Plasma-functionalized Carbon Nanotubes Research Articles

A New Design Strategy Enables High Mn‐Utilization Rate in Aqueous Zinc–Manganese Batteries: Constructing Cathodic Local Mn‐Rich Region

AbstractThe deposition–dissolution mechanism with a two‐electron transfer reaction endows aqueous Zn–Mn batteries with a desirable theoretical energy density. However, due to the limited solubility of traditional manganese‐based materials and the competitive Mn shuttle behavior, the practical performance is unsatisfactory. Herein, by synergistically incorporating a novel Mn‐rich Mn4N cathode with a plasma functionalized carbon nanotubes film (PCNT) interlayer, an aqueous Zn–Mn battery with a high Mn‐utilization rate and high energy/power density is successfully developed. Specifically, the Mn4N cathode boasts high manganese content and dissolution activity, thereby offering a copious supply of Mn2+ ions for the battery system. The PCNT interlayer, with abundant micropore structures and functional groups, not only restrains the Mn2+ shuttle by entrapping the dissolved Mn2+ but also offers copious reaction sites, ensuring concentrating Mn2+ on the cathodic side and maximizing their contribution to the electrochemical reaction. Consequently, Mn4N‐PCNT exhibits a low polarization voltage and superior Mn‐utilization rate (64.8%). Without the MnSO4 additive, Mn4N‐PCNT achieves an ultra‐high energy density of 821.9 W h kg−1 and remarkable long‐term cycling stability (90% capacity retention over 9000 cycles). The delightful results demonstrate the practical application potential of Mn4N‐PCNT and open up new avenues for the rational design of advanced Zn–Mn batteries.

Surface functionalization of carbon nanotubes via plasma discharge: A review

• Plasma is mainly used as a non-destructive and fast method for the functionalization of carbon nanotubes. • The nature change of the carbon nanotubes occurs via functional groups formed on nanotubes using plasma functionalization. • Plasma Functionalized carbon nanotubes can dramatically improve some properties in the polymer matrix. • The creation of active sites on nanotubes by the plasma treatment can be used for grafting with metals. The use of carbon nanotubes in a wide range of academic and industrial fields has received considerable attention due to their uniqueness in structures and properties. Despite these advantages, there are still some significant challenges and drawbacks such as insolubility which can have negative impacts on the application process. The introduction of functional groups on the surface of carbon nanotube can overcome this obstacle. Plasma functionalization can be a preferred method in comparison to other ones as a quick and relatively non-destructive, as well as environmentally-friendly method for the surface functionalization of carbon nanotubes. This review presents a brief introduction to the types, properties, and functionalization methods of carbon nanotubes for a better understanding. The focus of this review is on the modification of carbon nanotubes through different types of plasma functionalization methods, notably plasmas that operate at an ambient temperature and atmospheric pressure, to improve their properties. It also investigates the results obtained from analytical methods for plasma treated carbon nanotubes.

Dynamic viscosity of methane hydrate systems from non-Einsteinian, plasma-functionalized carbon nanotube nanofluids.

The viscosity of oxygen-functionalized multi-walled carbon nanotube (O-MWCNT) nanofluids was measured for concentrations from 0.1 to 10 ppm under conditions of 0 to 30 MPag pressures and 0 to 10 °C temperatures. The presence of O-MWCNTs did not affect the temperature dependence of viscosity but did reduce the effective viscosity of solution due to cumulative hydrogen bond-disrupting surface effects, which overcame internal drag forces. O-MWCNTs added a weak pressure dependence to the viscosity of solution because of their ability to align more with the flow direction as pressure increased. In the liquid to hydrate phase transition, the times to reach the maximum viscosity were faster in O-MWCNT systems compared to the pure water baseline. However, the presence of O-MWCNTs limited the conditions at which hydrates formed as increased nanoparticle collisions in those systems inhibited the formation of critical clusters of hydrate nuclei. The times to viscosity values most relevant to technological applications were minimally 28.02% (200 mPa s) and 21.08% (500 mPa s) slower than the baseline, both in the 1 ppm system, even though all systems were faster to the final viscosity. This was attributed to O-MWCNT entanglement, which resulted in a hydrate slurry occurring at lower viscosity values.

Fabrication and study of supercapacitor electrodes based on oxygen plasma functionalized carbon nanotube fibers

Abstract Dry-spun Carbon Nanotube (CNT) fibers were surface-modified by atmospheric pressure oxygen plasma functionalization using a well controlled and continuous process. The fibers were characterized by scanning electron microscopy (SEM), Raman spectroscopy, and X-ray Photoelectron Spectroscopy (XPS). It was found from the conducted electrochemical measurements that the functionalized fibers showed a 132.8% increase in specific capacitance compared to non-functionalized fibers. Dye-adsorption test and the obtained Randles-Sevcik plot demonstrated that the oxygen plasma functionalized fibers exhibited increased surface area. It was further established by Brunauer-Emmett-Teller (BET) measurements that the surface area of the CNT fibers was increased from 168.22 m2/g to 208.01 m2/g after plasma functionalization. The pore size distribution of the fibers was also altered by this processing. The improved electrochemical data was attributed to enhanced wettability, increased surface area, and the presence of oxygen functional groups, which promoted the capacitance of the fibers. Fiber supercapacitors were fabricated from the oxygen plasma functionalized CNT fiber electrodes using different electrolyte systems. The devices with functionalized electrodes exhibited excellent cyclic stability (93.2% after 4000 cycles), flexibility, bendability, and good energy densities. At 0.5 mA/cm2, the EMIMBF4 device revealed a specific capacitance, which is 27% and 65% greater than the specific capacitances of devices using EMIMTFSI and H2SO4 electrolytes, respectively. The practiced in this work plasma surface processing can be employed in other applications where fibers, yarns, ribbons, and sheets need to be chemically modified.

Cause of wear-resistance enhancement of a polyurethane film composite by plasma-functionalized carbon nanotubes

Our previous investigation demonstrated that the wear-resistance of polyurethane (PU) film was enhanced by making the film composite utilize carbon nanotubes (CNTs). The use of plasma-treated CNTs further provides enhancement; this led to the hypothesis that the improvement could be more effective by applying isocyanate groups modified on CNTs treated with plasma. This was determined as the plasma contained nitrogen and oxygen species and because a material with isocyanate groups can function as a hardener of polyurethane. This article documents findings ensuant to our previous publication. Here, we present our investigation of the microscopic morphology of the PU film (physical aspect) and identified the chemical bonds (chemical aspect) in order to present the theorem of the enhancement. Observation of the morphology showed no specialty on the PU films with plasma-treated CNTs. On the other hand, an observation with an organic fluorescence, acridine yellow, showed evidence of the chemical aspect used to enhance the film composite with CNTs. Therefore, we concluded that the most effective method was to use isocyanate groups attached through plasma treatment, in order to improve PU wear-resistance.

Quasi-static and dynamic interfacial evaluations of plasma functionalized carbon nanotube fiber

Carbon nanotube (CNT) fibers composed of well-oriented and twisted CNT bundles are desirable as a strong and lightweight reinforcement for the high-performance composites. Herein, CNT fibers were functionalized by atmospheric pressure helium/oxygen plasma to build up the sufficient fiber/matrix interfacial bonding. The micro-bond test (quasi-static test) and electrical resistance measurement under cyclic loading (dynamic test) were carried out to evaluate the interfacial properties between CNT fiber and epoxy resin. The results illustrated 84.6% improvement in the interfacial shear strength (IFSS) of the functionalized CNT fiber and epoxy from 17.37 MPa to 32.08 MPa, since the generated oxygenic groups and roughed morphology on CNT fiber surface. Moreover, the linear and repeatable gauge factors (between 1.1 and 1.4) of the functionalized CNT fiber embedded in epoxy under dynamic cyclic loading demonstrated their good interfacial bonding as well. In addition, the tensile strength of the functionalized CNT fiber showed 49.5% increment. Our study for the first time reveals the interface interaction in a fiber-matrix system to provide the direct evidence for the interfacial enhancement of the plasma functionalized CNT fiber. The interface-enhanced CNT fiber can be generally applied in composites with much improved mechanical and electrical performance.

Characterization of enhanced interfacial bonding between epoxy and plasma functionalized carbon nanotube films

The interfacial bonding between carbon nanotube (CNT) films and epoxy is usually fairly weak for high quality composites and difficult to be measured experimentally. In this study, the interfacial bonding strength between a CNT film and epoxy is measured using a peeling test. The CNT/epoxy interfacial bonding strength is altered by surface functionalization of the CNT film using atmospheric pressure helium/oxygen plasma. Furthermore, composites with the control and the modified CNT film impregnated in epoxy are manufactured, and their mechanical properties including peeling strengths and tensile strengths are improved remarkably due to enhanced CNT/epoxy bonding after plasma functionalization. The peeling strength between the CNT film and epoxy is increased by 156.6% and so is the fracture energy. The tensile strength of the functionalized CNT film/epoxy composites is 74.4% higher than that with original CNT film. The effect of the treatment time (0.1, 0.2 and 0.3s) is assessed by surface chemical and physical analyses, showing an improvement in the amount of oxygen-containing functional groups on CNT surface, and better dispersion of the CNTs in ethanol with increased treatment time. This benefits the wetting and infiltration into CNTs by epoxy to obtain a stronger interfacial bonding.

Porous boron-doped diamond/CNT electrode as electrochemical sensor for flow-injection analysis applications

Porous boron-doped diamond (p-BDD) electrodes were prepared and explored as a potential electrochemical sensor for applications in flow-injection analysis (FIA) coupled to amperometric detection systems. Porous BDD films were grown by Hot Filament Chemical Vapor Deposition (HFCVD) over oxygen plasma functionalized carbon nanotubes and, morphological and chemical characterizations of the obtained composite material were carried out by Field Emission Gun Scanning Electron Microscopy (FEG-SEM) and Raman spectroscopy. The analytical performance of the designed p-BDD electrode under FIA conditions was investigated using two model electroactive analytes, epinephrine (EP, an important neurotransmitter) and acetaminophen (AC, a commonly consumed analgesic). All experimental parameters, such as applied potential, flow-rate and injection volume for both analytes were optimized. Under the best experimental conditions, the analytical curves for EP and AC were linear from 0.60 to 30.0μmolL−1 (EP) and from 0.80 to 70.0μmolL−1 (AC), with detection limits of 0.50μmolL−1 and 0.70μmolL−1 for EP and AC, respectively. Measurement precision was demonstrated from a number of amperometric measurements performed for successive injections of standard AC and EP solutions. In addition, the applicability of the developed FIA procedure was reported for the AC and EP determination in human serum fluid.

H2O/air plasma-functionalized carbon nanotubes decorated with MnO2 for glucose sensing

MnO2 NPs were decorated on the DBD plasma-functionalized MWCNTs in H2O vapor-saturated air for glucose detection.

Influence of chemically and plasma-functionalized carbon nanotubes on high-performance polymeric nanocomposites

This investigation highlights different surface functionalization processes of multi-walled carbon nanotubes (MWCNTs) and their effects on mechanical properties of polyetherimide nanocomposite. Surfaces of MWCNTs were modified by chemical process and by low-pressure plasma process. There is a significant change in physicochemical characteristics of MWCNTs after chemical and low plasma treatment evident from scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy studies. Due to surface modification of CNTs, there is a significant change in surface morphology and increase in oxygen functionalities such as C=O, C–O, and COOH especially evident in low-pressure plasma treatment; however, differential scanning calorimeter and thermogravimetric analysis studies reveal that thermal properties of the composite do not alter as such. There is a significant increase in mechanical properties of high-performance polymeric nanocomposites when surface-functionalized MWCNTs are dispersed in polymeric matrix; however, surface characteristics of the composite remain almost unchanged evident from contact angle and surface energy studies.

Triggering compatibility and dispersion by selective plasma functionalized carbon nanotubes to fabricate tough and enhanced Nylon 12 composites

Here, we described a simple approach for the development of advanced composites based on Nylon 12 by selectively modified multiwalled carbon nanotubes (MWCNTs). Prior mixing, MWCNTs were modified by a new combination of plasma treatment i.e. oxygen + nitrogen (PL-MWCNTs) in order to improve its dispersion in the nylon matrix and enhance the interfacial adhesion by increasing the compatibility. With incorporation of only 1.2 wt % PL-MWCNTs, the tensile strength, Young's modulus, elongation at break and storage modulus of Nylon 12 were dramatically improved by ∼66%, 64%, 69% and 39%, respectively. These results were found to be higher than individual plasma treated CNTs. Such large increments were due to the effects of excellent homogeneous dispersion of PL-MWCNTs in the Nylon matrix and strong interfacial adhesion within themselves, which is believed to be effects of both oxygenated and nitrogenated functional groups generated on the surface of CNTs during plasma treatment.

Gas adsorption studies of CO2 and N2 in spatially aligned double-walled carbon nanotube arrays

Gas adsorption studies (CO2 and N2) over a wide pressure range on vertically, highly aligned dense double-walled carbon nanotube arrays of high purity and high specific surface area are reported. At high pressures, the adsorption capacity of these materials was found to be comparable to those of metal organic frameworks and mesoporous molecular sieves. These highly aligned CNT arrays were chemically modified by treating with oxygen plasma and structurally modified by decreasing the diameter of individual carbon nanotubes. Oxygen plasma treatment led to grafting of a large number of C–O functional groups onto the CNT surface, which further increased the gas adsorption capacity. It was found that gas adsorption is dependent on tube diameter and increases with decrease of the individual CNT diameter in the CNT bundles. As results of our studies we have found that at lower pressure regimes, plasma functionalized carbon nanotubes exhibit better adsorption characteristics whereas at higher pressures, lower diameter carbon nanotube structures exhibited better gas adsorption characteristics.

Plasma functionalization of as grown carbon nanotubes for efficient dispersion

We report a highly effective dispersion of plasma functionalized carbon nanotubes (CNT) and demonstrate the fabrication of CNT-based conductive films by spray deposition using the plasma treated CNT. We synthesized vertically aligned CNT (VCNT) with millimeter length scale through growth optimization of thermal chemical vapor deposition. The synthesized VCNT samples were transferred into a direct current plasma chamber which consists of parallel planar electrodes to endow hydrophilic functionalities through the argon or ammonia plasma treatment. As a result, the plasma treated VCNT could be uniformly dispersed in ethanol by simple ultrasonic treatment and remarkably enhanced dispersion rate comparing with non-treated CNT sample was obtained. Finally, we fabricated CNT-based transparent flexible conductive films using the plasma functionalized VCNT by spray deposition on polymer sheets. The effect of plasma treatment was discussed in terms of dispersion as well as sheet conductivity of the films for future application.

Gold clusters on oxygen plasma functionalized carbon nanotubes: XPS and TEMstudies

Oxygen plasma treated multi-walled carbon nanotubes (MWCNTs) have beendecorated with gold nanoclusters by thermal evaporation. Transmission electronmicroscopy (TEM) shows that the nature and extent of gold coverage can be varied bysimultaneously changing the parameters used for the plasma treatment and the goldevaporation time. The evaporated gold clusters on oxygen plasma treated MWCNTshave a more dense distribution than the clusters evaporated on as-synthesizedMWCNTs. Analyses of the valence band and the core levels by x-ray photoelectronspectroscopy (XPS) suggest poor charge transfer between the gold clusters and theMWCNTs.