摘要
沸石為高結晶性的微孔洞材料，沸石薄膜可用於催化反應或化工分離程序。二次生長法為最被廣泛使用的沸石薄膜製備方法，但是此方式需要的合成時間較長、且不利於工業量產。本論文提出一種可放大的溼式沈積法來製備沸石薄膜，並將此方法實現在FAU、AEI等兩種不同的沸石系統上。在本研究的第一部分，我們利用此方法來製備FAU型態的沸石薄膜。我們利用酸鹼值來調控FAU型態的沸石FAU懸浮溶液的穩定性，並且利用動態光散射來研究膠體懸浮溶液的性質。我們發現，在酸鹼值較高的情況下(pH=13.5)，膠體懸浮溶液的穩定性較差，成膜後其薄膜表面粗糙度較不佳；在酸鹼值較低的狀況下(pH=12.5)，沸石懸浮液較穩定、且可形成薄膜表面粗糙度較均一的薄膜。而酸鹼值較高的溶液所製備出的薄膜其沸石FAU晶格會轉換成另一種晶格並形成無孔較緻密的薄膜。我們也在不同頻率下量測這些FAU型態的沸石薄膜之介電常數，在高頻(1000 kHz)下，介電常數最低可達2.1。 本研究的第二部分，我們提出利用濕式沈積的法式製備出晶體有高度方向性排列的AEI型態沸石薄膜。我們將組成為磷酸鋁鹽的沸石AEI膠體懸浮溶液塗佈在矽晶圓基材上，製備出的沸石薄膜；同時利用略角入射廣角之X光散射技術得到2維的繞射圖譜。經由實驗與電腦模擬之繞射圖譜比對，確認了此沸石薄膜具有高度的方向性排列。同時我們也系統性地探討了晶體大小、塗布方法、基材種類等實驗條件對於沸石晶體在薄膜中沿著特定方向排列的影響。我們也觀察到有高度方向性排列的AEI型態沸石薄膜可以改善電性性質和分離效果。最後，我們也嘗試將沸石薄膜沈積在大尺寸的六吋晶圓上，證明此溼式沈積法有機會大規模製造具備高度方向性排列之沸石薄膜。
並列摘要
Zeolites are microporous materials with high crystallinity. Zeolite membranes and thin films can be used for catalytic reaction or separation processes in the chemical industry. Secondary growth is the most popular approach to the preparation of zeolite thin films and membranes; however, this process is time-consuming and is difficult for large-scale production. In this thesis, we proposed a scalable wet deposition method for preparing zeolite thin films. As a proof of concept, we implemented this method to fabricate zeolite thin films with two different zeolites: FAU and AEI. The first part of this thesis discusses, the fabrication of zeolite FAU thin films. Zeolite FAU suspensions are prepared at various pH values. Dynamic light scattering (DLS) was used to investigate the colloidal properties of the zeolite FAU suspensions. It was found that high pH value (pH = 13.5) destabilize the colloidal suspensions and results in high surface roughness of thin film. For the thin films formed from suspensions with high pH value, the zeolite FAU crystals transform into a dense phase. At relatively low pH value (pH = 12.5), the colloidal suspension is more stable. The thin film samples cast using this FAU suspension yields thin films with uniform morphology. We measured the dielectric constant of zeolite FAU thin film samples at various frequency. At high frequency (1000 kHz), thin films with a zeolite FAU structure exhibited dielectric constant as low as 2.1. In the second part of the study, we proposed a new approach to fabricating zeolite AEI thin films with high degree of crystal orientation via direct wet deposition. We deposit the colloidal suspensions that comprise aluminophosphate zeolite AEI on silicon wafer substrate. We combine the experimental and simulated 2D patterns of grazing-incidence wide-angle X-ray scattering (GIWAXS) to investigate the polycrystal orientation distribution in zeolite thin films. We elucidate the influence of crystal size, the deposition method, and substrate surface properties on the degree of preferred crystal orientation. Improved electrical properties and separation performance were observed for the zeolite thin films/membranes with high degree of preferred crystal orientation. Finally, we apply this method on the deposition of zeolite AEI thin films on a 6-inch silicon wafer to demonstrate the scalability of the proposed wet deposition technique.
參考文獻
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