Bending Analysis of Multiwall Carbon Nanotube Reinforced Functionally Graded Composite Cylindrical Shell

In the present study, the effective electric, thermal, and moisture properties of carbon nanotube (CNT) epoxy composites are derived by considering the agglomeration effect of CNT concentrations in the epoxy matrix. In this direction, the Voigt and Reuss homogenization method is adopted in the derivations. It is well known from experiments that the CNT thermal and electrical conductivities and the epoxy hygro-thermal expansion coefficients have significant effects on the behavior of CNT nanocomposites. Moreover, it has been experimentally proved that the agglomeration of CNTs in the matrix with high and low concentrations of the CNTs certainly affects the resistivity and, hence, the thermal expansion properties. Therefore, the effective elastic, thermal, electrical, and moisture properties for the randomly distributed CNTs in the matrix has been derived in terms of the agglomeration volume fractions of CNTs. In the effective relations, a single agglomeration parameter is considered to be active for a given potential. The results of variation in the hygro-electro-thermal properties due to change in CNT volume fraction as well as agglomeration parameters have been presented. The results and observation show that CNT agglomeration has a strong influence on the effective hygro-thermo-electric properties of the nanocomposites.

Carbon nano tubes have established their capabilities to be used as the major reinforcing material in the polymer-based matrix due to their advanced properties of high aspect ratio (L/D) and nanostructure and hence show broad possibility in enhancing the multi-functionality of the advanced engineering materials. To disperse carbon nano tube in epoxy equally and uniformly, ultra-sonication technique is used. Chemically functionalised multi-walled carbon nanotube (MWCNT)/Epoxy resin composites were prepared by hand lay-up manufacturing process. MWCNTs were first treated by a concentrated H2SO4 with the help of mixture and then were treated with triethylenetetramine (TETA), proving improvement in mechanical behaviour of composites. Chemical treatment and functionalization decrease the crystalline content of MWCNT; also, it does not affect its internal structure largely. Thus, modulus of elasticity, tensile strength and flexural strength of composites are enhanced effectively.

Buckling analysis of piezoelectric cylindrical composite panels reinforced with carbon nanotubes

This paper investigates the effect of multiwalled carbon nanotubes on the mechanical and electrical properties of epoxy resins and epoxy composites. The research concerns multiwalled carbon nanotubes obtained by catalytic chemical vapor deposition, subjected to purification processes and covalent functionalization by depositing functional groups on their surfaces. The study included the analysis of the change in DC resistivity, tensile strength, strain, and Young’s modulus with the addition of carbon nanotubes in the range of 0 to 2.5 wt.%. The effect of agents intended to increase the affinity of the nanomaterial to the polymer on the aforementioned properties was also investigated. The addition of functionalized multiwalled carbon nanotubes allowed us to obtain electrically conductive materials. For all materials, the percolation threshold was obtained with 1% addition of multiwalled carbon nanotubes, and filling the polymer with a higher content of carbon nanotubes increased its conductivity. The use of carbon nanotubes as polymer reinforcement allows higher values of tensile strength and a higher strain percentage to be achieved. In contrast, Young’s modulus values did not increase significantly, and higher nanofiller percentages resulted in a drastic decrease in the values of the abovementioned properties.

This paper presents approaches to and the results of finite-element analysis of static buckling in cylindrical sandwich panels. The core layer of the panels is a polylactide honeycomb core 3D printed using the Fused Deposition Modeling (FDM) additive technology. The two thin face layers are made of carbon fiber reinforced polymer. Such structures are promising for use as structural elements of rockets and drones. For them, the determination of stability under longitudinal and radial loads is an important issue. The global buckling of a cylindrical panel under longitudinal loads and the local buckling of a honeycomb core as a plate structure under radial loads are studied. The geometrically nonlinear deformation of a cylindrical panel under a combination of transverse and radial loads is studied. Seven cylindrical sandwich panels with the radius-to-thickness ratio in the range 5 ? R/h ? 50 and a sandwich plate are considered. The effect of the radius of curvature on the characteristics of local and global buckling is investigated. The problem is solved by the finite element method using the ANSYS software system. The convergence of the finite element model was investigated. For this purpose, a strained state under the action of a longitudinal load was studied. The finite-element mesh parameters were selected to ensure the convergence of the results. Two finite element models, an “exact” one and an “approximate” one, were constructed to investigate global buckling under longitudinal loads. The «exact» model includes a honeycomb core represented by its geometry. In the «approximate» model of the sandwich panel, the honeycomb core is replaced with an equivalent homogenized layer. It was found that for longitudinal loads the modes of the global buckling of the cylindrical sandwich panels and the sandwich plate under study are almost the same. It was shown that the critical loads obtained by the «exact» and the «approximate» model are close. It was found that when a cylindrical panel is deformed under the action of a combination of longitudinal and radial subcritical loads, the calculated results for the «exact» and the «approximate» model are close. Therefore, longitudinal buckling can be considered using the homogenized model, which is much simpler in terms of computations.

This work presents chemical functionalization of multi-walled carbon nano tubes (MWCNTs) through chemical modifications. Antibacterial conjugated MWCNTs were synthesized involving the sequential steps of carboxylation. Formation of the active intermediates using Hydroxy benzo triazole (HOBt) was done in order to achieve conjugated 2-mercapto benzo imidazole (MWCNT-h) as the final compound. The modification of MWCNTs with antibacterial drug was checked by Fourier transform-infrared spectroscopy, Raman spectroscopy and Thermo gravimetric analysis. Size and surface characteristics of chemically modified MWCNTs were monitored by scanning electron microscopy and Atomic Force Microscope (AFM). Minimal Inhibitory Concentration (MIC) and Antimicrobial activity of functionalized and carboxyl MWCNTs was studied on two Gram-negative bacteria as well as one Gram positive bacteria. The MIC results show that functionalized MWCNTs with anti-bacterial drugs have more effective results than bare drug and carboxyl MWCNTs individually against all studied bacteria.

Since their discovery (Iijima, 1991), carbon nanotubes (CNTs) have been attracted much attention due to their excellent mechanical, physical and chemical properties. In the past thirty years, thousands of articles have been published to discuss their growth, properties, and applications. For the CNT growth, there are three main methods: arc discharge, laser ablation and chemical vapour deposition (CVD). Compared with the first two methods, CVD was regarded as the most promising one for industrial application with low cost, although it usually introduces more defects in CNTs during the growth process. Furthermore, CVD is the preferred choice to grow patterned CNTs on substrates for nanoelectronic applications. Typically, nanotubes are grown by CVD on metal catalyst particles or islands that are deposited on top of semiconducting or insulating materials, such as alumina, silicon and silicon oxide. These non-conducting substrates assist in the formation of small islands or nanoparticles of metal catalyst on their surfaces, which is necessary for the CNT growth. However, for many applications, such as displays, cell electrodes, gigascale interconnects, high electrical and thermal conductivities are required, usually needing a conductive substrate to connect with CNTs. Furthermore, minimization of the contact resistance between metal substrate and CNTs is also a major challenge in nanoelectronics. Apart from geometrical factors, contact resistance depends mostly on alignment of Fermi energy levels of CNT and substrate. Since multi-walled CNTs are predominantly metallic (Single-walled CNTs can be adjusted to be metallic by controlling their structure), a metallic substrate to connect with CNTs is expected to have least contact resistance. In order to assemble the CNTs on metal substrate with fine patterned architectures, the obvious and effective way would be to grow CNTs directly on metal substrates. Herein, the current development of direct growth technique and its applications were summarized.

Perovskite solar cells (PSCs) made with metal halide are affordable and can give better efficiency values than older versions but their low efficiency values is still a concern. Two Perovskite solar cells were fabricated and one had Multi wall Carbon nanotube (MWCNT) in its design. The effect of the Multi-wall Carbon nanotube (MWCNT) on their performance and power conversion were studied. MWCNT and m-TiO2 materials were characterised using UV-vis spectroscopy and their optical energy band gap values were obtained. The TiO2 showed a prominent peak at 319 nm with absorbance 0.5 and its optical energy bandgap of 2.59 eV falls in the visible region showing it is a clean energy source with implications for solar energy conversion. The MWCNT has 2.19 eV and showed multiple peaks. A prominent peak at 329 nm with absorbance 0.6 which was blue shifted and a peak at 517 nm with absorbance 0.3 was red-shifted. The PSC with the MWCNT in the light had a fill factor of 0.53 but 0.47 was obtained for the PSC without the MWCNT. The PSC with MWCNT had power conversion efficiency (PCE) of 40.1 % in the dark, a value which was 2.7 % higher than the PCE of 37.4 % obtained for the same cell in light. Furthermore, the PSC without the MWCNT in the dark had a fill factor of 0.87 while the PSC with MWCNT in the dark had a fill factor was 0.51. The PSC with MWCNT had better power conversion efficiency when in the dark than in light.

ABSTRACTThe carbon nanotubes (CNTs) and CNTs doping with Fe based composites were rapid fabricated by gaseous detonation decomposition of oxygen, benzene and ferrocene mixed precursors. A series of novel experiments were designed to investigate the condensation and formation of carbon structural nanomaterials. The TEM, EDS, EDX, XRD and Raman characterizations provide fundamental evidence of the high yield and purity of the CNTs, CNTs doping with Fe composites during the gaseous detonation reaction process. The results showed that CNTs, CNTs with Fe based nanocrystals, spherical CCFNPs and their mixed products are with variant morphologies. The obtained CNTs is multi-walled carbon nanotubes and CNTs doping with a body-centered cubic iron or iron carbide cores, which can be obtained respectively through adjusting and controlling the detonation reaction environment and the precursors.

For enhancing the interfacial adhesion of glass fabric (GF)/epoxy composites, silanized multi‐walled carbon nanotubes (MWCNTs) were used to treat GF surface, where carboxyl MWCNTs were functionalized by silane coupling agents based on the covalent or non‐covalent bonding, followed by the vacuum infusion process of laminated composites. A detailed study was employed to confirm the effects of silanized MWCNTs uniform dispersion and interfacial properties of resultant composites. Making full use of suitable silane coupling agents (γ‐aminopropyltriethoxysilane) treatment, the uniform MWCNTs dispersion and strong fiber/matrix interfacial adhesion could be achieved. Compared with the control sample, flexural and interlaminar shear strengths of resultant composites were enhanced by about 24% and 22%, respectively, indicating superior mechanical strength for composites; flexural modulus and storage modulus in the glassy state were improved by about 36% and 68%, respectively, suggesting higher stiffness for composites; the work of fracture (Wf) under interlaminar shear tests was raised by about 188%, revealing better interlaminar fracture toughness of composites. In addition, glass transition temperature of resultant composites also increased. This work provides a guiding strategy for manufacturing fiber‐reinforced composites requiring adjustable strength, stiffness, and toughness.Highlights Silane coupling agent was grafted on MWCNTs by covalent/non‐covalent bonding. Active groups of silanized MWCNTs induced crosslinking reactions with matrix. Silanized MWCNTs dispersion and glass fiber/matrix adhesion were improved. Strengthening/toughening mechanisms of laminated composites were analyzed.

Electrochemical behavior of rigid carbon nanotube composite electrodes

Utilizing synergetic effects of different fillers is an important strategy to design and develop high-performance nanocomposites. However, owing to the well-known problems such as dispersion, solution viscosity control, and so on, synergetic enhancement effects are usually offset by the defects induced by fillers in highly loaded nanocomposites. In this work, remarkable synergetic efficiency was realized in graphene nanoplatelet (GNP) and multiwalled carbon nanotube (CNT) highly loaded epoxy composites through a well-designed fabrication method. Dramatic thermal conductivity enhancement was observed in the epoxy composites with 10–50 vol% nanocarbon filler due to synergetic effects. For example, the composite with 20 vol% CNTs and 20 vol% GNPs possess a thermal conductivity up to 6.31 W/mK. This is even much higher than that of the composites with individual 50 vol % CNTs or 50 vol% GNPs. A maximum thermal conductivity 7.30 W/mK was obtained, which is 38-fold of that of the pure epoxy resin. Thermal trans...

Epoxy resin is widely used in various industrial fields due to its good adhesion, corrosion resistance and the like, but its thermal conductivity is low and it is difficult to meet the heat dissipation requirements. In order to obtain epoxy composites with high thermal conductivity and excellent electrical insulation, an effective method for functionalizing boron nitride (BN) and multi-walled carbon nanotubes (CNTs) is proposed. The BN and CNTs were first ultrasonically mixed, and then functionalized by a simple dip coating procedure with polydopamine (PDA) coating (named as m(BN/CNT)). Fourier transform infrared spectroscopy, thermogravimetric analysis and X-ray photoelectron spectroscopy analysis demonstrated the successful functionalization of PDA on BN and CNTs surfaces. Adding 20 vol% m(BN10/CNT1) increased the thermal conductivity of the epoxy composite by 231% compared to pure epoxy matrix, while still maintained a volume resistivity above 1014 Ω·cm. Dynamic mechanical analysis and scanning electron microscopy showed that PDA functionalization improved the interfacial interaction between BN, CNTs and the matrix, thus ensuring the improved thermal and mechanical properties.

The effective dispersion of carbon nanotubes (CNTs) in a thermoset was achieved using ionic liquid as the dispersion-curing agent. We preferentially dispersed multiwalled carbon nanotubes (MWCNTs) down to individual tube levels in epoxy resin. Here the dispersion is ruled by the depletion of physical bundles within the MWCNT networks, for which molecular ordering of ionic liquids is considered responsible. The quantitative analyses using ultra small angle X-ray scattering (USAXS) confirmed the dispersion of individual MWCNTs in the matrix. The distance between the dispersed nanotubes was calculated at different nanotube loadings using the power law fitting of the USAXS data. The fine dispersion and subsequent curing, both controlled by ionic liquid, lead to composites with substantially enhanced fracture mechanical and thermomechanical properties with no reduction in thermal properties. Merging processing techniques of nanocomposites with ionic liquid for efficient dispersion of nanotubes and preferential curing of thermosets facilitates the development of new, high performance materials.

<p>Carbon nanotubes (CNTs) are a group of pure carbon solid materials that possess one-dimensional structures with diameters down to less than one nanometre. They have interesting physical properties such as very high tensile strength, metallic and semiconducting conductivity, and great potential for applications. This work investigates the synthesis, alignment and purification of multi-walled carbon nanotubes, which were characterized by Electron Microscopy, measurement of electrical properties and Raman scattering. Synthesis of multi-walled carbon nanotubes (MWNTs) was carried out by Chemical Vapour Deposition, using three different precursors: Fe(NO3)3, ferrocene and iron phthalocyanine. Vertically aligned "forests" of large numbers of MWNTs were achieved using ferrocene and iron phthalocyanine as precursors. Products from iron phthalocyanine yield more graphitic CNT nanostructures, as determined by Scanning Electron Microscopy, Transmission Electron Microscopy, Thermogravity Analysis, Raman microscopy and Energy Dispersive X-ray spectroscopy. Patterned growth of vertical MWNTs arrays with a resolution of 2 microns was also obtained, using a predeposited substrate. A High Resolution Transmission Electron Microscope was employed to investigate the inner structures of individual MWNTs, giving well-resolved images of concentric nanostructures with inter-lattice spacings of 0.34 nm. Techniques for purification and manipulation of CNTs are required before CNTs' excellent properties can be exploited. In this thesis, dielectrophoresis (DEP) under high-frequency AC voltages using an array of micron-scale electrodes was adopted as the technique to align MWNTs between these, electrodes. This technique is effective for MWNTs since their long cylindrical structure and the high mobility of their charge carriers allow them to be electrically polarised. As a result, MWNTs experience large DEP forces in an AC electric field. In our experiments, inter-digitated electrodes were used to apply the electric field to CNT suspensions in various solvents. Alignment of CNTs along their axis was achieved within the gaps between adjacent electrodes at a frequency larger than 1.1 MHz, The AC admittance changes between the electrodes were monitored and were observed to be a clear reflection of the accumulation process of MWNTs. Also it was identified that distilled water was a better solvent than ethanol and isopropanol for DEP purpose on MWNTs. In addition, a prototype device was built to selectively purify MWNTs from as-grown samples by combining DEP and re-circulating fluid flow. It was found that this device is able to decrease the impurity content of MWNTs, which is collected on the electrode array, from the suspension of as-grown samples.</p>