Conventional and microwave-assisted sintering of ZnO-containing CAC-bonded alumina-based refractory castables

Author(s)

Borges, O. H. ; Cardoso, A. L. F. ; Moreira, M. H. ; Klein-Gunnewiek, R. F. ; Pandolfelli, V. C.

• Document type: Journal article
• Source: Journal of the European Ceramic Society; v. 43, n. 14, p. 9-pg., 2023-11-01.

Abstract

Recent studies have pointed out that ZnO can induce early spinel formation in alumina-based refractories, giving rise to gahnite (ZnAl2O4). Besides that, the high microwave absorption of zincite enables the likelihood of applying this sintering technique to compositions comprising this oxide. In this work, microwave and conventional sintering were applied to ZnO-containing alumina-based refractory castables. Microwave-processed samples displayed higher densification, enhanced mechanical properties at RT, a faster sintering schedule, and 70%-lower energy consumption compared to the conventionally produced counterparts, which could be attributed to the higher heating rates and enhanced ion diffusion induced by the electromagnetic-assisted sintering. Moreover, thermodynamic and experimental analyses indicated that the oxidation of SiC used as microwave susceptors induced zinc volatilization, resulting in small (similar to 40 mu m) pores in a densified refractory matrix. Although not necessarily detrimental to the castables' properties, this volatilization was reduced by controlling the atmosphere of the microwave cavity during sintering. (AU)

• FAPESP's process: 21/00251-0 - Analysis of refractory castables drying via computational modelling and neutron tomography
• Grantee: Murilo Henrique Moreira
• Support Opportunities: Scholarships in Brazil - Doctorate
• FAPESP's process: 21/00114-2 - Development of advanced eco-friendly spinel-containing castables to replace chromite-based refractories
• Grantee: Otávio Henrique Borges
• Support Opportunities: Scholarships in Brazil - Doctorate