Solid-phase transformations

Shock-wave compression is also used to study solid-solid phase transformation. Bancroft et al. [58] report a previously unknown phase transformation... 

Twinning is itself a kind of solid solid phase transformation with the first and seeond phases having the same erystal strueture (henee the same pressure-volume response) but with prineipal erystallographie orientation at some angle to the original orientation. This results in a eontribution to plastie shear deformation under both quasi-statie and shoek-wave eonditions [61]. 

Determination of the influence of crystal structure and reactant environment on deammination and dehydration processes is complicated by the several solid phase transformations that are a characteristic feature of many ammonium salts. Sublimation and/or melting may also occur. Deammination and dehydration steps are generally reversible. At high temperatures, however, particularly in the presence of a residual oxide... 

From Fig.2 (a), A solid phase transformation fiom hematite, Fc203 to magnetite, Fe304, is observed, indicating that the active sites of the catalj are related to Fc304. Suzuki et. al also found that Fe304 plays an important role in the formation of active centers by a redox mechanism [6]. It is also observed that the hematite itself relates to the formation of benzene at the initial periods, but no obvious iron carbide peaks are found on the tested Li-Fe/CNF, formation of which is considered as one of the itsisons for catalyst deactivation [3,6]. 

Zinc biphenylenebis(phosphonate) was obtained with a linear chain rather than a layer structure when the same preparative method was used as for the zinc phenylenebis(phosphonate) layer structure. The presence of base allows a solid phase transformation from the linear chain to the layer structure. 

As a suitable model reaction, the coupling of various substituted carboxylic acids to polymer resins has been investigated by Stadler and Kappe (Scheme 7.8) [28]. The resulting polymer-bound esters served as useful building blocks in a variety of further solid-phase transformations. In a preliminary experiment, benzoic acid was attached to Merrifield resin under microwave conditions within 5 min (Scheme 7.8 a). This functionalization was additionally used to determine the effect of micro-wave irradiation on the cleavage of substrates from polymer supports (see Section 7.1.10). The benzoic acid was quantitatively coupled within 5 min via its cesium salt utilizing standard glassware under atmospheric reflux conditions at 200 °C. 

TG analysis also represents a powerful adjunct to DTA or DSC analysis, since a combination of either method with a TG determination can be used in the assignment of observed thermal events. Desolvation processes or decomposition reactions must be accompanied by weight changes, and can be thusly identified by a TG weight loss over the same temperature range. On the other hand, solid-liquid or solid-solid phase transformations are not accompanied by any loss of sample mass and would not register in a TG thermogram. 

Martinez, C.E. McBride, M.B. (1998) Coprecipitates of Cd, Cu, Pb and Zn in iron oxides solid phase transformation and metal solubility after aging and thermal treatment. Clays Clay Min. 46 537-545... 

All of our observations lead us to believe that the crystallization of VPI-5 involves a solid phase reordering process. This solid phase transformation does not involve TBA as either a template or a space-filler. TBA may be present in the solid phase in very low concentrations that are below detection limits by IR and NMR and may still play some role in the crystallization mechanism. Also, it may serve to moderate the pH of the reaction mixture during its formulation and heating such that certain aluminophosphate precursor species are present in the solid phase. Here we will explore these two possibilities in order to further understand the crystallization process for forming VPI-5. 

Let us first consider the liquid-solid phase transformation. At the melting point (or more appropriately, fusion point for a solidification process), liquid and solid are in equilibrium with each other. At equilibrium, we know that the free energy change for the liquid-solid transition must be zero. We can modify Eq. (2.11) for this situation... 

Solidification. When the ingot or casting solidifies, there are three main possible microstructures that form (see Figure 7.5). We will describe here only the final structures the thermodynamics of the liquid-solid phase transformation have been described previously in Chapter 2. The outside layer of the ingot is called the chill zone and consists of a thin layer of equiaxed crystals with random orientation. 

Phase Transform., Inst. Metal. Conf. Ser. 3,2, 98 (1979) P. R. Williams, M. K. Miller G. D. W. Smith, Proc. Int. Conf. Solid-Solid Phase Transform. Metal Soc., AIME, Warrendale, PA (1981). 

McNicol et al. (49) used luminescence and Raman spectroscopy to study structural and chemical aspects of gel growth of A and faujasite-type crystals. Their results are consistent with a solid-phase transformation of the solid amorphous network into zeolite crystals. Beard (50) used infrared spectroscopy to determine the size and structure of silicate species in solution in relationship to zeolite crystallization. 

D. de Fontaine. Studies of the thermodynamics of ordering by the cluster variation method. In H.I. Aaronson, D.E. Laughlin, R.F. Sekerka, and C.M. Wayman, editors, Proceedings of an International Conference on Solid- Solid Phase Transformations, pages 25-47, Warrendale, PA, 1981. The Metallurgical Society of AIME. 

F.K. LeGoues, H.I. Aaronson, Y.W. Lee, and G.J. Fix. Influence of crystallography upon critical nucleus shapes and kinetics of homogeneous f.c.c.-f.c.c. nucleation. I. The classical theory regime. In International Conference on Solid—>Solid Phase Transformations, pages 427-431, Warrendale, PA, 1982. The Minerals, Metals and Materials Society. 

As a suitable model reaction, the coupling of various substituted carboxylic acids to polymer supports has been investigated (Scheme 7.7)27. The resulting polymer-bound esters served as useful building blocks in a variety of further solid-phase transformations. In a preliminary experiment, benzoic acid was attached to Merrifield resin under... 

The high purity (>95%) of the released product from resin 14 prompted us to investigate the potential of radical release as a traceless linker concept. To our knowledge, thermolytic radical fragmentation of covalent bonds is a mechanism of bond dissociation that has not been exploited so far for linker chemistry and for solid-phase transformations. Cleavage yields, determined by releasing nonvolatile products, were found to be higher than 90%. 

Z.A. Matysina and D.V. Schur, Hydrogen and solid phase transformations in metals, alloys andfullerites (in Russian). (Izd. Nauka i obrazovanie, Dnepropetrovsk, 2002). 

The superscript ° indicates that this equation is for a gas at the standard state of 1 bar. Standard states will be discussed in greater detail later in this chapter. For a solid, the calculation just includes the first integral (to 7), and for a liquid, the first two terms plus the second integral (to 7). If there are any solid-phase transformations at temperatures T, with heats of transformation A H, additional terms of the form A H/T must be included. 

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