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 composed of carbon. 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 and 2300 degrees Celsius. 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 of methane and hydrogen with vaporized chlorinated chlorine (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.

What is the strength 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. The thermal expansion coefficient of 6.73×10-6/ is equal to 1.95×10-4O*cm. In general, hafnium (HfO2) is combined with carbon to create powders in a reducing or inert environment. Hafnium carburide can react at a temperature between 1900 and 2300°C. It forms a solid with many compounds such as ZrC and TaC. It is characterized by a high melting temperature and elasticity coefficient.

Is hafnium carbide poisonous?
During animal studies, the intraperitoneal routes of trichlorooxidation were found to be toxic. There have been no reported cases of industrial poisoning. Carbide : Pure carbon is very low in toxicity for humans. It may be processed into graphite and charcoal, or it can even be safely consumed.
Why is the melting point of hafnium carbide high?
Hafnium carburide is resistant to corrosion as it forms a thin oxide film over 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?
Hafnium can be found in zirconium-containing mineral zirconium. 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% HfO2 is also used to produce zircon. 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 similar to that of zirconium and can be divided into 5 steps.
First, the ore is decomposed. The first method is to chlorinate zircon in order for (Zr Hf)Cl4. At 600, the zircon melts with zircon and NaOH. At this temperature, over 90% of (Zr Hf O2) is transformed into Na2 Zr Hf O3, while SiO2 turns to Na2SiO3, after which it is removed using water solution. 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 the difference in the vapor pressure between HfCl4 (ZrCl4) and ZrCl4 (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 (ZrHf)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.

Third step: Prepare crude HfCl4 to be reduced by a second chlorination. The fourth stage is the purification of HfCl4 followed by magnesium reduction. This is the same process as purification and reduction ZrCl4 with the resultant semi-finished hafnium. The fifth step involves vacuum distillation to remove MgCl2 as well as recover the excess metal magnesium. The final 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 smaller pieces. These pieces will be used as electrodes for consumables. It is also important to avoid spontaneous combustion when breaking the sponge hafnium. By the iodide decomposition process, the sponge hafnium purification is similar to that of titanium and zirconium. 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
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 a perfect 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-based alloys are 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 point compound ever known, is 4215degC.

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