Silicate / metallic / chalcogenide glasses; Tg and structural relaxation; fragility; sol-gel; photonic and optical glass; vitrification of nuclear waste; fictive temperature.
Glass and Amorphous Materials
Silicate glass network (Zachariasen)
Zachariasen 1932 random-network rules: SiO2 glass forms continuous random network of corner-sharing SiO4 tetrahedra; modifiers (Na2O, CaO)…
Metallic glass (amorphous metal)
Klement-Willens-Duwez 1960 first metallic glass via splash-quench; bulk metallic glasses (Pd-Cu-Si, Vitreloy 1) achieve mm thickness; high…
Chalcogenide glass and photonics
Ge / As / Se / Te chalcogenides have low phonon energies enabling mid-IR optics; photo-darkening and photo-induced refractive-index changes…
Glass transition Tg (kinetic)
Tg defined operationally where viscosity reaches 10^12 Pa s; depends on cooling-rate (kinetic, not thermodynamic transition); WLF equation…
Fragility (strong vs fragile)
Angell strong-vs-fragile classification: strong (SiO2, GeO2) Arrhenius-like viscosity; fragile (o-terphenyl, polymers) super-Arrhenius VFT…
Glass relaxation (stretched exponential)
Kohlrausch-Williams-Watts (KWW) phi(t) = exp[-(t/tau)^beta] with beta in 0.3 to 1; broad relaxation-time spectrum from heterogeneous…
Borosilicate glass (Pyrex)
Schott / Corning borosilicate (B2O3 + SiO2 + Na2O + Al2O3) has low thermal-expansion (3 ppm / K) for thermal-shock resistance; standard for…
Sol-gel glass process
Hydrolysis-condensation of metal alkoxides (TEOS) at room temperature produces glass; enables low-T thin films, aerogels, hybrid…
Colored glass (transition-metal redox)
Cobalt blue (Co2+), iron green/amber (Fe2+/Fe3+), gold ruby (Au nanoparticles, Cassius purple 1685), uranium glass (UO2 fluorescence);…
Glass-ceramics (Pyroceram / Zerodur)
Stookey 1957 (Corning) controlled crystallization yields glass-ceramic with very-low thermal-expansion; Zerodur (Schott) for telescope…
Vitrification of nuclear waste
Borosilicate glass blocks immobilize fission-products (Cs-137, Sr-90, actinides); La Hague (France) and Hanford (USA) vitrify high-level…
Glass fictive temperature (Tool-Narayanaswamy)
Tool 1946: fictive temperature Tf characterizes structural state of glass at given history; TNM model of structural relaxation widely used…
Silica network Q-species (Qn distribution)
Engelhardt-Michel 1987 NMR Q-species classification: Q4 (4-bridging O fully-polymerized), Q3 (3-bridging + 1-non), Q2-Q0;…
Anderson 1979 frustration / glass transition
Anderson 1979: glass-transition reflects frustrated competition between local-energy-minimization + global-packing-constraints;…
Vogel-Fulcher-Tammann viscosity
VFT eta(T) = eta_0 exp(B / (T - T_0)) describes super-Arrhenius viscosity divergence above T_g; T_0 is Vogel temperature; D = B / T_0 is…
Stokes-Einstein violation (supercooled)
Above T_g but below 1.2 T_g, diffusion-coefficient D and viscosity eta decouple from Stokes-Einstein D = kT/6 pi eta r; D decoupled by…
Microheterogeneity (spatial-glass)
Adam-Gibbs 1965 cooperatively-rearranging-region picture; modern 4-point density-correlation (Berthier-Biroli 2011) reveals 5-20 nm…
Boson peak (low-frequency excess vibration)
Universal anomaly in glass: excess low-frequency (~1 THz) vibrational density-of-states above Debye prediction g(omega) ~ omega^2; not…