In this study, polyimide (PI)-based activated carbon fibers (ACFs) were prepared for application as electrode materials in electric double-layer capacitors by varying the steam activation time for the PI fiber prepared under identical cross-linking conditions. The surface morphology and microcrystal structural characteristics of the prepared PI-ACFs were observed by field-emission scanning electron microscopy and X-ray diffractometry, respectively. The textural properties (specific surface area, pore volume, and pore size distribution) of the ACFs were calculated using the Brunauer–Emmett–Teller, Barrett–Joyner–Halenda, and non-local density functional theory equations based on N2/ 77 K adsorption isotherm curve measurements. From the results, the specific surface area and total pore volume of PI-ACFs were determined to be 760–1550 m2/ g and 0.36–1.03 cm3/ g, respectively. It was confirmed that the specific surface area and total pore volume tended to continuously increase with the activation time. As for the electrochemical properties of PI-ACFs, the specific capacitance increased from 9.96 to 78.64 F/g owing to the developed specific surface area as the activation time increased.

Evaporative emissions, a major cause of air pollution, are primarily produced by automobiles and can be recovered using adsorbents. This study investigated the effect of the textural properties of polyimide (PI)-based activated carbon fibers (PIACFs) on the adsorption and desorption performance of n-butane, which are a type of evaporative emissions. PI-ACFs were prepared by varying the activation time while maintaining the identical crosslinking and carbonization conditions. The surface morphology and microstructural properties of the ACFs were examined using a field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD), respectively. The textural properties of ACF (specific surface area, pore volume, and pore size distribution) were analyzed using N2/ 77 K adsorption and desorption isotherm curves. The n-butane adsorption and desorption performance were evaluated according to modified ASTM D5228. From the results, the specific surface area and total pore volume of ACFs were determined to be 680–1480 m2/ g and 0.28–1.37 cm3/ g, respectively. Butane activity (BA) of the ACFs increased from 14.1% to 37.1% as the activation time increased, and especially it was found to have highly correlated with pore volume in the 1.5–4.0 nm range.

In this study, we utilized a multi-step stabilization method, incorporating dry-oxidation, to produce high-density polyethylene (HDPE)-based activated carbon fibers. This stabilization was achieved through electron-beam irradiation, sulfonation, and dry oxidation. The stabilized fibers were carbonized and activated at 900 ℃. The crystallite characteristics of the activated carbon fibers were observed using X-ray diffraction, and their surface morphologies were analyzed through scanning electron microscopy. The textural properties were analyzed using N2/ 77 K adsorption–desorption isothermal curves. And leveraging the microdomain model, we explored the influence of these stabilization methods on the HDPE-based activated carbon fibers texture properties. The results show that HDPE fibers treated with sulfonation only at 100 ℃ for 60 min were not sufficiently cross-linked and were completely decomposed during the carbonization stage. However, the sulfonated fibers treated with the new dry-oxidation process maintained their shapes and were successfully activated. The specific surface area of the resulting activated carbon fibers was as much as 2000 m2/ g.

In this study, Pitch-derived activated carbon (PAC) pellets were by steam activation for automotive carbon canisters. The crystal structure of PAC was analyzed using X-ray diffraction. The textural properties of PAC were studied by Brunauer– Emmett–Teller (BET), Horvath-Kawazoe (HK), and Non-Localized Density Functional Theory (NLDFT) equations with N2/ 77 K isotherm adsorption/ desorption curves. The butane adsorption capacity of the PAC pellets was analyzed according to the ASTM D5228 standard. With increasing steam activation time, the specific surface area and total pore volume of the PAC increased 650–1950 m2/ g and 0.27–1.02 cm3/ g, respectively. The mesopore ratio of PAC increased with increasing activation time and was observed up to 28.4% at 190 min. The butane adsorption capacity of the PAC increased and was observed to range from 10.86 to 51.55%. A close relationship between butane adsorption capacity and pore size (1.47–2.39 nm) was found. Finally, the butane activity of PAC was found to be 51.55% for the steam activated at 950 ℃ for 190 min; this butane activity is 24% better than that of the coconut-derived activated carbon (41.43%) with a similar specific surface area, indicating that pitch is a suitable material for the activated carbon of automotive carbon canisters.

Traditional piles used for deep foundation, such as steel, concrete, and timber, are susceptible to corrosion and a reduction in structural capacity over time. This has led to the development of new materials like concrete-filled FRP piles (CFFP). CFFP is a composite pile filled with concrete and covered with a fiber-reinforced plastic (FRP) shell, providing non-corrosive reinforcement and protection to the concrete. As a result, CFFP is a highly promising candidate for implementation in various fields due to its structural advantages and necessity. Compared to traditional concrete piles, CFFP can be installed with less damage and a lower blow range due to its elastic modulus, damping ratio, and specific weight. The bearing capacity of a pile is influenced by various factors, including its stiffness, residual stress, and axial load resistance. Due to competitive pricing, glass fiber has been widely utilized, and there is a growing interest regarding carbon-fiber-reinforced concrete piles due to the excellent mechanical properties of carbon fiber. The remarkable stiffness and strength attributes of carbon fibers are evident in CFRP-confined piles, which present a notably wide range of load-bearing capacities, boasting an ultimate axial load capacity ranging from 500 to 4000 kN. Furthermore, CFFPs have been confirmed to have superior lateral load resistance compared to conventional piles, attributed to the reinforcement provided by FRP materials. Conventional piles face a challenge in that their structural characteristics deteriorate in the corrosive marine environment, with a projected lifespan of less than 20 years. In contrast, the service life of CFFPs is estimated to range from 50 to 75 years.

In recent times, there has been a significant demand for supercapacitors in energy storage applications due to their rapid charging– discharging capabilities, high power density, and excellent stability. Nevertheless, the synthesis of electrode materials with a substantial surface area, exceptionally high porosity, and superior electrochemical performance is still challenging. Activated carbons with a distinctive porous structure and exceptional electrochemical properties emerged as promising electrode materials for supercapacitors. In this study, we used a porous activated carbon (PAC) derived from petroleum coke followed by KOH activation as an efficient anodic electrode material. The ultra-high Brunauer–Emmett–Teller surface area of 2105.6 m2 g− 1 with stacked layers of carbon atoms arranged in a two-dimensional hexagonal structure makes the PAC an efficient candidate for a supercapacitor electrode. The PAC delivers a specific capacitance of 470 F g− 1 at a current density of 0.5 A g− 1 over a potential window of 0 to −1 V. The excellent cycling stability in a three-electrode setup with a capacitance retention of ⁓98% even at a high current density of 10 A g− 1 makes the PAC a potential anodic electrode material for high-performance supercapacitor applications.

Evaporative emission generated through the fuel supply system of a gasoline automobile is prevented into the atmosphere through an activated carbon canister system. In this study, the oxygen functional group of activated carbon was controlled using a simple gas phase treatment to improve evaporative emission reduction performance, and the adsorption/desorption performance of evaporative emissions was evaluated according to microwave heating conditions. Microwave heating was used to remove the oxygen functional group of the activated carbon efficiently. Microwave heating was found to remove oxygen functional groups in a short treatment time (1–7 min). Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, and scanning electron microscope–energy-dispersive X-ray spectroscopy were employed to investigate modifying the oxygen functional group of the activated carbon. Using N2/ 77K adsorption/desorption isotherm, the textural properties of the activated carbon according to microwave heating conditions were examined. The Brunauer–Emmett–Teller (BET) equation was used to calculate the specific surface area of the activated carbon, and the Dubinin–Radushkevich (DR) equation was used to calculate the micropore volume of activated carbon. Microwave heating effectively increased the butane working capacity, which is the neat adsorption capacity of activated carbon, from 7.12 g/100 ml to a maximum of 8.04 g/100 ml.

To address the need for a suitable thermoplastic resin-based sizing agent for accommodating the increasing demands of carbon fiber-reinforced plastic, in this work, alcohol-soluble polyamide 6 (PA6) and silane were chemically combined in a certain ratio to improve the mechanical interface properties of the carbon fiber/PA6 composite, and the enhancement in the mechanical interface strength of the final composite according to the treatment time was confirmed. Carbon fiber surface properties were analyzed through ultrahigh-resolution field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy, and Fourier transform infrared spectrometry. The tensile strength of carbon fibers before and after hybrid sizing treatment and the mechanical interfacial shear strength of the final composite were analyzed using tensile and universal testing machines, respectively. After the hybrid sizing treatment, the introduction of the sizing agent to the carbon fiber surface was confirmed through FE-SEM, and a simultaneous increase in the surface roughness was observed. Moreover, the interfacial adhesion was confirmed to increase significantly, as compared to that of the desized carbon fiber. Therefore, this modified sizing agent treatment serves as an effective method for improving the mechanical interfacial adhesion between the carbon fiber and the PA6 matrix.

Abstract In this study, micro-defects on/in carbon fibers were modified by irradiation with an electron beam, which improved the mechanical strength of single carbon fibers. The electron beam irradiation was 10 kGy (using a 1.5 MeV accelerator in the air). The total doses ranged from 100 to 500 kGy. The tensile strength of the single carbon fiber was measured using a universal testing machine. The micro-defects on the fiber surface were observed with scanning electron microscopy and atomic force microscopy, and those in the fiber were evaluated by Raman spectroscopy. In conclusion, the electron beam treatment produced changes in the micro-defects on/in the carbon fibers, resulting in up to 14% improvement in the tensile strength of single carbon fiber.

In this work, the correlation between the pore characteristics of activated carbon (AC) and the adsorption/desorption characteristics of evaporated fuel was studied. AC was prepared by various physical re-activation methods using coconut-derived commercial AC. Pore characteristics of the re-activated AC were investigated using N2/ 77 K adsorption isotherms. The structural characteristics of the AC were observed by X-ray diffraction and Raman spectroscopy. The butane working capacity was observed according to ASTM D5228. From the results, the specific surface area and total pore volume of the ACs were determined to be 1380–2040 m2/g and 0.60–0.96 cm3/g, respectively. It was also observed that various pore size distributions were found to be dependent on the functions of the activation method and time. A close relationship between butane activity/ retentivity and micropore/mesopore volumes was found. In addition, it was inferred that the volume fraction of micropores and sub-mesopores with diameters between 1.5 and 3.0 nm primarily controls butane activity.

In this study, we prepared ACFs with a high specific surface area from various precursors (rayon, pitch, and oxidized polyacrylonitrile-based fibers) by a steam-activation technique and investigated the effects of the micropore and mesopore fraction on 2-CEES adsorption behaviors. The activation time was precisely controlled so that the activation yield was in the range of 35–40% to ensure the mechanical properties of the ACFs. The N2 adsorption isotherm characteristics at 77K were confirmed by Brunauer–Emmett–Teller, Barrett–Joyner–Halenda and non-local density functional theory equations. The adsorption capacities of the ACF were measured by breakthrough experiments in the gas phase (750 μg/mL of 2-CEES in N2 flow). The removal efficiency of the ACFs was evaluated and compared with that of AC. From the results, specific surface areas and total pore volume of the ACF were determined to be 1380–1670 m2/g and 0.61–0.82 cm3/g, respectively. It was also observed that various pore characteristics of ACF were found to be dependent on crystallite structure of each precursor. The break through time (C/C0 = 0.10) was in the order of Oxi-Pan-H-9-2 < Saratoga AC < Rayon-H-9-3 < Pitch-H-9-4. This indicates that 2-CEES adsorption capacity could be a function not only of specific surface area or total pore volume, but also of sub-mesopore volume fraction in the range of 1.5–2.5 nm of adsorbents.

In this study, activated carbon with well-developed mesopores was fabricated using kenaf short fibers as a representative biomass. Concentrated phosphoric acid was selected as an activation agent to create highly developed porous structures, and pore development was observed to occur in relation to the weight ratio of phosphoric acid and kenaf. The pore characteristics of the kenaf-based activated carbon were determined using the N2/ 77K adsorption isotherm, and its microcrystalline structure was analyzed using X-ray diffraction. The highest specific surface area (1570 m2/g) was observed when the weight ratio of phosphoric acid to kenaf was 3:1, and the highest mesopore fraction (74%) was observed at 4:1. The carbonization yield was 45–35%, which is higher than that of commercial activated carbon. The production of porous carbon material by this method offers high potential for application because it can be controlled over a wide range of average pore diameter from 2.48 to 5.44 nm.