In this research, X-ray Diffraction is used to detect the existence of the In metal signal of the Indium Nitride (InN) through the analysis of two samples grown from the plasma-assisted molecular beam epitaxy (PAMBE). Sample A was grown on the Al2O3(0001) substrate with Gallium Nitride as a buffer layer, while Sample B was grown directly on the Si(111) substrate. Through X-ray Diffraction, we discovered the In(101) signal on Sample A and the InN(10-11) signal on Sample B. However, the two peaks of both signals were so close that it was difficult to differentiate them. Besides, the scanning electron microscope failed to show the existence of the In metal on the surface of both InN samples. Therefore, the high temperature XRD was employed to identify the true signal based on the different melting points between InN and In. Further, an acid etching method was also applied to recognize the existence of the In metal on the surface of the sample.

The lifetime of the high temperature ceramic coating 7 wt.% yttria-stabilized zirconia (7YSZ) is reduced when calcium-magnesium-alumino-silicate (CMAS) particulates enters aero-engines during operation in a sandy or dusty environment, melts, and infiltrates into the coating. 7YSZ undergo both chemical and mechanical degradation from CMAS infiltration during cycling. Characterization methods with synchrotron X-ray diffraction (XRD) provides a non-destructive means to measure the impact of time and temperature on coating degradation with high spatial resolution of 7YSZ coatings infiltrated and annealed by CMAS for 1 hour and 10 hours as well as at 1225 °C and 1250 °C. Additionally, qualitative results of cross-sectional scanning electron microscopy (SEM) allows for the additional observation and validation of the extent of degradation the coatings experience from CMAS infiltration. The XRD measurements show the extent of degradation is more sensitive to temperature around the melting range of CMAS with an increase of approximately 42.8% in the concentration of the monoclinic phases present in the coating at the surface when increasing the annealing temperature from 1225 °C to 1250 °C. It was also found that the degradation was more significant in the first hour of infiltration. There was an increase of 21.5% in the concentration of the monoclinic phases present within the coating at the surface when increasing the annealing time from 1 hour to 10 hours. The results presented within this thesis resolve the impact of time and temperature on the infiltration kinetics of CMAS in coatings which are important considerations in mitigating CMAS infiltration.

Esta dissertação de mestrado descreve o estudo realizado sobre como a oferta de estrôncio afeta a razão Sr/Ca em hidroxiapatita formada in vitro. Este trabalho pretende dar subsídios para que posteriormente seja possível fazer um estudo da razão Sr/Ca em função da temperatura também em hidroxiapatita formada in vitro. Foram utilizadas células osteoblásticas da linhagem MG-63 com concentrações de estrôncio no meio de cultura que variaram de 0,0 até 33,0 microgramas por mL de meio. Os nódulos ósseos formados pelas células foram caracterizados pelas técnicas Absorção de Infravermelho por Transformada de Fourier (FT-IR), que foi utilizada com o objetivo de identificar ligações de fosfato nas amostras, e Difração de Raios-X (XRD), que teve como objetivo confirmar a presença de hidroxiapatita nos minerais formados e comparar a cristalinidade do material com e sem estrôncio. A quantificação da razão Sr/Ca foi feita utilizando as técnicas Retro-espalhamento Rutherford (RBS) e Emissão de Raios-X por Indução de Partículas (PIXE), que são capazes de fazer a identificação e quantificação elementar. Os resultados obtidos mostram que os nódulos formados são compostos por hidroxiapatita. Com relação à quantificação, mostrou-se que não foi possível substituir mais de 10% do íons de cálcio por íons de estrôncio, o que está de acordo com previsões teóricas. Além disso, para altas concentrações de estrôncio no meio a mineralização do cálcio diminuiu duas ordens de grandeza e as medidas da razão Sr/Ca obtiveram resultados bastante dispersos, indicando uma possível mudança metabólica das células que parece inviabilizar o bom funcionamento fisiológico das mesmas. / This Masters dissertation describes the study of how the availability of strontium affects Sr/Ca ratio of in vitro hydroxyapatite. This work intends to provide the basic understanding needed to a future study of how temperature changes Sr/Ca ratio in this material. MG-63 cells were grown in the culture medium doped with 0.0, 1.0, 2.0, 4.1, 8.2, 16.4, 22.9 and 33.0 micrograms of Sr/mL. The nodules formed by osteoblastic cells were characterized by Fourier Transform Infrared Spectroscopy (FT-IR) technique, used to identify phosphate domain, and X-Ray Diffraction (XRD) technique, which was used to verify the presence of crystallized hydroxyapatite in the mineral composition with and without strontium. Quantification of Sr/Ca ratio was made using the Rutherford Backscattering (RBS) and Particle Induced X-Ray Emission (PIXE) techniques, which are used to do elementary identification and quantification. The results of characterization confirmed the presence of hydroxyapatite in the cultivated MG-63 cells. The experiments have shown that it was not possible to replace more than 10% of the calcium ions by strontium, which is consistent with theoretical predictions. In addition, high concentrations of strontium in the growing solution, reduced the mineralization yield and also the Sr/Ca ratio, indicating a possible change in the metabolism of the cells.

Esta dissertação de mestrado descreve o estudo realizado sobre como a oferta de estrôncio afeta a razão Sr/Ca em hidroxiapatita formada in vitro. Este trabalho pretende dar subsídios para que posteriormente seja possível fazer um estudo da razão Sr/Ca em função da temperatura também em hidroxiapatita formada in vitro. Foram utilizadas células osteoblásticas da linhagem MG-63 com concentrações de estrôncio no meio de cultura que variaram de 0,0 até 33,0 microgramas por mL de meio. Os nódulos ósseos formados pelas células foram caracterizados pelas técnicas Absorção de Infravermelho por Transformada de Fourier (FT-IR), que foi utilizada com o objetivo de identificar ligações de fosfato nas amostras, e Difração de Raios-X (XRD), que teve como objetivo confirmar a presença de hidroxiapatita nos minerais formados e comparar a cristalinidade do material com e sem estrôncio. A quantificação da razão Sr/Ca foi feita utilizando as técnicas Retro-espalhamento Rutherford (RBS) e Emissão de Raios-X por Indução de Partículas (PIXE), que são capazes de fazer a identificação e quantificação elementar. Os resultados obtidos mostram que os nódulos formados são compostos por hidroxiapatita. Com relação à quantificação, mostrou-se que não foi possível substituir mais de 10% do íons de cálcio por íons de estrôncio, o que está de acordo com previsões teóricas. Além disso, para altas concentrações de estrôncio no meio a mineralização do cálcio diminuiu duas ordens de grandeza e as medidas da razão Sr/Ca obtiveram resultados bastante dispersos, indicando uma possível mudança metabólica das células que parece inviabilizar o bom funcionamento fisiológico das mesmas. / This Masters dissertation describes the study of how the availability of strontium affects Sr/Ca ratio of in vitro hydroxyapatite. This work intends to provide the basic understanding needed to a future study of how temperature changes Sr/Ca ratio in this material. MG-63 cells were grown in the culture medium doped with 0.0, 1.0, 2.0, 4.1, 8.2, 16.4, 22.9 and 33.0 micrograms of Sr/mL. The nodules formed by osteoblastic cells were characterized by Fourier Transform Infrared Spectroscopy (FT-IR) technique, used to identify phosphate domain, and X-Ray Diffraction (XRD) technique, which was used to verify the presence of crystallized hydroxyapatite in the mineral composition with and without strontium. Quantification of Sr/Ca ratio was made using the Rutherford Backscattering (RBS) and Particle Induced X-Ray Emission (PIXE) techniques, which are used to do elementary identification and quantification. The results of characterization confirmed the presence of hydroxyapatite in the cultivated MG-63 cells. The experiments have shown that it was not possible to replace more than 10% of the calcium ions by strontium, which is consistent with theoretical predictions. In addition, high concentrations of strontium in the growing solution, reduced the mineralization yield and also the Sr/Ca ratio, indicating a possible change in the metabolism of the cells.

This is the first systematic report on the synthesis of mechanically alloyed Fe-Ni powders ball milled at liquid nitrogen temperature. Pure Fe-Ni samples were ball milled in a SPEX 8000 shaker mill at liquid nitrogen temperature. X-ray diffractometry was used to determine the phase fractions of the bcc and fcc phases in the alloys and to determine the lattice parameters and crystallite size. The main objective of this project is to study how the milling at low temperatures affects the region of two phase co-existence, phase structure and crystallite size. It was found that the composition ranges of the bcc and fcc single phase regions were extended well beyond the equilibrium ranges. The results obtained for the samples ball milled at liquid nitrogen temperature were compared to the previous samples ball milled at room temperature.

Abstract SrTiO3 is cubic at room temperature, and retains cubic until the phase transition to tetragonal at 105K (-168oC). It is a wide-band-gap semiconductor having an energy gap Eg ≈ 3.0 eV, when its semiconductivity is greatly improved by doping with donor oxides, e.g.Nb2O5 or heat treatment in low oxygen partial pressures (Po2). Donor oxides in solid solution with SrTiO3 forming substitutional defects create electron or cation vacancies as the principal charge compensation defect. In-gap levels are also modified by the oxygen partial pressure (Po2) adopted in sintering, which generates oxygen vacancies in order to maintain the overall charge neutrality in the ceramic. In this research, donor-doping and Po2 used in sintering are investigated for the in-gap-level modification using the cathodoluminescence (CL) spectrometry equipped with a scanning electron microscope (SEM). Other analytical techniques, e.g. transmission electron microscopy (TEM) will be used for characterizing the defect structure. Preliminary results suggest that the in-gap levels are registered at 3.10 eV and 2.69 eV, representing the intrinsic Eg and a donor-level created by oxygen vacancies, respectively.

Lead zirconate titanate (PZT) thin films have been extensively investigated for many applications, such as MEMS devices (actuators, sensors, transducers, SAW devices) and memory devices (DRAM, NVFRAM). In this study, the sputtering deposition methods were used to fabricate the PZT thin films. Multilayer Si/SiO2/Ti/Pt was used as substrate, in which the thickness of SiO2, Ti and Pt layer was 250, 50 and 150nm. In order to improve the electric and piezoelectric properties of PZT thin films, the few nanometer thick layer of Ti on the platinum have been used for fabricating oriented PZT thin films. Then, the PZT thin films required the heat treatment for crystallization of perovskite structures. RTA and FA were taken for the heat treatment. The crystallographic and surface characteristics of PZT thin films were determined by XRD and Optical Microscope. Finally, PZT thin films deposited on two kinds of substrates were successfully transformed from amorphous phase to perovskite phase by two kinds of the annealing processes. The Ti seed layer yielded (111)-textured PZT even for thin seed layer. But, it also had less tolerances to anneal. Si/SiO2/Ti/Pt/PZT structures were the better way to fabricate the PZT thin films, which had the preferred orientations of (100¡^,(110¡^,and (200).

<p> Fo. determinative curves for lattice planes (301), (311), and (401) were calculated from four natural olivines. 2θ values for each olivine were computed from the lattice parameters using the reciprocal lattice d* for the orthorhombic crystal system d*hkl = [h^2/a^2 + k^2/b^2 + l^2/c^2]^1/2 combined with the Bragg equation λCuKα = 2 sin θhk / d*hkl </p> <p> XRD patterns for 10 natural olivines were used to determine their respective Fo. composition. Errors were calculated for the Fo. composition of the natural olivines yielding an accuracy from the determinative curves of± 6 wt. % Fo. An olivine of 90 wt. % Fo. was X-rayed and plotted along the determinative curves giving values of Fo. composition for (301), (311) and (401) of 89, 87 and 85 wt. % respectively.</p> <p> The effect of Ni, Mn and Ca substituting into the (Mg, Fe) olivine structure causing Δ2θ shifts was also considered and found to be negligible for natural (Mg, Fe) olivines.</p> / Thesis / Bachelor of Science (BSc)

Glass-ceramic composites and nanocrystalline glass-ceramics containing barium titanate (BT) or potassium sodium niobate (KNN) ferroelectric phases have been studied, with particular regard to their use as dielectric energy storage materials. Barium borosilicate glass (BBS) was used as a sintering aid for BT and KNN, producing glass-ceramic composites. The temperatures required to achieve densification were reduced from 1400 to 1200 °C for BCZT (Ca, Zr-doped BT) and 1170 to 1050 °C for KBN (Bi, Na, K, Zr-doped KNN) by the use of glass additives. An unexpected observation, found in both BCZT and KBN systems, was the heterogeneous dissolution of dopant elements into the glass, inducing additional anomalies in the relative permittivity-temperature relationships. For BCZT, the orthorhombic-tetragonal phase transformation temperature shifted upwards to ≈ 50 °C, which was attributed to modification of the Ca/Zr ratio by preferential dissolution of Ca into the glass phase. Similarly, for KBN the dopant elements appeared to be leached into the liquid phase during sintering, resulting in relative permittivity-temperature characteristics similar to those of pure KNN. A modified BBS glass having various KNN contents was prepared by the conventional melt-quenching method and then heat-treated to induce crystallisation, producing nanocrystalline glass-ceramics. It is shown that crystallisation of an intermediate barium niobate phase initiates at temperatures in the region of 650 °C; this is subsequently converted into perovskite KNN together with a second phase of Ba3Nb5O15 at temperatures from 700 to 800 °C. The final crystallite size was in the region of 30±7 nm. The highest dielectric energy storage density of 0.134(4) J cm-3 was obtained for a glass-modified BT ceramic at an electric field level of 5 kV mm-1. However, the energy storage efficiency of the BT-based ceramics was relatively poor and they displayed a general tendency for saturation, indicating potentially poor performance at higher field levels. On the other hand, the KNN-based ceramics exhibited slightly lower energy storage density values, up to 0.108(1) J cm-3, but with much improved linearity and energy storage efficiency. Therefore, the latter is considered to be more suitable as energy storage dielectrics. The BBS-KNN glass-ceramics yielded relatively low energy storage density, 0.035(2) J cm-3, but the dielectric linearity and storage efficiency were similar to or better than those of the KNN ceramics, indicating good potential for use as energy storage dielectrics at very high electric field levels as a result of their nanocrystalline microstructures.

This thesis investigates some of the physics of semiconducting low-dimensional structures at low temperatures, as well as investigating the effects of defects on low-dimensional structures and magnetic fields on charge recombination in organic photovoltaics (OPVs). The applications of the systems studied vary from photodetectors, to LEDs, lasers and solar cells. We synthesised Cs2CuCl4 and CsCuCl3 nanoparticles. By varying the ratio of coordination solvents in the synthesis we can control the composition and morphologies of the fabricated nanoparticles, including dots, rods and wires. These nanocrystals showed broadband green emission upon excitation with sub-300 nm radiation, which we showed was due to emission from an intra-band Cu(II) defect. We also fabricated a variety of alkylammonium lead iodide materials. We found that hexylammonium lead iodide and dodecylammonium lead iodide emit broadband red light at low temperatures due to a Frenkel defect (f-centre). Additionally, we see evidence of biexciton emission in dodecylammonium lead iodide films at high excitation densities below temperatures of 225 K. The films in this study were seen to adopt two coexistent phases of dodecylammonium lead iodide, both a monoclinic P121/a structure and an orthorhombic Pbca structure, at room temperature. These films were used as the gain medium in a biexciton vertical cavity laser. This device was constructed from a distributed Bragg reflector coated with dodecylammonium lead iodide, a poly(methylmethacrylate) spacer layer, and an evaporated silver mirror. The onset of lasing was seen at 5.6 × 1018 excitations/cm3 at 75 K. Finally, the modulation of open-circuit voltage and short-circuit current by applied magnetic field in OPV devices made from PIDTPhanQ and PC(71)BM was investigated. We saw that magnetic fields influenced the recombination of charge-transfer (CT) states, and simulations indicated that the formation of CT states had a significant contribution from the bimolecular recombination of free charges. The simulations also showed that singlet CT state lifetimes were much smaller than triplet CT state lifetimes.