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New materials and alloys are constantly being created, making it difficult to determine the material with the highest melting point. Currently, hafnium tantalum carbide has the highest melting point at 4488 K. Carbon has the highest melting point of chemical elements at 4300-4700 K, while tungsten has the second highest at 3695 K. Ceramics are sometimes used for hardware requiring high melting points. Under extreme pressure, the melting point increases, while it decreases with decreasing pressure.
This is a difficult question to answer because new materials and alloys are continually being created, and the material with the highest melting point now may change as new compounds are synthesized. Currently the record holder is hafnium tantalum carbide (Ta4HfC5), a refractory compound with a melting point of 4488 K (4215 °C, 7619 °F). By mixing various metals to create alloys, even higher melting points can be achieved. Materials with such outstanding physical properties are sometimes referred to as superalloys.
The chemical element with the highest melting point is carbon, at 4300-4700 K (4027-4427°C, 7280-8000°F). The second highest melting point of the chemical elements is tungsten, at 3695 K (3422 °C, 6192 °F), which is why it is used as a filament for light bulbs. Sometimes tungsten is called the element with the highest melting point because carbon does not actually melt under atmospheric pressure, but sublimes (transitions directly from a solid to a gas) at 4000 K (3727°C, 6740°F ).
When very high melting points are desired in a piece of hardware, ceramics are sometimes used. One example is during Project Pluto in the 1950s, when American scientists attempted to create a nuclear-powered ballistic missile with a gigawatt-level unshielded reactor. The reactor produced such immense heat that a ceramic frame and components were required.
Under extreme pressures, the melting point increases. The Earth’s inner iron core, for example, has a temperature of about 5,000-6,000°C (>9,000°F), but it is solid, because the pressure is about 3 million times greater than at the surface. Conversely, as the pressure decreases, the melting point also decreases. On the surface of Mars, the pressure is so low that liquid water would evaporate almost immediately. This is why we have observed evidence of small temporary springs created on Mars but no permanent bodies of water.
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