摘要
采用DTA技术，通过改变升温速率研究了γ－Mo2N合成过程中的热变化，并经XRD、BET及IR测试，对DTA曲线中的谱峰进行归属，考察了中间产物．DTA结果表明，在MoO3和NH3程序升温反应过程中有放热峰及吸热峰出现，且随升温速率的升高，放热峰面积与吸热峰面积之比逐渐减小．结合XRD及IR结果可知，DTA曲线中的放热峰可归属为由MoO3变化为MoO2的还原峰，吸热峰则归属为由MoO2变化为Mo2N的氨化峰．在低升温速率（≤3K／min）时，氮化产物为γ－Mo2N；而在高升温速率（≥5K／min）时，氮化产物中除γ－Mo2N外还有MoO2生成，且升温速率越高，产物中MoO2的含量越高．NH3先与MoO3反应生成MoO2，然后MoO2再被氮化为γ－Mo2N.
The thermal change in the synthesis of γ-Mo2N by temperature-programmedreaction of MoO3 with ammonia has been studied by differential thermal analysis (DTA)technique, IR, BET and XRD measurements. The DTA results show that both exothermic andendothermic peaks appear in the process. With the increase of temperature-elevation rate,the areas of the exothermic peaks increase, and the areas of the endothermic peaks decrease.XRD and IR results show that the exothermic peaks are attributed to the reduction of MoO3to MoO2 and the endothermic peaks can be assigned to the nitridation of MoO2 to γ-Mo2N.The nitriding product is γ-Mo2N at the lower rates of increasing temperature (≤3 K/min),whereas the products are γ-Mo2N and MoO2 at the higher heating rates(≥5 K/min). Andthe higher the rate, the more MoO2 was formed in the final product. It is suggested that NH3first interacts with MoO3 and reduces the MoO3 into MoO2, and then the MoO2 is nitridedin to γ-Mo2N.
出处
《高等学校化学学报》
SCIE
EI
CAS
CSCD
北大核心
1997年第10期1675-1679,共5页
Chemical Journal of Chinese Universities
