Structure of Shock Wave in Nanoscale Porous Nickel at Pressures up to 7 GPa

Abstract

The structure of shock waves in pressed porous samples of nickel nanoparticles was investigated in a series of uniaxial planar plate impact experiments in the pressure range of 1.6–7.1 GPa. The initial porosity of the samples was about 50%. Wave profiles were obtained using laser velocimetry techniques. The nanomaterial demonstrated a complex response to shock loading including the development of a two-wave structure associated with precursor and compaction waves. The effect on profiles and measurements of the observed precursor reverberations propagating between the front of a compaction wave and a monitored sample surface was described. The obtained wave profiles were used to estimate the thicknesses of precursor and compaction wave fronts.

Effect of porosity on rapid dynamic compaction of nickel nanopowder

“…This effect for 50% porous nNi is highlighted in our previous work. 11 The precursor velocity in the 94% porous nNi increases slightly with increasing applied load (Fig. 4).…”

“…Details of the experimental arrangement are presented in our previous works. 11,33 The calculation of the wave velocity was based on determining the times of wave arrival at the buffer/sample and sample/ window interfaces. The former time was obtained using the impact time, buffer thickness (B2 mm) and wave velocity in the buffer plate, which is known from the Hugoniot of buffer material (D16 aluminum alloy 24 ) and impact conditions.…”

“…3 A thorough analysis of the two-step nature of a shock wave traveling in samples of pressed 50 nm nickel powder (r 0 = 4.62 g cm À3 , j E 50%) at pressures up to 7 GPa was performed in our previous work. 11 It indicated that the average particle size parameter also may not significantly affect the rise time of the main plastic deformational part of such a wave.…”

“…Investigations of rapid dynamic compression of nanoscale granular systems are of great importance due to their extensive and expanding use in various physical and chemical applications. [1][2][3][4][5][6][7][8][9][10][11] A shock compaction wave in a powder medium not only elevates its parameters such as pressure, temperature and density but also irreversibly transforms a morphology of constituents and partly or completely eliminates the void content. In turn, granules disturb a shock front forming its irregular structure.…”

“…A number of experimental and simulation studies revealed aspects of the shock response of metallic and nonmetallic nanoscale porous systems. [1][2][3][4][5][7][8][9][10][11]15,[25][26][27] Trunin et al examined the shock-loading behavior of highly porous nanogranular nickel (nNi) containing particles with sizes less than or equal to 20 nm. 25 Their work demonstrated the effect of initial density r 0 in the range of 0.444 to 0.887 g cm À3 on the nNi Hugoniot for pressures up to several tens gigapascals.…”