HUGONIOT AND PHASE TRANSITION IN SILICON NITRIDE POROUS SAMPLES

An experimental investigation of phase transition (PT) from hexagonal silicon nitride β‐phase to cubic c‐phase in porous samples was conducted in the range of pressure of 15–50 GPa. In that range the Hugoniot of porous β–Si3N4 samples was constructed. The loading of the samples was made through Al and Cu shields by Al impactors accelerated with explosive products. The boundary velocity between the sample surface and water window was registered by laser Doppler velocimeter VISAR. One of the main goals of the research was to observe two‐wave front configuration caused by the phase transition for more accurate PT pressure definition from the profile and the second wave front diffusion which takes information about PT kinetics. The registered profiles shown the absence of two‐wave configuration on the shock wave front which probably caused by high porosity of the samples (∼15%). Moreover, there was no any diffusion in the wave front which perhaps connected with fast PT kinetics. The presence of PT was found f...