Functionalized Carbon Nanotubes Research Articles

Functionalized Carbon Nanotube Guided Growth of HMX Crystals with Improved Thermal Stability and Reduced Sensitivity

Functionalized Carbon Nanotube Guided Growth of HMX Crystals with Improved Thermal Stability and Reduced Sensitivity

Polyethyleneglycol-polyhydroxylbutyrate functionalized carbon nanotubes for industrial electroplating wastewater treatment

This study focuses on the production and purification of multi-walled carbon nanotubes (P-CNTs) via a catalytic chemical vapor deposition method and subsequent functionalization with amino polyethylene glycol (NH2-PEG) and its mixture with polyhydroxybutyrate (PHB) through a multi-step purification process to produce NH2-PEG-CNTs and NH2-PEG-PHB-CNTs, respectively. The developed nanoadsorbents were used to treat electroplating wastewater via batch adsorption to sorb potentially toxic metals and emerging pollutants. The nanoadsorbents were characterized before and after treatment with wastewater after thermal regeneration analyzed using HRSEM/EDS/SAED, DLS Nanozetasizer, BET, TGA/DTG, and FTIR. The nanoadsorbents showed a homogeneous distribution of clean and smooth crystalline interwoven tubular/cylindrical shapes and sizes, with broad polydispersed/high aspect ratio, large surface area, mesopores, and functional groups. The batch adsorption study showed simultaneous multi-capturing of toxic metals from industrial electroplating wastewater with a directly proportional relationship between contact time, adsorbent dosage andtemperature, and electrostatic activities via the positive surface charge of the nanoadsorbents (pH > pHzpc). The highest removal of Fe (15.86 %), Ni (79.82 %), Pb (79.82 %), and Cu (84.97 %) were obtained using NH2-PEG-PHB-CNTs. In addition, the ANOVA results show that the adsorption process depends on other parameters such as the concentration of toxic metals in the wastewater, its hydration energy, electronegativity, ionic mobility in the electrostatic activities, pH of the nanoadsorbents, water holding capacity of the polymer-functionalized nanoadsorbents, and synergistic effects of the bi-polymer. Moreover, the nanoadsorbents have a stable morphology after thermal regeneration for reusability purposes, and treated wastewater can be safely reused in the electroplating industry or for other purposes, such as agriculture.

Calculation of Density of States of Pristine and Functionalized Carbon Nanotubes: A DFT Approach

Calculation of Density of States of Pristine and Functionalized Carbon Nanotubes: A DFT Approach

Thermal properties and mechanical behavior of functionalized carbon nanotube-filled polypropylene composites using molecular dynamics simulation

Polypropylene (PP) is widely recognized as an environmentally friendly material for cable insulation due to its good insulation performance and environmental friendliness. One common method for enhancing the overall performance of PP is the addition of nanoparticles. To analyze the influence of different functionalized multi-walled carbon nanotubes (MWCNT) fillers on the properties of PP/MWCNT composite materials from a microscale perspective, molecular dynamics is used to construct pure PP models and models filled with untreated carbon nanotubes (UFCNT), amino-functionalized carbon nanotubes (AFCNT), carboxyl-functionalized carbon nanotubes (CFCNT), and hydroxyl-functionalized carbon nanotubes (HFCNT) (functionalized MWCNT with 4 or 8 functional groups grafted onto them). The simulation results indicate that the doping of nanotubes can effectively enhance the thermodynamic properties of PP. Among them, PP/CFCNT-8 exhibits the most significant improvement in melting temperature and mechanical properties, with an increase in melting temperature of 88.85 K and a 184.52 % increase in Young's modulus. The melting temperature of PP/HFCNT-8 is second only to PP/CFCNT-8, with an increase of 82.59 K. The results indicate that the thermodynamic properties of PP nanocomposites filled with functionalized MWCNT are improved with the grafting rate. The filling of functionalized MWCNT alters the microscale properties of PP composites, with a significant decrease in root mean square displacement (RMSD), and improvement in free volume fraction (FFV) as well as interfacial binding energy, which can better maintain the electrical properties of PP insulation materials. Applying functionalized carbon nanotubes to filled PP can significantly increase the electrical insulation properties of PP cable materials, which provides meaningful guidance for adopting polypropylene cable insulation materials.

Influence mechanism of functionalization of CNTs on the thermal transport property of their nanofluids

Carbon nanotube (CNT) nanofluids have promising application prospects as the working fluids in energy and power systems due to their prominent thermal properties, while the poor stability of CNT nanofluids is one of the biggest obstacles to their practical application. The addition of functional groups on CNTs is a good method to improve the dispersion of CNT nanofluids, while the influence mechanism of this strategy on the thermal transport property is not clear. In this work, the thermal conductivities of CNT, CNT-OH, and CNT-COOH nanofluids were investigated by experiments and molecular dynamics (MD) simulations to reveal the influence mechanism of functionalization on the thermal transport ability of CNT nanofluids. Both experimental measurements and MD simulations indicate the significant suppression of functionalization on the thermal transport property of CNT nanofluids. Furthermore, the influence mechanism of functional groups on the thermal conductivity of CNT nanofluids has been revealed by analyzing the effect of the thermal conductivities of CNTs, the formation of hydrogen bonds, the mean square displacement of water molecules, and the interlayer thermal resistance of CNT and water. This work is helpful to the utilization of CNT nanofluids as working fluids in energy systems.

Artificial intelligence models for methylene blue removal using functionalized carbon nanotubes

This study aims to assess the practicality of utilizing artificial intelligence (AI) to replicate the adsorption capability of functionalized carbon nanotubes (CNTs) in the context of methylene blue (MB) removal. The process of generating the carbon nanotubes involved the pyrolysis of acetylene under conditions that were determined to be optimal. These conditions included a reaction temperature of 550 °C, a reaction time of 37.3 min, and a gas ratio (H2/C2H2) of 1.0. The experimental data pertaining to MB adsorption on CNTs was found to be extremely well-suited to the Pseudo-second-order model, as evidenced by an R2 value of 0.998, an X2 value of 5.75, a qe value of 163.93 (mg/g), and a K2 value of 6.34 × 10–4 (g/mg min).The MB adsorption system exhibited the best agreement with the Langmuir model, yielding an R2 of 0.989, RL value of 0.031, qm value of 250.0 mg/g. The results of AI modelling demonstrated a remarkable performance using a recurrent neural network, achieving with the highest correlation coefficient of R2 = 0.9471. Additionally, the feed-forward neural network yielded a correlation coefficient of R2 = 0.9658. The modeling results hold promise for accurately predicting the adsorption capacity of CNTs, which can potentially enhance their efficiency in removing methylene blue from wastewater.

Fabrication of an efficient hierarchical mesoporous 2D-MoS2/CNT/polypyrrole based composite electrodes for competitive and selective U6+ removal using capacitive deionization: Mechanistic evaluation through cyclic voltammetry

In this work, efficient and selective carbonaceous electrode materials based on hierarchical mesoporous functionalized carbon nanotubes, 2D-MoS2 nanosheets electrodeposited with variable content of polypyrrole (PPy) were prepared. The simple etching reaction between HNO3 and carbon nanotubes did not only modify the surface but also improved its hydrophilicity. The annealing of carbon nanotubes and electrodeposition of PPy increased the mesopore volume to total volume ratio (Vmeso/Vt) from 0.42 to 0.86. The composite materials were characterized wisely using different characterization techniques and employed for efficient U6+ electro-assisted sorption through capacitive deionization. Electrode material with PPy content (0.3 M) exhibited good specific capacitance Csp (100.2 F/g), improved Vmeso (0.61 cm3/g), superb Vmeso/Vt ratio (0.86) and large specific surface area SBET (149.7 m2/g). The stated electrode showed fast sorption kinetics (teq=30 min), admirable selectivity and exhibited the experimental sorption capacity of 274.50 mg/g at − 0.90 V. Electrochemical impendence spectroscopic study revealed that the resulting material exhibited relatively small charge transfer resistance (1.19 Ωcm2), minute electrolytic resistance (0.91 Ωcm2) and large double layer constant phase element (0.0368 S sn/ cm2). These significant characteristics promoted U6+ ions diffusion inside the hierarchical porous electrode surface for better performance of electrosorption process. This new class of hierarchical mesoporous composite electrodes may be used as potential supercapacitor materials not only for removal of uranium but also for other potent desalination applications.

High strength, anti-static, thermal conductive glass fiber/epoxy composites for medical devices: A strategy of modifying fibers with functionalized carbon nanotubes

Abstract A series of aliphatic amine-functionalized multiwalled carbon nanotubes (MWCNTs) wherein varied secondary amine numbers were grafted on the MWCNTs’ surface were synthesized and further dispersed onto the glass fibers for reinforcing epoxy-based composites. By tuning secondary amine numbers of aliphatic amines, the dispersion of MWCNTs and ultimately mechanical, thermal, and conductive properties of epoxy-based composites could be adjusted. Using an optimal secondary amine number of aliphatic amine (triethylenetetramine), the interlaminar shear strength, tensile strength, and flexural strength of epoxy-based composite increased by 43.9%, 34.8%, and 35.0%, respectively; the work of fracture after interlaminar shear tests increased by 233.9%, suggesting strengthening/toughening effects of functionalized MWCNTs; significant reduction in surface resistance and increased thermal conductivity were also obtained, implying the superior conductive properties for composites. This work offers a new strategy for designing fiber-reinforced composites with high strength, excellent antistatic properties, and good thermal conductivity for medical device applications.

Response Surface Modeling of the Steady-State Impedance Responses of Gas Sensor Arrays Comprising Functionalized Carbon Nanotubes to Detect Ozone and Nitrogen Dioxide.

Carbon nanotube (CNT) sensors provide a versatile chemical platform for ambient monitoring of ozone (O3) and nitrogen dioxide (NO2), two important airborne pollutants known to cause acute respiratory and cardiovascular health problems. CNTs have shown great potential for use as sensing layers due to their unique properties, including high surface to volume ratio, numerous active sites and crystal facets with high surface reactivity, and high thermal and electrical conductivity. With operational advantages such as compactness, low-power operation, and easy integration with electronics devices, nanotechnology is expected to have a significant impact on portable low-cost environmental sensors. Enhanced sensitivity is feasible by functionalizing the CNTs with polymers, metals, and metal oxides. This paper focuses on the design and performance of a two-element array of O3 and NO2 sensors comprising single-walled CNTs functionalized by covalent modification with organic functional groups. Unlike the conventional chemiresistor in which the change in DC resistance across the sensor terminals is measured, we characterize the sensor array response by measuring both the magnitude and phase of the AC impedance. Multivariate response provides higher degrees of freedom in sensor array data processing. The complex impedance of each sensor is measured at 5 kHz in a controlled gas-flow chamber using gas mixtures with O3 in the 60-120 ppb range and NO2 between 20 and 80 ppb. The measured data reveal response change in the 26-36% range for the O3 sensor and 5-31% for the NO2 sensor. Multivariate optimization is used to fit the laboratory measurements to a response surface mathematical model, from which sensitivity and selectivity are calculated. The ozone sensor exhibits high sensitivity (e.g., 5 to 6 MΩ/ppb for the impedance magnitude) and high selectivity (0.8 to 0.9) for interferent (NO2) levels below 30 ppb. However, the NO2 sensor is not selective.

Synergistic Effect of Carbon-Based Reinforcements on the Mechanical Properties of Cement-Based Composites

Carbon reinforcements are used to improve the mechanical properties of cement, allowing the preparation of a strengthened and toughened composite. Functionalization through a reaction with acid is necessary to guarantee both a good dispersion in water and a strong interaction with cement. Different functionalized reinforcements improve the mechanical properties of the composites in comparison with pristine cement. The use of a combination of carbon fibers, carbon nanotubes, and graphene nanoplatelets were analyzed in order to verify their synergistic effect. The use of functionalized carbon nanotubes and carbon fibers demonstrates an improvement of 71% in flexural strength and 540% in fracture energy.

Sensitive Detection of a Gaseous Analyte with Low‐Power Metal–Organic Framework Functionalized Carbon Nanotube Transistors

AbstractA highly sensitive and low‐power sensing platform for detecting ethanol molecules by interfacing high‐purity, large‐diameter semiconducting carbon nanotube transistors with a metal–organic framework layer is presented. The new devices outperform similar graphene‐based metal–organic framework devices by several orders of magnitude in terms of sensitivity and power consumption, and can detect extremely low ethanol concentrations down to sub‐ppb levels while consuming only picowatts of power. The exceptional sensor performance results from the nanotube transistor's high on/off ratio and its sensitivity to charges, allowing for ultra‐low power consumption. The platform can also compensate for shifts in threshold voltage induced by ambient conditions, making it suitable for use in humid air. This novel concept of MOF/CNTFETs could be customized for detecting various gaseous analytes, leading to a range of ultra‐sensitive and ultra‐low power sensors.

The oxygen-doped self-supporting functional carbon nanotube sponge realized the synergistic enhancement of lithium ion transport and lithium polysulfide reaction

Lithium-sulfur (Li-S) batteries are one of the most promising energy storage systems, in which the severe shuttle effect causes the loss of the sulfur active species and unacceptable capacity and cycling stability. Here, a self-supporting functional carbon nanotube sponge (FCNTS), electrostatically repelling polysulfide anions and allowing Li+ to pass through, is synthesized by etching channels and introducing enriched anions on CNTs based on the “Donnan effect”. The experimental results confirmed that FCNTS accelerated the Li-ion transport, that is, the Li+ transfer rates of the FCNTS materials were 8.226 (Li2S4 reduction) and 3.627 times (Li2S oxidation) that of the CNTs blank samples, respectively. Meanwhile, defects and O-group modified FCNTS regulated the local charge density of carbon-based materials, which enriched the reduction current response of the soluble Li2S4 and the oxidation current of Li2S2/Li2S around the cathode more than 1.9 and 1.6 times that of the CNTs blank samples, respectively. This significantly improved the kinetics and suppressed the overpotential. Thus, the cells assembled by S@FCNTS achieved a high-rate performance (866.9 mAh∙g−1 at 2 C), excellent stability (fading rate of only 0.035% per cycle after 500 cycles at 2 C), and a high area capacity of 13.2 mAh∙cm−2 at a high sulfur load of 10.9 mA∙cm−2. This work demonstrates a dynamic polysulfide-interception strategy to facilitate the utilization of polysulfides and provides a promising idea for the design of multi-functional sulfur storage electrode materials for high-load LSBs.

Evaluation of Fe3O4 incorporated functionalized carbon nanotube self-standing buckypaper as electrodes for solid-state symmetric supercapacitor

Iron (II, III) oxide and carbonaceous materials drawn considerable attention in energy storage owing to their special features. In this study, simple reverse co-precipitation, acid functionalization and vacuum filtration methods adopted to synthesis Fe3O4 nanoparticles of size 11 nm and –COOH acid functionalized multi-wall carbon nanotubes (FMWCNT). And further used them to prepare and optimize Fe3O4 in FMWCNT as 15 wt% and 25 wt% self-standing buckypapers of around 30-μm thickness as electrodes for solid-state symmetric capacitor in the form of coin cell. The results show that 15 wt% and 25 wt% of Fe3O4-FMWCNT buckypapers hybrid nanostructures have Fe3O4 nanoparticles successfully incorporated in FMWCNT. The 25 wt% Fe3O4-FMWCNT electrodes with charge transfer resistance of 140 Ohm showed high areal specific capacitance (Cs) 78.5 mF/cm2 and retained 80 % of its Cs until 800 cycles even at high current density of 1 mA/cm2, scan rate of 100 mV/s whereas 15 wt% Fe3O4-FMWCNT showed low Cs of 47 mF/cm2 and retained 80 % of its Cs over 5000 cycles whereas only FMWCNT show Cs is 36 mF/cm2 with 54 Ohm. Finally, a solid-state symmetric supercapacitor coin cell with self-standing 25 wt% Fe3O4-FMWCNT buckypaper showed an excellent power density of 129.5 mW cm−3 and energy density of 3.6 mWh cm−3 is the innovation of the current work. This is mainly attributed to the combined effect of pseudocapacitive behavior from Fe3O4 by faradaic reaction with additional charge transfer resistance and electric double layer (EDLC) behavior from FMWCNTs by non-faradaic of electronic, ionic transport during charging-discharging. As-made solid-state symmetric supercapacitor appears as a high-performance storage device without extra support of current collectors for practical applications and for fabrication of planar capacitors.

A review on adsorption of heavy metals from wastewater using carbon nanotube and graphene-based nanomaterials.

The rampant rise in world population, industrialization, and urbanization expedite the contamination of water sources. The presence of the non-biodegradable character of heavy metals in waterways badly affects the ecological balance. In this modern era, the unavailability of getting clear water as well as the downturn in water quality is a major concern. Therefore, the effective removal of heavy metals has become much more important than before. In recent years, the attention to better wastewater remediation was directed towards adsorption techniques with novel adsorbents such as carbon nanomaterials. This review paper primarily emphasizes the fundamental concepts, structures, and unique surface properties of novel adsorbents, the harmful effects of various heavy metals, and the adsorption mechanism. This review will give an insight into the current status of research in the realm of sustainable wastewater treatment, applications of carbon nanomaterials, different types of functionalized carbon nanotubes, graphene, graphene oxide, and their adsorption capacity. The importance of MD simulations and density functional theory (DFT) in the elimination of heavy metals from aqueous media is also discussed. In addition to that, the effect of factors on heavy metal adsorption such as electric field and pressure is addressed.

Chemiresistive sensing with functionalized carbon nanotubes

Chemiresistive sensing with functionalized carbon nanotubes

Chemiresistive sensing with functionalized carbon nanotubes

Chemiresistive sensing with functionalized carbon nanotubes

Interfacial bonding mechanism between fire exposed and functionalized carbon nanotube mortar

Reinforced concrete structures need to be repaired after exposure to fire, in which the weakness of the interfacial transition zone between the repair mortar and the old concrete substrate is a crucial problem. Carbon nanotube can be added into repair mortar to address the above-mentioned problem because of its bridging, pore filling and nucleation effects. However, the bonding mechanism of functionalized carbon nanotube repair mortar and the old concrete is not yet fully understood. Therefore, this study investigates the bonding performance between different functionalized carbon nanotube repair mortar and old mortar substrate exposed to high temperature. Firstly, to evaluate the roughness of old mortar exposed to high temperature, three-dimensional microscope and mercury intrusion porosimetry were performed in this paper. Secondly, thermogravimetric analysis and X-ray diffraction were carried out to further analyze the phase composition of the repair mortar. Thirdly, microstructure of the interfacial transition zone was investigated by electron backscatter diffraction characterization and microhardness measurements. Fourthly, the bonding mechanism of interface between new and old mortar was discussed. The results show that the surface roughness of the old mortar can gradually increase with increasing of temperature, which improves the interfacial mechanical interlocking. The functionalized carbon nanotube can reduce the content and orientation of calcium hydroxide and improve the microhardness of the interfacial transition zone. Finally, an interfacial bonding strength prediction model considering porosity and the reinforcing effects of different functionalized carbon nanotube is proposed. The findings of current study can benefit further research and application of nanomaterials in the field of structural repair and maintenance.

Investigation of thermal properties of carbon nanotubes and carboxyl group - functionalized carbon nanotubes

Thermal properties characterizations for carbon nanotubes (CNTs), carboxyl group-functionalized carbon nanotubes (FCNT), and graphite were presented in the paper. TGA/DSC and TEM techniques were used for characterization. The features of TGA characteristics transformation for synthesized carbon nanomaterials were investigated. The specific heat capacities of the samples at a constant pressure increased as the temperature increased.

Enhanced extreme temperature bending and delamination resistance of GFRP composites through z-directional aligned nano-reinforcement: Emphasizing the effects of CNT functionalization

Laminated FRP composites' weak out-of-plane mechanical performance prevents their usage in structural applications where homogeneous load bearing qualities are required. In this regard, a z-directional nano-reinforcement approach was implemented to mitigate the poor in-plane shear and out-of-plane response of laminated glass fiber epoxy (GE) composites under extreme in-service temperature conditions. CNT and functionalized CNT (FCNT) were dispersed separately in the GE composites' epoxy matrix and subjected to a z-direction electric field alignment treatment. Flexural and short beam shear tests of GE composites with random and aligned CNT/FCNT were performed at room temperature, in-situ cryogenic and elevated temperature conditions (RT, CT and ET, respectively). GE composite with aligned FCNT (A-FCNT-GE) consistently outperformed other composites at all considered temperatures with remarkable improvements, specifically ∼39%, ∼41% and ∼47% in flexural strength, and ∼30%, ∼30%, and ∼24% in interlaminar shear strength (ILSS) over the control GE composite at RT, CT and ET, respectively. Dynamic mechanical thermal analysis suggested that the synergetic impact of functionalization and alignment of FCNT improved the viscoelastic properties of the A-FCNT-GE composite across a range of temperature conditions. Fractography analysis provided insight into the interfacial and interlayer mechanisms that improved the extreme temperature condition mechanical performance. The reliability of electric field aligned FCNT as a z-directional nano-reinforcement in laminated composites at extreme temperature conditions was established in this study.

Recent advances of carbon nanotubes in perovskite solar cells

AbstractPerovskite solar cells (PSCs) have exhibited tremendous potential in photovoltaic fields owing to their appreciable performance and simple fabrication. Nevertheless, device performances are still required to be further improved before commercial applications. As one‐dimensional materials, carbon nanotubes (CNTs) have been utilized to regulate stability and efficiency of PSCs because of their excellent chemical stability, flexibility, as well as tunable optical and electrical characteristics. In this review, we comprehensively summarize various functions of CNTs in PSCs, such as transparent electrodes, hole/electron‐transport layers, counter electrodes, perovskite additives, and interlayers. Additionally, applications of CNTs toward the advancement of flexible and semitransparent PSCs are provided. Finally, we preview the challenges and research interests of using CNTs in high‐efficiency and stable perovskite devices.