S. N. Kul'kov

Porosity and mechanical properties of zirconium ceramics

The article studies the porous ceramics consisting of ultra-fine ZrO2 powders. The porosity of ceramic samples varied from 15% to 80%. The structure of the ceramic materials had a cellular configuration. The distinctive feature of all experimentally obtained strain diagrams is their nonlinearity at low deformations characterized by the parabolic law. It was shown that the observed nonlinear elasticity for low deformations shown in strain diagrams is due to the mechanical instability of cellular elements of the ceramic framework.

Thermal tests and their effect on the micro- and macrostructure of nanocrystalline ZrO2

The paper examines the effect of thermal tests involving water quenching at 1000°C on structural and phase transformations in nanostructured ceramics based on ZrO2 partially stabilized by Mg+2 in high-temperature modifications. The ceramics have different amounts of magnesia in the ZrO2–MgO solid solution and, as a consequence, different ratios of high- and low-temperature modifications of zirconia. It is shown that the ZrO2–MgO solid solution decomposes regardless of its magnesia content with increasing number of thermal tests, but the ceramics remain resistant to thermal shock even in case of complete MgO removal, i.e., zirconia destabilization.

The Influence of Temperature on the Properties of ZrW2O8

A single-phase zrW2o8 was prepared by the hydrothermal route via decomposition of zrW2o7(oH1.5,cl0.5)•2H2o at 843 k. tem, in situ high-temperature XrD and tG-DtA analyses of the zrW2o8 synthesized were performed. the morphology of the material was represented as elongated particles with an intrinsic block structure. the stability fields of zrW2o8 were determined. the zrW2o8 demonstrated a negative thermal expansion behavior from 298 to 1023 k. keywords: zirconium tungstate; Hydrothermal synthesis; negative thermal expansion coefficient. Elena Dedova Graduated at the national research tomsk state university (russia) in 2010. At present she is post-graduate student in strength Physics and materials science sB rAs under the guidance Prof. kulkov. topic of her Ph.D. work is “structure features and properties of tungstate zirconium and alloys Al zrW2o8”. elena Dedova is author and co-author of 25 articles. Fernando Pedraza is a professor of Laboratoire des sciences de l’ingénieur pour l’environnement in the université de La rochelle (France). At present he is the vice-president of université de La rochelle and responsible for the international relations. Prof. Fernando Pedraza is a well known expert of aeronautical materials including high temperature oxidation and corrosion of turbines and has several scientific publications in these fields. János Erdélyi Graduated at the mechanical engineering Faculty in university of miskolc (Hungary) in 2004. At present he is assistant professor in the inst. Dep. of ceramics and silicate engineering under the guidance of Prof. Gömze. He prepared and successfully completed his Ph.D. thesis in 2013. Dr. erdélyi is author and co-author of 22 articles. Prof. Sergey N. Kulkov Prof. kulkov is head of Department of ceramics in the institute of strength Physics and materials science of the russian Academy of science since 1989. He has got scientific degrees „Doctor of Physics and mathematical sciences” in 1990. since 1992 he’s working as professor both in tomsk state university and in tomsk Polytechnic university. in 1997 he had a soros Professor grant. His research works are represented in 5 books, more than 150 articles, 18 patents and many international symposiums and conferences. At present he is head of department „theory of strength and mechanic of solids”, member of „the American ceramic society” of „the APmi international” and the Dym At society (France).

Vacuum sintering of a ceramic based on zirconium dioxide

The results of a study of the phase composition and mechanical properties of a ceramic based on ZrO2-Y2O3 after vacuum sintering of powders with complex morphology in a wide range of temperatures and sintering holding times are reported. Dense ceramic materials with high mechanical properties were obtained.

High temperature vacuum sintering of plasmochemical powders based on ZrO2

The phase composition and mechanical properties of ZrO2-based ceramics prepared by sintering plasmochemical powders of complex morphology in air and in vacuum were compared. Sintering at a high temperatures in vacuum produced material exhibiting high density and good mechanical properties, in which the zirconium dioxide was entirely in the tetragonal form.

Formation of Structure and Closed Porosity under High-Temperature Firing of Granules of Porous Glass-Ceramic Material

On the basis of broken glass, clay, and organic additives, granular insulating glass crystalline material and technology of its production is developed. The regularities of the effect of composition and firing temperature on the properties of the granules are specified. The resulting granular thermally insulating material is produced with a bulk density of 200–290 kg/m3, pellet strength of 0.82–2.5 MPa, thermal conductivity of 0.067–0.087 W/(m °C), and water absorption of 2.6–3.2% by weight. The effect of the basic physical characteristics of the components of the charge on the process of pore formation is studied. According to the results of investigations, the basic parameters affecting the sustainability of the swelling glass are specified. The rational charge composition and thermal and gas synthesis mode are chosen so that the partial pressure of gases is below the surface tension of the melt. This enables the formation of granules with small closed pores and vitrified surface. The article presents the results of studies on the use of foamed glass ceramic materials for pipe insulation of heating mains.

Zirconia-based sintered ceramics for biomedical applications

A porous ceramics obtained from ultra-fine powders has been studied. The porosity of ceramic samples was from 15 to 80%. The structure of the ceramic materials was a cellular structure. A distinctive feature of all deformation diagrams obtained in the experiment was their nonlinearity at low deformations which was described by the parabolic law. It was shown that the observed nonlinear elasticity for low deformations on deformation diagrams is due to mechanical instability of the cellular elements in the ceramic carcass.

Effect of annealing on the structure and phase transformation in ZrO2–MgO ceramic powders

The structure and phase composition of ZrO2–MgO powders with the MgO content from 9 to 43 mol % obtained by the plasma chemical method after annealing at 700–1400°С are studied. Differential scanning calorimetry and powder thermogravimetric analysis are carried out. It is found that, in the course of heating, the mass loss and the endothermic reactions energy increase with the increase in the MgO content. In the initial state, the powders containing more than 25 mol % of MgO are supersaturated solid solutions of cubic ZrO2. Water desorption processes and decomposition of residual nitrates are observed in powders up to 420°С. The endothermic peak at high temperatures is due to the dehydration process and decomposition of the cubic ZrO2 solid solution.

The Preparation and Structural Features of Zirconium Tungstate Possessing Abnormal Thermal Properties

Single-phase ZrW2O8 was prepared by hydrothermal synthesis via the decomposition of ZrW2O7(OH1.5, Cl0.5) · 2H2O at 570°C. Transmission electron microscopy, in situ high-temperature X-ray diffraction, and thermogravimetric-differential thermal analyses of synthesized ZrW2O8 were performed. The morphology of the material was represented as rod-shaped particles having a block structure. The stability fields of ZrW2O8 were determined. ZrW2O8 demonstrated a negative thermal expansion behavior from 25 to 750°C.

Technological Properties of Ultradisperse Plasmochemical Powders

The casting properties and the moldability of ultradisperse plasmochemical powders based on aluminum and zirconium oxides are studied after synthesis and annealing at different temperatures. It is demonstrated that after relatively low-temperature annealing it is possible to obtain slip with satisfactory casting properties without a significant increase in the size of crystallites in the powder particles.