Amorphous Glassy Phases

Thermoplastics are based on linear or branched polymers, copolymers or their blends that are reversibly transferred at heating into a plastic or viscoplastic state as a result of melting of the crystalline and/or softening of the amorphous (glassy) phase [29]. Inhibited CM based on thermoplastics are largely adopted in anticorrosion techniques. Most thermoplastics are produced at a large scale in petrochemical enterprises and are comparatively... 

X-ray diflEraction (XRD) analysis has been a useful tool to check the presence of minerals (viz., Mullite, Hematite, Magnetite and ot-Quartz) as the main crystalline phase in the fly ash and its zeolites, in addition to the presence of amorphous glassy phase [16, 38]. Furthermore, micrographs obtained by scanning electron microscopy (SEM) of the fly ash and its zeohtes, as depicted in Fig. 2.6a, have been found to be a useful tool for demonstrating the shape and grain size of constituent minerals (refer Table 2.5 [8, 24]). 

The elemental analysis from Table 8.1 indicates that the nepheline and diopside phases are present in addition to the amorphous glassy phase, hence revealing stability of the KMBY glass-ceramic after 500 h heat treatment The sodium, potassium, and lithium (minor constituent) containing glass SCN-1 was studied for the isothermal ageing tests in dual environments of dilute hydrogen inside the test... 

As mentioned earlier, if there is a large disparity in sttiicture at the film-substrate interface, such as a crystalline phase growing on an amorphous, glassy, substrate, the film may detach and grow a separate morphology. 

The chains that make up a polymer can adopt several distinct physical phases the principal ones are rubbery amorphous, glassy amorphous, and crystalline. Polymers do not crystallize in the classic sense portions of adjacent chains organize to form small crystalline phases surrounded by an amorphous matrix. Thus, in many polymers the crystalline and amorphous phases co-exist in a semicrystalline state. 

Another characteristic point is the special attention that in intermetallic science, as in several fields of chemistry, needs to be dedicated to the structural aspects and to the description of the phases. The structure of intermetallic alloys in their different states, liquid, amorphous (glassy), quasi-crystalline and fully, three-dimensionally (3D) periodic crystalline are closely related to the different properties shown by these substances. Two chapters are therefore dedicated to selected aspects of intermetallic structural chemistry. Particular attention is dedicated to the solid state, in which a very large variety of properties and structures can be found. Solid intermetallic phases, generally non-molecular by nature, are characterized by their 3D crystal (or quasicrystal) structure. A great many crystal structures (often complex or very complex) have been elucidated, and intermetallic crystallochemistry is a fundamental topic of reference. A great number of papers have been published containing results obtained by powder and single crystal X-ray diffractometry and by neutron and electron diffraction methods. A characteristic nomenclature and several symbols and representations have been developed for the description, classification and identification of these phases. 

General characteristics of alloys such as those presented in Fig. 3.3 have been discussed by Fassler and Hoffmann (1999) in a paper dedicated to valence compounds at the border of intermetallics (alkali and alkaline earth metal stannides and plumbides) . Examples showing gradual transition from valence compounds to intermetallic phases and new possibilities for structural mechanisms and bonding for Sn and Pb have been discussed. Structural relationships with Zintl phases (see Chapter 4) containing discrete and linked polyhedra have been considered. See 3.12 for a few remarks on the relationships between liquid and amorphous glassy alloys. 

Structural relations between quasicrystals and other intermetallic phases. As discussed in several sections of the review published by Kelton (1995) on quasicrystals and related structures, numerous studies and observations indicate structural similarities between non-periodic quasicrystal phases with crystalline phases and also, on the other hand, with amorphous, glassy and liquid phases. 

Fig. 9 Plots of the transfer rates of electrons, holes, and overall DNA radicals at 77 K vs hydration levels lower axis) as well as vs the distance between DNA ds s (upper axis). Values of D s are estimated from the work of Lee et al. [39]. The results show that as amorphous (glassy) hydration increases up to T=22 D20/nucleotide, D s increases and transfer rate decreases. At T=30 D20/nucleotide, the ice is formed, and leaves the actual amorphous hydration level at around 14 D20/nucleotide with the remainder in the ice phase. The plot clearly shows equivalent transfer rates for both hydration levels at 14 and 30 D20/nucleotide. This result suggests that Djs plays an important role in hydration-dependent hole and electron transfer in DNA [7dj. Reprinted with permission from the J. Phys. Chem. Copyright (2001) American Chemical Society...

Ion implantation also has promise in other tields involv ino surface technology for example, new metallurgical phases w ith prior unknown properties can be I untied. In some eases. Mich as heav y implantations of tantalum irt copper of phosphorus in iron, amorphous or glassy phases can be formed. Or. if the implanted atoms ore mobile, inclusions and precipitates can he formed as. for example, implanted argon and helium atoms are insoluble in metals and may form bobbles. The composition of a surface layer can be changed by differential sputtering caused by the implanted ions. 

Block copolymers of the A—B—A type where A is a thermoplast and B an elastomer can have properties at ambient temperatures which would normally be expected from a crosslinked rubber. The cause of this phenomenon are the physical crosslinks produced by the thermoplastic blocks which may be either crystalline or amorphous (glassy). Above the melting temperature of the hard phase such materials flow and can be processed by the usual thermoplastic processing techniques. 

Finally, one should take note of the fact that in all Si3N4 ceramics a residual, continuous glassy phase remains between the crystalline phases, even after prolonged annealing time at temperatures above 1300 K. This amorphous phase is neglected in all phase diagrams (Sect. 3), yet strongly affects the properties. Therefore much effort has been made to characterise the amorphous phase which will be treated in more detail in Sect. 6.1.4.3. 

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