Glass-forming compounds

In equations (3.16) and (3.17), AX, where X is , or Cp, is given by X(liquid) - X(glass). Indeed the two expressions (3.16 and 3.17) provide a means of experimental verification of the two theories because variation of glass transition with pressure can be experimentally determined along with other quantities, namely, Aar, Ayff and AC/.. Some of these quantities have been measured on several polymeric and non-polymeric glass-forming compounds and the data are presented in Table 3.1. It is evident that... 

Modifiers in glass are compounds that tend to donate anions to the network, whereas the cations occupy "holes" in the disordered stmcture. These conditions cause the formation of nonbridging anions, or anions that are connected to only one network-forming cation, as shown in Figure 2. Modifier compounds usually contain cations with low charge-to-radius ratios (Z/r), such as alkali or alkaline-earth ions. 

The flame retardant mechanism for phosphorus compounds varies with the phosphorus compound, the polymer and the combustion conditions (5). For example, some phosphorus compounds decompose to phosphoric acids and polyphosphates. A viscous surface glass forms and shields the polymer from the flame. If the phosphoric acid reacts with the polymer, e.g., to form a phosphate ester with subsequent decomposition, a dense surface char may form. These coatings serve as a physical barrier to heat transfer from the flame to the polymer and to diffusion of gases in other words, fuel (the polymer) is isolated from heat and oxygen. 

S. Grigalevicius, J.V. Grazulevicius, V. Gaidelis, and V. Jankauskas, Synthesis and properties of poly(3,9-carbazole) and low-molecular-mass glass-forming carbazole compounds, Polymer, 43 2603-2608, 2002. 

A very productive strategy for the synthesis of glass-forming materials is the use of highly branched rigid structures. As a suitable center for starburst molecules with a threefold symmetry, triarylamine or benzene are used most frequently. Due to the large number of starburst molecules described in the literature, we divide this class into two subgroups, compounds based on the triarylamine and the benzene centers. 

As had been found in the glass-forming systems, the predicted undercoolings for compounds could vary markedly both between various types alloy systems and between various competing phases in the same alloy system. 

The compounds containing ammonium cations of lower symmetry have melting point below room temperature some are glass forming. 

At the same time, the limestone combines with various impurities to form a glass-like compound called slag. This is removed when the white-hol iron is poured out into moulds and cooled into bars of "pig iron."... 

Uses of Barium. The major use of barium metal for a number of years has been as a getter for oxygen in electronic vacuum tubes. A layer of the metal is deposited inside the glass envelope of the tube. Minute quantities of gases that leak into tine tube react with the banum layer to form compounds. If the gases remained free, they would alter the conductance of the Lube and cause deterioration of its performance. 

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