Of cobalt metal

Cobalt difluoride, used primarily for the manufacture of cobalt trifluoride, CoF, is available from Advance Research Chemicals, Inc., Aldrich Chemicals, and PCR in the United States, Fluorochem in the UK, and Schuhardt in Germany. The 1993 price varied from 60 to 200/kg depending on the quantity and the price of cobalt metal. C0F2 is shipped as a corrosive and toxic material in DOT-approved containers. 

The mauve colored cobalt(II) carbonate [7542-09-8] of commerce is a basic material of indeterminate stoichiometry, (CoCO ) ( (0 )2) H20, that contains 45—47% cobalt. It is prepared by adding a hot solution of cobalt salts to a hot sodium carbonate or sodium bicarbonate solution. Precipitation from cold solutions gives a light blue unstable product. Dissolution of cobalt metal in ammonium carbonate solution followed by thermal decomposition of the solution gives a relatively dense carbonate. Basic cobalt carbonate is virtually insoluble in water, but dissolves in acids and ammonia solutions. It is used in the preparation of pigments and as a starting material in the preparation of cobalt compounds. 

Cobalt(II) acetylacetonate [14024-48-7] cobalt(II) ethyUiexanoate [136-52-7] cobalt(II) oleate [14666-94-5] cobalt(II) linoleate [14666-96-7] cobalt(II) formate [6424-20-0], and cobalt(II) resinate can be produced by metathesis reaction of cobalt salt solutions and the sodium salt of the organic acid, by oxidation of cobalt metal in the presence of the acid, and by neutralization of the acid using cobalt carbonate or cobalt hydroxide. 

Cobalt(Il) dicobalt(Ill) tetroxide [1308-06-17, Co O, is a black cubic crystalline material containing about 72% cobalt. It is prepared by oxidation of cobalt metal at temperatures below 900°C or by pyrolysis in air of cobalt salts, usually the nitrate or chloride. The mixed valence oxide is insoluble in water and organic solvents and only partially soluble in mineral acids. Complete solubiUty can be effected by dissolution in acids under reducing conditions. It is used in enamels, semiconductors, and grinding wheels. Both oxides adsorb molecular oxygen at room temperatures. 

Prices of cobalt compounds are directiy related to the cost of cobalt metal which fluctuates widely. Zaire is the primary cobalt suppHer. The price of cobalt metal was 46.30/kg in July 1992, down from 76.75/kg in December 1991, but up from the 27.56/kg July 1991 price. Annual usage of cobalt in the western world averaged 15,950 t in 1980—1984. The nonmetaUic uses of cobalt were about 35% in 1984 and estimated to be 40% in 1990 (1,8,9). 

The high cost of cobalt metal has led to substitution such that alloys containing low or no cobalt are produced where possible. Because the cost of cobalt compounds in specialty appHcations is usually much less significant than in alloys, there is less incentive to develop alternatives. 

The oxidation of cobalt metal to inactive cobalt oxide by product water has long been postulated to be a major cause of deactivation of supported cobalt FTS catalysts.6 10 Recent work has shown that the oxidation of cobalt metal to the inactive cobalt oxide phase can be prevented by the correct tailoring of the ratio Ph2cJPh2 and the cobalt crystallite size.11 Using a combination of model systems, industrial catalyst, and thermodynamic calculations, it was concluded that Co crystallites > 6 nm will not undergo any oxidation during realistic FTS, i.e., Pi[,()/I)i,2 = 1-1.5.11-14 Deactivation may also result from the formation of inactive cobalt support compounds (e.g., aluminate). Cobalt aluminate formation, which likely proceeds via the reaction of CoO with the support, is thermodynamically favorable but kinetically restricted under typical FTS conditions.6... 

Bartholomew and coworkers32 described deactivation of cobalt catalysts supported on fumed silica and on silica gel. Rapid deactivation was linked with high conversions, and the activity was not recovered by oxidation and re-reduction of the catalysts, indicating that carbon deposition was not responsible for the loss of activity. Based on characterization of catalysts used in the FTS and steam-treated catalysts and supports the authors propose that the deactivation is due to support sintering in steam (loss of surface area and increased pore diameter) as well as loss of cobalt metal surface area. The mechanism of the latter is suggested to be due to the formation of cobalt silicates or encapsulation of the cobalt metal by the collapsing support. 

There seems to be several mechanisms leading to the activity loss oxidation of cobalt metal, sintering of cobalt metal particles as well as sintering of the support and formation of stable cobalt-support metal oxides (silicates or aluminates). Oxidation by water is a key issue, possibly occurring on all supports and on unsupported cobalt. A thermodynamic analysis of this effect was reported by van Steen et al.,40 and they describe the FTS reaction system in terms of reactions (1) and (2) below ... 

The dust and powder of cobalt metal, ores, and some compounds, such as cobaltous nitrate [ColNOfljT bH O], are flammable and toxic if inhaled. Cobaltous acetate [ColCjHjOjlj dHjO], which is soluble in water, is not allowed to be used in food products because of its toxicity. 

Fra. 10. Spectra of cobalt metal and four cobaltous ealta, showing progressive change from low amplitude Type III spectrum to high amplitude Type 1 spectrum as the cobalt atom is shielded from heavy element neighbors. 

Cobalt(II) chloride is prepared by the action of cobalt metal or its oxide, hydroxide, or carbonate with hydrochloric acid ... 

Cobaltous oxalate dihydrate, CoC 04-2H 0 tpink). is obtained by adding oxalic acid or an alkaline oxalate to a cobaltous salt solution. This is the commercial form of tile salt and is important as the starting material in ihe preparation of cobalt metal powders. 

What is the number of 60Co atoms produced in a 10-mg sample of cobalt metal exposed for 2 min to a thermal neutron flux of 2 x 1013 n/cm2-s in a reactor The cross section for producing 10.5-min 60Com is 16 bams, while the cross section for producing 5.3 y 60Co is 20 bams. What is the disintegration rate of the cobalt sample 4 h after the end of the irradiation ... 

At present 60Co sources are made in England, Canada, and the United States. The primary source manufactured in the United States is the BNL standard source (5), which is in the form of a strip of cobalt metal about % inch wide, 1 foot long, and 60 mils thick, doubly encapsulated in thin stainless steel jackets. The total amount of self-absorption of 7-rays in this source is less than 10%—i.e., over 90% of the 7-rays are available for absorption in target material. 

Figure 1 Stability of HCo(CO)4/Co2(CO)g species with respect to precipitation of cobalt metal (cobalt concentration is 0.4 wt%)...

FMR spectra of cobalt metal catalysts are shown in Fig. 2. FMR spectroscopy is a useful tool for studying very small magnetic particles. For sufficiently small single-domain magnetic particles, rapid thcimal fluctuations of the magnetization vector tend to average out anisotropic... 

Use Ceramics, pigments, catalyst, preparation of cobalt metal, semiconductors. 

The lack of activity of Co/MgO is due to the non availability of cobalt metal due to the formation of a CoO/MgO solid solution during activation. In contrast, the relatively high dispersion of Co/zeolite suggests that cobalt metal is available on the catalyst surface. The sample is inactive possibly because the number of Co° atoms in each cluster is less than a lcwer limit required for dissociative CO chemisorption. Chemisorption with retention of integrity, as is measured in the dispersion experiment, is not subject to such a constraint. 

Ferromagnetic resonance (FMR) spectra of cobalt metal were recorded at X-band frequencies on a Vartan E-4 spectrometer. DPPH and weak pitch were used as standards for g factor. Transmission electron microscopy (TEM) was done with JEOL 200CX microscope using 160 KeV electrons. 

Cobalt. The reaction of cobalt metal with two mole equivalents of PMe3l2 yields [Col3(PMe3)2] (Equation 6). 

Co doped into single crystals of cobalt metal shows a magnetic hyper-fine pattern similar to that of a-iron with a field of —316 kG at room temperature and a value of e qQ of —0-064 mm s [80]. The latter value is nonzero because of the hexagonal symmetry of the cobalt. Application of an external magnetic field parallel and perpendicular to the c axis showed that the external field was strictly additive in both directions. This implies that the hyperfine field is isotropic, an unexpected result when the local environment is non-cubic as seen from the finite quadrupole splitting. 

Leonard A and Lauwerys R (1990) Mutagenicity, carcinogenicity and teratogenicity of cobalt metal and cobalt compounds. Mutat Res 239 11-21. 

The cemented carbides are large-particle composites. These materials are used as cutting tools to machine hard steels. The first cemented carbide made was formed of tungsten carbide particles embedded in a matrix of cobalt metal. The hard carbide cuts the steel but is brittle. The toughness comes from the cobalt matrix. 

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