T. A. Khabas

Zirconia-based solid electrolyte obtained by tape casting

The possibility of using tape casting to produce solid electrolyte films with a thickness of 100–300 μm from zirconia stabilized with oxides of scandium and cerium is considered. A method of slip casting onto a moving tape is used to produce rather thin ceramic sheets with a thickness of less than 1 mm. An organic slip based on azeotropic mixture of isopropyl alcohol and methyl ethyl ketone is used in the present work. The effect of solvents on the properties of the obtained film and sintered ceramic is analyzed. Dibutylphthalate, polyethylene glycol, and benzyl butylphthalate are used as plasticizers. The effectiveness of these plasticizers is based on the possibility of producing a slip with a viscosity of 2000–4000 mPa s by using them. Polyvinyl butyral appears to be the most optimal temporary binder, because it is satisfactorily removed in a continuous mode of annealing of plated ceramic blanks. The maximum density of ceramic plates is achieved at the annealing temperature of 1500°C. It is shown that the working range of the obtained solid electrolyte is 800–850°C, as the maximum ionic conductivity (more than 0.15 Ω−1 cm−1) is registered in it.

Developing porous ceramics on the base of zirconia oxide with thin and permeable pores by crystallization of organic additive method

In this paper porous ceramics on the base of ZrO2 nanopowders and micropowders has been developed by freeze-casting method. A zirconia/carbamide slurry was frozen in mold and dehydrated in CaCl2 at room temperature. This simple process enabled the formation of porous ceramics with highly aligned pores as a replica of the carbamide crystals. The samples showed higher porosity of 47.9%. In addition, these materials could be used as membrane for air cleaning.

Study of Preparation of Prescribed Pore Configuration in Zirconium Dioxide Ceramic Due to Carbamide Directional Solidification

The possibility is demonstrated of preparing porous ceramic based on zirconium dioxide micro- and nanopowder using crystallization of carbamide in a suspension. Different suspension cooling regimes are studied for oxide powders (in air, in a freezing chamber, in snow). It is shown that sintered ceramic porosity and pore size depend directly on suspension composition and cooling method. As a result of this ceramic is prepared with porosity of 30 – 60% with pore diameter of 0.2 – 200 μm.

Effect of Modifying Additions on Synthesis and Properties of Cordierite-Mullite Ceramic from Kazakhstan Resources

Results are given for a study of the effect of LiF, ZnO, and Ce2O3 modifying additions on synthesis and properties of cordierite-mullite ceramic from Kazakhstan resources. It is established that addition of LiF, ZnO, and Ce2O3 facilitates activation of synthesis for cordierite-mullite ceramic based on natural raw material. Addition of LiF reduces the temperature for the start of eutectic melt development, facilitating intensification of cordierite formation, and ZnO and Ce2O3 act by a solid-phase mechanism. Introduction of LiF, ZnO, and Ce2O3 into the composition of cordierite-mullite ceramic in an amount of 0.5 – 2.0% makes it possible to reduce its firing temperature and increase density, strength, and chemical and thermal stability.

Crystal phase formation in colored leucite-reinforced glass-ceramics for dental restorations

The influence of additives of rare earth elements on the crystallization and properties of glassceramic materials such as coatings for metal crowns in prosthetic dentistry was studied. A material for coatings was synthesized from a mixture based on potassium feldspar with the addition of oxides of alkali metals in the form of carbonates and fluorides as well as salts and oxides of rare earth elements. The additives of rare earth elements were introduced to give the coatings natural color. It was shown that the additives influence both the color and the phase composition of a coating by impeding crystallization. Upon the increase in the content of additives by more than 0.5 wt %, the thermal expansion coefficient of glass-ceramic materials increases.

Study of the SHS Addition Effect on Phase Composition of Cordierite Ceramics

Ceramic cordierite-based materials are widely used in metallurgy, mechanical engineering and in the chemical industry as refractories, filters and catalyst supports. In this article, the activation of the synthesis of cordierite ceramics additives obtained by SHS is described. These additives consist of a mixture of mineral and alumina nanopowder in various ratios.

Increase in strength of porous alumina ceramic by additives of aluminum oxide nanopowder

Sintering of alumina ceramic with 95% Al2O3 [VK 95-1] content with additives of aluminum oxide nanopowder and without it is studied. The increase in strength by 32 ± 3% is ensured by additives of 1.5 ± 0.5 wt %. The strength reaches 170 ± 5 MPa, which allows it to be used as dental prosthesis forms in stomatology.

Heat-Insulating Ceramics which Have a Nanoporous Structure and are Made with the Use of Ash-Bearing Wastes from Power Plants

It is determined that the pore-forming effect exhibited by ash and ash microspheres in compositions with clayey rocks is due not only to certain structural features (the presence of spherical hollow particles) and the makeup of the ash components (the presence of residual fuel in the ash) but also to physico-chemical processes (the synthesis of anorthite and mullite) which take place in clay – ash-and-clay – ash- microsphere systems and prevent shrinkage during sintering.

Non-metal dental ceramics on the base of titanium oxide

The growing trend goes today to the production of metal-free denture. On the one hand, the reason for this is the rapid development of the CAD/CAM technology and on the other hand, the best aesthetics and biocompatibility of ceramics - in particular the titanium dioxide ceramics - in comparison with metals. The possibility of using titanium oxide with additives of different compounds for dentistry is studied in this work.

Development of compositions of glass-ceramic coverings for titanium-containing alloys

The durability of metal-ceramic compositions, including a porcelain fused metal crown, depends on the structure of coverings and pretreatment of the surface of metal. Multicomponent structures are investigated. The influence of separate initial components of a glass bath on masking ability and adhesive strength of glass-ceramic coverings is analyzed.