https://scholarworks.unist.ac.kr/handle/201301/69 2026-04-08T00:28:18Z 2026-04-08T00:28:18Z 김성준 함준혁 김지현 https://scholarworks.unist.ac.kr/handle/201301/90217 2026-01-09T09:56:27Z 2025-04-22T15:00:00Z

Title: 고질소 오스테나이트 스테인리스 강의 미세조직 변화에 미치는 열시효 효과 Author(s): 김성준; 함준혁; 김지현

2025-04-22T15:00:00Z Jeong, Junhyuk Lee, Yunju Song, Inyoung Kim, HanSoo Kim, Ji Hyun https://scholarworks.unist.ac.kr/handle/201301/90212 2026-01-09T09:56:24Z 2025-09-21T15:00:00Z

Title: Thermal Aging Behavior of Polymers under 110℃ Air Oxidative Conditions Author(s): Jeong, Junhyuk; Lee, Yunju; Song, Inyoung; Kim, HanSoo; Kim, Ji Hyun Abstract: In this study, five types of polymers fluoroelastomer (FKM), ethylene propylene diene monomer (EPDM) rubber, ethylene propylene rubber (EPR), chloroprene rubber (CR), and silicone rubber (SR) were subjected to thermal aging in air at 110°C for up to 30 days to comparatively evaluate their aging behaviors. Changes in key functional groups were monitored using Fourier-transform infrared (FT-IR) spectroscopy, with peak intensities normalized to those of unaged reference specimens. Element analysis (EA) was employed to quantify variations in carbon, hydrogen, nitrogen, and oxygen contents, and these results were systematically correlated with observed variation in hardness values. The results revealed distinct differences in thermal-oxidative durability among the tested materials. EPR and CR exhibited pronounced oxidative degradation, as evidenced by significant increases in both the carbonyl FT-IR peak and oxygen content, accompanied by marked increases in hardness. In contrast, FKM, EPDM, and SR demonstrated comparatively high stability, showing minimal variation in hardness values under the same conditions.

2025-09-21T15:00:00Z Kim, Seongjun Ham, Junhyuk Kim, Ji Hyun https://scholarworks.unist.ac.kr/handle/201301/90213 2026-01-09T09:56:25Z 2025-08-10T15:00:00Z

Title: Thermal Aging Effect on the Microstructural Evolution and Mechanical Properties of High-Nitrogen Austenitic Stainless Steel Author(s): Kim, Seongjun; Ham, Junhyuk; Kim, Ji Hyun

2025-08-10T15:00:00Z 정준혁 이윤주 송인영 김한수 김지현 https://scholarworks.unist.ac.kr/handle/201301/90186 2026-01-09T06:50:29Z 2025-04-09T15:00:00Z

Title: 원자력 발전소 감마선 환경에서의 EPDM 열화거동 평가 Author(s): 정준혁; 이윤주; 송인영; 김한수; 김지현 Abstract: This study evaluates the degradation behavior of ethylene propylene diene rubber (EPDM) under gamma irradiation in normal operating conditions and design basis accident conditions of nuclear power plants (NPPs). Polymeric materials used in nuclear power plants, such as cables and sealing materials, are known to be vulnerable to degradation when exposed to environmental factors such as radiation for normal operation and accident periods. The degradation of these polymeric materials can affect the functionality of safety-related equipment and components, resulting in an effect on the safety of NPPs. EPDM is used in safety-related equipment, such as insulation and jackets for cables, and the assessment of its radiation-induced degradation is imperative. To evaluate the degradation behavior of EPDM, gamma irradiation was performed at a total integrated dose (TID) of 200, 400, 800, 1200, 1600, and 2000 kGy with a dose rate of 9 kGy/hr in atmospheric air. EPDM was evaluated through hardness tests, thermogravimetric analysis (TGA), Fourier transformed infrared (FT-IR) spectroscopy, and element analysis (EA) to evaluate the materials properties under gamma irradiation. As the gamma irradiation dose increased, a hardening phenomenon was observed, characterized by an increase in hardness. The evaporation of additive such as oil was accelerated by gamma irradiation, resulting in to increasing of weight loss. The FT-IR spectrum analysis revealed the scission of EPDM polymer chains and the evaporation of additives, suggesting insights into the molecular degradation mechanism

2025-04-09T15:00:00Z