Other Amorphous Materials

Silicon nitride, oxynitride and silicon aluminium oxynitride (SiAlON) compounds are of considerable technical interest as advanced ceramics because of their stability and chemical inertness at elevated temperatures, and their excellent mechanical properties. Si MAS NMR has proved to be useful in studying various aspects of these compounds, including their formation and structure, the processes by which they are 

NMR can be used for phase identification ( fingerprinting ) of these compounds by comparing their spectra with those of well-characterised single-phase material, for differentiating between the various polymorphs, with the possibility of making semi-quantitative estimates, and for providing structural information by identifying the local atomic environments or structural sub-units. 

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Although glasses and other amorphous materials are difficult to characterize, this does not make them useless. For example, amorphous silicon can be used to transform solar energy into electricity, and glasses obviously find applications in window panes, bottles, drinking glasses, etc. 

We concentrate in this section on the application of MD techniques to the structure of glasses, although later sections consider other amorphous materials and techniques, principally RMC. 

Electrical characteristics obtained in the literature will be discussed in terms of the two classes of conjugated materials deHned previously. The main data obtained with conjugated polymers and other amorphous materials are listed in Table I. These semiconductors generally behave as p-type, unless quoted as otherwise. The range of values, given for some compounds, indicates that various experimental attempts have... 

L. C. E. Struik, Physical Aging in Polymers and Other Amorphous Materials, Elsevier, Amsterdam, 1976. 

Stapron S offers better price performance and processability over many traditional thermoplastics used in consumer products where high heat resistance and good stiffness are required. Its similar shrinkage to other amorphous materials, such as mPPO and PC/ABS al-... 

Mn(n) EPR spectra provide information about the environment of the Mn(II) ion in amorphous materials, which is reflected in the values of parameters g, D, and E and tire linewidth. As for proteins wifli Mn(II) complexes, signal broadening due to motional effect or by structural variations diminishes as the composition of the complex approaches that of the fiilly functional state of the protein. Hence, the improvement in the resolution of the spectrum provides some insight into the fidelity of the structure under investigation. The interpretation of the structure is facilitated by studying the various glassy spectra provided in this article, since a close parallel of biological systems exists with analysis of other amorphous materials in the solid state. 

Amorphous carbon (a-C) films have a uniquely intrinsic stress ( 12 GPa) that is almost one order of magnitude higher than those found in other amorphous materials such as fl-Si, a-Ge, or metals (<1 GPa) [98]. Applying pressiue to a material, one can modify its electronic properties, e.g., band structure, resistivity, work function, due to the stress [99]. Poa et al. [98, 100] found a correlation between the stress and the threshold field for electron emission, as shown in Fig. 16.14. 

It is possible to produce some amorphous compound semiconductors such as amorphous GaAs. These materials have a distinction between dangling bonds associated with the cation and the anion. Therefore, non-bonding states of type (4) would not necessarily he at or near the middle of the mobility gap. In principle, H passivation of such states is also possible. These materials are generally less stable and less homogeneous in amorphous form than other amorphous materials and are not widely used in technology apphcations. 

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