Physical and chemical properties of Nickel
Nickel — malleable and ductile metal available rolled in a thin foil. The limit of the tensile strength of 40−50 kgf/mm2, the elastic limit of 8 kgf/mm2, yield 12 kgf/mm2; Rel. the elongation of 40%; normal elasticity modulus of 205 GN/m2; Brinell hardness number of 600−800 Mn/m2. From absolute zero to 631°K Nickel is ferromagnetic. The ferromagnetism of Nickel due to the structural features of the outer electron shells. For the same reason, alloys and a number of derivatives of Nickel (oxides, and compounds with the Halogens.) with magnetically ordered ferro-, rarely ferrimagnetic structure. Under normal conditions, Nickel has a β-structure with face-centered cubic lattice (a = 3,5236. But after cathode sputtering in an atmosphere of H2, Nickel acquires α-structure with a dense hexagonal lattice (a = 2,65 [pic], C = 4,32 [pic]), which at t°>200 °C goes into cubic. A Nickel with a cubic lattice specific weight 8.9 g/cm3 (at 20°C), it melts at 1453 °C and boils at ~3000°C; specific heat capacity at 20 °C 0,44 Kj/(kg-K); t°the coefficient of linear expansion of 13.3x10-6 (0−100°C); conductivity at 25 °C 90,1 вмl (m-K)[0,215 cal/(cm-sec-oC)].
The chemical activity of Nickel is between noble metals and iron. In the compounds of Nickel is most often divalent. Powder absorbs N2, CO; but saturated with gases, Nickel loses its mechanical advantages. Oxygen Nickel comes into contact at 500 °C. the Fine powder of Nickel is pyrophoric — ignites spontaneously in air. Nitrous NiO — greenish crystals, insoluble in water (mineral bunsenite). Hot Nickel with Halogens forms a NiX2. Burning in sulfur vapor, forms sulfide Ni3 S2. Monosulfide Nickel NiS obtained by heating NiO with sulfur. Nitrogen does not interact with this metal up to 1400 °C. Nitride of Ni3 N is formed when flowing NH3 over NiF2, NiBr2, or heating the powder of Nickel with nitrogen at 445 °C. the hot vapor of phosphorus is formed, the phosphide Ni3 P2. With arsenic connection Ni5 As2, Ni3 As (mineral maucherite) and NiAs. In the lattice of Nickel arsenide — type hexagonal arrangement of the atoms of arsenic, which is squeezed between the Nickel atoms. This structure is typical for many intermetallic compounds. Unstable carbide Ni3 C is formed after a long (hundreds of hours) carburizing (cementation) of Nickel powder in a CO atmosphere at 300 °C. Molten Nickel easily dissolves carbon, which when cooled is released in the form of graphite. With the loss of graphite is reduced ductility of Nickel.
Nickel is less chemically active than iron, more resistant to the action of acids and moisture. With organic acids react only after prolonged exposure. In hydrochloric and sulphuric acids, and dissolves slowly in dilute nitric — easily, and concentrated nitric acid passivate Nickel, although to a lesser extent than Fe. Acid salt of Nickel is bivalent. Almost all of them are water soluble, which give an acidic reaction. Only poorly soluble salts of carbonic and phosphoric acids. Sulfate NiSO4 kristallizuetsya in the form of emerald-green crystals of Nickel sulfate NiSO4 x7H2 O. During the calcination up to 800 °C, nearly all the salts of Nickel are decomposed. This metal is resistant to strong alkalis, but dissolves in ammonia solution in the presence of (NH4)2 CO3 with the formation of intensely blue solutions. The property of selective formation of Aminatou used in the hydrometallurgical method for Nickel from ores.
When heated, Nickel reacts with SO2, NH4 and NOx, as well as in the form of finely ground powder of CO with the formation of carbonyl Ni (CO)4. Thermal dissociation of carbonyl getting the pure Nickel.
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