Homogeneous Distribution Of CNTs Research Articles

Quantitative morphometry of topological graphene-based aerogels and carbon foams by x-ray micro-computed tomography

In this work, we report quantitative morphometry of freeze-dried graphene-based aerogels (i.e., graphene aerogel-GA, nitrogenated GA-NGA, graphene-carbon nanotube hybrid-Gr-MWCNTs, carbon foam-CF, and CF-GA hybrid-CF-GA) and monoliths, prepared by hydrothermal and organic sol-gel methods, respectively. X-ray micro-computed tomography (XMCT) in combination with scanning and transmission electron microscopy allowed visualization of internal microstructures in three-dimensional space. Quantitative morphometry analysis through the reconstructed volume renderings from two-dimensional sliced images revealed hierarchical structures possessing interlaced thin sheets, honeycomb organization, and topological interconnected pore background domains. The influence of small-diameter functionalized multi-walled carbon nanotubes (MWCNTs) inclusions to graphene-like sheets and integration with CF is assessed through quantitative morphometry analysis in terms of volume-weighted pore size, wall thickness, and porosity levels. Hybrid composite porous solids elucidated cross-linking reinforced by a homogeneous distribution of CNTs into complex sheets of GA and CF matrices. A consistent trend impacting porosity and interconnectedness was found following NGA ≥ GA > CF > Gr-MWCNT2:1 > CF-GA > Gr-MWCNT3:1 > Gr-MWCNT5:1, from XMCT image processing and analyses in corroboration with physical properties and reliability. The experimental results provide insights and guide the design of characteristic porous carbonaceous and graphene-based functional nanomaterials for energy sciences, environmental engineering, and fundamental reactive transport of fluids.

Simultaneously optimized thermoelectric and mechanical performance of p-type polycrystalline SnSe enabled by CNTs addition

A series of SnSe/carbon nanotubes (SnSe/CNTs) composites, with homogeneous distribution of CNTs, were fabricated by combining solution synthesis with fast sintering. Enabled by CNTs addition, both the electrical conductivity and power factor are improved significantly; the lattice thermal conductivity is suppressed due to strengthened phonon scattering. As a result, a maximum zT of 0.90 is obtained in the SnSe/CNTs composite with 0.20 wt.% CNTs, ∼ 90% higher than that of SnSe. In addition, the composite with 0.35 wt.% CNTs exhibits a dramatically increased compressive strength of 135 MPa, representing an ∼ 81% increase. This work offers a composite design strategy for synergistically improving both thermoelectric and mechanical properties of polycrystalline SnSe.

Fabrication of Metal/Carbon Nanotube Composites by Electrochemical Deposition

Metal/carbon nanotube (CNT) composites are promising functional materials due to the various superior properties of CNTs in addition to the characteristics of metals, and consequently, many fabrication processes of these composites have been vigorously researched. In this paper, the fabrication process of metal/CNT composites by electrochemical deposition, including electrodeposition and electroless deposition, are comprehensively reviewed. A general introduction for fabrication of metal/CNT composites using the electrochemical deposition is carried out. The fabrication methods can be classified into three types: (1) composite plating by electrodeposition or electroless deposition, (2) metal coating on CNT by electroless deposition, and (3) electrodeposition using CNT templates, such as CNT sheets and CNT yarns. The performances of each type have been compared and explained especially from the view point of preparation methods. In the cases of (1) composite plating and (2) metal coating on CNTs, homogeneous dispersion of CNTs in electrochemical deposition baths is essential for the formation of metal/CNT composites with homogeneous distribution of CNTs, which leads to high performance composites. In the case of (3) electrodeposition using CNT templates, the electrodeposition of metals not only on the surfaces but also interior of the CNT templates is the key process to fabricate high performance metal/CNT composites.

Tuning the Piezoresistive Behavior of Poly(Vinylidene Fluoride)/Carbon Nanotube Composites Using Poly(Methyl Methacrylate).

In conductive polymer composites (CPCs), which can be used as both strain sensors and materials with self-diagnosis capabilities for structural health monitoring, the piezoresistive sensitivity can be tuned by changing the electrical filler network structure, mainly influenced by the conductive filler content. Typically, the electrical resistance increases exponentially with strain, and the piezoresistive sensitivity and linearity cannot be improved simultaneously. In this work, we report a facile method to tune the piezoresistive behavior of melt-mixed poly(vinylidene fluoride) (PVDF)/carbon nanotube (CNT, 0.75-2.0 wt %) composites using blending with poly(methyl methacrylate) (PMMA, 5-30 wt %). PVDF and PMMA are completely miscible in the melt state regardless of the proportion. For PVDF-rich blends, the crystallization of PVDF induces separation of the PVDF crystal region from the miscible PVDF/PMMA amorphous blend part during the cooling process. Addition of PMMA tuned the piezoresistive strain behavior and improved the electrical conductivity and toughness at the same time. The PVDF/PMMA/CNT composites show higher sensitivity at low strains than their PVDF/CNT counterparts with comparable initial resistivity. For example, ΔR/R0 at 5% strain is 18.6% for the PVDF(80)/PMMA(20) blend containing 0.75 wt % CNT versus 11.0% for PVDF containing 1 wt % CNT, both having a volume resistivity of around 104 Ω·cm. The PVDF/PMMA/CNT blend composites also show a less steep exponential increase in the sensing response at higher strains, indicating better linearity. These differences are due to the altered microstructure of the composites and the more homogeneous distribution of CNTs between the smaller and less numerous PVDF crystallites when PMMA is added. The concept of modifying the composite microstructure by adding another commercially available miscible polymer offers a simple and effective way to tune the piezoresistive behavior and improve mechanical properties of CPC sensor materials.

Influence of nanostructured Cu on the mechanical properties of Cu–MWCNTs composites

Abstract In the present investigation, Cu-multiwalled carbon nanotubes (MWCNTs) nanocomposites were developed through mechanical milling using nanostructured Cu as a matrix and MWCNTs as nanofillers. The influence of nanostructured Cu on the microstructure, microhardness, and wear behavior of Cu-MWCNTs nanocomposites was also studied. The crystallite size of nanostructured Cu powder via mechanical milling for 25 h was found to be 16 nm. The major challenge associated with the development of Cu-MWCNTs nanocomposites is the uniform dispersion of the CNTs in the Cu matrix, which was addressed by incorporating nanostructured Cu, leading to the homogeneous distribution of CNTs and good bonding between the CNTs and the Cu matrix. A significant improvement in relative density and microhardness with <3 wt.% MWCNTs was observed compared to pure asreceived Cu and its composites. The hardness of Cu-3 wt.% MWCNTs nanocomposite developed using nanostructured Cu were achieved at <800 MPa, which is about 2.3 times higher than that of the as-received Cu sample (~ 359 MPa). The significant increment in mechanical and wear properties mainly originates from fine-grain strengthening effects and solid solution strengthening. The wear mechanisms in the various nanostructured Cu-MWCNTs composites were studied in detail and oxidation wear was identified as one of the main wear mechanisms.

Influence of nanostructured Cu on the mechanical properties of Cu–MWCNTs composites

Abstract In the present investigation, Cu-multiwalled carbon nanotubes (MWCNTs) nanocomposites were developed through mechanical milling using nanostructured Cu as a matrix and MWCNTs as nanofillers. The influence of nanostructured Cu on the microstructure, microhardness, and wear behavior of Cu-MWCNTs nanocomposites was also studied. The crystallite size of nanostructured Cu powder via mechanical milling for 25 h was found to be 16 nm. The major challenge associated with the development of Cu-MWCNTs nanocomposites is the uniform dispersion of the CNTs in the Cu matrix, which was addressed by incorporating nanostructured Cu, leading to the homogeneous distribution of CNTs and good bonding between the CNTs and the Cu matrix. A significant improvement in relative density and microhardness with <3 wt.% MWCNTs was observed compared to pure asreceived Cu and its composites. The hardness of Cu-3 wt.% MWCNTs nanocomposite developed using nanostructured Cu were achieved at <800 MPa, which is about 2.3 times higher than that of the as-received Cu sample (~ 359 MPa). The significant increment in mechanical and wear properties mainly originates from fine-grain strengthening effects and solid solution strengthening. The wear mechanisms in the various nanostructured Cu-MWCNTs composites were studied in detail and oxidation wear was identified as one of the main wear mechanisms.

Effect of CNTs content on the microstructures and properties of CNTs/Cu composite by microwave sintering

Cu matrix composites reinforced with 0-3 wt% CNTs are fabricated via molecular-level mixing, microwave sintering and rolling technology. A homogeneous distribution of CNTs is exhibited in copper matrix. Clean CNTs/Cu interfaces perform high bonding strength. Electrical conductivity and relative density of microwave sintered CNTs/Cu composites decrease with increase in CNTs content. There exists maximum for hardness of CNTs/Cu composites which rise and then fall with the rise of CNTs content. When CNT contents are less than 1 wt%, it provides a good control over microstructures with low porosity and small pore size. Subsequent rolling process enables better microstructure and performance of sintered composites which shows tensile strength of 218 MPa, the elongation of 37.75%, and the electrical conductivity of >98% IACS compared to pure copper. Our studies provide a robust approach to high-performance CNTs/Cu composites by microwave sintering.

Wear Resistance and Surface Hardness of Carbon Nanotube Reinforced Alumina Matrix Nanocomposite by Cold Sprayed Process

Carbon nanotube reinforced alumina matrix nanocomposite was fabricated by cold spray process on Al-Si alloys surfaces. The effects of various amounts of CNTs from 0, 2 and 4 wt % on alumina powders were investigated. Results show that the improvement in both wear resistance and hardness was provided by 2 wt. % CNTs reinforcement. The hardness of carbon nanotube reinforced alumina matrix nanocomposite was increased due to an enhanced load sharing of homogeneously distributed carbon nanotubes. Homogeneous distribution of CNTs within the Al2O3 matrix and strong interfacial connection between CNTs-Al2O3 give nanocomposites with superior wear properties.

Zirconia-based nanocomposite toughened by functionalized multi-wall carbon nanotubes

In the present work, we have reported a novel approach to fabricate 3Y-TZP/carbon nanotube (CNTs) nanocomposites with improved fracture toughness using spark plasma sintering technology through the incorporation of functionalized multi-walled carbon nanotubes. For this approach, homogeneous distribution of CNTs in ceramic matrix has been achieved up to 4wt% CNTs content, revealed by SEM observations of both composite powders and fracture surfaces of sintered specimens. In addition, Raman spectroscopic indicates that CNTs can be retained at high sintering temperatures from 1250 to 1400°C. A clear improvement in the fracture toughness was achieved after adding CNTs, and the specimen with 4wt% CNTs sintered at 1300°C exhibited the best indentation toughness of 6.24MPam1/2, increasing 31% over monolithic ZrO2 sintered at the same temperature. Furthermore, the fracture mode transition and the activated toughening mechanisms during crack propagation were taken into account to explain the improvement in fracture toughness.

Carbon Nanotubes as Highly Conductive Nano-Fillers in Metallic Matrices

. A baseline electroless deposition processes for Cu on CNTs has been developed. This process results in the formation of copper particles of few tens of nanometres. Using this process in a CNT loaded solution it is possible to obtain a homogeneous distribution of CNTs and Cu, even for volume fraction of CNTs as high as 17 v%. By the application of wet chemical processing it is possible to penetrate the natural felt-like structure of the CNTs and to fill the gaps with copper particles. Variations of the baseline deposition process have been established, allowing adding small amount of nickel on the CNT prior to the copper deposition to strengthen the interfacial bonding between matrix and CNTs. Hot pressing of the highly CNT loaded metal matrix composites has been developed; it allows producing bulk material that can be handled. The microstructure of these materials has been investigated and samples have been machined for further testing, i.e. mechanical characterization and thermo-physical properties.

Characterization of Carbon Nanotubes/Cu Nanocomposites Processed by Using Nano-sized Cu Powders

AbstractCarbon nanotubes (CNTs) have attracted remarkable attention as reinforcement for composites owing to their outstanding properties1-3. CNT/Cu nanocomposites were fabricated by mixing the nano-sized Cu powders with multi-wall carbon nanotubes and followed by the spark plasma sintering process. The CNT/Cu nanocomposite fabricated from nano-sized Cu powders shows more homogeneous distribution of CNTs in matrix compared to that fabricated from macro-sized Cu powders. The hardness of CNT/Cu nanocomposite fabricated from nano-sized Cu powders increases with increasing the volume fraction of CNTs, while the hardness of that fabricated from macro-sized Cu powders decreases with the addition of CNTs.