What is hafnium caride?
Hafnium carbonide (HfC), is a chemical compound made of hafnium, carbon. It is one of most refractory binary substances known, with a melting temperature of 3900degC. Its oxidation resistance is low and it oxidizes at temperatures of 430°C. This compound could be part of future spacecraft’s heat shield.
Carbonization often lacks carbon so it is usually described as HfCx (x = 0,5 to 1,0). It has a cubic crystal structure (salt rock), of any x values.
Hafnium carbide can be made with hafnium oxide (HfO2) and carbon under an inert or reduced atmosphere. The reaction temperature is between 1900 and 2300 degrees Celsius. Hafnium carbonide can be combined with many compounds (such ZrC and TaC). ).
The hafnium IV oxide, which is formed by the reduction of hafnium caride powder with carbon, is at 18002000degC. It takes a long period to remove all oxygen. You can make a high purity HfC coating by using a mixture of methane, hydrogen, and vaporized chlorine chloride (IV). This process is called chemical vapor despatch. HfC’s technical complexity and high cost of synthesis mean that it is not widely used. However, HfC does have some advantages such as a high hardness (>9 Mohs), and melting point.
HfC x magnetism changes from diamagnetism to paramagnetism when x is larger than 0.8. TaCx, which has the same crystal structure of HfCx, exhibits the opposite behavior: para-paramagnetic transformation with increasing x.
What is hafnium carbide used for?
Hafnium carbonide is well-suited to rocket nozzles. It can be used in ceramics as well as for the nose cone on space rockets that enter the atmosphere.
What is the strength of hafnium carbide
W-based, Mo-based alloys containing hafnium carbide exhibit superior stress fracture properties than those containing HfC. MoHfC steel exhibits greater stress rupture and tensile strength than WHfC under pressures up to 1400K.
Hafnium carbid has a density 12.7g/cm3 with a melting point 3890degC. This is among the highest melting points of any single compound. The volume resistance is 1.95×10-4O*cm (2990), and the thermal expansion coefficient of 6.73×10-6/. Hafnium dioxide (HfO2), and carbon can be used to produce powder in an inert atmosphere or reducing environment. The reaction temperature for hafnium carbonide is 1900-2300. It can also form solid solutions with many compounds (such ZrC or TaC). It has a high melting points and high elastic coefficients, excellent electrical and thermal conductivity, and good impact performance.
Is hafnium carbide poisonous?
Trichlorooxidation was toxic via the intraperitoneal route in animal studies. There have been no reports of industrial poisoning. Carbide – Pure carbon is extremely toxic to humans. It can be safely consumed in the form graphite or charcoal and even safe ingested.
Why does hafnium caride have a high melting temperature?
Hafnium carbonide is highly resistant to corrosion, as it forms an oxide coating on the exposed surface. A report by Chemical World says that, of all the known three-element compounds with melting points of at least 7,457 degrees Fahrenheit (4.125 degrees Celsius), the mixture carbide of tungsten or hafnium has the highest.
Introduction to Hafnium: What is Hafnium anyway?
Hafnium is often found in nature alongside zirconium. Minerals containing zirconium also contain hafnium. The nature of hafnium, zirconium and hafnium are identical. Zirconium is the predominant source of hafnium. Industry uses between 0.5 and 2% HfO2 in zircon. Secondary zirconium oxide ore from beryllium zircon can have up to 15% HfO2. Metamorphic zircon made from stone can also contain more than 5% HfO2. These two minerals are rare and not commonly used in industry. Hafnium can be primarily recovered from the process of making zirconium.
The process of melting hafnium is similar to that of zirconium. It can be divided into five steps.
The first is to decompose the ore. There are three ways to decompose ore: 1. Zircon is chlorinated in order to obtain (Zr.Hf.Cl4). 2 Alkaline Fusion of Zircon, Zircon and NaOH Melt at 600. More then 90% of (Zr.Hf)O2 is transformed to Na2 (Zr.Hf)O3, and the SiO2 transforms into Na2 (Zr.Hf)O3. The water solution is used to remove the Na2SiO2. After being dissolved into HNO3, Na2 (Zr,Hf)O3 is the best solution to seperate zirconium and hafnium. It contains SiO2 collloid, making solvent extraction and separation challenging. After immersion in water, 3Sinter with SiF6 to obtain K2(Zr. Hf.F6) solution. The solution can be used to fractionally separate zirconium from hafnium.
The second step is to separate zirconium (and hafnium) using solvent extraction. These can be achieved with the HNO3–TBP system or the hydrochloric Acid-MIBK system (methyl isobutylketone). The multi-stage fractionation technology that utilizes the difference between the vapor pressures of HfCl4 & ZrCl4 melts in high pressure (above twenty atmospheres) has been extensively studied. It can eliminate secondary chlorination processes and lower costs. However, because of the corrosion problems of (Zr. Hf.Cl4 & HCl), it can be difficult to find the right fractionation column material. It will also reduce ZrCl4 & HfCl4 quality and increase purification cost.
The third step is to chlorinate HfO2 again to make crude HfCl4. The fourth step is purification of HfCl4 (and magnesium reduction). This process is identical to the purification and reduction ZrCl4, but the semi-finished product that is obtained is crude sponge haffnium. Vacuum distillation is the fifth step in the process of removing MgCl2 from crude sponge hafnium and recovering excess metal magnesium. The end product is sponge-metal hafnium. The fifth step will be water immersion if sodium is used as a reducing agent instead of magnesium.
You should take extra care to remove the hafnium sponges from the crucible in order to prevent spontaneous combustion. For large pieces of sponge hafnium to be used in consumable electrodes and ingots, they must be broken up into small pieces. It is also important to prevent spontaneous combustion when breaking. Further purification of sponge hafnium via the iodide heat decomposition process is possible. The control conditions for zirconium are slightly different. The sponge hafnium pieces around the iodination tube are kept at 600 degrees Celsius, while the hot wire in its center is at 1600 degrees Celsius. This temperature is higher than that of the 1300 degreeC when the zirconium crystal rod was made. . Forging, extrusion, drawing, and other steps are used to form hafnium. This is the same process as zirconium processing. The main function of hafnium lies in the production of control rods that can be used to power nuclear reactors.
Hafnium application
Pure hafnium can be easily processed, has high-temperature resistance, and resistance to corrosion. It is an important material for the atomic energy industry. Hafnium’s large thermal neutron capture area makes it an ideal neutron absorber. This can be used to control an atomic reactor and protect it from damage. Hafnium can also be used to propel a rocket. The electrical industry can manufacture the cathode to X-ray tube cathodes. The hafnium-based alloy can be used for the protection of rocket nozzles, gliding reentry aircraft and the HfTa alloy can be used for making tool steel and resistance materials. Hafnium is an additional element in heat resistant alloys like tungsten and molybdenum. Due to its high hardness/melting point, HFC is a good choice for cemented carbide additives. 4TaC*HfC’s melting point is approximately 4215degC. It is the highest-melting compound currently known.
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