Peculiarities of the Phase Formation during Electroconsolidation of Al2O3–SiO2–ZrO2 Powders Mixtures

Abstract

This paper is devoted to the sintering process of Al2O3–SiO2–ZrO2 ceramics. The studied method was electroconsolidation with directly applied electric current. This method provides substantial improvements to the mechanical properties of the sintered samples compared to the traditional sintering in the air. The research covered elemental and phase analysis of the samples, which revealed phase transition of high-alumina solid solutions into mullite and corundum. Zirconia was represented mainly by tetragonal phase, but monoclinic phase was present, too. Electroconsolidation enabled samples to reach a density of 3.0 g/cm3 at 1300 °С, while the sample prepared by traditional sintering method obtained it only at 1700 °С. For the composite Al2O3—20 wt.% SiO2—10 wt.% ZrO2 fabricated by electroconsolidation, it was demonstrated that fracture toughness was higher by 20–30%, and hardness was higher by 15–20% compared to that of samples sintered traditionally. Similarly, the samples fabricated by electroconsolidation exhibited elastic modulus E higher by 15–20%. The hypothesis was proposed that the difference in mechanical and physical properties could be attributed to the peculiarities of phase formation processes during electroconsolidation.

Thickness effect of an alumina–zirconia–mullite composite coating on the properties of zirconia

“…The mullite distributed in the coating material can eliminate the localised micro-residual stress at grain boundaries caused by the completely different Young's modulus and CTE of alumina and zirconia, so as to avoid the possibility of delamination. 13,14 The EDS results (Fig. 8) show that Si is uniformly distributed in the sintered coating material, meaning that no big dimensional inclusions formed.…”