The hafnium wire GFI-1
Hafnium metal is extracted from zirconium ores. It has high ductility in pure form and can roll out into a thin wire, a thickness of a few microns. The cost of 99% purity hafnium is about 780 dollars for 1 kg of Hafnium (Hf) is a severe refractory silvery-white metal of the periodic system, at number 72. Hafnium has a densely Packed hexagonal structure of the crystal lattice with relative density for 13, 31 g/cm3. A valence of +4, the boiling point of HF is 5400 °C, the melting point is 2150 °C. the capture cross Section for thermal neutrons is about 100 barns, which is three orders of magnitude greater than zirconium — 0.2 barns, and therefore, zirconium is used in nuclear reactors must not contain hafnium. Natural 174Hf isotope has a weak α — activity with a half-life equal to 2x101015 years.
Hafnium wire and the circle have high strength, refractoriness and resistance to corrosion. Their melting point is 2150 °C. At normal temperatures in air, hafnium capable of forming a protective oxide film. Hafnium compared to zirconium, not so resistant to alkalis and acids, it dissolves in concentrated hydrofluoric and sulfuric acid, but it is more stable in water superheated steam, air and molten alkali metals. Adding it to the Nickel improves corrosion resistance and strength, improve the strength of welds and the weldability. The service life of these products is much higher such. The circle and the wire is durable, reliable and demand in the most challenging conditions in modern production. Hafnium circle is produced by way of powder metallurgy at the end of the recovery of hafnium metal and treatment with electron beam, plasma melting or vacuum arc. The circle is a prefabricated cylindrical shape, further rolled to a very thin wire.
The finished circle of hafnium must be clean, smooth, without impurities, cracks. It allowed irregularities that do not appear in size beyond the boundaries of permissible variations in dimensions according to GOST. Possible small risks, defects, changes the colors that are defined in the standard. The color change depends on the conditions and terms of storage of material.
To obtain the necessary quality, hafnium legarrette special additives (silicon, boron) or an addition of tungsten, tantalum, cobalt. This metal is used for very heat resistant and critical details in rocket technology and nuclear energy.
The main drawback is the high cost of production. Hafnium belongs to the group of rare metals, the weight it is quite heavy and is for 13, 31 g/cm3, very refractory.
The use of wire and circle
Hafnium wire is used in various fields. Television technologies and electronics of the hafnium wire is made the cathode, the grid of the microwave generators, and vacuum tubes. This wire is often used as a high wire, in the manufacture of thermocouples for temperature compensation. Smaller than that of molybdenum, niobium, tungsten low electron work function (of 3.53 eV) and heat resistance make it possible to use hafnium in the electronic devices and in the manufacture of cathodes for electron beam guns. It is made from welding electrodes to metals in argon and cathodes for welding in carbonic gas low-carbon steel. The resistance of electrodes of this type in the atmosphere of CO2 is almost four times more than tungsten. Electrodes for the production of oxygen-plasma and air-plasma cutting of metals used in the alloy of hafnium-tantalum 4:1, whose resource exploitation in comparison with pure hafnium is much higher. Hafnium wire is indispensable in electroplating. It is used to make electrodes for EDM machines, which produces a controlled decomposition of compounds by using galvanic current. This wire is an important part of the mechanisms that operate in a vacuum its constant clients are the physical research laboratory, institutes. The wire is used as a hafnium sputtering under vacuum conditions, which protects against corrosion.
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