Transformation of glass

Thermodynamic properties and solubility of the sediments. From a comparison of the tabulated thermodynamic constants (Naumov et al., 1971) it follows that the transformation of glass into a-Si02 is accompanied by a 2.2 kcal/mol change in enthalpy. Values of the isobaric-isothermic potential of formation of amorphous silicas were calculated on the basis of a comparison... 

Besides the amorphous structure, both inorganic and organic glasses exhibit another characteristic property, the so-called transformation (glass transition). Transformation of glass may be demonstrated on the diagram of temperature dependence of some physical property, for instance, specific volume (Jones, 1956),... 

Van Duinen RNB, Davidson CL, De Gee AJ, Feilzer AJ (2004) In situ transformation of glass-ionomer into an enamel-like material. Am J Dent 17 223 van Meerbeek B, Vargas M, Inoue S, Yoshida Y, Peumans M, Lambrechts P, Vanherle G (2001) Adhesives and cements to promote preservation dentistry. Oper Dent26 Sll9... 

Glasses, like metals, are formed by deformation. Liquid metals have a low viscosity (about the same as that of water), and transform discontinuously to a solid when they are cast and cooled. The viscosity of glasses falls slowly and continuously as they are heated. Viscosity is defined in the way shown in Fig. 19.7. If a shear stress is applied to the hot glass, it shears at a shear strain rate 7. Then the viscosity, ij, is defined by... 

The usual type of glass paddle stirrer is also widely used in conjunction with an electric motor fitted with either a transformer-type, or a solid-state, speed controller. The stirrer may be either connected directly to the motor shaft or to a spindle actuated by a gear box which forms an integral part of the motor housing by these means, wide variation in stirrer speed can be achieved. 

Combinatorial approach to unsymmetrically tiered macromolecules [214] is a brand new area of research which would allow dendrimerization of materials (e. g., glass, classical polymers, fibers) and thus enable fine tuning of macromole-cular properties. For example, treatment of an amine terminated dendrimer with a mixture of complementary, isocyanate-based monomers [215, 216] affords a heterogeneous surfaced dendrimer. Selective transformation of the surface nitrile moieties via metal-catalyzed reduction to obtain a new polyamine dendrimer allows further combinatorial-based elaboration as illustrated in Fig. 42. 

Anaerobic decolorization of azo dyes was started back in the 1970s. Reticulated sintered glass was used as immobilization of anaerobic bacteria for the decolorization of wastewater and transformation of the azo dye to degradable products [58], Full decolorization was achieved in less than 4 h HRT, and in addition to it, methane as biogas was also produced. 

Silica-based materials obtained by the sol-gel process are perhaps the most promising class of functional materials capable to meet such a grand objective. In the sol-gel process liquid precursors such as silicon alkoxides are mixed and transformed into silica via hydrolytic polycondensation at room temperature. Called soft chemitry or chimie douce, this approach to the synthesis of glasses at room temperature and pressure and in biocompatible conditions (water, neutral pH) has been pioneered by Livage and Rouxel in the 1970s, and further developed by Sanchez, Avnir, Brinker and Ozin. 

Field studies on the transformation of endrin in the atmosphere were not located in the available literature. Photochemical isomerization of endrin, primarily to the pentacyclic ketone commonly called delta ketoendrin or endrin ketone, was observed after exposure of thin layers of solid endrin on glass to sunlight (Burton and Pollard 1974). Minor amounts of endrin aldehyde were also formed in this reaction. Results of seasonal studies indicated that this isomerization would proceed with a half-life (first-order kinetics) of 5-9 days in intense summer sunlight, with complete conversion to the pentacyclic ketone in 15-19 days. Knoevenagel and Himmelreich (1976) reported that photodegradation of solid endrin in the laboratory... 

---