Extended structural integrity in network glasses and liquids

Abstract Brillouin scattering measurements of B 2 O 3 , GeO 2 and SiO 2 glasses and liquids, to temperatures ≤ 1550°C, reveal anomalous thermo-mechanical behavior. Transverse acoustic waves are supported by the liquids of all three oxides. In all systems, the longitudinal and shear elastic moduli increase with increasing temperature below, and again far above the glass transition. This apparent strengthening of the glassy network below T g is less pronounced, the more fragile the glass former, while in the molten state the opposite seems to be the case. This positive temperature dependence of the elastic properties can be explained by localized structural reorganizations which do not require the breaking of network bonds. The decrease in elastic moduli immediately above T g , characteristic of fragile systems, is due to the increase of the average network ring size, achieved through a low-activation energy neighbor exchange mechanism. The ability of these liquids to support shear stresses at very high temperatures indicates a persistent network structure.

[1]  Grimsditch.  Annealing and relaxation in the high-pressure phase of amorphous SiO2. , 1986, Physical review. B, Condensed matter.

[2]  J. Bass,et al.  The complex mechanical modulus as a structural probe: The case of alkali borate liquids and glasses , 1995 .

[3]  V. Heine,et al.  Rigid unit modes in the molecular dynamics simulation of quartz and the incommensurate phase transition , 1991 .

[4]  Wright,et al.  Irreversible structural changes in vitreous B2O3 under pressure. , 1996, Physical review. B, Condensed matter.

[5]  J. Mayer,et al.  Interatomic Distances in Crystals of the Alkali Halides , 1933 .

[6]  Meng,et al.  Brillouin scattering from amorphous materials at high pressures. , 1988, Physical review. B, Condensed matter.

[7]  M. Vukcevich.  A new interpretation of the anomalous properties of vitreous silica , 1972 .

[8]  F. Frey,et al.  Dynamic structure determination for two interacting modes at the M-point in α- and β-quartz by inelastic neutron scattering , 1980 .

[9]  R. E. Strakna.  INVESTIGATION OF LOW-TEMPERATURE ULTRASONIC ABSORPTION IN FAST-NEUTRON IRRADIATED SiO$sub 2$ GLASS , 1961 .

[10]  Bhadra,et al.  Shear waves through the glass-liquid transformation. , 1989, Physical review letters.

[11]  Kieffer.  Mechanical degradation and viscous dissipation in B2O3. , 1994, Physical review. B, Condensed matter.

[12]  O. Anderson,et al.  Ultrasonic Absorption in Fused Silica at Low Temperatures and High Frequencies , 1955 .

[13]  E. Whalley,et al.  ‘Melting ice’ I at 77 K and 10 kbar: a new method of making amorphous solids , 1984, Nature.

[14]  D. Anderson,et al.  Molecular dynamic simulations of the infrared dielectric response of silica structures , 1993 .