Preparation and properties of Cu matrix composite reinforced by carbon nanotubes

Cu matrix composites reinforced by carbon nanotubes(CNTs) were prepared. The effect of carbon nanotubes on mechanical and tribological properties of the Cu matrix composites were investigated. The chemical method for coating CNTs was reported. The morphology of the fracture surfaces and worn surface were examined by SEM.The results show that Cu/coated-CNTs composites have higher hardness, much better wear resistance and antifriction properties than those of the reference Cu alloy (Cu-10Sn) and Cu/uncoated-CNTs composite sintered under the same conditions. The optimal mechanical properties of the composites occurred at 2. 25%(mass fraction) of CNTs. The excellent wear resistance and anti-friction properties are attributed to the fiber strengthening effect of CNTs and the effect of the spherical wear debris containing carbon nanotubes on the tribo-surface.     

碳纳米管增强铜基复合材料的制备、力学性能及电导率

以CNTs、电解Cu粉、Cu(CH_3COO)_2·H_2O为原料,采用混酸处理、分子水平法结合行星球磨两步混合工艺制备含0.5%～2%(质量分数)CNTs的Cu基复合粉末,然后通过放电等离子烧结技术制备了Cu-CNTs复合材料,探讨了制备工艺及CNTs含量对Cu-CNTs复合材料的组织、电导率和力学性能的影响规律。结果表明:当CNTs含量小于1.0%时,采用两步混粉工艺制备的Cu-CNTs复合粉体均匀性、分散性良好,经烧结后可获得致密度高、CNTs分布均匀的Cu-CNTs复合材料;当CNTs含量大于1.0%时,复合材料的致密度及CNTs分布均匀性明显降低;随CNTs含量的提高,复合材料的强度先升高后降低,塑性和电导率趋于降低;相对高能球磨、分子水平法等单一混粉工艺而言,两步法制备的Cu-1.0%CNTs复合材料综合性能更优,其电导率为51.7 MS/m(89.1%IACS),维氏硬度为1130 MPa,抗拉强度为279 MPa,断后伸长率为9.8%。     

电流对碳纳米管增强铜基复合材料载流摩擦学性能的影响

采用粉末冶金方法在相同的工艺条件下制备纯铜和碳纳米管含量为10%（体积分数）的铜基复合材料。在一种销盘式载流摩擦磨损试验机上考察了不同电流条件下2种材料的载流摩擦磨损性能。结果表明：纯铜和铜基复合材料的摩擦系数和磨损率均随电流的增大而增大,但是电流对纯铜材料的影响更加显著;纯铜材料的主导磨损机制是电弧烧蚀磨损,而铜基复合材料的主导磨损机制是塑性流动变形;碳纳米管可以改善铜基复合材料的载流摩擦磨损性能。     

Friction and wear properties of copper matrix composites reinforced by tungsten-coated carbon nanotubes

Carbon nanotubes (CNTs) were coated by tungsten layer using metal organic chemical vapor deposition process with tungsten hexacarbonyl as a precursor. The W-coated CNTs (W-CNTs) were dispersed into Cu powders by magnetic stirring process and then the mixed powders were consolidated by spark plasma sintering to fabricate W-CNTs/Cu composites. The CNTs/Cu composites were fabricated using the simi-lar processes. The friction coefficient and mass wear loss of W-CNTs/Cu and CNTs/Cu composites were studied. The results showed that the W-CNT content, interfacial bonding situation, and applied load could influence the friction coefficient and wear loss of W-CNTs/Cu com-posites. When the W-CNT content was 1.0 wt.%, the W-CNTs/Cu composites got the minimum friction coefficient and wear loss, which were decreased by 72.1% and 47.6%, respectively, compared with pure Cu specimen. The friction coefficient and wear loss of W-CNTs/Cu composites were lower than those of CNTs/Cu composites, which was due to that the interfacial bonding at (W-CNTs)-Cu interface was bet-ter than that at CNTs-Cu interface. The friction coefficient of composites did not vary obviously with increasing applied load, while the wear loss of composites increased significantly with the increase of applied load.     

钛对碳纳米管增强铝基复合材料组织与性能的尺寸效应

通过粉末冶金的方法,制备了致密和较高强度的CNT/Al复合材料,并系统地研究了在制备粉末阶段时引入不同粒径的钛粉后,对复合材料的组织结构与力学性能的影响。结果表明,在一定范围内,钛颗粒尺寸与制备的CNT-Ti/Al复合材料力学性能成反比。当加入的钛颗粒粒径为80 nm时,CNT-Ti/Al复合棒材力学性能最佳。其主要原因包括两个方面:一是钛颗粒有助于碳纳米管的分散,同时自身作为一种第二相强化基体;二是制备过程的热反应,使复合材料组织中生成了一种核壳结构,极大地增强了其界面结合与碳纳米管的载荷转移。     

Gra./Cu和CNTs/Cu复合材料的截流值与阴极斑点研究

采用粉末冶金方法制备石墨铜复合材料(Gra./Cu)和碳纳米管铜复合材料(CNTs/Cu),研究2种铜基复合材料的真空电弧截流现象和阴极斑点特性。结果表明,与Gra./Cu相比,CNTs/Cu在真空放电过程中电弧更加稳定,且分散性好,截流值小;在正对阳极处CNTs/Cu的真空电弧烧蚀坑明显比Gra./Cu的细小,灼痕直径约为0.1～5μm,分布面积也较小,而Gra./Cu的灼痕直径为10～100μm;两者的相同之处在于,在电击穿过程中阴极斑点的运动呈一种随机的、突变式的跳跃,而且选择性发生在Cu相上,Cu相被消耗。总之,CNTs/Cu比Gra./Cu具有更高的耐电弧烧蚀能力,CNTs的加入可以有效地增加铜基复合材料的电弧稳定性和降低截流值。     

铝基体上碳纳米管原位均匀合成及其复合材料的性能

采用负载于铝粉上的镍催化剂,成功地在650℃通过化学气相沉积法在钳基体中原位合成碳纳米管。结构农征表明,所合成的碳纳米管具有较高的石墨化程度和平直的石墨壳层。通过该方法实现铝粉中碳纳米管的弥散分布,其分散效果优于传统机械混合方法。利用所合成的碳纳米管／铝原位复合粉末,采用粉末冶金工艺制备碳纳米管／铝基复合材料。性能测试表明,制备的复合材料的力学性能和尺寸稳定性得到显著提高,其原因在于铝基体中碳纳米管的均匀分散和碳纳米管－铝基体之间良好的界面结合。     

Fabrication,microstructures, and properties of copper matrix composites reinforced by molybdenum-coated carbon nanotubes

Multiwalled carbon nanotubes(CNTs) were coated by a molybdenum layer using carbonyl thermal decomposition process with a precursor of molybdenum hexacarbonyl.The Mo-coated CNTs(Mo-CNTs) were added into copper powders to fabricate Mo-CNT/Cu composites by means of mechanical milling followed by spark plasma sintering.The Mo-CNTs were uniform dispersion in the Cu matrix when their contents were 2.5 vol.%-7.5 vol.%,while some Mo-CNT clusters were clearly observed at additions of 10.0 vol.%-15.0 vol.% Mo-CNTs in the mixture.The mechanical,electrical,and thermal properties of the Mo-CNT/Cu composites were characterized,and the results showed that the tensile strength and hardness were 2.0 and 2.2 times higher than those of CNT-free specimens,respectively.Moreover,the Mo-CNT/Cu composites exhibited an enhanced thermal conductivity but inferior electrical conductivity compared with sintered pure Cu.The uncoated CNT/Cu composites were fabricated by the similar processes,and the measured tensile strength,hardness,thermal conductivity,and electrical conductivity of the CNT/Cu composites were lower than those of the Mo-CNT/Cu composites.     

球磨时间和转速对CNTs／Al-2024复合粉末变化的影响

通过机械球磨和热挤出的方法制备碳纳米管（CNTs）增强铝基复合材料。在2024铝合金中加入1％CNTs,并在不同条件下进行球磨。通过X射线衍射仪（XRD）、场发射扫描电镜（FESEM）以及力学性能测试等方法对球磨过的粉末和块体材料的显微组织的变化和力学性能进行测试。研究碳纳米管浓度和球磨时间对CNTs／Al-2024复合材料显微组织的影响。通过对显微组织的观察,讨论粉末在球磨过程中的变形行为。结果表明：在CNTs含帚相同的条件下,粉末颗粒尺寸随着球磨时间和转速的增加而减小,当球磨时间达到15h,粉末颗粒尺寸最小。由于CNTs的加入,铝合金复合材料的拉伸性能有所提高。     

碳纳米管增强TiNi复合钎料的制备与表征

针对CNTs增强TiNi复合钎料制备中存在CNTs的均匀分散性差、结构完整性差、碳基团与基体易反应而导致基体材料污染等问题,采用PECVD方法低温原位在Ni-TiH₂基体上制备CNTs/TiNi复合钎料,采用XRD,SEM,Raman,TEM等对制备的复合钎料进行表征与分析.结果表明,该方法不仅保证了复合钎料中CNTs的结构完美和均匀分散性,而且保证了TiH₂不会因温度过高分解,避免了复合钎料体系中钛与碳之间反应,真正意义上实现了CNTs对TiNi复合钎料的强化.通过复合钎料中CNTs的增强效果,缓解钎焊接头的残余应力,提高钎焊接头的力学、热学及高温性能,可实现陶瓷、复合材料与金属复合构件的可靠连接及高温使用.     

Effect of carbon nanotubes on corrosion of Mg-CNT composites

Carbon nanotubes (CNTs) may be added to Mg matrix to produce composites of better mechanical properties, but their effect on the corrosion behaviour is not well understood. The corrosion resistance of pure Mg and its composites reinforced with 0.3 and 1.3 wt.% CNTs was studied in 3.5 wt.% NaCl solution using immersion testing and electrochemical measurements. It was found that the corrosion rate was increased considerably by the presence of CNTs because of microgalvanic action between the cathodic CNTs and the anodic Mg matrix.     

Cu含量对CNTs/Al-Cu复合材料显微组织和压缩力学性能的影响（英文）

通过热压烧结和热轧制备碳纳米管(CNTs)增强的Al-Cu基复合材料,系统研究Cu含量对Al与CNTs的界面反应、含Cu沉淀物的析出行为及相应复合材料力学性能的影响。研究表明,提高Cu含量不仅能使复合材料制备过程中含Cu析出相的数量和尺寸增加,而且能促进CNTs与Al基体之间的界面反应,加剧CNTs转化为Al₄C₃。由于含有1%Cu(质量分数)的复合材料保持CNTs的原始结构,因此,它在所有复合材料中具有最高的强度、弹性模量和硬度。此外,增加Cu含量还能改变影响复合材料强度的主要强化机制。     

钨粉化学镀铜对W／15Cu电子封装材料性能的影响

采用化学镀铜的方法在钨粉中加入诱导铜，经压型，熔渗后制成W／15Cu合金。用扫描电镜研究了材料的显微结构，并测出合金样品的密度、气密性、热膨胀系数等物理性能，通过与传统工艺制备的W／15Cu合金的显微组织以及物理性能方面做比较，讨论了钨粉化学镀铜对W／15Cu合金性能的影响。结果表明，钨粉化学镀铜对于提高钨生坯成形性能、改善钨铜复合材料的显微组织结构、提高材料物理性能方面都有很大作用。经过综合比较，镀铜含量以2％为宜。     

Effect of Ball Milling on the Defeat of Few-Layer Graphene and Properties of Copper Matrix Composites

Graphene-reinforced copper composites recently have attracted more attention, since they exhibited excellent mechanical properties and could be used widely in many fields. Few-layer graphene （FLG） and copper powder were mixed by ball milling to produce homogeneous composite powders. Then, FLG-reinforced copper composites （FLG/Cu） were fabricated by spark plasma sintering （SPS） using the composite powders with a FLG volume fraction of 2.4 vol%. The effects of the rotating speed and the time of ball milling were analyzed based on the microstructure evolution and properties of the FLG/Cu composites. Obvious strengthening effect of FLG was found for the composites, and the conductance of the composite reaches 70.4% of IACS. The yield strength of the composite produced by ball milling at a speed of 100 r/rain for 4 h is 376 MPa, which is 2.5 times higher than that of copper and higher than that of copper composite enhanced by 5 vol% CNTs （360 MPa）. The defects produced in FLG with the increase of rotating speed and time could reduce the mechanical and conductive properties of the composites.     

Functionally graded carbon nanotubes/hydroxyapatite composite coating by laser cladding

Functionally graded carbon nanotubes/hydroxyapatite (CNTs/HA) composite coatings have been fabricated by laser cladding technique using CNTs/HA composite powders. As the feedstock for laser deposition, CNTs/HA composite powders were prepared by ball-milling different weight ratios (1%, 3% and 5%) of CNTs with HA powders. CNTs/HA composite coatings were fabricated with CNTs/HA composite powders and functionally graded coating was fabricated by sequentially depositing different CNTs/HA composite coatings on pure titanium. The phase composition, microstructure, micro-hardness, bonding strength and in vitro cellular responses of the composite coatings and the functionally graded composite coating were studied. The results show that the crystallinity of CNTs/HA composite coatings increased with increasing amount of CNTs in the powder mixture. The CNTs were dispersed homogeneously in the coatings to form an interconnected web and the cylinder graphic structure of CNTs was not changed after laser irradiation. Compared with pure HA coating, the maximum increase of the micro-hardness of CNTs/HA composite coatings was 46.8% and the micro-hardness of the functionally graded coating increased gradually through the thickness of this coating. Furthermore, the bonding strength of the functionally graded coating was nearly twice higher than that of pure HA coating. The in vitro cellular biocompatibility tests reveal that the functionally graded composite coating has comparable in vitro bioactivity with pure HA coating.     

成分和烧结温度对ZrO_2颗粒增强型钛基复合材料力学性能的影响

钛利用粉末冶金方法制备钛基复合材料。采用X射线衍射仪、金相显微镜、扫描电镜及力学性能测试仪研究材料成分和烧结温度对显微结构及性能的影响。结果表明：加入ZrO2颗粒能够提高粉末冶金钛基复合材料的力学性能。加入4%ZrO2,在1100°C下烧结4h,得到的钛基复合材料的相对密度为93.9%,屈服强度能达到1380MPa（比纯钛高570MPa）,并且具有良好的塑性（极限应变超过24%）。     

机械合金化对W-20Cu复合材料的显微组织与性能的影响

采用机械合金化结合粉末冶金技术制备W-20Cu（vo1％）复合材料。利用扫描电镜和金相显微镜对不同球磨时间的W-20Cu复合材料显微组织进行表征，并对材料的各项物理性能进行测试。结果表明，随着球磨时间的延长，W-20Cu烧结体的组织越来越均匀，Cu相分布也越来越均匀。W-20Cu烧结体密度、收缩率、硬度、抗弯强度随球磨时间的延长而增大；球磨20h的W-20Cu复合粉烧结体热导率达到峰值（130．61Wm^-1K^-1），继续球磨，热导率减小。综合考虑所有研究结果，通过机械合金化所制备的W-Cu复合粉体可以获得具有优异综合物理性能的W-20Cu复合材料。     

Improvement of mechanical properties of Sn-58Bi alloy with multi-walled carbon nanotubes

Carbon nanotubes (CNTs) reinforced Sn-58Bi composites were successfully fabricated through ball-milling method and low temperature melting process.The influence of multi-walled carbon nanotubes (MWCNTs) on the mechanical strength and ductility of Sn-58Bi lead-free alloy was studied.The mechanical test results show that the bending strength of Sn-58Bi-0.03CNTs (mass fraction,%) composite is increased by 10.5% than that of the Sn-58Bi alloy,which can be attributed to the reduction of Sn-rich segregation and the grain refinement.The toughness of Sn-58Bi-0.03CNTs composite is increased by 48.9% than that of the matrix materials.It is indicated that the influence of CNTs on the strength of Sn-58Bi-xCNTs composite is insignificant.In addition,the fracture mechanism of CNTs reinforced Sn Bi composite was analyzed.The corresponding fracture surface comparison between the Sn-58Bi-0.03CNTs composite and the monolithic Sn-58Bi alloy was made to identify the influence of CNTs on the fracture behavior and the reinforcing effect of CNTs.     

原位生长碳纳米管及其在SiC_f/SiC复合材料中的应用

采用碳纳米管改善纤维与基体间的界面结合,同时利用碳纳米管自身的优异性能对碳化硅纤维增强碳化硅复合材料(SiCf/SiC)进行二次增强。通过化学气相沉积工艺(CVD)在SiC纤维编织件内原位生长碳纳米管,优化碳纳米管原位生长过程中的碳源流量、反应温度和反应时间等工艺参数,对碳纳米管的原位生长工艺及机理进行系统分析,并结合先驱体浸渍裂解工艺(PIP)制备CNTs-SiCf/SiC复合材料,探讨原位生长碳纳米管的引入对复合材料力学性能的影响。结果表明,优化后的工艺参数如下:反应温度750℃,C2H2、H2和N2流量比1/1/3,C2H2流量100~150 mL/min,反应时间60 min;碳纳米管的引入使SiCf/SiC复合材料的弯曲强度、弯曲模量和断裂韧性分别提高了16.3%、90.4%和106.3%。     

稀土La对Al2O3/Cu复合材料组织与性能的影响

利用机械合金化法结合放电等离子烧结制备Al2O3/Cu铜基复合材料,采用XRD、SEM、硬度、抗拉强度和电导率等测试研究La含量对Al2O3/Cu复合粉末和烧结材料组织及性能的影响。结果表明:添加0.05%的稀土La有利于机械合金化过程中Cu晶粒的细化和Al2O3颗粒的弥散分布,从而提高烧结材料的显微硬度和抗拉强度。烧结材料的导电率随着La含量的增加先升后降,当La的质量分数为0.10%时,Al2O3/Cu复合材料的导电率提高11.3%IACS。