Phase evolution and lightweight application of dolomite@Al2O3 spherical particle with core–shell structure

Abstract

AbstractDolomite@Al2O3 spherical particles with core–shell structure were fabricated by using the dolomite powders as the core and wrapping corundum powders on their surface. The phase evolution and microstructure of the dolomite@Al2O3 spherical particles with different firing temperatures were studied. As the spherical particles fired at different temperatures, the dolomite in the spherical core decomposed into MgO and CaO. Due to the Kirkendall effect, MgO and CaO diffused into the shell of the spherical particle and left Kirkendall holes in the core. The holes produced by the Kirkendall effect and the decomposition of dolomite act together to form a hollow structure in the center. And during the diffusion process, MgO and CaO reacted with corundum to generate spinel and calcium hexaaluminate. A small amount of spinel and calcium hexaaluminate can form a ternary compound Ca2Mg2Al28O46. Moreover, simulation software Factsage and Abaqus were used separately to help prove the phase evolution and the introduction of spherical particles to the properties of refractories. To test the lightweight effect of dolomite@Al2O3 spherical particles on refractories, it was introduced into spinel–corundum refractories as medium particles in different content and fired at different temperatures. The results show that after firing at 1650°C for 3 h with introducing 30% dolomite@Al2O3 spherical particles, the samples can reach a high compressive strength (128 MPa), high refractoriness under load (1683°C), and low thermal conductivity (1.79 W (m K)−1).