Hafnium carbide melting point

The silvery, shiny, ductile metal is passivated with an oxide layer. Chemically very similar to and always found with zirconium (like chemical twins, with almost identical ionic radii) the two are difficult to separate. Used in control rods in nuclear reactors (e.g. in nuclear submarines), as it absorbs electrons more effectively than any other element. Also used in special lamps and flash devices. Alloys with niobium and tantalum are used in the construction of chemical plants. Hafnium dioxide is a better insulator than Si02. Hafnium carbide (HfC) has the highest melting point of all solid substances (3890 °C record ). 

Hafnium carbide (HfC) This alloy has one of the highest melting points of any binary compound (3.890°C). It is extremely hard and resists corrosion while absorbing slow neutrons. Therefore, it is an ideal metal in the manufacture of control rods for nuclear reactors. 

Hafnium carbide has an extremely high melting point (3887 °C) and may find use as an alternative to tantalum carbide in the production of very hard metal components.28... 

Hafnium carbide has a melting point of 3890°C and exhibits extreme hardness and good electrical conductivity. It is used as an oxidation-resistant coating for composites and as a coating for superalloys [10]. The material is prepared by the CVD of a mixture of hafnium tetrachloride, methane and hydrogen [193, 194]. 

Hafnium is a lustrous, silvery, ductile metal with a high melting point. The mechanical properties of the metal are markedly affected by traces of impurities such as O, N, and C which have an embrittling effect on the metal, making it difficult to fabricate. The alloy tantalum hafnium carbide (Ta4HfCs), with a melting point of 4215 °C, is one of the most refractory substances known. 

Ceramic borides, carbides and nitrides are characterized by high melting points, chemical inertness and relatively good oxidation resistance in extreme environments, such as conditions experienced during reentry. This family of ceramic materials has come to be known as Ultra High Temperature Ceramics (UHTCs). Some of the earliest work on UHTCs was conducted by the Air Force in the 1960 s and 1970 s. Since then, work has continued sporadically and has primarily been funded by NASA, the Navy and the Air Force. This article summarizes some of the early works, with a focus on hafnium diboride and zirconium diboride-based compositions. These works focused on identifying additives, such as SiC, to improve mechanical or thermal properties, and/or to improve oxidation resistance in extreme environments at temperatures greater than 2000°C. 

Graphite can thus be considered the most refractory of cill the elements, tungsten being second-best with a melting point of 3680 K. However hafnium carbide (HfC) and tantalum carbide (TaC) are reported to have higher melting points (approximately 4220 K and 4270 K respectively) and are the most refractory of all materials.f ... 

From the above short review, it appears that most of the present nuclear reactors use a narrow sampling of neutron absorber materials. This, of course, first results from the neutron properties of the elements. This is also a consequence of the materials and elaboration processes availability. For example, AIC has been developed as a surrogate to hafnium and boron is mainly used as boron carbide. This is always a compromise regarding the previous examples, AIC has the lowest melting point of all the core materials and boron carbide is a brittle ceramic enduring premature cracking. 

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