Glass, thermal treatment

Fig. 9.5. X-ray diffractogram of an UV-exposed and thermally treated photo-structruable FS21 glass (thermal treatment Ih, 590° C) [128]...

Selenium purification by zone refining is not feasible. At practical zone-refining speeds, crystallization does not occur and impurities do not segregate. However, a controlled differential thermal treatment of selenium in a long vertical glass tube has been described (45). The treatment time is several weeks to several months. 

The attack of most glasses in water and acid is diffusion controlled and the thickness of the porous layer formed on the glass surface consequently depends on the square root of the time. There is ample evidence that the diffusion of alkali ions and basic oxides is thermally activated, suggesting that diffusion occurs either through small pores or through a compact body. The reacted zone is porous and can be further modified by attack and dissolution, if alkali is still present, or by further polymerisation. Consolidation of the structure generally requires thermal treatment. 

The aim of the work was the development of a technique to deposit enzyme LB films on the surface of small glass spheres and to test the enzymatic activity of such samples before and after thermal treatment. 

Simple electroless techniques have been used for the formation of CdTe layers following an anodic or a cathodic route of deposition. For instance, spontaneous cathodic formation of CdTe was observed on Ti or glass electrodes short circuited with a corroding A1 contact (electron source) in a solution of Cd " " and HTe02 ions [96]. After thermal treatment and subsequent growth of an a-Pb02 layer on them, the as-obtained CdTe thin films were found to exhibit n-type behavior in alkaline polysulfide PEC cells. 

Lashtchenova, T. N. Stefanovsky, S. V. 1998a. Immobilization of incinerator ash in Synroc-glass material. In Proceedings of the ITS International Conference on Incineration Thermal Treatment Technologies, Salt Lake City, 603-607. 

Lifanov, F. A., Kobelev, A. P. etal. 1998. Incorporation of intermediate-level liquid radioactive nuclear power plant wastes in glass and ceramics. Proceedings of the IT3 International Conference On Incineration and Thermal Treatment Technologies. Salt Lake City, 609-612. 

The procedure to obtain glass-ceramics does not differ very much from the vitrification process, as it typically only requires an additional carefully controlled thermal treatment, which induces devitrification. In particular, a partly... 

The glass transition temperatures ofthe polyimides are 195-250 °C their 10% weight loss temperamres (dynamic thermogravimetric analysis, air, AT = 4.5 °C/min) are 390-422 °C. Of particular interest are the dielectric constants of these polyimides. At a relative humidity of 50% these constants are 2.70-2.90 and are comparable with constants of the best fluorinated polyimides [21, 50-55]. The lowest dielectric constant (2.70) was observed for polyimide based on 6F dianhydride, containing the highest amount of fluorine. Thermal treatment of this polymer film at 280-290 °C for 1 hour led to a decrease (2.45) of dielectric constant due to the possible formation of nanofoams [56]. 

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