Guerette Michael, Ackerson Michael R, Thomas Jay, Yuan Fenglin, Bruce Watson E, Walker David, Huang Liping
Department of Materials Science and Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.
Department of Earth and Environmental Sciences, Rensselaer Polytechnic Institute, Troy, NY 12180, USA.
Sci Rep. 2015 Oct 15;5:15343. doi: 10.1038/srep15343.
Silica glass has been shown in numerous studies to possess significant capacity for permanent densification under pressure at different temperatures to form high density amorphous (HDA) silica. However, it is unknown to what extent the processes leading to irreversible densification of silica glass in cold-compression at room temperature and in hot-compression (e.g., near glass transition temperature) are common in nature. In this work, a hot-compression technique was used to quench silica glass from high temperature (1100 °C) and high pressure (up to 8 GPa) conditions, which leads to density increase of ~25% and Young's modulus increase of ~71% relative to that of pristine silica glass at ambient conditions. Our experiments and molecular dynamics (MD) simulations provide solid evidences that the intermediate-range order of the hot-compressed HDA silica is distinct from that of the counterpart cold-compressed at room temperature. This explains the much higher thermal and mechanical stability of the former than the latter upon heating and compression as revealed in our in-situ Brillouin light scattering (BLS) experiments. Our studies demonstrate the limitation of the resulting density as a structural indicator of polyamorphism, and point out the importance of temperature during compression in order to fundamentally understand HDA silica.
众多研究表明，石英玻璃在不同温度下受压时具有显著的永久致密化能力，可形成高密度非晶态（HDA）石英。然而，导致石英玻璃在室温冷压缩和热压缩（如接近玻璃转变温度）时发生不可逆致密化的过程，其本质上的共性程度尚不清楚。在这项工作中，采用热压缩技术在高温（1100 °C）和高压（高达8 GPa）条件下对石英玻璃进行淬火处理，相对于环境条件下的原始石英玻璃，这导致密度增加约25%，杨氏模量增加约71%。我们的实验和分子动力学（MD）模拟提供了确凿证据，表明热压缩HDA石英的中程有序与室温下冷压缩的对应物不同。这解释了如我们的原位布里渊光散射（BLS）实验所示，前者在加热和压缩时比后者具有更高的热稳定性和机械稳定性。我们的研究证明了所得密度作为多晶态结构指标的局限性，并指出了压缩过程中温度对于从根本上理解HDA石英的重要性。
