多壁碳纳米管（MWNTs)增强铝基复合材料的制备及力学性能研究

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	多壁碳纳米管（MWNTs)增强铝基复合材料的制备及力学性能研究
	许世娇
学位类型	硕士
导师	肖伯律 ; 马宗义
	2012
学位授予单位	中国科学院金属研究所
学位授予地点	北京
学位专业	材料工程
关键词	碳纳米管铝硝酸处理高能球磨粉末冶金 Carbon Nanotubes Aluminum Nitric Acid Treament High Energy Ball-milling Powder Metallurgy
摘要	"航空航天与交通运输等领域的发展，对高性能轻质材料需求十分旺盛。铝基复合材料因其优异的力学与物理性能，已成为一类重要的工程材料，在上述领域中具有广阔的应用前景。碳纳米管（CNTs）具有优异的力学和导电导热等综合性能，是铝基复合材料理想的增强体。但由于缺乏有效的分散方法，CNTs的优异性能难以完全发挥。为实现CNTs的有效分散并提高其增强效果，本研究分别选用浓硝酸处理和高能球磨来分散CNTs，并用粉末冶金工艺制备了CNTs增强铝基（CNT/Al）复合材料。系统地研究了硝酸浸泡时间、球磨时间对不同体积分数CNTs的分散效果和损伤的影响，以及由此引起的CNT/Al复合材料微观结构和力学性能的变化。主要研究结果如下：采用硝酸对CNTs进行切断和官能化处理，并结合超声分散将CNTs与铝粉混合。随着硝酸处理时间的延长，CNTs的团聚数量逐渐减少，但损伤程度随之增加。微观结构观察和复合材料拉伸性能测试表明8 h为酸处理的最佳时间。选择8 h硝酸处理的CNTs制备了0.75 vol.%和1.5 vol.%CNT/2009Al复合材料，屈服强度分别为338和346 MPa，比基体材料提高了11.2 %和13.8 %。从微观组织观察结果来看，由于混合过程引起的CNTs团聚以及铝粉表面积较小，硝酸处理方法难以使高含量的CNTs在铝粉中均匀分散。采用高能球磨对CNTs和铝粉进行球磨。随着球磨时间从2 h增加到12 h，CNTs逐渐分散，但CNTs的损伤也随之增加。采用粉末冶金工艺将不同球磨时间的混合粉末制备了0.75 vol.%CNT/Al复合材料。拉伸测试表明，随着球磨时间的增加，CNT/Al复合材料的屈服和抗拉强度连续增加，但延伸率却先增加后下降，在球磨6 h时达最大值。去除铝粉的应变硬化因素，CNTs的增强效率在球磨时间为6 h时达到了最大值，强度相对于同样工艺下制备的基体材料提高了42.3 %。选择6 h的球磨时间制备了0.75, 1.5, 3 vol.% CNT/Al复合材料，微观结构分析表明，当CNTs含量为0.75 和1.5 vol.%时，CNTs在复合材料中分散均匀，但当含量增加到3 vol.%时，则出现了较多的CNTs团聚。拉伸实验表明，CNTs含量为1.5 vol.%时，力学性能达到了最大值，屈服强度相对于纯铝基体提高了53.6 %。理论计算和实验值对比研究表明，细晶强化和载荷传递为CNT/Al复合材料的主要强化机制。
其他摘要	"The development of aviation, aerospace, transportation and other industries have a strong demand for high performance and lightweight materials. Aluminum matrix composites (AMCs) have became one of the important engineering materials and possessed a wide application prospect in the above-mentioned fields for their excellent mechanical and physical properties. Carbon nanotubes (CNTs) are the ideal reinforcement of AMCs for their excellent mechanical, conductive and other comprehensive properties. However, the superior reinforcing effect of CNTs cannot be achieved completely in AMCs due to lacking of effective dispersion method. To improve the dispersion uniformity and strengthening effect of CNTs, nitric acid treatment and high energy ball-milling were chosen to disperse CNTs respectively, and CNTs reinforced aluminum (CNT/Al) matrix composites were fabricated via powder metallurgy (PM) route in this study. The effect of nitric acid soak time and ball-milling time on dispersion and damage of CNTs and the microstructure and mechanical properties of CNT/Al composites were investigated systematically. CNTs were cut and functionalized by nitic acid treatment and then mixed with Al powders combining with ultrasonic dispersion. As the refluence time increased, the CNT clusters gradually decreased, but the damage degree increased. Microstructure and tensile tests showed that 8 h was the best refluence time. 0.75 vol.% and 1.5 vol.%CNT/2009Al composites were fabricated using the CNTs that were acid treated for 8 h. Tensile tests indicated that the yield strength (YS) of the 0.75 vol.% and 1.5 vol.%CNT/2009Al composites reached 338 and 346 MPa, which increased by 11.2 % and 13.8 %, respectively, compared with that of the unreinforced matrix alloy. From the results of microstructure observation, it was concluded that the nitric acid treatment was difficult to uniformly disperse the high content CNTs in Al powders because of the CNT clusters caused by mixing process and the small surface areas of Al powders. The mixture powders of CNTs and Al were subjected to high energy ball-milling. CNTs were gradually dispersed into the Al matrix, but damaged seriously as ball-milling time increased from 2 h to 12 h. The mixture powders were ball-milled for different times, and then consolidated via the PM process. The tensile tests showed that as the ball-milling time increased, the YS and ultimate tensile strength (UTS) of the CNT/Al composites increased continuously, while the elongation increased first and then decreased after 6 h ball-milling. By deducting the contribution of the strain hardening of the Al matrix, it was found that the strengthening of CNTs reach the maximum at 6 h ball-milling time, the YS of the composite increased by 42.3 % compared with that of the matrix with the same processing history. The CNTs and Al mixture powders with different CNT contents (0.75, 1.5 and 3 vol.%) were ball-milled for 6 h and then were consolidated via the PM process. Microstructure examinations showed that the CNTs in the composites could be uniformly dispersed when the CNT content was 0.75 and 1.5 vol.%. However, lots of CNT clusters were formed when the CNT addition reached to 3 vol.%. Tensile tests indicated that 1.5 vol.% CNT/Al composite exhibited the highest tensile properties, and the YS was improved by 53.6 % compared with that of the Al matrix. Both grain refinement and load transferring were proved to be the main strengthening mechanisms of the CNT/Al composites by comparing the theoretical calculation and experimental results.
文献类型	学位论文
条目标识符	http://ir.imr.ac.cn/handle/321006/64554
专题	中国科学院金属研究所
推荐引用方式 GB/T 7714	许世娇. 多壁碳纳米管（MWNTs)增强铝基复合材料的制备及力学性能研究[D]. 北京. 中国科学院金属研究所,2012.