Electroless plating Ni-P matrix composite coating reinforced by carbon nanotubes

Ni-P matrix composite coating reinforced by carbon nanotubes (CNTs) was deposited by electroless plating. The most important factors that influence the content of carbon nanotubes in deposits, such as agitation, surfactant and carbon nanotubes concentration in the plating bath were investigated. The surface morphology, structure and properties of the Ni-P-CNTs coating were examined. It is found that the maximum content of carbon nanotubes in the deposits is independent of carbon nanotubes concentration in the plating bath when it is up to 5 mg/L. The test results show that the carbon nanotubes co-deposited do not change the structure of the Ni-P matrix of the composite coating, but greatly increase the hardness and wear resistance and decrease the friction coefficient of the Ni-PCNTs composite coating with increasing content of carbon nanotubes in deposits.     

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。     

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.     

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.     

Mechanical properties of Cu-based composites reinforced by carbon nanotubes

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碳纳米管/镍基复合镀层的腐蚀行为

采用复合沉积方法在普通碳钢基底上沉积碳纳米管／镍基复合镀层。用腐蚀实验、电化学方法研究了复合镀层在3．5％NaCl溶液中的耐腐蚀性能，并讨论了其耐腐蚀机理，对普通碳钢和纯镍镀层也进行了比较研究。结果表明：碳纳米管的加入显著提高了复合镀层的耐腐蚀性能；耐腐蚀的原因在于碳纳米管的复合镀层更加致密，隔离了腐蚀介质，并阻止了蚀坑的增大，同时，碳纳米管促进了镍的纯化，从而提高镀层的耐蚀性。     

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.     

TC4合金表面Cu/石墨复合镀层的摩擦磨损行为

采用无氰电镀工艺在TC4合金表面制备了Cu/石墨复合镀层,研究了镀层的组织结构和摩擦磨损行为。结果表明,采用无氰电镀方法能够在TC4合金表面制备出组织致密且与基体结合紧密的Cu/石墨复合镀层,但增加镀层中石墨的含量会降低镀层与基体合金的结合强度,并导致硬度小幅下降。摩擦磨损实验结果表明,Cu/石墨复合镀层具有优良的摩擦磨损防护性能,归因于石墨有效降低了镀层的摩擦系数和磨损率;对镀层磨损形貌、磨损产物和摩擦系数的综合分析结果表明,纯铜镀层的摩擦磨损机制主要为犁削磨损、黏着磨损和剥层磨损,Cu/石墨复合镀层的磨损机制为轻微的削层磨损和疲劳磨损。     

Compressive strength of carbon nanotubes grown on carbon fiber reinforced epoxy matrix multi-scale hybrid composites

The characteristics of interface between fiber reinforcement and matrix have a strong influence on the properties of a composite material. Multiwalled carbon nanotubes were grown on carbon fibers by catalytic decomposition of acetylene using thermal chemical vapor deposition technique at 700 °C to modify the fiber surface. Unidirectional multi-scale composites were fabricated using these carbon nanotubes grown fibers with epoxy matrix. As the nanotubes were directly grown on the fibers they get strongly attached with the fibers thus modifying their surface condition which in turn alters the fiber/matrix interface. Modification of the fiber/matrix interface is therefore expected to change the properties of composites. The compressive strengths of these composites were measured which showed a significant enhancement of 43% and 94% in the longitudinal and transverse compressive strengths respectively as compared to composites made of carbon fibers which underwent a similar thermal cycle but without carbon nanotubes growth. The morphology of CNTs grown on carbon fibers was examined at nano-level using HRTEM which showed growth of carbon nanotubes with different morphology and diameter ranging from 5-50 nm.     

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.     

石墨对C/Cu复合材料微观组织及摩擦磨损性能的影响

利用机械合金化和放电等离子烧结技术制备C/Cu复合材料,用扫描电镜、透射电镜、X射线衍射仪、显微硬度计和销-盘摩擦磨损试验机对复合粉末和烧结体的组织结构、硬度、摩擦学行为进行了分析.结果表明:C/Cu复合粉末中Cu相粉末由纳米/亚微米复合颗粒组成,石墨主要以纳米层片状结构和非晶态存在,放电等离子体烧结体组织致密、细小且均匀,随着碳含量增加,烧结体的硬度与密度减小;C/Cu复合材料烧结样品在摩擦过程中形成润滑膜,表现出较低的摩擦系数和良好耐磨性,其磨损机制主要为氧化磨损、粘着磨损和剥层磨损.     

铝合金表面多层复合纳米碳管/钛的激光合金化

在铝合金表面使用真空镀的方法形成CNT8／Ti／AL／…多层复合，经激光合金化形成复合涂层。利用X射线衍射、扫描电镜对复合层相构成及微观组织进行了分析。结果表明，复合层中存在着TiC颗粒和碳纳米管CNTs；CNTs仍保留其原有的管状结构，且在复合层中相互缠绕呈网状均匀弥散分布；反应原位合成的TiC颗粒尺寸均匀细小，附着于CNTs上从而改善了CNTs与基体之间的结合性能；复合涂层已合金化，与基体的界面为冶金结合。     

Characterization and mechanical testing of alumina-based nanocomposites reinforced with niobium and/or carbon nanotubes fabricated by spark plasma sintering

Alumina-based nanocomposites reinforced with niobium and/or carbon nanotubes (CNT) were fabricated by advanced powder processing techniques and consolidated by spark plasma sintering. Raman spectroscopy revealed that single-walled carbon nanotubes (SWCNT) begin to break down at sintering temperatures >1150 °C. Nuclear magnetic resonance showed that, although thermodynamically unlikely, no Al₄C₃ formed in the CNT-alumina nanocomposites, such that the nanocomposite can be considered as purely a physical mixture with no chemical bond formed between the nanotubes and ceramic matrix. In addition, in situ single-edge notched bend tests were conducted on niobium and/or CNT-reinforced alumina nanocomposites to assess their toughness. Despite the absence of subcritical crack growth, average fracture toughness values of 6.1 and 3.3 MPa m^1/2 were measured for 10 vol.% Nb and 10 vol.% Nb-5 vol.% SWCNT-alumina, respectively. Corresponding tests for the alumina nanocomposites containing 5 vol.% SWCNT, 10 vol.% SWCNT, 5 vol.% double-walled-CNT and 10 vol.% Nb yielded average fracture toughnesses of 3.0, 2.8, 3.3 and 4.0 MPa m^1/2, respectively. It appears that the reason for not observing improvement in fracture toughness of CNT-reinforced samples is because of either damage to CNTs or possibly non-optimal interfacial bonding between CNT-alumina.     

原位合成Al_3Ti颗粒增强铝基复合涂层(英文)

以直径200μm、纯度99.5%的钛丝丝网为反应源,通过熔渗-原位反应法制备一种Al3Ti金属间化合物颗粒增强铝基表面复合涂层。差热分析结果表明,在890°C下,Ti丝和Al熔体间发生反应。采用XRD、SEM以及显微硬度和磨损测试对所得到的复合涂层进行表征。结果表明:当保温时间为20min时,钛丝反应完全,原位合成为块状和条状的Al3Ti颗粒;颗粒的显微硬度大约为基体显微硬度的4.5倍;在载荷10N的干滑动磨损条件下,与没有增强的Al基体相比较,保温20min所制备的复合涂层表现出较好的耐磨性,其磨损机制为粘着磨损和磨粒磨损共存。     

Influence of adding carbon nanotubes and graphite to Ag-MoS_2 composites on the electrical sliding wear properties

Silver matrix composite brushes were fabricated by means of powder metallurgy,which included pressing at 300 MPa and then sintering for 1 h in pure H2 protective atmosphere at 700℃ and repressing at 500 MPa.Four kinds composites with different compositions were produced,and the mechanical properties and electrical wear performance were investigated.The results showed that the composite added with carbon nanotubes had a higher hardness and strength,a lower contact voltage drop and an excellent anti-wear prop...     

Fabrication of aluminum matrix composite reinforced with carbon nanotubes

1.0wt.% carbon nanotube （CNT） reinforced 2024Al matrix composite was fabricated by cold isostatic press and subsequent hot extrusion techniques. The mechanical properties of the composite were measured by a tensile test. Mean-while,the fracture surfaces were examined using field emission scanning electron microscopy. The experimental results show that CNTs are dispersed homogeneously in the composite and that the interfaces of the Al matrix and the CNT bond well. Although the tensile strength and the Young’s modulus of the composite are enhanced markedly,the elongation does not decrease when compared with the matrix material fabricated under the same process. The reasons for the increments may be the extraordinary mechanical properties of CNTs,and the bridging and pulling-out role of CNTs in the Al matrix composite.     

Ni-P-多壁碳纳米管复合镀层的制备及摩擦磨损性能(英文)

采用湿式球磨对多壁碳纳米管(MWNTs)预处理,通过化学镀制备Ni-P-MWNTs复合镀层;对45钢、传统Ni-P镀层和Ni-P-MWNTs复合镀层在干摩擦条件下的摩擦磨损性能进行考察和比较。结果表明,球磨后MWNTs长径比降低,长度均匀,且多数端部处于敞开状态。与45钢和Ni-P镀层相比,Ni-P-MWNTs复合镀层的减摩耐磨能力显著强化。当复合镀层中MWNTs的质量分数为0.74%~1.97%时,其摩擦因数和磨损率随MWNTs含量的增加而减少;对于MWNTs质量分数为1.97%的复合镀层,其摩擦因数和磨损率仅为0.08和6.22×10?15m3/(N·m)。复合镀层优良的摩擦磨损性能归因于MWNTs优异的力学性能和自润滑特性。     

短炭纤维增强C/C-SiC制动材料的摩擦磨损性能

采用温压？原位反应法制备C/C-SiC复合材料,利用QDM150型摩擦试验机研究短炭纤维（SCF）长度和纤维体积分数对C/C-SiC制动材料摩擦磨损性能的影响。结果表明：C/C-SiC制动材料能够保持较高且稳定的摩擦因数;SCF的体积分数将影响C/C-SiC制动材料的摩擦磨损性能,纤维体积分数为10%时,材料具有适中的摩擦因数和较低的磨损率;SCF长度对C/C-SiC制动材料的摩擦磨损性能有显著影响,炭纤维长度为12 mm时,材料具有最佳的摩擦磨损性能。     

激光熔覆Cu/WCP复合涂层

采用激光熔覆表面改性方法，在45号钢基体上表面熔覆Cu/WCp复合涂层。试验研究了WC含量对熔覆复合涂层的组织特点和耐摩擦磨损性能的影响规律。研究结果表明，通过调整WC的加入量可获得α-Cu固溶体＋WC双相组织，当WC的加入量超过30％时，熔覆层中出现小圆点状的WC颗粒，表明WC有一定程度的熔化和熔解；Cu/WCp复合熔覆层与基体金属之间存在过渡区，其组织为钢基体＋WC混合组织。采用40Cr磨轮对Cu/WCp熔覆层进行摩擦磨损试验，结果表明，WC加入量为10％时，摩擦系数与磨损量最小；采用硬质合金磨轮进行磨损试验，当WC加入量为30％时，摩擦系数最小，而加入量为10％，磨损量较小。     

Graphene-coated copper foam interlayer for brazing carbon/carbon composite and niobium

Problems such as poor structural integrity, inhomogeneous dispersion, and agglomeration of graphene in the brazing seam are typically encountered for graphene additives in a brazed joint interface. To resolve these problems, a plasma-enhanced chemical vapor deposition process was employed for in-situ preparation of a high-quality graphene-coated copper (Cu) foam composite interlayer prior to be applied for brazing carbon/carbon composite and niobium. The prepared graphene and the brazed joints were characterized via Raman spectroscopy, scanning electron microscopy, and high-resolution transmission electron microscopy. The results revealed that graphene was evenly distributed in the brazing seam with the help of the Cu foam, which was characterized by interconnected porosity. Simultaneously, the excellent chemical inertia of graphene inhibited the collapse of the Cu foam, based on which the thermal residual stress in the joint was effectively mitigated due to the synergistic reinforcement effect of the Cu foam (with good plastic deformation capacity) and graphene (with extremely low coefficient of linear expansion). This effect led to significant improvement in the average shear strength of the joint.