Amorphous metallic alloys

By rapid quenching of a suitable alloy from the melt at a cooling rate of about 10 -10 K/s, an amorphous metallic state will be produced where crystallization is suppressed. Commonly, casting through a slit nozzle onto a rotating copper wheel is used to form a ribbonshaped product. The thickness of the ribbons is typically between 20 and 40 p,m. 

The soft magnetic amorphous alloys are based on the ferromagnetic elements Fe, Co, andNi with additions of metalloid elements, the so-called glass forming elements Si, B, C, and P. The most stable alloys contain about 80 at.% transition metal (TM) and 20 at.% metalloid (M) components. 

Depending on their base metal they exhibit characteristic differences of technical significance. Accordingly they are classified into three groups Fe-based alloys, Co-based alloys, and Ni-based alloys. The characteristic variation of their intrinsic magnetic properties saturation polarization Is, saturation magnetostriction A.S, and the maximum field induced magnetic 

Iron-Based Amorphous Alloys Of all amorphous magnetic alloys, the iron-rich alloys on the basis Fe.v.80 (Si, B) 20 have the highest saturation polarization of 1.5-1.8 T. Because of their relatively high saturation magnetostriction (A,s) of around 30 x 10 , their use as soft magnetic material is limited. The application is focused on transformers at low and 

Compared to grain-oriented silicon steels the iron-rich amorphous alloys show appreciably lower co-ercivity and consequently lower total losses. 

The physical and magnetic properties of a characteristic commercial Fe-rich Metglas amorphous alloy are shown in Fig. 4.3-21 and Table 4.3-21 [3.22], 

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F. E. Tuhotsky, Amorphous Metallic Alloys, Butterworths, London 1983, p. 360. 

Only about 10 elements, ie, Cr, Ni, Zn, Sn, In, Ag, Cd, Au, Pb, and Rh, are commercially deposited from aqueous solutions, though alloy deposition such as Cu—Zn (brass), Cu—Sn (bronze), Pb—Sn (solder), Au—Co, Sn—Ni, and Ni—Fe (permalloy) raise this number somewhat. In addition, 10—15 other elements are electrodeposited ia small-scale specialty appHcations. Typically, electrodeposited materials are crystalline, but amorphous metal alloys may also be deposited. One such amorphous alloy is Ni—Cr—P. In some cases, chemical compounds can be electrodeposited at the cathode. For example, black chrome and black molybdenum electrodeposits, both metal oxide particles ia a metallic matrix, are used for decorative purposes and as selective solar thermal absorbers (19). 

CO oxidation, 28 108 iron catalyst, 30 168 kinetics, 28 250-257 complicated, 28 257-263 latest developments in, 5 1 over amorphous metal alloys, 36 372-374 over iron, 36 24-25 on alumina support, 36 47 antipathetic behavior, 36 150, 152 particle size and, 36 131-132 promotion by potassium, 36 36-37 over rhenium. 36 24-25 promotion by potassium, 36 37 photocatalysis over perovskites, 36 304 Anunoxidation, 30 136-137 allyl alcohol, 30 157-158... 

SMSI, 36 220-221 electrode reaction, 32 292-294 electrolytic evolution on amorphous metal alloys, 36 336-338 ESR of, 22 295... 

V. Kesavan, D. Dhar, Y. Koltypin, N. Perkas, O. Palchik, A. Gedanken, and S. Chandrasekaran, Nanostructured amorphous metals, alloys, and metal oxides as new catalysts for oxidation, Pure Appl. Chem. 73, 85-91 (2001). 

Zolotukhin TV., Physical properties of amorphous metallic alloys . Metallurgy, Moscow, (1986) p. 176. 

Most amorphous metallic alloys do not show a metal-insulator transition. They do, however, show moderate changes in the resistivity with temperature, some of which can be interpreted in terms of the quantum interference effect, together with the interaction effect of Altshuler and Aronov (Chapter 5, Section 6). These will be described below. Amorphous alloys of the form Nb Six Au Six etc. do, however, show a metal-insulator transition of Anderson type, and some of those are treated in Chapter 1, Section 7. 

W. Frank, U. Hamlescher, H. Kronmuller, P. Scharwaechter, and T. Schuler. Diffusion in amorphous metallic alloys—Experiments, molecular-dynamics simulations, interpretation. Phys. Scripta, T66 201-206, 1996. 

H. Mehrer and G. Rummel. Amorphous metallic alloys—diffusional aspects. In H. Jain and D. Gupta, editors, Diffusion in Amorphous Materials, pages 163-176, Warrendale, PA, 1994. The Minerals, Metals and Materials Society. 

Luborsky. F.E. ed. Amorphous Metallic Alloys. Buiterworths, London. 1983. 

When one component of a bimetallic alloy is leached out, a finely divided metal powder of high surface area results. One of the oldest of these so-called skeletal metal catalysts is Raney nickel10,11. Nickel boride is a more recently developed hydrogenation catalyst prepared by the reduction of nickel salts with sodium borohydride12-14. Bimetallic catalysts are often used to achieve selective saturation of a double bond in bifunctional unsaturated systems, e.g. in dienes. Amorphous metal alloys, a newly developed class of metal catalysts15,16, have also been applied in the hydrogenation of alkenes and dienes. 

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