Preparation and Characterization of Niobium Carbide and Carbonitride

다국어 초록 (Multilingual Abstract)

Unsupported niobium carbide powders of NbC were prepared by carburization of commercial niobium pentoxide in flowing CH4-H₂ mixtures. Several routes of synthesis were investigated, leading to final carbides with specific surface areas ranging from 10 to 50 m²g -1. During direct carburization, after the first step of reduction of Nb₂O5, to NbO₂, a long induction period which was succeeded by an accelcratory period, was observed for the rcduction/carburization to NbC. In the presence of a catalyst of methlane 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 he observed. The preparations through niobium oxynitride lead to face-centered cubic carbonitrides with speeific surface areas ranging from 27 to 49 m² g-1. Chemical composition and ceil parameter of these cabonitrides vary slightly with the synthesis conditions. After a reducing treatment, as for NbC, CO chemisorption was also observed.

목차 (Table of Contents)

• INTRODUCTION
• EXPERIMENTAL
• RESULTS
• DISCUSSION
• CONCLUSION
• REFERENCES