Physicochemical transformations of boron carbide at high temperatures and high pressures of shock compression

Experiments were carried out on multiple shock wave compression and subsequent storage of powdered samples of boron carbide. The samples were subjected to the stepwise shock compression. Steel-tungsten capsule was used for saving of shocked samples. The maximum pressures in the sample under study reached $70$ GPa. X-ray phase analysis, electron microscopy, and X-ray spectral microanalysis of boron-carbide samples before and after loading were performed. It is shown that as a result of the impact of dynamic pressures $P_{\mathrm{tr}} = 63(7)$ GPa and temperatures $T_{\mathrm{tr}} = 1600(200)$ K, new reflexes appear on the X-ray diffraction patterns of the shocked boron-carbide samples, which are presumably due to the formation of graphite and tungsten borides. Assessment of the temperature and pressure at the beginning of physical and chemical transformations and melting of powdered boron carbide under stepwise shock compression is discussed.