Effects of high pressure on the low-temperature sintering of dense amorphous SiBCN monoliths

In this study, amorphous SiBCN powders were mechanical milled and consolidated by low-temperature sintering at different pressure to provide an insight into the densification and mechanical behavior of dense amorphous SiBCN monoliths. Results show that the mechanical properties undergo a gradual variation closely related to the microstructural evolution. The increased degree of densification with few defects and free volume results in significantly improving Young's modulus and nano hardness in case of high pressure application. The consolidation at relatively low pressure (3 GPa) occurs by heavy deformation with the support of limited short-range diffusion, whereas the densification at higher pressure (5 GPa) is mostly diffusion controlled showing a classic sintering mechanism. At 1000 °C, higher pressure (5 GPa) suppresses crystallization leading to an effective solid-state reaction, while SiBCN monoliths consolidated by lower pressure (3-4 GPa) show a hybrid structure of dominant amorphous phases and few nanocrystals.