Multi-walled Carbon Nanotubes Loading Research Articles

Efficient electrical conductivity and electromagnetic interference shielding performance of double percolated polymer composite foams by phase coarsening in supercritical CO2

There is a growing interest in porous conductive polymer composites (CPCs) in view of lower density and more sufficient material utilization than solid counterparts, but they are still limited by poor performance. Few measures have been taken to deal with the problem by now. Herein, double percolated structure, supercritical carbon dioxide (scCO2) annealing treatment and scCO2 foaming were first combined to fabricate polystyrene (PS)/poly (methyl methacrylate) (PMMA)/multi-wall carbon nanotube (MWCNT) composite foams with porous double percolated structure. Due to the effective phase coarsening in scCO2 before foaming, the composite foams with density of 0.49 g/cm3 exhibited excellent electrical conductivity of 2.69 S/m and electromagnetic interference shielding effectiveness of 25.30 dB at thin thickness of 2 mm and low MWCNT loading of 2 vol%. In addition, absorption was the dominant shielding mechanism. For composite foams, the percolation threshold decreased from 0.14 vol% to 0.07 vol% after phase coarsening in 180 °C scCO2. This work provides a green and versatile method for preparing porous CPCs with double percolated structure and improved electrical conductivity.

Dielectric Hole Collector toward Boosting Charge Transfer of CsPbBr3 Hybrid Nanogenerator by Coupling Triboelectric and Photovoltaic Effects

AbstractCoupled triboelectric‐photovoltaic effect by collecting photogenerated charge carriers is increasingly important to dramatically improve the short‐circuit current output of triboelectric nanogenerators (TENG), especially for the all‐inorganic cesium lead bromide (CsPbBr3) halide perovskite combined with the optoelectronic and dielectric properties as a fundamental friction layer in TENG. Herein, hole‐extraction polydimethylsiloxane (PDMS)‐multi‐wall carbon nanotubes (MWCNTs) composite film (PC) is applied into the fabrication of vertical contact‐separation mode CsPbBr3/PC hybrid TENG with dual role of negative triboelectrification layer and photogenerated hole collector. Through precisely regulating the surface potential of PC films by tuning the MWCNT loadings, the charge quantity is greatly enhanced thanks to the triboelectric‐photovoltaic coupling effect. The best hybrid TENG at MWCNTs loading of 16 wt% achieves a transferred charge of 0.358 mC under illumination, which is nearly 30,000 times higher than that of the pristine PDMS based TENG. Impressively, the champion hybrid TENG at MWCNTs loading of 12 wt% yields a power rating density of 8.24 W m−2. This work demonstrates the PC hole collector to be a promising conductive triboelectric counterpart for efficient charge separation and extraction toward booting current density of hybrid triboelectric‐photovoltaic devices.

Well‐dispersed poly(ether‐ether‐ketone)/multi‐walled carbon nanotube nanocomposites prepared via a simple solution mixing approach

AbstractIncorporation of reinforcing nanoparticles, like multi‐walled carbon nanotubes (MWCNTs), in a polymer matrix is an effective way to enhance mechanical properties and expand structural applications of engineering polymers such as poly(ether‐ether‐ketone) (PEEK). Good dispersion of MWCNTs is critical for achieving optimal properties. In this work, a simple solution mixing approach was utilized to prepare PEEK nanocomposites reinforced with MWCNTs. By direct mixing of PEEK/dichloroacetic acid solution and MWCNT/N‐methyl‐2‐pyrrolidone solution, PEEK nanocomposites with individually dispersed MWCNTs were prepared. A PEEK wrapping of MWCNT mechanism is proposed to explain why this simple solution mixing approach resulted in such a good dispersion. Thermal stability of PEEK is not affected but crystallization is impeded due to the confinement effect of well‐dispersed MWCNTs. Young's modulus is increased by ca 20% while coefficient of thermal expansion above the glass transition temperature is decreased by ca 30% with only 1.5 wt% MWCNT loading in PEEK, which is critical for a variety of high‐temperature applications. © 2021 Society of Industrial Chemistry.

Electromagnetic interference shielding performance of carbon nanostructure reinforced, 3D printed polymer composites

We report the electrical, mechanical and electromagnetic interference (EMI) shielding performance of polypropylene random copolymer (PPR)/multi-wall carbon nanotube (MWCNT) nanocomposites enabled via customized fused filament fabrication process. The electro-conductive PPR/MWCNT filament feedstocks were fabricated via shear-induced melt-blending process that allows 3D printing of nanoengineered composites even at higher MWCNT loading (up to 8 wt%). The uniform dispersion of MWCNTs in PPR matrix confirmed via Raman spectroscopy and scanning electron microscopy facilitates better mechanical, electrical and EMI shielding performance. The results furthermore show enhanced shielding properties and higher attenuation for the nanocomposites printed in 90° direction (~ − 37 dB for 8 wt% MWCNT loading). Effective interfacial adhesion between the beads with lesser extent of voids (confirmed via micro-computed tomography) endorsed low transmission loss in nanocomposites printed in 90° direction compared to samples printed in 0° direction. Surface architected structure (frustum shape) reveals higher specific shielding effectiveness (maximum ~ − 40 dBg−1cm3, + 38%) over the plain structure. The realization of excellent shielding effectiveness (~ 99.9% attenuation) of additive manufacturing-enabled PPR/MWCNT nanocomposites demonstrates their potential for lightweight and strong EMI shields.Graphical

Synthesis and characterization of zirconium(IV) molybdosulphosalicylate, multi-walled carbon nanotubes and polypyrrole based ternary nanocomposites: Adsorption and lead sensing studies

The present paper reports the facile synthesis of zirconium molybdosulphosalicylate cation exchanger [Zr(IV)MoS] and its successive nanocomposites of polypyrrole bearing different weight percent of multiwalled carbon nanotubes (MWCNTs) using a simple sol-gel approach via in-situ oxidative polymerization (ZP, 1-ZMP and 2-ZMP having nil, 0.1 and 0.25 g MWCNTs respectively). The nanocomposites were systematically characterized by FTIR, SEM, TEM, XRD and TGA. The spectral data is indicative of the polymerization of pyrrole on the ZMP nanoparticles. The TEM images also signify the encapsulation of Zr(IV)MoS on pyrrole matrix while MWCNT appears as long threads. The TGA profiles of ZP, 1-ZMP and 2-ZMP are suggestive that as the loading of MWCNT is increased, the thermal stability also gets enhanced. ZP, 1-ZMP and 2-ZMP were also analysed for their adsorption behavior against Ni(II), Cu(II) and Pb(II) ions where maximum absorption efficiency was observed in the case of 1-ZMP nanocomposite. Similarly, the ZP, 1-ZMP and 2-ZMP nanocomposites were also screened for their probable lead sensing application using cyclic voltammetry and the possible mechanism of Pb2+ion detection in the presence of 2-ZMP was also explored.

Covalently immobilized cobalt Phthalocyanine@MWCNT PDMS hollow fiber membrane for highly selective, reversible and bio-inspired oxygen transport

Facilitated oxygen transport is an effective strategy for the oxygen transport that may enhance the oxygen permeance and its selectivity, which may provide oxygen rich permeate that can be used in medical applications as in the present COVID-19 pandemic situation for providing the sufficient oxygen to the patients. This study presents the bio-inspired oxygen transport by covalently bonded Cobalt Phthalocyanine complex anchored on multi walled carbon nanotube (MWCNT) via axial ligand, incorporated in PDMS hollow fiber membranes with 0.05, 0.1, 0.5 and 1.0 wt % loadings. Successful functionalization of MWCNT was confirmed by Raman spectroscopy and X-ray photoelectron spectroscopy. The membranes were thoroughly characterized by using FE-SEM with elemental mapping, ATR-IR, DSC and TGA analysis. It demonstrated facilitated oxygen transport through the covalently immobilized Cobalt complex of the membrane with high oxygen permeance of 49 GPU as well as exceptional oxygen selectivity of 17 at 0.5 wt % Cobalt Phthalocyanine@ MWCNT loading. These values are highest among the known Cobalt complex based hollow fiber composite membranes in the literature suggesting its best utility in selective oxygen concentration for practical applications.

Abrasive Wear Behavior of CNT-Filled Unidirectional Kenaf–Epoxy Composites

Kenaf (Hibiscus Cannabinus) fibers have received significant attention for replacing the usage of synthetic fibers, especially glass fiber, in the fabrication of fiber-reinforced polymer (FRP) composites. The aim of this research was to study the change in wear behavior of kenaf-epoxy fiber composites by filling them with multiwall carbon nanotubes (MWCNT). In particular, the effect of untreated MWCNT (PMWCNT), acid-treated MWCNT (AMWCNT), and silane-treated MWCNT (SMWCNT) was studied, using three different MWCNT loadings, i.e., 0.5, 0.75, and 1 wt.%. The abrasive wear test was conducted to measure the wear properties of the composites. A thermal infrared camera was also used to measure the punctual contact temperature during the abrasive wear test, while the abraded surfaces were analyzed using the stereomicroscope. Starting from the considerable reduction of wear rate with the introduction of kenaf fibers, it was observed that PMWCNT provided some further, yet modest, reduction of wear rate only at the higher loadings. In contrast, the inclusion of AMWCNT proved to increase the specific wear rate of the epoxy-kenaf composites, an effect worsened at higher loadings. This may be due to the weakened interfacial bonding between the AMWCNT and epoxy. On the other hand, the presence of SMWCNT improved the interfacial bonding between CNT and epoxy, as shown by an increase in contact temperature. However, the increase in bonding strength was stipulated to have caused the rougher worn debris, thus inducing a three-body abrasive wear effect.

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.

Effect of Multi-Walled Carbon Nanotubes on Strength and Electrical Properties of Cement Mortar.

This work aims to investigate the effects of multi-walled carbon nanotubes (MWCNTs) on the strength and electrical properties of cement mortar. MWCNTs were added to cement mortar in four different concentrations: 0.00 wt.%, 0.01 wt.%, 0.015 wt.%, and 0.02 wt.% by the mass of cement. The consistency, density, setting time and compressive and flexural strength of mixes were tested and analyzed at 28 and 90 days curing time. Mechanical performance tests confirm an increase of 25% and 20% in the ultimate compressive and flexural strength respectively, which results from MWCNT 0.02 wt.% loading at 90 days curing time. The resistivity measurements in mortars with 0.01 and 0.015 wt.% MWCNT loading result up to 10% decrement at both 28 and 90 days curing. Activation energy calculations show fully accordance with these statements, resuming that 0.01 wt.% MWCNT appears to be the most effective loading scheme to produce certain conductivity enhancement in cement mortar.

Multiwalled carbon nanotubes/castor‐oil–based waterborne polyurethane nanocomposite prepared using a solvent‐free method

In this article, castor‐oil–based emulsifier was prepared by the esterification reaction between castor oil and maleic anhydride in the solvent‐free and catalyst‐free conditions, and the emulsifier was used to fabricate the multiwalled carbon nanotubes/castor‐oil–based waterborne polyurethane (WPU) nanocomposite in the absence of solvent. The structure of castor‐oil–based emulsifier was characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy, and the thermal properties, mechanical properties, hydrophobicity and morphology of pure WPU and nanocomposite films with different content of multi‐walled carbon nanotubes were investigated. The result showed that due to interaction between polymer matrix and multiwalled carbon nanotubes, the tensile strength was improved and thermal stability of polyurethane films was enhanced from 223°C to 248°C with multiwalled carbon nanotubes loading up to 0.5 wt%. In addition, because of lower surface energy and higher roughness of materials, water contact angle of polyurethane films was increased from 69.1° to 86.9°. However, when the content of multiwalled carbon nanotubes of nanocomposite was 0.5 wt%, the elongation at break decreases. The reason was attributed to the fact that the agglomeration of nanoparticles was observed in the scanning electron microscope image with multiwalled carbon nanotubes loading up to 0.5 wt%, which destroyed structure of the polymer.

Thermo-resistive and thermo-piezoresistive sensitivity of carbon nanostructure engineered thermoplastic composites processed via additive manufacturing

We experimentally examine the thermo-resistive and thermo-piezoresistive sensitivity of multiwall carbon nanotube (MWCNT)/polypropylene random copolymer (PPR) nanocomposites processed via fused filament fabrication (FFF) process. The filament feedstocks were fabricated by melt blending of neat PPR with a predetermined amount of MWCNTs (either 4, 6 or 8 wt%) using a twin-screw extruder. Thermo-resistive characteristics of MWCNT/PPR composites were measured under both constrained and unconstrained heating from approximately 30-100 °C. For all MWCNT concentrations considered here, negative temperature coefficients of resistivity (TCR) were observed for both constrained and unconstrained heating, as a consequence of thermal fluctuation-induced tunneling at MWCNT junctions. The highest thermo-resistive sensitivity was measured for the composite with the lowest MWCNT concentration (4 wt%) under unconstrained conditions, reporting a TCR of −12,800 × 10−6/°C, which is higher in magnitude than that of other polymer nanocomposites reported in the literature. Moreover, the MWCNT/PPR composites exhibit strong thermo-piezoresistive response under tensile loading. For 4 wt% MWCNT loading, the gauge factor (measured over 0–20% strain range) of the composite increased from 27.8 to 52.3 when the temperature was raised from 30 °C to 60 °C. Our results further evince higher thermo-piezoresistive sensitivity i.e., a gauge factor as high as 395 at 60 °C. The electron tunneling and hopping, both thermally-assisted and activated by mechanical deformation of the PPR matrix, significantly increase the thermo-piezoresistance with the increase in temperature in this range. The excellent thermo-resistive and thermo-piezoresistive characteristics of MWCNT/PPR composites reported in this study would enable the development of smart nanocomposites for self-sensing both temperature and strain/damage state.

Electrical Joule heating of cementitious nanocomposites filled with multi-walled carbon nanotubes: role of filler concentration, water content, and cement age

In the study at hand the Joule heating effect of electrically conductive cementitious nanocomposites filled with different loadings of multi-walled carbon nanotubes (MWCNTs) is investigated. Nanofiller dispersions were initially prepared via ultrasonication in deionized water (d-H2O) utilising a commercial superplasticizer as surfactant. Electrically percolated nanocomposites were fabricated via shear mixing and subsequent casting into moulds. Storing the prepared samples under different humid conditions enabled explanation of the role of water content as well as cement age on Joule heating performance. All prepared specimens were investigated at ages of 3 d, 7 d and 28 d by applying two different DC bias voltages. Infrared-thermography (IR-T) images were recorded after 1 min, 5 min and 10 min in order to visualize the differences in the Joule heating effect as a function of time, keeping contact with the DC bias voltage. The observed results showed a significant dependency of the Joule heating effect on water content as well as on filler concentration. Moreover, increasing cement age provided more effective electrical heating. This work elucidates the complexity of the electrical heating phenomena occurring in cementitious/MWCNT nanocomposites via the well-known Joule heating effect because it contributes to the understanding of the underlying mechanism. The main parameters used and the corresponding results are envisaged to be applicable for large-scale, heatable concrete structures in future respecting buildings temperature, aerial control, de-icing, thermal management, and better energy efficiency, etc.

Analysis of Viscoelastic Behavior of Polypropylene/Carbon Nanotube Nanocomposites by Instrumented Indentation.

In this work, the viscoelastic behavior of polypropylene (PP)/multi-walled carbon nanotube (MWCNT) nanocomposites was investigated by indentation testing and phenomenological modeling. Firstly, indentation tests including two-cycle indentation were carried out on PP/MWCNT nanocomposite with three MWCNT loadings (1, 3 and 5 wt %). Next, the Maxwell–Voigt–Kelvin model coupled with two-cycle indentation tests was used to predict the shear creep compliance function and the equivalent indentation modulus. The indentation hardness and elastic modulus of the PP/MWCNT nanocomposites extracted based on the Oliver and Pharr method were compared with the equivalent indentation modulus predicted based on the Maxwell–Voigt–Kelvin mode. The experimental results indicated that the addition of nanotubes into the polypropylene has a positive effect on the micro-mechanical properties of PP/MWCNT nanocomposites. Indentation hardness and elastic modulus increased significantly with increasing MWCNT loading. The creep resistance at the micro-scale of the PP/MWCNT nanocomposites improved with the addition of MWCNTs, with creep displacement reduced by up to 20% by increasing the carbon nanotube loading from 1 to 5 wt %. The Maxwell–Voigt–Kelvin model with three and five Voigt–Kelvin units accurately predicted the shear creep function and its change with increasing MWCNT loading. However, the equivalent indentation modulus was found to be sensitive to the number of Voigt–Kelvin units: the more Voigt–Kelvin units, the better the model predicts the equivalent indentation modulus.

Thermal Behavior and Flammability of Epoxy Composites Based on Multi-Walled Carbon Nanotubes and Expanded Graphite: A Comparative Study

Reduction of flammability and improvement of thermal stability of polymers during heating can be achieved by the introduction of fillers. Epoxy composites filled with different loadings of multi-walled carbon nanotubes (MWCNTs) and expanded graphite (EG) were prepared. The thermal oxidation stability of the prepared samples was investigated under heating in an oxidizing atmosphere using thermal analysis. The hardness was measured using the Shore D hardness test. The flammability of the prepared composites was evaluated by the ignition temperature and time-to-ignition. It was found that there was a rise in temperature corresponding to a 5% weight loss during heating for both epoxy/MWCNT and epoxy/EG composites compared to neat epoxy resin. The Shore D hardness of epoxy/MWCNT composites increased with content growth up to 0.1 wt.% and decreased with further concentration rise. The addition of MWCNTs and EG leads to an increase in the ignition temperature. It has been shown that MWCNTs improve the thermal behavior of epoxy resin in a low temperature region (below ~300 °C) whereas EG shows almost the same thermal behavior above 300 °C. The improvement of thermal properties can be achieved using MWCNTs and EG as fillers.

Dynamic Viscosity of Purified Multi-Walled Carbon Nanotubes Water and Water-Propylene Glycol-Based Nanofluids

We report in this study the experimental investigation of the dynamic viscosity of purified multi-walled carbon nanotubes (MWCNT) water and water-propylene glycol-based nanofluids in the temperature range 10–80 °C. Four weight concentrations of MWCNTs are considered, between 0.005 and 0.1 wt.%. Triton X-100, a common nonionic surfactant, is used to disperse the nanotubes and stabilize the nanofluids as evidenced by optical characterization. Purified and non-damaged MWCNTs are used for nanofluid preparation by the two-step method. MWCNT characterization is deeply investigated from a set of complementary techniques such as thermogravimetric analysis, transmission electron microscopy, and Raman spectroscopy. The studied nanofluids behave as Newtonian fluids for low nanotube content while a shear-thinning behavior is noticed for higher concentration. Finally, the viscosity enhancement of nanofluids with MWCNT loading is compared to the modified Maron–Pierce model considering the presence of aggregates and their size obtained from optical observations.

Electrical properties of solution cast films of polystyrene/polyaniline-multiwalled carbon nanotube nanocomposites

Self-standing films of camphor sulphonic acid doped polyaniline (PANI) and polystyrene (PS) with different multiwalled carbon nanotube (MWNT) loadings are successfully prepared by solution casting method. The presence of MWNT is characterized by X-ray diffraction and Raman spectroscopy. Raman modes confirm the presence of PANI and MWNTs. Transmission electron microscope images confirm the presence and dispersion of MWNTs in the film. The temperature-dependent electrical conductivity of the films is measured in the temperature range 10–300 K for different loadings of MWNTs. The nanocomposite films show a very low percolation threshold with nearly three order enhancement of electrical conductivity with MWNT loadings. The electrical conductivity variation with temperature follows the fluctuation induced tunnelling model. The films show two order increases in mobility with 1.45 wt% MWNT loadings. Hall Effect study confirms that the PANI-PS blend films switched from p-type to n-type behaviour with the addition of MWNT.

21.4% efficiency of perovskite solar cells using BMImI additive in the lead iodide precursor based on carbon nanotubes/TiO2 electron transfer layer

Carbon nanotubes (CNT) are unique one-dimensional structures that have been widely used for enhancing optoelectronic devices because of their fascinating properties. In this work, the impact of multi-walled CNT (MWCNT) on photovoltaic (PV) performance of mesoporous-titanium dioxide (m-TiO2) based perovskite solar cells (PSCs) is investigated. First, the incorporation of 1-Butyl-3-methylimidazolium iodide (BMImI) within the lead iodide (PbI2) precursor caused suppressing PbI2 residue from perovskite (PVK) film as proved via X-ray diffractometer (XRD). The loading of MWCNT in the m-TiO2 electron transfer layer (ETL) led to the formation of PVK with bigger grains and higher crystallinity with improved light absorbance. The power-conversion efficiency (PCE) of the PSC was remarkably boosted to 21.4% for the device containing 0.2% MWCNT versus 12.5% for the control device without any additives. MWCNT loaded in TiO2 provides a fast charge transfer within the ETL, resulting in an improving in the short circuit current (Jsc) value. This can be assigned to an enhanced band level alignment of the m-TiO2 after the incorporation of MWCNT. Moreover, it is found that the loading of MWCNT into m-TiO2 ETL decreases the hysteresis phenomenon and enhances the heat and humidity stability of the PSCs.

Electromagnetic Shielding Effectiveness and Conductivity of PTFE/Ag/MWCNT Conductive Fabrics Using the Screen Printing Method

The management of the electromagnetic interference (EMI) of thin, light, and inexpensive materials is important for consumer electronics and human health. This paper describes the development of conductive films that contain a silver (Ag) flake powder and multiwall carbon nanotube (MWCNT) hybrid grid on a polytetrafluoroethylene (PTFE) film for applications that require electromagnetic shielding (EMS) and a conductive film. The Ag and MWCNT hybrid grid was constructed with a wire diameter and spacing of 0.5 mm. The results indicated that the proposed conductive films with 0.4 wt% MWCNTs had higher electromagnetic shielding effectiveness (EMSE) and electrical conductivity than those with other MWCNT loading amounts. The results also showed that the film with 0.4 wt% MWCNT loading had a high 62.4 dB EMSE in the 1800 MHz frequency and 1.81 × 104 S/cm electrical conductivity. This combination improved stretchability, with 10% elongation at a 29% resistivity change rate. Conductive films with Ag/MWCNT electronic printing or lamination technologies could be used for EMI shielding and electrically conductive applications.

Synthesis and cyclic voltammetry of CrFe2O4/(MWCNTs)x nanohybrids

The chemical co-precipitation route was opted for the synthesis of chromium ferrite (CrFe2O4) nanoparticles and the pristine multi-walled carbon nanotubes (MWCNTs) were used for the preparation of desired CrFe2O4/(MWCNTs)x; x = 0, 5, 10, 15, and 20 wt% nanohybrids using the ultra-sonication method. Toluene was used for the first time as dispersive medium for the preparation of these nanohybrids. The crystalline structure, morphology, vibrational modes, and electrochemical performance of these nanohybrids were characterized by using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscope (SEM), energy dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, electrochemical impedance spectroscopy (EIS), and cyclic voltammetry. The structural properties of pristine MWCNTs, CrFe2O4 nanoparticles, and CrFe2O4/(MWCNTs)x nanohybrids are evaluated by XRD and Raman spectroscopy. The SEM images presented the attachment of CrFe2O4 nanoparticles on the surface of MWCNTs. The specific capacitance was decreased with increasing number of cycles, while it was observed to be increased with increasing MWCNTs content. From EIS, the decrease in charge transfer resistance was observed with the increased loadings of MWCNTs, which showed the enhanced electrochemical behavior of these nanohybrids. Therefore, the significant improvement in electrochemical properties showed that these nanohybrids can be promising candidates for energy storage devices like lithium-ion (Li-ion) batteries.

Remarkable Thermal Conductivity Enhancement in Carbon-Based Ionanofluids: Effect of Nanoparticle Morphology.

Transfer of the excellent intrinsic properties of individual carbon nanoparticles into real-life applications of the corresponding heat transfer fluids remains challenging. This process requires identification and quantification of the nanoparticle–liquid interface. Here, for the first time, we have determined geometry and properties of this interface by applying transmission electron cryomicroscopy (cryo-TEM). We have systematically investigated how the particle morphology of carbon-based nanomaterials affected the thermal conductivity, specific isobaric heat capacity, thermal diffusivity, density, and viscosity of ionanofluids and/or bucky gels, using a wide range of fillers, especially single-walled carbon nanotubes (SWCNTs) and multiwalled carbon nanotubes (MWCNTs), both with extreme values of aspect ratio (length to diameter ratio) from 150 to 11 000. Accordingly, hybrid systems composed of various carbon nanomaterials and ionic liquid, namely 1-ethyl-3-methylimidazolium thiocyanate [EMIM][SCN], were prepared and characterized. Most of the analyzed nanodispersions exhibited long-term stability even without any surfactant. Our study revealed that the thermal conductivity could be remarkably improved to the maximum values of 43.9% and 67.8% for ionanofluid and bucky gel (at 1 wt % loadings of MWCNTs and SWCNTs), respectively, compared to the pristine ionic liquid. As a result, the model proposed by Murshed and co-workers has been improved for realistic description of the concentration-dependent thermal conductivity of such hybrid systems. The obtained results undoubtedly indicate the potential of ionanofluids and bucky gels for energy management.