Homogeneous Distribution Of Carbon Nanotubes Research Articles

A Study of Silver Decoration on Carbon Nanotubes via Ultrasonic Chemical Synthesis and Their Reinforced Copper Matrix Composites.

The homogeneous distribution of carbon nanotubes (CNTs) in the Cu matrix and good interfacial bonding are the key factors to obtain excellent properties of carbon nanotube-reinforced Cu-based composites (CNT/Cu). In this work, silver-modified carbon nanotubes (Ag-CNTs) were prepared by a simple, efficient and reducer-free method (ultrasonic chemical synthesis), and Ag-CNTs-reinforced copper matrix composites (Ag-CNTs/Cu) were fabricated by powder metallurgy. The dispersion and interfacial bonding of CNTs were effectively improved by Ag modification. Compared to CNTs/Cu counterparts, the properties of Ag-CNTs/Cu samples were significantly improved, with the electrical conductivity of 94.9% IACS (International Annealed Copper Standard), thermal conductivity of 416 W/m·k and tensile strength (315 MPa). The strengthening mechanisms are also discussed.

Multiwall carbon nanotubes-based composites – mechanical characterization using the nanoindentation technique

Abstract We report on mechanical properties of multiwall carbon nanotubes (MWNTs)-polymer composites using the nanoindentation technique. The nanoindentation experiments conducted on thin films containing MWNTs revealed that the presence of nanotubes does not affect the nanomechanical properties of the composites. Even a layer-by-layer assembly of MWNTs with a high concentration and a homogeneous distribution of carbon nanotubes does not ensure reinforcement of the composites. For that reason, we synthesized and utilized carbon nanotubes with a silica shell. Nanohardness and Young’s modulus have been found to increase strongly with increasing content of these nanotubes in the polymer matrix. The silica shell on the surface of a nanotube enhances its stiffness and rigidity. Our composites, at 4 wt.% of the silica-coated MWNTs, display a maximum hardness of 120 ± 20 MPa and a Young’s modulus of 9 ± 1 GPa. These are, respectively, 2 and 3 times higher than those for the polymeric matrix.

Droplet size controllable fabrication of Pickering emulsion stabilized by soy protein isolate-carbon nanotubes/carboxymethyl cellulose sodium

ABSTRACT Pickering emulsion plays an important role in various industrial fields including food, catalysis, and bioscience. Soy protein isolate (SPI) has been proved feasible for stabilizing Pickering emulsion after modification, though such methods were either difficult to proceed or application restrictive. Herein, we report a simple fabrication of oil-in-water Pickering emulsion using a complex of SPI and carbon nanotubes (CNTs)/carboxymethyl cellulose sodium (CMC-Na). The stability of our emulsion could be kept at a wide range of CNTs diameter, oil fraction, and pH, while the emulsion droplet size might be controlled through the tuning of pH and dispersed phase solvent as well. A strong interaction between SPI and CNTs/CMC-Na is a key factor for the homogeneous distribution of CNTs at the aqueous–organic interface, which benefits the Pickering emulsion formation. Our work will offer some useful thoughts for improving the stability of protein-integrated emulsion.

Mechanical and tribological properties of Self-Lubricating Al 6061 hybrid nano metal matrix composites reinforced by nSiC and MWCNTs

Numerous investigations have been carried out using carbon nanotubes (CNTs) as reinforcement in different matrix materials. Uniform dispersion of CNTs throughout the matrix material has been the main challenge. This is due to the higher surface area of the Nano particulates, which led to form clusters because of van der Waals forces. Hence, a homogeneous distribution of CNTs is essential as it translates into homogeneous properties throughout the metal matrix composite materials. Al 6061 matrix composite materials reinforced with CNTs and nSiC were fabricated by mechanical ball milling and sintering. nSiC Nano particulate was used as a secondary dispersion agent to distribute CNTs uniformly throughout the Al 6061 matrix. The ball milled composite powders and bulk composites were studied using optical microscopy, FESEM, elemental mapping, XRD, Raman Spectroscopy analysis, and microhardness. The wear characteristics of these hybrid Nanocomposites were evaluated using Pin-On-Disc. Effect of nSiC addition to the existing Al 6061 + MWCNTs has been investigated. The microhardness of the fabricated hybrid composites is 3 times higher than the single reinforcement of MWCNTs in Al 6061 matrix. The formation of new phases like Al4C3 and CrC play a major role in enhancing the hardness of the composites. The surface roughness of the hybrid composites is directly proportional to its hardness. The uniform distribution of hardness in hybrid nanocomposites results in reduction of wear rate.

Spark Plasma Sintering of Hybrid Nanocomposites of Hydroxyapatite Reinforced with CNTs and SS316L for Biomedical Applications

Background: The development of new bioimplants with enhanced mechanical and biomedical properties have great impetus for researchers in the field of biomaterials. Metallic materials such as stainless steel 316L (SS316L), applied for bioimplants are compatible to the human osteoblast cells and bear good toughness. However, they suffer by corrosion and their elastic moduli are very high than the application where they need to be used. On the other hand, ceramics such as hydroxyapatite (HAP), is biocompatible as well as bioactive material and helps in bone grafting during the course of bone recovery, it has the inherent brittle nature and low fracture toughness. Therefore, to overcome these issues, a hybrid combination of HAP, SS316L and carbon nanotubes (CNTs) has been synthesized and characterized in the present investigation. Methods: CNTs were acid treated to functionalize their surface and cleaned prior their addition to the composites. The mixing of nano-hydroxyapatite (HAPn), SS316L and CNTs was carried out by nitrogen gas purging followed by the ball milling to insure the homogeneous mixing of the powders. In three compositions, monolithic HAPn, nanocomposites of CNTs reinforced HAPn, and hybrid nanocomposites of CNTs and SS316L reinforced HAPn has been fabricated by spark plasma sintering (SPS) technique. Results: SEM analysis of SPS samples showed enhanced sintering of HAP-CNT nanocomposites, which also showed significant sintering behavior when combined with SS316L. Good densification was achieved in the nanocomposites. No phase change was observed for HAP at relatively higher sintering temperatures (1100°C) of SPS and tricalcium phosphate phase was not detected by XRD analysis. This represents the characteristic advantage with enhanced sintering behavior by SPS technique. Fracture toughness was found to increase with the addition of CNTs and SS316L in HAPn, while hardness initially enhanced with the addition of nonreinforcement (CNTs) in HAPn and then decrease for HAPn-CNT-SS316L hybrid nanocomposites due to presence of SS316L. Conclusion: A homogeneous distribution of CNTs and SPS technique resulted in the improved mechanical properties for HAPn-CNT-SS316L hybrid nanocomposites than other composites and suggested their application as bioimplant materials.

Processing and Properties of CNTs/ADC12 Nanocomposite

Carbon nanotubes (CNTs)-reinforced ADC12 nanocomposite was successfully fabricated via casting. The CNTs-Al master alloy was prepared by hot extrusion, and the CNTs were dispersed into the matrix by a high-intensity ultrasonic treatment during the casting process to yield 0.5, 1.0, 1.5 wt.% of the CNTs/ADC12 composite. The key step in arriving at homogeneous distribution of CNTs was preparation of the CNTs-Al master alloy and the introduction of a high-intensity ultrasonic treatment method. The cavitation bubbles that adhered to the aggregated CNTs closed rapidly and released large amounts of energy, which had an impact via the cavitation effect, which made the aggregated CNTs dissociate and disperse homogeneously into the melt. Under the conditions of ultrasonic power of 2.1 kW and ultrasonic time of 10 min, the mean diameter of α-Al was 53.2 μm, which was 58.9% lower than that of the matrix. The microhardness and the ultimate tensile strength (UTS) of nanocomposite with 1.0 wt.% CNTs addition increased by 29.3 and 27%, respectively, as compared with the matrix. CNTs can be dispersed in the matrix homogeneously. It was observed by scanning electron microscope (SEM) that CNTs as a load-bearing element were embedded in the matrix independently, enhancing the mechanical properties. This suggested that the improvement of mechanical properties could be attributed to the size and degree of CNTs clustering, the load transfer from the matrix to the CNTs and the grain refinement of the nanocomposite.

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.

The influence of CNTs on the microstructure and strength of Al-CNT composites produced by flake powder metallurgy and hot pressing method

During the mechanical milling of powders for the production of metal matrix composites, the work hardening of metals occurs along with the distribution of reinforcing particles, which reduces the ductility and formability of the powders. The use of milling for a short time, in addition to creating homogeneity for reinforcing particles on the surface of flaky metal particles, causes less work-hardening of powders and allows better densification of composite powders. In this research, aluminum-carbon nanotubes (Al-CNT) nanocomposites were fabricated using flake powder metallurgy and hot pressing method. The homogeneous distribution of carbon nanotubes in the aluminum matrix and density close to the theoretical density were obtained through the manufacturing process. After the addition of carbon nanotubes, the grain size of matrix phase reduced from 106 nm to 56 nm in 4 vol% reinforcement. The increase of carbon nanotubes at 2 and 4 vol% increased the yield strength and compressive strength from 176 MPa and 201 MPa to 241 MPa and 251 MPa and reduced the fracture strain from >20% to 4%, respectively. The increased strength depends on the fine grains of the matrix phase, the proper distribution of carbon nanotubes and their strengthening effect.

Multi-functionality of carbon nanotubes reinforced 3 mol% yttria stabilized zirconia structural biocomposites

The effect of the addition of carbon nanotubes (CNT) on the densification, microstructural, mechanical, wear performance and biocompatibility of 3mol% yttria stabilized zirconia (3YSZ) have been investigated in the present study. The retention of high temperature phases (tetragonal and cubic) was found to increase with CNT addition in 3YSZ. Enhancement in the mechanical properties (hardness and elastic modulus) with CNT reinforcement is attributed to the refinement of grain size, enhanced densification and homogeneous distribution of CNT (up to 6vol%). Correspondingly, fracture toughness increased from 5MPam1/2 (in 3YSZ) to 10.1MPam1/2 with CNT reinforcement (for 12vol%) through energy dissipating mechanisms such as crack branching, CNT bridging, and crack-deflection, evidenced by the fractographs of 3YSZ-CNT composites. The toughening contribution with CNT reinforcement is observed to dominate over that of t→m transformation up to 38 times, evaluated using a modified fractal model. However, this effectiveness decreased with CNT agglomeration. The physical damage in the bacterial cell is observed to increase with CNT addition. The present findings promote 3YSZ-CNT as an optimal structural and antibacterial multifunctional biomaterial.

Antimicrobial activity of new carboxymethyl chitosan–carbon nanotube biocomposites and their swell ability in different pH media

ABSTRACTNew carboxymethyl chitosan–carbon nanotube (CMCS-CNT) biocomposites were prepared and characterized by Fourier transform infrared spectroscopy, transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and normal photography. The recorded images of the CMCS-CNT biocomposites showed homogeneous distribution of carbon nanotubes into the carboxymethyl chitosan (CMCS) matrix. Their antimicrobial activity and swell ability in different pH media have been investigated. They showed a higher antimicrobial activity against tested gram-positive and gram-negative bacteria. The inhibition zone diameters are closer to that recorded for the commonly used antibiotics. They showed an increase in the swell ability in different pH media relative to the parent CMCS. It would be expected that these nanobiocomposites are promising candidates for medical applications.

A novel processing route to develop alumina matrix nanocompositesreinforced with multi-walled carbon nanotubes

In the present work, we have reported a novel approach to fabricate carbon nanotubes (CNTs)/alumina nanocomposites with improved fracture toughness using a simple heterogeneous nucleation through the incorporation of functionalized multi-walled carbon nanotubes (MWCNTs). For this approach, homogeneous distribution of CNTs in ceramic matrix has been achieved up to 5.7vol.% CNTs content, revealed by SEM observations of both composite powders and fracture surfaces of sintered specimens. Excellent comprehensive mechanical properties as high as 6.03±0.45MPam1/2 fracture toughness and 19.18±0.33GPa hardness are obtained in alumina nanocomposite with 5.7vol.% MWCNTs fabricated via spark plasma sintering (SPS) with subsection pressure method, increasing 53% and 30% over that of pure alumina sintered under the same sintering condition, respectively. Furthermore, the fracture mode transition and the activated toughening mechanisms during crack propagation are taken into account to explain the improvement in fracture toughness.

Homogeneous Distribution of Carbon Nanotubes in Copper Matrix Nanocomposites Fabricated via Combined Technique

Carbon nanotubes (CNTs) with its exceptional thermal and mechanical properties hold the promise of delivering high performance nanocomposite materials. To utilize CNTs as effective reinforcement in metal nanocomposites, appropriate dispersion and robust interfacial adhesion between individual CNT and metal matrix have to be certain. This work presents a novel combined technique of nanoscale dispersion (NSD) of functionalized multiwalled carbon nanotubes (MWCNTs) in copper (Cu) matrix composite followed by powder injection molding (PIM). MWCNTs contents were varied from 0 to 10 volume fraction. Evidences on the existence of functional groups and microstructural analysis of the fabricated nanocomposites were determined using TEM, EDX, FESEM and FTIR. Thermal conductivity and elasticity measurements were also performed. The results showed that the impurities of the pristine MWCNTs such as Fe, Ni catalyst, and the amorphous carbon have been significantly removed after sonication process. FESEM and TEM observations showed high stability of MWCNTs at elevated temperatures and uniform dispersion of MWCNTs in Cu matrix at different volume fractions and sintering temperatures (950, 1000 and 1050 � C). The experimentally measured thermal conductivities of Cu/MWCNTs nanocomposites showed remarkable increase (11.25% higher than pure sintered Cu) with addition of 1 vol.% MWCNTs, while the modulus of elasticity (Young’s modulus) of Cu/MWCNTs nanocomposites sintered at 1050 � Cf or 2hw asincreased

Ultrasound Assisted Hybrid Carbon Epoxy Composites Containing Carbon Nanotubes

A simple approach has been reported toward the development of hybrid nano/microfiber composite structures with improved mechanical properties. Ultrasound assisted atomization process has been utilized for depositing carbon nanotubes (CNTs) on the surface of carbon fiber (CF) cloth using dilute solutions of CNTs in N, N-dimethylformamide (DMF). Dilute solutions with three different CNT concentrations such as 1 × 10−4 g/ml, 5 × 10−4 g/ml, and 10 × 10−4 g/ml were fed into an ultrasonic atomizer probe using a positive displacement syringe pump and sprayed directly on CF cloth rested on a hot plate inside a deposition chamber. Several layers of hybrid CF cloths containing CNTs were used to fabricate composite laminates using a vacuum assisted resin transfer molding (VARTM). Although the dispersion of CNTs in DMF was found very well for all three concentrations, the distribution of CNTs on CFs was only found homogeneous for 1 × 10−4 g/ml solution. It was found that the hybrid composite containing 0.3 wt. % CNTs loading fabricated using 1 × 10−4 g/ml solution showed about 25% improvement in flexural strength, although moderate improvement in flexure modulus was achieved for all three concentrations. The improved strength is believed to be due to homogeneous distribution of CNTs, which resulted in increased surface roughness and mechanical interlocking between fibers and matrix.

Characteristic evaluation of Al 2O 3/CNTs hybrid materials for micro-electrical discharge machining

The characteristic evaluation of aluminum oxide (Al 2O 3)/carbon nanotubes (CNTs) hybrid composites for micro-electrical discharge machining (EDM) was described. Alumina matrix composites reinforced with CNTs were fabricated by a catalytic chemical vapor deposition method. Al 2O 3 composites with different CNT concentrations were synthesized. The electrical characteristic of Al 2O 3/CNTs composites was examined. These composites were machined by the EDM process according to the various EDM parameters, and the characteristics of machining were analyzed using field emission scanning electron microscope (FESEM). The electrical conductivity has a increasing tendency as the CNTs content is increased and has a critical point at 5% Al 2O 3 (volume fraction). In the machining accuracy, many tangles of CNT in Al 2O 3/CNTs composites cause violent spark. Thus, it causes the poor dimensional accuracy and circularity. The results show that conductivity of the materials and homogeneous distribution of CNTs in the matrix are important factors for micro-EDM of Al 2O 3/CNTs hybrid composites.

Carbon nanotube reinforced metal matrix composites - a review

<title/>This review summarises the research work carried out in the field of carbon nanotube (CNT) metal matrix composites (MMCs). Much research has been undertaken in utilising CNTs as reinforcement for composite material. However, CNT-reinforced MMCs have received the least attention. These composites are being projected for use in structural applications for their high specific strength as well as functional materials for their exciting thermal and electrical characteristics. The present review focuses on the critical issues of CNT-reinforced MMCs that include processing techniques, nanotube dispersion, interface, strengthening mechanisms and mechanical properties. Processing techniques used for synthesis of the composites have been critically reviewed with an objective to achieve homogeneous distribution of carbon nanotubes in the matrix. The mechanical property improvements achieved by addition of CNTs in various metal matrix systems are summarised. The factors determining strengthening achieved by CNT reinforcement are elucidated as are the structural and chemical stability of CNTs in different metal matrixes and the importance of the CNT/metal interface has been reviewed. The importance of CNT dispersion and its quantification is highlighted. Carbon nanotube reinforced MMCs as functional materials are summarised. Future work that needs attention is addressed.

Fabrication and effective thermal conductivity of multi-walled carbon nanotubes reinforced Cu matrix composites for heat sink applications

A novel particles-compositing method was used for the first time to disperse different contents of multi-walled carbon nanotubes (CNTs) in micron sized copper powders, which were subsequently consolidated into CNT/Cu composites by spark plasma sintering (SPS). Microstructural observations showed that the homogeneous distribution of CNTs and dense composites could be obtained for 0–10 vol.% CNT contents. The CNT clusters were appeared in the powder mixture with 15 vol.% CNTs, which resulted in an insufficient densification of the composites. The effective thermal conductivity of the composites was analyzed both theoretically and experimentally. The addition of CNTs showed no enhancement in overall thermal conductivity of the composites due to the interface thermal resistance associated with the low phase contrast of CNT to copper and the random tube orientation. Besides, the composite containing 15 vol.% CNTs led to a rather low thermal conductivity due possiblely to the combined effect of unfavorable factors induced by the presence of CNT clusters, i.e. large porosity, lower effective conductivity of CNT clusters themselves and reduction of SPS cleaning effect. The CNT/Cu composites may be a promising thermal management material for heat sink applications.

コロイドプロセスを用いて作製したカーボンナノチューブ／銅複合材料の熱伝導率

Carbon nanotubes (CNT) have many interesting properties such as high thermal conductivity. Therefore, Cu/CNT composites are expected to be applied as heat sink material with good thermal properties.In this study, Cu/CNT precursor in which CNT distributed homogeneously was fabricated by colloidal process, and homogeneous distribution of CNT in Cu matrix was also observed in Cu/CNT composites sintered by spark plasma sintering (SPS). According to the analysis of gas generated from high-temperature precursor, structural defect of CNT, and oxygen content, SPS proved useful to reduce CNT's structural defects compare to conventional sintering methods. Using SPS in vacuum atmosphere, composites can be successfully formed with low temperature in short time. Existence of amorphous layer at Cu/CNT and Cu/Cu interface was observed by FETEM.

Multiwall carbon nanotubes-based composites – mechanical characterization using the nanoindentation technique

Abstract We report on mechanical properties of multiwall carbon nanotubes (MWNTs)-polymer composites using the nanoindentation technique. The nanoindentation experiments conducted on thin films containing MWNTs revealed that the presence of nanotubes does not affect the nanomechanical properties of the composites. Even a layer-by-layer assembly of MWNTs with a high concentration and a homogeneous distribution of carbon nanotubes does not ensure reinforcement of the composites. For that reason, we synthesized and utilized carbon nanotubes with a silica shell. Nanohardness and Young's modulus have been found to increase strongly with increasing content of these nanotubes in the polymer matrix. The silica shell on the surface of a nanotube enhances its stiffness and rigidity. Our composites, at 4wt.% of the silica-coated MWNTs, display a maximum hardness of 12020MPa and a Young's modulus of 91GPa. These are, respectively, 2 and 3 times higher than those for the polymeric matrix.

Multiwall carbon nanotube/epoxy composites produced by a masterbatch process

A masterbatch process based on a minicalander (three-roller mill) and a vacuum dissolver was developed in order to produce multiwall carbon nanotube/epoxy composites with loading fractions of 0.5, 1.0, and 2.0 wt.%. TEM and SEM analyses were performed to investigate the dispersion results. A contrast imaging in the SEM backscattering mode revealed a homogeneous distribution of carbon nanotubes in the whole volume of the material. Furthermore, an interesting correlation was found to exist between the network structure formed by the nanotubes in the epoxy matrix and the appearance of fracture surface of the nanocomposites. Furthermore, the nanocomposites exhibited an electrical conductivity in the regime of some 10−2 S/m.

Microstructures and tensile behavior of carbon nanotube reinforced Cu matrix nanocomposites

Carbon nanotubes (CNTs) have been considered as an ideal reinforcement to improve the mechanical performance of monolithic materials. However, the CNT/metal nanocomposites have shown lower strength than expected. In this study, the CNT reinforced Cu matrix nanocomposites were fabricated by spark plasma sintering (SPS) of high energy ball-milled nano-sized Cu powders with multi-wall CNTs, and followed by cold rolling process. The microstructure of CNT/Cu nanocomposites consists of two regions including CNT/Cu composite region, where most CNTs are distributed, and CNT free Cu matrix region. The stress–strain curves of CNT/Cu nanocomposites show a two-step yielding behavior, which is caused from the microstructural characteristics consisting of two regions and the load transfer between these regions. The CNT/Cu nanocomposites show a tensile strength of 281 MPa, which is approximately 1.6 times higher than that of monolithic Cu. It is confirmed that the key issue to enhance the strength of CNT/metal nanocomposite is homogeneous distribution of CNTs.