Multi-walled Carbon Nanotubes Content Research Articles

In vitro physiological and biochemical response of Stevia rebaudiana exposure to carbon nanotubes: Hormetic and photomixotrophic effect

Multi-walled carbon nanotubes (MWCNTs) are cylindrical rolled sheets with different applications in plant biotechnology due to their physicochemical characteristics. This study aimed to evaluate the in vitro physiological and biochemical responses of stevia (Stevia rebaudiana Bertoni) exposure to different concentrations of MWCNTs during multiplication phase in liquid medium using temporary immersion bioreactors. The MWCNTs were characterized regarding their properties by transmission electron microscope. Different treatments (0, 25, 50 and 100 mg/L) of MWCNTs were added to Murashige and Skoog semisolid culture medium at the proliferation phase. At 30 d of in vitro multiplication, the number of shoots, shoot length, number of leaves, dry matter, and antioxidant capacity were evaluated, as well as total chlorophyll, carotenoid, macro and micronutrient, phenolic, Phosphoenolpyruvate (PEP) and Rubisco contents. The results showed that adding MWCNTs at low doses (25 and 50 mg/L MWCNT) led to an increase in the in vitro multiplication rate and a higher number of leaves, while, at the highest dose (100 mg/L MWCNT), there was an inhibition of these variables. MWCNT treatments had an effect on Mg, Fe and C elements. The accumulation of photosynthetic pigments was associated with a higher PEP content in MWCNT treatments. Phenolic content increased at a concentration of 100 mg/L MWCNT, while antioxidant capacity increased at a concentration of 50 mg/L MWCNT. In conclusion, the usage of low MWCNT doses could be used to induce a hormetic response and to promote photosynthesis during in vitro propagation of stevia.

Enhanced physical and mechanical properties of Cu-based nanocomposites with bundled multi-layered carbon nanotubes incorporation: fabrication and comparative analysis via conventional sintering and SPS techniques

The current investigation delves into the influence of incorporating bundled multi-layered graphene sheets, specifically multiwalled carbon nanotubes (MWCNTs), on the microstructure, as well as the physical and mechanical attributes of Cu-based nanocomposites. Various weight percentages (1%, 2%, 3%, and 5%) of MWCNTs were infused into the Cu matrix, and the fabrication of these nanocomposites was conducted through the powder technology route. The fabrication process occurred under an argon atmosphere utilizing both conventional sintering and spark plasma sintering (SPS) techniques. The conventionally sintered Cu-based nanocomposite reinforced with 1% MWCNT exhibited the highest relative density (~86%), hardness (~551.12 MPa), compressive strength (~459 MPa), and outstanding resistance to wear. Conversely, the SPS-fabricated nanocomposite reinforced with the same MWCNT concentration demonstrated the highest relative density (approximately 94.25%) and compressive strength (~688 MPa), while the nanocomposite reinforced with 2% MWCNT displayed the highest hardness (~1178 MPa) and resistance to wear. Notably, a higher concentration of MWCNTs was observed to adversely affect the physical, mechanical, and wear properties of the Cu-MWCNT nanocomposites, irrespective of the chosen sintering technique for their production.

Evaluating the osteogenic properties of polyhydroxybutyrate-zein/multiwalled carbon nanotubes (MWCNTs) electrospun composite scaffold for bone tissue engineering applications

In this investigation, the electrospun nanocomposite scaffolds were developed utilizing poly-3-hydroxybutyrate (PHB), zein, and multiwalled carbon nanotubes (MWCNTs) at varying concentrations of MWCNTs including 0.5 and 1 wt%. Based on the SEM evaluations, the scaffold containing 1 wt% MWCNTs (PZ-1C) exhibited the lowest fiber diameter (384 ± 99 nm) alongside a suitable porosity percentage. The presence of zein and MWCNT in the chemical structure of the scaffold was evaluated by FTIR. Furthermore, TEM images revealed the alignment of MWCNTs with the fibers. Adding 1 % MWCNTs to the PHB-zein scaffold significantly enhanced tensile strength by about 69 % and reduced elongation by about 31 %. Hydrophilicity, surface roughness, crystallinity, and biomineralization were increased by incorporating 1 wt% MWCNTs, while weight loss after in vitro degradation was decreased. The MG-63 cells exhibited enhanced attachment, viability, ALP secretion, calcium deposition, and gene expression (COLI, RUNX2, and OCN) when cultivated on the scaffold containing MWCNTs compared to the scaffolds lacking MWCNTs. Moreover, the study found that MWCNTs significantly reduced platelet adhesion and hemolysis rates below 4 %, indicating their favorable anti-hemolysis properties. Regarding the aforementioned results, the PZ-1C electrospun composite scaffold is a promising scaffold with osteogenic properties for bone tissue engineering applications.

Coupled effect of MWCNTs concentration and induced pore structures on compressive performance and elastic modulus of ultra-high toughness cementitious composites: Experimental and theoretical studies

Due to the superior mechanical properties and electrical conductivity of multi-walled carbon nanotubes (MWCNTs), their integration into cementitious composites can improve compressive strength and self-sensing capabilities. However, balancing high mechanical strength with high conductivity is challenging as high MWCNT dosages can impede strength development. We addressed this by studying the effect of MWCNTs concentration (0–1.1 wt% of cementitious binders) and induced pore structures on the compressive performance and elastic modulus of ultra-high toughness cementitious composites (UHTCC), both experimentally and theoretically. It was found that as the MWCNTs concentration increased, the porosity continued to increase, while the compressive strength fluctuated. Two failure patterns were identified, i.e., quasi-brittle failure and ductile failure. Analysis showed MWCNTs could promote cement binder hydration, increasing matrix density but the strength development was curbed by increased porosity. A balance was achieved at 0.7 wt% MWCNTs. Further investigations using the Eshelby-Mori-Tanaka method discussed how MWCNT concentration, mechanical properties, distribution, porosity, and pore geometry influenced the elastic modulus. Ultimately, we developed a UHTCC-MWCNT composite with 1.1 wt% MWCNTs, which exhibited substantial improvements in compressive strength (44.85 MPa) and conductivity (9.78✕10−3 S/m), showing increases of 22.18 % and 18,132.6 % respectively, compared to the reference group.

Piezoresistive response of MWCNTs/Epoxy mixtures with load-sensing capability

The impact of automobiles on pavement infrastructure is escalating with the expansion of economic activity and road networks. Overloading of freight trucks has emerged as a significant challenge in the realm of heavy vehicle control and management, primarily due to the adverse effects on road surfaces and traffic safety. Self-sensing pavement materials offer the prospect of autonomous monitoring of forces exerted on the pavement without relying on embedded sensors. These materials are engineered by integrating conductive fillers into a polymer matrix to enhance their ability to detect stress or strain while preserving their mechanical properties. Nano-conductive materials possess the potential to revolutionize traditional paving materials in terms of performance and applications. In this study, epoxy resin was selected as the base material due to its favorable physical and chemical characteristics. Multi-walled carbon nanotubes (MWCNTs) were chosen as the conductive filler to formulate a MWCNTs/Epoxy mixture. The dispersion impact of the high-speed shear method on MWCNTs was verified. Subsequently, a hybrid resistance measuring method was developed using conductive copper foil as an electrode. An exploratory investigation was conducted to evaluate the piezoresistive response of MWCNTs/Epoxy mixtures under varying temperatures and loading frequencies. The study revealed that the MWCNTs content near the percolation threshold yields an improved piezoresistive response. The gauge factor of MWCNTs/Epoxy mixtures is up to 150, which is much higher than that of conductive asphalt mixture. Furthermore, the mixture exhibited robust and consistent piezoresistivity across different temperatures (ranging from 0°C to 60°C) and loading frequencies (ranging from 1 Hz to 10 Hz).

Lightweight, compressible, stretchable, ultra-soft, and mechanically stable composites for piezo-electric energy generators and strain sensing

Fabricating rubber composites with desired densities, compressibilities, stretchabilities, mechanical strengths, and self-healing properties is challenging. The present study focused on designing balanced properties, paying special attention to the mechanical stability required for piezo-electric energy generators for soft applications. To achieve these goals, silicone rubber (SR) was used as the host matrix, and multi-walled carbon nanotubes (MWCNTs) were used as the filler. MWCNTs were used as filler to reinforce composites and make them electrically conductive. Adding silicone oil as a thinner reduced compressive modulus and tensile strength but improved stretchability. The compressive modulus of the SR control was 1.86 MPa, and it increased to 3.29 MPa when 2 phr of MWCNTs were added. However, it was decreased sharply to 1.14 MPa when 30 % thinner was added (the T30 sample). Similarly, the stretchability of the SR control was 143 %, and it increased to 159 % and 200 % when 2 or 10 phr (the T10 sample) of MWCNTs were added, respectively. Biomechanical tests showed that a thumb pressure generated the highest output voltages of 4.2 and 4.31 mV at MWCNT contents of 2 and 10 phr, respectively. Finally, strain sensing tests on the 2 phr MWCNT sample show good sensitivity (0.29 < GF < 0.95), a wide detection range (0 % < Δε < 40 %), and excellent linearity (0.998 < R2 < 0.949). Overall, adding thinner up to 10 phr provided the best formulation for mechanical stability and robust performance with optimum energy generation and high stretchability.

Multi-walled carbon nanotubes affect yield, antioxidant response, and rhizosphere microbial community of scented rice under combined cadmium-lead (Cd–Pb) stress

Rice production is threatened by heavy metal stress. The use of multi-walled carbon nanotubes (MWCNTs) in agriculture has been reported in previous studies. We aimed to quantify the impact of MWCNTs on the growth and physiological characteristics of scented rice under cadmium (Cd) and lead (Pb) stresses. Therefore, a pot experiment was conducted, two scented rice varieties Yuxiangyouzhan and Xiangyaxiangzhan were used as materials grown under different concentrations of MWCNTs (0, 100, and 300 mg kg−1 recorded as CK, CNPs100, and CNPs300, respectively). The yield, antioxidant response, and rhizosphere microbial community of scented rice were studied. The results showed that compared with the CK treatment, the CNPs100 and CNPs300 treatments increased leaf dry weight by 17.95%–56.22% at the heading stage, and the H2O2 content in leaves decreased significantly by 36.64%–42.27% at the maturity stage. Under CNPs100 treatment, the grain yield of two scented rice varieties increased significantly by 17.54% and 27.40%, respectively. The MWCNTs regulated the distribution of the Cd and Pb in different plant tissues. The content of Cd (0.11–0.20 mg kg−1) and Pb (0.01–0.04 mg kg−1) in grain were at a safety level (<0.2 mg kg−1). Moreover, MWCNTs increased soil microbial community abundance and altered community composition structure under Cd–Pb stress, which in turn improved agronomic traits and quality of scented rice. Overall, this study suggested that the application of MWCNTs regulates the growth, yield, physiological response, and soil microbial community, the genotypes response effect of scented rice to MWCNTs is needed further studied.

Synergetic effect of multiwalled carbon nanotubes on mechanical and deformation properties of engineered cementitious composites: RSM modelling and optimization

Engineered cementitious composites (ECC) have outstanding energy absorption and ductility, but their primary drawbacks continue to be their poor elastic modulus and severe drying shrinkage. Therefore, the incorporation of multiwalled carbon nanotubes (MWCNTs) to mitigate the stated drawbacks and also the influence of MWCNTs on the mechanical characteristics of ECC has been examined. However, the primary goal of this research investigation is to apply the response surface methodology (RSM) modelling for optimizing multiple objectives, effectively handling variable interactions, and achieving significant improvements. A total of thirteen mixtures were produced through RSM modelling using two input factors including different concentrations of MWCNTs at 0.05 %, 0.065 %, and 0.08 %, as well as varying concentrations of PVA fiber at 1 %, 1.5 %, and 2 %. The central composite design (CCD) technique of RSM modelling was used in the production of these mixtures. The results demonstrated that the incorporation of 0.05 % MWCNTs and 1 to 1.5 % PVA fiber together considerably enhanced all of the characteristics of the ECC. The optimum compressive strength, flexural strength, tensile strength, and modulus of elasticity of the ECC were recorded by 74.28 MPa, 14.14 MPa, 5.51 MPa, and 31.10 GPa at 0.05 % MWCNTs at 28 days correspondingly. Furthermore, the drying shrinkage is getting decreased as the extent of MWCNTs increases in ECC. It has been concluded that the use of 0.05 % of MWCNTs and 1 % to 1.5 % of PVA fiber provided good outcomes for construction purposes.

Macro- and microstructural evolution of cement paste modified with MWCNTs under thermal shock conditions

The study investigates the influence of multi-walled carbon nanotubes (MWCNTs) on the macro- and microstructure of cement paste (CP) subjected to thermal shock conditions. CPs with 0–0.3 % MWCNTs content, exposed to a sudden temperature load in a range 50–600 °C, were analyzed in terms of mechanical properties, chemical and phase composition, air pore structure, and microstructure of cement hydration products (Si/Ca, Al/Ca, portlandite, unhydrated part of cement). The research found the optimum MWCNT range to be 0.05–0.1 %, enhancing CP's thermal performance by strengthening cement hydration products and their cohesion, by more the nucleation effect than bridging effect. With the application of MWCNTs, the density of the solid cement phase increased, and the amount of the unhydrated part of cement decreased by up to 21.5 %, at 0.1 % MWCNTs content. Unfortunately, the increase in the MWCNTs content resulted in an increase in the pore volume in the worst case, up to 12.7 %, but it did not negatively affect the strength parameters. The MWCNTs effect caused an increase in tensile strength (fcf) by up to 41.0 % at temperatures above 400 °C, where in the most favorable case improvement in compressive strength reached 16.7 %. The study showed that MWCNTs as an admixture to cement composites is suitable for environments where there is a high variability in terms of thermal loads.

Research on the deformation law of ultra-thin fiber metal laminates under the synergistic effect of nano-reinforcement and scale effect

At present, titanium alloy/carbon fiber reinforced polymer (TA1/CFRP) laminates, representing the latest fourth generation of fiber metal laminates (FMLs), are predominantly applied in the field of aerospace. The miniaturization of traditional FMLs in thickness or plane size to the micron level for the study of structural properties of ultra-thin laminates will further expand the application of FMLs in the field of micro-devices. Given that carbon nanotubes have a strengthening mechanism in polymers. However, most existing studies have focused on the effect of carbon nanotubes on the properties of macro-scale FMLs, while the enhancement mechanism of the interfacial and mechanical properties of ultra-thin micro-scale FMLs has not been studied, leaving the mechanism still unclear. Based on this, this paper explores the interfacial deformation mode, damage fracture and performance enhancement mechanism of the ultra-thin TA1/CFRP laminates by comparing the parameters of tensile strength and elongation under quasi-static conditions and different process parameters of multi-walled carbon nanotubes content, test temperature, geometry size and grain size. Meanwhile, the correlation law between high-speed tension and quasi-static tension is determined, a 29.3 % increase in tensile strength as the strain rate rises from 0.001 s−1 to 100 s−1, yielding the basic deformation law of ultra-thin FMLs.

Wear debris analysis of Al-Si/MWCNT nanocomposite during dry sliding wear tests

This study demonstrates the enhancement of wear resistance achieved by incorporating multi-walled carbon nanotubes (MWCNTs) in LM6 aluminum alloy to form nanocomposites. Experiments on wear resistance study were performed at different test parameters for various compositions of MWCNT in LM6 alloy. The size and nature of debris obtained post experiments were significantly dependent on the MWCNT contents. Wear resistance was found to increase with increase in the MWCNT fraction in the nanocomposite. The worn surface and the shape as well as the size of the debris were studied under scanning electron microscopy (SEM). Energy-dispersive spectroscopy (EDS) analysis of the worn surfaces was used to detect and measure the constituents present in the debris. SEM micrographs of the nanocomposites show that the features of the wear debris are completely altered when MWCNT was added. Further the wear mechanism underwent a change from oxidative in LM6 to that of ploughing in LM6 nanocomposite. The recorded surface roughness values also confirm the above findings and show significantly reduced surface roughness (∼82%, 0.75 wt% MWCNT). These results clearly demonstrate the advantage of addition of MWCNT for enhancing resistance to wear in LM6 alloys.

Enhancing Photovoltaic Performance with BaTiO3/MWCNTs Composite Photoelectrodes in Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) have attracted renewed research interest as a potential low-cost substitute for conventional silicon photovoltaics. This work aims to improve the photovoltaic performance of the DSSCs by incorporating multi-walled carbon nanotubes (MWCNTs) into the BaTiO3 photoelectrode. The pure BaTiO3 and BaTiO3/MWCNT nanocomposites were sensitized with N719 dye and fabricated into solar cell devices for testing. The structural characterization confirmed the successful formation of the nanocomposite with an optimal dispersion at 6% of MWCNT incorporation, beyond which agglomeration effects manifested. The optical analysis verified the modulation of defect states and bandgap engineering induced by the MWCNT network. The morphological studies revealed irregular nanoparticle clusters with embedded nanotubes. Solar cell testing under AM1.5G-simulated sunlight demonstrated a peak power conversion efficiency of 4.044% for 6% of MWCNT doping, constituting a 6-fold increment versus pure BaTiO3 (0.693%). It originated from the simultaneous enhancements in the open-circuit voltage and short-circuit current enabled by the favorable band structure alterations and percolation-assisted charge transport. However, further increasing MWCNT content deteriorated the device metrics, owing to emerging limitations like trapping. The rational integration of multi-walled carbon nanotubes with lead-free ferroelectric metal oxides can contribute to the development of emerging organic-inorganic hybrid solar platforms.

UV-Irradiation Effects on the Structural, Optical and Electrical Characteristics of Soft Blended Polymeric Materials Loaded with Multi-Walled Carbon Nanotubes (MWCNTs)

Undoped and doped polyvinylpyrrolidone/carboxy-methyl cellulose/zinc sulfide/nickel oxide (PVP/CMC/ZnS/NiO) nanocomposite blends with multi-walled carbon nanotubes (MWCNTs) were prepared using sol-gel and solid-state reactions and casting techniques. Various blends were formed and their composition and morphologies were characterized using X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques. The structures of the nano-fillers were examined using the XRD technique. The influence of the concentrations of MWCNTs on the linear and nonlinear optical parameters of PVP/CMC/ZnS/NiO nanocomposite blends was examined. The optical band gap energies were decreased from (direct, indirect: 5.31, 5.06) eV for undoped blends to 4.38 and 3.34 eV for the blends doped with the highest concentration of MWCNTs (0.15 wt%). The refractive indices of the various blends were calculated based on the obtained optical band gap energies using various models. The effect of MWCNTs concentrations on the dielectric constants, energy density, electric modulus and ac conductivity at room temperature of the PVP/CMC/0.5ZnS-0.5NiO/x wt% MWCNTs samples were explored using an Inductance, L, Capacitance, C, and Resistance, R (LCR) meter bridge.

Conductive polymer composites-enable self-sensing twisted string actuators

Twisted string actuators (TSAs) are innovative linear soft actuators that can mimic natural muscle contraction. However, obtaining feedback on their stroke requires cumbersome external sensors that compromise their compliance. We addressed this by developing self-sensing strings using conductive polymer composites (CPCs). The CPC strings exhibit electrical resistance changes in response to strain, enabling stroke sensing by the strings themselves. We fabricated CPCs strings with varying concentrations of multi-walled carbon nanotubes (MWCNTs). Characterization revealed excellent conductivity, tensile strength exceeding 30 N, tunable strain sensitivity via MWCNTs concentration variation, as well as stable and repeatable strain-dependent resistance changes. Optimization via a high-strength core fiber enabled the CPCs strings to withstand over 6[Formula: see text]kg loading with enhanced stroke and minimal resistance variation. We achieved at least a 97.8% linear correlation between resistance change rate and contraction rate in twisting experiments. This research provides a self-contained stroke sensor compatible with high-load soft TSAs, overcoming limitations of external sensors. The simple yet effective sensing mechanism could spur adoption of TSA in robotics.

Analysing the shape memory behaviour of MWCNT-enhanced nanocomposites: a comparative study between experimental and finite element analysis

Shape memory polymers (SMPs) are known for their unique ability to withstand large deformations and revert to their original shape under specific external stimuli. However, their broader application in biomedical and structural applications is restricted by limited mechanical and thermal properties. Introducing multi-walled carbon nanotubes (MWCNTs) into SMPs has proven to significantly enhance these characteristics without affecting their inherent shape memory features. This study investigates shape memory nanocomposites (SMNCs) through dynamic and thermogravimetric analyses, along with tensile, flexural, and shape memory testing, and explores fracture interfaces using scanning electron microscopy. Findings indicate optimal shape memory, thermal, and mechanical properties with 0.6 wt% MWCNT content, showcasing a shape recovery ratio of 93.11%, storage modulus of 4127.63 MPa, tensile strength of 55 MPa, and flexural strength of 107.94 MPa. Moreover, incorporating MWCNTs into epoxy demonstrated a reduction in recovery times by up to 50% at 0.6 wt% concentration. Despite a slight decrease in shape fixity ratio from 98.77% to 92.11%, shape recoverability remained nearly consistent across all samples. The study also introduces a novel finite element (FE) method in ABAQUS for modeling the thermomechanical behavior of SMNCs, incorporating viscoelasticity, validated by matching experimental results with FE simulations, highlighting its accuracy and practical applicability in engineering.

Effects of Nanoparticles on the Mechanical Properties of the Composites Prepared from Biological and Chemical Gels

Poly (N-isopropyl acrylamide) (PNIPAm) and polyacrylamide (PAAm) are widely used in antifouling research because of their non-harmful nature and their high water-absorbing capacity. In addition, hydrogels such as these two, should be investigated for their mechanical properties because their mechanical properties influence the antifouling paint containing them remaining on the surface of the vessels. In this research PAAm, PNIPAm, and kappa carrageenan (κC) doped with graphene oxide (GO) and multi-walled carbon nanotubes (MWCNTs) composite gels were examined for their mechanical properties for use in antifouling paints as a potential material. For increasing the mechanical properties of composites, GO and MWCNTs are often used as doping materials. In the research described here, a compressive test was used to determine the elasticity, and the modulus was calculated. The toughness was calculated from the slope of the stress-strain curve. The PAAm, PNIPAm, and κC doped with GO and MWCNT exhibited excellent swelling and deswelling behavior and good mechanical properties as composites. The results showed that the composites’ mechanical characteristics increased with an ideal loading concentration of GO and MWCNTs. This study was inspired by our belief of a shortage of research on antifouling materials that are sensitive to the environment. We wanted to create materials that were both effective against fouling and environmentally safe by integrating the beneficial characteristics of hydrogels with potential materials inside antifouling paint. This study, we suggest, is an important step toward the development of antifouling materials with high mechanical performance that are also environmentally friendly.

Nerve tissue regeneration based on magnetic and conductive bifunctional hydrogel scaffold

The growth of neurons is often influenced by magnetic and electrical physical factors, and there is more and more research focused on designing a magnetic and conductive engineering scaffolds for nerve injury repair. In this study, electrospun poly lactic-co-glycolic acid (PLGA) fibers containing Fe3O4 magnetic nanoparticles were cryo-cut into magnetic short fibers (MSFs) and subsequently incorporated into sodium alginate (SA)/carboxymethyl chitosan (CMCS) hydrogel along with the addition of multi-wall carbon nanotubes (MWCNTs). MSFs can also achieve alignment by external magnetic fields within the hydrogel to construct magnetic and conductive bifunctional MSF/MWCNT/SA/CMCS hydrogel with anisotropic structure. The magnetic-conductive bifunctional hydrogel exhibited good magnetic responsiveness, electrically activity and mechanical property, in which both conductivity and mechanical property increased with the enhancement of MWCNTs contents. Notably, appearing of aligned structure significantly promoted the mechanical property of MSF/SA/CMCS hydrogel. The MSF/SA/CMCS hydrogel with aligned structure also facilitated greater primary neuron cells proliferation than random ones. Compared with individual magnetic or conductive hydrogel, there was a significant increase in cell viability in the primary cultured cortical neurons on MSF/MWCNT/SA/CMCS hydrogel with aligned structure. Simultaneously, electrical stimulation (ES) combined with magnetic stimulation (MS) delivered via magnetic and conductive bifunctional MSF/MWCNT/SA/CMCS hydrogel with aligned structure produced a better effect on promoting neuronal growth compared with individual ES or MS. Besides, hot plate measurement indicated that MSF/MWCNT/SA/CMCS hydrogel with aligned structure and MS significantly decreased the mice licking latency after sciatic nerve injury. Animal behavior studies confirmed the protective role of synergistic MS with magnetic hydrogel. Such hydrogel scaffolds have long-term potential for nerve tissue regeneration.

Mechanical improvement of carbon fiber/epoxy composites by sizing functionalized carbon nanotubes on fibers

AbstractA sizing agent mainly consisting of polyethersulfone and acidified multi‐walled carbon nanotubes (MWCNT) was developed for surface modification of carbon fibers (CF) to enhance the interfacial bond and to form carbon fiber‐carbon nanotube (CF‐MWCNT) multiscale reinforcements. To prepare the modified carbon fiber/epoxy resin composites (CFRP), a vacuum molding technique was used in this study. The effects of the MWCNT‐containing sizing agent on the morphology and chemical structure of the CF surface were observed by scanning electron microscopy and Fourier transform infrared spectroscopy. The influence of MWCNT length and content on the mechanical properties of CFRP were also studied. The experimental results showed that the strength of the CFRP decreased with the increase of MWCNT length, and the MWCNT with a content of 0.05 wt% had a good reinforced effect on the CFRP. After the sizing treatment, the interlaminar shear strength (ILSS) of the CFRP is increased. These enhancements are attributed to the improved mechanical bonding and chemical bonding between CF and resin matrix. The MWCNT provides nanosized rough surface to CF and these acidified MWCNTs attached to the surface of CF with polar oxygen‐containing functional groups improve the compatibility with reinforcement and resin matrix.Highlights Carbon fiber was modified by a sizing agent mainly consisting of polyethersulfone and acidified carbon nanotube (CNT). CNTs enhance the interfacial chemical bonding and mechanical bonding. The CNT length affects the mechanical properties of the carbon fiber/epoxy resin composites (CFRP). The modified carbon fiber has enhanced the mechanical properties of the CFRP.

Influence of multi-walled carbon nanotubes on thermal behaviour and mechanical properties of pineapple leaf fibre-based natural rubber composites

Replacing synthetic fibres with natural fibres as reinforcement fillers in natural rubber (NR) tends to yield eco-friendly bio-composites. This study investigated the tensile and hardness properties, and the thermal behaviour of pineapple leaf fibre (PALF)-reinforced NR composites with and without the addition of multi-walled carbon nanotubes (MWCNT). The fibre content was varied at 0, 10, 20, and 30 parts per hundred rubber (phr) and the MWCNT content was fixed at 10 phr. The surface morphology of the tensile-fractured specimens was examined using scanning electron microscopy (SEM) to identify the rubber-matrix adhesion and tear mechanisms of the fibres in the NR matrix. The results revealed that including the PALF and MWCNT allowed the NR composites to exhibit excellent stretching stress at low elongations. Additionally, the composites displayed enhanced stiffness, further increasing the hardness of the composite, ranging from 46.8 to 62.8 Shore A. However, PALF reduces the thermal stability of the composite, where the initial degradation temperature increases. From the thermogravimetric analysis, the residues remaining in the NR composites ranged from 6 to 13% at various fibre loadings. Therefore, this study provides valuable insights into the tensile and hardness properties and the thermal behaviour of PALF-reinforced NR composites to improve end-use properties.

Performance enhancement of nanofluid-based photovoltaic/thermal system with a novel finned multi-block container of phase change material in the summer season of northern India

This study describes the outdoor experiments conducted on a photovoltaic/thermal (PV/T) system during the summer months of May and June in the year 2023, in northern India. The main goal of this paper is to reduce the temperature of a photovoltaic (PV) module for effective thermal regulation by implementing a hybrid cooling strategy in a PV/T system. This is achieved by integrating two techniques: multi-walled carbon nanotubes (MWCNT)-water nanofluid as the working fluid for active cooling and paraffin wax as the phase change material (PCM) for passive cooling. Therefore, the present study aims to design, fabricate, and test an innovative thermal collector with a multi-block finned absorber plate positioned beneath the PV module to promote uniform heat transfer distribution and mitigate temperature stratification within each PCM block. The proposed PV/T-PCM system's performance is assessed from energetic, exergetic, economic, and environmental standpoints compared to the PV/T system and conventional PV module. The present study also examines the impact of different concentrations (0.1–0.2 %) of MWCNT and volumetric flow rates (0.5–1.5 l/min) of both water and nanofluids as heat transfer fluids. It is shown that a desirable flow rate of 1.5 l/min yields the most favorable outcomes. The PV/T-PCM (0.2 %) system has been found to exhibit the highest levels of energetic and exergetic electrical and thermal efficiencies, with reported values of 13.25 %, 65 %, 12.81 %, and 1.66 %, respectively. The economic assessment demonstrates that the proposed PV/T-PCM system, integrating water and nanofluid, results in cost savings of 17.41 % and 19.63 % compared to a traditional uncooled PV system. In the context of environmental sustainability, the highest net CO2 mitigation is estimated to be 18.01 tons for the nanofluid-based PV/T-PCM system. Thus, the results confirm that the proposed PV/T-PCM (0.2 %) system, incorporating a hybrid cooling technique, achieves optimal performance.