Browsing by Author "Lin, Ming Chang"

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Ab Initio Chemical Kinetics for Nitrogen Tetroxide Reactions with 1,1-and 1,2-Dimethylhydrazines
(1970-01-01)
Le Huyen, Trinh
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Raghunath, Putikam
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Lin, Ming Chang
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交大名義發表
;
應用化學系
This work employed the quantum-chemical method at the CCSD(T)/6-311+G(3df,2p)//B3LYP/6-311+G(3df,2p) level to study the mechanisms and kinetics of N2O4 (NTO) with H2NN(CH3)(2) and CH3NHNHCH3 hypergolic initiation reactions, the processes critical to the chemical rocket propulsion of the N2O4-hydrazine propellant systems. The reaction of N2O4 with the dimethylhydrazines (DMHZ's) can be started by the fast reaction of DMHZ's with ONONO2, taking place after the novel N2O4 -> ONONO2 transformation with each of DMHZ's as a spectator within the NTO-DMHZ collision complexes, through loose, roaming-like transition states during the bimolecular encounters. The barriers for such isomerization processes were found to be 7.2 and 9.9 kcal/mol for H2NN(CH3)(2) and CH3NHNHCH3, respectively. The kinetics of these reactions have been computed in the temperature range 200-2000 K; the results indicate that under the ambient temperature and pressure condition, the half-life of NTO in the presence of an excess amount of H2NN(CH3)(2) is predicted to be 3.3x10(-5) s. The results of a similar estimate for CH3NHNHCH3 is about 2 orders of magnitude longer; both estimates indicate that very effective hypergolic reactions can occur upon mixing in these systems.
Development of Novel Mixed Halide/Superhalide Tin-Based Perovskites for Mesoscopic Carbon-Based Solar Cells
(2020-04-02)
Rameez, Mohammad
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Shahbazi, Saeed
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Raghunath, Putikam
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Lin, Ming Chang
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Hung, Chen Hsiung
Tin perovskites suffer from poor stability and a self-doping effect. To solve this problem, we synthesized novel tin perovskites based on superhalide with varied ratios of tetrafluoroborate to iodide and implemented them into solar cells based on a mesoscopic carbon-electrode architecture because film formation was an issue in applying this material for a planar heterojunction device structure. We undertook quantum-chemical calculations based on plane-wave density functional theory (DFT) methods and explored the structural and electronic properties of tin perovskites FASnI(3-x)(BF4)(x) in the series x = 0, 1, 2, and 3. We found that only the x = 2 case, FASnI(BF4)(2), was successfully produced, beyond the standard FASnI(3). The electrochemical impedance and X-ray photoelectron spectra indicate that the addition of tin tetrafluoroborate instead of SnI2 suppressed trap-assisted recombination by decreasing the Sn4+ content. The power conversion efficiency of the FASnI(BF4)(2) device with FAI and Sn(BF4)(2) in an equimolar ratio improved 72% relative to that of a standard FASnI(3) solar cell, with satisfactory photostability under ambient air conditions.
太陽能及乙醇/氫氣轉換之量子化學計算模擬及實驗驗證
(2006)
林明璋
;
Lin, Ming Chang
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國立交通大學理學院{分子科學研究中心}
本計劃將結合於2004年5月由「國家高速網路與計算中心」協助組織的「台灣計算化學聯盟」(Taiwan Computational Chemistry Consortium, TCCC)中的兩組計算化學家，利用最先進的計算技術進行大尺度的理論計算，以瞭解製造InN/TiO2奈米粒子薄膜和乙醇-氫氣轉化的機制。第一組專家將研究自組官能基加上拉電子或推電子的元素，如>BO-Ti,>PO-Ti或>Si=(OTi)2等對InN和TiO2的結合強度以及其對光電轉換效率的影響。這些界面物質可以利用氫氧化的TiO2或(HO-Ti)x與BCl3, PCl3或SiCl4反應，脫去HCl而形成。利用量子化學計算可以來研究這些反應在TiO2上之產物結構。官能化的表面也可與三甲基銦, (CH3)3In, NHx (x=1, 2)或SiHx (x=1-3)反應以產生量子點(quantum dots, QDs) 及/或InN和Si的奈米粒子薄膜，以增進InN/QDs/TiO2系統中的光電流。實驗上，活化的NHx和SiHx可以利用熟知的NH3和SiH4利用微波或催化分解來產生。吾人將與核能研究所密切合作進行相輔相成的理論和實驗工作，以對製程的改進和提昇太陽能的轉換效率作出貢獻。第二組專家將以Schmidt等人[Science, 2004, 303, 993]所使用之技術作為依據，對燃料電池所應用到的乙醇轉化為氫氣的過程加以研究。實驗的工作也將和理論計算工作同時進行，以一個小的反應器來鑑測各種催化劑對於乙醇的部份氧化之效果。實驗的結果可以和理論計算結果相互比對並相輔相成。吾人將先進行Rh/CeO2系統的研究以瞭解Rh/CeO2將乙醇轉化為氫氣的機制並找出為何它可以有如此高的轉化效率的原因。所得的數據將可與其他有可能較具經濟效益的奈米粒子催化劑，如Cu/Al2O3等之研究相比較。實驗與理論的密切結合將可以很有效地產生有用的數據以供實際設計及製造較具經濟效益且具相似轉化效率的燃料電池參考。此計劃亦將訓練一批優秀的計算化學家以及博、碩士班學生，為台灣相關的材料化學之理論研究作出貢獻。
應用於太陽能轉換之量子點敏化InN/TiO2奈米粒子薄膜研發
(2006)
林明璋
;
Lin, Ming Chang
;
國立交通大學理學院{分子科學研究中心}
本計劃擬分三部份進行量子點增益的InN/TiO2奈米粒子薄膜研發：A. InN//InP Q-dots//TiO2薄膜的製備－InP量子點可以利用有機金屬化學蒸鍍法(OMCVD)，將TMIn和PH3沈積在TiO2奈米粒子薄膜上產生InP。InP與TiO2的鍵結強化可以利用預先將TiO2羥基化後再與In(CH3)3反應形成一層TiO-In(CH3)2。根據我們最近所進行的量子化學計算結果顯示此TiO-In之鍵結應該相當強。InP量子點也可以利用如Nozik所使用之濕式化學反應來合成。B. InN//Si Q-dots//TiO2薄膜的置備－藉由電漿沈積法，使用適當的矽元素之化學蒸鍍前驅物，如SiH4或Si2H6，則可以很有效率地在TiO2奈米粒子薄膜上生長矽量子點或矽奈米粒子。我們預期矽元素經電漿化學蒸鍍在Ti(O-SiXn), X=H, Cl的吸附層上，視化學蒸鍍的時間而定，可在TiO2奈米粒子薄膜上形成矽量子點或矽奈米粒子。接著，我們可利用有機金屬化學蒸鍍法，以InN或InGaN(以In(Ga)N代表之)包覆那些附著於TiO2上的Si量子點。此In(Ga)N不僅具有光學活性，且很穩定在光電轉換應用中保護矽量子點使之不與空氣起化學反應，或者在分解水的應用中不與電解液溶液反應。倘若In(Ga)N//Si Q-dots// TiO2系統被證實在光電轉換中極有效率，則此體系可能是一個極具經濟效益的系統，因為相較之下，多晶形矽系統需要極大量的高品質之矽。而此系統的研製將與核能所的科學家共同合作。在本計畫中，所有研製出來的薄膜都將利用薄膜的光電流量測以分析其電子轉移的效率，並利用紫外/可見光及紅外光區的飛秒雷射系統以泵-探（pump-probe）技術研究其電子轉移的動態學。此外，我們亦將利用相關設施進行薄膜表面的特性分析，如：X光光電子譜(XPS)、紫外光光電子譜(UPS)及X光繞射。C. 在In(Ga)N及TiO2中間加入金及其他金屬量子點以促進太陽能轉換效率。