Niobium carbide

Chemical Properties

Niobium carbide is a green cubic crystal with metallic luster and belongs to the sodium chloride type cubic crystal system. The relative density is 8.47, the lattice constant a=0.447nm, and the melting point is 2300°C. Microhardness>235Gpa (>2400kg/mm2), harder than corundum. Elastic modulus 338000N/mm2, thermal expansion coefficient 6.65×10-6/K, thermal conductivity 14w/(m.K), heat of formation -140.7kJ/mol, specific heat capacity 36.8J/(mol.K), resistivity 35μΩ.cm. Insoluble in water and in all acids except a mixture of nitric acid and hydrogen fluoride. It is stable at 1000-1100°C, and rapidly oxidizes to niobium pentoxide at temperatures above 1100°C. Niobium carbide is easy to melt in titanium carbide, zirconium carbide, tungsten carbide and other compounds, and together form an isomorphous solid solution mixture.

Physical properties

Lavender gray powder, soluble in HF-HNO₃ mixture. Wear resistant film, coating graphite in nuclear reactors. Oxidation in air becomes severe only above 1000°C.

Uses

Niobium carbide (NbC) is amongst the hardest technical compounds known. It should thus be excellently suited for machining applications and wear protection. It is used to make hard-tipped tools and special steels and to coat graphite in nuclear reactors.

Application

niobium carbide (NbC) is extremely hard refractory materials. TiC, ZrC, VC and NbC are commercially used in tool bits for cutting tools. HfC and NbC can also be used as refractory coatings in nuclear reactors.

Flammability and Explosibility

Non flammable