Cubic Zirconia European
Zirconium is a silvery-grey lustrous metal with a yellowish tinge, an element of side groups chem. system with atomic number 40, and denoted by the symbol Zr. Zirconium is ductile and resistant to corrosion. The name zircon probably originated from the Arabic — cinnabar (zarkûn) or Persian Golden color (zargun).
Properties of zirconium
From α-zirconium specific gravity is 6.5 g/cm3; temperature at 25−100°C specific heat equal to 0,291 kJ/(kg•K), melting point is 1855 °C; boiling point equal 4409 °C; coefficient of linear thermal expansion at a temperature of 20−400°C is 6. 9x10-6; coefficient of thermal conductivity at 50 °C is equal to 20, and 96 W/(m•K); resistivity of zirconium at a temperature of 20 °C is 0.44 micro-Ohm • mm2/m.
Physical qualities Zr | |
---|---|
Atomic (molar) mass, g/mol | 91,224 |
The degree of oxidation | 4, 3, 2, 1, 0 |
Density [g/cm3] | 6,5 |
The melting temperature t°C | 1855°C |
The heat of fusion kJ/mol | 19,2 |
The thermal conductivity K [W/(m·K)] | 22,7 |
Heat of evaporation kJ/mol | 567 |
Zirconium at a temperature of 0.7°K becomes a superconductor. It is a paramagnetic metal and a specific magnetic susceptibility increases with heat and achieves a temperature of 73 °C — 1,28x10-6, and at 327 °C — 1,41x10-6. Pure Zirconia lends itself easily to cold and hot working (rolling, forging, stamping). The impurity of oxygen, nitrogen, hydrogen, carbon, sulfur makes Zirconia very fragile. At 20 °C modulus of elasticity equal to 9700 kgf/mm2; tensile strength is 25.3 kgf/mm2; Brinell hardness equal 64−67 kgf/mm2; also the hardness is directly dependent on the admixture of oxygen. This metal not be cold pressure treatment in O2 — 0,2% or more. The only plant for the production of Zirconia in the country is Chepetsk mechanical plant (Udmurtia, Glazov).
Application. Metallurgy
Zirconia is a good deoxidizer and diazotation, it is more effective than manganese, silicon, titanium. When the doping with zirconium to 0.8% mechanical properties, the machinability of steel is improved and the copper adds even greater strength and heat resistance with low loss of electrical conductivity.
Nuclear power
Zirconia has a high melting point and narrow is the capture cross section in thermal neutrons. This metal and its alloys (without mixture of hafnium) is therefore used in the manufacture of fuel assemblies — fuel systems and casings for nuclear reactors.
Superconductor
The alloy of zirconium is 25% and niobium up to 75% (at 4.2° K becomes a superconductor) and can withstand up to 100 thousand A/cm2 load.
Pyrotechnics
Zirconia is able at a temperature of 250 °C to spontaneously ignite in air and burn with virtually no smoke with high speed. At this point the temperature reached 4650 °C — the highest possible for the metal fuel, emitting a bright light, used in fireworks, fireworks, the manufacture of flares, torches, flare, patavium (FOTAB). Zirconium alloys with cerium to create a large luminous flux. Zirconium powder mixed with potassium chlorate salt is a smokeless facility at the fuses and signal lights, replacing the lead azide and mercury fulminate .
Construction material
Zirconium is used to make acid-chemical reactors, pumps, valves, replaced the noble metals. Zirconium in the nuclear energy sector is the main material of membranes for fuel elements. «Obezzhelezivaniya» zirconium is used as a refractory for lining glass furnaces and metallurgical furnaces and in the production of building ceramics, glazes, enamels for sanitary ware.
Life and medicine
Zirconium is biologically inert material, more resistant to biological environments, in contrast to titanium, due to what is used in the production of joint, dental and bone prostheses, and surgical instruments. The zirconium chemical inertness makes it possible to produce exclusive dishes with great hygienic properties.
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