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Structural Differentiation between Layered Single (Ni) and Double Metal Hydroxides (Ni–Al LDHs) Using Wavelet Transformation
The Journal of Physical Chemistry A ( IF 2.9 ) Pub Date : 2017-09-07 00:00:00 , DOI: 10.1021/acs.jpca.7b07940
Matthew G. Siebecker 1 , Donald L. Sparks 1
Affiliation  

Layered double hydroxides (LDHs) are anionic clays important in disciplines such as environmental chemistry, geochemistry, and materials science. Developments in signal processing of extended X-ray absorption fine structure (EXAFS) data, such as wavelet transformation (WT), have been used to identify transition metals and Al present in the hydroxide sheets of LDHs. The WT plots of LDHs should be distinct from those of isostructural single metal hydroxides. However, no direct comparison of these minerals appears in the literature using WT. This work systematically analyzes a suite of Ni-rich mineral standards, including Ni–Al LDHs, single metal Ni hydroxides, and Ni-rich silicates using WT. The results illustrate that the WT plots for α-Ni(OH)2 and Ni–Al LDHs are often indistinguishable from each other, with similar two-component plots for the different mineral types. This demonstrates that the WT of the first metal shell often cannot be used to differentiate an LDH from a single metal hydroxide. Interlayer anions adsorbed to the hydroxide sheet of α-Ni(OH)2 affect the EXAFS spectra and are not visible in the FT but are clearly resolved and discrete in the WT.

中文翻译:

小波变换在层状单(Ni)和双金属氢氧化物(Ni-Al LDHs)之间的结构区分

层状双氢氧化物(LDHs)是在诸如环境化学,地球化学和材料科学等学科中很重要的阴离子粘土。扩展的X射线吸收精细结构(EXAFS)数据的信号处理技术的发展,例如小波变换(WT),已被用于识别LDH氢氧化物片中存在的过渡金属和Al。LDH的WT图应与同构单金属氢氧化物的WT图不同。但是,在文献中,使用WT不能直接比较这些矿物。这项工作使用WT系统分析了一套富镍矿物质标准品,包括Ni-Al LDH,单金属Ni氢氧化物和富Ni硅酸盐。结果表明,α-Ni(OH)2的WT图Ni-Al LDH和Ni-Al LDH通常彼此难以区分,不同矿物类型具有相似的两成分图。这证明了第一金属壳的WT通常不能用于将LDH与单一金属氢氧化物区分开。吸附到α-Ni(OH)2的氢氧化物片上的层间阴离子会影响EXAFS光谱,在FT中不可见,但在WT中被清楚地分辨和离散。
更新日期:2017-09-07
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