刘庆冬
,
褚于良
,
王泽民
,
刘文庆
,
周邦新
金属学报
将Nb-V微合金钢在1200 ℃固溶0.5 h后淬火, 然后在450 ℃回火4 h, 结合扫描电子显微镜(SEM)和透射电子显微镜(TEM), 用三维原子探针(3DAP)研究渗碳体内部和渗碳体/基体界面处的元素分布和成分变化. 结果显示, 淬火样品中C原子由于自回火而出现轻微偏聚, 其它合金原子V,Nb, Si, Mn, Mo和Al等分布均匀. 450 ℃回火4 h样品中出现C原子偏聚区, 在该区域内, Mn含量较高, Mo和V轻微偏聚, Si和Al很少, 对应渗碳体析出, Si富集在渗碳体/基体界面处; 另外, 观察到C和V明显偏聚的单原子面, 周围富集Si和Mn, 对应合金碳化物析出初期形成的G.P.区, 成分主要为V4C3.
关键词:
偏聚
,
G.P. zone
,
Cementite
王丙寅
,
于小虎
,
霍春芳
,
王建国
,
李永旺
催化学报
doi:10.1016/S1872-2067(12)60703-7
采用自旋极化密度泛函理论和周期平板模型,对C2H4在铁基费托合成催化剂活性相之一Fe3C(100)表面从热力学和动力学两个方面分析了C2H4在Fe3C(100)表面进行脱氢和裂解反应的竞争性.结果表明,C2H4在Fe3C(100)表面的μ-bridging吸附比π、di-σ吸附更加稳定;C2H4与Fe3C(100)面的相互作用导致C2H4的C原子部分发生重新杂化(sp2→sp3),使C原子呈近四面体结构.在Fe3C(100)表面C2H4易于发生脱氢反应,C-C键裂解反应不具有竞争性.亚乙烯基CCH2和乙烯基CHCH2是Fe3C(100)表面最丰的C2物种,或是C2H4参与链增长的主要单体形式.
关键词:
乙烯
,
碳化铁
,
吸附
,
脱氢
,
裂解
,
费托合成
,
密度泛函理论
M. Bahgat
,
null
材料科学技术（英文）
Iron carbides are very promising metallurgical products and can be used for steelmaking process, where it plays as an alternative raw material with significant economic advantages. Also it has many other applications, e.g. catalysts, magnets, sensors. The present review investigates the different properties and uses of the iron carbides. The commercial production and the different varieties for the iron carbides synthesis (gaseous carburization, mechanochemical synthesis, laser pyrolysis, plasma pyrolysis, chemical vapor deposition and ion implantation) were reviewed. Also the effect of different factors on the carburization process like gas composition, raw material, temperature, reaction time, catalyst presence and sulfur addition was indicated.
关键词:
Iron carbides
,
null
,
null
,
null
