Volume 68 (2016)
List of Contents
Volume 68, Issue 1
- The influnece of rheological properties of Ti2AlC slurry on the microstructure of porous carbides manufactured by the gel-casting method
- Strony: 4-8
Ternary carbides such as MAX phases are nano-layered ceramics that exhibit a unique combination of characteristics typical of both ceramics and metals. In porous forms they can be used for example as catalyst supports or as preforms for metal-ceramic interpenetrating composites. In this work porous Ti2AlC foams were manufactured by the gel-casting method with the use of agarose as a gelling agent. The rheological properties of Ti2AlC slurries with different agarose content were investigated. A correlation between the viscosity of the starting slurry and the microstructure of the final foam has been found. The mean cell size and window size as well as the total porosity decreased with increasing agarose concentration in the starting slurry.
- Basic properties of the PFN ceramic doped by potassium
- Strony: 9-13
In the work, PFN ceramics were obtained by a one-step synthesis. The ceramics were modified with the help of potassium incorporated in an amount of 1.0%, 2.0%, 3.0%, 4.0% and 6.0 mol%. Effects of the potassium dopant on the crystal structure, microstructure and main properties of the PFN ceramics were studied. It has been shown that the heterovalence doping of PFN by the potassium in the amount of 2.0-4.0 mol%. had a positive effect on the density and microstructural homogeneity of the ceramic samples. Such a potassium admixture limited the formation of the non-ferroelectric (pirochlore) phase during the technological process. Measurements of dielectric properties of the doped compositions have shown that potassium causes a decrease of the maximum permittivity and reduces slightly the degree of blur of the phase transition. There is also an increase in the dielectric loss and electrical conductivity. There was no a clear trend in the effect of the incorporated potassium additive on the basic parameters of the PFN ceramics.
- Surface modificcation of glass packaging by nanoparticles of aluminium compounds with the addition of Li2O
- Strony: 14-16
The results of modification of glass packaging by nanoparticles of aluminium compounds with the addition of Li2O marked on hot surfaces of products were presented in this work. Strength tests such as internal pressure, vertical load and impact strength proved the obtainment of modified surfaces of the glass which increased strength of bottles. The satisfactory results were obtained with respect to transparency, chemical resistance and surface microhardness. SEM investigations of the modified functional coatings on the glass surface are also presented.
- The influence of corona discharge on properties of glass surfaces
- Strony: 17-21
Surface treatment of glass in the low temperature plasma is becoming increasingly important due to its good performance and low cost of the equipment. The paper presents preliminary results of research on effects of low temperature plasma generated in the process of corona discharge on physical properties and chemical composition of the glass surface. Treatment of the glass in the plasma led to the reduction in an equilibrium contact angle of 37º for the untreated glass to 5.5º after a few seconds of treatment. XPS analysis showed an increased concentration of sodium and OH groups on the plasma treated surface and an increase in surface activity.
- Impact of chemical composition and morphology on the porous materials sorptivity
- Strony: 22-27
The development of transport, technology and industry results in more frequent problems with uncontrolled oil spill which could contaminate the environment, polluting at the same time water, soil and air. There are several methods of removing the spills of petroleum derivatives. Among the most commonly used methods to remove them is to collect oil with mineral sorbents. Due to availability, easy usage and accessible price the user is able to select such a product that will be effective and will not be toxic to the environment. According to the users, absorbency is the most important parameter for sorbents used both on paved surfaces and water surface. Good sorption properties of the sorbent make possible the use of small quantities of the product to collect a relatively large oil spill. The main aim of this article is to show the influence of the chemical composition and morphology of selected mineral sorbents which are available on the Polish market on their sorption properties. Presented are the results of optical microscopy observation, scanning electron microscopy, a qualitative analysis of the chemical composition by EDS and absorbency tests performed by the gravimetric method.
- Merging of fly ashes derived from the combustion of municipal waste
- Strony: 28-31
Ashes and fly ash derived from the combustion of municipal wastes contain a series of dangerous elements in their compositions, including heavy metals that are posing a threat to man and his environment. The particles of the solid body included in the air are regarded as fly ash. Industrial ash is posing the greatest threat to the health of the man when particles are 0,1-100 μm in size. One of the ways for immobilizing them can be through immobilization in the glassy matrix that will allow the ecologically safe neutralizing by the storage. The technology of manufactirung glass-ceramic material is presented in this work. Glass-ceramic materials were obtained through the sintering process. Used were in particular waste materials, derived from municipal incinerators in the form of ash, as well as waste cullet from Huta Szkła Gospodarczego Tadeusz Wrześniak Sp. z o.o. Mixed ash from the cullet was compressed, and then subjected to a heat treatment of 850 °C. Crystalline phases were identified stating that wollastonite was the dominating phase. Examinations of the microstructure were also performed with a scanning microscope. They also conducted a research for leaching of chlorine and sulphur ions from the received samples of glass-ceramic.
- Synthesis and sintering of the BLT ceramics doped with Fe3+
- Strony: 32-37
A goal of this study was to prepared Ba1-xLaxTi1-x/4O3 (BLT) ceramics doped with iron, and characterized by a perovskite structure ABO3. Excess amounts of the oxide donor Fe3+ dopant for substituting titanium ions were incorporated to the basic BLT ceramics, thereby obtaining materials having the general formula Ba1-xLaxTi1-yFeyO3 (BLTF) where x = 0.003 and y = 0 (BLTF0), y = 0.001 (BLTF1), y = 0.002 (BLTF2) and y = 0.003 (BLTF3). The materials were obtained by synthesizing powders with a conventional method, in which simple oxides for the synthesis in solid phase were used (MOM method), and the resultant powders were consolidated by using natural sintering method or hot pressing. All the ceramic powders were subjected to thermal (TG/DTA) and differential thermogravimetric (DTG) analyses. The chemical composition of ceramic BLTF powders was determined by using energy dispersive spectroscopy (EDS). Microstructures of both the powders and BLTF ceramics were observed by using scanning electron microscopy (SEM). The EDS measurements proved the obtainment of assumed chemical composition of the BLTF ceramics within the experimental error of ± 3%.
- Preparation of barium titanate La3+-doped ceramics by the sol-gel method
- Strony: 38-43
The (Ba1-xLax)Ti1-x/4O3 (BLT) ceramics with a lanthanum content of 0 £ x £ 0.005 were prepared by using the sol-gel method. Amorphous gels of BLT were calcined at a temperature of 850 ºC and pressed into pellets. The compacts were next sintered by the free sintering method at a temperature of 1450 ºC for 4 h. Simultaneous thermal analysis (STA) was used, in which both thermal analysis (DTA) and mass change effects (TG and DTG) were measured concurrently on the same sample using a derivatograph MOM Q-1500D. The morphology of BLT ceramics was studied by scanning electron microscopy (HITACHI S-4700). The crystalline structure of BLT ceramics was studied by the X-ray diffraction method.
- The properties of piezoelectric ceramic fibres
- Strony: 44-48
Ceramic piezoelectric materials can be prepared in various forms and shapes, starting from traditional bulk volumetric ceramics, and thin or thick ceramic layers finally ending in the form of ceramic fibres or even virtually any shape which is associated with novel production methods taking advantage of 3D printers. Piezoelectric fibres have a number of advantages compared to volumetric ceramics of the same type. Among them are improved anisotropy of properties, impossible to achieve in bulk ceramics, flexibility and associated with this greater mechanical strength. However, the methods, the quality of the starting components and the conditions for preparing this type of piezoelectric fibres still remain a vast area of research and investigations in order to effect optimum electrical and electromechanical properties of the final material. Objects of the experiment were to produce piezoelectric fibres by the extrusion method, examine electrical and piezoelectrical parameters, and comparative analysis with commercial bulk ceramics properties.
- Investigation of the hydration process of calcium aluminate cement without and with the addition of colloidal silica)
- Strony: 49-55
This paper presents the study of a hydration process of calcium aluminate cement paste containing colloidal silica. The cement pastes prepared without and with addition of colloidal silica were cured at 50 °C for 3 days and 42 days. Results of studies of the phase composition and the microstructure of cement pastes are shown, and the thermal decomposition mechanism of C-A-H and C-A-S-H (C ≡ CaO, A ≡ Al2O3, S ≡ SiO2, H ≡ H2O) phases is studied. For this purpose, XRD, SEM/EDS and DTA-TG-EGA techniques were used.
- Influence of deflocculants on the properties of slurries used for the preparation of ceramic proppants
- Strony: 56-60
The purpose of this study was to investigate the rheological properties of ceramic slurries assigned for the preparation of ceramic proppants used in the process of hydraulic fracturing in shale gas extraction deposits. The slurries contained 50 wt% of solid phase (kaolin, clay, bauxite or a mixture of them) in water. Three kinds of different deflocculants: ammonium poly(acrylate), isodecyl benzoate, sodium poly(acrylate) were used in an amount of 0.25 wt% in relation to the solid phase. The study identified by XRD and XRF the qualitative composition of the raw materials used to produce the slurries, and the size distribution was determined by using a particle size analyzer. Standard industrial parameters of slurries were examined, comprising dynamic viscosity, kinematic viscosity, density and pH. The studies indicated the effect of deflocculants on the properties of slurries. It has been found that the nature of the deflocculant has a significant impact on the properties of the obtained slurries which may be useful in the formation of ceramic proppants.
- Directions in development of mills for raw materials and mineral binders grinding
- Strony: 61-69
The paper presents main directions in development of mills used in milling processes of mineral raw materials for cement production and cement clinker, lime, gypsum, and coal. These are new constructions of gravity (ball-pipe) mills and high energy mills, including vibratory, planetary and high pressure roll mills also called presses. These mills are used as preliminary or final mills. The high-energy mills have more than twice output power per volume unit of the mill chamber, when compared to the gravity mills. The vibratory mills are characterized by 3-5 times bigger output power, whereas the Hicom planetary mills have 100-150 bigger output power. The bigger power made possible the construction of mills with larger capacities, smaller sizes and weight, and lower power consumption. The other direction concerns the development of high pressure grinding rolls (HPGR) that include Beta Mill, Horo Mill and Premill. The paper reports some parameters of the mentioned mills and the main directions in development of their construction, that is, an increase in dimensions of grinding chambers and power of drive systems, and new solutions of main working units.
- Supporting effect of silver on BSCF cathodes for SOFC
- Strony: 70-75
Cathode materials for solid oxide fuel cells should show good catalytic activity in the oxygen reduction reaction (ORR), high electronic and ionic conductivities at relatively low temperature, and the thermal expansion coefficients (TECs) compatible with the electrolyte. Ba0.5Sr0.5Co0.8Fe0.2O3–δ (BSCF) shows one of the greatest catalytic activity in ORR which occurs on the overall surface of the electrode. Oxygen vacancies in BSCF permit to transport a significant amount of oxygen ions. Nevertheless, BSCF revealed its high TEC and low electrical conductivity. Some properties of the electrode can be improved by adding a second phase to the BSCF electrode. Silver shows the greatest electronic conductivity among metals; it is cheap and has excellent catalytic activity in the ORR. Moreover, the presence of Ag in the composite cathode increases the electronic conductivity of the cathode and reduces the area specific resistance (ASR). The goal of this work is to make comparison among properties of the BSCF cathode, the Ag cathode, the cathode with silver interlayer between BSCF and electrolyte (Ag|BSCF), and the Ag|BSCF cathode with the additional silver layer on the top of the cathode (Ag|BSCF|Ag). The cathodes were prepared on the Ce0.8Sm0.2O1.9 electrolyte disks and tested using scanning electron microscopy (SEM) and electrochemical impedance spectroscopy. SEM examinations of the obtained electrodes revealed consistent with the goal, well connected, porous 3D structures. The contact was significantly better in case of the composite electrodes. Equivalent electrical circuits were used for fitting impedance spectra. The circuits consisted of a resistor R0 and three (or two) resistors and capacitors parallel connected in pairs (Ri, Ci) and combined in series. The fitting errors were smaller than 0.7% in all cases. The m and α coefficients were received from Arrhenius plots of ASR and the fitting, and indicated that the charge transfer was the rate-determining step for the Ag|BSCF|Ag electrode, whereas for the BSCF and Ag|BSCF electrodes it was the oxygen ions transport through the BSCF. Activation energies of ASR for the BSCF, Ag, Ag|BSCF and Ag|BSCF|Ag cathodes were similar, yielding the values of 55.1 kJ∙mol-1, 47.7 kJ∙mol-1 , 47.7 kJ∙mol-1 and 37.9 kJ∙mol-1, respectively.
- Strony: 76-78
List of Contents
Volume 68, Issue 2
- Kinetics of cement hydration in the presence of some additives and admixtures
- Strony: 86-92
The mixtures of portland cement with by-pass cement kiln dust (CBPD) were investigated. The rate of heat evolution on the hydration of this mixture, as well as the chemical shrinkage, rheological properties and strength development were examined. The substitution of low amount of cement (up to 10%) by the kiln dust does not affect practically the properties of cement based composites with respect to setting or hardening. At higher amount of kiln dust the hydration process is accelerated because of the presence of well soluble components, however, the “dissolution” effect is also observed. The experiments with some carbonate waste material have been maintained with the aim to reduce the effect of soluble, aggressive salts that accelerate the hydration from one side, but contribute to the corrosion process from another one.
- A probabilistic model of the gravitational classification process in the fluidized bed
- Strony: 93-97
The results of theoretical and experimental studies of the classification process in a fluidized bed jet mill are presented in the paper. In the experimental studies, the effect of both working air volumetric flow rate and classifier rotor speed on material mass in the fluidized bed was investigated. The gravitational classification process in the fluidized bed is the subject of theoretical analysis presented in the paper. In this case, the size distribution of particles occurs due to the random drifting of fines from a layer. Therefore, a probabilistic model is proposed to the mathematical description of the process. The principles of statistical physics are used in the model. The article also presents results of the experimental verification of the gravitational classification model that prove the adequacy of the mathematical description and the real process.
- Study of the possibility of mullite synthesis by the microwaves process
- Strony: 98-104
Small presence of mullite in nature results in practical importance of a synthetic mineral. Preparation of mullite is related to the properties of raw materials such as: chemical purity, grain size, phase and the synthesis process at a high temperature. The synthesis of mullite with the use of a microwave oven is presented. Al2O3, and SiO2 powders with micrometer and nanometer grain sizes were used for the synthesis. The test results include the phase composition of products in relation to the properties of raw materials and synthesis temperature.
- Preparation of barium titanate nanopowders by hydrothermal method
- Strony: 105-109
In this work the experimental conditions for growth of BaTiO3 nanoparticles in aqueous solutions using of barium nitrate, chloride or hydroxide were studied at 100-200°C. In all of the studied cases XRD proved the existence of BaTiO3 after hydrothermal synthesis. However, the morphology of the obtained powders was different. At lower temperatures (100-150 °C) star-like or polyhedron nanoparticles were observed. Synthesis at 200 °C allowed obtaining spherical particles of size and degree of agglomeration dependent on the process time and the type of the substrates used.
- The effect of addition of fly ashes on crystallization of silicate glasses
- Strony: 110-114
The paper analyzes the susceptibility to the process of crystallization of silicate glasses obtained on the basis of classic glass raw materials with the addition of fly ashes. Due to the fact that glass is a material with the disordered structure, it was essential to define the basic temperature parameters closely related to phenomena occurring during the heating of glass. For this purpose, the tested material was subjected to thermal analysis. On its basis the appropriate temperatures have been selected at which the devitrification process of tested glasses was carried out. Microstructural changes that occurred during the thermal treatment (the shape and size of crystals being formed) and the phase composition of the glass-ceramic material were characterized. The obtained results allowed assessing effects of the addition of fly ashes on the crystallization process of the obtained silicate glasses.
- The use of fibrous amorphous waste as an additive for road marking paints
- Strony: 115-119
The disposal of waste is a necessary activity, bringing multilateral benefits, particularly in economic and environmental aspects. The paper proposes the use of the amorphous waste received in the production of glass fibres to improve the quality of road markings. The influence of different amounts of the additive and the degree of fineness of the waste on the functional properties such as abrasion resistance and reflectivity was examined. It has been stated that the tested amorphous waste material can be a very cheap replacement for glass microspheres used in paints for road markings.
- The effect of alternative fuels on the operation of Portland cement clinker kiln installation and the properties of common cements
- Strony: 120-124
The effect of solid alternative fuels RDF introduced by the main burner to the rotary cement clinker kiln on processes occurring in the installation was studied. The change of cement clinker properties, resulting from the use of alternative fuel co-processed with the coal one was discussed. It has been found that the Portland cement CEM I 42.5 produced from the clinker obtained in this system complies well with the standard quality requirements.
- Technical progress in cement milling technology on an example of the ODRA cement plant
- Strony: 125-133
Milling is the most energy-consuming technological operation of cement production. Tube ball mills have played dominant role in the cement technology since many years. Ascending costs of energy force searching for new, more energy-saving milling methods. The current state of the cement milling techniques is shown in the paper, together with an example of modern, productive and energy-saving installations used in the ODRA Cement Plant. The modernized milling line brought the plant many advantages, including the lowered unitary energy consumption, the increased productivity, and the improvement of cement quality parameters.
- The use of waste glasses for immobilization of sediments originated from the neutralization of industrial sewage
- Strony: 134-139
Vitrification is one of the most effective methods of immobilization of hazardous waste. Toxic elements are incorporated into the glass structure. Waste bulb and tampered glasses were studied. Two kinds of sediments from the neutralization of industrial sewage were used as an immobilized waste. Thermal properties of the base glasses and glasses formed during vitrification of glass-waste mixtures were determined. Hydrolytic resistance tests proved the possibility of usage of both bulb and tampered waste glass to the immobilization of the sediments.
- Electrical properties of Ba(Ce0.95Ti0.05)0.8Y0.2O3 solid electrolyte
- Strony: 140-144
The aim of the presented work was determination of electrical properties of oxide solid electrolyte of the formula Ba(Ce0.95Ti0.05)0.8Y0.2O3. Phase compositions of powder prepared by the mechanosynthesis method as well as of sintered bodies were confirmed by the X-ray diffraction technique (XRD). Material electrical properties were studied by electrochemical impedance spectroscopy in the frequency range of 0,1-107 Hz, the temperature range of 300-700 °C and different atmospheres: 10% hydrogen in argon, argon and 3000 ppm ammonia in helium. The analysis of experimental spectra was conducted by the method of fitting the best equivalent circuits. Basing on the specific conductivities results, Arrhenius plots were depicted, distinguishing the results obtained at high, medium and low frequencies. The activation energy values with uncertainties were calculated by means of linear regression analysis. The Arrhenius plots exhibiting total conductivities were also depicted. The comparison of the results obtained in different atmospheres and wide range of temperatures facilitated explanation of electrical conduction mechanisms in the investigated material.
- Preparation of TiO2 nanocrystals with different particle size and specific surface area by the sol-gel method
- Strony: 145-149
The paper describes a sol-gel method for preparing nanocrystaline powders with various particle size and phase composition (anatase/rutile). The XRD analysis showed that TiO2, depending on the calcination temperature, crystallizes in the tetragonal structure of anatase (T ≤ 540 C) or tetragonal structure of anatase and rutile (T = 560 °C). The increase in calcining temperature results in the transformation of anatase to rutile, particle agglomeration and sintering, entailing particle growth and reduction of specific surface area of the powders.
- Oligomeric ozonidy - synthesis, properties and biological impacts on selected pathogenic fungi
- Strony: 150-155
Ozone is a gas with high chemical activity and strong oxidizing properties. Oxidizing properties of ozone are used to destroy pathogenic micro-organisms, including bacteria, fungi and viruses. However, the use of ozone in the gaseous form for therapeutic purposes is cumbersome and not always possible. Biocidal properties exhibit also some vegetable oils treated with ozone for a specific time. The article describes the procedure for the synthesis of biologically active polymeric compounds (ozonides). The synthesis was based on olive oil. Using infrared spectroscopy, structural changes under the influence of ozone on the oil were analyzed. The observed changes relate mainly to the formation of oxygenated compounds building a ring, which then go into linear forms. Changes in viscosity as a function of ozonization time indicate the formation of branched structures, and passing the polymeric forms in the oil. Under the influence of ozone the chromophore dyes contained in the oil are oxidised. The high activity of ozone in relation to coloured compounds contained in the oil was confirmed by UV-VIS spectroscopy. Studies results of the bioactivity of the synthesized oligomeric ozonides on selected pathogenic fungi confirmed the strong antifungal activity of these compounds.
- Influence of selected organic compounds on the type of corrosive changes of historical glass depending on the state of their behaviour
- Strony: 156-161
The main goal of this research was investigation of the influence of chosen organic compounds on the corrosion of XVIII c. historical glass; acetic acid and formaldehyde were selected. Glass objects exhibited in museums can suffer from vapours of these organic compounds due to the reaction which results in leaching elements from the glass. A glass sensor method was applied to have more experimental material. The studies were carried out by using modern physico-chemical methods such as optical and scanning electron microscopy, induced coupled plasma mass spectroscopy, and Fourier transform infrared spectroscopy. The information obtained provide a valuable source of knowledge about the chemical reactions on the glass surface due to corrosion. The results derived from this work are useful for the design and implementation of exhibition recommendations and better planning of conservation tasks
- Selected research problems of the oxygen reduction reaction at the Pt|8YSZ interface
- Strony: 162-167
This paper presents the investigations of the oxygen reduction process in the O2|Pt| 8YSZ (8 mol.% Y2O3 in ZrO2) system using the quasi metallic point and porous platinum electrodes. The chronoamperometric and electrochemical impedance spectroscopy measurements were performed for the O2|Pt|8YSZ system at 700 °C after polarization of the platinum electrode with a negative overpotential of DE = -0.5. The increase in absolute values of current, which flowed in the O2|Pt|8YSZ half-cell, was noticed for both types of platinum electrodes during the long-term polarization. Electrochemical impedance spectroscopy investigations revealed a decrease of ohmic resistance Rs which should not be dependent on the applied voltage. The decrease in polarization resistance Rp was also noticed, being mainly related to the electrode reaction kinetics of oxygen reduction. The main reason for the observed changes in the Rp and Rs resistances during the long time polarization at the overpotential of -0.5 V could be related to variations of the Pt electrode geometry. These facts were confirmed by the SEM/EDX analysis. The platinum electrode polarized with the negative overpotential is a source of dendrite-like particles deposited on the 8YSZ surface. Thus, expansion of the metallic dendrite structure in the place of direct contact with the quasi point electrode caused a increase of the three phase boundary area. As a consequence of this, a continuous increase in current for the O2|Pt|8YSZ system was observed. These observations agree with the XPS/ESCA investigations which identified changes in the surface structure of the 8YSZ ceramic electrolyte that occurred during the long-time polarization.
- Mechanical properties of pressure sintered alumina-graphene composites
- Strony: 168-175
The work concerns the alumina-graphene materials sintered by two different pressure methods. The preparation route of the matrix-graphene mixture was discussed in the paper. The prepared compositions with different amount of graphene were hot-pressed or spark plasma sintered. The influence on uniaxial pressure during the sintering process on the microstructure was studied by the SEM microstructural observations and ultrasonic measurements. The work presents also the results of measurements of elastic and mechanical properties. Wear tests were made and friction coefficients determined by the ball-on-disk method.
- Modeling of thermal residual stresses in the SiC-TiB2 composite system considering real microstructure and thermo-mechanical properties anisotropy
- Strony: 176-182
The results are presented concerning simulations of the distribution of thermal residual stresses in a ceramic matrix particulate-reinforced composite in the SiC-TiB2 system. The stresses arise during cooling of the material after sintering due to differences in thermal expansion and elastic properties of the component phases, and belong to the most important factors for increasing fracture toughness of ceramic composites. A computational model was built on the basis of the real microstructure of the SiC-TiB2 composite. The material properties of component phases used in calculations included their temperature dependences. A temperature difference caused shrinkage and residual stress was adopted by means of the analysis of the sintering curves. The simulations were performed by using the finite element method. The results of simulations were compared with the calculated values of residual stresses, basing on analytical models and experimental data. The comparison shows good agreement. This allows an elaborated model to be used to solve more complex problems concerning fracture analysis of ceramic matrix composites.
- Strony: 183-184
List of Contents
Volume 68, Issue 3
- Study of ceramic pigments with perovskite structure
- Strony: 188-192
Our attention was focused on preparation of inorganic pigments based on the perovskite structure of SrSnO3, in which part of tin ions was substituted by ions of terbium and titanium or terbium and cerium. The particle size (d50) of all pigments is between 2-3 μm. Powders with the general formula SrSn0.6-xTixTb0.4O3, where x = 0.1-0.6, provide an intensive yellow colour hue in application into an organic binder, and white glossy surfaces in application into a ceramic glaze. A SrSn0.4Ti0.2Tb0.4O3 sample offers the best colour parameters in application into the organic binder: the highest amount of yellow hue (b* = 58.95) and the highest saturation (C = 59.05). Powders with the general formula SrSn0.6-xCexTb0.4O3, where x = 0.1-0.6, also provide an intensive yellow colour hue in application into the organic binder and dark yellow-orange glossy surfaces in application into the ceramic glaze. The most interesting yellow colour hue has powder SrSn0.4Ce0.2Tb0.4O3 applied into the organic binder. In application into the ceramic glaze, an increase of cerium ions content in pigment shifts the hue from yellow to dark orange.
- The effect of firing temperature on colour and structural properties of malayaites with Cr
- Strony: 193-198
Malayaites are calcium tin silicate compounds derived from natural occurring mineral the malayaite which has the chemical formula CaSnSiO5. Malayaites are characterized by monoclinic crystal structure consisting of chains of distorted SnO6 octahedra connected with tops of SiO4 tetrahedra, forming a framework containing chains of CaO7 polyhedra. This incurred structure is then stable for bond of metal ion and takes part in the final pigment colouring. In this contribution the compounds with the chemical formula of Ca(SnCr)SiO5±δ (molar ratio of Cr/Sn = 0.015) were prepared. For the synthesis the classical ceramic method was used, i.e. procedures of calcination in an electric furnace at the temperatures 1200-1500 °C for 4 h (one-step calcination) and multiple calcination (two-step calcination) for obtaining products with higher quality. Therefore, the objective of this work was to compare samples which were prepared by the one-step and also two-step calcination procedures. The two-step calcination procedure was carried out at two temperatures, during which the first calcination was always held at 1100 °C for 4 hours. The second calcination was performed for 4 h at an appropriate temperature from the range 1200-1500 °C. The colour properties were studied by a spectrophotometer ColorQuest XE (HunterLab, USA). The colour moved from pink to burgundy in dependence on temperature of calcination. The phase composition of tested compounds was verified by using X-ray diffraction analysis with using a diffractometer D8 Advance (Bruker, GB). A particle size distribution of heat treatment samples was measured by Mastersizer 2000/MU (Malvern Instruments, Ltd., GB). The signal was evaluated on the basis of Fraunhofer bending. Thermal stability was investigated by heating microscope EM201-12 (Hesse-Instruments, Germany).
- The effect of preparation method on pigmentary properties of manganese doped cassiterite pigments
- Strony: 199-203
The presented work deals with the possibility of synthesis of blue-violet cassiterite pigments, in which a part of tin ions was substituted by cobalt and manganese ions. In this case, phosphorous is used as a charge-compensating element. The compounds with the formula Sn0.752Co0.08P0.16Mn0.008O2 were prepared by solid state reaction, using the classical ceramic method, and also the method of mechanical activation. The goal was to develop conditions for synthesis and the most suitable preparation method of these pigments. The temperature range was chosen from 1350 °C to 1500 °C. The synthesised pigments were characterised in terms of colour properties after their application into the transparent ceramic glaze P 074 91 and into the organic binder. They were also studied with respect to their phase composition as well as the particle size distribution.
- Synthesis and characterization of the Bi2Ce2-xZrxO7 pigments
- Strony: 204-207
This contribution is focused on the synthesis, characterization and optical properties of new inorganic pigments, being environment-friendly and enable to substitute some toxic metals in interesting colour compounds. The pigments were prepared by the solid-state reaction. The colour properties of prepared applications were investigated depending on the content of Zr and temperature of calcination (800-1000 °C after step 50 °C). The optimum conditions for the pigments synthesis were determined. The pigments were evaluated from the standpoint of their particle sizes. Characterization of Bi2Ce2-xZrxO7 pigments (x = 0 to 2 after step 0.25) suggests that they have a potential to be alternative yellow or orange colourants for paints, plastics, ceramics and building materials.
- The manufacturing of silver nanoparticles by arcing
- Strony: 208-212
The paper presented a method for producing silver nanoparticles by arcing. The particle size distribution and morphology analysis results of the obtained silver nanoparticles are presented. XPS analysis confirmed the presence of silver in the metallic state, however, the nanoparticles are surrounded by a layer of adsorbent containing molecules of ethyl alcohol. The synthesized particles had the spherical shape with various diameters in the range of 4 nm to 120 nm.
- Different approaches to heat transfer in calcined bed of particle limestone batch – Part I: Simplified model of heat transmission
- Strony: 213-217
Heat transport to a calcined limestone particle surface from a flowing gaseous mixture and surfaces of the other particles surrounding the particle occurs by radiation, convection and conduction. On the whole it is assumed that a basic part of heat transport to a limestone batch occurs by radiation. A simplified model of heat transfer is shown in this paper. The model is used to the rough calculation of the heat flux transported to the particle during calcination within a layer ,and an assumption is formulated applying to the packing of particles in a small volume of particle layer. The calculation results of experiments carried out for determination of calcined particles emissivity for chosen limestones and produced limes will be shown in the second part of the paper together with the calculation results of other model coefficients.
- Different approaches to heat transfer in calcined bed of particle limestone batch Part II: The coefficients of the simplified model
- Strony: 218-223
Emissivity of three limestone types and related limes was determined and the results shown in the paper. The limestone samples were taken from industrially exploited deposits. The measurements revealed high values of hemispherical emissivity of limestone surfaces originated from wet slashing test samples with a diamond saw. The values ranged from 0.95 to 0,96, and were slightly small than hemispherical emissivity of lime. Heat fluxes due to radiation and convection, which flow to the calcined particle surface, were calculated and compared. The calculations indicated an insignificant contribution to the process from convection.
- Slag corrosion of MgO-C materials in attitude of dimensional analysis
- Strony: 224-229
Working conditions for refractory materials applied in various high temperature devices are variable, and the lifetime of these materials depends on many different factors. Therefore an attempt to determine a dimensionless dependency of wear degree of MgO-C materials used for a steel ladle lining has been undertaken. The form of the dimensionless equation consists of key factors of ladle operating conditions and corrosive effect of slag on the refractory lining. The equation is characteristic for a specific high temperature device, but its constant and exponents are variable and distinctive to the type of refractory material in use. The relationship, which was elaborated, was accurate for the material MWH643 used in refractory linings of steel ladles.
- The Potential Use of Calcite Wastes in The Production of Clay Masonry Units
- Strony: 230-235
The use of carbonate wastes in ceramic masonry units production might be an environmental friendly way to utilize them. While the presence of coarse-grained calcite in the clay raw material can lead to destruction of the fired product, the controlled amount of fine-grained calcite addition can lead to enhancement of ceramic material properties. Such a fine-grained calcite is present in wastes from limestone aggregates washing and also from Maerz furnace bag filters.
This paper presents laboratory research on the usefulness of carbonate wastes in production of ceramic masonry units. As additives to kaolinite-illite clay, the waste from washing limestone aggregates and the waste from Maerz furnace bag filters were used. As a comparison, ceramic material with the addition of pure calcite to clay also was made.
Selected properties of ceramics materials such as water absorption, porosity, density, frost resistance, and compressive strength were determined. The addition of wastes and calcite to raw material mixtures was at a level of 5%, 10% or 15% by weight. The firing temperature were 950 °C and 1050 °C.
Studies confirmed the possibility of use of the calcite wastes as an additive in production of ceramic masonry units protected and unprotected from external factors (according to PN-EN 771-1).
- Influence of dolomite addition to masses made from Triassic clay on application properties, phase composition and microstructure of ceramic materials produced
- Strony: 236-241
Poland is a country rich in dolomites. During the extraction and processing of this raw material, dusts are generated which may have potential application in the ceramic building materials. Due to the high content of CaO and MgO being fluxes, the usage of dolomite as an additition to ceramic masses should intensify the process of sintering, and consequently affect the physical and mechanical properties of resultant ceramics. In this paper, the results of research of ceramic materials obtained from masses based on Triassic clay added by the dolomite Ołdrzychowice addition of 0%, 5%, 10% and 15% by weight are presented. Two firing temperatures: 950 °C and 1050 °C were used. Water adsorption, apparent density, frost resistance, compressive strength and flexural strength were determined. Phase composition of the obtained materials was also measured. Microstructure analysis was made by SEM using photomicrographs of microsections. It has been found that the addition of dolomite to Triassic clay may increase the mechanical strength; the max. 15% increase was measured in case of both the flexural strength of materials added with 5% dolomite and the compressive strength of materials added with 15% dolomite fired at 1050°C. Analysis of the phase composition showed new crystalline phases such as diopside or anorthite which crystallised in materials obtained from masses containing the dolomite. It has been found that the addition of the dolomite to Triassic clay in the amount ranging from 5% to 15% improves frost resistance of ceramic materials fired at 1050 °C, suggesting their potential use for building walls unprotected against external influences.
- Effect of a zinc oxide additive on properties of glazes in the SiO2-Al2O3-CaO-K2O-Na2O-ZnO system
- Strony: 242-245
The paper presents the results of research concerning raw aluminosilicate ceramic glazes in the multicomponent SiO2-Al2O3-CaO-K2O-Na2O-ZnO system with a variable content of zinc oxide (0%, 5%, 10%, 15%, or 20% by weight). A phase composition analysis (XRD) showed all the fired glazes to be fully amorphous materials. The effects of zinc oxide additives on the transition temperature (Tg) of glazes was determined by the dilatometric method (DIL). The influence of ZnO on viscosity and surface quality (roughness) of glazes was also investigated.
- The effect of zirconium oxide on the surface parameters of porcelain glazes
- Strony: 246-253
Zirconium raw materials are commonly used as a glaze opacifer. Moreover, the presence of zirconium oxide and/or zirconium silicate in the composition of a glaze improves its mechanical and chemical properties. In this paper the influence of addition of zirconium oxide on surface parameters of porcelain glazes is presented. Twelve glazes with a constant molar ratio of SiO2/Al2O3 and Na2O/K2O and a variable molar ratio of CaO/MgO were examined. Zirconium oxide was added in three different amounts 1.5 wt.%, 3 wt.% and 6 wt.%. to the glazes. Glazes without additions of zirconium oxide were also prepared as a reference sample. Whiteness in the CIELab system and roughness were measured on surfaces of the glazes. Furthermore the chemical durability tests were performed. Interesting dependences between the amount of zirconium oxide and surface parameters were obtained as a results.
- Influence of granulation parameters in the high-energy mixer on a shape of light proppants prepared from the masses containing fly ashes
- Strony: 254-258
Proppants in the form of millimeter-size sintered granules are used for the fracturing of a rock mass during extraction of shale gas. Creation of a mechanical support and maintenance of pits after the gas extraction are among other things the proppant tasks. The criteria for suitability of proppants comprise their shape, size, and compressive strength, of which the first two criteria are closely related to the granulation process. This paper describes influence of granulation parameters of a high-energy mixer on the shape and size of lightweight proppants based on stoneware.
- Lightweight fired aggregate with the addition of zeolites after sorption of oil products
- Strony: 259-266
In this work we tested the suitability of zeolite sorbent gained from the sorption of petroleum compounds as an additive raw material for production of lightweight aggregates. The starting material of montmorillonite clay was modified with different amount of zeolite Na-P1 synthesized from fly ash after using it in the process of sorption of diesel. The resulting mixtures were tested using a high temperature microscope. The results indicated the 10% additive of overworked zeolites to the weight of raw materials as optimal. The paper shows also the physical properties of aggregates which were obtained with the 10% waste sorbent addition by sintering at 1170 °C. It has been found that the resultant material had the properties of lightweight aggregate.
- Montmorillonite-indomethacin/naproxen hybrid materials: preparation, selection of the optimum conditions of intercalation and characterisation
- Strony: 267-273
The aim of the study was to investigate the use of montmorillonite (MMT) as a potential drug carrier. Two medicines with a negative electrokinetic potential were selected for intercalation of montmorillonite, namely indomethacin and naproxen, having anti-inflammatory and analgesic properties. Montmorillonite-based drug carriers were prepared by a 24 hours stirring of suspension with an aqueous solution of both dissolved drugs at 20 °C, 50 °C and 80 °C. The obtained materials were tested for the amount and ways of incorporation of the drug in the montmorillonite structure. Changes in electrokinetic potential of the obtained carriers (MMT-drug hybrids) as compared to the starting montmorillonite were determined by measuring the zeta potential. The presence of the drug introduced into the interlayer spaces of MMT was examined using the following measurement methods: X-ray diffraction (XRD), infrared spectroscopy (FTIR) and scanning electron microscopy (SEM). The results confirmed the possibility of drug incorporation into the structure of the mineral. The efficiency of intercalation was found to be depended on the temperature of process, and the most preferred one from that viewpoint was the processing at a temperature of 50 °C. However, the negative zeta potential of the drug prevented the complete intercalation of the drug between the layers of montmorillonite.
- Abstracts of Workshop on Contemporary Bioceramics - Kraków, September 12th, 2016
- Strony: 274-281
- Spis treści tomu 68
- Abstracts of Workshop on Extraordinary Boride Ceramics for Advanced Engineering Applications - Kraków, September 11th-12th, 2016
- Strony: 282-283
- Spis treści tomu 68
- Polish company launches an innovative SPS device
- Strony: 284-287
The article deals with the comparative analysis of two methods of materials consolidation under pressure: (i) HP (Hot Pressing), and (ii) SPS (Spark Plasma Sintering). The paper presents the first Polish commercial SPS device developed by GeniCore, and designed for sintering of a wide range of materials.
- Strony: 288-291
List of Contents
Volume 68, Issue 4
- The effect of mechanochemical processing on formation of Ca-α-SiAlON:Eu2+ powders
- Strony: 300-304
The Ca-α-SiAlON:Eu2+ powders were developed by combining mechanochemical processing (MCP) of the initial powders with the subsequent solid state reaction in the reducing atmosphere of a graphite furnace. The photoluminescence (PL) spectra of the mono-phase Ca-α-SiAlON:Eu2+ phosphor powder were compared to the mono-phase powders produced without the MCP step. Specimens were synthesized in the temperature range of 1450-1650 °C for 2 h under a nitrogen flow. Mechanochemical processing of the initial mixture of nitrides led to their surface oxidation and formation of a larger amount of the oxynitride liquid. On the other hand launching the Eu2+ ions among additives during MCP and the subsequent Ca-Al-Si-Eu-O-N eutectic liquid formation during the thermal treatment is responsible for a higher optical performance of the resultant phosphor.
- Synthesis of Si2Al4O4N4 powder by SHS method
- Strony: 305-309
The self-propagating high temperature synthesis, SHS, was used to prepare sialon with the assumed stoichiometry of Si2Al4O4N4 (z = 4). Powders of elemental Al, elemental Si, Al2O3 and SiO2 were chosen to prepare starting mixtures. Molar proportions between elemental silicon and elemental aluminium were changed, and the amounts of aluminium and silicon oxides resulted from the assumed stoichiometry. The mixtures of powders in the form of a loose bed were placed within a high-pressure reactor in a graphite container. The SHS reaction was initialized by a flow of current through the container. The reaction was carried out in the nitrogen atmosphere under a pressure of 0.1 MPa, 1 MPa, or 3 MPa. The influence of composition, grain size distribution of the starting powders and nitrogen pressure on SHS synthesis products was checked by the XRD and SEM methods.
- The influence of aluminium borate whiskers on the structure of residue amorphous glass ceramic matrix composites made of Al2O3
- Strony: 310-314
Two types (A and B) of porous abrasive composites were produced with the participation of glass crystal material from the system of ZnO-B2O3-Al2O3-SiO2 and microcrystalline alumina. After the thermal processing of the composites at 1050 °C for 3 h, glass crystal material with a fine crystalline gahnite phase constituted the ceramic matrix of composite A; in composite B, Al4B2O9 whiskers constituted an additional phase in the matrix. Composites B with the participation of the whisker phase are characterized by a very uniform positioning of the adhesive on alumina grains, which was the result of a change in the amorphous structure of the residue as compared to the residues in the composite A. It was demonstrated by the FTIR method that the framewark of boric aluminium silicate residue glass in the composite A underwent a reconstruction in the composite B. As a result of crystallization of whiskers, structural units [BO3] dominate in the amorphous residue of the matrix, resulting in lowering the residue glass temperature. An ideal distribution of a thin matrix on Al2O3 grains possesses undoubtedly an additional (apart from whiskers) positive impact on the mechanical strength of the composite.
- The influence of certain technological parameters on the quality of ceramic pigments
- Strony: 315-319
Ceramic pigments are fine grained, insoluble, crystalline coloured compounds with the structure of selected natural minerals. The criterion of quality is an attractive and intense colour gained after firing by ceramics when decorated with a very little amount of the pigment. The properties of the colouring pigment are determined by the type and quality of the crystal structure, the type of chromophore built to it, and the particle size distribution and morphology of grains in connection with the dispersive colouring mechanism of ceramics. Production of pigments, that show a set of specified properties, is conditioned by the use of technological parameters comprising the chemical composition, quantitative and qualitative amount of mineralizers and modifiers, synthesis temperature, grinding, that are matched to the specificity of pigments in crystallographic groups.
- Structural, transport, and electrochemical properties of Na0.7Fe0.5Mn0.5O2 cathode material for Na-ion batteries
- Strony: 320-323
This work presents a high-temperature method of synthesis of a new cathode material for Na-ion batteries with the layered structure P2-Na0.7Fe0.5Mn0.5O2. The crystal structure and temperature dependence of electrical conductivity of the obtained material were investigated. The synthesized powder was applied as cathode material in Na/Na+/NaxFe0.5Mn0.5O2-type cells. Specific capacity of the cathode material, reversibility and stability during charge-discharge cycles measurements were carried out in order to characterize electrochemical properties of the cells. The highest discharge capacity of the Na/Na+/NaxFe0.5Mn0.5O2 cell was about 200 mAh/g with C/20 current rate. The monotonous voltage changes were recorded in the range of 2-3 V. Results obtained by the in-situ XRD technique during the process of charging and discharging of the Na/Na+/Na0.7Fe0.5Mn0.5O2 type cell provide a conclusion that the crystal structure of cathode material does not change during the electrochemical deintercalation/intercalation process of sodium except of reversible changes of structure parameters.
- Mechanical properties of graphene flake-reinforced Y2O3 ceramics at elevated temperatures
- Strony: 324-328
The influence of graphene flakes and temperature (in the range of 20 °C to 800 °C) on mechanical properties of Y2O3-graphene composites was studied. In order to obtain samples the commercial nano-sized Y2O3 powder with a purity of 99.99% and GO flakes obtained in ITME were used. The composites were manufactured basing on an aqueous mixture of both components, which was dried and sintered using HP and SPS methods. The composites contained 1% and 3% by weight of graphite oxide (GO). Raman spectroscopy confirmed the presence of reduced graphene oxide (RGO) in the resulting composites. It was found that as a function of the GO content the bending strength σc increased by approx. 21% and 28% for composites sintered using HP and SPS, respectively. In turn, the KIc fracture toughness decreased as a function of the GO content in the HP sintered samples, but it increased by approx. 78% for the samples sintered using SPS. In case of the HP sintered samples, σc increased by 15% at 800 °C for Y2O3, but did not change for the composites with GO. On the other hand, for the SPS sintered samples, σc did not change for Y2O3, but it increased by approx. 8% and 19% for the composites with 1% and 3% GO additive, respectively. KIC decreased as a function of temperature for the Y2O3 sintered by HP, but it increased by 39% and 73% for the composites with 1% and 3% GO additive, respectively. In case of the SPS sintered ceramics KIC increased at 800 °C by approx. 88% for Y2O3, 20% and 26% for 1% and 3% GO additive. The mechanism of toughening by RGO flakes consisted of twisting the plane of fracture and blocking of crack propagation.
- Fireproof additives in polyvinyl acetate wood adhesives
- Strony: 329-334
Preliminary results of research on the development of a recipe of wood adhesive with selected ceramic additives aimed at improving its fireproof properties are presented. A basic medium was dispersion with pH in the range 3-5 based on polyvinyl acetate, to which various fire retardants such as silica, aqueous solutions of sodium and lithium silicates, urea and aluminum chloride were introduced. Their task is to help, among other things, to create a thermally insulating charred layer, to reduce the flammability of laminated wood, or to produce radicals which inhibit the combustion process. Such prepared mixtures were tested towards its rheological (viscosity measurements in different temperatures), thermal (TG/DTA analysis) and strength (tensile strength) properties. It was noticed that the best miscibility characterizes the adhesive mixtures with aqueous solutions of lithium and sodium silicates with molar modulus 3.2 and 4.5, respectively, and pH = 11. Addition of sodium and lithium silicates, as well as addition of silica, increased viscosity of the tested mixtures at room temperature from about 3000 mPa∙s up to 14 000 mPa∙s, while the presence of salt and urea did not cause major changes. An increase in temperature caused a decrease in viscosity. Only in the case of the D2 adhesive with 15 wt% of urea the viscosity of the mixture remained stable up to 60 ºC. The results of thermal analysis showed that the total change in weight of the tested samples were greater than 90%, and the maximum loss in mass was in the temperature range of 300-350 ºC (approx. 60% of total weight). The additives did not significantly affect the weight loss, but shifted the characteristic temperatures to higher values. The carried out tensile strength tests revealed that the applied fire retardants did not significantly impair the strength parameters of adhesive joints, and in some cases even improved them. A maximum extension stress for pure glue was 6.34 MPa, and for other tested mixtures it fell within the range of 6.17-6.87 MPa. Only for D2 adhesive with 15 wt% of aluminum chloride this value was significantly lower (5.18 MPa).
- The possibility of intensification of graphite nanopowder production in the vibratory tube mill
- Strony: 335-339
An experiment of preparation of graphite nanopowder was conducted in the laboratory vibratory mill with kinematic actuation of oscillating motion at low vibration frequency of 12 Hz. The milling process of graphite powder occurred in a wet environment of ethylene glycol aqueous solution. The graphite used in the experiment had a BET specific surface area of 3.12 m2/g. Research in milling process was performed in a standard chamber and in a chamber equipped with an additional cylindrical element which reduced a zone of the lowest activity of grinding media. During the milling in the standard chamber, Graphite powders with a BET surface area of 46 m2/g and 57 m2/g were obtained after a milling time of 9 h and 12h, respectively; in the chamber equipped with the additional cylindrical element the powders of a surface area of 63 m2/g and 72 m2/g appeared at the same milling times, respectively. An equivalent grain size of graphite particles, calculated on the basis of the specific surface area values, was 49 nm and 39 nm for the milling in the standard chamber and one equipped with the additional cylindrical element, respectively. The results indicate good usability of vibratory mills for production of graphite nanopowders preferably in case of the chamber equipped with an element which intensifies the milling process.
- Fused magnesia-doloma co-clinker for production of carbon-bonded dolomite bricks
- Strony: 340-345
Fused magnesia-doloma co-clinkers with 60 wt.% of MgO and less than 2 wt.% of fluxes have been prepared. Carbon-bonded dolomite bricks were obtained using co-clinkers, resin and scale graphite. Corrosion tests were carried out in an induction furnace using a synthetic slag. The samples prepared from fused co-clinkers were compared with carbon-bonded brick based on sintered clinker with 4,4 wt.% content of fluxes and magnesia-carbon brick, both of them produced using the same binder. The quantitative evaluation of the results of corrosion resistance of the tested materials were carried out.
- Magnesia raw materials from alternative resources
- Strony: 346-354
The results of R&D works are presented, concerning the obtainment of magnesia raw materials derived from saline water. The works were done in frames of realization of a POIG project: Action 1.4 "The application of aggregates obtained from domestic alternative resources in refractory materials" by Zakłady Magnezytowe ,,ROPCZYCE” S.A. in cooperation with the Faculty of Materials Science and Ceramics at the AGH-UST in Kraków. Magnesium hydroxide was precipitated by using an experimental line and calcined in a tunnel furnace of Zakłady Magnezytowe ,,ROPCZYCE” S.A., using specially prepared coffers. The obtained caustic magnesia was fused in an electrical arc furnace of an innovative line for fusion developed during the realization of the project and it was used for the manufacturing of magnesia aggregate. The determination of calcination losses and chemical composition of magnesia products has been done in each technological stage. Selected fractions of the magnesia aggregate were characterized with respect to their phase composition, chemical composition in microareas, and microstructure. The magnesia aggregate derived from the saline water fulfilled requirements expected by aggregates that are used for production of basic refractory materials.
- Magnesia-carbon products made from raw materials originated from alternative resources - properties and application
- Strony: 355-361
Magnesia in the unfired refractories containing carbon is the main factor which influences resistance to corrosion and erosion processes, occurring in the steelmaking process. The careful selection of raw materials determines durability of refractory linings. The article presents the properties of the magnesia-carbon refractories produced using raw materials from alternative sources and the results of tests of their use in a steel ladle. The article is a summary of the results obtained during the performance of research and development conducted in the framework of a POIG project: Action 1.4 "The application of aggregates obtained from domestic alternative resources in refractory materials".
- The calcium zirconate refractory material and its behaviour in contact with molten steel
- Strony: 362-368
The behaviour of material composed of calcium zirconate and zirconium oxide after working in contact with molten steel was presented in this work. The calcium zirconate - zirconium oxide material was obtained by 2-step firing at 1100 °C and 1600 °C. The commercially available steel was used. A corrosion test was conducted under reducing atmosphere at a temperature of 1500 °C. A plate of steel was placed on a calcium zirconate pellet. The microstructure was observed under an electron scanning microscope (SEM) which allowed distinguishing 3 zones in the corroded material: a reaction zone in contact with steel, a transient zone, and an unchanged area. The content of calcium zirconate in the CaZrO3-ZrO2 material decreased against the zirconium oxide after the corrosion test. In the reaction zone the ZrO2 layer was created as a results of reaction between calcium zirconate and alloying components of steel such as silicon and aluminium. Compactness measurements showed that bulk density and apparent porosity changed slightly which could suggest that molten steel poorly penetrates the studied refractory material during the corrosion test.
- Influence of Gd2O3 on the developing of low-phonon oxyfluoride glass-ceramics
- Strony: 369-375
The aim of the research was to determine the influence of Gd2O3 addition on thermal stability of glasses from the BaF2-NaF-Gd2O3-Al2O3-SiO2 system. Thermal analysis was carried out using the DSC method. An impact of Gd2O3 on thermal parameters such as transformation temperature (Tg), onset temperature of crystallization (Tx), peak crystallization temperature (Tp), change of specific heat capacity (Δcp), and enthalpy of crystallization (ΔH) were determined. On the basis of the thermal analysis, controlled crystallization was conducted. The glass-ceramic materials were identified by XRD. It is stated that the addition of Gd2O3 to the aluminosilicate glass increases the transformation temperature, at the same time reducing the Δcp and thermal stability ΔT values. This results in a decrease in ΔH. The complete substitution of Al2O3 with Gd2O3 leads to the formation of Gd9.33(SiO4)6O2. Simultaneously, crystallization of Na-silicates is not observed. Because of the participation of Gd in the formation of fluoride phases (BaGdF5, GdF3), crystallization of Gd9.33(SiO4)6O2 is impeded.
- Calcined aluminium oxide nanopowders of boehmite origin and narrow particle size distribution
- Strony: 376-383
The synthesis of aluminium oxide powders composed of nanocrystalline particles of high temperature polymorphs that show extremely narrow size distributions is reported. Al(NO3)3∙9H2O was used as a reagent in two bottom-up synthesis processes: i) calcination of precursor boehmite obtained through controlled dehydroxylation of aluminium hydroxide, and ii) calcination of a hydrothermally crystallized precursor boehmite. The former method is solely the solid state synthesis of the product, the latter one involves crystallization of the precursor in a liquid state. Both methods, creating different crystallization conditions for boehmite, deliver alumina particles of different mechanical strength and therefore different behaviour during comminution. The processes of alumina nanopowder preparation were accompanied by intensive attrition milling at crucial manufacturing stages. The influence of the applied ways of boehmite precursor preparation on the morphology and size distribution of alumina particle was studied. The nano-powder composed of α-Al2O3 and a mixture of θ-Al2O3 and α-Al2O3 was produced in the case of the conventional calcination and hydrothermal method, respectively. The additional attrition milling of the hydrothermal boehmite product heated for 1 h at 450 °C decreased a crystallization temperature of α-Al2O3 from 1297 °C to 1199 °C when compared to the unmilled product. A crystallization temperature of 1185 °C was determined for the solely calcined alumina powder. The hydrothermal treatment followed by pre-calcination at 450 °C and attrition milling allowed obtaining mesoporous θ-Al2O3 nano-particles of elongated shapes and sizes in the range of 60-300 nm with a median of 150 nm when crystallized for 0.5 h at 1040 °C. When the same comminution conditions applied to the finally calcined precursor, the alumina powder originated from the precursor, which has not been treated hydrothermally, was composed of particles ranging from 35 nm to 3 μm with a median of 200 nm and the presence of some amount of the fraction of 20-180 μm. Thus, a significant role of the hydrothermal treatment combined with low temperature pre-calcination and attrition milling has been proved for the manufacturing of narrow distribution Al2O3 nanopowders.
- Sorting machines for spherical grinding media
- Strony: 384-389
In ball mills, vibratory mills, and stirred ball mills, the most commonly used working parts are spherical grinding media that wear out unevenly during grinding, resulting in an unfavorable change in their size distribution followed by deterioration of technological conditions of the grinding process, harmful clogging of sieve compartments, and damage of transport equipment of a grinding system. In the paper given are examples of design solutions currently manufactured grinding media sorting machines, descriptions of their structure, and basic technical parameters. There is also presented our own concept of a new device for sorting balls, being several times more productive. This device has a modular structure, so it can be adapted to sort grinding media with a diameter from a few to 120 mm.
- Strony: 390-397
- List of Content for Volume 68
- Strony: 398-406
- Spis treści tomu 68