Search Results (2,130)

The development of miniaturized sensors has become relevant for the detection of chemical/biological substances, since they use and detect low concentrations, such as flocculants based on amines for the mining industry. In this study, buckypaper (BP) films based on carboxylic acid functionalized multi-walled carbon nanotubes (f-MWCNTs) were produced through vacuum filtration on cellulose filter paper to carry out sensory function in samples containing ether-amine (volumes: 1%, 5%, 10% and 100%). The morphological characterization of the BPs by scanning electron microscopy showed f-MWCNT aggregates randomly distributed on the cellulose fibers. Vibrational analysis by Raman spectroscopy indicated bands and sub-bands referring to f-MWCNTs and vibrational modes corresponding to chemical bonds present in the ether-amine (EA). The electrical responses of the BP to the variation in analyte concentration showed that the sensor differentiates deionized water from ether-amine, as well as the various concentrations present in the different analytes, exhibiting response time of 3.62 ± 0.99 min for the analyte containing 5 vol.% EA and recovery time of 21.16 ± 2.35 min for the analyte containing 10 vol.% EA, revealing its potential as a real-time response chemiresistive sensor. Full article

The catalytic decomposition of CH₄ is a promising method for producing high-purity CO_x-free hydrogen. A Ni-Al-LDH catalyst synthesized via coprecipitation was modified with alkali metals (Mg, La, Ca, or Li) through reconstruction to enhance catalytic activity and resistance to deactivation during catalytic methane decomposition (CMD). The catalysts were evaluated by two activation methods: H₂ reduction and direct heating with CH₄. The MgNA-R catalyst achieved the highest CH₄ conversion (65%) at 600 °C when reduced with H₂, attributed to a stronger Ni-Al interaction. Under CH₄ activation, LaNA-C achieved a 55% conversion at the same temperature, associated with a smaller crystallite size and higher reducibility due to La incorporation. Although all catalysts deactivated due to carbon deposition and/or sintering, LaNA-C was the only sample that could resist deactivation for a longer period, as La appears to have a protective effect on the active phase. Post-reaction characterizations revealed the formation of graphitic and filamentous carbon. Raman spectroscopy exhibited a higher degree of graphitization and structural order in LaNA-C, whereas SEM showed a more uniform distribution of carbon filaments. TEM confirmed the presence of multi-walled carbon nanotubes with encapsulated Ni particles in La-promoted samples. These results demonstrate that La addition improves the catalytic performance under CH₄ activation and carbon structure. This finding offers a practical advantage for CMD processes, as it reduces or eliminates the need to use hydrogen during catalyst activation. Full article

As a novel carbon material, multi-walled carbon nanotubes (MWCNTs) have attracted significant research interest in energetic applications due to their high aspect ratio and exceptional physicochemical properties. However, their inherent structural characteristics and poor dispersion severely limit their practical utilization in solid propellant formulations. To address these challenges, this study developed an innovative reverse-engineering strategy that precisely confines MWCNTs within a three-dimensional Fe₂O₃ gel framework through a controllable sol-gel process followed by low-temperature calcination. This advanced material architecture not only overcomes the traditional limitations of MWCNTs but also creates abundant Fe-C interfacial sites that synergistically catalyze the thermal decomposition of glycidyl azide polymer-based energetic thermoplastic elastomer (GAP-ETPE). Systematic characterization reveals that the MWCNTs@Fe₂O₃ nanocomposite delivers exceptional catalytic performance for azido group decomposition, achieving a >200% enhancement in decomposition rate compared to physical mixtures while simultaneously improving the mechanical strength of GAP-ETPE-based propellants by 15–20%. More importantly, this work provides fundamental insights into the rational design of advanced carbon-based nanocomposites for next-generation energetic materials, opening new avenues for the application of nanocarbons in propulsion systems. Full article

Silver nanoparticles (AgNPs), iron oxide nanoparticles (Fe₂O₄NPs), and multiwalled carbon nanotubes (MWCNTs) are widely used in various applications, such as biomedicine, environmental remediation, and agriculture. In addition, these nanomaterials can affect the production of bioactive compounds in plants that have pharmacological activities. In the current study, the in vitro plant cultures of Chinese lobelia (Lobelia chinensis Lour.) were established in MS medium and treated with 0, 12.5, 25, 37.5, and 50 mg L⁻¹ AgNPs or Fe₂O₄NPs, or MWCNTs. Initially, plants were grown for four weeks without any elicitors, and after that, the cultures were treated with nano-elicitors for one week. After five weeks, the effects of nano-elicitors were estimated on growth, total phenolic, flavonoids, polyacetylenes, and ABTS/DPPH/FRAP antioxidant activity was investigated. The results showed that lower levels of AgNPs (25 mg L⁻¹), Fe₂O₄NPs (25 mg L⁻¹), and MWCNTs (12.5 mg L⁻¹) favored the accumulation of fresh and dry biomass. Whereas, 37.5 mg L⁻¹ AgNPs, 25 mg L⁻¹ Fe₂O₄NPs, and 37.5 mg L⁻¹ MWCNTs enhanced the accumulation of total phenolics, flavonoids, specific phenolic compounds including chlorogenic acid, catechin, phloretic acid, coumaric acid, salicylic acid, naringin, myricetin, linarin, and polyacetylenes viz. lobetylonin and lobetyolin in higher concentrations. The plant extracts elicited by nanomaterials also depicted very good antioxidant activities according to ABTS, DPPH, and FRAP assays. These results suggest that specific nanomaterials, and at specific levels, could be used for the production of bioactive compounds from shoot cultures of Chinese lobelia. Full article

Epoxy resins are widely used as protective coatings in civil infrastructure, yet sulfate-rich environments accelerate their deterioration. This study evaluates the effectiveness of multi-walled carbon nanotubes (MWCNTs) in enhancing the sulfate resistance of epoxy resins. Neat and MWCNT-reinforced epoxy specimens (0.25 wt.% and 0.5 wt.%) were fabricated, heat cured at 100 °C and exposed to a solution of sulfuric acid and sodium chloride maintaining a pH of less than 3 for 0, 30, and 60 days. Analytical techniques, including scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS), revealed distinct degradation patterns: the neat epoxy exhibited puncture damage and extensive salt deposition, while the MWCNT-reinforced specimens showed crack propagation mitigated by nanotube bridging. Heat curing introduced micro-voids that exacerbated sulfate ingress. The salt deposition surged to 200 times for the MWCNT-reinforced specimens compared to the neat ones, whereas crack width was higher in the MWCNT reinforced specimen compared to their neat counterparts, given that crack-bridging was observed. These findings highlight the potential of MWCNTs to improve epoxy durability in sulfate-prone environments, though the optimization of curing conditions and dispersion methods is critical. Full article

A novel type of multifunctional hybrid membranes combining modified chitosan, functionalized multi-walled carbon nanotubes (MWCNTs), and rare earth element ion-imprinted polymers (REEIIPs) were designed and characterized. The synthesized materials were characterized by thermogravimetric analysis (TGA), scanning electron microscopy (SEM), vibrating sample magnetometry (VSM), X-ray diffraction (XRD), X-ray micro-tomography, and Fourier transform infrared spectroscopy (FTIR). The hybrid membranes were also studied in terms of their mechanical and rheological properties. The key element of the proper preparation of hybrid membranes using the casting method in an external magnetic field was to synthesize membrane components with appropriate magnetic properties. It was found that they showed tunable weak ferromagnetic properties, and the increase in modified nanotube addition caused the rise in the membrane’s saturation magnetization, which for Nd-selective hybrid membranes reached 0.44 emu/g. Also, the increase in thermooxidative stability was noted after introducing functionalized nanotubes into polymer matrices, which, in the case of Gd-selective membranes, were stable even up to 730 °C. The rise in the modified MWCNT addition and selection of appropriate REE ion-imprinted polymers improved mechanical (Rm and E values increase even twice) and rheological parameters (almost double growth of E′ and E″ values) of the tested membranes. Synthesized hybrid membranes showed a high rejection of matrix components and an increase in retention ratio with rising MWCNT-REEIIP addition, ultimately reaching 94.35%, 92.12%, and 90.11% for Nd, Pr, and Gd, respectively. The performed analysis confirmed homogeneous dispersion, phase compatibility, network integration, formation of a complex 3D microstructure, and improved operational stability of created hybrid membranes, which is significant for their future applications in Nd, Pr, and Gd recovery from coal fly ash extracts. Full article

The growing need for lightweight, customizable electromagnetic wave absorbers with weather resistance in aerospace and electromagnetic compatibility applications motivates this study, which addresses the limitations of conventional materials in simultaneously achieving structural efficiency, broadband absorption, and environmental durability. We propose a fused deposition modeling (FDM)-based approach for fabricating lightweight wave-absorbing structures using acrylonitrile-styrene-acrylate (ASA)/multi-walled carbon nanotube (MWCNT) composites. Results demonstrate that CST Studio Suite simulations reveal a minimum reflection loss of −18.16 dB and an effective absorption bandwidth (RL < −10 dB) of 3.75 GHz for the 2 mm-thick composite plate when the MWCNT content is 2%. Through FDM fabrication and structural optimization, significant performance enhancements are achieved: The gradient honeycomb design with larger dimensions achieved an effective absorption bandwidth of 6.56 GHz and a minimum reflection loss of −32.60 dB. Meanwhile, the stacked stake structure exhibited a broader effective absorption bandwidth of 10.58 GHz, with its lowest reflection loss reaching −22.82 dB. This research provides innovative approaches for developing and manufacturing tailored lightweight electromagnetic wave-absorbing structures, which could be valuable for aerospace stealth technology and electromagnetic compatibility solutions. Full article

This study explores using polyvinylidene fluoride (PVDF) membranes modified with multi-walled carbon nanotubes (MWCNTs) to treat simulated and industrial brine from coal power stations. The MWCNTs were acid-treated and characterized using Fourier Transform Infrared Spectroscopy (FTIR), Raman, and nitrogen sorption at 77 K, Thermogravimetric analysis (TGA), and Transmission electron microscopy (TEM). The desired membranes were obtained by casting from a solution of N-Methyl-2-pyrrolidone, PVDF, various weight percentages of MWCNTs, and a small amount of polyvinylpyrrolidone. The acid treatment of the MWCNTs introduced oxygen moieties on the surface, and increased pore volume and surface area while maintaining crystallinity and structural integrity remain preserved. The maximum rejection rate achieved was 41.82% with 1 wt.% of acid-treated MWCNTs in the PVDF membrane. Acid-treated MWCNTs loaded membranes had an improved rejection rate, which was 5× higher than membranes without MWCNTs. Full article

This study presents a multi-modal investigation into the wear behavior of bio-based epoxy composites reinforced with multi-walled carbon nanotubes (MWCNTs) at 0–0.75 wt%. A Taguchi L16 orthogonal array was employed to systematically assess the influence of MWCNT content, load (20–50 N), and sliding speed (1–2.5 m/s) on wear rate (WR), coefficient of friction (COF), and surface roughness (Ra). Statistical analysis revealed that MWCNT content contributed up to 85.35% to wear reduction, with 0.5 wt% identified as the optimal reinforcement level, achieving the lowest WR (3.1 mm³/N·m) and Ra (0.7 µm). Complementary morphological characterization via SEM and AFM confirmed microstructural improvements at optimal loading and identified degradation features (ploughing, agglomeration) at 0 wt% and 0.75 wt%. Regression models (R² > 0.95) effectively captured the nonlinear wear response, while a Random Forest model trained on GLCM-derived image features (e.g., correlation, entropy) yielded WR prediction accuracy of R² ≈ 0.93. Key image-based predictors were found to correlate strongly with measured tribological metrics, validating the integration of surface texture analysis into predictive modeling. This integrated framework combining experimental design, mathematical modeling, and image-based machine learning offers a robust pathway for designing high-performance, sustainable nanocomposites with data-driven diagnostics for wear prediction. Full article

Carbon nanotubes are promising in agriculture for improving crop resilience and delivering agrochemicals. However, their effects on insect pests, especially chewing pests such as the fall armyworm (Spodoptera frugiperda), remain underexplored. In this study, we investigated how two types of functionalized multi-walled carbon nanotubes—hydroxylated (MWCNTs-OH) and carboxylated (MWCNTs-COOH), both obtained from Jiangsu Xianfeng Nano (Nanjing, China)—affect the pest’s development and reproduction. Using an age-stage two-sex life table approach, we fed larvae diets containing 0.04, 0.4, or 4 mg/g of these nanomaterials. Both types of MWCNTs exhibited concentration-dependent inhibitory effects. At the highest dose (4 mg/g), larval development was significantly prolonged, adult pre-oviposition periods increased, and fecundity (egg production) sharply declined, especially with MWCNTs-OH. Population growth parameters were also suppressed: net reproductive rate (R₀), intrinsic rate of increase (r), and finite rate of increase (λ) were reduced at 4 mg/g, particularly with MWCNTs-OH, while mean generation time (T) was extended with MWCNTs-COOH. Overall, MWCNTs-OH demonstrated a greater inhibitory impact compared to MWCNTs-COOH. These findings suggest that functionalized MWCNTs could serve as potential novel pest control agents against S. frugiperda by impeding its development and reproduction. Full article

There is a lack of an effective approach to measure vacuum conditions inside sealed vacuum electronic devices (VEDs) and other small-space vacuum instruments. In this study, the application performance of an innovative low-pressure gas sensor based on the emission enhancements of multi-walled carbon nanotube (MWCNT) field emitters was investigated, and the in situ vacuum performance of X-ray tubes was studied for the advantages of miniature dimension and having low power consumption, extremely low outgassing, and low thermal disturbance compared to conventional ionization gauges. The MWCNT emitters with high crystallinity presented good pressure sensing performance for nitrogen, hydrogen, and an air mixture in the range of 10⁻⁷ to 10⁻³ Pa. The miniature MWCNT sensor is able to work and remain stable with high-temperature baking, important for VED applications. The sensor monitored the in situ pressures of the sealed X-ray tubes successfully with high-power operations and a long-term storage of over two years. The investigation showed that the vacuum of the sealed X-ray tube is typical at a low 10⁻⁴ Pa level, and pre-sealing degassing treatments are able to make the X-ray tube work under high vacuum levels with less outgassing and keep a stable high vacuum for a long period of time. Full article

Films of functionalised multiwalled carbon nanotubes (MWCNTs) were fabricated as interlayers (interfacial layers between the cathode and separator) in a lithium–sulfur battery (LSB). Phenylsulfonate functionalisation of commercial MWCNTs was achieved via diazotisation to attach lithium phenylsulfonate groups and was characterised by IR and XPS spectroscopies. SEM-EDX showed sulfur and oxygen colocations due to the sulfonate groups on the interlayer surface. However, CHNS elemental microstudies showed a low degree of functionalisation. Without an interlayer, the LSB produced stable cycling at a capacity of 600 mA h g⁻¹_sulfur at 0.05 C for 40 cycles. Using an unfunctionalised interlayer as a control gave a capacity of 1400 mA h g⁻¹_sulfur for the first cycle but rapidly decayed to the same 600 mA h g⁻¹_sulfur at the 40th cycle at 0.05 C, suggesting a high degree of polysulfide shuttling. Adding a lithium phenylsulfonated interlayer gave an initial capacity increase to 1100 mA h g⁻¹_sulfur that lowered to 800 mA h g⁻¹_sulfur at 0.05 C by the 40th cycle, showing an increase in charge storage (33%) relative to the other cells. This performance increase has been attributed to lessened polysulfide shuttling due to repulsion by the phenylsulfonate groups, increased conductivity at the separator-cathode interface and an increase in surface area. Full article

Polystyrene (PS), a thermoplastic polymer, is used in many applications due to its mechanical performance, good chemical inertness, and excellent processability. However, it is doped with different nanomaterials for reasons such as improving its electrical conductivity and mechanical properties. In this study, carbon nanotube (CNT)-added PS composites were produced with the aim of combining the properties of CNTs, such as their low weight and high tensile strength and Young’s modulus, with the versatility, processability, and mechanical properties of PS. In this study, multi-walled carbon nanotube (MWCNT)-reinforced polystyrene (PS) composites with different percentage ratios (0.1, 0.2, and 0.3 wt%) were prepared by a plastic injection molding method. The mechanical, microstructural, and thermal properties of the fabricated PS/MWCNT composites were characterized by Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR) Spectroscopy, Atomic Force Microscopy (AFM) and Thermogravimetric Analysis (TGA) techniques. AFM analyses were carried out to investigate the surface properties of MWCNT-reinforced composite materials by evaluating the root mean square (RMS) values. These analyses show that the RMS value for MWCNT-reinforced composite materials decreases as the weight percentage of MWCNTs increases. The TGA results show that there is no change in the degradation temperature of the 0.1%- and 0.2%-doped MWCNT composites compared to pure polystyrene, but the degradation of the 0.3%-doped MWCNT composite is almost complete at a temperature of 539 °C. Among the PS/MWCNT composites, the 0.3%-doped MWCNT composite exhibits more thermal stability than pure PS and other composites. Similarly, the values of the percentage elongation and tensile strength of 0.3% MWCNT-doped composites was obtained as 1.91% and 12.174% mm², respectively. These values are higher than the values of 0.1% and 0.2% MWCNT-doped composite materials. In conclusion, the mechanical and thermal properties of MWCNT-reinforced PS polymers provide promising results for researchers working in this field. Full article

Carbon nanotube (CNT) fiber research focuses on developing functional fabrics with dual or multifunctional capabilities. This study investigates CNT fibers fabricated via dielectrophoresis (DEP) with the incorporation of 10 wt.% carbide-derived carbon (CDC), referred to as CNTCDC fibers. The linear actuation behavior of the CNT and the CNTCDC fibers is compared using identical electrolyte concentrations in both a polar aprotic solvent (propylene carbonate, PC) and a polar protic solvent (aqueous solution, aq). Electromechanical deformation (EMD) is studied through cyclic voltammetry and chronoamperometry. The CNTCDC fiber outperformed the pristine CNT fiber, exhibiting primary expansion during discharge in PC (stress: 1.64 kPa, strain: 0.1%) and during charge in water (stress: 1.32 kPa, strain: 0.047%). By contrast, the pristine CNT fibers showed mixed actuation responses in both solvents, resulting in diminished net stress and strain. Chronopotentiometric measurements indicated that the CNTCDC fibers achieved their highest specific capacitance in aqueous media, reaching 223 ± 17 F g⁻¹ at ±0.8 A g⁻¹, with a capacity retention of 94.2% at ±32 A g⁻¹. Fundamental characterization techniques, including scanning electron microcopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and Raman spectroscopy, are employed to analyze fiber morphology and composition. The dual functionality of CNTCDC fibers, as both actuators and energy storage elements, is demonstrated. Full article

Titanium alloy/carbon fiber-reinforced polymer (TA1/CFRP) laminates, representing the latest fourth generation of fiber metal laminates (FMLs), is a kind of high-performance composite material. However, the fragility of the fiber/resin and metal/resin interface layers in these composites directly impacts their mechanical properties. To enhance these properties, this paper investigates the preparation process of multi-walled carbon nanotube (MWCNT)-reinforced ultra-thin TA1/CFRP laminates and explores the impact of MWCNT content on the interlayer properties of these ultra-thin TA1/CFRP laminates. Initially, the challenge of dispersing carbon nanotubes using ultrasonic dispersion devices and dispersants was addressed. Vacuum-curing pressure studies revealed minimal overflow at 0.8 bar vacuum. Subsequently, the impact of MWCNT content on interlayer properties was investigated. The results indicated a significant increase in interlayer shear strength and interlayer fracture toughness with MWCNT additions at 0.5 wt% and 0.75 wt%, whereas the interlayer properties decreased at 1.0 wt% MWCNT. Fracture morphology analysis revealed that MWCNT content exceeding 0.75 wt% led to agglomeration, resulting in resin cavity formation and stress concentration. Full article