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The high-temperature plasma process has demonstrated great potential in growing high-quality boron nitride nanotubes (BNNTs) with small diameters (∼5 nm) and few walls (3–4 walls) and led to successful commercialization with a high production rate approaching 20 g/h. However, the process is still accompanied by the production of BN impurities (e.g., a-BN, BN shell, BN flakes) whose physicochemical properties are similar to those of BNNTs. This renders the post-purification process very challenging and thus hampers the development of their practical applications. In this study, we have employed both experimental and numerical approaches for a mechanistic understanding of BN impurity formation in the high-temperature plasma process. This study suggests that the flow structure of the plasma jet (e.g., laminar or turbulent) plays a key role in the formation of BN impurities by dictating the transport phenomena of BNNT seeds (e.g., B droplets), which play an important role in BNNT nucleation. We discussed that the turbulence enhances the radial diffusion of B droplets as well as their interparticle coagulation, which leads to a significant reduction in the population of effective BNNT seeds in the BNNT growth zone (T < 4000 K). This results in the generation of unreacted BN precursors (e.g., B-N-H species) in the BNNT growth zone that eventually self-assemble into BN impurities. Our numerical simulation also suggests that a higher thermal energy input makes the flow more turbulent in the BNNT growth zone due to the elevated velocity difference between the plasma jet and ambient cold gas. This finding provides critical insight into the process design that can suppress the BN impurity formation in the high-temperature plasma process.

Nitrogen (N)-doped nanostructured carbons have been actively examined as promising alternatives for precious-metal catalysts in various electrochemical energy generation systems. Herein, an effective approach for synthesizing N-doped single-walled carbon nanohorns (SWNHs) with highly electrocatalytic active sites via controlled oxidation followed by N2 plasma is presented. Nanosized holes were created on the conical tips and sidewalls of SWNHs under mild oxidation, and subsequently, the edges of the holes were easily decorated with N atoms. The N atoms were present preferentially in a pyridinic configuration along the edges of the nanosized holes without significant structural change of the SWNHs. The enriched edges decorated with the pyridinic-N atoms at the atomic scale increased the number of active sites for the oxygen reduction reaction, and the inherent spherical three-dimensional feature of the SWNHs provided good electrical conductivity and excellent mass transport. We demonstrated an effective method for promoting the electrocatalytic active sites within N-doped SWNHs by combining defect engineering with the preferential formation of N atoms having a specific configuration.

There is a growing demand for the development of a melt process-based nanocomposite manufacturing process capable of minimizing the incorporation of expensive carbon nanotubes (CNTs) by inducing a uniform dispersion of multi-walled CNTs (MWNTs). In this study, we proposed a nanocomposite manufacturing process that includes both physical particle mixing using high-speed rotation and anionic polymerization of e-caprolactam (CL) to induce a uniform dispersion of MWNTs. MWNTs were uniformly dispersed by powder mixing and then wrapped with polyamide 6 polymers by in-situ polymerization of CL. The synergistic effect of the two sub-processes resulted in an enhanced dispersion of MWNTs and prevented aggregation of the MWNTs. The composites fabricated by the proposed process exhibited electrical conductivities of 4.49 × 10−5 S/m and 1.45 × 10 S/m at 1 wt% and 3 wt% MWNTs, respectively, indicating that by applying the proposed process it is possible to incorporate a smaller amount of MWNT to achieve electrical conductivities applicable for electrostatic discharge (ESD) (>1 X 10−5 S/m) and electromagnetic interference shielding effectiveness (EMI SE) (>10 S/m) applications. An ESD chip tray and EMI SE mobile phone case were fabricated using the prepared composite, and it was verified that the ESD and EMI SE performances can be realized.

Structures can be loaded statically or dynamically with a wide range of strain rate. With high strain rates, the relationship between stress and strain is not the same as that in static loading. It has been observed that polymer composite properties are dependent upon the strain rate at which they are tested. The most commonly used method for determining the dynamic response of materials is the Split Hopkinson pressure bar test, which can test materials at strain rates as high as 1200/s to 4200/s. It is observed that the compressive strength of thermoset epoxy resin increases up to 107% at a high stain rate compared with that at quasi-static loading. This shows strongly sensitive compressive behavior at high strain rates; i.e. the structural properties of the reinforcement and energy absorption capacity are affected at high strain rates. Reinforcing nitrogen doped multi-walled carbon nanotubes (MWCNTs) can effectively improve the compressive strength as well as the strain energy of the epoxy matrix due to their uniform dispersion in the epoxy matrix.

Research interest in boron nitride nanotubes (BNNTs) has increased after the recent success of large-scale BNNT syntheses using high-temperature-pressure laser ablation or high-temperature plasma methods. Nonetheless, there are limits to the application and commercialization of these materials because of the difficulties associated with their fine structural control. Herein, the growth kinetics of BNNTs were systemically studied for this purpose. The growth pressure of the nitrogen feed gas was varied while the growth temperature remained constant, which was confirmed by black body radiation measurements and calculations based on a heat loss model. Changing from the diffusion-limited regime to the supply-limited regime of growth kinetics based on the optimized BNNT synthesis condition afforded the control of the number of BNNT walls. The total amount of BNNTs possessing single and double walls was over 70%, and the BNNT surface area increased to 278.2 m2/g corresponding to small wall numbers and diameters. Taking advantage of the large surface area and high-temperature durability of the material, BNNTs utilized as a recyclable adsorbent for water purification. The efficiency of the BNNTs for capturing methylene blue particles in water was approximately 94%, even after three repetition cycles, showing the potential of the material for application in the filter industry.

In this study, nitrogen doped carbon nanotube reinforced epoxy nanocomposites were characterized through experiments and molecular dynamics (MD) simulation. Carbon nanotubes were functionalized by nitrogen inductively coupled plasma. They were made into a nanocomposite by a solvent-free mixing method. The various characteristics of nanocomposites, including nitrogen doped carbon nanotubes were analyzed by the following experiments: a Raman spectra, an X-ray photoelectron spectroscopy (XPS), quasi-static tensile tests, a scanning electron microscopy (SEM), and a transmission electron microscopy (TEM). In addition, an MD simulation was performed to predict the mechanical properties of nanocomposites and the results were compared to the test measurements. It showed that the effective dispersion of nitrogen doped carbon nanotubes was important to improve the mechanical characteristics of the nanocomposites.

Continuous fiber-reinforced composites are important materials that have the highest commercialized potential in the upcoming future among existing advanced materials. Despite their wide use and value, their theoretical mechanisms have not been fully established due to the complexity of the compositions and their unrevealed failure mechanisms. This study proposes an effective three-dimensional damage modeling of a fibrous composite by combining analytical micromechanics and evolutionary computation. The interface characteristics, debonding damage, and micro-cracks are considered to be the most influential factors on the toughness and failure behaviors of composites, and a constitutive equation considering these factors was explicitly derived in accordance with the micromechanics-based ensemble volume averaged method. The optimal set of various model parameters in the analytical model were found using modified evolutionary computation that considers human-induced error. The effectiveness of the proposed formulation was validated by comparing a series of numerical simulations with experimental data from available studies.

The morphological analysis of the end of boron nitride nanotubes (BNNTs) using high-resolution transmission electron microscopy (HR-TEM) can provide valuable insight into the growth mechanism in high temperature pressure (HTP) laser ablation where the best quality of BNNT materials can be obtained so far. Two growth modes of BNNT coexisting during the synthesis process have been proposed based on HR-TEM observation and length analysis. One is the root growth mode, in which boron nitride (BN) species formed via the surface interaction between surrounding N2 molecules and boron nanodroplets incorporate into the tubular structure. Another mode called open-end growth mode means the prolongation of tube growth from the exposed BN edge surrounding the surface of boron nanodroplets which is constructed by the heterogeneous nucleation of absorbed BN radicals from the gas plume. The statistical data, the proportions of end structures and the length of BNNTs, could be fitted to two growth modes, and the open-end growth mode is found to be especially effective in producing longer nanotubes with a higher growth rate. The scientific understanding of the growth mechanism is believed to provide the control for optimized production of BNNTs.

With the growing industrial demand for carbon fiber-reinforced thermoplastic polymers (CFRTPs), there is an urgent need to improve their adhesion to conventional metal substrates. In this study, the effect of plasma gas and Ar incorporation on the shear strength between CFRTP and Al was examined. Although NH3 plasma had a greater effect on the surface properties of CFRTP than O2 plasma, the incorporation of Ar into O2 plasma showed a 280% improvement in shear strength relative to the untreated reference. Plasma treatment proved effective only on the CFRTP surface, with the failure mode switching from adhesive to substrate failure. Spectroscopic analyses revealed that functional groups like C O, O C O, or H2N C were either newly generated or their quantity increased on the CFRTP surface. Additionally, CFRTP itself acts as an oxygen source, and its shear strength improved significantly under Ar plasma treatment, even without external O2 supply.

Developing methods to assemble nanomaterials into macroscopic scaffolds is of critical significance at the current stage of nanotechnology. However, the complications of the fabrication methods impede the widespread usages of newly developed materials even with the superior properties in many cases. Here, we demonstrate the feasibility of a highly-efficient and potentially-continuous fiber-spinning method to produce high-performance carbon nanotube (CNT) fiber (CNTF). The processing time is, The tensile strength of a carbon nanotube fiber is predicted to increase as its constituent nanotubes become more perfectly and densely aligned. Here, the authors present an optimized direct-spinning and chlorosulfonic acid densification method to rapidly produce carbon nanotube fibers with excellent mechanical and electrical properties.

There is growing interest in carbon fibre fabric reinforced polymer (CFRP) composites based on a thermoplastic matrix, which is easy to rapidly produce, repair or recycle. To expand the applications of thermoplastic CFRP composites, we propose a process for fabricating conductive CFRP composites with improved electrical and thermal conductivities using an in-situ polymerizable and thermoplastic cyclic butylene terephthalate oligomer matrix, which can induce good impregnation of carbon fibres and a high dispersion of nanocarbon fillers. Under optimal processing conditions, the surface resistivity below the order of 10+10 Ω/sq, which can enable electrostatic powder painting application for automotive outer panels, can be induced with a low nanofiller content of 1 wt%. Furthermore, CFRP composites containing 20 wt% graphene nanoplatelets (GNPs) were found to exhibit an excellent thermal conductivity of 13.7 W/m·K. Incorporating multi-walled carbon nanotubes into CFRP composites is more advantageous for improving electrical conductivity, whereas incorporating GNPs is more beneficial for enhancing thermal conductivity. It is possible to fabricate the developed thermoplastic CFRP composites within 2 min. The proposed composites have sufficient potential for use in automotive outer panels, engine blocks and other mechanical components that require conductive characteristics.

A bundle of carbon fibers (CFs) with 24,000 filaments was prepared using atmospheric pressure plasma and heat simultaneously for only 30 min, followed by the carbonization process. Conventional thermal stabilization process takes more than few hours to prevent the ignition of the polyacrylonitrile (PAN) fiber when large-tow PAN fibers are stabilized. The CFs produced using the plasma stabilization process had a tensile strength as high as 2.6 GPa. This strength level, which is slightly higher than that of CFs stabilized by the conventional process for 120 min, satisfies the demands in automobile applications. It is believed that the plasma-based stabilization process provides a potential solution not only for shortening the process time but also for providing continuous stabilization of large-tow carbon fibers.

The effect of atmospheric-pressure plasma treatment on the mechanical properties of carbon nanotube (CNT) fibers was investigated. When the CNT fibers were irradiated with RF atmospheric-pressure plasma, it was confirmed that functional groups such as hydroxyl or carboxylic acid groups were generated on the surface of the CNT fibers. The mechanical properties of CNT fibers were improved as a result of the plasma treatment because the functional groups on individual CNTs were able to induce hydrogen bonds between them. After plasma treatment with gas flow of argon (10 lpm) and oxygen (100 sccm), the tensile strength of the pure CNT fiber increased by approximately 40%, from 0.62 N/tex to 0.86 N/tex, and the modulus increased by approximately 20%, from 27.9 N/tex to 32.9 N/tex.

Reducing the price of carbon fiber (CF) is crucial to the wider application of CFRP in automobiles for energy reduction. Because process costs account for 46% of the total cost of CF, interest has increased in the development of affordable processes such as microwave plasma carbonization, which can reduce the cost. In this study, the concept of a two step microwave plasma carbonization process is suggested to enhance the mechanical properties of the CF made with the plasma process. Compared with single step carbonized CF, the two step carbonized CF had 171% improved tensile strength because of the synergetic effect of the low power and high power carbonization steps. Two step or multi step carbonization process is expected to be another improvement of the microwave plasma carbonization process in that it not only reduces the energy consumption of the process but also improves the mechanical properties of CF.

Microwave heating is investigated as an alternative method of carbonization process for carbon fiber (CF) in order to reduce the energy costs. In this study, a microwave plasma system is designed for the carbonization process, and stabilized polyacrylonitrile fiber is carbonized using the system. Compared with the CF fabricated by conventional thermal carbonization process, plasma-carbonized CF has higher surface roughness, which can enhance the mechanical interlocking between resin and CF and increase the mechanical properties of the CF Reinforced Polymer (CFRP). Furthermore the mechanical properties of the CF didn't fall behind that of the conventionally carbonized one. As a result, microwave plasma carbonization is a good candidate for the next-generation carbonization processes in the CF industry.

Microwave plasma equipment was designed and manufactured to improve the interfacial bonding and mechanical interlocking between carbon fiber fabric (CFF) and the polymer matrix. Tensile specimens for the composites reinforced with the as-received and microwave plasma-treated CFFs were prepared using high-speed fabrication with a polymerizable and low-viscosity cyclic butylene terephthalate (CBT) oligomer matrix. Compared with the polymerized CBT (pCBT) matrix, the tensile strengths of the as-received and plasma-treated CFF reinforced composites (CFFRCs) were enhanced by approximately 362.5% and 436.3%, respectively. A high carbon fiber content of 70 vol.% was achieved without introducing pores and/or defects into the CFFRC due to the low viscosity and high impregnation characteristics of the CBT resin. It was confirmed that the microwave plasma can increase the surface roughness of the tested CFF without varying the chemical composition and defect level of the CFF. In addition, the interfacial bonding and mechanical interlocking between the CFF and polymer matrix were improved.

The lack of cost effective, industrial‐scale production methods hinders the widespread applications of graphene materials. In spite of its applicability in the mass production of graphene flakes, arc discharge has not received considerable attention because of its inability to control the synthesis and heteroatom doping. In this study, a facile approach is proposed for improving doping efficiency in N‐doped graphene synthesis through arc discharge by utilizing anodic carbon fillers. Compared to the N‐doped graphene (1–1.5% N) synthesized via the arc process according to previous literature, the resulting graphene flakes show a remarkably increased doping level (≈3.5% N) with noticeable graphitic N enrichment, which is rarely achieved by the conventional process, while simultaneously retaining high turbostratic crystallinity. The electrolyte ion storage of synthesized materials is examined in which synthesized N‐doped graphene material exhibits a remarkable area normalized capacitance of 63 µF cm−2. The surprisingly high areal capacitance, which is superior to that of most carbon materials, is attributed to the synergistic effect of extrinsic pseudocapacitance, high crystallinity, and abundance of exposed graphene edges. These results highlight the great potentials of N‐doped graphene flakes produced by arc discharge in graphene‐based supercapacitors, along with well‐studied active exfoliated graphene and reduced graphene oxide.

Carbon fibers (CFs) were prepared by the plasma-assisted stabilization (PAS) of polyacronitrile (PAN) fibers. PAS was found to be an efficient treatment for stabilizing the precursor fibers in terms of the time, cost and mechanical properties compared to conventional thermal stabilization (CTS). The efficient stabilization of PAN by a radio-frequency capacitive plasma discharge was confirmed using FT-IR and DSC. The tensile strength and modulus of CFs from PAS were superior to those of CFs from CTS. These results suggest that PAS is an efficient treatment for the manufacture of CFs, which can save time and energy.

A study to replace a high temperature thermal carbonization process with microwave plasma process is carried for PAN fiber as a starting material. Near atmospheric pressure microwave plasma (1 Torr~45 Torr) was used to control to get the fiber temperature up to 1000 o C. Even argon is an inert gas, its plasma state include high internal energy particles; ion (15.76 eV) and metastable (11.52 eV). They are very effective to lower the necessary thermal temperature for carbonization of PAN fiber and the resultant thermal budget. The carbonization process was confirmed by both EDS (energy dispersive spectroscopy) of plasma treated fibers and OES (optical emission spectroscopy) during processing step as a real time monitoring tool. The same trend of decreasing oxygen content was observed in both diagnostic methods.

Multi-hollow cathode (MHC) discharge was investigated under various discharge conditions such as the discharge gas of Ar, Ne, and Kr, a pressure range from 64.5 mTorr to 645 mTorr, and a RF current range from 1 A to 9 A, in RF capacitively coupled plasma (CCP) with the cathode electrode having a number of holes of various hole diameters. The plasma parameters of electron density and electron temperature were measured with a compensated Langmuir probe and the electrical characteristics were obtained by using an RF impedance monitor (ENI-INC, V-I probe). It was found that the electron density significantly changes by controlling the discharge parameters, especially the gas pressure, with the cathode electrode of a fixed hole diameter. Furthermore, we could find that there is the optimum range of the discharge parameters that the electron density is maximized at a fixed hole diameter and the close relationship between the hole diameter and the discharge parameters. Comparing the MHC characteristics against the discharge gas to those of the conventional CCP, we could find that the variation behavior of the electron density against RF power for each discharge gas in the MHC was entirely different from that in the conventional CCP. These phenomena were explained by considering the power dissipation mode of electrons against the discharge conditions.

Silicon nitride films have been deposited on p-type Si (100) by mercury-sensitized photo-chemical vapor deposition (photo-CVD) method varying deposition pressure and substrate temperature. Energy dispersive X-ray fluorescence spectra of the samples show that the incorporation of mercury in the films, if any, is below 20 ppm. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy studies show the incorporation of oxygen and hydrogen in all the films, which is a function of the deposition parameters. Higher substrate temperature favors the formation of SiH bonds and reverse is the case for the formation of SiNH bonds. The sample deposited at low temperature (170 °C) shows the presence of less unreacted silicon (4%) in comparison to the sample (12.5% unreacted silicon) deposited at higher deposition temperature (250 °C), but the variation of pressure shows no significant change in terms of the unreacted silicon. The incorporated hydrogen and oxygen passivate surface defects thereby influencing interface electronic state densities ( D it ) and fixed insulating charges ( Q ss ).

Zirconia-coated NiO powder was prepared by a newly developed surface-induced coating using thermal hydrolysis of Zr(NO 3 ) 2 ·6H 2 O in a mixed solvent of alcohol and water. Amorphous zirconium hydroxide was uniformly coated on the surface of NiO powder with the thickness of 20 nm. The ZrO 2 coating layer was crystallized to tetragonal ZrO 2 with the size of 40–60 nm at 900°C. The coated NiO powder containing 15 vol.% ZrO 2 , was found to have a similar isoelectric point to that of the ZrO 2 . The surface-induced ZrO 2 coating was a more efficient method for the prevention of Ni sintering than the mechanical mixing.

The multi-holed electrode that has been reported to enhance the electron density of the capacitively coupled plasma is now being adopted to speed up the processes. However, the discharge condition when the multi-holed electrode enhances the electron density of the discharge at fixed power is not studied. At low pressure, the multi-holed electrode increased the electron density of the plasma at fixed power. However, the multi-holed electrode is experimentally revealed to lower the electron density at high pressure. In this paper, the different roles of the multi-holed electrode are experimentally studied.