published_or_final_version / abstract / Chemistry / Doctoral / Doctor of Philosophy

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分層次的多孔材料在自然界中非常廣泛的被發現，例如動物的肺部、樹葉以及矽藻的骨骼。最近一些年，大孔(macropores)連同介孔(mesopores)或者(或與)微孔(micropores)等結構的分層次的多孔材料的製備與合成吸引了材料化學領域諸多的注意力，以期他們在催化、吸附解附、藥物釋放、感測器以及組織工程等多種方向中發揮潛在的應用。 / 本論文中我們將介紹一種簡單而靈活的的基於微粒穩定的高內相乳液(Particle-stabilized high internal phase emulsion)的方法，製備得到具有分層次多孔結構的二氧化鈦材料，擁有增強的光催化活性。由微凝膠軟球和二氧化鈦硬球共同作用，我們得到穩定的水包油高內相乳液體系。在除去液體相時將會促使形成幾十微米的大孔結構，約十微米的介孔連通窗格，以及分佈在大孔壁上的約一百納米的微孔，這三種不同尺寸的孔隙結構在三維方向上互相連通。初始合成的二氧化鈦材料由掃描電子顯微鏡(SEM)，X射線衍射(XRD)，壓汞儀來表徵其内部結構，同時測試其相對應的羅丹明光降解效率。結果清晰地顯示，微粒穩定的範本法可以成功的形成擁有多種且互不相同的多層次多孔結構。同時這種具有大孔和微孔的多層次孔隙結構的二氧化鈦材料，表現出非常有效的光化學催化性質，顯示了其在分離、淨化等過程的巨大潛在應用價值。 / Hierarchical porous materials occur widely in nature, including for example the lungs of animals, the leaves of trees, and diatom skeletons. In recent years, the synthesis of new hierarchical porous materials containing macroporous along with micro-and/or mesoporous has attracted considerable attention in material chemistry, because of their potential use in diverse applications such as catalysis, adsorption and separations, drug delivery, sensors and tissues engineering. / In this thesis, we present a simple and flexible method to synthesize hierarchically porous structured titania with enhanced photocatalytic activity using particle-stabilized high internal phase emulsions (Pickering HIPEs). Starting with a highly concentrated emulsion stabilized by both soft microgels and TiO₂solid nanoparticles, three-dimensionally interconnected porous titania materials with ordering on three different scales, that is, macroporous (~50μm), interconnected throat (~10μm), and nanoporous walls (~100 nm), are successfully obtained after drying and sintering. The so-prepared materials are characterized by scanning electron microscopy (SEM), X-ray diffraction, mercury intrusion, and the corresponding photocatalytic activity is evaluated by measuring the photodegradation of Rhodamine B in water. Our results clearly show that particle-stabilized emulsion templating can successfully lead to hierarchical porous material with multiple and discrete pore scales. Moreover, these hierarchically porous TiO₂ containing macroporous along with nanopores walls can be very efficient photocatalysts, suggesting their great potential applications in separation and purification process. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Li, Xiaodong. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references. / Abstracts also in Chinese. / 摘要 --- p.I / Abstract --- p.II / Tableof Contents --- p.III / Acknowledgement --- p.VI / Chapter Chapter 1 --- Introduction to Porous Materials: Design, Synthesis and Applications --- p.1 / Chapter 1.1 --- Hierarchical Porous Materials in Nature --- p.1 / Chapter 1.2 --- Artificial Hierarchical Porous Materials --- p.2 / Chapter 1.3 --- Non-Templating Methods --- p.3 / Synthesis of Hierarchical Porous Materials with Single Composition --- p.5 / Chapter 1) --- meso-macroporous zirconium oxides --- p.5 / Chapter 2) --- meso-macroporous titanium oxides --- p.6 / Synthesis of Hierarchical Porous Materials with Multiple Composition --- p.9 / Chapter 1.4 --- Templating Methods --- p.10 / Chapter 1.5 --- Combination of Template and Non-template Methods --- p.12 / Chapter 1.6 --- Potential Application of Porous Materials --- p.13 / HPLC separation --- p.13 / Hierarchical catalysis --- p.14 / Electrode materials for fuel cell applications --- p.15 / Biomaterials engineering --- p.15 / Chapter 1.7 --- Objective of the Research --- p.16 / Chapter References --- p.18 / Chapter Chapter 2 --- Preparation of Hierarchically Structured TiO₂ Using High Internal Phase Emulsions (HIPEs) Stabilized by Binary Nanoparticles as the Templates --- p.22 / Chapter 2.1 --- Introduction to Particle Stabilized HIPEs --- p.22 / Chapter 2.2 --- Experiment Part --- p.26 / Chapter 2.2.1 --- Materials --- p.26 / Chapter 2.2.2 --- pNIPAM-co-MAA microgels synthesis and Characterization --- p.26 / Chapter 2.2.3 --- Synthesis of Hierarchical Porous TiO₂ Materials templating from HIPEs Stabilized by Binary Nanoparticles --- p.29 / Chapter 2.3 --- Results and Discussion --- p.32 / Chapter 2.3.1 --- HIPEs Stabilized Solely by Microgel Particles --- p.32 / Chapter 2.3.2 --- HIPEs Stabilized by Binary Nanoparticles --- p.35 / Chapter 1) --- Sintering effect on the porous TiO₂ monolith --- p.40 / Chapter 2) --- Microgel/TiO₂ ratio effect on the porous materials --- p.45 / Chapter References --- p.52 / Chapter Chapter 3 --- Photo-Catalytic Activity of the TiO₂-based Hierarchically Structured Porous Materials --- p.54 / Chapter 3.1 --- Introduction --- p.54 / Chapter 3.2 --- Experiment Section --- p.55 / Chapter 3.3 --- Result and Discussion --- p.56 / Chapter 1) --- Influence of sintering temperature on the porous materials --- p.56 / Chapter 2) --- Influence of internal phase volume fraction on the photocatalytic activity . --- p.59 / Reference --- p.63 / Chapter Chapter 4 --- Conclusion --- p.64

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Understanding the transport of three fluid phases through porous media has important applications in subsurface contaminant remediation, oil and gas recovery, and geological CO��� sequestration. Existing transport models may be improved by including physical phenomena that govern fluid flow at the pore scale. In particular, thermodynamic arguments suggest that hysteresis in the capillary pressure-saturation (P[subscript c]-S) relationship may be resolved by including an additional parameter, fluid-fluid interfacial area per volume (a[subscript nw]). Synchrotron-based Computed X-ray Microtomography (CMT) is a method that allows observation of fluid interfaces. Flow experiments were conducted using CMT to investigate uniqueness of the P[subscript c]-S[subscript w]-a[subscript nw] relationship in a porous media system containing three immiscible fluid phases. Drainage and imbibition surfaces were fit to P[subscript c]-S[subscript w]-a[subscript nw] data collected over a limited range of water saturations. The root-mean-square error (RMSE) between the drainage and imbibition surfaces was negligible, indicating that the P[subscript c]-S[subscript w]-a[subscript nw] relationship is unique. These results are a first step in validating the P[subscript c]-S[subscript w]-a[subscript nw] relationship for three-phase porous media systems. In addition, spreading intermediate-phase layers were observed to bring oil and solid into contact, which in the presence of X-rays changed the solid wettability within a relatively short time period. These observations confirm a proposed theoretical scenario that three-phase systems are more susceptible to wettability changes than to two-phase systems due to intermediate-phase spreading behavior. / Graduation date: 2013

Graduation date: 1996

Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 144-155). Available also in a digital version from Dissertation Abstracts.

Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, December 2009. / Thesis Advisor(s): Hixson, Robert S. Second Reader: McNelley, Terry. "December 2009." Description based on title screen as viewed on January 27, 2010. Author(s) subject terms: Porous foams, dynamic compaction, multi-layered armor, ballistic performance, shock wave attenuation. Includes bibliographical references (p. 89-90). Also available in print.

Thesis (M.S.)--West Virginia University, 2001. / Title from document title page. Document formatted into pages; contains viii, 79 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 77-79).