• Research Paper

    Experimental and Numerical Wear Behavior Analysis of Piston Made of Hybrid Aluminum Metal Matrix Composite
    R. Hemanth Kumar, V. S. K. Venkatachalapathy
    The use of aluminum-based hybrid metal matrix composite (HMMC) materials, especially in engine components like pistons, is intended to improve wear resistance … + READ MORE
    The use of aluminum-based hybrid metal matrix composite (HMMC) materials, especially in engine components like pistons, is intended to improve wear resistance and overall performance. Crucial tribological indicators, such as wear and friction coefficients, underscore the significance of these materials. However, present aluminum alloys have limited wear because of clustered reinforced particles and relatively high coefficients of thermal expansion (CTE), resulting in inadequate anti-seizure properties during dry sliding conditions. This research introduces a novel “Hybrid Metal Matrix Composite of Al7068 Reinforced with Fly Ash-SiC-Al2O3”. Al7068 is employed for its superior strength-to-weight ratio and specific modulus, which is ideal for components exposed to cyclic loads and varying temperatures. The integration of fly Ash (FA), silicon carbide (SiC), and alumina (Al2O3) as reinforcements enhances wear resistance, diminishes particle clustering, improves stiffness, mitigates CTE discrepancies, and fortifies the composite against strain and corrosion, thereby enhancing its overall performance. The Stir-casting method was used with optimized reinforcement percentages (10 % total), and comprehensive evaluations through wear tests and mechanical property analyses determined the composite's optimal composition. The proposed HMMC variant with the most suitable reinforcement percentage exhibited enhanced engine piston functionality, reduced wear, low deformation of 0.20 mm, and a comparatively higher ultimate tensile strength of 190 megapascals (Mpa). - COLLAPSE
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    27 July 2025

  • Research Paper

    Enhanced Electrochemical Properties of NaFe2PO4(SO4)2 via Co2+ Doping as Cathode Material for Sodium-ion Batteries
    Yao Liu, Yilei Sun, Haixia Wang, Zeda Meng, Won-Chun Oh
    Sodium-ion batteries (SIBs) offer a viable alternative to partially or fully replace lithium ion batteries (LIBs) due to their lower cost and … + READ MORE
    Sodium-ion batteries (SIBs) offer a viable alternative to partially or fully replace lithium ion batteries (LIBs) due to their lower cost and increased safety. This paper outlines the compositional optimizations, crystallographic evaluations, and electrochemical behavior of a novel mixed NASICON polyanionic compound, NaFe2PO4(SO4)2 (NFPS). X-ray photoelectron spectrometry (XPS) results showed that cobalt doping produces a higher concentration of oxygen defects compared to undoped samples. Scanning electron microscopy (SEM) analysis results revealed that the modified sample has more uniform pores and pore distribution. Brunauer-Emmett-Teller (BET) measurements showed that doping of Co2+ reduces the specific surface area of NFPS-Co0.08 compared to NFPS. This shortens the sodium ion diffusion pathway and promotes ion dynamics. The addition of Co2+ to the sample significantly improved its performance during galvanostatic charge-discharge tests. The electrochemical activity also is significantly enhanced by Co2+ doping. Na0.84Co0.08Fe2PO4(SO4)2 exhibits superior rate and cycling performance compared to pristine NFPS. After 80 cycles at 25 mA g-1, NFPS-Co0.08 retained discharge specific capacity of 60.8 mA h g-1, which is 1.24 times greater than that of NFPS. - COLLAPSE
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    27 July 2025

  • Research Paper

    Influence of End-Cap Modeling on Optoelectronic and Photovoltaic Properties of Fluorine-Substituted Bis-Benzothiadiazoles
    Prabhat Gautam, Anurag Gautam, Rekha Sharma, Sangram Keshari Das, Neeraj Kumar
    Efficient donor-acceptor (D-A) molecular scaffolds should be developed for the advancement of organic solar cells (OSCs). Density functional theory (DFT) and time-dependent … + READ MORE
    Efficient donor-acceptor (D-A) molecular scaffolds should be developed for the advancement of organic solar cells (OSCs). Density functional theory (DFT) and time-dependent density functional theory (TDDFT) studies provide an effective methodology to perform initial studies to design and investigate D-A molecular systems. Two fluorine-substituted bis-benzothiadiazoles (FBBTs) are designed and optimized using the DFT method. The results show better planarity for FBBT2, which is attributed to π-extension between the FBBT units. A series of D-A small molecules CB1-4 are designed utilizing FBBT2 to study the effect of systematically substituting carbazole donor and cyano-based acceptor groups on the optoelectronic properties of FBBT. DFT calculations are performed using the B3LYP functional. The designed D-A scaffolds exhibit systematic tuning of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), HOMO-LUMO gap (from 2.333 eV to 1.825 eV). The observed HOMO-LUMO gap follows the trend CB1 > CB2 > CB4 > CB3. The Voc (open-circuit voltage) and power conversion efficiency (PCE) for CB1-4 are presented with the PC71BM acceptor. The overall trend observed for the Voc follows the order CB1 < CB4 < CB2 < CB3. The PCE trend observed using the Scharber model follows the trend CB3 > CB4 > CB2 > CB1. The results show that end cap modeling of π-extended FBBT with cyano-based acceptor groups significantly improves the observed PCE and Voc. - COLLAPSE
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    27 July 2025

  • Research Paper

    Development of In-situ Permeation Measuring System Based on Manometric Analysis Method for Evaluating High-Pressure Hydrogen Permeation Properties of Polymer Materials up to 100 MPa

    최대 100 MPa 고분자 소재의 고압 수소 투과 특성 평가를 위한 압력 분석법 기반의 In-situ 투과 측정 시스템 개발

    Ji Hun Lee

    이지훈

    A high-pressure in-situ permeation measuring system was developed to evaluate the hydrogen permeation properties of polymer sealing materials in hydrogen environments up … + READ MORE
    A high-pressure in-situ permeation measuring system was developed to evaluate the hydrogen permeation properties of polymer sealing materials in hydrogen environments up to 100 MPa. This system employs the manometric method, utilizing a compact and portable manometer to measure the permeated hydrogen over time, following high-pressure hydrogen injection. By utilizing a self-developed permeation-diffusion analysis program, this system enables precise evaluation of permeation properties, including permeability, diffusivity and solubility. To apply the developed system to high-pressure hydrogen permeation tests, the hydrogen permeation properties of ethylene propylene diene monomer (EPDM) materials containing silica fillers, specifically designed for gas seal in high-pressure hydrogen environments, were evaluated. The permeation measurements were conducted under pressure conditions ranging from 5 MPa to 90 MPa. The results showed that as pressure increased, hydrogen permeability and diffusivity decreased, while solubility remained constant regardless of pressure. Finally, the reliability of this system was confirmed through uncertainty analysis of the permeation measurements, with all results falling within an uncertainty of 11.2 %. - COLLAPSE
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    27 July 2025

  • Research Paper

    Strength Properties of Reactive Powder Concrete Mixed with Various Shapes of Gamma Irradiated Recycled Polyethylene Terephthalate

    감마선을 조사한 다양한 형태의 재활용 PET 혼입 RPC의 강도 특성

    Jijon Kang, Seongyoung So

    강지존, 소승영

    Since the first introduction of plastics, the issue of recycling has been repeatedly discussed. Plastics with limited biodegradability accumulate in the soil … + READ MORE
    Since the first introduction of plastics, the issue of recycling has been repeatedly discussed. Plastics with limited biodegradability accumulate in the soil and ocean when deposited in landfills, causing environmental problems, and when incinerated emit a large amount of carbon. In particular, polyethylene terephthalate (PET) is now an indispensable material in daily life, and the waste it generates is also significant. In response, we sought a way to use PET waste as a concrete additive. Typically, adding PET damages the physical strength of concrete, and to solve this problem, gamma ray irradiation was first applied to the PET. The overall peak intensity of the fourier transform infrared spectroscopy (FT-IR) absorption spectrum of gamma-ray-irradiated PET increased, and the surface hydrophilicity of the material increased. In addition, it was confirmed that surface roughness increased when PET was irradiated with gamma rays. The strength of concrete mixed with gamma-irradiated PET was measured, and the compressive strength increased compared to concrete mixed with non-gamma-irradiated PET, and in the case of fibrous PET, the flexural strength increased. - COLLAPSE
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    27 July 2025

  • Research Paper

    Eco-Friendly Bio-Templated Synthesis of Hierarchically Micro/Nano-Structured Ag Photocatalyst

    생체 주형을 활용한 마이크로/나노 계층 구조를 갖는 은 광촉매의 친환경적 합성

    Won Woo Park, Woo Chan Hwang, Soo Hyun In, Han Sung Choi, Heejoon Kim, Seong-Hyeon Seo, Jeonghyun Yun, Mi Young Han

    박원우, 황우찬, 인수현, 최한성, 김희준, 서성현, 윤정현, 한미영

    Silver nanoparticles (AgNPs) are promising photocatalysts with a broad light absorption range and high catalytic activity. However, conventional synthesis methods often involve … + READ MORE
    Silver nanoparticles (AgNPs) are promising photocatalysts with a broad light absorption range and high catalytic activity. However, conventional synthesis methods often involve toxic chemicals, limiting their environmental applicability. In this study, we developed an eco-friendly bio-templating method to synthesize hierarchical micro/nano-structured silver (MNAg) photocatalysts that uses plant leaves, including Nelumbo nucifera (lotus leaf), Rosa sp. (rose petal), and Limonium sinuatum (statice petal), as natural templates. By modifying the leaf surfaces with citrate functional groups, AgNPs were selectively formed along the microstructures of the templates, preserving their hierarchical morphology. MNAg photocatalysts were subsequently obtained through controlled calcination, and successfully retained the microscale structure of the original template. The surface morphology, chemical composition and crystalline structure of the MNAg were characterized using scanning electron microscopy (SEM), field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), and X-ray diffraction (XRD), confirming the successful formation of hierarchical AgNPs. The optical behavior of the MNAg, characterized with diffuse reflectance spectroscopy (DRS), demonstrated broadened absorption across the visible region, which is attributed to plasmonic coupling among the densely packed AgNPs, partially interconnected along the hierarchical surface. The photocatalytic performance of the MNAg materials was evaluated for methylene blue degradation under UV-Vis illumination. The MNAg derived from lotus leaves exhibited the highest photocatalytic efficiency. This study presents a sustainable route to hierarchical Ag photocatalysts, highlighting the potential of bio-inspired nanomaterials for environmental applications. - COLLAPSE
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    27 July 2025

  • Research Paper

    Optimization of Machine Learning Models for Predicting the Saturation Magnetization of SmCo Permanent Magnet Materials

    SmCo 영구자석 소재의 포화자화값 예측을 위한 기계학습 모델 최적화

    Chunghee Nam

    남충희

    As demand grows for electric vehicles and advanced mobility technologies, developing materials for permanent magnets has become increasingly essential. Among them, SmCo-based … + READ MORE
    As demand grows for electric vehicles and advanced mobility technologies, developing materials for permanent magnets has become increasingly essential. Among them, SmCo-based permanent magnets are gaining attention due to their superior thermal stability compared to conventional NdFeB magnets, making them promising candidates for high-temperature motor applications. However, optimizing the magnetic properties of SmCo alloys remains challenging due to their complex phase structures and elemental interactions. In this study, we develop and optimize machine learning (ML) models to predict the saturation magnetization of SmCo permanent magnets using only composition-based descriptors. A dataset comprising various SmCo alloys was analyzed, with features extracted using Matminer and Pymatgen modules. We applied Random Forest (RF), eXtreme Gradient Boosting (XGB), and Support Vector Regression (SVR) models and compared their regression performance using R2 score and Root-mean-squared-error (RMSE). The RF model demonstrated the best generalization and prediction accuracy. To identify the most influential features, we used permutation feature importance. Further, we refined the feature set using a genetic algorithm (GA), ultimately selecting 9 key features that yielded the highest model performance (R2 = 0.963, RMSE = 4.22 emu/g). This study highlights the potential of combining machine learning with genetic optimization to accelerate the design of high-performance, thermally stable SmCo permanent magnets. - COLLAPSE
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    27 July 2025

  • Research Paper

    Fabrication and Evaluation of Multilayer Pore-Filling Cation Exchange Membrane for Suppressing Property Degradation by Multivalent Ions

    다가이온에 의한 특성 열화를 줄이기 위한 다층구조 세공충진 이온교환막의 제막 및 특성 평가

    Woohyun Choi, Yeongseo Kim, Jeong Geun Park, Min-Gyu Kim, Yeon-Gil Jung, Hae-Kwon Jeong, SeungCheol Yang

    최우현, 김영서, 박정근, 김민규, 정연길, 정해권, 양승철

    Multivalent ions in natural aqueous solutions—such as seawater, brackish water, and freshwater—can negatively affect the performance of ion exchange membranes (IEMs) used … + READ MORE
    Multivalent ions in natural aqueous solutions—such as seawater, brackish water, and freshwater—can negatively affect the performance of ion exchange membranes (IEMs) used in electrochemical energy and environmental devices. In this study, a pore-filling cation exchange membrane (CEM) permeable to multivalent ions was fabricated to minimize performance degradation caused by such ions. To achieve this, multilayer pore-filling CEMs were prepared by performing two impregnation processes using monomer electrolyte solutions of different compositions (varying deionized water content and monomer-to-crosslinker ratios). As a result, a highly crosslinked electrolyte polymer formed on the internal side of the CEM, while a low-crosslinked polymer formed on the external side. Due to the presence of the low-crosslinked outer polymer layer, the multilayer pore-filling CEM exhibited a smaller increase in resistance caused by Mg2+ ions. Furthermore, based on the correlation between permselectivity and resistance measured in a 0.45 M NaCl + 0.05 M MgCl2 solution, which simulated the Mg2+ concentration in seawater, an optimal structure of multilayer pore-filling CEM was identified, and it exhibited a minimized increase in resistance and a permselectivity of over 90 %. - COLLAPSE
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    27 July 2025

  • Research Paper

    Effect of Delayed Quenching on Mechanical Properties of High-Strength API X70 Linepipe Steels

    고강도 API X70 라인파이프강의 기계적 특성에 미치는 지연 급랭의 영향

    Min-Seop Jeong, Dong-Kyu Oh, Seung-Hyeok Shin, Myeong-Gyu Seo, Kyutae Kim, Byoungchul Hwang

    정민섭, 오동규, 신승혁, 서명규, 김규태, 황병철

    This study examines the effect of delayed quenching (DQ) temperature on the microstructure and mechanical properties of API X70 linepipe steels. Three … + READ MORE
    This study examines the effect of delayed quenching (DQ) temperature on the microstructure and mechanical properties of API X70 linepipe steels. Three types of steels were fabricated by varying the DQ conditions: Base (without DQ), LDQ (low-temperature delayed quenching at 700 °C), and HDQ (high-temperature delayed quenching at 740 °C). The microstructures were characterized using optical microscopy, scanning electron microscope (SEM), and electron back-scattered diffraction (EBSD), and their mechanical properties were evaluated through tensile and Charpy impact tests. The Base specimen exhibited the finest effective grain size and the highest bainite fraction, resulting in superior yield strength and impact toughness. In contrast, the LDQ specimen showed increased pearlite content and coarser grains, leading to the highest tensile strength due to work hardening, but reduced impact properties due to crack initiation at the pearlite regions. The HDQ specimen, with the highest ferrite fraction, showed the best ductility and acceptable strength, as well as improved low-temperature toughness owing to increased resistance to cleavage propagation. EBSD analysis confirmed that finer grains and higher fractions of high-angle grain boundaries play a crucial role in enhancing impact energy and lowering the ductile-to-brittle transition temperature (DBTT). These findings highlight the importance of optimizing DQ parameters to achieve a balanced combination of strength–toughness in high-strength linepipe steels. - COLLAPSE
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    27 July 2025
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