Search Results (449)

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

This study consisted of the injection molding simulation of polycaprolactone (PCL)-based nanocomposites reinforced with multi-walled carbon nanotubes (MWCNTs) for biomedical implant manufacturing. The simulation was additionally supported by experimental validation. The influence of varying MWCNT concentrations (0.5%, 5%, and 10% by weight) on key injection molding parameters, i.e., melt flow behavior, pressure distribution, temperature profiles, and fiber orientation, was analyzed with SolidWorks Plastics software. The results proved the low CNT content (0.5 wt.%) to be endowed with stable filling times, complete mold cavity filling, and minimal frozen regions. Thus, this formulation produced defect-free modular filament sticks suitable for subsequent 3D printing. In contrast, higher CNT loadings (particularly 10 wt.%) led to longer fill times, incomplete cavity filling, and early solidification due to increased melt viscosity and thermal conductivity. Experimental molding trials with the 0.5 wt.% CNT composites confirmed the simulation findings. Following minor adjustments to processing parameters, high-quality, defect-free sticks were produced. Overall, the PCL/MWCNT composites with 0.5 wt.% nanotube content exhibited optimal injection molding performance and functional properties, supporting their application in modular, patient-specific biomedical 3D printing. Full article

Cement–based mortars are essential in both modern construction and heritage conservation, where balancing mechanical strength with material compatibility is crucial. Mortars containing ––binders with low hydraulic activity, such as CEM II/B–L, often exhibit increased porosity and diminished strength, limiting their suitability for structurally demanding applications. This study investigates the potential of multiwalled carbon nanotubes (MWCNTs) to enhance the mechanical and microstructural properties of mortars formulated with both CEM II/B–L and CEM I binders. The influence of CNT incorporation was systematically assessed through compressive and flexural strength tests, vacuum saturation tests, mercury intrusion porosimetry (MIP), scanning electron microscopy (SEM), and differential thermal analysis (DTA). The results demonstrate significant mechanical improvements attributable to nanoscale mechanisms including crack bridging, pore–filling, and stress redistribution. Microstructural characterization revealed a refined pore network, increased densification of the matrix, and morphological modifications of hydration products. These findings underscore the effectiveness of CNT reinforcement in cementitious matrices and highlight the critical role of binder composition in influencing these effects. This work advances the development of high–performance mortar systems, optimized for enhanced structural integrity and long–term durability. Full article

A flexible and highly sensitive piezoresistive strain sensor was fabricated through the application of CO₂ laser ablation on a composite film composed of multi-walled carbon nanotubes, carbon black, and polydimethylsiloxane (MWCNT/CB/PDMS). The results of scanning electron microscopy (SEM) surface analysis shows that the “bush-like” conductive structure on the PDMS-based composite material membrane post-laser ablation is formed. Transmission electron microscopy (TEM) images and X-ray diffraction (XRD) spectra of the ablation products indicated the formation of an amorphous carbon layer on the surface of carbon nanomaterials due to laser ablation. Experimental findings revealed that the sensitivity (GF) value of the sensor based on CNT0.6CB1.0-P3.0 is up to 584.7 at 5% strain, which is approximately 14% higher than the sensitivity 513 of the sensor previously prepared by the author using CO₂ laser ablation of MWCNT/PDMS composite films. The addition of a very small volume fraction of CB particles significantly enhances the piezoresistive sensitivity of the sensor samples. Combined with the qualitative analysis of microscopic morphology characterization, CB and MWCNT synergistically promote the deposition of amorphous carbon. This phenomenon increases the probability of tunnel effect occurrence in the strain response region of the sensor, which indirectly confirms the synergistic enhancement effect of the combined action of CB and MWCNT on the piezoresistive sensitivity of the sensor. Full article

Carbon nanotubes (CNTs) have emerged as pivotal nanomaterials in sensing technologies owing to their unique structural, electrical, and mechanical properties. Their high aspect ratio, exceptional surface area, excellent electrical conductivity, and chemical tunability enable superior sensitivity and rapid response in various sensor platforms. This review presents a comprehensive overview of recent advancements in CNT-based sensors, encompassing both single-walled (SWCNTs) and multi-walled carbon nanotubes (MWCNTs). We discuss their functional roles in diverse sensing applications, including gas sensing, chemical detection, biosensing, and pressure/strain monitoring. Particular emphasis is placed on the mechanisms of sensing, such as changes in electrical conductivity, surface adsorption phenomena, molecular recognition, and piezoresistive effects. Furthermore, we explore strategies for enhancing sensitivity and selectivity through surface functionalization, hybrid material integration, and nanostructuring. The manuscript also covers the challenges of reproducibility, selectivity, and scalability that hinder commercial deployment. In addition, emerging directions such as flexible and wearable CNT-based sensors, and their role in real-time environmental, biomedical, and structural health monitoring systems, are critically analyzed. By outlining both current progress and existing limitations, this review underscores the transformative potential of CNTs in the design of next-generation sensing technologies across interdisciplinary domains. Full article

Rubber is widely used in daily lives, such as in automobile tires, conveyor belts, sealing rings, and gaskets. The performance of rubber determines its service life. Therefore, it is of crucial importance to improve the performance of rubber. Theoretical studies have found that the inherent properties of nanofillers themselves, the interfacial bonding force between fillers and the matrix, and the uniform dispersibility of nanofillers in the polymer matrix are the most significant factors for enhancing the performance of rubber nanocomposites. This study systematically investigated the synergistic enhancement effect of silicon carbide (SiC) and multi-walled carbon nanotubes (MWCNTs) on the mechanical and thermal properties of ethylene–butene–terpolymer (EBT) composites. By optimizing the addition amount of fillers and improving the interfacial bonding between fillers and the matrix, the influence of filler content on the properties of composites was studied. The results demonstrate that the addition of SiC and MWCNTs significantly improved the storage modulus, tensile strength, hardness, and thermal stability of the composites. In terms of mechanical properties, the tensile strength of the composites increased from 6.68 MPa of pure EBT to 8.46 MPa, and the 100% modulus increased from 2.14 MPa to 3.81 MPa. Moreover, hardness was significantly enhanced under the reinforcement of SiC/CNT fillers. In terms of thermal stability, the composites exhibited excellent resistance to deformation at high temperatures. Through the analysis of the mechanical and thermal properties of the composites, the synergistic enhancement mechanism between SiC and MWCNTs was revealed. The research results provide a theoretical basis for the design and engineering applications of high-performance ethylene–butylene rubber composites. Full article

Pulmonary exposure to carbon nanotubes (CNTs) has been linked to a series of adverse respiratory effects in animal models, including inflammation, genotoxicity, fibrosis, and granuloma formation, the degree and characteristics of which are considered dependent upon the detailed physicochemical properties of the material as inhaled. To further explore the effect of variations in physicochemical properties on pulmonary effects, two different multi-walled CNTs (MWCNTs) were tested in vivo: a pristine MWCNT (pMWCNT) (NM-401) and a surface-modified MWCNT (MWCNT-COOH). Female Sprague–Dawley rats were whole-body exposed for 28 days to MWCNT aerosols (pMWCNT (0.5 and 1.5 mg/m³) and MWCNT-COOH (1.5 and 4.5 mg/m³)) and followed up to 1 year post-exposure. The inhalation exposures resulted in relatively low estimated lung deposition. Bronchoalveolar lavage fluid (BALF) analysis indicated inflammation levels broadly consistent with deposited dose levels. Lung histopathology indicated that both MWCNTs produced very limited toxicological effects; however, global mRNA expression levels in lung tissue and BALF cytokines indicated different characteristics for the two MWCNTs. For example, pMWCNT but not MWCNT-COOH exposure induced osteopontin production, suggestive of potential pre-fibrosis/fibrosis effects linked to the higher aspect ratio aerosol particles. This is of concern as brightfield and enhanced darkfield microscopy indicated the persistence of pMWCNT fibres in lung tissue. Full article

The aim of this study was to evaluate the effect of multi-walled carbon nanotubes (CNTs) on various material properties of the polyamide 66 (PA66) nanocomposites. This is achieved first by investigating the effect of CNTs (0.1–5 wt.%) on the material properties of PA66 pellets, and second, on the injection-molded PA66/CNT nanocomposites. Thermal analysis revealed that CNTs do not have a significant effect on the melting behavior and melting temperature of PA66/CNT nanocomposites, but they increase the crystallization temperature of the nanocomposites. Rheological analysis showed that the melt shear viscosity of the PA66 increased with increasing CNT content particularly above 1 wt.%. Additionally, the PA66 nanocomposites exhibit shear-thinning behavior, and this effect is more significant at higher CNT contents. The FT-IR analysis revealed the absence of chemical bonds between PA66 and CNTs and, consequently, the uniform dispersion of CNTs in the PA66 matrix. Mechanical testing indicated that the inclusion of CNTs (0.1 to 5 wt.%) in PA66 matrix could not improve the tensile modulus to a great extent, while it decreased the ultimate tensile strength of PA66 nanocomposites under tension. On the other hand, CNTs positively influenced the mechanical behavior under bending (+15% increase at 5 wt.%). Among the nanocomposites, PA66 filled with 5 wt.% CNTs exhibited the optimal mechanical performance in terms of tensile strength (58 MPa), tensile modulus (2689 MPa), bending modulus (2072 MPa), and bending strength (104 MPa). The experimental results also showcase the significant improvement in the tensile and bending mechanical properties of the injection-molded PA66 nanocomposites after thermal annealing at −40 °C and 180 °C for one hour. This experimental study provides guidelines for the structure–property–processability of the PA66 nanocomposites, revealing the complex relationship between the CNTs and the enhancement of mechanical properties, while highlighting the potential of thermal annealing in improving the mechanical performance of PA66 nanocomposites. This will be further investigated to promote the use of PA66 nanocomposite in industrial applications. Full article

In this study, a Brönsted–Lewis bifunctional acidic catalyst PW/UiO/CNTs-OH was synthesized via the hydrothermal method. The parameters for the esterification reaction of oleic acid with methanol catalyzed by PW/UiO/CNTs-OH were optimized using central composite design-response surface methodology (CCD-RSM). A biodiesel yield of 92.9% was achieved under the optimized conditions, retaining 82.3% biodiesel yield after four catalytic cycles. The enhanced catalytic performance of PW/UiO/CNTs-OH can be attributed as follows: the [Zr₆O₄(OH)₄]¹²⁺ anchored on the surface of multi-walled carbon nanotubes (MWCNTs) can serve as nucleation sites for UiO-66, not only encapsulating H₃[P(W₃O₁₀)₄] (HPW) but also reversing the quadrupole moment of MWCNTs to generate Lewis acid sites. In addition, introduction of HPW during synthesis of UiO-66 decreases the solution pH, inducing the protonation of p-phthalic acid (PTA) to disrupt the coordination with the [Zr₆O₄(OH)₄] cluster, thereby creating an unsaturated Zr⁴⁺ site with electron pair-accepting capability, which generates Lewis acid sites. EIS analysis revealed that PW/UiO/CNTs-OH has higher electron migration efficiency than UiO-66 and PW/UiO. Furthermore, NH₃-TPD and Py-IR analyses showed that PW/UiO/CNTs-OH possessed high densities of Lewis acidic sites of 83.69 μmol/g and Brönsted acidic sites of 9.98 μmol/g. Full article

Nanotubes (NTs) are nanosized tube-like structured materials made from various substances such as carbon, boron, or silicon. Carbon nanomaterials (CNMs), including carbon nanotubes (CNTs), graphene/graphene oxide (G/GO), and fullerenes, have good interatomic interactions and possess special characteristics, exploitable in several applications because of the presence of sp2 and sp3 bonds. Among NTs, CNTs are the most studied compounds due to their nonpareil electrical, mechanical, optical, and biomedical properties. Moreover, single-walled carbon nanotubes (SWNTs) have, in particular, demonstrated high ability as drug delivery systems and in transporting a wide range of chemicals across membranes and into living cells. Therefore, SWNTs, more than other NT structures, have generated interest in medicinal applications, such as target delivery, improved imaging, tissue regeneration, medication, and gene delivery, which provide nanosized devices with higher efficacy and fewer side effects. SWNTs and multi-walled CNTs (MWCNTs) have recently gained a great deal of attention for their antibacterial effects. Unfortunately, numerous recent studies have revealed unanticipated toxicities caused by CNTs. However, contradictory opinions exist regarding these findings. Moreover, the problem of controlling CNT-based products has become particularly evident, especially in relation to their large-scale production and the nanosized forms of the carbon that constitute them. Important directive rules have been approved over the years, but further research and regulatory measures should be introduced for a safer production and utilization of CNTs. Against this background, and after an overview of CNMs and CNTs, the antimicrobial properties of pristine and modified SWNTs and MWCNTs as well as the most relevant in vitro and in vivo studies on their possible toxicity, have been reported. Strategies and preventive behaviour to limit CNT risks have been provided. Finally, a debate on regulatory issues has also been included. Full article

Carbon fibers, with high modulus of elasticity, tensile strength, and electrical conductivity, can modify the mechanical and electrical properties of cementitious composites, facilitating their practical application in smart infrastructure. This study investigates the effects of carbon nanofibers (including carbon nanotubes, a special type of carbon nanofibers) and micron carbon fibers with different aspect ratios and surface treatments on the uniaxial tensile and electrical properties of cementitious composites. The results demonstrate that appropriate carbon fiber doping markedly improves the uniaxial tensile strength of cementitious composites, with enhancement effects following a gradient trend based on a geometric scale: carbon nanotubes (CNTs) < carbon nanofibers (CNFs) < short-cut carbon fibers (CFs). Hydroxyl-functionalized multi-walled carbon nanotubes (MWCNTs) form continuous conductive networks due to surface active groups (-OH content: 5.58 wt.%), increasing the composite’s electrical conductivity by two orders of magnitude (from 3.56 × 10⁸ to 2.74 × 10⁶ Ω·cm), with conductivity enhancement becoming more pronounced at higher doping levels. Short-cut CFs also improve conductivity, with longer fibers (6 mm) exhibiting a 12.4% greater reduction in resistivity. However, exceeding the percolation threshold (0.5–1.0 vol.%) leads to limited conductivity improvement (<5%) and mechanical degradation (8.7% tensile strength reduction) due to fiber agglomeration-induced interfacial defects. This study is a vital reference for material design and lays the groundwork for self-sensing cementitious composites. Full article

We are committed to writing this narrative review given that carbon-based nanomaterials are revolutionizing dental medicine. Since the groundbreaking discovery of carbon nanotubes in 1991, their dental applications have skyrocketed. The numbers speak for themselves: in 2024, the global carbon nanotubes market hit USD 1.3 billion and is set to double to USD 2.6 billion by 2029. Over the past few decades, various forms of carbon nanomaterials have been integrated into dental practices, elevating the quality and effectiveness of dental treatments. They represent a transformative advancement in dentistry, offering numerous benefits such as augmented mechanical properties, antimicrobial activity, and potential for regenerative applications. Both carbon nanotubes (CNTs) and carbon dots (CDs) are derived from carbon and integral to nanotechnology, showcasing the versatility of carbon nanostructures and delivering cutting-edge solutions across diverse domains, such as electronics, materials science, and biomedicine. CNTs are ambitiously examined for their capability to reinforce dental materials, develop biosensors for detecting oral diseases, and even deliver therapeutic agents directly to affected tissues. This review synthesizes their current applications, underscores their interdisciplinary value in bridging nanotechnology and dentistry, identifies key barriers to clinical adoption, and discusses hybrid strategies warranting further research to advance implementation. Full article

Carbon nanotube (CNT)–metal Schottky contacts are widely employed in different types of electronic devices, including field effect transistors (FET) and gas sensors. CNTs are normally considered stable on electronic properties with gas adsorptions. In this work, performance changes of the multi-walled carbon nanotube (MWCNT)–metal junctions related to hydrogen adsorptions were illustrated. MWCNT/Pd and MWCNT/Au Schottky junctions based resistive sensors were constructed to investigate the low-pressure gas sensing performances for hydrogen in the range of 10⁻⁶~10⁻³ Pa. Two types of sensors presented opposite behaviors with hydrogen adsorptions, i.e., the sensor resistance rose for the MWCNT/Pd sensor but dropped for the MWCNT/Au sensor with increasing hydrogen pressure. The work function reductions of Pd and CNT are considered the key cause, which could change the Schottky barrier properties dramatically. This behavior may play crucial roles for the accurate utilization of CNT-based Schottky devices. Full article

This work addressed the fine dispersion of Multiwalled Carbon Nanotubes (MWCNTs) in a polymer matrix to obtain Mixed Matrix Membranes (MMMs) suited for gas separation. Not-purified MWCNTs were effectively loaded within a polyether block amide (Pebax^®2533) matrix, up to 24 wt%, using ultrasonication as well as a third component (polysorbate) in the dope solution. The obtained flexible thin films were investigated in terms of morphology, thermal properties, characterized by SEM, FT-IR, DSC, TGA, and gas permeation tests. The response to temperature variations of gas permeation through these nanocomposite specimens was also investigated in the temperature range of 25–55 °C. Defect-free samples were successfully obtained even at a significantly high loading of CNTs (up to 18 wt%), without a pre-treatment of the fillers. A remarkable enhancement of gas permeability upon the nanocarbons loading was reached, with a threshold value at a loading of ca. 7 wt%. The addition of polysorbates in the ternary MMMs further improves the dispersion of the filler, enhancing also the permselectivity of the membrane. Full article

This study used a direct dispersion and filtration technique to produce hybrid buckypaper (BP) composites of copper oxide nanoparticles (NPs) and entangled multiwalled carbon nanotubes (CNTs). The photocurrent generation of the BP sheets under two different (direct and gradient) illumination conditions was investigated by varying copper oxide loadings (10–50 wt%). The structure and morphology of the composites examined through X-ray diffraction and scanning electron microscopy (SEM) confirmed the presence of monoclinic cupric oxide nanoparticles in the CNT network. The difference in electrical resistivity between bulk-filled and surface-filled CuO-BP composites was assessed using the four-probe Hall measurement. The studies disclosed that the surface-loaded CuO on the CNT network demonstrated a superior ON and OFF response under the gradient illumination conditions with peak values of 17.69 μA and 350.04 μV for photocurrent and photovoltage, respectively. The significant photocurrent observed at zero applied voltage revealed the existence of a photovoltaic effect in the BP composites. An intense photoresponse was detected in the surface-filled sample CuO-BP composite in both illumination conditions. Additionally, at an illumination level of 150 W/m², wavelength-dependent photovoltaic effects on pure BP were observed using red, green, and blue filters. Full article