This thesis presents a study of pH-responsive doubly crosslinked microgels (DX MGs) and associated investigations to enhance their performance. The potential application of this material is soft tissue engineering, so the research concerns mechanical properties, other properties like swelling, microporous and conductivity are also discussed. The MG particles are based on poly(EA/MAA/x), where EA is the ethyl acrylate, MAA is the methacrylate acid and x represents the crosslinker. The particles were subsequently functionalised using glycidyl methacrylate (GMA) to introduce vinyl groups in the MG particles. The formation of DX MGs includes a pH triggered swelling of MG particles in the dispersion to form a physical gel and a heat-triggered free-radical reaction to form a covalent hydrogel. The starting point of this study was using graphene oxide (GO) nanosheets to prepare DX MGs composites with a high modulus. We mixed low concentrations of GO with MG particles and formed DX MG/GO gels. Both shear and compressive modulus linearly increased with the concentration of GO, but the ductility of gels was slightly reduced. The moduli for the DX MG/GO gels was increased by a factor of 5 - 6 when only 1.0 wt.% of GO was included. The next study used muti-wall carbon nanotubes (CNTs) which are widely used to prepare electrical conductive composites. A big challenge for applying CNTs is that they easily form large aggregates in water, which was solved by the space-filling and volume excluded properties of MG particles. The ductility of the composite DX gels increased with CNT concentration, as did the modulus. The conductivity of gels significantly increased with the concentration of CNT and they had a very low percolation threshold. The cytotoxic study for the composite gels showed that they were not toxic, so they may be suitable for soft tissue engineering. The effect of crosslinking monomers in MG preparation was studied in the last part of the research. Three types of poly(EA/MAA/x) MGs were studied and compared. The x value was 1 mol. % of divinylbenzene (DVB); 1,4-butanediol diacrylate (BDDA) or a 1:1 mixture of both DVB and BDDA. The MGs containing DVB demonstrated higher swelling and more ductile properties and could withstand ~76% of compressive deformation. Moreover, the effects of intra-MG crosslinking of the MGs on the swelling behaviour and the mechanical properties were investigated.

Choi Ching Yeung = 鎂和氧化銀粉反應制備鎂基復合材料 / 蔡靜洋. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2004. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / Choi Ching-Yeung = Mei he yang hua yin fen fan ying zhi bei mei ji fu he cai liao / Cai Jingyang. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgement --- p.iv / List of Figures --- p.xi / List of Tables --- p.xvi / Chapter Chapter 1 --- Introduction --- p.1.1 / Chapter 1.1 --- Metal matrix composites (MMCs) --- p.1.1 / Chapter 1.1.1 --- Introduction --- p.1.1 / Chapter 1.1.2 --- Reinforcement in metal-matrix composites --- p.1.1 / Chapter 1.1.2.1 --- Particle-reinforced composites --- p.1.2 / Chapter 1.1.2.2 --- Laminated composites --- p.1.2 / Chapter 1.1.2.3 --- Fibre-reinforced composites --- p.1.2 / Chapter 1.1.3 --- Conventional fabrication of metal matrix composites --- p.1.6 / Chapter 1.1.3.1 --- Liquid state processes --- p.1.6 / Chapter 1.1.3.1.1 --- Liquid infiltration --- p.1.6 / Chapter 1.1.3.1.2 --- Pressure infiltration --- p.1.8 / Chapter 1.1.3.1.3 --- Spray forming --- p.1.10 / Chapter 1.1.3.2 --- Solid-state process --- p.1.11 / Chapter 1.1.3.2.1 --- Powder consolidation --- p.1.11 / Chapter 1.1.3.2.2 --- Diffusion bonding --- p.1.11 / Chapter 1.1.3.2.3 --- In-Situ processes --- p.1.13 / Chapter 1.1.4 --- Properties of metal matrix composites --- p.1.13 / Chapter 1.2 --- Magnesium based metal matrix composites --- p.1.14 / Chapter 1.2.1 --- Properties of Mg-based metal matrix composites --- p.1.14 / Chapter 1.2.2 --- Application of Mg-based metal matrix composites --- p.1.16 / Chapter 1.3 --- Magnesium and silver (I) oxide --- p.1.16 / Chapter 1.3.1 --- Magnesium --- p.1.16 / Chapter 1.3.2 --- Silver (I) oxide --- p.1.17 / Chapter 1.4 --- Pervious works --- p.1.17 / Chapter 1.5 --- Aims of Current works --- p.1.18 / Chapter 1.6 --- Thesis layout --- p.1.20 / References --- p.1.21 / Chapter Chapter 2 --- Methodology and fabrication --- p.2.1 / Chapter 2.1 --- Introduction --- p.2.1 / Chapter 2.1.1 --- Powder metallurgy --- p.2.1 / Chapter 2.1.1.1 --- Powder production --- p.2.3 / Chapter 2.1.1.2 --- Powder consolidation --- p.2.4 / Chapter 2.1.1.3 --- Sintering process --- p.2.6 / Chapter 2.1.1.4 --- Properties of sintered parts --- p.2.10 / Chapter 2.2 --- Sample preparation --- p.2.12 / Chapter 2.3 --- Characterization methods --- p.2.13 / Chapter 2.3.1 --- Thermal analysis - Differential Thermal Analysis (DTA) --- p.2.13 / Chapter 2.3.2 --- Phase determination - X-ray Powder Diffractometry (XRD) --- p.2.13 / Chapter 2.3.3 --- Microstructure analysis --- p.2.14 / Chapter 2.3.3.1 --- Scanning electron microscopy (SEM) --- p.2.14 / Chapter 2.3.3.1 --- Transmission electron microscopy (TEM and HRTEM) --- p.2.14 / Chapter 2.3.4 --- Physical property - Thermomechanic analyser (TMA) --- p.2.14 / Chapter 2.3.5 --- Mechanical property - Vickers hardness measurement --- p.2.15 / References --- p.2.16 / Chapter Chapter 3 --- Thermal analysis of Mg-Ag20 --- p.3.1 / Chapter 3.1 --- Introduction --- p.3.1 / Chapter 3.2 --- Experiments --- p.3.2 / Chapter 3.3 --- Results --- p.3.2 / Chapter 3.3.1 --- DTA curve of the Mg-30wt%Ag20 --- p.3.5 / Chapter 3.3.2 --- DTA curve of the pure Ag20 powder --- p.3.7 / Chapter 3.4 --- Discussions --- p.3.7 / Chapter 3.5 --- Conclusions --- p.3.10 / References --- p.3.11 / Chapter Chapter 4 --- Fabrication and characterization of Mg-£-AgMg3 MMCs --- p.4.1 / Chapter 4.1 --- Introduction --- p.4.1 / Chapter 4.2 --- Experiments --- p.4.2 / Chapter 4.2.1 --- Sample preparation --- p.4.2 / Chapter 4.2.1.1 --- Effect of temperature --- p.4.2 / Chapter 4.2.1.2 --- Effect of time --- p.4.3 / Chapter 4.2.1.3 --- Effect of composition --- p.4.3 / Chapter 4.2.1.4 --- Effect of cooling rate --- p.4.3 / Chapter 4.3 --- Results --- p.4.4 / Chapter 4.3.1 --- Samples sintered at different temperatures --- p.4.4 / Chapter 4.3.1.1 --- XRD spectra --- p.4.4 / Chapter 4.3.1.2 --- SEM micrographs and EDS analysis --- p.4.7 / Chapter 4.3.1.3 --- Discussions --- p.4.11 / Chapter 4.3.2 --- Sample with different dwelling times --- p.4.13 / Chapter 4.3.2.1 --- SEM micrographs --- p.4.13 / Chapter 4.3.2.2 --- Weight loss against dwelling time --- p.4.16 / Chapter 4.3.2.3 --- Discussions --- p.4.18 / Chapter 4.3.3 --- Samples with varied weight percentage of Ag2O --- p.4.19 / Chapter 4.3.3.1 --- SEM micrographs --- p.4.19 / Chapter 4.3.3.2 --- Discussions --- p.4.22 / Chapter 4.3.4 --- Samples with different cooling rate --- p.4.23 / Chapter 4.3.4.1 --- XRD patterns --- p.4.23 / Chapter 4.3.4.2 --- Optical photographs --- p.4.25 / Chapter 4.3.4.3 --- SEM micrographs --- p.4.28 / Chapter 4.3.4.4 --- TEM micrographs and high-resolution TEM micrographs…… --- p.4.31 / Chapter 4.3.4.5 --- Discussions --- p.4.35 / Chapter 4.3.4.5.1 --- XRD spectra --- p.4.35 / Chapter 4.3.4.5.2 --- Optical photographs --- p.4.35 / Chapter 4.3.4.5.3 --- SEM micrographs --- p.4.35 / Chapter 4.3.4.5.4 --- TEM micrographs --- p.4.36 / Chapter 4.4 --- Conclusions --- p.4.37 / References --- p.4.38 / Chapter Chapter 5 --- Mechanical hardness and thermal expansion of Mg-Ag20 --- p.5.1 / Chapter 5.1 --- Introduction --- p.5.1 / Chapter 5.2 --- Mechanical properties --- p.5.1 / Chapter 5.2.1 --- Experiments --- p.5.1 / Chapter 5.2.2 --- Results --- p.5.2 / Chapter 5.2.3 --- Discussions --- p.5.8 / Chapter 5.3 --- Thermal properties --- p.5.9 / Chapter 5.3.1 --- Experimental details --- p.5.9 / Chapter 5.3.2 --- Results --- p.5.10 / Chapter 5.3.3 --- Discussions --- p.5.12 / Chapter 5.4 --- Conclusions --- p.5.13 / References --- p.5.14 / Chapter Chapter 6 --- Conclusions and future works --- p.6.1 / Chapter 6.1 --- Conclusions --- p.6.1 / Chapter 6.2 --- Further works --- p.6.2

Cheng, Ka Wing = 聚合物太陽能電池的研究 / 鄭家榮. / "December 2010." / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 93-96). / Abstracts in English and Chinese. / Cheng, Ka Wing = Ju he wu tai yang neng dian chi de yan jiu / Zheng Jiarong. / Abstract --- p.i / 概要 --- p.iii / Acknowledgements --- p.iv / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- The Rise of Organic Photovoltaics --- p.1 / Chapter 1.2 --- General Review on Organic Photovoltaics --- p.3 / Chapter 1.2.1 --- Physics of Organic Photovoltaics --- p.4 / Chapter 1.2.2 --- Performance Analysis --- p.10 / Chapter 1.2.3 --- Calibration --- p.11 / Chapter 1.2.4 --- Device Architectures --- p.14 / Chapter 1.3 --- Morphology and Performance of Bulk Heterojunction Polymeric Solar Cells --- p.17 / Chapter 1.3.1 --- Choice of Solvent --- p.17 / Chapter 1.3.2 --- Effect of Annealing --- p.18 / Chapter 1.4 --- The Quest of Higher Efficiency --- p.18 / Chapter 1.5 --- Structure of This Thesis --- p.19 / Chapter 2 --- Optical Properties in a Multilayered Solar Cell --- p.21 / Chapter 2.1 --- Introduction --- p.21 / Chapter 2.2 --- Electromagnetic Waves in a Multilayered Thin Film --- p.22 / Chapter 2.3 --- Microcavity Effect --- p.33 / Chapter 2.4 --- Conclusion --- p.34 / Chapter 3 --- Improvement of Solar Cell Efficiency: Result of Simulation --- p.36 / Chapter 3.1 --- Introduction --- p.36 / Chapter 3.2 --- P3HT:PCBM Bulk Heterojunction Solar Cells --- p.36 / Chapter 3.2.1 --- Standard Devices --- p.37 / Chapter 3.2.2 --- Standard Devices with Inserted Silver Layer --- p.39 / Chapter 3.2.3 --- Silver Layer Inserted Devices Without PEDOT:PSS ... --- p.44 / Chapter 3.3 --- MEH-PPV:PCBM Bulk Heterojunction Solar Cells --- p.46 / Chapter 3.3.1 --- Standard Devices --- p.46 / Chapter 3.3.2 --- Standard Devices with Inserted Silver Layer --- p.50 / Chapter 3.3.3 --- Silver Layer Inserted Devices Without PEDOTiPSS . . --- p.52 / Chapter 3.4 --- Discussion --- p.54 / Chapter 3.5 --- Conclusion --- p.56 / Chapter 4 --- Experimental Results --- p.57 / Chapter 4.1 --- Introduction --- p.57 / Chapter 4.2 --- A General Study on Traditionally Structured Solar cell --- p.58 / Chapter 4.2.1 --- Standard Bulk Heterojunction Devices --- p.58 / Chapter 4.2.2 --- Effects of the Metal Electrodes --- p.59 / Chapter 4.2.3 --- Effects of Annealing Time --- p.60 / Chapter 4.3 --- Modified P3HT:PCBM Bulk Heterojunction Solar Cells --- p.61 / Chapter 4.3.1 --- Optimized Standard Devices --- p.61 / Chapter 4.3.2 --- Standard Devices with Inserted Silver Layer --- p.63 / Chapter 4.3.3 --- Silver Inserted Devices Without PEDOTiPSS --- p.64 / Chapter 4.4 --- Discussion --- p.68 / Chapter 4.5 --- Conclusion --- p.71 / Chapter 5 --- Conclusion --- p.73 / Chapter 5.1 --- Suggestion of Future Works --- p.75 / Chapter A --- Simulation Codes --- p.77 / Chapter A.1 --- P3HT:PCBM (1:1) Standard Device --- p.77 / Chapter B --- Instrumentation --- p.87 / Chapter C --- Sample Preparation --- p.90 / Bibliography --- p.93

Ce mémoire présente l’étude de protections anti-oxydation (PAO) de matériaux composites SiC/SiC. Ces matériaux sont dotés de propriétés spécifiques (légèreté, résistance aux chocs thermiques et tenue mécanique à haute température) par l’association de fibres et d’une matrice SiC liées par une interphase en carbone. Néanmoins, cette interphase s’oxyde dès 400°C entraînant la décohésion entre les fibres et la matrice et ainsi la perte des propriétés mécaniques. En vue d’applications dans le domaine de l’aéronautique civile, la PAO doit être opérationnelle à basse température (400-650°C) et sur de longues périodes (de l’ordre de plusieurs milliers d’heures). Deux types de protections ont été proposés et étudiés: (i) une protection rigide formée par traitement thermique d’un mélange entre une solution de phosphate d’aluminium et de silice. La structure du revêtement a ensuite été caractérisée par RMN, DRX et MEB et mise en relation avec l’efficacité de la protection. (ii) une protection dynamique basée sur l’utilisation de verres de phosphate formulés afin de présenter des caractéristiques de viscosité optimales pour la PAO. Les formulations ont été caractérisées par analyses thermiques (ATD, ATM, HSM) et par RMN. Une démarche raisonnée a été mise en œuvre en corrélant les propriétés thermiques aux caractéristiques structurales des oxydes utilisés. Ces deux revêtements étudiés améliorent la durée de vie du matériau, mais sans atteindre la spécification attendue. Nous concluons que la protection dynamique est plus adaptée à l’application basse température et proposons des voies d’amélioration. / This work presents anti-oxidation coating (AOC) of composite materials SiC/SiC. These materials have specific properties (lightness, excellent resistance to thermal shocks, and mechanical endurance at very high temperature) due to the combination of SiC fibers and SiC matrix linked by a C interphase. This interphase oxidizes under air above 400°C, leading to fiber/matrix debonding and thus compromising the mechanical properties. In view of application in civil aeronautics, the AOC have to be operational at low temperatures (400-650°C) and for prolonged periods (of the order of thousands of hours). Two types of coatings were proposed and examined: (i) a rigid coating obtained through the thermal treatment of a mixture of aluminium phosphate solution and silica. The structure of the coating has been characterized by NMR, XRD and SEM and related to the efficiency of the protection. (ii) a dynamic coating, based on phosphate glasses formulated to present optimum viscosity characteristics. The different glasses were characterized by thermal analyses (DTA, TMA, HSM) and by NMR. A thought approach was implemented by correlation between thermal properties and structural characteristics of oxides used. These two coatings improve the material lifetime even if the expected specification was not accomplished. To conclude, the dynamic coating is more adapted to low temperature use and we suggest some improvements.

Hu, Zhuofeng. / Thesis Ph.D. Chinese University of Hong Kong 2014. / Includes bibliographical references. / Abstracts also in Chinese. / Title from PDF title page (viewed on 24, October, 2016).

No description available.

Polymer organosilicate nanocomposites have attracted significant attention over the last decade due to improved mechanical, thermal, and barrier properties. Several nanocomposite researchers have recognised potential for biomedical applications, however none have conducted biological investigations. In this project, the predicted ability of the organosilicate to enhance biostability, modulate the release of included drugs, and confer biofunctionality and control over the host response, were assessed as the three primary hypotheses. The studies were conducted with the objective being employment as urinary device biomaterials. Of prime importance was that no detrimental change in cytocompatibility was resultant. Biomedical thermoplastic elastomeric polyurethane organosilicate nanocomposites were prepared from poly(ether)urethane of 1000g/mol poly(tetramethylene oxide) polyol, 4,4??? diphenylmethane diisocyanate, and 1,4 butanediol chain extender chemistry, and various organosilicates with loadings from 1w% to 15w%, using a solution casting technique. Initially, partially exfoliated nanocomposites were produced using a commercially available organosilicate, Cloisite?? 30B. These nanocomposites displayed several advantageous properties, namely i) significant anti-bacterial activity, reducing S. epidermidis adherence after 24h to ~20% for a 15w% organosilicate loading, ii) enhanced biostability, with a 15w% organosilicate loading displaying only slight degradation after a 6 week subcutaneous in vivo ovine implantation, and iii) static modulation of model drug release as a factor of drug properties and organosilicate loading. The former was attributed to the Cloisite?? 30B quaternary ammonium compound, while the latter two were likely primarily barrier effect related and due to changes to poly(ether)urethane permeability. Electrostatic and chemical interactivity between drug and organosilicate was also implicated in the observed drug release modulation. Unfortunately, a lack of in vitro cytocompatibility and poor in vivo inflammatory response will limit in vivo use. Utilising bioinert 1-aminoundecanoic acid as an alternative organic modification, cytocompatible intercalated nanocomposites were produced thus likely allowing in vivo nanocomposite use and exploitation of the barrier effect related properties. However, these nanocomposites were not antibacterial. Variation of the organic modification and/or use of co-modification were viable means of modulating host response and biofunctionality, however nanoscale dispersion of co-modified silicate was poor. Use of nanocomposite technology was concluded beneficial to existing biomaterials, and specifically to biomaterial application as urinary catheters / stents.

My research has focussed on the development of a technique to tailor photochromic switching rates by creating a customised local environment for the dye within an otherwise rigid host matrix. Living radical polymerisation offers the potential to design such a system. A living radical initiator based on a spirooxazine compound was used to polymerise a polymer chain of well controlled molecular weight and polydispersity. This technique facilitated the construction of a conjugate with every photochromic moiety convalently attached to a polymer chain with uniform characteristics. The photochromic behaviour of these new polymer-spirooxazine conjugates were investigated in a cross-linked polymer matrix with a Tg of approximately 120??C. It is well known that photochromic switching is susceptible to local environment effects such as rigidity, free volume and polarity.1, 2 The goal of these systems was to create a uniform local environment which would facilitate controlled changes in the photochromic switching rates. The photophysical investigation of these systems demonstrated the success of this technique. The photochromic rates were directly related to the characteristics of the polymer conjugate. It was postulated the conjugates acted as a customised local environment for the photochromic moiety, encapsulating it from the host matrix. Consequently systematic tailoring of the photochromic switching rates was achieved by changes in the characteristics of the attached polymer. To our knowledge this is the first technique to control local environment of a photochromic compound and thus the first example of systematic tuning of photochromic switching rates. Throughout this research, several characteristics of the attached polymer were modified to give a series of rules for the tuning of photochromic switching rates using this technique. The largest variation in switching speed is achieved through variation of Tg. A range of photochromic rates from extremely slow to near solution-like can be easily achieved. The necessary variations in Tg can be achieved easily using living radical polymerisation techniques. The use of different homopolymers, block and random copolymers were all demonstrated successfully in this work. For finer tuning of the photochromic rates, changes in chain length can be used. It was also found the best living radical polymerisation method for this work was ATRP due to the bulky or incompatible halogen which contributed to efficient encapsulation. However this endgroup effect is only important in systems which do not have a low Tg component. The incorporation of such a component overrides all other contributions to the overall behaviour.

Cement is the world's most popular building material, yet surprisingly its composition is not fully understood. Due to the complex nature of cement constituents, there is currently no reliable method to quantitatively determine the composition of cement. Partly this arises from the fact that the crystal structure of the main component of cement, tricalcium silicate, has not been fully determined. There has been an increase in the use of Rietveld refinement of powder diffraction data for the analysis of cement in recent years. The method has emerged as a valuable tool for the quantitative determination of the composition of cement. A further advantage of the method is its ability to refine complex crystal structures, such as tricalcium silicate. Despite the increased application of this method, few publications exist concerning the evaluation or improvement of the method for the purpose of cement analysis. In this work, the Rietveld method has been critically investigated as a tool for the identification and quantification of the different phases in cement clinker. Laboratory X-ray, synchrotron, neutron, and combined diffraction data are all used in the investigations. For the first time, comparisons of analysis results using various sources are made, rather than comparing the results from various methods. Inconsistencies in the results were found, and their causes were investigated and identified. The reliability of this method was shown to be dependent on the quality of the diffraction data, both in terms of the counting statistics and the resolution, and on the ability of the structures used in the Rietveld model to describe the phases in the sample. The only previously existing structural model for triclinic tricalcium silicate is shown, in this work, inadequate as a description of the form found in cement. Consequently, the triclinic crystal structures of tricalcium silicate were re-investigated. Using synchrotron powder diffraction data, the lattice dynamics during the T1-T2 transition were observed in detail for the first time. Superstructure reflections were observed for the two structures. The first model for the average sub-structure of the T2 form is presented. Structural modulation in the T1 form was re-investigated. The parent sub-structure, suitable for Rietveld refinement, corresponding modulation wave-vector, and superspace group of the superstructure, were identified.

Polymer materials are commonly reinforced with organic or inorganic fillers to improve their mechanical properties and to reduce the cost. Such reinforcement strongly depends on the characteristics of fillers (e.g. size, shape, aspect ratio and surface feature) and their dispersion in polymer matrix. The use of inorganic fillers exploits the synergistic effect of high mechanical strength and heat durability of fillers and processing ease of polymers. However, it often causes interfacial incompatibility and an increase in density and a loss of tenacity and opacity. Because layered clays possess rich intercalation chemistry and can be delaminated into disk-like nanopartciles, we investigate the possibility of developing polymer nanocomposites from montmorillonite (MMT). As a result, two nanomaterials, intercalated polyaniline (PANI) nanocomposites and exfoliated PS nanocomposites, have been fabricated via in situ polymerization. Morevoer, experimental work shows that the surface modification of clays and the dispersion of organically modified clays (i.e. organoclays) are crucial to the success of fabricating polymer nanocomposites. Therefore, molecular dynamics (MD) simulations are used to investigate such fundamental aspects on the structure and dynamics of organoclays and the interfacial interactions and structure of diblock copolymer (i.e. PU) nanocomposites. The simulated results are in good agreement with the available experimental data. For organoclays, the results indicate that the alkyl chains exhibit strong layered structures in the interlayer space of clays. Such layering behaviors strongly depend on the chain length and layer charge. More importantly, a pseudo-quadrilayer structure is observed for organoclays modified with dioctadecyldimethyl ammoniums in which the alkyl chains do not lie flat within a single layer but interlace and spread into the adjacent layers. Finally, different orientaion of chain segments is found in the middle and end segments, and within and out of the layer structure. For polyurethane (PU) nanocomposites, van der Waals interaction between apolar alkyl chains and PU soft segments dominates the interactions between organoclay and PU. In addition, hydrogen bonding can form between the siloxane oxygen of clay surface and nitrogen (hard segment) or oxygen (soft segments) of PU. Furthermore, there is no distinct phase-separated structure for PU in the nanocomposites, which is attributed to the results of competitive interactions among PU, alkyl ammonium and clay surface.