Four separate coprecipitation routes were applied to the preparation of Ni_xMn_(1-x)(OH)2 mixed hydroxides with x = 1, 5/6, 2/3, 1/2, 1/3, and 0, beginning with divalent nitrates. The structure and morphology of the samples were studied by X-ray diffraction and scanning electron microscopy techniques. Intentionally bubbled air during coprecipitation was found to create layered double hydroxide (LDH) phases for x = 5/6, coexisting LDH and Mn3O4 phases for 5/6 > x > 0, and Mn3O4 for x = 0. On the basis of the structures observed, these trends could be attributed to the relative ease of oxidation of Mn~(2+) to Mn~(3+). Pure hydroxides, with the expected Ni(OH)2 structure, were prepared for all x when air was excluded from the coprecipitation reaction. Spherical and dense particles could be prepared for all compositions attempted when ammonia was added during coprecipitation under anaerobic conditions.
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机译：采用四条独立的共沉淀路线制备 x = 1、5/6、2/3、1/2、1/3 和 0 的 Ni_xMn_（1-x）（OH）2 混合氢氧化物，从二价硝酸盐开始。采用X射线衍射和扫描电子显微镜技术研究了样品的结构和形貌。发现共沉淀过程中有意的气泡空气在 x = 5/6 时会产生层状双氢氧化物 （LDH） 相，在 5/6 > x > 0 时产生共存的 LDH 和 Mn3O4 相，在 x = 0 时产生 Mn3O4。根据观察到的结构，这些趋势可以归因于Mn~（2+）对Mn~（3+）的相对容易氧化。当共沉淀反应中排除空气时，制备了具有预期Ni（OH）2结构的纯氢氧化物。在厌氧条件下共沉淀期间加入氨时，可以制备球形和致密颗粒。
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