Acta Chimica Sinica ›› 2012, Vol. 70 ›› Issue (16): 1731-1736.DOI: 10.6023/A12070376 Previous Articles     Next Articles

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卢亚骏, 王浩然, 顾煜, 徐岚, 孙晓骏, 邓意达   

  1. 上海交通大学金属基复合材料国家重点实验室 材料科学与工程学院 上海 200240
  • 投稿日期:2012-07-06 发布日期:2012-07-13
  • 通讯作者: 邓意达
  • 基金资助:
    项目受国家自然科学基金(No. 51001075)、上海市优秀学科带头人(No. 11XD1402700)和上海市教委“曙光计划”跟踪(No. 10GG06)资助.

Studies on the Growth Mechanism of Hydrothermal Synthesis of α-Ni(OH)2 Nanowires

Lu Yajun, Wang Haoran, Gu Yu, Xu Lan, Sun Xiaojun, Deng Yida   

  1. State Key Laboratory of Metal Matrix Composites, Shanghai Jiaotong University, Shanghai 200240
  • Received:2012-07-06 Published:2012-07-13
  • Supported by:
    Project supported by the National Natural Science Foundation of China (No. 51001075), Program of Shanghai Subject Chief Scientist (No. 11XD1402700), Following Research Project supported by the “Dawn” Program of Shanghai Education Commission (No. 10GG06).

SO42- ions and OH- ions play important roles in hydrothermal synthesis of Ni(OH)2 nanostructures with only inorganic nickel salt and NaOH. The whole process could be divided into 2 parts, the preparation of Ni(OH)2 gel and its hydrothermal reaction. According to our analysis, the former one is an ionic-reaction which produces amorphous Ni(OH)2. It is the later one when Ni(OH)2 gel crystallizes that dominates the polymorph and morphology of final products. The influence of OH- on morphologies of Ni(OH)2 has been studied by changing the ratio of n(SO42-)/n(OH-). To discuss the effect of SO42- ions in hydrothermal system on crystal growth, we wash the gel which is prepared by NiCl2 and NaOH with the mixture solution of Na2SO4 and NiSO4 for different times, so that Cl- ions in the gel solution could be replaced by SO42- ions in varying degrees. Then the nanosized Ni(OH)2 products is prepared by hydrothermal treatment. Also, the samples were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). TEM results show that there will be 2 main nanostructures in different hydrothermal conditions: nanowires and nanosheets. XRD and FTIR results reveals that the nanowires is Ni(SO4)0.3(OH)1.4, one kind of α-Ni(OH)2, and the nanosheet is β-Ni(OH)2. We finally got a conclusion that low amount of OH- and pure SO42- environment is advantageous to synthesis of α-Ni(OH)2 nanowires. Since α-Ni(OH)2 is hydroxyl-deficient and consists of stacked Ni(OH)2-x layers toward which the SO42- ion has a higher affinity than other ions such as Cl- and SO42-, the SO42- ion is able to enter its interlayers. The structure is stabilized due to the strong coordination bonds between SO42- and Ni2 in Ni(OH)2-x layers. Also, free Ni2 ions in solution would be linked to intercalated SO42- through coordination bonds, so that new Ni(OH)2-x layers could form constantly and stack along the c-axis. As a result, there will be a preferential growth in the [001] direction. However, this process is not likely to continue when there is high amount of OH-, which may cause high Coulomb repulsion along the [001] direction.

Key words: hydrothermal synthesis, α-Ni(OH)2 nanowires, growth mechanism