Hafnium can form alloys with other metals, the most representative of which is hafnium tantalum alloy, such as pentacarbide tetratantalum and hafnium (Ta4HfC5), which has a high melting point. The melting point of pentacarbide tetratantalum and hafnium can reach 4215 ℃, making it the currently known substance with the highest melting point.
Hafnium, with the chemical symbol Hf, is a metallic element that belongs to the transition metal category. Its elemental appearance is silver gray and has a metallic luster. It has a Mohs hardness of 5.5, a melting point of 2233 ℃, and is plastic. Hafnium can form an oxide coating in the air, and its properties are stable at room temperature. Powdered hafnium can spontaneously ignite in the air, and can react with oxygen and nitrogen at high temperatures. Hafnium does not react with water, dilute acids such as hydrochloric acid, sulfuric acid, and strong alkaline solutions. It is soluble in strong acids such as aqua regia and hydrofluoric acid, and has excellent corrosion resistance.
The element hafnium was discovered in 1923. Hafnium has a low content in the Earth’s crust, only 0.00045%. It is generally associated with metallic zirconium and has no separate ores. Hafnium can be found in most zirconium mines, such as beryllium zircon, zircon, and other minerals. The first two types of ores have a high content of hafnium but low reserves, and zircon is the main source of hafnium. On a global scale, the total reserves of hafnium resources are over 1 million tons. Countries with larger reserves mainly include South Africa, Australia, the United States, Brazil, India, and other regions. Hafnium mines are also distributed in Guangxi and other regions of China.
In 1925, two scientists from Sweden and the Netherlands discovered the element hafnium and prepared metal hafnium using the fluorinated complex salt fractional crystallization method and the metal sodium reduction method. Hafnium has two crystal structures and exhibits hexagonal dense packing at temperatures below 1300 ℃（ α- When the temperature is above 1300 ℃, it presents as a body centered cubic shape（ β- Equation). Hafnium also has six stable isotopes, namely hafnium 174, hafnium 176, hafnium 177, hafnium 178, hafnium 179, and hafnium 180. On a global scale, the United States and France are the main producers of metal hafnium.
The main compounds of hafnium include hafnium dioxide (HfO2), hafnium tetrachloride (HfCl4), and hafnium hydroxide (H4HfO4). Hafnium dioxide and hafnium tetrachloride can be used to produce metal hafnium, hafnium dioxide can also be used to prepare hafnium alloys, and hafnium hydroxide can be used to prepare various hafnium compounds. Hafnium can form alloys with other metals, the most representative of which is hafnium tantalum alloy, such as pentacarbide tetratantalum and hafnium (Ta4HfC5), which has a high melting point. The melting point of pentacarbide tetratantalum and hafnium can reach 4215 ℃, making it the currently known substance with the highest melting point.
According to the “2022-2026 Deep Market Research and Investment Strategy Suggestions Report on the Metal Hafnium Industry” released by the Xinsijie Industry Research Center, metal hafnium can be used to manufacture incandescent lamp filaments, X-ray tube cathodes, and processor gate dielectrics; Hafnium tungsten alloy and hafnium molybdenum alloy can be used to manufacture high-voltage discharge tube electrodes, while hafnium tantalum alloy can be used to manufacture resistance materials and tool steels; Carbide carbide (HfC) can be used for rocket nozzles and aircraft forward protective layers, while hafnium boride (HfB2) can be used as a high-temperature alloy; In addition, metal hafnium has a large neutron absorption cross-section and can also be used as a control material and protective device for atomic reactors.
Industry analysts from Xinsijie stated that due to its advantages of oxidation resistance, corrosion resistance, high temperature resistance, and ease of processing, hafnium has a wide range of downstream applications in metals, alloys, compounds, and other fields, such as electronic materials, high-temperature resistant materials, hard alloy materials, and atomic energy materials. With the rapid development of industries such as new materials, electronic information, and aerospace, the application fields of hafnium are constantly expanding, and new products are constantly emerging. The future development prospects are promising.