Volume 64 (2012)
List of Contents
Volume 64, Issue 1
- Diagrams of point defects concentration for metal oxides Ni1-δO, Co1-δO, Mn1±δO AND Cu2±δO
- Strony: 4-10
Diagrams of point defects concentration in metal oxides Ni1-δO, Co1-δO, Mn1±δO and Cu2±δO, covering all the types of defects in the cation sublattice, are presented in this work. A new method was used for the calculation of the diagrams. It is based on an equation describing the formation and decay of determined quantities of point defects and derived standard Gibbs energy of formation of cation vacancies, intrinsic ionic and electronic defects, oxygen pressure at which the oxide attained stoichiometric composition. The calculations were performed using the results of studies of deviation from stoichiometry and electrical conductivity obtained by several authors.
- Influence of deposition conditions of titania thin films by magnetron sputtering on catalytic, hydrophilic and bactericidal properties of the layers
- Strony: 11-21
As is generally known there are actually two distinct photo-induced phenomena in TiO2. The fi rst is the well-known photocatalytic phenomenon, which leads to the breakdown of organics, and the second, more recently discovered one involves high wettability. The latter phenomenon has been termed “superhydrophilicity”. In this work, fi lm parameters influencing the photocatalytic activity and hydrophilicity were investigated. To do that thin films of TiO2 were prepared by magnetron sputtering. Ethanol concentration versus time was measured and reaction rates for the photocatalytic breakdown were calculated. Wettability conversion was analysed by the measurement of contact angle as a function of UV illumination time. Contact angle decrease rate was also calculated. Antimicrobial activity of the films deposited on conventionally produced ceramic wall tiles against Salmonella Enteritidis, Staphylococcus aureus, Pseudomonas aeruginosa and Escherichia coli was determined. The results clearly indicated that the bactericidal action of UV radiation was much stronger on the surfaces of tiles with TiO2 than on the tiles uncovered. In conclusion, the use of ceramic wall tiles coated with TiO2 films in hospitals, clinics, outpatient clinics and doctors’ surgeries and veterinary clinics as well as in food processing industry, catering outlets, laboratories, and wherever UV radiation is applied to disinfect the surface should greatly improve the efficiency of disinfection and help to radically improve the hygienic conditions prevailing in these areas.
- Birefringence of glass-air photonic crystal fibre induced by elliptical micro holes of cladding
- Strony: 22-25
In this paper, we report on the fabrication of the birefringent photonic crystal fibre with a photonic cladding composed of elliptical holes ordered in a rectangular lattice. Choice of such configuration allows obtaining birefringence in photonic crystal fibres. In this case two-fold rotational symmetry is achieved and the polarized orthogonal modes (HE11x and HE11y) are not degenerated. We discuss the influence of structural parameters including the ellipticity of the air holes and the aspect ratio of the rectangular lattice on the birefringence and on the modal properties of this glass-air microstructural fibre.
- Multiferroic composites on the basis of pfn powder and epoxy resin
- Strony: 26-32
There are presented the technology and the basic physical properties of a multiferroic composite in the paper. Ferroelectromagnetic powder of PbFe0.5Nb0.5O3 (PFN) was a basic component of the composite, and epoxy resin has been used as a binding material (matrix). Two techniques were used to obtain the PFN ceramic powder: (i) a two-stage columbite method, (ii) a wet chemical method of solution precipitation. Contents of the components were as follows: 80% PFN powder and 20% epoxy resin. Microstructural, internal friction and basic dielectric investigations of the composites have been performed. These investigations showed that the microstructure and properties of the composite depend on the method of PFN powder manufacturing. The epoxy resin decreases density of the material and considerably reduces its dielectric permittivity. Epoxy/ceramic composites originated from PFN obtained by the two-stage columbite method showed the optimal properties.
- Ceramic-polymer composites for microwave applications
- Strony: 33-37
In this paper we report the results of a study of microstructure and dielectric properties of ceramic-polymer composites composed of barium strontium titanate Ba0.5Sr0.5TiO3 (BST50/50), Ba0.6Sr0.4TiO2 (BST60/40), Ba0.7Sr0.3TiO3 (BST70/30) and polyvinylidene fluoride (PVDF). The composites BST50/50//PVDF, BST60/40//PVDF and BST70/30//PVDF were obtained by the hot pressing method for volume fraction of BST ceramic powder cv = 1.47%, 3.04%, 4.75% and 6.6%. The morphology of BST50/50//PVDF, BST60/40//PVDF and BST70/30// PVDF composite powders and the composite microstructure was observed by transmission and scanning electron microscopy, respectively. Dielectric properties of the composites were measured by the impedance spectroscopy method. The split-post dielectric resonator (SPDR) was used for the measurements of the real and imaginary part of dielectric permittivity of the BST//PVDF composites in the microwave frequency range of f = 3-10 GHz.
- Optical parameters of polycrystalline ytterbium doped yttrium-aluminum garnet (Yb:YAG)
- Strony: 38-41
The aim of the work was to fabricate transparent Yb:YAG ceramics by reactive sintering of oxides, and determine optical properties as a function of doping amount and ceramics microstructure. 1 at.% Yb:YAG ceramics of 80.5% transmission at 1.2 μm and 77.7% at 400 nm was obtained. Emission and f uorescence decay characteristics of obtained ceramics are in accordance with the literature data concerning single crystal materials of the same doping level.
- Application of solid state fabricated perovskite-like materials fabricated by solid state method for manufacturing of membranes separating oxygen from air
- Strony: 42-47
Three types of mixed oxides with the perovskite-like structure: La0,6Sr0,4Fe0,8Co0,2O3+δ, Ba0,5Sr0,5Co0,8Fe0,2O3+δ i La2Ni0,9Co0,1O4-δ were synthesised by the solid state method, and characterized. Analysis of XRD patterns revealed that differences in cation dimensions forming the perovskite structure are the reason of structural imperfections and lattice stresses. The manufactured powders were composed of one phase and revealed very low porosity of particles, which favours the obtainment of dense sinters. In order to improve the forming properties of the powders, granulates were prepared, that showed higher specifi c surfaces in comparison with the original powders. The additional heat treatment during the fabrication of powders improved the perovskite-like structure of the studied materials. The manufactured membranes showed good mechanical strengths and relatively low thermal expansion coefficients. SEM micrographs of membrane surfaces revealed the presence of large grains and narrow grain boundaries, which allowed transport of oxygen ions through membranes to be easy through the membranes. The highest value of oxygen permeation flux of 0.822 ml/(cm2·min) at 950°C was measured for the thin dense membranes fabricated from Ba0,5Sr0,5Co0,8Fe0,2O3+δ.
- Influence of surface and morpfological properties on deflocculation of nanozirconia powders
- Strony: 48-52
An effective deflocculation process is crucial in the optimization of colloidal processing in advanced ceramics manufacturing. The deep knowledge of morphological and surface properties of the nanopowders is necessary to choose effectively working deflocculation agents. The collection of the above-mentioned factors is studied in this work in terms of their influence on deflocculation of nanozirconia suspensions by the D-fructose addition. Nanozirconia ceramics possess the high applicable potential in many fields of the modern advanced technology. Therefore, there is a pressing need to develop some efficient methods of nanozirconia shaping. The work presented deals with some morphological and surface properties of the selected nanozirconia powders, both of them were yttria-stabilized powders (3 mol.% of Y2O3). The powders were dispersed in water – D-fructose solutions of different concentration. Recently performed studies show that D-fructose is an effectively working dispersant of Al2O3 nanosuspensions. It was attempted to carry these promising results on nanozirconia powders in order to obtain time-stable zirconia nanosuspensions of relatively low viscosity and high solid phase loading. However, it turned out that D-fructose has a totally different effect on nanozirconia. Moreover, it was demonstrated that D-fructose interacts in other way with ZrO2 nanopowders purchased from different manufacturers. While, some differences in the behaviour of ZrO2 and Al2O3 can be excluded by different chemical nature of both substances, insofar as signifi cant differences in behaviour within the powders derived from one oxide are much more difficult to explain. It was assumed, therefore, that the above-mentioned differences in behaviour of nano-ZrO2 powders originate from their morphological and surface properties which were intensively studied in this paper.
- Influence of la-doping on properties of Bi4Ti3O12 ceramics
- Strony: 53-58
La-modifi ed Bi4Ti3O12 is a typical ferroelectric, piezoelectric and electro-optic material, having relatively low coercive fi eld, low dielectric constant, high Curie temperature and high breakdown strength. In the present research, Bi4Ti3O12 ceramics doped with La (BiTLa) were synthesized by the standard solid-state reaction method from the mixture of oxides at 1000 °C for 3 h. Ceramic powders of Bi4-xLaxTi3O12 for x = 0, 0.25, 0.75 were next pressed, and the compacts were sintered by natural sintering at temperatures of 1000°C and 1100°C with a soaking time of 2 h. A thermal analysis was carried out for the stoichiometric mixture of starting oxides. The influence of La-doping on the chemical composition and microstructure of BiTLa ceramics was studied by scanning electron microscopy (HITACHI S-4700) and energy dispersion spectroscopy. The crystal structure of Bi4-xLaxTi3O12 ceramics was determined by X-ray diffraction. The temperature dependence of the impedance was measured in the frequency range of (1-100) kHz.
- Influence of CaO content on the microstructure of porous ZrO2/Al2O3 composite sinters
- Strony: 59-64
The presented paper addresses selected issues relating to the technology of manufacturing ceramic composites (ZrO2)x(Al2O3)100%-x for x = 100%, 90% and 80 wt%. The presented materials have been produced by mixing component powders and consolidation of the resultant mixtures by using natural sintering at T = 1350°C for a time of t = 2 hours. The composites with no and with a calcium oxide admixture of 5 wt% added as the sintering aid were single and double sintered. To carry out observation of the fracture morphology, scanning electron microscopy was used. An analysis of the chemical composition evaluation was made by using EDS.
- Analysis of wear resistance of oxide coating in cooperation with ceramic balls
- Strony: 65-70
In this article, there are shown the results of tribological, stereometric and surface morphology tests carried out with ceramic materials: WC, Si3N4, ZrO2 and Al2O3 used for cooperation with aluminium oxide coating. The aim of the study was to determine the usefulness of these materials for cooperation with anodic oxide coating under dry friction conditions. This paper is a continuation of the research on the cooperation of APT with plastics. Oxide coatings were formed on EN AW-5251 aluminium alloy by the electrochemical method in the ternary electrolyte system. Tribological tests were carried out by using a T-01 tester with the ball-on-disc friction system and under dry friction conditions, and for rotational motion. Other test parameters were accepted in according to guidelines of the VAMAS program. Test results established that the selected materials have behaved in various manners during tribological cooperation with oxide coating. Ceramic materials were very different each other in the frictional wear intensity and other tribological characteristics. It was revealed that ZrO2 material is not suitable for cooperation with anodic hard coating under dry friction conditions. For other materials, the smaller friction wear intensities were obtained.
- Influence of spinel phase on selected thermal properties of glass-ceramic materials from the ZAS system
- Strony: 71-77
Effects of crystalline phases on selected thermal properties of glass-ceramics from the CaO-MgO-Al2O3-SiO2 and ZnO-B2O3Al2O3-SiO2 systems, designed for binding abrasive grains in an abrasive tool, were studied. Changes in thermal diffusivity and thermal conductivity depending on the chemical composition of materials were shown. The maximum values of the thermal diffusivity of d = 0,73 mm2/s and the thermal conductivity of λ= 3,36 W/(m·K) were obtained for glass-ceramic material containing the zinc spinel phase.
- Physical properties and phase transformations in the PLZT and PLZTS ceramics
- Strony: 78-83
This paper presents the results of preparing and investigating the solid solutions of the formulae (Pb1-xLax)(Zr1-yTiy)O3, where x = 0.03 or 0.06, y = 0.9, (PLZT) and (Pb1-xLax)[(Zr1-yTiy)1-zSnz]O3, where x = 0.04, y = 0.9, z = 0.02, 0.04, 0,06, 0,08, (PLZTS). These materials belong to perovskite type oxygen octahedral compounds. The investigated ceramic samples were obtained by using the classical ceramic technology, utilizing oxides. The results of investigations of the microstructure, dielectric permittivity and P-E hysteresis loops are presented. In the case of PLZT 3/90/10 it has been stated that this material exhibits well defi ned antiferroelectric properties at room temperature. In the case of PLZTS it has been stated that there is rather weak dependency between the Tm temperature, at which the dielectric permittivity reaches its maximum value, and PbSnO3-content. Analysing the λ(E) relationship, which was obtained as the derivative of the P-E curve, it has been stated that PLZT 3/90/10 is rather not a suitable material to use in making devices that require high values of dielectric permittivity in high electric fields. Alternative PLZTS ceramics showed rather low fi elds of electric breakthrough.
- Improvement possibilities of refractory lining wear resistance by ceramic welding
- Strony: 84-88
The ceramic welding technique is applied for regeneration of coke battery walls and also for glass tanks repairing. It consists in spraying a mix, containing the refractory grains and exothermic additives, on a hot surface of refractory lining. The process was characterized in the paper. The results of investigations on application of the ceramic welding method for forming the layers on refractory cement castable to improve its wear resistance have been presented. The properties of silica and corundum–zirconia layers were compared. It has been found that the composition and thermal expansion of the layer were important for improving the wear resistance. The latter feature should be similar to the thermal expansion of a material on which the layer is deposited. The corundum–zirconia layer showed three times higher wear resistance than the castable one.
- Effect of sintering atmosphere on microstructure and properties of Al2O3-Ni composites
- Strony: 89-93
This paper presents the effect of sintering atmosphere (air, argon, hydrogen) on the microstructure and selected properties of Al2O3-Ni composites. The composites were obtained by pressing and sintering of Al2O3 and Ni powders. The use of different sintering atmospheres has led to composites of various phase compositions. The composites sintered in argon shown the presence of NiO in addition to Al2O3 and Ni. X-ray diffraction studies revealed NiO in an outer layer of the material. In the case of sintering in air, the NiAl2O4 spinel phase was detected, either on the sample surface and in the sample interior. The fact provides a characteristic blue-turquoise color of the sample throughout its cross section. The presence of NiAl2O4 was confi rmed by X-ray diffraction studies. The formation of NiO and NiAl2O4 indicates oxidation of Ni particles during the consolidation process. In the case of sintering in argon, the NiO layer is formed at the Ni/Al2O3 interface as a result of oxygen absorption on the surface of Ni particles during mixing and pressing the powders. Sintering in air led to the formation of spinel. In particular, there was a complete transition of Ni to the spinel NiAl2O4 in the outer layer. Sintering in the reducing atmosphere of H2 provides a two-phase composite structure composed of nickel particles distributed in the Al2O3 matrix. Differences in the composite phase-compositions cause differences in their density, porosity and hardness. The highest density and hardness were obtained for the composites sintered in H2.
- Composite layers Ni-P with ceramic powders as a dispersion phase
- Strony: 94-97
The paper presents the results of studies of the structure and some properties of composite nickel layers with the dispersion phase as ceramic powders obtained by the sol-gel method. Two types of powders were used: nanometric titanium carbide and mixture of carbides and borides, which contained e.g. TiB2, B4C and TiC, also of a nanometric size. The layers were deposited by chemical reduction on St3S steel. For comparison, on the same substrate, Ni-phosphorus coatings were obtained. The coatings were deposited from alkaline bath. The electroless deposition processes were performed with different contents of ceramic powders: 1 g/dm3, 5 g/dm3 and 10 g/dm3. Basing on the mass increase, a rate of layer rise was determined, which allowed the effectiveness of the process to be evaluated. The topography of the obtained layers and their cross-sectional structure were characterized by using scanning electron microscopy with EDS attachment. Computer image analysis was applied to determine the content of the dispersed ceramic phase in the composite material. Characteristics of the surface morphology of the layers was performed by using an optical profilometer. The roughness and microhardness values were determined. It was found that the presence of TiC powder in the bath increases the speed of the deposition process while multiphase powders slows the process, and it is less efficient in terms of the ceramic phase content built in the layer. It was also found that the composite layers showed much higher surface roughness and higher microhardness than the Ni-P layer.
- Manufacturing of Sr0,7Ba0,3Nb2O6ceramics with oriented microstructure by hot pressing
- Strony: 98-102
Ceramics with the oriented microstructure were obtained for electronic applications. Main application areas of piezoelectric and pyroelectric ceramic materials were fi rstly reviewed. Majority of piezoelectric materials produced industrially are based on Pb(Zr1-xTix)O3 solid solutions (PZT). The PZT ceramics composed of the paraelectric phase formed during sintering have the cubic structure, which does not favour the formation of texture. The texture can be obtained in the case of the materials showing anisotropic grain growth. Materials with the structure of tetragonal tungsten bronze (TBW) create the group of materials with elementary cells another than the cubic one. Barium strontium niobate SrxBa1-xNb2O6 (SBN) is a ferroelectric material of the TBW structure in the range of 0.25 < x < 0.75. In this work, hot pressing was applied to manufacture the Sr0,7Ba0,3Nb2O6 ceramics (SBN70), showing the oriented microstructure. Powders were synthesized by the sol-gel method. The SBN70 ceramics with the oriented microstructure can be used in designing piezoelectric and piroelectric transducers.
- Analysis of chemical and phase composition of archaeological pottery vessels
- Strony: 103-107
The aim of research presented in the article was to analyze the chemical and phase compositions of archaeological ceramic vessels. The studies used scanning electron microscopy coupled with X-ray microanalysis, an X-ray fluorescence spectrometer and an X-ray diffractometer. Pieces of IX-XI century ceramic archaeological vessels of the Menkendorf-Szczecin type originating from sites in present Poland and German were the test material. The clay matrix and admixtures were subjected to studies and observations by using scanning electron microscopy, which allowed chemical analysis in micro-areas to be performed. Studies using the fluorescence spectrometer allowed us to analyze the chemical composition of powdered portions of the samples. The analysis of phase composition of the powdered samples was performed by X-ray diffraction. The SEM-EDS studies showed the presence of the most common inclusion in the form of quartz. The fluorescence spectrometry measurements showed that the content of Al2O3 was similar and amounted to (18-19) wt% in all tested samples, indicating that the vessels have been manufactured from plastic clays. The XRF studies also showed the presence of a number of other oxides such as SiO2, Fe2O3, Na2O, K2O and CaO. The XRD studies confirmed the presence of SiO2 (quartz), NaAlSi3O8 (albite) and Al2O3 (corundum) in all samples.
- Fabrication of transparent Y2O3 ceramics by hot-pressing
- Strony: 108-114
The aim of the work was to fabricate yttria ceramics, which is transparent in the range of infrared light, by using commercially available micropowders. Influence of sintering aids (Eu2O3, La2O3) on optical transmission and the microstructure of the obtained ceramics was examined. It was found that the addition of 1 wt.% Eu2O3 or 1 wt.% La2O3 leads to obtain translucent materials. Transmission values of Eu:Y2O3 and La:Y2O3 ceramics, in the 2-6 μm wavelength range, vary from 2% to 60% and from 50% to 70%, respectively. Further improvement of optical properties of both ceramics was observed after the incorporation of the addition of 1 wt.% LiF.
- Ni-Al composites produced by the pulse plasma method assisted with the SHS reaction
- Strony: 115-119
Both NiAl and Ni3Al matrix composites containing dispersed diamond particles were manufactured from nickel, aluminium and diamond powders by using the pulse plasma sintering (PPS) method with participation of the self-propagating high-temperature synthesis (SHS). NiAl and Ni3Al sinters with no diamond particles were also prepared using the same way. The NiAl and Ni3Al sinters had 100% and 97,8% of theoretical density (TD), respectively. Average grain sizes of 5.3 μm and 4.9 μm were measured for the NiAl and Ni3Al sinters, respectively, which is 2-3 times smaller than in the case of conventionally sintered materials. Both NiAl and Ni3Al sinters had a hardness of 350 HK1. X-ray diffraction showed no graphitization of diamond in the NiAl/diamond and Ni3Al/diamond sinters. Density of the NiAl matrix diamond sinter was 5.11 g/cm3, i.e. 100% TD, and the value of 6.12 g/cm3 was measured for the Ni3Al matrix diamond sinter, which is about 2% less than the theoretical density. The hardness of the NiAl matrix diamond composites was higher than the NiAl matrix alone by about 210 HK1, and in the case of the Ni3Al matrix diamond composites it is higher by 130 HK1 when compared to Ni3Al. Strong connection between diamond participles and matrix in the Ni3Al/diamond sinters is correlated with the formation of Ni3AlC0.5 carbide formation at the diamond-Ni3Al interface.
- Physicochemical behaviour of complex oxides obtained From the Mn-Co-O system using wet chemistry methods
- Strony: 120-130
Manganese cobaltite spinels have recently been studied as potential candidates for protective-conducting coatings on the surface of ferritic stainless steels. Because they exhibit high electric conductivity and are effi cient at blocking chromium diffusion, they may be applied as coatings on metallic interconnects in IT-SOFCs. Manganese cobaltite spinels were synthesized using the sol-gel, coprecipitation and solid-state reaction methods. The structure and morphology of the powders and bulk samples, as well as the electrical conductivity of bulk samples, were investigated using XRD, SEM and EIS, respectively. The prepared Mn1+xCo2-xO4 spinels exhibited various microstructures, high electrical conductivity and structural stability. Tetragonal-cubic phase transition and its infl uence on the electrical properties of Mn1.5Co1.5O4 at elevated temperatures were studied.
- Physicochemical properies of the crofer 22 APU/La0,6Sr0,4Co0,2Fe0,8O3 materials for sofc interconnects
- Strony: 131-141
In this work, La0,6Sr0,4Co0,2Fe0,8O3 (LSCF48) cathode material was used to obtain a conductive coating on Crofer 22 APU ferritic steel interconnect in order to produce a SOFC stack. The LSCF48 coating was deposited on the steel surface via screen-printing and then was subjected to the appropriate thermal treatment. Three types of samples were prepared for physicochemical studies: (i) samples of pure steel (Crofer 22 APU), (ii) samples with coating deposited on the substrate without surface modifi cation (Crofer 22 APU/LSCF48) and (iii) samples with coating deposited on the substrate after its oxidation at 1073 K for 24 hrs in air (Crofer 22 APU/Cr2O3/LSCF48). From the oxidation kinetics study of the afore-mentioned samples carried out at 1073 K for 528 hrs in air, it follows that the Crofer 22 APU/LSCF48 system shows the highest resistance against corrosion in cyclic oxidation conditions. Such a favorable phenomenon is the result of good adhesion between the afore-mentioned coating without the transient Cr2O3 layer and the metallic substrate, due to the formation of an intermediate reaction layer at the metal/coating interphase. The formation of this intermediate reaction layer also leads to lower area specific resistance in air at 1073 K in comparison to pure Crofer 22 APU steel.
- Strony: 142-152
List of Contents
Volume 64, Issue 2
- Transport Phenomena and Diffusion Anomalies in Glass
- Strony: 156-161
Mass transport processes in glass can be differentiated according to the type of diffusion species: gases, network modifiers and network formers. The mobilities of these species give rise to a variety of diffusion-controlled processes and properties. Interface reactions (such as dissolution of sand grains by sodium silicate melts, corrosive attack of refractory material by glass melts, devitrification in a soda-lime-silica glass) will be discussed where the chemical potential is the driving force for establishing „up-hill” diffusion profiles. With the help of phase diagrams the diffusion pathways can be predicted. The formation of the tin concentration maximum (“tin hump”), which is found in nearsurface regions at the bottom side of float glass, is a further example of up-hill diffusion, in this case induced by redox reaction. The result of the mixed-alkali effect of a homogenously melted soda-potassia-lime-silica glass series and of an ion-exchanged glass (soda-lime-silica glass treated in KNO3) is compared with respect to their electrical resistivity. In ion-exchanged glass only sodium acts as a charge carrier, whereas in regular mixed-alkali glasses both alkalis can be responsible for electrical conduction. Moreover, sodium diffusion anomalies in SiO2 glasses are reviewed and a possible mixed-alkali effect on the impurity level between sodium and the OH content is revealed. A further sodium diffusion anomaly (sharp increase of mobility) was detected in silica glass at the temperature of the α-β quartz phase transformation, thus indicating that a preordered quartz-type structure seems to exist in silica glass. Finally, the role of the diffusivities of network oxygen, molecular oxygen and silicon in silica glass is interpreted. The oxygen mobilities govern the growth of passivating SiO2 layers on silicon-containing materials (such as silicon, silicon carbide, silicon nitride) whereas the silicon mobility is responsible for viscous flow.
- Field Test of Hydrophobic and Superhydrophobic Surfaces in a Paper Machine for Easy-to-Clean Application
- Strony: 162-167
Hydrophobic and superhydrophobic surfaces were field-tested on two locations in a paper machine to see the easy-to-clean property, compared with a reference surface. One test site was near machine wire which was wet place exposed to fibres and wood extracts, and the other was at size roll, where was much drier and surfaces were exposed to glue aerosol. The test period was 16 days. At the end of the field test, all the surfaces were covered with substances collected from the paper machine environment. The surfaces were then washed by pressurized water. For the surfaces tested near the machine wire, the collected substances could only be washed away slightly and therefore no surface was easy-to-clean. However, for the surfaces tested at the size roll, the washed hydrophobic and superhydrophobic surfaces became quite clean. The field-tested surfaces were characterized visually and by stereomicroscopy, scanning electron microscopy and contact angle measurement. The results show that the application of hydrophobic and superhydrophobic surface as easy-to-clean surface depends on the testing location where different types of substances exist. The hydrophobic surface works almost as good as the superhydrophobic surface in size roll to have easy-to-clean property.
- Mechanical properties and microstructure of 1Y2Nd-TZP/20 vol.% alumina nanocomposites
- Strony: 168-171
Zirconia based composites are frequently used in mechanical and biomedical components demanding high strength and toughness. In the present study, alumina toughened zirconia ceramics were manufactured from 1 mol.% yttria 2 mol.% neodymia stabilized TZP blended with 20 vol.% alumina by hot pressing at 1250-1450°C/1 h/60 MPa. Mechanical properties, phase composition and microstructure were investigated. The co-stabilized ATZ material exhibits a combination of high 4-pt bending strength of 1300 MPa and very high fracture resistance of 11 MPa∙√m. The threshold stress intensity of 5 MPa∙√m indicates a high resistance to subcritical crack growth. The microstructure shows a homogeneous dispersion of alumina grains in a bimodal zirconia matrix consisting of transformable fi ne grains and untransformable large cubic grains. Most favourable properties are developed at sintering temperatures of 1350–1400°C, at higher temperature the material decomposes to monoclinic and cubic losing its high strength and toughness.
- Active glasses and optical fibres as a luminescent source of radiation
- Strony: 172-176
In the paper, spectroscopic properties of fluorosilicate and fluorophosphate glass systems co-doped with Nd3+/Yb3+ ions were investigated. The optimization of the molar concentration of dopants was determined with respect to the spectral overlaps of the emission cross-section of neodymium ions and the absorption cross-section of ytterbium ions. As a result of the optical excitation with a laser diode at a wavelength of 808 nm, the strong and wide emission was observed corresponding to a superposition of optical transitions 4F3/2 → 4I11/2 (Nd3+) and 2F5/2 → 2F7/2(Yb3+). The optimization of Nd3+/Yb3+transfer in both glasses allowed us to fabricate optical fibres that showed narrowing and red-shifting of the amplified spontaneous emission (ASE) at 1.1 μm.
- Positron life time spectroscopy as a tool to study the defect degree of materials with disordered structure
- Strony: 177-180
The paper presents the use of positron lifetime spectroscopy PALS to study the defect degree of structures of disordered materials. Oxide glass, chalcogenide glass and polymer were used in the study. The PALS method is particularly sensitive to detect the structure of disordered materials with structural defects that can trap both the positron (linear defects) and positronium (the free volume). As a result of the measurements, curves describing the dependence of the number of counts of annihilation acts as a function of time were obtained. The positron lifetime spectra were resolved into three components τ1, τ2 and τ3. The component τ1 is responsible for the free positron annihilation and the annihilation with electrons of vacancy-type point defects. The component τ2 is related to the presence of bulk defects that arise at the grain boundaries, dislocations or clusters of vacancies. The component τ3 is assigned to the pick-off annihilation of ortho-positronium (o-Ps) by the free volume, and gives information on the geometric parameters of the free volume. The calculated parameters of uptake of the positron and positronium in the structurally disordered materials under consideration allowed us to draw conclusions about the degree and nature of their defects..
- Hot embossing – an inexpensive formation method for optical structures
- Strony: 181-187
The fabrication of microstructures can be performed by several procedures including mechanical micromachining, lithographic processes, epitaxy, ions technology, and many other different available techniques. Most of them are cost- and time-consuming methods. Hot embossing (HE) is a profi table alternative to these micro replication processes, because it’s a low cost method, which is adequate for mass production of a wide range of structures. In the article, we present the short description of this replication method and the results of our preliminary works in developing of the hot-embossing process in the case of multicomponent glasses well fitted for the NIR region.
- Application of two-stage oxidation method for growth mechanism studies of rutile scale on titanium
- Strony: 188-191
The growth mechanism of rutile scale on titanium using the marker method was investigated in 60th years of the preceding century by Kofstad. For a temperature of 900 °C, a Pt-marker was found on the surface of the rutile layer. Above-mentioned result, as well as the studies of electric conductivity of TiO2, have allowed Kofstad to propose a model of the defect structure of this oxide, in which oxygen vacancies were suggested as the predominant point defects. This model has been accepted to be a correct one for a long time but has seemed doubtful recently. It is worth to note, that the marker localization on the surface of the scale does not give one-valued answer concerning the predominant mechanism of reagents transport in the oxide layer. The marker is localized on the scale surface both in case of the predominant transport of the oxygen via point defects and via two- and three-dimensional defects in the oxide (grain boundaries, micro-cracks, open pores). In order to settle the matter, it belongs to carry of a two-stage oxidation experiment using the 16O2 and 18O2 oxygen isotopes. In this paper, the results of the two-stage oxidation of titanium at 900 °C are presented. The depth-concentration profiles of the oxygen isotopes in the rutile scale were determined using the SNMS surface-analytical technique. The obtained results exclude oxygen diffusion via point defects in TiO2-x as the predominant mechanism of reagents transport in the layered rutile scale on titanium.
- Filter pressing of fine yttria powders
- Strony: 192-197
The work presents preliminary results of investigations on consolidation and sintering of fine yttria powders. Aim of the work was the production of dense, fine-grained materials being transparent in IR and showing enhanced hardness. In order to achieve this goal nanometric powders were consolidated by filter pressing of aqueous suspensions. This method should lead to green bodies with uniform microstructures, showing narrow pore size distributions. The investigations were carried out on commercial powder produced by Nanoamor and powder synthesised in ITME (Warsaw). Both powders consisted in nanometric crystallites that formed bigger submicron or micrometric agglomerates. Aqueous suspensions of both powders were filter pressed and sometimes subsequently isostatically pressed. The green samples were sintered in air or vacuum at 1500, 1600 and 1700 °C. Additionally, effects of LiF on sintering was evaluated. Density of the sintered samples and their microstructure were investigated, and in the case of the best densified materials also Vickers hardness and IR transmittance were evaluated. The results indicate that sole filter pressing led to materials with substantial porosity and wide pore size distribution. This disadvantageous phenomenon, affecting strongly the sintering process resulted from agglomeration of both powders. The pore size distribution in the green samples was improved by isostatic pressing of the filter pressed samples. In all the samples consolidated from suspensions and sintered in air or vacuum significant grain growth was observed as well as entrapment of pores inside the grains. On the other hand, grains in the samples isostatically pressed from dry powders were much finer. This phenomenon may be related to susceptibility of the nanometric yttria powders to small differences in pore size distribution or introduction some contaminations during colloidal processing that cause the grain growth. The above mentioned phenomena adversely affected IR transmittance and hardness of the filter pressed samples.
- Influence of surface refining on increase in mechanical resistance of glass containers
- Strony: 198-202
One of the very important factor, which increases the mechanical resistance of glass packaging, is a coating method. The aim of this work is to show the research results of mechanical resistance of glass containers refined by using various treatment methods. The results of comparative research of the mechanical resistance of glass containers coated with nanoparticles of alumina compounds and tin oxide are shown. The presented research results concerning the implemented hot end coating method, which utilizes nanoparticles of aluminium compounds, may act as guidelines for improvement of the production process in Pol−Am−Pack. S.A. Oddział Huta Szkła “ORZESZE” in the future.
- Bioactive glass from the CaO-P2O5-SiO2 system as a component of composites for medical applications
- Strony: 203-208
The aim of this study was to fabricate and evaluate both Ti- and TiO2-matrix composites modified with bioactive glasses. The glasses were produced by the sol-gel method (BGZ), named A2 and S2, and had the chemical composition of 54CaO-40SiO2-6P2O5 (mol. %) and 16CaO-80SiO2-4P2O5 (mol. %), respectively. Concentrations of added bioglasses were 10 wt% and 25 wt% for the Ti-BGZ and TiO2-BGZ composites, respectively. Scanning electron microscopy and X-ray diffraction were used to characterize the microstructure and phase composition of the obtained materials. The composites were also characterized for their mechanical properties, i.e. compressive strength. The bioactivity of composites was assessed by determining the changes of surface morphology of the composites after soaking in simulated body fluid (SBF) for 21 days. It was found that the addition of bioactive glasses into the Ti matrix results in compressive strength values comparable to cortical bone, and the incorporation of bioactive glasses to the TiO2 matrix leads to the strengthening of the materials which was adequate for bone implants. Both Ti-BGZ and TiO2-BGZ composites showed good bioactive properties.
- Manufacturing and characteristics of the structure of TiO2 nanotubes
- Strony: 209-213
Titania nanotubes have wide practical applications mainly in catalytic and photocatalytic processes. The main advantage of the nanotubes with respect to TiO2 in a powder form is much greater surface development and higher activity. However, TiO2 nanotube material is still little explored especially for photocatalytic applications as thin films. This paper describes a procedure for the synthesis of titanium nanotubes by the hydrothermal method in an alkaline solution. The aim of this study was to compare the structure of the materials depending on a crystalline form of starting material. The characteristics of the structure of nanotubes was based on FTIR and Raman spectroscopy, the phase composition was determined by using X-ray diffraction and the morphology of the fibers was analyzed by scanning and transmission microscopy.
- Preparation of polycrystalline aluminium nitride with yttria additive
- Strony: 214-218
Aluminium nitride polycrystals are characterized by high thermal conductivity, good temperature and chemical stability as well as good mechanical strength. AlN has piezoelectric properties and it is a broad-band semiconductor. Owing to that, it is more and more widely used in electronics, engineering, nuclear power engineering and military industry. AlN polycrystals are mostly produced through sintering doped with yttria and alumina additives. As large quantity of additives decreases thermal conductivity of AlN, in this paper polycrystals with the least possible amount of oxides were aspired to be produced. Two methods of obtaining the AlN polycrystals were used: hot pressing and pressureless sintering. Samples were hot pressed in the nitrogen atmosphere at 1900 °C for 2 hours. Pressureless polycrystals were sintered in the nitrogen atmosphere at 1830 °C for 5 hours and 1900 °C for 2 hours. Densities of all the samples were examined by means of Archimedes method. To investigate phase composition of polycrystals, X-ray diffraction was used. On X-ray diffraction patterns, the following phases of Y-Al-O-N type were detected: yttrium aluminium Garnet (Y3Al5O9-YAG), yttrium aluminate perovskite (YAlO3-YAP), yttrium aluminium monoclinic (Y4Al2O9-YAM). These phases were established as a result of reaction Y2O3 with Al2O3 during sintering process. The presence of alumina in this system resulted from passivation of AlN powder being used for sintering. The highest factor of thermal conductivity, that is 250 W/(m·K), was obtained for specimens pressurelessly sintered at 1900°C for 2 h, doped with 5 wt% Y2O3.
- Lead-bismuth glasses for midir microstructured fibers and microoptical elements manufacturing
- Strony: 219-224
Three component PbO-Bi2O3-Ga2O3 glasses are characterized by high middle infrared transmittance up to 8 μm, but they show large susceptibility for crystallization. For a rise of the thermal stability of glasses, their compositions were modifi ed by addition of GeO2, SiO2, Tl2O, CdO, Nb2O5. There have been obtained the glasses that can be suitable for the manufacturing of microstructured fibers and microoptical elements. The growth of thermal stability of glasses unfavourably resulted in an IR absorption cut off shift into shorter wavelengths.
- Application of mechanochemical methods for preparation of glass sealants
- Strony: 225-228
Mechanical activated barium silicate glasses were studied as a potential sealant for joining of different materials. Thermal properties of BaO–SiO2–MgO–ZnO system glasses containing less than 40 mas.% of SiO2 as the network forming component were studied. Mechanical activation on the thermal properties were investigated. The progress of melting was tested by using high temperature microscopy. Mechanical activation causes a decrease of the melting temperature and an increase of crystallization tendency of the investigated materials. The prospective glasses are indicated for sealant applications.
- Selection of fining agent for glass batches with increased content of recycled glass
- Strony: 229-233
The melting of a glass batch consits of several chemical and physical processes. In this paper an attempt is made to select the most effective fining agent for glass batches for glass containers, containing 60 wt% recycled glass partially replacing the traditional glass-making raw materials. Glass composed of 73.0 wt% SiO2, 1.0 wt% Al2O3, 10.0 wt% CaO, 2.0 wt% MgO and 14.0 wt% Na2O was studied. The glass batch was prepared from raw materials used in the industrial glass melting process, selected fining agents and recycled glass. The content and chemical composition of residual gases were studied as a function of refining agent applied and chemical composition of glass. The results are helpful for solving technological problems.
- Studies on application of waste cathode ray tube glass for production of glazes, fluxes and colour structural ceramic components
- Strony: 234-238
The need to utilize waste cathode ray tubes (CRT) and the potential use of the results in practice were the reasons to undertake this study. The possibility of use of waste CRT glass as a full-value secondary raw material for the manufacture of widely understood ceramic products was investigated. The collected knowledge on the composition and properties of the glass will make possible its conscious development and re-enter to the market. A series of parameters of CRT glass was determined, which allows new decoration agents to be designed. It has been found that there was a real possibility of using this waste material for manufacturing matting colours for lighting glass, fluxes for colours for pottery and porcelain, tile glazes (after modifications of the composition), ceramic countertops, floor and facade tiles, as well as for glazes with special effects.
- Optical characteristics of inorganic oxide glasses coloured with manganese ions
- Strony: 239-243
The aim of this study was to determine the influence of K2O, Na2O and Li2O modifiers of silicate and phosphate glass networks on the valence state of manganese. Our attention was attracted by glass matrices based on the oxide systems composed of 33R2O-67SiO2 and 20R2O-15Al2O3-65P2O5 (where R = Li, Na and K) doped with manganese ions. UV-VIS-NIR spectroscopy is the most often used method allowing to determine the local state of transition metal ions in glasses. We used the method to study influence of the glass matrix on the local state of manganese ions. EPR spectroscopy was used as a supplementary experimental technique to confirm the spectroscopic results. The optical properties of alkali silicate and phosphate glasses, containing manganese additives and manufactured under oxidizing conditions, have been determined and related to the valence state of manganese. It has been found that manganese in the studied glasses was present in divalent and trivalent forms occupying octahedral ligand fields, being the most stable oxidation state.
- Hydrophobic properties of thin gel layers doped with zinc oxide
- Strony: 244-247
Hydrophobic coatings doped with zinc oxides were prepared by sol-gel technique, electrostatic deposition on glass soda-calcium–silicate. For the synthesis of a matrix, the following precursors, containing both silicon and titanium were used: TEOS (tetraethyl orthosilicate), TEOT (tetraethyl orthotytanate), PDMS (polydimethylsiloxane). Then, all matrices were doped with zinc oxide nano-powders. The obtained thin films showed high transmittance in the range 250-1050 nm, which was determined by UV-VIS measurements performed by using a Jasco V 660 spectrometer. All coatings had increased hydrophobic properties, as confirmed by the contact angle examinations. The layer originated from PDMS had a contact angle of 105°. The microstructure of all samples was observed by a scanning electron microscope equipped with an EDX detector. The SEM observations confi rmed nano-cystallization of hydrophobic compounds on the surface of the thin layers.
- Lanthanides in chalcogenide glasses
- Strony: 248-251
The synthesis of tellurite glasses doped with rare earth (RE) is presented. The study is focused on investigation of the effect of Nd3+, Er3 + and Pr3 + active dopants on selected optical properties of tellurite glasses. The refractive index of the glasses was measured. The spectral dependence of ellipsometric angles Ψ and Δ of the tellurite glass samples was determined. The optical measurements were conducted on Woollam M2000 spectroscopic ellipsometer in a spectral range of 190-1700 nm. The radiative transition probabilities for excited levels of Nd3+, Er3+, Pr3+ have been calculated using the standard Judd–Ofelt (J-O) theory.
- The glass sensor method and thermovision measurements applied as complementary studies for preparation of conservative activity
- Strony: 252-256
Exposed and stored glass historical objects are being influenced by different media and local circumstances. Basically their deterioration process is mainly dependent on their chemical composition. Unstable glasses, with low durability are suffering and very often reach high level corrosion. To preserve them as an over cultural heritage good conservation work must be done. Suitable conservation activity or over sustainable conservation should be preceded by some experiments. Because of very specific and unique character of the objects testing methods have to be very precisely chosen to be adequate for size and shape of obtained samples for analysis. The glass sensor method as well as thermovision measurements should be apply to check some suggestions for sustainable or standard conservation activity. For better interpretation thermovision data, complementary infrared mapping was done for chosen glass. These methods have been applied in few chosen museum in Poland and in London. Obtained results have been presented in this paper as a confirmation their suitable and fruitful applications.
- Influence of methylcellulose viscosity on properties of gypsum mortars
- Strony: 257-260
In the paper, problems connected with using cellulose ethers as a substance with ability to retain water in mortar were discussed. The results concerning influence of methylcellulose viscosity on technological properties of gypsum plaster mortars and their physical properties as setting time, bending and compressive strength and adhesion are presented. On the base of microscopic observations, a methylcellulose viscosity impact on the microstructure of hardened gypsum mortars was discussed.
- Characteristics of clinker bricks manufactured from thermally modified carboniferous clay shale
- Strony: 261-271
Carboniferous shales are usually kaolinitic in their nature. They can be used as primary raw materials for clinker materials manufacturing. However, usually except of above mentioned kaolinite carboniferous shale contains organic matter and often siderite and pyrite. If present, siderite and pyrite significantly reduce possibility of utilization as the raw material in clinker materials manufacturing. The reason is that clinker materials are burnt in reducing atmosphere. This atmosphere leads to the reduction of iron to metallic iron. As a result of this process rusty inclusions or even metallic melts, which are obvious defects can be noticed. Nevertheless, problems connected with the iron presence can be significantly limited, or even eliminated by reducing the amount of organic matter present within the shale. This goal can be achieved when shale is subjected to suitable thermal treatment. Present paper presents results of investigations on the optimization of initial shale thermal treatment, in order to obtain a full value raw material for sintered clinker materials. Characterization of materials obtained after preliminary treatment covers their basic technical properties as well as some selected microstructural features.
- Oxyfluoride glass-ceramics with GdF3
- Strony: 272-276
Glass-ceramics with the low phonon phases of fluorides as a transparent materials for optoelectronic application were studied. Glasses based on the SiO2–Al2O3–Na2F2–Na2O–GdF3 system was obtained. Their chemical composition was modified with B2O3, BaO or MgO. The study shows that formation of GdF3 is much more difficult than LaF3 from alumino-silicate glasses. It is possible to induce the formation of low phonon phases NaGdF4 and BaGdF5 at the first stage of crystallization when B2O3 or BaO are the components of the glass.
- Modern refractory materials for glass furnaces
- Strony: 277-281
In glass industry, beside expensive, fused refractory materials, there is a big interest in fired silica-alumina materials. Their chemical composition and properties cause that they are being widely used in construction of glass furnaces (crowns, walls) and regenerators. The presence of mullite phase in these materials also improves many properties of these products. In this paper, fused silica and modern silica- alumina materials produced by Vesuvius are presented, the examples of their application and quality control. Vesuvius provides solutions to satisfy the increasing technological requirements whilst reducing the downtime maintenance of the customer’s equipment.
- Optical parameters of thin silica films on silicon substrates
- Strony: 282-285
Studies of optical properties of thin silica fi lms are shown in the paper. The films were manufactured by the sol-gel method combined with spreading on a silicon substrate by immersing. The studies were performed by ellipsometric and spectrophotometric methods to determine optical characteristics of the films such as dispersion dependences of refractive indices or extinction coeffi cients. Moreover, the thickness and porosity of the films were determined. The silica layers are used as antireflective coatings and components of planar optical fibres due to low values of refractive index (1,22-1,25).
- 60 Years of glass science and education in AGH
- Strony: 286-293
60 years ago, in the year 1952, the Department of Glass Technology (DGT) has been founded at the Faculty of Ceramics of the AGH University of Science and Technology in Cracow, as the fi rst department of such a profi le at the European Universities. Scientific achievements of the Department of Glass Technology and Amorphous Coatings, which continues the tradition of DGT, are shortly described. They comprise the traditional glass technology, modern advanced glasses and glass ceramics, including materials for optoelectronics, bioactive materials, hybrid inorganic-organic glasses and coatings on glass, protective enamels and thin layers on metals, glassy state of matter theory and glass crystallization, as well as glass archeometry and studies on corrosion and conservation of ancient glasses.
- Strony: 294-299
List of Contents
Volume 64, Issue 3
- Influence of aluminium phosphate addition on the properties of low cement corundum castables
- Strony: 304-308
In the paper, the results of a study were presented on simultaneous usage of high alumina cement and aluminium phosphate as main components of phosphate bonded castable batches. The advantageous influence of aluminium phosphate addition on mechanical strength of the studied pastes and castables in the temperature range 400-1000 °C was ascertained. The good mechanical strength after curing at room temperature was maintained. The low cement corundum castables with the aluminium phosphate addition possess very good physical and technological properties, when fired at a temperature of 1500 °C.
- Limitation of shrinkage of cement mortars containing fly ash
- Strony: 309-313
The increasing amount of ashes originating from the combustion of alternative fuels causes a need to find ways for their practical application. The utilization of new ashes demands the knowledge about their properties. The present study focuses on the ashes from the combustion of bituminous coal and wood-biomass. The basic properties of both ashes were estimated. The analysis was carried out concerning the development of shrinkage deformations in mortars with and without an air entraining agent, containing 20% fly ash related to the cement mass. It has been found that the presence of the air entraining agent, as well as the origin and the form of fly ash had an essential effect on shrinkage of mortars. Moreover, the development in time of shrinkage deformations in the case of mortars containing fly ash proceeds in a different manner than for mortars without the addition.
- Influence of grinding process parameters on the surface state of WCCo/diamond composite produced by PPS
- Strony: 314-318
WC composites with the addition of cobalt are valued construction and tool materials. Due to high hardness, wear resistance and fracture toughness, cemented carbide tools are more than 50% of cutting tools market. In order to increase wear resistance of WCCo tools, diamond particles are added. Composites consisted of WCCo with distributed 30 vol. % of diamond particles were obtained, by the PPS method (Pulse Plasma Sintering) invented and developed at the Department of Materials Science and Engineering at the Warsaw University of Technology. This method enables to sinter materials at lower temperatures than traditional methods need, obtaining dense materials with densities closed to theoretical values. Preparation of a surface is very important issue for the quality of composite WCCo/diamond blades. In this paper, characteristics of WCCo/diamond composite surfaces are presented after the grinding process performed at a MVM LA 500 grinding machine. This work was supported by UDA-POIG.01.03.01-14-063/08-00 project implemented at the Faculty of Materials Science and Engineering of the Warsaw University of Technology. This study was aimed to create grinding machining parameters, compare efficiency of grinding wheels in order to obtain surface with the possible low Ra parameter value. Influence of peripheral velocity, rotation direction, grain size and grinding wheel matrix was investigated.
- Properties of a WCCo composite sintered by the pps method
- Strony: 319-323
Tungsten carbide is known for its high-temperature melting point, high hardness, good thermal and electrical conductivity and chemical stability at high temperature. The high hardness of the carbide and the associated high wear resistance predispose it as a perfect material for the manufacture of cutting tools. However, the tools made of solid tungsten carbide simultaneously reveal high brittleness. It can be reduced by the addition of metallic phase distributed among WC grains. Since 1927, cobalt is successfully applied as an addition to the WC matrix. Because of their properties, WCCo composites are valued cutting tool materials. Nowadays over 50% of manufacturing cutting tools are made of WCCo composites.
Sintering of tungsten carbide is carried out with no external pressure applied at 1400 °C to 1500 °C, depending on the content of cobalt. Total time of the sintering process, without taking into account the processes of grinding and mixing, is several hours. The modern method which enables to carry out the process of sintering at lower temperatures and at significant shorter times (about 10 minutes) is the Pulse Plasma Sintering method (PPS), elaborated and developed at the Faculty of Materials Science and Engineering at the Warsaw University of Technology. The essence of this process involves the use of electric pulse to heat the compressed powder. Heating the powder with current pulses is due to release of Joule\'s heat in the places of contact of sintered powder. The pulses are obtained as a result of battery of capacitors battery with a capacity of 300 µF.
The paper presents the results of examinations of the microstructure and properties of WC-Co composites with 6 wt.% content of cobalt, produced by Pulse Plasma Sintering technique. The method enabled to obtain sinters showing density close to the theoretical one and hardness of 1930 ± 30 HV30 in a short time (approx. 10 minutes). The average grain size of WC in the sintered composite containing 6 wt.% Co is 0.42 microns and the largest share of grains occurs in the range of 0.4-0.6 microns.
- Sintered carbide composites enriched witch cubic boron nitride particles (cBN/WC-Co)
- Strony: 324-328
Cubic boron nitride (cBN) and cemented carbide (WC-Co) are commonly used as a cutting tools material for the sake of their high hardness and wear-resistance. In this work, a WC-Co composite consolidated with cBN particles was obtained. The cBN/WC-Co composite cannot be produced by using conventional sintering, which is conducted at temperatures between 1350 ºC and 1500 ºC, since cBN undergoes the transformation into hBN within this temperature range. With the PPS (Pulse Plasma Sintering) method, dense sinters consisted of the WC-6 vol. % Co matrix and 30 vol. % cBN particles with the sizes of 4-8 µm and 6-12 µm were obtained. The composites were sintered for 5 min at temperatures of 1100, 1150 and 1200 °C under a pressure of 100 MPa. The scanning electron microscope observations of the composite microstructure and the X-ray analysis revealed no phase transformation from metastable cBN into stable hBN. Microstructural porosity was observed as non-sintered WC grains at the sintering temperature of 1100 °C. Densities of the 1150 °C and 1200 °C sinters approached the theoretical density (TD) whereas the 1100 °C sinters density reached about 98% of TD.
- New composite material – diamond in a sintered carbide matrix intended for machining wood-based materials
- Strony: 329-332
For the sake of significantly higher wear resistance of sintered diamond than cemented carbides, wood machining tools made from cemented carbides are increasingly replaced with sintered diamond tools (PCD –Polycrystalline Diamond). High prices of PCD blade tools are brought about the high cost of diamond sintering. Also the fracture toughness of PCD blades is smaller than the cemented carbides.
This paper presents the results of examination of the composites containing 30 vol.% of diamond distributed in the WC-6 wt.% Co matrix, that were sintered by using the PPS method (Pulse Plasma Sintering). The sintering process was conducted in the conditions of thermodynamic instability of diamond. Cemented carbides are commonly sintered at 1400-1500 °C, depending on the cobalt content. Diamond is unstable at the sintering temperatures of cemented carbides and therefore transforms into graphite. PPS is the sintering method in which a sintered material is heated by periodically repeated high-current electric pulses generated by discharging a capacitor battery. The sintering process was conducted at a temperature of 1100 °C for 5 min. Due to specific sintering conditions during the PPS process, dense sinters of 1.8 mm in height and 20 mm in diameter, showing the strong bonding between diamond particles and the sintered carbide matrix, were obtained. The X-Ray analysis and SEM observations revealed no diamond ito graphite transformation. Hardness and thermal conductivity of the WCCo /diamond composites were higher than measured for the cemented carbide WC6Co.
- Cu-diamond composites with high thermal conductivity obtained by the PPS method
- Strony: 333-337
One of the main challenges in fabrication of copper/diamond composites, apart from graphitization at high temperatures, is a lack of wettability of diamond by copper and the absence of chemical reactions, providing the formation of Cu-carbon compounds needed for a good joint between the diamond and the copper. Moreover, the large mismatch in the values of thermal expansion coefficients of these materials is a reason for high thermal stresses during sintering that are disadvantageous to the cohesion of the diamond/copper interface. The thermal stresses promote voids formation, which reduces the thermal conductivity of the composite. In metal-diamond composites, the quality of the interface has a crucial effect on their thermal conductivity and mechanical properties. Strong and “clean” bond of the diamond to the matrix should assure high strength and minimum thermal resistance of the interface. In the present work, an attempt has been made to fabricate the copper matrix composite with 50 vol.% of diamond by using the Pulse Plasma Sintering (PPS) technique in the conditions of thermodynamical instability of diamond. The composites have been fabricated at 900 °C under 60 MPa. The phase composition, density and microstructure studies showed a relative density of 99,8% and the absence of graphite. The microstructure examinations revealed uniform distribution of diamond particles in the copper matrix. Good bonding of the diamond to the matrix have been assured by a layer of chromium carbide at the interface.
- The use of glass-ceramic glazes from the MgO-Al2O3-SiO2 system in industrial conditions
- Strony: 338-341
Glass-ceramic glazes with improved mechanical properties prepared and obtained in a laboratory were compared with the glazes fired in industrial conditions. The tested glazes for floor tiles based on compositions located in the primary field of cordierite crystallization within the MgO-Al2O3-SiO2 system. Starting frits and glazes were examined with the use of DTA, XRD and SEM methods. Glazed tile surfaces were characterized with respect to microhardness and wear resistance (weight loss after 6000 rotates according to PN-EN ISO 10545-7 standard). The results obtained for the industrial and laboratory prepared glazes were very similar to each other, particularly in terms of high abrasion resistance. The studied glazes showed high microhardness in the range of 6–7.5 GPa, and increased wear resistance measured by a loss of weight below 100 mg/ 55 cm2.
- Surface modification of Ti-6Al-4V substrate in plasma conditions
- Strony: 342-347
Titanium alloys, e.g. Ti-6Al-4V, are widely used as biomaterials, mainly in bioengineering and medicine. Their structure and physicochemical parameters enable extensive applications in orthopaedics, implantology, traumatology and dentistry. Studies on improvement of the usage parameters of titanium alloys, such as tribological and corrosion-resistance, with no loose of biocompatibility are still in progress. The plasma assisted chemical vapour deposition (PA CVD) technique with its ion etching, nitrogenation, ion implantation and/or surface coating widens possibilities of the new biomaterials discovery. In this study, the results of surface modification of the Ti-6Al-4V alloy by plasma assisted micro-wave chemical vapour deposition will be presented. Selected parameters of individual processes were strictly controlled, and a sequence of the processes was changed in every case. The chemical composition, microstructure, structure in atomic scale and microhardeness of the Ti-6Al-4V alloy before and after plasmochemical modification were precisely investigated. It was demonstrated that in case of the surface modification of the Ti-6Al-4V alloy more beneficial is plasmochemical nitrogenation of its surface before the a-SiCNH layer obtaining. The results of this study undoubtedly show that the construction and physicochemical parameters of the tested materials strongly depend on the type of applied processes in a microwave reactor.
- Glass-ceramic materials for stomatological applications
- Strony: 348-354
An important issue in the dentistry is to produce materials both similar to natural tooth appearance and having high mechanical properties. Presently commercially available materials are used for reconstruction of tooth crowns, both as individual units and complex systems (bridges restorations). For this type of reconstruction the material of glass-ceramic system Li2O-SiO2 base is used, where Li2Si2O5( lithium disilicate) in an amount of up to 70% is the primary crystalline phase. IPS e. max CAD is currently in use as the material for such reconstructions. It has the color of natural teeth: it is translucent and its bending strength is 360-400 MPa. The aim of our research is to produce translucent glass-ceramic also based on the crystallization of Li2Si2O5 but with improved mechanical strength when compared to commercially available materials. Such materials with high mechanical properties are very useful for the preparation of permanent implants in the form of bridges consisting of two and more units. Our research was directed to modify the chemical composition of patent glass in such a way that the new material would also contain Li2Si2O5 (lithium disilicate) as the primary crystalline phase, but in the same time improving the mechanical, thermal and chemical properties of the remaining glassy phase in the material. For this purpose, the dopes such as CaO, Al2O3 and ZrO2 were introduced to the chemical composition in amounts bigger than for IPS e. max CAD. In the case of glass-crystalline materials enriched in CaO or Al2O3 there was no significant change of properties compared with IPS e. max CAD, while a marked improvement in the strength parameters was obtained for ZrO2-rich materials (flexural strength about 470 MPa). In addition, the material enriched in ZrO2 was characterized with a very good microstructure and translucency required for this type of application.
- Composite materials based on low-porous calcium phosphate granules for medical applications
- Strony: 355-359
Composite bone substitutes based on low-porous calcium phosphate granules were obtained by mixing HA, TCP or BCP granules with binders on the basis of calcium sulfate hemihydrate (CSH) and hydroxyapatite. As liquid phases distilled water or the 1% chitosan solution in 0.3% acetic acid were applied. Combining cement type self-setting binders and calcium phosphate granules resulted in new composites with good surgical handiness, excellent biocompatibility and appropriate mechanical properties.
- Rational management of combustion process by-products in sintered ceramic materials
- Strony: 360-363
An environmental protection subject is still present and important in every area of human life. The paper presents the concept of an effective method to carry slag, originating from the incineration of solid waste, containing finely powdered glass cullet, in a functional glass-crystalline material, and selected properties of the resultant product were determined. For this project, container glass cullet and slag from incineration of solid waste of the Upper Silesian region were selected. The raw materials were ground, and then batches prepared. In order to prepare the samples, the mixture of powders was subjected to uniaxial compression, and then cylindrical green compacts were thermally treated in an electric furnace. The obtained sinters were evaluated microscopically. X-ray studies were performed, and apparent density, open porosity and water absorption were determined.
- Crystallization of silicate-phosphate glasses from the NaCaPO4-SiO2 system
- Strony: 364-366
The paper presents results of research on the crystallization of silicate-phosphate glasses from the NaCaPO4-SiO2 system. On the basis of thermal studies (DTA), it has been shown that crystallization of these glasses was a multistep process. The analysis of DTA curves, enabled to determine the characteristic temperatures for the glassy phase. On this basis, glass annealing parameters in a gradient furnace were established. Structural studies (MIR, XRD) of the output glasses and the obtained glass-crystalline materials enable to describe the crystallization process.
- The mechanism of ballistic ceramics fragmentation
- Strony: 367-370
This paper describes an acoustical mechanism of ballistic ceramics fragmentation under the projectile impact. Presented considerations take into account the generation of acoustic waves in a body of ceramic armor by a penetrating projectile. In presented approach, the role of periodic stresses in the armor ceramics is recognized as crucial for their failure. Starting from the dynamic Hertz problem, the ceramic armor effectiveness is discussed in terms of acoustical parameters of ceramic materials. We conclude that the acoustical impedance and its geometrical distribution are essential for the ceramic armor protective properties. Final conclusion suggests a way to improve the ballistic effectiveness of ceramics and any armor as well.
- Preparation of black glasses based on ladder-like silsesquioxanes
- Strony: 371-373
The paper presents a method for obtaining homogenous black glasses based on ladder-like silsesquioxanes. The structural research (XRD, MIR) of xerogels obtained by using a sol-gel method evidenced their ladder-like structure. In order to obtain black glasses, solid materials of dried xerogels were burned in an inert atmosphere at 800°C: the temperature was selected basing on DTA studies. Structural studies (MIR, XRD) after the burning shown that the resultant black glasses were fully amorphous.
- Usage of volcanic rocks in the building industry
- Strony: 374-377
Volcanic rock is an excellent resource that does not require significant modification. Used for the production of chimney blocks, it makes them to have good insulating characteristics and high resistance to acids. The study investigated the phase composition and microstructure of both natural volcanic rock derived from the still active volcano of Stromboli and a chimney block, which contained in its composition a volcanic rock that originated from Ireland. Phase compositions of the volcanic rock and the building material used in the chimney systems were different.
- Deposits between a shank and a lining as the secondary corrosive menace of industrial ferroconcrete chimneys
- Strony: 378-386
In typical industrial ferroconcrete chimneys, there is the space between a shank and a lining assigned for the thermal insulation. In the paper, the assessment of menaces coming from corrosion products accumulated within that space to the ferroconcrete chimneys is shown. The studies of materials taken from many chimneys indicated that the thick layer of deposits has been formed in the shank/lining space, displaying very aggressive chemical behaviour relating to both the shank concrete, ceramics and pointing material for lining. The results of the study concern effects of the deposit on a degree of secondary contamination and destruction of materials in the operated chimneys.
- Studies of the kinetics of drug release from bioceramic implants
- Strony: 387-392
In this work, in vitro stability of cement type ceramic biomaterials was estimated at a temperature of 37 °C using a phosphate buffer of pH 7.4 or SBF (Simulated Body Fluid). The first type of materials consisted of α-TCP mixed with a 1% chitosan solution in 0.5% acetic acid. The second group of potential drug carriers was obtained on the basis of MgHAp-gypsum and MgCHAp-gypsum, using water as a setting liquid. The profile and kinetics of in vitro drugs release (doxycycline-DOX, cefuroxim-CFU and pentoxifylline-PTX) were investigated for α-TCP with the 1% chitosan solution, because this material was the most stable in the experimental conditions. The drugs were distributed homogeneously in the bioceramic implants and released from their whole volume. The aim of the experiment was to determine the mechanism of drugs release from the carriers, applying Korsenmeyer-Peppas or Higuchi model. The results showed that the release profiles depended on the drug used. The highest release rate was observed for PTX and the lowest for DOX. The values of diffusion exponent n, being a factor determining the mechanism of drug release, for PTX and CFU were equal to 0.5, which proved that these medicaments were released according to the Fickian diffusion regime. In the case of DOX, the value of this exponent was equal to 0.7, indicating that the mechanism of DOX release was anomalous.
- Characterization of Hydroxysodalite Powders Obtained by the Microwave Hydrothermal Method
- Strony: 393-399
Hydroxysodalites having the general formula of Na6+x [AlSiO4]6 (OH)x nH2O (where 0 ≤ x ≤ 2, 0 < n ≤ 8) are derivatives of sodalites, and belong to the group of clathrasils or zeolites. In terms of crystallographic structure, hydroxysodalites are interesting from the point of view of their application as a material for membranes used in processes of small molecule separation, eg. ammonia or water from gaseous or liquid mixtures. The aim of the work was to obtain fine powders of hydroxysodalite by the microwave hydrothermal method. The powders were synthesized from aqueous solutions having the composition of 1 g Si : 0,26 g Al : 16,4 g Na : 128,9 g H2O made on the basis of soda-water-glass, sodium aluminate, sodium hydroxide and redistilled water, using a Teflon reactor and a microwave dryer (as a source of microwaves). The power of microwaves within the range of 70-200 W and the times of 30, 45, and 60 minutes were applied. The obtained series of powders were characterized by the XRD, IR and SEM methods. The possibility of obtaining hydroxysodalite powder with the size of agglomerates reaching approx. 2 μm (SEM) and the size of crystallites of approx. 50 nm (XRD), using 150-W microwave power for 60 min was shown. The results of the work will be used to develop a greater-scale production of hydroxysodalite powders for microporous membrane layers on ceramic supports designed for use in processes of alcohol dehydration, e.g. propan-1-ol or ethanol, and manufactured by the seeding and secondary growth hydrothermal method.
- Glass-ceramics as a modern material
- Strony: 400-404
An effective way to strengthen glass runs through the directed crystallization which yields glass-ceramics more durable in terms of mechanical, chemical and thermal properties than the original glass. The process of crystallization is composed of an appropriate heat treatment at temperatures between the glass transition and liquidus temperatures typically ranging from about 500 °C to about 1000 °C. In this paper, studies were directed to obtain nearly transparent (nano-glass-ceramics), translucent and opaque glass-ceramic materials in the Li2O-Al2O3-SiO2 system. This creates a wide range of possibilities for application of the products, starting from the construction industry and households, through the use in reconstructive cosmetic dentistry to various thermally and chemically resistant items of technical equipment. Chemical compositions of glasses have been developed with a varying output ratio of primary Li2O/Al2O3 ingredients and a different content of silica. Lenses were subjected to DTA thermal studies, and on this basis the parameters of crystallization were determined. After the directed crystallization, the resultant products were characterized in terms of phase composition and microstructure. It was found that two-Li2Si2O5 lithium silicate and lithium aluminosilicates are the main phases that crystallize in the material. Temperature ranges required to obtain the transparent, translucent and opaque glass-ceramic materials were determined. Mechanical strength and thermal expansion coefficients of these materials were measured.
- Waste materials as a source of nucleating agents of crystallization for kinescope glass cullet
- Strony: 405-410
The paper presents the characteristics of waste materials used as nucleating agents for crystallization of kinescope glass cullet. Glass batches containing kinescope glass cullet added with different kind of raw materials such as calsiglass, GGBF slag and FBC fly ash were prepared. Types of phase transformations that occur during heating each glass were determined by the DTA method. Glass-ceramics materials were prepared by thermal treatment of glasses at the crystallization temperature. Furthermore a series of sintered glass-ceramics was obtained from the batches containing the kinescope glass cullet mixed with Gres Porcellanato and kaolin clay, respectively. Crystalline phases were identified by XRD and SEM methods. The obtained results showed the influence of chemical composition of raw materials on physico-chemical changes occurring upon heating of glass.
- Manufacturing of glass-ceramics on the basis of perlite ore and expanded perlite wastes
- Strony: 411-416
Expanded perlite belongs to raw materials that can be used to obtain new materials for potential broad applications in the building materials branch. Perlite dust with a particle size of < 0,1 mm is produced during expanding perlite ore. It has no extensive applications and becomes an arduous waste material. The aim of this work was to develop new products basing on perlite ore and waste perlite dust, showing properties of light weight glass-ceramics, that would be useful for the building industry. The evolved products and technologies significantly broaden the range and possibilities of perlite ore applications in the building industry, and contribute to the protection of natural environment through the perlite waste management.
- Nano-structured coatings on glass manufactured by pyrolysis
- Strony: 417-422
The bases of the hot coating process of glass involving pyrolysis are described in the paper, and the results of the usage of this method for the development of industrial technology of manufacturing of nanostructured thin oxide coatings on glass package products directly in the glass formation line are shown. Fine dispersions of coordination complexes in the form of metal acetylacetones were used as precursors of metal oxide coatings in the developed technology. The pyrolytic decomposition of those compounds appears on a hot glass surface giving a durable joint between the coating and the glass substrate as a result of chemical bonding within the interface. The manufactured coatings were resistant to the action of atmospheric agents, and they improved the scratch resistance of products due to decreased friction. The metal oxide coatings allows glass products to obtain anti-solar properties, desired colour, decorative attributes, and increased chemical and mechanical surface resistance.
- Microstructure and electrical properties of composite materials in the interconnect/cathode/electrolyte system for protonic solid oxide fuel cell (SOFC-H+) applications
- Strony: 423-432
In order to develop fabrication technology of metallic interconnects based on stainless ferritic steels for protonic solid oxide fuel cells (SOFC-H+) the long-term compatibility of the interconnect/cathode/electrolyte system must be studied. Crofer 22 APU was used as the metallic interconnect, onto which a La0.6Sr0.4Co0.8Fe0.2O3-d (LSCF48) cathode layer was screen-printed. In turn, another layer, consisting of a protonic solid electrolyte, was screen-printed on the LSCF48 cathode layer. In this research, barium cerate and strontium cerate based compounds doped with Nd, Sm, Dy, Yb and Y were used as the solid electrolytes. Only the Crofer 22 APU/LSCF48/BaCe(1-x)MxO3-x/2 (where: M = Nd, Sm i Dy) composites were found to be chemically stable after oxidation at 1073 K for 150 hrs in air. The analysis of the interaction between the oxide layers and the steel substrate was carried out using scanning electron microscopy combined with energy dispersion spectroscopy. The influence of solid electrolyte doping on the physicochemical properties of the system was discussed on the basis of electrical resistance measurements of the studied samples using impedance spectroscopy. From the results, the applicability of the composites for the construction of a SOFC-H+ fuel cell was determined.
- Strony: 433-434
List of Contents
Volume 64, Issue 4
- Phosphate ceramics for radioactive waste immobilization – a review
- Strony: 438-442
Nuclear industry creates same quantities of wastes polluted with radionuclids. The wastes require to be neutralized by immobilization of the included radio and toxic elements, which allows to deposit them safely in geological repositories. Nowadays harmful elements are secured by closing them in ceramic structures that are proof for external factors. To immobilize nuclear waste in the UE and in the world, borosilicate glasses of SiO2–B2O3–Al2O3–Na2O type are used. They can be used only in a limited way to immobilize wastes containing salts (e.g., chlorides, sulphates) and metallic elements. Such the wastes are trendy closed in a phosphate glass structure which is build of iron and alumina phosphates as network formers and alkalis as network modifiers. There were also investigated the methods of incorporation of radioactive elements into the crystal structure of minerals by sintering. An idea also appeared to immobilize nuclear wastes in glass–ceramic materials in that the elements of limited solubility in glass are closed in crystal phases that are placed in a glassy matrix. All of those processes are often called as the ceramization of radioactive wastes. In the work, a review of worldwide used methods of radioactive waste immobilization with phosphate ceramics is done.
- Magnetoelectric properties of 0.5Bi0.95Dy0.05FeO3-0.5Pb(Fe2/3W1/3)O3 solid solution
- Strony: 443-446
Pb-based complex perovskites doped with Fe3+, like Pb(Fe2/3W1/3)O3 (PFW), were found to be interesting because of their unique relaxor and magnetoelectric behaviours. PFW is a ferroelectric material with the ferroelectric Curie temperature, TC, being between 150 K and 200 K, and at the same time it is an antiferromagnetic material with the magnetic Neel temperature of about 400 K. BiFeO3 is a well known perovskite compound which exhibits ferroelectric (TC = 1110 K) and antiferromagnetic (TN = 610 K) ordering simultaneously. A polycrystalline sample of 0.5Bi0.95Dy0.05FeO3–0.5Pb(Fe2/3W1/3)O3 was synthesized by using the standard sintering procedure. Magnetization vs. magnetic field (at 4.2 K) curves were determined. The magnetoelectric properties of the sample were obtained.
- Piezoelectric transformer with magnetic feedback
- Strony: 447-451
Dense lead lantanium zirconate titanate (PLZT) ceramics is typically used for the fabrication of high power piezoelectric devices. The replacement of a small amount of lanthanium ions with iron(III) ones into the PLZT structure (PLFZT) leads to a multiferroic material with both piezoelectric and magnetic properties. Powders of Pb0.91La0.09(Zr0.65Ti0.35)0.9775O3 and Pb0.91(La0.5Fe0.5)0.09(Zr0.65Ti0.35)0.9775O3 were prepared by direct solid state reaction, and the phase composition, microstructure, dielectric permittivity and dielectric loss were determined for the sintered materials. The PLFZT material was used to construct a piezoelectric transformer with magnetic feedback, which converted an electrical a.c. input voltage into ultrasonic vibrations, and reconverted them back to an output as a.c. voltage proportionally to the magnetic field intensity. In despite of relatively low electromagnetic feedback, a substantial shift of voltage frequency and a voltage drop were observed in the magnetic field.
- Synthesis and properties of a sulfate-aluminate sinter for the manufacturing of expansive cements
- Strony: 452-456
The expansive binders were produced by mixing Portland cement with an expansive additive manufactured by sintering from calcium aluminate-sulfate (yeelimite), calcium sulfate (anhydrite) and lime. The studies were focused on the synthesis of this aluminate–sulphate–lime additive, determining the temperature of burning process as a parameter controlling the relative activity of components, and subsequently on the mixture proportions to ensure the hydration process, resulting in non-shrinkage or expansion effects. In the experiments, the proportions of expansive mixture and cementitious materials were varied. The investigations with aim to find the relationship between the volume changes and the composition of initial mixtures in cement pastes and mortars (with sand) were also carried out. The expansion was evaluated by using both the standard Graf-Kaufman apparatus and the equipment allowing continuous measurements on the samples placed in special moulds (restricted expansion). The compressive strength development was determined on standard mortars. The kinetics of hydration and phase composition of the products were characterized. In the environment of hydrating cement, the expansive additive transforms into ettringite at “right time” to give the expansion, when the plastic material transforms to a more rigid matter but before the ultimate hardening takes place.
- Whether sodium, potassium and calcium aluminosilicates can compose a refractory material?
- Strony: 457-462
The article discusses changes in the phase composition of aluminosilicate materials being a result of impact of the alkaline environment. Studying the microstructure (SEM/EDS) of the materials after hot working in a thermal device allowed their new phase composition to be determined. As a result of the potassium and calcium attack on the andalusite and mullite refractory materials, potassium and calcium aluminosilicates from the K2O-Al2O3-SiO2 and CaO-Al2O3-SiO2 systems came into being in a form of K[AlSi2O6] and K[AlSiO4], and Ca2Al[SiAlO7], respectively. Theoretical calculations revealed a synthesis of new compounds accompanied by volume changes. Nevertheless, the microscopic observations (SEM) showed no effects of disintegration of the refractory material.
- Hydraulic properties of selected compounds from the CaO-ZrO2-Al2O3 system
- Strony: 463-467
The article compares hydraulic properties of calcium monoaluminate CaAl2O4 (CA) and calcium-zirconium aluminate Ca7Al6ZrO18 (C7A3Z). The microcalorimetric investigation has shown that the C7A3Z phase reacts with water very quickly, especially in the first 2 hours after the beginning of the experiment. Hydration of calcium-zirconium aluminate proceeds with the formation of high refractory calcium zirconate with the melting point of 2345 ˚C). The monoaluminate CaAl2O4 reacts with water definitely slower. The unhydrated Ca7Al6ZrO18 and CaAl2O4 phases and calcium zirconate CaZrO3 were exclusively found by XRD. Microscopic observations (SEM) indicated different morphologies of the hydrates.
- Manufacturing and properties of BaBi2Nb2O9 of Aurivillius structure
- Strony: 468-472
BaBi2Nb2O9 (BBN) is a ferroelectric material which possesses many interesting properties, that are a consequence of not only its chemical composition, but also specific structure. Multilayer perovskite structures of Aurivilius type, to that BBN belongs, overweight the monolayer ones with better anisotropy, higher values of mechanical elastic coefficients and higher strength. Ceramics powders obtained in our experiment were produced taking advantage from the sol-gel method, and were densified with two methods, namely conventional pressureless sintering and hot pressing. Our main point was to make comparative analysis of chosen sintering routes on key BBN ceramics properties such as density, stoichiometry and microstructure and consequent dielectric properties to final application connected conclusions.
- Sintered ceramic materials produced in the recycling process of casting molds from precision castings
- Strony: 473-477
The present work relates to investigations of the possibility to produce sintered materials in the recycling process of ceramic moulds coming from precise casts for air engines elements. On the basis of conducted investigations of powders before and after milling, and tests of their pressing and sintering it has been affirmed that the recycling process of the spent ceramic moulds is possible. It was applied to presses The powders derived from the ground moulds with and with no additions of modifiers were studied. Both types of the powders gave good results when processed by pressing and sintering. Surfaces of compacts and sintered bodies were smooth, and did not undergo foliation, and also they did not crumble.
- Preparation, properties and photocatalytic activity of thin SiO2-TiO2 doped with vanadium
- Strony: 478-484
In our investigation, V-doped SiO2/TiO2 thin films were prepared on glass substrates by the dip coating sol-gel technique. The chemical composition of the films was studied by photoelectron spectroscopy (XPS). Transmittances of the samples were characterized using a UV-VIS spectrophotometer. Subsequently the band-gap energy (Eg) was estimated for the films. The photocatalytic effect was investigated for the obtained samples. Gels obtained from sols were characterized by FTIR spectroscopy. It was found that the vanadium additive decreases the optical band gap of SiO2/TiO2 films.
- Glass-ceramic materials with the use of CRT glass cullet
- Strony: 485-489
The paper presents the results of a study focused on the influence of recycling materials on the nature of phase transformations, that take place during thermal treatment of glasses containing CRT cullet, calsiglass, calumite and spodumen. The type of the phase transformation was determined by DTA. To produce materials such as glass–ceramics, the basic glasses had been heat-treated at temperatures of maximum of crystallization peaks. The type of crystalline phases was determined by XRD and SEM. The obtained results enabled to establish the impact of chemical compositions of the waste materials on physicochemical changes occurring during the glass thermal treatment, and also to improve the melting process. Moreover, the effects of the amount of recycling materials on physicochemical properties of glass-ceramics obtained by glass directed crystallization were established.
- Thermoelectric properties of Mg2Si manufactured by the SPS technique
- Strony: 490-493
The object of this study was to obtain single-phase polycrystalline Mg2Si by a direct reaction between silicon and magnesium using the spark plasma sintering (SPS) technique. Both synthesis and densification of the material took place in graphite dies in an SPS apparatus. To determine the phase composition of the produced samples, X-ray diffraction investigations were performed. The microstructure and chemical composition of studied materials were analyzed using a scanning electron microscope (SEM) equipped with an EDX detector. Homogeneity of thermoelectric properties of the samples was investigated using a scanning thermoelectric microprobe (STM). The carrier concentration was measured by the Hall method. In addition, thermoelectric properties, i.e. electrical conductivity, Seebeck coefficient and thermal conductivity at the temperatures ranging from 300-650 K, were measured. The obtained samples of Mg2Si showed high homogeneity of both phase composition and thermoelectric properties.
- Studies on crystallisation of amorphous layers of Al2O3 obtained by MOCVD
- Strony: 494-499
Al2O3 layers were synthesised at temperatures of 700-1000°C in the air atmosphere by the MOCVD method using aluminium acetyloacetonate as the precursor. Quartz glass tubes and plates were used as substrates. In the temperature range of 700-850°C, the presence of homogeneous nucleation process wasn’t observed in spite of the use of high reagent concentrations. The growth rate of the layers significantly increased in that temperature range. At about 1000°C, the process of homogeneous nucleation occurred during the layer synthesis. Al2O3 nanocrystallites were observed by scanning electron microscopy for the samples obtained at 700°C. An increase of temperature increased the amount and size of the Al2O3 nanocrystallites. The X-ray analysis of the layers synthesized at 800°C indicated the presence of low temperature Al2O3 phases, and in the case of the layers synthesized at 950°C it showed the appearance of α-Al2O3 phase. An increase of the synthesis temperature also caused the increased roughness of deposited layers. Transparency tests showed that the crystallisation process decreased transparency of the resultant layers.
- Effect of Tm2O3 doping on microstructure and optical properties of Tm:YAG ceramics
- Strony: 500-505
The aim of the work was to obtain transparent thulium doped yttrium aluminium garnet ceramics by reaction sintering using commercial powders and Y2O3 obtained in ITME. Sintered samples were subjected to the microstructure and optical analysis, including transmission and emission spectra measurements as a function of Tm+3 doping level. The optimal set of powders contained Y2O3 obtained by the AHC precipitation (ITME) and Al2O3 TM-DR prepared by TAIMEI. Only in case of this combination, no unreacted areas were observed. 2 at.% Tm:YAG ceramics obtained this way had the highest transmission. For wavelength 1 µm it was 79%. For comparison, the transmission of ceramics prepared from commercial Y2O3 was only 70%. Emission spectra of the obtained ceramics were similar to that of Tm:YAG single crystal.
- The manufacturing of MgAl2O4 and Co:MgAl2O4 nanopowders by the two-stage precipitation method
- Strony: 506-511
A novel precipitation procedure was applied to manufacture MgAl2O4 and Co:MgAl2O4 precursors which enable avoiding the formation of rod-like particles. The synthesis was divided into two steps. The first one included co-precipitation of Mg6Al2(CO3)(OH)16·4H2O followed by ageing, and the second one comprised precipitation of ammonium dawsonite into the hydrotalcite suspension. MgAl2O4 and Co:MgAl2O4 precursors prepared in that manner were calcined for 2 h at 1050°C in air. The powders consolidated during free-sintering in vacuum resulted in translucent ceramics with density above 99.9%.
- Mechanochemistry of phosphate glasses
- Strony: 512-518
The effect of mechanical activation on the structure and thermal transformations of phosphate glasses from the P2O5–Al2O3–Na2O–Fe2O3 system has been studied. Such glasses are used in nuclear technology for immobilization of radioactive wastes. The glasses were activated by grinding in a planetary mill. The mechanical activation causes a decrease of both the Tg temperature and the glass crystallization temperature. The type of crystalline phases formed and the quantitative proportions between them change as a result. The mechanical activation influenced the structure of the studied glasses creating a tendency to shift band maxima towards lower wave numbers.
- Infrared mapping in the study of fireproof silicaorganic composites
- Strony: 519-523
Infrared mapping in the study of fireproof silicaorganic composites
The article presents the results of the use of infrared mapping for studies of fire resistance of silicaorganic composites used as building barriers. For this purpose, a test stand consisting of a thermal imaging camera (NEC Thermo Gear G100) and a furnace equipped with a removable burners fueled with propane-butane was designed. Test samples of two sizes, i.e. 20 cm ´ 30 cm and 10 cm ´ 10 cm for the point temperature of < 180 ºC and the average temperature of < 140 ºC can be tested for fireproof (EI) properties in this device. A composite was prepared, basing on water glass R-145 and a mixture of polymers which fulfils requirements specified by the fireproof classification (EI). Optimal conditions for measuring fire resistance of thin building barriers were determined. The research carried out for transparent gels showed that the best results are obtained when the thickness of fireproof gel is 2 mm. It was also found that the analysis of the results derived from the infrared camera can be used to evaluate the extent of operation of two mechanisms for thermal insulation, i.e. heat absorption during evaporation of the gel and formation of the insulating layer.
- Possibilities of increasing mechanical resistance of glass containers
- Strony: 524-529
For many years, there has been scientific and industrial research into how to increase mechanical resistance of glass containers. One of the very important factors, which influenced an improvement in mechanical resistance of glass packaging, was the development of dry and hot coating methods. The aim of this work is to show the research results concerning the mechanical resistance of glass containers modified by using various treatment methods. We will show what a glass container surface looks like after the forming process and after hot end coating treatment. We will do this by using nanoparticles of aluminium and tin compounds at a temperature around softening point. In our work, the various results of the mechanical resistance of glass containers were compared. These results may act as guidelines for determination of future factors in glass container production.
- Synthesis, structure and dielectric properties of Bi1−xNdxFeO3
- Strony: 530-535
In the present research, Bi1−xNdxFeO3 ceramics was synthesized by the standard solid-state reaction method from the mixture of oxides, followed by free sintering at temperature T = 1000°C. Investigation of crystal structure, dielectric properties of the diamagnetically substituted Bi1−xNdxFeO3 samples has been carried out. Stoichiometric mixture of the powders was thermally analysed with Netzsch STA-409 system so parameters of the thermal treatment were determined. Bi1−xNdxFeO3 ceramics was studied in terms of its chemical composition (EDS), crystalline structure (XRD), microstructure (SEM) and dielectric properties over a range of frequency (20 Hz – 1 MHz) at room temperature. Dielectric properties has been studied by impedance spectroscopy. It was found that chemical composition of the ceramic samples corresponds well to the initial stoichiometry of the ceramic powders. It was found that an increase in Nd content (x) caused a decrease in the average size of the ceramic grains. Crystalline structure of Bi1−xNdxFeO3 ceramics for x ≤ 0.2 has been described by rhombohedral symmetry whereas for x ≥ 0.3 by orthorhombic symmetry.
- Influence of binder type on rheological properties of slurries for porous ceramic materials
- Strony: 536-540
In the present study, porous ceramic materials were prepared by the polymeric sponge method. Polyurethane sponge (Kureta) was used as a substrate. Porous ceramic materials were obtained on the basis of aluminium oxide (α-Al2O3, Almatis), aqueous suspensions prepared with binders of two types: polyvinyl alcohol and a dispersion based on methacrylic acid esters and styrene. The paper presents the results of studies on the rheological properties of the ceramic slurries and the results of strength tests of the resultant ceramic materials.
- Crystal structure and magnetoelectric properties of 0,7Bi0,95Dy0,05FeO3–0,3Pb(Fe1/2Nb1/2)O3 And 0,7Bi0,95Dy0,05FeO3–0,3Pb(Fe2/3W1/3)O3 solid solutions
- Strony: 541-548
Multiferroics are new materials that exhibit at least two types of ordering in one phase for example ferroelectric and ferromagnetic. In the last couple of years, multiferroics become a subject of many theoretical and practical studies because of their unusual properties. In the present work, two kinds of solid solutions 0,7Bi0,95Dy0,05FeO3–0,3Pb(Fe1/2Nb1/2)O3 and 0,7Bi0,95Dy0,05FeO3–0,3Pb(Fe2/3W1/3)O3 were synthesized.
According to X-ray studies, both materials crystallized in the rhombohedral R3c structure. Mössbauer spectroscopy measurements confi rmed a random distribution of Bi3+ and Pb3+ cations at their sublattice. A gradual reduction of iron magnetic moments with increasing Pb content in the second coordination sphere was observed. Magnetoelectric voltage coeffi cient was also examined and the ME parameter was almost 4 times higher for solid solutions with Pb(Fe1/2Nb1/2)O3 than Pb(Fe2/3W1/3)O3.Pb(Fe1/2Nb1/2)O3.
- Effects of porosity characteristics on freeze-thaw and freeze-deicing salt resistances of scc
- Strony: 549-557
The influence of a new generation of superplasticizers (SPs), viscosity modifying (VMA) and anti-foaming (AFA) admixtures on the internal frost resistance, frost resistance in the presence of deicing salts, durability coefficient (DF) and parameters of air-voids of both hardened non air-entrained and air-entrained self-compacting concretes (SCC) is investigated. The research results showed that SCC is frost resistant despite the fact that the parameters of air-voids were different than recommended by the standard. Moreover, the type of SP significantly affects the frost-resistance of SCC.
- The influence of methylcellulose viscosity on properties of gypsum plaster mortars
- Strony: 558-562
Methylcellulose is a very important component of mortars though its content is low and generally do not exceeds tenth part of percent of dry material mass. Application of the admixture allows obtaining required properties of building mortars. In the paper, the results of laboratory experiments concerning influence of hydroxypropylmethylcellulose viscosity on selected physical properties of gypsum plaster mortars and microstructure of hardened gypsum mortars are presented. Mortars with metylcellulose admixture have increased ability to retain water. However, they have bigger water requirement/demand for obtaining the same consistence. The methylcellulose addition improves adhesion, water entrainment and positively influences non standard properties as overlaying and treatment, assuring proper quality of mortar. SEM observations of hardened gypsum mortar indicate the influence of methylcellulose addition on the microstructure. Gypsum mortars with no methylcellulose addition contain big and good shaped gypsum crystals. The microstructure of mortars with the methylcellulose addition is composed of smaller but properly formed gypsum crystals, so called swallow-tails, and membranes spreading in mortar pores made from methylcellulose. The methylcellulose admixture retards the binders hydration process and thereby influences the size of created crystals.
- Rheology of gels used in fireproof barriers
- Strony: 563-566
Rheology is the science dealing with deformation and flow of materials. One of its tasks is to measure viscosity of fluids for determining the influence of temperature and time on the course of gelation of the suspension. The basic aim of this study was to examine the effect of temperature on the rate and way of gelation of a silicaorganic mixture based on sodium water glass with the addition of polymer. The influence of other modifiers, such as carbon dioxide, on properties of the tested suspension was also examined. Aging tests, conducted at different intervals, were designed to check the stability of the gel. These measurements provided information on the rheological nature of silicaorganic suspensions. The study was conducted by using a Brookfield viscometer, model DV-III.
- The influence of calcium carbonate content on colour of fired red clays
- Strony: 567-571
In this paper, the influence of calcium carbonate content on colour of fired red clays from Patoka, Kozów and Pałęgi deposits was investigated. Calcium oxide arising during the firing process reacts with clays. The degree of this reaction has the influence on the formation of efflorescences on a body surface after soaking in water. The measurements of colour of the surface, using a Konica-Minolta Spectrophotometer CM-700d, allow determining reactivity of calcium oxide with clays during sintering in the temperature range between 900°C and 1150°C.
- Thermal conductivity of polycrystalline AlN
- Strony: 572-576
Thermal conductivity of modified AlN polycrystals is reported. The AlN polycrsytals has been prepared from commercially available aluminium nitride powder (H.C. Starck). A Laser Flesh Analyzer LFA 427 was used to evaluate thermal diffusivity of the materials. Pressureless sintering and hot pressing were used for obtaining dense polycrystals. Aluminium nitride samples with different contents of yttrium oxide and carbon nanotubes were prepared. The influence of thermal treatment of the samples on their thermal conductivity was determined. The results were combined with SEM and EDS examinations of the microstructure. The research was conducted within a project no. POIG.01.01.02-00-97/09-01 “New constructional materials with the enhanced thermal conductivity”
- Chemical stability of BaCe0,85Y0,15O3-δ + Ce0,85Y0,15O2-δ electrolyte composites for use in a dual-cell concept
- Strony: 577-583
The aim of this work is to determine the chemical stability of BaCe0.85Y0.15O3-δ and Ce0.85Y0.15O2-δ electrolyte materials in the form of powders and bulk samples. The samples underwent ageing for 600 hrs at both room temperature and 873 K in a CO2/H2O gas mixture. To determine the physicochemical processes that took place during the powder and bulk sample ageing process in the above-mentioned conditions, differential thermal analysis and thermogravimetry were used. However, the chemical composition analysis of the gases released from the studied samples during their heating was carried out by a mass spectrometer. Analysis of the phase and chemical composition, as well as the morphology of the samples was carried out via X-ray diffraction and scanning electron microscopy combined with energy dispersion spectroscopy. It was shown that at room temperature the composite powders and bulk samples adsorb small amounts of water vapour, however the absorption of CO2 was not determined. At 873 K it was determined that the afore-mentioned materials mainly adsorb CO2, while they are resistant against water vapour. The ratio of CO2 to the amount of Ba in the samples is dependent on the type of studied sample and the chemical composition of a given composite.
- Multicore fibre doped with Nd3+ ions for fibre sources of coherent radiation
- Strony: 584-588
In the paper, the phase–locking of the 19–core optical fibre doped with Nd3+ is presented. The influence of material and geometrical parameters of the active 19-core optical fibre and phase deviation on the beam quality factor of the laser beam in the far–field diffraction region has been analysed. The beam quality factor of the manufactured multicore fibre equals BQF = 0.71, when V = 2.4 and d = 18 µm. Based on a developed model of supermode generation in the multicore fibre laser, the impact of the coupling value between the cores on the difference in radiation phases between particular emitters during the development of the laser action was considered. As a result of the conducted analysis, a double-clad 19-core optical fibre doped with neodymium ions has been designed and manufactured, and its luminescence spectra and far field diffraction pattern have been measured.
- Strony: 589-592
- List of Content for Volume 64
- Strony: 593-603
- Spis treści tomu 64