Multicomponent glass

Note that the concentrations of additive oxides differ. No attempt has been made to scale this effect with additive concentration). This curious reduction effect is not easily understood but emphasizes the complex nature of the glasses including the possible cooperative involvement of the multiple components. Similarly complex phenomena might influence leaching behavior in the complex, multicomponent glasses of interest for radioactive waste storage. 

We wish also to mention the discovery of an unusual magnetic field dependence of specific heat in some multicomponent glasses in the 0.3 tK range [46]. A theoretical explanation of the phenomenon can be found in ref. [[47] pp. 17-46]. 

Yinnon H. and Gooper A.R. (1980) Oxygen diffusion in multicomponent glass forming silicates. Phys. Chem. Glasses 21, 204-211. 

A number of empirical expressions exist for estimating the modulus of multicomponent glasses based upon composition. One particularly useful one that provides an absolute value for the modulus, E, is based upon the density of the glass, p, and the packing density, Vt, dissociation energy, f/, mole %, pt, and molecular weight. Mi, of the components ... 

Table 5.6 Factors Used to Determine Elastic Modulus in Multicomponent Glasses Using Eq. (5.55)...

A number of multicomponent glasses have in recent years been found to show a tendency to metastable separation into two or more liquid phases. The resulting microheterogeneous regions impair the structural continuity by more or less distinct phase boundaries. The phenomenon of phase separation will be dealt with later (see Chapter II, Section 6.5). 

Figure 5.2-2. Schematic of the doublecrucible method for producing multicomponent glass fibers.

At least three corners must be shared. For one-component glasses, each polyhedron shares corners with at least three other polyhedra, such that the network is continuous in three dimensions. In multicomponent glasses additional cations are distributed throughout holes in the network. 

X-ray scattering studies often lead to ambiguous answers concerning the local structure, especially in the case of multicomponent glasses. As EXAFS provides a partial radial distribution function, this method becomes very powerful when the distribution relative to each atomic species can be joined up. This situation is often encountered in metallic glasses. 

The study clearly demonstrates the powerful role which molecular dynamics can play in interpreting diffraction data for multicomponent glasses. This is particularly true for systems, such as Na20-Si02, where it is not possible to use techniques such as isotopic substitution to investigate the individual component correlation functions. 

The subtractive methods practically can only be used to produce single films with lower refractive indices than those of the multicomponent glass substrates. Consequently in optics their use is limited to reflection-reducing films. This limitation does not exist with the additive film formation methods. With additive methods, it is possible to deposit in any sequence low- or non-absorbing compound films with various refractive indices as well as absorbing an highly reflecting metal or alloy films and mixtures of both types of films. It is obvious therefore that the subtractive methods are almost completely superseded by additive ones. The additive film formation methods can be classified into chemical and physical methods and further into wet or dry processes the latter may run at atmosphere or under vacuum. 

Other examples for multicomponent glass layers prepared by dip-coating are... 

Thermodynamically, a multicomponent glass can usually be treated as a homogeneous solid solution. It might then be expected that for chemically similar molecules the conventional mixing rules might apply, perhaps even be reflected in the Tg omposition relationship. This has indeed been found to be the case for binary PHC blends, where neither... 

For multicomponent glasses, the desired additions may be in the form of alkoxides (7) or soluble salts such as acetates and nitrates ( ). In this way glasses containing B, Al, Ti, Na, K, transition metals, rare earths and others are relatively straightforward in practice to prepare. A longer chain alcohol such as propanol may be used to slow the rates of the chemical reactions and allow adequate time for complete mixing. 

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