Wuppertal, Univ., Diss., 2004. / Computerdatei im Fernzugriff.

Wuppertal, University, Diss., 2004.

Magistriniame darbe yra nagrinėjami švaraus opalo pralaidumo spektrai. Nustatyta, kad stop juostos padėtis priklauso nuo spindulio kritimo kampo į bandinį. Apskaičiuoti pagrindiniai parametrai: tarp-plokštuminis atstumas d, opalo sferų diametras D, bandinio lūžio rodiklis n ir opalo sferų lūžio rodiklis . Pagamintas opal-FeTTPS hibridinis darinys ir išnagrinėtas jo pralaidumas bei magnetinis cirkulinis dichroizmas. Nustatyta, kad FeTTPS stop juostos padėtis prie įvairių kampų šiek tiek skiriasi nuo švaraus opalo. Hibridinio darinio magnetinis cirkulinis dichroizmas kinta keičiant kritimo kampą ar stop juostos padėtį. / In this work transmission optics of opal photonic crystals and infiltrated with iron porphyrin was studied. Work analyses synthetic opal crystals grown by means of sedimentation from the spheres of SiO2. Samples were 0.9 mm thick, and their surfaces planes were parallel (111) to crystallographic planes. In these samples, the stop band due to Bragg reflection from the (111) plane was observed in the spectral region of 0.45-0.7 µm at angles of light incidence. Iron porphyries FeTTPS magnetic circular dichroism was also investigated. Synthetic opal crystals composed of silica spheres were infiltrated with (c=10 mM, pH=6.8) buffered phosphate solution of iron porphyrin. In optical studies the FeTPPS-impregnated opal samples were immersed in hexane solution to vary average refractive index of composite system and to control the mutual positions of the opal stop band and absorption bands of FeTPPS. FeTPPS magnetic circular dichroism spectra dependency on opal stop band position was noted. The experimental opal transmission spectra date were analyzed in which the optical response of the opal and infiltrated with iron porphyrin was calculated by using a Bragg’s law and it was found that spacing between adjacent [111] lattice planes d is 254.95 nm, opal crystal composed of silica spheres of diameter is 312 nm and average refractive index of composite system – 1.35.

Thesis (M.Sc.)--University of Adelaide, Dept. of Geology, 1984. / Typescript (photocopy).

Heidelberg, Universiẗat, Diss., 2002.

No description available.

Artificial opals are self-assembled face centered cubic (fcc) structures of  spherically shaped beads, which interesting applications as photonic band gap materials. Inverse opals are photonic crystals consisting of fcc paced voids of a low refractive index material imbedded in a high refractive index material. Such structures has been used to enhance the photocatalytic effect of different materials and motivates further studies to improve the deposition process of the opal templates and their inversion. We state the fabrication method to design and model metal oxide inverse opals. We have successfully created alumina and alumina-titania inverse opals. With the help of simulations, we engineered inverse opals with self-assembly and atomic layer deposition.

No description available.

Graduate

Opaline silica (opal-A) is thermodynamically unstable at surface conditions and readily transitions into opal-CT and at higher temperatures and pressures, quartz. Past work has used the temperature dependency of this phase transition for paleothermometry in opal-bearing sedimentary rocks. Those works determined that bulk concentrations of silica, organic material, and detrital minerals influenced the phase transition temperature. However, previous work only addressed the influence of these impurities on a macroscale and ignore potential microtextural interactions of silica and organic material. In this thesis, I present a set of experiments designed to characterize the effect of organic matter distribution on the opal-A to opal-CT transition in siliceous sedimentary rocks. Silica, humic acid, and mock seawater solution were loaded into Parr hydrothermal vessels as bulk sediments or in defined physical configurations (stratified or intermixed) and were heated at 200°C for up to 14 weeks. The solid products of these experiments were analyzed using X-Ray diffraction (XRD), Raman spectroscopy and Fourier-transform infrared (FTIR) spectroscopy. In organic-free experiments, the broad opal-A diffraction peak at 22° 2θ narrowed over the course of 14 weeks, suggesting increased internal ordering. FT-IR spectra showed changes in the position of the Si-O-Si stretching mode peak at 1060 cm-1 with silica diagenesis. Opal-CT may have been observed to occur sporadically in some stratified experiments and associated controls, but apparently did not occur in intermixed configurations. In stratified experiments, no correlation was observed between opal-A full-width half maximum and proximity to the humic acid layer. Similarly, no trend was observed between FT-IR peak positions and proximity to humic acid. These results suggest that the presence of organic matter does play a role in inhibiting the internal ordering of opal; however, the configuration might not be a primary factor in this transition. The results of this study may be applicable to the Monterey Formation and other hydrocarbon-bearing siliceous sedimentary formations. Our results suggest that the maturation of oil reservoirs in the Monterey Formation may be constrained solely on the silica phases present. / Geology