Cobalt, properties

CO hydrogenation activity was found to depend on both the amount of available surface cobalt metal and the environment of the reduced cobalt. Factors influencing these cobalt properties included the type of support, the type of cobalt species present on a given support, and the presence of additives. Due to the interrelationship of these properties, a detailed examination of the activity and structure of each catalyst is needed in order to determine the importance of each factor for CO hydrogenation activity. 

Bucher J P, Douglass D C and Bloomfield L A 1991 Magnetic properties of free cobalt clusters Phys. Rev. Lett. 66 3052... 

Pathmamanoharan C and Philipse A P 1998 Preparation and properties of monodisperse magnetic cobalt colloids grafted with polyisobutene J. Colloid Interface Sol. 205 304-53... 

Gobalt is a brittle, hard metal, resembling iron and nickel in appearance. It has a metallic permeability of about two thirds that of iron. Gobalt tends to exist as a mixture of two allotropes over a wide temperature range. The transformation is sluggish and accounts in part for the wide variation in reported data on physical properties of cobalt. 

Platinum-cobalt alloys have magnetic properties. One such alloy made of 76.7% Pt and 23.3%... 

Copper, nickel, cobalt, iron, and zinc (270) for their physical properties using ultraviolet and infrared spectrometry (271). 

Chemical ingenuity in using the properties of the elements and their compounds has allowed analyses to be carried out by processes analogous to the generation of hydrides. Osmium tetroxide is very volatile and can be formed easily by oxidation of osmium compounds. Some metals form volatile acetylacetonates (acac), such as iron, zinc, cobalt, chromium, and manganese (Figure 15.4). Iodides can be oxidized easily to iodine (another volatile element in itself), and carbonates or bicarbonates can be examined as COj after reaction with acid. 

Cobalt difluoride [10026-17-2] C0F2, is a pink solid having a magnetic moment of 4, 266 x 10 J/T (4.6 Bohr magneton) (1) and closely resembling the ferrous (Fep2) compounds. Physical properties are Hsted in Table 1. Cobalt(II) fluoride is highly stable. No decomposition or hydrolysis has been observed in samples stored in plastic containers for over three years. 

Tables 10 and 11 list typical compositions of cast and wrought cobalt-base alloys, respectively. Stress—mpture properties of two wrought cobalt alloys, Haynes 188 and L-605, are compared to those of iron—nickel alloys ia Figure 10 (49). The cobalt alloys generally are inferior ia strength to the strongest cast nickel-base superaHoys. Tensile strengths at low and iatermediate temperatures are particularly deficient for the cobalt alloys.

Table 13 is a representative Hst of nickel and cobalt-base eutectics for which mechanical properties data are available. In most eutectics the matrix phase is ductile and the reinforcement is britde or semibritde, but this is not invariably so. The strongest of the aHoys Hsted in Table 13 exhibit ultimate tensile strengths of 1300—1550 MPa. Appreciable ductiHty can be attained in many fibrous eutectics even when the fibers themselves are quite britde. However, some lamellar eutectics, notably y/y —5, reveal Htde plastic deformation prior to fracture. 

Soft magnetic materials are characterized by high permeabiUty and low coercivity. There are sis principal groups of commercially important soft magnetic materials iron and low carbon steels, iron—siUcon alloys, iron—aluminum and iron—aluminum—silicon alloys, nickel—iron alloys, iron-cobalt alloys, and ferrites. In addition, iron-boron-based amorphous soft magnetic alloys are commercially available. Some have properties similar to the best grades of the permalloys whereas others exhibit core losses substantially below those of the oriented siUcon steels. Table 1 summarizes the properties of some of these materials. 

Chromium—Cobalt—Iron Alloys. In 1971, a family of ductile Cr—Co—Fe permanent-magnet alloys was developed (79). The Cr—Co—Fe alloys are analogous to the Alnicos in metallurgical stmcture and in permanent magnetic properties, but are cold formable at room temperature. Equivalent magnetic properties also can be attained with substantially less Co, thereby offering savings in materials cost. 

Vanadium—Cobalt-Iron Alloys. V—Co—Fe permanent-magnet alloys also are ductile. A common commercial ahoy, Vicahoy I, has a nominal composition 10 wt % V, 52 wt % Co, and 38 wt % Fe (Table 10). Hard magnetic properties are developed by quenching from 1200°C for conversion to bcc a-phase foUowed by aging at 600°C (precipitation of fee y-phase). The resulting properties are isotropic, with ca kJ/m ... 

Molybdenum, an unusually versatile alloying element, imparts numerous beneficial properties to irons and steels and to some alloy systems based on cobalt, nickel, or titanium. Comprehensive summaries of uses through 1948 (24) and 1980 (25) are available. 

In the other market areas, lead naphthenates are used on a limited basis in extreme pressure additives for lubricating oils and greases. Sodium and potassium naphthenates are used in emulsiftable oils, where they have the advantage over fatty acid soaps of having improved disinfectant properties. Catalyst uses include cobalt naphthenate as a cross-linking catalyst in adhesives (52) and manganese naphthenate as an oxidation catalyst (35). Metal naphthenates are also being used in the hydroconversion of heavy petroleum fractions (53,54) and bitumens (55). 

The second principal advantage is that CYANEX 272 is the only one of the three above-mentioned compounds that extracts cobalt in preference to calcium (52). This property can minimise or eliminate the solvent losses that are associated with calcium extraction and the subsequent precipitation of gypsum cmds in the scmbbing or stripping circuits. This is illustrated in Eigure 1 where calcium extraction is shown as a function of pH for the three subject reagents. 

Vitahium FHS ahoy is a cobalt—chromium—molybdenum ahoy having a high modulus of elasticity. This ahoy is also a preferred material. When combiaed with a properly designed stem, the properties of this ahoy provide protection for the cement mantle by decreasing proximal cement stress. This ahoy also exhibits high yields and tensile strength, is corrosion resistant, and biocompatible. Composites used ia orthopedics include carbon—carbon, carbon—epoxy, hydroxyapatite, ceramics, etc. 

The extraction of metal ions depends on the chelating ability of 8-hydroxyquinoline. Modification of the stmcture can improve its properties, eg, higher solubility in organic solvents (91). The extraction of nickel, cobalt, copper, and zinc from acid sulfates has been accompHshed using 8-hydroxyquinohne in an immiscible solvent (92). In the presence of oximes, halo-substituted 8-hydroxyquinolines have been used to recover copper and zinc from aqueous solutions (93). Dilute solutions of heavy metals such as mercury, ca dmium, copper, lead, and zinc can be purified using quinoline-8-carboxyhc acid adsorbed on various substrates (94). 

The electro deposition of tungsten aUoys of iron, nickel, and cobalt is commercially feasible but has remained largely experimental. The properties of these aUoys should, however, be of sufficient interest for engineering appHcations. 

Approximately 25—30% of a reactor s fuel is removed and replaced during plaimed refueling outages, which normally occur every 12 to 18 months. Spent fuel is highly radioactive because it contains by-products from nuclear fission created during reactor operation. A characteristic of these radioactive materials is that they gradually decay, losing their radioactive properties at a set rate. Each radioactive component has a different rate of decay known as its half-life, which is the time it takes for a material to lose half of its radioactivity. The radioactive components in spent nuclear fuel include cobalt-60 (5-yr half-Hfe), cesium-137 (30-yr half-Hfe), and plutonium-239 (24,400-yr half-Hfe). 

The properties of hydrated titanium dioxide as an ion-exchange (qv) medium have been widely studied (51—55). Separations include those of alkaH and alkaline-earth metals, zinc, copper, cobalt, cesium, strontium, and barium. The use of hydrated titanium dioxide to separate uranium from seawater and also for the treatment of radioactive wastes from nuclear-reactor installations has been proposed (56). 

A wide range of cutting-tool materials is available. Properties, performance capabilities, and cost vary widely (2,7). Various steels (see Steel) cast cobalt alloys (see Cobalt and cobalt alloys) cemented, cast, and coated carbides (qv) ceramics (qv), sintered polycrystalline cubic boron nitride (cBN) (see Boron compounds) and sintered polycrystalline diamond tbin diamond coatings on cemented carbides and ceramics and single-crystal natural diamond (see Carbon) are all used as tool materials. Most tool materials used in the 1990s were developed during the twentieth century. The tool materials of the 1990s... 

Cast-Cobalt Alloys. Cast-cobalt alloys were introduced about the same time as HSS for cutting tool appHcations. Popularly known as StelHte tools, these materials are Co-rich Cr—W—C cast alloys having properties and appHcations in the intermediate range between HSS and cemented carbides. 

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