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首页> 外文期刊>Zeitschrift fur Anorganische und Allgemeine Chemie >Preparation and properties of nickel and iron oxides obtained by calcination of layered double hydroxides
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Preparation and properties of nickel and iron oxides obtained by calcination of layered double hydroxides

机译：层状双氢氧化物煅烧制得的镍和铁氧化物的制备及性能

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摘要

A constant pH precipitation method has been applied to obtain solids with Ni/Fe molar ratios of 2/1, 3/2, 1/1, 2/3, and 1/2. In all cases, a phase with the hydrotalcite-like structure is obtained, containing Ni-II and Fe-III in the brucite-like layers and carbonate in the interlayer, and, for samples with a Ni/Fe molar ratio lower than 2/1, amorphous hydrated iron oxides, undetected by X-ray diffraction, are also formed. The solids have been characterized by element chemical analysis, powder X-ray diffraction, differential thermal analysis, thermogravimetric and differential thermogravimetric analysis, FT-IR spectroscopy, temperature-programmed reduction and assessment of specific surface area by nitrogen adsorption at -196 degrees C. In all cases reduction leads to zero-valent state for the metals, reduced nickel particles probably favouring reduction of Fe-III species; the specific surface area increases with the iron content, probably due to the amorphous nature of the hydrated iron oxides formed. Calcination at 1200 degrees C in air leads to well crystallized solids, formed by NiFe2O4 spinel and, additionally, rocksalt-type NiO for Ni/Fe ratios larger than 1/2. In this way, solids with tailored compositions of these two phases can be prepared.
机译：已采用恒定pH沉淀法获得Ni / Fe摩尔比为2 / 1、3 / 2、1 / 1、2 / 3和1/2的固体。在所有情况下，均获得具有水滑石样结构的相，在水镁石样层中包含Ni-II和Fe-III，在中间层中包含碳酸盐;对于Ni / Fe摩尔比小于2 /如图1所示，还形成了未通过X射线衍射检测到的无定形水合氧化铁。通过元素化学分析，粉末X射线衍射，差示热分析，热重和差示热重分析，FT-IR光谱，程序升温还原以及在-196℃下通过氮吸附评估比表面积来表征固体。在所有情况下，还原都会导致金属的零价态，还原的镍颗粒可能有助于还原Fe-III物种;比表面积随铁含量的增加而增加，这可能是由于所形成的水合氧化铁的非晶性所致。在1200摄氏度的空气中煅烧会产生良好结晶的固体，该固体由NiFe2O4尖晶石和另外的盐盐型NiO（对于Ni / Fe比率大于1/2）形成。以这种方式，可以制备具有这两相的特定组成的固体。

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