Characteristics amorphous

Research has led to alloys which undergo laser-induced crystallization within about 50 ns. This is possible, for example, with TeGe alloys, which also possess the necessary temperature stability up to 180°C and exhibit sufficient reflection (crystalline phase) and transmission characteristics (amorphous phase), respectively. TeGe alloys have not found a practical use because of the formation of depressions in the memory layer typical for them after repeated... 

We have found that high molecular weight poly (p-PIN)s readily yields fibers by manual drawing from the melt. X-ray analysis of melt-drawn fibers showed a characteristic amorphous halo with a d spacing at 6.2 A. 

At the macroscopic level, a solid is a substance that has both a definite volume and a definite shape. At the microscopic level, solids may be one of two types amorphous or crystalline. Amorphous solids lack extensive ordering of the particles. There is a lack of regularity of the structure. There may be small regions of order separated by large areas of disordered particles. They resemble liquids more than solids in this characteristic. Amorphous solids have no distinct melting point. They simply become softer and softer as the temperature rises. Glass, rubber, and charcoal are examples of amorphous solids. 

The overall goal of this study is to develop superior catalysts suitable for use in modem advanced slurry phase or membrane reactors. Successful investigations have produced an iron-based unsupported catalyst with high activity and extended catalyst life (improved attrition resistance). This catalyst was used by the authors to understand the phase transformations from iron oxide precursors after activation to iron carbide crystallites and to characterize the presence of characteristic amorphous carbon species that have been reported to envelop the spent Fe-FTS catalyst grains in form of surface layers. Previous studies suggest two different phases to be considered as the active phase including iron oxide and a mixture of x snd e -carbides (Table 1) and in some instances minor amounts of metallic iron, however the spatial distribution of the different... 

Examples of binary amorphous Tb-Fe alloys for magneto-optical applications were presented by Tsunashima et al. (1981), Honda et al. (1983b) and Kobayashi et al. (1981, 1983). The former authors used amorphous double layer films Gd-Fe/ Tb-Fe, in which the exchange coupling between those films had led to improved writing characteristics. Amorphous alloys in which Tb is combined with two different 3d metals were investigated by Tsujimoto et al. (1983), while Tsujimoto et al. (1980) studied the magnetic properties of multilayered amorphous films. 

There are a few drawbacks of thermoplastics. Some thermoplastics do not fully crystallize below the glass hansition temperature (Tg) and retain some or all of then-amorphous characteristics. Amorphous and semiamorphous plastics are less resistant to chemical attack and environmental stress cracking because of the lack of crystalhne structure. Amorphous and semiamorphous plastics are typically used when there is high optical clarity because light is scattered strongly by crystallites larger than its wavelength [5]. 

Amorphous silicates are produced by destabilization of soluble siUcates to yield amorphous discrete particles in varying degrees of aggregation. The high specific surface area in combination with an organophilic surface is responsible for the excellent ink adsorption characteristics. Amorphous silicate also has the potential to increase somewhat the bulk of the paper sheet. 

One of the most characteristic amorphous bands of PLLA at 1265 cm , which was assigned to coupling of the C—O—C stretching and C—H deformation modes was also missing from the spectra of the 20/80 PHB-co-HHx/PLLA blend. Thus, the spectra of the 20/80 PHB-co-HHx/PLLA blend were very similar to the neat crystalline PLLA spectra. Infrared microspectroscopy revealed that PHB and PHB-co-HHx, but not PLLA, were crystallized in the 80/20 blends. These results also indicated that the PHB-co-HHx component, when dispersed in a PLLA matrix at a relatively low level, did not undergo significant crystallization. 

Figure 4.7 Various representations of the properties of a mixture of crystalline and amorphous polymer, (a) The monitored property is characteristic of the crystal and varies linearly with 0. (b) The monitored property is characteristic of the mixture and varies linearly with 0 between and P, . (c) X-ray intensity is measured with the sharp and broad peaks being P. and P., respectively.

Principal Adsorbent Types. Commercially useful adsorbents can be classified by the nature of their stmcture (amorphous or crystalline), by the sizes of their pores (micropores, mesopores, and macropores), by the nature of their surfaces (polar, nonpolar, or intermediate), or by their chemical composition. AH of these characteristics are important in the selection of the best adsorbent for any particular appHcation. 

Docusate Calcium. Dioctyl calcium sulfosuccinate [128-49-4] (calcium salt of l,4-bis(2-ethylhexyl)ester butanedioic acid) (11) is a white amorphous soHd having the characteristic odor of octyl alcohol. It is very slightly soluble in water, and very soluble in alcohol, polyethylene glycol 400, and com oil. It may be prepared directly from dioctyl sodium sulfo succinate dissolved in 2-propanol, by reaction with a methan olic solution of calcium chloride. 

In an amorphous material, the aUoy, when heated to a constant isothermal temperature and maintained there, shows a dsc trace as in Figure 10 (74). This trace is not a characteristic of microcrystalline growth, but rather can be well described by an isothermal nucleation and growth process based on the Johnson-Mehl-Avrami (JMA) transformation theory (75). The transformed volume fraction at time /can be written as... 

Some amorphous copoly(ether—sulfone) fkms have been prepared (117) with Ts around 130°C with no loss in weight up to 400°C in ak or N2. Other backbones iavestigated in this class of polymers are copoly(ether—amides) (118) and copoly(ether—ketones) (119). These polymers show good mechanical properties, flow characteristics, and abrasion resistance. 

Properties. One of the characteristic properties of the polyphosphazene backbone is high chain dexibility which allows mobility of the chains even at quite low temperatures. Glass-transition temperatures down to —105° C are known with some alkoxy substituents. Symmetrically substituted alkoxy and aryloxy polymers often exhibit melting transitions if the substituents allow packing of the chains, but mixed-substituent polymers are amorphous. Thus the mixed substitution pattern is deUberately used for the synthesis of various phosphazene elastomers. On the other hand, as with many other flexible-chain polymers, glass-transition temperatures above 100°C can be obtained with bulky substituents on the phosphazene backbone. 

---