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Ermittlung der plutonium .Konzentrationsverteilung in Uran und Plutoniumdioxiden mit hilfe der roentgenographischen analyse / Determination of the distribution of plutonium concentration in uranium- and plutonium dioxide by X-ray analysisRIELLA, HUMBERTO G. 09 October 2014 (has links)
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12890.pdf: 2186659 bytes, checksum: 087fa0b384ece6d4147a0d60df0a8644 (MD5) / Tese (Doutoramento) / IPEN/T / Universitaet Karlsruhe - Fakultaet fuer Maschinenbau
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Ermittlung der plutonium .Konzentrationsverteilung in Uran und Plutoniumdioxiden mit hilfe der roentgenographischen analyse / Determination of the distribution of plutonium concentration in uranium- and plutonium dioxide by X-ray analysisRIELLA, HUMBERTO G. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:38:46Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:03:02Z (GMT). No. of bitstreams: 1
12890.pdf: 2186659 bytes, checksum: 087fa0b384ece6d4147a0d60df0a8644 (MD5) / Tese (Doutoramento) / IPEN/T / Universitaet Karlsruhe - Fakultaet fuer Maschinenbau
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Hot-wire chemical vapour deposition of carbon NanotubesCummings, Franscious Riccardo January 2006 (has links)
Magister Scientiae - MSc / In this study we report on the effect of the deposition parameters on the morphology and structural properties of CNTs, synthesized by means of the hot-wire chemical vapour deposition technique. SEM, Raman and XRD results show that the optimum deposition conditions for the HWCVD synthesis of aligned MWCNTs, with diameters between 50 and 150 nm and lengths in the micrometer range are: Furnace temperature of 500 ºC, deposition pressure between 150 and 200 Torr, methane/hydrogen dilution of 0.67 and a substrateto- filament distance of 10 cm. / South Africa
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Approaches to studying smectic layer elasticity and field induced deformationsSiemianowski, Simon Dominik January 2010 (has links)
The initial aim of the work presented in this thesis was to examine smectic layer compressibility with a view to improving our understanding of the stability of intermediate phases. A natural starting point was to investigate the smectic-A phase, as it is the most basic of the smectic phases. The response of the layered structure to external fields is also a focus of this thesis as electric and magnetic fields enable the layer properties to be probed. Investigations into the reorientation dynamics of smectic-A layers in magnetic fields were performed using geometries and cell thicknesses (>50 μm) that are not feasible using electric fields. Data presented in this thesis show that three distinct reorientation mechanisms can occur, one of which is previously unreported and bridges the gap between the previously known mechanisms. The new mechanism observed in 270 μm and 340 μm thickness cells exhibits multiple stage reorientation on a timescale between tens and hundreds of seconds. Using conventional electro-optic techniques combined with a theoretical approach developed by others, this thesis presents a new technique to provide measurement of relative smectic layer compressibility of eight smectic-A liquid crystalline materials. The method presented here combines data on cell thickness, dielectric anisotropy and the measurement of the voltage threshold of the toroidal to stripe domain transition. As expected, the experimental data indicated that materials with shorter molecular lengths had the largest relative layer compressibility. Finally, direct measurement of smectic layer compressibility was investigated and the design of an apparatus capable of such measurements was undertaken. Preliminary results from such an apparatus are presented along with a discussion on the steps taken to develop the design.
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Incorporating Electrochemistry and X-ray Diffraction Experiments Into an Undergraduate Instrumental Analysis CourseMolina, Cathy 05 1900 (has links)
Experiments were designed for an undergraduate instrumental analysis laboratory course, two in X-ray diffraction and two in electrochemistry. Those techniques were chosen due their underrepresentation in the Journal of Chemical Education. Paint samples (experiment 1) and pennies (experiment 2) were characterized using x-ray diffraction to teach students how to identify different metals and compounds in a sample. in the third experiment, copper from a penny was used to perform stripping analyses at different deposition times. As the deposition time increases, the current of the stripping peak also increases. the area under the stripping peak gives the number of coulombs passed, which allows students to calculate the mass of copper deposited on the electrode surface. the fourth experiment was on the effects of variable scan rates on a chemical system. This type of experiment gives valuable mechanistic information about the chemical system being studied.
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Defect Measurement In Metal Oxides After CorrosionJeanis, Ian Lander 03 September 2021 (has links)
No description available.
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THERMOELECTRIC STUDIES OF THE TIN TELLURIDESong, Shaochang January 2023 (has links)
The lead-free tin telluride (SnTe) is considered as a potential candidate to substitute lead
telluride (PbTe) for thermoelectric power generation based on their similar crystal and
electronic structures. However, the relatively high lattice thermal conductivity and low
Seebeck coefficient of pristine SnTe are detrimental for real-life applications. This
dissertation explored elements-doping/substituting of SnTe to overcome those
shortcomings and improve SnTe thermoelectric performance.
A series of the Sn1-xGexTe phases were synthesized and studied. When the Ge amount
reaches 50% or higher, Sn1-xGexTe undergoes a phase transition from the rock-salt structure
(Fm3̅m) to the rhombohedral one (R3m). The Sn0.5Ge0.5Te phase was explored in more
details because it delivers the best thermoelectric performance with the Sn1-xGexTe series.
The electron-richer Sb and Bi were substituted on the Sn/Ge site to optimize the charge
transport properties, and Cu2Te was added into the matrix to improve the thermoelectric
performance further.
The In/Sb and In/Bi co-doping on the Sn/Ge sites was employed for Seebeck coefficient
optimization. A comparative study of the electronic structure of the Sn0.5Ge0.5Te-based
samples was performed. The calculations indicated a band convergence and changes in the
valence band, thus providing insight into the co-doping effects.
Suppression of the lattice thermal conductivity of SnTe was performed via alloying with
AgSnSe2 and PbTe, which introduced strong atomic disorder. Additionally, AgSnSe2
showed a hole donor behavior in SnTe, and the increased carrier concentration compensated for the reduction in the carrier mobility, thus rendering a decent electrical
conductivity in alloyed samples. As a result, the alloying effectively improved the samples'
thermoelectric performance. / Thesis / Doctor of Philosophy (PhD) / In recent decades, renewable energy has attracted a lot of attention due to an increase in
the global energy use and depletion of fossil fuel reserves. Thermoelectric materials are
expected to play a vital role as green energy generators to overcome the upcoming energy
crisis as they can directly convert waste heat into electricity through the Seebeck effect.
In this dissertation, the main goal is optimizing the thermoelectric performance of SnTe for
the above room temperature applications. Different doping/ substituting/alloying strategies
were applied to improve the performance. The obtained thermoelectric properties of the
SnTe-based materials were rationalized in terms of the charge carrier behavior, changes in
the electronic structure, and phonon propagation.
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SYNTHESIS, STRUCTURE, AND LUMINESCENT PROPERTIES OF NEW GERMANATE PHASESNovikov, Sergei January 2022 (has links)
A series of new germanates was prepared and their structures were characterized with X-ray diffraction (XRD). We employed solid-state synthesis, flux growth, and crystallization from melts to obtain crystals of the new materials. The crystals were studied by means of single crystal XRD, providing the information on the structure and composition of the new materials. Germanates suitable to accommodate Mn4+ – a well-known activator ion for the preparation of the rare-earth-free red phosphors – were of a particular interest. The Ge4+ substitution for Mn4+ is possible if the crystal structure features octahedrally coordinated germanium atoms, and we indeed were able to prepare such germanates.
The crystal structures of the following phases were characterized: Mg3Ge1-O4(1-)F2(1+2) ( ≈ 0.1), Mg14Ge4O20F4, Mg2Pb2Ge2O7F2, Sr3GeO4Cl2, Ba3GeO4Br2, Sr6Ge2O7Cl6, Ba5GeO4Br6, Na2BaGe8O18, Rb2BaGe8O18, Na0.36Sr0.82Ge4O9, Na2SrGe6O14, and K2SrGe8O18. Two phases, Mg3Ge1-O4(1-)F2(1+2) and Na0.36Sr0.82Ge4O9 demonstrate deficiency on certain crystallographic sites. We analyzed the connectivity of the GeO4 and GeO6 units in the new and reported tetra- and octagermanates. Despite the similar stoichiometry, the connectivity of GeOn polyhedra is different in RI2Ge4O9, RIIGe4O9 and RIRIIGe8O18 germanates (RI = alkali, RII = alkaline earth metal).
The Ge4+ substitution for Mn4+ was successfully done for the Na2BaGe8O18, Rb2BaGe8O18, Na2SrGe6O14, and K2SrGe8O18 phases yielding new red phosphors. Based on the powder XRD data, the optimal synthetic strategies were developed yielding high purity (≈ 99 wt. %) samples. The photoluminescent excitation and emission spectra were collected for the new phosphors. Strong absorption of the UV light and emission in the far-red region of the visible spectra were confirmed, which is in a good agreement with the literature. The Mn4+ doping level was optimized to achieve the highest luminescence in the studied phases. Temperature-dependent luminescence spectra were collected for the Na2SrGe6O14 : Mn4+ and K2SrGe8O18: Mn4+, and the K2SrGe8O18: Mn4+ showed the highest resistance to temperature quenching. / Thesis / Doctor of Philosophy (PhD)
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Rapid Modal Analysis of an Amphibolite by Calibrated X-Ray Diffraction PatternsCorkery, M. Timothy 04 1900 (has links)
<p> A coarse grained amphibolite from the metamorphosed rim of the Whitestone Anorthosite was prepared in several ways for the purpose of determining the modal abundance of the constituent minerals by calibrated X-ray diffraction. A simple two component amphibolite consisting of plagioclase and amphibole was chosen and five major methods of mounting the specimens for X-ray diffraction were employed.</p> <p> It was hoped that a method could be found which would produce randomly oriented, homogeneous samples. A series of such samples each of a different component ratio would then provide a calibration curve from which the mode of a whole rock specimen could be estimated.</p> <p> The calibrated X-ray charts were produced on Philips scanning X-ray diffractometers.</p> <p> The inconsistencies in the results indicate that better technical procedures are required.</p> / Thesis / Bachelor of Science (BSc)
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X-Ray Crystal Structure Investigation of [Re(C5H5N)4 O2]Cl.2H20Krishnamachari, Narasimhan 05 1900 (has links)
<p> The crystal structure of dioxotetrapyridine-rhenium(V) chloride dihydrate has been determined by single crystal x-ray diffraction methods. The structure has been found to belong to the trans-dioxo- group of compounds. The Re=O bond in the structure has been shown to have a bond-order of about 2, with the average Re=O bond length of 1.76(J) A. The probable structures of the monohydrate and anhydrous dioxotetrapyridine-rhenium(V) chloride have been discussed on the basis of the observed pseudo-symmetric structure for the dihydrate with a non-centrosymmetric space group. The nature and strength of the hydrogen bonds in the structure have also been discussed.</p> / Thesis / Master of Science (MSc)
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