Multi-walled Carbon Nanotubes Wt Research Articles

Thermal, Rheological, Mechanical, and Electrical Properties of Polypropylene/Multi-Walled Carbon Nanotube Nanocomposites.

In this paper, nanocomposites based on polypropylene (PP) filled with up to 5 wt.% of multi-walled carbon nanotubes (MWCNTs) were investigated for determining the material property data used in numerical simulation of manufacturing processes such as the injection molding and extrusion. PP/MWCNT nanocomposite pellets were characterized for rheological behavior, crystallinity, specific volume and thermal conductivity, while injection-molded samples were characterized for mechanical and electrical properties. The addition of MWCNTs does not significantly change the melting and crystallization behavior of the PP/MWCNT nanocomposites. The effect of MWCNTs on melt shear viscosity is more pronounced at low shear rates and MWCNT loadings of 1–5 wt.%. However, with the addition of up to 5 wt.% of MWCNTs, the PP/MWCNT nanocomposite still behaves like a non-Newtonian fluid. The specific volume of the PP/MWCNT nanocomposites decreases with increasing MWCNT loading, especially in the MWCNT range of 1–5 wt.%, indicating better dimensional stability. The thermal conductivity, depending on the pressure, MWCNT wt.% and temperature, did not exceed 0.35 W/m·K. The PP/MWCNT nanocomposite is electrical non-conductive up to 3 wt.%, whereas after the percolating path is created, the nanocomposite with 5 wt.% becomes semi-conductive with an electrical conductivity of 10−1 S/m. The tensile modulus, tensile strength and stress at break increase with increasing MWCNT loading, whereas the elongation at break significantly decreases with increasing MWCNT loading. The Cross and modified 2-domain Tait models are suitable for predicting the melt shear viscosity and specific volume as a function of MWCNTs, respectively. These results enable users to integrate the PP/MWCNT nanocomposites into computer aided engineering analysis.

Influence of CNT-based Nanocomposites in Dynamic Performance of Redundant Articulated Robot

SUMMARYIn this study, AA5083-reinforced multiwalled carbon nanotubes (MWCNT) nanocomposites were selected as the alternate material for a redundant articulated robot (RAR) design by varying the composition of MWCNT wt%. By assigning AA5083-reinforced MWCNT as a custom material to the parts of RAR developed by Solid Works and exported to MATLAB/SimMechanics platform to convert the model into multi-body system blocks. The dynamic parameter torque was observed utilising simulation capability in a SimMechanics second-generation environment. The simulation results inferred that AA5083 reinforced with increased wt% of MWCNT has better properties suitable for RAR design.

Mechanical, Electrical and Rheological Behavior of Ethylene-Vinyl Acetate/Multi-Walled Carbon Nanotube Composites.

This paper investigates the rheological, mechanical and electrical properties of a Ethylene-Vinyl Acetate (EVA) polymer filled with 1, 3 and 5 wt.% multi-walled carbon nanotubes (MWCNTs). The melt flow and pressure-volume-Temperature (pvT) behaviors of the EVA/MWCNT composites were investigated using a high-pressure capillary rheometer, while the electro-mechanical response was investigated on injection-molded samples. Rheological experiments showed that the melt shear viscosity of the EVA/MWCNT composite is dependent on nanotube loading and, at high shear rates, the viscosity showed temperature-dependent shear thinning behavior with a flow index n < 0.35. The specific volume of the EVA/MWCNT composite decreased with increasing pressure and MWCNT wt.%. The transition temperature, corresponding to the pvT crystallization, increased linearly with increasing pressure, i.e., about 20 to 30 °C when cooling under pressure. The elastic modulus, tensile strength and stress at break increased with increasing MWCNT wt.%, whereas the strain at break decreased, suggesting the formation of MWCNT secondary agglomerates. The electrical conductivity of the EVA/MWCNT composite increased with increasing MWCNT wt.% and melt temperature, reaching ~10−2 S/m for the composite containing 5 wt.% MWCNTs. Using the statistical percolation theory, the percolation threshold was estimated at 0.9 wt.% and the critical exponent at 4.95.

Carbon nanotube loaded electrospun scaffolds based on thermoplastic urethane (TPU) with enhanced proliferation and neural differentiation of rat mesenchymal stem cells: The role of state of electrical conductivity

Electromagnetic stimulation has been shown as an effective strategy to enhance neural cells regeneration. The use of electrically conductive materials including polymer nanocomposites for the construction of scaffolds with potential to repair the injured nervous system has attracted great attentions. In the present study, attempts have been made to fabricate nanostructured fibrous scaffolds based on flexible thermoplastic polyurethane (TPU) and surface functionalized multiwalled carbon nanotubes (MWNT) via electrospinning process in order to examine and highlight the influence of state of electrical conductivity of scaffolds upon neural cells proliferation and differentiation. For this purpose, various scaffolds comprising different wt.% of MWNTs were prepared and their electrical conductivity, microstructural and mechanical characteristics were studied using two probe electrometer, scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM) and tensile measurements. Cellular behavior, proliferation and neural differentiation of rat mesenchymal stem cells (RMSC) seeded on the fabricated scaffolds with different state of conductivity were investigated both in the presence and absence of an external electromagnetic stimulation. Results revealed a linear correlation between electrical conductivity and cell signaling as well as neural gene expression. It is demonstrated that MWNT particles are encapsulated by the TPU and mostly oriented along the nanofibers axis by the electric field imposed on the jetted fibers during electrospinning process. Reinforcement of both bulk and surface modulus was exhibited by MWNT loaded scaffolds, indicating intensification of the interface between TPU and surface modified MWNT partices. Electrical conductivity of scaffolds versus MWNT wt% showed to follow percolation model with a threshold around 2.5 wt% of MWNTs, implying the involvement of both tunneling and conduction mechanisms for the passage of the electron current throughout the scaffolds upon stimulation. RMSCs cultured on MWNT loaded nanofibrous scaffolds with conductivity above threshold exhibited enhanced neural differentiation, suggesting the crucial role of state of electrical conductivity of the scaffolds for directing the proliferation and differentiation of stem cells towards the neural tissues.

Vibration and mode shape analysis of sandwich panel with MWCNTs FG-reinforcement core

The goal of this study is to fill this apparent gap in the area about vibration analysis of multiwalled carbon nanotubes (MWCNTs) curved panels by providing 3-D vibration analysis results for functionally graded multiwalled carbon nanotubes (FG-MWCNTs) sandwich structure with power-law distribution of nanotube. The effective material properties of the FG-MWCNT structures are estimated using a modified Halpin-Tsai equation. Modified Halpin-Tsai equation was used to evaluate the Young\'s modulus of MWCNT/epoxy composite samples by the incorporation of an orientation as well as an exponential shape factor in the equation. The exponential shape factor modifies the Halpin-Tsai equation from expressing a straight line to a nonlinear one in the MWCNTs wt% range considered. Also, the mass density and Poisson\'s ratio of the MWCNT/phenolic composite are considered based on the rule of mixtures. Parametric studies are carried out to highlight the influence of MWCNT volume fraction in the thickness, different types of CNT distribution, boundary conditions and geometrical parameters on vibrational behavior of FG-MWCNT thick curved panels. Because of using two-dimensional generalized differential quadrature method, the present approach makes possible vibration analysis of cylindrical panels with two opposite axial edges simply supported and arbitrary boundary conditions including Free, Simply supported and Clamped at the curved edges. For an overall comprehension on 3-D vibration analysis of sandwich panel, some mode shape contour plots are reported in this research work.

Carbon Nanotubes Reinforced Al-11 wt% Si Alloy via Plasma Spray

In this work, multi-walled carbon nanotubes (MWCNTs) with different portions (0.5, l, 2, 4) wt% were added to a gas atomized Al-ll wt% Si powder. The Al-ll wt% /MWCNTS nanocomposite powder was examined by FESEM, Raman spectroscopy, X-ray diffraction (XRD). Air plasma spraying (APS) was used to spray Al-ll wt% Si/MwCNTs nanocomposite powder on aluminum alloy AA6082-T6 substrates. Al-ll wt% Si/MWCNTs nanocomposite coating layer was examined using FESEM/EDS, Raman spectroscopy, XRD and HRTEM. SEM/EDS showed that Al4C3 is formed at the interface e between the coating layer and the substrate in Al-ll wt% Si/4 wt% MWCNTs plasma spray coating. The adhesion test showed good adhesion in the ranges 5-l5 MPa between the coating layer and the substrate. Microhardness test of the air plasma sprayed (APS) Al-ll wt% Si/MWNTs nanocomposite layer is increased with the MWCNTs wt%.

Evaluation of multi-walled carbon nanotube concentrations in polymer nanocomposites by Raman spectroscopy

A new Raman spectroscopic methodology is proposed to monitor the weight fraction of Multi-Walled Carbon Nanotubes (MWCNTs) in polymeric nanocomposites. In order to disentangle the parameters affecting the frequency of the Raman bands and their intensity, this methodology involves the acquisition of sets of Raman spectra as a function of MWCNTs loading, excitation laser power and temperature. In the specific case of isotactic polypropylene (iPP), any interaction of the carbon nanotubes with the polymeric host has minimal effect on the frequency of the MWCNTs G band (∼1584cm−1); the same holds for the influence of residual stresses acting on the MWCNTs. The parameter that primarily alters the CNTs Raman bands frequency is temperature, determined by the excitation laser intensity, the MWCNTs concentration and the thermal properties of the polymer matrix. This is demonstrated by confocal micro-Raman spectra collected from agglomerates and from micro-Raman spectra of samples containing either poorly or well dispersed MWCNTs. A direct correlation of the G band frequency with the effective MWCNT wt% loading in the nanocomposites is confirmed after careful and systematic experiments performed on prototype well-dispersed samples.

Vibration Characteristics of Multi-walled Carbon Nanotubes/epoxy Composites Beam

Composites are composed of matrix and reinforcement. Generally the matrix is a polymer material. Carbon nanotubes have excellent mechanical properties, electrical and thermal properties and can be used as a reinforcement. In this study, multi-walled carbon nanotubes (MWNTs)/epoxy specimens was prepared with different MWNTs wt% to explore the vibration characteristics of composites beam. Vibration characteristics including mode shapes and natural frequencies. We measured the Young's modulus, Poisson's ratio and density of the specimens, used as the parameters in finite element analysis to obtain the mode shape and natural frequency of cantilever composite beams. The experiment and simulation results showed that adding MWNTs had some influence on the resonant frequency.

MWCNTs/P(St-co-GMA) Composite Nanofibers of Engineered Interface Chemistry for Epoxy Matrix Nanocomposites

Strengthened nanofiber-reinforced epoxy matrix composites are demonstrated by engineering composite electrospun fibers of multi-walled carbon nanotubes (MWCNTs) and reactive P(St-co-GMA). MWCNTs are incorporated into surface-modified, reactive P(St-co-GMA) nanofibers by electrospinning; functionalization of these MWCNT/P(St-co-GMA) composite nanofibers with epoxide moieties facilitates bonding at the interface of the cross-linked fibers and the epoxy matrix, effectively reinforcing and toughening the epoxy resin. Rheological properties are determined and thermodynamic stabilization is demonstrated for MWCNTs in the P(St-co-GMA)-DMF polymer solution. Homogeneity and uniformity of the fiber formation within the electrospun mats are achieved at polymer concentration of 30 wt %. Results show that the MWCNT fraction decreases the polymer solution viscosity, yielding a narrower fiber diameter. The fiber diameter drops from an average of 630 nm to 460 nm, as the MWCNTs wt fraction (1, 1.5, and 2%) is increased. The electrospun nanofibers of the MWCNTs/P(St-co-GMA) composite are also embedded into an epoxy resin to investigate their reinforcing abilities. A significant increase in the mechanical response is observed, up to >20% in flexural modulus, when compared to neat epoxy, despite a very low composite fiber weight fraction (at about 0.2% by a single-layer fibrous mat). The increase is attributed to the combined effect of the two factors the inherent strength of the well-dispersed MWCNTs and the surface chemistry of the electrospun fibers that have been modified with epoxide to enable cross-linking between the polymer matrix and the nanofibers.

Adhesive strength of nano-size particles filled thermoplastic polyimides. Part-I: Multi-walled carbon nano-tubes (MWNT)–polyimide composite films

In this study, adhesive properties of thermoplastic polyimides (PI) filled with multi wall carbon nano-tubes (MWNT) are investigated. The PIs studied are ODPA/3, 4′-ODA/PA (amorphous) and BPDA/3, 4′-ODA/PA (semi-crystalline). The PIs are prepared via a two-step method involving poly(amide acid) (PAA) stage followed by thermal or chemical imidization to obtain polyimide in film or powder form. The MWNT are mixed in low wt% (0.1–1.5) during synthesis at PAA stage through mechanical agitation and sonication. PI-MWNT film composites were characterized using DMTA and tensile testing to determine viscoelastic behavior and mechanical properties. Adhesive strength and adhesive energy of bonded samples, prepared with PI-MWNT films and powder composites, were determined using single lap joints test and wedge test methods, respectively. The fractured bonded surfaces were examined by scanning electron microscope to determine failure patterns. The results showed that viscoelastic behavior of PI–MWNT composite films changes from liquid-like to solid-like by increasing MWNT content. Elastic modulus and strength at break of PI-MWNT composite films were found to increase with increase in MWNT wt%. However, elongation at break and breaking energy of PI–MWNT composite films and lap shear strength and adhesive energy of bonded samples were found to initially increase with increase in MWNT wt%, but then after a critical value decreases. The SEM analysis showed that bonded joints prepared with PI–MWNT composite films containing high wt% of MWNT failed in adhesive mode showing poor wetting of adherend surfaces.