Preparation and Characterization of Niobium Carbide and Carbonitride

✍ Scribed by Hak Soo Kim; Guy Bugli; Gérald Djéga-Mariadassou

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 170 KB
• Volume: 142
• Category: Article
• ISSN: 0022-4596
• DOI: 10.1006/jssc.1998.7993

✦ Synopsis

Unsupported niobium carbide powders of NbC were prepared by carburization of commercial niobium pentoxide in flowing CH 4 -H 2 mixtures. Several routes of synthesis were investigated, leading to final carbides with specific surface areas ranging from 10 to 50 m 2 g ؊1 . During direct carburization, after the first step of reduction of Nb 2 O 5 to NbO 2 , a long induction period which was succeeded by an acceleratory period, was observed for the reduction/carburization to NbC. In the presence of a catalyst of methane decomposition, this induction period was eliminated but the superficial carbon free contamination of the final carbide was increased. However, this contamination can be removed by a reducing treatment and CO chemisorption can be observed. The preparations through niobium oxynitride lead to face-centered cubic carbonitrides with specific surface areas ranging from 27 to 49 m 2 g ؊1 . Chemical composition and cell parameter of these cabonitrides vary slightly with the synthesis conditions. After a reducing treatment, as for NbC, CO chemisorption was also observed.