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Design of high energy density lithium storage materials is one of the everlasting issues in energy storage systems to realize a fully clean and sustainable energy grid. Here, 2,9-dimethyl quinacridone was selected as a precursor to prepare carbon-based electrode via low temperature heat-treatment process from 750 °C to 1050 °C. The pyro-polymerization of 2,9-dimethyl quinacridone induced a distinctive morphological transformation from rice husk-shaped 2,9-dimethyl quinacridone to carbon nanofibers. Electrode fabricated from pigment derived carbon nanofibers (PCNF) pyrolyzed at 750 °C maintained 878 mAh g-1 at a current density of 1 A g-1 and good Coulombic efficiency up to 98% after 1000 cycles. Furthermore, it delivered 337 mAh g-1 at a high current density of 25 A g-1. The superior performance was attributed to the stable structure of pristine 2,9-dimethyl quinacridone giving high thermal stability and crystallinity owing to well-defined π-π and hydrogen bonding interactions, thus rendering a stable microstructure with a large d-spacing of (002) plane of 3.580 A, as well as efficient surface redox reactions. Density functional theory calculations indicated that the large interlayer distance could facilitate fast lithium ion insertion/extraction because of a ∼38% lower energy barrier for lithium ion insertion than compared with graphite.

Bipolar plates (BPs) for fuel cell applications must meet minimum conductivity requirements while maintaining light weight and sufficient mechanical strength to be thinned and easily fabricated. Here, we prepare BPs comprising fluorinated ethylene–propylene (FEP), graphite flakes (GFs), graphite nanoplates (GnPs), and silicon carbide (SiC) particles for fuel cell applications. SiC particles decorated on large GFs and GnPs improve the flexural strength of the composites relative to the corresponding composites without SiC, resulting in increases of ∼24% and ∼130%, respectively. The improved mechanical properties of the FEP/GnP/SiC and FEP/GF/SiC composites are due to the uniform dispersion of SiC particles and strong chemical bonding between GF (or GnP) and SiC particles in the FEP matrix. Incorporating SiC particles into the FEP/GnP (or GF) composite plate provides a robust, scalable strategy for realizing high-performance, high-temperature fuel cell BPs.

This study aimed to investigate the effect of impregnation pressure on the decrease in porosity of impregnated bulk graphite. The correlation between pitch impregnation behavior and the pore sizes of the bulk graphite block was studied to determine the optimal impregnation pressure. The densities and porosities of the bulk graphite before and after pitch impregnation under various pressures between 10 and 50 bar were evaluated based on the Archimedes method and a mercury porosimeter. The density increased rates increased by 1.93–2.44%, whereas the impregnation rate calculated from the rate of open porosity decreased by 15.15–24.48%. The density increase rate and impregnation rate were significantly high when the impregnation pressures were 40 and 50 bar. Compared with impregnation pressures of 10, 20, and 30 bar, the minimum impregnatable pore sizes with impregnation pressures of 40 and 50 bar were 30–39 and 24–31 nm, respectively. The mercury intrusion porosimeter analysis results demonstrated that the pressure-sensitive pore sizes of the graphite blocks were in the range of 100–4500 nm. Furthermore, the ink-bottle-type pores in this range contributed predominantly to the effect of impregnation under pressure, given that the pitch-impregnated-into-ink-bottle-type pores were difficult to elute during carbonization.

This study investigates the toughening effect of the novel in-situ polytriazole toughening agent (PTS), synthesized via azide–alkyne click reaction during epoxy curing reaction. Three different types of epoxy resins, DGEBA, TGAP and DGEBF, and 4,4′-DDS were modified with PTS and their fracture toughness and tensile properties were evaluated. When the epoxy resin has an excellent miscibility with the solid SPB, one monomer of PTS, the toughening effect was the best, improving the fracture toughness of the epoxy resin by 67% only with 5phr PTS without any decrease in the tensile properties of the resulting epoxy resin.

Interfacial adhesion between carbon fiber and epoxy resin mostly determine the mechanical properties of the carbon fiber/epoxy composites and the chemical structures of epoxy resin and hardener plays an important role. In this regard, stereoisomerism of epoxy hardeners, such as 3,3′ and 4,4′-DDS (diaminodiphenylsulfone), can have significant influence on the fracture toughness of the cured epoxy and related carbon fiber composites. Therefore, this study aims to investigate the influence of stereoisomerism of epoxy hardeners on fracture toughness of the carbon fiber/epoxy composites. Triglycidyl aminophenol (TGAP) are selected as epoxy resin and 3,3′- and 4,4′-DDS are selected as epoxy hardener. Wetting behaviors and fiber matrix adhesion of TGAP/DDS mixtures onto carbon fiber are investigated and fracture toughness (KIC) of TGAP/DDS mixtures are also investigated. Then, the mode II fracture toughness test of the carbon fiber/TGAP/DDS composites are carried out to investigate the influence of hardener stereoisomerism on fracture toughness of the resulting composites. Wetting and fiber matrix adhesion to carbon fiber of TGAP/3,3′-DDS was better than those of TGAP/4,4’-DDS and KIC of TGAP/3,3′-DDS was also better than that of TGAP/4,4′-DDS. As a result of the synergistic effect of better wetting, fiber matrix adhesion, and fracture toughness of TGAP/3,3′-DDS, the mode II fracture toughness of the carbon fiber/ TGAP/3,3’-DDS composites was almost twice of that of the carbon fiber/ TGAP/4,4′-DDS composites. Based on the results reported in this study, stereoisomerism of the epoxy hardeners can influence the fracture toughness of the resulting composites as well as that of the resin itself. In other words, only small difference, such as the spatial arrangement of the molecular structure of epoxy hardeners can cause huge difference in the mechanical properties of the resulting composites.

Petroleum pitch‐based graphite blocks (GBs) attract considerable attention owing to their low cost, high yield, and possible application as heat sink components. However, no studies have systematically investigated the particle size distribution of GBs, their structures, and the relationship between the structures and thermal properties resulting from graphitization. Hence, herein, we present a novel method for fabricating petroleum pitch‐based GBs using natural graphite flakes (GFs) of sizes ranging between 50 and 500 μm and a bimodal particle size distribution. Furthermore, the effects of the mean GF particle size, pitch binder content, and microstructure of the GBs with low GF contents on compression molding with elevated hot‐pressing temperatures after graphitization are investigated. To investigate the effect of packing density with a GF size of 500 μm, we mix a small‐sized GF (50 μm) and low pitch binder content by kneading. In particular, specimens in the in‐plane direction with a bimodal particle size distribution of GFs and 10 wt% pitch binder yield optimum density and thermal conductivity values of 1.74 g m−3 and 384 Wm−1 K−1, respectively, after high‐temperature graphitization at 2600°C. These findings provide insights for developing high‐performance GBs for use in heat sink components with high thermal conductivity.

This study investigated the toughening effect of in situ polytriazoleketone (PTK) and polytriazolesulfone (PTS) toughening agent when applied to various epoxy resins, such as diglycidyl ether of bisphenol A (DGEBA), diglycidyl ether of bisphenol F (DGEBF), and triglycidyl p-aminophenol (TGAP) with 3,3′-diaminodiphenylsulfone as a curing agent. The fracture toughness, tensile properties, and thermal properties of the prepared epoxy samples were evaluated and compared. When PTK was mixed with DGEBF, the fracture toughness was improved by 27% with 8.6% increased tensile strength compared to the untoughened DGEBF. When PTS was mixed with TGAP, the fracture toughness was improved by 51% without decreasing tensile properties compared to the untoughened TGAP. However, when PTK or PTS was mixed with other epoxy resins, the fracture toughness decreased or improved with decreasing tensile properties. This is attributed to the poor miscibility between the solid-state monomer of PTK (4,4′-bis(propynyloxy)benzophenone (PBP)) or PTS (4,4′-sulfonylbis(propynyloxy)benzene (SPB)) and the epoxy resin, resulting in the polymerization of low molecular weight PTK or PTS in epoxy resin. Therefore, the toughening effect of PTK or PTS can be maximized by the appropriate selection of epoxy resin based on the miscibility between PBP or SPB and the resin.

In this study, self-cleaning polyester (PET) fabrics were prepared using TiOF2 and hexadecyltrimethoxysilane(HDS) treatment. TiOF2 was synthesized via direct fluorination of a precursor TiO2 at various reaction temperatures. The prepared PET fabrics had superior photocatalytic self-cleaning properties compared with anatase TiO2/HDS-treated PET fabrics under UV and sunlight with 98% decomposition of methylene blue. TiOF2/HDS-treated PET fabrics also had superior superhydrophobic self-cleaning properties compared with anatase TiO2/HDS-treated PET fabrics with a 161&deg, water contact angle and 6&deg, roll-off angle. After the self-cleaning tests of the non-dyed TiOF2/HDS-treated PET fabrics, we prepared dyed TiOF2/HDS-treated PET fabrics to test practical aspects of the treatment method. These PET fabrics were barely stained by tomato ketchup, even when stained, they could be self-cleaned within 4 h. These results suggest that practical self-cleaning PET fabrics with superhydrophobicity and photocatalytic degradation could be prepared using TiOF2/HDS-treatment.

This study investigates the detoxification properties of guanidinylated chitosan against chemical warfare agents and its application to the preparation of military protective clothing. Guanidinylated chitosan was synthesized by chitosan guanidinylation with cyanamide. The detoxification properties of the guanidinylated chitosan were then evaluated using a chemical warfare agent simulant, called diisopropylfluorophosphate (DFP). Cotton fabric was treated with 1 wt.% of guanidinylated chitosan in acetic acid and water solution using the simple and conventional textile treatment method of pad&ndash, dry&ndash, cure. The detoxification properties of the guanidinylated chitosan-treated cotton fabric were evaluated to investigate the application of guanidinylated chitosan to the preparation of military protective clothing. Subsequently, 71.3% of DFP was hydrolyzed to non-hazardous diisopropylhydrogenphosphate (DHP) in 2 h because of the base organocatalytic activity of 0.02 g guanidinylated chitosan itself. Moreover, 60.1% of DFP was hydrolyzed by the catalytic activity of the guanidinylated chitosan-treated cotton fabric, which contained only 0.0002 g of guanidinylated chitosan. This result shows that the guanidinylated chitosan itself has detoxification properties for hydrolyzing DFP to DHP, and its detoxification properties can be more efficient when applied to cotton fabric because it showed 84.3% of the detoxification properties with only 1 wt.% of guanidinylated chitosan. For the first time, this study shows that guanidinylated chitosan has considerable detoxification properties and can be used as an agent to prepare protective clothing.

This study provides an economical and effective method to improve the interlaminar properties of carbon fiber-reinforced polymers (CFRPs) using aluminum trihydroxide (ATH) microparticles. ATH microparticles are cheap and are expected to show good affinity to epoxies in the matrix and sizing agents of the carbon fibers owing to the presence of three hydroxyl groups. In addition, ATH particles are reported to improve the mechanical properties of polymers when used as the reinforcement. In this study, ATH microparticles of various sizes, 1.5, 10, and 20 µm, were used to improve the interlaminar properties of the CFRPs. ATH particles with a size of 1.5 μm improved the tensile properties of the ATH/epoxy resin and did not significantly alter the curing behavior. The interfacial adhesion between the carbon fiber and the epoxy resin was also improved, and the impregnation of the resin mixture remained similar to that of the neat resin, resulting in no significant void and defect formation. Considering the above results, the resulting 1.5 μm ATH-reinforced CFRP showed improved interlaminar properties compared to CFRP without ATH. However, 10 and 20 μm ATH-reinforced CFRPs showed deteriorated interlaminar properties due to the diminished tensile properties of the resin itself and resin impregnation, which resulted in more voids and defects, despite the interfacial adhesion between the fiber and the matrix resin.

Porous polyimide (PI) films are a promising low-k dielectric material for high-frequency data transmission with low signal attenuation. Pores are generated by non-solvent induced phase separation (NIPS) during phase inversion of polymer solution via non-solvent accumulation and solvent diffusion. In this study, aromatic PI was employed as a matrix for NIPS, and the influence of polymer concentration and liquid—liquid demixing time on the morphology of pores in the PI films was investigated. This ensured control over the porous structure of the PI film and provided desirable dielectric properties in a broad frequency range of 100 Hz–30 MHz (1.99 at 30 MHz) and thermal stability (Td5% > 576 °C, Tg > 391 °C). This study addresses the effect of polymer concentration and coagulation time on the morphology and physical properties of PI sponge films and provides guidance on the design and optimization of architectures for polymeric materials requiring pore modification.

The purpose of this study is to investigate the potential of using a pelletized pitch in a continuous process for the economical preparation of large-scale pitch-based carbon fibers. The pitch was pelletized before spinning because the pitch powder can agglomerate in the feed throat of a screw extruder, which can render uniform heating difficult. Using the pelletized pitch in a single-screw extruder spinning apparatus, the pitch fiber can be spun to a great length as long as the amount of pitch pellets is sufficient. To evaluate the benefits of using pitch pellets in the continuous carbon fiber spinning process, isotropic and mesophase pitch fibers were prepared by both the conventional batch process using pitch powder and continuous process using pitch pellets. Even with a huge difference in the thermal energy used, the carbon fibers prepared using the pelletized-pitch-based continuous process had better tensile properties than those prepared using the conventional process. This suggests that the continuous process using pitch pellets has the potential to be an economical large-scale process for carbon fiber preparation.

In this work, we investigated the influence of the solvents used in the catalyst ink on performance of the proton exchange membrane fuel cells (PEMFCs). The mobility of the polymeric chains in 2.5 wt% Nafion dispersion is measured by fluorine-19 nuclear magnetic resonance after the use of different organic solvents including isopropyl alcohol (IPA), dimethyl sulfoxide (DMSO) and N-Methyl-2-pyrrolidone (NMP). Subsequently, the electrochemical properties, e.g., direct-current polarization and electrochemical impedance spectra, are characterized. As a result, the catalyst layer fabricated from the solvents with high main-chain mobility created more intimate contact at triple-phase boundary, enlarging the electrochemically available surface area and reducing the charge-transfer resistance, mainly due to a strong interaction between solvent molecule and Nafion ionomer. It is demonstrated that the use of the membrane electrode assemblies (MEAs) fabricated from NMP- and DMSO-based catalyst inks enable a H 2 /O 2 PEMFC to yield 100% and 33% higher power densities at 0.6 V, respectively, as compared to the MEA fabricated from IPA-based catalyst ink.

In this study, we investigated the role of the surface fluorine in carbon electrode materials in the energy storage of the corresponding electric double-layer capacitors (EDLCs). And in order to reach this goal, the highly graphitic material multi-walled carbon nanotubes (MWCNTs) were fluorinated to minimize the changes in the textural properties after fluorination and the textural, surface chemical, and electrochemical properties of the resulting MWCNTs were evaluated. The fluorination of the MWCNTs did not change their textural properties because of their highly graphitic properties. The surface fluorine contents of the fluorinated MWCNTs varied depending on the fluorination conditions. The electrochemical properties of the fluorinated MWCNT-based electrodes improved by 31.4–37.7% compared to those of the pristine MWCNTs, depending on the current-density load (0.2–1.5 A/g). The increase in the retained capacitance is due to the surface fluorination of the MWCNTs. The role of the surface fluorine on the MWCNTs for the improved electrochemical properties of the fluorinated MWCNT-based electrodes is explained using a simple computational study. The surface fluorine induces charge transfer on the surface of the MWCNTs, resulting in a more nucleophilic surface that improves the interaction between the surface of the fluorinated MWCNTs and H3O+.

Shear-thickening fluid-impregnated aramid (STF-im-AR) fabrics have been manufactured for advanced soft body armor applications for which they provide improved ballistic and stab resistances. It is not yet clear whether or not such improvements can be attributed solely to the STF. In this study, the rate-dependent behavior of an STF-im-AR fabric was investigated at the fabric level, using uniaxial tensile, bias-extension, and picture-frame tests. Rate-dependent behavior of the STF-im-AR fabric was observed during uniaxial tensile testing; however, the effect of the STF treatment was slight and consistent with only the inherent effect of the polymeric nature of its constituent fibers. The shear rigidity of the STF-im-AR fabric increased, due to the presence of the STF and the sensitivity of the fabric's shear stiffness to changes in the shear strain rate also increased slightly. This rate-sensitive shear stiffness of STF-im-AR fabrics may contribute to improved ballistic and stab resistances.

Impregnation of shear-thickening fluid(STF) into high-strength fabrics makes a considerable improvement on the ballistic performance of fabric armors. Understanding dissipation augmentation due to shear thickening effects on yarn-yarn and yarn-projectile friction is of great importance in liquid armor research. This paper takes a shear- thickening effect into account in numerical simulations by using a velocity-dependent friction model. Impact simulations were performed to validate the friction model as well as to evaluate the ballistic performance of STF-fabrics. Impact simulations on neat fabrics were also conducted to provide baseline results for comparison.

Multi-walled carbon nanotube (MWCNT)/epoxy composites were prepared using MWCNT fluorinated to different extents. The mechanical properties, fracture surface morphologies and electromagnetic interference shielding efficiency (EMI-SE) of these composites were evaluated for epoxy matrices containing MWCNT with degrees of fluorination. The tensile strengths of the MWCNT/epoxy composites improved by 31% with treated MWCNT compared to that of the epoxy composites with untreated MWCNT. The EMI-SE values of the fluorinated MWCNT/epoxy composites improved up to 26% with increasing fluorination extent. The mechanical and electrical properties enhancement of the composites were attributed to the fluorinated MWCNT, which improved both the dispersion of the MWCNT in epoxy matrix and interfacial interactions between the MWCNT and the epoxy matrix.

To improve mechanical strength of carbon foams, the carbon black (CB) added carbon foams were fabricated by impregnating different contents of carbon black (CB) and mesophase pitch using polyvinyl alcohol (PVA) solution into polyurethane foam and being followed by heat treatment. The cell wall-thicknesses of carbon foams were controlled by adding amounts of CB, and it was confirmed that the compressive strength of carbon foams was increased as increasing cell wall-thickness. The compressive strength had the highest value of with the highest bulk density of when adding 5 wt% CB in carbon foam. However, the thermal conductivity was decreased by adding CB in carbon foam. The results indicated that the thermal conductivities of carbon foams were reduced by increased interlayer spacing () with the addition of CB in carbon foams.

Generally, detoxification fabrics are defined as fabrics that remove or inhibit the production of toxic compounds, especially chemical warfare agents such as nerve gas agents. They are usually prepared using a complicated and time-consuming method. This study suggests a facile treatment method for preparing detoxification fabrics against nerve gas agents using polyethyleneimine and microwave curing. The detoxification properties of polyethyleneimine and microwave-treated polypropylene nonwoven fabric were evaluated using diisopropylfluoro-phosphate, which is a nerve agent simulant. The treated polypropylene fabric decontaminated 53.6% of diisopropylfluorophosphate (DFP) in 2 h at 32 &deg, C, and the half-life of DFP on the surface of the treated fabric was 122 min. The result indicates that the treated fabric can act as a basic organocatalyst for the DFP hydrolysis and has a shorter half-life owing to the large number of amine groups. Therefore, the facile treatment method has the potential for use in the preparation of detoxification fabrics.

We evaluated the use of polyethersulfone (PES) as reinforcement material to increase the mechanical and thermal properties of triglycidyl-p-aminophenol (TGAP) epoxy resin. The enhancement of the mechanical properties of the PES/epoxy composites was indicated by 44%, 35%, and 11% increases in tensile strength, impact strength, and fracture toughness, respectively. TGA revealed that the thermal stability of the PES/epoxy composites also improved by 17%, which was calculated using the integral procedural decomposition temperature (IPDT). These results are attributed to the good distribution and formation of the semi-interpenetrating polymer networks (semi-IPNs) that composed the epoxy network and the linear PES.

To fabricate carbon foams with high compressive strength and thermal conductivity, carbon foams were prepared by curing and heat treatment of a polymer solution containing CMC, isotropic pitch and fluorinated CNTs. The CNTs were fluorinated at different fluorine gas pressures (F 2 :N 2 = 3:7, 5:5, and 7:3). The highly heat-treated carbon foams containing fluorinated CNTs prepared with F 2 :N 2 = 5:5 had the highest thermal conductivity of 3.18 ± 0.01 W/mK, and compressive strength of 2.42 ± 0.22 MPa, which were approximately 15% and 133% higher, respectively, than those of the highly heat-treated carbon foams containing un-fluorinated CNTs due to increased crystallinity of CNTs and their adhesion with pitches in highly heat-treated carbon foams through fluorination of CNTs.

Graphite foams (GFs) were prepared by adding different amounts of mesophase pitch (MP) into polyvinyl alcohol-acrylic acid (PVA-AAc) solution followed by the heat treatment. It was confirmed that the pore diameters of GFs were controlled by the slurry concentration, which was the mesophase content added in polymer solution, and their thermal conductivity and com- pressive strength were also controlled by porosities of GFs formed at different conditions. The resulting GFs in this study had the highest thermal conductivity of 53.414 ± 0.002 W/mK and compressive strength of 1.348 ± 0.864 MPa at 0.69 in porosity. The thermal conductivity of MP based GFs increased approximately 23 times higher than that of using isotropic pitch based GFs due to the developed graphitic structure.

Graphite foams can be prepared by various methods, such as a blowing, the use of polymer based templates, and the compression of graphite and/or graphite sheets. Adding fillers to graphite foams can lead to improved thermal conductivity and compressive strength. The mechanical properties of graphite foam with carbon material added are negatively affected by the low dispersibility, alignment and interfacial adhesion of the fillers in the foam. This study reviews studies that have investigated various fabrication methods, the addition of carbon materials, and surface treatments of graphite foams to improve their thermal and mechanical properties.

The surfaces of multi-walled carbon nanotubes (MWCNTs) were thermally fluorinated at various temperatures to enhance the electrochemical properties of the MWCNTs for use as electric double-layer capacitor (EDLC) electrodes. The fluorine functional groups were added to the surfaces of the MWCNTs via thermal fluorination. The thermal fluorination exposed the Fe catalyst on MWCNTs, and the specific surface area increased due to etching during the fluorination. The specific capacitances of the thermally fluorinated at 100 °C, MWCNT based electrode increased from 57 to 94 F/g at current densities of 0.2 A/g, respectively. This enhancement in capacitance can be attributed to increased polarization of the thermally fluorinated MWCNT surface, which increased the affinity between the electrode surface and the electrolyte ions.

The pitch-based high crystallinity cokes are investigated by evaluating its potential as electrode materials for electric double layer capacitors (EDLCs). After activation process, the high crystallinity cokes-based activated carbon (hc-AC) demonstrates great potential for use as an electrode material for EDLCs. The specific capacitance of hc-AC with the carbon to KOH ratio of 1:3 is 276 F g−1, even with a low specific surface area of 983 m2 g−1. These results are comparable to that of the most commonly used material for EDLCs, MSP 20 (256 F g−1), which has a high specific surface area of 1807 m2 g−1.

In this study, we investigate Li adsorption mechanisms on the C 60 -SWCNT hybrid system using density functional theory. It is found that the Li adsorption energy of the C 60 -SWCNT hybrid system is increased in comparison to that of the pure SWCNT. The Li adsorption energy ranges from −1.917 eV to −2.642 eV for the single-Li adsorbed system and from −2.351 eV to −2.636 eV for the double-Li adsorbed system. It is also found that the adsorption energy becomes similar at most positions throughout the structure. In addition, the Li adsorption energy of 31-Li system is calculated to be −1.863 eV, which is significantly lower than the Li–Li binding energy (−1.030 eV). These results infer that Li atoms will be adsorbed on the space 1) between C 60 and C 60 ; 2) between SWCNT and C 60 ; 3) the rest of the space (e.g. between SWCNTs), rather than form Li clusters. As more Li atoms are adsorbed onto the C 60 -SWCNT hybrid system due to such improved Li adsorption capability, the metallic character of the system is enhanced, which is confirmed via the band structure and electronic density of states.

To investigate the relationship between textural properties and electrochemical properties, activated carbon nanofibers were manufactured using an electrospinning process followed by chemical activation using KOH or NaOH. The specific surface area of the KOH-activated carbon nanofibers was higher than that of NaOH-activated carbon nanofibers; however, the total pore volume and mesopore volume of the NaOH-activated carbon nanofibers were greater than those of the KOH-activated carbon nanofibers when the same number of moles of KOH and NaOH were used. The specific capacitances increased as the specific surface area and pore volume of the activated carbon nanofibers were increased. However, the specific capacitance obtained at a high scan rate (50 mV/s) and the retained capacitance of the activated carbon nanofibers increased with increasing total pore and mesopore volume, especially for mesopores with diameters of 2–4 nm.

In this study, we investigated the role of fluorination in improving the electrochemical properties of activated carbon nanofiber (ACNF) electrodes. The ACNFs were prepared with various textural properties and then fluorinated. The electrochemical properties of the resulting ACNFs were subsequently evaluated to investigate the effect of the fluorination of the prepared ACNFs with various textural properties on the electrochemical properties. The specific capacitances of the ACNF electrodes increased by 15.8–47.3% after fluorination, although the specific surface area and the total pore volume decreased significantly; these results suggest that the introduction of C F functional groups onto the ACNF surface was more important than the induction of changes in the textural properties of the ACNF samples with respect to improving the electrochemical properties of the ACNF electrodes. The retained capacitances of the ACNF electrodes also increased 2–12% after fluorination, although the etching effect of the fluorination significantly collapsed the mesopores; these results suggest that the C F functional groups were electrochemically active even at a high scan rate.

This study investigated the potential of direct fluorination as a multifunctional surface modification method for an aramid fabric. The aramid fabric was fluorinated at temperatures of 30, 90, and 150 °C. As the fluorination temperature increased, the fluorinated aramid fabric became more hydrophobic and oleophobic, with a water contact angle of 129.3° and a diiodomethane contact angle of 108.6° when the fluorination temperature was 150 °C. Thus, the fluorinated fabric could be defined as an omniphobic surface. Both the phenol resin wettability and the impregnation of the fluorinated aramid fabric improved as the fluorination temperature increased, suggesting better interfacial adhesion between the fabric and the polymer matrix. Direct fluorination of an aramid fabric can be an efficient multifunctional surface modification method to achieve omniphobicity in the aramid fabric for the protection, self-cleaning, and improved interfacial adhesion between the fabric and resin for fiber-reinforced polymer composites.

The surface of phenol-based activated carbon (AC) was seriatim amino-fluorinated with solution of ammonium hydroxide and hydrofluoric acid in varying ratio to fabricate electrode materials for use in an electric double-layer capacitor (EDLC). The specific capacitance of the amino-fluorinated AC-based EDLC was measured in a 1 M H 2 SO 4 electrolyte, in which it was observed that the specific capacitances increased from 215 to 389 F g −1 and 119 and 250 F g −1 with the current densities of 0.1 and 1.0 A g −1 , respectively, in comparison with those of an untreated AC-based EDLC when the amino-fluorination was optimized via seriatim mixed solution of 7.43 mol L −1 ammonium hydroxide and 2.06 mol L −1 hydrofluoric acid. This enhancement of capacitance was attributed to the synergistic effects of an increased electrochemical activity due to the formation of surface N- and F-functional groups and increased, specific surface area, and mesopore volumes, all of which resulted from the amino-fluorination of the electrode material.

s To improve the electrochemical performance of an activated carbon (AC)-based electric double-layer capacitor (EDLC), the AC surface, which is used as an electrode, was modified using physicochemical base tuning that uses different concentrations of ammonium hydroxide. The effect of the treatment on the surface and electrochemical properties of the AC electrodes was investigated. The specific capacitance of a 13 vol%-solution-treated sample was increased to 385 F/g at a scan rate of 5 mV/s, which was 17% higher than the value of 328 F/g obtained for the untreated samples. This increase can be attributed to an increase in the mesopore volume ratio due to the etching effect of the reaction between the carbon surfaces and ammonium hydroxide. Moreover, nitrogen functional groups, which were introduced by the treatment, also improved the electrochemical properties of the resulting AC-based electrode. Therefore, a simultaneous etching and nitrogen-introducing method with ammonium hydroxide can easily introduce nitrogen functional groups on the surface of an AC electrode. This method is very effective for preparing AC for use in an EDLC with improved electrochemical properties.

To improve the electrical performance of activated carbon (AC)-based electric double-layer capacitors (EDLCs), the surface of AC was modified with gas phase ammonia treatment at 1073 K with different treatment times to carry out simultaneous etching and N-doping. The effects of the treatment on AC surfaces and their electrochemical properties were investigated. The specific capacitances of samples treated for 22 min were increased to 426 F/g at scan rates of 10 mV/s, which corresponded to a 76.8% increase as compared with 241 F/g of samples measured as received from the manufacturer. The increase is attributed to an increase in the specific surface area and the total pore, micro- and mesopore volumes due to the etching effect of the high-temperature ammonia gas reaction. Moreover, N-functional groups, which were introduced by the treatment, also aided to improve the electrochemical properties of the resulting AC-based electrode. Therefore, the simultaneous etching and N-doping method with ammonia gas at high temperature can easily introduce nitrogen functional groups on the AC surface. In addition, the reaction of nitrogen gas with AC can affect its specific surface area and surface pore structure, which is very effective in preparing AC for EDLCs with improved electrochemical properties.

The surface of phenol-based activated carbon (AC) was fluorinated at room temperature with different F 2 :N 2 gas mixtures for use as an electrode material in an electric double-layer capacitor (EDLC). The effect of surface fluorination on EDLC electrochemical performance was investigated. The specific capacitance of the fluorinated AC-based EDLC was measured in a 1 M H 2 SO 4 electrolyte, in which it was observed that the specific capacitances increased from 375 and 145 F g −1 to 491 and 212 F g −1 with the scan rates of 2 and 50 mV s −1 , respectively, in comparison to those of an unfluorinated AC-based EDLC when the fluorination process was optimized via 0.2 bar partial F 2 gas pressure. This enhancement in capacitance can be attributed to the synergistic effect of increased polarization on the AC surface, specific surface area, and micro and mesopore volumes, all of which were induced by the fluorination process. The observed increase in polarization was derived from a highly electronegative fluorine functional group that emerged due to the fluorination process. The increased surface area and pore volume of the AC was derived from the physical function of the fluorine functional group.

This study reports the application of illite as a clay filler and direct fluorination as an organophilic modification for clays. Illite was also modified using conventional methods, with reagents such as 3-aminopropyltrimethoxysilane and hexadecyl-trimethoxysilane for comparison of the resultant illite/polypropylene (PP) composites with the fluorinated illite/PP composites. The thermal properties, flame retardancy, and mechanical properties of the resultant composites were also investigated. Fluorination of illite resulted in exfoliation and more thermally stable organophilic modification compared with the conventional silane treatment. When comparing two different silane-treated illite/PP composites with fluorinated illite/PP composites, fluorinated illite had better thermal stability and exfoliation after modification and more improved dispersion in PP matrix. This resulted in improved thermal stability, flame retardancy, and mechanical properties compared with the silane-treated illite/PP composites. The fluorinated illite/PP composite exhibited a 28% increase in thermal stability and a 50% increase in flame retardancy compared with neat PP. Fluorination of illite yielded at least 50% further improvement in the thermal stability and flame retardancy of the resulting illite/PP composites compared with the conventional silane treatments.

The surface of a phenol-based activated carbons (ACs) used as an electrode in an electric double-layer capacitor (EDLC) was oxyfluorinated at room temperature with different F 2 :O 2 gas mixtures, and the effects of these surface modifications on EDLC electrical performance were investigated. The specific capacitance of the oxyfluorinated AC-based EDLC was measured in a 1 M H 2 SO 4 electrolyte, in which it was observed that the specific capacitances increased from 375 and 145 F g −1 to 391 and 189 F g −1 with the scan rates of 5 and 50 mV s −1 , respectively, over compared to those of an untreated AC-based EDLC when the oxyfluorination ratio was at the optimal F 2 :O 2 = 5:5. This was attributed to the synergistic effect of surface chemical compositions and textural properties of the resulting oxyfluorinated AC, which had the highest micropore volume, an optimal mesopore volume, and electrochemically active surface functional groups, such as C–F and quinone C O.

To investigate new applications for illite as an additive for carbon-based composites, the com- posites were prepared with and without illite at different heat-treatment temperatures. The ef- fects of the heat-treatment temperature on the chemical structure, microstructure, and thermal oxidation properties of the resulting composites were studied. As the heat-treatment tempera- ture was increased, silicon carbide SiC formation via carbothermal reduction increased until all the added illite was consumed in the case of the samples heat-treated at 2,300°C. This is attributed to the intimate contact between the SiO2 in the illite and the phenol carbon precur- sor or the carbon fibers of the preform. Among composites prepared at all temperatures, those with illite addition exhibited fewer pores, voids, and interfacial cracks, resulting in larger bulk densities and lower porosities. A delay of oxidation was not observed in the illite-containing composites prepared at 2,300°C, suggesting that the illite itself absorbed energy for exfolia- tion or other physical changes. Therefore, if the illite-containing C/C composites can reach a density generally comparable to that of other C/C composites, illite may find application as a filler for C/C composites. However, in this study, the illite-containing C/C composites exhibited low density, even when prepared at a high heat-treatment temperature of 2300°C, although the thermal oxidation of the resulting composites was improved.

C/SiC composites were prepared by boron nitride (BN)-assisted liquid silicon infiltra tion (LSI), and their anti-oxidation and mechanical properties were investigated. The microstructures, bulk densities, and porosities of the C/SiC composites demonstrated that the infiltration of liquid silicon into the composites improved them, because the layered-structure BN worked as a lubricant. Increasing the amount of BN improved the anti-oxidation of the prepared C/SiC composites. This synergistic effect was induced by the assistance of BN in the LSI. More thermally stable SiC was formed in the composite, and fewer pores were formed in the composite, which reduced inward oxygen diffusion. The mechanical strength of the composite increased up to the addition of 3% BN and decreased thereafter due to increased brittleness from the presence of more SiC in the composite. Based on the anti-oxidation and mechanical properties of the prepared composites, we concluded that improved anti-oxidation of C/SiC composites can be achieved through BN-assisted LSI, although there may be some degradation of the mechanical properties. The desired anti-oxidation and mechanical properties of the composite can be achieved by optimizing the BN-assisted LSI conditions.

A high-performance NO gas sensor was prepared by inducing thermal fluorination of carbon nanotube semiconductors. Thermal fluorination of multi-walled carbon nanotubes (MWCNTs) was carried out at various temperatures (100 ∼ 1000 °C) to investigate the effects of the reaction temperature. The mechanism of high-performance NO gas sensor electrode was shown to depend on the fluorination temperature in a way that can be divided into three regions, separated at 400 and 1000 °C. In the first temperature region, the induction of fluorine functional groups onto MWCNTs showed the opposite trend in electrical resistance change comparing with traditional p-type MWCNTs. In the second temperature region, the induced fluorine functional groups were attenuated by generated fluorinated carbon gases resulting in the decomposition of MWCNTs and the recovery of traditional p-type gas sensor behavior. In the highest temperature region above 1000 °C, reoriented carbon structure was observed, showing bent nanotubes produced from destruction by fluorination and subsequent reorientation due to the high temperature. The gas sensing responsiveness was significantly improved by the thermal fluorination, which causes electrophilic attraction, creates adsorption sites for target NO gases and improve hydrophobicity for gas sensing stability in humid condition. In conclusion, a high-performance gas sensor was obtained by thermal-fluorination of MWCNTs.

Oxy-fluorination of carbon preforms with various F2:O2 gas mixtures were examined to improve the mechanical and thermal properties of carbon fiber-reinforced carbon composites (C/C composites). The oxy-fluorination of the preforms introduced functional groups onto the preform surface, which improved their thermal properties. Oxy-fluorination also improved the interfacial adhesion of the C/C composites, resulting in increased flexural strength and anti-oxidation. Two synergistic effects of oxy-fluorination on the carbon preform are suggested. One optimizes interfacial adhesion by forming hard chemical bonds and soft electrophilic bonds between the surface functional groups of the oxy-fluorinated carbon preforms and the functional groups of the carbon precursors. The other improves anti-oxidation of the C/C composites by improving the thermal properties of the carbon preform itself and interfacial adhesion which resulted in reducing pores, voids, and interfacial cracks.

This study introduces amino-fluorination, a novel chemical modification method for activated carbon (AC), and investigates the surface and electrochemical properties of the resulting AC. The procedure was modified by controlling the surface reaction with concentrated ammonium hydroxide and diluted hydrofluoric acid or diluted ammonium hydroxide and concentrated hydrofluoric acid. Amino-fluorination of AC with concentrated ammonium hydroxide and diluted hydrofluoric acid significantly increased the specific surface area, total pore volume, mesopore volume, and number of N- and F-containing surface functional groups and decreased the number of O-containing surface functional groups. These changes resulted in improving the specific capacity to 417 F/g at a scan rate of 10 mV s −1 from the specific capacity of raw AC-based EDLCs (241 F/g). On the other hand, amino-fluorination of AC with diluted ammonium hydroxide and concentrated hydrofluoric acid increased the specific surface area, total pore volume, mesopore volume, and number of N-, O-, and F-containing surface functional groups. These changes resulted in the highest specific capacitance for the prepared AC-based EDLCs (485 F/g), with a 101% increase compared to the raw-AC-based EDLCs. Therefore, the amino-fluorination of AC is a simple and efficient way to enhance the performance of AC-based EDLCs.

To investigate potential use of a layered silicate, illite, for carbon fiber-reinforced (C/C) composites, the C/C composites were prepared at different carbonization temperatures, specifically 1000 °C and 1650 °C using illite. The physical and chemical changes in the prepared C/C composites that were induced by the addition of illite and anti-oxidation and mechanical properties of the composites were investigated. A carbothermal reaction occurred due to the addition of illite when the composite was prepared at 1650 °C, which resulted in the formation of SiC from the illite and carbon. The physical structures of the composites changed due to the increased interfacial adhesion between the reinforcing carbon fibers and the carbon matrix, which resulted increased bulk densities, and decreased porosities. The carbothermal reaction and physical structural changes that were induced by the addition of illite synergistically improved the anti-oxidation properties of the prepared composites, which were observed as a delay in oxidation. In addition, illite filler also improved flexural strength of the composite, due to the increased interfacial adhesion induced by illite addition. Therefore, the application of the layered silicate, illite, for C/C composites can be quite promising.