Characterization of synthetic nanocrystalline mackinawite: Crystal structure, particle size, and specific surface area
Characterization of synthetic nanocrystalline mackinawite: Crystal structure, particle size, and specific surface area
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DOI：
10.1016/j.gca.2007.11.008
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发表时间：
2008-01-15
影响因子：
5
通讯作者：
Hayes, Kim F.
中科院分区：
文献类型：
--
作者：
Jeong, Hoon Y.;Lee, Jun H.;Hayes, Kim F.
通过使硫化钠和氯化亚铁的水溶液反应3天来合成硫化铁。通过X射线粉末衍射（XRPD），确定所得到的相主要是具有晶胞参数a = B = 3.67埃和c = 5.20埃的纳米晶mackinawite（空间群：P4/ nmm）。铁K边XAS分析也表明了镁钠闪石的优势。相对于结晶良好的mackinawite，观察到合成mackinawite的晶格膨胀沿着c轴。与相对短时效相相比，这里制备的mackinawite由较大的晶粒组成，晶格间距较小。HR-TEM对晶格条纹的直接观察证实了布拉格衍射法在从XRPD图确定纳米晶麦基诺石晶格参数中的适用性。估计的纳米晶mackinawite的粒度和外部比表面积（SSA（退出））的变化显着与所使用的方法。基于XRPD图测量微晶尺寸的Scherrer方程的使用受到由于多分散颗粒的存在而导致的Scherrer常数（K）的不确定性的限制。多晶颗粒的存在也可能导致通过Scherrer方程的不准确的粒度估计，因为微晶和粒度不相等。TEM观察得到最小的SSA（出口）为103 m（2）/g。由于样品制备过程中干燥导致的颗粒聚集，该测量结果不代表分散颗粒。相比之下，EGME方法和PC测量产生更高的SSA（出口）（EGME为276-345 m2/g，PC为424 +/- 130 m2/g）。这些与以前通过对颗粒聚集不敏感的方法测得的结果合理一致。(C)2007爱思唯尔有限公司保留所有权利。
Iron sulfide was synthesized by reacting aqueous solutions of sodium sulfide and ferrous chloride for 3 days. By X-ray powder diffraction (XRPD), the resultant phase was determined to be primarily nanocrystalline mackinawite (space group: P4/ nmm) with unit cell parameters a = b = 3.67 angstrom and c = 5.20 angstrom. Iron K-edge XAS analysis also indicated the dominance of mackinawite. Lattice expansion of synthetic mackinawite was observed along the c-axis relative to well-crystalline mackinawite. Compared with relatively short-aged phase, the mackinawite prepared here was composed of larger crystallites with less elongated lattice spacings. The direct observation of lattice fringes by HR-TEM verified the applicability of Bragg diffraction in determining the lattice parameters of nanocrystalline mackinawite from XRPD patterns. Estimated particle size and external specific surface area (SSA(exit)) of nanocrystalline mackinawite varied significantly with the methods used. The use of Scherrer equation for measuring crystallite size based on XRPD patterns is limited by uncertainty of the Scherrer constant (K) due to the presence of polydisperse particles. The presence of polycrystalline particles may also lead to inaccurate particle size estimation by Scherrer equation, given that crystallite and particle sizes are not equivalent. The TEM observation yielded the smallest SSA(exit) of 103 m(2)/g. This measurement was not representative of dispersed particles due to particle aggregation from drying during sample preparation. In contrast, EGME method and PCs measurement yielded higher SSA(exit) (276-345 m2/g by EGME and 424 +/- 130 m(2)/g by PCs). These were in reasonable agreement with those previously measured by the methods insensitive to particle aggregation. (C) 2007 Elsevier Ltd. All rights reserved.