Carbon Nanotubes Reinforced Copper Matrix Research Articles

The Effect of Surface Coating Treatment on the Properties of Carbon Nanotube Reinforced Copper Matrix Composites

The Effect of Surface Coating Treatment on the Properties of Carbon Nanotube Reinforced Copper Matrix Composites

The Effect of Surface Coating Treatment on the Properties of Carbon Nanotube Reinforced Copper Matrix Composites

Herein, the surface of multi‐walled carbon nanotubes (MWCNTs) is treated with HNO3 oxidation to carry on oxygen‐containing functional groups. Then, the pretreatment surface of MWCNTs are plated with copper to improve the low wettability of carbon nanotubes (CNTs). Finally, metal matrix composite blocks with excellent properties are prepared by spark plasma sintering (SPS). When the content of the reinforcing phase is 0.25 wt%, the tensile strength and hardness of Cu‐MWCNTs/Cu composite compared with pure copper are increased by 34.6% and 136.1%, respectively.

Fabrication and characterisation of carbon nanotube reinforced copper matrix nanocomposites

ABSTRACT Carbon nanotube reinforced metal matrix nanocomposite can be fabricated by using several processes: namely powder metallurgy, molecular-level-mixing, electrodeposition, melt stirring, etc. In this work, carbon nanotube reinforced copper matrix nanocomposites were fabricated by employing the simple powder metallurgy method. Prepared nanocomposites have been characterized by using various characterisation techniques: namely compression test, hardness and density measurement. Morphology and microstructure of composite samples were characterised by using SEM. Properties of the metal matrix nanocomposites were correlated with the microstructure. Experimental results revealed that the density and the specific wear rate of the nanocomposites samples are slightly decreased with the increment of carbon nanotube reinforcement in the metal matrix. Compressive strength of the nanocomposite samples are dramatically increased (155% improvement) with carbon nanotube reinforcement in the copper matrix, while Rockwell hardness number of the samples are slightly increased (22.5% improvement) with an increment of carbon nanotube reinforcement in the matrix material.

Hot Oscillatory Pressing of Carbon Nanotube-Reinforced Copper Matrix Nanocomposite.

Carbon nanotube reinforced copper matrix nanocomposites have great potential in machinery, microelectronics, and other applications. The materials are usually prepared by powder metallurgy processes, in which consolidation is a key step for high performance. To improve the density and mechanical properties, the authors explored the use of hot oscillatory pressing (HOP) to prepare this material. A carbon nanotube reinforced copper matrix nanocomposite was synthesized by both HOP and hot pressing (HP) at various temperatures, respectively. The samples prepared by HOP exhibited significantly higher density and hardness than those prepared by HP at the same temperature, and this was because the oscillatory pressure of HOP produced remarkable plastic deformation in copper matrix during sintering. With the decrease of sintering temperature in HOP, the amount of deformation defect increased gradually, playing a key role in the increasing hardness. This work proves experimentally for the first time that HOP can produce much more plastic deformation than HP to promote densification, and that HOP could be a very promising technique for preparing high-performance carbon nanotube reinforced copper matrix nanocomposites.

Fabrication of carbon nanotubes/Cu composites with orthotropic mechanical and tribological properties

In this work, Multi-Walled Carbon Nanotubes reinforced copper matrix composites were prepared through a series of preparation processes including ultrasonic and nitrogen-assisted mixing, electroless Nickel–Copper bilayers plating, hot extrusion and cold drawing. The mechanical and tribological properties of the composites were enhanced with the increase of MWCNTs. The Cu matrix composites enhanced with 10 vol% MWCNTs showed significant improvements in the mechanical and tribological properties. Compared with the pure Cu sample prepared by the same method, the tensile strength and yield strength of the composite increased by 52.15% and 56.67%, while the friction coefficient and wear rate decreased by 66.8% and 62.3%, respectively. Better than most of the reported data. The 3 vol% MWCNTs in the composites exhibited the highest strengthening efficiency. Due to the directional arrangement of the MWCNTs in the Cu matrix, the composites showed obvious orthogonal anisotropy, and the properties in the parallel drawing direction were much better than those in the vertical drawing direction. Dislocation and load transfer effect are considered as the main mechanism of mechanical properties enhancement. The formation of self-lubricating layer, load transfer, efficient derivation of friction heat and orientation arrangement of MWCNTs were the reasons which lead to the friction performance enhancement.

Simple and efficient preparation of uniformly dispersed Carbon nanotubes reinforced Copper matrix composite powders by in situ chemical vapor deposition without additional catalyst

Carbon nanotubes (CNTs) reinforced Copper (Cu) matrix composite powders have been successfully prepared by in situ chemical vapor deposition (CVD) using Cu-0.6 wt% Al alloy powders without additional catalyst. The catalyst for CNTs growth is nano-copper particle (∼28 nm), and the interaction between Cu and Al2O3 would promote the formation of nano-copper particles (∼28 nm). The high quality multi-walled CNTs obtained dispersed uniformly on and well bonded to the composite powders. And the formation mechanism was discussed, the results show that part of the growth of CNTs follows tip-growth mode and the others without catalyst particles at the top follow the base-growth mode. This providing a simple and effective method for in situ preparation of CNTs/Cu composite powder with uniform dispersion of CNTs.

Influence of acid-treated time of carbon nanotubes on mechanical property in carbon nanotubes reinforced copper matrix composites

Carbon nanotubes reinforced copper matrix (CNT/Cu) composites with high mechanical properties were successfully fabricated by wet mixing and spark plasma sintering (SPS). The effects of CNTs acidification time and CNTs content on the microstructure and mechanical properties of composites were characterized by SEM, FTIR, Raman, HR-TEM and tensile tests. The composites with 24 h acid-treated CNTs (0.5 wt%) and sintered at 837 K had the most optimal mechanical properties, which primarily stemmed from the use of oxygen as an atomic transient agent to form solid Cu-CNT interfacial bonding, the complete densification of the composites and the uniform dispersion of the CNTs. From the density functional calculations, the strong contact mode of Cu2O-CNT is conducive to the improvement of mechanical properties. In addition, the reinforcing effect of surface modification at different acidification times of CNTs was studied and discussed by the strengthening models. This study describes an approach for uniformly dispersing CNTs to enhance the mechanical properties of CNT/Cu composite materials with strong interface bonding and enhancement.

Enhanced mechanical properties and wear resistance of cold-rolled carbon nanotubes reinforced copper matrix composites

Multi-walled carbon nanotube (MWCNT)/Cu composite containing 0.5 vol% MWCNTs were prepared by a high energy ball milling followed by conventional sintering and finally cold rolling. Microstructure studies showed that MWCNTs were uniformly dispersed and implanted inside the Cu matrix. The MWCNT/Cu composites showed an improvement in hardness and tensile strength up to 37% and 44% respectively compared to those of pure Cu. The enhancement is attributed to the uniform dispersion and strengthening due to the addition of MWCNTs. The yield strength of the composite has been quantified by several strengthening mechanisms including grain boundary strengthening, dislocation strengthening, Orowan strengthening and load transfer. The calculated results indicated that the load transfer strengthening has the largest contribution to the yield strength of the composite which implied the key role of the interfacial bond strength between MWCNTs and Cu matrix on the strengthening behaviors. The friction coefficient and specific wear rate of the composites were reduced with the addition of MWCNT content due to the self-lubrication effect of CNTs and high mechanical properties.

Mechanical properties and failure mechanisms at high temperature in carbon nanotube reinforced copper matrix nanolaminated composite

Copper matrix composites are widely used as strong conducting materials. Mechanical properties and failure behavior at high temperatures are investigated for carbon nanotubes/copper matrix nanolaminated composites with well-balanced strength and ductility in this work. Tensile strength of the composite decreased considerably as temperature increased because of matrix softening and Cu grain coarsening. Deformation mechanism is controlled by pipe diffusion mechanism at 573 K, while lattice diffusion at 773 K. The failure behavior is shown to transform from interfacial debonding of CNT-matrix to Cu matrix failure as the temperature increases. CNTs are pulled-out on fractured surfaces at both room and high temperature, but with different morphologies. Elemental analysis and microstructural observations indicated that the interface shear strength is between the matrix strength of 75 MPa at 773 K and 320 MPa at room temperature. The results shed light on designing advanced copper matrix composites for applications at high temperature.

Effect of thermal cycling on the mechanical properties of carbon nanotubes reinforced copper matrix nanolaminated composites

The effect of thermal cycling on the mechanical properties of metal matrix composites (MMCs) reinforced with micro-fillers have been studied for a long time, but that for nano-size-reinforcements remains largely unexplored, such as carbon nanotubes (CNTs). We have fabricated CNTs/Cu laminated MMCs with well-balanced tensile strength and elongation via flake powder metallurgy. In this work, the effect of thermal cycling on their mechanical properties are investigated in a temperature range of –196/+ 200 °C. The thermal cycling results in reductions in strength and elongation and modulus, but the strengthening role of CNTs remains in some extents as compared to the pure Cu counterpart. Tensile tests at room temperature show that high strain hardening ability can be regained even after a sharp stress drop in the thermally cycled composites. The observations on transmission electron microscope (TEM) and scanning electron microscope (SEM) show that the amount of crack increases gradually in the composites upon thermal cycling. Nevertheless, CNT bridges are often found bestriding the cracks and impeding their propagating. The TEM results indicate high density of dislocation in the Cu matrix after thermal cycling, but it decreases after enough thermal cycles, which might be attributed to the stress releasing caused by crack propagation. The failure mode is dominated by the inter-carbon-layer fracture of the multi-walled CNTs in the composites subjected to thermal cycling and tensile loading.

Enhancing the strength of carbon nanotubes reinforced copper matrix composites by optimizing the interface structure and dispersion uniformity

Interface between carbon nanotubes (CNTs) and copper matrix is generally weak mechanical bonding due to the lack of wetting and interaction between them. In the present study, the homogeneous distribution of CNTs in copper matrix was realized through a novel mixing method and spark plasma sintering (SPS). The interface structures of CNTs/Cu composites were optimized by using decorated CNTs. Transmission electron microscopy (TEM) observation revealed the formation of interfacial products, amorphous transition areas and interfacial stress zones at the decorated-CNT/Cu interfaces. The compressive tests showed that the composite containing 2 vol% of Ni-coated CNTs has a maximum compression yield strength of 554 MPa, which was increased by 55% and 30% compared with that of pure Cu and the composite reinforced with pristine CNTs, respectively. The strong strengthening effects of the decorated CNTs can be attributed to their interaction with Cu matrix. The strengthening mechanisms, load transfer efficiency and interfacial shear strength were also discussed from the point of interface structure. This work underscores the importance of the surface state of CNTs on the interface structure in metal matrix composites, and may provide insights into the composites where reinforcements and matrix are lack of wetting and interactions.

Enhanced mechanical properties and high electrical conductivity in multiwalled carbon nanotubes reinforced copper matrix nanolaminated composites

Multiwalled carbon nanotubes/copper (MWCNTs/Cu) composites with a nanolaminated structure have been successfully prepared via flake powder metallurgy. The key strategies are to achieve uniform dispersion of carbon nanotubes in copper matrix and laminated structure, leading to high strengthening efficiencies and architecture toughening. As a result, the composites show balanced failure strength and elongation and high electrical conductivity. The tensile strength of 1.0 vol% MWCNTs/Cu laminated composite is 395 MPa, 87% higher than that of coarse-grained Cu. At the same time, the enhancement on strength does not cause serious deterioration in failure elongation and electrical conductivity. A satisfied uniform elongation in excess of 20% and an electrical conductivity more than 90% International Annealed Copper Standard (IACS) are retained in the composite. Characterizations by in-situ digital image correlation and X-ray tomography indicate efficient stress transferring during loading as well as laminated structure guiding crack propagation, contributing to the good strength-elongation balance. Additionally, the electrical conductivity of the composites is anisotropic because of the laminated structure.

Balancing the strength and ductility of carbon nanotubes reinforced copper matrix composites with microlaminated structure and interdiffusion interface

Microlaminated carbon nanotubes (CNTs) reinforced Cu matrix composites were prepared by combination of composite electrodeposition and spark plasma sintering (SPS). Interdiffusion transition regions formed between CNTs and Cu matrix under high sintering temperature, which were responsible for the balanced strength and ductility of the composites.

Mechanical properties and microstructure characterization of well-dispersed carbon nanotubes reinforced copper matrix composites

Copper (Cu) matrix composites reinforced with 0.3, 0.5, 1.0, and 2.0 vol% multi-wall carbon nanotubes (MWCNTs) were processed by ultrasonication and high-energy attritor milling of pure copper powder with carbon nanotubes (CNTs), followed by spark plasma sintering and annealing. Microstructural characterization shows that the CNTs are well-dispersed in Cu-0.5 vol% CNTs composite, and the aggregation of CNTs increases with the increase in the volume fraction of carbon nanotubes. Raman spectroscopy results indicate that there is an increase in the number of defects in the nanotube after milling and sintering of the composite. Mechanical property and strengthening mechanism analysis indicates that the grain size effect, hindering effect of dislocations interacting with the grain boundary, and load transfer effect are the main mechanisms affecting the mechanical properties of composites, and the experimental strength of the composite can be close to 81% of the theoretical strength.

Enhanced strength and excellent transport properties of a superaligned carbon nanotubes reinforced copper matrix laminar composite

Superaligned carbon nanotube (SACNT) reinforced copper matrix laminar composites have been fabricated by means of the traditional copper sulfate electroplating process. The mechanical properties and transport properties of the Cu/SACNT composites with different SACNT content have been studied systematically, and the experimental results show that the as-prepared composites possess a better comprehensive performance than pure copper. The simple rule of mixtures (ROM) has been used to estimate the potential maximum properties of the Cu/SACNT composites. The Cu/SACNT composite is considered to be a promising material for electronics and communications applications.

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.

Predicting the hardness of carbon nanotube reinforced copper matrix nanocomposites using two adaptive fuzzy inference system identifiers

The paper deals with devising two different fuzzy inference systems to predict the hardness of copper/carbon nanotube nanocomposite. These composites are outstanding candidates for thermal management applications in electronic packaging due to the high conductivity of copper. Knowing the extraordinary properties of carbon nanotubes, it seems that copper-based composites reinforced with small amount of carbon nanotubes, resulted in improved mechanical properties. Hence, carbon nanotube reinforced copper matrix nanocomposites are fabricated by hot-press sintering of high energy ball milled copper/carbon nanotube powders. Different milling factors are investigated. Finally the Vickers hardness of sintered nanocomposites is reported. To simulate a predictive framework for current case study, two different machine learning algorithms are engaged. The first learning algorithm is the classic least square optimization method, which provides the requirements for fast adaption of the consequent parts of fuzzy inference system. The second method learning algorithm uses the rudiments of neural computing through layering the fuzzy inference system and using back-propagation optimization algorithm. Based on the experiments, the authors realize that the adopted fuzzy systems can effectively extract the knowledge required for predicting the hardness of copper/carbon nanotube nanocomposite.

Effect of Balls/Powder Weight Ratio in Milling on Microstructure and Properties of MWCNTs/Cu Composites

High energy milling (HEM) was used to the preparation of multi-walled carbon nanotubes reinforced copper matrix (MWCNTs/Cu) composite powders in this paper. And the MWCNTs/Cu composite material was prepared by the cold-press sintering method. The influence law of balls/powder weight ratio to the MWCNTs/Cu composite powders was discussed. Particle size distribution and fracture micrograph were analyzed by XRD and SEM. The results show that particle size distribution of CNTs/Cu composite powders reached a minimum, when the balls/powder weight ratio was 10: 1. The particle size distribution (D50) of CNTs/Cu composite powders was 22.33μm. The CNTs distributes homogeneously , which is in favor of the mechanical combination of the CNTs and Cu substrate. The tensile strength of CNTs/Cu composite reached 189 MPa.

Carbon nanotubes–reinforced copper matrix composites produced by melt stirring

Due to their geometry and extraordinary mechanical properties, carbon nanotubes have been envisioned as promising enhancements for metal matrix composites. In this article, we report on our melt stirring approach for incorporation of carbon nanotubes into a copper alloy matrix and on the experimental results obtained by assessing the material properties. The existence of carbon nanotubes in the copper matrix after processing was proven by Raman analysis. We found that the small amounts of carbon nanotubes (0.1 wt%) in the composites influenced mechanical and abrasive wear properties.

Experimental and numerical investigation into the effect of carbon nanotube buckling on the reinforcement of CNT/Cu composites

Abstract Carbon nanotube reinforced copper matrix (CNT/Cu) composites with high strength and good damping have been developed using acid treatment, sintering processes and consolidation techniques. Strengthening of the composites as a result of nanotube buckling has been demonstrated by experimental nanoindentation tests and molecular dynamics (MD) simulations. The experimental results show that the buckling behavior of additional CNTs in the CNT/Cu composites varies with the slenderness ratio of CNTs. Specifically, this study shows that the significant buckling behavior of CNTs in the CNT/Cu composites where the shorter CNTs (with a smaller slenderness ratio) give rise to a global buckling and the slender CNTs (with a larger slenderness ratio) induce local buckling. The MD simulation results reveal that the buckling behavior of the CNTs plays a key role in increasing the mechanical strength of CNT/Cu composites by acting as a “buffer” in releasing excess strain in the Cu matrix.