水热氢还原法制备纳米金属镍粉的非均相反应机制研究
文献类型：学位论文
| 作者 | 徐菊 |
| 学位类别 | 硕士 |
| 答辩日期 | 2001-06 |
| 授予单位 | 中国科学院研究生院 |
| 导师 | 喻克宁 |
| 关键词 | 水热 氢气还原 纳米镍粉 反应机制 |
| 其他题名 | Studies on the Mechanism of Heterophase Reaction in Preparation of Nanometer-sized Nickel Powders by Hydrothermal Hydrogen Reduction |
| 学位专业 | 材料化学 |
| 中文摘要 | 该文对氢氧化镍浆化氢还原制备纳米金属镍粉的反应机理及表观反应动力学进行了研究.首先对硫酸镍和氢氧化钠溶液混合后得到的氢氧化镍前驱物的构成进行了研究.采用此法制纳米金属镍粉是一个复杂的气-液-固三相反应.实验表明，动力学曲线呈S型.各反应参数如温度、催化剂用羄147L俊⒔涟枳佟⒔褐心俊⑶夥盅沟榷哉龇从λ璧氖奔渚杏跋?研究表明，该反应受传质的影响较大，反应重现性的好坏甚至能否进行等都与传质状况有关. |
| 英文摘要 | The reaction mechanism and kinetics of preparing nanometer-sized nickel powders by hydrothermal hydrogen reduction of fresh Ni(OH)_2 slurries were studied. The compositions of hydrothermal precursors and samplings at different reaction steps were examined by XRD and FT-IR. The obvious differences among their compositions at different amount of alkaline added were found: 80% of' stoichiometric alkali added, the compositions of precursor and samplings were basic nickel sulfate (the formula is Ni(SO_4)_(0.3)·(OH)_(1.4)); 90% added, the compositions of precursor were nickel hydroxide (the formula is Ni(OH)_2) and few basic nickel sulfate, the compositions of samplings at the reaction fraction≥0.25 were nickel hydroxide; 100-130% added, the compositions were nickel hydroxide. The calculation and measurement indicated the concentration of nickel ions in the solution at pH>12 was less than 1.0 mg/1. It's consumed the reaction mechanism at pH>12 was different from that at pH<7, which was based on a process of nickel hydroxide dissolution and reduction of Ni~(2+) ions. The various nickel hydroxides with different morphology and size were selected to be reduced by hydrogen. The samplings at different reaction steps were examined by SEM and TEM. The results at pH>12 indicated that there were similarity in the morphology and size of nickel particles and their parent precursors, but the results at pH<7 were reverse. This may confirm that the mechanism of hydrogen reduction of Ni(OH)_2 slurry at pH>12 was a heterogenous reaction of Ni(OH)_2 solid particles and activated hydrogen occurred at the surface of Ni(OH)_2. The present preparation of nanometer-sized nickel powders involved complex gas-liquid-solid reaction. The curve of kinetics was S-type. The reaction may be separated into the initial-stage, the medium-stage and the late-stage. In the initial-stage, the apparent reaction rate was limited by the rapidity of transferring activated hydrogen to the surface of nickel hydroxide by impact and the number of efficient impacts. In the medium-stage, the apparent reaction rate was determined by the rate of reaction between nickel hydroxide and activated hydrogen. In the late-stage, the rate was controlled by the rapidity of transferring activated hydrogen to the inner of nickel hydroxide. Temperature, the amount of catalyst, stirring speed, the content of nickel in the slurries and hydrogen pressure had effects on the apparent reaction rate. The optimum conditions for the reduction were proposed as follows: temperature>180℃, the amount of catalyst≥2mg/l, stirring speed≥600min~(-1), the content of nickel in the slurries≤40g/l and hydrogen pressure≥2.0MPa. It took about 30 min to finish the reaction under the conditions. The impeller pattern played an important role on the apparent reaction rate. The Rushton turbine(RT), marine propeller(MP) and pitched blade turbine (PBT) were selected to do the experiments. The PBT offered the highest reaction rate. |
| 语种 | 中文 |
| 公开日期 | 2013-09-26 |
| 页码 | 72 |
| 源URL | [http://ir.ipe.ac.cn/handle/122111/1893]  |
| 专题 | 过程工程研究所_研究所（批量导入） |
| 推荐引用方式 GB/T 7714 | 徐菊. 水热氢还原法制备纳米金属镍粉的非均相反应机制研究[D]. 中国科学院研究生院. 2001. |
入库方式： OAI收割
来源：过程工程研究所
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