M.Tech. (Biomedical Technology) / Collagen Type I (Col- I) as well as collagen types III and V, form most of the connective tissues, smooth muscle cells and, endothelial cells in wound healing (Stuart and Leaper, 2008). Col-I is also the main extracellular matrix (ECM) protein (Ricard-Blum and Ruggiero, 2005). Low intensity laser irradiation (LILI) is a non-invasive, photobiomodulatory therapy. Huang et al., (2009a) have shown LILI to be involved in Col-I production both in vitro and in vivo. Enhanced collagen production in human skin fibroblasts is common shortly after irradiation (Illsley et al., 2000). However, its synthesis in wounded fibroblasts has not been well established in an in vitro model. Healing is impaired in chronic diabetic wounds which exhibit reduced proliferation rate and collagen synthesis (Beldon, 2010; Falanga, 2005). Studies have shown that LILI using a wavelength of 632.8 nm was not the only wavelength biostimulated in cultured cells: biological responses were also generated from various wavelengths within the visible to Near Infrared (NIR) spectral region (Hawkins and Abrahamse, 2005; Karu and Kolyakov, 2005). This study aimed to establish if LILI influenced collagen production and related cellular responses at a wavelength of 660 or 830 nm, with a fluence of 5 J/cm2 in an in vitro normal and wounded fibroblasts model. The study also evaluated the expression profiling of genes related to the ECM and adhesion. This study was performed on isolated human skin fibroblasts collected from a consenting adult undergoing abdominoplasty. Cells were routinely cultured according to standard techniques (Houreld and Abrahamse, 2010; Hawkins and Abrahamse, 2007a; Hawkins and Abrahamse, 2006a; Hawkins and Abrahamse, 2005).

Contrairement aux métaux conventionnels, les verres métalliques amorphes présentent des arrangements atomiques à courte distante. Ce résultat conduit à des propriétés physiques et chimiques fondamentalement différentes de leurs homologues cristallins. Cette étude porte sur la caractérisation et la compréhension de la nanocristallisation de verres métalliques amorphes massifs (BMG) Zr-Al-Ni-Cu induite par traitement thermique, broyage mécanique et faisceaux d’électrons pulsés à fort courant (HCPEB). Deux alliages amorphes massifs ont été cristallisés par broyage mécanique et HCPEB : le classique Zr65Al7.5Ni10Cu17.5 et un nouvel alliage Zr58Al16Ni11Cu15 développé en utilisant un modèle basé sur l’association de clusters. Les échantillons initiaux et traités ont été caractérisés en combinant les microscopies électroniques en transmission (MET) et à balayage (MEB), la diffraction d’électrons rétrodiffusés (EBSD), l’analyse thermique différentielle (ATD) et la spectroscopie Raman afin d’analyser finement les évolutions microstructurales. Les nanocristallisations induites par broyage et HCPEB sont très différentes de celles obtenues par traitements thermiques. Ces travaux de recherche permettent une avancée dans la compréhension des mécanismes de cristallisations mécanique et sous irradiation. Les résultats peuvent être utilisés pour réaliser des structures composites de BMGs avec l’objectif final d’améliorer leur ductilité / Unlike conventional metals, the atomic arrangements in metallic glasses have only short-range order. This results in many physical and chemical properties that are fundamentally different from those of their crystalline counterparts. This study is devoted to charactering and understanding nanostructures and nanocrystallization of Zr-Al-Ni-Cu bulk metallic glasses induced by thermal annealing, ball milling, and high-current pulsed electron beam (HCPEB) treatment. Two Zr-Al-Ni-Cu BMGs were used: the classic Zr65Al7.5Ni10Cu17.5 alloy and a new Zr58Al16Ni11Cu15 alloy developed by using a cluster-based approach. The initial and treated samples were characterized by the combination of transmission electron microscopy (TEM), scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), X-ray diffraction (XRD), differential thermal analysis (DTA) and Raman spectroscopy in order to analyze accurately the microstructure evolution encountered in the materials. The nanocrystallization behaviour under ball mill and HCPEB is significantly different from the one observed via thermal annealing. The significance of this research is the advancement of the fundamental understanding of mechanical and the electron beam irradiation-induced crystallizations. This research may be used for the design of BMG-related composite structures with the ultimate goal of improving their ductility

The effect of ion irradiation and annealing on the microstructure and migration behaviour of implanted Sr and Ag in SiC have been investigated. SiC is used as the main barrier for fission products in modern high temperature gas cooled reactors. An understanding of the transport behaviour of the implanted ions under irradiation by swift heavy ions (SHI) will shed some light into SiC’s effectiveness in the retention of fission products. The diffusion behaviour of silver (Ag) and strontium (Sr) implanted separately into SiC was investigated after irradiation by xenon ions and isochronal annealing methods from 1100 ˚C up to temperatures of 1500 ˚C in step of 100 ˚C for 5 hours. Ion implantation and ion irradiation were performed at room temperature. The implantation fluences in all cases were in the order of 2×10 16 ions per cm 2 . Some of the implanted samples were then irradiated by SHI at different fluences (i.e. 3.4×10 14 and 8.4×10 14 ions per cm 2 ). The implantation depth profiles before and after irradiation and annealing were determined by Rutherford backscattering spectroscopy (RBS). The microstructure of SiC individually implanted with Ag and Sr were investigated using Raman spectroscopy and scanning electron microscopy (SEM). Implantation of Ag and Sr amorphized the SiC, while SHIs irradiation of the as-implanted SiC resulted in limited recrystallization of the initially amorphized SiC. Annealing at 1100 °C caused more recrystallization on the un-irradiated but implanted samples compared to SHI irradiated samples. This poor recrystallization of the irradiated SiC samples was due to the amount of impurities (i.e. concentration of Ag or Sr atoms) retained after annealing at 1100 o C. Raman and SEM results showed that annealing of the un-irradiated but implanted samples at 1100 °C resulted in large average crystal size compared to the irradiated samples annealed in the same conditions. RBS results showed that SHI irradiation alone induced no change in the implanted Ag and Sr. However, annealing the SHI irradiated samples iscohonally up to 1500 ˚C showed a strong diffusion and release of Ag and Sr as compared to the un-irradiated but implanted samples. The differences in the migration behavior of Ag and Sr is due to the difference in SiC structure and recrystallization in the irradiated and un-irradiated but implanted samples. / Thesis (PhD (Physics))--University of Pretoria, 2019. / National Research Foundation (NRF) and The World Academy of Sciences (TWAS). / Physics / PhD (Physics) / Unrestricted

Thesis. 1977. M.S.--Massachusetts Institute of Technology. Dept. of Nuclear Engineering. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Includes bibliographical references. / M.S.

京都大学 / 新制・課程博士 / 博士(医学) / 甲第24504号 / 医博第4946号 / 新制||医||1064(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 溝脇 尚志, 教授 浅野 雅秀, 教授 鈴木 実 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Inconel X-750 is a Ni-rich super-alloy with high strength and creep resistance. In CANDU reactors, it is used as tight fitting fuel channel annulus spacers (in the form of a spring). Unlike other reactor designs, the CANDU reactor has a high thermal neutron flux spectra, which, combined with the higher thermal neutron cross section of 58Ni results in an enhancement of the radiation damage and the internal production of helium and hydrogen. In recent years, it has been observed these spacers are losing ductility and strength following irradiation. The mechanical property evolution of these components is dependent on the irradiation temperature and dose. The primary degradation mechanism remains unclear, and thus provides the focus of this investigation. Inconel X-750 irradiated to these extreme conditions have never been examined prior to this research. The microstructural characterization included in this dissertation include: fractography, microstructural evolution and mechanical property evolution. The discussion of the microstructural evolution is focused on the characterization of helium bubbles. The bubbles form homogeneously in the matrix and aligned along sinks such as dislocations, grain boundaries and precipitates. Electron energy loss spectroscopy (EELS) has been used to probe individual nano-sized bubbles to provide insights into the helium density, helium-to-vacancy ratio, and pressures through the use of a hard sphere equation of state (HSEOS). In addition to understanding the influence of irradiation on helium bubbles, the evolution of secondary strengthening precipitates, gamma prime, are of interest as these precipitates play an important role on the strength and creep resistance of the unirradiated material. The stability of these precipitates with irradiation is thus an important factor to consider with respect to the microstructural degradation. The microstructure is linked to the mechanical properties via microhardness testing on adjacent material. A major contribution to this field is an approach to utilize a focused ion beam (FIB) and transmission electron microscopy (TEM) to perform high ii resolution failure analysis of an intergranular fracture surface. Although this technique is not altogether revolutionary, the application of this approach towards post irradiation examination of heavily irradiated Inconel X-750 is unique. This approach provides direct evidence of likely degradation mechanisms, and provides insights for future post irradiation failure analysis for other applicable nuclear components. Working with ex-service material creates some complications with respect to known and unknown variables making it difficult to assess all factors responsible for material degradation. To compliment the program, a controlled proton irradiation program has been performed to gain additional insights into in the effects of irradiation on the microstructure and mechanical property evolution of Inconel X-750, due to the inability to perform controlled experiments with in-service reactor components. In addition to providing a detailed analysis of a CANDU component’s degradation, this study provides comprehensive information on irradiation damage processes applicable to other reactor core components. / Thesis / Doctor of Philosophy (PhD)

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The requirements for the next generation of nuclear reactors call for more radiation tolerant materials. One such material, nanostructured ferritic alloys (NFA) are a candidate material for use in cladding. The radiation tolerance of NFAs comes from the high number density of small oxide nanofeatures composed of Y, Ti, and O. These oxide nanofeatures or nano-oxides act as alternative nucleation sites for bubbles of transmutation He, thus preventing the accumulation of He atoms at the grain boundaries which would embrittle the metal. To further study the material, a mean-field rate theory model (MF-RTM) was created to simulate the radiation-induced segregation (RIS) of the alloy components Y, Ti, and O to the grain boundaries. Later, a kinetic Monte Carlo model (KMC) was made that replicated the results from the rate theory for the radiation induced segregation. Then the KMC model was modified to study the nano-oxide behavior in a range of different behaviors; the nano-oxide precipitation kinetics during heat treatment, resistance to dissolution under irradiation regimes similar to reactor conditions, and ability to trap He bubbles on the nano-oxide surfaces rather than the grain boundary. This KMC model is more complex than others as it includes 5 different atomic species (Fe, Y, Ti, O, and He) which migrate through three different mechanisms. Findings from the precipitation heat treatments were able to replicate the size, number density, and composition of nano-oxides from experiments and determined vacancy trapping at oxide interfaces was a significant for the NFA's coarsening resistance as opposed to interference from dislocations. In the irradiation simulations, the resistance of the nano-oxides to dissolution was confirmed and found the excess vacancy population plays an important role in healing the nano-oxides. He bubbles formed in the KMC simulations were found to preferentially form at the oxide interfaces, particularly the <111> interface, rather than the grain boundary and the characteristics of the He bubbles match expectations from literature. In the development of the KMC model, new insights into steady-state detection concepts were also found. A new type of steady-state detection (SSD) algorithm is described. Additionally, a method of forecasting the number of data points needed to make an accurate determination of steady-state, a 'predicting the pre-requisite to steady state detection' (ppSSD), is explored. / Doctor of Philosophy / Nuclear reactors need more radiation tolerant materials in the future, such as nanostructured ferritic alloys (NFA), used for nuclear fuel rod cladding, whose large amount of nanometer sized oxide particles contribute substantially to the radiation resistance of the metal overall. A mean-field rate theory method(MF-RTM) and a Kinetic Monte Carlo (KMC) computer model were made to study radiation induced segregation in the material. A more complex 5 element (Fe, Y, Ti, O, and He) KMC code was later developed to study the influence of the oxides at high temperatures and dose rates to gain insight into the causes the oxides remarkable thermal stability and resistance to irradiation. At all stages, the KMC model was able to replicate material behavior under high temperature heat treatment and irradiation. The model was used to simulate the formation of these oxides under different temperatures during their initial processing to gain more knowledge on how the oxide characteristics (size and number density) are influenced by temperature so we can tailor the processing method to achieve an ideal distribution of oxides in the material. Additionally, a mechanism for the oxides resistance to high temperature coarsening unrelated to the expected one caused by dislocations. The irradiation resistance of oxides to dissolution from irradiation was also investigated. While experimental measurements give a before and after picture of a material that underwent irradiation, the KMC can show the time evolution of the oxide size with increasing irradiation damage so the mechanisms behind the radiation resistance can be understood. The oxides remained stable at all temperatures and dose rates. Excess vacancies were found to play an important role in stabilizing the oxides against radiation damage. The KMC model also confirmed the ability of the oxides to trap transmutation He at the interfaces rather than the grain boundary and observed the process of He bubble nucleation. The He bubble form at the <111> oxide interface and they possess similar characteristics of He bubbles expected from literature. Additionally, a novel steady-state detection (SSD) algorithm was developed that can be used for long-term simulations and a method to determine how many data points the algorithm needs to accurately detect steady state is described here.