P. Wiśniewski

Effect of the bonding ceramic material on the size of pores in porous ceramic materials

Abstract The results of studies on the effect of the grain size and amount of ceramic bonding materials (ceramic binder) on the size of pores in porous ceramic materials are presented. Electrocorundum and silicon carbide of various grain sizes were used as the grain material. Borosilicate glass was used as a ceramic binder for electrocorundum, whereas a mixture of kaolin with feldspars was used as that for silicon carbide. The sintering conditions were chosen so as the borosilicate glass was in a melted form, and the ceramic binder for silicon carbide only sintered during the sintering process. The studies showed that the mean pore size of the porous ceramic material decreases with an increase in the amount of the sintering ceramic binder and increases with that of the melting ceramic binder during the sintering process.

VINYL ACETATE COPOLYMERS IN DIE PRESSING OF ALUMINA

The studies on the application of the emulsions of poly(vinyl acetate-co-allyl ether)s containing nonionic hydrophilic poly(oxyethylene) fragments as binders in the die pressing of alumina is presented. It was found that introduction of hydrophilic fragments into molecules of a typical water dispersible polymer led to better polymer affinity to the ceramic powders. It was also shown that low molecular mass of such copolymers should be relatively low ca 1500 g mol–1 to increase the density and thickening uniformity of the samples before and after sintering. The resultant sinters indicated exceptionally high mechanical strength (bending strength ca 500 MPa).

Chemical processes in kaolin sintered with NaH2PO4

The results of experiments on application of NaH2PO4 as a binding agent for ceramic kaolin samples were presented. The experiments were carried out at temperatures of 973, 1073 and 1173 K and NiO and CoO additives were used as tempering agents. The parameters of the obtained samples with NaH2PO4 were compared with the samples compressed with water only. The materials of 3-4 times higher bending strength, lower water absorption as well decreased open porosity were prepared during these experiments. The binding function of the NaH2PO4 additive relies on creation of some compounds in reaction between the products of its condensation and products of kaolin decomposition. Finally a ceramic material of prospective properties was created.

Effect of Water-Soluble Alumoxycarboxylates on the Properties of Alumina Molded by Die Pressing

Studies on obtaining new ceramic materials are at present one of most dynamically developing fields of modern material science. Ceramic materials owe their progress to low thermal conductivity, resistance to corrosive action of many media at elevated temperatures, mechanical strength, etc.

Water Thinnable Polymeric Binders in Die Pressing of Alumina

In modern ceramics technology, in die pressing, a narrow range of water-soluble organic binders, such as poly(vinyl alcohol) and methylcellulose, is most often applied. The samples obtained with the binders mentioned are characterized by relatively low density (<65% of theoretical density) and small mechanical strength before sintering. The disadvantages of classical pressing are minimized by selecting suitable materials of which the matrix for pressing is made, application of appropriate pressing parameters (pressing pressure, rate, e.t.c.), and first of all by the optimization of the rheological properties of the ceramic powders formed. The polymeric dispersions and organic binders provide the pressed ceramic powders with optimal properties from the point of view of thickening abilities and mechanical strength of the pressed samples.