Materials Multicomponent

There are several approaches to the preparation of multicomponent materials, and the method utilized depends largely on the nature of the conductor used. In the case of polyacetylene blends, in situ polymerization of acetylene into a polymeric matrix has been a successful technique. A film of the matrix polymer is initially swelled in a solution of a typical Ziegler-Natta type initiator and, after washing, the impregnated swollen matrix is exposed to acetylene gas. Polymerization occurs as acetylene diffuses into the membrane. The composite material is then oxidatively doped to form a conductor. Low density polyethylene (136,137) and polybutadiene (138) have both been used in this manner. 

One of the key issues of mechanical behavior of multicomponent materials such as TPV is the stmcture and properties of the interface regions. The phase image in Figure 20.1 Id shows a part of TPV sample with few mbber domains surrounded by iPP matrix. An extended rectangle area outlined with a white dotted box includes several interfaces between mbber domains and the plastic matrix. Examination of the interfaces is a challenging task and one possible approach is AFM-based... 

Sperling, L.H., Polymeric Multicomponent Materials, Wiley, New York, 1999. 

The sol-gel technology, based on various alkoxides, allows production of classical silica glasses, as well as multicomponent materials, merging silicates with titanates, borates and a variety of other oxides (Zn, La, Al, Li, B, K, etc.). The alkoxide gel method can be also used for production of certain non-silicate oxide glass-like materials (e.g., ZrCV, etc.)25. 

Mass spectra of numerous single compounds are available in reference libraries. However these spectra have not always been obtained in the same conditions as those used in DE or DI EI-MS modes and the spectra of molecules of specific interest in the field of cultural heritage have not been systematically registered. It is thus of importance to achieve mass spectra on a set of standard molecular constituents in order to study their mass spectral fingerprint in detail before investigating the more complex mass spectra of multicomponent materials. 

General. We have studied the characterization of multicomponent materials by combining modem analytical instrumentation with a commercially available AI expert system development tool. Information generated from selected analytical databases may be accessed using TIMM, ( The Intelligent Machine Model, ) available from General Research Corp., McLean, VA. This Fortran expert system shell has enabled development of EXMAT, a heuristically-1inked network of expert systems for materials analysis. 

Multicomponent material comprising multiple, different (non-gaseous) phase domains in which at least one type of phase domain is a continuous phase. 

In thermal transport there was need of considering only temperature as the driving potential. However, in the case of multicomponent material transport it is necessary to evaluate the behavior of each component. Such relationships lead to rather complicated expressions when the diffusion of each of the components is considered individually. For this reason it is often appropriate to focus attention on one component and consider the characteristics of the remainder of the components in the phase as invariant. In the present discussion only the behavior of one component will be considered, but it should be realized that the effect of the properties of the phase upon the diffusion coefficient must be taken into account. 

The principal structural factor to be considered in hardness testing of multicomponent materials is the degree of consolidation of the material under test, in other words, the compactness of its structure (Colwell et al.,... 

G. Betz and G. K. Wehner, Sputtering of multicomponent materials, in Sputtering by Particle Bombardment, Vol. II, Springer-Verlag, New York, 1983, p. 11. 

The fact that LEIS provides quantitative information on the outer layer composition of multicomponent materials makes this technique an extremely powerful tool for the characterization of catalysts. Figure 4.18 shows the LEIS spectrum of an alumina-supported copper catalyst, taken with an incident beam of 3 keV 4He+ ions. Peaks due to Cu, A1 and O and a fluorine impurity are readily recognized. The high intensity between about 40 and 250 eV is due to secondary (sputtered) ions. The fact that this peak starts at about 40 eV indicates that the sample has charged positively. Of course, the energy scale must be corrected for this charge shift before kinematic factors V/fcj are determined. 

The chemical properties of particles are assumed to correspond to thermodynamic relationships for pure and multicomponent materials. Surface properties may be influenced by microscopic distortions or by molecular layers. Chemical composition as a function of size is a crucial concept, as noted above. Formally the chemical composition can be written in terms of a generalized distribution function. For this case, dN is now the number of particles per unit volume of gas containing molar quantities of each chemical species in the range between ft and ft + / ,-, with i = 1, 2,..., k, where k is the total number of chemical species. Assume that the chemical composition is distributed continuously in each size range. The full size-composition probability density function is... 

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