【作者】 郭艳辉；

【导师】 陈纪忠；

【作者基本信息】 浙江大学 ， 化学工程， 2008， 博士

【摘要】 微细铜粉导电、导热性能优异，低价易得，在现代工业及国防诸多领域有广泛的应用。目前已在导电涂料、防静电填料、微电子材料、电磁屏蔽材料、高级润滑剂等方面有具体应用。但由于尺寸小活性高，微细铜粉在空气中容易氧化，而一经氧化，铜粉就失去了许多优异的性能。本文通过观测分析铜粉在150～600℃的空气中氧化所得产物的形貌和结构，提出了不同温度段微细铜粉空气氧化历程的模型，在此基础上进一步推导了各温度段铜粉氧化增重的表达式；铜粉在150～600℃间空气氧化增重的实验数据回归模拟表明，所得公式能够较好地反映铜粉在该温度段的空气氧化规律。研究结果显示微细铜粉在较低温度下（150～300℃）氧化时生成的氧化膜较致密，反应阻力主要源于氧化物晶格和氧化物中的“小孔”对铜离子迁移的阻碍，其氧化增重由抛物线和对数两部分组成，随着温度的提高，对数部分所占比重不断增加；中温阶段（250～400℃）时氧化物中的“小孔”较多，氧化增重主要服从对数规律；在高温阶段（500～600℃）由于应力作用氧化层产生大量裂缝，加速了氧化的进行，产物先线性快速增重，基本氧化完全后增重速度减慢。为了提高铜粉的抗氧化性，本文首先开发了多种聚苯胺包覆铜粉的方法，制备得到了不同包覆形貌的复合物，结果表明聚苯胺包覆可有效地提高铜粉的抗氧化性能。在非催化包覆法中将过硫酸铵（APS）的水溶液直接滴加到铜粉／苯胺的悬浊液中进行反应，结果显示反应中过硫酸铵将与铜反应，使其转化为Cu²⁺。实验进一步采用表面活性剂预处理、预氧化、苯骈三氮唑（BTA）预处理三种方法对铜粉进行预保护，然后再进行聚合反应。结果显示，表面活性剂预处理不能有效地保护铜粉，制备产物包覆效果较差；预氧化及BTA预处理保护效果较好，预氧化处理法最终得到产物的包覆层致密完整、表面光滑，BTA处理法得到产物的包覆层完整、呈纤维状。在催化氧化包覆法中，实验将APS与H₂O₂的混合液不断滴加到铜粉／苯胺悬浊液中，快速高效地制备了聚苯胺包覆层。本文认为包覆过程主要反应为：其中铜离子由反应Cu+S₂O₈^2-=Cu²⁺+2SO₄^2-生成，在铜离子的催化作用下苯胺被H₂O₂氧化生成聚苯胺，并在铜粉表面沉积形成了包覆层。实验制备的聚苯胺／铜复合物在程序升温的空气中均经历了先失重后增重的过程，失重段对应包覆层在空气中的挥发、分解，随着聚苯胺包覆层的破坏铜粉的氧化不断加剧。实验制备得到的半氧化状态聚苯胺包覆层可以使铜粉的起始抗氧化温度由200℃提高到335℃，进一步的保护作用可持续到400℃。实验尝试了用氧化铁包覆铜粉以对其改性的方法，结果表明改性后铜粉的抗氧化性能有一定的提高，但在处理过程中部分铜粉被氧化生成了氧化亚铜。实验最后用KSCN水溶液处理铜粉，使其表面部分铜转化为了β-CuSCN并包覆于铜颗粒表面。结果表明β-CuSCN包覆层为双层结构，外层为块状附着的β-CuSCN，内层为与铜粉紧密相连、致密的β-CuSCN三维结构薄膜包覆层；内层β-CuSCN对铜粉起着最直接的保护作用，块状附着层对致密层有修复作用，可以延长对内核的保护。热重显示，β-CuSCN的包覆可明显提高铜粉的抗氧化性能，处理后铜粉的起始氧化温度可由200℃提高到390℃左右。本文认为该法包覆层的生成反应为：4Cu+O₂+4SCN^-+2H₂O=4CuSCN+4OH^-。滴加酸可以消耗生成的碱从而促使上述反应向生成CuSCN的方向移动，形成完整的β-CuSCN保护膜，但H⁺用量过多会使部分铜将被氧化为Cu²⁺，实验发现酸用量与KSCN等摩尔时效果最好。更多还原

【Abstract】 Copper powder has excellent electric and thermal conduction and low price. Nowadays it is widely used in modern industry and defense-related technology such as conducting paint, electrostatic dissipation stuff, microelectronics material, electromagnetic interference （EMI） shielding, advanced lubricant, etc. However micron or nano size copper powder is very active and can be oxidized by air easily. After being oxidized, copper powder will lose lots of its fine properties.In this paper, the morphology and structure changes of fine copper powder during its oxidization between 150-600℃were observed. Then the processes of the oxidation of fine copper powder were proposed. Based on these models, new kinetic equations were deduced to simulate the oxidation process. The analog results agree well with the data gained from the oxidation of copper.Results show the oxidation patterns are not the same in different temperature ranges. In low temperature range （150-300℃） the oxide film is compact, the reacting resistances mainly come from the penetration of copper ion through the crystal lattice and "minipore" of oxide; the weight-gain was composed of two parts: parabolic part and logarithmic part, and the logarithmic part increases with increasing the temperature. In middle temperature range （250-400℃）, there are a lot of "minipores" in the oxide, the oxidation follows the logarithmic rate law. In high temperature range （500-600℃）, the huge inner stresses in the oxide will induce many cracks which are benefit for the oxidation, the oxidation follows the linear rate law in the beginning and then its speed slows down when most of the copper is oxidized.To improve copper powder’s oxidation resistance, several methods were tried to coat copper powder with polyaniline, and the products made were of different morphologies. Results show that polyaniline coating is benefit to improve the oxidation resistance of copper powder.Firstly, non-catalytic coating method was tried, Ammonium persulfate （APS） was added into aniline/copper particles suspension. Results show that copper will be corroded by APS during the process. To avoid this shortage, before the polymerization, copper powder was pretreated by surfactant, oxidation, inhibitor Benzotriazole （BTA）. Results show that the surfactants cann’t protect copper powder thoroughly and promote the formation of coating layer, but pre-oxidation and BTA pretreatment are effective. In the pre-oxidation method, the final coating layer is compact and smooth. And BTA pretreatment method could form fiber liked polyaniline coating layer.In catalytic oxidation method, APS and H₂O₂ solution was added into aniline/copper particles suspension to produce polyaniline coating on copper powder. In the method, it isassumed that the main reaction is Cu²⁺ ionis produced by the reaction Cu+S₂O₈^2-=Cu²⁺+2SO₄^2-, and with the catalysis of Cu²⁺, aniline was oxidized by hydrogen peroxide to form the polyaniline coating layer on copper particles.The polyaniline/copper composites undergo weight loss stage and then weight-gain stage in air. The weight loss stage may correspond to the loss of bound water, oligomer and the decomposition of polyaniline. The weight increases rapidly with decomposition of polyaniline. The half oxidize polyaniline could improve the starting oxidation temperature from 200℃to 335℃, and the protection can continue to 400℃.In another experiment, copper particles were coated by ferric oxide. Result shows that the oxidation resistance can only be improved a little by this modification, and some copper was oxidized into cuprous oxideAt last, fine copper powder was treated by potassium rhodanate solution andβ-CuSCN coating layer was produced. It is found that theβ-CuSCN coating film has two layers: the outer is block coating layer, the inner is a thin three dimensional polymer layer composed of close-packedβ-CuSCN units. It is the inner layer that directly protects the copper; the outer one could repair the inner layer as it is damaged. The thermal analysis shows that theβ-CuSCN layer can apparently improve the oxidation resistance of copper powder. After the treatment the oxidation starting temperature of copper powder could be improved from 200℃to around 390℃.The coating layer forming reaction is 4Cu+O₂+4SCN^-+2H₂O=4CuSCN+4OH^-. Adding acid could remove the alkaline generated and benefit the generation of CuSCN, but if it is too much, copper will be corroded into Cu²⁺. The optimal H⁺: SCN^- ratio is 1:1.更多还原