Charge Composition Development for Heat-Resistant Ceramics

Abstract

This article presents the results of the charge composition development for heat-resistant ceramics production based on low-plasticity clay with the addition of 10 wt. % of cerium oxide and 5 wt. % of boric acid as functional additives. It has been stated that self-glazing effects on the surface and ceramic particles glazing in the products depth are observed during joint introduction of these additives. These effects occur as boric acid, being a strong flux, forms a vitreous phase and reduces liquid-phase sintering temperature of ceramics. This vitreous phase based on borosilicates includes cerium oxide, as well as silicon, aluminum, calcium and magnesium oxides, which are characterized by high melting points, chemical resistance and heat resistance. This vitreous phase is represented in the structure of the material in the form of the layers between the ceramic particles and forms a single frame possessing low thermal coefficient of linear expansion, which contributes to the compaction, open porosity reduction, material strength characteristics and heat resistance increase. The advantages of cerium oxide are the reduction of the difference between thermal coefficients of linear expansion between the amorphous and crystalline phases in the material, as well as the ability of this substance to serve as a catalyst for hydrocarbons and soot oxidation when heated. The obtained results allow using the obtained ceramics for lining thermal units and flue channels operated at high temperatures and in aggressive environments, alongside the production of self-cleaning walls without interrupting thermal units operation.