Chromium thermal properties

Chromium carbide is important in powder preparations designed for thermal spray apphcations of corrosion and wear-resistant coatings on tool and machine parts. Lower carbon carbides of chromium are important in hardfacing tods and electrodes for weld-apphed ovedays on machine wear surfaces. However, these carbides are usually formed in situ from Cr and C in the rod and not added as preformed carbides. The properties of Ci2C2 are hsted in Table 2. 

Compare the properties of the trioxides of the chromium subgroup elements (their colour, thermal stability, oxidizing ability, and reaction with water). 

Chromium improves mechanical properties while retaining high thermal and electrical conductivities. 

Berg NO, Berlin M, Bohgard M, et al. 1987. Bronchocarcinogenic properties of welding and thermal spraying fumes containing chromium in the rat. Am J Ind Med 11 39-54. 

When 8-hydroxyquinoline and derivatives of bis(8-hydroxy-quinoline) react with metal ions, coordination complexes and polymers are formed, respectively, which exhibit improved thermal stability. This paper reviews the reaction of first-row transition metal ions with such ligands and their effect on the stabilization of these organic molecules. For the polymers containing divalent Mn, Co, Ni, Cu, or Zn the decomposition temperature is related to the periodic properties of the metal as well as the composition of the ligand to which the metal is coordinated. Trivalent chromium produces a crosslinked polymer when it reacts with bis(8-hydroxy-5-quinolyl)methane, and the thermogram for this polymer is also reported. 

Pentacarbonyl(methoxymethylcarbene)tungsten(0) is a dull-yellow, crystalline solid mp 52°. It is appreciably more stable thermally and oxidatively than its chromium analog in the solid state at room temperature and may be stored at 5° for a period of 1 or 2 weeks without significant decomposition. It is soluble in aliphatic hydrocarbons such as n-pentane, n-hexane, n-heptane, and other common laboratory solvents such as benzene, 1,4-dioxane, tetrahydrofuran, chloroform, dichloromethane, and methanol it is slightly soluble in ethanol. The infrared spectrum (cyclohexane solution) has v(CO) bands at 2075, 1980, 1960, and 1947 cm"1. The nmr spectrum in chloroform-d has the methoxy proton resonance at t6.17 and the methyl proton resonance at t7.69. Other physical properties are reported in the literature.6,7... 

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