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The Faraday rotation spectrum of composites containing magnetite nanoparticles is found to be dependent on the interparticle spacing of the constituent nanoparticles. The composite materials are prepared by combining chemicallysynthesized Fe3O4 (magnetite) nanoparticles (8 nm diameter) and poly(methylmethacrylate) (PMMA). Composites are made containing a range of nanoparticle concentrations. The peak of the main spectral feature depends on nanoparticle concentration; this peak is observed to shift from approximately 470 nm for (dilute composites) to 560 nm (concentrated). A theory is presented based on the dipole approximation which accounts for optical coupling between magnetite particles. Qualitative correlations between theoretical calculations and experimental data suggest the shifts in spectral peak position depend on both interparticle distance and geometrical configuration.

There is a raising need to design a safe and efficient cryogenic fuel tank for the new generation of reusable launch vehicles. The new tank design focuses on composite materials that can achieve the drastic reduction of empty/non-payload and structural weight. In addition to the materials to be compatible with cryogenic temperatures, interior components of the vehicle may be subjected to significantly elevated temperatures due to heat conduction from the vehicle surfaces during and after atmospheric re-entry. Therefore, there is the need to understand the performance of the composites after experiencing extreme thermal environments. Polymer-layered nanocomposites were studied to determine if they can reduce the permeation to the liquid nitrogen used as fuel in the next generation of space vehicles. Due to the non-permeable nature of the silicates and the exfoliated structure they adopt into the polymer matrix the addition of nanoclays into a polymer is expected to reduce the permeation to several gases without sacrificing the mechanical strength of the nanocomposite as well as providing additional improvements such as increase of thermal stability of the nanocomposite. Several types of matrixes modified with different types and content of nanoclays were tested and their permeability coefficient was calculated. The permeability values obtained for the different formulations assisted to understand the transport properties of nanoclay modified composites. In addition to this, thermal characterization was performed with the help of dynamic mechanical analysis, thermogravimetric analyses and differential scanning calorimetry studies. To determine if the nanoclay modified nanocomposites were affected by extreme temperatures the samples were subjected to thermal cycling. Comparison of the transport and thermal properties before and after cycling helped to analyze the effect of the addition of the nanoclays in the nanocomposites. Positron annihilation spectroscopy (PAS) was utilized to comprehend how the distribution of the free volume was affected by the presence of the nanoclays and by the thermal cycling applied. Different permeability models were utilized in an attempt to validate the experimental results of the different nanocomposite structures. This analysis was used to provide additional insight into many aspects of the experimental results obtained in this study.

School of Chemical and Metallurgical Engineering, Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, South Africa August 2017 / Global warming, resulting from emission of greenhouse gases (GHGs), is the cause of drastic climate changes that threatens the economy and living conditions on the planet. Currently, recovery and mitigation of these greenhouse gases remains a technological and scientific challenge. Various recovery processes for the mitigation of GHGs have been reported including among others carbon capture and storage (CCS). The most mature and applied technology in CCS process involves the absorption of carbon dioxide on amine based solvents. However, studies have shown that this process has several drawbacks that include low stability and high energy required to strip off the absorbed CO2 and regenerate the solvent. This presents an opportunity for the development of new materials for CO2 capture such as zeolite membranes. Previous studies have shown that the separation of CO2 can be achieved with high selectivity at low temperatures using thin-film SAPO-34 membranes (thin layers on supports). This is because CO2 adsorbs strongly on the membranes compared to other gases found in flue gas. In the thin-film membranes supported on ceramic or sintered stainless steel, thermal expansion mismatch may occur at higher operating temperatures resulting in loss of membrane selectivity due to the formation of cracks. A new method is required to overcome the aforementioned problems, thereby enhancing the separation application of the membranes at higher temperatures. The effective separation and capture of CO2 from the coal-fired power plant flue gas is an essential part in the CCS process (Figueroa et al., 2016; Yang et al., 2008). Currently, the capture stage is a huge contributor to the overall cost of CCS (Yang et al., 2008). This is due to the high-energy intensity and inefficient thermal processes applied in the separation and capture in various industrial applications (Yang et al., 2008). This work presents the use of nanocomposite SAPO-34 zeolite membranes synthesized via the pore-plugging hydrothermal method for the separation of CO2 during post-combustion CO2 capture. The SAPO-34 membranes used were supported on asymmetric α-alumina as membrane supports. The membranes were characterized with a combination of dynamic and static physicochemical techniques such as Basic Desorption Quality Test (BDQT), X-ray diffraction (XRD) spectroscopy, Scanning Electron Microscopy (SEM), Fourier Transform Infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The characteristic peaks at 2θ = 21°, 26°, and 32° on the XRD pattern confirmed the presence of SAPO-34 with a rhombohedral crystalline structure. The SEM images showed the formation of the cubic crystalline which were consistent with the reported morphology of SAPO-34. FTIR spectra showed the presence of the essential double-6 membered rings (D6R) and TO4 structural groups in surface chemistry of crystalline materials further confirming the presence SAPO-34. The TGA confirmed that the membranes possessed high thermal stability. To assess the feasibility of the synthesis process, the nanocomposite zeolites were grown within the tubular supports. The SEM images of the cross-section of the membrane confirmed the presence of the zeolites within the pores of the support confirming the fabrication of nanocomposite membranes by the pore-plugging synthesis method. The permeation tests used a dead-end filtration mode to measure the single gas permeance and the ideal selectivity of CO2 and N2 were calculated. The BDQT was essential in the study of the quality of the as-synthesized nanocomposite membranes. The quality of the membranes increased with an increase in the synthesis layers of the membranes. However, with an increase in synthesis layers, the membrane thickness also increases. The membrane thickness affected the gas permeance for CO2 and N2 significantly. The permeance of the N2 gas decreased from 10.73 x10-7 mol.s-1.m2Pa-1 after the first synthesis to 0.31 x10-7 mol.s-1.m2Pa-1 after seven synthesis layers. Alternatively, the more adsorbing gas CO2 decreased from 12.85 x10-7 mol.s-1.m2Pa-1 to 2.44 x10-7 mol.s-1.m2Pa-1. The performance of these zeolite membranes depends significantly on the operating conditions. Hence, we studied extensively the influence of the various operating conditions such as temperature, feed pressure and feed flowrate in this work. Results indicated that the membrane separation performance in this study is largely dependent on the temperature. In addition, the ideal selectivity decreased significantly with an increase in temperature. High temperatures results in less adsorption of the highly adsorbing CO2 gas, the permeance reduces significantly, while the permeance of the less adsorbing N2 increased slightly. The feed flow rate has less effect on the adsorbing gas while the non-absorbing gas increased resulting in a decrease in the ideal selectivity as well. The nanocomposite membranes in this study have a low flux compared to their thin film counterparts. An increase in feed pressure significantly increased the flux significantly as well as the ideal selectivity. Maxwell-Stefan model simulation was done in this study to describe the permeance of pure CO2 single gas permeance as a function of temperature. This model considered explicitly the adsorption-diffusion mechanism, which is the transport phenomenon, involved in the transport of CO2 through the zeolite membrane. The description of the support material was included in the model as well. However, the model was only applied to the CO2 gas permeation well within the experimental data. We then compared the model was with the experimental results and a good correlation was observed. In conclusion, SAPO-34 nanocomposite zeolite membranes were obtained at low temperatures (150 °C) with a short synthesis time (6 h). In addition, the high thermal stability of the as-synthesized SAPO-34 membranes makes them ideal for high temperature CO2 separation such as the intended post-combustion carbon capture. The BDQT revealed that the quality of the membranes was related to the thickness of the membranes. Therefore, better membrane quality was obtained with relatively thicker membranes. The separation performance evaluation was conducted on the membrane with the greatest quality. Our findings demonstrate that the performance of the membranes depends extensively on the operating conditions. / MT2018

Este trabalho apresenta a preparação e caracterização de compósitos baseados em poli (tereftalato de butileno) PBT e argila brasileira modificada preparados por intercalação por fusão. Os nanocompósitos de PBT com 3 e 5 %, em peso, de argila organicamente modificada, pela adição de um sal quaternário amônio, foram preparadas pelo processo de extrusão utilizando-se uma máquina extrusora dupla rosca. Após o processo de extrusão, os materiais foram injetados para obtenção de corpos-de-prova para os ensaios de caracterização. Parte dos corpos-de-prova foram submetidos ao processo de irradiação utilizando-se um acelerador de feixes de elétrons de 1,5 MeV, à temperatura ambiente e na presença de ar. As amostras de PBT puro e nanocompósitos irradiadas e não irradiadas foram caracterizadas por meio de ensaios mecânicos de tração, flexão e impacto, ensaios de temperatura de distorção térmica (HDT), difração de raios - X (DRX), microscopia eletrônica de varredura (MEV), índice de fluidez, termogravimetria (TG) e calorimetria exploratória diferencial (DSC) e a correlação entre as propriedades foi discutida. Os resultados mostraram que a adição da argila, em ambas as porcentagens, promoveu aumento superior a 50 % na resistência a tração na ruptura e um ganho de cerca de 35 % na temperatura de distorção térmica quando comparado ao polímero puro. O tratamento por radiação ionizante de feixe de elétrons nas doses utilizadas neste estudo não apresentaram mudanças significativas nas propriedades dos materiais. / This work describes the preparation and characterization of composites based on poly (butylene terephthalate) - PBT and brazilian modified clay prepared by the melt intercalation. PBT nanocomposites with 3 and 5 % by weight of organically modified clay, by the addition of a quaternary ammonium salt, were prepared by extrusion using a twin-screw extruder machine. After the extrusion process, the materials were injected to obtain specimens tests samples for the characterization tests. Part of the specimens samples were irradiated using an electron beam accelerator with 1.5 MeV at room temperature in the presence of air. Samples of pure PBT and irradiated and non-irradiated nanocomposites were characterized by mechanical tests of tensile, flexural and impact, heat distortion temperature (HDT), X - ray diffraction (XRD), scanning electron microscopy (SEM), melt flow index (MFI) thermogravimetry (TG) and differential scanning calorimetry (DSC) and the correlation between the properties was discussed. The results showed that the addition of clay, in both percentages, promoted an increase greater than 50 % in tensile strength at break and a gain of around 35% in heat distortion temperature when compared to the pure polymer. The treatment with ionizing radiation of electron beam at the doses used in this study showed no significant changes in material properties.

As argilas são utilizadas em grande número nas mais diversas áreas tecnológicas e uma das áreas de maior interesse em pesquisa é a sua utilização em nanocompósitos silicato/polímeros. Esses nanocompósitos são obtidos a partir da dispersão de argila, em dimensão nanométrica, em um polímero com um enorme potencial de uso em diversos mercados, devido aos efeitos sinergéticos que ocorrem em relação as suas propriedades em comparação com os polímeros puros e os compósitos. A incorporação da argila, geralmente é pela transformação da argila esmectítica sódica em organofílica e utilizando os processos de polimerização in situ, solvente comum ou através do polímero fundido. Este trabalho utiliza um novo procedimento que utiliza uma argila esmectítica sódica comercial, sem a transformação em organofílica para a incorporação em plastisol. O procedimento é feito através de dispersão mecânica da argila e a sua incorporação à formulação do plastisol, evitando que ocorra uma degradação térmica dos sais utilizados para a transformação das argilas. Também foram realizados estudos com o plastisol puro e com um nanocompósito obtido com argila organofílica comercial visando fazer uma análise comparativa de suas propriedades com argilas preparadas em laboratório. As caracterizações foram feitas por DRX e ensaios mecânicos. / Clays are most used in many different tecnology áreas and one of most area research interest is its use in nanocomposite silicate/polymers. Those nanocomposites are got from the clay disperce, in nanometric dimension, in a polymer with a large use power at many markets, due to sinergetic effects that happen linked to its properties compareing to the pure polymers and the composit. The clay.s entry, in general is by the smectite clays sodic transformation into organophilic and using the polymerization process in situ, common solvent or through melted polymer. This work uses a new procedure that uses a smectite sodic commercial clay, without the organophilic transformation entry to plastisol. The procedure is done through clay.s mechanics disperce and its entry to the plastisol.s formulation, averting that happen a termic degradation of the used salt to the clay.s transformations. Were also carried out studies with pure pastisol and with a nanocomposite got with organophilic commercial clay wanting to do a comparative analysis of its properties with laboratoties prepared clays. The characterizetions were done by DRX and mechanics studies.

Este trabalho apresenta a preparação e caracterização de compósitos baseados em poli (tereftalato de butileno) PBT e argila brasileira modificada preparados por intercalação por fusão. Os nanocompósitos de PBT com 3 e 5 %, em peso, de argila organicamente modificada, pela adição de um sal quaternário amônio, foram preparadas pelo processo de extrusão utilizando-se uma máquina extrusora dupla rosca. Após o processo de extrusão, os materiais foram injetados para obtenção de corpos-de-prova para os ensaios de caracterização. Parte dos corpos-de-prova foram submetidos ao processo de irradiação utilizando-se um acelerador de feixes de elétrons de 1,5 MeV, à temperatura ambiente e na presença de ar. As amostras de PBT puro e nanocompósitos irradiadas e não irradiadas foram caracterizadas por meio de ensaios mecânicos de tração, flexão e impacto, ensaios de temperatura de distorção térmica (HDT), difração de raios - X (DRX), microscopia eletrônica de varredura (MEV), índice de fluidez, termogravimetria (TG) e calorimetria exploratória diferencial (DSC) e a correlação entre as propriedades foi discutida. Os resultados mostraram que a adição da argila, em ambas as porcentagens, promoveu aumento superior a 50 % na resistência a tração na ruptura e um ganho de cerca de 35 % na temperatura de distorção térmica quando comparado ao polímero puro. O tratamento por radiação ionizante de feixe de elétrons nas doses utilizadas neste estudo não apresentaram mudanças significativas nas propriedades dos materiais. / This work describes the preparation and characterization of composites based on poly (butylene terephthalate) - PBT and brazilian modified clay prepared by the melt intercalation. PBT nanocomposites with 3 and 5 % by weight of organically modified clay, by the addition of a quaternary ammonium salt, were prepared by extrusion using a twin-screw extruder machine. After the extrusion process, the materials were injected to obtain specimens tests samples for the characterization tests. Part of the specimens samples were irradiated using an electron beam accelerator with 1.5 MeV at room temperature in the presence of air. Samples of pure PBT and irradiated and non-irradiated nanocomposites were characterized by mechanical tests of tensile, flexural and impact, heat distortion temperature (HDT), X - ray diffraction (XRD), scanning electron microscopy (SEM), melt flow index (MFI) thermogravimetry (TG) and differential scanning calorimetry (DSC) and the correlation between the properties was discussed. The results showed that the addition of clay, in both percentages, promoted an increase greater than 50 % in tensile strength at break and a gain of around 35% in heat distortion temperature when compared to the pure polymer. The treatment with ionizing radiation of electron beam at the doses used in this study showed no significant changes in material properties.

In this work the potential of graphene-like particles for mechanical reinforcement is investigated. Different polymer processing methods are studied from traditional ones to more advanced techniques. The potential of graphene as a reinforcement for polymer composites is addressed as a result of polymer modifications and the morphology of the graphene like particles. First, a composites of polycarbonate (PC) and graphite nanoplatelets (GNP) are produced by a traditional melt-mixing method. The GNP composites present a low mechanical reinforcing efficiency which is believed to be due to a poor dispersion of the GNP and a weak interaction between the GNP and the matrix. Secondly, solution cast composites of polyvinyl alcohol (PVA) with very low loadings of graphene oxide (GO) are produced. The polymer morphology undergoes some modifications after the addition of GO. A strong increase of the Tg is observed after the addition of GO which is the result of a reduction in polymer mobility, while a dramatic increase of the mechanical properties is seen as well. Uni-axial drawing is applied in order to align the particles. No polymer modifications are observed between the drawn PVA and the drawn nanocomposites due to the strong alignment of the polymer chains during the drawing. Mechanical reinforcement is observed after addition of the GO showing real reinforcement. Finally, a more advanced processing method is investigated using spraying. The condition of spraying a layer of polymer and GO is studied. Finally a hierarchical composite of PVA - GO is produced by this spraying method. 150 bi-layers are deposited to create a film with improved mechanical properties at a loading of 5.4 wt.% GO. The Young’s modulus and strength of these films doubled or nearly doubled which is believed to be due to the high level of structural organization of the layered nanocomposite incorporating the 2D GO nanofiller, together with hydrogen bonding between the PVA and the GO sheets.

An innovative method has been developed for synthesizing aluminum-aluminum nitride nanocomposite materials wherein the reinforcing nano-sized aluminum nitride particles are formed in-situ in a molten aluminum alloy. This method, which circumvents most issues associated with the traditional ways of making nanocomposites, involves reacting a nitrogen-bearing gas with a specially designed molten aluminum alloy. The method ensures excellent dispersion of the nanoparticles in the matrix alloy, which is reflected in enhanced mechanical properties. In this thesis, the author reviews the limitations of the conventional methods of manufacturing nanocomposites and develops thermodynamic and kinetic models that allow optimizing the in-situ gas-liquid process to produce quality nanocomposite material. Also, in this thesis, the author reports the measured room temperature and elevated temperature tensile properties of materials that were made by the optimized process and compares the measured values to their counterparts obtained for the base alloy. A 75 pct. increase in room temperature yield strength is obtained when the base alloy is reinforced with one pct. nano-size aluminum nitride particles and this significant increase in yield strength is accompanied by only negligible loss of ductility.

Siu, King Sang = 網狀合金的白鑄鐵的退火處理 / 蕭健生. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2008. / Includes bibliographical references. / Abstracts in English and Chinese. / Siu, King Sang = Wang zhuang he jin de bai zhu tie de tui huo chu li / Xiao, Jiansheng. / Abstract --- p.i / 摘要 --- p.iv / Acknowledgments --- p.v / Table of contents --- p.vi / List of table captions --- p.viii / List of figure captions --- p.ix / Chapter Chapter 1 --- Introduction / Chapter 1.1 --- Composite Materials --- p.1 / Chapter 1.2 --- Nanostructured Material --- p.2 / Chapter 1.3 --- Typical Methods of Fabrication of Nanostructure Material --- p.3 / Chapter 1.4 --- Combination of the Ideas of Nanostructure and Composite --- p.4 / Chapter 1.5 --- Phase Separation --- p.5 / Chapter 1.6 --- Nucleation and Growth --- p.6 / Chapter 1.7 --- Spinodal Decomposition --- p.8 / Chapter 1.7.1 --- The Initiation of Spinodal Decomposition --- p.8 / Chapter 1.7.2 --- Dynamics of Spinodal Decomposition --- p.9 / Chapter 1.7.2.1 --- Classical Equation of Diffusion --- p.9 / Chapter 1.7.2.2 --- Factors Deterring Spinodal Decomposition and Formation of Spinodal Network --- p.10 / Chapter 1.7.3 --- Relationship between Wavelength of Spinodal Network and Undercooling --- p.11 / Chapter 1.7.4 --- "Comparing Nucleation and Growth, and Spinodal Decomposition" --- p.11 / Chapter 1.8 --- How to achieve large undercooling --- p.12 / Chapter 1.9 --- Thermal annealing --- p.12 / Chapter 1.9.1 --- Recovery --- p.13 / Chapter 1.9.2 --- Recrystallization --- p.13 / Chapter 1.9.3 --- Grain Growth --- p.14 / Chapter 1.9.4 --- Equation of Ideal Grain Growth --- p.14 / Chapter 1.9.5 --- Factor that slow down grain growth --- p.15 / Chapter 1.10 --- Prospect of this Thesis Project --- p.16 / References --- p.17 / Figures --- p.19 / Chapter Chapter 2 --- Experimental Method / Chapter 2.1 --- Introduction --- p.26 / Chapter 2.2 --- Sample Fabrication --- p.26 / Chapter 2.3 --- Procedures for Preparing Thermal Annealing --- p.26 / Chapter 2.3.1 --- Preparation of Vacuum Environment --- p.26 / Chapter 2.3.2 --- Sealing Silica Tube --- p.27 / Chapter 2.4 --- Furnance --- p.27 / Chapter 2.5 --- Samples Analysis --- p.27 / Chapter 2.5.1 --- Optical Microscope --- p.27 / Chapter 2.5.2 --- Scanning Electron Microscope (SEM) Analysis --- p.27 / Chapter 2.5.3 --- Transmission Electron Microscope (TEM) Analysis --- p.28 / Chapter 2.5.3.1 --- Sample Preparation --- p.28 / Chapter 2.5.3.1.1 --- "Grinding, Polishing and Pouching" --- p.28 / Chapter 2.5.3.1.2 --- Dimpling --- p.29 / Chapter 2.5.3.1.3 --- I on Milling --- p.29 / Chapter 2.5.3.2 --- Phase Identification --- p.30 / References --- p.31 / Figures --- p.31 / Chapter Chapter 3 --- Grain Growth in Fe81C17Si5 / Chapter 3.1 --- Abstract --- p.34 / Chapter 3.2 --- Introduction --- p.35 / Chapter 3.3 --- Experimental --- p.36 / Chapter 3.4 --- Result --- p.37 / Chapter 3.5 --- Discussion --- p.44 / References --- p.48 / Figures --- p.49 / Chapter Chapter 4 --- High temperature thermal annealing of Fe81C14Si5 network alloys / Chapter 4.1 --- Abstract --- p.74 / Chapter 4.2 --- Introduction --- p.75 / Chapter 4.3 --- Experimental --- p.76 / Chapter 4.4 --- Result --- p.77 / Chapter 4.5 --- Discussion --- p.83 / References --- p.86 / Figures --- p.87