• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 859
  • 161
  • 72
  • 59
  • 41
  • 12
  • 6
  • 6
  • 6
  • 5
  • 5
  • 5
  • 5
  • 5
  • 5
  • Tagged with
  • 1345
  • 1121
  • 135
  • 133
  • 116
  • 111
  • 111
  • 104
  • 102
  • 102
  • 101
  • 94
  • 84
  • 81
  • 78
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Fabrication of hierarchical porous materials by templating particle-stabilized high internal phase emulsions.

January 2012 (has links)
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
32

Fabrication and characterization of surface engineered one-dimensional cadmium selenide nanostructure =: (硒化鎘一維納米結構之表面處理及其表徵). / 硒化鎘一維納米結構之表面處理及其表徵 / Fabrication and characterization of surface engineered one-dimensional cadmium selenide nanostructure =: (Xi hua ge yi wei na mi jie gou zhi biao mian chu li ji qi biao zheng). / Xi hua ge yi wei na mi jie gou zhi biao mian chu li ji qi biao zheng

January 2008 (has links)
Lam, Ngai Sze. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / Lam, Ngai Sze. / Abstract --- p.i / Acknowledgements --- p.iii / Table of contents --- p.iv / List of Figures --- p.viii / List of Tables --- p.xiii / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Background --- p.1 / Chapter 1.1.1 --- Properties of CdSe --- p.1 / Chapter 1.1.2 --- Synthesis of CdSe one-dimensional (ID) nanostructure --- p.5 / Chapter 1.1.3 --- Application of CdSe nanostructures --- p.8 / Chapter 1.1.4 --- Significance of surface engineering --- p.10 / Chapter 1.1.4.1 --- Surface passivation --- p.11 / Chapter 1.1.4.2 --- Surface functionalization --- p.11 / Chapter 1.1.4.3 --- Modulation of optical/electrical properties --- p.12 / Chapter 1.2 --- Present study --- p.14 / Chapter 1.2.1 --- Objective --- p.14 / Chapter 1.2.2 --- General methodology --- p.14 / Chapter Chapter 2 --- Instrumentation --- p.19 / Chapter 2.1 --- Introduction --- p.19 / Chapter 2.2 --- Setup of Sample Preparation --- p.19 / Chapter 2.2.1 --- Synthesis --- p.19 / Chapter 2.2.1.1 --- Thermal evaporation apparatus --- p.19 / Chapter 2.2.1.2 --- Microwave assisted chemical synthesis --- p.21 / Chapter 2.2.2 --- Sample handling --- p.22 / Chapter 2.2.3 --- Other treatments --- p.22 / Chapter 2.3 --- X-ray photoelectron spectrometer (XPS) --- p.22 / Chapter 2.3.1 --- Basic Principle --- p.22 / Chapter 2.3.2 --- Instrumentation --- p.24 / Chapter 2.3.3 --- Charging problem --- p.27 / Chapter 2.3.4 --- Qualitative analysis --- p.27 / Chapter 2.3.5 --- Quantitative analysis --- p.28 / Chapter 2.3.5.1 --- Curve fitting --- p.28 / Chapter 2.3.5.2 --- Atomic percentage --- p.29 / Chapter 2.3.5.3 --- Thickness determination --- p.29 / Chapter 2.4 --- Photoluminescence --- p.30 / Chapter 2.4.1 --- Basic principle --- p.30 / Chapter 2.4.2 --- Instrumentation --- p.31 / Chapter 2.5 --- Other equipments --- p.32 / Chapter Chapter 3 --- Synthesis of CdSe Nanorods --- p.34 / Chapter 3.1 --- Introduction --- p.34 / Chapter 3.2 --- Thermal evaporation --- p.34 / Chapter 3.2.1 --- Experimental procedures --- p.34 / Chapter 3.2.2 --- Characterization --- p.35 / Chapter 3.3 --- Microwave assisted method --- p.41 / Chapter 3.3.1 --- Experimental procedures --- p.41 / Chapter 3.3.2 --- Characterization --- p.42 / Chapter 3.4 --- Summary --- p.47 / Chapter Chapter 4 --- Surface Treatment of CdSe Nanorods --- p.49 / Chapter 4.1 --- Introduction --- p.49 / Chapter 4.2 --- Experimental procedures --- p.50 / Chapter 4.3 --- Results and Discussion --- p.51 / Chapter 4.3.1 --- Formation of Se-coated CdSe NRs --- p.51 / Chapter 4.3.2 --- Desorption and thinning --- p.56 / Chapter 4.3.3 --- Surface degradation --- p.67 / Chapter 4.4 --- Summary --- p.69 / Chapter Chapter 5 --- Surface Capping of CdSe Nanorods --- p.73 / Chapter 5.1 --- Introduction --- p.73 / Chapter 5.2 --- Experimental procedures --- p.73 / Chapter 5.3 --- Results and Discussion --- p.74 / Chapter 5.3.1 --- Capping of thiol with halo-functional group --- p.74 / Chapter 5.3.1.1 --- Compositional analysis --- p.75 / Chapter 5.3.1.2 --- PL analysis --- p.79 / Chapter 5.3.2 --- Capping of DNA --- p.81 / Chapter 5.3.2.1 --- Compositional analysis --- p.81 / Chapter 5.3.2.2 --- PL analysis --- p.83 / Chapter 5.4 --- Summary --- p.92 / Chapter Chapter 6 --- Conclusions and Future Work --- p.94 / Chapter 6.1 --- Conclusions --- p.94 / Chapter 6.2 --- Future work --- p.95
33

Polymer-layered silicate nanocomposites by melt processing

Shah, Rhutesh Kishorkant, January 1900 (has links) (PDF)
Thesis (Ph. D.)--University of Texas at Austin, 2006. / Vita. Includes bibliographical references.
34

One-Dimensional nanostructured polymeric materials for solar cell applications

Mavundla, Sipho Enos. January 2010 (has links)
<p>This work entails the preparation of various polyanilines with different morphologies and their application in photovoltaic solar cells. Zinc oxide (ZnO) with one-dimensional and flower-like morphology was also prepared by microwave irradiation and used as electron acceptors in photovoltaics devices. The morphological, structural, spectroscopic and electrochemical characteristics of these materials were determined by scanning electron microscopy (SEM), X-Ray diffraction (XRD), Raman, Fourier-transformed infrared spectroscopy (FTIR), ultraviolet and visible spectroscopy (UV-Vis), photoluminescence(PL), thermal gravimetric analysis (TGA) and cyclic voltammetry (CV) experiments. Devices fabricated from these materials were characterized under simulated AM 1.5 at 800 mW.</p>
35

Synthesis and characterizations of nanostructured MnO2 electrodes for supercapacitors applications

Mothoa, Sello Simon January 2010 (has links)
<p>The objective of this research was to develop highly efficient and yet effective MnO2 electrode materials for supercapacitors applications. Most attention had focussed on MnO2 as a candidate for pseudo-capacitor, due to the low cost of the raw material and the fact that manganese is more environmental friendly than any other transition metal oxide system. The surface area and pore distribution of MnO2 can be controlled by adjusting the reaction time. The MnO2 synthesised under optimum conditions display high capacitance, and exhibit good cycle profile. This work investigates the ways in which different morphological structures and pore sizes can affect the effective capacitance. Various -MnO2 were successfully synthesised under low temperature conditions of 70 oC and hydrothermal conditions at 120 oC. The reaction time was varied from 1 to 6 hours to optimise the conditions. KMnO4 was reduced by MnCl.H2O under low temperature, whereas MnSO4.4H2O, (NH4)2S2O8 and (NH4)2SO4 were co-precipitated under hydrothermal conditions in a taflon autoclave to synthesise various -MnO2 nano-structures.</p>
36

Fabrication and characterization of one dimensional ZnO nanostructures /

Cheng, Chun. January 2009 (has links)
Includes bibliographical references (p. 136-150).
37

Localized-denisty-matrix method and its application to nano-size systems

Liang, Wanzhen. January 2001 (has links)
Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 148-161).
38

Experimental investigations of magnetic and magneto-rheological materials and their rigidification properties /

Glaser, Radek, January 2009 (has links)
Thesis (M.S.) in Mechanical Engineering--University of Maine, 2009. / Includes vita. Includes bibliographical references (leaves 214-219).
39

A catalytic architecture composed of titanium silicalite-1 and nanostructured support for oxime synthesis /

Yip, Chi Kin. January 2009 (has links)
Includes bibliographical references (p. 205-222).
40

Silver nanocluster single molecule optoelectronics and its applications

Lee, Tae-Hee. January 2004 (has links) (PDF)
Thesis (Ph. D.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2004. / Srinivasarao, Mohan, Committee Member; Sherrill, C. David, Committee Member; Orlando, Thomas, Committee Member; EL-Sayed, Mostafa, Committee Member; Dickson, Robert, Committee Chair. Vita. Includes bibliographical references (leaves 136-159).

Page generated in 0.1057 seconds