CrN powder was synthesized by nitriding Cr metal in ammonia gas flow, and its chemical reaction mechanism and nitridation process were studied. Through thermodynamic calculations, the Cr-N-O predominance diagrams were...CrN powder was synthesized by nitriding Cr metal in ammonia gas flow, and its chemical reaction mechanism and nitridation process were studied. Through thermodynamic calculations, the Cr-N-O predominance diagrams were constructed for different tempera- tures. Chromium nitride formed at 700-1200℃ under relatively higher nitrogen and lower oxygen partial pressures. Phases in the products were then investigated using X-ray diffraction （XRD）, and the Cr2N content varied with reaction temperature and holding time. The results indicate that the Cr metal powder nitridation process can be explained by a diffusion model. Further, Cr2N formed as an intermediate product because of an incomplete reaction, which was observed by high-resolution transmission electron microscopy （HRTEM）. After nitriding at 1000℃ for 20 h, CrN powder with an average grain size of 63 nm was obtained, and the obtained sample was analyzed by using a scanning electron microscope （SEM）.展开更多
A series of monometallic nitrides and bimetallic nitrides were prepared by temperature-programmed reaction with NH3. The effects of Co, Ni and Fe additives and the synergic action between Fe, Co, Ni and Mo on the amm...A series of monometallic nitrides and bimetallic nitrides were prepared by temperature-programmed reaction with NH3. The effects of Co, Ni and Fe additives and the synergic action between Fe, Co, Ni and Mo on the ammonia decomposition activity were investigated. TPR-MS, XRD were also carried out to obtain better insight into the structure of the bimetallic nitride. The results of ammonia decomposition activity show that bimetallic nitrides are more active than monometallic nitrides or bimetallic oxides.展开更多
Fe3Mo3C has been prepared and its activity for ammonia synthesis was evaluated.As had been observed previously for Co3Mo3C,it was found to be inactive at 400℃.At 500℃activity developed and this can be related to the...Fe3Mo3C has been prepared and its activity for ammonia synthesis was evaluated.As had been observed previously for Co3Mo3C,it was found to be inactive at 400℃.At 500℃activity developed and this can be related to the substitution of lattice carbon by nitrogen.Application of a simple topotactic route to prepare Ni2Mo3C from Ni2Mo3N proved unsuccessful,with the resultant carbonitride formed under optimal synthesis conditions being active for ammonia synthesis at 400℃.展开更多
基金financially supported by the Innovation Foundation of Shanghai University (Nos. sdcx2012033 and sdcx2012062)the Special Research Foundation for Training and Selecting Outstanding Young Teachers of Universities in Shanghai (No. B.37-0407-12-008)+1 种基金the National Natural Science Foundation of China (Nos. 51072112 and 51272154)the Projects of International Cooperation and Exchanges NSFC (No. 51311130110)
文摘CrN powder was synthesized by nitriding Cr metal in ammonia gas flow, and its chemical reaction mechanism and nitridation process were studied. Through thermodynamic calculations, the Cr-N-O predominance diagrams were constructed for different tempera- tures. Chromium nitride formed at 700-1200℃ under relatively higher nitrogen and lower oxygen partial pressures. Phases in the products were then investigated using X-ray diffraction （XRD）, and the Cr2N content varied with reaction temperature and holding time. The results indicate that the Cr metal powder nitridation process can be explained by a diffusion model. Further, Cr2N formed as an intermediate product because of an incomplete reaction, which was observed by high-resolution transmission electron microscopy （HRTEM）. After nitriding at 1000℃ for 20 h, CrN powder with an average grain size of 63 nm was obtained, and the obtained sample was analyzed by using a scanning electron microscope （SEM）.
文摘A series of monometallic nitrides and bimetallic nitrides were prepared by temperature-programmed reaction with NH3. The effects of Co, Ni and Fe additives and the synergic action between Fe, Co, Ni and Mo on the ammonia decomposition activity were investigated. TPR-MS, XRD were also carried out to obtain better insight into the structure of the bimetallic nitride. The results of ammonia decomposition activity show that bimetallic nitrides are more active than monometallic nitrides or bimetallic oxides.
文摘Fe3Mo3C has been prepared and its activity for ammonia synthesis was evaluated.As had been observed previously for Co3Mo3C,it was found to be inactive at 400℃.At 500℃activity developed and this can be related to the substitution of lattice carbon by nitrogen.Application of a simple topotactic route to prepare Ni2Mo3C from Ni2Mo3N proved unsuccessful,with the resultant carbonitride formed under optimal synthesis conditions being active for ammonia synthesis at 400℃.
