Pure metal powders

Nitriding Metals or Metal Hydrides. Metals or metal hydrides may be nitrided using nitrogen or ammonia. Pure metal powders or pure metal hydride powders yield nitride products that are nearly as pure as the precursors. 

Once initiated, zirconium and carbon powders react exothermically in a vacuum or inert atmosphere to form zirconium carbide. With the greater availabiHty of relatively pure metal powders, this technique is coming into common use for the production of several refractory carbides. Zirconium carbide is not a fixed stoichiometric compound, but a defect compound with a single-phase composition ranging from ZrCQ to ZrCQ at 2400°C. 

When the coating metal halide is formed in situ, the overall reaction represents the transfer of coating metal from a source where it is at high activity (e.g. the pure metal powder, = 1) to the surface of the substrate where is kept less than 1 by diffusion. The formation of carbides or intermetallic compounds such as aluminides or silicides as part of the coating reaction may provide an additional driving force for the process. 

Plasma processes have been successfully demonstrated for production of metals from their oxides and chlorides intermediates. Reducing agents are, of course, to be used. Thus, a plasma-based process involving reduction of tantalum chloride in hydrogenous atmosphere has been claimed to yield highly pure metal powder suitable for making of porous capacitor of high capacitance. 

Examples Pure metal powders may be compressed into solid discs or cylinders which can be used as electrodes. Likewise, the analyzing alloys can also be used. 

Fast reactions between pure metal powders (A1 + Ni, A1 + Ti and A1 + Ni + Ti) have been studied by Javel etal. (1997) by using time-resolved X-ray diffraction with the help of synchrotron radiation. The sample (20 X 10 X 2 to 3 mm3 was prepared under purified argon by cold pressing the metal powders mixed in the required proportion. It was then placed in a reaction chamber kept under He gas. A mylar window allows the incident and diffracted X-ray beams to pass in and out. Two small heating devices (tungsten coils on alumina supports) were included. The first one was used to keep the sample at a uniform temperature before ignition and the second one to start the self-propagating reaction at one end of the sample. X-rays irradiated the centre of the specimen. 

See Ref. 5. All catalysts pure metal powders. Experiments performed in a flow apparatus under comparable conditions for all metals hydrogen/heptane mole ratio of 5 1. From M. S. Davis and G. A. Somorjai, in "The Chemical Physics of Solid Surfaces (D. A. King and D. P. Woodruff, eds.), Vol. 4, Elsevier, Amsterdam. 

High pure metal powders can be prepared from metal carbonyls. Thus, US irradiation provokes the irreversible destruction of Fe(CO)5 and formation of Fe3(CO)12 836 [Scheme (3.291)] [750] ... 

Zinc Promoter Pure metal powder <45 pm mostly 0.5 wt.% Zn related to contact mass weight. 

Oxide powders Pure metal powders Carbide powders Nitride powders... 

The temperature attained by the wire-screen heating elements was related to the time of current flow by a calibration method. Times required to melt pure metal powders of like particle size and amounts as the coal were determined by trial and error. A number of calibration points were thus established, and the temperature at the end of the current pulse was proportional to the time of current flow in the region to 1450 °C. The heating rate was therefore a constant 8250°C/sec. 

A similar regularity in the mass distribution of the various Zr-substituted met-cars was observed for different Ti/Zr molar ratios and was used as an argument in favor of a pentagonal dodecahedron structure in which all metal sites are equivalent. In subsequent studies, binary metal metallocarbohedrenes of titanium and other metals Ti cM Ci2 (x -I- y = 8) have been obtained either by the standard method using pure metal powders of Ti and M as a target for laser vaporization and a mixture of helium with 10% methane as carrier gas (M = Nb, Ta, Y, Si), or by direct laser vaporization of a mixture of titanium carbide and pure M metal (M = Y, Nb, Mo, Ta, W). ... 

Jovic VD, Nikolic ND, Lacnjevac UC, Jovic BM, Popov KI (2012) Morphology of different elecirodeposited pure metal powders. In Djokic SS (ed) Electrochemical production of metal powders, modem aspects of electrochtanistry, vol 54. Springer, New York, pp 63—123... 

In most processes that use SX, gold is removed from solution first, followed by palladium, and then platinum. The remaining PGMs are recovered in a variety of ways, either up-front or at the end of the overall flow sheet. In each case, a pure solution of the respective metal is obtained, which is then subjected to a reduction to produce the pure metal powder or sponge. The final products are obtained by melting to obtain ingots, granules, or delivery bars. 

Morphology of Different Electrodeposited Pure Metal Powders... 

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