Hydrogen metal alloys

Hydrogen-storage alloys (18,19) are commercially available from several companies in the United States, Japan, and Europe. A commercial use has been developed in rechargeable nickel—metal hydride batteries which are superior to nickel—cadmium batteries by virtue of improved capacity and elimination of the toxic metal cadmium (see BATTERIES, SECONDARYCELLS-ALKALINe). Other uses are expected to develop in nonpolluting internal combustion engines and fuel cells (qv), heat pumps and refrigerators, and electric utility peak-load shaving. 

Mechanical properties of hydrogenated titanium alloys are strongly dependent on the applied stress tensor, especially on its hydrostatic component. This was illustrated by the high-pressure tensile and extrusion tests on the Ti-6Al-2.5Mo-2Cr alloy and the same alloy hydrogenated to a = 0.15 wt.%H. Tests were carried out using the apparatus at the Institute of Metal Physics UD RAS operating at hydrostatic pressures of machine oil to 15 kbax and temperatures to 250°C. 

The NO reduction over Cu-Ni-Fe alloys has been studied recently by Lamb and Tollefson. They tested copper wires, stainless steel turnings, and metal alloys from 378 to 500°C, at space velocities of 42,000-54,000 hr-1. The kinetics is found to be first order with respect to hydrogen between 400 and 55,000 ppm, and zero order with respect to NO between 600 and 6800 ppm 104). The activation energies of these reactions are found to be 12.0-18.2 kcal/mole. Hydrogen will reduce both oxygen and NO when they are simultaneously present. CO reduction kinetics were also studied over monel metals by Lunt et al. 43) and by Fedor et al. 105). Lunt speculated that the mechanism begins by oxidant attack on the metal surface... 

Medvedev IG. 2004. To a theory of electrocatalysis for the hydrogen evolution reaction The hydrogen chemisorption energy on the transition metal alloys within the Anderson-Newns model. Russ J Electrochem 40 1123-1131. 

In this paper, results on the ECH of representative substrates are presented i) in order to illustrate the advantages and the limitations of the ECH at Raney metal electrodes as a method of hydrogenation of organic compounds and ii) in order to discuss some synthetic and mechanistic aspects. The Raney metal electrodes consisted of Raney metal particles embedded in a nickel matrix (1) or dispersed in a lanthanum polyphosphate matrix (2), or of pressed Raney metal alloy of which the outmost layer only has been leached (3). 

Fortunately, virtually everything said about hydrogenations is applicable to deuteriumations. Exceptions are certain rates and certain processes using metal and metal alloy membranes for hydrogenations (deuteriumations). Differences between the formation of the P-hydride and p-deuteride phases in these latter cases affect the reaction outcomes. Such differences between hydrogenations and deuteriumations are pointed out and discussed where appropriate. 

Relatively little attention has been devoted to the direct electrodeposition of transition metal-aluminum alloys in spite of the fact that isothermal electrodeposition leads to coatings with very uniform composition and structure and that the deposition current gives a direct measure of the deposition rate. Unfortunately, neither aluminum nor its alloys can be electrodeposited from aqueous solutions because hydrogen is evolved before aluminum is plated. Thus, it is necessary to employ nonaqueous solvents (both molecular and ionic) for this purpose. Among the solvents that have been used successfully to electrodeposit aluminum and its transition metal alloys are the chloroaluminate molten salts, which consist of inorganic or organic chloride salts combined with anhydrous aluminum chloride. An introduction to the chemical, electrochemical, and physical properties of the most commonly used chloroaluminate melts is given below. 

Hydrogen Storage Alloy and Hydrogen Storage Systems, http //www.jmcusa.com/mhl.html, Japan Metal and Chemical Company (USA), Inc, April 2007. 

Thomas, R.C. and Hughes, R.C., Sensors for Detecting Molecular Hydrogen Based on Pd Metal Alloys, Journal of Electrochemical Society, 144(9), 3245,1997. 

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