Niobium Powders of Mesoporous Structure

Abstract

The mesoporous structure of niobium powders of specific surface areas from 32 to 150 m²/g obtained through reduction of niobium-oxide compounds by magnesium vapors has been investigated. A doubling of the specific surface area of magnesium-thermic niobium powders in comparison to tantalum powders has been shown to be caused by the larger volume and smaller size of pores. For a powder with a specific surface area of 150 m²/g, 90% of the surface is governed by pores of sizes smaller than 5 nm. Although the X-ray pattern of the powder corresponds to the metal niobium, 96.5% of this powder weight consists of a natural surface-oxide film, according to the TGA data. The thickness of this oxide decreases in comparison with the surface oxide on the compact metal depending on the powder mesoporous structure.