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Chemical effects of organo-silanized SiO2 nanofillers on epoxy adhesives
허준혁,이진웅,이병상,조희훈,임병권,이정헌 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.54 No.-
Although thermal and mechanical effects of organo-silanized SiO2 nanofillers (NFs) incorporated into epoxy resins have been actively studied by many researchers, their chemical properties have rarely been reported. In this work, we investigated the chemical effects of organo-silanized SiO2 NFs on epoxy adhesives with (3-glycidoxypropyl) methyldiethoxysilane (GPTMS) and (3-aminopropyl) trimethox- ysilane (APTMS)-functionalized SiO2 NFs. After curing epoxy-functionalized NF (EPOXY-NF) with triethylenetetramine (TETA) hardener, we were able to verify chemical crosslinking of the TETA hardener on EPOXY-NF with X-ray photoelectron spectroscopy, vacuum Fourier-transform infrared spectroscopy, and zeta potential analysis. Similarly, we found that after curing amine-functionalized NF (NH2-NF) with bisphenol A diglycidyl ether (DGEBA) epoxy resin, the resin was chemically crosslinked on NH2-NF as well. Finally, when we evaluated adhesion properties of adhesives composed of DGEBA resin/NH2-NF and TETA hardener/EPOXY-NF on the basis of ASTM D3163, we observed improvements in the shear strength of 79 and 49%, respectively, in comparison with bare SiO2 NF. This suggests that the chemical effects of organo-silanized SiO2 NFs indeed contribute to the adhesion properties of adhesives.
허준혁,Anup Pandith,조찬식,김홍석 대한화학회 2018 Bulletin of the Korean Chemical Society Vol.39 No.12
A novel pyrene-conjugated 2-(2?-hydroxyphenyl)thiazole probe (HPTP, 1) was prepared, and its photophysical and sensing properties were investigated and compared to those of four model compounds. HPTP effectively detects CN? and glycerol in DMSO, with ?turn off? at 425?nm and ?turn on? at 495?nm. The sensing ability of 1 towards CN? ions in DMSO, mediated by the hydrogen bonding-induced disaggregation of aggregates, resulted in the quenching of ESIPT emission at 425?nm. By contrast, in a DMSO?glycerol mixed medium, the aggregate size increased together with the increased degree of intermolecular π?π interactions between two pyrene units located on adjacent molecules, and resulted in partial inhibition of energy/charge transfer from the pyrene unit to the thiazole unit in the excited state. Excitation energy transfer with increased photostability of the ESIPT core was effectively demonstrated in Candida albicans cell lines.
고등학교 지구과학 수업에서 플래시 파노라마 기반 가상 야외 답사의 활용이 학생들의 공간 시각화 능력 및 화산 개념 이해에 미치는 영향
허준혁,이기영 한국지구과학회 2013 한국지구과학회지 Vol.34 No.4
While virtual field trips (VFT) are considered as an attractive alternative to traditional field experience, it isunclear how VFT are best used in Earth Science curriculum. In this study, we investigated the effects of flash panorama-based VFT on students’ spatial visualization ability and their understanding of volcanic concept in high school EarthScience class. To investigate the effects of instructional treatment, we conducted pre and post-test on participants’ spatialvisualization ability and their understanding of volcanic concept, and analyzed using analysis of covariance (ANCOVA)and linear regression. Findings are as follows: First, the change in students’ spatial visualization ability in experimentalgroup was significantly higher than that of control group, especially in spatial manipulation category. Second, the changein students’ understanding of volcanic concept in experimental group was higher than that of control group in most of thecategories, but it is statistically not significant. Last, the change in correlation between spatial visualization ability andunderstanding of volcanic concept in experimental group was remarkably high compared to control group. 가상 야외 답사(VFT)는 전통적인 야외 답사의 매력적인 대안으로 간주되지만, 지구과학 교육과정에서 어떻게 가장 효과적으로 활용될 수 있는지는 아직 명확하지 않다. 이 연구에서는 플래시 파노라마 기반 VFT를 활용한 지구과학 수업이 고등학교 학생들의 공간 시각화 능력과 화산 개념 이해에 미치는 영향을 알아보았다. 플래시 파노라마 기반 VFT 활용의 효과를 알아보기 위해 수업 처치 사전 및 사후에 공간 시각화 능력 및 화산 개념 검사를 실시하였으며, 수업 처치 결과를 분석하기 위해 공변량 분석과 선형 회귀 분석을 수행하였다. 연구 결과는 다음과 같다. 첫째, 실험집단의 공간 시각화 능력 향상 정도가 통제 집단에 비해 통계적으로 유의미하게 더 높게 나타났다. 특히, 공간 시각화 능력의 세 가지 하부 범주 중 공간 조작 능력 향상이 가장 큰 것으로 나타났다. 둘째, 대부분의 범주에서 실험 집단의 화산 개념 이해 향상 정도가 통제 집단에 비해 더 높게 나타났으나, 1개 범주를 제외하고 통계적으로 유의미한 차이는 아니었다. 셋째, VFT 활용 후 실험 집단이 통제 집단에 비해 공간 시각화 능력과 화산 개념 이해 간의 상관관계가 현저하게 증가하였다.