Wear behavior of Cu matrix composites reinforced with mixture of carbon and carbon nanotubes

In order to improve wear resistance and decrease the cost, carbon and carbon nanotubes reinforced copper matrix composites were fabricated by the power metallurgy method. The effects of carbon (carbon and carbon nanotubes) volume fraction and applied load on the friction coefficient and wear rate under dry sliding of the composites were investigated at room temperature. By scanning electron microscopy (SEM), the worn surfaces and debris were observed, and wear mechanism was also analyzed and discussed. The experimental wear process consists of the run-in, steady wear and severe wear process with the increasing of sliding distance. Both the friction coefficient and wear rate of the composites first decrease and then increase with the increasing of carbon volume fraction. The minimum friction coefficient and wear rate are obtained when carbon is 4.0vol%. The wear mechanisms of the composites change from the adhesive wear and delamination wear to abrasive wear with the increasing of carbon volume fraction. Funded by the National Natural Science Foundation of China (50873047) and the Natural Science Foundation of Gansu Province (3ZS061-A25-039)     

粉末冶金法制备Al2O3陶瓷颗粒增强铜基复合材料的研究

研究了Al2O3陶瓷颗粒弥散强化铜基复合材料的制备工艺.采用化学镀法制备Cu/Al2O3复合粉体,采用干压成型的方法将Cu/Al2O3复合粉体压制成型,在N2保护条件下进行烧结,制备出了Al2O3陶瓷颗粒弥散强化铜基复合材料,并采用OM,SEM,EDS等分析测试技术对复合材料的组织进行了观察分析,结果表明,用该方法制备的铜基复合材料中Al2O3颗粒分布均匀,Al2O3与铜基体结合良好.     

Aluminum matrix composites reinforced by molybdenum-coated carbon nanotubes

To extend the application of carbon nanotubes (CNTs) and explore novel aluminum matrix composites,CNTs were coated by molybdenum layers using metal organic chemical vapor deposition,and then Mo-coated CNT (Mo-CNT)/Al composites were prepared by the combination processes of powder mixing and spark plasma sintering.The influences of powder mixing and Mo-CNT content on the mechanical properties and electrical conductivity of the composites were investigated.The results show that magnetic stirring is better tha...     

Mechanical properties and microstructure of sulfur aluminate cement composites reinforced by multi-walled carbon nanotubes

The effect of multi-walled carbon nanotubes (MWCNTs) on the mechanical properties and microstructure of sulfur aluminate cement (SAC) composites was investigated. The dispersed MWCNTs were added into SAC in various weight contents.The results of mechanical properties of the MWCNTs/SAC composites indicated that the addition of 0.08 wt% MWCNTs can improve the SAC compressive strength, flexural strength, and bend-press ratio by 15.54%, 52.38%, and 31.30% at maximum, respectively. The degree of SAC hydration and porosity and pore size distribution of the matrix were measured by X-ray diffraction (XRD), thermal analysis (TG/DTG), and mercury intrusion porosimetry (MIP). Results show that the addition of MWCNTs in SAC composites can promote the hydration of SAC and the formation of C-S-H gel, reduce the porosity and refine the pore size distribution of the matrix. The microstructure was characterized by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). It is found that the MWCNTs have been dispersed homogeneously between the hydration products of SAC paste and act as bridges and networks between cracks and voids, which prevents the development of the cracks and transfers the load.     

碳纳米管增强钛基复合材料的界面应力分布

为了了解工业领域中综合性能优异的金属基复合材料,采用结构分析软件ANSYS建立了有限元模型,研究了复合材料界面应力场的分布情况.结果表明,在受压载荷作用下,钛基复合材料发生屈服现象的可能性较小,但碳纳米管的顶部界面边缘处出现了明显的应力集中现象,导致此处发生断裂破坏的可能性相对较大.在拉伸载荷作用下,钛基复合材料的应力分布比较均匀,且未出现明显的应力集中现象,因而复合材料发生屈服、断裂破坏的可能性较小.当碳纳米管的相位角为15°时,复合材料发生界面脱离和基体开裂的可能性相对较小.     

Fabrication of high strength carbon nanotube/7055Al composite by powder metallurgy combined with subsequent hot extrusion

Bimodal carbon nanotube reinforced 7055Al(CNT/7055Al) composites containing coarse grain bands and ultra-fine grain zones were fabricated by high energy ball milling, vacuum hot pressing followed by hot extrusion. The effect of extrusion temperature varied from 320℃ to 420℃ on the microstructure evolution and tensile properties were investigated. Microstructure observation indicates that the elongated coarse grain bands aligned along the extrusion direction after extrusion. The width of the coarse grain bands increased, and the length of the coarse grain bands increased firstly and then decreased with the increase of extrusion temperature. The grain size of the ultra-fine grain zones changed little after hot extrusion, but the ultra-fine grains coarsened after subsequent heat treatment, especially for the composite extruded at low temperature of 320℃. By observing the CNT distribution, it was found that the higher temperature extrusion was beneficial to the CNT orientation along the extrusion direction.Furthermore, a precipitated free zone formed at the boundary between the coarse grain band and the ultra-fine grain zone as the composite extruded at high temperature of 420℃. As the result of the comprehensive influence of the above microstructure, the tensile strength of the composite extruded at moderate temperature of 370℃ reached the highest of 826 MPa.     

Adsorption behavior of heavy metal ions by carbon nanotubes grown on microsized Al2O3 particles

Carbon nanotubes （CNTs） were grown on the surface of microsized Al2O3 particles in CH4 atmosphere at 700℃ under the catalysis of Fe-Ni nanoparticles. The CNTs on Al2O3 were used for adsorbing Pb^2＋, Cu^2＋, and Cd^2＋ from the solution and the results were compared with active carbon powders, commercial carbon nanotubes, and Al2O3 particles. The as-grown CNTs/Al2O3 have demonstrated extraordinary absorption capacity with further treatment or oxidation, as well as hydrophilic ability that other CNTs lacked. The adsorption capacity of CNTs on Al2O3 is superior to other adsorbents and the preference order of adsorption on composite Al2O3 is pb^2＋〉Cu^2＋〉Cd^2＋. It seemed that the adsorption of those Pb^2＋, Cu^2＋, and Cd^2＋ did not change the surface properties of composite particles. The adsorption behaviors of Pb^2＋, Cu^2＋, and Cd^2＋ by CNTs on Al2O3 match well with the Langmuir isothermal adsorption model and the second order kinetic model. The calculated saturation amount adsorbed by 1 g of CNTs on Al2O3 are 67.11, 26.59, and 8.89 mg/g for Pb^2＋, Cu^2＋, and Cd^2＋ in single adsorption test, respectively.     

Preparation of Nb3Al superconductor by powder metallurgy and effect of mechanical alloying on the phase formation

Railway Engineering Science - Adoption of powder-in-tube method to fabricate superconducting wire can realize a large application of Nb3Al prepared by powder metallurgy. Powder metallurgy was used...     

Electrochemical Intercalation of Lithium into Raw and Mild Oxide-treated Carbon Nanotubes Prepared by CVD

The raw carbon nanotubes ( CNTs ) prepared by chemical vapor deposition ( CVD ) were used in electrochemical lithiation. To remove the impurity the mild oxidation was done on the samples. The electrochemical characteristics of the two samples are investigated by the galvanostatic charge-dischorge measurements and cyclic voltammetry. The structural and interfacial changes of the CNTs electrode were analyzed by XRD and FTIR. The samples show a reversibility of lithium intercalation and de-intercalation. The reversible capacities of the first five cycles are larger than 300 mAh/ g and the irreversible capacity of the first cycle was much larger than that mentioned in literatures. There is no identical change in the structure during the charge and discharge. The reactions at the interface between electrode and the electrolyte are similar to those of other carbonaceous materials.     

碳纳米管增强复合材料的界面破坏形态及改善措施

以碳纳米管增强树脂基复合材料的二维平面模型为对象,在考虑基体材料非线性的情况下,探讨碳纳米管增强复合材料的界面层特性对复合材料破坏形态的影响。通过对破坏端部的局部处理,提出两种提高复合材料抵抗损伤破坏能力的方法。第一种方法是改变纤维及界面层端部与基体的界面特性即软化界面,用内聚力模型模拟界面,通过内聚力阻扰裂纹的扩展;第二种方法是改变碳纳米管的端部形状即封闭碳纳米管及界面层,通过改变碳纳米管的应力分布状态来提高复合材料的抗破坏能力。     

碳纤维与玻璃纤维增强聚合物复合材料耐久性

通过快速碳化、模拟海水潮汐作用的干湿循环、冻融循环作用以及纵向拉伸试验,研究了特定环境对碳纤维与玻璃纤维增强聚合物复合材料(CFRP与GFRP)纵向受拉性能的影响.试验结果表明:CFRP在这三种环境下强度变化不大,弹性模量有所提高,延伸率在干湿循环下略有降低.GFRP的力学性能在这三种环境下也都有不同程度的退化.湿度或水分和温度变化是影响FRP性能的重要环境因素.     

Mg_2Si/Al梯度复合材料的耐磨性

利用SEM、EDS等技术观察了变质前后的Mg2Si/Al梯度复合材料和HT200的磨损表面,对比研究了3种材料在不同载荷、不同磨损速率情况下与45钢对磨的干滑动磨损行为。结果表明:变质后的初生Mg2Si颗粒细小、圆整、分布更加均匀,能够起到更强的支撑作用,且不易破碎,很大程度上抑制了塑性变形的出现,抗黏着磨损能力有了明显的提高,说明变质后的复合材料具有更高的耐磨性。实验发现,由于HT200和45钢组成共轭摩擦副,磨损严重,加上复合材料增强颗粒的作用,使得复合材料的耐磨性远远高于HT200。Mg2Si/Al梯度复合材料的失效机制主要是黏着磨损和磨粒磨损。     

Comments on Adsorption behavior of heavy metal ions by carbon nanotubes grown on microsized Al2O3 particles

Rcently, Hsieh and Horng [1] published the paper entitled as above. In section 3-results and discussion,the authors mentioned the first and the second order kinetic models without any quotations.     

Effects of carbon nanotubes by electrophoretic deposition on interlaminar properties of two dimensional carbon/carbon composites

Carbon nanotubes(CNTs) were deposited uniformly on carbon cloth by electrophoretic deposition(EPD). Thereafter, CNT-doped clothes were stacked and densified by pyrocarbon via chemical vapor infiltration to fabricate two-dimensional(2 D) carbon/carbon(C/C) composites. Effects of EPD CNTs on interlaminar shear performance and mode Ⅱ interlaminar fracture toughness(GⅡc) of 2 D C/C composites were investigated. Results showed that EPD CNTs were uniformly covered on carbon fibers, acting as a porous coating. Such a CNT coating can obviously enhance the interlaminar shear strength and GⅡc of 2 D C/C composites. With increaing EPD CNTs, the interlaminar shear strength and GⅡc of 2 D C/C composites increase greatly and then decrease, both of which run up to their maximum values, i e, 13.6 MPa and 436.0 J·m-2, when the content of EPD CNTs is 0.54 wt%, 2.27 and 1.45 times of the baseline. Such improvements in interlaminar performance of 2 D C/C composites are mainly beneficial from their increased cohesion of interlaminar matrix, which is caused not only by the direct reinforcing effect of EPD CNT network but also by the capacity of EPD CNTs to refine pyrocarbon matrix and induce multilayered microstructures that greatly increase the crack propagation resistance through "crack-blocking and-deflecting mechanisms".     

Compressive testing and failure analysis of three-dimensionally reinforced carbon/carbon composites

It is important to reveal the performance of carbon/carbon composites subjected to complex loading,which can provide a basis for developing the failure laws of carbon/carbon composites.The uniaxial and...     

Bending behavior of carbon nanotube-reinforced composites

The multi-scale modeling method was utilized to study the bending characteristics of a carbon nanotube(CNT)and CNT-reinforced composites.Through combining molecular dynamics and continuum mechanics,the tensional and flexural modulus of a CNT were calculated by a finite element model constructed by reticulate beams with solid cylinder shape and energy equal to C-C bonds.Then,another beam element with hollow cylinder shape and equivalent stiffness was utilized in place of a CNT in a matrix,thus,a multi-scale representative volume element(RVE)model of CNT-reinforced composite was established.Using this RVE model,the bending behavior of CNT-based composites was analyzed.The influence of diameter D,length L,aspect ratio L/D,volume fraction,chiral of CNTs and shape of RVE as well as the arrangement of CNTs in matrix on the reinforcement effect of flexural modulus of resultant nanocomposites were further discussed.The obtained data provide useful information for the design of CNT-reinforced composites.     

聚合物/碳纳米管导电复合材料研究进展

在聚合物基体中加入碳纳米管可以制备综合性能优异的导电聚合物复合材料,而具有取向结构的聚合物/碳纳米管复合材料在光、电、磁、生物功能材料中具有潜在的应用前景.基于碳纳米管的电学性质,综述了聚合物/碳纳米管导电复合材料的三种制备方法(熔融共混法、溶液共混法和原位聚合法)以及国内外研究进展,着重介绍了具有取向结构的聚合物/碳纳米管导电复合体系的制备方法,包括模板组装、力场排列、电场排列以及磁场排列等,并分析比较了各种方法的基本原理和特点.最后对聚合物/碳纳米管导电复合材料的应用情况及研究前景进行了初步的探讨.     

碳纳米管/PTFE基复合材料摩擦学性能的研究

以碳纳米管(CNTs)为填料制备了，PTFE基复合材料，并研究了，该复合材料在干摩擦条件下与不锈钢对摩时的摩擦磨损行为，实验结果表明，CNTs／PTFE复合材料的摩擦系数随着CNTs含量的增加呈降低的趋势，其耐磨性能明显优于纯PTFE，当CNTs的体积分数为15％～20％时，其抗磨性能最好，MSEM观察发现纯PTFE的断面上分布着大量的带状结构，而填充了CNTs后，则未观察到这种带状结构，这说明CNTs有效地抑制了PTFE结构的破坏，对PTFE和CNTs／PTFE复合材料的摩擦表面的SEM观察发现，前者的摩擦表面分布着较明显的犁削和粘着磨损的痕迹，而后者的摩擦表面则平整光滑，这表明以CNTs作为填料可有效地抑制PTFE的磨损。     

Thermal expansion and mechanical properties of middle reinforcement content SiCp/Al composites fabricated by PM technology

Middle reinforcement content SiCp/Al composites(Vp=30%, 35% and 40%) for precision optical systems applications were fabricated by powder metallurgy technology. The composites were free of porosity and SiC particles distributed uniformly in the composites. The mean linear coefficients of thermal expansion(20-100 ℃) of SiCp/Al composites ranged from 11.6×10-6 to 13.3×10-6 K-1 and decreased with an increase in volume fraction of SiC content. The experimental coeffi cients of thermal expansion agreed well with predicted values based on Kerner's model. The Brinell hardness increased from 116 to 147, and the modulus increased from 99 to 112 GPa for the corresponding composites. The tensile strengths were higher than 320 MPa, but no signifi cant increasing trend between tensile strength and SiC content was observed.