铜包钨复合粉体的电沉积制备技术的研究

发布时间：2018-06-16 11:55

本文选题：铜包钨粉 + 粉体电镀　；参考：《湖南大学》2014年硕士论文

【摘要】：铜包钨粉是广泛应用于电接触材料、电极材料、军工材料、高密度合金以及电子封装和热沉材料等领域的先进包覆粉体复合材料。采用电镀的方法制备铜包钨粉克服了传统的化学镀方法出现的施镀效率低，镀液循环性差，产品不纯，环境污染等缺陷。本文以粒径分布3-16m钨粉为基体，采用间歇电镀的方法制备铜包钨粉，研究了电镀制备铜包钨粉的工艺和大超电势下铜的成核机理。并研究了铜包钨粉对钨铜复合材料显微组织结构及性能的影响。采用扫描电镜（SEM）、能谱分析（EDX）、X射线衍射仪（XRD）等测试手段对复合粉体表面形貌、镀层表面的元素及相组成进行了分析。具体研究成果如下： 1、获得了合适的电镀工艺，CuSO460g dm 3，浓H2SO440cm3dm 3，十二烷基硫酸钠0.1g dm3，控制8-12g·dm3钨粉装载量，用12-16A·dm2阴极电流密度，在20-30h1搅拌频率下对钨粉施镀，可以制得包覆完好的铜包钨粉复合粉体。镀层平均厚度约为2.5m，铜含量可达到54.3wt%，钨铜复合粉体的制备效率大大提高。 2、铜离子在钨粉表面能量低的地方呈点状沉积，然后不断生长，最后扩展到整个钨粉表面形成包覆层，镀层均匀致密；EDX和XRD结果显示复合粉体中无杂质存在，表面的铜镀层以晶态形式存在，镀层较厚且包覆完整。 3、施加合适的电流密度和搅拌频率能够有效地控制铜在粉体上电镀，合适的搅拌频率，可以避免电镀过程钨粉的团聚现象，将电镀钨粉打碎并重新分散，，促使内层粉体与表层粉体不断地变化、转换，保证粉体受镀的均匀性。 4、大超电势下铜的成核遵循瞬时成核机理，且沉积电势越负，铜的成核越向瞬时成核曲线方向偏移。大的电流密度下铜的成核密度大，有利于在大比表面积的钨粉表面形成均匀致密的铜镀层。 5、研究了有机添加剂在电解液中的作用，适量聚乙二醇能有效增大阴极极化，增大电化学反应电阻，提高极化超电势，使铜电结晶的成核尺寸减小，从而获得均匀致密的铜镀层。 6、铜包钨粉能够改善钨铜复合材料的组织均匀性，降低材料的孔隙度。铜基体形成连续三维导电网络结构，钨颗粒更趋弥散，增强了铜、钨间的界面结合力。钨铜复合材料的密度、硬度和导热导电性显著提高，热膨胀系数明显降低，钨铜复合材料的性能有显著提高。
[Abstract]:Copper coated tungsten powder is an advanced coated powder composite which is widely used in the fields of electrical contact materials, electrode materials, military materials, high density alloys, electronic packaging and heat sink materials. The preparation of copper coated tungsten powder by electroplating overcomes the disadvantages of the traditional electroless plating methods such as low plating efficiency, poor cycling of bath, impure products and environmental pollution. In this paper, copper coated tungsten powder was prepared by intermittent electroplating using 3-16m tungsten powder with particle size distribution as substrate. The preparation process of copper coated tungsten powder and the nucleation mechanism of copper under large superpotential were studied. The effect of copper-coated tungsten powder on microstructure and properties of tungsten-copper composite was studied. The surface morphology, elements and phase composition of the composite powder were analyzed by means of SEM and EDXX X ray diffractometer (XRD). The specific research results are as follows: 1. The suitable electroplating process of CuSO4 60g dm ~ (3), concentrated H _ 2SO _ 4 _ (40) cm ~ (3) cm ~ (-3), sodium dodecyl sulfate 0.1 g / dm ~ (3), controlling the loading amount of 8-12g dm3 tungsten powder, using 12-16A dm2 cathode current density, plating tungsten powder at 20-30h1 stirring frequency, has been obtained. Copper-coated tungsten powder composite powder can be prepared. The average thickness of the coating is about 2.5 m, the copper content can reach 54.3 wts. the preparation efficiency of the W-Cu composite powder is greatly improved. 2. The copper ion deposits in the place of low energy on the surface of tungsten powder and then grows continuously. The results of edX and XRD show that there is no impurity in the composite powder, and the copper coating on the surface exists in the form of crystal. The coating is thicker and the coating is intact. 3. The appropriate current density and stirring frequency can effectively control copper electroplating on the powder, and the appropriate stirring frequency can avoid the agglomeration of tungsten powder in the electroplating process. Breaking and redispersing the electroplated tungsten powder can cause the inner layer powder and the surface powder to change, transform, and ensure the uniformity of the powder plating. 4. The nucleation of copper follows the instantaneous nucleation mechanism under large superelectromotive force, and the deposition potential is more negative. The nucleation of copper shifts to the instantaneous nucleation curve. Under the condition of high current density, copper has high nucleation density, which is conducive to the formation of uniform and dense copper coating on tungsten powder with large specific surface area. 5. The role of organic additives in electrolyte was studied. Proper amount of polyethylene glycol can effectively increase the cathode polarization, increase the electrochemical reaction resistance, increase the polarization superpotential, and reduce the nucleation size of copper electrocrystallization. 6. Copper coated tungsten powder can improve the microstructure uniformity and decrease the porosity of tungsten copper composite. The copper matrix forms a continuous three-dimensional conductive network structure, and the tungsten particles become more dispersive, which enhances the interfacial adhesion between copper and tungsten. The density, hardness, thermal conductivity and thermal expansion coefficient of tungsten and copper composites were improved significantly, and the properties of tungsten and copper composites were improved significantly.
【学位授予单位】：湖南大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TB331;TB44

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