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.     

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.     

Mechanical properties of Cu-based composites reinforced by carbon nanotubes

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Properties of copper/graphite/carbon nanotubes composite reinforced by carbon nanotubes

Electroless Cu plating was used for flake G powder and CNTs, Cu-G-CNTs (copper/graphite/carbon nanotubes) composites were manufactured by means of powder metallurgical method. The influences of CNTs on the mechanical properties, conductivity properties, friction, and wear performance of the composite were examined. The results indicate that adding a small amount of CNTs can improve comprehensive property of the composites, especially mechanical property. However, excessive CNT, which is easily winding reunion and grain boundary segregation, results in performances degradation.     

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。     

Experimental investigation of drilling damage and stitching effects on the mechanical behavior of carbon/epoxy composites

The main purpose of composite materials drilling is the need to put together different parts of a structure, in aeronautics for example. Machining generates damages which affect mechanical properties and have to be taken into account during manufacturing process. The objective of this study is to experimentally analyze the influence of drilling on a carbon/epoxy composite, to investigate the relationships among damages, cutting forces, mechanical properties of the drilled specimens and crack propagation. Stitching and a range of spindle speed and feed have been tested when drilling with a classic twist drill. The effect of each parameter has been assessed in terms of thrust force, moment (during machining) and defects, and then linked to mechanical test results. Experimental results have shown significant influences of feed and composite configuration on delamination. Furthermore, cyclic tensile tests have shown that reducing damage and using stitching help increasing tensile strength.     

Rapid and scalable method for direct and indirect microstructuring of vertical aligned carbon nanotubes

Multi-walled carbon nanotube (MWCNT) films are grown by chemical vapor deposition (CVD) on silicon substrates using an alumina buffer and a Fe/Co layer as catalyst with different Fe/Co ratios. For both coatings, a scalable wet-chemical technique is applied. The highest CNT forests (100–125 μm) are obtained with Fe content between 60 and 80 wt.%. After deposition of the films, direct laser interference patterning (DLIP) method is used for fabricating micro patterns of the CNTs, using a frequency tripled Nd:YAG laser emitting 10 ns pulses. Two different approaches for fabricating periodic MWCNT arrays are presented. The first approach is the direct patterning of the CNT layer itself (CNT-DLIP) obtaining well defined line-like structures with 10 μm spatial period. By adjusting the laser fluence (from 150 to 250 mJ cm^− 2) and the number of laser pulses (from 1 to 20), the morphology (structure depth and line width) of the fabricated arrays can be varied. Thermal simulations of the CNT ablation process validate the experimental observations. The second approach involves indirect patterning of the CNTs, by fabricating line-like structures on the iron/cobalt catalyst layer (CAT-DLIP). In the last case, moderate energy densities (100 mJ cm^− 2) permitted to remove the catalyst layer locally at the interference maxima positions. By altering the number of laser pulses from 1 to 20 the line width can be tuned. The CNT forests are subsequently grown on the patterned catalyst.     

Drilling delamination and thermal damage of carbon nanotube/carbon fiber reinforced epoxy composites processed by microwave curing

The drilling-induced delamination and thermal damage of carbon fiber reinforced epoxy composite materials are serious problems especially for high value components of the aviation industry. To suppress the delamination and drilling ablation, an innovative approach was employed in this study. The multiwalled carbon nanotubes (MWCNTs) were introduced to the matrix resin to improve the interlaminar strength and thermal conductivity. The as-prepared composite was processed by microwave curing to enhance the interface strength between carbon fiber and the carbon nanotubes modified matrix. During the drilling processes, optical fiber Bragg grating sensors were utilized to precisely measure the drilling temperature. Experimental results indicated that the interlaminar fracture toughness was increased by more than 66% compared to that of the traditional thermal cured samples without MWCNTs. And the delamination factor was decreased by 16% according to the computerized tomography scanning results. The maximum drilling temperature of the MWCNTs reinforced composite was below the glass transition temperature of the matrix resin and declined by 23 °C compared to traditional composites. With this novel method of carbon nanotube modification and microwave curing, we provide the capability of reducing the drilling delamination and thermal damage of carbon fiber composites simultaneously, and explored the possibility of manufacturing and machining integration.     

玄武岩颗粒增强7A04铝基复合材料的界面结构及力学行为

采用喷射成形技术制备7A04铝合金及玄武岩颗粒增强7A04铝合金复合材料,利用金相显微镜(OM)、透射电镜(TEM)、扫描电镜(SEM)和能谱(EDS)分析复合材料微观组织和界面结构,对比研究复合材料的力学性能。结果表明:玄武岩颗粒在铝基体中弥散分布,并与铝基体形成强力结合界面,玄武岩颗粒边缘的SiO₂不断被反应生成的Al₂O₃取代,形成一层几十纳米厚度的高温反应层,反应生成的Al₂O₃强化玄武岩颗粒与铝基体的结合界面;弥散分布的玄武岩颗粒促进基体中位错增殖、空位形成和析出相的析出,析出相主要以板状的η(MgZn₂)相和亮白色条状或椭球状的T(Al₂Mg₃Zn₃)相为主,结合界面、高位错密度及弥散分布的第二相显著提高复合材料的力学性能,添加玄武岩颗粒的7A04铝合金复合材料的屈服强度和极限拉伸强度分别达667 MPa和696 MPa,与未添加玄武岩颗粒的7A04铝合金相比分别提高10.4%和...     

Electrochemical hydrogen storage of NdMg12–Ni composites modified with carbon nanotubes and BN particles

In this work, the electrochemical performance of NdMg₁₂–Ni composite electrode in alkaline solution and the effect of the surface modification with carbon nanotubes (CNTs) and boron nitride (BN) particles on the NdMg₁₂–Ni composite were investigated. The NdMg₁₂ alloy was synthesized by a salt-cover-melting and a subsequent quenching process. The NdMg₁₂–Ni–BN and NdMg₁₂–Ni–CNTs composites were prepared by ball-milling NdMg₁₂ alloy, Ni powders and CNTs or BN particles. It is found that CNTs or BN particles are mainly attached onto the surface of the NdMg₁₂–Ni composite after the ball-milling process. The electrochemical experiment results indicate that the NdMg₁₂–Ni composites modified with CNTs or BN particles have the improved electrochemical performance. In particular, the NdMg₁₂–Ni–5 wt.% CNTs and NdMg₁₂–Ni–3 wt.% BN composites have the higher initial discharge capacity of 416.6 mAh/g and 442.9 mAh/g, respectively, larger than the original NdMg₁₂–Ni composite. The large amount of grain boundaries and crystalline defects, induced during the ball-milling process, can accelerate the bulk hydrogen diffusion and provide more surface active sites for the electrochemical reaction of the composites. However, the cycle stability of the composites modified by CNTs or BN particles is still not satisfactory for the practical application.     

不同涂层碳纳米管对增强镁基复合材料力学性能的影响

采用化学镀的方法在用化学气相沉积法(CVD)制备的一维多壁碳纳米管(MWNTs)上化学镀镍、镍-锌处理,然后在氩气的保护下,采用搅拌铸造的方法与镁复合,制得碳纳米管增强镁基复合材料.在MTS电液伺服机上对其抗拉强度和伸长率进行了测试,同时,采用TEM和SEM方法对复合材料的微观组织和机构进行分析.试验结果表明:随着碳纳米管含量的增加,复合材料的抗拉强度和伸长率逐渐提高,当镀镍碳纳米管的体积百分数达到1.0%时,抗拉强度和伸长率分别提高了105%和96%;相应的镀镍锌的碳纳米管复合材料则分别提高了124%和107%,但当碳纳米管的含量达到1.5%时,抗拉强度和伸长率都明显的降低.     

激光焊接颗粒增强铝基复合材料中TiB2颗粒的演变行为（英文）

研究大功率激光器焊接TiB2颗粒增强铝基复合材料时TiB2粒子的演变行为。采用X射线衍射(XRD)、扫描电镜(SEM)及能谱(EDS)分析焊缝内粒子的物相、热力学过程及形貌特征;同时对TiB2和铝基体的界面反应进行讨论。结果表明:当TiB2团簇尺寸大于激光光斑直径时,焊缝中部的TiB2粒子会熔融在一起,较大尺寸的TiB2会发生断裂;当与铝熔体接触后,熔化后的TiB2粒子会与Al发生反应生成Al3Ti和AlB12,并且焊缝中部的界面反应比焊缝边缘的剧烈。     

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.     

Particle shape effects on ductility of SiC particle reinforced LD2 matrix composites investigated by AFM based nanoindentation

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The surface fractal investigation on carbon nanotubes modified by the adsorption of poly(acrylic acid)

In this paper, surface fractal analysis is carried out to study the surface of carbon nanotubes after the adsorption of poly(acrylic acid) (PAA) using the thermodynamic method. The fractal dimension (d_SF ) of a fractal surface, BET surface area (S_BET) and pore size distribution (PSD) are calculated from low-temperature nitrogen adsorption isotherms. The value of d_SF declines as the adsorption amount of PAA increases, which means the adsorption may lower the surface roughness of the carbon nanotubes. The PSD pattern was modified obviously after the adsorption of PAA because of the pore-blocking effect. Additionally, an excellent linear decrease in the BET surface area of carbon nanotubes is found as the adsorption amount of PAA increases, which can be attributed to both the pore-blocking effect and the surface-screening effect. The results of the present work may facilitate our understanding of the interaction between polymer and the carbon nanotubes at the microscale occurring on irregular interfaces.     

Effects of heat treatment on mechanical properties and microstructure of tungsten fiber reinforced grey cast iron matrix composites

In this study, grey cast iron matrix composites reinforced by different volume fractions of tungsten fibers (Vr=0.95 %, 1.90 %, 2.85 %, 3.80 %) were investigated in as-cast and under the heat treatment temperatures of 1,000℃ and 1,100℃. The microstructure and mechanical properties of the composites were analyzed and tested by means of SEM, micro-hardness tester and three-point bend testing. The results show that with increasing of the volume fraction of tungsten fibers, the composites reinforced by the tungsten fiber have higher flexural strength and modulus than that of cast iron without reinforcement, and the flexural strength increases with the increasing of heat treatment temperatures. Due to diffusion reaction between matrix and reinforcing phases, the process of heat treatment, the number of graphite flakes in the matrix seemingly becomes lower; and some hard carbide particles are formed around the residual tungsten fibers. Not only does the hardness of both matrix and reinforcement change tremendously, but also the region of reinforcement is also extended from the original 0.11 mm to 0.19 mm in radius.     

Ti2SnC质量分数对铜基复合材料显微组织及性能的影响

为了制备强度高导电性能优异的铜基复合材料,以三元层状导电陶瓷Ti2SnC作为增强相,通过直热法粉末烧结技术制备Ti2SnC/Cu复合材料。研究了在烧结温度800℃、成型压力45MPa、保温时间30min、真空度50Pa的成型条件下,质量分数分别为0、5%、8%、10%的Ti2SnC增强相对复合材料的显微结构、硬度、抗拉强度、抗冲击韧性和导电率等性能的影响。结果表明:Ti2SnC的质量分数为5%时,综合性能最优,致密度和导电率分别达到94%、39%IACS,抗拉强度248MPa,硬度为88.7HBS,可适用于受电弓滑板。     

钛合金/碳纤维布复合材料的界面与力学性能的研究

本文选用Ti-6Al-4V钛合金为基体,镀铜碳纤维布为增强相来制备钛合金/碳纤维布复合材料。通过放电等离子烧结法(SPS)对镀铜碳纤维布与钛合金薄片进行叠层烧结,制备钛合金/碳纤维布叠层复合材料,并对其界面形貌、微观组织与力学性能进行表征。结果表明：镀铜碳纤维均匀分布在钛合金/碳纤维布复合材料中,CuTi, Cu和少量的TiC沿着纤维和基体的界面分布。钛合金/碳纤维布复合材料具有比钛合金略高的塑性,同时屈服强度和抗压强度与钛合金相比有了明显的提高。碳纤维表面电镀铜对复合材料界面有着重要的影响：(1)显着降低钛合金/碳纤维布复合材料的烧结温度;(2)提高了碳纤维和钛基体之间的润湿性,改善了界面结合,从而提高了钛合金/碳纤维布复合材料的力学性能;(3)有效地抑制TiC脆性相的产生,与未镀铜的碳纤布增强钛复合复合材料相比,镀铜碳纤维布/钛合金复合材料具有更好的塑性。     

Composition-controlled synthesis, structure and magnetic properties of ternary FexCoyNi100−x−y alloys attached on carbon nanotubes

Fe_xCo_yNi_100−x−y alloy nanoparticles with controllable compositions attached on the surface of carbon nanotubes (CNTs) were synthesized using an easy two-step route including adsorption and reduction processes. The nanocomposites have been characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), selected area electron diffraction (SAED), energy-disperse X-ray spectroscopy (EDS) and vibrating sample magnetometer (VSM). The effect of the alloy composition on microstructure and magnetic properties of ternary FeCoNi alloys attached on carbon nanotubes have been studied. During the nominal composition range (x = 21, 24, 33, 37, 46 and y = 60, 46, 48, 48, 35), Fe_xCo_yNi_100−x−y alloy nanoparticles attached on CNTs are quasi-spherical, fcc–bcc dual phase, and the coercivity (H_c) and saturation magnetization (M_s) vary with the alloy composition. The H_c of Fe_xCo_yNi_100−x−y alloy nanoparticles attached on CNTs decreases and M_s increases with increasing Fe content. These demonstrate that the two-step route is promising for fabricating alloy nanoparticles attached on CNTs for magnetic storage and ultra high-density magnetic recording applications.     

碳颗粒尺寸对自发渗透原位制备TiCp/Mg微观组织的影响

利用原位反应自发渗透技术制备了组织均匀且致密度高的TiCp/Mg复合材料, 研究了原位反应温度以及碳颗粒尺寸对制备的TiCp/Mg复合材料微观组织的影响.结果表明: 当使用大尺寸碳粒子(≤100μm)时, 随着反应温度的提高, 原位生成物TiCp的含量增加, 但有残留反应物Ti和C的存在; 碳粒子尺寸减小(≤30μm)时, 原位反应较完全, 不再有残留物存在; 原位反应产物组织中, 增强相TiCp主要呈互穿网络状、颗粒状以及片状等形态; 增强相的尺寸随碳粒子尺寸的减小而减小, 在碳颗粒尺寸为1.5μm时TiC更易呈现等轴颗粒状, 尺寸约为0.5～2.0μm.