Bulk glasses

Analysis of the glass at room temperature occurs via the equations shown above. Bulk Si02 

1989 Garofalini 1990), consistent with experimental data (Bunker et al. 1989a,b) 

Self-diffusion of ions in silica has been measured both experimentally and computationally. Experimentally, Mikkelsen (Mikkelsen Jr. 1984) used SIMS (secondary ion mass spectroscopy) to measure the concentration profiles of labeled O deposited on silica to obtain the diffusion coefficient. Brebec et al (Brebec et al. 1980) used labeled Si and SIMS analysis for determining Si diffusion. Hetherington (Hetherington et al. 1964) used viscosity measurements of commercial silica to determine diffusion constants. Their experimental data are shown in Table 1, along with results from several computational studies. 

While Table 1 shows both the bulk and surface diffusion constants, only the bulk data will be discussed here, with the surface data discussed below. 

While Table 1 shows a similarity among simulation results, it also shows significant differences among the experimental data as well as between the experimental data and the simulation results. A possible reason for the differences among the experimental data may be the different types of silica used in the experiments and the effect of impurities in 

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AH commercial as well as most experimental glass-ceramics are based on siUcate bulk glass compositions. Glass-ceramics can be further classified by the composition of thek primary crystalline phases, which may consist of siUcates, oxides, phosphates, or borates. 

Worldwide siUcate production is estimated to be approximately 4 x 10 t/yr. The 1995 prices for typical products are given in Table 4. The price for a hquid product, normalised to a 100% soHds basis, is usually close to the price of the corresponding bulk glass. International trade of sibcates, especially bquid products, is limited by the cost of transportation rather than production costs. Production of sibcates has increased in the 1990s (Table 5). This growth is primarily attributed to an increase in the use of sibcate to make derivatives and also to use in peroxide bleaching. 

Zirconium tetrafluoride [7783-64-4] is used in some fluoride-based glasses. These glasses are the first chemically and mechanically stable bulk glasses to have continuous high transparency from the near uv to the mid-k (0.3—6 -lm) (117—118). Zirconium oxide and tetrachloride have use as catalysts (119), and zirconium sulfate is used in preparing a nickel catalyst for the hydrogenation of vegetable oil. Zirconium 2-ethyIhexanoate [22464-99-9] is used with cobalt driers to replace lead compounds as driers in oil-based and alkyd paints (see Driers and metallic soaps). 

Table 1. Bulk glass forming alloy systems and the produetion methods, d is the smallest sample dimension.

Figure 2. Bulk glass formation range in Pd-Ni-P system. Filled eireles denote the formation of amorphous phase, open eireles denote the formation of erystalline phases.

Bulk glass leach rates based on various isotopes were calculated by the equation ... 

The leach rates seen here can be compared to those from a similar test on simulated waste glass of the same composition. The leach rates for cesium and strontium from the fully radioactive Rlass were the same as the leach rates of the simulated glass. Although both tests were done on bulk glass samples, they differed in configuration. The fully radioactive samples were disks cm (height) x 3.5 cm (diameter)], and the... 

Other Aluminosilicates, Transparent mullite glass-ceramics can be produced from modified binary Al C —Si02 glasses (21). In these materials, the bulk glass phase separates into tiny alumina-rich droplets in a siliceous matrix. Further heat treatment causes these droplets to crystallize to mullite spherulites less than 0.1 Jim in size. When doped with ions such as Cr3+, transparent mullite glass-ceramics can be made to absorb broadly in the visible while fluorescing in the near-ii (22,23), thereby making them potentially useful for luminescent solar collectors. 

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