Yu. I. Komolikov

Technology of ceramic micro and ultrafiltration membranes (review)

Technological properties and structural and performance characteristics of ceramic filtering cells are discussed. Methods for the preparation of porous materials for micro and ultrafiltration are reviewed.

Sintering of Composite Ceramic Based on Zirconium and Aluminum Oxide Powders

Dilatometry is used to study kinetic features of sintering composite ceramic of the ZrO2 (Y)–Al2O3 system in the zirconium dioxide concentration range, stabilized with Y2O3, from 0 to 100 wt.%. Composites are prepared by mixing aqueous dispersions of the corresponding oxides. It is shown that within the heating regime with a constant shrinkage rate for composite ceramic xZrO2(Y) – (100 – x)Al2O3, within which x has a value from 0 to 100, does not proceed linearly. The maximum shrinkage rate and minimum temperature for the start of compaction applies to compositions containing 25 – 35 wt.% ZrO2(Y).

Choice of material for molding porous ceramic diaphragms

Basic requirements are formulated for starting materials for manufacturing porous ceramic diaphragms, and alumina-containing raw materials of domestic and overseas production are studied. Porous ceramic is manufactured with 35% open porosity and ultimate strength in compression of 72 MPa.

High-strength ceramic from zirconium dioxide partly stabilized with ytterbium oxide

ConclusionsIn the Yb2O3-ZrO2 system it is possible to obtain high-strength ceramic by using the method of low-temperature sintering of active ZrO2 powders with concentrations of 3.0–3.5% Yb2O3. The factors determining the strength of the ceramic are the size of the grains and the concentration of tetragonal phase.

Influence of the Procedure of Getting of a Highly Dispersed Additive on the Properties of Corundum Ceramics

We present the results of investigations of the process of sintering and the changes in the properties of corundum ceramics depending on the content and type of introduced highly dispersed Al2O3. The specimens are produced by the slip casting and sintered at various temperatures. It is shown that, for the other identical conditions, it is reasonable to use highly dispersed powders with spherical particles with an aim to improve the physicomechanical properties of corundum ceramics. In the production of dense ceramics, the shape of particles of highly dispersed powders does not have any significant influence on the decrease in the temperature of sintering.

CHANGE IN CORUNDUM-ZIRCONIA CERAMIC PORE STRUCTURE DURING HEAT TREATMENT

Results are given for a study of sintering and its effect on corundum ceramic pore structure with addition of zirconium dioxide. Powder composites of Al2O3 and ZrO2 (stabilized with 5 wt.% Y2O3) are prepared by slip casting and different temperature sintering regimes. It is established that under stable uniform conditions the original pore surface, sintering temperature, and isothermal soaking duration affect the change in pore surface during sintering.

Properties of the partially stabilized zirconium dioxide crystals

Etude des proprietes physicomecaniques des cristaux de zircone stabilisee par 5 a 6% en poids de Y 2 O 3

High-strength ceramic made from tetragonal zirconia with additions of alumina

The aim of this investigation was to study the possibility of preparing high-strength ceramic from tetragonal ZrO/sub 2/ containing additions of Al/sub 2/O/sub 3/ by mixing powders in water suspensions. The prepared and stabilized suspensions of powdered ..cap alpha..-Al/sub 2/O/sub 3/ and ZrO/sub 2/ with an addition of 5% Y/sub 2/O/sub 3/ were mixed in a rotating polyethylene drum. The specimens were obtained by casting in gypsum molds, and fired in air in an electric furnace at 1400-1550/sup 0/C. The measurements of the bending strength were made by the three-point technique at 20/sup 0/C according to GOST 5458-75 on ground specimens measuring 4 x 5 x 50 mm, and for the x-ray analysis they used the DRON1-UM diffractometer. The relative density of the ceramic was assessed with respect to the apparent density and the density of the monocrystals of tetragonal ZrO/sub 2/ (6.12 g/cm/sup 3/) and of corundum (3.99 g/cm/sup 3/); the open porosity was determined according to GOST 2409-67. The results are shown.

Influence of grain size on the strength of ceramics made from hafnium dioxide partly stabilized with yttrium oxide

ConclusionsThe strength of fine-grained ceramics made from hafnium oxide with an addition of 3–5% Y2O3 largely depends on the size of the component grains. Ceramic with a grain size of about 1 μm containing 4% Y2O3 has a bending strength of about 480 N/mm2, which is twice as high as for ceramics made of cubic HfO2.

High-strength ceramics from tetragonal zirconium dioxide

ConclusionsUsing as an example solid solutions of Y2O3 in ZrO2 we demonstrated the possibility of obtaining ceramics from tetragonal ZrO2 containing 3.5% Y2O3 possessing high mechanical properties up to temperatures of 700°C.