Low-temperature sintering of boehmite ceramics utilizing a hydraulic alumina precursor and the enhancement of mechanical properties by α-Al ₂ O ₃ compounding

The conventional manufacturing processes of ceramics involve high-temperature sintering at temperatures above 1000 °C. Therefore, current research is focused on low-temperature sintering methods to reduce energy consumption and carbon dioxide emissions. This study demonstrates a low-temperature manufacturing process for boehmite ceramics, which are difficult to fabricate via conventional sintering methods. The proposed method is conducted at temperatures below 180 °C and involves the application of heat and pressure to a hydraulic alumina – water mixture, promoting the hydration reaction of hydraulic alumina. The resulting boehmite ceramics exhibit a biaxial flexural strength of 45 ± 6 MPa and a Vickers hardness of 1.8 ± 0.1 GPa. Furthermore, the addition of 50 vol% of α-Al2O3 particles to boehmite ceramics increases the biaxial flexural strength and Vickers hardness of the ceramics to 149 ± 6 MPa and 2.9 ± 0.1 GPa, respectively. Overall, this work clarifies the mechanical performance of bulk boehmite ceramics fabricated via a hydration-driven route using hydraulic alumina and suggests that α-Al2O3 compounding, combined with microstructure/defect control, can serve as a useful strategy in low-temperature consolidated/sintered ceramics.