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1
Egan, John Mathew. "Solid state diffusion in Pd₂Si." Master's thesis, University of Cape Town, 1986. http://hdl.handle.net/11427/22141.
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The atomic transport processes ocurring in the Pd/Si system have been investigated. The Pd₂Si system has been studied to try and establish the mechanism(s) of diffusion by which the growth of Pd₂Si proceeds under thermal annealing. Using a deposited Ti marker, the dominant moving species during Pd₂Si formation in the temperature range 250-400°C has been determined to be silicon. Palladium transport appears to occur during the initial stages of formation of Pd₂Si. Once several hundred angstrom of Pd₂Si has been formed, palladium transport seems to be replaced by silicon transport. Silicon tracer experiments, in conjunction with Si selfdiffusion measurements. indicate that silicon mobility is exceptionally high during the formation of Pd₂Si on Si substrate. During growth. the mobility of silicon is orders of magnitude higher than under equilibrium conditions. This is thought to suggest a vacancy mechanism of diffusion, and is expected that large numbers of vacancies are generated at the growth interface during silicide formation. Silicon self-diffusion in Pd₂Si has been investigated. The results indicate that grain-boundary diffusion could be operative under equilibrium conditions. Under the assumption that grain-boundary diffusion does occur during thermal annealing in the range 350-550°C, it is deduced that at all times the grain-boundary diffusivity is so much greater than the lattice diffusivity, that the grain-boundaries are effectively able to act as sources for the grains. The activation energy for lattice self-diffusion of silicon in Pd₂Si which has grown on Si<100> substrate, has been determined to be 0.8±0.3eV. This value is thought to support recent kinetic results which indicate that the activation energy for growth of Pd₂Si is in the region of 1eV.
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Gustafsson, Christina. "Solid state characterisation and compaction behaviour of pharmaceutical materials." Doctoral thesis, Uppsala University, Department of Pharmacy, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-509.
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In this thesis, factors important in tableting operations and for tablet properties have been studied and characterised by different spectroscopic techniques as well as by some more conventionally used particle characterisation techniques. The spectroscopic techniques solid-state NMR, FT-IR and NIR spectroscopy, proved to be valuable tools in the estimation of particle and tablet properties, offering both specificity and sensitivity in the measurements. Because of the large amount of information obtained in a spectrum, multivariate data analysis was in some cases used in the processing of the spectral data. Correlations between the solid state structure measured by spectroscopy and the particle and tablet properties could be obtained including useful prediction models.
The surface area obtained using different principles has in this thesis been shown to reflect different properties and tableting behaviour of a collection of pharmaceutical materials. The particle shape and the external surface area of the powders measured by permeametry, were found to be important factors for the tensile strength of tablets made of hydroxypropyl methylcellulose. Furthermore, the external surface area could be used to access dominating interparticulate bonding mechanisms in compacts of different materials by normalising the tablet tensile strength for the tablet surface area. It was also shown that for materials prone to develop solid bridges, the actual surface area participating in the bonding was more important than the average interparticulate distance.
When studying the properties of microcrystalline cellulose and cellulose powder from the alga Cladophora sp., the cellulose fibril surface area estimated by solid-state NMR resulted in better correlations to the tableting behaviour and to tablet disintegration than the external permeametric surface area did. It was suggested that the difference in fibril surface area of the two celluloses was the primary factor responsible for properties like the crystallinity and the disintegration of the tablets.
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Hu, Jiahuan. "Strain-Induced Crystallization of Natural Rubber and Isoprene Rubber Studied by Solid-State NMR Spectroscopy." University of Akron / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=akron1397087771.
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Esser, M. J. Daniel. "Diode-end-pumped solid-state lasers." Thesis, Link to the online version, 2005. http://hdl.handle.net/10019/1020.
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Jackson, P. "Dipolar coupling in solid-state NMR." Thesis, Durham University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379058.
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Prakash, Arati Prakash. "Magneto Thermal Coupling in Solid State Transport." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1514502118670282.
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Brown, Marco J. "Selective inversion in solid-state deuteron NMR." W&M ScholarWorks, 1996. https://scholarworks.wm.edu/etd/1539623900.
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Deuteron NMR selective inversion (SI) is developed to study slow molecular motions in solids. Theoretical and practical aspects of selective inversion of spin-1 nuclei in solids are presented. Differences between powdered solids and liquids are considered. Double sideband modulated (DSBM) shaped pulses are shown to improve the performance of SI pulses. DSBM and DANTE selective pulses are compared for off-resonance SI applications. Common spin-{dollar}{lcub}1{rcub}\over{lcub}2{rcub}{dollar} shaped pulses are tested for suitability to solid state deuteron NMR. Simple, short pulses are shown to be most effective due to fast spin-spin relaxation and large underlying homogeneous linewidths in solids.;The power and utility of selective inversion is demonstrated by investigating the molecular dynamics of polycrystalline dimethylsulfone-{dollar}\rm d\sb6{dollar} (DMS). Quantitative information on the slow two-site jump motion in DMS is obtained. The complementary nature of selective inversion and quadrupolar echo lineshape (QELS) experiments is explored. Combination of QELS and SI extends the range of rates observed, increasing the accuracy of the information obtained. For DMS, motional rates were measured over a 80 K range (motional rates of {dollar}\rm 3\times 10\sp1{lcub}-{rcub}5\times 10\sp{lcub}4{rcub}\ s\sp{lcub}-1{rcub}),{dollar} permiting the barrier to slow rotation to be accurately characterized. SI was also used to observe the limiting homogeneous linewidth as a function of resonance offset and temperature. The temperature dependence of the homogeneous linewidth is shown to be sensitive to motion in the kilohertz range.;SI was used to quantify the molecular dynamics in some complex systems. SI and QELS experiments were performed on host urea-{dollar}d\sb4{dollar} in different urea inclusion compounds (UIC). Rotation rates about both the CO and CN bonds of urea-{dollar}d\sb4{dollar} in the UICs were determined as a function of temperature. Activation energies were obtained, and the results are discussed with respect to guest-host interactions in the UICs. Preliminary results are presented on quadrupolar echo lineshape simulations which include empirical, anisotropic homogeneous linewidth corrections. The modified simulations give significantly different best-fit motional rates than conventional QELS analysis. This allows some of the systematic errors of QELS analysis to be evaluated.;SI experiments were conducted, over a 125 K range, to study backbone motion in bisphenol-A polycarbonate. These experiments failed to detect the presence of any large angle slow motion of methyl groups in the isopropylidene moiety. This negative result suggests that cis-trans isomerization of the carbonate group is not the origin of the backbone motion.
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Vlassarev, Dimitar. "DNA Characterization with Solid-State Nanopores and Combined Carbon Nanotube across Solid-State Nanopore Sensors." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10310.
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A DNA molecule passing through a nanopore in a liner and sequential fashion allows for unprecedented interrogation of the polymer. Adding transverse electrodes that are comparable in size and sensitive to the DNA molecule, can further the attempts to rapidly sequence DNA. Carbon nanotubes are comparable in size and interact strongly with the DNA molecule. This makes them an excellent choice for integration with nanopores. Only the section of the carbon nanotube in immediate proximity to the nanopore should be sensitive to the DNA molecules. Atomic layer deposition of metal-oxides passivates the sections of the carbon nanotube that are not to interact with the DNA molecule. The coating also protects the thin film interconnects leading to the carbon nanotube. Hafnium oxide is superior to aluminum oxide in chemical resistance and electrical insulation but leads to a high failure rate of the carbon nanotube across nanopore devices. Aluminum oxide, combined with gold thin film interconnects to the carbon nanotube, produced the first functioning devices in electrolyte. These devices had concurrently functioning ionic (current across the nanopore) and transverse (current through the carbon nanotube) channels. No concurrent DNA translocation signal was recorded on the ionic and nanotube current traces. Analyzing the translocation events recorded on the ionic channel indicated that double-stranded DNA (dsDNA) passed through the carbon nanotube articulated nanopore an order of magnitude slower than it would have through a comparable unarticulated nanopore. The slower translocation observed is a necessary condition for sequencing. Investigating dsDNA translocation under various experimental conditions led to the discovery of a new interaction between the molecule and small nanopores. A dsDNA molecule is trapped when the electric field near the nanopore attracts and immobilizes a non-end segment of the molecule at the nanopore orifice without inducing folded translocation. In this work, the expression “trapped dsDNA” will exclusively refer to the immobilization of a dsDNA molecule at the orifice of the nanopore. The ionic current through the nanopore decreases when the dsDNA molecule is trapped by the nanopore. By contrast, a translocating dsDNA molecule under the same conditions causes an ionic current increase. Finite element modeling results predict this behavior for the conditions of the experiment.Physics
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Preda, Florentina Maria. "Dynamics of polyamide in the solid state in presence of solvents and in the molten state." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSE1001/document.
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Dynamique du polyamide dans l'état solide en présence de solvants: Les polyamides sont une famille de polymères thermoplastiques semi-cristallins largement utilisés dans l'industrie automobile grâce à leur excellente stabilité thermique et propriétés mécaniques. Cependant, ces propriétés peuvent être affectées par la sorption de l'eau présente dans l'atmosphère ou de l'éthanol présent dans les biocombustibles. Les cinétiques de sorption et la sorption à l'équilibre dépendent des mécanismes d'interaction entre le solvant et le polyamide et des mécanismes de sorption et de diffusion. La diffusion et la sorption de solvants dans les polyamides sont des phénomènes complexes à cause de l'existence d'interactions spécifiques (liaisons hydrogène), d'hétérogénéités dynamiques dans la phase amorphe, de changements dans la dynamique du polymère en présence de solvants et de l'existence d'une phase cristalline. Puisque l'accessibilité de la phase amorphe peut avoir une influence sur les mécanismes de diffusion et de sorption, la diffusion et la sorption de différents solvants (eau, alcools de tailles différentes) ont été comparés dans un polyamide 100% amorphe et son homologue semi-cristallin. Nous avons confirmé que la phase amorphe d'un polymère semi-cristallin n'est pas entièrement accessible à l'eau, ce qui est en accord avec la littérature. Une deuxième partie de cette étude a été consacrée à la relation entre la diffusion de solvants et la dynamique de la phase amorphe. Premièrement, nous avons mis en évidence que les mécanismes de diffusion Fickien et non-Fickien peuvent être expliqués par la variation des coefficients de diffusion avec la concentration de solvant. Deuxièmement, l'influence de la relaxation du polymère a été évaluée par Spectroscopie Diélectrique. Une simple comparaison des échelles de temps de la diffusion et de la relaxation alpha, associée à la transition vitreuse, indique que les deux phénomènes ne sont pas directement corrélés. Cependant, la diffusion semble corrélée à la relaxation secondaire beta, qui décrit la dynamique locale des groupements amide en présence d'eauDynamics in the solid state in presence of solvents: Polyamides are a family of semi crystalline thermoplastic polymers widely employed in the automotive industry due to its excellent thermal stability and mechanical properties. However, polyamide can be significantly affected by the absorption of low molecular weight penetrants like water. The rate of sorption and amount of absorbed solvent depend on the mechanisms of interaction between solvent and polyamide, along with sorption and diffusion mechanisms. Diffusion and sorption of solvents in polymers can be very complex because of the existence of specific interactions (non-polar or polar), dynamic heterogeneities in the amorphous phase, modification of the polymer dynamics induced by the solvents and different crystalline phases. In polyamide/solvent systems, all of these factors have to be taken into account. A first part of this study focused on the accessibility of the amorphous phase in semicrystalline polyamides. A comparison between a 100% amorphous polyamide and its semicrystalline counterpart of equivalent chemical structure suggests that the amorphous phase in semi-crystalline polyamide is not entirely accessible to the solvents. A second part of this study focused on the diffusion mechanisms of water and ethanol in polyamide. Fickian or non- Fickian diffusion mechanisms could be explained by the variation of the diffusion coefficients as a function of solvent concentration. Moreover, the relationship between water diffusion and the dynamics of the amorphous phase in polyamide was investigated. A simple comparison of dielectric characteristic relaxation times with the timescale of diffusion suggests that diffusion and polyamide alpha relaxation (associated to the glass transition) should not be directly correlated. However, diffusion is correlated to the secondary beta relaxation, which encompasses the local chain dynamics of hydrogen bonded amide groups in the presence of water. A mechanism of diffusion based on the trapping of water molecules between neighboring sorption sites (amide groups) is proposed in these strongly interacting polymers
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Johnson, D. R. "The microstructure of all-solid-state batteries." Thesis, University of Oxford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375262.
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Elder, Ian F. "Diode-pumped two micron solid-state lasers." Thesis, University of Strathclyde, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.284812.
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Calmes, Lonnie Kirkland. "Solid-state Raman image amplification." Diss., The University of Arizona, 1998. http://hdl.handle.net/10150/288920.
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Amplification of low-light-level optical images is important for extending the range of lidar systems that image and detect objects in the atmosphere and underwater. The use of range-gating to produce images of particular range bins is also important in minimizing the image degradation due to light that is scattered backward from aerosols, smoke, or water along the imaging path. For practical lidar systems that must be operated within sight of unprotected observers, eye safety is of the utmost importance. This dissertation describes a new type of eye-safe, range-gated lidar sensing element based on Solid-state Raman Image Amplification (SSRIA) in a solid-state optical crystal. SSRIA can amplify low-level images in the eye-safe infrared at 1.556 μm with gains up to 106 with the addition of only quantum-limited noise. The high gains from SSRIA can compensate for low quantum efficiency detectors and can reduce the need for detector cooling. The range-gate of SSRIA is controlled by the pulsewidth of the pump laser and can be as short as 30-100 cm, using pump pulses of 2-6.7 nsec FWHM. A rate equation theoretical model is derived to help in the design of short pulsed Raman lasers. A theoretical model for the quantum noise properties of SSRIA is presented. SSRIA results in higher SNR images throughout a broad range of incident light levels, in contrast to the increasing noise factor with reduced gain in image intensified CCD's. A theoretical framework for the optical resolution of SSRIA is presented and it is shown that SSRIA can produce higher resolution than ICCD's. SSRIA is also superior in rejecting unwanted sunlight background, further increasing image SNR. Lastly, SSRIA can be combined with optical pre-filtering to perform optical image processing functions such as high-pass filtering and automatic target detection/recognition. The application of this technology to underwater imaging, called Marine Raman Image Amplification (MARIA) is also discussed. MARIA operates at a wavelength of 563 nm, which passes most efficiently through coastal ocean waters. The imaging resolution of MARIA in the marine environment can be superior to images produced by laser line scan or standard range-gated imaging systems.
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Van, der Westhuizen Gysbert Johannes. "Numerical design of an optical solid-state amplifier." Thesis, Stellenbosch : Stellenbosch University, 2007. http://hdl.handle.net/10019.1/21915.
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Lynch, Jonathan William. "Laser (Cooling) Refrigeration in Erbium Based Solid State Materials." Diss., Temple University Libraries, 2015. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/358684.
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PhysicsPh.D.
The objective of this study was to investigate the potential of erbium based solid state materials for laser refrigeration in bulk material. A great deal of work in the field has been focused on the use of ytterbium based ZBLAN glass. Some experiments have also reported cooling in thulium based solid state materials but with considerably less success. We proposed that erbium had many attractive features compared to ytterbium and therefore should be tried for cooling. The low lying energy level structure of erbium provides energy levels that could bring obtainable temperatures two orders of magnitude lower. Erbium transitions of interest for cooling fall in the near IR region (0.87 microns and 1.5 microns). Lasers for one of these transitions, in the 1.5 micron region, are well developed for communication and are in the eye-safe and water and atmosphere transparent region. Theoretical calculations are also presented so as to identify energy levels of the eleven 4f electrons in Er3+ in Cs2NaYCl6:Er3+ and the transitions between them. The strengths of the optical transitions between them have been calculated. Knowledge of such energy levels and the strength of the laser induced transitions between them is crucial for understanding the refrigeration mechanisms and different energy transfer pathways following the laser irradiation. The crystal host for erbium was a hexa-chloro-elpasolite crystal, Cs2NaYCl6:Er3+ with an 80% (stoichiometric) concentration of erbium. The best cooling results were obtained using the 0.87 micron transition. We have demonstrated bulk cooling in this crystal with a temperature difference of ~6.2 K below the surrounding temperature. The temperatures of the crystal and its immediate surrounding environment were measured using differential thermometry. Refrigeration experiments using the 1.5 micron transition were performed and the results are presented. The demonstrated temperature difference was orders of magnitude smaller. Only a temperature of ~0.015 K below the temperature of the surrounding environment was observed in this case. These results are in agreement with another group’s that has observed cooling, though a slightly poorer temperature difference, using this transition of erbium (Condon et. al., 2009). Cooling was also attempted in the 0.87 micron transition of another crystal host, KPb2Cl5:Er, which has a concentration of about one percent of erbium. We did not observe any cooling in this crystal. However, the first cooling reports in erbium based systems were with this crystal where another group observed cooling by 0.7 K using the same transition (Fernández, García-Adeva, & Balda, 2006).
Temple University--Theses
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Orr, Simon Timothy. "Multinuclear solid-state NMR of fuel cell materials." Thesis, University of Warwick, 2010. http://wrap.warwick.ac.uk/35532/.
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This thesis describes the application of multinuclear solid-state NMR to three materials systems: first, components of polymer-based proton-exchange fuel cells including the fluoropolymer membranes (Chapter 4) and the precious metal supported catalysts (Chapter 5); secondly, the formation of a complex bismuth niobium aluminoborosilicate glass-ceramic with novel dielectric properties (Chapter 6); finally, platinum (II) dialkyldithiophosphates which belong to a class of compounds (metal dialkyldithiophosphates) some of which are used in mineral separation processing (Chapter 7). A full investigation into the effects of different conditions during sample preparation and 19F NMR experiments on fluoropolymer membranes recommended unmilled preparation, dry storage and magic angle spinning below 24 kHz for the study of structural differences between membranes. The application of 19F NMR to a range of commercial and experimental fluoropolymer membranes revealed that the equivalent weight does not affect the mobility of the polymer molecules such that can be detected by this technique. Calculations of equivalent weight from 19F NMR differed with quoted values by up to 14%. Discrepancies were smallest in the short sidechain polymers, as low as 3%. The assignment of spectra was invariant with sidechain structure apart from a change in the number of ester links. The presence or absence of oxygen affected chemical shielding even around nuclei separated by several bonds. Differences in 1H linewidths between membranes could not be interpreted without the control and comparison of manufacturing techniques. It is desirable to remove the necessity for organic solvents in membrane casting. However, membranes cast from aqueous solution do not possess the same properties as those from propanol. It had been proposed that rapid drying of water cast membranes would result in a structure more similar to those from organic solvent. 1H NMR revealed that the opposite is the case, rapid drying makes the ordinarily more inhomogeneous aqueous membranes even more so. The application of both 19F and 1H NMR revealed that the monomolecular layers of fluoropolymer deposited on the surface of fuel cell catalysts to aid proton conductivity are categorically different in nature to the same materials in the bulk state. 19F NMR suggests a polymer structure either more disordered, greatly less mobile or both. 1H NMR displayed water environments that could not be reconciled to the standard model of rapid exchange between bulk water and water associated with acid groups. Spectral differences caused by solvent and polymer loading were discussed. The first complete and quantitative Fourier transformed 195Pt NMR spectra of platinum fuel cell catalysts, acquired using a field sweeping method, are analysed for deviation from the cubooctohedral particle model and surface oxidation. A combination of 11B, 27Al and 29Si studies of the BN1 ceramic system after different temperature heat treatments confirmed much of the previous work on phase evolution. However, it was shown that kyanite does not make up a significant proportion of the material until heat treatment reaches 1000 ºC and that aluminium impurities in bismuthbiobate crystals appear to increase with treatment temperature. The nature and abundance of glassy phases in the system are explored for the first time. Field sweep 195Pt NMR was employed to characterise the 195Pt chemical shift anisotropy of five platinum (II) dialkyldithiophosphates complexes. Additionally the 31P chemical shift anisotropies of two of the complexes, previously unpublished are presented.
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Bhattacharya, Prodipta. "Solid state NMR studies of ferroelectric relaxor materials." Thesis, University of Warwick, 2005. http://wrap.warwick.ac.uk/66666/.
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Multi-nuclear solid state nuclear magnetic resonance has been used to investigate the local atomic structure of the relaxor ferroelectric materials, lead magnesium niobate titanate (PMN-PT) and sodium potassium bismuth titanate (NKBT). In addition to these two series of materials, numerous precursor and model niobate compounds have also been analysed in order to gain a insight into the structures and phases present in these materials. The PMN-PT series was investigated using 93Nb, 207Pb and 170 NMR techniques. A total of 14 PMN-PT samples, from pure PMN to PMN-90PT, were investigated in order to fully understand the transitions taking place over the entire compositional range. 9~b proved to be the most informative nucleus, owing to its high sensitivity to the changes occurring at the B-site of the perovskite structure. We discovered three distinct niobium environments. We then proposed a new randomsite random-layer model explaining the distribution of the cations among two different layers ß' and ß". The high level of correlation between the theoretical predictions and the experimental results suggests that there are actually two different ways that PMN-PT behaves, one for titanium concentrations less than 25% and the other for concentrations over 25%. This was also clearly visible in our PMN-PT spectra, as a sharp line present in titanium concentrations below 25%, that disappears in the concentrations above 25%. We have also tied in our results with the existing literature on PMN-PT to identify possible links to the dielectric response and phase transitions in the material. NKBT was investigated using both 23Na and 39K MAS NMR techniques. The 23Na data proved most informative and results were obtained at different fields and different spinning speeds. We were then able to extract calculated isotropic chemical shift values and quadrupolar parameters to understand the subtle changes taking place. The preliminary results hint that there are some interesting changes taking place around the morphotropic phase boundary in the material.
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Vlachou, Maria C. "17O solid state NMR study of ceria systems." Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/108288/.
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Ceria is a highly commercial, valuable material. Its diverse set of real-world applications demonstrates its far-reaching influence on modern society. Indeed, one only has to consider its extensive employment as an essential component of automotive, three-way catalysis (TWC) for reducing pollutants in vehicular exhaust gases; a technology that is used on a daily basis by millions of people, to appreciate its importance. Its popularity is partially due to its extraordinary oxygen storage capacity, i.e. its ability to release and store oxygen through redox reactions mediated by the two oxidation states of cerium (Ce3+/Ce4+). This unique ability can be heavily influenced by ceria’s particle size and shape, dopant concentration and surface chemistry, and is still a very active area of research today. Whilst there have been over 26,000 scientific publications on ceria since the 1950s, and although the bulk-ceria oxygen chemical shift (877 ppm) was first observed with 17O solid-state NMR in 1989, it is only within the past decade that solid-state NMR has been employed as a probe for ceria’s structure-function relationships. This study presents an extensive 17O solid-state NMR investigation into various ceria systems, in conjunction with complementary Raman spectroscopy (for which the literature is abundant). An alternative spectral assignment for the 17O NMR spectrum of nanoceria based on experimental deductions and DFT quantum mechanical calculations is proposed. The current working assignment for nanoceria is based on the work of Wang et al., where DFT calculations of a core-shell model are used to deconvolute the NMR data. In contrast to this model, it is suggested that the most upfield peak at δCG = 822 ppm (that is actually part of a multicomponent region centred at ~830 ppm), corresponds to oxygen species displaced from their standard sublattice positions, to occupy a Frenkel type defect site. The resonance regions observed at ~830 and 920 ppm are proposed to be bulk oxygen environments feeling the effects of the Frenkel defect and concomitant oxygen vacancy. For reduced ceria systems, a broad component is detected that spans > 1000 ppm, and is assigned to oxygen directly bonded to Ce3+, in agreement with the current working model. Finally, it is observed that the most deshielded peak at ~1030 ppm is multi-component and (one of these components) possesses an extensive spinning sideband manifold in comparison to the other 17O resonances. Variable temperature investigations show a small inverse temperature dependence of the peak positions, suggesting weak pseudocontact paramagnetic shifts are influencing the spectrum. In light of this, the peak at ~1030 ppm is assigned to oxygen in closer proximity to (but not directly bonded) to Ce3+, as is reported by current 27Al solid-state NMR studies of Ce3+ doped systems and as is reflected by the extensive sideband manifold. The novel 17O preparation treatments implemented in this work were engineered to probe oxygen environments near defects. Ceria’s defects are manipulated by exposure to certain temperature/atmospheric conditions, and when these replicate those of possible catalyst operating temperatures with 17O enriched gas, 17O is able to probe the distribution of oxygen in distinct sites that are important to the OSC process. A prereduction of ceria was therefore implemented, following 17O2 reoxidation to target these sites. This process was also able to identify a surface reorganization mechanism in which a low reoxidation temperature/ pressure of 17O2 is insufficient to reverse the onset of bulk oxygen diffusion induced by the reduction, an effect which is seen to be enhanced with the loading of Pd. Furthermore, the storage of these treated systems dictates the evolution of the 17O species, with an almost closed-system (to air) detecting the pathway of reoxidised oxygen species to more stable sites over time. Ceria zirconia systems are also investigated in this work. The 17O solid-state NMR spectra show an even greater sensitivity to the 17O2 enrichment conditions. The pre-reduction of the systems induces a greater oxygen removal compared to pure ceria, and thus an increase in Ce3+ paramagnetic centres, i.e. the broad component (> 1000 ppm) characterising the oxygen-Ce3+ bond reveals a greater relative intensity. The complication of increasing Ce3+ paramagnetic centres near the 17O adsorption sites is evidenced by the significant loss in 17O spectral resolution. These effects are exacerbated when ceria zirconia is supported with Pd, known to (stably) reduce the state of the system even further. A straight exchange of the 17O isotope in ceria zirconia helps to inhibit these effects, allowing observation of (1) the chemical shift of the bulk-ceria oxygen move to a more shielded position compared to the pure ceria material at 877 ppm (caused by the inherent contraction of the ceria zirconia lattice), and (2) a broad resonance at ~730 ppm, attributed to oxygen species bridging cerium and zirconium.
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Kuan, Aaron. "Ultra-Thin Solid-State Nanopores: Fabrication and Applications." Thesis, Harvard University, 2016. http://nrs.harvard.edu/urn-3:HUL.InstRepos:33493498.
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Solid-state nanopores are a nanofluidic platform with unique advantages for single-molecule analysis and filtration applications. However, significant improvements in device performance and scalable fabrication methods are needed to make nanopore devices competitive with existing technologies. This dissertation investigates the potential advantages of ultra-thin nanopores in which the thickness of the membrane is significantly smaller than the nanopore diameter. Novel, scalable fabrication methods were first developed and then utilized to examine device performance for water filtration and single molecule sensing applications.
Fabrication of nanometer-thin pores in silicon nitride membranes was achieved using a feedback-controlled ion beam method in which ion sputtering is arrested upon detection of the first few ions that drill through the membrane. Performing fabrication at liquid nitrogen temperatures prevents surface atom rearrangements that have previously complicated similar processes. A novel cross-sectional imaging method was also developed to allow careful examination of the full nanopore geometry.
Atomically-thin graphene nanopores were fabricated via an electrical pulse method in which sub-microsecond electrical pulses applied across a graphene membrane in electrolyte solution are used to create a defect in the membrane and controllably enlarge it into a nanopore. This method dramatically increases the accuracy and reliability of graphene nanopore production, allowing consistent production of single nanopores down to subnanometer sizes.
In filtration applications in which nanopores are used to selectively restrict the passage of dissolved contaminants, ultra-thin nanopores minimize the flow resistance, increasing throughput and energy-efficiency. The ability of graphene nanopores to separate different ions was characterized via ionic conductance and reversal potential measurements. Graphene nanopores were observed to conduct cations preferentially over anions with selectivity ratios of 100 or higher for pores as large as 20 nm in diameter, suggesting that porous graphene membranes can be used to create highly effective cation exchange membranes for electrodialysis filtration. These surprisingly high selectivities cannot be explained by current models of ionic conduction in graphene nanopores, motivating the development of a new model in which elevated concentrations of mobile cations near the graphene surface generate additional ion selectivity.Engineering and Applied Sciences - Applied Physics
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Maker, Gareth Thomas. "Diode laser pumped solid state lasers." Thesis, University of Southampton, 1990. https://eprints.soton.ac.uk/397281/.
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This thesis deals with the development of diode laser pumped solid state lasers. The earliest work presented enabled 125W peak power, single frequency Q-switched pulses to be obtained from a 100mW diode laser pumped Nd:YAG laser. Using a 500mW diode laser as a pump source for C.W. Nd:YAG and Nd:YLF oscillators an Yb:Er fibre laser was pumped, producing 0.75mW C.W. power at a wavelength of 1.56µm. Acousto-optic mode-locking techniques were used to provide C.W. mode-locked pulse durations in Nd:YAG and Nd:YLF of 55ps and 18ps respectively, at repetition rates of 240MHz. Frequency modulation mode-locking was shown to be a superior technique, giving pulse durations of 11.5ps and 10ps in diode laser pumped Nd:YAG and Nd:YLF oscillators respectively. FM operation of diode laser pumped Nd:YAG lasers was investigated, yielding a maximum FM bandwidth of 70GHz. Spatial hole burning was considered to be an important factor in this result. Using a 1W diode laser to pump a mode-locked and Q-switched Nd:YLF oscillator peak power levels of 70kW were obtained at a wavelength of 1.047µm. Frequency doubling this output in MgO:LiNbO3 with an energy conversion efficiency of 47% enabled other tunable lasers to be pumped using the second harmonic. Firstly, a synchronously pumped rhodamine 6G dye laser is described which is capable of producing 3.2ps mode-locked pulses in a Q-switched envelope with peak powers of around 10kW. Secondly, a synchronously pumped doubly resonant optical parametric oscillator tunable between 983nm and 1119nm is described. Lastly, a Ti:Sapphire laser producing 400ns pulses with peak powers of 3W at a wavelength of 755nm is demonstrated. This oscillator could be wavelength tuned between 746nm and 838nm. A highly efficient method of frequency doubling C.W. mode-locked lasers was developed. Using an external resonant cavity a frequency doubling energy conversion efficiency of 61% to 532nm was achieved, giving 87mW average power in 8.5ps pulses.
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Haydock, Sarah Amanda. "In situ vibrational spectroscopy of thin organic films confined at the solid-solid interface." Thesis, University of Oxford, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.270369.
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Drummond-Brydson, Richard. "Electron energy loss spectroscopy in solid-state chemistry." Thesis, University of Cambridge, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.237906.
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Cheng, Chi-Feng. "Solid-state NMR studies of mesoporous molecular sieves." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243004.
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Canessa, E. "Statistical physics of colloidal dispersions." Thesis, University of East Anglia, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314412.
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Bates, Matthew. "Theoretical investigation of solid state cooling using spin models." Thesis, University of Warwick, 2015. http://wrap.warwick.ac.uk/79564/.
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A mean field spin model coupled to a thermal model of a solid is used as a description of the electrocaloric effect in relaxor ferroelectrics at both first and second order transitions. This theoretical model is also used in efforts to find the tricritical point of transitions to maximise the adiabatic temperature change due to the electrocaloric effect while minimising the hysteresis losses in a cooling cycle. The electrocaloric effect is the adiabatic temperature change exhibited by a material under the sequential application then removal of electric fields. Relaxor ferroelectrics are materials with two interaction scales, local interactions in polarised nano regions (PNRs) and longer range interactions between PNRs. Electric dipoles are modelled as spins and their alignment due to an external field is used to examine polarisationelectric field loops. The results are compared to experimental data to determine values of parameters that may be used in simulations to model the electrocaloric effect. I reproduced simulations of the electrocaloric effect in the ferroelectric material lead zinc niobate-lead titanate [Pb(Zn1=3Nb2=3)O3-PbTiO3] by coupling the dipolar entropy of the spins to the entropy of a thermal lattice one can examine the temperature increase that must occur as the dipolar entropy decreases in an external field. The results of this simulation agree with experiment. Novel work is carried out in a prediction of the strength of the electrocaloric effect in polyvinylidene fluoride trifloroethylene, P(VDF-TrFE), using a simulation where the material parameters are determined from the comparison of simulated polarisation-electric field hysteresis loops with experimental results. The simulations suggest that P(VDF-TrFE) is a material worth investigating experimentally because even though it has a weak electrocaloric strength, under large fields the potential adiabatic temperature change at room temperature has promise for replacing conventional refrigerants. Due to the simplicity of this coupled model and the physical similarities between the electrocaloric effect and the magnetocaloric effect (an analogous effect observed in certain magnetic materials where an adiabatic temperature change is seen under the application and removal of a magnetic field) an investigation is also carried out on the magnetocaloric material iron rhodium (FeRh). In simulations I varied global and local stoichiometry to affect the ordering of spins and thus the entropy and strength of the magnetocaloric effect. I compared the results of our simulations with experiment and examine the variation in peak isothermal entropy change and adiabatic temperature change under variation in stoichiometry as well as the effects on the full width at half maximum. The results show that a simple model can give a qualitative representation of the effect. Work of a different nature is presented at the end of the thesis due to it being a short and complete topic which interested me during my PhD. Details are given on how Catalan numbers may be used to determine the depth of leaves in binary tree graphs and path length between them using both diagrammatic notation and the methodology of generating functions. An analytic solution is drawn from a combinatoric problem that initially appeared to only be soluble by brute force numerics.
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Blackband, S. J. "NMR imaging of liquid-solid systems." Thesis, University of Nottingham, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356019.
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Fleming, F. A. "Proton conduction in solid germanium phosphates." Thesis, University of Leeds, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356446.
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Bollig, Christoph. "Single-frequency diode-pumped solid-state lasers." Thesis, University of Southampton, 1997. https://eprints.soton.ac.uk/378587/.
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The work discussed in this thesis covers two broad areas: Novel techniques for the single-frequency operation of miniature, diode-pumped solid-state lasers and the high-power (i.e. multi-watt) operation of diode-bar end-pumped lasers in the eyesafe 2 μm wavelength region. A monolithic Nd-doped phosphate glass laser is described, in which uni-directional, hence single-frequency operation is enforced by the acousto-optic effect in the laser medium. The loss difference for the two counter-propagating waves relies on an acousto-optic self-feedback mechanism which can yield high loss differences even for very small diffraction efficiencies. Reliable single-frequency output is maintained indefinitely with an applied radio-frequency power of 0.2 W. Single-frequency output powers up to 30 mW for 400 mW of pump power are demonstrated. A technique is developed which facilitates reliable single-frequency operation of actively Q-switched lasers at repetition rates beyond the inverse lifetime of the upper laser level. Stable single-frequency operation of a Q-switched laser requires the initial establishment of a stable prelase which is free from spiking. Relying on the natural decay of spiking limits repetition rates and hence average power. Using feedback suppression of spiking, a Q-switched Nd:YAG laser is demonstrated which operates on a single frequency at repetition rates up to 25 kHz, with 88% of available cw power extracted. In the second part of this thesis, the high-power operation of diode-bar end-pumped solid-state lasers operating in the eyesafe 2 μm wavelength region is discussed. Efficient operation of a Tm:YAG laser end-pumped by a beam-shaped 20W diode bar is demonstrated. At a mount temperature of 20°C an output beam of 4.1 W with M2 values of 1.2 and 1.4 in the orthogonal planes is obtained for 13.5 W of diode power incident on the rod. This laser is then used to intracavity-pump a Ho:YAG laser, which avoids the upconversion problems usually associated with Tm3+-Ho3+-codoped lasers. At a mount temperature of 10°C for both the Tm:YAG and the Ho:YAG rods, an output power of the Ho:YAG of up to 2.1 W at 2097 nm is obtained for 9.2 W of diode power incident on the Tm:YAG rod.
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Goddard, Yanina Anatolievna. "Solid state NMR characterization of conductive polyanilines." W&M ScholarWorks, 2004. https://scholarworks.wm.edu/etd/1539623435.
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Different forms of ring deuterated polyaniline with different conductivity have been characterized by solid state deuteron nuclear magnetic resonance.;Quadrupole echo (QE) spectra of all forms of polyaniline consist of a superposition of lineshapes for nearly rigid aromatic rings and a small fraction of rings which undergo fast 180?? flips. The intensity of the fast flipping component is temperature dependent and different for conductive emeraldine salt (ES) and non-conductive emeraldine base (EB). This is a manifestation of the different structure and morphology of these polymers.;Simultaneous measurements of QE lineshapes and the relaxation time anisotropies allowed an accurate description of motion in polyanilines. Slow, small-angle libration in an asymmetric cone provided the best description for the "rigid" fractions of EB and ES. The broadening of deuteron QE lineshapes is consistent with the presence of a distribution of cone angles. Relaxation time measurements also reveal a relatively narrow distribution of librational rates for the EB sample. For ES, the magic angle spinning (MAS) spectra show the existence of two resolved signals with different relaxation rates, which are ascribed to microscopic domains with very different electrical properties. The unexpectedly short relaxation time found for nonconductive domains in ES can be explained by the presence of localized, unpaired electrons.;Spin count experiments proved that in highly conductive ES samples, loss of NMR signal intensity occurs not only because of high RF reflectance but also because of irreversible dephasing before signal acquisition due to interactions of nuclear spins with localized unpaired electrons.;Deuteron MAS spectra provided unique information about small frequency shifts. Compared to non-conductive EB, conductive emeraldine salts have an additional manifold of spinning sidebands, which is shifted ∼5.8 ppm towards higher frequencies. These shifted sidebands arise from quasi-metallic regions of the sample, where deuteron spins interact with delocalized electrons (Knight shift). The experimental temperature dependence of the intensity of the shifted peak can be explained using models developed for amorphous semiconductors. The observation of a Knight shift has an important consequence for the theory of electrical conduction in polyaniline: it implies that polarons are the charge carriers.
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Dauphinais, Guillaume. "Fabrication, structural relaxation, and flow in solid-state nanopores." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=107651.
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Single solid-stat nanopores have been fabricated in free-standing layers of amorphous silicon nitride. Using a focused electron beam and a focused ion beam, diameters ranging from about 0.7 nm to a few hundred nanometerswere achieved. Structural relaxation of nanopores fabricated by focused electron beam was observed. Depending on the initial diameter and on the length of the nanopores, two distinct phases for the relaxation process were found. An experimental setup for themeasurement of pressure-driven mass flow of helium through a single nanopore was built. The conductance of nanopores with diameters ranging from 25 nm to 315 nm was measured. A semi-phenomenological model was developed and it was shown to quantitatively describe the conductance of fluid through a short cylindrical nanopore.Des nanopores ont été fabriqués dans de minces couches suspendues de nitrure de silicium amorphe. En utilisant un faisceau d'électrons focalisé et un faisceau d'ions focalisé, des diamètres entre 0.7 nm et 315 nm ont été obtenus. La relaxation struturelle de nanopores fabriqués par faisceau focalisé d'électrons a été observée. Dépendamment du diamètre inital du nanopore et de sa longueur, deux phases distinctes ont été identifiées. Un montage expérimental permettant la mesure de l'écoulement de masse d'hélium causé par l'application d'une différence de pression a été réalisé. La mesure de conductance de nanopores ayant un diamètre compris entre 25 nm et 315 nm a été effectuée. Un simple modèle phénoménologique permet de décrire quantitativement l'écoulement de gaz dans un court nanopore cylindrique.
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Reams, Patrick William. "Solid-state N.M.R. studies of platinum and tin compounds." Thesis, Durham University, 1986. http://etheses.dur.ac.uk/6793/.
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High-resolution solid-state N.M.R. studies of dilute spins are now possible using cross-polarisation and MAS techniques. A systematic evaluation has been undertaken to determine their applicability to spin-½ metal nuclei, in particular (^195)Pt and (^119)Sn. In addition, an extensive (^13)C and (^31)p solid-state N.M.R. study has been carried out on a selection of Pt(II) complexes, supplying information on isotropic (scalar) coupling constants and shielding anisotropy. The majority of (^119)Sn and (^195)Pt spectra exhibit a multitude of spinning sidebands due to the large shielding anisotropy present. The tin systems under study have been of type R(_3)SnX (where R = Alkyl, phenyl and X = F, OH, CI); some are shown to be polymeric in the solid-state with penta-coordinate tin present. Where possible, correlations with X-ray crystallographic data and solution-state N.M.R. studies are giving. The interactions present in Pt(IV) compounds containing directly bonded quadrupolar nuclei have been studied and imply motional activity present in the solid- state. A more comprehensive study of these effects is given for two tin systems (Ph(_3)SnCl and (NH(_4))(_2)SnCl(_6)), whereby observed splittings can be accounted for by a combination of (^119)Sn-Cl dipolar and scalar coupling. The interplay of tensor properties between spin-½ nuclei, namely (1) dipolar coupling, (11) indirect (scalar) coupling and (111) shielding anisotropy is explored in solid-state (^195)pt-(^31)p and (^119)sn-(^19)f systems. The theory for such tensorial interplay is given for an AX(_2) system.
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Westwood, Stephen Mark. "The physics of magnetic particle inspection." Thesis, Durham University, 1993. http://etheses.dur.ac.uk/5525/.
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This thesis describes the results of an investigation into the Physics of Magnetic Particle Inspection. This is a non destructive technique used to detect the presence of surface breaking cracks in ferrous metals. On applying a magnetic ink to the surface of the part being magnetised, particles will be attracted towards any regions of flux discontinuity. This allows the defect to be visible to the eye. The main areas of study were the magnetic properties of the inks used, a computer simulation of the indication process and work of a more practical nature concerning MPI. From the magnetic measurements it was found that field induced agglomeration of the particles imparts the ink with a coercivity and remanence which varies with concentration. Low field time decay measurements show the existence of two reversal mechanisms within the magnetic ink, i.e. Brownian and Neel. The effect interparticle interactions have on a single aggregate has been studied by the use of remanence curves and this was found to lower the aggregates' magnetisation. This therefore lowers the magnetic force on a particle during the inspection process. The spin reversal mechanism has also been determined. The computer simulation of the indication mechanism originally written by McCoy has been improved to accommodate time varying waveforms. Results from this investigation indicate that the rms of the waveform is the important parameter when specifying field values for magnetisation levels for low remanence steels. This is contrary to the British Standard BS 6072 but in agreement with the draft European Standard. It was also found that increasing the paint layer thickness decreased the number of particles at a crack. This variation was found to be similar to the variation of the magnetic leakage field from the crack with increasing paint thickness. From a study of the effects of viscosity and radii on the number of particles arriving at a crack, we find that for particles whose radius is greater than 10 microns no change is observed as the viscosity is altered. Thyristor controlled power supplies are increasingly being used to magnetise inspection pieces and for this reason the relationship between the mean and rms of the waveform has been determined. It was found that the relationship between the two is non linear. This has implications if the user wishes to remain within BS 6072. Experimental verification of the simulation results is also presented. An offshoot of this is a possible method of determining the crack width using MPI, this is also presented. Finally it was noted that upon increasing the applied magnetic field, particles present at the crack rotated through 180 degrees. This also occurred upon decreasing the magnetic field. Investigation of this unusual effect are reported as well as a possible mechanism for it.
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Brierley, Richard Thomas. "Far-from-equilibrium many-body physics in solid state systems." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610799.
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Gullans, Michael John. "Controlling Atomic, Solid-State and Hybrid Systems for Quantum Information Processing." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:11146.
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Quantum information science involves the use of precise control over quantum systems to explore new technologies. However, as quantum systems are scaled up they require an ever deeper understanding of many-body physics to achieve the required degree of control. Current experiments are entering a regime which requires active control of a mesoscopic number of coupled quantum systems or quantum bits (qubits). This thesis describes several approaches to this goal and shows how mesoscopic quantum systems can be controlled and utilized for quantum information tasks.Physics
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Marasli, Necmettin. "The measurement of solid-liquid surface energy." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260154.
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Codd, Sarah. "3DFT NMR imaging of solid-like materials." Thesis, University of Kent, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318105.
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Young, Kevin Edward. "Ionic conductivity in silicate - containing solid electrolytes." Thesis, University of Exeter, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335654.
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Akeroyd, Frederick Anthony. "The sticking of molecules to solid surfaces." Thesis, University of Cambridge, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309088.
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Smith, Thomas Benjamin. "Entanglement and measurement of solid-state qubits." Thesis, The University of Sydney, 2020. https://hdl.handle.net/2123/24894.
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A full-scale quantum computer requires physical qubits that can be controlled with high precision and accuracy. Unfortunately, few state-of-the-art qubits can perform all their elementary operations (preparation, measurement, single-qubit gates and two-qubit gates) with sufficient fidelity. In this thesis, we investigate alternative schemes for such operations in solid-state qubits. Specifically, two-qubit gates and measurements, which are often the noisiest of the four.
We first provide a preliminary introduction to quantum computing, and describe how quantum information can be encoded and manipulated in quantum systems. We include background information for the three different solid-state qubit architectures that feature in this thesis: spin qubits, superconducting qubits and Majorana qubits.
Following this, we investigate a scheme for mediating a two-qubit interaction between spin qubits via a multielectron quantum dot. We study a multielectron dot in detail, and characterise its exchange interaction with a single spin. With the aid of a theoretical model, we show that the multielectron dot possesses an irregular triplet-preferring ground state, analogous to Hund's rule from atomic physics. Using these findings, we then demonstrate that the multielectron dot can be used to mediate a fast, long-range exchange interaction between two spin qubits.
Subsequently, we examine two resonator-based measurement schemes for Majorana qubits. We first propose a readout technique based on a longitudinal qubit-resonator interaction. This leads to a measurement that is fast, high-fidelity and quantum non-demolition (QND). We then investigate a more conventional dispersive readout scheme. Not only does this yield a high quality measurement, but it can also offers a more protected readout mechanism in comparison to the dispersive readout of conventional superconducting qubits.
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Yeung, R. R. "Nuclear spin relaxation and morphology of solid polyolefins." Thesis, University of East Anglia, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.356619.
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Ioannou, Andreas Stylianou. "Development of solid state thick film zirconia oxygen gas sensors." Thesis, Middlesex University, 1992. http://eprints.mdx.ac.uk/6549/.
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Aspects relating to and including the development of thick film amperometric zirconia oxygen sensors were investigated. These devices, which were operated in the range 550-950°C, had a laminated structure in which a cathode, an electrolyte and an anode were printed, in that order, onto a planar alumina substrate. The anode and electrolyte were porous and during sensor Operation also acted as a diffusion barrier, restricting the rate of oxygen diffusion to the cathode. A thick film platinum heater was also developed to maintain the sensor at its operating temperature while acting simultaneously as a résistance thermometer; it was screen-printed onto the substrate on the reverse side to the sensor. The individual components were characterised and optimised prior to assembly of complete sensors. Zirconia films were deposited by screen-printing onto alumina substrates. Careful attention was paid to formulation of zirconia inks, drying and firing procedures. Temperatures above 1350°C were necessary to sinter the zirconia to a low (<0.1%) though not zero porosity. The high sintering temperatures were found to result in the diffusion of impurities from the 96% alumina Substrate into the zirconia film which accelerated grain growth. X-ray diffraction showed that the grain growth resulted in transformation of the metastable tetragonal zirconia to the monoclinic form: where this occurred frequency response analysis of the films showed the expected decrease in ionic conductivity. These effects were absent on high purity (99.6%) alumina substrates. Platinum-zirconia cermets were investigated as possible electrodes. When screen-printed and fired at 1000°C for 1 hour and operated in the range 500-700°C, electrode activity was orders of magnitude greater than for pure porous platinum electrodes and increased substantially with increasing zirconia fractions provided electronic continuity was maintained within the film. High firing temperatures (> 1000°C), which were necessary for preparing a sensor with co-fired electrolyte and electrodes, decreased electrode activities although cermets remained greatly superior to pure platinum. Planar amperometric zirconia oxygen sensors were prepared using thick-film technology exclusively. When a voltage (0.5-1.4 V) was applied between the electrodes, a current flowed which was directly proportional to the oxygen concentration in the range up to 21%; this has not previously been achieved with such sensors. Characteristics were shown to be dependent upon firing temperature and substrate purity. Interestingly, temperature coefficients of the output were positive and negative for sensors fired at temperatures up to 1400 and above 1450°C respectively. Operation in the combustion products of a gas-burning flue demonstrated linear dependence upon calculated oxygen concentration. Heaters, printed using either fritted or unfritted platinum inks, were given extended treatments in a furnace at elevated temperatures (1000-1300°C) to accelerate ageing effects. Measurements were made of résistance (at 20°C), platinum evaporation rate and film cross-sectional area and these were correlated with the microstructure. The variation of résistance (at 20°C) of the films was analysed using effective medium theory invoked in order to quantify the blocking effect of the non-metallic fractions. During the initial phase (résistance decreasing) the governing factor was probably the high resistance of necks between contacting platinum particles. During the subsequent phase (resistance increasing) the resistance was controlled principally by the formation and growth of voids.
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Alsanoosi, A. M. "Quantum tunnelling motion of methyl groups in the solid state." Thesis, University of Nottingham, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.304699.
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Ridder, Trent D. "Exploring expanded wavelength regions with solid state focal plane detectors." Diss., The University of Arizona, 2000. http://hdl.handle.net/10150/289195.
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This dissertation research has focused on the design of two spectroscopic instruments that operate outside of the UV/visible region for the analysis of volatile organic hydrocarbons and hard-to-separate hydrocarbon mixtures. The first design was solid state near infrared spectrometer. The fast acquisition rate of the NIR spectrometer allowed the monitoring of the bromination of 1-hexene. The concentrations of 1-hexene and 1,2-dibromohexane were determined for the reaction using classical least squares. The root mean squared errors of prediction for 1-hexene and 1,2-dibromohexane concentrations were 0.01 and 0.003 M, respectively. This research project also focused on the investigation of the effects of instrumental parameters on partial least squares models by comparing the results obtained from four different spectrometers. The results indicate that instrumental parameters, such as resolution and wavelength coverage, have a larger effect on experimental results than the analysis method (NIR or Raman). The second instrument design investigated here was a vacuum ultraviolet ICP-AES which monitored the 130 to 200 nm wavelength range. Fifteen nonmetals were used to determine the quantitative characteristics of the design. All elements demonstrated detection limits in the ppb range. The most sensitive emission line in this work was the aluminum 167.079 nm line which had a detection limit of 200 ppt. A VUV atomic emission line database was developed to provide an analytical reference for future investigations. The database included the emission lines from 76 elements over the 130 to 195 nm wavelength region. Over 2200 lines were observed and reported. Over 1000 of the lines were previously unreported in the two major existing references for the VUV. This work is the first VUV reference to provide truly comparable intensities for a large number of elements. A GC-VUV-ICP-AES was developed to investigate the potential of VUV-ICP atomic emission spectroscopy to provide both quantitative and qualitative information for mixtures. Chlorine and carbon chromatograms were obtained simultaneously for volatile organic hydrocarbon (VOC) mixtures. The work showed that GC-VUV-ICP-AES has the potential of generating empirical formulas for compounds by simultaneously quantitating each element in the compound and determining their ratios.
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Glasson, Philip Henry. "Surface state electrons in a helium micro-channel." Thesis, Royal Holloway, University of London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272323.
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Jin, Gongjiu. "DLTS studies of surface state effects in GaAsFETs." Thesis, Lancaster University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316292.
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Rollins, Jameson Graef 1976. "Intensity stabilization of a solid-state laser for interferometric gravitational wave detectors." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/29368.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Physics, 2004.Includes bibliographical references (p. 69-71).
A high-power, low noise photo-detector, in conjunction with a current shunt actuator has been used in an AC-coupled servo to stabilize the intensity of a 10 Watt continuous-wave Nd:YAG laser. A relative intensity noise of 1 x 10⁻⁸ [square root] Hz at 10 Hz has been achieved.
by Jameson Graef Rollins.
S.M.
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Fairbanks, Matthew Stetson 1981. "Electron transport in micro to nanoscale solid state networks." Thesis, University of Oregon, 2010. http://hdl.handle.net/1794/10585.
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xvi, 116 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.This dissertation focuses on low-dimensional electron transport phenomena in devices ranging from semiconductor electron 'billiards' to semimetal atomic clusters to gold nanoparticles. In each material system, the goal of this research is to understand how carrier transport occurs when many elements act in concert. In the semiconductor electron billiards, magnetoconductance fluctuations, the result of electron quantum interference within the device, are used as a probe of electron transport through arrays of one, two, and three connected billiards. By combining two established analysis techniques, this research demonstrates a novel method for determining the quantum energy level spacing in each of the arrays. That information in turn shows the extent (and limits) of the phase-coherent electron wavefunction in each of the devices. The use of the following two material systems, the semimetal atomic clusters and the gold nanoparticles, is inspired by the electron billiard results. First, the output of the simple, rectangular electron billiards, the magnetoconductance fluctuations, is quite generally found to be fractal. This research addresses the question of what output one might expect from a device with manifestly fractal geometry by simulating the electrical response of fractal resistor networks and by outlining a method to implement such devices in fractal aggregates of semimetal atomic clusters. Second, in gold nanoparticle arrays, the number of array elements can increase by orders of magnitude over the billiard arrays, all with the potential to stay in a similar, phase-coherent transport regime. The last portion of this dissertation details the fabrication of these nanoparticle-based devices and their electrical characteristics, which exhibit strong evidence for electron transport in the Coulomb-blockade regime. A sketch for further 'off-blockade' experiments to realize magnetoconductance fluctuations, i.e. phase-coherent electron phenomena, is presented.
Committee in charge: Jens Noeckel, Chairperson, Physics; Richard Taylor, Member, Physics; Heiner Linke, Member, Physics; David Strom, Member, Physics; James Hutchison, Outside Member, Chemistry
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Sean, David. "On the mobility of partially denatured DNA in gel electrophoresis: a theoretical investigation." Thesis, University of Ottawa (Canada), 2010. http://hdl.handle.net/10393/28742.
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There are technologies which exploit a rapid reduction of the gel electrophoretic mobility of DNA arising from partial denaturation. The underlying phenomenon behind these experiments---the mechanisms which reduce the mobility---are not very well understood. Such is the purpose of my thesis.
The first chapter provides a brief introduction to the field of polymer physics. The subjects covered are carefully chosen to directly relate to the forthcoming research. There is a published semi-empirical formula used to model the rapid decrease of mobility which is largely considered to be consistent with experimental data. The second chapter of this thesis demonstrates that there is a fundamental confusion in the literature regarding the fitting parameter Lr, in the said formula. By going back to the original derivation, a physical interpretation can be given to L r. This interpretation yields theoretical values which are consistent with what has been published. However, we find that an underlying assumption---that the effect of the denaturation does not depend on its position along the DNA fragment---may systematically overestimate experimental observations of Lr.
To measure the impact of this assumption, a simulation model of DNA is presented. The article presented in the third chapter reveals that indeed, the position of the denatured region affects the migration of the DNA fragment. A refined version of the formula which takes these factors into account is proposed. The simulations also reveal that, for certain fields, an unexpected conformation completely dominates during migration of the fragment. This surprising result: a squid-like conformation, is explored in chapter four.
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McGowan, Shona. "«In situ» study of amorphous semiconductor crystallization by dynamic transmission electron microscopy." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=86999.
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Amorphous silicon is an important material of particular interest in the context of thin film transistors and display technologies. It also provides an ideal model system for the study of crystallization dynamics, and to this end we have investigated the crystallization of thin amorphous semiconducting films, including silicon and germanium, in the Dynamic Transmission Electron Microscope (DTEM) at Lawrence Livermore National Laboratory.Crystallization is initiated in the DTEM by a laser pulse that deposits sufficient heat into the system to activate the transition. A variable time delay after this initiation pulse, the sample is probed by a short photoelectron pulse in the TEM, generating a diffraction pattern or image with nanosecond time resolution. Thus, using the DTEM we can gain access to the kinetics of crystallization and details of the nucleation mechanism in situ through time-resolved diffraction patterns and images of the specimen.
In the crystallized silicon film, three distinct phenomena were observed as the incident fluence on the sample was increased: for low fluences, the film underwent solid state crystallization, for surface melting, large, radially oriented crystals were observed and when the entire film was melted, the silicon dewetted from the substrate and coalesced into crystalline droplets on the surface. Modelling of heat conduction in the laser-heated film supports this interpretation. Preliminary experiments were also carried out in amorphous germanium.
Le silicium amorphe est un matériau important en particulier, pour la fabrication de matériau polycristallin pour transistor couches minces. Il fournit également un système modèle idéal pour l'étude de la dynamique de cristallisation, et à cet effet, nous avons étudié la cristallisation des films couche mince en semiconducteurs amorphes, y compris le silicium et le germanium, dans le microscope Électronique en Transmission Dynamique (METD) à Lawrence Livermore National Laboratory.
La cristallisation est amorcée dans le METD par une Impulsion de laser qui dépose dans le système la chaleur suffisante pour activer la transition. Un délai variable après cette impulsion de déclenchement, l'échantillon est sondée par une impulsion de photoélectron dans le MET, produisant soit diffraction ou une image avec la résolution temporelle de nanoseconde. Ainsi, utilisant le METD nous pouvons accéder à la cinétique de la cristallisation et les détails du mécanisme de nucléation emphin situ par les diagrammes diffraction et les images de l'échantillion avec résolution temporelle sur une échelle de nanoseconde.
Dans la pélicule cristallisée de silicium, on a observé trois phénomènes distincts à mesure que le fluence incident sur l'échantillon était augmenté : pour les fluences réduits, la pellicule a subi la cristallisation l'état solide, pour la fonte à la surface, des grands cristaux radialement orientés ont été produits et quand la pellicule entier a été fondu, le silicium fondu a été fusionnés dans les gouttelettes cristallines sur la surface. La modélisation de la conduction de chaleur dans la pellicule chauffée par le laser soutient cette interprtation de l'évolution de la structure observée. Des exériences préliminaires ont été aussi effectuées en germanium amorphe.
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Yu, Victor. "Optics and chemical vapour deposition of graphene monolayers on various substrates." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=97052.
Full textAbstract:
Graphene-based devices are typically fabricated by exfoliation on substrates such as SiO2/Si. This is a disordered surface which can degrade the intrinsic properties of graphene such as mobility. Hence, in order to optimize device performance, we investigated the possibility to deposit graphene on more ordered surfaces such as GaAs, despite the difficulty in locating exfoliated graphene on such substrates. We show that the optical contrast of graphene can be greatly enhanced by increasing theincident angle of the light on the substrates (SiO2 and GaAs). In the second part, we move beyond the standard exfoliated graphene production to present a method for large-scale graphene synthesis by chemical vapour deposition (CVD). We varied various growth conditions to understand and optimize the mechanisms of graphene synthesis and the subsequent transfer techniques.Les dispositifs à base de graphène sont généralement fabriqués par exfoliation sur des substrats de SiO2/Si, mais ces surfaces désordonnées peuvent dégrader les propriétés intrinsèques du graphène, comme la mobilité. Par conséquent, en vue d'optimiser la performance des dispositifs, nous avons étudié la possibilité de déposer le graphène sur des surfaces plus ordonnées, comme le GaAs, malgré la difficulté augmentée de l'identification du graphène exfolié sur ces surfaces. Nous démontrons que le contraste optique du graphène peut être grandement renforcé en augmentant l'angle d'incidence de la lumière sur les substrats (SiO2 et GaAs). Dans la seconde partie, nous allons au-delà de la production standard du graphène exfolié pour présenter une méthode de synthèse de graphène à grande échelle par dépôt chimique en phase vapeur. Nous modifions les paramètres de croissance pour mieux comprendre et optimiser les mécanismes de croissance et les techniques de transfert subséquent.
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Feng, Zimin. "SymGF: a symbolic tool for quantum transport theory." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=107697.
Full textAbstract:
In this thesis, I report the development and application of a symbolic derivation tool named "SymGF'' - standing for Symbolic Green's Function, that can automatically and analytically derive quantum transport expressions and the associated Keldysh nonequilibrium Green's functions (NEGF). Quantum transport happens in open systems consisting of a scattering region coupled to external electrodes. When there are strong electron-electron interactions in the scattering region, analytical derivations of the Green's functions can be very tedious and error prone. Running on a personal computer, SymGF derives the necessary analytical formulas at a level of correlation specified by the user, using the equation of motion (EOM) method. The input to SymGF are the second quantized form the device Hamiltonian, the (anti)commutators of the operators that appear in the Hamiltonian, and a truncation rule for the correlators which determines the accuracy of the final outcome. The output of SymGF are the analytical expressions of transport properties such as electric current and conductance in terms of various Green's functions; as well as the Green's functions themselves in terms of the unperturbed non-interacting Green's functions that can be obtained straightforwardly. For systems where electron-electron interaction can be neglected, the transport problems can be easily solved and SymGF is not necessary - even though SymGF gives the same answer; but for interacting systems SymGF drastically reduces the mathematical burden of analytical derivations. We have tested SymGF for several transport problems involving Kondo resonances where analytical derivations were done by humans: exactly the same results were obtained by SymGF but in a tiny fraction of time. We have applied SymGF to new and very hard problems that resist analytical derivations by hand, including quantum transport in a double quantum dot system; transport through a single quantum dot in parallel to a direct lead-to-lead tunneling. Finally, at the post-analysis level, we have combined SymGF with an ab initio numerical modeling method to calculate quantum transport features involving atomistic degrees of freedom.Dans cette thèse, je présente le développement et lesapplications d'un outil de calcul symbolique connu sous le nom de "SymGF" (Symbolic Green's Functions) qui permet d'obtenir des expressionsanalytiques pour le transport quantique et les fonctions de Green de Keldyshpour les systèmes hors équilibre (FGHE). Le transport quantiquesurvient dans les systèmes ouverts constitués d'une régiondiffusante\ couplée à des électrodes externes. Lorsque lesinteractions électrons-électrons sont importantes dans cette région, la dérivation analytique des fonctions de Green peut devenirfastidieuse et propice aux erreurs. Par contre, à l'aide d'un ordinateurpersonnel, la méthode SymGF permet d'obtenir rapidement les formulesanalytiques nécessaires, en utilisant les équations du mouvement(EOM) du système, à un niveau de corrélation spécifiépar l'utilisateur. Les entrées nécessaires à la méthodeSymGF sont l'Hamiltonien en seconde quantification du système, lesrelations d'anti-commutation des opérateurs impliqués et les règles de coupure pour les fonctions de corrélation, ce qui déterminela précision du résultat final. Les sorties sont les expressionsanalytiques des propriétés de transport tels que le courant électrique et la conductance en fonction des différentes fonctions deGreen en plus de l'expression de ces dernières en fonction des fonctionsde Green du système non perturbé et sans interactions, pouvant être calculées directement.Pour les systèmes où les interactions électrons-électronspeuvent être négligés, le transport peut être étudiéplus facilement et la méthode SymGF n'est plus nécessaire, mêmesi elle reste toujours aussi juste. Par contre, pour les systèmes avecinteractions, elle permet de réduire drastiquement les difficultésmathématiques reliées à la dérivation analytique. Nousl'avons testée pour plusieurs situations impliquant des résonancesde Kondo, où les dérivations analytiques avaient déjà été effectuées, et les résultats furent reproduis parfaitement enune fraction du temps. Nous avons aussi appliqué cette méthode àde nouveaux problèmes très compliqués qui résistaienttoujours au traitement analytique; tels le transport quantique dans undouble point quantique et le transport dans un point quantique en parallèle avec une simple jonction tunnel. Finalement, en vue d'analyses futures,nous avons combiné la méthode SymGF avec un méthode desimulation numérique ab initio afin de calculer les caractéristiques du transport quantique impliquant des degrés de libertéatomiques.