Dissertations / Theses on the topic 'Thermal and Thermokinetic Characterization'
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1
Flity, Hassan. "Modélisation de la dégradation et combustion du bois de construction." Electronic Thesis or Diss., Université de Lorraine, 2023. http://www.theses.fr/2023LORR0250.
Abstract:
L'utilisation du bois dans la construction présente de nombreux avantages, mais aussi des risques en termes de sécurité incendie. La littérature regorge d'études, qu'elles soient expérimentales ou numériques, sur le comportement au feu du bois. Cependant, les résultats, divers et variés, ne permettent pas d'identifier un comportement intrinsèque au bois, et le cadre réglementaire doit se résoudre à de nombreuses hypothèses simplificatrices. L'objectif de ce travail de thèse est d'étudier la dégradation thermique du bois à l'échelle du cône calorimètre. L'originalité de l'étude repose sur l'adoption d'une démarche à complexité croissante, l'utilisation d'une métrologie méticuleuse et sur une caractérisation la plus complète possible des propriétés des échantillons de bois étudiés. La dégradation implique de nombreux processus qui interagissent entre eux, tels que le séchage, la pyrolyse et la combustion avec ou sans flamme, entraînant des transferts de chaleur et de masse. Vu la complexité d'étudier tous ces phénomènes simultanément, la stratégie adoptée a consisté à séparer autant que faire se peut les différents phénomènes par le biais de modèles et d'expériences spécifiques. Pour s'affranchir du problème du séchage et des transferts hydriques, l'ensemble du travail a été réalisé sur du bois anhydre. Dans un premier temps, des méthodes de caractérisation spécifiques ont été utilisées afin de déterminer les propriétés thermiques du bois et du charbon. Ces expériences ont permis d'établir des lois de comportement pour certaines de ces propriétés, facilitant ainsi leur intégration dans un modèle. Ensuite, une campagne expérimentale a été réalisée sur le bois à l'échelle matière en utilisant des techniques telles que l'analyse thermogravimétrique et la calorimétrie différentielle de balayage, sous atmosphère inerte. À cette échelle, le bois est thermiquement mince, ce qui a permis de développer un modèle cinétique capable de prédire la perte en masse, la vitesse de perte en masse et la chaleur absorbée ou générée par le bois lors de la pyrolyse, en fonction de la température. Ensuite, une campagne expérimentale a été réalisée sur des échantillons de bois à l'échelle du cône calorimètre sous atmosphère inerte afin de valider le modèle de pyrolyse 3D développé pour la prédiction de la pyrolyse du bois, en l'absence de combustion, lorsque celle-ci est principalement pilotée par les transferts thermiques dans le matériau. Des essais sous air ont enfin été réalisés en vue d'une modélisation globale de la combustion du bois anhydre, nécessitant une caractérisation précise de la combustion du charbon et de l'apport de chaleur associé et du flux de chaleur apporté par la flammeThe use of wood in construction offers numerous advantages, but also poses fire safety risks. Several studies available in the literature, whether experimental or numerical, have investigated the fire behavior of wood. However, the diverse and varied results do not allow the identification of the intrinsic behavior of wood, and regulatory frameworks have to rely on numerous simplifying assumptions. The objective of this thesis is to study the thermal degradation of wood at the cone calorimeter scale. The uniqueness of the study lies in the adoption of an increasingly complex approach, the use of meticulous metrology, and the most comprehensive characterization of the properties of the wood samples under investigation. Degradation involves numerous interacting processes such as drying, pyrolysis, and combustion with or without flames, resulting in heat and mass transfer. Given the complexity of studying all these phenomena simultaneously, the strategy adopted was to separate the different phenomena as much as possible through models and specific experiments. In order to overcome the problem of drying and hydric transfer, all the work was carried out on dry wood. First, specific characterization methods were used to determine the thermal properties of wood and charcoal. These experiments helped to establish behavioral laws for some of these properties, facilitating their integration into a model. Subsequently, an experimental campaign was conducted at the material scale of wood using techniques such as thermogravimetric analysis and differential scanning calorimetry under an inert atmosphere. At this scale, wood is thermally thin, which allowed the development of a kinetic model capable of predicting mass loss, mass loss rate, and heat absorbed or generated by wood during pyrolysis as a function of temperature. Next, an experimental campaign was carried out on wood samples at the scale of the cone calorimeter in an inert atmosphere to validate the 3D pyrolysis model developed to predict wood pyrolysis in the absence of combustion, driven primarily by heat transfer within the material. Finally, tests in an air environment were conducted for a comprehensive modeling of dry wood combustion, which requires a precise characterization of char combustion, the associated heat generated, and the heat flux supplied by the flame
2
De, Indrayush. "Thermal characterization of nanostructures using scanning thermal microscopy." Thesis, Bordeaux, 2017. http://www.theses.fr/2017BORD0563/document.
Abstract:
La caractérisation thermique est cruciale pour la conception et le développement d'applications critiques dans divers domaines. Elle trouve son utilisation dans la détection de défauts et de points chauds dans la fabrication de semi-conducteurs, l'imagerie sous-sol ainsi que la recherche de transport thermique et de charge à des longueurs inférieures à 100 nm. La capacité de comprendre et de contrôler les propriétés thermiques des nanostructures à un niveau de sous-micron est essentielle pour obtenir les performances souhaitées. Pour atteindre cet objectif, la microscopie thermique à balayage (SThM) est très bien adaptée pour cartographier la conductivité thermique à la surface des matériaux et des appareils à l'échelle nanométrique.SThM est une technique d'imagerie "champ proche". C'est une méthode de contact, la sondeétant en contact avec la surface à une force contrôlée. STHM utilise une structure cantilever identique à celle des sondes utilisées dans un Microscope à Force Atomique (AFM). La principale différence est le fait qu'un capteur thermique est intégré à la pointe de la sonde. En outre, ce capteur peut également être utilisé comme chauffage dans le cas d'éléments thermorésistants tels que Pt ou Pd. Par conséquent, le SThM est le résultat d'un AFM équipé d'une sonde thermique. Cet instrument fournit une résolution sous-micromètre dans la résolution spatiale, c'est-à-dire plus que la résolution des techniques optiques dans la gamme de longueurs d'onde visible. La résolution classique qui est réalisée de nos jours est de l'ordre de moins de 100nanomètres alors que celle obtenue avec la première sonde Wollaston était environ 10 fois plus élevée.Par conséquent, mesurer la température et les propriétés thermiques de la matière à la microscales ont deux objectifs difficiles qui ont monopolisé l'énergie et le temps de nombreux chercheurs partout dans le monde depuis plusieurs décennies. Ces deux objectifs ne sont pas similaires. Tout d'abord, la mesure d'une température dans un domaine dont la dimension caractéristique est inférieure au micromètre semble moins difficile que mesurer la conductivité thermique d'un matériau à cette échelle. [...]The objective of this thesis is to master quantitative aspects when using nearfield thermal microscopy by using the scanning thermal microscopy technique (SThM). We start by taking an in-depth look into the work performed previously by other scientist and research organizations. From there, we understand the progress the SThM probes have made through the decades, understand the probe sensitivity to the range of conductivity of the materials under investigation, verify the resistances encountered when the probe comes in contact with the sampl and the applications of SThM.Then we look into the equipment necessary for performing tests to characterize material thermal properties. The SThM we use is based on atomic force microscope (AFM) with a thermal probe attached at the end. The AFM is described in this work along with the probes we have utilized.For the purpose of our work, we are only using thermoresistive probes that play the role of the heater and the thermometer. These probes allow us to obtain sample temperature and thermalconductivity. We use two different types of thermal probes – 2-point probe and 4-point probe with SiO2 or with Si3N4 cantilever. Both the probes are very similar when it comes to functioning with the major difference being that the 4-point probe doesn’t have current limiters. Then, we present the use of recent heat-resistive probes allowing to reach a spatial resolution of the orde rof 100 nm under atmosphere and of 30 nm under vacuum. These probes can be used in passive mode for measuring the temperature at the surface of a material or component and in activemode for the determination of the thermal properties of these systems. Using thermoresistive probes means that no specialized devices are necessary for operation. Using simple commercialsolutions like simple AC or DC current and Wheatstone bridge are sufficient to provide basic thermal images. In our case we have also utilized other industrial devices and a home madeSThM setup to further improve the quality of measurement and accuracy. All the elements of the experimental setup have been connected using GPIB and that have been remotely controlled from a computer using a code developed under Python language. This code allows to make the frequency dependent measurement as well as the probe calibration. [...]
3
Li, Yifan Li. "NANOSCALE THERMAL CHARACTERIZATION BY SCANNING THERMAL MICROSCOPY (STHM)." University of Akron / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=akron159057422807603.
4
Shope, David Allen 1958. "Thermal characterization of VLSI packaging." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276686.
Abstract:
With electronic packaging becoming more complex, simple hand methods to model the thermal performance of the package are insufficient. As computer aided modeling methods came into use, a test system was developed to verify the predictions produced by such modeling methods. The test system is evaluated for operation and performance. Further, the premise of this type of test (the accurate calibration of packaged temperature-sensitive-parameter devices can be done) is investigated using a series of comparative tests. From this information, causes of possible/probable errors in calibration are identified and related to the different methodologies and devices used. Finally, conclusions are presented regarding the further improvement of the test system and methodologies used in this type of testing.
5
Crain, Kevin Richard. "Mechanical characterization and thermal modeling of a MEMS thermal switch." Online access for everyone, 2005. http://www.dissertations.wsu.edu/Thesis/Fall2005/k%5Fcrain%5F120905.pdf.
6
Ferrando, Villalba Pablo. "Thermal characterization of Si-based nanostructures." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/399339.
Abstract:
La termoelectricitat és una tecnologia prometedora per recol·lectar energia a partir de diferències de temperatura ambientals. El desenvolupament de materials més eficients que converteixin calor en electricitat d’aquesta manera és necessari per obrir nous espais d’aplicació. S’ha demostrat que nanoestructurar un material és una bona manera d’augmentar la figura de mèrit termoelèctrica a materials cristal·lins per mitjà d’una reducció en la conductivitat tèrmica a causa d’un nombre major de col·lisions de fonons. Aquesta tesi té com a objectiu entendre millor processos que afecten el transport tèrmic a materials basats en silici. Al Capítol 1, una introducció general exposa la necessitat de reduir el consum de combustibles fòssils i en general de fer ús d’energies renovables. També, es raona el benefici de poder alterar les propietats tèrmiques d’un material per millorar l’administració de calor en certs sistemes. Al Capítol 2 es fa un resum de la teoria rere el transport tèrmic. Primer, es deriva l‘equació del calor a través del marc de la termodinàmica clàssica i s’introdueixen els fonons com a quasipartícules que transporten calor. L’aplicació de l’equació de transport de Boltzmann sobre electrons i fonons permet entendre l’efecte de diferents mecanismes de col·lisió a la figura de mèrit dels materials, la qual cosa permet raonar vàries estratègies per millorar-la. Al Capítol 3 es desenvolupen les eines necessàries per mesurar la conductivitat tèrmica de nanomaterials. Primer es preparen 2 criòstats i els seus sistemes de control i després s’explica el desenvolupament de 3 sensors. Les estructures suspeses permeten mesurar la conductivitat en membranes i nanofils. S’explica la seva fabricació i es fa un anàlisi exhaustiu de funcionament i d’incerteses. El mètode 3ω s’introdueix per mesurar la conductivitat a capes primes (en direcció perpendicular al pla) i a materials macroscòpics. Es demostra l’origen del voltatge 3ω i es relaciona amb aquestes conductivitats. Finalment es desenvolupa el sensor de 3ω-Völklein per caracteritzar la conductivitat en el pla de capes primes mentre s’estan creixent. Al Capítol 4 es mesura la conductivitat tèrmica de membranes de Si i es troba la reducció esperada pels efectes de mida, així com efectes de confinament a la membrana de 17.5 nm de gruix. A més s’optimitza la nanolitografia per FIB sobre les membranes amb un estudi sistemàtic, tot trobant una resolució de 200 nm amb una dosi de 50 μC/cm2. Al Capítol 5 s’estudia la conductivitat tèrmica de nanofils porosos de Si amb diferents porositats, longituds i mides. Es troba una tendència de la conductivitat amb el diàmetre dels fils que suggereix que el nucli dels fils és menys porós que la closca. La conductivitat del silici estructural resulta ser 50 vegades menor que la del Si macroscòpic, prometent una bona figura de mèrit. Al Capítol 6 es mesura la conductivitat tèrmica d’unes superxarxes de SiGe novedoses, les quals consten de períodes amb gradients de concentració. Mostren conductivitats molt reduïdes, per sota de la capa prima d’aliatge. La mesura de la superxarxa més gruixuda confirma l’absència d’efectes de coherència dels fonons. Al Capítol 7 es mesura la conductivitat tèrmica d’una membrana de nitrur de silici mentre es dipositen capes de TPD (vidre orgànic) i Indi. Els resultats mostren una reducció inicial en la conductància que no es pot explicar per la llei de Fourier, i que és deguda a l’augment de col·lisions difusives entre els fonons i les vores de la capa. Aquest efecte pot ser extrapolat a altres nanomaterials termoelèctrics, reduïnt la seva conductivitat. També es monitoritza la dinàmica de creixement d’ambdós materials a través de la seva senyal en conductància.Thermoelectricity is a promising technology for scavenging energy from environmental temperature differences. The development of materials that transform heat into electricity in a more efficient way making use of this principle is necessary for opening new application niches. Nanostructuring a material has been demonstrated to increase the thermoelectric figure of merit of crystalline materials via a thermal conductivity reduction driven by enhanced phonon scattering. This thesis is committed to give a better insight into the processes that affect thermal transport in potential Si-based nanomaterials for thermoelectric generation. In Chapter 1, a general introduction exposes the need for reducing fossil fuel consumption and generally using renewable energies. Also, the benefit of tuning the thermal conductivity of materials for thermal management applications is discussed. Chapter 2 provides an overview of the theory behind thermal transport. First, the heat equation is derived from the classical irreversible thermodynamics framework. Then, phonons are introduced as heat carrying quasiparticles. The application of the Boltzmann Transport Equation to both phonons and electrons allows understanding the effect of different scattering mechanisms on the thermoelectric properties of materials. Finally, several strategies for enhancing the figure of merit of materials are reviewed. In Chapter 3, the necessary tools for measuring the thermal conductivity of nanomaterials are developed. Two cryostats are set up along with the temperature control systems that allow measuring at stable temperatures. Later, three sensors are developed for measuring the thermal conductivity of different materials. First, suspended structures intended for measuring the in-plane thermal conductivity of suspended membranes and nanowires are fabricated, and the errors and uncertainties produced in such measurements are characterized. Second, the 3ω method is introduced, allowing the measurement of the out-of-plane thermal conductivity in thin films. The emergence of the 3ω voltage is demonstrated, and the relation between this voltage and the thermal conductivity of the substrate and the thin-film is found. Finally, a sensor for the 3ω-Völklein method is developed, which allows characterizing the in-plane thermal conductivity of thin-films during the layer growth. In Chapter 4, the thermal conductivity of suspended Si membranes is measured, finding the expected reduction in thermal conductivity due to phonon surface scattering, as well as confinement effects in the 17.5 nm thick membrane. Moreover, the nanopatterning of these Si membranes with focused ion beam (FIB) is optimized through a systematic study of its amorphization finding an optimal spatial resolution of 200 nm when using 50 μC/cm2. In Chapter 5, the thermal conductivity of porous Si nanowires is studied for wires with different porosity, length and diameters, showing an unexpected dependence on its diameter that suggests that the wire core is generally less porous than the shell. The structural Si thermal conductivity is found to be one fiftieth of that of the bulk, promising a good thermoelectric figure of merit. In Chapter 6, the thermal conductivity of a novel SiGe graded superlattice is measured, showing a considerable reduction in its thermal conductivity, even below the thin-film alloy limit. The measurement of the thickest superlattice confirms the absence of coherent phonon effects. In Chapter 7, the thermal conductance of a suspended SiNx membrane is measured with a high precision while depositing on it organic (TPD) and metallic (Indium) materials. The results show an initial conductance reduction that cannot be explained with the Fourier law. This reduction is found to be related to an increased diffusive boundary scattering, which could be easily extrapolated to other thermoelectric nanomaterials, reducing their thermal conductivity. Also, the growth dynamics of both materials are characterized through their signal in the conductance.
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Mutnuri, Bhyrav. "Thermal conductivity characterization of composite materials." Morgantown, W. Va. : [West Virginia University Libraries], 2006. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4468.
Abstract:
Thesis (M.S.)--West Virginia University, 2006.Title from document title page. Document formatted into pages; contains vii, 62 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 61-62).
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Wei, Xiaohao, and 魏晓浩. "Nanofluids: synthesis, characterization and thermal conductivity." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B44765861.
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Hanuska, Alexander Robert Jr. "Thermal Characterization of Complex Aerospace Structures." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36617.
Abstract:
Predicting the performance of complex structures exposed to harsh
thermal environments is a crucial issue in many of today's aerospace
and space designs. To predict the thermal stresses a structure might
be exposed to, the thermal properties of the independent materials
used in the design of the structure need to be known. Therefore, a
noninvasive estimation procedure involving Genetic Algorithms was
developed to determine the various thermal properties needed to
adequately model the Outer Wing Subcomponent (OWS), a structure located at the trailing edge of the High Speed Civil Transport's (HSCT) wing tip.
Due to the nature of the nonlinear least-squares estimation method
used in this study, both theoretical and experimental temperature
histories were required. Several one-dimensional and two-dimensional finite element models of
the OWS were developed to compute the transient theoretical
temperature histories. The experimental data were obtained from
optimized experiments that were run at various surrounding
temperature settings to investigate the temperature dependence of the
estimated properties. An experimental optimization was performed to
provide the most accurate estimates and reduce the confidence
intervals.
The simultaneous estimation of eight thermal properties, including the
volumetric heat capacities and out-of-plane thermal conductivities of
the facesheets, the honeycomb, the skins, and the torque tubes, was
successfully completed with the one-dimensional model and the results used to
evaluate the remaining in-plane thermal conductivities of the
facesheets, the honeycomb, the skins, and the torque tubes with the
two-dimensional model. Although experimental optimization did not eliminate all
correlation between the parameters, the minimization procedure based
on the Genetic Algorithm performed extremely well, despite the high
degree of correlation and low sensitivity of many of the parameters.Master of Science
10
VanDerheyden, Andrew Louis. "Characterization of thermal coupling in chip multiprocessors." Thesis, Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51892.
Abstract:
For semiconductor processors temperature increases leakage current, which in turn in- creases the temperature of the processor. This increase in heat is seen by other parts of the processor since heat is diffusive across a processor die. In this way, cores are thermally coupled to one another such that when the temperature of one core increases, the temperatures of all cores on the same die can also increase. This increase in temperature and power consumption is not accompanied by any increase in performance. Cores on a chip can also be performance coupled to one another since cores can share data between them. These interactions between cores present new challenges to microarchitects who seek to optimize the energy consumption of a chip multiprocessor (CMP) comprised of multiple symmetric or asymmetric processing cores. This thesis seeks to understand and model the impact of thermal coupling effects between adjacent cores in a chip multiprocessor starting with measurements with a commercial multi-core processor. The hypothesis is that the thermal coupling of compute cores will be influenced by the adjacent core’s performance characteristics. Specifically, we expect thermal coupling is related to the nature of the workloads, e.g. compute intensive workloads will increase coupling over memory intensive workloads. However, we find that simpler parameters such as frequency of operation have more impact on coupling behaviors than the workload behaviors such as memory intensity or instruction retirement rates. A model is developed to capture thermal coupling effects and enable schemes to mitigate its impact.
11
Drummond, Kevin P. "Thermal Characterization of Graphitic Carbon Foams for Use in Thermal Storage Applications." Ohio University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1345476294.
12
Oener, Erhan. "Thermal characterization of polyester/cellulosic blended materials." Thesis, University of Leeds, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.329259.
13
Whang, Jihye 1976. "Thermal characterization and modeling of LDMOS FETs." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/86560.
14
Mayhew, Eric Kenji. "THERMAL CHARACTERIZATION OF ONE-DIMENSIONAL CARBON NANOSTRUCTURES." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1370033766.
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Demko, Michael Thomas. "Novel Thermal Characterization Methods for Micro/Nanomaterials." Case Western Reserve University School of Graduate Studies / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=case1215008098.
16
Bai, Mingwen. "Fabrication and characterization of thermal barrier coatings." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/fabrication-and-characterization-of-thermal-barrier-coatings(172aebcf-e7a5-45e3-977a-5d79140ff2bc).html.
Abstract:
New methods in the fabrication of top coat and bond coat have been introduced to improve the efficiency and performance of advanced thermal barrier coatings (TBCs).i. Top coat. Thick yttria-stabilized-zirconia (YSZ) coatings (300-400 μm) have been fabricated by using electrophoretic deposition (EPD) method. The EPD coatings have more favorable microstructures with uniformly distributed porosity and stronger bonding, in comparison with conventional air-plasma spray (APS) coatings. ii. Bond coat. Pt-diffused single γ’-phase bond coat has been fabricated by applying selective etching prior to the electroplating of Pt on CMSX-4 single crystal superalloys. The concern on the compromised scale adhesion caused by the depletion of Pt is effectively avoided, as Pt remains stable in a coherent γ’-phase layer after long-term diffusion and oxidation. Considerable cost of Pt could also be reduced. Commercial TBCs, comprising an electron beam physical vapour deposition (EBPVD) top coat, a Pt-enriched intermetallic bond coat and a CMSX-4 single crystal superalloy, have also been investigated focusing on the failures that typically occurred at the scale/alloy interface. Advanced characterization techniques have been used to study the chemical factors (Al, Pt, S, Hf, etc.) that determine the durability of TBCs. Mechanisms have been discussed that control the TBCs behaviours of diffusion, oxidation, and adhesion. i. Diffusion. A depletion of Pt near the scale/alloy interface inevitably occurs at high temperatures, which significantly weakens the scale adhesion. Mechanisms controlling the diffusion of Pt in Ni-based single crystal superalloys at high temperatures have been investigated focusing on the evolution of phase, microstructure, and composition. It was found that Pt has negative chemical interactions with Al, Ti and Ta, all of which could stabilize Pt in β- and γ’-phases, and therefore avoid the depletion of Pt. ii. Oxidation. Selective oxidation behaviour of Ni-based superalloys has been studied by using thermodynamic calculations, which is mainly affected by alloy compositions, oxygen partial pressures and temperatures. It was found that the formation of a protective α-Al2O3 scale is more favoured under lower oxygen partial pressures and higher temperatures. The additions of Al and Pt in Ni-based superalloys could also promote the formation of Al2O3 and the exclusion of NiO and spinel. The additions of reactive elements (RE), however, are less effective and may even cause severe internal oxidations due to a competitive oxidation between Al and RE.iii. Adhesion. Sulphur effect in TBCs mainly refers to a segregation of sulphur at the scale/alloy interface, which significantly deteriorates the scale adhesion to alloys. High resolution secondary ion mass spectrometry (Nano-SIMS) was employed to trace sulphur in commercial TBCs. The undesired “sulphur effect” on scale adhesion was suggested to be caused by the formation of residual sulphides beneath the scale with weaker ionic bonding to alloy cations, rather than a segregation of sulphur atoms. Possible solutions have been suggested to alleviate the sulphur effect in TBCs.
17
Copenhaver, David C. "Thermal characterization of honeycomb core sandwich structures." Thesis, This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-11182008-063547/.
18
Bohnert, Alex M. "Thermal characterization of a Hall Effect thruster /." Wright-Patterson Air Force Base, Ohio : Ft. Belvior, VA : Alexandria, Va. : Air Force Institute of Technology ; Available to the public through the Defense Technical Information Center ; Available to the public through the National Technical Information Service, 2008. http://www.dtic.mil/dtic/.
Abstract:
Thesis (M.S. in in Aeronautical Engineering)--Air Force Institute of Technology, March 2008."Presented to the Faculty, Department of Aeronautics and Astronautics Graduate School of Engineering and Management, Air Force Institute of Technology Air University, Air Education and Training Command in partial fulfillment of the requirements for the Degree of Master of Science in Aeronautical Engineering, March 2008."--P. [ii]. Thesis advisor: Dr. William Hargus. "March 2008." "AFIT/GA/ENY/08-M01." Includes bibliographical references. Also available online in PDF from the DTIC Online Web site.
19
Botha, Subelia Senara. "Synthesis and characterization of nanofluids for cooling applications." Thesis, University of the Western Cape, 2006. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_1995_1210758997.
Abstract:
Low thermal conductivity is a primary limitation in the development of energy-efficient heat transfer fluids that are required in numerous industrial sectors. Recently submicron and high aspect ratio particles (nanoparticles and nanotubes) were introduced into the heat transfer fluids to enhance the thermal conductivity of the resulting nanofluids. The aim of this project was to investigate the physico-chemical properties of nanofluids synthesized using submicron and high aspect ratio particles suspended in heat transfer fluids .
20
Gurrum, Siva P. "Thermal Modeling and Characterization of Nanoscale Metallic Interconnects." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10435.
Abstract:
Temperature rise due to Joule heating of on-chip interconnects can severely affect performance and reliability of next generation microprocessors. Thermal predictions become difficult due to large number of features, and the impact of electron size effects on electrical and thermal transport. It is thus necessary to develop efficient numerical approaches, and accurate metal and dielectric thermal characterization techniques. In this research, analytical, numerical, and experimental techniques were developed to enable accurate and efficient predictions of interconnect temperature rise.
A finite element based compact thermal model was developed to obtain temperature rise with fewer elements and acceptable accuracy. Temperature drop across the interconnect cross-section was ignored. The compact model performed better than standard finite element model in two and three-dimensional case studies, and the predictions for a real world structure agreed closely with experimentally measured temperature rise.
A numerical solution was developed for electron transport based on the Boltzmann Transport Equation (BTE). This deterministic technique, based on the path integral solution of BTE within the relaxation time approximation, free electron model, and linear response, was applied to a constriction in a finite size thin metallic film. A correlation for effective conductance was obtained for different constriction sizes.
The Atomic Force Microscope (AFM) based Scanning Joule Expansion Microscopy (SJEM) was used to develop a new technique to measure thermal conductivity of thin metallic films in the size effect regime. This technique does not require suspended metal structures, and thus preserves the original electron interface scattering characteristics. The thermal conductivities of 43 nm and 131 nm gold films were extracted to be 82 W/mK and 162 W/mK respectively. These measurements were close to Wiedemann-Franz Law predictions and are significantly smaller than the bulk value of 318 W/mK due to electron size effects. The technique can potentially be applied to interconnects in the sub-100 nm regime.
A semi-analytical solution for the 3-omega method was derived to account for thermal conduction within the metallic heater. It is shown that significant errors can result when the previous solution is applied for anisotropic thermal conductivity measurements.
21
Ramadurai, Krishna. "Carbon nanostructures for thermal applications: Synthesis and characterization." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3284482.
22
SANO, MONICA ARI. "SYNTHESIS AND CHARACTERIZATION OF LOW THERMAL EXPANSION OXIDES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2007. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=11333@1.
Abstract:
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORMateriais que apresentam expansão térmica baixa ou negativa possuem grande potencial de emprego em diversas aplicações que requerem resistência ao choque térmico, assim como para aplicações odontológicas, em placas de circuitos eletrônicos, em componentes ópticos e para produzir compósitos em que compensam a expansão térmica positiva de outros materiais. Por este motivo, o estudo e a produção de materiais com expansão térmica controlada têm crescido nos últimos anos. No presente trabalho, foram estudadas algumas famílias de óxidos com estruturas que apresentam este tipo de comportamento. Foi avaliada a expansão térmica em três sistemas da família A2M3O12 com o intuito de produzir materiais com expansão térmica controlada pela substituição química do cátion A pelos cátions Al, Cr e Fe. Os sistemas produzidos foram: Cr2xFe2-2xMo3O12 (molibdato de cromo - ferro), Al2xCr2- 2xMo3O12 (molibdato de alumínio - cromo) e Al2xFe2-2xMo3O12 (molibdato de alumínio - ferro). Além destes, o composto HfMgMo3O12 foi também sintetizado para testar a viabilidade de substituição dos cátions A trivalentes por um cátion divalente e um tetravalente. Foi possível obter soluções sólidas monofásicas e seus parâmetros de rede variam linearmente com o aumento no conteúdo do cátion de maior tamanho, conforme a lei de Vegard. Análise térmica realizada por DSC permitiu determinar a temperatura de transição de fase da estrutura monoclínica (P21a) à ortorrômbica (Pbcn). Os valores encontrados foram: para o Al2Mo3O12, 200oC, para o Cr2Mo3O12 , 403oC e para o Fe2Mo3O12, 512oC. Coeficientes de expansão térmica intrínsecos foram determinados por difração de raios-X utilizando luz síncrotron, encontrando-se valores bem reduzidos para todos os sistemas estudados, a saber: para o Al2Mo3O12, (alfa)l = 2,32 x 10- 6/oC, para o Cr2Mo3O12 , (alfa)l = 0,65 x 10-6/oC e para o Fe2Mo3O12, (alfa)l = 1,72 x 10-6/oC.
Negative and low thermal expansion materials have important potential applications as resistance to thermal shock, as well as, for odontological applications, printed circuit boards, optical components and to produce composites to compensate the positive thermal expansion of materials. For this reason, the study and production of materials with controlled thermal expansion have increased in the recent years. In the present work, some oxide families with structures that present this type of behavior were investigated. The thermal expansion in three systems of A2M3O12 family was evaluated in order to produce materials with controlled thermal expansion through the chemical substitution of cation A with Al, Cr and Fe. The produced systems were: Cr2xFe2-2xMo3O12 (chromium - iron molybdate), Al2xCr2-2xMo3O12 (chromium - aluminum molybdate) and Al2xFe2-2xMo3O12 (aluminum - iron molybdate). Besides that, HfMgMo3O12 was synthesized to test the viability of substitution of trivalent cations for one divalent plus one tetravalent. It was possible to obtain single- phase solid solutions and their lattice parameters increased linearly with the increase of the largest cation content, following the Vegard`s law. Thermal analysis carried out by DSC allowed the determination of the phase transition temperature from monoclinic (P21a) to orthorhombic (Pbcn) structure. The values were 200oC for Al2Mo3O12, , 403oC for Cr2Mo3O12 , and 512oC for Fe2Mo3O12. Intrinsic thermal expansion coefficients were determined by X-rays diffraction using syncrotron radiation, and low values were found for all studied systems: (alfa)1 = 2,32 x 10- 6/oC for Al2Mo3O12, (alfa)1 = 0,65 x 10-6/oC for Cr2Mo3O12 , and (alfa)1 = 1,72 x 10-6/oC for Fe2Mo3O12.
23
Foster, Daniel. "Mechanical and Thermal Characterization of Ultrasonic Additive Manufacturing." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1398997070.
24
Emeric, Pierre Richard. "Characterization of composite materials from temporal thermal response." W&M ScholarWorks, 1995. https://scholarworks.wm.edu/etd/1539623868.
Abstract:
There is an increasing interest in the characterization of complex structures with thermographic techniques. Typical of these structures are multilayered systems and fiber reinforced composites where structural thermal response is a function of the combined responses of the constituents. In this work, techniques are presented for measuring the early thermal response. For multilayer structures, the response is reduced to the thermal properties of the constituents. For fiber reinforced composites, the short term response enables detection of the fibers.;A measurement system was developed consisting of an infrared detector focused on a single point on the structure. An input heat flux was provided by either an Argon laser or a flash lamp depending on the configuration. to measure the spatial variations in the thermal response, specimens were mounted on a translation stage.;Initial measurements with the system were performed on multilayered structures. An analytical solution was developed for the thermal response of a two or three layer system, given the thermal properties of the layers. This solution was combined with a nonlinear estimation routine to enable the determination of the properties of the constituents from the thermal properties of the structure. This technique was applied to the characterization of a thermally thin layer on a thermally thick layer. It was also applied to the characterization of the center layer of a three layer structure.;Subsequent measurements were performed on a ceramic composite (reaction bonded silicon nitride reinforced with SiC fibers). Images of the spatial variations in the thermal response were obtained by translation of the composite. to give insights in the significance of the data, a two dimensional analytical solution was developed for the thermal response of a fiber embedded in a matrix material. Predicted responses of the structure were compared with the measured responses.
25
Li, Buxuan. "Synthesis and characterization of high thermal conductive polymers and fabrication of polymer based thermal strap." Thesis, Massachusetts Institute of Technology, 2021. https://hdl.handle.net/1721.1/130863.
Abstract:
Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, February, 2021Cataloged from the official PDF version of thesis.
Includes bibliographical references (pages 66-70).
Polymers have infiltrated almost every aspect of modern technology. Without polymer products, the society would look very different. As one of the most important and common engineering materials, traditional polymers are both electrically and thermally insulating, due to its organic nature and amorphous structures. In the late 20th century, electrically conductive polymers has been discovered. Thermally conductive polymers, however, were not demonstrated until the recent decades. Polymers are shown to have great potential in thermal conduction, even divergent thermal conductivity in theory. This counterintuitive finding is attributed to its one-dimensional periodic structure, where repeating monomers are connected by strong covalent bonds.
Researchers have learned that special dynamics exist in non-linear one-dimensional chains since the Fermi-Pasta-Ulam-Tsingou report, where the evolution of state space was found to be non-ergodic, enabling an infinite long lifetime of excitations. As a result, such 1D nonlinear system favors scatter-free phonon transport. Molecular dynamics simulation shows a single polyethylene (PE) chain could have divergent thermal conductivity. Calculations from first principle also confirm the thermal conductivity is approximately 160 W/mK for bulk PE and 1400 W/mK for a single PE chain, with a three phonon process taken into consideration. In experiments, researchers measured enhanced thermal conductivity in stretched PE in the 1970s. In the last decades, researchers have made progress by demonstrating PE nanofibers with a thermal conductivity of over 100 W/mK. Recently, 2D PE films were fabricated and measured to have metal-like thermal conductivity of over 60 W/mK.
With all these progresses, in this thesis, we aimed to develop scalable polyethylene films with high thermal conductivity and investigating temperature-dependent thermal transport properties. A differential steady state method was used to measure the thermal conductivity of the synthesized PE films. A thermal annealing of PE films was performed along with the temperature dependence test where a transition temperature was identified. Below the transition temperature, thermal annealing increased the thermal conductivity at room temperature. Above the transition temperature, thermal annealing irreversibly decreased the thermal conductivity. Our PE films featured reasonable thermal conductivity of 20~60 W/mK depending on draw ratio and much lower density comparing to metals such as copper and aluminum. A potential application of such films is a light-weight thermal strap, which is important for space technologies.
We designed a strategy to overcome the issue that such films have a poor cross-plane thermal conductivity. We proved the idea based on both simulation and experiments. In simulations, we derived a steady state solution of a full-size physical device with conduction and radiation included. In experiments, we conducted a unit test on laboratory scale samples and argued its ability of scaling up by showing that multilayer PE films performed as expected.
by Buxuan Li.
S.M.
S.M. Massachusetts Institute of Technology, Department of Mechanical Engineering
26
Kaleli, Kadir. "Nano Structural Metal Composites: Synthesis, Structural And Thermal Characterization." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12609674/index.pdf.
Abstract:
In this work , metal functional polymers, namely Cr-PS-b-P2VP, Co-PS-b-P2VP, Au-PS-b-P2VP, Fe-PS-b-P2VP and Mo-PS-b-P2VP were prepared by thermal reaction of hexacarbonylchromium, Cr(CO)6, octacarbonyldicobalt,Co2(CO)8, hydrogentetrachloroaurate(III), H(AuCl4).4H2O, trichloroiron(III), FeCl3.6H2O, molybdenum(VI)oxide, MoO3 and PS-b-P2VP. TEM images indicated formation of AuIII, Cr and Co nanoparticles. On the other hand, crystalline structures were detected for Fe-PS-b-P2VP and Mo-PS-b-P2VP. Samples involving nanoparticles were further characterized by FTIR, UV-Vis and direct pyrolysis mass spectroscopy techniques. FTIR analysis indicated dissapearance of characteristic carbonyl peaks of Cr(CO)6 and Co2(CO)8 for Cr-PS-b-P2VP and Co-PS-b-P2VP samples. The appearance of a peak at about 467 cm-1 supported the formation of metal-nitrogen bond. Pyrolysis mass spectrometry analysis showed an increase in the thermal stability of P2VP chains involving coordinated pyridine units. The thermal stability of these chains increased in the order Co<Cr <
Au3+ indicating stronger coordination in the same order.
27
Bagherifam, Shahla. "Thermal Characterization Of Phenol And Bisphenol-a Based Polybenzoxazines." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610409/index.pdf.
Abstract:
Although, several researches on synthesis and characterization of benzoxazines and
polybenzoxazines have appeared in the literature, detailed studies on thermal
characterization are still limited. In this study, polymerization and thermal
degradation mechanisms of benzoxazines were investigated via direct pyrolysis mass
spectrometry. Benzoxazine monomers prepared by reactions of phenol or bisphenol-
A with aniline or methyl amine were analyzed to investigate the effects of the
structures of phenyl and amine groups on both polymerization and thermal
degradation behaviours.
It has been proposed in the literature that polymerization of benzoxazines occurs by
ring opening polymerization of oxazine ringcleavage of O-CH2 bond of the oxazine ring and attack of n-CH2 group to phenol or bisphenol-A ring. However, the direct pyrolysis mass spectrometry analyses of polymerization and thermal degradation of benzoxazines pointed out that after the cleavage of O-CH2 bond of the oxazine ring, polymerization proceeded through opposing pathways. Strong evidences confirming coupling of (CH3)NCH2 or (C6H5)NCH2 groups yielding dimers involving diamine linkages were detected. Polymerization of the dimer by the reactions with the corresponding monomers was proposed. In case of benzoxazines based on bisphenol-A, the results indicated polymerization of the dimer ii by coupling of both of the oxazine rings. On the other hand, polymerization of the dimer through the ethylene units (vinyl polymerization) in case of benzoxazine monomer based on phenol and methyl amine was also noted. For polybenzoxazines based on aniline another polymerization pathway involved attack of radicals generated by cleavage of the oxazine ring to aniline ring. Multi-step thermal decomposition was observed for all the polybenzoxazines under investigation confirming the presence of units with different structures and stabilities.
28
Tonolla, Diego [Verfasser]. "Acoustic and thermal characterization of river landscapes / Diego Tonolla." Berlin : Freie Universität Berlin, 2011. http://d-nb.info/102551114X/34.
29
Johnson, Jeremy A. (Jeremy Andrew). "Optical characterization of complex mechanical and thermal transport properties." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68543.
Abstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemistry, 2011.Page 176 blank. Cataloged from PDF version of thesis.
Includes bibliographical references (p. 163-175).
Time-resolved impulsive stimulated light scattering (ISS), also known as transient grating spectroscopy, was used to investigate phonon mediated thermal transport in semiconductors and mechanical degrees of freedom linked to structural relaxation in supercooled liquids. In ISS measurements, short optical pulses are crossed to produce a periodic excitation profile in or at the surface of the sample. Light from a probe beam that diffracts off the periodic material response is monitored to observe the dynamics of interest. A number of improvements were put into practice including the ability to separate so-called amplitude and phase grating signal contributions using heterodyne detection. This allowed the measurement of thermal transport in lead telluride and gallium arsenide-aluminum arsenide superlattices, and also provided the first direct observation of the initial crossover from diffusive to ballistic thermal transport in single crystal silicon and gallium arsenide at room temperature. Recent first-principles calculations of the thermal conductivity accumulation as a function of phonon mean free path allowed direct comparison to our measured results. In an effort to test theoretical predictions of the prevailing first principles theory of the glass transition, the mode coupling theory (MCT), photoacoustic measurements throughout much of the MHz acoustic frequency range were conducted in supercooled liquids. Longitudinal and shear acoustic waves were generated and monitored in supercooled liquid triphenyl phosphite in order to compare the dynamics. An additional interferometric technique analogous to ISS was developed to probe longitudinal acoustic waves at lower frequencies than was typically accessible with ISS. Lower frequency acoustic data were collected in supercooled tetramethyl tetraphenyl trisiloxane in conjunction with piezotransducer, ISS, and picosecond ultrasonics measurements to produce the first truly broadband mechanical spectra of a viscoelastic material covering frequencies continuously from mHz to hundreds of GHz. This allowed direct testing of the MCT predicted connection between fast and slow relaxation in supercooled liquids. Measurements of the quasi-longitudinal speed of sound in the energetic material cyclotrimethylene trinitramine (RDX) were also performed with ISS and picosecond ultrasonics from 0.5 to 15 GHz in order to resolve discrepancies in published low and high frequency elastic constants.
by Jeremy A. Johnson.
Ph.D.
30
Maheswaram, Manik Pavan Kumar. "Characterization of Pharmaceutical Materials by Thermal and Analytical Methods." Cleveland State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=csu1358131244.
31
Shrestha, Binod. "Characterization of lignin thermal processing in a biorefinery perspective." Electronic Thesis or Diss., Université de Lorraine, 2016. http://www.theses.fr/2016LORR0007.
Abstract:
La conversion thermochimique de la lignine est un aspect important de la bioraffinerie lignocellulosique avec pour objectif la production de fibres de carbone, d’additifs polymères, de composés aromatiques verts ou de biocarburants. Dans ce travail, la lignine Protobind 1000 a été caractérisée, dans un premier temps, par thermogravimétrie, calorimétrie, rhéologie in-situ, RMN in-situ du proton, RMN ex-situ du carbone et du phosphore. Plusieurs techniques d’analyses (analyse élémentaire, GPC-UV, FTIR et LDI-FTICRMS) ont été utilisées pour comprendre le ramollissement et la pyrolyse de la lignine et un mécanisme physico-chimique global de conversion thermo-chimique de la lignine a été proposé. Après des études préliminaires de rhéologie in-situ à haute température et en mélangeur interne, l’extrusion de la lignine a été réalisée en utilisant une extrudeuse bi-vis (Process 11). La fenêtre de fonctionnement du procédé a été déterminée à partir de l’étude de l'évolution du couple à différents débits (0.1-0.3 kg.h-1) et vitesse de rotation des vis (300-600 rpm) et pour une température du fourreau fixée à 150 °C. Deux profils de vis ont été par ailleurs étudiés pour évaluer l’impact de l’intensité du mélange sur le ramollissement de la lignine. Les extrudâts de lignine obtenus pour différentes conditions d'extrusion ont été caractérisés par FTIR, GPC-UV/ETCS, et RMN 2D du liquide. Ces analyses ont montré qu’aucun changement structurel majeur ne se produit durant l’extrusion à chaud. Enfin, les interactions entre la lignine et différents solvants (eau, éthanol et soude aqueuse) ont été étudiées par rhéologie in-situ, DLS, mesure du potentiel zêta, SAXS et analyse visuelle en temps réel. La liquéfaction de la lignine a ensuite été effectuée en réacteur fermé dans de l'éthanol et les produits de liquéfaction ont été analysés par absorption et fluorescence UV, spectroscopie UV-Raman et GPCThe thermo-chemical conversion of lignin is an important aspect of lignocellulosic biorefinery in order to produce carbon fibers, polymer additives, green aromatics or biofuels. Protobind 1000 lignin was characterized by thermogravimetry, calorimetry, in-situ rheology, in-situ 1H NMR, solution state 13C and 31P NMR. A multiple techniques including elemental analysis, GPC-UV, FTIR, solid-state NMR and LDI-FTICRMS, were performed to understand the softening and pyrolysis of lignin. An overall physical and chemical mechanism of thermo-chemical conversion of lignin has been proposed. A twin screw extrusion of lignin was carried out using Process 11, following the in-situ high temperature rheology and rheomix internal mixing. The operating window was derived from torque evolution at varying throughputs of 0.1-0.3kg.h-1 and rotation speed of 300-600 rpm at barrel temperature of 150°C for two screw configurations. The lignin extrudates obtained at key extrusion conditions were characterized by FTIR, GPC-UV/ELSD, solution state 1H-13C HSQC NMR. The analysis of lignin melts shows no major structural changes concluding twin screw extruder as a hot melt feeder. The lignin characterization in a liquid media i.e. H2O, ethanol and aq. NaOH, were studied by wet rheology, DLS, zeta potential measurement, SAXS and real-time visual analysis. The lignin liquefaction was carried out in ethanol and the liquefaction products were analysed by UV resonance Raman spectroscopy, GPC-UV and UV-Visible absorption and fluorescence spectroscopy. The structural changes undergone by lignin during liquefaction was accounted
32
Assy, Ali. "Development of two techniques for thermal characterization of materials : Scanning Thermal Microscopy (SThM) and 2ω method." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0001/document.
Abstract:
Deux techniques de caractérisation thermique des matériaux et d’analyse du transfert de chaleur aux micro- et nano- échelles ont été étudiées et sont présentées dans ce mémoire. La première technique est la microscopie thermique à sonde locale (SThM). La pointe d’un microscope à force atomique intègre un élément résistif. Utilisée en mode contact, cette pointe, chauffée par effet joule, permet l'excitation thermique localisée de l’échantillon. La détermination des propriétés thermiques de l’échantillon nécessite l'analyse de la réponse de cette pointe avec un modèle du système sonde-échantillon et de son environnement. Un état de l'art général des études réalisées en SThM permet de poser les questions scientifiques actuellement traitées dans le domaine. Une attention particulière est accordée à l'interaction thermique sonde-échantillon. L’étude ici présentée tient compte des propriétés thermiques, de la rugosité et de la mouillabilité de la surface de différents échantillons. Une nouvelle méthodologie est établie pour la spécification du transfert de chaleur échangée par conduction thermique au travers du ménisque de l'eau formé au contact sonde-échantillon. Cette méthodologie est basée sur l'analyse de la dépendance à la température de la sonde des courbes de force-distance obtenues à l'air ambiant. Elle est appliquée à trois sondes de taille, forme et constitution différentes: la sonde Wollaston, la sonde KNT et une sonde en silicium dopé. Quels que soient la sonde et l'échantillon, la contribution du ménisque d’eau à l'interaction est montrée être inférieure à celle de l'air. La conductance thermique au contact solide-solide est déterminée pour différents échantillons. Cela a permis d’identifier le coefficient de transmission de phonons dans le cas de la sonde KNT et des échantillons non-métalliques. La conduction thermique via l’air dépend fortement de la conductivité thermique de l'échantillon. La sensibilité à la conductivité thermique pour les sondes Wollaston et KNT est part ailleurs montrée fortement réduite pour les matériaux de conductivité thermique supérieure à 10 et quelques W.m-1.K-1 respectivement. La seconde technique développée est une méthode d’analyse thermique moins locale nécessitant l’instrumentation de la surface de l’échantillon avec un réseau de sondes résistives filiformes. L’un des fils du réseau, chauffé par un courant alternatif à la fréquence f, a le rôle de source excitatrice continue et à la fréquence 2f de l’échantillon. Un modèle analytique 2D, basé sur le principe des ondes thermiques et développé pour identifier les propriétés thermiques d’échantillons anisotropes est présenté. Des simulations par éléments finis et avec ce modèle ont été utilisées pour dimensionner le montage expérimental et valider la méthode sur un échantillon de silicium pur. Les résultats obtenus à des températures de l’échantillon variant de l’ambiante à 500 K corroborent ceux de la littératureTwo techniques to characterize the thermal properties of materials and to analyze the heat transfer at the micro/nanoscales have been studied and are presented in this manuscript. The first technique is an Atomic Force Microscopy (AFM)-based Scanning Thermal Microscopy (SThM) technique. Operating in its active mode, the AFM probe integrates a resistive element that is electrically heated. Used in AFM contact mode, it allows the localized thermal excitation of the material to be studied. The determination of the sample thermal properties requires the analysis of the probe thermal response through the modeling of the probe-sample system including its surrounding. Through a state of the art of the SThM studies, the current scientific questions and the analytical models used to analyze the probe-sample system are exposed. Special attention is given to the probe-sample thermal interaction that conditions the tip-sample interface temperature. In this work, a new methodology based on the analysis of the dependence of force-distance curves on probe temperature obtained in ambient air has been established. It permits the study and the specification of the heat rate exchanged between probe and sample through thermal conduction through water meniscus. The methodology has been applied with samples with different thermal properties, surface roughness and wettability to three resistive probes different in size and heater configurations: Wollaston, KNT and doped silicon (DS) probes. Whatever the probe and the sample are, the contribution of water meniscus in the probe-sample interaction has been shown to be lower than the one through air. The thermal conductances at the solid-solid contact were determined for various samples. This allowed identifying the phonon transmission coefficient in the case of KNT probe and a nonmetallic sample. The heat conduction through air strongly depends on the sample thermal conductivity. Moreover, the sensitivity to sample thermal conductivity for the Wollaston and KNT probes is shown to be strongly reduced for thermal conductivities larger than 10 and few W.m-1.K-1 respectively. The second technique developed in this thesis is a less local thermal analysis method. It operates by contact, requiring the implementation of the sample with a network of resistive wire probes. One wire of the network is heated by an alternating current at frequency f and has the role of heating source, continuous and at 2f frequency, for the sample. A 2D analytical model, based on the principle of thermal-waves, was developed to identify though the measurements the effective thermal properties of anisotropic samples. Finite element simulations and this model were used to design the experimental set-up and validate the method on a sample of pure silicon. The results obtained at sample temperatures ranging from ambient to 500 K are consistent with literature
33
Shrestha, Ramesh. "Micro-Pipette Thermal Sensor: A Unique Technique for Thermal Characterization of Microfluids, Microspheres, and Biological Cells." Thesis, University of North Texas, 2020. https://digital.library.unt.edu/ark:/67531/metadc1703406/.
Abstract:
In this research work, an innovative method for measurement of thermal conductivity of a small volume of liquids, microsphere, and the single cancer cell is demonstrated using a micro-pipette thermal sensor (MPTS). The method is based on laser point heating thermometry (LPHT) and transient heat transfer. When a single pulse of a laser beam heats the sensor tip which is in contact with the surrounding liquids or microsphere/cells, the temperature change in the sensor is reliant on the thermal properties of the surrounding sample. We developed a model for numerical analysis of the temperature change using the finite element method (FEM) in COMSOL. Then we used MATLAB to fit the simulation result with experiment data by multi-parameter fitting technique to determine the thermal conductivity. To verify the accuracy in the measurement of the thermal conductivity by the MPTS method, a 10µl sample of de-ionized (DI) water, 50%, and 70% propylene glycol solution were measured with deviation less than 2% from reported data. Also, to demonstrate that the method can be employed to measure microparticles and a single spherical cell, we measured the thermal conductivity of poly-ethylene microspheres with a deviation of less than 1% from published data. We estimated the thermal conductivity of two types of cell culture growth media for the first time and determined the thermal conductivity of cancerous Jurkat Clone E6-1 to be 0.538 W/m.K ± 2%. Using the sensor of 1-2μm tip size, we demonstrated the MPTS technique as a highly accurate technique for determining the thermal conductivity of microfluidic samples, microparticles, biological fluids, and a non-invasive method for measuring the thermal conductivity of single cancer cell. This MPTS technique can be beneficial in developing a diagnosis method for the detection of cancer at an early stage. We also compared three effective thermal conductivity models for determining the weight percentage of Jurkat cell, considering water and protein as the major constituents. We discovered that a combination of Maxwell-Euken and effective medium theory model provides the closest approximation to published data and, therefore, recommend for the prediction of the cell composition.
34
Katsis, Dimosthenis C. "Thermal Characterization of Die-Attach Degradation in the Power MOSFET." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/26206.
Abstract:
The thermal performance of the power MOSFET module is subject to change over its lifetime. This is caused by the growth of voids and other defects in the die-attach layer. The goal of this dissertation is to develop measurement techniques and finite element simulations that can measure the changes in thermal performance caused by changes in die-attach voided area. These experimental results and simulations can then be used to create predictions of the thermal performance of a particular power semiconductor module at various stages of die-attach fatigue. In the results and simulations presented, a relationship is developed between thermal impedance and void area coverage. This dissertation starts by presenting an analysis of the thermal and mechanical stresses needed for crack and void growth in the power semiconductor die-attach region. Accelerated life testing is then performed for both commercial and prototype power semiconductor devices to generate the stresses needed to precipitate void growth. Representative groups of lead and lead-free solders are then tested to compare levels of die-attach degradation under accelerated life conditions. Hardware is developed to experimentally measure thermal impedance using temperaturesensitive characteristics of the power MOSFET. The power semiconductor devices that were subjected to accelerated life testing are then measured with this hardware. The results show that die-attach voided area coverage increases thermal impedance. Representative lumped parameter thermal models that use R-C circuits are derived to demonstrate the ability of the thermal impedance analyzer to determine the differences in the die-attach layer. Finite element modeling (FEM) is then used on representative voided devices to support these results, with additional emphasis on peak temperatures caused by hotspots located over the voided areas. Experimental techniques are further applied to measurement of cooling trends that occur due to the existence of voids in the die-attach layer. These measurements are correlated with finite element thermal simulations to develop a relationship between thermal impedance, hotspot temperature, die-attach void size, and total voided area coverage.Ph. D.
35
Wu, Zhaohui. "Modeling and characterization of high-temperature silicon-based thermal sensors." Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B31057652.
36
Kutukcu, Mehmet Nuri. "Synthesis and Characterization of Low and Negative Thermal Expansion Materials." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7636.
Abstract:
The preparation and thermophysical properties of some In(I), Ga(I) and Ag(I) substituted NZP type materials were explored. Many compositions with the NZP framework show low and negative thermal expansion.
Previously reported material, GaZr2(PO4(3, transforms from one NZP related phase into another NZP type phase due to oxidation under air above 300oC. In addition, it exhibits hysteresis under inert atmosphere; the cell parameters are different on heating and cooling cycles for a given temperature. The synthesis, and characterization of a new material, InZr2(PO4)3, is outlined. It crystallizes in space group R -3 c. In addition, as GaZr2(PO4)3, it oxidizes above 300oC under air and exhibits hysteresis under inert atmosphere. Furthermore, the synthesis of AgTixZr2-x(PO4)3 solid solution compositions, their ion exchange characteristics with Ga(I) and their thermophysical properties are described. Thermal expansion anisotropy (the difference between a and c ) of the solid solutions decreases as the bigger ion, Zr4+, is substituted by the smaller one, Ti4+. Thermal expansion characteristics of GaZr2(PO4)3, InZr2(PO4)3 and AgZr2(PO4)3 are compared with MZr2(PO4)3 ( M = Li, Na, K, Rb, Cs). Ionic radii for Ga(I) and In(I) in a six coordinate oxygen environment were proposed.
37
Argin, Emir. "Structural And Thermal Characterization Of Polymers Via Pyrolysis Mass Spectrometry." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12606680/index.pdf.
Abstract:
In the first part of this study, the structtural and thermal characterization of electrochemically and chemically polymerized poly(paraphenylene vinylene), (PPV), have been investigated by direct pyrolysis mass spectrometry. Thermal characteristics, and degradation products of electrochemically prepared poly(paraphenylene vinylene). Pyrolysis study indicated that thermal decomposition of PPV occurs at least two steps. The first being due to the loss of supporting electrolyte present and the second being decomposition of the polymer backbone.In the second part of the study, direct insertion probe pyrolysis mass spectrometry (DIP-MS) technique was used to perform the thermal and the structural characterization of electrochemically synthesized polyaniline,PANI. The effect of dopant used (HCL, HNO3 and H2SO4) and synthesis period have been investigated. For all the samples studied, three main thermall degradation stages have been recordedevolution of low molecular weight species, evolution of dopant based products and evolution of degradation products of polymer.
38
Orhan, Tugba. "Nano Structural Metal Nano Composites: Synthesis, Structural And Thermal Characterization." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12610799/index.pdf.
Abstract:
Recently, the use of block copolymers in preparation of nanocomposites has received great attention as they form well-defined micelles. In this work, the synthesis of different metal functional copolymers, nano structural metal composites and investigation of their reaction mechanism and thermal characteristics by pyrolysis mass spectroscopy have been aimed. Namely, polyisoprene-block-poly2vinylpyridine, (PI-b-P2VP) and poly2vinylpyridine-block-polymetylmethacrylate, (PMMA-b-P2VP) were used as block copolymers and the thermal reaction of these copolymers with two different transition metal complexes Cr(CO)6 and HAuCl4.3H2O were investigated which mostly lead to the coordination of metal through nitrogen atom of the pyridine ring which then degrates to form nano particles. The samples were further characterized by TEM, ATR-FT-IR, UV-Vis and Direct-Pyrolysis Mass Spectroscopy techniques.
TEM images proved the formation of nanoparticles and the results showed that synthesized Au nanoparticles have 2 to 3 fold larger size than Cr nanoparticles. ATR-FT-IR spectrum of metal functional copolymers showed that the disappearance of characteristic peaks of pyridine stretching and bending mode when metal coordinates to the pyridine nitrogen. Furthermore, the spectrum indicated the appearance of a new absorption peak at around 740 cm-1 which may be a clue for the coordination of gold(III) ion to the pyridine nitrogen. Different from chromium case, in the spectrum of Au3+-(PMMA-b-P2VP), CO stretching frequency of PMMA which may appear at around 1720&ndash1718 cm-1 decreased in intensity while a new absorption peak appeared at around 1600 cm-1. This results reveals that electron deficient gold (III) ion prefers the coordination from both donor atoms namely carbonyl oxygen PMMA and pyridine nitrogen of P2VP in order to compensate its electron deficiency. In the UV-Vis spectrum of copolymers, Cr-functional copolymers showed a sharp absorption peak appeared at around 290 nm is attributed to a MLCT transition from chromium atom to * orbital of pyridine group. Furthermore, Au-functional copolymers showed a completely new absorption band at around 320 nm which can be associated again with a LMCT transition since gold is electron deficient and more willing to accept electrons from the ligand. Pyrolysis mass spectrometry analysis showed that poly2vinylpyridine blocks for each copolymers were affected similarly but polyisoprene block was not affected much from the coordination of metal compared to poly(methyl methacrylate) block in copolymers. For (PI-b-P2VP), Au3+ coordination to copolymer resulted in the higher thermal stability compared to Cr coordination. For (PMMA-b-P2VP), different from Cr, Au3+ coordination to P2VP nitrogen atom was extensive and PMMA based products changed drastically due to the coordination of electron deficient Au3+ to PMMA carbonyl group.
39
Kulkarni, Raghav Shrikant. "Characterization of carbon fibers: coefficient of thermal expansion and microstructure." Texas A&M University, 2004. http://hdl.handle.net/1969.1/3073.
Abstract:
The focus of the research is to develop a consistent and repeatable method to
evaluate the coefficient of thermal expansion (CTE) of carbon fibers at high
temperatures. Accurate measurement of the CTE of carbon fibers is essential to
understand and develop optimal processing procedures as well as computational
simulations to predict properties and allowables for fiber-reinforced composites. The
mismatch between the coefficient of thermal expansion of the fiber and the matrix has a
profound impact on the development of residual stresses and the subsequent damage
initiation and progression, potentially diminishing the performance of composite
structures.
In situ transmission electron microscopy (TEM) is selected to perform the
experimental work on account of the high resolution and the capability of evaluating
both the longitudinal and transverse CTE. The orthotropy in the CTE is tested by
rotating the fibers through 45° about their axis. The method is validated by testing
standard tungsten filaments of known CTE. Additionally, the microstructure of the fibers
is studied in a field emission scanning electron microscope as well as through selected
area diffraction patterns in a TEM to observe presence of any potential orthotropy. The
pitch based P55 fiber revealed a cylindrically orthotropic microstructure, but the PAN
based IM7 and T1000 fibers did not reveal any orthotropy. Finite element models of
hexagonally arranged IM7 fibers in a 977 epoxy matrix are developed using PATRAN
and analyzed using the commercial FEA code ABAQUS 6.4. The fiber properties were
considered temperature independent where as the matrix properties were varied linearly
with temperature. The lamina properties evaluated from the finite element modeling are
in agreement with the experimental results in literature within 10% in the temperature
range of room temperature to the stress free temperature of the epoxy, however at
cryogenic temperatures the difference is greater. The residual stresses developed during
processing of the composite indicated a potential location for fiber matrix debonding to
be in the matrix dominant regions.
40
Jadhav, Amol D. "Processing, characterization, and properties of some novel thermal barrier coatings." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1183851697.
41
Patel, Niranjan M. "Multicomponent network and linear polymer systems : thermal and morphological characterization /." Diss., This resource online, 1990. http://scholar.lib.vt.edu/theses/available/etd-07122007-103930/.
42
Galyean, Christina Pilkey. "Investigation and characterization of a thermal infrared all-sky imager." Thesis, Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/28004.
43
Wu, Zhaohui, and 吳朝暉. "Modeling and characterization of high-temperature silicon-based thermal sensors." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B31057652.
44
Granestrand, Jonas. "Material characterization for studying thermal deactivation of automotive SCR catalysts." Thesis, KTH, Skolan för kemivetenskap (CHE), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-147524.
Abstract:
Thermalageing of the commercial selective catalytic reduction catalysts used inScania’s trucks was investigated using catalyst characterization techniques.Catalyst samples were oven-aged at 550 °C for up to 990 hours and investigatedwith nitrogen adsorption, oxygen chemisorption, X-ray fluorescence, X-raydiffraction, X-ray photoelectron spectroscopy and temperature-programmeddesorption of ammonia. The two latter methods are new to Scania and wereevaluated in depth. Furthermore, field-aged samples, which had had theircatalytic performance tested in another study, were investigated, in an attemptto find some link between characterization results and catalytic activity. Theinvestigation of oven-aged samples yielded information about the timescales ofcarrier sintering and sintering of catalytically active material, showing theformer to be much slower than the latter. It was also noted that the rate withwhich the catalyst’s ability to store ammonia decreases during thermal ageingwas similar to the rate of sintering of catalytically active material,suggesting that the loss of ammonia storage capability due to thermal ageing isrelated to sintering of the catalytically active material. X-ray photoelectronspectroscopy revealed that the fraction of vanadium in the outermost surfacelayer of the catalysts had increased during ageing. At the same time, thischaracterization technique appeared to have a low repeatability, possibly dueto the investigated catalyst having a high surface inhomogeneity. Whether ornot 500 ppm of NOx was present in the ageing atmosphere did notappear to affect the deactivation of the catalyst. Finally, no clear link couldbe found between characterization results and catalytic activity for field-agedsamples.
45
Baliga, Radhika. "Thermal and electrical characterization of a micro-hotplate for calorimetry." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/33101.
Abstract:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.Includes bibliographical references (p. 104-105).
This thesis characterizes a micro-hotplate designed at Draper Laboratory. This hotplate will be integrated into a calorimetry system that measures the heat released or absorbed by a reaction. An analytical thermal model is developed to quantify the heat transfer mechanisms between the hotplate and the environment. The analytical model is verified through experimental measurements conducted with the device operating in both ambient conditions and vacuum. In ambient conditions, the heat transfer is dominated by air conduction as predicted by the model. Air conduction can be reduced by operating the device in a medium with a lower thermal conductivity. The relatively short timescale over which the hotplate comes to thermal equilibrium with the environment limits the types of reactions that can be measured with the device. The performance of the hotplate can be improved by operating it in vacuum, by constructing it from a material with a lower emissivity, or by decreasing its surface area. The noise spectral density of the hotplate's resistive temperature sensor is characterized. The hotplate's ability to resolve temperature is limited by the flicker noise in the sensor.
by Radhika Baliga.
M.Eng.
46
Hauf, Dagmar E. (Dagmar Elisabeth). "Two-parameter characterization of crack-tip fields during thermal transients." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/36473.
47
Carnicero, Dominguez Bernardo Antonio. "Characterization of Pyranometer Thermal Offset and Correction of Historiacal Data." Thesis, Virginia Tech, 2001. http://hdl.handle.net/10919/33785.
Abstract:
The Eppley Precision Pyranometer (PSP) is a
radiometer used in networks around the world to measure
downwelling and upwelling diffuse and total hemispherical
broadband solar irradiances. PSP's present an offset in the
signal, called thermal offset, produced by a radiation heat
exchange between the glass dome, which defines the spectral
throughput and the detector. This offset can reach up to 15\% of
the total value of the signal when measuring diffuse irradiance
under clear sky conditions. The thermal offset is characterized by
monitoring the temperature gradient between the dome and detector
using thermistors at key locations. The temperatures are acquired
by using thermistors. Relationships between the thermal offset and
the temperature gradient are established using nighttime data and
subsequently used to estimate the offset during daytime. To
correct historical data the thermal offset is related to other
variables such as the output of a Precision Infrared Pyrgeometer
(PIR) or the fraction of cloud cover in the sky. The use of
thermistors is a very reliable method to estimate and correct the
thermal offset. The relationships between the offset and the IR
output and between the offset and the cloud cover fraction provide
good estimates of the thermal offset in historical data sets,
reducing it 60\% to 100\% depending on the instrument and the
relationship used.Master of Science
48
Kelly, Shawn Michael. "Characterization and Thermal Modeling of Laser Formed Ti-6Al-4V." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/33104.
Abstract:
The current work focuses on three aspects of laser formed Ti-6Al-4V: an evaluation of the as-deposited and heat treated macro and microstructures and preliminary results obtained from a model developed to calculate the temperature profile resultant of the laser forming process. A â solution treat and ageâ heat treatment with a variable cooling rate was performed on the Laser Formed Ti-6Al-4V single line builds. Increasing the cooling rate decreases the acicular alpha grain size in the basketweave Widmanstätten alpha plus untransformed beta microstructure. Distinct features of the as-deposited macrostructure include: large columnar prior-beta grains that have grown epitaxially through multiple deposited layers; a well defined heat affected zone in the substrate; and the presence of â layer bands,â a macroscopic banding present at the top of every layer except for the last three layers to be deposited. The nominal microstructure between the layer bands consists of acicular basketweave Widmanstätten alpha outlined in untransformed beta. The alpha grain width is smaller just above a layer band and larger just below a layer band. The microstructure of the layer band consists of larger colonies of acicular alpha outlined in untransformed beta. The gradient in the alpha grain size and presence of the layer band is due to thermal cycling as opposed to segregation effects which were ruled out using quantitative compositional analyses. Through analysis of the microstructural results the gradient in the nominal microstructure and formation of the layer band in layer n was caused by the deposition of layer n+2, and n+3, respectively.
A thermal model has been developed to assist in the prediction and interpretation of the as-processed microstructure. The model is used to explain that the microstructural evolution of the layer bands and gradient microstructure in layer n is due to the deposition of layer n+2. The difference in the two analyses of microstructural evolution based on microstructural observations and thermal model results are due to differences in the parameter sets used to build and model the deposit.
Master of Science
49
Zhao, Qi. "Characterization and Thermal Decomposition Behavior of Carbon Nanotubes and Nanocomposites." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1378113311.
50
Gupta, Tripti Thapa. "Characterization and Optimization of Non-thermal Plasma for Biofilm Sterilization." University of Toledo / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=toledo152547566313079.