Jingshi Wu

Structural response of a highly viscous aluminoborosilicate melt to isotropic and anisotropic compressions

Aluminoborosilicate melts of E-glass composition have been compressed at pressures up to 500 MPa and subsequently cooled (4–5 K min−1) under pressure from well above the glass transition to room temperature. It is found that increasing uniaxial pressure lead to anisotropic glasses with increasing permanent birefringence, while increasing isostatic pressure resulted in isotropic glasses with increasing density (compaction of 2.1% at 500 MPa). Static and magic-angle spinning nuclear magnetic resonance spectroscopy of B11, N23a, A27l, and S29i were performed to explore pressure-induced changes in the short-range structure of these glasses. NMR experiments readily detected increasing BIV, AVl, and AVIl concentrations with pressure as well as a decrease in the mean distance of sodium to oxygen atoms (0.7% at 500 MPa), but no detectible evidence of short-range structural orientation around these atoms in the birefringent glasses were found. Quantifying the changes in the local boron, aluminum, silicon, and sodi...

Raman, Brillouin, and nuclear magnetic resonance spectroscopic studies on shocked borosilicate glass

Using Brillouin and Raman scattering and NMR techniques, we have investigated the elastic and structural properties of four post-shocked specimens of borosilicate glass, recovered from peak pressures of 19.8, 31.3, 40.3, and 49.1 GPa. The Raman spectra of shock-wave compressed borosilicate glass for peak pressures of 19.8 and 31.3 GPa show two new peaks at 606 cm−1 and near 1600 cm−1, while a peak at ∼923 cm−1 disappears in these glasses following shock-loading. The mode at 606 cm−1 is correlated with four-membered rings, composed of one BO4 and three SiO4 tetrahedra (a reedmergneritelike configuration). Modes near ∼1600 cm−1 are of uncertain origin, while that at 923 cm−1 may associated with silica tetrahedra with two nonbridging oxygens, although standard models of this type of glass suggest that total nonbridging oxygen contents should be low. The Raman spectra for the shocked samples at 40.3 and 49.1 GPa are similar to that of the unshocked sample, suggesting that much of the irreversible density and ...

Temperature calibration for high-temperature MAS NMR to 913 K: 63Cu MAS NMR of CuBr and CuI, and 23Na MAS NMR of NaNbO3.

The solid-state phase transitions of CuBr, CuI and NaNbO(3) can be readily observed using (63)Cu and (23)Na high-temperature magic-angle spinning nuclear magnetic resonance spectroscopy. Temperature has large, linear effects on the peak maximum of (63)Cu in each solid phase of CuBr and CuI, and there is large jump in shift across each phase transition. The (23)Na MAS NMR peak intensities and the line widths in NaNbO(3) also clearly show its high-temperature transition to the cubic phase. These data can be used to calibrate high-temperature MAS NMR probes up to 913 K, which is two hundred degrees higher than the commonly-used temperature calibration based on the chemical shift of (207)Pb in Pb(NO(3))(2).