The Effect of a Carbon Additive on Compaction of Partially Stabilized Zirconia Powders upon Pressing and Sintering

Abstract

Zirconia ceramics exhibits high functional and strength properties. The range of its application is continuously expanding. The use of nanopowders makes it possible to obtain fine-grained ceramics with improved characteristics. Zirconium dioxide has a high hardness, which ensures increased mold wear. In addition, nanoparticles are prone to agglomeration, which affects compaction upon pressing and sintering. These problems can be solved by introducing microadditives, e.g., carbon. The effect of the type and concentration of a carbon additive on the parameters of zirconia ceramics fabricated from powder raw materials synthesized by sol‒gel and plasma-chemical methods has been explored. The shrinkage of the ceramic samples of two types with carbon additives of three types (multiwalled carbon nanotubes (MWNTs), amorphous carbon, and amorphous carbon with MWCNTs) has been studied by dilatometry. It has been established that the additives do not affect the shrinkage rate and that the highest rate of shrinkage of the sample is almost equal to the shrinkage rate upon sintering of the ceramics without additives. The effect of a carbon additive on the density and microhardness of the ceramics has been determined. It is shown that the additives introduced into the ceramics fabricated from the powders synthesized by the sol‒gel technology reduce the density and microhardness, while the density of the ceramics made of the plasma-chemical powders increases up to a certain additive concentration threshold for carbon of all the types discussed in this study.