Ceramic particles reinforced copper matrix composites manufactured by advanced powder metallurgy:preparation, performance, and mechanisms

Copper matrix composites doped with ceramic particles are known to effectively enhance the mechanical properties,thermal expansion behavior and high-temperature stability of copper while maintaining high thermal and electrical conductivity.This greatly expands the applications of copper as a functional material in thermal and conductive components,including electronic packaging materials and heat sinks,brushes,integrated circuit lead frames.So far,endeavors have been focusing on how to choose suitable ceramic components and fully exert strengthening effect of ceramic particles in the copper matrix.This article reviews and analyzes the effects of preparation techniques and the characteristics of ceramic particles,including ceramic particle content,size,morphology and interfacial bonding,on the diathermancy,electrical conductivity and mechanical behavior of copper matrix composites.The corresponding models and influencing mechanisms are also elaborated in depth.This review contributes to a deep understanding of the strengthening mechanisms and microstructural regulation of ceramic particle reinforced copper matrix composites.By more precise design and manipulation of composite microstructure,the comprehensive properties could be further improved to meet the growing demands of copper matrix composites in a wide range of application fields.

Fabrication of superaligned carbon nanotubes reinforced copper matrix laminar composite by electrodeposition

A new kind of laminar metal matrix nanocomposite（MMC） was fabricated by an electrodeposition process with copper and superaligned carbon nanotubes film（SACNT film）.The SACNT film was put on a titanium plate and then a layer of copper was electrodeposited on it.By repeating the above process,the laminar Cu/SACNT composite which contains dozens or hundreds of layers of copper and SACNT films was obtained.The thickness of a single copper layer was controlled by adjusting the process parameter easily and the thinnest layer is less than 2 μm.The microscopic observation shows that the directional alignment structure of SACNT is retained in the composite perfectly.The mechanical and electrical properties testing results show that the tensile and yield strengths of composites are improved obviously compared with those of pure copper,and the high conductivity is retained.This technology is a potential method to make applicable MMC which characterizes high volume fraction and directional alignment of carbon nanotubes.

Effects of rare earth element lanthanum on the microstructure of copper matrix diamond tool materials

Effects of rare earth element La on the microstructure of Cumatrix diamond tools were researched under the conditions of variousmaterials components and the process parameters in order to improvematerials properties. SEM, XPS and X-ray were used to investigate thefracture section, microstructure and the element valence inmaterials. The Results shown that the combination of rare earthelement La and transition element Ti is advantageous to the bondingstate Between diamond particles and matrix, so it can improve thematerials properties. Suitable sintering temperature is 790 deg. C.

Improving effect of carbonized quantum dots(CQDs)in pure copper matrix composites

Carbon quantum dots(CQDs),which contain a core structure composed of sp^(2)carbon,can be used as the reinforcing phase like graphene and carbon nanotubes in metal matrix.In this paper,the CQD/Cu composite material was prepared by powder metallurgy method.The composite powder was prepared by molecular blending method and ball milling method at first,and then densified into bulk material by spark plasma sintering(SPS).X-ray diffraction,Raman spectroscopy,infrared spectroscopy,and nuclear magnetic resonance were employed to characterize the CQD synthesized under different temperature conditions,and then CQDs with a higher degree of sp^(2)were utilized as the reinforcement to prepare composite materials with different contents.Mechanical properties and electrical conductivity results show that the tensile strength of the 0.2 CQD/Cu composite material is~31%higher than that of the pure copper sample,and the conductivity of 0.4 CQD/Cu is~96%IACS,which is as high as pure copper.TEM and HRTEM results show that good interface bonding of CQD and copper grain is the key to maintaining high mechanical and electrical conductivity.This research provides an important foundation and direction for new carbon materials reinforced metal matrix composites.

Microstructure and properties of copper matrix composites reinforced by nano-SiC and nano-Al_2O_3 particles

Copper/silicon carbide composites （Cu/SiC） and copper/alumina composites （Cu/Al2O3） were fabricated by the powder metallurgy method. The influence of reinforcement particles contents on the relevant properties of the composites and the microstructure of Cu/SiC and Cu/Al2O3 composites were studied. The reinforcement effects of nano-SiC and nano-Al2O3 particles were compared. The experimental results show that with the increase of the amount of nano-SiC and nano-Al2O3 particles, the density of the both composites decreases, the resistivity increases, whereas the hardness increases firstly and then drops. The softening temperatures of the composites are above 700℃ which is far higher than that of the pure copper, leading to the improvement of the thermal stability of the composites at high temperatures. Considering all factors, the reinforcement effects of nano-SiC are better than those of nano-Al2O3 when their contents are the same in the copper matrix.

Thermo-physical Properties of Continuous Carbon Fiber Reinforced Copper Matrix Composites

Continuous carbon fiber reinforced copper matrix composites with 70%(volume fraction) of carbon fibers prepared by squeeze casting technique have been used for investigation of the coefficient of thermal expansion(CTE) and thermal conductivity.Thermo-physical properties have been measured in both,longitudinal and transversal directions to the fiber orientation.The results showed that Cf/Cu composites may be a suitable candidate for heat sinks because of its good thermo-physical properties e.g.the low CTE(4.18×10-6/K) in longitudinal orientation and(14.98×10-6/K) in transversal orientation at the range of 20-50℃,a good thermal conductivity(87.2 W/m·K) in longitudinal orientation and(58.2 W/m·K) in transversal orientation.Measured CTE and thermal conductivity values are compared with those predicted by several well-known models.Eshelby model gave better results for prediction of the CTE and thermal conductivity of the unidirectional composites.

Fabrication and thermal conductivity of copper matrix composites reinforced by tungsten-coated carbon nanotubes

Carbon nanotubes （CNTs） were coated by tungsten using metal organic chemical vapor deposition. Magnetic stirring was employed to disperse the W-coated CNTs （W-CNTs） in a Cu matrix, and then, the mixed powders were consolidated by spark plasma sintering. The W-CNTs obtained a uniform dispersion within the Cu matrix when the W-CNT content was less than 5.0vo1%, but high content of W-CNTs （10vol%） resulted in the presence of clusters. The W-CNT/Cu composites containing low content of W-CNTs （〈5.0vol%） exhibited a higher thermal conductivity than the sintered pure Cu, while the CNT/Cu composites exhibited no increase in thermal conductivity after the incorporation of uncoated CNTs. The W-CNT content was found to play a crucial role in determining the thermal conductivity of the W-CNT/Cu composites. The thermal conductivity of the W-CNT/Cu composites increased first and then decreased with the W-CNT content increasing. When the W-CNT content was 2.5vo1%, the W-CNT/Cu composite obtained the maximum value of thermal conductivity. The thermal resistance of the （W-CNT）-Cu interface was predicted in terms of Maxwell-Gamett effective medium approximation, and its calculated value was about 3.0× 10-9 m2.K.W-l.

Hybrid effect on mechanical properties and high-temperature performance of copper matrix composite reinforced with micro-nano dual-scale particles

A dual-scale hybrid HfB_(2)/Cu-Hf composite with HfB_(2) microparticles and Cu_(5) Hf nanoprecipitates was designed and prepared.The contribution of the hybrid effect to the mechanical properties and high-temperature performances was studied from macro and micro perspectives,respectively.The hybrid of dual-scale particles can make the strain distribution of the composite at the early deformation stage more uniform and delay the strain concentration caused by the HfB_(2) particle.The dislocation pinning of HfB_(2) particles and the coherent strengthening of Cu_(5) Hf nanoprecipitates simultaneously play a strengthening role,but the strength of the hybrid composite is not a simple superposition of two strengthening mod-els.In addition,both Cu_(5) Hf nanoprecipitates and HfB_(2) microparticles contribute to the high-temperature performance of the composite,the growth and phase transition of nanoprecipitates at high temperature will reduce their contribution to strength,while the stable HfB_(2) particles can inhibit the coarsening of matrix grains and maintain the high-density geometrically necessary dislocations(GNDs)in the matrix,which ensures more excellent high-temperature resistance of the hybrid composite.As a result,the hy-brid structure can simultaneously possess the advantages of multiple reinforcements and make up for the shortcomings of each other.Finally,a copper matrix composite with high strength,high conductivity,and excellent high-temperature performance is displayed.

Tribological properties of copper matrix composites reinforced with homogeneously dispersed graphene nanosheets

Graphene reinforced copper matrix composites （Gr/Cu） were fabricated by electrostatic self-assembly and powder metallurgy. The morphology and structure of graphene oxide, graphene oxide-Cu powders and Gr/Cu composites were characterized by scanning electronic microscopy, transmission electronic microscopy, X-ray diffraction and Raman spectroscopy, respectively. The effects of graphene contents, applied loads and sliding speeds on the tribological behavior of the composites were investigated. The results indicate that the coefficient of friction of the composites decreases first and then increases with increasing the graphene content. The lowest friction coefficient is achieved in 0.3 wt~ Gr/Cu composite, which decreases by 65% compared to that of pure copper. The coefficient of friction of the composite does not have significant change with increasing the applied load, however, it increases with increasing the sliding speed. The tribological mechanisms of the composite under different conditions were also investigated.

Significant strengthening of copper-based composites using boron nitride nanotubes

Nanotubes, such as boron nitride nanotubes (BNNTs) and carbon nanotubes (CNTs), exhibit excellent mechanical properties. In this work, high-quality BNNTs were synthesized by ball milling and annealing. Subsequently, well-dispersed 3vol%BNNTs/Cu and 3vol%CNTs/Cu composites were successfully prepared using ball milling, spark plasma sintering, and followed by hot-rolling. Moreover, the mechanical properties and strengthening mechanisms of BNNTs/Cu and CNTs/Cu composites were compared and discussed in details. At 293 K,both BNNTs/Cu and CNTs/Cu composites exhibited similar ultimate tensile strength (UTS) of~404 MPa, which is approximately 170%higher than pure Cu. However, at 873 K, the UTS and yield strength of BNNTs/Cu are 27%and 29%higher than those of CNTs/Cu, respectively.This difference can be attributed to the stronger inter-walls shear resistance, higher thermomechanical stability of BNNTs, and stronger bonding at the BNNTs/Cu interface as compared to the CNTs/Cu interface. These findings provide valuable insights into the potential of BNNTs as an excellent reinforcement for metal matrix composites, particularly at high temperature.

Thermal Performances of High-Temperature Thermal Energy Storage System with Tin Embedded in Copper Matrix by Theoretical Methods

There is a critical need to develop advanced high-temperature thermal storage systems to improve efficiencies and reduce the costs of solar thermal storage system.In this work,two typical systems composed with Cu as matrix and Sn as the phase change material(PCM)are explored,namely,the 3-deimentional(3D)structure system by embedding Sn particles into Cu matrix and the 2-deimentional(2D)structure system by embedding Sn wires into Cu matrix.Given the thermophysical properties of a nanomaterial could be importantly different from that of a bulk one,we thus firstly derive the thermophysical properties of PCM and matrix theoretically,like the thermal conductivity by kinetic method and the specific heat capacity based on Lindemann’s criterion.And then,these properties are utilized to estimate the energy storage ability in both 3D and 2D structure system,and the influence of structure on heat transfer efficiency is theoretically investigated in both 3D and 2D structure system.Results turn out that 3D structure system is a better choice than a 2D structure system,because of larger specific surface area,a larger sensitive heat capacity and a larger thermal conductivity.When the feature size of the PCM decreases to be less than a critical value which is about 500 nm for Sn,the thermal conductivity of the system decreases exponentially while the heat storage capacity increases lineally.Moreover,when the feature size of Sn geometry is less than a critical value,which is 15 nm for 3D structure system and 25 nm for 2D structure,the Cu matrix can’t play a role in improving the effective thermal conductivity of the whole system.

增强体表面改性在高导热金属基复合材料中的应用

随着电子技术的高速发展和电子器件的更新换代,电子封装材料的性能需求越来越高。金属基复合材料,尤其是铝基和铜基复合材料具有高导热、低膨胀、高稳定性等特点,是具有广阔应用前景的电子封装材料。然而,金刚石、石墨烯、硅等增强体与基体的润湿性差,或者在高温下与基体发生有害的界面反应,限制了此类高导热金属基复合材料的开发和应用。本文简述了金属基复合材料的界面研究进展,结合影响金属基复合材料界面结合的因素,提出了几种改善界面结合的方法。增强体表面改性是改善金属基复合材料界面的重要途径之一,常用工艺有磁控溅射法、化学气相沉积法、溶胶凝胶法、化学镀法等;最后,对增强体表面改性在高热导金属基复合材料中的应用进行分析和展望。

<i>In Situ</i>Analysis of Copper Alloys by Femtosecond Laser Ablation Inductively Coupled Plasma Mass Spectrometry: Constrains on Matrix Effects

Direct analysis of copper-base alloys using laser ablation techniques is an increasingly common procedure in cultural heritage studies. However, main discussions remain focused on the possibility of using non-matrix matched external reference materials. To evaluate the occurrence of matrix effects during in situ microanalysis of copper-base materials, using near infrared femtosecond laser ablation techniques (NIR fs-LA-ICP-MS), two bronzes, i.e., (Sn-Zn)-ternary and (Sn)-binary copper-matrix reference materials, as well as a reference synthetic glass (NIST-SRM-610) have been analyzed. The results have been compared to data obtained on a sulfide-matrix reference material. Similar values in relative sensitivity averages of 63Cu, 118Sn and 66Zn, as well as in 118Sn/63Cu and 66Zn/63Cu ratios were obtained, for all analyzed matrix types, i.e., copper-base-, silicate-, and sulfide-reference materials. Consequently, it is possible to determinate major and minor element concentrations in copper alloys, i.e., Cu, Sn and Zn, using silicate and sulfide reference materials as external calibrators, without any matrix effect and over a wide range of concentrations (from wt.% to ppm). Equally, Cu, Sn and Zn concentrations can be precisely determined in sulfides using homogeneous alloys (reference) materials as an external calibrator. Thus, it is possible to determine Cu, Sn and Zn in copper-base materials and their ore minerals, mostly sulfides, in a single analytical session, without requiring specific external calibrators for each matrix type. In contrast, immiscible elements in copper matrix, such as Pb and Fe show notable differences in their relative sensitivity values and ratios for different matrix-materials analyzed, implying that matrix-matched external calibrations remain to be applied for their trace quantification.

Bending results of graphene origami reinforced doubly curved shell

The present work investigates higher order stress,strain and deformation analyses of a shear deformable doubly curved shell manufactures by a Copper(Cu)core reinforced with graphene origami auxetic metamaterial subjected to mechanical and thermal loads.The effective material properties of the graphene origami auxetic reinforced Cu matrix are developed using micromechanical models cooperate both material properties of graphene and Cu in terms of temperature,volume fraction and folding degree.The principle of virtual work is used to derive governing equations with accounting thermal loading.The numerical results are analytically obtained using Navier's technique to investigate impact of significant parameters such as thermal loading,graphene amount,folding degree and directional coordinate on the stress,strain and deformation responses of the structure.The graphene origami materials may be used in aerospace vehicles and structures and defence technology because of their low weight and high stiffness.A verification study is presented for approving the formulation,solution methodology and numerical results.

粉末冶金制备碳纳米管增强铜基复合材料研究进展

碳纳米管具有优异的力学性能和导电、导热性能,作为增强体引入铜基体中有望开发出新一代高强、结构功能一体化的复合材料。然而,碳纳米管在铜基体中的分散性较差及其与铜的润湿性问题,成为制备碳纳米管增强铜基(CNTs/Cu)复合材料的主要挑战,并显著影响了复合材料的性能。本文对目前有关制备碳纳米管增强铜基复合材料的主要方法包括碳纳米管前期预处理方法、碳纳米管在铜粉末中分散的方法、复合材料的烧结方法进行总结,概述复合材料的力学性能、摩擦磨损性能以及导电导热性能的研究进展,并提出思考和展望,以便为制备CNTs/Cu复合材料研究提供参考。

镀铜石墨对铜基制动闸片组织及性能的影响

采用化学镀的方式在鳞片状石墨表面镀铜来改善铜基制动闸片中石墨和铜基体的界面结合,制定了化学镀铜配方及工艺,并研究了4种不同镀液温度对镀铜效果的影响。对镀铜后的石墨进行显微组织观察和能谱分析可知:随镀液温度的升高,镀铜效果先升后降,最好的施镀温度为50℃。用热压烧结法制备出镀铜石墨/铜基制动闸片(FM1)与非镀铜石墨/铜基制动闸片(FM0),并对其进行力学性能、物理性能测试以及制动测试,并采用扫描电镜和能谱仪对制动闸片在制动前后的表面形貌进行观察及分析。结果表明:与FM0相比,FM1中石墨分布更细小均匀,因此样品的致密度较高,硬度、抗压强度和热导率也随之增大。在不同制动初速度下,随制动初速度的提高,两种闸片的摩擦系数均出现先略微增高、后平稳,然后显著降低的趋势,但FM1的摩擦系数总体比FM0的摩擦系数更高且稳定,线磨损率也相对较小。在350 km/h高速制动条件下,由于摩擦热引起的材料表面软化,两种制动闸片的摩擦系数差别不大,都呈现显著下降趋势。

壳核结构氧化铝@石墨烯复合粉末增强铜基复合材料摩擦学性能研究

如何充分发挥润滑组元和耐磨组元的协同作用以提高铜基复合材料摩擦学性能仍面临具大的挑战。以石墨烯为润滑组元,氧化铝为耐磨组元,对比了氧化铝和石墨烯组装为壳核结构前后对铜基复合材料摩擦学性能的影响。结果表明,与氧化铝和石墨烯分别以独立相分布于铜基体的情况相比,氧化铝和石墨烯组装为壳核结构后可以提高铜基复合材料的致密度、硬度,并有利于在磨痕表面形成连续且具有保护性的摩擦层。因此,在10~40 N载荷范围内干摩擦,后者比前者具有更低的摩擦因数和磨损率。

基体铬合金化增强石墨烯/铜复合材料摩擦学性能研究

如何通过优化石墨烯/铜复合材料的界面结构来提高复合材料的摩擦学性能成为石墨烯增强铜基复合材料领域重要的研究方向之一。采用铜铬合金(CuCr)作为基体材料,还原氧化石墨烯(RGO)作为增强相,通过溶液搅拌混合和热压烧结工艺制备得到了RGO/CuCr复合材料。对比了添加铬元素前后复合材料的减摩耐磨性能,基于磨痕表面成份和形貌的分析探讨了铜基体铬合金化对石墨烯/铜复合材料摩擦学性能的作用机制。结果表明,铜基体铬合金化使复合材料具有更小更稳定的摩擦因数和更低的比磨损率,特别是在高载荷工况下。性能提高的原因归结为铜基体铬合金化有利于在摩擦过程中复合材料表面形成致密而连续的富石墨烯摩擦层。

铜基体铬合金化对二硫化钼/铜复合材料摩擦学性能的影响及作用机制研究

基于铜基体铬合金化的策略,研究了铬含量对二硫化钼/铜复合材料在氮气气氛下摩擦学性能的影响。结果表明,在复合材料中加入1.5wt%铬,摩擦系数低至0.07,磨损率为2.4×10^(-4)mm^(3)·N^(-1)·m^(-1),分别是未添加铬的复合材料的64%和20%。通过透射电镜、X射线光电子能谱、扫描电镜分别对二硫化钼/铜界面结构、摩擦层成分及磨痕亚表层形貌进行了详细的分析,揭示了铜基体铬合金化对二硫化钼/铜复合材料摩擦学性能的作用机制。

挤压速度对搅拌摩擦反挤压法制备Cu-5%Ti_(2)SnC复合丝材性能的影响

对粉末冶金法制备的含5%(体积分数)Ti_(2)Sn CMAX相的初始复合材料进行搅拌摩擦反挤压(FSBE)处理,研究FSBE工艺的轴向横移速度对Cu-Ti_(2)Sn C复合线材显微组织、力学性能、电学性能和磨损性能的影响。结果表明,随着挤压速度的增加,显微组织中孪晶增多,Ti_(2)SnC颗粒细化,MAX相和Cu基体之间的界面结合改善。当转速为600r/min,轴向横移速度为25mm/min时,Cu-Ti_(2)SnC复合线材具有最大的硬度、屈服强度和极限抗拉强度,分别为HV 132.7、278.34MPa和485.15MPa,这是其更强的界面结合和更细的MAX相导致的。此外,当转速为600 r/min,轴向横移速度为25 mm/min时,Cu-Ti_(2)SnC复合丝的电导率最高,达到89.21%(IACS),磨损率最低,为0.0015 mg/m,这是其更大的晶粒尺寸、更强的界面结合与更低的密度导致的。