concretes was investigated. It was found out that already a very small addition of nano-scaled powders leads to a considerable increase of the hot crushing strength of the materials under consideration. The results of the examinations indicated that the very pure alumina product containing no alkali contributes to an increase of the aluminium oxide content in the local ternary system Na2O-Al2O3-SiO2 in the grain boundary. A reducing of the amount of the liquid phase in this zone and increasing the hot mechanical properties of the material are resulting.
- Rheological parameters of kaolin KOC water suspensions
- Strony: 197-202
Water suspended bodies are present in all technologies of fine ceramics and in majority of cases of technical ceramics. The rheologically stable suspensions result from unique properties of the clayey mineral - water system. In connection with technological skills of the regulation of viscosity, tixothropy and density by the usage of rheological auxiliaries (fluidizers, plasticizers, stabilizers, preservants etc), there is wide range of opportunities to adjust the rheological parameters of ceramic powder suspensions to requirements of the manufacturing process. Since a few years, the high - energy milling techniques are widely used in technologies of preparing the bodies. In the paper, the results of research into the rheological parameters as a function of grain size are shown, related to the kaolin KOC after a high energy milling process, using MicroCer Ball Mill.
- The effect of content of TiB2 particles synthesized in situ on mechanical comminution of the zirconia composite powders
- Strony: 203-206
In the work, an effect of volume content of titanium diboride particles in the ZrO2/TiB2 composite powders on comminution susceptibility and admixture of the grinding media material (3Y-TZP) during wet attrition grinding was studied. The composite ZrO2/TiB2 powders were manufactured by the in situ method, using the high temperature reaction, which proceeded in solid state among TiO2 dissolved in the zirconia solid solution, amorphous boron and carbon at 1300°C. The phase composition of the powders and TiB2 crystallite sizes were determined qualitatively by X-ray diffractometry. The study was based on an analysis of the specific surface area determined by the BET adsorption method before and after comminution. The admixture of grinding media was measured with the gravimetric method. It was observed that titanium diboride particles synthesized in situ inhibit an increase of the specific surface area of the zirconia composite powders above a
content of ~29 vol.%, decreasing the comminution susceptibility. The significant admixture of zirconia grinding media was found independently on the TiB2 content in a range of 21-38 vol.%. This behaviour is suggested to be related to the TiB2 particle size and the morphology of composite particles of the zirconia powders, manufactured in the in situ process.
- Formation of submicron and nanometric zirconia powders for fuel cells
- Strony: 207-217
8 mol.% Y2O3-ZrO2 (8YSZ) submicro- and nano-powders were prepared by a coprecipitation method and then were either thermally heated or hydrothermally treated. The powders were used to formation of thin foils by means of the doctor blade method. Apparent density, absorbability and open porosity of the electrolyte foils were determined. The effect of sintering conditions on the foil microstructure has been discussed.
- Immobilization of heavy metal cations within the fired materials based on natural smectite and zeolite
- Strony: 218-223
The work presents results of the application of natural sorbents for immobilization of heavy metal cations (Cd2+, Cr3+, Pb2+, Zn2+ or Ag+) performed from aqueous solutions and of usage them to prepare building materials. Sorption was conducted on sodium form of natural clinoptilolite and smectite originated from Poland.
Both sorbents containing various heavy metal cations were applied to obtain building materials. It was demonstrated that the samples composed of 80% smectite - 20% clinoptilolite and 80% smectite - 20% sand, fired at 900°C or 1100°C are safe materials with insignificant leaching of cations. It was found that the temperature of sintering, the introduction of heavy metal ions into materials and a kind of leaching component had the clear influence on bulk density and compressive strength. A range of compressive strength of about 3-17 MPa was measured. The influence of heavy metal cations on the compressive strength values was significant and dependent on the valence of cation immobilized. However, the cations did not modify the phase composition and the microstructure of materials. Effectiveness of cation immobilization in the mineral matrix is shown.
In the work, results of IR spectroscopy, X-ray diffraction analysis, SEM observations, AAS analysis and technological investigations are presented.
- Fabrication, characteristics and biological evaluation of highly porous hydroxyapatite bioceramics
- Strony: 224-229
The aim of this study was fabrication, characteristisation of phase composition and microstructure, as well as biological evaluation of the highly porous hydroxyapatite-based implantation materials. The methods of gelcasting of foams and replacement of porous organic matrix were used to fabricate the materials. It was stated that each method results in obtaining monophase hydroxyapatite bioceramics with the size of macropores up to 900 μm. When the gelcasting of foams method was applied, windows were additionally present in the walls surrounding the spherical macropores. Interesting pores architecture of the material produced on the basis of polyurethane spongy let a more homogeneous cell distribution in the whole volume of the samples to be obtained during the cell culture.
- Strony: 230-232
List of Contents
Volume 62, Issue 3
- Detection of Amorphous Silica in Air-Oxidized Ti3SiC2 at 500–1000°C
- Strony: 235-238
In this paper we describe the use of secondary-ion mass spectrometry (SIMS) and nuclear magnetic resonance (NMR) to detect the existence of amorphous silica in Ti3SiC2 oxidised at 500-1000°C. The formation of an amorphous SiO2 layer and its growth in thickness with temperature was monitored using dynamic SIMS. A duplex structure with an outer layer of TiO2 and an inner mixture layer of SiO2 and TiO2 was observed. Results of NMR verify for the first time the direct evidence of amorphous silica formation during the oxidation of Ti3SiC2 at the temperature range 500-1000°C.
- Effects of Alumina Powder Characteristics on the Reactive Sintering of CaO-Al2O3
- Strony: 239-243
The microstructure of fired materials resulting from the reactive sintering of mixtures in the system alumina –lime depends on the characteristics of the starting components. This work aims to better understand the effect of some characteristics of the starting component of alumina (specific surface area, particle size distribution, morphology, impurities) on the microstructure evolution during thermal treatments of materials in the system Al2O3-CaO.
- Determination of the Fracture Toughness Parameters of Quasi-Brittle Materials Using Cylindrical Samples
- Strony: 244-248
A method of determination of the critical stress intensity factor for brittle and quasi-brittle materials (ceramics, cement based materials) is proposed. In the approach proposed the process of sample fracture develops from the vertex of a V-shaped notch, in contrast to standard methods, where the fracture process starts from a crack tip. For the compressed cylindrical sample with central diamond-shaped hole, the stress intensity factors were calculated for an arbitrary vertex angle. The critical values of SIF were obtained by considering a deformation fracture criterion based on the Dugdale model of failure with the assumption that the fracture process zone starts from the notch vertex. The approach presented can be applied to the analysis of the fracture process in the vicinity of stress concentrators such as sharp and round notches formed in the sample.
- Fractographical Characteristic of Admixtures in Medieval Pottery
- Strony: 249-254
The principal aim of the investigations described in the paper was to characterize the structure of fragments of ceramic vessels found in the region of Wyszogród, Poland, and dated from 7th to 9th century. The ceramic fragments were examined by optical and scanning electron microscopy. The material was subjected to qualitative and quantitative analyses. The qualitative description included the identification of the kind of admixtures, determination of their distribution and description of the structure of the ceramic matrix. This was done using fractographic examinations of vessel fractures which permitted identifying the shape, color, and admixture distribution, and also enabled us to observe the structure of the ceramic matrix in particular cracks and delaminations. The quantitative analysis consisted of the measurements of the size of the admixtures. Observations combined with a point analysis of the chemical composition performed in a scanning electron microscope supplemented the examinations of the kind and structure of the admixtures. The admixtures were characterized using the methods of quantitative description.
- Application of the Barium-β”-Alumina Solid-State Electrolyte to the Thermodynamic Study of the BaO-ZrO2 System
- Strony: 255-258
The standard molar Gibbs free energies of formation of BaZrO3, Ba2ZrO4 and Ba3Zr2O7 have been determined by the galvanic cells involving Ba-b”-alumina as a solid-state electrolyte. The emf of the cells:
Pt| O2 | BaO | Ba-b”-Al2O3 |BaZrO3, ZrO2 | O2 |Pt,
Pt| O2 | BaO | Ba-b”-Al2O3 | BaZrO3, Ba3Zr2O7 | O2 |Pt,
Pt| O2 | BaO | Ba-b”-Al2O3 | Ba3Zr2O7, Ba2ZrO4 | O2 |Pt,
has been measured in the temperature range from 1073 to 1273 K.
The standard molar Gibbs free energies of formation of BaZrO3, Ba2ZrO4, and Ba3Zr2O7 from BaO and ZrO2 have been calculated. The standard molar Gibbs free energies of formation of barium zirconates from elements have been estimated and compared with the data obtained by other authors.
- Superplastic Properties of Zirconia-Hafnia Composites Doped with Various Oxides
- Strony: 259-265
The influence of 1 mol% dopant of various oxides on the superplastic flow of yttria stabilized tetragonal zirconia ceramics and zirconia – 10 mol% hafnia composite was examined in the temperature range 1553 – 1773 K. It was claimed that doping caused the increase of superplastic strain rate in zirconia and in zirconia-hafnia composite in comparison with undoped materials. The maximum strain rate for zirconia was measured for GeO2 addition; it was 16x higher than in pure ceramics, but for zirconia-hafnia the maximum strain rate was for SiO2 dopant (4x higher than in pure composite). There is a linear relationship between the grain boundary diffusion coefficient of Zr4+ and superplastic strain rate for zirconia ceramics. For zirconia-hafnia composite this relationship is not so obvious because of high strain rate for SiO2 addition.
- Shot Peening in Structural Ceramics
- Strony: 266-271
Car and aircraft manufacturers commonly use shot peening technique to modify material surface layers and improve the strength of metal components. As it occurred, the same technique can be applied for brittle ceramics. High compressive stresses up to 2.4 GPa were introduced into the near surface region of alumina and zirconia ceramics maintaining its surface integrity by ultrasonic shot peening. The dependence between diameter of tungsten carbide balls, treatment time (at constant mass of balls in the housing and vibration amplitude) and level of compressive stress introduced was determined for nano and micro sized grains of both ceramics. An increase of hardness and surface resistance to fracture with an increasing level of compressive stress was found. Surface layers of ceramics deformed by shot peening have been analysed by the classical XRD, X-ray texture test, using Euler circle and ESEM/EBSD methods.
- Diffraction Study of Thermal Dissociation of Ti3AlC2 in Vacuum
- Strony: 272-274
Titanium aluminum carbide exhibits a unique combination of characteristics of both metals and ceramics coupled with an unusual combination of mechanical, electrical and thermal properties. In this paper, the effect of high-vacuum annealing on the phase stability and phase transition of Ti3AlC2 at up to 1550°C was studied using in-situ neutron diffraction. The decomposition of Ti3AlC2 into TiC was observed from the change of relative phase abundances as a function of temperature. The apparent activation energies of phase decomposition was determined to be -71.9 kJ/mol. Near-surface composition depth profiling using grazing-incidence synchrotron radiation diffraction has revealed a graded phase composition in vacuum-decomposed surfaces.
- Modeling of the Residual Stresses and their Effects on the TBC System After Thermal Cycling Using Finite Element Method
- Strony: 275-279
The main goal of this work is to study the effects of the residual stresses due to the coating process on the final stress distribution within the Thermal Barrier Coatings system (TBCs) after thermal cycling. The thermo-mechanical Finite Element Model (FEM) was developed to estimate the stress distribution. This model takes into account several phenomena: residual stress generation during the spraying of coatings, morphology of the top-coat/ bond-coat interface, oxidation at the bond-coat/top-coat interface, plastic deformation of the bond-coat and creep of all layers during thermal cycling. As results, we observed a critical stress after coating spraying, corresponding to a low substrate temperature and high cooling rate during spraying of the top-coat material.
- High Temperature Mechanical Spectroscopy of α-SiAlON Ceramics with Different N/O Ratios
- Strony: 280-282
High temperature mechanical properties of the silicon nitride based ceramics (such as SiAlON) depend highly on the formation of the grain boundary glassy phase obtained from sintering. In the present study, in order to investigate the effect of grain boundary chemistry and the N/O ratio on the chemical composition of a-SiAlON, the raw powders were hot-pressed for 4h at 2073 K under a pressure of 35 MPa, using two different sintering aids (Y3+ and Yb3+), both with the oxygen rich (Y2O3 and Yb2O3) and the nitrogen rich (YN and YbN) compounds. The mechanical spectroscopy investigations of Y-SiAlON show a relaxation peak related to the glassy phase located on the triple-point junctions at around 1250 K. In the case of Yb-SiAlON, on the contrary, the absence of relaxation peaks stems from the very low content of glassy phase, together with the presence of elongated grains. In addition, the lower height of mechanical loss peaks in nitrogen rich Y-SiAlON samples versus oxygen rich ones is related to the substitution of oxygen by nitrogen in the [SiO4] tetrahedral network that leads to a higher bond density in the glassy phase and high viscosity of the glassy phase at high temperatures.
- Effect of Atmosphere Change Paths on the Induced Chemical Expansion
- Strony: 283-287
This study presents the relevant aspects of the approach developed at Institut PRISME to model strain in the mixed ionic and electronic conductors (MIEC) membrane for reforming of methane into synthesis gas (H2/CO). This macroscopic approach is based on the assumption of strain partition and on the choice of oxygen activity as a state variable. It leads to a thermo-chemo-mechanical model taking into account oxygen diffusion as well as elastic, thermal and chemical expansion phenomena. A chemical expansion model is proposed. The kinetics of a macroscopic bulk diffusion model has been fitted by simulation to chemical dilatometry tests. The transient and the steady-state stress distribution in a membrane reactor for partial oxidation of methane (POM) have been simulated in various conditions.
- Ultrasonication as a Method for Examination of Glasses Derived from UV Curable Nanosilica Pastes
- Strony: 288-293
Ceramics and glasses are well suited as materials for chemical microreactors working at high temperatures and chemically aggressive environments. Such microreactors are conveniently produced by rapid prototyping of UV curable dispersions. Ultrasonic methods can provide information on the mechanical properties by the detection of defects and discontinuity of such materials. The technique is used here to study the effect of the paste composition on the properties of the final glasses. The effects of the base monomer type, crosslinker concentration and photoinitiators were examined. The results of ultrasonic measurements were applied to determine both the materials constants and dependences of ultrasonic wave speeds on the original paste composition. It was shown that ultrasonic tests can be useful for optimization of compositions of UV curable ceramic pastes, used in rapid prototyping.
- Characterization of Thermal Decomposition Products of Cerium Acetate by High Temperature FTIR Spectroscopy
- Strony: 294-296
In the present work, thermal decomposition of cerium(III) acetate hydrate (Ce(CH3CO2)3·1.5H2O) was studied in argon gas atmosphere by using thermogravimetric-differential thermal analysis techniques (TG-DTA) and in-situ High Temperature FTIR Spectroscopy technique (HT-FTIR). The obtained FTIR results were combined with the results of performed TG/DTA experiments in the present work and the literature data. A good agreement between the thermal analyses and FTIR results was found, and possible decomposition mechanism is discussed.
- Sintering and Grain Growth Behaviour of Ultra Fine Al2O3 Powder
- Strony: 297-300
The sub-micrometer alumina powder with an average particle size of 150 nm was sintered, using two different methods, i.e. conventional sintering (CS) and two-step sintering (TSS). While the grain size of full-dense structures produced by conventional sintering ranges between 1-2 µm, the application of an optimum TSS regime led to a remarkable decrease of grain size down to ~500 nm. The results show that low temperature isothermal dwell at 1150°C after heating the green compacts up to 1300°C decreased the grain size from 1.2 μm to 850 nm. A further decrease of the first step temperature to 1250°C led to the formation of a finer structure with an average grain size of 500 nm.
- Analysis of Residual Stresses Using the sin2Ψ Method for Al2O3 Materials before and after Grinding and Heat Treatment Processes
- Strony: 301-306
This work presents the results of analysis of residual stresses generated at various stages of production of Al2O3 sinters (sintering, mechanical processing). Residual stresses were determined by the g-sin2Ψ X-ray method. The process of ceramic sintering of Al2O3 was carried out at varying parameters: temperature and heating time, heating rate, cooling rate. After mechanical processing (grinding), the materials were subjected to heat treatment, consisting of heating to temperatures in the range of 600 - 1200°C. In order to determine the mechanical properties of the materials, HV30, HV0.3 and HV0.1 hardness measurements were made. KIc and HVG stress intensity index values were also determined.
- Alumina Layers Synthesized on Cemented Carbide Tools by MOCVD Method
- Strony: 307-310
This paper shows the results of investigation of a synthesis of pure aluminium oxide layers on cemented carbide cutting tools by the MOCVD (Metalorganic Chemical Vapour Deposition) method using Al(O2C5H7)3 as a precursor. The layers were deposited at 800°C in two stages. Initially, as carrier gases ammonia (99.95 % pure) and/or argon (99.995 % pure) were used. Then, a thin and continuous Al2O3+C layer was obtained. It was so-called the intermediate layer. In the second stage, air was added into a CVD reactor and then a thicker external carbon-free Al2O3 layer was synthesized. The average growth rate of the layers was about 5 mm/h. The obtained layers were additionally annealed in air at temperatures up to 1050°C, which caused formation of a-Al2O3.
Structure and microstructure of the layers were examined. Microhardness tests were performed by Vickers method over a load of 1N. The average value of microhardness of the layers with no annealing was about 0.98 GPa. After annealing at 1050°C, the average value of the microhardness amounted to about 2.25 GPa. Adhesion of Al2O3 layers to the substrate of cemented carbides was examined by the scratch test. Estimated average value LC for the not annealed Al2O3 layer of 5 mm thickness was 41 N. In the case of samples annealed at 1000°C this value reached even 85 N.
- Electrical Properties of Acceptor-Doped BaCeO3
- Strony: 311-315
Barium cerate exhibits high protonic conductivity in gas atmospheres containing water vapour, especially when modified with a trivalent dopant such as Y, Gd, Yb, Nd, Sm or Dy. Such materials can be used as solid electrolytes in intermediate temperature solid oxide fuel cells. In the present work, the influence of Y and Gd dopants on the electrical properties of BaCeO3 was investigated using the Electrochemical Impedance Spectroscopy (EIS) technique. Oxygen nonstoichiometry and valence of cerium were studied with the analytical iodometric method. Samples were prepared in solid-state reactions. It was found that the electrical properties depend on the preparation method. Doping with an acceptor, in this case Y or Gd, leads to substantial changes to both bulk and grain boundary electrical conductivity in comparison with undoped materials.
- BaCe(Ti,Y)O3 – Ceramic Protonic Conductors for Hydrogen Purification
- Strony: 316-321
The aim of this work was to construct the model of electrochemical hydrogen pump and to determine its performance. The influence of titanium and yttrium on physicochemical properties of BaCeO3 material selected for pump construction was investigated. X-ray diffraction (XRD), differential thermal analysis and termogravimetry (DTA, TG), scanning electron microscopy (SEM) and DC electrical measurements were used as experimental techniques. It was found the introduction of titanium caused an improvement of corrosion resistance against CO2 and better sinterability . On the other hand, doping by Ti decreased the total and ionic conductivities of the material. Doping by yttrium caused the opposite effect; the increase of electrical conductivity was observed. Basing on the obtained results the optimal composition of the material was selected from the point of view of the construction of electrochemical membrane for hydrogen purification.
- Perovskite Membranes for Oxygen Separation and Oxy-Combustion Processes
- Strony: 322-327
Mixed oxides with the perovskite-like structure possessing mixed electronic and ionic electrical conductivities are proposed for dense ceramic membranes production for both oxygen separation and oxy-combustion processes. In this study three perovskite-type mixed oxides La0.6Sr0.4Fe0.8Co0.2O3+δ (LSCF), Ba0.5Sr0.5Co0.8Fe0,2O3+δ (BSCF) and La2Ni0.9Co0.1O4-δ (LNC), considered to be the most promising materials due to high oxygen fluxes, are utilized for both plate and tubular membranes fabrication. For providing the appropriate efficiency of the oxygen production the main role is played by thickness as well as outer surface development of membranes. On account of this, three configurations of plate membranes were tested, i.e. thick dense membranes, thin dense diaphragms on porous support and thick dense membranes coated on both sides with porous thin layers. Tubular membranes, more useful in industrial practice due to their larger effective surface, mechanical stability and easiness of application, were prepared in two configurations, i.e. dense thin-walled tubes made by isostatic pressing and extrusion methods, as well as thin dense membrane, coated on the porous tube. The basic physicochemical properties of the obtained diaphragms were determined. Some of them were characterised by the measurement of the oxygen permeation flux.
- Manufacturing and Properties of Ceramics Originated from Zirconia-Ceria Nanopowders Doped with Yttria
- Strony: 328-334
Ceria-zirconia nanopowders doped with yttrium(III) oxide were prepared by a soft chemistry route. A concentration of ceria in the 8 mol% yttria-zirconia nanopowder changed from 0 % to 100 %. In the route, a water solution of zirconium(IV) oxychloride, yttrium(III) chloride and cerium(III) nitrate was treated with ammonia to co-precipitate a deposit, which was calcined for 2 h at 900°C in air to obtain crystalline nanopowder. Consolidation of the nanopowders was performed by means of cold isostatic pressing under 220 MPa and natural sintering for 2 h at 1550°C in air.
The effects of the ceria concentration on properties of both yttria-zirconia-ceria nanopowders and bulk materials were investigated by TG-DTA, XRD, BET, SEM and Vickers’ indentation. The thermal behaviour of co-precipitated materials, crystal structure and crystallite size of the nanopowders, evolution of the microstructure and mechanical properties of the bulk materials were found to depend on ceria concentration.
- Design of Alumina-Zirconia Nanocomposite Powders for Implants Development
- Strony: 335-341
A 95 vol.% alumina – 5 vol.% zirconia composite powder was produced following a simple surface modification procedure, starting from a zirconium chloride aqueous solution and a commercial, ultra-fine a-alumina powder. The evolution of phases as well as of the nano-microstructure was followed as a function of powder heat-treatments prior to sintering, in order to develop a preliminary “nano-powder engineering” approach, in view of a controlled tailoring of the microstructural features of the dense materials.
- Gelcast Components Having Controlled Porosity Features Obtained from a Natural Hydroxyapatite Powder
- Strony: 342-348
An innovative gelcasting process was developed in order to obtain macroporous hydroxyapatite (Ca10(PO4)6(OH)2, HAp) scaffolds having controlled porosity features. Two different HAp powders have been employed. The former is a natural carbonated hydroxyapatite nanopowder, produced by extraction from pig bones. The latter, used as a reference, is a commercially available HAp powder. On the natural HAp, a preliminary treatment was carried out in order to limit carbonates decomposition during sintering. After calcination at 700°C the powder was in fact washed in pure distilled water, thus to eliminate the highly soluble Ca(OH)2.
The porous materials were produced, exploiting PE spheres, having two different size distributions, as pore former for tailoring the porosity size and volume. Moreover, the polymerization of the agar as a natural gelling agent was exploited for controlling the pore distribution.
- Crystallization of 45S5 during Isothermal Heat Treatment
- Strony: 349-354
Bioglass 45S5 has been shown inter alia to enhance bone growth, making it an interesting material for implants and scaffolds. Scaffolds are sintered from powdered glasses, and are partially crystalline. Crystallization of powdered 45S5 is well reported in the literature. 45S5 easily crystallizes also during hot-working to various implants. Crystallization of 45S5 plates at isothermal treatments was studied systematically for up to six hours at ten different temperatures (600-1000°C). The samples were inserted into a preheated furnace, and after the treatment the samples were rapidly cooled in the nitrogen flow. XRD, SEM, and optical microscope were used to identify the phase changes. According to the optical microscope images, the phase separation commenced around 600°C. The phase separated regions became more apparent at 700°C, and above 800°C a uniform crystal structure was observed. According to SEM, the crystal aggregates in the bulk showed truncated cube-like morphology (10‑40 µm). At higher temperatures two different crystal structures could be identified on the surface. The X-ray diffraction pattern evolution was followed as the functions of time and temperature. The first peaks were observed at 650°C and the best match was obtained with Na2CaSi2O6. An evident broadening of the main peak (at 2θ ≈ 34°), leading to a separation into two peaks, was observed around 700°C; the separation of the peaks increased linearly as the function of temperature. On plate surfaces the crystallization was similar to the reported results with powdered samples, while in the cross-sectional surface only one crystalline phase was observed.
- Development and Mechanical Characterization of Hydroxyapatite Micro/Macro-Porous Scaffolds by an Innovative Gel-Casting Process
- Strony: 355-362
An innovative gel-casting process was developed in order to obtain micro and macro porous hydroxyapatite (Ca10(PO4)6(OH)2, HA) scaffolds to be used in regenerative medicine for bone tissue reconstruction. The micro-porous materials were prepared using HA suspensions having different solid loadings (in the range of 55 - 60 wt%) and gelling agent contents (in the range of 0.3 - 0.75 wt%). After the set-up of the operative parameters, macro-porous components were also prepared by using commercial polyethylene spheres (PE), sieved in the range 355 - 420 mm, as a fugitive agent, added to the ceramic suspensions before casting. The PE amount was fixed for obtaining a porosity of 60 vol.% in the fired materials. The mechanical investigation was carried out on both dense and porous samples. The compressive tests, 4-point bending tests and micro-hardness measurements were performed in order to determine Young’s modulus, compressive strength, ultimate tensile stress and fracture toughness. Good correlations between mechanical properties were found. The results obtained for micro and macro-pororous specimens were related with a model based on the ideal cell. An extensive microstructural characterization was carried out by SEM and coupled to mechanical data in view of the validation of modelling tools based on DIB-FEA (digital image based finite element analysis) procedures.
- Effect of Sintering Atmosphere on the Selected Properties of the Natural Origin Hydroxyapatite Materials
- Strony: 363-365
Natural origin hydroxyapatite was extracted from the long cortical part of pig bones by treatment with the hot NaOH solution. After that, the material was carefully washed with distilled water, dried, and calcined in air at 450ºC. The samples compacted under 200 MPa were subjected to heat treatment at 1000ºC in air, CO2, O2, Ar and N2 atmospheres. It was found that sintering atmosphere influences greatly densification of the system, sample morphology, chemical stability and elastic properties. The materials sintered in air showed high density characterized by low open porosity and relatively large faceted grains. Heat treatment in the remaining atmospheres led to essentially lower densification. Grain sizes in these cases were much smaller. It was found that CO2 atmosphere arrested decomposition of the material; no free CaO appeared, and additional CO32- groups were built into the hydroxiapatite structure.
- Preliminary Approach to Application of Modified Smectite Clay to Form Tablets in Direct Compression Process
- Strony: 366-368
In this study, the modified smectite clay was used as a disintegrating agent and its suitability to form placebo tablets by the direct compression method was evaluated. The modification of the commercial purified smectite clay (Veegum®F, R.T. Vanderbilt Company, Inc.) was done in aqueous NaCl solution to provide relatively short disintegration time of tablets while maintaining their sufficient mechanical properties. To evaluate the influence of the new material on the quality of tablets obtained, the following parameters were investigated: disintegration time, hardness and friability. It was stated that the modified clay material may be used to form tablets by the direct compression method.
- The Influence of Titanium on Physicochemical Properties of Ti-modified Hydroxyapatite Materials
- Strony: 369-375
The current and very popular approach to improving physicochemical and biological properties of hydroxyapatite implants is to incorporate some ions to HA structure. In this study we report the influence of titanium additives on sinterability, phase composition, microstructure, flexural strength and chemical stability of Ti-modified hydroxyapatite ceramics. Hydroxyapatite powders doped with various concentrations of Ti (0.5, 1.0 and 2.0 wt%) were produced by a wet method. In such a synthesis CaO, H3PO4 and TiCl3 were applied as reactants. The modification of HA structure by incorporation of titanium caused thermal decomposition of hydroxyapatite. During heat treatment perovskite (CaTiO3) and αTCP as the secondary phases were formed. Titanium additives decreased sinterability and flexural strength of Ti-HA ceramics. The obtained materials were chemically stable (pH values measured in SBF were close to the physiological value - during the 90 days of incubation changed in the narrow range from 7.48 to 7.70). Ionic conductivity of aqueous extracts was low (5-45 μS) and increased with the amount of titanium additive. The bioactive potential of Ti modified HA-ceramics was confirmed.
- Contribution of the Microwave Sintering for Getting Nanosized ZnO Based Ceramics for Varistors
- Strony: 376-381
Zinc oxide is a well-known material, used especially as varistors. The electrical properties of the zinc oxide varistor are strongly correlated to the final microstructure. The breakdown voltage is particularly grains size dependent. In this paper, a wet chemical route was used to get nano-sized ZnO based powder, with a very narrow granulometric distribution centred at roughly 20 nm. The used synthesis method is based on the direct precipitation of the zinc oxalate solution. The conventional sintering of this nano-sized powder leads to a slight decrease of the grain size (around 2 µm), compared to the grain size observed in a material originated from the powder conventionally synthesized and sintered (> 4 µm). Despite this slight grain size modification, a strong increase of the breakdown voltage is evidenced in the samples obtained through the liquid route. When the microwave sintering process is used to sinter nano-sized ZnO powder, nano-sized grains bulk ceramics are obtained owing to the very short thermal cycle (less than 5 minutes). It is undoubtedly clear that the microwave sintering allows both maintaining the grain size at the nanometric scale and achieving very high density. In that case, a high resistivity increasing below the breakdown voltage is observed and the breakdown voltage is becoming too high (> value) to be measured. Otherwise, it is clearly indicated that the very short time of the heating process induces a modification of the secondary phases composition, which are mainly localized at the grain boundaries.
- The Influence of Hybrid Deflocculant on Hardening Process of Refractory MCC-type Castable
- Strony: 382-385
The influence of different types of deflocculants and their combinations upon structural formation during hardening of MCC-type refractory castable with mulite aggregates was analyzed using an ultrasonic method.
It was established that the structure of castable formed in two stages when the sodium tripolyphosphate deflocculant was used. In the first stage the speed of ultrasound reached approximately 2500 m/s, while in the second one it was approximately 5000 m/s. With polycarboxylate ether (Castament FS 20), as many as three stages were detected in formation of castable. The speed of ultrasound in every stage was as follows: 1000 m/s, ~2500 m/s and ~5000 m/s. In case of a hybrid deflocculant, three stages of structural formation remained, however, in the second stage the speed of ultrasound impulse exceeded 3000 m/s.
When the hybrid deflocculant was used, the cold compressive strength (CCS) of castable after the hardening process ranged within 58 - 65 MPa. It did not differ much from CCS of castable with the additives of sodium tripolyphosphate or polycarboxylate ether (about 55 MPa). Nonetheless, after drying of castable at 110°C and its firing at temperature of 800-1000°C, CCS of castable with the hybrid deflocculant was twice higher than that of CCS of castable where only the sodium tripolyphosphate or polycarboxylate ether deflocculant was used.
- TEXTURE AND MICROSTRUCTURE OF THE STONEWARE DINNERWARE PRODUCTS
- Strony: 386-392
Texture and microstructure of the stoneware dinnerware products, formed from plastic and castable masses were examined. Microstructural parameters such as: specific surface area, volume and shape of macro- and mesopores, relative and apparent densities were determined in the selected samples fired for “biscuit” and hard fired. The influence of a forming method on density and microstructural parameters of the products were determined. Microstructure of the green products and products fired at 820°C and 1250°C depends on the shaping method applied. Type, volume and size distribution of pores being present in the green bodies strongly influenc microstructure of the ‘biscuit’ and hard fired products.
- The Influence of Production Technologies on a Degree of Ferroelectric Diffuse Phase Transition in the PZT Ceramics
- Strony: 393-399
Admixed solid solutions of the PZT type were used as a material to test the influence of ceramic material production technologies on a degree of phase change broadening. It has been shown in the work that two main factors decide about the degree of phase change broadening in PZT, that is composition fluctuations in the ceramic micro-volumes and heterogeneity in the distribution of defects and mechanical stresses. Technological conditions applied have a great influence on the two factors above.
While comparing the degree of phase change broadening for different ceramic materials of the PZT type it is important to use the same criterion.
- Diffuse phase transition of polycrystalline (Ba0.9Sr0.1)TiO3
- Strony: 400-402
The results of X-ray diffraction (XRD) and dielectric measurements performed for polycrystalline (Ba0.9Sr0.1)TiO3 (BS10T) are presented. Data from these measurements show a presence of diffuse phase transition (DPT) between cubic and tetragonal structure at a temperature of 373 K. The temperature Tm of the maximum of real part permittivity (e\') does not depend on the frequency of the applied electric field. A phase angle, F » -90°, between current and applied voltage, suggests an occurrence of polar regions (clusters) below 400 K i.e. in the DPT temperature range of and in the paraelectric phase.
- Properties of Al2O3-Ag Nanopowders Produced by an Innovative Thermal Decomposition–Reduction Method and Chemical Silver Nitrate Reduction
- Strony: 403-408
The present study is concerned with the morphology, physical properties and biocidal activity of the Al2O3-Ag nanopowders produced by two methods: the thermal decomposition-reduction and the silver nitrate reduction. The innovative method of thermal decomposition-reduction has been described in our earlier publication and is protected by our patent application, whereas the silver nitrate reduction method is commonly used in industry at the present.
The nano-powders produced by these two methods differ considerably from one another in terms of their morphology and physical properties. The proposed method of thermal decomposition-reduction gives Al2O3-Ag nano-powders which are not only much less agglomerated with the average agglomerate sizes below 1 µm, but also the average size of their particles is considerably smaller (below 60 nm). Moreover their specific surface is larger (above 200 m2·g-1) and they have good bactericidal and fungicidal properties.
- Use of Ultrasonic Method in the Study of Glass Fertilizers Biodegradation
- Strony: 409-414
In the study, an ultrasonic method was used to examine examine the interaction between glassy fertilizer and acidic solutions (HCl, citric acid), simulating conditions of the natural soil environment. The course of biodegradation of the glass has been studied by observing microscopic changes in the surface, measuring changes in glass mass, and determining velocity of longitudinal ultrasonic waves propagating within it. In an initial period of dissolution of glass, a significant decrease was detected for both the mass and the propagation velocity of longitudinal ultrasonic wave. After this period of time, the ultrasonic wave velocity changed depending on the solution used. The observed changes in velocity of propagation of ultrasonic waves are explained on the basis of a complex mechanism of glass fertilizer dissolution.
- Metallic Interconnect as a Key Element of Solid Oxide Fuel Cells
- Strony: 415-427
The present paper describes the construction of a solid oxide fuel cell with particular emphasis on the significance of the metallic interconnect. Some criteria for the selection of materials for interconnects were discussed; due to the specific operating conditions of the cells, these criteria are far more strict than in the case of other components of SOFCs, regardless of their configuration. A serious issue in the application of interconnects is the gradual increase in area specific resistance connected with an increase in the thickness of oxide scales during high-temperature oxidation of ferritic steel. Overly high electrical resistance of the scale may lead to a decrease in the power output of the whole stack of the SOFC. Furthermore, due to the formation of such a scale some volatile chromium oxides and oxyhydroxides vaporize, incorporating themselves into the electrode material and increasing its activation polarization, which results in lower durability of the SOFC. In order to prevent these detrimental processes, it is necessary to modify the physicochemical properties of metallic alloys. This is usually achieved by covering the surface of ferritic steels with conducting protective coatings with thermal expansion coefficients close to that of the metallic matrix and the cathode material. With regard to this issue, a critical review of the current knowledge on the research concerning physicochemical properties of metallic interconnects modified with conducting protective coatings of various composition is presented.
- Application of Waterjet Technology to Ceramic Decoration Manufacturing
- Strony: 428-432
The classification of waterjet techniques was shown, which includes waterjet and abrasive waterjet machining. Aplications of the waterjet technology were listed, and examples of objects made by using the method were shown. Usage of the waterjet technology by Polish producers of ceramic tiles together with example products were described.
- Strony: 433-438
List of Contents
Volume 62, Issue 4
- Coupled Microstructural and Transport Effects in p-type Perovskites for Hydrocarbon Sensing
- Strony: 442-448
The chemical gas sensor system of propane (C3H8) and propene (C3H6) detection in a SrTi0.8Fe0.2O3 matrix was considered. A model was formulated which incorporated the coupled processes of gases diffusing into a porous ceramic and then participating in two chemical reactions: a reversible oxygen adsorption and a two-step surface reaction which consumed the target gas. Microstructural properties of the sensor matrix were coupled with the diffusion and surface chemistry processes. The base state of the electroceramic material was determined through the solution of its equilibrium defect chemistry.
- Dielectric Properties of Composites in the CaO-CuO-TiO2 System
- Strony: 449-455
Since ultra-high dielectric constants (> 104) with weak temperature and frequency dependence were observed in non-ferroelectric materials such as CaCu3Ti4O12 and CuO, it is very meaningful to study the dielectric properties not only of CaCu3Ti4O12 and CuO, but also of other members in the CaO-CuO-TiO2 system in order to find other compositions with similar characteristics, to discover the underlying mechanisms and to search for new composites with even better dielectric properties.
The dielectric properties of the composites in ternary systems CuO-CaCu3Ti4O12-CaTiO3 and CaCu3Ti4O12-CaTiO3-TiO2 have been tentatively investigated in the present study. The frequency and temperature dependences of permittivity and impedance in the range of 102-5 x 106 Hz and 25-130°C were investigated in the representative high permittivity (> 104) composite with molar fraction of Cu/Ti/Ca of ~85/10/5 in the ternary CuO-CaCu3Ti4O12-CaTiO3 system. Strong hints suggest an important effect of grain boundary contributions on dielectric properties. Preliminary results demonstrated that a multiphase microstructure consisting of larger grains with predominant phase surrounded by smaller grains with secondary phases played an important role for enhancing the dielectric response due to possible barrier layer effects caused by the grain boundary of the composites.
- Deposition of PZT on Copper-coated Polymer Films
- Strony: 456-460
In this work we analyze the deposition process of (111)-textured Pb(Zr,Ti)O3 (PZT) thin perovskite films directly on copper-coated polymer films. Cu thin films with a thickness of about 200 nm were deposited by DC sputtering in a reel-to-reel processing system onto Kapton® HN films with a thickness of 25 µm comprising an in-situ reactively sputtered dielectric TiO2-x adhesion layer. PZT thin films with a thickness of 200 to 400 nm were deposited using a pulse-modulated RF plasma jet system consisting of a hollow cathode for reactive sputtering.
- Optimization of Thermoelectric Properties of CoSb3 by Donor Doping
- Strony: 461-464
Cobalt triantimonide CoSb3 is a narrow-band semiconductor with very promising chemical and transport properties which make it a potential candidate for high-temperature thermoelectric applications. The work presents the results of theoretical investigations concerning optimization of concentration of donor carrier n in order to receive maximum value of thermoelectric figure of merit ZT.
- Structural and Thermoelectric Properties of AgSbSe2-AgSbTe2 System
- Strony: 465-470
Nine compounds with nominal composition AgSbSexTe2-x (x = 0.00, 0.25,...,2.00) were synthesized by the direct fusion technique. The thermal analysis and X-ray diffraction revealed that a partial substitution of Te by Se atoms leads to the stabilization of the cubic crystal structure of alloys. SEM observations of samples fracture showed changes from the Widmanstatten-type into glass-like microstructure for AgSbTe2 and AgSbSe2, respectively. The electrical conductivity, thermal conductivity and Seebeck coefficient were measured as a function of temperature in the range from 300 to 520 K. Electrical conductivity has semiconductor properties within the homogeneous region and semimetalic for the rest of samples. The thermal conductivity is very low as it is in the case of phonon glasses and increases only slightly with temperature. Samples in the homogeneous region have very high positive Seebeck coefficient of about 400-600 µV∙K-1 at RT which gives us the opportunity for optimal doping. The ZT parameter describing usefulness of thermoelectric materials, is about 0.65 for the undoped AgSbSe0.25Te1.75 sample at a temperature of 520 K.
- Model Explanation of Electrical Characteristics Anomalies in PLZT Graded Structure for Piezoelectric Transformers
- Strony: 471-476
In this paper, the influence of one directional diffusion between the two components in functionally graded structure (FGS) on the impedance (dielectric) spectrum of the system was investigated. Lanthanum-modified lead zirconate titanate (PLZT) ceramic materials have gained considerable attention due to their photostriction which is the superposition of photovoltaic and piezoelectric effects. The idea of functionally graded materials (FGM) implemented in the construction of piezoelectric transformer (PT) can be used for direct converting photonic energy to electrical one by implementing photostrictive actuators with a piezoelectric generator in one graded structure of PT. The presented measurements revealed complexity of the integration process of functionally graded materials and high electrical anisotropy of this graded structure. Impedance spectroscopy (IS) proved to be the method capable to present such an inequality in the form of well separated semicircles. Additionally, it was demonstrated that the characteristics of the graded structure is not a simply addition result of starting materials parameters but is deeply influenced predominantly by a diffusion direction. Finally, the influence of the directional diffusion process on impedance spectra was explained by RC electrical model and confirmed experimentally by XPS method.
- Structure and Electric Properties of Double Magnesium Zirconium Orthophosphate
- Strony: 477-480
Double magnesium zirconium orthophosphate (MZP) is a magnesium ion conducting material. In this work, an MZP structure and properties were studied, especially in relation to its possible application as an active material in gas sensors. Double magnesium zirconium orthophosphate was produced both by sol-gel and solid state methods. The phase composition of the material was studied by X-ray diffraction method. Influence of the synthesis method on the quality of obtained material was significant. The single phase material was obtained by the sol-gel method. The precursors (ZrOCl2∙6H2O, NH4H2PO4 and Mg(NO3)2∙8H2O) were dissolved in water, the solutions mixed and then dehydrated for 12 h using a hot plate at 75°C. Dried powder was ball milled for 12 h and then uniaxially pressed into pellets that were sintered at various temperatures in the range of 700–1200°C. The influence of a synthesis method on electric conductivity of the samples was investigated by impedance spectroscopy (IS). Cyclic voltammetry (CV) was used to examine the possibility of application of MZP as a sensor in the presence of various gases.
- Junctions and Diffusion Barriers for High Temperature Thermoelectric Modules
- Strony: 481-485
Thermoelectric modules based on doped bismuth telluride (Bi2Te3) are commonly used for the construction of thermoelectric generators (TEGs) and heat pumps. However, due to low operating temperature (< 200ºC), TEGs based on this material reveal low efficiency. In order to obtain high effectiveness in energy conversion, one needs to design high temperature modules made of new thermoelectric materials.
The goal of the present work has been to develop the method of preparation of ohmic junctions between semiconducting CoSb3 element and metallic Cu electrode, for temperatures up to 600ºC. In order to protect thermoelectric material from interaction with a solder and the electrode material, the appropriate diffusion barriers were applied.
The junctions were formed by the resistance soldering technique in the protective atmosphere of Ar + H2. Lead-free alloys based on Ag and Cu were used as the solder. Diffusion layers of Ni were prepared via the magnetron sputtering technique. The chemical and microstructural properties of the junction area were analyzed by scanning electron microscope (SEM) equipped with EDX analyzer. Resistivity measurements and current–voltage characteristics were used to determine the contact resistance and ohmic contact quality between the metal and the semiconductor. Other physico-thermal properties, such as thermal expansion, were also characterized.
- Fibrous Composite with Threshold Strength in Three Dimensions
- Strony: 486-489
In the present work, a fibrous composite consisting of square fibers separated with thin compressive layer is designed. Due to the crack arresting effect of the compressive layer, this composite is expected to show three-dimensional threshold strengths corresponding to applied stresses in the direction perpendicular to the fiber side face and parallel to the fiber central axis, respectively. In accordance with the above designing concept, Si3N4/TiN fibrous composites with distinctive threshold strengths were readily prepared through a simple double-laminating procedure. It is found that the threshold strengths increase with the TiN content in the fiber; and for the same material, its axial threshold strength is larger than the radial one. The fundamental reasons for that are investigated.
- Protective Coating to Suppress Degradation of CoSb3 Thermoelectric at Elevated Temperatures
- Strony: 490-495
A polymer-metal hybrid coating has been developed to prevent degradation of the CoSb3 skutterudite in contact with air at elevated temperature. Uncoated and coated CoSb3 specimens were exposed to air at 500, 600 and 700°C for up to 80 hours. The performance of materials was evaluated on the basis of mass changes, visual inspection, and systematic analysis of specimen surfaces, fractures and cross-sections in terms of the chemical and phase composition as well as microstructure. It has been found that the coating system used in this work was effective up to 600°C. It significantly reduced the access of gases, extent of oxidation and sublimation of antimony which limit the lifetime and efficiency of thermoelectric generators.
- Particulate Composites in the Al2O3-YAG System
- Strony: 496-499
Contrary to the composites in the Al2O3–ZrO2 system, materials with Al2O3 matrix and YAG (Y3Al5O12) inclusions are much less recognized. YAG is one of the three compounds in the Y2O3-Al2O3 system of the highest alumina content. It is well known that YAG polycrystals belong to the materials of especially high creep resistance. Since coefficients of thermal expansion of YAG and alumina do not differ essentially from each other, the YAG inclusions in the alumina matrix seem to lead to a material of interesting mechanical properties.
Only a few publications concern the preparation of such composites by powder sintering. In the present work Y2O3 was introduced to alumina by yttrium hydroxide precipitated within the alumina powder suspension. By low temperature calcinations a homogenous alumina/yttria mixture was received. Yttria content corresponded to 20 vol.% YAG after the reaction. It was found that at 1500ºC YAG and a-alumina were the only phases present in the system. The investigation of the resulting material microstructure revealed a uniform distribution of sub-micrometer YAG particles. Hardness of the material was similar to that of dense alumina and fracture toughness (KIc ≈ 6 MPa×m1/2) was close to the observed in the case of the 3-YTZP material.
- High Temperature Oxide Electrolytes for Electrochemical Devices Application
- Strony: 500-505
A coprecipitation–calcination method was used to synthesise powders of 25 mol% Y2O3 in ZrO2 (25YSZ) or 12.5 mol% Y2O3 - 12.5 mol% Yb2O3 in ZrO2 (12.5Yb12.5YSZ) solid solutions. The pellets were cold isostatically pressed and then sintered for 2 h at 1500°C. The corrosion resistance of 25YSZ, 12.5Yb12.5YSZ solid solutions, and CaZrO3-based samples against molten metals, i.e., copper, nickel or iron, were also examined. Based upon this investigation, it is evident that stability of both zirconia with 25 mol% Y2O3 in solid solution and the calcium zirconate containing 48 % CaO material is limited in molten iron. Electrical conductivity measurements were performed by dc four probe and ac impedance spectroscopy methods in the temperature range of 200-1000°C. The highest value of ionic conductivity was found for the sintered samples of 12.5 mol% Y2O3 - 12.5 mol% Yb2O3 in ZrO2. These results indicate that partial substitution of Yb2O3 for Y2O3 in the 25YSZ solid solution leads to an increase of electrical conductivity compared to the solid solution of 25 mol%Y2O3 in ZrO2. It was also found that ionic oxide transference numbers (tion) of 25YSZ and 12.5Yb12.5YSZ solid solutions were close to 1, what indicated on pure oxide ionic conduction in the materials prepared. Test results are also reported for 25YSZ and 12.5Yb12.5YSZ applied as electrolytes in electrochemical oxygen gas sensors as well as in solid oxide cells, involving NiLa2O4 or NiAl2O4. In this way, the Gibbs free energy of formation of NiLa2O4 or NiAl2O4 in the temperature range 800-1000ºC was determined. These materials seem to be promising solid oxide electrolytes for electrochemical oxygen probes, and solid oxide galvanic cells designed to study thermodynamic properties of materials important for SOFC technology and other areas of energy industry.
- Sintering of Nanocrystalline Zinc Oxide via Conventional Sintering, Two Step Sintering and Hot Pressing
- Strony: 506-509
Two-step sintering and hot pressing methods were applied on nanocrystalline ZnO to control the accelerated grain growth occurring during the final-stage of sintering. The sintering conditions (temperature and total time) and results (density and grain size) of two-step sintering (TSS), conventional sintering (CS) and hot pressing (HP) methods were compared. The grain size of the high density (> 98 %) ZnO compact produced by the two-step sintering was smaller than 1 μm; while the grain size of those formed by the conventional sintering method was ~4 μm. The HP technique versus CS was shown to be a superior method to obtain higher final density (99 %), lower sintering temperature, shorter total sintering time and rather fine grain size. The maximum density achieved via HP, TSS and CS methods were 99, 98.3 and 97 %, respectively. The final grain size of samples obtained by HP was larger than that of TSS method. However, the ultra-prolonged sintering total time (88 ks) and the lower final density (98.3 %) are the drawbacks of TSS in comparison with the faster HP method (17 ks and 99 %, respectively).
- Bonding of Porous Alumina Structures with Zirconia Nanoparticles
- Strony: 510-515
Porous alumina coatings with a final thickness in the order of 0.1 mm were produced by spraying ethanolic dispersions of particle mixtures onto steel substrates, followed by drying and heating at 500°C for 60 min. The coatings consisting only of a mixture of coarse and sub-µm sized alumina particles are generally poor in adherence and in abrasion resistance. By including a colloid of nanoscaled zirconia (d » 7 nm, calculated from the specific surface area) to the dispersion, coatings with clearly improved mechanical properties can be obtained. The zirconia fraction of 8 vol.% (related to the ceramic content) causes strong bonding between the alumina particles and the substrate.
This bonding effect is quantified by bending tests, which have been performed after spray drying the dispersions, pressing the powders to form mechanical testing beams and applying a heat treatment at 500°C. The bending tests reveal that strengths are improved at least by a factor of 5 when the nanoparticles are present in the mixture.
The described method to establish ceramic bonds in ceramic structures at temperatures, which are far below usual sintering temperatures, is a typical effect which arises in the nano size range, as the nanoparticles’ high reactivity based on their large specific surface area is deployed.
- Microstructure, thermal behaviour and luminescent properties of electrospun Eu-doped TiO2 nanofibers.
- Strony: 516-520
Pure and europium-doped titania nanofibers were successfully fabricated by the electrospinning technique, using a single multielement titanium/europium source. Eu content was 5 mol.%. Microstructure was studied by means of scanning electron microscopy (SEM), thermal behaviour followed by thermogravimetric and differential thermal analysis (TG-DTA). Phase analysis was performed by means of X-ray diffraction (XRD) and high temperature X-ray diffraction analysis (HT-XRD) up to 1100°C. Luminescence measurements were performed using a laser excitation source at 395 nm. All electrospun materials consisted of randomly oriented nanofibers of a fairly uniform diameter. The average fiber size was 80 ± 20 nm and 40 ± 10 nm for Eu-doped and undoped TiO2 calcinated at 500°C, respectively. The presence of europium shifted toward higher values either the crystallization temperature of anatase and the anatase to rutile phase transition, the latter being accompanied by the formation of the EuTi2O7 phase. The doped samples show a strong luminescence of Eu3+ ions. The emission spectra are dominated by the 5D0→7F2 emission, suggesting a notable distorsion around the Eu3+ ions. The broadening of the bands points to the presence of a relevant inhomogeneous disorder around the Eu3+ sites.
- Diatoms as a Source of New Materials
- Strony: 521-524
Diatoms are unicellular eukaryotic algae which can be found in almost all aqueous and humid environments. Characteristic features of diatoms is that their frustules have a unique morphology (in particular, the pattern of nanostructures, such as pores, ridges, areoles and other forms), and their cell walls are made of silica (hydrated silicon dioxide). Because of this specific morphology, diatoms can be used for manufacturing bio- or chemical sensors, membranes, biotemplates, biocapsules, carriers, or even nanoreactors. For certain applications, diatoms have to be processed and sintered.
The paper presents some initial results obtained in experiments on the consolidation of diatoms. In particular, attention was paid to the preservation of the nanopores that naturally exist in diatoms, since the nanopores present in bulk materials inside the sintered grains can enhance fracture toughness. The diatoms and bulk materials obtained by pressing and sintering were examined by scanning electron microscopy (SEM).
The SEM observations revealed the effects of sintering of diatoms and changes of their morphology. The diatoms were treated as a powder, i.e., they were consolidated by die pressing and then sintered. After the process of consolidation, most of the pores naturally existing in diatoms were closed. The results suggest that because of their highly diversified shapes the diatoms cannot be uniformly consolidated by die pressing. The highest relative density achieved was 83 %.
- Comparative Study on Effect of Iron Oxide Doped Alumina-Based Catalysts via Sol-Gel and LFS Methods on CNTs Growth by Methane Decomposition
- Strony: 525-528
By using the sol-gel technique and the liquid flame spray method (LFS), three different iron oxide doped alumina-based catalysts (Catalysts A, B and C) were prepared by using iron nitrate and ferrocene as the iron source. Multiwalled carbon nanotubes were obtained by a decomposition of methane gas over Catalysts A and C, but not over Catalyst B. X-ray diffraction, transmission electron microscopy and the nitrogen adsorption /desorption test were used to compare the three different catalysts and discuss the influence of the different catalysts on the formation of the multiwalled carbon nanotubes.
- Synthesis of CeO2 Nanocrystalline Powder by Precipitation Method
- Strony: 529-532
Ceria (CeO2) is an important rare earth oxide and has been widely investigated in the automotive exhaust purification, oxygen storage and release catalysis, and solid oxide fuel cell applications. In recent years, due to the excellent physical and chemical properties of nano-sized particles, which are significantly different from those of bulk particles, there is considerable interest in enhancing catalytic activity, sinterability, and other properties by decreasing the grain size into a nanometer range. In the present study, a simple precipitation procedure for the synthesizing of CeO2 nanocrystalline powder (~13 nm) is presented. The structural evolutions and morphological characteristics of the nanopowder were investigated using X-ray diffractometry (XRD), scanning electron microscopy (SEM), thermo-gravimetry (TG), and Fourier transform infrared spectroscopy (FTIR). XRD results showed that face centered cubic CeO2 particles with crystallite size in nanometer scale were formed. By increasing the calcination temperature from 100 to 300°C, the crystallite size decreases from 20 to 13.9 nm. By increasing the temperature more than 300°C, crystallite size of ceria increases. SEM studies showed the morphology of the prepared powder is sphere-like with a narrow size distribution.
- Alumina-YAG Micro-Nanocomposites: Elaboration and Mechanical Characterization
- Strony: 533-539
A surface doping of commercial alpha alumina powders was performed to develop Al2O3 - 5 vol.% YAG (Y3Al5O12) composites made by micronic or highly sub-micronic alumina particles and very fine YAG grains, yielded on the alumina surface by in-situ reaction.
In fact, the alumina powders were firstly dispersed in the aqueous suspension by ball-milling for different times as a function of the starting raw material and then an yttrium chloride solution was added as a precursor. After a controlled drying carried out by atomization, the modified powders were treated up to 1500ºC, following the phase development by XRD. Using these results, a suitable powder pre-treatment was selected; in particular, a flash heating by soaking the powders in a furnace kept in the range 1050-1150ºC was set up to control yttrium-aluminates crystallization and crystallite growth.
After that, green bodies were prepared by uniaxial pressing of dried powders as well as by slip-casting of slurries having a proper solid content. Pressureless sintering was optimized by the dilatometric study up to 1500ºC for 3 h. Less-conventional sintering routes, such as hot-pressing and spark plasma sintering, were also employed. The fired microstructures obtained by conventional or non-conventional densification routes were compared by SEM characterization. Finally, the sintered materials were submitted to a standard mechanical characterization (hardness and fracture toughness) in order to define the relationship between micro-nanostructural features and mechanical behaviour.
- Preparation and Characterization of Au Supported MOx-Al2O3 (M = Mn, Cu) Powders for Low-Temperature CO Oxidation
- Strony: 540-544
MOx–Al2O3 (M = Mn, Cu) powders were synthesized by the spray pyrolysis process and then used as a support for Au/(Mn,Cu)Ox–Al2O3 catalysts preparation via the deposition–precipitation method. Gold catalysts on oxide supports were tested for oxidation of CO. The samples were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy–dispersive X–ray spectroscopy (EDS), and via determination of specific surface area by the BET method. The SEM results showed that all catalysts have a small-dimension circular shape of particles. Catalysts obtained with the spray-pyrolysis method were found to have great specific surface areas. Gold catalyst containing copper oxide on alumina is shown to be more active than manganese oxide on the same support.
- TiO2-based Nanopowders for Gas Sensor
- Strony: 545-549
Flame spray synthesis (FSS) was used to grow TiO2-based nanopowders from which TiO2:Cr nanosensors were obtained. Structural properties of crystalline TiO2:Cr nanopowders at different Cr loadings (0.1–5.0 at.%) have been investigated. Material studies have been performed using standard methods: X-ray diffraction (XRD) transmission electron microscopy (TEM) and Brunauer-Emmett-Teller adsorption isotherms analysis (BET). High specific surface area (37-126 m2/g) and small crystallite size (9-27 nm) have been reached. Incorporation of Cr into TiO2 lattice affects the specific surface area of nanopowders, the crystallite size and the rutile to anatase ratio. Gas sensing characteristics of TiO2:Cr nanosensors upon interaction with H2 have been recorded in the self-assembled experimental system. The detection of hydrogen was carried out over the concentration range of 50-3000 ppm at the temperatures extending from 200 to 400ºC. It is demonstrated that nanomaterials based on TiO2:Cr are attractive for ultimate sensors applications due to a decrease in the operating temperature down to 210-250ºC, accompanied by an increase in the sensor response. Taking into account the possible operating costs, the best candidates for the commercial use are TiO2:1 at.% Cr and TiO2:5 at.% Cr nanosensors.
- Grain Size and Grain Size Distribution of ZrO2:Pr Ceramic Nanopowders Determined by Different Methods
- Strony: 550-555
The aim was to compare size readings for the same ceramic nanopowders as reported by different characterization methods. Capabilities of TEM, XRD and BET characterization techniques, such as size vs. size distribution output, crystalline phase resolution, ability of error estimation of the size as well as dispersion of size readings are briefly described.
- Microstructural and Thermal Characterization of the TeO2–WO3 System
- Strony: 556-559
In the present study, thermal behaviour and microstructure of the TeO2–WO3 system have been investigated. Different compositions of (1−x)TeO2 – xWO3 system (x = 0.02, 0.05, 0.15, 0.25 and 0.40 in molar ratio) were prepared. The samples waited at 750°C in a platinum crucible for 30 min and then quenched in a water bath. DTA studies were performed on glassy samples. Afterwards, all samples were heat-treated at 550°C for 24 h and furnace cooled to obtain phase equilibrium. XRD and SEM/EDS studies were performed on the crystallized samples for microstructural analysis.
- In-Situ Analysis of Corrosion of Glazed Surfaces Using Confocal Optical Microscopy
- Strony: 560-564
The topographic analysis was studied as a method to examine surface-level reactions of glazes in aqueous solutions. Glazed surfaces typically have some microroughness caused by crystalline phases embedded in the glassy matrix and also macroroughness (waviness) due to variations in the coating thickness or irregularities in the clay body. The surface topography is usually given in the form of average values of various three-dimensional parameters measured in relation to a certain surface waviness. The surface roughness of matt glazes is typically higher than 0.4 µm. Selective corrosion of one of the phases in the glaze surface is likely to affect the microroughness. The average surface roughness of two matt glazes was measured with the confocal optical microscope for four parallel samples of each surface before and after four days of immersion in one acidic and two alkaline detergent solutions as well as in distilled water. One sample of each surface was also studied in-situ, i.e. in the same location as a function of the immersion time. The changes in the surface composition due to corrosion were analyzed with SEM-EDX. If the roughness was caused mainly by crystalline inclusions partially embedded in the glassy phase, their selective corrosion could not always be deduced from the average roughness values only. However, the in-situ observation enabled the authors to identify changes in the surface profile also in such cases where corrosion did not markedly affect the average surface roughness values. In-situ analysis with confocal optical microscopy was found to give a quick and efficient estimation of micro-level reactions of glazed surfaces in aqueous solutions.
- Effect of Pigments on Crystal Phases in Non-Fritted Matte Glaze
- Strony: 565-568
Recently, porcelain with matte glaze, as a unique and attractive coating on ceramic products, has attracted many architects and interior designers\' attention. Production of matte glaze was a challenge for sanitary ware manufacturers due to long firing cycle, raw glaze, and single firing condition and being hygienic that is very important. Although, using frit facilitates making matte glaze, its high price and reduction of firing temperature keep manufacturers away from its production. In this investigation, the matte glaze has been designed and produced based on the fact that increasing CaO content in glaze composition induces crystal growth; besides, coloured matte glaze has been investigated, different pigments have various effects on crystal morphology and microstructure that they have been studied by XRD. The surface quality of this glaze has been observed by confocal optical microscope. At the end, standard tests for sanitary ware were passed and confirmed the quality.
- Adherence of Gold Layers to Glass Surface - Spectroscopic Studies
- Strony: 569-571
Sputtering deposition of gold on glass sheets is widely applied not only in the electronic industry but also in the case of architectural glass. One the most important parameters determining practical application is gold adherence to the glass surface. Gold adherence is usually poor as gold is not reactive towards the glass components. One of possible solutions is to apply a thin oxide under-layer. The influence of Cu, Ni and CuNi oxide layers on the gold adherence to the glass surface have been studied. Photoelectron spectroscopy was used to follow changes in the oxidation state of the metallic ions after gold deposition.
- Interaction of Glassy Fertilizers and Toxic Elements
- Strony: 572-576
The immobilization of lead and cadmium contamination in soils by precipitation of non-assimilable for plants Pb- and Cd-phosphates was considered. A glassy fertilizer of the controlled release rate of the nutrients for plants as a source of phosphate anions was applied. Thermal analysis methods (TG/DTG/DTA) were used for the identification of components of Pb- and Cd-precipitates, which, being in statu nascendi, have the nonstoichiometric composition and disordered crystallographic structure difficult to identify by XRD method. The negative role of Pb and Cd complexing citric acid solution simulating the natural soil conditions, which inhibits the Pb- and Cd-phosphates formation, was stated.
- Pigments in the Y2O3–Al2O3–Cr2O3 System
- Strony: 577-581
The paper presents the results of research on preparation and properties of ceramic pigments in the Y2O3-Al2O3-Cr2O3 system which were obtained by the solid state reaction. The chromium ions were used as chromophores in these pigments. The pigments were finally synthesized for 6h at 1500ºC. They were applied for colouring of transparent glaze used for glazing gres porcellanato tiles.
- Polish Feldspar Raw Materials for the Domestic Ceramic Tile Industry –Current State and Prospects
- Strony: 582-585
The development of the Polish ceramic tile industry, observed since the mid-1990s, resulted in the increased demand for raw materials, especially feldspar and/or feldspar-quartz ones, which constitute 50-60 % of the gres porcellanato tile body composition. In 2007 the consumption of feldspar raw materials in Poland approached ca. 900,000 tpy, more than 80 % of which accounted for the tile industry . Their domestic production, ranging from 400,000 to 600,000 tpy in recent years, has been supplemented by importation, predominantly from the Czech Republic and Turkey.
The Strzeblów Mineral Mines of Sobótka (Lower Silesia) is the oldest and the largest Polish feldspar producer. The company offers basically feldspar-quartz grits with min. 7.5 % K2O+Na2O, K2O/Na2O ≥ 1, and ca. 0.5 % Fe2O3, which are mainly used in the ceramic tile manufacturing. The viscosities of the melt calculated from chemical analyses are as follows: 24.04×103 Pa×s at softening temperature (i.e., 1260ºC) and 5.64×103 Pa×s at melting temperature (1360ºC).
The growth of the Polish tile industry resulted in increasing interest in alternative sources of feldspar raw materials. The examples of them are weakly weathered pegmatites and granitoids occurring in the marble quarry of Sławniowice near Nysa (Lower Silesia), containing ca. 6.5 wt.% K2O with Na2O. The essential constituents of these rocks are feldspars and quartz, with a subordinate amount of mafic and clay minerals. Their suitability, after simple processing (crushing, milling, blending), for the production of gres porcellanato tiles has been checked in the course of industrial-scale examinations. This has been also confirmed by proper viscosities of the molten raw material studied, i.e., 21.31×103 Pa×s at softening temperature (1250ºC) and 4.22×103 Pa×s at melting temperature (1350ºC).
- Investigations of Thermal Properties of Glass-Crystalline Samples from CMAS System by the Nondestructive Photoacoustic Method
- Strony: 586-590
The goal of investigations presented in this paper was to change the microstructure of a glass-crystalline material in order to improve its thermal diffusivity. Thermal diffusivity is an important thermo-physical parameter, which determinates the diffusion of heat through a sample. The paper presents results of nondestructive photoacoustic (PA) studies of this parameter for investigated ceramic material. The thermal diffusivity values are evaluated by the fitting of amplitude and phase theoretical characteristics to experimental data in a proposed PA model. The analysis of the data shows that the change of the microstructure of a glass-crystalline material successfully changes the thermal parameters of investigated ceramic material.
- Radon exhalation from cement-matrix composites in the function of technological parameters
- Strony: 591-595
Rn-222 radon is a colour-free and odour-free inert gas. Radon, existing in the air that surrounds us, is a part of atoms that released from mineral structures (i.e., cement composites). Such radon atoms create the fraction released directly or the fraction released indirectly. The transfer of gas radon to pore space is the first stage of its migration in the environment.
In this paper, the research results relying on measurements of radon exhalation (ERn [Bq/m²h]) from composites made from ISP slag (waste from zinc steelworks, fractions 0-4 mm and 0.125-4 mm) and CEM I 32,5 R Portland cement with the variable values of w/c ratio. The results of porosity measurements of the composites by means of mercury porosimetry were also presented.
- Preliminary investigation OF the manurial glass selective milling IN A prototype centrifugal mill
- Strony: 596-600
Manurial glass requires a size reduction to graining which belongs to the grain class of 0-0.8 mm, when a content of 0-0.3 mm grain class is below 15 %. A laboratory investigation has shown that the centrifugal mill of entoleter type is the most useful tool for this kind of selective milling. There is an MW-300 prototype of industrial centrifugal mill developed basing on that result. This mill presents wide technological possibilities. It is equipped with a rotor with replaceable blades and a lining composed of blades adjustable in two planes. An experimental technological line used the mill; it contained auxiliary devices such as cell feeder, feed reservoir, vibrating feeder and vibrating screen, arrangement of recirculation and cleaning of the technological air as well as electric arrangements of admission and steering.
The paper shows a description of the construction and basic technical parameters of this semi-technical centrifugal mill and the full technological line together with a method and a scheme of investigation. The method contained conditions and execution of the investigation, which led to ground manurial glass in the final production stage. The investigation programme encompassed determination of the effect of rotor rotational speed, kind of feed, mill efficiency, intensity of air flow and orientation angle of blades on grain size distribution of glass being comminuted and resultant output, i.e., a content of 0-0.8 mm grain class and undersize in the 0-0.3 mm class. The pilot character of the line determined its total and technological efficiencies that belonged to the ranges 180-260 kg/h and 95-130 kg/h, respectively. The maximum content of 0,3-0,8 mm grain class, minimum content of 0-0,3 mm grain class, and near the largest efficiency of mill were selected as the milling process quality criteria. The milling product containing 45-55 % of desirable grains in the 0.3-0.8 mm class and 9-12 % undersize in the 0-0.3 mm class was obtained after single application of the material to the mill. Oversize grains above 0.8 mm, separated by a vibratory sifter, turned back to milling. The modernization of prototype vibrating screen assured the reduction in content of the 0-0,3 mm class in the final product to below 5 %, and, thus, receiving the balanced product of manurial glass independently of remaining parameters of the mill and the milling system.
- Investigation of load movement in a vibratory mill
- Strony: 601-607
A movement of load composed of the grinding media and the material that is comminuted causes the milling process in mills with free grinding media, including a vibratory mill. Chamber vibrations are responsible for the load movement. The milling process has a dynamic character, and its intensity is governed by the crash frequency of grinding media, the magnitude of force spent on mutual crashes and the mechanism of energy transmission from grinding media to the comminute material. The grinding media in a layer neighbouring the vibrating chamber receive energy in the first place and the largest amount. The grinding media from further layers situated closer to a geometrical axis of the cylinder-shaped chamber receive energy originated from grinding media in the external layer. Therefore, they have smaller energy, reduced by a part used for the milling, mixing and material transport processes. Such a phenomenon causes a decrease in intensity of the milling process in the direction towards the chamber axis. As a result, it determines the construction of multi-chamber vibratory mills containing small diameter chambers, which is already complicated due to the presence of large number of the chambers, coming to six.
The research objective of the work is to investigate a movement of load in the chamber of classic vibratory mill and in chambers modified with a constructional unit of cylindrical shape built-in the centre of chamber to enlarge intensity of the milling process. The investigations were performed on the laboratory vibratory mill by using movie and photographic recording for visualization. The variable parameters were as follows: diameter of ball-shaped grinding media, degree of filling of the chamber, frequency and amplitude of chamber vibrations, and diameter of the constructional unit applied. The chamber of 0.21 m in diameter, the frequency of chamber vibrations of 10-16 Hz and the amplitude of chamber vibrations of 5-10 mm were applied. The results shown in the form of photographic material proved the presence of a low activity central zone of grinding media in the chamber of classic mill. A significant increase of movement intensity in the chambers equipped with the constructional unit was detected. The unit placed in geometrical axis of the chamber eliminated the low activity central zone of grinding media by delivering the same energy that the chamber delivers to the nearest layer of grinding media. The possibility of developing the vibratory mills of less complicated construction, having decreased energy consumption for the milling process, creates a practical aspect of the presented results.
- Glass sealants for high temperature oxide fuel cells (SOFC)
- Strony: 608-617
The barium silicate glasses were studied as a potential sealant for planar SOFC fuel cells to join YSZ ceramics and steel interconnectors. The present paper describes the results of an investigation of the alkali-metal free glasses, based on the BaO–MgO–ZnO–SiO2 system, and containing less than 40 wt.% of SiO2 as the network forming component. The influence of a change in the proportion of alkaline-earth oxides BaO, MgO, ZnO added as modifiers on the structure and thermal properties of the glasses will be demonstrated. The analysis of local atomic interactions in terms of the electronegativity value is used to explain the relationship between glass structure and properties. The prospective glass is indicated for sealant applications.
- Reconstruction of composition and manufacturing technology of building materials for the conservation of monuments
- Strony: 618-621
The authors make investigations on reconstruction of the original manufacturing technology of the 19th century building material called Chausseestaub. The possibility of beginning the laboratory production of the material which was widely used in the 19th and 20th centuries especially in decorative architecture of small residences is determined. The authors show the preliminary results of a phase composition investigation made for survived architectural and sculpture fragments originated from the Wilanów Palace Museum.
- List of Content for Volume 62
- Strony: 622-632
- Spis treści tomu 62