碳分子篩薄膜應用於微機電-有機氣體濃縮晶片之研製 A Micro Fabricated Vapor Preconcentrator Employing Carbon Molecular Sieve Thin Film

Date
2012
Authors
陳瑋如
Wei-Ru Chen
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Abstract
本研究以自製之高溫燒結碳膜,探討其對於空氣中揮發性有機化合物(VOCs)之吸附效能。首先在缺氧及高溫條件下,利用不同的碳化條件,將原料熱裂解成多孔性碳結構體,尋求最佳碳化條件,製出微孔結構活性碳,並進行活性碳之物理性質分析,包括:以場效發射式掃描電子顯微鏡(FE-SEM)觀察材料表面縱深形貌及微結構影像、以微孔隙分析儀測定BET比表面積等。為配合微機電製程開發,以陽極接合封裝的晶片型前濃縮裝置,將碳材與適當溶劑混合形成液態物,灌入晶片形成一層均勻薄膜,燒結成多孔吸附劑,進行相關探討。本研究以纖維素和saran當作實驗材料,其最佳製程條件分別為:從室溫開始,以10℃/min之速率升溫至600℃,並維持恆溫2hr; 以及以10℃/min之速率升溫至700℃,並維持恆溫1hr。本實驗依不同碳材之性能,找出適合其指標性氣體,探討其在碳材上之吸附與破出行為,並將此自製碳材送測比表面積分析,得到數據分別為308 m2/g和899 m2/g,皆可與市售碳材進行比較。其中由saran燒製所得的碳分子篩膜吸附容量極高,以toluene為標的氣體,此自製碳膜皆可達到103~104倍的高濃縮倍率。最後將各脫附實驗結果代入Wheeler model,推估吸附劑之吸附容量與動力係數,證明自製碳膜之耐用度良好,本研究所建立之吸附膜製程未來可以廣泛應用於各式微晶片採樣器設計上。
In this study, the adsorption of volatile organic compounds (VOCs) by the synthesized porous carbon based film was investigated. For developing a VOC micro preconcentrator chips, we directly synthesized carbon based adsorbent film inside a pre-sealed and anodic bonded micro device. The precursor material was mixed with a solvent and injected into the chip channel to form a thin layer then pyrolyzed at high temperature and under the oxygen free atmosphere to form a microporous film. The physical properties including surface morphology, microstructure image, and BET surface area were inspected by FE-SEM and specific surface area& pore size distribution analyzer. When using cellulose as the starting material, it was slowly heated at a rate of 10 ℃/min from room temperature to 600 ℃ and maintained for two hours under high purity nitrogen atmosphere. While for saran, it was heated to a higher temperature 700 ℃ and maintained for only one hour. The BET surface area obtained was 308 m2/g and 899 m2/g, respectively, which was sufficiently comparable to many commercial adsorbents. The adsorption /desorption experiment was performed using toluene as the target VOC. It revealed that the carbon film obtained possesses very good performance where the preconcentration factor can achieve 103 to 104. Finally, we applied Wheeler model to assess the thermodynamic capacity of our synthesized adsorbent film. The carbon films in this study show good durability, reproducibility that can be applied in various designs of VOC micro preconcentrator chips.
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Keywords
吸附, 破出, 有機揮發性氣體, 前濃縮, Adsorption, Breakthrough, VOCs, Preconcentration
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