Niobium is a rare high melting point metal with silver gray, soft texture, and ductility. At room temperature, niobium does not react with air and will not be completely oxidized when red hot in oxygen. Niobium can combine directly with sulfur, nitrogen, and carbon at high temperatures. "Niobium does not react with inorganic acids or bases, nor is it soluble in aqua regia, but it is soluble in hydrofluoric acid.". The content of niobium in the crust is 20 ppm, and the distribution of niobium resources is relatively concentrated. Due to its excellent superconductivity, high melting point, corrosion resistance, and wear resistance, niobium is widely used in the fields of steel, superconducting materials, aerospace, atomic energy, and other fields.