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


Aug 17, 2023

If you are looking for high-quality products, please feel free to contact us and send an inquiry, email:

What is Hafnium Carbide? Hafnium carburide (HfC), a chemical compound composed of hafnium, is a combination of carbon and hafnium. It is 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 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), which is obtained by reducing powdered hafnium with carbon, has a temperature of 1800-2000degC. 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 gas mix of methane (methane), hydrogen and vaporized chlorine chloride IV. HfC’s limited use is due to its high cost and technical complexity.
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 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. The reaction temperature for hafnium carburide is between 1900 and 2300°C. It can form a solution solid with many compounds, such as ZrC or 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 processed into graphite and charcoal, or it can even be safely consumed.
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 carbide mixed of tungsten hafnium, has the highest melting points of all three-element compound, 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. HfO2 content in zircon 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 is recovered mostly in the production of zirconium.

The hafnium melting process is almost identical 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. The (Zr Hf O2) is transformed to Na2 (Zr Hf O3) and the siO2 into Na2SiO3, 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. 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 is a technology that uses the difference in the vapor pressure between HfCl4 (ZrCl4) and ZrCl4 (HfCl4) melts at high pressures. This can eliminate secondary 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 products is crude 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 sodium instead of magnesium is used as a reducing agent, then 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. The iodide decomposition technique is used to purify sponge hafnium in the same way 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. Hafnium is primarily used to produce control rods for reactors.
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 a perfect neutron absorption device that can be used for control rods and protection devices in atomic reactors. 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 point compound ever known, is 4215degC.

(aka. Technology Co. Ltd., a global chemical materials supplier and manufacturer with more than 12 years of experience in providing high-quality Nanomaterials and chemicals. Currently, we have successfully developed a number of materials. Our Hafnium Carbide (HfC), powder is of high purity and has a low impurity level. Contact us if you need to.