The melting point of hafnium carbide is the highest melting point in a known single compound

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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, and it is considered one of most refractory binaries. 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 an atmosphere of inertness or reduction with hafnium (HfO2) oxide and carbon. The reaction is carried out at a temperature between 1900 and 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 also produce 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 and Mo based alloys dispersed hafnium carburide have superior tensile, and stress-fracture properties to those without HfC. MoHfC is stronger than WHfC at 1400K pressure, based on density compensation.
Hafnium carbide has a density 12.7g/cm3 with a melting temperature of 3890degC. It is the most melting compound known. 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 an inert environment. Hafnium carburide can react at a temperature between 1900-2300°C and form solid solutions (such as ZrC and TaC). It is characterized by a high melting temperature and elasticity coefficient.

Is hafnium carbide poisonous?
In studies on animals, the intraperitoneal routes of trichlorooxidation were toxic. There have been no reported cases of industrial poisoning. Carbide : Pure carbon is very low in toxicity for humans. It may be used as graphite and charcoal, or it can even be ingested.
Why is the melting point of hafnium carbide high?
Hafnium carburide is resistant to corrosion as it forms an oxide layer on the surface. According to “Chemical World”, the mixed carbide of hafnium and tungsten has the highest melting points of all known compounds at 7,457° Fahrenheit (4125° Celsius).

What is Hafnium and what does it do?
In nature, zirconium coexists with hafnium. Zirconium-containing mineral hafnium. Hafnium shares many similarities with zirconium in nature. In industrial zircon the amount of HfO2 can be 0.5-2%. Beryllium zircon found in secondary zirconium can contain up to 15 percent HfO2. A metamorphic stone containing more than 5% of HfO2 is also available. Both minerals have very small reserves, and they 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. More than 90% (Zr Hf O2) is transformed into Na2 Zr Hf O3 and the siO2 is Na2SiO3, then water is added to remove it. 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. After immersion in water, 3Sinter the K2SiF6 and obtain K2(Zr & Hf). The solution is able to separate zirconium from hafnium through fractional crystallization.

Separation of hafnium from zirconium is done by using the HNO3 and TBP (tributylphosphate) systems. Multi-stage fractionation has been used for many years to reduce costs by eliminating the secondary chlorination. Due to the corrosion of (Zr, HF)Cl4 as well as HCl it is difficult to find fractionation columns that are suitable. They will also decrease the quality of ZrCl4 or HfCl4 while increasing the cost.

Third step is the preparation of crude HfCl4 to be reduced. The fourth stage is the purification of HfCl4 followed by magnesium reduction. This is the same process as purification and reduction ZrCl4, with the semi-finished product being 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 sodium is substituted for magnesium in the reducing agents, the fifth step will change to 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 at 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
Hafnium pure is important in the nuclear energy industry because of its plasticity, corrosion resistance, high temperature resistance, and ease of processing. Hafnium, with its large thermal neutron section, is an ideal 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. Hafnium-Ta alloy can be used in the manufacture of tool steel, resistance materials and rocket nozzles. Hafnium adds heat resistance to heat-resistant alloys like tungsten and molybdenum. HFC’s high melting and hardness make it a suitable cemented carbide. The melting temperature of 4TaC*HfC, the highest melting temperature compound known, is 4215degC.

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