Polymorphic phases

The complexity of the typical solid deformation response can be further compounded by the presence of one or more polymorphic phase transformations, and a host of other phenomena typical of solids. Table 1.1 lists a number of such phenomena. 

The ideas developed in this chapter are descriptive of shock waves in fluids. Solids have many significant features that distinguish them from liquids and gases, such as shear strength, polymorphic phase transformations, heterogeneous structure, anisotropy, and viscoplastic behavior. The influences of these special properties of solids on shock compression are the topics of several of the other chapters, and for the most part are ignored in this introduction to the basic principles of shock compression. 

Shock loading in most metals and alloys produces greater hardening than quasi-static deformation to the same total strain, particularly if the metal undergoes a polymorphic phase transition, such as is observed in pure iron [1]-[10]. Figure 6.1 compares the stress-strain response of an annealed... 

These shock data are the limiting elastic compression just prior to a polymorphic phase... 

Linear trans-quinacridones exhibit multiple crystal modifications. This phenomenon is reflected in the different reflection angles which are observed in the X-ray diffraction spectra of the pigment powders. This effect may be exemplified by describing the polymorphous phases of unsubstituted quinacridone. 

Sulfur trioxide is prepared in the laboratory by heating fuming sulfuric acid, condensing its vapors, and collecting in a cool receiver. When vapors are condensed below 27°C in the presence of trace moisture, aU three polymorphic phases of SO3 are produced. They can be separated by fractional distillation. Condensation of the vapors above 27°C forms the hquid variety of gamma-sulfur trioxide. 

Although the detailed information on the polymorphic phases has to be obtained with e.g., diffraction and scanning probe methods, our eyes are attracted by the beauty of optical microscope images often encountered with polymorphs under transformation. Figure 5.17 shows an optical microscopy image of a / -NPNN thin film (thickness 2 pm) on a glass substrate, exhibiting a transformation at... 

J. A. Wilson and A. D. Yoffe, Adv. Phys., 18, No. 73, 193-335 (1969). This article offers a complete discussion of the polymorphic phases found in the various layered transition metal dichalcogenides. 

Strain-annealing, devitrification or polymorphic phase change... 

It is likely that oligothiophenes, as many other organic materials, exhibit an intrinsic tendency to form several polymorphic phases, such that small grains of structural minority phases can be easily formed. The respective vibronic energies can be obtained which are in very close agreement (AE <15 cm [) to those reported for matrix isolated 4T. This result clearly indicates that the observed luminescence come from undistorted 4T molecules. 

A Polymorphic Phase Change in the Cluster Complex, [ 3-S(AulCNC7H13)3]2(SbF6)2... 

Fig. 3.23 NM R spectra for macroscopic polymorphic phases of phospholipids in bilayers, hexagonal HM, and isotropic phases (small vesicles, micelles, inverted micelles, and cubic phases). Similar spectra are recorded for any one phase regardless of which...

Keywords hydrogen accumulator, hydrated methane, polymorphism, phase transition, nanostructure of ice, modeling... 

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