Volume 66 (2014)
List of Contents
Volume 66, Issue 1
- NiAl and Ni3Al sinters produced by Pulse Plasma Sintering with the SHS reaction
- Strony: 4-9
The NiAl and Ni3Al matrix composites were prepared from mixtures of Ni and Al powders by using pulse plasma sintering (PPS) with participation of the self-propagation high-temperature synthesis (SHS). The sintering processes were conducted under 100 MPa for 5 min at temperatures of 1000 °C or 1100°C. The NiAl and Ni3Al sinters had above 98% of theoretical density apart from the sintering temperature. Both NiAl and Ni3Al sinters had fine grained microstructures; an average grain size was 8 µm and 4 µm, respectively. The NiAl and Ni3Al bodies sintered at 1000 °C had the hardness of 290 HV10 and 305 HV10, respectively.
- Durability of cutting blades made of WCCo/diamond composites in machining MDF
- Strony: 10-13
The paper presents the results of durability tests of cutting blades made of composites containing WC6%Co and 30 vol.% of diamond particles of 8-10 µm or 16-20 µm in size. The composites were sintered by using the PPS method (Pulse Plasma Sintering), which has been developed at the Faculty of Materials Science and Engineering at the Warsaw University of Technology. The sintering process was conducted for 10 minutes at a temperature of 1050 °C under a pressure of 100 MPa or 120 MPa, depending on the size of diamond particles. The composites had a density close to the theoretical one (more than 99% TD) and a hardness HK1 of 2000. Cutting tests were carried out on MDF with a density of 720-750 kg/m3. Blades of composite material: WC6%Co with the 16-20 µm diamond showed the lifetime more than eight times longer when compared to the HM cemented carbide blades.
- The microstructure of the plasma-sprayed ZrO2 coatings after laser remelting treatment
- Strony: 14-19
The basic objective of the study was an analysis of the microstructure of ZrO2-based complex oxide coatings obtained by the plasma spraying method, and remelted with the use of the CO2 laser in the continuous operation mode. The optical microscopy, the scanning electron microscopy, and the confocal microscopy techniques were used in the investigation of the microstructure. Besides, a quantitative assessment of porosity and investigation of the surface morphology were performed. The investigations in question allowed us to illustrate the extent and nature of changes caused by the laser surface treatment. In all the analysed cases a significant reduction of porosity of the coatings was observed after the laser treatment with a simultaneous change in the morphology of pores in the coating. Together with the remelting treatment distinct spheroidization of the pores and their coalescence occurred. As for the pores located close to the base-coating interface it was demonstrated that their presence to a large extent results from the transformation of the local areas originally showing lack of adherence of the sprayed material to the base. A characteristic feature of the remelted coatings was the loss of laminability of the microstructure which is typical for the coatings obtained by the use of the APS method, and it results from the methodology of spraying of the coating material over the base. Additionally, distinct fragmentation of the microstructure, homogenization of the material, and a change in the morphology of the output phases were observed with the remelting treatment of the oxide coatings. Significant increases of hardness and abrasion resistance of the analyzed samples were observed as the effects of changes in the microstructure of the sprayed materials.
- The photocatalytic activity of titanium dioxide thin films containing TiO2 nanotubes
- Strony: 20-26
Titanium dioxide nanotubes have a number of practical applications, especially in the catalytic and photocatalytic processes. They are used more often than typical powder materials, because of a much larger degree of surface development. Effects of TiO2 nanotubes on the photocatalytic activity of coatings obtained from a titanium dioxide sol and their optical properties are still poorly investigated. This paper describes a synthesis procedure of the sol containing titanium dioxide nanotubes and preparation of thin films on the glass surface by the dip-coating sol–gel technique. The structure, optical properties, photocatalytic activity, and wetting contact angles of the coatings were characterized.
- Optical, thermal and structural studies of ternary TeO2–WO3–PbO glasses modified with lanthanum and lutetium oxides
- Strony: 27-31
The goal of this work was to investigate the influence of lanthanum and lutetium oxides on physicochemical properties of the TeO2-WO3-PbO glass matrix. Differential thermal analysis DTA, XRD, SEM measurements have been considered in terms of the La2O3 and Lu2O3 addition. Raman and MIR spectroscopy was used for characterization of glasses. The Raman spectra of the glasses were interpreted in terms of the structural transformations produced by the modifiers. The reflectance, transmittance and ellipsometric measurements have been done. Decreasing of the refractive index of the base glass with the Lu3+ and La3+ ion doping has been found.
- Examination of crushing rock crystal in a vibratory jaw crusher
- Strony: 32-36
Examinations of the rock crystal vibratory disintegration process were performed in a experimental vibratory jaw crusher type KW 40/1. The work contains a diagram, technical description and basic parameters of the crusher. Rock crystal with two grain ranges of 10-30 mm and 10-20 mm was used as a feed. The aim of the research was to determine possibility of using the vibratory jaw crusher to very fine crushing of the material while maintaining its high purity. Crystal rock has a density of about 2.65 g/cm3, and its hardness is 7 on the Mohs scale. The tests were conducted for the two feed ranges at two values of an outlet gap (e = 1,0 mm and e = 2,5 mm) and a fixed frequency of jaws vibration (f = 18 Hz). It was observed that the process of vibratory crushing the rock crystal samples went very well. Analyses of size distribution curves show that about 95% of the product mass is below 5,0 mm of particle diameter, and 30% below 1,0 mm. The good results of crushing indicate that the vibratory jaw crusher can be successfully used for crushing rock crystal, e.g. before the final grinding process.
- Scale-up of YAl0.97Cr0.03O3 pigment synthesis
- Strony: 37-44
Scale-up of ceramic pigments synthesis is often a challenge for engineers and manufacturers. Large batches of pigment are usually produced by mixing and homogenisation of smaller portions of calcined powders. In this paper, the scale-up problem has been analysed in the case of red perovskite-type pigment in the Y2O3-Al2O3-Cr2O3 system. Powders of yttrium-aluminium perovskite doped with chromium with a nominal composition of YAl0.97Cr0.03O3 were prepared from aluminium hydroxide and respective oxides with 5% additions of CaF2 as a mineralizer. The starting powder mixtures in the amount of 1 g, 5 g, 10 g, 20 g and 40 g were calcined in corundum crucibles at 1300 °C for 1 h, 3 h or 6 h. The experimental results revealed that the sample quantity and calcination time affect the phase and chemical compositions, morphology and colour parameters of the powders.
- Application of the finite element method in the study of metallic interconnects for solid oxide fuel cells in selected geometric systems
- Strony: 45-48
The paper presents the results of simulations carried out by using the finite element method for the three-dimensional model of a working element of SOFC. The basic physical properties of particular geometric arrangements were analysed based on MOLB-type and planar-type cell stacks. The investigated materials were modelled after an intermediate-temperature solid oxide fuel cell (IT-SOFCs). The study was focused on determining the impact of the interconnect’s wear level on turbulence, affecting the flow of gaseous media.
- Optimization of the conditions for receiving quantum dots by the SILAR route
- Strony: 49-54
In order to deposit quantum dots of PbS and CdS successive ionic layer adsorption and reaction, SILAR route was employed. Water- and methanol-based solutions of sodium sulfide(II), lead(II) nitrate and cadmium sulfate were used. A concentration of solutions varied from 0.001-0.1 M and a number of cycles changed from 5-15. The EDS analysis confirmed the presence of sulphur and lead or cadmium in the obtained structures. Based on the XRD results it was found that both PbS and CdS crystallizeed in the cubic structure. SEM images allowed us to determine the relationship between size of deposited QDs and SILAR parameters such as the solution concentration, the number of cycles and the solvent type. In the case of both sulphides, deposition from the water-based solutions of concentrations up to 0.01 M creates the conditions suitable for crystallization of individual QDs. Along with the increase in the solution concentration the size of QDs increases. Similar effects are observed in case of the increase in the number of cycles regardless of the solvent type. The usage of more concentrated solutions (≥ 0.1 M) leads to partial agglomeration. Changing the solvent to methanol leads to smaller nanostructures.
- Calcareous gaize from Ożarów as an active mineral admixture for blended cement
- Strony: 55-61
The influence of gaize (a calcareous sediment rock) on hydration of the ordinary Portland cement (OPC) was investigated. Calcareous gaize was characterized by means of different techniques: X-ray diffraction, pozzolanic activity determination, scanning electron microscopy (SEM, EDS), and thermogravimetric analysis. Three cements containing 15%, 25% and 35% of calcareous gaize were produced by intergrinding. The following parameters of hydrated pastes and mortars were determined: water demand, initial and final setting time and compressive strength for mortars up to 90 days old. The hydration process of cement mixtures with the gaize addition was also investigated using calorimetry and SEM microscopy. Additional properties were determined: density, Blaine surface area and particle size distribution. CEM I was used as a reference cement. It has been found that the addition of gaize ranging from 15% to 35% permits to obtain binders meeting the requirements of cements CEM II/A-M 42,5R, CEM II/B-M 42,5R and CEM II/B-M 42,5N, when the calcareous gaize is treated as a mix of natural pozzolana and limestone.
- Transport of water in expanded perlite mortars modified by admixtures
- Strony: 62-67
The lightweight cement mortars with expanded perlite reveal high porosity and, as a consequence, their insulating properties can be lowered due to the presence of environmental humidity. The studies were performed with aim to find out the mix composition of cement - perlite mortars and to optimize their parameters; first of all to reduce their density and water absorption by use of admixtures. Three series of mortars of similar consistency were produced. A water repellent and air entraining agents were used to improve the microstructure of mortars. The density and capillary suction were measured and observations of the microstructure were carried out by SEM. The transport of water in the admixtured mortars was significantly slowed and limited. The proportions, giving the lowered density at fairly low absorbability, have been pointed out. The advantageous effect of an air entraining agent has been proved too.
- The influence of calcium carbonate addition for sintering different types of kaolines
- Strony: 68-76
The sintering process of ceramic materials depends on various factors such as the type of sintered material, initial densification of mass, homogeneity of powder packing, reactions and phase transformations, occurring during heating process, quantity and properties of liquid phase and firing conditions. In the article the sintering process of ceramic masses made of kaolin and calcium carbonate was analyzed, and selected properties of sintered materials were determined. The masses were prepared from two kaolines, containing different amounts of quartz. Thermal properties of the masses were studied by the dilatometric method and heating microscopy. Density, water absorption, porosity, flexural strength and phase compositions were determined for materials fired at 1220 °C or 1350 °C. The studies confirmed that the influence of CaCO3 on sintering process of ceramics depends on the type of kaolin, the quantity of calcium carbonate added and firing temperature. Apart from components existed in sintered kaolines without CaCO3 addition such as mullite, quartz, tridymite and amorphous substance, in the materials added with CaCO3 anorthite and gehlenithe has been also found. The presented results provide a basis for studies on the effects of calcium carbonate on sintering and properties of the masses for building ceramics.
- The effect of temperature on microstructure of amorphous refractory fibre materials
- Strony: 77-80
Within the study the heat-insulating plates made of fibrous aluminosilicate refractory material intended for use at temperatures up to 1400 °C were investigated. Both phase and microstructural analysis and the assessment of the linear shrinkage of the material have been held at the temperature range of 900-1400 °C, and excluded the possibility of using this material in accordance with recommendations of a manufacturer. Crystallization of vitreous aluminosilicate fibres occurred at the temperature significantly lower than the classification one. The process of devitrification and the intensive decrease of viscosity during annealing of the material at the temperature below the classification limit has led to very significant degradation of the internal microstructure of the material, loss of fibrous properties, and the shrinkage which exceeded the limit value given in the class.
- The influence of full water saturation on selected physico-mechanical properties of ceramic body
- Strony: 81-87
The article presents the results of research concerning an impact of water on selected properties of ceramic ordinary and clinker bricks. As diagnostic features, describing effects of water on the ceramic brick behaviour, compressive strength, hardness and linear elongation were selected in the dry state and the state of full water saturation. For studies, two types of ceramic bricks were selected with significantly different mechanical and physical properties. The compressive strength of the bricks was 35 MPa and 70 MPa, respectively. Porosity and absorbability also differentiated the two materials. In case of the brick of lower strength total porosity was 46%, but the ceramic brick of higher strength showed a total porosity of 31%, an increased content of non-reacted clay raw materials, and therefore increased susceptibility to water. The volumetric absorbability of both brick materials was 40% and 26%, respectively. The tests were also carried out on clinker bricks of a strength more than100 MPa, a total porosity of 22% and a volumetric absorbability of 15%. The clinker bricks showed a full resistance to water action.
- Corrosion resistance of refractories based on calcium dialuminate
- Strony: 88-93
The aim of this work was to study the corrosion resistance of refractory materials based on calcium dialuminate against alkali silicate melts. The tests were carried out using the so-called deformation method. This method allows following both the dissolution of the refractory particles in the melt and the washing out process of the refractory particle from the material. Both processes are crucial for the course of the corrosion process. For the investigations, mixtures with variable ratio refractory material to alkali silicate were prepared. The samples were then heated in a hot stage microscope in the temperature range 20°C - 1500°C in air. From the change of the sample contour following characteristic points were determined: sintering temperature, softening temperature, melting temperature and flow temperature. The corrosion phenomena were studied using the following investigations: microstructure examination of the samples, chemical and mineralogical analysis. The obtained results indicate a good corrosion resistance of the calcium dialuminate material against the alkali-silicate melts used in the tests.
List of Contents
Volume 66, Issue 2
- Sintering of nanocrystalline nitride-boride phases
- Strony: 98-102
The study presented in this paper describes issues related to pressure sintering and investigation of TiN-TiB2 composites obtained by using nanopowders originated from various producers. Six types of commercial powders that contained TiN and TiB2 phases were used. Composite mixtures of 70 wt.% TiN - 30 wt.% TiB2 and 50 wt.% TiN - 50 wt.% TiB2 were sintered. There was a strong correlation between the phase composition of the starting powders and the phase composition and properties of related sinters. The formation of hexagonal boron nitride was especially disadvantageous due to its low hardness, and resulted from the presence of remnants of sassolite (boric acid) in the titanium diboride powders. It was confirmed that the phase composition of the powders had a strong influence on the SPS sintering process and sample consolidation. This was proved by sintering curves registered by an SPS apparatus. The sintering curves for the nano-powders differed from the curves registered for micrometric powders. Density, hardness and Young’s modulus were the criteria of densification of powder mixtures. For characterization of the nanopowder morphology and the microstructure of the sintered bodies, transmission electron microscopy and scanning microscopy were used, respectively. Phase analysis was performed by the X-ray diffraction method, whereas chemical analysis was carried out by using an EDS spectrometer. The SPS sintered materials showed the highest value of density and the highest hardness HV0.3, when sintered at 35 MPa for 10 minutes at a temperature of 1900 °C.
- The influence of preparation on selected properties of calcium dialuminate refractory materials
- Strony: 103-108
Optimal conditions of obtaining the new generation refractory materials have been determined in the study. Calcium dialuminate (CA2) is a constitutive component of the material in question. This chemical compound is characterized with exceptionally low thermal expansion and a melting temperature of about 1760 °C. The former feature creates a peculiar technical advantage protecting shape wares against cracking caused by excessive temperature differences developed on their cross-sections during operation. Good corrosion resistance related with its non-silicate chemical composition is also expected. The study is aimed at obtaining the final products containing CA2 in their chemical compositions and an admixture of high-refractory compounds characterized with low thermal expansion and limited open porosity. As commonly known, the presence of open pores fosters action of destructive corrosion in the environment of aggressive liquids and gases. Several sets of shaped wares formed under various pressure and fired at temperatures up to 1600 °C have been tested. The material firing shrinkage, apparent density, porosity, gas-permeability and phase composition have been determined. The influence of the shaped ware phase composition on their thermal properties has been discussed.
- Preliminary experimental studies of producing a limestone-based sorbent in a vibratory mill
- Strony: 109-114
Studies on the possibility of producing a limestone-based sorbent by using a periodic working laboratory vibratory mill were conducted. The milling process was carried out in a steel chamber in air, using steel grinding media. The studies focused on the production of limestone powders containing a size grade of 0-63 μm more than 70%; the powders can be used in flue gas desulphurization processes. Grain sizes of the milling products were measured with a laser granulometer LAU-15. The influence of size of grinding media on limestone particle size distributions was studied, and effects of the use of an activator on the control grain sizes: d97, d90 and d50 were determined. An additional aim of the work was the production of limestone powder containing the largest amount of a size grade of 0-10 μm. This kind of powder may be used as a filler for polymers. The feedstock for the grinding was limestone with grain sizes ranging from 0.1 mm to 0.40 mm; it was the waste product coming from a roller grinding mill. The research program included four series of the limestone milling for 2.5 min, 5 min, 10 min and 15 min. In The studies was also established The filling degree of the chamber, the oscillation frequency and the Frude number were 0,70, 12 Hz and 6, respectively. The limestone powders were produced, showing the contents of the size grades of 0-63 μm and 0-10 μm ranging from 78% to 89% and from 65% to 95%, respectively. This proves that the vibratory mills are suitable for producing limestone-based sorbents.
- Basic physical characteristics of selected mineral sorbents
- Strony: 115-120
Spills of petroleum substances are neutralized by collecting oil from the environment. This task is realized by using both mechanical methods and absorbent materials called sorbents; the mechanical methods use specially designed devices that collect the spilled oil from the surface of water or soil as appropriate mixtures. The aim of this study was to show differences in characteristics of selected mineral sorbents available on the Polish market. The sorbents selected for the study had different chemical compositions and grain sizes. The observations had been taken from optical microscopy, which permitted to evaluate the microstructure and porosity of samples to some extent. Oil absorption capacity of sorbents had been measured.
- Study of the topography and roughness of the glaze surface as modified by selection of raw materials grain size
- Strony: 121-125
The presented paper shows a new, simple method for improving the surface properties, such as smoothness, gloss and whiteness, of ceramic glazes. This method consists in making the intentional selective choice of the grain size of selected raw-material components. In the investigation, the variable factor was the grain size distribution of hard raw materials, that is quartz, feldspar and zirconium silicate. The obtained results indicate that the proper selection of the grain size of individual raw materials markedly improves the surface quality.
- Surface investigation of ceramic materials by the secondary ion mass spectrometry method
- Strony: 126-128
Depth profiles of the near-surface region of sodium aluminosilicate glass and diamond film were obtained by the secondary ion mass spectrometry method. The profiles showed the dependence on oxygen and cesium ion beams. This effect is explained by various modification mechanisms of the surface treated with primary ions.
- Synthesis of zeolites from perlite and their sorption properties
- Strony: 129-134
The paper presents research in synthesis of zeolites using waste dusty fractions coming from the production of expanded perlite. The influence of concentration and amount of a aqueous solution of NaOH together with temperature and time of synthesis on the type and quantity of the resulting products was analyzed. Depending on the process conditions, zeolite Na-P1, zeolite X, zeolite A, and hydroxysodalite were the products identified by X-ray diffraction analysis (XRD). The presence of the zeolite phases has been confirmed by mid-infrared spectroscopic measurements and scanning electron microscope observations. It has been found that it is possible to optimize the synthesis parameters. The perlite dust transforms into the zeolitic material just after 24 h synthesis in the NaOH aqueous solution of concentration above 3.0 mol/dm3 at ≥ 60 °C. Basing on the content of the A and X zeolites, and the microstructure of the obtained samples, the zeolite materials of potentially high sorption capacity were selected. Cation exchange capacities of the selected samples were determined. It has been found that sodium zeolites obtained from the perlite dust can be successfully used in sorption processes.
- Hydrolytic resistance of glasses for immobilization of hazardous wastes
- Strony: 135-140
Vitrification is currently the most effective method of disposal of hazardous wastes. This method permanently immobilizes toxic elements into the glass structure, that behave like glass modifiers. Glass coming from the P2O5-Fe2O3 system was studied with respect to the radioactive waste immobilization. Na2SO4 and CaCl2 were used as model wastes. Borosilicate glass for immobilization of medical ashes was also studied. Hydrolytic resistance of the glasses prepared from glass-waste mixtures was investigated. The obtained results confirmed usefulness of the glasses for the vitrification of the studied wastes.
- TiO2 with amine groups: Synthesis, characteristic and porosity
- Strony: 141-145
In this paper two TiO2 powders with amine groups were prepared by the sol-gel technique, applying titanium(IV)(triethanolaminato)-isopropoxide (TEAIP) as a precursor. Two TiO2 powders differing in the content of amine groups has been prepared (TiO2-13 and TiO2-14). Particle sizes of the TiO2 powders were investigated by zeta potential. Influence of the amount of TEAIP on absorption in the UV-Vis range and porosity of TiO2 powders was studied.
- The influence of Na2O to K2O molar ratio on some properties of sanitary glazes
- Strony: 146-150
Industrial applications of sanitary glazes require not only sufficiently high surface properties of glazed products, but also technological parameters allowing the reduction of production costs. Chemical composition belongs to the most important factors determining properties of glazes. Determination of the exact role of individual components of a glaze is essential to achieve better functionality of products, and to modify selected surface properties of the glazed products, positively affecting their quality. This applies also to understanding practical behaviour of glazes during real industrial firing cycles. In this work, the influence of variable amounts of Na2O and K2O on technological properties of glazes was investigated. Five experimental glazes that differed in a mole ratio of sodium and potassium oxides in the glaze composition were prepared. Viscosity, characteristic temperatures and thermal expansion coefficients were determined by means hot stage microscopy and dilatometry. The obtained results permitted to assign the transformation temperature for each glaze.
- Effect of kaolin and limestone admixtures on mechanical properties of glass-epoxy laminate
- Strony: 151-155
Glass-epoxy laminates with extenders was studied. EM-1002/450 and EM-1002/600 made by Krosglass S.A. and polyester resin Polimal 109 were used to obtain the laminates. The mates was prepared based on the emulsion preparation. The kaolin and limestone extenders were added to the laminates in an amount of 5 wt.%, 10 wt.% and 15 wt.%, respectively. Their influence on tensile and flexural strength was studied. It has been found that the extenders do not induce a decrease in mechanical strength. The laminates showed the flexural and compression strength of 105-110 MPa and 250-300 MPa, respectively. The extenders’ admixture impacts colour of the laminates. The limestone shifts the colour from white to cream and the kaolin induces grayness.
- Sintering of B4C based composites containing TiB2, TiC or TiN additives
- Strony: 156-164
In the work, different sintering methods of boron carbide based materials were compared. Phases, that lead to generation of thermal stresses, were incorporated to the composites’ matrix to enhance fracture toughness. The stresses can be generated because of a difference in thermal expansion coefficients of constituent phases. Titanium carbide, titanium nitride and titanium diboride were used as the dispersed particles in the boron carbide matrix in quantities up to 20 vol.%. The particulate composites were obtained on the way of pressureless sintering, hot-pressing and spark plasma sintering. The phase composition, microstructural features, densification and basic mechanical properties were determined for the sintered composite materials, and analyzed. On the base of recorded results it was shown that the SPS technique cannot be applied for sintering of these materials. The B4C-TiB2 hot-pressed composite system manifested to be the most promising one. The incorporation of smaller than 15 vol.% of TiB2 to the B4C matrix caused an increase in hardness, bending strength and fracture toughness of the hot-pressed composites when compared to the pure B4C materials.
- Crystallization of silicate-phosphate glasses from the NaCaPO4–SiO2–BPO4 system
- Strony: 165-169
In this paper, silicate-phosphate glasses from the NaCaPO4-SiO2 system with the addition of boron ions were the subject of interest. The devitrification of this glasses was conducted. Thermal investigations (DSC) have shown that the introduction of B3+ ions changes the course of crystallization from multistep to one-step process (presence of only a weak exothermic peak on DSC curves) for silicate-phosphate glasses. The direct crystallization of selected glasses from the NaCaPO4-SiO2-BPO4 system was carried out in a gradient furnace. XRD and MIR methods were used to study the structure of the glass-crystalline materials. The results confirmed the appearance of only one crystalline phase after heat treatment of the glasses and showed their high thermal resistance.
- Pulsed Thermoelectric Machine
- Strony: 170-174
A new type of thermoelectric transport is described, consisting of pulses of charge carriers that “fly” periodically through the external circuit from the hot end of the sample to the cold end, with a determined duration of the “on” and “off” times of the electric contacts, while maintaining continuously the thermal contacts. It is shown that such a non-equilibrium ideal thermal “machine” works cyclically with improved efficiency compared with efficiencies of the thermoelectric devices operated in an equilibrium transport regime, but the electric flow and power are increased, as a consequence of concentrating the charge carriers on pulses of a small spatial extent. The machine is reversible, in the sense that it can operate either as a thermoelectric generator or as an electro-thermal cooler. So, it is described special designing a new thermoelectric generator to fulfill the needs of pulse operating, and a setup able to measure the thermoelectric parameters of Non Steady-State (pulse) operated generators. Preliminary measurements show a minimum two times increase of delivered electrical power, using the same heat power input when we are working in the pulse operation. It is confirmed existence of a lower limit of frequency where the electrical power starts to increase comparing with the DC operation, and a superior limit of frequency where the increase is too low to be taken into consideration. All these results are strong confirmation of the theory of “pulsed thermoelectricity”.
- Effects of nano-nickel and MgO addition to alumina based matrices on properties of the resultant composites
- Strony: 175-184
Ni/Al2O3 composites were produced by using alumina nano- and micropowders, and 1.7 vol.% Ni nano-particles prepared by an oxalate method. Uniform mixtures of alumina and nano-nickel particles were consolidated by the SPS method for 7 min at 1400 °C in argon. Effects of second-phase nano-particles, MgO-dopant and particle size of alumina powder on the microstructure and, in turn on, the resultant density, hardness, fracture toughness and wear resistance of the composites were studied. XRD, SEM, EDS, image analysis, Vickers indenting and wear resistance testing were used to determine the microstructural and mechanical properties of the studied materials. The MgO-dopant controlled the microstructure of Al2O3 polycrystals limiting abnormal grain growth, but in case of the Ni/Al2O3 composites a pinning effect, coming from nickel nano-particles, was more pronounced in reducing alumina grain sizes than a solute drag mechanism incorporated by the MgO additive. The alumina matrix composite hardened with nickel nano-particles was produced which showed a hardness of 18.3 GPa and very high wear resistance, as a result of the Hall-Petch effect.
- Dielectric properties of the PZT ceramics obtained by the sol-gel method and doped by chromim, manganium and tantalum
- Strony: 185-190
In this paper we obtained multicomponent PZT ceramics doped by chromium, manganese and tantalum oxides. Ceramic powder with a composition of Pb(Zr0,70Ti0,30)O3 was synthesized by the sol-gel method. In the next step, the powder was doped by an oxide: Cr2O3, MnO2 or Ta2O5. Two compositions of ceramic powders were obtained with constant amounts of manganese (1.0%) and chromium (0.15%) oxides, but with different percentages of tantalum oxide (0.03% and 0.05%). Synthesis of the materials was carried out by solid phase reaction, using calcination of powder compacts compacting method, while the sintering was performed by two methods: free sintering (FS) – with no pressure, and hot pressing (HP). For the obtained ceramic samples, microstructural, X-ray, EDS, basic dielectric property and electrical hysteresis loop investigations were carried out. The studies have shown that the use of the hot pressing method allows obtaining the materials with higher values of maximum electric permittivity, but with higher values of dielectric losses, when compared with the FS obtained ones. The doping of the basic PZT composition by tantalum, manganese and chromium oxides decreases the temperature of phase transition (Tm) and increases the ferroelectric hardness. The properties of multicomponent free sintered PZT ceramics permit its use for construction of high-frequency piezoelectric electroacoustic transducers.
- Investigations of rock crystal milling in the vibratory mill
- Strony: 191-196
Investigations of very fine grinding of rock crystal were carried out in a periodic laboratory vibratory mill of low frequency of vibrations of 10-16 Hz. The purpose of the research was to obtain a rock crystal powder which contains a grain class of 0-60 μm and 0-10 μm in amounts of above 80% and above 50%, respectively, and shows the highest purity, due to its potential medical and cosmetic application. The milling feed was the material of grain size below 5,0 mm pre-crushed in a vibratory crusher. The study was conducted in a chamber lined with polymeric material, and ceramic grinding media were the working elements. The research program included determination of the influence of vibration frequency and grinding time on parameters of the grain size of rock crystal powder. The amount of the grain class of 0-60 μm and 0-10 μm was within a range of (73-99)% and (39-72)%, respectively. The results indicate that the rock crystal powder of the desired particle size and purity can be made in the vibratory mill of low frequency of vibrations for less than 30 minutes.
- High efficiency inductive thermoelectric generator – illusion or reality
- Strony: 197-202
Direct current thermoelectric generators are well known. We present a thermal to electricity generator based on the Seebeck effect, connected to an inductive load operated at around 100 kHz. Jon Schroeder, in 1995, published a brochure on a similar device. In 2008, an efficiency was measured on his generator of 15%. Due to the design, no temperature measurements could be made, but estimating the temperature difference, this efficiency is about double the efficiency of a thermo-electric generator (DC). Two prototypes are designed with electrical and thermal measurements. This is a paradigm for thermoelectrics: A possible solution to \"beat\" the ZT materials barrier. We need to validate the prior measurements of 2008, and to try and understand the mechanisms, that produce such a high efficiency.
- Strony: 203-208
List of Contents
Volume 66, Issue 3
- Chemical reactivity of the 3Y-TZP/Al2O3 composite electrolyte with the lscf48 cathode material for IT-SOFC applications
- Strony: 212-217
The paper presents the evaluation of chemical stability of composite electrolyte with the partially stabilized zirconia matrix and aluminium oxide inclusions (3Y-TZP/Al2O3) in relation to the La0.6Sr0.4Co0.2Fe0.8O3 (LSCF48) electrode. Phase analysis of the 3Y-TZP/Al2O3-LSCF48 mixture batched in a weight ratio of 1:1, and annealed in air at 1073 K revealed the presence of the starting components only while the increase of annealing temperature up to 1273 K (for 5 h and 100 h) caused the formation of new crystalline phases, mainly of SrZrO3 and CoFe2O4. These studies indicate the potential for the application of 3Y-TZP/Al2O3 in intermediate-temperature solid oxide fuel cells (IT-SOFCs) due to the chemical compatibility with the LSCF48 cathode at the expected operation temperature of a cell (1073 K). Due to structural changes of the mixture annealed at 1273 K, the electrolyte-cathode connector cannot be exposed to that temperature for a long time during the manufacturing stage of a fuel cell.
- Preparation of stabilized zirconium dioxide in the form of spherical particles as an inert matrix for transmutation of actinides by the modified sol-gel method
- Strony: 218-223
Production of stabilized zirconium dioxide by the modified sol-gel method was elaborated to obtain the inert matrix (IM) for transmutation of actinides. The double extraction process and complex sol-gel process (CSGP) with ascorbic acid (ASC) as complexion agents was used. The process was combined with synthesis. Zirconia dioxide for spherical grains was stabilized by calcium or yttrium oxides and doped by surrogates. In experimental used cerium and neodymium oxides were applied as the surrogates of plutonium and americium isotopes. The last stage of the synthesis comprised controlled heat treatment. Analyses of physical form and structure of the grains were performed by using a scanning electron microscope and a diffractometer with Cu-Kα radiation, respectively. The SEM and XRD analyses confirmed that the material has been obtained in the form of spherical grains composed of stabilized zirconium dioxide, and it may be used as the inert matrix for actinides transmutation, and in the recycling process.
- Silicon carbide ceramic aircraft brakes
- Strony: 224-228
The commonly used materials for undercarriage brakes applied in landing gear brakes are designed on the basis of C/C composites. Their main disadvantage is the braking efficiency which decreases versus braking time (i.e. the fading effect). The main issue of this work is the concept of replacement in the aircraft undercarriage brakes contemporary used materials, by ceramic friction pads, for which the braking efficiency is supposed to be stable during a braking process. In the presented work the fabrication method of silicon carbide (FCP13RTP, Saint Gobain) friction pads is presented. The obtained samples were characterized in terms of their thermal diffusivity and thermal conductivity. Additionally, slow and fast breaking tests were performed for silicon carbide friction pads. The thermal conductivity of the test samples of silicon carbide decreases from 150 W/(m·K) to 90 W/(m·K) in the temperature range of 25 °C-300 °C. The silicon carbide friction pads have an average dynamic friction coefficient of 0.43, and the friction surface temperature does not exceed 200 ºC during braking.
- The influence of microstructure on the magnetoelectric effect in ceramic composites
- Strony: 229-234
In the multiferroic composite material, the ferroelectric and ferromagnetic properties are closely correlated through the coupling interaction between the electric and magnetic orders. We attempted to receive the magnetoelectric composite materials and to determine the values of magnetoelectric coupling coefficient. The microstructure of obtained ferroelectric-ferromagnetic composite materials were also studied. The main component of the ferroelectric-ferromagnetic composite was PZT type powder (with ferroelectric properties) which was synthesized using the sintering of a mixture of simple oxides in a solid phase. The second element of the ferroelectric-ferromagnetic composite was the ferrite powder with ferromagnetic properties. The ferrite powder was synthesized using calcination. Next, the mixed components were compacted by pressing, consequently pressureless sintered and characterized. Based on the theoretical model of coupling between ferroelectric and ferromagnetic properties in multiferroic composites, values of the magnetoelectric coupling coefficients were specified.
- Microstructure and electrical properties of a spinel coating on selected ferritic stainless steels
- Strony: 235-244
An important technological aspect in production of generators is selection of appropriate structural materials which is a prerequisite for obtaining a high level of energy efficiency and reliability of these devices. The essential component of a fuel cell is an interconnect which supplies gaseous fuel and the oxidant through a system of channels, and also provides a medium for the generated electric current to travel through. In the case of intermediate-temperature solid oxide fuel cells (IT-SOFC), ferritic stainless steel forms a core of the interconnect; the steel undergoes corrosion during the cell’s operation, forming a protective coating mainly composed of the Cr2O3 scale. However, the scale is characterized by a relatively high electrical resistance, and its formation furthermore entails the evolution of chromium oxides and oxyhydroxides that poison the remaining elements of the cell, reducing its overall efficiency. In order to prevent these processes from taking place, an attempt was made to apply a manganese cobalt-doped yttrium spinel as a protective-conducting ceramic layer on ferritic steel. The paper presents physicochemical properties of different species of pure ferritic steels and steels with the coating composed of the Y0.1Mn1.45Co1.45O4 spinel.
- The use of asbestos wastes in ceramic masses for the manufacture of building ceramics
- Strony: 245-252
The paper presents the results of studies where asbestos-cement was used as an additive to a ceramic mass designed for production of building bricks. In these study, both raw and calcined at 700 °C asbestos-cement wastes were used. Ceramic masses contained up to 10 wt% of asbestos materials. After formed, the green compacts were fired in a laboratory furnace at temperatures of 950-1050 °C. After firing, the basic ceramic product properties such as linear shrinkage, water absorption, open porosity, apparent density, compressive strength and freeze resistance were determined. The microstructure of the obtained materials was examined by scanning electron microscopy (SEM), and the mineral composition was determined by X-ray diffraction (XRD). The results of this study indicate that asbestos-containing materials can be used as one of the raw materials in the manufacture of ceramic products, but only as a small share in ceramic masses.
- Thermophysical properties of barium borosilicate glass used for seals in IT-SOFC
- Strony: 253-258
This work presents the results of studies on thermophysical properties of barium borosilicate glass from the SiO2-B2O3-BaO-MgO system for application as a glass sealant for IT-SOFC fuel cells. The glass exhibited unsuitable thermal stability (DT = 117 °C). The thermal conductivity was determined as a = 0,78 mm2/s, whereas the thermal conductance was λ = 1,8 W/(m·K). The thermal expansion coefficient was 13.8·10-6 K-1. The softening point was determined as Tm = 805 °C. The glass exhibited very good wettability (θ = 27°). The established values of thermophysical parameters suggest that the glass is suitable for seals and further may be tested in IT-SOFC cells.
- SiC-based materials obtained by the slip casting method
- Strony: 259-265
The paper presents results of a research designed to obtain dense material of silicon carbide formed into shapes by slip casting, using aqueous suspensions. Alumina oxide and yttrium oxide were used as sintering additives in a weight ratio of 3:2 in an amount of 10% by mass relative to the dry weight. The slurry was electrostatically stabilized by changing pH. Determination of the zeta potential as a function of pH, and viscosity tests performed as a function of pH and volume concentration of solid phase allowed selecting proper parameters of the suspension such as a solid volume loading of 30% and a pH value of ~ 8,5. The results of these investigations confirmed that it is possible to produce pseudoplastic slurries suitable for slip casting. The increase in strength of green bodies, allowing for their preliminary processing, was obtained by addition of a commercial acrylic binder (Duramax™ B – 1000). SiC casts were pressureless sintered at 2050 ºC, which led to high densities and fine, homogeneous microstructures. A fracture toughness test revealed positive effects of the sintering additives on fracture toughness of the material, increasing a KIc value to ca 5 MPa·m1/2.
- Effect of synthesis conditions and Al2O3/Fe2O3 molar ratio on the type of formed calcium aluminoferrites
- Strony: 266-273
The present study concerns with the influence of Al2O3/Fe2O3 (A/F) molar ratios exceeding the borderline composition of C6A2F and tending towards phases with higher Al2O3 content on the type and diversity of calcium aluminoferrites formed. The conditions of synthesis are also taken into account. The author demonstrated that for A/F ratios higher than one the additional, crystalline phases such as C12A7 and C3A are formed in addition to calcium aluminoferrites. It was determined that a low cooling rate of systems with an A/F value below 0.58 favours the exclusive formation of calcium aluminoferrites. Above this value, various concentrations of C12A7 and C3A phases are observed. Rapid cooling of systems with A/F values equal to ca 4 results in the formation of a single phase with varying chemical composition; above this value, glassy calcium aluminoferrites are formed. The investigations also indicated that a decrease in the A/F molar ratio of alloys is followed by a decrease in the volume of the unit cell.
- Archaeometric analysis of the prehistoric pottery using SEM-EDX
- Strony: 274-280
This article presents the results of an archaeometric analysis performed on a collection of 50 Early Bronze Age pottery sherds. The potsherds were obtained from six archaeological sites located on the Chełmno Land: Biały Bór, Grudziądz Mniszek, Małe Radowiska, Toruń Grębocin, Wałyczyk, Zieleń and one on the Dobrzyń Land: Skrzypkowo. All the materials analyzed in the article are connected with the Iwno Culture societies from the turn of the 3rd and 2nd millenium B.C. The potsherds were grinded, and the chemical composition of the resultant powder was identified by Energy-Dispersive X-ray Spectroscopy (EDX) combined with a scanning electron microscopy (SEM). Chemical matrix spectrograms were obtained. The spectrograms allowed performing quantitative determination of the following elements: C, Na, Mg, Al, Si, P, K, Ca, Ti, Mn, Fe, Cu. Data set was statistically elaborated using an archaeometric analysis, including i.a. the discriminant analysis. It permitts to follow an association rules within the individual sets, such as the site (from where the potsherds were excavated), technological groups (which the potsherds were classified into) and additionally within one settlement microregion. The results of the discriminant analysis indicated the variables (elements concentration) that best of all discriminate the set of the analyzed potsherds in terms of their provenance and their belonging to the technological groups. Analysis of mean values of the Al concentration indicates a level of 11-13 wt% (except of the pottery from Biały Bór site where the elevated concentration of Al – amounted to 16 wt% was registered). On this basis, it has been found that the vessels manufacturers from each the Early Bronze Age settlements used plastic clay sources. In contrast, low mean concentration of P (amounted to about 1-2 wt%) indicates that a practice of weakening the clay paste with floral additives did not take place. The obtained results permitted to draw conclusions on the use of similar clay sources by the communities of the Iwno Culture, especially within the settlement microregion Małe Radowiska-Wałyczyk-Zieleń. In addition, the presence of a tendency of cultivating some technological canon within vessels manufacturing, which included differentiation between “representative” and ”kitchen” pottery, was observed. This tendency had been permanently existing in the pottery manufacturing rules and it had been cultivated regardless of a place of habitation, and access to raw material sources.
- Phase and microstructural changes in the ceramic-carbon filters during cast-steel filtration
- Strony: 281-285
Trials of cast steel filtration using two types of newly-developed foam filters, in which carbon bonded ceramic particles, have been conducted. In one of the filters, the source of carbon was composed of flake graphite and coal-tar pitch, while in the other one the graphite was replaced by a cheaper carbon precursor. The newly-developed filters were fired at 1000 °C which is much lower than in the case of the currently applied ZrO2-based filters. During filtration trials, the filters were subjected for 30 seconds to the attack of a flowing stream of metal, having a temperature of 1650 °C. Properties of the filters were characterised before and after the filtration trial. It has been found that molten metal reacted with material of the filter wall surface, which resulted in local changes in its microstructure and phase composition with no degradation of the filters’ mechanical properties and no secondary contamination of cast steel.
- Low temperature oxidation of CO on Au-Al2O3-Co3O4 catalysts
- Strony: 286-291
In this paper, some physicochemical properties and results of catalytic measurements for low temperature CO oxidation of selected gold catalysts deposited on γ-Al2O3, Co3O4 and Al2O3-Co3O4 (1:1 molar ratio) were described. The catalytic supports were prepared with a spray pyrolysis method by using aqueous solutions of aluminium and cobalt nitrates. The spray pyrolysis method guarantees the one-stage synthesis of powders with spherical-shape of particles and high homogeneity of chemical composition. The gold particles were deposited on the supports in an amount of 2 wt%. The prepared samples were characterized by XRD, N2 adsorption, SEM, LALLS for particle size analysis, and with respect to catalytic activity in the reaction of low temperature CO oxidation. The highest activity showed Au/Co3O4 which had 90% CO conversion at 148 °C.
- Preliminary studies in production of glass micropowder in a vibratory mill
- Strony: 292-297
Studies of glass micropowder manufacturing in a very fine grinding process were carried out in a laboratory vibratory mill of low-frequency of vibrations (10-16 Hz). Before milling, glass was in the form of glass fibers. The purpose of this study was to obtain glass micropowder which shows the greatest possible content of size fractions 0-1 μm and 0-2 μm and the highest level of purity, obtained at minimum frequency vibrations of a mill chamber. The milling feed was glass fiber cut into pieces of a length of approximately 10 mm and a diameter of about 15 μm. The research of the milling process was carried out in the chamber lined with plastic or ceramics. Grinding media were ceramic balls made of corundum. The milling process was carried out in two stages. At first, glass fiber sizes were reduced below 200 μm preliminary. In the second stage, the final process of micropowder producing was performed. The results indicate that the glass micropowder containing (30-58)% of the grain class 0-1 μm and (48-83)% of the grain class 0-2 μm, and maintaining high purity can be produced by using the vibratory mill of low frequency of vibrations. This means that vibratory mills may be used for the production of glass micropowders from glass fibres for the industrial scale. The glass micropowder can be used in refining the surface of glass package.
- The physical processes responsible for energy dissipation in PFN ceramics
- Strony: 298-301
In the work, physical processes responsible for dispersing the elastic strain energy of mechanical pulses were determined as well as an influence of hard additives on the internal friction was determined in PFN ceramics. Getting to know the appropriateness of these materials is significant due to their wide applications, as condensers, piroelectric detectors, piezoelectric transducers. Samples of PFN ceramics were composed of Pb(Fe0.5Nb0.5)O3 material which was non-doped and doped with chromium (1-3 at.%). In measurements of mechanical properties, a method of the internal friction was used (TW). Great interest in this method in the research on the real structure of ceramic materials is caused by a fact that it is possible to obtain information about the behaviour of material on the atomic level by watching macroscopic pulses of the sample. In the work, temperature dependences of internal friction were described for the examined multiferroik ceramics that were received at a heating speed of 3 K/min and different frequencies. An influence of the chromium content on mechanical properties of inspected ceramics was also described, including dynamic Young’s modulus and internal friction both at room temperature and at a temperature of the phase transition.
- Lead-gallium glasses stabilised with SiO2 for transmission in near infrared
- Strony: 302-309
The paper presents an effect of SiO2 dopant on the thermal stability and the UV-VIS and IR transmission of lead-gallium glass. These glasses, due to the absence of typical glass-forming components, are characterized by an increased tendency to crystallize. Despite this, they are interesting materials due to the shift of IR edge up to 6-7 µm. Base glass (0,75PbO-0,25Ga2O3) was modified by an addition of 5 mol%, 10 mol% and 15 mol% of SiO2. The DTA/DSC analysis showed the multi-stage crystallization of the glasses which changed with the amount of silica dopant. The XRD analysis confirmed that different forms of lead oxide crystallized at first during heat treatment of the glass, whereas the Ga2PbO4 phase was formed at higher temperatures. The silica admixture allowed a few percent of BaF2 to be introduced into the lead-gallium glass structure. It has been found that transparent glass-ceramics based on lead-gallium glass with the low phonon barium fluoride phase can be obtained during the thermal treatment. The study of UV-VIS-IR transmission shows that SiO2 in lead-gallium glasses diminishes the absorption band in the range of 2,6-4 µm as a result of the presence of hydroxyl groups, and reduces transmission at the range of 5-6,5 µm from 10% to 20%, simultaneously. The incorporation of SiO2 into the glass structure contributed to the transmission increase at the region of shorter wavelengths, and the UV-edge shift is observed. It was confirmed the the BaF2-dopant has no effect on the transmittance of the analyzed spectrum.
- Hydrothermal hydration of selected refractory aggregates containing calcium zirconate
- Strony: 310-315
This work presents a hydration test of sintered and fused refractory aggregates based on CaZrO3 and the CaZrO3-MgO system. The phase composition of starting materials was identified by X-ray powder diffractometry. The hydration test was carried out in an autoclave, according to ASTM 544-92 at a temperature of 162 °C under an autogenous saturated water vapour pressure. After-hydration, the samples were analyzed by the XRD, and DTA/TG methods. The microstructure was observed using a scanning electron microscope combined with an energy-dispersive X-ray spectrometer (SEM/EDS). The results showed that the phase composition and microstructure of aggregates, that were produced during heat treatment, play a key role in controlling their susceptibility to hydration. The fused aggregates and those enriched with calcium zirconate, and impoverished with MgO were found to be less prone to hydration in comparison to the sintered ones.
- The influence of Cu ions in the Li4Ti5O12 spinel structure on electrochemical properties
- Strony: 316-320
The influence of Cu ions in the Li4Ti5O12 spinel structure on electrochemical properties
- Light weight glass-ceramic aggregates for building industry
- Strony: 321-330
The requirements for new materials with improved functional properties, environmental friendly and, if possible, not more expensive than the materials traditionally used in building materials technologies are connected with the continuous development of building technologies. That means the necessity to use the commonly available and relatively cheap raw materials as well as waste and less conventional components for obtaining novel materials for the use in building industry. Perlite is the promising raw material with potential to be used for producing new building materials apart from its traditional applications in the thermally expanded form. Additionally, as a secondary product of the perlite expansion process, the fraction of expanded perlite with very small grain size of < 0.1 mm is produced as a waste material. The Institute of Ceramics and Building Materials – Division of Glass Building Materials has undertaken research work on production technology of light weight glass-ceramic aggregates for the use in building industry. The technology uses superfine-grained raw perlite and waste fraction of the expanded perlite or waste phosphate sludge.
- Nickel oxide in technology of basic refractory materials – the perspective of use
- Strony: 331-335
The paper presents investigations performed for confirming that NiO can be a perspective addition for magnesia-spinel materials. The investigations included the NiO, CoO, MnO and Mn2O3 addition incorporated into spinel material as the solid solution components. The spinel reactivity examination was focused on the reaction with sulphur oxides, SO2/SO3, at temperatures ranging from 600 °C to 800 °C. It has been stated that the NiO addition positively influenced chemical reactivity of spinel without degradation of other investigated properties. The only observed disadvantage was a slight decrease in thermal shock resistance.
The data collected in the paper show areas of potential utilisation of the NiO-modified spinel in refractory materials technology. New refractory materials made from spinel added with NiO can be perspective for copper converter linings or rotary kilns in cement industry which utilises alternative fuels. This material could also replace magnesia materials in regenerators of glass furnaces that are exposed on the negative action of both sulphur oxides and thermal shocks. The studied magnesia-spinel products have better resistance on both mentioned, destructive factors.
- Model research on filling motion during ball mills operation
- Strony: 336-340
Ball mills are used in the cement industry for many years. In that kind of devices, the crushing process occurs as a result of collisions between grinding media and particles of material to be ground, and what is more, walls of the mill. Further, the described process embodied the mutual friction of the crushed particles. The aim of experimental research was to determine the behaviour of the grinding media while operating in a ball mill, and simultaneosly to measure rotational speeds of a drum, for which the milling process occurs with an appropriate intensity. The research was conducted on a test-bench that included, as a main feature, a rotating drum with a diameter of 700 mm and a width of 30 mm, posted on a rotating shaft. An examination of behaviour of the grinding media placed in the drum was possible to achieve due to recording data by a fast-speed camera. Based on registered bitmaps, assayed by using an analyzer DPIV (Digital Particle Image Velocimetry), local field speeds and a trajectory of moving particles were determined. This has allowed us to determine the rotational speeds that correspond to characteristic moments of the particle movement i.e.: the beginning of cascading, so-called the kidney phenomenon; the beginning and the end of cataracting motion; the commencement of swirling of the first grinding medium – critical speed, and the moment when the whole charge start to centrifuge. A polydisperse mixture including two types of spherical particles made of plastic material (a diameter of 6 mm) and Zirblast B60 (a diameter of 125-250 μm) constituted the charge. The research was conducted for three grinding media filling-degrees of 20%, 25%, and 30% at a constant content of material to be ground established on 10%. With an increase in the filling degree characteristic moments occured at similar or lower rotational speeds. The study was carried out in order to determine the impact of inner surface of the ball mill on kinetics of grinding media motion for three types of lining; plastic, rubber and galvanized steel tape was placed on a drum’s smooth contour wall. The use of the lining caused a reduction in the speed at which characteristic moments occurred. The end of the cataracting corresponds to a rotational speed of 0.6-0.8 critical speed, designated on experimental way. A trajectory at the end of the cataracting motion corresponds to the longest descending path of a moving grinding medium. The applied research methodology has allowed us to determine the behaviour of grinding media while operating of a ball mill. The test results confirm the influence of filling degree and also the type of lining on the behaviour of grinding media. This indicates the desirability to carry out further research on the kinetics of milling.
- Effects of firing conditions on evolution of microstructure of magnesia-chromite materials
- Strony: 341-344
In this work, the evolution of microstructure was studies in material of magnesia-chromite bricks prepared under industrial conditions. The magnesia-chromite material was sintered in three different temperatures. The phase composition and microstructure were examined applying scanning electron microscopy (SEM) combined with EDS analysis. The bulk density, apparent porosity, pore size distribution and gas permeability were measured, allowing to draw the conclusion that heat treatment influences greatly the development of microstructure of magnesia-chrome refractory materials. Firing at 1690 °C increased the open porosity and gas permeability which has been attributed to the sintering of fine particles around coarse ones. A temperature of 1500°C used for firing does not permit to complete the sintering process.
- Salt-Assisted SHS Synthesis of Aluminium Nitride Powders
- Strony: 345-350
Powders of aluminium nitride can be prepared by self-propagating high-temperature synthesis (SHS) between aluminium and nitrogen but its high exothermic effect causes melting and/or evaporation of aluminium and low efficiency of such reaction. A presence of inorganic salt in the starting powder mixture can decreases a heat evolved in the SHS reaction, hinders melting and coalescence of aluminium, and helps penetration of nitrogen into interior of a powder bed. Mixtures of alumina powder and different amounts of some easy decompose ammonium salts were subjected to the SHS reaction under 0.1 or 1 MPa nitrogen. The powders were composed of aluminium nitride, unreacted aluminium and in some cases aluminium oxynitride and corundum. Different factors influence an optimum conditions for the AlN synthesis: the amount of salt, which increase leads to a decrease temperature of the system, the nitrogen pressure, the higher the pressure the higher the reaction temperature, and the presence of oxygen in the system.
List of Contents
Volume 66, Issue 4
- The refractory lining of a rotary–rocking furnace in lead metallurgy
- Strony: 362-366
A metallurgical process with particular references to factors influencing the service life of the refractory lining was characterized. The influence of a charge composition on chemical corrosion of the lining was studied applying thermodynamic calculations. The amount of liquid phases and the extraction degree of selected components of refractory material to slag were calculated. The results of calculations were confronted with industrial tests of the refractories. On that basis, the conclusions referring to the selection of refractory materials were formulated, taking into consideration the chemical character of the charge with reference to the concentration of sulphide and oxide components.
- Hydration characteristics of calcium zirconium aluminate in the presence of reactive alumina
- Strony: 367-374
Calcium zirconium aluminate exhibits high hydraulic activity. The aim of this work is to study the hydraulic properties of Ca7ZrAl6O18. Application of Ca7ZrAl6O18 as a hydraulic binder in high-alumina and corundum refractory concretes, which contain reactive Al2O3 micropowder, has been proposed to be a promising route. For this purpose, the hydration of calcium zirconium aluminate with and without of Al2O3 addition was studied. Calorimetric studies of binders revealed that the total amount of generated heat decreased after 12 h of hydration in binder based on Ca7ZrAl6O18 and reactive Al2O3 micropowder. Based on the XRD, DTA-TG and SEM analyses it was concluded that the curing temperature determines the type and structure of calcium aluminate hydrates formed during the hydration of Ca7ZrAl6O18 phase.
- Evolution of andalusite microstructure during mullitization process
- Strony: 375-382
The natural andalusite in three grain fractions: 0-1 mm, 1-3 mm and 3-8 mm is studied. SiO2 and Fe2O3 were main impurities. The lowest concentration was detected for the 3-8 mm fraction. The aim of the study was to observe microstructural changes and to analysis the phase composition of raw andalusite heat treated at temperatures ranging from 800 °C to 1600 °C as a function of particle size. The mullitization rate of andalusite at various stages of heat treatment was evaluated. Observations the studied andalusite fractions were carried out using scanning electron microscopy (SEM) combined with chemical analysis in microregions (EDS). Phase components were identified by X-ray diffraction (XRD). Densities were determined by helium pycnometry. It has been found that the mullitization process commenced at 1300 °C and completely ceased at 1500 °C. The formation of the characteristic microstructure, consisting of mullite grains and an amorphous silicate phase which fills the space between the mullite grains, is carried out in two stages. First, at 1300–1500 °C, mullite grains of different shapes are formed, including the needle-shaped habit. At higher temperatures (1600 °C), when the process is completed, the needle-shaped mullite transforms to the flaky one. The formation of amorphous silicate phases was favored by an increase in concentration of impurities. The mullitization runs faster in finer grain size fractions with higher impurity concentrations.
- Thermal analysis of phases from the MgO-SiO2-H2O system
- Strony: 383-387
The aim of this study was to characterize influence of chemical composition on changes of hydrated phases from the MgO-SiO2-H2O phase system during thermal decomposition. The reaction of MgO, SiO2 and water creates the MSH phase. Interest in this phase is connected with its potentially wide applications in building and refractory materials industry. From the point of view of the refractory materials, behaviour of this phase during heating is extremely important and indicates on possibility of industrial application. Samples subjected to study consisted of MgO, SiO2 in different molar ratio and water to solid ratio of 2. The obtained mixtures were aged for selected times. The examination of the aged pastes included thermal, XRD and SEM-EDS analyses. The study revealed that changes of the internal arrangement of paste and the creation of new hydrated phases associated with layered magnesium silicates occurred during aging.
- The role of Cr(VI) sulphate reducers as cement materials modifying agents
- Strony: 388-392
Chemical compounds in the form of metal sulphates are frequently used as reducing agents of hexavalent chromium which is present in the cement. However, they influence the properties of the hydrating material. The study was performed using iron(II) sulphate, being the most widespread compound for reducing Cr(VI) to Cr(III)), and sulphates of tin(II) and manganese(II). The influence of the latter one on the cement hydration is still little recognized. The sulphates were introduced at various concentrations to cement prepared by grinding the Portland cement clinker with gypsum. Apart from the studies on the effectiveness of the reduction of chromium(VI) due to the various metal sulphates, a series of calorimetric tests was also carried out, showing in the continuous way a course of the hydration process. Moreover, the assessment of characteristics of the rheological properties of cement mix and the ionic conductivity was studied in a cement slurry. The standard water consistency, and both initial and final setting times of cement grouts doped with 1% metal sulphates were defined. The results clearly show the changes that take place during the hydration of cement doped with sulphates of iron, tin and manganese, when compared to the cement with no additives. These changes affect strength of the hydrated material.
- Effects of aluminate glassy phase on polymorphic transformation of β-C2S to γ-C2S
- Strony: 393-400
The process of polymorphic self-desintegration of calcium orthosilicate is a known phenomenon, and is the basis of the comprehensive method developed by Grzymek which comprises simultaneous production of aluminium oxide and high-alite Portland cement. In the paper the influence of the quantity of glassy phase, coming from aluminate phase (C12A7), and the course of cooling process on the polymorphic transition of β-C2S to γ-C2S was studied. It is indicated that the changeable quantity of aluminate phase influences both the stabilization of β-C2S to γ-C2S polymorphic transition, and the temperature changes of α’L-C2S to β-C2S transitions. The presence of the aluminate phase also leads to acceleration of self-desintegration based on the polymorphic transition of calcium orthosilicate.
- A calculation method of specific permeability of selected dolostones
- Strony: 401-407
During thermal decomposition of carbonate raw materials, e.g. dolomite, carbon dioxide flows from a reaction front to environment through produced, porous dolomitic lime. In mathematical models of carbonate raw materials thermal decomposition the carbon dioxide flux is written using Darcy’s equation. Specific permeability of porous dolomitic lime is a factor included in the equation. Therefore the aim of the paper is the proposal of a calculation method of dolomitic lime specific permeability. Knowledge of the dolomitic lime specific permeability may be a base of mathematical modelling of thermal decomposition of dolomite, which occurs during production of various goods e.g. glass or refractories.
- The influence of zinc oxide on microstructural features of crude ceramic glazes
- Strony: 408-411
In the present study the influence of zinc oxide (ZnO) on microstructural properties of row ceramic glazes from the SiO2-Al2O3-MgO-CaO-K2O-Na2O system were examined. The microstructure of glazes were determined by scanning electron microscopy (SEM) with an elemental composition analyzer in microareas (EDS), X-ray diffraction (XRD) and infrared spectroscopy (FTIR). X-ray diffraction, mid-infrared spectroscopy (MIR) and far-infrared spectroscopy (FIR) showed that zinc oxide incorporated to the glazes in an amount of 6% weight was a modifier of the glaze structure.
- The effect of thermally activated carbon shale on quality of sand-lime autoclaved bricks
- Strony: 412-420
The study summarises the results of laboratory testing of sand-lime materials, that were made of component mix of natural silica sand and burnt lime, and modified by adding variable amounts of carbon shale. This shale was added to the standard component mix containing lime and sand in the molar ratio CaO/SiO2 = 0,09. The carbon shale was in the natural form or followed thermal treatment at various temperatures and times of exposure. It displayed the required pozzolanic activity. The effectiveness of the use of this additive was estimated basing on the results of comparative analysis covering the basic functional parameters of two types of products: the reference sample (with no shale added) and several experimentally obtained sand-lime products differing in their qualitative and quantitative composition. Specification of thus obtained autoclaved materials is provided, alongside the results of structural and microstructure testing by the XRD, DTA, TG, IR and SEM methods.
- Surface redistribution of sodium created by ion beam and plasma in oxide glasses
- Strony: 421-423
The surface of compound silicate glass was modified by an oxygen ion beam, and the surface of float glass by low-temperature argon plasma. The sodium surface redistribution observed in these glasses was explained by the mechanical and field interactions of the ion beam and the thermal and field interactions of the plasma with sodium ions.
- Functional coatings obtained on soda-lime-silica glasses using chemical etching
- Strony: 424-428
The paper reports an attempt of obtaining the functional coatings on soda-lime-silica glasses by wet chemical etching. Based on a literature review, hydrofluoric acid has been selected as an etching medium. All glass samples were subjected to dealkalization before the chemical etching process. The etched glasses were characterized with respect to their optical properties, microstructures and wetting properties measured by static contact angle. The wet etching process was controlled by measurements of pH. The obtained glass surfaces showed an increase in degree of roughness, a relative increase of static contact angle when compared to the base glass, and an increased level of transmittance in the visible and near infrared wavelength range.
- Analysis of the chemical and phase composition of doped Mg2Si obtained by direct reaction of the elements
- Strony: 429-434
The aim of the study was to experimentally investigate the possibility of introducing dopants into the Mg2Si structure that include In, Ce and B and have not yet been studied, but could favourably affect the thermoelectric properties of the materials obtained. In order to verify the test methods comparative tests were also carried out for well-known dopants of Sn, Ge and Bi. The synthesis of polycrystalline materials with nominal compositions of Mg2Si0.9A0.1 (A = Sn, Ge, Bi, In or B) and Mg1.8Ce0.2Si was carried out in sealed tantalum ampoules (T = 1073 K, t = 7 days) in the presence of molten Mg. The reaction products were consolidated using the PECS technique (Pulsed Electric Current Sintering Technique), using T = 1023 K, t = 15 min and p = 30 MPa. The chemical composition of polished specimens was studied by carrying out point and linear analyses, using a scanning electron microscope with an EDS attachment for chemical composition analysis. The study did not reveal the presence of In, B and Ce dopants in grains of the received samples, which may indicate a lack of solubility in the structure of Mg2Si.
- Sintering the selected transition metal carbides without activators by SPS method
- Strony: 435-439
This paper presents results of sintering transition metal carbides without the addition of sintering activators. The groups of transition metal carbides include compounds derived from the direct connection of metal with carbon; the former one belongs to the groups from IV to VI of the Periodic Table of Elements. The mechanical properties of sintered carbides are determined mainly by the densification and grain size of a sintered material. The high melting temperature and low self-diffusion coefficients make it difficult to obtain fully dense carbide materials. In the case of conventional sintering method of metal-like carbides activating additives are used or the sintering process is carried out with the addition of metals e.g. cobalt, nickel or molybdenum. During the study, the sintering titanium, zirconium, vanadium, niobium and tantalum carbide powders was carried out without activating additives by using the Spark Plasma Sintering method. Samples were sintered at 2200 °C. Sintering time was 5 min and 30 min. Microstructure was observed by using scanning electron microscopy, and densities, Young's moduli and hardness were measured. The best properties were obtained for the zirconium carbide powder sintered for 30 min. For this material, the relative density and Young's modulus was 98% and about 93% of the theoretical value, respectively.
- The synthesis and sintering of tantalum diboride TaB2 using SPS method
- Strony: 440-445
Ceramic materials composed of a matrix based on borides, carbides and nitrides of transition metals have strong covalent bonds and high melting points over 3000°C. These materials show stability of physical and mechanical properties over a wide temperature range, and therefore can be used as responsible components of thermal protections, machine parts working at high temperatures or other elements for applications which require a resistance to oxidation. This paper presents reactive sintering as a method of the obtaining tantalum diboride TaB2. The synthesis of tantalum and boron powders and the sintering process were carried out in a single technological stage using the SPS/FAST method (Spark Plasma Sintering, Field Assisted Sintering Technology). Sintering processes were carried out for 5 min at a temperature of 2200 °C. Heating rates ranged from 50 °C/min to 400 °C/min. The study aimed to determine the influence of heating rate on the microstructure and properties of the sintered materials. The results of X-ray phase composition and SEM analyses are presented. The density by hydrostatic method, Young's modulus by ultrasonic method, and hardness by Vickers’ indentation were also determined for a complete characterization of the materials.
- Modelling of temperature distribution in the Bridgman type toroidal apparatus
- Strony: 446-450
The simulation was aimed to determine the temperature distribution in the Bridgman-type toroidal apparatus in the initial stage of the sintering process. Calculations were performed using the finite element method (FEM). A geometric model, which mapped a graphite heating element, sintered material and mineral-polymer gaskets, fulfilling also the role of a medium for pressure transmission, and both electrical and thermal insulator, was used. Heating in the model was realized by the flow of electric current whose changes as a function of time correspond to actual values, which occur during the sintering process in a high-pressure high-temperature apparatus (HPHT). Verification of the results was made on the basis of comparison of the calculated values of current voltage, current flow, and temperature to the values recorded in the control measurements. The resulting good agreement between calculated and measured values allows further development of the presented model, including next stages of the HPHT process.
- The effect of admixtures of polypropylene and acrylic fibres on shrinkage cracks of renovation plasters
- Strony: 451-462
Formation of shrinkage cracks in renovation plasters is still a topical subject. We know the causes for shrinkage cracks formation, but in literature it is difficult to find an answer to the question of what to do to reduce this vulnerability. One way is to use reinforcement in the form of fibres. The effect of incorporation of polypropylene and polyacrylonitrile fibres to restoration mortars on the formation of shrinkage cracks. For this purpose, a recipe of dry mixture consisting of silica sand, cement, aeration additives and lightweight aggregate (perlite) has been prepared. The mixture was stirred with dry fibres for approx 60 s, and then with water for additional 60 s. The resultant mortar was then transferred to the testing gutter, and thickened. Thus prepared sample was cured at 53 °C in an oven equipped with air circulation. After this cycle, shrinkage cracks appeared in the surface of the sample. The type, length, and fibre content dependence of the resistance to cracking of the renovation plasters was studied by measuring the length and width of cracks. To verify the optimization method and to optimize the size and number of fibres introduced to a plaster, the statistical approach based on the multiple regression analyses was used. A significant reduction in the width and the length of shrinkage cracks has been obtained in case of the renovation plasters reinforced with polypropylene fibres with circular cross-sections and acrylic ones when their length and the amount was about 12 mm and about 1.2 kg/m3, respectively. The fibrillated polypropylene fibres were less effective in reducing the formation of shrinkage cracks. The influence of fibres on the formation of shrinkage cracks in the restoration plasters during the curing was studied on the basis of changes in the average width and the total length of the cracks per testing gutter. The mathematical calculations confirmed the usefulness of the gutter method to evaluate the susceptibility of a plaster to create shrinkage cracks.
- Fracture toughness of hot-pressed Si3N4-graphene composites
- Strony: 463-469
The work concerns the influence of microstructure on fracture toughness of hot-pressed silicon nitride-graphene composites. The phase analysis was carried out to identify constituent phases of the matrix. The presence of graphene was controlled by analysis of Raman spectra, and a graphene phase distribution in the composite microstructure was studied by SEM observations with EDS analysis. The microstructural observations of fractures and polished surfaces of the composites were made to determine the arrangement of the graphene phase. The fracture toughness was measured with the use of the three-point bending test on notched beams. The results of KIC measurements were supported in interpretation by the SEM observations of the crack propagation.
- Strony: 470-480
- List of Content for Volume 66
- Strony: 481-490
- Spis treści tomu 66