Carbon vacancy ordering in zirconium carbide powder
Carbon vacancy ordering in zirconium carbide powder
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DOI：
10.1111/jace.16964
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发表时间：
2020-04
影响因子：
3.9
通讯作者：
Yue Zhou;T. Heitmann;E. Bohannan;Joseph C. Schaeperkoetter;W. Fahrenholtz;G. Hilmas
中科院分区：
文献类型：
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作者：
Yue Zhou;T. Heitmann;E. Bohannan;Joseph C. Schaeperkoetter;W. Fahrenholtz;G. Hilmas
采用直接反应法合成了碳化锆（ZrCx）粉末，在粉末中发现了有序碳空位.使用氢化锆（ZrH2）和炭黑作为起始粉末，其中ZrH2：C = 1：0.6的摩尔比。粉末在1300°C或2000°C下反应。通过X射线衍射（XRD）检测的主相是ZrCx。通过透射电子显微镜（TEM）在任一温度下合成的粉末中没有观察到过量的碳。通过中子粉末衍射（NPD）和选区电子衍射（SAED）进一步证实了碳空位的有序性。缺碳ZrCx中的空位表现出金刚石立方对称性，其超晶胞由8个（2 × 2 × 2）具有岩盐结构的ZrCx晶胞组成。Rietveld精修的中子衍射图显示，合成温度没有显着的影响，在ZrCx粉末的空位有序的程度。直接合成的ZrC0.6导致在部分有序的碳空位，而不需要在以前的实验研究中报道的延长等温退火。
Ordered carbon vacancies were detected in zirconium carbide (ZrCx) powders that were synthesized by direct reaction. Zirconium hydride (ZrH2) and carbon black were used as starting powders with the molar ratio of ZrH2:C = 1:0.6. Powders were reacted at 1300°C or 2000°C. The major phase detected by x‐ray diffraction (XRD) was ZrCx. No excess carbon was observed by transmission electron microscopy (TEM) in powders synthesized at either temperature. Ordering of the carbon vacancies was identified by neutron powder diffraction (NPD) and further supported by selected area electron diffraction (SAED). The vacancies in carbon‐deficient ZrCxexhibited diamond cubic symmetry with a supercell that consisted of eight (2 × 2 × 2) ZrCxunit cells with the rock‐salt structure. Rietveld refinement of the neutron diffraction patterns revealed that the synthesis temperature did not have a significant effect on the degree of vacancy ordering in ZrCxpowders. Direct synthesis of ZrC0.6resulted in the partial ordering of carbon vacancies without the need for extended isothermal annealing as reported in previous experimental studies.