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%。     

Effects of ply-orientation on microstructure and properties of super-aligned carbon nanotube reinforced copper laminar composites

The super-aligned carbon nanotube (SACNT) films reinforced copper (Cu) laminar composites with different orientations of CNT ply were fabricated by electrodeposition. The results show that the tensile strength and yield strength of cross-ply composite with 5.0% (volume fraction) of SACNT reach maximum of 336.3 MPa and 246.0 MPa respectively, increased by 74.0% and 124.5% compared with pure Cu prepared with the same method. Moreover, the electrical conductivities of all the prepared composites are over 75% IACS. The result of TEM analysis shows that the size of Cu grain and the thickness of twin lamellae can be reduced by adding SACNT, and the refining effect in cross-ply composites is more significant than that in unidirectional ply composites. The enhanced strength of the Cu/SACNT composites comes from not only the reinforcing effect of SACNT films but also the additional strengthening of the Cu grain refinement caused by CNT orientation.     

Mechanical properties of Cu-based composites reinforced by carbon nanotubes

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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.     

Structure and electrical resistivity of the Al-carbon nanotube composites

In this paper the microstructure and the electrical resistivity of the hot-pressed Al-carbon nanotube composites have been measured. The results show that there is A1C or A1C₂ phases in the structure, the electrical resistivity of the samples with carbon nanotubes at room temperature is slightly higher than that of the samples without carbon nanotubes. There is an abrupt drop of the electrical resistivity of the Al-carbon nanotube composites at about 80 K, which is similar to the superconducting transition.     

碳纳米管-银复合材料的制备工艺和电导率

采用粉末冶金方法制备碳纳米管-银复合材料,研究了制备工艺、碳纳米管含量对碳纳米管-银基复合材料密度、硬度、抗弯强度、电导率的影响.结果表明:采用复压烧结,烧结温度为700℃时,复合材料的性能较好;碳纳米管和银的弱界面结合,使得碳纳米管对复合材料的强化效果不明显;当碳纳米管的体积含量大于10%时,碳纳米管在晶界上发生偏聚,碳纳米管-银界面对电子产生散射,导致复合材料的电阻率迅速增加.     

碳纳米管-银复合材料力学性能研究

采用粉末冶金方法制备碳纳米管-银复合材料，研究了碳纳米管的含量对碳纳米管-银复合材料的硬度、抗弯强度影响。实验表明：当碳纳米管的含量小于11％时，复合材料的密度、硬度较好，碳纳米管起到了增强作用；当碳纳米管的含量大于11％时，由于碳纳米管的团聚，导致复合材料密度、硬度迅速下降；由于碳纳米管和银的弱界面结合，以及碳纳米管在拉应力条件下载荷传递的效力比在压应力时低，使得碳纳米管对复合材料抗弯强度的增加不明显。     

碳纤维表面生长纳米碳管及其增强的炭/炭复合材料

采用化学气相沉积工艺在碳纤维表面生长了纳米碳管,将此种碳纤维作为增强材料,以中间相沥青为基体炭前驱体采用浸渍炭化工艺制备了炭/炭复合材料.观察了所得复合材料断口的微观形貌,测试了抗弯强度及热物理性能.结果表明,碳纤维表面的纳米碳管可以有效地提高纤维与基体的粘结力,复合材料的抗弯性能提高了50%,而对复合材料的导热性能影响较小.     

碳纳米管铜基复合颗粒的制备

采用混酸纯化法在碳纳米管表面引入羟基和羧基等基团.利用明胶使碳纳米管均匀地分散在五水硫酸铜溶液中,用葡萄糖在碱性条件下还原得到氧化亚铜内嵌碳纳米管复合颗粒,将其还原获得铜基内嵌碳纳米管复合颗粒.SEM和TEM观察结果表明碳纳米管均匀地分布在几百纳米至1μm的复合颗粒中.XRD分析表明得到的产物是纯净的Cu2O和Cu颗粒.复合球形貌影响因素研究发现明胶在复合物成球过程中起着关键性的作用,明胶与CNTs质量比为5～7时配比效果最佳.     

Enhanced thermal and electrical properties of poly (D,L-lactide)/multi-walled carbon nanotubes composites by in-situ polymerization

Biodegradable poly (D,L-lactide) (PLA)/carboxyl-functionalized multi-walled carbon nanotubes (c-MWCNTs) composites were achieved via in-situ polymerization. These as-prepared composite materials were characterized with FT-IR, XRD, TG, DSC, SEM, and high insulation resistance meter. The results demonstrate that the multi-walled carbon nanotube was carboxyl functionalized, which improved the collection between c-MWCNTs and PLA, and further realized the graft copolymerization of c-MWCNTs and PLA. There is a higher glass transition temperature and a lower pyrolysis temperature of PLA/c-MWCNTs composites than pure PLA. The c-MWCNTs gave a better dispersion than unmodified MWCNTs in the PLA matrix, and an even coating of PLA on the surface of c-MWCNTs was obtained, which increased the interfacial interaction. High insulation resistance analysis showed that the addition of c-MWCNTs increased the electric conductivity, and c-MWCNTs performed against the large dielectric coefficient and electrostatic state of PLA. These results demonstrated that c-MWCNTs modified PLA composites were beneficial for potential application in the development of heat-resisting and conductivity plastic engineering.     

铝合金的力学性能及其电导率

评述了影响铝合金力学性能和电导率的主要因素，说明铝合金的力学性能与其电导率有一定的关联。介绍了电导率在铝合金热处理工艺制定和力学性能检测中的应用，指出借助于电导率的测定，可以初步推测铝合金的某些力学性能和初步优化铝合金的某些热处理工参数，达到测试快速、无损和简便的目的。     

Fabrication of carbon nanotube reinforced AZ91D composite with superior mechanical properties

AZ91D alloy composites with 1.0% CNTs have been fabricated by a method combined ball milling with stirring casting. The composite was investigated using optical microscopy(OM), X-ray diffraction(XRD), Fourier transform infrared spectroscope (FT-IR), scanning electron microscope (SEM), transmission electron microscope (TEM) and room temperature (RT) tensile test. The results show that CNTs were homogeneously distributed in the matrix and maintained integrated structure. The yield strength and ductility of AZ91D/CNTs composite were improved by 47.2% and 112.2%, respectively, when compared with the AZ91 alloy. The uniform distribution of CNTs and the strong interfacial bonds between CNT and the matrix are dominated to the simultaneous improvement of yield strength and ductility of the composite. In addition, the grain refinement as well as the finer β phase (Mg₁₇Al₁₂) with homogenous distribution in the matrix can also slightly assist to the enhancement of the mechanical properties of the composite.     

Mechanical properties and creep resistance of Mg-Li composites reinforced by MgO/Mg_2Si particles

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Preparation and mechanical properties of carbon/carbon composites with high textured pyrolytic carbon matrix

Short carbon fiber felts with an initial porosity of 89.5% were deposited by isobaric, isothermal chemical vapor infiltration using natural gas as carbon source. The bulk density of the deposited carbon/carbon (C/C) composites was 1.89 g/cm³ after depositing for 150 h. The microstructure and mechanical properties of the C/C composites were studied by polarized light microscopy, X-ray diffraction, scanning electron microscopy and three-point bending test. The results reveal that high textured pyrolytic carbon is deposited as the matrix of the composites, whose crystalline thickness and graphitization degree highly increase after heat treatment. A distinct decrease of the flexural strength and modulus accompanied by the increase of the toughness of the C/C composites is found to be correlated with the structural changes in the composites during the heat treatment process.     

Preparation of three-dimensional braided carbon fiber reinforced mullite composites from a sol with high solid content

To prepare the three-dimensional braided carbon fiber reinforced mullite (3D C/mullite) composites, an Al₂O₃-SiO₂ sol with a solid content of 20% (mass fraction) and an Al₂O₃/SiO₂ mass ratio of 2:1 was selected as the raw material. Characteristics and mullitization of the sol were analyzed throughly. It is found that the formation of mullite is basically completed at 1300 °C and the gel powders exhibit favorable sintering shrinkage. The 3D C/mullite composites without interfacial coating were fabricated through the route of vacuum impregnation-drying-heat treatment. Satisfied mechanical properties with a flexural strength of 241.2 MPa and a fracture toughness of 10.9 MPa·m^1/2 are obtained although the total porosity reaches 26.0%. Oxidation resistances of the composites at 1200, 1400 and 1600 °C were investigated. Due to the further densification of matrix, the 3D C/mullite composites show tiny mass loss and their mechanical properties are well retained after oxidation at 1600 °C for 30 min.     

炭/炭复合材料航空刹车副的湿态摩擦性能

对两种不同的炭/炭复合材料湿态下的摩擦磨损性能进行对比分析。结果表明:具有粗糙层热解炭的炭/炭刹车副由于其晶格结构较为完善,生长组织择优取向度和各向异性度均高于含有光滑层结构热解炭的炭/炭刹车副。前者的石墨化度及可石墨化能力均大于后者,由于前者的表面缺陷较少,所吸附的水分子较少,因而在湿态下刹车时,其刹车力矩将很快恢复到正常干态刹车时的力矩水平,对环境的适应能力大于光滑层结构的炭/炭刹车副。     

激光熔铸多壁纳米碳管增强铝基复合材料

利用激光熔铸技术制备多壁纳米碳管增强铝基复合材料,并使用SEM、XRD对其熔铸成形性以及纳米碳管与基体金属界面结合行为进行观察和分析.结果表明,在单位面积激光能量为800×105J/m2时,纳米碳管增强铝基复合材料能够熔合而不破坏纳米碳管结构;在该复合材料中适量添加表面张力较低的金属Mg,可降低基体铝的表面张力,进而降低铝-纳米碳管的液固界面能,改善铝合金和纳米碳管的润湿性;当纳米碳管含量为5%(质量分数)时,并添加3%(质量分数)合金化元素Mg,激光熔铸的复合材料熔合性较好,铸块致密,在复合铸块的断口上能观察到增强体纳米碳管.     

2%C/MoSi_2复合材料的组织结构与性能

采用热压烧结工艺制得了 2 %C/MoSi2 (质量分数 )复合材料 ,并测定了材料的显微组织和结构、室温和高温力学性能、耐磨性能以及电阻率。结果表明 :C/MoSi2 复合材料由大量的MoSi2 、多量的Mo5Si3 和少量的 β SiC组成 ,其硬度Hv为 10 6 0 ,抗弯强度为 470MPa ,断裂韧性为 5 .12MPa·m1/ 2 ,80 0℃的硬度Hv为 75 0 ,12 0 0℃的抗压强度为 45 0MPa ,140 0℃的抗压强度为 142MPa ;在Al2 O3 和SiC磨盘上表现出优异的耐磨性能 ,材料的电阻率为 34 9nΩ·m。与纯MoSi2 相比 ,2 %C/MoSi2 复合材料在硬度、抗弯强度、断裂韧性、高温抗压强度、弹性模量和耐磨性能等方面都有较大的提高。