Chromium, powder

In a chemical vapor deposition (CVD) variant of conventional powder metallurgy processing, fine chromium powder is obtained by hydrogen reduction of Crl2 and simultaneously combined with fine thorium(IV) oxide [1314-20-17, H1O2, particles. This product is isostaticaHy hot pressed to 70 MPa (700 atm) and 1100°C for 2 h. Compacts are steel clad and hot roUed to sheets (24). 

Chromium powder is often included in the aluminising mixture. Chromium and aluminium may diffuse together (chromaluminising ) or by balancing the activities of chromium in the alloy and the pack, de-chromising may be prevented. Alloying of the chromium and aluminium powders may be used to control aluminising. 

Evaporation of mercury from mercury amalgam leaves pyrophoric chromium [1]. Increasing the temperature at which hexacarbonylchromium is thermally decomposed increases the surface area and pyrophoricity of the chromium powder produced [2],... 

The displacement mechanism involves placing the iron alloy packed in chromium powder, NH4C1, and 1 i in a sealed retort, which is heated to promote vapor deposition and diffusion processes. The exact chemistry is not known, hut the following steps probably occur ... 

The pentafluoride is a red solid (m.p. 30 °C) which can be prepared1324,1325 by the action of fluorine on chromium powder and probably has a distorted trigonal bipyramidal structure in... 

Manganese and chromium powders have also been reported to activate aluminum trichloride.32 Thus, l,2-dichloro-l,l,2,2-tetrafluoroethanc (CF2ClCF Cl) can be converted into l,l-dichloro-l,2,2,2-tetrafluoroethane(CFCl2CF3), and chlorofluoroethane 1 into 2 under mild conditions and in high yield. 

Chromium powder by reduction of oxide with calcium, 6 50... 

Highly reactive aluminum powders,5 chromium powders,8 and tin powders85 have been produced by the reduction of metal salts in ethereal or hydrocarbon solvents. However, very limited use of these metals to date precludes any discussion of their usefulness in organic and organometallic synthesis. 

Weigh l.Og1 of dried2 (85°C) soil of <0.5 mm into a double-neck round-bottom digestion flask. Add 2.059 g of chromium powder and then 10ml ethanol (95% concentration) to the digestion flask and swirl to wet the sample. Place the digestion flask in the heating mantle and connect to the condenser, with all apparatus in an efficient fume cupboard. 

SULFUROUS OXIDE (7446-09-5) SO, Noncombustible liquefied gas under pressure or liquid. Contact with air forms hydrogen chloride fumes. Violent reaction with water or steam, forming sulfurous acid, a medium-strong acid and corrosion hazard. Reacts violently with acetylene, acrolein, alcohols, aluminum powder alkali metals (i.e., potassium, sodium) amines, ammonia, bromine pentafluoride butadiene caustics, cesium acetylene carbide chlorates, chlorine trifluoride chromium powder copper or copper alloy powders chlorine, diethylzinc, fluorine, ethylene oxide lead dioxide lithium acetylene carbide diamino-, metal powders monolithium acetylide-ammonia nitryl chloride potassium acetylene carbide potassium acetylide, potassium chlorate rubidium carbide silver azide sodium acetylide staimous oxide. Decon oses in... 

NITROGEN MONOXIDE (10102-43-9) A strong oxidizer. Reacts with air, forming nitrogen dioxide. Violent reaction with reducing agents, anhydrous ammonia, alcohols, butadiene, carbon disulfide, charcoal, chromium powders, dichlorine oxide, 1,3,5-cycloheptatriene,... 

Chromium(V) fluoride has been prepared by the static fluorination of chromium powder by elemental fluorine at 400° and 200 atm and by the high temperature, high-pressure static fluorination of chromium(III) fluoride. The procedure described below involves fluorination of chromium(VI) difluoride dioxide, Cr02p2, by elemental fluorine under rather mild conditions, which is the most convenient method. Chromium(V) fluoride is a useful precursor to a large number of complex salts that contain CrP and Crp7. ... 

Electrolytic chromium powder is heated for 2 hours at 800-900°C in a quartz or porcelain tube while a dry, Og-free stream of Ng is passed through. After cooling, the product is ground in an agate mortar and calcined again for 2 hours In a stream of Ng. The final product is treated with HCl until nothing further dissolves (the HCl liquid remains colorless). The black residue is thoroughly washed and dried. 

S. N. Chakrabarty and 8. Dutt studied organic syntheses with chromium powder. 

Two-stage processes, the essential features being the production of chromous chloride followed by the action of the activator on the metal surface in the presence of a reducing atmosphere [144], for example, hydrogen or a mixture with hydrogen chloride is passed over anhydrous CrCl2 (or chromium powder) at 850°C-1000°C and then over the steel substrate at 1000°C-1200°C for a period of several hours. 

Chromium. Molybdenum. Tungsten. Cocondensation of PH3 with chromium vapor at 60 K leads to the formation of a PH3 complex of Cr [78]. Chromium powder with PH3 forms phosphides of different composition at 700 to 950 C. The reaction at 850 C yields CrP, whereas at 950 C only the lowest phosphide, CrgP, is obtained the latter dissociates at 10OO C to give Cr [79]. Gaseous PH3 is inert in the presence of metallic Mo on an AI2O3 support at about 350 C [80]. The reaction of PH3 with W at 850 C gives WP [81]. 

The material in this study consisted of aluminium nitride and pure chromium powder from Alfa Aesar (Johnson Matthey, Karlsruhe, Germany), chromium(llI)nitride and aluminium powder from Sigma-Aldrich (Munich, Germany). The particle sizes of the powders were around 40 microns. The chromium(lII)nitride powder consists of 85% Cr N and 15% CrN. Four different groups of compositions were made, as shown in figure 1. 

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