Multiphase solid state

Interfacial polarizations have been recorded for many multiphase solid-state polymer systems semicrystalline polyamides... 

Although the parameters in equation [15.2] are a common type of data, their measurement for commercial polymers is difficult because of their multiphase solid state morphology. It was found that blocking force can be more easily estimated from the following equation ... 

Traditional solid-state synthesis involves the direct reaction of stoichiometric quantities of pure elements and precursors in the solid state, at relatively high temperatures (ca. 1,000 °C). Briefly, reactants are measured out in a specific ratio, ground together, pressed into a pellet, and heated in order to facilitate interdiffusion and compound formation. The products are often in powdery and multiphase form, and prolonged annealing is necessary in order to manufacture larger crystals and pure end-products. In this manner, thermodynamically stable products under the reaction conditions are obtained, while rational design of desired products is limited, as little, if any, control is possible over the formation of metastable intermediates. ... 

Yang J., Winter M., Besenhard JO. Small particle size multiphase Li-alloy anodes for lithium-ion batteries. Solid State Ionics 1996 90 281-87. 

N. Kuiiyama, D. Chartouni, M. Tsukahara, K. Takahashi, H.T. Takeshita, H. Tanaka, L. Schlapbach, T. Sakai, I. Uehara, Scanning tunneling microscopy in situ observation of phase-selective cathodic hydrogenation of a V-Ti-Ni-based multiphase alloy electrode, Electrochem. Solid-State Lett. 1 (1998) 37-38. 

It is important to mention that the structure/properties relationships which will be discussed in the following section are valid for many polymer classes and not only for one specific macromolecule. In addition, the properties of polymers are influenced by the morphology of the liquid or solid state. For example, they can be amorphous or crystalline and the crystalline shape can be varied. Multiphase compositions like block copolymers and polymer blends exhibit very often unusual meso- and nano-morphologies. But in contrast to the synthesis of a special chemical structure, the controlled modification of the morphology is mostly much more difficult and results and rules found with one polymer are often not transferable to a second polymer. 

Let us concentrate a little longer on ceramics. Here micro-analysis only slowly won ground and the application of solid state physics lagged behind. Very slowly the relationship between the properties of a material and its microstructure was being discovered. Metallurgy had already been characterized by a theoretical approach for some time and consequently metals were about 15 times as important as ceramic materials in 1960 (see Ashby s graph). This was of course influenced by the fact that metals have relatively simple structures which, in their turn, simplify theoretical comtemplations. Ceramic structures are very often complex and are characterized by multiphase systems. However, at present ceramic materials are approached much differently than for instance in 1900. 

The strength of Mossbauer spectroscopy is its ability to provide information about the environment of metal centres in large molecules, polymers and minerals, in both single- and multiphase specimens. The drawbacks of the technique are the limited number of elements to which it can be applied in practice, its insensitivity, its limitation to solid state studies, and the need for a suitable radioactive source. 

The idea about the summation of the times of consecutive steps of the examined solid-state process is of primary importance for understanding the peculiarities of multiphase growth of compound layers in binary heterogeneous systems. Moreover, even in the case of formation of a single compound layer, this idea makes it possible to reveal a few aspects of reaction... 

F.J.J. van Loo. Multiphase diffusion in binary and ternary solid-state systems // Prog.Solid St.Chem.- 1990.- V.20.- P.47-99. 

In spite of their seeming variety, theoretical approaches of different authors to the consideration of solid-state heterogeneous kinetics can be divided into two distinct groups. The first group takes account of both the step of diffusional transport of reacting particles (atoms, ions or, in exceptional cases if at all, radicals) across the bulk of a growing layer to the reaction site (a phase interface) and the step of subsequent chemical transformations with the participation of these diffusing particles and the surface atoms (ions) of the other component (or molecules of the other chemical compound of a binary multiphase system). This is the physicochemical approach, the main concepts and consequences of which were presented in the most consistent form in the works by V.I. Arkharov.1,46,47... 

Up to now the number of materials which have been subjected to solid-state extrusion is very small. The deformation mechanisms and the correlation of the deformation Conditions with the extrudate properties are far from being understood. This holds especially for multiphase polymers. We have reported a field of polymer science which seems to be still in its beginning. 

A solid-state fermentation is a multiphase system and the homogeneity in the solid phase is generally imperfect making it more difficult to model the process. 

Our recent work on the bismuth-cerium molybdate catalyst system has shown that it can serve as a tractable model for the study of the solid state mechanism of selective olefin oxidation by multicomponent molybdate catalysts. Although compositionally and structurally quite simple compared to other multiphase molybdate catalyst systems, bismuth-cerium molybdate catalysts are extremely effective for the selective ammoxidation of propylene to acrylonitrile (16). In particular, we have found that the addition of cerium to bismuth molybdate significantly enhances its catalytic activity for the selective ammoxidation of propylene to acrylonitrile. Maximum catalytic activity was observed for specific compositions in the single phase and two phase regions of the phase diagram (17). These characteristics of this catalyst system afford the opportunity to understand the physical basis for synergies in multiphase catalysts. In addition to this previously published work, we also include some of our most recent results on the bismuth-cerium molybdate system. As such, the present account represents a summary of our interpretations of the data on this system. 

Silica, alumina, and silica-alumina samples are often complex materials, sometimes multiphase systems, almost always having a distribution of structures at the surface. From the point of view of catalysis, structures at both the surface and in the interior (bulk properties) are important. In this chapter we focus on surfaces. Because of NMR s sensitivity to local structure and its forgiveness of long-range disorder, solid-state NMR is one of the methods of choice for studying the structures of these materials. NMR is, of course, also a powerful tool for studying dynamics. 

There is a growing interest in the development of multiphase ceramics. Both the processing and the use of each of the materials described above may involve a solid-state reaction and the movement of a phase boundary. There are, of course, many other situations in which solid-state... 

Lorcher, R., Strecker, K., Riedel, R., Telle, R., and Petzow, G. in Solid State Phenomena 8 9, Proc. Int. Conf. Sintering of Multiphase Metal and Ceramic Systems, Upadhyaya, G. S. (Ed.), Sci-Tech Publications, Vaduz, Gower Publ. Co., Brookfield, VT, 1990, pp. 479-492. 

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