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What is Hafnium Carbide? Hafnium carburide (HfC), a chemical compound composed of hafnium, is a combination of carbon and hafnium. Its melting temperature is approximately 3900degC. The oxidation resistance of this compound is extremely low. At 430degC, oxidation begins. This compound might be used in the heat shield of future spacecraft.
Carbonizations are usually devoid of carbon. Therefore, their composition is typically expressed as HfCx (x = 0,5 to 1,0). The crystal structure is cubic (salt).
Hafnium carburide is normally synthesized in a reducing or inert atmosphere with hafnium (HfO2) dioxide and carbon. The reaction is carried out at a temperature between 1900-2300degC. Hafnium carburide can form solid solutions with many compounds such as ZrC or TaC. ).
The hafnium oxide (IV) obtained by reducing powdered hafnium with carbon is between 1800 and 2000degC. To remove all the oxygen, it takes a lot of time. Chemical vapor deposition can be used to obtain a coating of high purity HfC from a mixture containing methane, hydrogen and vaporized chlorine chloride (IV). HfC’s limited use is due to its technical complexity and high cost.
HfC-x undergoes a change from paramagnetism to diamagnetism when x is increased. TaC has the same structure as HfC but exhibits the opposite behavior.

What is hafnium carbide used for?
Hafnium carbide is an excellent material for rockets. It can also be used for ceramics, other industries and as the nose of space rockets which re-enter our atmosphere.

How powerful is hafnium carbide?
W-based or Mo-based alloys that are dispersed with Hafnium Carbide exhibit superior tensile strength and stress rupture properties than those without the HfC. MoHfC is stronger than WHfC at 1400K pressure, based on density compensation.
Hafnium carbide has a density 12.7g/cm3 as well as a melting temp of 3890degC. It is the most melting point known among single compounds. Volume resistivity of hafnium carbide is 1.95×10-4O*cm (2990) and the thermal expansion coefficient is 6.73×10-6/. In general, hafnium (HfO2) is combined with carbon to create powders in a reducing or inert environment. The reaction temperature for hafnium carburide is between 1900-2300°C. It can form solid solution with a variety of compounds (such ZrC, TaC etc.). It is characterized by a high melting temperature and high elastic co-efficient, as well as good electrical and thermal conductivity.

Is hafnium carbide poisonous?
In studies on animals, the intraperitoneal routes of trichlorooxidation were toxic. No industrial poisoning has been reported. Carbide : Pure carbon is very low in toxicity for humans. It may be processed into graphite and charcoal, or it can even be safely ingested.
Why does hafnium carburide have a melting point so high?
Hafnium carburide is resistant to corrosion as it forms an oxide layer on the surface. A report in “Chemical World”, states that among the three element compounds, the mixed carbide tungsten-hafnium compound has the highest melting points of any known compound, at 7,457° Fahrenheit (4125° Celsius).

What is Hafnium and what does it do?
Hafnium can be found in zirconium-containing mineral zirconium. Hafnium shares many similarities with zirconium in nature. The amount of HfO2 found in zircon for industrial use is between 0.5-2 %. Beryllium zircon found in secondary zirconium can contain up to 15 percent HfO2. A metamorphic stone containing more than 5% HfO2 is also used to produce zircon. Both minerals are small and have never been used by the industry. Hafnium is recovered mostly in the production of zirconium.

The hafnium melting process is essentially the same as zirconium’s, with five general steps.
First, the ore is decomposed. The first method is to chlorinate zircon in order to get (Zr Hf)Cl4. At 600, the zircon melts with zircon and NaOH. At this temperature, over 90% of the (Zr & Hf O2) is transformed into Na2 & Hf O3, while SiO2 turns to Na2SiO3, a compound that is then removed by water. After dissolving in HNO3, the Na2 (Zr,Hf)O3 solution can be used to separate zirconium from hafnium. The colloid SiO2 makes extraction with solvents and separation difficult. 3Sinter the K2SiF6 and obtain K2(Zr, Hf )F6 after water immersion. The solution is able to separate zirconium from hafnium through fractional crystallization.

Separation of hafnium from zirconium is done by using solvent extraction, with a hydrochloric system (MIBK – methyl isobutylketone) and HNO3 – TBP (tributylphosphate). Multi-stage fractionation has been used for many years to reduce costs by eliminating the secondary chlorination. Due to corrosion problems with (Zr, HF)Cl4 or HCl it is hard to find fractionation columns that are suitable. They will also lower the quality of ZrCl4 or HfCl4 as well as increase purification costs.

The fourth step is purification of HfCl4 and magnesium reduction. The fourth stage is the purification of HfCl4 followed by magnesium reduction. This is the same process as purification and reduction ZrCl4 and the semi-finished product obtained is crude sponge Hafnium. The fifth step involves vacuum distillation to remove MgCl2 as well as recover the excess metal magnesium. The finished product will be sponge metal hafnium. If the reducing agents are sodium or magnesium instead, the fifth step will be water immersion.

To avoid spontaneous combustion, take extra care to remove the hafnium crucible sponge. The sponge hafnium pieces need to be broken up into small pieces. These pieces will be used as electrodes for consumables. It is also important to avoid spontaneous combustion when breaking the sponge hafnium. The iodide decomposition technique is used to purify sponge hafnium in the same manner as zirconium and titanium. The control conditions differ slightly from zirconium. The temperature of the sponge hafnium in the iodination chamber is 600degC. Meanwhile, the temperature of the wire in the center of the tank is 1600degC. . Hafnium is processed and formed by forging and extrusion. The primary purpose of hafnium in the production of control rods for reactors is to be used as a nuclear fuel.
Hafnium application
Pure hafnium exhibits plasticity, is easy to process, has high temperature resistance, and resists corrosion. It is a key material for the atomic energy sector. Hafnium, with its large thermal neutron section, is a perfect neutron absorption device that can be used for an atomic power reactor as a control rod or protection device. Hafnium is used in rocket propellers. In the electrical industry, cathodes for X ray tubes can also be produced. The alloy hafnium is used in the manufacture of tool steel, resistance materials and rocket nozzles. Hafnium adds heat-resistant properties to alloys like tungsten and molybdenum. HFC’s high melting and hardness make it a suitable cemented carbide. The melting temperature of 4TaC*HfC measures 4215degC. This is the highest melting temperature compound.

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