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Cesium Lead Halide 페로브스카이트 양자점의 음이온 교환 반응 동역학
이시맥(See Maek Lee),정현성(Hyunsung Jung),박운익(Woonik Park),임현섭(Hyunseob Lim),방지원(Jiwon Bang) 한국표면공학회 2018 한국표면공학회지 Vol.51 No.5
Cesium lead halide perovskite quantum dots (QDs) have recently emerged as highly promising opto-electronic materials. Despite the relative facile anion exchange reactions in cesium lead halide perovskite QDs, in depth study of the anion exchange reactions such as reaction kinetics are required that can provide insight into the crystal transformation in the cesium lead halide perovskite QDs. Herein, we investigated the anion exchange reaction from CsPbI₃ QDs to CsPbBr₃ QDs with varying the particle size of the starting CsPbI₃ QDs. By characterizing the PL spectra in the anion exchange reaction process, we observed that discontinuous PL peak shifts during I-to-Br anion exchange reaction in starting CsPbI₃ QDs over a critical size. Origin of the discontinuous I-to-Br anion exchange kinetics are mainly due to thermodynamically unstable nature of the CsPb(Br/I)₃ alloy QDs.
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Macro fiber composite (MFC) 센서를 이용한 음향방출 기술 기반 배관 누수 감지 시스템
박재현,이시맥,이범주,김선주,유형민 한국복합재료학회 2023 Composites research Vol.36 No.6
본 연구에서는 기존 배관 가스 누출 감지에 사용되던 음향방출 센서가 실시간 모니터링에 적용될 때 발생할 수 있는 문제들을 개선하기 위해, Macro-fiber composite (MFC) 트랜스듀서를 음향방출 센서로 사용하여 가스 누출 감지 시스템에 적용하였다. 적용 전 MFC의 구조를 최적화 하기위해 구조해석을 진행하여 제작하였고, 그 결과 MFC가 가지는 유연성으로 굴곡진 배관에 잘 밀착되어 AE 신호를 문제없이 수신할 수 있었다. AE 신호 분석 결과 고압 누출, 저압 누출 모두 파라미터 값 변화에 유의미한 결과를 보였으며, 특히, FFT 그래프의 파라미터에서 고압 누출의 경우 누출이 없는 경우 대비 120% ~ 626 %의 변화량, 저압 누출의 경우 9% ~ 22%의 변화량을 보였다. 또한, 누출 발생 부위에서의 거리에 따라, 거리가 멀수록 이러한 파라미터 변화량이 줄어드는 경향을 보여, 추후 파라미터 변화량 감지를 통해 누출 감지가 가능할 뿐만 아니라, 변화량으로부터 누출 발생 위치를 파악할 수 있을 것으로 보인다. In this study, aimed at improving the existing acoustic emission sensor for real time monitoring, a macro-fiber composite (MFC) transducer was employed as the acoustic emission sensor in the gas leak detection system. Prior to implementation, structural analysis was conducted to optimize the MFC's design. Consequently, the flexibility of the MFC facilitated excellent adherence to curved pipes, enabling the reception of acoustic emission (AE) signals without complications. Analysis of AE signals revealed substantial variations in parameter values for both high-pressure and low-pressure leaks. Notably, in the parameters of the Fast Fourier Transform (FFT) graph, the change amounted to 120% to 626% for high-pressure leaks compared to the case without leaks, and approximately 9% to 22% for low-pressure leaks. Furthermore, depending on the distance from the leak site, the magnitude of change in parameters tended to decrease as the distance increased. As the results, in the future, not only will it be possible to detect a leak by detecting the amount of parameter change in the future, but it will also be possible to identify the location of the leak from the amount of change.
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PZT 파우더 첨가에 따른 티타늄 파우더/폴리머 콘크리트 복합재료의 진동 특성 및 압축 물성 분석
박재현,김석룡,김경수,김건,김석호,이범주,정안목,안종욱,김선주,이시맥,유형민,Park, Jaehyun,Kim, Seok-Ryong,Kim, Kyoung-Soo,Kim, Geon,Kim, Seok-Ho,Lee, Beom-Joo,Jeong, Anmok,An, Jonguk,Kim, Seon Ju,Lee, Si-Maek,Yoo, Hyeong-Min 한국복합재료학회 2022 Composites research Vol.35 No.3
In this study, Ti powder/Polymer concrete composites were processed by adding the PZT powder, one of the piezoelectric materials, to improve the vibration damping effect of Polymer concrete. Ti powder was added at a constant ratio in order to maximize the vibration damping effect using the piezoelectric effect. Three types of composite material specimens were prepared: a specimen without PZT powder, specimens with 2.5 wt% and 5 wt% of PZT powder. The vibration characteristics and compression properties were analyzed for all specimens. As a result, it was confirmed that as the addition ratio of PZT powder increased, the Inertance value at the resonant frequency decreased due to the piezoelectric effect when the vibration generated from Ti powder/polymer concrete was transmitted. Especially, the Inertance value was decreased by about 19.3% compared to the specimen without PZT at the resonant frequency. The change in acceleration with time also significantly decreased as PZT powder was added, confirming the effect of PZT addition. In addition, through the compression strength test, it was found that the degree of deterioration in compression properties due to the addition of PZT up to 5 wt% was insignificant, and it was confirmed that the powder was evenly dispersed in the composites through the cross-sectional analysis of the specimen.
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