Dispersion Of Multi-walled Carbon Nanotubes Research Articles

Analysis of the thermoelectrical performance of samples made of Coir Agricultural Wastes combined with MWCNT

A biomaterial made of coir and Multi-Walled Carbon Nanotubes (MWCNTs) is presented which exhibits a relatively high-Temperature Coefficient of Resistance (TCR) and thermal insulation properties. Bolometers usually offer acceptable thermal isolation, electrical resistance, and high TCR. Fibers from agricultural waste materials such as coir has a synergistic effect as thermal insulating material and noise reducer. Based on it, powdered coir pills were used as pilot samples, as well as 2 other samples with different dispersions of MWCNTs, sodium dodecyl benzene sulfonate (SDBS) and polyvinylpyrrolidone (PVP) solution. The 3 kinds of samples were thermo-electrically characterized to determine their bolometric performance. Thermal conductivity of k = 0.045 W/m K was obtained by solving the Fourier’s law substituting the data into the equation describing heat flux on the sample around room temperature. Results show that adding different concentrations of MWCNT to powdered coir will lead to films with lower electrical resistance, therefore the thermal conductivity increases while thermal resistance decreases. Finally, the bolometric performance shows a maximum peak with a relatively high TCR of − 40.4% at a temperature of 300.3 K, this synthesized material outperforms by almost 1 order of magnitude larger than commercial materials. Results in this work also indicate that it is possible to tune bolometric parameters of this kind of samples and to use them as thermal insulators in the construction industry, when building roofs and walls.

Experimental Studies and Analytical Analysis of Thermophysical Properties of Ethylene Glycol–Water-Based Nanofluids Dispersed with Multi-walled Carbon Nanotubes

The present study investigates the thermal conductivity and dynamic viscosity of ethylene glycol–water solutions dispersed with oxidized multi-walled carbon nanotubes. The physico-thermal properties and Mouromtseff number (Mo) were used to evaluate the heat transfer properties of the nanofluids. Ethylene glycol–water mixtures were chosen as base fluids, and the volume fraction of ethylene glycol varied from 100 % to 0 % (pure water). Oxidized multi-walled carbon nanotubes in weight percentages of 0.0625, 0.125, 0.25, and 0.5 were dispersed in ethylene glycol–water mixtures to achieve the best stability. The stability of the nanofluids was monitored by UV–Vis spectroscopy for 2 months. The dispersion of multi-walled carbon nanotubes in the base fluids resulted in a significant improvement in thermal conductivity. To derive correlations for thermal conductivity and dynamic viscosity, 1 500 data points were collected for all possible combinations of temperature, weight percent of multi-walled carbon nanotubes, and ethylene glycol content. The Mouromtseff number (Mo) showed that dilute nanofluids at low concentrations are the most effective heat transfer medium in turbulent flow.

Electrical conductivity and tensile properties of carbon nanotube reinforced styrene-ethylene-butylene-styrene thermoplastic elastomer nanocomposites

In this study, nanocomposites based on styrene-ethylene-butylene-styrene (SEBS) thermoplastic elastomer (TPE) filled with multiwall carbon nanotubes (MWCNT) were produced using twin-screw extrusion. Two types of pre-mixing methods were applied to assess the dispersion-ability of the MWCNT. In Method A, the SEBS, MWCNT, and paraffinic process oil were mixed together in one step and fed simultaneously into the hopper for melt extrusion. In Method B, the MWCNT were first mixed with paraffinic process oil before being added to SEBS. The dispersion of MWCNT in SEBS TPE was characterized by transmission electron microscopy. The effects of the MWCNT on the electrical resistivity and tensile properties of the SEBS TPE were determined. A balance of tensile properties and electrical properties can be achieved by adding 3 wt% MWCNT into SEBS TPE, especially using Method B. Pre-mixing of MWCNT with paraffinic process oil promotes better dispersibility, higher electrical conductivity, and better tensile properties.

A dendrite suppression coating formulated via electrophoretic deposition using Bi-functional surfactants for Zn-ion batteries

Aqueous Zn-ion batteries (ZIBs) are promising for large-scale energy storage due to their low cost and high safety. However, ZIBs suffer from Zn dendrite growth and side reactions over the charge-discharge processes. Herein, a facile and scalable strategy was developed based on electrophoretic deposition (EPD) of surfactant-stabilized multi-wall carbon nanotubes (MWCNT) to enhance the reversibility of Zn foil. The MWCNT coating provides high surface area and improved electronic conductivity, thus facilitating rapid charge transfer behavior over the Zn 2+ plating/stripping processes. The results indicated that cationic surfactants, cetyltrimethylammonium bromide (CTAB), are feasible to improve the stability of Zn anode as electrolyte additives in parallel to dispersion and charging of MWCNT. Single-crystalline cryptomelane-type α-MnO 2 nanowires were successfully synthesized by oxalate-reduction of potassium permanganate under ambient conditions. The ZIBs, prepared by α-MnO 2 nanowire cathode and MWCNT coated Zn anode, demonstrated surpassing rate capacity and long cycling stability. The interfacial analysis of electrodes, based on surface tension and contact angle measurements, shed some light on the design and development of multi-functional additives for advanced ZIBs. • A dendrite suppression coating was fabricated by electrophoretic deposition. • Surfactants are found to be electrolyte additives paralleled to CNT deposition. • Single-crystalline α-MnO 2 nanowires were synthesized under ambient conditions. • Interfacial properties were analyzed for wettability and tension measurements.

Mechanical properties and microcosmic mechanism of multi-walled carbon nanotubes reinforced ultra-high strength concrete

There have been much research on carbon nanotubes (CNTs) modified cement-based materials. However, few studies utilized multi-walled CNTs (MWCNTs) to prepare the ultra-high strength concrete (UHSC). This study aims to discover a new UHSC reinforced by MWCNTs and reveal the enhancement mechanism of MWCNTs. In this study, the mechanical properties of UHSC with different contents of MWCNTs (both dispersed and undispersed) were tested. The element distribution and microstructure of UHSC were observed by energy-dispersive spectrum (EDS) and scanning electron microscopy (SEM). In addition, the pore structures of UHSC were exhibited through X-ray CT images. The result shows that the compressive strength and flexural strength of UHSC reached the maximum value with the addition of 0.1 wt% dispersed MWCNTs. The dispersed aqueous solution of 0.1 wt% MWCNTs can be uniformly distributed in the UHSC matrix, and MWCNTs can fill the initial defects and bridge the microcracks inside the UHSC. Moreover, with the addition of 0.1 wt% dispersed MWCNTs, the number of pores decreased by 59.98%, and the porosity of UHSC decreased by 14.41%. The expectation of this study is to provide a reference for the better preparation of UHSC.

Development of a Nafion-MWCNTs and in-situ generated Au nanopopcorns dual-amplification electrochemical aptasensor for ultrasensitive detection of OTA

Trace detection of ochratoxin A (OTA) in foods is essential to mitigate risks to human health. Herein, a label-free electrochemical (EC) aptasensor based on dual-signal amplification of Nafion dispersed multi-walled carbon nanotubes (Nafion-MWCNTs) and Au nanopopcorns was developed for ultrasensitive detection of OTA. Nafion solution prevented the leaching of MWCNTs, and the Nafion-MWCNTs modified screen-printed carbon electrode (SPCE) acted as the sensing substrate which facilitated the uniform distribution of the electrodeposited Au nanopopcorns. The in-situ generated Au nanopopcorns could not only load a large amount of aptamers for specific identification of OTA, but also promote the electron transfer of the sensing platform. The incorporation of Nafion-MWCNTs and Au nanopopcorns realized dual-amplification of the aptasensor due to the enhanced conductivity and the increased electroactive surface area of the electrode. The modified electrodes were characterized through scanning electron microscopy, X-ray photoelectron spectroscopy and EC evaluation. Under optimal conditions, the electrochemical impedance spectroscopy (EIS) was measured for the determination of OTA. The as-fabricated Au nanopopcorns/Nafion-MWCNTs impedimetric aptasensor displayed excellent sensitivity with a detection limit as low as 1 pg/mL and a wide linear range of 1 pg/mL-10 ng/mL for OTA. Practical application of the aptasensor in the spiked malt samples achieved satisfactory recoveries of 89.82–95.65 %, which was also successfully verified to detect OTA in eleven batches of actual malt samples collected from the local market. The creative aptasensor is simple, cost-effective, sensitive, and accurate, showing great promise for on-site monitoring of other trace contaminants in foods by simply replacing the aptamers.

Isolation and Characterization of Cellulose Nanofibers from Wheat Straw and Their Application for the Supercapacitor

As a by-product of wheat planting, wheat straw is an abundant agricultural residue with the highest cellulose content of all agricultural fibers. Its resourceful utilization contributes to alleviating the environmental problems it caused. In this study, cellulose from wheat straw (WS) is used as a dispersing agent to prepare a novel multi-walled carbon nanotube-modified nickel foam (NF) electrode. The new electrode is investigated for electrochemical properties relevant to supercapacitors. The 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) oxidation is chosen to produce cellulose nanofibers (CNF) from wheat straw. The prepared CNF is used to facilitate the uniform dispersion of multi-walled carbon nanotubes (MWCNT) and favor the formation of a stable CNF-CNTs membrane on the nickel foam skeleton. The influence of dispersing materials and content of CNF on the electrochemical performance of electrodes is investigated. It is revealed that the incorporation of CNF can improve the electrochemical stability of electrodes. Moreover, it also exhibits optimum capabilities (70.2% capacitance retention from 1 to 40 mA cm−2) when CNF:MWCNT = 1:0.7. The areal capacity of the CNF-MWCNT/NF electrode for a scanning rate of 5 mV s−1 is twice that of the MWCNT/NF electrode and 30 times that of the NF electrode, indicating it is a promising candidate to ensure the synchronization of a green environment and energy development.

Structural Health Monitoring of the Carbon Fiber Reinforced Epoxy/MWCNTS Composites under Vibration Loading, Using Electrical Resistance Change Method

This work aims to investigate the structural deterioration of the Carbon Fiber Reinforced Epoxy (CFRE) composite under vibration loading by monitoring the variation of the electrical resistance of the composite. The vacuum assisted resin transfer moulding process is used to fabricate the CFRE composites. Multiwall Carbon Nanotubes (MWCNTs) (0.5% wt) are added to the non-conductive resin to increase its electrical conductivity before CFRE fabrication. The tests were carried out by monitoring the variation in electrical resistance of the CFRE composite at 90 Hz frequency vibration loading. The dispersion of MWCNTs into the matrix and the damage of CFRE composite are illustrated by the SEM images. The results show that the electrical resistance change can be considered as a good indication to detect damage in CFRE (modified with 0.5 wt % MWCNTs) under vibration loading.

Preparation of three-dimensional interconnected graphene/ionic liquid composites to enhanced thermal conductivities for battery thermal management

The development of phase change materials with a high latent heat of fusion and thermal conductivity is a key issue that needs to be addressed in power batteries thermal management system. In this study, an imidazolium ionic liquid ([C16MIM]Br) suitable for latent heat storage was synthesized by quaternization reaction. The composite phase change material of ionic liquid/graphene/carbon nanotube aerogel was prepared by hydrothermal self-assembly and vacuum impregnation method utilizing the unique π-π interaction between the delocalized electron of the heterocyclic cation of the ionic liquid and the sp2 bonded carbon materials. The prepared ionic liquid-based phase change materials had high latent heat of phase change, excellent thermal stability, and enhanced thermal conductivity. The thermal conductivity of the composite material reached 0.751 W/(m·K) at a carbon nanotubes addition of 15 wt%, which was 232% higher than that of the pure ionic liquid (0.226 W/(m·K)). The enhancement was attributed to the three-dimensional network in the graphene/multi-walled carbon nanotubes aerogel which was beneficial to improve the dispersion of multi-walled carbon nanotubes in the matrix and promote the uniform penetration of the ionic liquid phase change material. As a result, the designed structure provided effective ways for phonon transmitting and improved the thermal conductivity of the composites.

Mechanical Properties of AA2024 Aluminum/MWCNTs Nanocomposites Produced Using Different Powder Metallurgy Methods

Metal matrix composites are a class of materials with high potential for industrial application due to the multifaceted properties that they possess. In the present research, mechanical alloying via ball milling was used to produce AA2024 powder that was subsequently reinforced with multiwalled carbon nanotubes (MWCNTs). Dispersion of the MWCNTs in the AA2024 matrix was achieved also by ball milling. Two different powder metallurgy sequencies, (i) double pressing double sintering and (ii) hot pressing were used for compaction and consolidation of the AA2024 reinforced by MWCNTs. The produced nanocomposites outperform the pristine AA2024 in terms of compressive strength, elongation to failure, and microhardness. The strengthening mechanism was associated with the homogeneous distribution of MWCNTs in the AA2024 matrix and their efficient interfacial bonding, which was attested also by microstructural characterization. Hot pressing resulted in higher mechanical properties of the nanocomposite material. However, when reinforcement content was above 2 wt.% a dramatic decrease of mechanical properties was observed, attributed to clustering and inhomogeneous dispersion of the MWCNTs. The homogeneous dispersion of MWCNTs in the AA2024 matrix and the retaining of their structural integrity are pivotal in increasing the mechanical properties, which can be directly associated with the efficient interfacial load transfer between MWCNTs and AA2024 matrix.

Industrial block copolymer surfactants: Diversity of associative forms and interaction with carbon nanomaterial

• Upon copolymer micellization alteration of micelle shape and hydrodynamic size takes place. • Hypothesis about the double-stage nature of copolymer micellization was proposed. • Diversity of associative forms of MWCNT-block copolymer complexation was revealed. • Interaction of block copolymers can results in liquid crystal structuring. In this work, we studied self-association/micellization of several block copolymers based on PEO and PPO blocks – two poloxamers and reverse-sequential poloxamine in aqueous solutions and dispersions of multi-walled carbon nanotubes (MWCNTs). To study this process the number of NMR experiments was used, such as self-diffusion measurements and spectral analysis including alterations of chemical shift and resonance line width. The absence of strictly defined critical micelle concentration, when micelles of constant size start forming, was found. The obtained results proved that amphiphilic copolymers alter micelle shape and hydrodynamic size upon the growth of polymer concentration. The hypothesis about the double-stage nature of copolymer molecules association/micellization has been proposed. At the first stage the polymers hydrophobic blocks connect into cord-like associates/micelles and then these associates join into spherical micelles or liquid-crystalline domains. The transmission electron microscopy of block copolymers revealed a variety of their associative forms. The interaction peculiarities of various associates for different block copolymers with MWCNTs were considered. In poloxamers/MWCNTs dispersions the central hydrophobic blocks of poloxamers can be adsorbed on the hydrophobic surface of MWCNTs, isolating a part of the nanotube surface, thereby preventing their sticking. For the X-shaped diproxamine another mechanism of interaction with carbon surface was proposed, which makes it possible to explain the opposite NMR effects in the presence of MWCNTs. The transmission electron microscopy revealed a variety of associative forms of block copolymers studied.

Obvious improvement of dispersion of multiwall carbon nanotubes in polymer matrix through careful interface design

AbstractHerein, a simple and effective approach has been proposed to enhance the interfacial strength between multiwall carbon nanotubes (MWCNTs) and polymer matrix for improving the dispersion of MWCNTs. In more detail, a soluble polyaniline derivate containing polar group (POMA) was selectively incorporated into the binary blend of poly(amide‐imide) (PAI) and MWCNTs. The surface energy and atomic force microscope measurements suggested that POMA was located at the interface of PAI and MWCNTs. Fourier transform infrared measurement indicated that POMA simultaneously interacted with MWCNTs and PAI by hydrogen bonding and π–π interaction, providing stronger interfacial strength between conductive filler and polymer matrix. As a result, the dispersion of MWCNTs and the surface roughness of PAI composites were obviously improved, which is helpful for charge and load transfer in the PAI/MWCNTs/POMA ternary films. As a result, the conductivity increased by 250% from 13 S m−1 for PAI/MWCNTs binary composites to 48 S m−1 for PAI/MWCNTs/POMA ternary composites, and the tensile strength increased from 52 MPa for PAI/MWCNTs binary composites to 66 MPa for PAI/MWCNTs/POMA ternary composites. These findings imply that polar aromatic polymers with suitable surface energy will be a desirable compatibilizer for optimizing the dispersion of carbon nanotubes in the polymer matrix.

Optimization of Binary Polymer Concentration for Dispersion of Multiwalled Carbon Nanotubes in Aqueous Solution

AbstractThe dispersion of carbon nanotubes (CNTs) is a challenging step in the preparation of conducting composites. Stabilizing CNT suspensions in a liquid solution with surfactants and polymers as dispersants is the most common method. This study aimed to investigate a systematic route to the degree of dispersion of functionalized multiwalled carbon nanotubes (F‐MWCNTs) in aqueous solution, assisted by four types of binary dispersants (i.e., polymer/surfactant). A UV‐Vis spectroscopy‐based method was employed to accurately determine the optimum F‐MWCNTs concentration in blended binary polymer with application of the Boltzmann sigmoidal model. The model represents the concentration of dispersed F‐MWCNTs attained versus the initial concentration of F‐MWCNTs used, and it was found that the model fits the experimental data. The significance of the parameters related to the Boltzmann sigmoidal model for the dispersion behavior of F‐MWCNTs is discussed. The model could be a tool to prepare optimally dispersed F‐MWCNTs in various types of liquid solutions.

Effect of Carbon Nanotube Content and Mechanical Milling Conditions on the Manufacture of AA7075/MWCNT Composites

Aluminium matrix composites (AlMCs) of AA7075 aluminium alloy reinforced with 0.5 and 1 wt.% multiwall carbon nanotubes (MWCNTs) were fabricated with powder metallurgy techniques using three different mechanical milling strategies, varying the milling energy and the stage in which the reinforcements were added to the pre-alloyed matrix powders. In this paper, we focus on the influence of these parameters on the dispersion of MWCNTs. Characterization of the obtained composite powders by X-ray diffraction and scanning electron microscopy showed that the evolution of the particle size and morphology of the composite powders is influenced by milling conditions and MWCNT content; however, under the conditions tested in this study, there were no significant differences in crystallite size and lattice strain. The best distribution of the reinforcements was obtained after milling 7075 powders and MWCNTs in a high-energy cycle (HEBM), varying the rotation speed between 1200 and 1300 rpm. Raman spectroscopy was used to assess the damage induced by the milling process in the nanotubes, and no reaction products were detected under any of the tested conditions. Nanoindentation tests were performed to measure the elastic modulus and hardness of the composite powders, revealing that the best mechanical behaviour was achieved by the 7075-0.5 wt.% MWCNT composites obtained by the HEBM route.

Fabrication of MA-EPDM grafted MWCNTs by reactive extrusion for enhanced interfacial adhesion and mechanical properties of PP/MA-EPDM composite

Maleic anhydride modified ethylene-propylene-diene tripolymer (MA-EPDM) is an efficient toughening agent for other polymers such as polypropylene (PP). However, the rubber toughened plastics always exhibit a trade-off between stiffness and toughness. In this study, PP/MA-EPDM blend had functionalized multi-walled carbon nanotubes (MWCNTs) incorporated for reinforcement of both stiffness and toughness. PP and MA-EPDM were melt-extruded with amine group functionalized MWCNTs. During the extrusion, MA-EPDM was grafted to the MWCNTs by the reaction between MA and amine groups (MWCNTs-g-MA-EPDM), resulting in the fabrication of PP/MA-EPDM/MWCNTs-g-MA-EPDM composite. The MWCNTs-g-MA-EPDM were extracted from the composite by dissolving and removing PP and unreacted MA-EPDM using a solvent to characterize resulting properties. The interfacial adhesion of MWCNTs-g-MA-EPDM to PP and MA-EPDM blend was characterized by using a drop-on-fiber method. The MWCNTs-g-MA-EPDM exhibited enhanced interfacial adhesion and better MWCNT dispersion in the composite compared to the pristine MWCNTs. As a result, the PP/MA-EPDM/MWCNTs-g-MA-EPDM composite exhibited the highest tensile strength, tensile modulus and impact strength of the composites examined.

Effect of surfactant types on the foam stability of multiwalled carbon nanotube stabilized foam

Multiwalled Carbon nanotube (MWCNT) serves as one of emerging and attractive materials for stabilizing foams due to its small size, special surface property and rod-like structure. The combination of MWCNT and surfactant has been regarded as an effective strategy to improve foam stability in porous media. However, the effects of surfactant types on the dispersity of MWCNT and on the stability of MWCNT stabilized foams have yet to be clearly understood. More importantly, the lack of comprehensive study of the synergistic interactions between surfactants and MWCNTs seriously limits the understanding of MWCNT’s foam-stabilizing mechanism, restricting its application as the foam stabilizer. Herein, this paper aims to systematically study the foam-stabilizing performance and mechanism of different surfactant/MWCNT foam systems. Combining with the experimental results obtained from ultraviolet and visible spectrophotometry and zeta potential tests, environmental scanning electron microscope analyses, contact angle measurements, optical microscope observations, and surface tension and dilational viscoelastic modulus determinations, the foam-stabilizing mechanism of different surfactant/MWCNT foam systems can be conjectured as follows. Compared with anionic and nonionic surfactants (SDS and OP-10) modified MWCNT, the MWCNT modified by the cationic surfactant (CTAB) can yield better dispersity due to the larger electrostatic repulsion and higher steric resistance between MWCNTs after the adsorption of CTAB. The highly dispersed MWCNTs have small sizes, which make them enter the foam film easily and tend to aggregate at Plateau border. These aggregations can significantly slow down the film drainage. In addition, MWCNTs can improve the viscosity of foam film, which helps to increase the resistance of gas diffusion and mitigate bubble coalescence. After being adsorbed by surfactants, the modified MWCNT can adsorb on the air-water interface. Due to the higher detachment energy, the CTAB modified MWCNT has a stronger adsorption capacity at the air-water interface compared with SDS and OP-10 modified ones. This tight adsorption can improve the dilational viscoelastic modulus and thus enhance foam stability. Finally, the dual-sand pack experiments proved that the CTAB/MWCNT stabilized foams have good potential for conformance control in heterogenous reservoirs.

Synthesis of MWCNTs from xylenes for fabrication of highly electrically conductive and gas-sensitive polymer composites

For Multi-Walled Carbon Nanotubes (MWCNTs), high quality, purity, and low cost are very desirable. Therefore, in this reported research work, qualitative and pure MWCNTs were synthesized using a cheap and affordable carbon source-xylenes (a mixture of isomers) by the Aerosol Chemical Vapor Deposition Method (A-CVD). The high quality, purity, and homogeneity of the synthesized material have been verified by Raman spectroscopy, EDX, XRD, and SEM results. In the present study, Polystyrene/xMWCNT, Polyvinyl acetate/xMWCNT, and Polyvinyl alcohol/xMWCNT composites with different MWCNT contents of (x = 1, 2, 4, 8, and 16) wt% were prepared by an optimized technique for irreversible dispersion of MWCNTs inside polymers, which was developed by our research group. SEM analysis results revealed that the MWCNTs are well incorporated inside all three polymer matrices, and a highly dispersed distribution of MWCNTs has been obtained inside all three matrices due to this technique. Also, the electrical conductivity of the prepared composites was measured, and the prepared nanocomposites show high electrical conductivity for all concentrations of MWCNTs. Based on the maximum dispersion of MWCNTs inside the PS polymer matrix, the highest electrical conductivity is observed for this composite, which once more proves that the dispersion technique as well as the nature of the polymer play an important role in the preparation of highly electroconductive nanocomposites (1%-0.136 S/m; 2%-1.053 S/m; 4%-5.376 S/m; 8%-71.48 S/m; 16%-933.71 S/m). Comparison of electrical conductivity results of these composites with literature results demonstrates the advantages of this technique in substitution of the another dispersion methods. The nanocomposites prepared by our research group also show a sensor effect (change of resistivity) under different gases (methane, propane, carbon monoxide). It is interesting that, for analyzed gases, the resistivity of some nanocomposites increased, whereas for others it decreased. This effect can be explained by the different nature of the adsorption interaction between the analyzed gas and the polymer composite, and this depends on the chemical composition and properties of both gases and polymer matrices.

Embedding Multi-Wall Carbon Nanotubes as Conductive Nanofiller onto Bi2Te3 Thermoelectric Matrix

Thermoelectric Generators (TEGs) are devices that have the ability to directly convert heat into electrical power, or vice-versa, and are being envisaged as one off-the-grid power source. Furthermore, carbon-based materials have been used as a conducting filler to improve several properties in thermoelectric materials. The present work studied the influence on the thermoelectric performance of Bi2Te3 bulk materials by incorporating different concentrations of Multi-Walled Carbon Nanotubes (MWCNT). In order to control and understand the influence of MWCNT dispersion in the nanocomposite, two different production methods (manual grinding and ultrasonication) were carried out and compared. It was verified that a larger dispersion leads to a better outcome for thermoelectric performance. The achieved Seebeck coefficient was up to -162 µV K-1 with a Power Factor of 0.50 µW K-2m-1, for the nanocomposite produced with 11.8 %V of MWCNT. This result demonstrates the ability to increase the thermoelectric performance of Bi2Te3 throughout the addition of MWCNT.

Static and dynamic moduli of elasticity and drying shrinkage behavior of concrete containing multi-walled carbon nanotubes

This paper investigated the efficiency of concrete reinforced with multi-walled carbon nanotubes (MWCNTs) specimens in terms of fresh concrete slump, compressive strength, static and dynamic moduli of elasticity, the drying shrinkage strain, and microstructure. In addition, the particle sizes distribution of MWCNTs dispersions in water was investigated by the dynamic light scattering (DLS) test. The dispersion sonicated with an ultrasonic probe had a smaller distribution range with a higher rate in smaller particle sizes compared with the dispersion sonicated with an ultrasonic bath. By incorporation of MWCNTs with an amount of 0.05–0.2% of cement weight, the fresh concrete workability, and the 365 day-age drying shrinkage strain are reduced up to 20% and 24%, respectively; also, the compressive strength, the static modulus of elasticity, and the dynamic modulus of elasticity increased up to 35.4%, 8.9%, and 5%, respectively. The SEM studies showed the bridging behavior of MWCNTs in the cement paste matrix at the nanoscale, and map analysis showed the distribution and the aggregation of MWCNTs in some parts of the concrete mixture.

Nonlinear vibrations and viscoelasticity of a self-healing composite cantilever beam: Theory and experiments

A self-healing beam was fabricated by using a microencapsulated healing agent (5E2N) with dispersed multi-walled carbon nanotubes (MWCNT). Grubbs’ catalyst was dispersed in the epoxy matrix reinforced with MWCNT. The self-healing material was specifically realized for this study modifying a formulation developed for satellites. Experiments were conducted on the self-healing beam in order to identify the viscoelastic material properties by vibration measurements. In addition, large-amplitude vibration experiments were carried out on the self-healing cantilever beam. A refined third-order shear deformation theory was developed to model the nonlinear vibrations of the cantilever beam. The model retains rotary inertia and in-plane and rotational nonlinearities in addition to traditional von Kármán nonlinear terms; it uses the mechanical properties experimentally identified. A satisfactory comparison of experimental and numerical results for nonlinear vibrations of the self-healing cantilever beam is presented for five different excitation levels.