Hydrogen occlusion

Occurrence and History of Palladium—Preparation—Physical Varieties Physioal Properties—Permeability to Hydrogen--Occlusion of Canos Occlusion of Hydrogen—Chemical Properties--Catalytic Activity Crystalline Palladium—Colloidal Palladium—Spongy Palladium —Palladium Black —Uses—Atomic Weight—Alloys. 

Boodey, J. B., Gao, M., Wei, W., and Wei, R. P., Hydrogen Occlusion and Hydride Eorma-tion in Titanium Aluminides, Proceedings of 124th International Symposium on Gamma Titanium Aluminides VII Microstructure and Mechanical Behavior, Las Vegas, NV,... 

Nishimiya N, Kishi T, Mizushima T, Matsumoto A and Tsutsumi K (2001), Hyperstoichiometric hydrogen occlusion by palladium nanoparticles included in NaY zeolite , J Alloys Compel, 319, 312. 

In order to investigate the effect of this characteristic hydrogen occlusion capacity for the catalytic reaction, FI2-D2 hydrogen exchange reaction and hydrogenation of C2H4 as well as CO-H2 reaction were carried... 

Cha] Chan, S.L.L, Charles, J.A., Effect of Carbon Content on Hydrogen Occlusivity and Embrit-... 

Other uses are as superconductive materials of TiNb, the shape memory alloy of Ti-Ni, the hydrogen occlusion alloy of Ti—Fe, and in computer equipment as nonmagnetic substance, artificial bones, dental roots, cardiac valves and cardiac pacemakers as nontoxic and biocompatible materials [3,5]. 

In Rocks.—In a state of "occlusion, or molecular condensation, hydrogen is to be found in most igneous rocks in association with other gases, the total volume of occluded gases being on the average about 4 5 times the volume of the rock. 

Finely divided nickel absorbs a large volume of hydrogen at high temperatures. Even at ordinary temperatures, considerable occlusion of hydrogen occurs on to the metal surface and no definite composition of any hydride formed is known. The metal activates molecular hydrogen to its atomic state, contributing to its catalytic action in hydrogenation of unsaturated compounds. 

Some interferences appear to be vapour-phase effects and are presumably due to occlusion of analyte elements into particles of matrix. The use of platforms in furnaces (see Section 3.6.3), the use of reactive purge gases (e.g. hydrogen) and dispersion of the matrix, e g. by using an organic acid such as ascorbic acid, can in some cases reduce such interferences. 

Morawetz RB, DeGirolami U, Ojemann RG, Marcoux FW, Crowell RM (1978) Cerebral blood flow determined by hydrogen clearance during middle cerebral artery occlusion in unanesthetized monkeys. Stroke 9 143-149 Moseley ME, Cohen Y, Mintorovitch J, Chileuitt L, Shimizu H, Kucharczyk JF, Wendland ME, Weinstein PR (1990) Early detection of regional cerebral ischemia in cats comparison of diffusion- and T2-weighted MRI and spectroscopy. Magn Reson Med 14 330-346... 

Endothermic occlusion takes place by diffusion of hydrogen into a metal lattice which is very little changed by the process. In exothermic occlusion by palladium, however, the face-centred cubic lattice (a phase) of palladium, with lattice constant 3.88 A, will accomodate, below 100°C, no more than about 5 at. % hydrogen, and then undergoes a transition to an expanded phase ( 3 phase), with lattice constant 4.02 A and H/Pd = 0.5—0.6. The H—Pd system thus splits into a and 3 phases in the manner familiar for two partially miscible liquids. The consolute temperature (rarely observable for solid phases) is about 310°C at H/Pd = 0.22. The phase diagram is, however, not well established because formation of the... 

Occlusion of Hydrogen by Cobalt.—Hydrogen is readily occluded by cobalt to an extent dependent upon a variety of factors. Chief amongst these are ... 

Preparation.—Metallic palladium is obtained by reduction of its salts. To this end ammonium chlor-palladite, (NH4)2PdCl4, is very suitable. Upon ignition in hydrogen, ammonium chloride and hydrogen chloride volatilise, leaving the metal behind in a porous, spongy condition.. In order to avoid occlusion of hydrogen the metal may be cooled in a current of carbon dioxide. 

Occlusion of Hydrogen.—Palladium possesses to a remarkable extent the power of absorbing or occluding hydrogen, and numerous researches have been carried out by different investigators with a view to determining the condition of the occluded gas, and the influence it has upon the properties of palladium. 

Alloying elements exert a very important influence upon the occlusion of hydrogen by palladium. The absorptive power of commercial palladium is from 10 to 20 per cent, less than that of the pure metal, a fact that is attributed to the presence of small quantities of platinum and ruthenium.6... 

The heat evolved on the occlusion of hydrogen by palladium black is nearly the same as that evolved by platinum black under similar conditions. The heat of occlusion remains constant for the different fractions of hydrogen occluded, namely, 4640 calories per gram of hydrogen, or 4370 calories if the external work done by the atmosphere is allowed for.1... 

The addition of gold to palladium first increases and then reduces the power of the latter metal to occlude hydrogen, the reduction being proportional to the amount of gold in the alloy. The occlusion is reduced to nil in the presence of 75 per cent, of gold.5... 

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