Transformation behavior

Fig. 18. Continuous-cooling transfomiation diagram for a Type 4340 alloy steel, with superimposed cooling curves illustrating the manner in which transformation behavior during continuous cooling governs final microstmcture (1). Ae is critical temperature at equiUbrium. Ae is lower critical...

The K-edge spectra of [Ni(287)2]2 and [Ni(cdt)2]2 are remarkably similar to each other and to those of natural hydrogenases.196 Some complexes with ligand (289) (R = NMe2, R = H, Me, NMe2) have been characterized using electronic and near infrared spectroscopy.823 Complex [Ni(289)2]2 served to study phase transformation behavior by microscopy and DSC.824... 

Based on the reversibility of their phase transformation behavior, polymorphs can easily be classified as being either enantiotropic (interchange reversibly with temperature) or monotropic (irreversible phase transformation). Enantiotropic polymorphs are each characterized by phase stability over well-defined temperature ranges. In the monotropic system, one polymorph will be stable at all temperatures, and the other is only metastable. Ostwald formulated the rule of successive reactions, which states that the phase that will crystallize out of a melt will be the state that can be reached with the minimum loss of free... 

Chemical solution deposition (CSD) procedures have been widely used for the production of both amorphous and crystalline thin films for more than 20 years.1 Both colloidal (particulate) and polymeric-based processes have been developed. Numerous advances have been demonstrated in understanding solution chemistry, film formation behavior, and for crystalline films, phase transformation mechanisms during thermal processing. Several excellent review articles regarding CSD have been published, and the reader is referred to Refs. 5-12 for additional information on the topic. Recently, modeling of phase transformation behavior for control of thin-film microstructure has also been considered, as manipulation of film orientation and microstructure for various applications has grown in interest.13-15... 

Polymorphs and solvated crystals is generally observed in pharmacentical indnstry [1], The bioavailability, stability, solnbility, and morphology of the pharmacentical products are very influenced by polymorphs [2-7], therefore the control of the polymorphic crystallization is very important. The crystallization process of polymorphs and solvated crystals is composed of competitive nucleation, growth, and transformation from a meta-stable form to a stable form [4], Furthermore, the crystallization behavior is influenced by various controlling factors such as temperature, supersaturation, additives and solvents [8], In order to perform the selective crystallization of the polymorphs, the mechanism of each elementary step in the crystallization process and the key controlling factor needs to be elucidated [8], On the other hand, we reported for L-Glutamic acid and L-Histidine system previously [4] that the nucleation and transformation behaviors of polymorphs depend on the molecular stractures. If the relationship between molecular stmcture and polymorphic crystallization behavior is known, the prediction of the polymorphism may become to be possible for the related compound. However, detail in such relationship is not clearly understood. 

If one tries to apply the definition (39) naively to degenerate states, one is faced with the problem that, for example, and have a different transformation behavior with respect to the spin rotation group SU2, hence would have no acceptable transformation behavior at all. The way out of this dilemma is to define the irreducible tensor components of in terms of those of yPf and y. ... 

What is the influence of important environmental variables such as temperature, pH, light intensity, redox condition, ionic strength, presence of certain solutes, concentration and type of solids, microbial activity, and so forth, on the transformation behavior of a given compound ... 

Hiramatsu, N. and Hirakawa, S. Melting and transformation behavior of gamma form Nylon 6 under high pressure. Polymer J. 14, 165 (1982)... 

The phase transformation behavior of Py-D3C was far simpler than that reported for tetrahydrofuran/N2- and tetrahydrofuran/Xe-D3C in reference 10. We attribute this difference in part to impurities in the samples employed, samples that contained methanol and ethylenediamine according to 13 C CPMAS NMR spectroscopy. We have observed that use of Si(OCH3)4 as a silica source or ethylenediamine as a catalyst in clathrasil synthesis introduces defects that can alter phase transition temperatures by as much as 30 °C and/or introduce new phase transformations. 

It should be pointed out that the polarizability tensor of a SRM may exhibit a more complicated transformation behavior than expressed by Eq. (3.47). This goes back to the fact, that the polarizability tensor involves all electronic states and the latter do not necessarily all have the same isometric group. 

The samples prepared without the HIP treatment showed substantially the same transformation behavior as the HIP-treated material, with one notable exception The monoclinic and tetragonal forms were seen to coexist over at least a 100 K temperature range in all vanadium-substituted samples that did... 

Figure 3.16 Enthalpy and heat capacity as a function of temperature for (a) first and (b) second order and lambda transformations [5][8]. Lambda transformation behavior is shown with dot-dot-dashed lines.

This is in contrast to the transformation behavior of the nominal stresses of the rubber matrix with a negative sign ... 

As it is well known, basis functions when used in a LCAO framework appear paired at the moment of computing integrals. The structure of the two centered pairs of CETO functions and their transformation behavior opens the way to describe simpler CETO forms, which may be employed, in turn, as integral building blocks. 

Anatase, brookite and rutile are three polymorphs of titanium dioxide. Anatase is a kind of thermodynamically metastable form while rutile is a kind of stable one. Anatase can transform irreversibly to rutile at elevated temperatures ranged from 400 to 1200 °C according to particle size, morphology and additives. The solid-state phase transformation behavior has been widely investigated while the phase evolution between anatase and rutile under hydrothermal condition has been little paid attention to so far [5]. In this work, the structural evolution from anatase to rutile under milder hydrothermal conditions is proposed as well [7, 10]. 

Sato, K. (1999). Solidification and phase transformation behavior of food fats— a review. Fett/Lipid, 101, 467-74. [28, 111]... 

Since the most important orbitals in the model system 3 (the D and A 71-orbitals and the relevant highest occupied and lowest unoccupied molecular orbitals (MO s) of each PE moiety) have the same qualitative nodal structure with respect to rotation about the OPE axis (i.e., a single node), we approximate the transformation behavior under such rotations (6>y) in terms of sin6> and cos /. Accordingly, the hopping integrals (T, t) in Eq. 101 may be elaborated as follows ... 

The influence of methanol proportions in solvents, and temperature, on the solubility and the transformation behavior of 2-(3-cyano-4-isobutyloxyphenyl) -methylthiazole-5-carboxylic acid (BPT) was investigated. The transformation behavior was explained by the chemical potential difference between the stable and metastable forms. It was shown that a specific solute-solvent interaction contributes to the preferential nucleation and growth of the stable or metastable forms and influences the transformation behaviors, and the solubility of the solvated crystals is much more influenced by the solvent compositions than the true polymorphs. The solubility ratio of the solvated crystals depends on the solvent composition, whereas the solubility ratio of the true polymorphs is considered to be independent of the solvents. The crystallization behavior was also investigated. The transformation rate after crystallization appeared to depend on the initial concentration of BPT and the addition rate of the antisolvent. The cause of this phenomenon was presumed to be a slight inclusion of the stable form in the metastable form <2005PAC581>. 

Table 1 shows the polymorphic behavior of the three TAG in which the saturated fatty acid at the the in-1 and in-2,3 positions is stearic and the sn-2 acid varied from oleic (SOS), ricinoleic (SRS) to linoleic (SLS). As a reference, a typical feature of polymorphic transformation of SOS from a to 3j forms through y, P and P2 is illustrated in Table 1 (10). As briefly mentioned in die previous section, one of the unique polymorphic properties in SOS is that the chainlength structure converted from DCL (a) to TCL (y, P, P2, and Pj), and the subcell structures of stearic and unsaturated acid leaflets in the TCL polymorphs changed in different manners. This transformation behavior is caused by the steric hindrance of steric and unsaturated acid chains, as well as by the structural stabilization of the aliphatic chains and glycerol groups altogether, as briefly summarized in the following.

Zhang H, Banfreld JF (2000) Understanding polymorphic phase transformation behavior during growth of nanocrystalline aggregates insights from Ti02. J Phys ChemB 104 3481-3487... 

The proper transformation behavior of the current density operator thus requires the presence of both possible operator orderings, which leads to the anticommutator form (7). For the charge operator one then obtains... 

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