Structural changes of SiO2 glass by mechanical milling

Structural changes of ground SiO2 glass were investigated using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, and Raman spectroscopy. SiO2 glass samples were ground in a ball mill for up to 500 h. Reduction in the particle size of ground SiO2 glass samples was observed up to ∼ 80 h of milling. After 80 h of milling, the particle size of ground SiO2 glass remained almost constant at approximately 3 μm. The first sharp diffraction peak (FSDP) position (q1) of the XRD pattern for ground SiO2 glass shifted from 1.500 (original) to 1.544 (500 h of milling) Å-1. The variation may be attributed to a change of the intermediate-range structure. The FSDP position of the 500 h ground SiO2 glass returned to the original value after annealing at 1000 °C. This annealing behavior includes two components. The variation in q1 for annealing up to ∼ 500 °C is small (0.0087 Å-1) and may be attributed to an increase of the Si-O-Si angle. However, for annealing at 500-1000 °C, a large variation was observed (0.0350 Å-1) and it may be attributed to a decrease of 3-membered rings. IR spectra of samples milled up to ∼ 80 h revealed sharpening of the ν = 1100 cm-1 band (Si-O stretching mode) and a decrease in the absorption of the ν = 800 cm-1 band (Si-O-Si bending mode). The IR analyses indicate the shrinkage of Si-O-Si linkages by milling. For over 80 h of milling, these variations are small. The particle size remains almost constant for over 80 h of milling, and therefore, only structural changes in a particle would be responsible for the changes in the IR spectra. The Raman spectra exhibited an increase in the luminescence intensity for milling up to ∼ 40 h. The luminescence may result from surface defect structures on SiO2 glass grains, and the increase in the luminescence intensity is consistent with particle size reduction by milling.