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In this research work, our goal is to scrutinize the case, where water-based nanofluids having single-wall and multi-wall carbon nanotubes (CNTs) flow through a vertical cone. The second law of thermodynamic is taken for the aim of scheming effective heat storage units. The body package is layered in convective heat and diluted permeable medium. The effects of Joule heating, rotary microorganisms, heat generation/absorption, chemical reactions, and heat radiation increase the novelty of the established model. By using a local similarity transformation technique, the partial differential equations (PDEs) change into a coupled differential equation. By using the numerical technique, bvp4c, to get the solution of the conservation equations and their relevant boundary conditions. The parameters appearing in the distribution analysis of the alliance are scrutinized in detail, and the consequences are depicted graphically. It can be perceived that in the situation of composed nanotubes, the velocity of fluid decreases as the magnetic field is increased.

Studies have increasingly aimed at improving the piezoresistive behavior of polymer‐based conductive composites (CPCs) for strain‐sensing, with inorganic nanomaterial enhancement offering research opportunities. This study investigates the impact of incorporating zinc sulfide nanospheres (ZnS NSs, 1–7 wt.%), synthesized via a one‐step hydrothermal method, into a poly(vinylidene fluoride) (PVDF) polymer matrix together with multi‐walled carbon nanotubes (MWCNTs). Field emission scanning electron microscopy (FE‐SEM), energy‐dispersive X‐ray spectroscopy (EDX), and X‐ray diffraction (XRD) analyses reveal that ZnS NSs comprise a mixture of ZnS0.96O0.04 and S phases. While of ZnS NSs minimally impact tensile properties of the PVDF/MWCNT composites, they reduce elongation at break at 5 wt.%. During 15‐cycle strain sensing up to 3% strain, ZnS NSs‐enhanced composites outperformed PVDF/1 wt.% MWCNT. The reference sample's resistance change ratio (ΔR/R0) decreased below 1% with increased cycles, while 1 wt.% ZnS NSs increased ΔR/R0 to 3%, reducing changes upon cycle increments. Higher ZnS NSs levels (3–7 wt.%) resulted in ΔR/R0 exceeding 4–5%, indicating enhanced strain sensing performance. Fourier‐transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA) showed limited impact of ZnS NSs on the thermal properties and microstructure of the composites. Novel strain sensing composites achieve enhanced piezoresistive performance through the strategic incorporation of zinc sulfide nanospheres (ZnS NSs) into poly(vinylidene fluoride) (PVDF) and multi‐walled carbon nanotubes (MWCNTs). The ZnS NSs significantly improve both electrical stability and sensitivity during cyclic strain measurements, opening new possibilities for high‐performance flexible sensor applications.

Piezoresistive tactile sensors made using nanocomposite polymeric materials have been shown to possess good flexibility, electrical performance, and sensitivity. However, the sensing performance, especially in the low-pressure range, can be significantly improved by enabling uniform dispersion of the filler material and utilization of effective structural designs that improve the tactile sensing performance. In this study, a novel flexible piezoresistive tactile sensor with a grid-type microstructure was fabricated using polymer composites comprising multi-walled carbon nanotubes (MWCNTs) as the conductive filler and polydimethylsiloxane (PDMS) as the polymeric matrix. The research focused on improving the tactile sensor performance by enabling uniform dispersion of filler material and optimizing sensor design and structure. The doping weight ratio of MWCNTs in PDMS varied from 1 wt.% to 10 wt.% using the same grid structure-sensing layer (line width, line spacing, and thickness of 1 mm). The sensor with a 7 wt.% doping ratio had the most stable performance, with an observed sensitivity of 6.821 kPa−1 in the lower pressure range of 10–20 kPa and 0.029 kPa−1 in the saturation range of 30–200 kPa. Furthermore, the dimensions of the grid structure were optimized and the relationship between grid structure, sensitivity, and sensing range was correlated. The equation between pressure and resistance output was derived to validate the principle of piezoresistance. For the grid structure, dimensions with line width, line spacing, and thickness of 1, 1, and 0.5 mm were shown to have the most stable and improved response. The observed sensitivity was 0.2704 kPa−1 in the lower pressure range of 50–130 kPa and 0.0968 kPa−1 in the saturation range of 140–200 kPa. The piezoresistive response, which was mainly related to the quantum tunneling effect, can be optimized based on the dopant concentration and the grid microstructure. Furthermore, the tactile sensor showed a repeatable response, and the accuracy was not affected by temperature changes in the range of 10 to 40 °C and humidity variations from 50 to 80%. The maximum error fluctuation was about 5.6% with a response delay time of about 1.6 ms when cyclic loading tests were performed under a normal force of 1 N for 10,200 cycles. Consequently, the proposed tactile sensor shows practical feasibility for a wide range of wearable technologies and robotic applications such as touch detection and grasping.

Herein, activated carbon (AC) and carbon nanotubes (CNTs) were synthesised from potato peel waste (PPW). Different ACs were synthesised via two activation steps: firstly, with phosphoric acid (designated PP) and then using potassium hydroxide (designated PK). The AC produced after the two activation steps showed a surface area as high as 833 m 2 g −1 with a pore volume of 0.44 cm 3 g −1 , where the raw material of PPW showed a surface area < 4 m 2 g −1 . This can help aid and facilitate the concept of the circular economy by effectively up-cycling and valorising waste lignocellulosic biomass such as potato peel waste to high surface area AC and subsequently, multi-walled carbon nanotubes (MWCNTs). Consequently, MWCNTs were prepared from the produced AC by mixing it with the nitrogen-based material melamine and iron precursor, iron (III) oxalate hexahydrate. This produced hydrophilic multi-wall carbon nanotubes (MWCNTs) with a water contact angle of θ = 14.97 °. Both AC and CNT materials were used in heavy metal removal (HMR) where the maximum lead absorption was observed for sample PK with a 84% removal capacity after the first hour of testing. This result signifies that the synthesis of these up-cycled materials can have applications in areas such as wastewater treatment or other conventional AC/CNT end uses with a rapid cycle time in a two-fold approach to improve the eco-friendly synthesis of such value-added products and the circular economy from a significant waste stream, i.e., PPW. Graphical abstract .

The mechanical properties of carbon fiber-reinforced epoxy composites were identified by adding carbon-based nano-reinforcements, such as multi-wall carbon nanotubes (CNTs) and graphene platelets (GP), into the epoxy matrix by conducting suitable experiments. The main focus of this study is to compare the tensile modulus, tensile strength, flexural modulus, flexural strength, and thermal conductivity of carbon fiber-reinforced epoxy composites with nanoparticle reinforcement. The results revealed that adding CNTs and GP nanoparticles improved the mechanical properties compared to a pure carbon fiber-reinforced plastic composite. However, compared to CNTs, the GP’s addition has increased the mechanical properties of the CFRP composite. In addition, scanning electron microscopy (SEM) images were presented to explore the microstructural characterization of carbon fiber-reinforced nanoparticle-reinforced composites. Further, using numerical studies, the transverse modulus, major and minor Poisson’s ratio of the carbon fibre reinforced with CNT and GP particle reinforcement were estimated. The current study is applied to the efficient design of nanoparticle reinforced carbon fibre reinforced composites.

This study investigated the synergistic effect of carbon black/multi-wall carbon nanotube (CB/MWCNT) hybrid fillers on the physical and mechanical properties of Ethylene propylene diene rubber (EPDM) composites after exposure to high-pressure hydrogen gas. The EPDM/CB/CNT hybrid composites were prepared by using the EPDM/MWCNT master batch (MB) with 10 phr CNTs to enhance the dispersion of CNTs in hybrid composites. The investigation included a detailed analysis of cure characteristics, crosslink density, Payne effect, mechanical properties, and hydrogen permeation properties. After exposure to 96.3 MPa hydrogen gas, the hydrogen uptake and the change in volume and mechanical properties of the composites were assessed. We found that as the MWCNT volume fraction in fillers increased, the crosslink density, filler–filler interaction, and modulus of hybrid composites increased. The hydrogen uptake and the solubility of the composites decreased with an increasing MWCNT volume fraction in fillers. Moreover, after exposure to hydrogen gas, the change in volume and mechanical properties exhibited a diminishing trend with a higher MWCNT volume fraction. We conclude that the hybridization of CB and CNTs formed strong filler–filler networks in hybrid composites, consequently reinforcing the EPDM composites and enhancing the barrier properties of hydrogen gas.

The incorporation of carboxyl functionalized multi-walled carbon nanotube (MWCNT- COOH) into a polymethyl methacrylate (PMMA) has been investigated. The resultant tensile and flexural mechanical properties have been determined. In this paper, a novel synthesis process for a MWCNT-reinforced polymer nanocomposite is proposed. The proposed method significantly eliminates the most challenging issues of the nano-dispersed phase, including agglomeration and non-homogeneous mixing within a given matrix material, and also resolves the issues occurring in conventional mixing processes. The results of scanning electron microscopy support these claims. This 3D-mixing process is followed by an extrusion process, using a twin-screw extruder for pristine MWCNT, and a compression molding process for COOH-MWCNT, to prepare test specimens for experimentally determining the mechanical properties. The test specimens are fabricated using 0.1, 0.5, and 1.0 wt.% MWCNT, with a remaining PMMA phase. The testing is conducted according to ASTM D3039 and ASTM D7264 standards. Significant improvements of 25.41%, 35.85%, and 31.75% in tensile properties and 18.27%, 48%, and 33.33% in flexural properties for 0.1, 0.5, and 1.0 wt.% COOH-MWCNT in PMMA, respectively, compared to non-functionalized MWCNTs, were demonstrated. The highest strength was recorded for the nanocomposite with 0.5 wt.% f-MWCNT content, indicating the best doping effect at a lower concentration of f-MWCNT. The proposed CNT-PMMA nanocomposite may be found suitable for use as a scaffold material in the domain of bone tissue engineering research. This type of research possesses a high strength requirement, which may be fulfilled using MWCNT. Furthermore, this analysis also shows a significant amount of enhancement in flexural strength, which is clinically required for fabricating denture bases.

The fabrication of a simple, label-free, electrochemical immunosensor for C-reactive protein (CRP) detection is presented using a custom-designed printed circuit board (PCB) gold electrode. To enhance the sensitivity of the sensing platform, the surface of the gold working electrode was modified with multi-walled carbon nanotubes (MWCNTs), leveraging its exceptional conductivity and biocompatibility. The label-free immunosensor operates on immunological principles, with anti-CRP antibodies covalently immobilized on the modified electrode to capture and quantify CRP levels, using differential pulse voltammetry (DPV). The immunosensor demonstrated high specificity to CRP, exhibiting a linear detection range of 1.25 to 80 μg/mL of CRP in 1 × PBS, and achieving a detection limit (LOD) of 0.745 µg/mL within 30 min. Notably, the immunosensor successfully detected CRP in human ethylenediaminetetraacetic acid (EDTA)-anticoagulated whole blood with a detection limit of 0.177 µg/mL, which is within the clinical range for sepsis (5 µg/mL). Furthermore, this immunosensor was able to detect CRP using only 2 µL of EDTA-anticoagulated whole blood samples. These findings highlight the potential of the CRP immunosensor platform for point-of-care (POC) testing in clinical settings, owing to its simple fabrication, ease of operation, low cost, and robust performance. Graphical abstract

Nowadays, the detection of volatile organic compounds (VOCs) at trace levels (down to ppb) is feasible by exploiting ultra-sensitive and highly selective chemoresistors, especially in the field of medical diagnosis. By coupling metal oxide semiconductors (MOS e.g., SnO2, ZnO, WO3, CuO, TiO2 and Fe2O3) with innovative carbon-based materials (graphene, graphene oxide, reduced graphene oxide, single-wall and multi-wall carbon nanotubes), outstanding performances in terms of sensitivity, selectivity, limits of detection, response and recovery times towards specific gaseous targets (such as ethanol, acetone, formaldehyde and aromatic compounds) can be easily achieved. Notably, carbonaceous species, highly interconnected to MOS nanoparticles, enhance the sensor responses by (i) increasing the surface area and the pore content, (ii) favoring the electron migration, the transfer efficiency (spillover effect) and gas diffusion rate, (iii) promoting the active sites concomitantly limiting the nanopowders agglomeration; and (iv) forming nano-heterojunctions. Herein, the aim of the present review is to highlight the above-mentioned hybrid features in order to engineer novel flexible, miniaturized and low working temperature sensors, able to detect specific VOC biomarkers of a human’s disease.

In this research, a nanocomposite material, Bentonite cross-linked multi-walled carbon nanotubes@soduim alginate (Be/CNTs@Alg), was synthesized by impregnating multi walled carbon nanotubes (CNTs) using a mixture of sodium alginate (Alg) on the surface of activated bentonite (Be). The composite was employed as a sorbent material to effectively remove Fe(II) and Mn(II) from the groundwater. Numerous characterization methods such as X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Brauner-Emmett-Teller (BET) analysis were employed. The study evaluated the influence of various factors including temperature, adsorbent dosage, contact time, initial metal ion concentration, agitation rate, and pH on Fe(II) and Mn(II) adsorption. Results showed that CNTs penetrated the bentonite interlayers. The nanocomposite had a BET surface area of 40.885 m²/g. The adsorption of both metal ions was fast and highly pH-dependent, with monolayer adsorption capacities calculated from the linear fitting were of 7.6277 mg/g for Fe(II) and 6.1009 mg/g for Mn(II), and from nonlinear fitting were of 7.929 mg/g for Fe(II) and 7.39137 mg/g for Mn(II) at 25 °C. Kinetic data fit the PSO model, and thermodynamic analysis indicated that the process was spontaneous and endothermic. The spatial interpolation of Fe and Mn proves effective for visualizing and managing Beni-Suef Quaternary Aquifer quality. The findings highlight the potential of the Be/CNTs@Alg composite for the uptake of Fe(II) and Mn(II), and its possible application in the decontamination of other pollutants from real groundwater.