Preparation, amorphous alloys

Table 1. Comparison of the transformation temperatures determined from DSC at heating rate is at 0.67 K/ s (if not indicated) for some typical amorphous alloys prepared by different methods. Tg glass transition temperature Txi onset crystallization temperature AT the width of supercooled liquid region, which is equal to Tx - Tg.

A number of investigations have reported a distinct difference in the transformation temperatures between the amorphous alloys prepared by melt cooling and that formed by solid-state amorphization techniques (e.g. ball milling or mechanical alloying). Fig. 8 compares the structural feature and transformation temperatures for Ti5oCu35Nii2Sri3 and... 

Various amorphous alloys can be prepared by plating". Plating is particularly suitable for the preparation of thinner amorphous alloys than is possible by melt spinning, e.g. < 1 tm, although production of defect-free alloys is difficult. 

The possible strategies are coprecipitation to prepare mixed hydroxides or carbonates [5], cosputtering of gold and the metal components of the supports by Ar containing O2 to prepare mixed oxides [23], and amorphous alloying to prepare metallic mixed precursors [24]. These... 

Oranges, citric acid in, 6 632t ORBIT PRINT SELECT software, 18 243 Orbitrap, 15 662-663 Orb web, structure of, 22 630 Ordered intermetallic alloys, 13 530 Order, in amorphous semiconductor structure, 22 128-129 Ordering, in ternary semiconductor alloy preparation, 22 158-159 Order of addition, in large-scale... 

Owing to their numerous actual and potential applications, several ternary and complex systems of these metals, especially of aluminium, have been investigated a few examples of the systematics of Al-Me-X alloys are presented in 5.18 and in Fig. 5.41. Recent contributions to this subject have been given with the study of the systems R-Al-Cu (Riani et al. 2005, and references there in). These rare earth alloys, characterized by the formation of several intermediate phases, are interesting also as raw materials for the preparation of amorphous alloys. Regularities in the trends of their properties have been underlined. The experimental and calculated data relevant to the binary systems Al-Fe, Al-Ni and Fe-Ni have been examined and discussed in a paper concerning the assessment of the ternary Al-Fe-Ni system (Eleno et al. 2006). 

A. Ye, Yermakov, Ye., Ye., Yurchikov, V.A. Barinov, Magnetic properties of amorphous powders of Y-Co alloys prepared by mechanical alloying, Fiz Metal. MetaUoved. Phys. Met. Metall. USSR), 52(52-56) (1981) 1184-1193. 

Methanation of C02 over Pd on zirconia and Ni on zirconia catalysts derived form amorphous Pd-Zr-, Ni-Zr-, and Ni-containing multicomponent alloys prepared by controlled oxidation-reduction treatment or generated under reaction conditions have been studied in detail. 

Several materials have been investigated as cathode activators. Among the most studied systems we find CuTi, CuZr, NiTi, NiZr, FeCo, NiCo. A variety of methods are available to prepare amorphous alloys [562] and, as expected, the resulting activity is largely dependent on them. Normally, amorphous phases are obtained by rapidly quenching a melt. The material can thus be obtained in the form of ribbons, but mechanical alloying by compaction is also possible [572]. The metallic components are usually alloyed with non-metallic components such as B, Si and P which stabilize the metastable non-crystalline structures. Electrodeposition is thus also a viable preparation route [573, 574],... 

A common observation in most cases is that the surface of amorphous alloys, especially those containing Ti, Zr and Mo, is largely covered with inactive oxides which impart low electrocatalytic properties to the material as prepared [562, 569, 575], Activation is achieved by removing these oxides either by prepolarization or, more commonly and most efficiently, by leaching in HF [89, 152, 576]. Removal of the passive layer results in a striking enhancement of the electrocatalytic activity [89], but surface analysis has shown [89, 577] that this is due to the formation of a very porous layer of fine particles on the surface (Fig. 32). A Raney type electrode is thus obtained which explains the high electrocatalytic activity. Therefore, it has been suggested [562, 578] that some amorphous alloys are better as catalyst precursors than as catalysts themselves. However, it has been pointed out that the amorphous state appears to favor the formation of such a porous layer which is not effectively formed if the alloy is in the crystalline state [575]. 

Rudenauer and coworkers [78, 79] use metallic glasses as standards for several reasons 1) the metallic glasses are single phase systems and are homogeneous at the micron scale 2) metallic glasses can be prepared in a broader concentration range than alloying components, and even insoluble elements can form an amorphous phase under suitable conditions 3) the ion yields of elements in isotopic amorphous alloys are not-dependent on the orientation of the bombardment surface and 4) amorphous alloys have metallic character. 

Mo are single phase, supersaturated solid solutions having an fee structure very similar to that of pure Al. Broad reflection indicative of an amorphous phase appears in deposits containing more than 6.5 atom% Mo. As the Mo content of the deposits is increased, the amount of fee phase in the alloy decreases whereas that of the amorphous phase increases. When the Mo content is more than 10 atom%, the deposits are completely amorphous. As the Mo atom has a smaller lattice volume than Al, the lattice parameter for the deposits decreases with increasing Mo content. Potentiodynamic anodic polarization experiments in deaerated aqueous NaCl revealed that increasing the Mo content for the Al-Mo alloy increases the pitting potential. It appears that the Al-Mo deposits show better corrosion resistance than most other aluminum-transition metal alloys prepared from chloroaluminate ionic liquids. 

Figures 4(a) and 4(b) show the relationship between the average grain size and the coercivity in various Fe-based nanocrystalline soft magnetic alloys prepared by crystallization of amorphous precursors (For details, see Herzer [13], Yoshizawa [31], Muller and Mattem [32], Fujii et al. [33], and Suzuki et al. [34, 35]). As shown in Fig. 4(a), the coercivity Ha of the nanocrystalline Fe-Si-B-M-Cu (M = IVa to Via metal) alloys follows the predicted D6 dependence in a D range below LO ( 30 to 40 nm for this alloy system) although the plots deviate from the predicted D6 law in the range below H0 1 A/m where the effect of grain refinement on is overshadowed by magneto-elastic and annealing induced anisotropies. Hence, the experiments are better described by Hc [a2 + where a...

Experimental Apparatus and Procedures. The amorphous alloys of about 15 microns thick and 3 mm wide ribbons were prepared by the disk method (8), the details of which have been described elsewhere (5). The important step of the method is the impinging of the molten mother alloy, held in a quartz tube with a small nozzle, onto the surface of a rotating disk of stainless steel. A flow type of a reactor apparatus, previously described (5), was used for the catalytic reaction. The reaction was carried out under atmospheric pressure and at temperatures from 220 to 370°C. The catalysts were pretreated with a stream of hydrogen in advance of a run. A gas chromatography was used for analyzing the hydrocarbons methane, ethylene, ethane, propylene, propane, butenes, butanes, total C5 hydrocarbons, and higher hydrocarbons (C6 to Cj0, not separated), as well as carbon monoxide, carbon dioxide and water. Alcohols and aldehydes could be detected by the gas chro-motography but were not found to be produced in sizable amounts. 

Liu B., Dai W., Wu G., Deng J.-F. Amorphous alloy/ceramic composite membrane preparation, characterization and reaction studies. Catalysis Letters 1997 49 181-188. 

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