No description available.

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Physics and Astronomy." Includes bibliographical references (p. 160-164).

A major problem associated with any power generation process in which coal is burned is the formation of ash and slag from the inorganic constituents of the coal. Ash deposition on heat transfer surfaces in coal-fired reactors is unavoidable and can have a significant effect on the performance and maintenance of boilers and gasifiers. A greater understanding of the thermal properties of coal ash deposits is important in reducing their negative impact. This work presents the development of an experimental method for making in situ measurements of the spectral emittance of coal ash deposits. It also provides measured emittances for two coals under oxidizing and reducing conditions. The experimental procedure consisted of burning coal in a down-fired entrained-flow reactor and collecting ash deposits on a circular probe under controlled conditions. Spectra collected from a Fourier transform infrared (FTIR) spectrometer were combined with an instrument response function to measure the spectral emissive power from the surface of the ash deposit. The spectral emissive power was used to infer the deposit surface temperature. These two measurements were used to calculate the spectral emittance of the deposit. This experimental method was validated by measuring the known temperature and spectral emittance of a blackbody radiator. The experimental method was used to find the spectral emittance of bituminous and subbituminous coals under both oxidizing and reducing conditions. The bituminous coal analyzed was Illinois #6 coal from the Crown III mine and the subbituminous coal analyzed was Wyoming coal from the Corederro mine. The spectral emittance of the subbituminous coal was lower than that of the bituminous coal under both oxidizing and reducing conditions. The emittances of both coals under reducing conditions were greater than those found under oxidizing conditions. A total band emittance was defined and calculated for each coal. The total band emittance as well as theoretical upper and lower total emittance limits were calculated as functions of temperature. There was little temperature dependence in the total emittance estimates.

Afin de répondre aux nouvelles exigences liées au développement durable, des entreprises telles que Saint- Gobain sont amenées à développer de nouveaux produits en vue de réduire les coûts de fonctionnement de leurs systèmes de fabrication de verre ainsi que les rejets de gaz à effet de serre. Une façon d’atteindre ces objectifs est d’améliorer l’isolation thermique des fours verriers par un accroissement des propriétés émissives des matériaux réfractaires constituants ces fours tels que le Jargal M et la BP mullite. La piste choisie pour l’amélioration des performances radiatives est la fonctionnalisation des matériaux de base afin qu’ils atteignent des hauts niveaux d’émissivité à la température de fonctionnement des systèmes de production. Cette stratégie permet de conserver les propriétés de résistance pyroscopique des matériaux de base tout en améliorant leurs performances radiatives. Une optimisation de ces deux matériaux a été effectuée par dopage avec des oxydes d’éléments de transition connus pour induire des propriétés hautement émissives dans le domaine de transparence de milieux diélectriques. Diverses techniques d’élaboration ont été testées comme le dopage en masse ou par imprégnation, afin de proposer des solutions efficaces et viables industriellement. L’étude de ces matériaux dopés a été réalisée par spectroscopie d’émission infrarouge en température à l’aide d’un dispositif expérimental développé au laboratoire CEMHTI utilisant un chauffage par laser CO2. Des observations par microsonde et microscopie électronique à balayage ont permis de corréler l’amélioration des propriétés radiatives à la texture, phases en présence et répartition des éléments dopants au sein des matériaux. Une étape de modélisation a également permis de compléter la démarche expérimentale en mettant en évidence l’influence de la texture et de la composition sur les propriétés radiatives. Cette partie intègre diverses étapes allant du traitement d’images issues de μ-tomographie X, la production de matériaux numériques ayant des textures maitrisées et leur caractérisation par simulation numérique utilisant les lois de l’optique géométrique et la méthode de lancer de rayons. / Evolution of global economy and green policy leads companies, like Saint-Gobain, to develop new productsto reduce the cost of their glass making systems and greenhouse gas emissions from glass furnaces. It isnecessary to improve thermal insulation of furnaces by increasing emittance property of refractory materialslike Jargal M and BP mullite. A way to improve radiative properties is the functionalization of materials toreach high levels of emissivity at working temperature and to keep refracterity of base materials.Improvement of optical properties of materials was made by adding emissive elements like transition oxides,known to induce high emissivity property in the transparent region of dielectric material. Several dopingtechnics were tested, for example mass doping or elements diffusion, to propose efficient and usefulsolutions for industries. Optical characterization was performed with an infrared spectrometry devicedeveloped in the CEMHTI laboratory, allowing measurement at high temperature thanks to CO2 laserheating. Microsonde and scanning electron microscopy observations were also done to correlateimprovement of radiative behavior with texture, phases and localization of doping elements into materials. Asimulation step has also been developed to complete experimental measurements and to show texture andvolume influences on radiative properties. This numerical procedure mixed image treatment from μ-tomography X analysis, generation of numerical samples with controlled texture and their characterization bynumerical simulation using geometrical optic laws and rays tracing procedure.

Sharp leading edges required for hypersonic vehicles improve the maneuverability as well as reduce aerodynamic drag. However, due to the sharp design, increased surface temperatures require materials that can withstand these extreme conditions. Ultra-high temperature ceramics are a material group being considered for the leading-edge material, specifically ZrB₂/SiC (ZBS) which has a high thermal shock resistance, melting temperature, and thermal conductivity. Studies done by Tan et. al. has shown that adding samarium (Sm) as a dopant to ZBS has an emittance of 0.9 at 1600^oC and develop oxide scales that have excellent ablation performance. However, it remained unknown how the Sm doped oxide scale formed as well as how the emittance and ablation performance are affected by the microstructure. This study investigates the oxide scale development of 3 mol% doped Sm-ZBS billets as well as how differences in microstructure affect the emittance and ablation performance. Samples were prepared via chemical infiltration of samarium nitrate into spray-dried powders of 80 vol.% ZrB₂/20 vol.% SiC; powders were then pressed into billets and pressureless sintered. Samples cut and polished from these billets were then oxidized for 10, 60, or 300 s, respectively, using an oxyacetylene torch. X-ray diffraction was used to determine the sequence of oxidation of Sm-ZBS, beginning with the formation of ZrO₂ and Sm₂O₃. The final oxide scale was determined to be c₁-Sm_0.2Zr_0.8O_1.9, with a melting temperature exceeding 2500^oC. SEM and EDS were also used to investigate the microstructural formation that occurs from the bursting of convection cells. Samples with different microstructures revealed similar topographical microstructures post-ablation due to the sequence of the oxide formation. However, samples with rougher surfaces and higher porosities had a higher concentration of trapped glass in the cross-sectional oxide scale. It was also found that due to differences in heating the sample during emittance testing compared to ablation testing, the oxide developed was identical for all the samples. It was also found that variances in microstructure had no effect on the spectral emittance of Sm-ZBS at ultra-high temperatures. The fabrication of c₁-Sm_0.2Zr_0.8O_1.9 (SZO) as a bulk billet was also investigated to use as a thermal barrier coating (TBC) in replacement of Sm-ZBS.

Following the discovery of the Higgs-like boson at the Large Hadron Collider, there is demand for precision measurements on recent findings. The Compact Linear Collider, CLIC, is a candidate for a future linear electron-positron collider for such precision measurements. In CLIC, the beams will be brought to collisions in the multi-TeV regime through high gradient acceleration with high frequency RF power. A high intensity electron beam, the so-called drive beam, will serve as the power source for the main beam, as the drive beam is decelerated in special structures, from which power is extracted and transfered to the main beam. When the drive beam is decelerated the beam quality deteriorates and the momentum spread increases, which makes the beam transport challenging. Dedicated diagnostics to monitor the momentum profile along each bunch train and transverse profile diagnostics will be needed to guarantee the reliability of the decelerator and consequently the power source of the main beam acceleration. A test facility, CTF3, has been constructed at CERN to validate key technical aspects of the CLIC concept. The beam quality in the decelerator will be investigated in the test beam line, TBL, where several power extraction structures reduce the drive beam energy by up to 55%. At the same time, the single-bunch rms energy spread grows from the initial value of 1% to almost 6%. To monitor the parameters of such a beam is challenging but crucial for the optimization of the beamline. In this thesis we report on progress made on adapting generally used methods for beam profile measurements to the demanding conditions of a wide momentum profile. Two detector technologies are used for measuring transverse profile and momentum profile and we discuss the performance of these instruments, in the view of the large momentum spread and with the outlook towards equivalent beam profile monitors in the CLIC decelerator.

Cool roofs are the roofs that can deliver high solar reflectance and high thermal emittance. The benefits associated with cool roofs include reduced cooling energy load, reduced air pollution and greenhouse gas emission, and improved human health and comfort. This study attempts to develop standard measurement method for evaluating the reflectance and emmittance of a cool roof material. First, a literature survey was conducted to analysis the current programs promoting the use of cool roofs in the world, and then more than 2000 cool roof materials¡¦ data were collected in this study. In addition, the dynamic building energy load simulation by using eQuest was conducted to investigate the energy-saving benefits of cool roof applied in Taiwan. The results indicated that the reflectance, emmittance and thermal conductivity have a significant effect on the roof heat gain. The higher reflectance or emmittance of the roof, the less heat gain absorbed in the roof. But, reflectance has a larger effect on roof energy-saving than emittance does. The energy-saving effect by using cool roof on the flat-type roof is larger than on low-slope type roof.

No description available.

The International Muon Ionization Cooling Experiment (MICE) is designed to demonstrate the currently untested technique of ionization cooling. Theoretically, this process can condition the high quality muon beams required to build a neutrino factory or muon collider which will be the next generation of machines for the study of Particle Physics. The beam line to transport muons into the MICE cooling channel lattice cell was installed in December 2009. Step I of the experimental programme, whose goal was to demonstrate that the beam line can generate beams similar to those expected in a neutrino factory cooling channel, was completed in August 2010. Methods were developed to use time difference measurements in the MICE time of flight counters (TOFs) to obtain a transverse spatial resolution of approximately 10 mm and to track muons through the focusing elements of the beam line, thus allowing the trace space vectors of individual muons to be reconstructed and their integrated path length to be calculated. The TOFs were used to make an absolute measurement of the momentum of muons with zero bias and a systematic error of less than 3 MeV/c. The measured trace space vectors of single muons were used to estimate the emittances and approximate optical parameters of eighteen muon beams. The results of beam line simulations were compared with the measurements and, once the effects of experimental resolution had had been included, found to be in good agreement. A sample of individual muons whose phase space vectors had been measured was injected into a simulation of the full MICE cooling channel; the beam was found to be suitable for demonstrating muon cooling, although some fine tuning of the cooling channel optics will eventually be required.

Avec l’augmentation de la température, certains composés oxydes, transparents dans le proche infrarouge, deviennent progressivement opaques à l’approche de la fusion. Un tel comportement est inhabituel et impacte profondément leurs propriétés radiatives. Afin de comprendre ce phénomène, des mesures par spectroscopie d’émission infrarouge ont été effectuées depuis la température ambiante jusqu’à la fusion sur plusieurs oxydes cristallins (Mg2SiO4, LiAlO2, LiGaO2, ZnO, YAlO3, LaAlO3, LiNbO3, MgO). Ces données ont été complétées ponctuellement par des mesures de conductivité électriques, de RMN et de diffraction des rayons X en température. L’analyse des données expérimentales du facteur d’émission menée à l’aide d’un modèle de fonction diélectrique semi-quantique et incluant un terme de Drude étendu, a permis de caractériser finement la réponse de ces matériaux et de proposer une origine physique pour le mécanisme responsable de l’opacification. Le phénomène est thermiquement activé et peut être expliqué par la formation et la mobilité de polarons. Ce travail a également montré l’existence d’un lien étroit entre la microstructure des composés et les caractéristiques de l’opacification. / With increasing temperature, some oxide compounds that are transparent in the near infrared range become progressively opaque when approaching the liquid phase. Such a behavior is unusual and deeply impacts their thermal radiative properties. To understand this phenomenon, infrared emittance spectra were acquired from room temperature up to the liquid state on several crystalline oxides (Mg2SiO4, LiAlO2, LiGaO2, ZnO, YAlO3, LaAlO3, LiNbO3, MgO). These data have been selectively completed by electrical conductivity measurements, NMR and X-ray diffraction experiments versus temperature. The analysis of the experimental emittance data with a semi-quantum dielectric function model including an extended Drude term, allowed to characterize finely the material responses and to suggest a physical origin for the opacification mechanism. The phenomenon is thermally activated and can be explained by the formation and the mobility of polarons. This work also showed the existence of a close link between the material microstructure and the characteristics of the opacification.