Structural transformations in laser shock-loaded quartz

Abstract

The kinetics of the phase transitions occurring in solid materials under strong compression are an issue of considerable interest, which can be studied using dynamic loading processes. Here, we investigate the phase transformation behavior of quartz under laser-induced shock compression of a very short duration (nanosecond order). Time-resolved measurements, coupled with simple computer simulations, have been used to characterize the pressure pulse induced in the samples. Recovery shots have been performed for postshock spectroscopy, that has revealed permanent structural changes of various types, depending on the experimental conditions (loading pressure, sample thickness, and initial temperature). The results, which differ notably from observations reported under quasi-static compression or longer pulsed loads (microsecond order), suggest a partial amorphization of the shocked samples, as well as the formation of a structure that can be compared to known orthorhombic high-pressure phases. They provide an insight into the early stages of the shock-induced transformation mechanisms in this widely studied material.

Influence of quartz anisotropy on shock propagation and spall damage

“…In recent papers, we have investigated the structural effects of laser-driven shocks on quartz [3,4]. Here, we report additional observations concerning spall damage in laser shock-loaded quartz samples, we explain the results in terms of orientated wave propagation due to quartz anisotropic crystalline structure, and we perform three-dimensional (3D) computer simulations to comfort this interpretation.…”

“…The angle between the major axis of the ellipsoid and Given the lateral dimensions of the samples, about 15 mm, this 'elliptical' damage observed at the back of all thick quartz samples shocked along the x-axis cannot be attributed to edge effects. It was not observed in laser shock experiments performed on thin quartz samples (less than 1 mm thick) reported elsewhere [3], where the propagation distances were small compared to the diameter of the irradiated spots (typically 3 mm). Thus, it is likely to result from specifically orientated wave propagation in quartz, due to the anisotropic structure of the quartz crystal.…”

“…The gold layer is ablated into a plasma cloud, whose expansion towards the laser source induces a short compressive pulse in the quartz sample, due to recoil action. Previous experiments and laser-matter interaction computations have shown that the corresponding loading pressures, which increase with laser intensity, range from about 12 to 84 GPa [3][4][5][6][7]. Unlike in most laser shock experiments that we reported in the past, the diameter of the irradiated surface is less than the target thickness, so that strains cannot be considered as uniaxial, and 3D effects have to be taken into account to describe stress wave propagation inside the sample.…”

Laser-induced shock waves in condensed matter: some techniques and applications

“…Although the examined portion was predominantly quartz, we observed changes in the Raman spectrum, indicating structural disorder characteristic of the onset of a coordination change in silica. Similar effects on the Raman spectrum of quartz had been found in recent laser shock experiments [47] which also indicate the transformation of quartz into a transitional phase observed in powder-gun experiments [48]. We plan to conduct micro-Laue diffraction on laser-shocked quartz crystallites in order to acquire detailed information on intermediate structures, as well as the transformation path from four-to six-fold coordinated silica.…”

“…Recovered samples are then post-examined with various analytical FIGURE 10 Ellipsometry signals recorded at the interface of Si (1 0 0) and window [37]: (a) below diamond-bct transition (Trident #14968, P 9 GPa) and (b) around diamond-bct transition (Trident #14969, P 14-17 GPa). techniques to investigate the physical, mechanical, and chemical effects of loading, including metallography [46] and Raman [47], X-ray, and neutron scattering. Although laser shock recovery has been extensively conducted at Trident (e.g., on Al, Cu, Ti, Si, NiTi, NiAl, SiO 2 , MgB 2 , and C), here we only discuss silica and carbon.…”