Shock compression behaviors of boron carbide (B4C)

Abstract

Hugoniot measurements on the highly dense, pure B4C polycrystal were performed by the inclined-mirror method to study the elastoplastic transition and to search phase transition. In inclined-mirror streak photographs, the smoothly jagged structure was observed at the free-surface shape in the plastic region. The Hugoniot-elastic limit (HEL) has been determined to be approximately 19.5GPa. In the plastic region, a kink was observed at a particle velocity of around 1.26km∕s. The shock velocity (US)–particle velocity (UP) Hugoniot relations in the plastic region were given by US=3.7+5.4UPkm∕s in the Up range of 0.54–1.26km∕s and US=9.61+0.73UPkm∕s in the Up range of 1.26–4.3km∕s. The S value (0.73) in US=C0+SUP above UP=1.26km∕s is significantly small compared with the result of Vogler et al. [J. Appl. Phys. 95, 4173 (2004)], and was much smaller than those of many oxides and nitrides. This material behaved as an elastoisotropic solid above the HEL and showed a large and linear change in the pressure-density plot above 38GPa (UP=1.26km∕s), which indicated the onset of a phase transition.

Mechanism for amorphization of boron carbide B4C under uniaxial compression

“…However, when compressed along the direction of the C-B-C chain, they found a 4% volume reduction for uniaxial pressure between 18.9 GPa and 22.8 GPa. They related this sudden change in volume to the bending of the 3-atom chain resulting in the amorphization of B 4 C. In a shock wave compression experiment on a highly dense, pure B 4 C polycrystalline sample, Zhang et al determined the HEL of this sample to be 19.5 GPa and that a large change in the pressure density plot above 38 GPa signaled an onset of a phase transition [18]. However, the exact nature of this high pressure phase was not elaborated.…”

Properties of B4C in the shocked state for pressures up to 1.5 TPa

“…Raman spectra up to 50 GPa 22,23 and X-ray diffraction measurements up to 126 GPa 24 have not observed any evidence indicative of a structural phase transition. Under dynamic compression (until recently 25 equation of states (EOS) data from shock compression have been available up to pressures of 200 GPa 4,5,[26][27][28][29][30][31][32][33][34][35] ) the behavior is more complex. Anomalies in the shock Hugoniot that are found between 20-60 GPa are suggestive of a phase transition 36 .…”

Equation of state, adiabatic sound speed, and Grüneisen coefficient of boron carbide along the principal Hugoniot to 700 GPa

“…B 4 C is the third hardest material after diamond and cubic boron nitride. It is of low density (2.52 g/cc) with high strength 1,2 , has a high melting point (2743 K) 3 and a low wear coefficient. 4 As a result, B 4 C is ideal for lightweight armor, 5 spacecraft whipple shielding, 6 wear-resistant materials, cutting tools, and for use in high-temperature electronic and thermoelectric devices.…”

“…[1][2][3][19][20][21][22][23][24][25] Two polymorphic phase transitions at pressures of 30-50 GPa and ∼ 50 GPa have been postulated and debated based upon nano-indentation experiments [26][27][28] , Hugoniot data and shock wave profile analysis. 2,3,24,25,29 Nano-indentation experiments [26][27][28] examined structural damage under contact loading of recovered samples. These experiments found narrow amorphous bands and local disorder areas and evidence for a high-pressure amorphous phase above 40 GPa.…”