Niobium Powders of Mesoporous Structure
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.
Keywordsniobium powder magnesium niobate magnesium-thermic reduction surface mesoporous structure natural surface oxide
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