Multi-walled Carbon Nanotubes Research Articles

Fe2O3-decorated multiwall carbon nanotube composites for boosted microwave absorption

Developing microwave absorption (MA) materials with a strong absorption ability over a wide bandwidth through a simple and environmentally friendly approach remains a tremendous challenge. Herein, we propose to use an Fe3+–tannic acid framework to assist the dispersion of multi-walled carbon nanotubes (MWCNTs) and successfully prepare MWCNTs/porous carbon/α-Fe2O3 composites through freeze-drying and subsequent heat treatment. The dielectric properties and MA performance can be regulated by the heat treatment temperature, which leads to tunable crystalline structure, composition, and graphitization degree of MWCNTs. Consequently, the MWCNTs/porous carbon/α-Fe2O3 composite heat-treated at 300 °C exhibits a high reflection loss (RL) of −58.9 dB and an effective absorption bandwidth (5.28 GHz) with a matched thickness of 2.26 mm at a filler proportion of only 5 wt%, and the related frequency bandwidth with RL below -10 dB reaches 14.3 GHz at a thickness of 2–5 mm. In conclusion,the balance between conduction and polarization loss endows the composite with excellent impedance matching and boosting MA performance. This study offers a guideline for fabricating excellent MA materials through a simple, environmentally friendly method.

Investigation of the strain rate and stretch level dependent behavior of elastomeric nanocomposites in complex uniaxial tests under finite strains

The mechanical behavior of elastomeric nanocomposites in experiments with nested stress-strain cycles and cyclic tests with increasing strain amplitude were considered. In our proposed testing procedures, long time stops at each stage of the change in loading direction were of great importance. This revealed two significant features of the behavior of elastomeric nanocomposites that have received little attention. It was shown that material softening (the Mullins effect) should be considered not only in the elastic part of the Cauchy stress tensor, but also in its dissipative part. The second peculiarity was the difference between the characteristic relaxation time at loading and the characteristic relaxation time at unloading observed in the experiments.This paper focuses on the behavior of highly-filled elastomeric materials based on different matrices (styrene-butadiene rubber (SBR) and nitrile-butadiene rubber (NBR)) and with different concentrations of carbon black (CB) or a combination of two fillers (CB and purified multi-walled carbon nanotubes (MWCNTs)).A mathematical model of the viscoelastic behavior of elastomeric nanocomposites under finite strains was proposed. It takes into account the peculiarities of the behavior of highly filled elastomers observed in the experiments. The specificity of the model consists in a new variant of the form of the free energy potential. It was shown that the new model satisfies the thermodynamic inequality, which is a consequence of the first law of thermodynamics and the second law in the form of the Clausius-Duhem inequality. A good agreement between theoretical calculations and experimental data was obtained.

Effect of Carbon Nanotubes Functionalization on the Chemical Composition and Electrochemical Characteristics of Composites with Layered Potassium Manganese Oxide

The influence of pretreatment of multiwalled carbon nanotubes (MWCNTs) in oxidizers (solutions of H2O2 and HNO3) on the structure and electrochemical properties of composites with layered potassium-manganese oxide (KxMnO2) was studied. Composites were obtained by soaking carbon nanotubes in an aqueous solution of KMnO4 at 60 °C. The electrochemical performance of the composites was evaluated by cyclic voltammetry and galvanostatic charge‒discharge methods. It has been established that stronger oxidation of the MWCNTs surface at the functionalization stage leads to a noticeable increase in the reaction rate as well as the optimal potassium content in the KxMnO2 composition, which provides higher capacitive characteristics of the composite (a maximum specific capacitance of 150 F g−1 and a rate capability of 43% with increasing density current from 0.1 to 2.0 A g−1). The resulting composites are promising active components for increasing the capacitive characteristics of conductive carbon black (CB). Compared with an electrode based only on CB, electrodes based on a combination of the composite and CB at a mass ratio of 1:1 showed specific capacitance values approximately 1.5 to 3 times greater, as well as a twofold increase in rate capability (from 35 to 70%) in the range of discharge current density 0.1 to 2.0 A g−1.

Label-free electrochemical immunosensor for rapid and highly sensitive detection of Brucella abortus in serum

Accurate and efficient detection of Brucella is crucial to control the disease and mitigate its impact on animal health and human safety. In this study, a simple and rapid label-free electrochemical immunosensor for the detection of Brucella abortus was fabricated based on the principle of current decrease after specific capture of the bacteria. A certain proportion of multi-walled carbon nanotubes (MWCNTs), dopamine hydrochloride (DA), and gold nanoparticles (AuNPs) were modified on the surface of a gold disc electrode. Then, Brucella abortus antibody and bovine serum albumin (BSA) were immobilized in sequence to complete the assembly of the sensor. The electrodes from various assembly steps were characterized by a cyclic voltammetry (CV) curve. The immunosensor exhibited high sensitivity with a wide linear range between 10 CFU/mL and 108 CFU/mL. Additionally, the sensor displayed good repeatability, stability, and interference resistance. The recovery rates for low, medium, and high concentrations of bacteria were all within the range of 90 % to 100 %, indicating a high level of accuracy. The method established in this study can provide reference and assistance for early diagnosis of Brucella abortus in clinical practice.

Fe3O4/f‐MWCNTs Nanocomposite: Efficient Electrode Material for Symmetric Hybrid Supercapacitors with 25 k Cycle Stability

AbstractFe3O4 with acid functionalized multiwalled carbon nanotubes (f‐MWCNTs) was synthesized using a simple ultrasonic‐assisted co‐precipitation method. The structural, morphological, and elemental composition of the composite material were determined using P‐XRD, FT‐IR, SEM‐EDS, and BET analysis. The electrochemical properties of the composite were analysed by CV, CP and EIS techniques. In a three‐electrode system setup, a specific capacitance (Cs) of 509 Fg−1 at 2 mVs−1 and 116 Fg−1 at 2.5 Ag−1 was achieved in 1 M KOH solution. The composite material was utilized in the design of a symmetric supercapacitor coin cell (CR2032) device. The coin cell exhibited Cs of 49 Fg−1 at 2 mVs−1 (0 to 1.8 V) and 19.2 Fg−1 at 1 Ag−1 (0 to 1.75 V) in 1 M KOH electrolyte, with a Cs retention of 80 % at the end of 25,000 charge‐discharge cycles at a high current density of 20 Ag−1. The coin cell demonstrated a maximum energy density of 8.2 Whkg−1 and power density of 17.5 kWkg−1. This study highlights an inexpensive, environmentally benign hybrid supercapacitor composite material synthesized by a facile method as a promising candidate for high‐performance supercapacitor applications.

A novel molecularly imprinted composite–based electrochemical sensor constructed from o-phenylenediamine and gold nanoparticle–embedded multiwalled carbon nanotube for ultra trace level detection of triclosan

A novel molecularly imprinted composite–based electrochemical sensor constructed from o-phenylenediamine and gold nanoparticle–embedded multiwalled carbon nanotube for ultra trace level detection of triclosan

Facilely prepared extreme environments tolerable PIF /c-CNTx composites for piezoresistive sensor based on powder foaming strategy

Polyimide foams (PIF) are widely used in piezoresistive sensors due to their light weight and weather resistance to weathering at extreme temperatures. Nevertheless, the mechanical strength of PIF prepared by freeze-drying method is poor, with only tens to hundreds of kPa ranging from 50 % to 80 % compression. Herein, a polyimide composite reinforced with –COOH functionalized multi-walled carbon nanotubes (PIF/c-CNTx) was produced via a thermal foaming process using a powder-based method. The PIF/c-CNTx composites exhibit ultra-low density (0.165 g/cm3), excellent mechanical properties (compressive strength of up to 2.5 MPa at 60 % compressive strain, tens to hundreds of times higher than similar materials) as well as stable compressive properties and recoverability in liquid nitrogen and at high temperatures up to 200 ℃. The PIF/c-CNTx piezoresistive sensor achieves excellent sensing capability over a wide strain range high sensitivity (GF = 12.9) and exhibit good stability over 5000 s of cyclic compression at a compression rate of 10 mm/min. The stability and reproducibility of the strong piezoresistive signal at extreme temperatures shows the great potential of PIF/c-CNTx composites as structural components under extreme conditions for applications in aerospace and polar exploration.

A simple strategy to significantly improve the anticorrosion and aging resistance of epoxy coatings by adding polyaniline modified multi-walled carbon nanotubes

Epoxy coatings are widely used for corrosion protection of metals, but under extremely harsh environments, the epoxy polymer chains such as the C-O bonds of epoxy ether and aromatic ether, and the -OH in the epoxy chain structure can also undergo aging and degradation, leading to the failure of the coating in service. How to extend the anti-aging capability of epoxy resins while maintaining their other properties unchanged has become a major challenge in the practical application of epoxy coatings. In this study, the polyaniline (PANI) modified multi-walled carbon nanotubes (MWCNT@PANI) were synthesized by polymerization in-situ and added to epoxy resin as an anti-aging filler. The various measurements have been adopted to characterize the composition and structure of MWCNT@PANI, and the anticorrosive performance of the composite coating for carbon steel were evaluated via salt spray, chemical aging and UV light aging. Results showed that the impedance value of the blank epoxy coating decreases by at least two orders of magnitude after the salt spray tests, and the contact angle decreases by about 30° and gradually changes from hydrophobic to hydrophilic, indicating a significant decline in corrosion resistance. In contrast, the composite coating confirmed the excellent anti-aging performance, while the impedance values increased by approximately 2-5 orders of magnitude compared to that in blank epoxy coatings, and remained around 1010 Ω·cm2. Given the dense encapsulation of MWCNT@PANI, the dispersion stability between the filler and EP can be improved, and the effective corrosion resistance performance was also supported by molecular dynamic simulation. Besides that, the ability of free radical quenching along with the labyrinth effect and hydrophobic interaction have also been investigated to explain the anticorrosion and anti-aging mechanism.

Compositing LaSrMnO3 perovskite and graphene oxide nanoribbons for highly stable asymmetric electrochemical supercapacitors

The anticipated large contribution of renewable energy resources to the sector of energy production strongly motivated the development of energy storage technologies, of which supercapacitors have drawn a lot of attention. In this work, Lanthanum-Strontium-Manganese-oxide (LSMO) perovskite nanoparticles, graphene oxide nanoribbons (GONRs), and LSMO-GONRs composite were synthesized and tested as electrode materials for supercapacitor applications. The LSMO was synthesized using the co-precipitation/calcination method, while the GONRs were synthesized using the oxidative unzipping of multi-walled carbon nanotubes. The physical/chemical structures were studied using XRD, FT-IR, SEM, TEM, SAED, and XPS. In 1 M KOH, the LSMO-GONRs electrode exhibited a specific capacitance of 490F/g compared to 342F/g and 294F/g for GONRs and LSMO electrodes, respectively, at 1 A/g, showcasing a performance that is not just superior but truly impressive, to the different types of perovskite/carbon-based material composites. The fabricated asymmetric SC device of LSMO-GONRs//GONRs exhibited a potential window of 1.7 V, a specific capacitance of 92.3F/g, an energy density of 38 Wh/kg, and a power density of 860 W/kg at 1 A/g. Moreover, the LSMO-GONRs//GONRs device showed excellent capacity retention and Coulombic efficiency after 10,000 cycles at 10 A/g, revealing the promising employment of LSMO-GONRs composite as a highly stable material for supercapacitor applications.

Fabrication and performance assessment of coin cell supercapacitors with multiwalled carbon nanotube-supported mixed metal oxide nanocomposites and redox additive electrolyte

In the realm of supercapacitor applications, the fabrication of coin cell supercapacitors with superior performances played a crucial role. In this work, an asymmetrical type coin supercapacitor was fabricated with multiwalled carbon nanotube supported mixed metal oxide (CuO/CoO@MWCNT - CCM) nanocomposites (NCs) and potassium ferrocyanide incorporated KOH based redox additive electrolyte (RAE). The synergistic effect and the enhanced conductivity by the mixed metal oxides and MWCNT, respectively, were acted as the performance enhancer for electrode performances. On the other hand, RAE with optimized concentration provided additional redox active sites for superior performances. The combined effect of CCM NCs and RAE, were responsible for the superior performances. CCM NCs were prepared by one-pot hydrothermal technique and characterized. Working electrodes with CCM NCs were fabricated by doctor blade method and evaluated in KOH and RAE. It exhibited 1838.55 Fg−1 of specific capacitance (Csp) in RAE. Assembled asymmetrical supercapacitors with CCM NCs modified working electrode and activated carbon based anode, delivered 123.91 Fg−1 of Csp at 2.75 Ag−1 in RAE. The assembled supercapacitors delivered the highest energy density of 27.53 Wh kg−1 and power density of 1875 W kg−1 in RAE with an impressive 82.89 % of cyclic retention after 5000 GCD cycles. Finally, an asymmetric coin cell supercapacitor (CR2302) was fabricated with CCM NCs and RAE. The fabricated coin cell delivered the charge and discharge capacities of 157.72 and 55.99 mAh g−1, respectively in KOH, whereas these values were significantly improved 172.46 and 126.2 mAh g−1 respectively, in RAE. It proved that the fabricated coin cell supercapacitors performed well in terms of maximum charge and discharge performances in RAE compared to conventional KOH.

Hydrothermal synthesis and characterization of samarium molybdate nanosheets modified multi-walled carbon nanotubes: real-time analysis of dimetridazole in environmental and biological samples

Dimetridazole (DMZ) is commonly used as a veterinary drug, resulting in high emissions and environmental pollution and DMZ residues are carcinogenic, genotoxic, and mutagenic to humans. Therefore, it is essential to construct a fast, sensitive and simple sensor to monitor DMZ. In this study, samarium molybdate nanosheets modified multi-walled carbon nanotube composites (SmM/MWCNT) were synthesized to modify GCE for detecting DMZ. The SmM/MWCNT material was also characterized by various analytical and spectroscopic techniques, such as FE-SEM, HRTEM, FT-IR, Raman spectroscopy, XRD, elemental mapping and XPS, to demonstrate the successful synthesis of the composite. Besides, the electrochemical behavior of SmM/MWCNT /GCE for DMZ was also investigated using CV and DPV, and the modified electrode showed good electrochemical sensing performance for DMZ with a low detection limit (0.08 μM), a wide linear range (0.1∼1000 μM), and excellent selectivity. Finally, the SmM/MWCNT/GCE was successfully applied to detect DMZ in environmental and biological samples, and satisfactory recoveries (95%∼105%) were obtained. To the best of our knowledge, the synthesis of SmM/MWCNT and its application in electrochemical sensors are reported for the first time, which demonstrates that it can provide a new route for real-time monitoring of environmental pollutants.

Printed flexible supercapacitors utilizing composites of MWCNT/MOF ultrathin nanosheets: Exploring 1D/2D structural adjustment

The self-stacking propensity of metal–organic frameworks (MOFs) during synthesis, combined with their intrinsic limitations in electrical conductivity and mechanical stability, constrains their utility as high-capacity energy sources in wearable electronics. Here, we employ a surfactant-assisted method to mitigate the Z-axis stacking of zinc metalloporphyrin organic frameworks (NMOFs), yielding ultrathin two-dimensional (2D) material sheets. By integrating carboxyl multiwalled carbon nanotubes into these nanosheets (denoted as C-NMOF-x), the lamellar structure of MOF is preserved while promoting the formation of rich multistage micropores and continuous conductive channels. This structural refinement remarkably enhances electrochemical properties, including capacitance, electronic conductivity, and cycling stability. Leveraging synergistic interactions, the resulting C-NMOF-4 composite achieves a specific capacitance of 0.152 mAh/g in a three-electrode system at a current density of 1 A/g. Furthermore, the modulated C-NMOF-4 composites are successfully formulated into homogeneous e-inks suitable for dispensing printing, enabling the mass production of flexible micro-supercapacitors (MSCs). Notably, these MSCs maintain 95 % of their capacitance even after 180° bending under wearable conditions. This surface and interface microstructure modulation strategy holds promise for enhancing the synergistic coupling effects of 2D materials and offers new avenues for the application of innovative 2D materials in wearable electronics.

Incorporation of SnSe2/SnO2 heterostructures in carbon nanotubes for excellent lithium storage performance

As a new type of negative electrode material, tin-based material exhibits a high theoretical capacity. However, tin-based anode materials always undergo severe volume change upon alloying reaction during lithium insertion and extraction, which leads to the pulverization of the active materials and poor electrochemical performance, seriously hampering its practical application. In this work, oxygen-containing group functionalized carbon nanotubes (FCNTs) were facilely obtained, and the three-dimensional crosslinked SnSe2-SnO2@FCNTs multiphase materials were prepared by solvothermal and high-temperature heat treatment. The formation of Sn-O-C bonds from oxygen-containing functional groups of FCNTs combined with Sn can promote the electric connection and integrity of the composites. The implanted defects in FCNTs can not only be beneficial to anchoring SnO2 and SnSe2 nanoparticles, but also helpful to the penetration of Li+ ions into the electrodes from electrolyte. In addition, the large Fermi energy difference between SnSe2 and SnO2 nanoparticles results in the formation of a built-in electric field at the interface of the multiphase materials, accelerating the diffusion of ions. The smaller size of the multiphase materials leads to significant pseudocapacitive behavior, which facilitates the highly reversible surface/interface adsorption. Under the multiple effects of FCNTs, SnSe2, and SnO2, the SnSe2-SnO2@FCNTs multiphase materials exhibited excellent electrochemical performance. At a current density of 0.1A·g-1, a discharge specific capacity of 898.0mAh·g-1 was achieved. When the current density was increased to 2A·g-1, it still exhibited a discharge specific capacity of 443.9mAh·g-1. After a long charge/discharge cycling at 1A·g-1 over 450 cycles, it still showed a specific capacity of ~ 400mAh·g-1. This work significantly demonstrated the enhanced Li-storage performance of SnSe2-SnO2 heterostructures incorporated in the functionalized multi-walled CNTs. This opens a new way to synthesize advanced tin-based materials as high-performance anodes for high-energy density lithium-ion batteries.

Synergistic effect of nickel and graphite powders on the thermoelectric properties of ultra-high-performance concrete containing steel fibers and MWCNTs

The study investigates the influence of multi-walled carbon nanotubes (MWCNTs) and conductive powders, namely nickel powder (NP) and graphite powder (GP), on the mechanical and thermoelectric properties of ultra-high-performance concrete (UHPC). Flowability tests indicate that the addition of MWCNTs and conductive powders affects the flow diameter, with higher concentrations resulting in decreased flowability. Thermalgravimetric analysis and Fourier transform infrared spectroscopy reveal that the enhancement of the hydration reaction by 0.1 % MWCNTs in UHPC reaches saturation at this concentration. Pore structure analysis demonstrates a reduction in porosity and a denser structure upon the addition of 0.1 % MWCNTs. Mechanical tests indicate that the incorporation of 0.1 % MWCNTs enhances compressive and tensile strengths, whereas the introduction of 0.3 % MWCNTs diminishes the mechanical performance. Moreover, the electrical conductivity and thermoelectric effect are enhanced with the addition of MWCNTs and conductive powders. However, a decline in thermoelectric effect is observed when 0.3 % MWCNTs are added, although the conductivity remained high. The optimal thermoelectric performance is achieved with the combination of 0.3 % MWCNTs and 5 % NP, yielding a maximum power factor (PF) of 2148.2 μW/m·K2 and a figure of merit (ZT) of 4.9 × 10⁻7.

Systematic Comparison of Extract Clean-Up with Currently Used Sorbents for Dispersive Solid-Phase Extraction

Dispersive solid-phase extraction (dSPE) is a crucial step for multiresidue analysis used to remove matrix components from extracts. This purification prevents contamination of instrumental equipment and improves method selectivity, sensitivity, and reproducibility. Therefore, a clean-up step is recommended, but an over-purified extract can lead to analyte loss due to adsorption to the sorbent. This study provides a systematic comparison of the advantages and disadvantages of the well-established dSPE sorbents PSA, GCB, and C18 and the novel dSPE sorbents chitin, chitosan, multi-walled carbon nanotube (MWCNT), and Z-Sep® (zirconium-based sorbent). They were tested regarding their clean-up capacity by visual inspection, UV, and GC-MS measurements. The recovery rates of 98 analytes, including pesticides, active pharmaceutical ingredients, and emerging environmental pollutants with a broad range of physicochemical properties, were determined by GC-MS/MS. Experiments were performed with five different matrices, commonly used in food analysis (spinach, orange, avocado, salmon, and bovine liver). Overall, Z-Sep® was the best sorbent regarding clean-up capacity, reducing matrix components to the greatest extent with a median of 50% in UV and GC-MS measurements, while MWCNTs had the largest impact on analyte recovery, with 14 analytes showing recoveries below 70%. PSA showed the best performance overall.

Exceeding the theoretical limit of interfacial evaporation efficiency by using the carbon-based aerogel evaporator with cold evaporation surface

Solar-driven interfacial evaporation technology has shown significant potential in the field of water treatment. Heat loss is still inevitable during the SIE process, since the temperature at the evaporation interface surpasses both the ambient temperature and the temperature of the water below. In this study, we presented a study on an aerogel composed of reduced graphene oxide (rGO), multi-walled carbon nanotubes (MWCNTs) and polypyrrole (PPy). The self-aggregation effect of rGO was mitigated through π-π interactions with MWCNTs and PPy, resulting in the formation of a three-dimensional porous structure. This provided the aerogel with a large specific surface area for pollutant adsorption and ample pore volume for photo-induced degradation and photothermal water purification. Using infrared thermography, thermocouples and numerical simulation, it was demonstrated that introducing a cold evaporation surface resulted in thermal flow reversal. This process allowed the evaporator to extract energy from bulk water, thereby enhancing solar evaporation. Due to this gain, under one sun illumination, the aerogel reached an evaporation rate as high as 3.31 kg·m−2·h−1 and achieved an evaporation efficiency of 135.6 %. Simultaneously, the aerogel exhibited a photocatalytic efficiency of over 90 % for various organic pollutants (methylene blue trihydrate, trypan blue and tetracycline hydrochloride). Moreover, it also demonstrated excellent purification ability for combined wastewater, including high-salinity water, seawater and lubricant/water emulsions. Therefore, high-performance interfacial evaporators hold great promise for achieving sustainable wastewater purification and serve as a valuable reference for the development of new solar energy conversion systems.

Evaluation of the Chemical Structure and Thermal Properties of Polyethylene Glycol (PEG)-Doped Polylactic Acid (PLA)/Multiwalled Carbon Nanotube (MWCNT) Composites

This study aimed to investigate the chemical structure, thermal properties, and stability of polylactic acid (PLA) composites blended with multi-walled carbon nanotubes (MWCNTs) and polyethylene glycol (PEG). The composites were fabricated using a masterbatch blending method with two different molecular weights (Mw) of PEG. The masterbatch was initially prepared using solvent casting with chloroform as the solvent, followed by melt blending using an extruder. ATR-FTIR spectroscopy identified strong hydrogen bonds between the C=O groups of PLA and the –OH groups of PEG, as evidenced by the peak at 1748 cm¹. Differential Scanning Calorimetry (DSC) revealed that incorporating 14 wt% of PEG 10,000 into PLA/MWCNT composite significantly enhances the melting enthalpy (∆Hm) from 18.3 J/g to 24.6 J/g and the degree of crystallinity from 2% to 17.3%. The glass transition temperature (Tg) decreased with the addition of PEG, indicating increased chain mobility, while the melting temperature (Tm) remained relatively constant around 158 oC regardless of the PEG Mw. Despite the plasticizing effect of PEG, the thermal stability of the composites was maintained across different PEG Mw. Scanning Electron Microscope (SEM) images showed that MWCNTs were well dispersed within the blend, facilitated by ultrasonic stirring during preparation.

Trace RuO2 nanoparticles loaded nickel-coated multi-walled carbon nanotubes to boost hydrogen evolution reaction under acidic and alkaline media

Developing low-cost catalysts with high activity for the Hydrogen Evolution Reaction (HER) is a main challenge to reduce the dependence on precious metals while maintaining the catalytic activity. In this study, nickel-plated multi-walled carbon nanotubes (Ni-MWCNTs) with a large number of active sites were selected, and Ni-MWCNTs electrocatalysts loaded with trace amounts of RuO2 nanoparticles were prepared by annealing treatment, which exhibited excellent HER performances in both acidic and alkaline media. The RuO2 nanoparticles loaded nickel-coated multi-walled carbon nanotubes (RuO2@Ni-MWCNTs) had a small electrochemical impedance spectrum (EIS) and a large electrochemically active surface area (ECSA). Notably, RuO2@Ni-MWCNTs with less than 1 % Ru content exhibited excellent catalytic activities in both acidic and alkaline solutions. The results showed that the overpotentials of RuO2@Ni-MWCNTs were 20.2 mV (alkaline) and 73.7 mV (acidic), respectively. After stabilization at 20 mA cm−2 for 90 h, the evaluation results showed that RuO2@Ni-MWCNTs could maintain their catalytic efficiency without significant degradation.

Alkali and Non-alkali Treated Coconut Coir Fiber-Reinforced Coconut Shell Powder/MWCNT-Filled Polyester Matrix Composite: An Experimental Comparison

Engineering, biomedical, and medicinal applications effectively employ the extraction of natural resources. Natural and recycled natural fibers are highly advantageous for producing hard-core and soft-core composite materials and equipment. Natural fiber processing can yield diverse material characteristics. Particularly, processes such as chemical treatment, heat treatment, fine coating, and polishing (gold) composites can significantly enhance the characteristics of these materials. A further selection of non-synthetic solutions is designated for material application and environmentally friendly biodegradation to the earth. Due to the non-destructive nature of composites, many synthetic resources are incorporated into the environment, which can lead to corrosion and atmospheric pollution. Therefore, the remarkable movement toward replacing these compounds with natural coconut fiber, whether refined or untreated, shell powder, and composites incorporating multi-walled carbon nanotubes (MWCNT) contributes to establishing a more environmentally sustainable society. This work included rigorous mechanical testing to compare the effects of alkali and non-alkali treatments. In particular, the tensile strength is 17.06% higher, the flexural strength is 7.35% higher, and the hardness on Shore D is 5.81% higher than that of non-alkali-treated material. The SEM analysis revealed the alkali-treated and untreated composites' consecutive failure zones, regions, and matrix structures.

Volatile capacitance of resistor with differential resistance

The differential current dV/dR in a resistor forms a volatile capacitance across itself. When the differential current is less than the Ohm current, V/R, the volatile capacitance is positive. Conversely, when it exceeds the Ohm current, the volatile capacitance becomes negative. If the differential current equals the Ohm current, the volatile capacitance is zero. The transition of this volatile capacitance from positive to negative has been observed in a combination of multi-walled carbon nanotube material and vacuum space. Additionally, we have fabricated a two-dimensional planar inductor without a coil using this negative capacitor.