Strength and elastic deformation of natural and synthetic diamond crystals shock compressed along [100]

Abstract

Plane shock wave experiments were conducted to determine the strength and elastic response of natural and synthetic diamond single crystals shocked along [100] to peak elastic stresses of ∼90 and ∼120 GPa. Velocity interferometry was used to measure particle velocity histories and shock velocities in the diamond samples. The maximum elastic wave amplitudes (89±3 GPa) for both crystal types were comparable. This value corresponds to shear stresses of 30 and 35 GPa (∼G/15) for the (111) [11¯0] and (111) [21¯1¯] slip systems, respectively. Surprisingly, the elastic limit (57±3 GPa) was lower for the higher peak stress. The elastic constant C111 was experimentally determined to be −7804±653 GPa.

Shock-compressed graphite to diamond transformation on nanosecond time scales

“…Hence, the previous suggestion 19 that shocked HOPG transforms to a diamond-like phase having a density 5% less than diamond is neither needed nor supported by our calculations. Instead, our calculations demonstrate that the stiffness and density of the high pressure phase of shocked HOPG are entirely consistent with the experimentally determined 26,27 elastic response of shockcompressed cubic diamond.…”

“…19 Additionally, our calculations show that the diamond phase formed responds as a nonlinear elastic solid, consistent with recent experimental results for shocked diamond single crystals. 26,27 The work described here has addressed long-standing scientific questions regarding the real time formation and mechanical response of the diamond phase in the shock-induced graphite to diamond transformation. However, our findings have also raised new and interesting questions: Are the findings reported here unique to HOPG, and what are the precise atomistic mechanisms that result in the HOPG-to-diamond transformation on such short time scales?…”

“…This need was addressed recently; 26,27 high quality wave profiles were measured for diamond single crystals shocked to 50 -120 GPa in plate impact experiments. These results have provided the third-order elastic constants 27 and the elastic limit for shocked diamond.…”

“…These results have provided the third-order elastic constants 27 and the elastic limit for shocked diamond. 26 Now that the shock response of cubic diamond is available 26,27 at stresses comparable to the endstates measured in shocked HOPG, 18,19 a comprehensive and detailed analysis of the measured wave profiles is in order.…”

Experimental Determination of Third-Order Elastic Constants of Diamond

“…The samples were cut, and polished to an optical finish, with the normal of the large face oriented along the [100], [110], or [111] direction and were verified to be within 3° of the indicated orientation using Laue x-ray diffraction. The experimental configuration used in this study is identical to that used in our earlier work and the details can be seen there [25]. Impactors were launched using a powder gun or a two stage gun to velocities ranging from 2.1 to 3.7 km/s to achieve the desired peak stresses.…”