Dipartimento di Fisica, Università di Perugia, I-06123 Perugia, Italy.
IMEM-CNR, I-43124 Parma, Italy.
Phys Rev Lett. 2014 Jan 31;112(4):045501. doi: 10.1103/PhysRevLett.112.045501. Epub 2014 Jan 29.
Positron annihilation lifetime spectroscopy is employed to measure the size of the interstitial void spaces characterizing the structure of a set of permanently densified SiO2 glasses. The average volume of the voids is markedly affected by the densification process and linearly shrinks by almost an order of magnitude after a relative density variation of 22%. In addition, x-ray diffraction shows that this change of density does not modify appreciably the short range order, which remains organized in SiO4 tetrahedra. These results strongly suggest a porous medium description for v-SiO2 glasses where the compressibility and the medium range order are dominated by the density variation of the voids volume up to densities close to that of α-quartz.
正电子湮没寿命谱被用来测量一组永久致密化的 SiO2 玻璃的结构特征的间隙空隙空间的大小。空隙的平均体积明显受到致密化过程的影响，在相对密度变化 22%后几乎线性收缩了一个数量级。此外，X 射线衍射表明，这种密度变化并没有显著改变短程有序，SiO4 四面体仍然保持有序。这些结果强烈表明 v-SiO2 玻璃是一种多孔介质，其可压缩性和中程有序性主要由空隙体积的密度变化决定，直到接近 α-石英的密度。
