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. It has a melting point of 3900degC, making it one of most refractory binary compound known. 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 1900-2300degC. 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 gas mix of methane (methane), hydrogen and vaporized chlorine chloride IV. HfC’s limited use is due to its technical complexity and high synthesis costs, despite its advantageous properties, including high hardness and melting point (>9 Mohs).
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- and Mo-based alloys dispersed with hafnium carburide exhibit superior tensile strength and stress rupture properties than alloys without HfC. MoHfC is stronger than WHfC at 1400K pressure, based on density compensation.
Hafnium carbide has a density 12.7g/cm3, and the melting point is 3890degC. It’s the highest melting point known for a single compound. Volume resistivity of hafnium carbide is 1.95×10-4O*cm (2990) and thermal expansion coefficient 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 of 1900-2300°C and form a solid with many compounds. 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 even eaten.
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. 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).

Introduction to Hafnium: What is Hafnium exactly?
In nature, zirconium coexists with hafnium. Zirconium-containing mineral hafnium. 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% of HfO2 is also available. Both minerals have very small reserves, and they have never been used by the industry. Hafnium primarily is recovered during the production of zirconium.

The hafnium melting process is basically the zirconium melting process, divided into 5 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, while the siO2 turns to Na2SiO3, before being 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. 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 using a difference in the vapor pressure between HfCl4 (ZrCl4) and ZrCl4 melts at high pressures above 20 atmospheres has been studied for a long time. This technology can eliminate the second chlorination and reduce costs. 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.

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 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 a hot 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
Pure hafnium exhibits plasticity, is easy to process, has high temperature resistance and corrosion resistance. It is an important element in the nuclear energy industry. Hafnium, with its large thermal neutron section, is an ideal neutron absorption device that can be used for a control rod or protection device in an atomic power reactor. 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. Due to its melting point and high hardness, it can be used in cemented carbide. The melting temperature of 4TaC*HfC has been measured at 4215degC. This is the highest melting temperature compound.

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