Surface Of Multi-walled Carbon Nanotubes Research Articles

Highly sensitive flexible pressure sensor based on laser ablated Ag-MWCNT /MXene for human motion detection

The complex and dynamic human environment, higher requirements are put forward for the high-performance flexible pressure sensors. The materials selection and microstructure design are crucial to achieve high sensitivity and stability. In this work, we fabricated pressure sensitive layer with multiple dimensional materials. Using laser ablation in liquid method, Ag nanoparticles were uniformly distributed in surface of multi-walled carbon nanotubes (MWCNT). Combined with the delaminated MXene, highly pressure sensitive composite could be prepared due to the reduction of contact resistance under pressure. The corresponding piezoresistive sensors showed high sensitivity (12.7 kPa−1), excellent response speed (150 ms), recovery speed (100 ms), and distinguished cycle stability (3000 cycles). Based on the performance of the sensor, it can realize the monitoring of tiny pressure on the human body, and further realize the detection of human activities and health. In addition, the sensor array has spatial recognition capability, providing a way of thinking for the development needs of future intelligent wearable electronic devices. The sensors can measure changes in resistance caused by finger bending, slight breathing, pulse, vocal cord vibration, and other movements to realize human activity and health monitoring. At the same time, the 3×3 sensor array system can recognize the layout of pressure in space. This simple preparation and low cost of the sensor can Facilitate the progress towards sophisticated wearable electronic gadgets.

Synthesis of Nitronyl Nitroxide Radical-Modified Multi-Walled Carbon Nanotubes and Oxidative Desulfurization in Fuel.

Novel and highly stable nitronyl nitroxide radical (NIT) derivatives were synthesized and coated on the surface of multi-walled carbon nanotubes (MWCNTs) to improve their desulfurization performance. They were characterized by FTIR, UV-vis, SEM, XRD, Raman spectroscopy and ESR. Thiophene in fuel was desulfurized by molecular O2, and the oxidation activity of these compounds was evaluated. At a normal temperature and pressure, the degradation rates of thiophene by four compounds in 4 h can reach 92.66%, 96.38%, 93.25% and 89.49%, respectively. The MWCNTs/NIT-F have a high special activity for the degradation of thiophene, and their desulfurization activity can be recycled for five times without a significant reduction. The mechanistic studies of MWCNTs/NIT composites show that the ammonium oxide ion is the key active intermediate in catalytic oxidative desulfurization, which provides a new choice for fuel oxidative desulfurization. The results show that NIT significantly improves the photocatalytic performance of MWCNTs.

Multimodal generation of luminol electrochemiluminescence through TEMPO functionalized carbon nanotubes

The utilization of an elaborate nanomaterial is still a prevalent method to generate luminol electrochemiluminescence (ECL). Herein, we report on the multimodal generation of anodic and cathodic luminol ECL through a metal-free nanomaterial. This nanomaterial was prepared by covalently grafting 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) on the surface of multi-walled carbon nanotube (MWCNT). TEMPO-MWCNTs modified electrode exhibit high electrocatalytic activities toward H2O, luminol, H2O2 and O2 during the oxidation/reduction processes. Such electrocatalysis has not only resulted in significant enhancement of luminol ECL, but also enabled the generation of three ECL peaks in luminol/O2 system and two ECL peaks in luminol/H2O2 system on the electrode via different pathways. The natures of these ECL peaks are also revealed through the spooling ECL spectra. Furthermore, an ECL sensor has been designed for sensitive detection of an organophosphorus pesticide (OP) based on the enhanced ECL of luminol/H2O2 system. Therefore, this work suggests that nitroxyl radical functionalized carbon nanomaterial can be used as a new electrocatalyst for studying luminol ECL in the presence of either an endogenous or exogenous co-reactant.

Novel electrochemiluminescence sensing platform for ultrasensitive detection of malathion residue in tea based on SiO2NSs doped Luminol/AgNPs as a signal amplification strategy

To address the potential hazards of organophosphorus pesticides (OPs) residues in tea, an electrochemiluminescence (ECL) aptasensor based on functionalized nanomaterials was constructed in this work. Firstly, gold nanoparticles (AuNPs) were attached on the surface of multi-walled carbon nanotubes (MWCNTs) by the constant potential electrodeposition to form a compound, and it was utilized to provide excellent immobilization sites for complementary DNA (cDNA). Subsequently, composite nanomaterials were synthesized by a one-pot method with aminated Luminol/silver nanoparticles@silica nanospheres (NH2-Luminol/Ag@SiO2NSs). Finally, NH2-Luminol/Ag@SiO2NSs was combined with a malathion aptamer (Apt) to obtain signal probes (SPs) for the construction of an aptasensor. The aptasensor had a wide linear range (1×10−3-1×103 ng/mL) and a low limit of detection (LOD) (0.3×10−3 ng/mL). It had the virtues of high sensitivity, wonderful stability and excellent specificity, which could be used for the detection of malathion residue in tea. The work provides a proven way for the construction of a rapid and ultrasensitive aptasensor with low-cost.

Heterogenization of Ionic Liquid on Multiwalled Carbon Nanotubes for Lead(II) Ion Detection.

The presence of lead(II) ion poses a significant threat to water systems due to their toxicity and potential health hazards. The detection of Pb2+ ions in contaminated water is very crucial. The ionic liquid functionalized multiwalled carbon nanotubes (IL@MWCNT) nanocomposite was fabricated using ionic liquid (IL) 1-methyl-3-(4-sulfobutyl)-imidazolium chloride and multiwalled carbon nanotubes (MWCNTs) for detection of lead(II) ions. It is a novel method to heterogenize the layer of IL on the surface of MWCNTs. The XPS and FTIR analyses confirm that the ionic liquid is not decomposed during annealing process. Moreover, the XRD analysis shows the presence of MWCNTs and carbon quantum dots (CQDs). The HRTEM results exhibit the aggregation of MWCNTs with IL, and formation of small distorted round shaped flakes of CQDs. Further, the successful heterogenization of IL on the surface of MWCNTs is also confirmed by TGA-DSC analysis. The quenching phenomenon of nanocomposite was observed by UV-Visible spectroscopy. The nanocomposite exhibits high performance for the selective detection of lead(II) ions in comparison to other metal ions. The presence of lead(II) ions eventually reduced the intensity of absorption. A limit of detection (LOD) of 9.16 nM was attained for Pb2+ ions in a concentration range of 0-20 nM.

Nano-Titanium Oxide-Coated Carbon Nanotubes for Photothermal Therapy in the Treatment of Colorectal Cancer.

Recent studies have shown that carbon nanotubes display good potential in tumor photothermal therapy. In this study, we aimed to investigate the therapeutic potential of nano-titanium oxide-coated multi-walled carbon nanotubes (MCNTs) against colorectal cancer (CRC). Firstly, we modified TiO2 nanosheets on the surface of MCNTs to obtain nano-TiO2-coated MCNTs. Next, we conducted cell compatibility validation on nano-TiO2-coated MCNTs, and found that nano-TiO2-coated MCNTs were safe within a certain concentration range (0∼200 μg/ml). Interestingly, nano-TiO2-coated MCNTs displayed a good killing effect in CRC cells under NIR laser irradiation. Subsequently, nano-TiO2-coated MCNTs markedly promoted the proapoptotic effects of NIR laser irradiation, and significantly inhibited the expression of cell cycle proteins CCNA1 and CCND1 in CRC cells under NIR laser irradiation, which indicated that nano-TiO2-coated MCNTs exerted anti-CRC effects under NIR laser irradiation by regulating cell apoptosis and cell cycle. Furthermore, nano-TiO2-coated MCNTs accelerated inhibitory effects on the AKT signaling pathway under NIR laser irradiation. Finally, a cell line-derived xenograft model was established, and the results showed that nano-TiO2-coated MCNTs significantly exhibited superior tumor-killing ability under NIR laser irradiation in vivo. Collectively, our results demonstrate that nano-TiO2-coated MCNTs with NIR laser irradiation may serve as an effective strategy for the treatment of CRC. This article is protected by copyright. All rights reserved.

Nano-etching of carbon nanofiber surface and subsequent Fe–N–C thin film coating for enhancement of oxygen evolution reaction

The oxygen evolution reaction (OER) is involved in many electrical–chemical energy conversion systems; however, the slow reaction rate of the OER leads to a high overpotential (η) and low energy efficiency. Recently, an extremely low-η OER phenomenon was observed at a carbonaceous Fe–N-doped thin film with enriched step edges on highly oriented pyrolytic graphite and the carbon fiber surface in an alkaline electrolyte, although the activity was limited. In this study, multi-walled carbon nanotubes (MWCNTs) were used as substrates to utilize their high specific surface areas to develop an active OER catalyst. Nanoscale etching of the MWCNT surface was performed by Fe3O4 nanoparticle loading and subsequent heat treatment in an inert atmosphere, followed by acid washing. Afterwards, a carbonaceous thin film containing Fe and N was coated on the surface via sublimation, deposition, and pyrolysis of Fe phthalocyanine (Pc). A roughened surface was observed for the FePc-derived thin film coated on the nano-etched MWCNT, in contrast to the smooth surface observed for the film coated on the MWCNT without nano-etching. The combination of the nano-etching and the thin-film coating enhanced the OER, which was analyzed by parallel Tafel processes.

Effect of MWCNTs surface functionalization on the characterization of PVA/MWCNTs nanocomposites

The present study aims to put forward the role of surface functionalization of multi-walled carbon nanotubes (MWCNTs) on the enhancement thermal and hydrophilicity properties of new nanocomposite based poly(vinyl alcohol)/surface functionalized MWCNTs (PVA/MWCNTs), prepared by a facile phase inversion process. In this study, the fabrication of PVA/MWCNTs nanocomposites is carried out using functionalized MWCNTs (f-MWCNTs) with different functional groups (–OH, –COOH, –NH2). The structural, morphological, thermal, hydrophilicity and physico-chemical properties of PVA/MWCNTs nanocomposites are characterized by XRD, FE-SEM, FT-IR, TGA and contact angle measurement. The FT-IR results confirm the formation of a hydrogen bond between MWCNTs and PVA chain. XRD analysis indicates an improvement in the crystallinity of the PVA/MWCNTs nanocomposite. TGA results reveal that the PVA/f-MWCNTs nanocomposites show higher thermal stability than pure PVA. It is revealed that PVA/MWCNTs nanocomposites based functionalized MWCNTs remarkably increase the degradation temperature, and thus enhancing the thermal properties. The highest weight loss (30.7 wt%) and degradation temperature (520 °C) values are obtained with PVA/f-MWCNTs(0.5 wt%). The contact angle measurement confirms that the hydrophobic properties of pure PVA became hydrophilic because of the functional groups of MWCNTs. The hydrophilicity of PVA/MWCNTs nanocomposites is increased with the increase in wt% of MWCNTs embedded in the nanocomposite.

Recyclable Ag-Au bimetallic nanoparticles supported on acid functionalized multi walled carbon nanotubes for effective catalytic applications

In the present investigation, in situ green reduction approach is used to uniformly decorate the Ag-Au bimetallic nanoparticles (BNPs) on the surface of acid functionalised multi-walled carbon nanotubes (MWCNTs). The adsorbed Terminalia catappa aqueous leaf extract biopolymers on the surface of MWCNTs can increase the in situ reduction of Ag, Au ions to Ag-Au BNPs and stabilise them which can operate as a capper/stabiliser and reductant agent. X-ray diffraction (XRD), high-resolution transmission electron microscopy (HR-TEM), scanning electron microscopy - energy dispersive x-ray spectroscopy (SEM-EDX), Fourier-transform infrared spectroscopy (FT-IR) and UV–visible spectroscopy techniques were employed to examine the structures, morphologies, composition, chemical bonds and optical properties of the functionalised MWCNTs and the nanohybrid. The results revealed that the spherical T.C-Ag-Au bimetallic nanoparticle with average size 12.4 nm was uniformly distributed on the surface of modified MWCNTs. Finally, evaluation of the catalytic activity of the T.C-Ag-Au BNPs decorated MWCNTs exhibited excellent catalytic performance for completing the reduction of 4-Nitrophenol (4-NP) and degradation of alizarin red (AR) dye at ambient temperature with a great rate constant and the degradation efficiency of 98.7% and 96.4%, respectively. The order of reaction, rate constant, half-life and mechanism of catalytic activity of the T.C-Ag-Au BNPs@COOH-MWCNTs nanohybrid were calculated using the Langmuir–Hinshelwood model. The catalyst can be retained and reapplied eight times without affecting its catalytic performance. The interaction between T.C-Ag-Au BNPs and MWCNTs has a synergistic effect, which is accountable for the enhanced catalytic activity.

Impact of Atomic Vacancy Defects on Vibrational Characteristics of Chiral MWCNT for Viruses/Bacteria

In this study the authors investigated the vibrations performance of chiral multi-walled carbon nanotubes (MWCNTs). They examined chiral MWCNTs with attached bacteria positioned at both the tip and middle sections of the nanotubes. The main goal of this research was to create a sensor with the ability to detect and distinguish bacteria or viruses that could potentially adhere to the surfaces of chiral MWCNTs. The authors considered two boundary conditions, fixed-fixed and fixed -free for the chiral MWCNT. They utilized a molecular structural mechanics approach. In this approach the vibrational responses of chiral MWCNT-based nano-biosensors with different diameters of the chiral MWCNTs were examined. The study’s objective was to fill research gaps by introducing an innovative approach for detecting defects in chiral MWCNTs through vibrational analysis. They simulated 432 MWCNT samples to investigate the vibrational performance of defective chiral MWCNTs. The results suggested that the first mode of the vibrational frequency of the chiral MWCNT is particularly significant for sensing applications. It was observed that as the percentage of vacancy defects increased, the natural frequency decreased for both boundary conditions.

Enhancement of oxygen evolution reaction by in situ growth PMo12@ZIF-67 on MWCNTs via perylene bisimide-based dispersant

The combination of metal organic frameworks (MOFs) and multi-walled carbon nanotubes (MWCNTs) can significantly improve their electrochemical performance. However, in most cases, chemical pre-treatment of MWCNTs is inevitable, which may compromise the ideal performance of the final composites. Herein, via a noncovalent functionalization method, PMo12@ZIF-67 was in situ grown on the surfaces of MWCNTs with the assistance of a new dispersant containing two triethylenetetramine (TETA) segments. In order to enhance the coordination of Co metal ions with the surface of MWCNTs, phenolic hydroxyl groups were incorporated into the dispersant through reaction with gallic acid (GA). After annealing, homogeneous CNT/Co6Mo6C2/Co composites were obtained, and they showed excellent performance on oxygen evolution reaction (OER). At a current density of 10 mA cm−2, the lowest overpotential is 263 mV, of which the performance is superior to that achieved by other in situ growth methods. The uniform distribution of coordination sites and subsequent in situ growth of MOFs on MWCNTs improved the electrical conductivity of the derivatives, thereby enhanced the utilization of catalytic active sites. This study presents a novel approach for synthesizing carbon-doped electrocatalytic materials, which demonstrates significant potential in various electrochemical applications.

Enzyme-free glucose detection via scalable and economical fabrication of nickel-polyvinylpyrrolidone-modified multi-walled carbon nanotubes

Development of accurate, reliable, and affordable glucose detection tools remains a top scientific priority. Nanotechnology and related materials are frequently utilized for this purpose. In this study, polyvinylpyrrolidone (PVP)-modified nickel (Ni) nanoparticles on multi-walled carbon nanotube (MWCNT) were prepared using a unique microwave synthesis technique. The synthesized particles were investigated by transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). TEM analysis revealed that well-dispersed Ni nanoparticles with an average size of about 4.11 nm were uniformly dispersed on the MWCNT surface in the presence of PVP particles. The obtained NiPVP@MWCNT was used for the glucose sensor and its performance was investigated. According to the results, the limit of detection (LOD) and limit of quantification (LOQ) values for NiPVP@MWCNT nanocomposite in the linear range of 0.1 mM - 1 mM were calculated as 0.364 mM and 1.215 mM, respectively. As a result of the selectivity test, it was observed that it was highly selective for glucose and the current values increased with increasing concentration. The developed nanostructures are efficient, highly stable, discriminative, and sensitive and have the potential to be used as glucose sensors in the market.

Electrochemical DNA-nano biosensor for the detection of Goserelin as anticancer drug using modified pencil graphite electrode.

Goserelin is an effective anticancer drug, but naturally causes several side effects. Hence the determination of this drug in biological samples, plays a key role in evaluating its effects and side effects. The current studies have concentrated on monitoring Goserelin using an easy and quick DNA biosensor for the first time. In this study, copper(II) oxide nanoparticles were created upon the surface of multiwalled carbon nanotubes (CuO/MWCNTs) as a conducting mediator. The modified pencil graphite electrode (ds-DNA/PA/CuO/MWCNTs/PGE) has been modified with the help of polyaniline (PA), ds-DNA, and CuO/MWCNTs nanocomposite. Additionally, the issue with the bio-electroanalytical guanine oxidation signal in relation to ds-DNA at the surface of PA/CuO/MWCNTs/PGE has been examined to determination Goserelin for the first time. It also, established a strong conductive condition to determination Goserelin in nanomolar concentration. Thus, Goserelin's determining, however, has a 0.21 nM detection limit and a 1.0 nM-110.0 µM linear dynamic range according to differential pulse voltammograms (DPV) of ds-DNA/PA/CuO/MWCNTs/PGE. Furthermore, the molecular docking investigation highlighted that Goserelin is able to bind ds-DNA preferentially and supported the findings of the experiments. The determining of Goserelin in real samples has been effectively accomplished in the last phase using ds-DNA/PA/CuO/MWCNTs/PGE.

Geometric Transformation of Modified Multiwalled Carbon Nanotubes-Based Heterometallic Nanostructured Material: A Model for the Electrochemical Discrimination of Insecticides.

Multifunctional carbon-based materials exhibit a large number of unprecedented active sites via an electron transfer process and act as a desired platform for exploring high-performance electroactive material. Herein, we exemplify the holistic design of a heterometallic nanostructured material (MWCNTs@KR-6/Mn/Sn/Pb) formed by the integration of metals (Mn2+, Sn2+, and Pb2+) and a dipodal ligand (KR-6) at the surface of multiwalled carbon nanotubes (MWCNTs). First, MWCNTs@KR-6 was readily synthesized via a noncovalent approach, which was further sequentially doped by Mn2+, Sn2+, and Pb2+ to give MWCNTs@KR-6/Mn/Sn/Pb. The designed material showed excellent electrochemical activity for the discrimination of insecticides belonging to structurally different classes. In contrast to that of the individual building components, both the stability and electrochemical activity of heterometallic nanostructured material were remarkably enhanced, resulting in a magnificent electrochemical performance of the developed material. Hence, the current work reports a comprehensive synthetic approach for MWCNTs@KR-6/Mn/Sn/Pb synthesis by synergizing unique properties of the heterometallic complex with MWCNTs. This work also offers a new insight into the design of multifunctional carbon-based materials for discrimination of different analytes on the basis of their redox potential.

New perspectives of Pt–CeO2 system: stabilization on MWCNTs for boosting activity and water‐resistance in CO oxidation at ambient temperatures

The present study elucidates new perspectives regarding the Pt–CeO2 system for CO oxidation. The successful deposition of highly dispersed Pt–CeO2 species onto the surface of multiwalled carbon nanotubes (MWCNTs) led to the formation of abnormally active and water‐resistant catalysts. The catalysts were investigated by structural (XRD, TEM), spectral (XPS), and kinetic (TPR–CO+O2, TPR–CO, TPR–H2) methods. The application of TPR–CO+O2 revealed the remarkably high activity of all Pt–CeO2/MWCNTs catalysts at temperatures below 0 °C. The study of the catalysts at ambient temperature demonstrated high CO conversion in the presence of water vapor at a concentration of 100 ppm CO. The experimental findings suggest that active sites, comprising platinum structures stabilized directly on the surface of MWCNTs, play a pivotal role in the oxidation of CO under humid conditions. A dual–site approach was employed to develop a kinetic model that effectively describes the experimental data. This model provides valuable insights into the mechanism of wet CO oxidation.

Polymerizable deep eutectic solvents: Convenient reactive dispersion media for the preparation of novel multi-walled carbon nanotubes-based functional materials

A new straightforward and green approach for the covalent functionalization of multi-walled carbon nanotubes (MWCNTs) was developed. This carbon nanostructure was efficiently derivatized by polymerizing proper deep eutectic monomers (DEM), a subclass of deep eutectic solvents (DES), based on a series of mono- and bis-vinyl imidazolium salts endowed with different functional groups (–OH, –NH2, –NH3+Br–) in the side chain or in the spacer. Herein, DEM systems played a triple role as convenient dispersion media for MWCNTs, efficient reactive systems, and also as structure-directing agents for the radical-initiated polymerization process onto the surface of MWCNTs. In addition, the new methodology allowed obtaining highly functionalized hybrid materials, as shown by thermogravimetric analyses, in short reaction times (<1h). Transmission electron microscopy (TEM) revealed that the polymeric network orderly develops along the surface of the nanotubes, which act as templating agent for both mono- and bis-vinyl imidazolium salts, despite the random nature of the polymerization process for the latter species. This new functionalization strategy of MWCNTs stands out for its environmentally friendly and time-saving nature leading to the formation of materials with significant potential for applications in a plethora of research fields. As a proof of their possible application, we tested these new hybrid materials as recoverable and recyclable catalysts for the conversion of CO2 into cyclic carbonates under solvent-free conditions, showing good catalytic performances, even in the absence of additional co-catalysts.

Curcumin coating: a novel solution to mitigate inherent carbon nanotube toxicity

Multi-walled Carbon Nanotubes (MWCNTs) are inert structures with high aspect ratios that are widely used as vehicles for targeted drug delivery in cancer and many other diseases. They are largely non-toxic in nature however, when cells are exposed to these nanotubes for prolonged durations or at high concentrations, they show certain adverse effects. These include cytotoxicity, inflammation, generation of oxidative stress, and genotoxicity among others. To combat such adverse effects, various moieties can be attached to the surface of these nanotubes. Curcumin is a known anti-inflammatory, antioxidant and cytoprotective compound derived from a medicinal plant called Curcuma longa. In this study, we have synthesized and characterized Curcumin coated-lysine functionalized MWCNTs and further evaluated the cytoprotective, anti-inflammatory, antioxidant and antiapoptotic effect of Curcumin coating on the surface of MWCNTs. The results show a significant decrease in the level of inflammatory molecules like IL-6, IL-8, IL-1β, TNFα and NFκB in cells exposed to Curcumin-coated MWCNTs as compared to the uncoated ones at both transcript and protein levels. Further, compared to the uncoated samples, there is a reduction in ROS production and upregulation of antioxidant enzyme-Catalase in the cells treated with Curcumin-coated MWCNTs. Curcumin coating also helped in recovery of mitochondrial membrane potential in the cells exposed to MWCNTs. Lastly, cells exposed to Curcumin-coated MWCNTs showed reduced cell death as compared to the ones exposed to uncoated MWCNTs. Our findings suggest that coating of Curcumin on the surface of MWCNTs reduces its ability to cause inflammation, oxidative stress, and cell death.Graphical (a) Synthesis of Curcumin-coated-Lysine-functionalized MWCNTs. (b) Flow of research depicting experimental groups and studies performed along with the underlying techniques used.

Ligand Exchange Reaction between Ferrocene and Multiwalled Carbon Nanotubes: A Contemporary Approach.

Ligand exchange reaction (LER) between carbon nanoparticles and ferrocene (Cp2Fe) was conducted several times, but there was no convincing evidence of half-sandwich CpFe+ coordination to multiwalled carbon nanotubes (MWCNT). In this study, MWCNT is modified by LER with ferrocene using AlCl3/Al as a catalytic system. The modified MWCNT (Fc-MWCNT) are investigated for better understanding of the processes taking place on the surface of MWCNT using different spectroscopic and electrochemical methods. The formation of the Fe-C covalent bond between CpFe+ and MWCNT is confirmed by changes in the Raman spectrum of Fc-MWCNT compared to pristine MWCNT. The densest structure of Fc-MWCNT is investigated by transmission electronic microscopy. According to density-functional theory calculations of the model interaction between Fe and coronene, the Fe-C bond length is 2.1687-2.1855 Å. X-ray photoelectron spectroscopy also confirms the coordination of the Fe atom to MWCNT by analysis of oxidation states of Fe 2p and deconvolution of C 1s. Utilization of cyclic voltammetry corroborated MWCNT modification via LER. These data are important for both theoretical and practical applications due to increased interest in LER-modified compounds in different areas including thermoelectric devices, sensors, and its potential application in the field of molecular machine construction.

Effects of PVA fibers and multi-walled carbon nanotubes reinforcement on uniaxial compression fatigue properties of Engineered geopolymer composites

As a new type of green and environmentally friendly cementing material, engineered geopolymer composites (EGC) have broad application prospects. In this study, uniaxial compression fatigue tests were conducted to investigate the fatigue properties of geopolymer material. A total of 137 samples were tested to investigate the effects of carbon nanotubes content, polyvinyl alcohol (PVA) fibers volume content, and maximum stress level on the fatigue life and deformation of geopolymers. The results showed that the fatigue life of geopolymers obeys Weibull distribution, and PVA fibers and multi-walled carbon nanotubes (MWCNTs) achieved multiscale enhancement of the fatigue life by up to 16.34 times. The total strain accumulation, residual strain, and fatigue stiffness of the geopolymers under fatigue loading exhibited a three-stage evolution rule, with stability within the secondary creep branch. In the process of EGC production, the innovative adoption of optimized MWCNTs surface modification and dispersion strategies improved the uniformity of MWCNTs distribution in the matrix. Scanning electron microscopy (SEM) confirmed the hybridization of MWCNTs and PVA fibers at the microscopic level, which can achieve multi-scale enhancement of geopolymers. This study successfully optimized the content of MWCNTs and PVA fibers, further expanding the application range of composite materials.

Effect of thiol-modified carbon nanotubes on curing, mechanical, and thermophysical properties of poly(ethylene trisulfide)

Herein, we performed grafting of thiol groups to the surface of multi-walled carbon nanotubes. Then, using them (CNTS), zinc oxide (ZnO), ethylene dichloride, and sodium trisulfide (Na2S3), poly(ethylene trisulfide) (PETS) nanocomposites were synthesized via in situ polymerization. After that, the samples were cured at 170°C using a rheometer. The structural characteristics of CNTS were identified by Fourier transform infrared (FTIR), Raman spectroscopies, and X-ray diffraction (XRD). The PETS characteristics were investigated by FT-IR, Raman, X-ray diffraction (XRD), and proton nuclear magnetic resonance (1H NMR). Also, the samples were studied using scanning electron microscopy (SEM), Shore A, tensile tests, and differential scanning calorimetry (DSC). The results showed that CNTS has a significant effect on the curing time of the nanocomposites, so that the curing time decreases with increasing CNTS content. Moreover, the nanocomposites had improved mechanical properties, indicating that they are more resistant to deformation and fracture. In addition, after the curing process, the melting temperature (Tm ) was not observed, and by increasing CNTS in composites, the glass transition temperature (Tg ) occurs at higher temperatures. Furthermore, the hardness of the samples showed a slight increase with higher CNTS content.