【作者】 苏青青；

【导师】 胡文彬；

【作者基本信息】 上海交通大学 ， 材料学， 2010， 硕士

【摘要】 碳纤维增强铜基复合材料具有优异的导电、导热、减磨和耐磨性能以及较低的热膨胀系数,在航空航天、机械和电子等领域具有广泛的应用前景。短碳纤维增强铜基复合材料的制备工艺一般采用粉末冶金法,由于碳纤维与铜粉间密度相差很大,球磨混合难以得到组织结构均匀和性能优异的碳纤维增强铜基复合材料。本文尝试采用碳纤维表面金属化新工艺预先制备短碳纤维/铜复合丝,后采用粉末冶金法制备短碳纤维增强铜基复合材料。此外,对采用空气氧化法进行碳纤维表面改性处理时,煅烧温度对表面含氧活性官能团的影响进行了分析,获得了碳纤维表面含氧活性官能团最多时的处理工艺参数。在此基础上,从外加电压和官能团两个角度出发,探讨了短碳纤维电镀铜的沉积机理。碳纤维表面金属化可采用化学镀工艺。目前化学镀铜多采用以甲醛为还原剂的配方体系,虽然这种方法较为成熟,但甲醛本身具有毒性。本论文尝试采用以次磷酸钠为还原剂的化学镀铜工艺制备了界面结合良好、镀铜层厚度均匀的短碳纤维/铜复合丝。对短碳纤维增强铜基复合材料的密度、导电性、导热性、热膨胀性以及纤维硬度进行测试,得到以下实验结果:碳纤维体积含量为10.2%时复合材料导电性(沿纤维轴向)最好,可达纯铜导电性的85%。分别在30oC和200oC下测量复合材料的导热率(沿纤维轴向),测得当短碳纤维体积含量为10.2%时,复合材料的导热性能最好,对应的导热系数分别为47.9 W/m K、67.9 W/m K。复合材料的热膨胀系数随着短碳纤维含量的增加而减小,当温度变化区间为30oC-100oC时,30%含量的碳纤维/铜复合材料的热膨胀系数最小,为13.9×10-6/K;当温度变化区间为30oC-200oC,最小的热膨胀系数为15.2×10-6/K。当纤维体积含量为30%时,短碳纤维增强铜基复合材料的显微硬度为121HV。未经过改性处理的碳纤维表面惰性大、表面能低,缺乏有化学活性的官能团,因而与基体材料进行复合时,常因界面结合不好而影响复合材料性能的发挥。无论采用化学镀还是电镀法制备短碳纤维增强铜基复合材料时,我们希望在碳纤维表面含氧活性官能团最多时进行表面金属化工艺。工业中常使用电化学氧化法将活性含氧基团引入碳纤维表面,但这种方法的后续处理工作十分繁琐,因此本文采用空气氧化法对碳纤维表面进行氧化处理。将经过不同煅烧温度对碳纤维进行1小时煅烧处理后的碳纤维进行XPS、FTIR等检测,得出以下结论:经400 oC煅烧1小时处理后,在保持碳纤维原有状态的基础上,碳纤维表面含氧活性基团-OH和C=O最多。论文对比分析了电压及表面活性官能团对电镀铜形貌的影响,尝试探讨了在短碳纤维表面电镀铜的沉积机理,并得出以下结论:对于电镀铜来说,外加沉积电位以及活性基团自身更低电极电位的加成作用才是反应的驱动力,因此当外加电位较低时,只有具有活性基团的位置才能发生反应沉积出铜,其他位置由于不能满足反应所需的最小驱动力而不能反应。当电位增大,活性官能团的促进作用逐渐不明显,由沉积电压控制的初始形核过程占主导地位,发生均匀形核过程,表面获得均匀光滑沉积层。更多还原

【Abstract】 Because of their excellent electrical、thermal conductivity and other properties, short carbon fiber reinforced Cu-based composites are widely used in the field of spaceflight, aviation, machine, electron, chemical industry, etc. Nowadays, powder metallurgy is a common-used method for acquiring the C/Cu composite. However, the homogeneity between the SCFs and Cu matrix is bad,which will cause the overall properties of the composites bad, restricting the short carbon fiber reinforced Cu-based composites further growth. A new method of pretreatment was used to make the SCFs/Cu composite filament. Then, powder metallurgy method was used to make the short carbon fiber reinforced Cu-based composites. Besides, we get the relationship between the surface oxygenic functional groups and the calcinations temperature, one of the most important parameters of air oxidation process. From the experimental result, optimum technology was acquired. In the end, we try to discuss the mechanism of the electro-copper plating from the perspectives of applied voltage and surface oxygenic functional groups respectively.Electro-less plating and electro plating are the wildly used methods. The electro-less copper plating with formaldehyde as reducing agent is a common method. However, because the reducing agent is a kind of toxic substance, this method is not environmentally friendly and unhealthy. We use the electro-less copper plating with sodium hypophosphite as reducing method to acquire the C/Cu composite wires, which are both environmental protection and healthy. In addition, the relationship between microstructure and properties, such as density, electrical conductivity, thermal conductivity, thermal expansivity and the HV value, is analyzed. Results were as follows: the electrical conductivity along the axis of the SCFs can reach 85% of the pure Cu, when 10.2% of the composites are the SCFs; Thermal conductivity is the best along the axis when 10.2% of the composites are the SCFs. The values are 47.9 W/m K at 30oC、67.9 W/m K at 200oC, respectively. In regard to the thermal expansivity, the best value appears when 30% of the composites are the SCFs. And the specific values are 13.9×10-6/K from 30oC to 100oC, 15.2×10-6/K from 30oC to 200oC. HV value can reach 121HV when the percent by volume of the SCFs is 30%.Carbon fibers untreated are surface inactive, low surface energy, and less oxygen functional groups. So, it will restrict the development of the composites because of the poor fiber/Cu interfacial adhension. We expect to make the SCFs metal-coated surface in the condition of the most oxygen functional groups both of adopting electroplating and electro-less plating method. Electrochemical oxidation is a commonly used method in daily industrial production. However, the follow-on work is cockamamie as well as inefficient while the air oxidation process is so convenient that we choose it as the method of surface treatment of SCFs. In this paper, we find the relationship between the calcining temperature and the quantity of the surface oxygenic functional groups. The XPS and FTIR show that there are the most oxygen-containing active function group, such as–OH and -C=O, when the calcining temperature is 400oC. In addition, we find that the driving forces of the reaction of the electro-plating are the applied voltage and the surface oxygenic functional groups. When the applied voltage is too low to promote the common reaction, only the positions which pocess the surface oxygenic functional groups can be deposited copper. This means that the surface oxygenic functional groups can lower the electrode potential of the carbon fibers. Then, the surface oxygenic functional groups will be weakened as the applied voltage is increased big enough to get the smooth Cu coating.更多还原