The World’s Top 10 High Melting Point Materials

6. Titanium Boride

Titanium boride powder is gray or gray-black in color and has a hexagonal (AlB2) crystal structure. It has a high melting point of 2980 ℃ and is very hard. Titanium diboride is highly resistant to oxidation at temperatures up to 1000 ℃ in air and is stable in HCl and HF acids. It is mainly used to prepare composite ceramic products. It is often used to manufacture molten metal crucibles and electrolytic cell electrodes due to its resistance to molten metal corrosion.

Titanium boride (TiB2) is the most stable compound of titanium and boron, with a C32 type structure that combines in its valence bond form. It belongs to the quasi-metallic compound of the hexagonal crystal system. The complete crystal structure has a = 0.3028 nm and c = 0.3228 nm. The crystal structure’s boron and titanium atomic planes alternate to form a two-dimensional network structure, where B is covalently bonded with the other three B atoms, and the excess electron forms a large π bond. The layered structure of boron atoms is similar to graphite, and the outer electrons of Ti make TiB2 highly conductive and give it a metallic luster. Meanwhile, the Ti-B bond between the boron and titanium atomic surfaces is responsible for this material’s high hardness and brittleness.

7. Rhenium

Rhenium is a rare chemical element (symbol: Re, atomic number: 75) that belongs to the transition metal of the sixth cycle in the periodic table. It is a heavy metal with a silver-white color known to have one of the highest melting and boiling points of all elements. The average rhenium content in the Earth’s crust is estimated to be one billionth, making it one of the rarest elements.

Rhenium is obtained as a byproduct of the molybdenum and copper extraction process. Its chemical properties are similar to technetium and manganese, and it can have oxidation states ranging from -3 to +7 in compounds.

Rhenium, which was discovered in 1925, is the last known stable element. It was named after the Rhine River in Europe.

One of the most significant practical applications of rhenium is in nickel rhenium high-temperature alloys, which manufacture combustion chambers, turbine blades, and exhaust nozzles for jet engines. These alloys contain up to 6% rhenium. Another major use of rhenium is as a catalyst in the chemical industry.

Due to its rarity and difficulty obtaining, rhenium is more expensive than diamonds. As of 2021, the world has only 2650 tons of proven reserves, according to survey data from the United States.

Rhenium is crucial in military strategy as it can be applied to high-efficiency jet and rocket engines.

8. Titanium Carbide

Titanium carbide (TiC) is a gray, cubic crystal system with a melting point 3140℃. It is insoluble in water and has high chemical stability, so it hardly reacts with hydrochloric and sulfuric acid. However, it can dissolve in aqua regia, nitric acid, hydrofluoric acid, and alkaline oxide solutions.

TiC has an iron-gray metallic luster and belongs to the NaCl type simple cubic structure. The lattice constant is 0.4329 nm, and the spatial group is Fm3m. Carbon atoms and titanium atoms are equivalent at the lattice position. TiC atoms combine with strong covalent bonds and have characteristics similar to metals, such as high melting point, boiling point, and hardness, which are second only to diamonds. It also has good thermal conductivity and exhibits superconductivity at extremely low temperatures. 

Titanium carbide (TiC) is commonly used to produce metal ceramics, heat-resistant alloys, hard alloys, wear-resistant materials, high-temperature radiation materials, and other high-temperature vacuum devices. The composite materials prepared with TiC have various applications in mechanical processing, metallurgy, minerals, aerospace, and fusion reactors.

9. Osmium

Osmium is a member of the platinum group of metals.It is located in the eighth group element and the sixth period of the periodic table.Its element symbol is Os, with an atomic number of 76 and a relative atomic mass of 190.2. Osmium is known for having the highest density among metals.

Osmium is typically found in osmium-iridium ores. It can be extracted by roasting the solid containing osmium in the air, absorbing the volatilized osmium tetroxide in an alcohol-alkali solution, obtaining osmium salt, and then reducing it with hydrogen gas to obtain metallic osmium. It is often used to manufacture alloys with ultra-high hardness. It is commonly alloyed with rhodium, ruthenium, iridium, or platinum and used as a bearing in record players, fountain pen tips, clocks, and instruments.

Osmium has the highest density among known metal elements, with a density of 22.59 grams per cubic centimeter, a melting point of 3045 ℃, and a boiling point above 5300 ℃. It has a hexagonal dense lattice structure and is a hard and brittle gray-blue metal that can easily turn into powder when pressed in an iron mortar. Osmium powder is blue-black and can self-ignite. The vapor of osmium is highly toxic and can intensely irritate the mucous membranes of the eyes, leading to blindness in severe cases.

10. Silicon Carbide

Diamond sand, which is also known as silicon carbide (SiC), is produced through a high-temperature smelting process of raw materials such as quartz sand, petroleum coke (or coal coke), and sawdust (which requires the addition of salt to produce green silicon carbide) in a resistance furnace. It has a melting point of 2700℃. Silicon carbide is also a rare mineral found in nature, known as masonite or carbo silicate. Out of contemporary non-oxide high-tech refractory materials such as carbon, nitrogen, boron and silicon carbide, the latter is the most widely used and economical. It is often referred to as gold steel or refractory sand. Currently, the industrial production of silicon carbide in China is divided into black silicon carbide and green silicon carbide. These are hexagonal crystals with a specific gravity of 3.20-3.25 and a microhardness of 2840-3320kg/mm2.