Demonstrating low-temperature sintering of boron carbide powders

Capability to sinter ceramics, especially carbides, at low temperature, is desired but is a challenge. Recently, cold sintering has been successfully demonstrated with oxides and other ceramics, but not with carbides due to high thermodynamic and chemical stability. In this work, low-temperature sintering of boron carbide (B₄C) was attempted at 1000-1400°C; the proposed sintering is to form B₄C nanoparticles with in situ carbothermal reduction from organic liquid-phase precursors (boric acid and glycerin), and then to sinter the formed B₄C nanoparticles, between B₄C micropowders, which are expected to increase packing density and enhance diffusion and densification. Formation of B₄C nanoparticles by in situ carbothermal reduction was confirmed, but only limited densification was observed due to material loss from chemical reactions and lack of pressurization. The achieved relative densities are low (57.7%-62.8%) but comparable with those achieved with pressureless sintering at >2000℃.