高压水热还原法制备超细高纯铜粉的实验研究

发布时间：2018-04-13 04:07

  本文选题：微晶纤维素 + 水热还原　； 参考：《辽宁科技大学》2017年硕士论文

【摘要】：基于超细粉体的小尺寸效应、量子尺寸效应、表面效应和宏观量子隧道效应等优异特性,超细铜粉可用作替代MLCC贵金属内电极的理想材料,在制作导电涂料、高级润滑油添加剂、催化剂及纳米铜材料方面也具有广泛的应用前景。目前制备超细铜粉的工艺方法主要有气相沉积法、机械化合法、电解法及液相还原法等,这些制备方法在产品纯度和颗粒度、生产成本、还原效率及环保等方面都各自存在着难以克服的缺点。因此,本研究提出了高压水热还原法制备超细铜粉的工艺思路,在高压反应釜内,以微晶纤维素作为还原剂,水热还原氧化铜粉制备球形超细铜粉。高压水热还原工艺对环境无污染,所得产品纯度高,粒径小,粒度分布窄而均匀。本文探讨了纤维素水热还原氧化铜的反应机制;利用XRD、SEM、激光颗粒分布测量仪等分析测试手段研究了反应温度、反应时间、还原剂用量、催化剂用量、液固比和搅拌速度对产物铜粉的纯度、物相组成、微观结构及粒度分布的影响,并对氧化铜的高压水热还原过程进行动力学分析,得出如下结论:(1)微晶纤维素在碱性溶液中可分解为低级羧酸、醛酮类产物,并进一步水解并放出H·形成还原性的水热介质,在水热介质中按CuO→Cu2O→Cu进程逐级还原。(2)在反应温度为220℃、反应时间为2h,微晶纤维素、CuO和NaOH质量比为6:5:5,液固比为4:1,转速为300r/min时,可制得纯度为99%以上的高纯铜粉。(3)水热还原过程的动力学研究表明,微晶纤维素水热还原CuO反应的表观活化能E=65.996kJ/mol,反应过程的速率限制环节受化学反应控制。(4)原料及产物的微观形貌表明,CuO颗粒粒径为4.28×10-6m,呈多边形晶型结构;随着水热还原过程的进行,逐渐在CuO晶体表面形成球形的Cu颗粒。(5)还原温度升高,颗粒粒径显著减小,颗粒粒度趋于均匀且分布变窄。当反应温度为215~230℃时,Cu颗粒平均粒径为2.3~2.4×10-7m。
[Abstract]:Based on the excellent properties of ultrafine powder, such as small size effect, quantum size effect, surface effect and macroscopic quantum tunneling effect, ultrafine copper powder can be used as an ideal material to replace MLCC noble metal internal electrode in making conductive coatings.High-grade lubricating oil additives, catalysts and nano-copper materials also have a wide range of applications.At present, the main methods of preparing ultrafine copper powder are vapor deposition, mechanization, electrolysis and liquid phase reduction, etc. These preparation methods are used in product purity and particle size, production cost, etc.Reduction efficiency and environmental protection have their own shortcomings which are difficult to overcome.Therefore, in this study, the technological idea of preparing ultrafine copper powder by high pressure hydrothermal reduction method was put forward. In the autoclave, the spherical ultrafine copper powder was prepared by hydrothermal reduction of copper oxide powder with microcrystalline cellulose as reducing agent.The high pressure hydrothermal reduction process has no pollution to the environment. The product is of high purity, small particle size and narrow and uniform particle size distribution.In this paper, the mechanism of hydrothermal reduction of copper oxide with cellulose was discussed, and the reaction temperature, reaction time, amount of reductant, amount of catalyst, and so on were studied by means of XRDX SEM and laser particle distribution analyzer.The effects of liquid-solid ratio and stirring speed on the purity, phase composition, microstructure and particle size distribution of copper powder were studied.It is concluded that microcrystalline cellulose can be decomposed into lower carboxylic acids, aldehydes and ketones in alkaline solution, and further hydrolyzed and released to form a reductive hydrothermal medium.When the reaction temperature is 220 鈩，

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