Tape, strip hafnium GFI-1
Feature sheet, tape from hafnium
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 sheets 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 lifetime of such sheets is much higher such. They are durable, reliable and demand in the most challenging conditions in modern production.
The finished sheet of hafnium must be clean, smooth, without impurities, cracks. The leaves are allowed bumps that don’t come 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.
The parameters of the leaves vary widely in thickness — from 5 mm, width — of 500−800 mm and a length of about 500−2000 mm. the deviation in length up to 20 mm in large sizes. The leaves can be random and measured length, which is non-multiple and multiple of 100. To obtain the necessary quality, hafnium legarrette special additives (silicon, boron) or an addition of tungsten, tantalum, cobalt. This sheet is used for very heat resistant and critical details in rocket technology and nuclear energy.
Durable, heat-resistant sheets are demanded in chemical industry, mechanical engineering and nuclear engineering. In electrical engineering and instrumentation from the hafnium tape is made of anodes and cathodes for electro-vacuum equipment. 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. Manufacture of various electric heaters and elements of the thermocouples of the hafnium strip, a thickness of 5−20 µm, possibly due to high resistance.
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