Low-temperature densification of α-Al2O3 through a modified cold-sintering process

α-Al2O3 is a technical/advanced ceramic used in applications such as electrical, wear, and corrosion resistance, with approximately 120,000 metric tonnes manufactured per year worldwide. As with all ceramics, processing takes place at high temperatures, in this case ~ 1600 °C to achieve the required densification.

In this proposal, a modified cold-sintering process will be used to consolidate pseudo-boehmite (Al(O)(OH)n) at 300 °C to form dense precursor monoliths which will then be converted into high-temperature α-Al2O3 at ~ 1100 °C. The pseudo-boehmite powder is functionalised using acetic acid which facilitates the cold-sintering process through the formation of a surface layer of acetate-alumoxane precursor ([Al(O)x(OH)y(O2CCH3)z]n) that decomposes on heating into alumina. The estimated energy saving of > 50 % by the reduction in sintering temperature from 1600 to 1100 °C is amplified by the cost savings relating to the use of metallic rather than MoSi2 or SiC based furnace elements. This project not only has the potential to benefit the ceramic sector by developing a novel low-temperature consolidation process for α-Al2O3, but also the chemical sector by creating a new market for organic acids. The global production of acetic acid in 2018 was reported to be ~18M metric tonnes worldwide and is forecast to increase to 21M metric tonnes by 2023.

Edoardo Mantheakis

University of Sheffield