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Nucleation and stability of defect clusters: New energetic model in the case of substituted wustites
Abstract For wüstite Fe1?z O (z < 0.08) an energetic model accounts for the stability of cubic defect clusters (m/n) which are partly ordered in the crystal. The Gibbs energy GT (N) associated with clusters, including their distorted envelope, is expressed as a sum of a volume term in N 3 and of surface terms in N 4; N is the number of bonds characteristic of the cluster size. In the case of a (10/4) type cluster, this energy is negative and minimum for Nm ranging between 4 and 5, when the volume and surface energies range between specific values. Using simple assumptions, a volume energy ?0.80 eV per vacancy is found in accordance with the value of stabilization energy calculated by theorists for the (10/4) cluster. The substitution of Fe2+ by Ca2+ should lead to a decrease of cluster size; this has been recently suggested by neutron diffraction studies. 相似文献
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费-托合成Fe1-xO基熔铁催化剂的研究 总被引:4,自引:0,他引:4
采用高温熔融法制备了用于费-托合成的Fe1-xO基熔铁催化剂,考察了其在n(H2)/n(CO)=2,温度573 K,压力1.4 MPa和空速为12?600 h-1下的催化性能. 结果表明,与Fe3O4基熔铁催化剂相比,Fe1-xO基熔铁催化剂具有较高的催化F-T合成反应的活性、较低的WGS反应选择性和较强的加氢能力. XRD结果表明,经F-T反应后的熔铁催化剂存在Fe5C2和Fe3O4两种物相,但Fe1-xO基熔铁催化剂中Fe5C2的晶粒尺寸小于Fe3O4基熔铁催化剂中Fe5C2的晶粒尺寸. 相似文献
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