Small Amount Of Carbon Nanotubes Research Articles

In situ foam 3D printed microcellular multifunctional nanocomposites of thermoplastic polyurethane and carbon nanotube

Electrically conductive and mechanically robust thermoplastic polyurethane (TPU)/carbon nanotube (CNT) foams were achieved using a novel in situ foam 3D printing (F-3DP) process. Thermally expandable microspheres (TEMs), as blowing agent, were incorporated into the TPU/CNT filaments and fed to the F-3DP process. Foams with uniform morphologies and repeatable properties were achieved in a wide density range by solely regulating the nozzle temperature and its correlated flow rate. Overall, the degree of foaming increased substantially with an increase in the temperature, providing a density range of 0.96 to 0.17 g/cm3. It was interestingly found that a small amount of CNT (1 wt%) increased the expansion ratio. A further increase of CNT (to 3 and 5 wt%), however, caused a reduction in the expansion ratio. These opposing trends were attributed to the competing effects of CNT on the melt's thermal conductivity and viscosity. Both CNT content and nozzle temperature exhibited significant impacts on the tensile properties and electrical conductivity. This resulted in foams with diverse Young's modulus and strain at break in the range of 3.9–29.5 MPa and 260 to 52 %, respectively. More importantly, the electrical conductivity increased up to several orders of magnitude, as the foam expansion was increased due to temperature rise. This interesting finding was thoroughly discussed in terms of the enhanced inter-bead adhesion, vanishing inter-bead gaps, and realignment of CNTs around the growing TEMs. The results demonstrate a great potential of F-3DP to produce functional foams with controllable density and performance in a wide range.

CARBON NANOSTRUCTURES OBTAINING FROM POLYMER MATERIALS

As part of the expansion of raw material base used in the development of technological and productive methods for the synthesis of carbon nanostructures (CNS) and solving the problem of environmentally friendly and economical polymer recycling, the results of investigation of microwave (MW) catalytic pyrolysis of macromolecular compounds from the range of polystyrene, polypropylene, polyethylene terephthalate, polyvinyl alcohol are presented. The information about existing approaches to solving these problems is briefly considered, and the prospects for MW processing of polymers are shown. The process was carried out by microwave treatment of a mixture of polymer raw materials acting as a carbon donor and substances-precursors of metal catalysts – cobalt and nickel compounds, their mixtures, as well as metal iron and nickel. Graphite and carbon fiber were used as temperature regulator. Experiments have demonstrated that effective conversion of the studied compounds occurs only in the presence of MW energy absorbers-converters, regardless of the nature of metal catalyst precursor. According to electron microscopy data, the resulting materials are a mixture of carbon nanostructures of disordered morphology with the predominant content of carbon nanotubes (CNTs) in the reaction products for experiments with polystyrene, polypropylene and polyethylene terephthalate. The use of polypropylene and polyvinyl alcohol leads to the production of carbon nanostructures containing only a small amount of CNTs. X-ray phase analysis data confirm the formation of multi-walled carbon nanotubes as the main structural component of the obtained carbon nanomaterials. It has been suggested that transformation pathways of the investigated hydrocarbons are similar, despite the difference in pyrolysis temperatures, which may be related to the simultaneous processes of polymer cracking, carbonization of decomposition products and CNS synthesis due to the rapid growth of reaction mass temperature during microwave treatment. The efficiency of different precursors of catalytic systems based on transition metals in the processes examined is substantiated. It has been shown that the high carbon content in feedstock promotes the formation of carbon nanostructures, but is not decisive for carbon nanotubes obtaining. For citation: Zaritovskii A.N., Kotenko E.N., Grishchuk S.V. Carbon nanostructures obtaining from polymer materials. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 5. P. 99-106. DOI: 10.6060/ivkkt.20246705.6957.

NO2 gas response and recovery properties of ambipolar CNT-FETs with various CNT/CNT junctions

Gas sensors based on ambipolar carbon nanotube (CNT) field-effect transistors with various amounts of CNTs were fabricated by dielectrophoretic assembly. The nitrogen dioxide (NO2) gas response and recovery properties of the transistors were measured to investigate the effect of CNT amount on gas response. For the device with a small amount of CNTs, responses from the CNT bulk and CNT/electrode contacts were observed. For devices with a large amount of CNTs, in which a network-like structure of CNTs was observed near the electrodes, an increased current in both electron and hole conduction regions was observed compared with that for the device with a small amount of CNTs. The increased current in the electron conduction region rapidly decreased during recovery. This response is consistent with that of CNT/CNT X-type contacts, which have a high resistance before NO2 adsorption. Equivalent circuits of CNT channels with CNT/CNT contacts were developed, allowing the transistor behavior to be qualitatively discussed. Evaluation of time constants revealed that CNT/electrode contacts and CNT/CNT X-type contacts exhibited high NO2 adsorption and desorption rates, respectively.

Styrene–butadiene rubber‐based nanocomposites toughened by carbon nanotubes for wide and linear electromechanical sensing applications

AbstractThe contribution from specific interactions between rubber and filler sometimes plays a crucial role in the mechanical reinforcement and electromechanical sensitivities of rubber composites. This research explores the physical, mechanical, and electromechanical properties of styrene‐butadiene rubber (SBR) composites reinforced with carbon nanotubes (CNTs). Mechanical, thermodynamic, and scanning electron microscopy studies reveal that CNTs primarily enhance the mechanical properties through physical interactions with the rubber. Notably, π‐stacking interactions between the aromatic π‐electrons in SBR and the delocalized π‐electrons in CNTs contribute to significant improvements in mechanical strength. For instance, adding 4 phr (per hundred grams of rubber) of CNTs results in an impressive 871% increase in fracture toughness compared to unfilled rubber. These composites also exhibit remarkable stress and strain improvements even with small amounts of CNTs, making them suitable for robust strain sensing applications. Specifically, the composite containing 3 phr of CNTs demonstrates superior strain sensitivity (2.87 < GF < 48.62), a wide detection range (0% < Δε < 187%), and excellent linearity (0.927 < R2 < 0.995). Lower CNT content enhances sensitivities but reduces overall linearity, while higher CNT content improves linearity but decreases sensitivity. Moreover, these composites perform exceptionally well under compressive forces, even at a 0.5 N applied force. Given their excellent response to mechanical forces and strain, these composites hold promise for applications like electronic skin, strain sensors, and energy‐harvesting devices.Highlights Carbon nanotubes (CNTs) were used as reinforcing fillers in SBR composites. CNTs significantly improve physical, mechanical, and electrical properties. Primarily, π‐stacking may be involved in enhancing these properties. The composites exhibit strong strain and force‐sensing capabilities. These composites could be valuable for wearable electronics in the future.

Comparative analysis of the effect of single-walled and multi-walled carbon nanotube additives on the properties of hydrocarbon-based drilling fluids

The article presents the results of a comprehensive comparative analysis of the effect of single-walled and multi-walled carbon nanotubes on the main performance characteristics of mineral oil-based drilling emulsions. Such a systematic comparative study of hydrocarbon-based solutions has been performed for the first time. Weight concentration of single-walled nanotubes varied from 0.01 % to 0.1 %, and of multi-walled ones, from 0.1 % to 0.5 %. The formulation and preparation technique of stable drilling emulsions with single-walled and multi-walled nanotube additives were practiced. The effect of nanotube additives on rheology, filtration, and antifriction properties, as well as colloidal stability, and clay inhibition kinetics of hydrocarbon-based drilling fluids has been studied. As a result of the study, it has been successfully demonstrated that adding even very small amount of carbon nanotubes allows significantly controlling the main performance characteristics of drilling fluids. Thus, adding just 0.025 wt% of single-walled nanotubes increases effective viscosity of the drilling fluid by about 45 %, the yield stress – by 1.7 times, colloidal stability – by 36 %, reducing at the same time filtration loss by 55 %, and friction factor – by 20 %. At the same time, it has been shown that using single-walled nanotubes is several times more efficient compared to adding multi-walled nanotubes, and hundreds of times more efficient compared to using spherical metal oxide nanoparticles.

Material Extrusion 3D Printing of PEEK-Based Composites.

High-performance thermoplastics like polyetheretherketone (PEEK), with their outstanding thermal stability, mechanical properties and chemical stability, have great potential for various structural applications. Combining with additive manufacturing methods extends further PEEK usage, e.g., as a mold insert material in polymer melt processing like injection molding. Mold inserts must possess a certain mechanical stability, a low surface roughness as well as a good thermal conductivity for the temperature control during the molding process. With this in mind, the commercially available high-performance thermoplastic PEEK was doped with small amounts of carbon nanotubes (CNT, 6 wt%) and copper particles (10 wt%) targeting enhanced thermomechanical properties and a higher thermal conductivity. The composites were realized by a commercial combined compounder and filament maker for the usage in a material extrusion (MEX)-based 3D-printer following the fused filament fabrication (FFF) principle. Commercial filaments made from PEEK and carbon fiber reinforced PEEK were used as reference systems. The impact of the filler and the MEX printing conditions like printing temperature, printing speed and infill orientation on the PEEK properties were characterized comprehensively by tensile testing, fracture imaging and surface roughness measurements. In addition, the thermal conductivity was determined by the laser-flash method in combination with differential scanning calorimetry and Archimedes density measurement. The addition of fillers did not alter the measured tensile strength in comparison to pure PEEK significantly. The fracture images showed a good printing quality without the MEX-typical voids between and within the deposited layers. Higher printing temperatures caused a reduction of the surface roughness and, in some cases, an enhanced ductile behavior. The thermal conductivity could be increased by the addition of the CNTs. Following the given results, the most critical process step is the compounding procedure, because for a reliable process-parameter-property relationship, a homogeneous particle distribution in the polymer matrix yielding a reliable filament quality is essential.

High‐Yield Exfoliation of Large MXene with Flake Sizes over 10 µm Using Edge‐Anchored Carbon Nanotubes

AbstractThe exceptional properties of 2D transition metal carbides and nitrides (MXene) have led to numerous promising applications. However, the performance of MXene is often dependent on the size of the flakes, and obtaining large‐sized, high‐quality MXene flakes remains challenging. Herein, a carbon nanotube (CNT)‐assisted exfoliation strategy is introduced, which significantly improves the yield of large‐flake MXene while entirely transforming the centrifugation residues into small‐flake MXene, resulting in waste‐free synthesis of MXene. The average size of the obtained MXene flakes can reach over 10 and 0.7 µm for the two populations, respectively. Additionally, the capacitive performance of MXene can be greatly enhanced with a small amount of CNTs. As a proof of concept, a planar interdigital micro‐supercapacitor with heterogeneous layers assembled by large‐ and small‐flake MXene simultaneously exhibits outstanding synergistic enhancement in volumetric capacitance (1072 F cm⁻3) and energy density (53.5 mWh cm⁻3). This CNT‐assisted method provides explicit directions for achieving the ideal utilization of MXene, improving the yield of large flakes while making judicious use of waste, to meet specific application needs.

Free Vibration Responses of Functionally Graded CNT-Reinforced Composite Conical Shell Panels.

Functionally graded CNT (carbon nanotube)-reinforced composites (FG-CNTRCs) are intensively studied because the mechanical behaviors of conventional composites can be dramatically improved. Only a small amount of CNTs are appropriately distributed through the thickness. However, the studies on conical shell panels have been poorly reported when compared with beams, plates and cylindrical shells, even though more parameters are associated with the mechanical behaviors of conical shell panels. In this context, this study intends to profoundly investigate the free vibration of FG-CNTRC conical shell panels by developing an effective and reliable 2-D (two-dimensional) numerical method. The displacement field is expressed using the first-order shear deformation shell theory, and it is approximated by the 2-D planar natural element method (NEM). The conical shell surface is transformed into the 2-D planar NEM grid, and the approach for MITC3+shell element is employed to suppress the shear locking. The developed numerical method is validated through the benchmark experiments, and the free vibration responses of FG-CNTRC conical shell panels are investigated with respect to all the associated parameters. It is found from the numerical results that the free vibration of FG-CNTRC conical shell panels is significantly influenced by the volume fraction and distribution pattern of CNTs, the geometry parameters of the conical shell, and the boundary condition.

Mixing carbon nanotubes with asphalt binder through a foaming process toward high-performance warm mix asphalt (WMA)

ABSTRACT This paper investigates mixing carbon nanotubes (CNTs) with asphalt binder through a foaming process to produce high-performance warm mix asphalt (WMA). Two different solvents of ethanol and a water-based surfactant are used to disperse the multi-walled CNTs. Initial morphological assessment of the two CNT solutions showed that a more homogenous dispersion of the CNTs was achieved using the water surfactant solution. The foaming performance, thermal, and rheological properties of the foamed asphalt mixed with different percentages of CNTs are further investigated. The test results showed that a very small amount of CNTs (0.06% ∼ 0.1% in weight of the binder) can effectively enhance the foaming performance for bubble stability without tangibly increasing the rheological properties of the foamed asphalt. The specific heat capacity of the foamed samples was smaller than the neat binder, whereas the glass transition temperature of the foamed samples shifted to a lower temperature as compared to that of the neat binder. The thermal conductivity of the 6% CNTs sample (0.24% wt. in asphalt binder) was improved by two-fold compared with the foamed unmodified asphalt, which indicates the potential of using CNTs in the binder for enhancement of thermal properties in asphalt pavements.

Microstructure and Electrical Conductivity of Cement Paste Reinforced with Different Types of Carbon Nanotubes.

Over the last few years, the addition of small amounts of carbon nanotubes (CNTs) to construction materials has become of great interest, since it enhances some of the mechanical, electrical and thermal properties of the cement. In this sense, single-walled and multi-walled carbon nanotubes (SWCNTs and MWCNTs, respectively) can be incorporated into cement to achieve the above-mentioned improved features. Thus, the current study presents the results of the addition of SWCNTs and MWCNTs on the microstructure and the physical properties of the cement paste. Density was measured through He pycnometry and the mass change was studied by thermogravimetric analysis (TGA). The microstructure and the phases were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Finally, the electrical conductivity for different CNT concentrations was measured, and an exponential increase of the conductivity with concentration was observed. This last result opens the possibility for these materials to be used in a high variety of fields, such as space intelligent systems with novel electrical and electronic applications.

Study on Thermal-Oxidative Aging Properties of Ethylene-Propylene-Diene Monomer Composites Filled with Silica and Carbon Nanotubes.

In this work, a small amount of carbon nanotubes (CNTs) was used to partially replace the silica in ethylene-propylene-diene monomer (EPDM) to prepare EPDM composites via mechanical blending. The mechanical properties, thermal-oxidative aging properties and thermal stability of the composites were systematically investigated. The results showed that with the increase of CNTs content, the Shore A hardness and stress at 100% strain of the composites increased, while the elongation at break decreased. With the aging time increasing, the aging coefficient and elongation at break of composites decreased while hardness increased due to the raise of crosslinking density. In addition, evidences were found to demonstrate the improved aging resistance by adding CNTs in the EPDM composites, including the less change in Shore A hardness, the smaller change ratio of elongation at break and the lower aging coefficient. When the content of CNTs reached 10 phr, the aging coefficient of the EPDM composite aged for 168 h was nearly twice that of the composite without CNTs, and the thermal stability of the EPDM composite with CNTs was improved as demonstrated by thermal analysis.

Enhancing the solar absorption capacity of expanded graphite-paraffin wax composite phase change materials by introducing carbon nanotubes additives

The potential solar thermal utilization of solar energy based on phase change materials (PCMs) is limited by their low thermal conductivity and weak solar absorption capacity. Among various additives used to enhance the thermal conductivity of PCMs, expanded graphite (EG) has been proved to be a low-cost but effective choice. This work aims to further enhance the solar absorption capacity of EG-paraffin wax composite PCMs by adding small amounts of carbon nanotubes (CNTs) as the light absorbent. The prepared composite PCMs with 5 wt.% EG and 2 wt.% CNTs show superior thermal conductivity (2.05 W/m⋅K), high solar absorption capacity (94.2%) while maintaining the high latent heat (159 kJ/kg). Moreover, these superior thermal and optical properties can be maintained after 1000 melting-freezing cycles. Our results provide a high-performance composite PCM that may be used in solar-thermal conversion applications.

Nanostructured thermoelectric composites for efficient energy harvesting in infrastructure construction applications

Although numerous investigations have been performed on thermoelectric (TE) fields, no notable studies have been conducted on TE structural materials. In this study, the electrical characteristics of cement were induced by incorporating carbon nanotubes (CNTs). Although cement can serve as a TE material owing to its low thermal conductivity, its extremely low electrical conductivity hinders its feasible application. The introduction of cement composites containing small amounts of CNTs is suggested as a solution. CNTs can improve the TE performance of cement-based composites because they exhibit superior electrical conductivity and are suitable as additives for carbon isotope-based composites. Such composite materials can be used as TE structural materials for energy harvesting in buildings. Therefore, to analyze the feasibility of the cement/CNT composites, the electrical conductivity, Seebeck coefficient, and thermal conductivity were measured by varying the CNT concentration using 4-probe measurement and ASTM D5470 methods. The electrical conductivity was improved by approximately 104 times as the CNT concentration increased from 0.0625 to 0.25 wt% while maintaining a relatively stable Seebeck coefficient, whereas the thermal conductivity remained in the insulating material region. The results showed that the critical CNT concentration associated with the percolation threshold was relatively low (∼0.1 wt%). This study may contribute to the development of self-powered sensor systems in buildings based on structural temperature differences.

Preparation and properties of reduced graphene oxide-carbon nanotubes aerogel/cotton flexible composite fabric with electromagnetic shielding function

The electromagnetic pollution has become a serious problem with the rapid development of electromagnetic industry. The present work prepared an electromagnetic interference (EMI) functional composite fabric. Reduced graphene oxide (rGO)-carbon nanotubes (CNTs) aerogel with three-dimensional (3-D) architecture were coated to the cotton fabric with the assistance of waterborne polyurethane (WPU). The structure of graphene aerogel was affected by the amount of CNTs. Small amount of CNTs is helpful to minish the pore size of aerogel and thus improve the EMI value. However, it has been shown that excess CNTs will destroy the 3-D architecture of graphene aerogel. Result shows that the EMI shielding effectiveness exceeded 35 dB when the weight ratio of rGO and CNTs was 7:3, and EMI value of the corresponding composite fabric samples reached 34 dB. Consequently, excellent EMI results were obtained by the unique 3-D rGO-CNTs aerogel in the case of a small nano-carbon material amount. The present work will be expected to make contributions to the practical application of rGO-CNTs aerogel.

High-Energy and High-Power Lithium-Ion Cells Enabled by Electrochemically Derived Carbon Nanotubes

A common approach to increasing packaged cell level energy density is to increase the mass fraction of active materials and decrease that of inactive materials such as conductive and polymeric additives in the electrodes, current collectors, and separators. To increase active materials, thick electrodes have been proposed and studied in the literature as a method for increasing the mass ratio of active materials to current collector foils. However, there are many challenges associated with increasing the thickness of cathodes. Notably, most cathode materials are inherently insulating and therefore require conductive additives to maintain electrical conductivity to facilitate charge transfer from the electrolyte-cathode interface back to the current collector. The length of this pathway increases with thicker cathodes and requires reconsideration of the conductive materials used to form this network. One dimensional (1D) CNTs have been demonstrated recently as superior conductive additives due to their line-to-line contact method and superior active-material surface coverage, which allows them to create a 3D conductive network at a low mass fraction of the electrode. In extreme conditions of battery operations, performance is limited by the inactive materials, rather than the active energy-storing materials in a cell. This holds true for thick coatings, as well as high rates of charge and discharge. Switching from traditional carbon blacks (CB) such as acetylene or furnace black to CNT additives allows for simultaneous improvements in thick electrodes which increase packaged cell-level energy density, as well as increased performance in extreme fast charging environments. SkyNano is commercializing a highly tunable molten-salt electrolysis process to make low-cost carbon nanotubes (CNTs) using electrochemical capture and conversion of atmospheric CO2 utilizing several highly scalable processes. This technology can be harnessed to produce carbon additives with precisely tuned properties to enable ultra-thick cathode coatings with high areal loadings that exhibit superior rate performance.Enabling the widespread commercialization of high-energy, advanced batteries with low cost for transportation electrification, renewable energy storage, and portable electronics will result in substantially reduced GHG emissions, increased mobility, and ubiquitous opportunity for personal connectivity. In addition SkyNano produces its CNTs through the consumption of ambient or flowing CO2 streams, which will contribute to slowing the increase in CO2 emissions and ultimately reducing the current atmospheric content of 420 ppm. CNTs provide many commercial advantages in advanced batteries: 1) using thicker, higher-energy electrodes by minimizing electronic conductivity losses; 2) higher power density (i.e., higher capacity at high discharge rates); 3) integrating multilayer electrode architectures; 4) higher loadings of Si at the anode by forming a more mechanically stable composite with graphite during electrochemical cycling; and 5) faster charging rates approaching 6C. In addition, SkyNano CNTs will be less expensive than current chemical vapor deposited CNTs and optimized for a both multilayer (thick) electrode and all-solid-state battery approaches. The proposed electrode designs rely on the use of conventional electrolytes, widely available active materials, and conventional electrode manufacturing approaches and require no CapEx to integrate into current manufacturing lines.Electrochemical performance data (rate capability, AC impedance, capacity retention during cycling, etc.) is discussed from both molten-salt electrolysis reactor and LIB operation points of view. Single unit-cell (“single-layer”) pouch cells were constructed (five replicates for each cell configuration) using three distinct cathode coatings, which had an average rated capacity of 134 ± 10 mAh. The cathode areal capacities were 3.1 mAh/cm2, and the anodes were 3.4 mAh/cm2, giving an N:P ratio of 1.1. It was found that both formulations F7 and F8 outperformed the Control 2 at all discharge rates above 0.5C. The scaled F7 pouch cells performed better than their half coin cell counterparts and significantly outperformed Control 2 (20.5%, 62.7%, and 46.7% capacity improvements at 2C, 3C, and 5C discharge rates, respectively), showing that only a small amount of CNTs is required to realize large improvements in cathode rate capability.

Flexible Resistance-Type Strain Sensors toward Monitoring Finger Movements

AbstractFlexible strain sensors with superior flexibility and high sensitivity are critical to artificial intelligence, and it is favorable to develop highly sensitive strain sensors by simple and cost-effective methods. We have prepared carbon-nanotubes-enhanced thermal polyurethane nanocomposites with good mechanical and electrical properties for the fabrication of highly sensitive strain sensors. The nanomaterials were prepared through a simple but effective solvent-evaporation method, and cheap polyurethane was used as the main raw material. Only a small quantity of carbon nanotubes (mass content 5%) was doped into a polyurethane matrix with aim of enhancing the mechanical and electrical properties of the nanocomposite. The resulting flexible nanocomposite films show a highly sensitive resistance response under an external strain stimulus. Strain sensors based on these flexible composite films deliver excellent sensitivity and conformality under mechanical conditions, and can detect finger movements precisely at various bending angles.

Enhancing in the hydrogen storage by SWCNT/HKUST-1 composites: Effect of SWCNT amount

Functionalized single-walled carbon nanotubes into HKUST-1 ([Cu3-(btc)2]; btc= 1,3,5-benzenetricarboxylate) metal organic framework composite materials were synthesized by solvothermal method and characterized using different techniques such as XRD, BET,TG, SEM, and in situ Raman spectroscopy. It is important to mention that for the first time the thermal stability of the materials was determined by in situ Raman spectroscopy. Our results demonstrated that the incorporation of functionalized SWCNTs into HKUST-1 a slight increase in the thermal stability of MOF was observed. Too, a significant enhancement in the hydrogen adsorption capacity from 23.5% at 77 K and 1 bar of in the composite materials was observed. After of 5 cycles, hydrogen uptake is still above 2.98 wt% for 0.5SW/HKUST-1 sample. The hydrogen adsorption isotherms in the composite materials were completely reversible, reflecting only the physisorption of hydrogen molecule in the structure surface. Our results showed that the composite material with small amount of carbon nanotubes can be a promising candidate for the hydrogen storage.

Three-Dimensional Interpenetrating Network Phase-Change Composites with High Photothermal Conversion and Rapid Heat Storage and Release

Solar thermal energy conversion and storage have gained more attention for solving energy crisis and environment issues. Phase-change materials with excellent thermal conductivity, high photothermal conversion efficiency, rapid heat storage and release, and good stability are required for solar thermal applications. In this study, three-dimensional (3D) interpenetrating network phase-change composites are fabricated by taking graphene-oxide (GO) aerogel (GA) containing a small amount of carbon nanotubes (CNTs) and carbon spheres (CSs) as support materials and vacuum impregnation melting polyethylene glycol (PEG) as the phase-change material. The 3D structure and abundant functional groups greatly improve the stability of phase-change composites. The addition of CNTs and CSs greatly increases the thermal conductivity and photothermal conversion capability of PCMs. Compared with pure PEG, thermal conductivity is increased by 181.58%, and photothermal conversion efficiency reaches 89.3%. Simulated results also confirm that GA-based phase change composites exhibit better thermal conductivity. Less thermal conductivity fillers and more phase-change material (96.4%) exhibit excellent thermal conductivity, high photothermal conversion efficiency, and a greater energy-storage density. The 3D phase-change composites are also applied for thermoelectric generation and show a stable output voltage of 35 mV for 300 s after removing the light source. The 3D interpenetrating network form-stable phase change composites based on black GA shows broad prospects in solar thermal energy applications.

Research on the dispersion of carbon nanotubes and their application in solution-processed polymeric matrix composites: A review

This review highlights and categorizes the approaches for preparation of CNTs dispersion and polymer/CNTs composites via solution-based strategies. Carbon nanotubes (CNTs) demonstrate unique physical and chemical properties, which allow several exciting potential applications in various fields including nanocomposites. Presently, the commercialized application of CNTs is still quite limited due to the formation of CNTs bundles, which significantly degrade the properties. Therefore, well dispersion of CNTs in nanocomposites is quite important, especially for CNTs/polymer composites, as a small amount of CNTs can improve the composite properties dramatically. This article will review the research on the dispersion of CNTs (including covalent and non-covalent functionalization) and the fabrication of CNTs/polymer composites through solution-based strategies by using the CNT dispersions. Moreover, the factors influencing the properties of CNTs/polymer composites will be discussed as well as the future outlook.

One-pot microwave-assisted combustion synthesis of Ni-Al2O3 nanocatalysts for hydrogen production via dry reforming of methane

Ni-based catalysts supported on Al2O3 were obtained via a simple, low cost and fast one-pot microwave-assisted combustion synthesis. The effect of fuel content (urea) was investigate. It was observed that the fuel ratio greatly influences the catalysts properties and performance. The results showed that the catalyst synthesized with low fuel content (Ni-LU) presented high specific surface area (265 m2/g), high degree of reduction and smaller nanometric Ni particles (~15 nm). In addition, the catalytic tests carried out at 700 °C for 20 h (GHSV = 72 Lh−1g−1) revealed high activity with low coke deposition. Further investigations were conducted on Ni-LU catalyst in order to better understand its catalytic properties. In-situ X-ray diffraction analysis (using synchrotron radiation) was used to evaluate the Ni particle size during the DRM, and indicated the sintering of Ni particles during the first hour of catalytic reaction. Furthermore, small amount of carbon nanotubes (CNT) with Ni particles encapsulated were observed by TEM analysis.