DSpace Community: KAIST Dept. of Nuclear and Quantum EngineeringKAIST Dept. of Nuclear and Quantum Engineeringhttp://hdl.handle.net/10203/192024-03-06T05:40:55Z2024-03-06T05:40:55ZCompensating isotope effect on molecular emission of hydroxyl and imidogen isotopologues in laser-induced plasmaChoi, Sung-UkJo, YongheumYun, Jong-Ilhttp://hdl.handle.net/10203/3175712024-01-09T05:00:29Z2024-02-01T00:00:00ZTitle: Compensating isotope effect on molecular emission of hydroxyl and imidogen isotopologues in laser-induced plasma
Authors: Choi, Sung-Uk; Jo, Yongheum; Yun, Jong-Il
Abstract: Background
The molecular isotopologues in laser-induced plasma exhibit riddling emission behaviors in terms of wavelength, intensity, and temporal evolution of spectra due to the isotope effect. Although this phenomenon introduces uncertainty to isotope analyses based on molecular spectra, its underlying mechanism remains undisclosed.
Results
In this study, laser-induced breakdown spectroscopy (LIBS) is employed to identify the emission behavior of hydrogen, oxygen, and nitrogen isotopologues in a plasma plume. The goal is to discern the details of the isotope effect and mitigate resulting uncertainty. The molecular emissions of hydroxyl (OH) and imidogen (NH) were measured from plasma ablated on isotopically enriched water samples. Time-resolved detection clearly reveals distinct isotopic disparities in intensity variation and optimum gate delay, which were attributed to plasma thermo-hydrodynamics. Lighter isotopologues exhibit earlier and faster associations than their heavier counterparts due to their fast reaction rates and expansion velocities. The extent of the isotope effect hinged on plasma characteristics governed by measurement conditions. Consequently, comparing spectral intensity between molecular isotopologues cannot directly indicate the nominal isotope abundance of the sample. To address it, a compensation strategy has been devised, quantifying isotope effects through parameters like the slope and optimum delay of time-resolved detection. The approach successfully predicts nominal isotope abundance using compensated intensity ratios, with an absolute bias of less than 3 %.
Significance
This study not only offered fundamental insights into the isotope effect in laser-induced plasma but also proposed an alternative method for isotope quantification that circumvents complicated calibration processes.2024-02-01T00:00:00ZUniformly scalable and stackable porous transport layer manufactured by tape casting and calendering for efficient water electrolysisPark, Seong HyeonKoo, Jong UnPark, Young JuneJang, SeungsooLee, Kang TaekHan, Hyuk SuRyu, Ho Jinhttp://hdl.handle.net/10203/3180452024-02-14T03:00:25Z2024-02-01T00:00:00ZTitle: Uniformly scalable and stackable porous transport layer manufactured by tape casting and calendering for efficient water electrolysis
Authors: Park, Seong Hyeon; Koo, Jong Un; Park, Young June; Jang, Seungsoo; Lee, Kang Taek; Han, Hyuk Su; Ryu, Ho Jin
Abstract: Proton exchange membrane water electrolysis (PEMWE) stands out as the most promising and eco-friendly technology for directly converting renewable energy into hydrogen. A critical element within a PEMWE cell is the porous transport layer (PTL), typically constructed from Ti to withstand the rigorous conditions of water electrolysis. Herein, we present a cost-effective and viable fabrication process for Ti-PTLs, utilizing tape -casting method in combination with a lamination-roll calendering procedure, facilitating precise thickness control. By systematical fine-tuning the debinding conditions, we obtained a phase-pure Ti-PTL endowed with a highlyinterconnected pore structure. A comprehensive analysis of digitally twinned Ti-PTL, constructed through a state -of -the -art three-dimensional (3D) reconstruction process, reveals a remarkable uniformity in the open pore structures across Ti-PTLs of varying thicknesses, highlighting their considerable practical potential. Furthermore, the electrochemical performance of PEMWE cells using our Ti-PTLs surpassed that of the benchmark commercial Ti-PTL, demonstrating the significant promise of our tape -casting process followed by lamination-roll calendering procedure in practical Ti-PTL fabrication.2024-02-01T00:00:00ZDevelopment of an on-demand flooding safety system achieving long-term inexhaustible cooling of small modular reactors employing metal containment vesselJae Hyung ParkJihun ImHyo Jun AnYonghee KimLee, Jeong-IkSung Joong Kimhttp://hdl.handle.net/10203/3181082024-02-19T04:00:13Z2024-02-01T00:00:00ZTitle: Development of an on-demand flooding safety system achieving long-term inexhaustible cooling of small modular reactors employing metal containment vessel
Authors: Jae Hyung Park; Jihun Im; Hyo Jun An; Yonghee Kim; Lee, Jeong-Ik; Sung Joong Kim2024-02-01T00:00:00ZAchieving superior strength and elongation from electrically assisted pressure joining of medium entropy alloy and Ti-6Al-4VAkmal, MuhammadKim, HyeongjinPhan, Van CongDo, Thanh ThuongHong, Sung-TaeRyu, Ho Jinhttp://hdl.handle.net/10203/3142832023-11-06T05:00:15Z2024-01-01T00:00:00ZTitle: Achieving superior strength and elongation from electrically assisted pressure joining of medium entropy alloy and Ti-6Al-4V
Authors: Akmal, Muhammad; Kim, Hyeongjin; Phan, Van Cong; Do, Thanh Thuong; Hong, Sung-Tae; Ryu, Ho Jin
Abstract: In the present study, two dissimilar alloys (Ti-6Al-4V and NbTiZr(MoTa)(0.1)) are joined using electrically-assisted pressure joining. This joining technique can produce components with superior mechanical properties (with a yield strength of similar to 980 MPa and elongation of similar to 0.5%), ensuring optimal performance under severe operating conditions. A detailed analysis of the joined interface related to phase analysis and mechanical mapping elaborated a strong joint having a high yield strength without any post-heat treatment. The findings of the present study contribute to the broader field of dissimilar metal joining and can serve as a reference for future research and development in the aerospace industry. This study demonstrates the feasibility of achieving strong and ductile solid-state joints between dissimilar alloys.2024-01-01T00:00:00Z