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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. The heat shield of future spacecraft may include this compound.
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), which is obtained by reducing powdered hafnium with carbon, has a temperature of 18002000degC. 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.
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 that do not contain 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 between 1900 and 2300°C. It forms a solid with many compounds, such as ZrC or TaC. It is characterized by a high melting temperature and high elastic co-efficient, as well as good electrical and thermo conductivity, low thermal expansion, and a good impact performance.
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 used as graphite and charcoal, or it can be ingested.
Why is the melting point of hafnium carbide high?
Hafnium carburide is resistant to corrosion as it forms an oxide layer on its 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?
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 mainly comes from the production of zirconium.
Hafnium smelting follows a similar process to that of zirconium and is generally 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. About 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 hafnium from zirconium through fractional crystallization.
Separation of hafnium from zirconium is done by using the HNO3 and TBP (tributylphosphate) systems. Multi-stage fractionation using vapor pressure differences of HfCl4 or ZrCl4 melts at high pressure (above twenty atmospheres) is a technology that has been studied for a long time. This 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, resulting in crude sponge 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 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 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 in 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 a key material for the atomic energy sector. 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 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, the highest melting point compound ever known, is 4215degC.
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