Дисертації: "Thermal properties of porous foam"

1

Anghelescu, Mihnea S. "Thermal and Mechanical Analysis of Carbon Foam." View abstract, 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&res_dat=xri:pqdiss&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&rft_dat=xri:pqdiss:3353337.

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2

Piquemal, Philippe. "Élaboration d'un nouveau matériau isolant phonique et thermique en verre expansé et mise au point d'un procédé utilisant un chauffage diélectrique." Nancy 1, 1988. http://www.theses.fr/1988NAN10203.

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On cherche à fabriquer un matériau en verre expansé (foamglass) ayant une bonne absorption acoustique à l'aide d'un processus d'expansion faisant appel au chauffage mixte diélectrique et infra-rouge. Deux types de matériaux à cellules ouvertes (petites bulles ou grandes bulles) sont conçus au laboratoire. On suit l'absorption aux moyennes et hautes fréquences (microondes). L'apport d'énergie électromagnétique au cours du chauffage infra-rouge favorisé l'expansion du matériau, alors que les microondes sont peu satisfaisantes

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3

Vijay, Dig. "Forced convective heat transfer through open cell foams." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2017. http://nbn-resolving.de/urn:nbn:de:bsz:105-qucosa-226330.

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The purpose of this study is to investigate forced convection of air through open cell foams. It can be numerically investigated either by implementing the time efficient macroscopic models or computationally expensive microscopic models. However, during the course of this study, it was observed that the macroscopic models are not sufficient for determining the desired key parameters. Nevertheless, it is still possible that these macroscopic models can be used to design an application accurately with minimum time efforts if the concerned key parameters are already known through other means. Accordingly, in this work, a methodology is developed to determine the desired key parameters by implementing the microscopic models, which are further used into the macroscopic models for designing different applications. To validate the proposed methodology, a set of steady state and transient forced convection experiments were performed for a set of ceramic foams having different pore diameter (10−30 PPI) and porosity (0.79−0.87) for a superficial velocity in the range of 0.5−10 m/s.

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4

Rodeheaver, Bret Alan. "Open-celled microcellular themoplastic foam." Thesis, Georgia Institute of Technology, 1999. http://hdl.handle.net/1853/18914.

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5

Geiger, Derek M. "AN EXPERIMENT ON INTEGRATED THERMAL MANAGEMENT USING METALLIC FOAM." DigitalCommons@CalPoly, 2009. https://digitalcommons.calpoly.edu/theses/75.

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This report details an approach to using metal foam heat exchangers inside an integrated thermal management system on a variable cycle engine. The propulsion system of interest is a variable cycle engine with an auxiliary, variable flow rate fan. The feasibility of utilizing an open-celled metallic foam heat exchanger in the ducting between the constant and variable-fans on this variable cycle engine to cool the avionics was explored using an experimental approach. Two heat exchangers, 6.3 inch width by 6.3 inch length by 0.5 inch thickness, were constructed from 20 and 40 pores per inch (PPI) metal foam and tested. Both were constructed using 6061-T6 aluminum open-cell metal foam with a relative density of 8% and brazed using 4047 aluminum braze to 0.02 inch thick sheet metal made of 6061-T6 aluminum. Both models were subjected to internal forced convection using heated air with flow rates of 4, 8, 12, 16, and 20 standard cubic feet per minute (SCFM). They were also subjected to external forced convection using blowers to supply cooling air to simulate the variable cycle engine’s fans. One duct was supplied with a constant 34 ft/s cooling flow, while the other cooling flow velocity was varied between 0% and 100% of this 34 ft/s, in 25% increments. The temperature and pressure of the flow internal to the metal foam, as well as the heat exchanger external surface and cold flow temperatures, were recorded. A hot-flow Reynolds number range of 1,300 to 6,400 was tested. Results showed expected trends for the hydraulic performance of both heat exchangers. The form factors were 50.4 and 54.8 ft^-1 and the permeabilities were 9.11E-7 and 6.32E-7 ft^2 for the 20 and 40 PPI heat exchangers, respectively. Due to a defect on one side of the 40 PPI heat exchanger, the thermal results are based only on the 20 PPI heat exchanger. While the present study examines a different metal foam heat transfer configuration than most other studies, the metal foam Nusselt numbers were comparable to past studies. In addition, the pumping power required was not excessive and would allow the thermal management system to be realized without an unreasonable energy input. Therefore, a metal foam heat exchanger integrated within the ducting of a variable cycle engine is deemed feasible. The pumping power and thermal resistance were used to create a performance predicting model of the 20 PPI heat exchanger. From this model, the optimized 20 PPI heat exchanger has a hot-flow rate of 10.5 SCFM. The resulting pumping power and thermal resistance are estimated to be 6.7 BTU/hr and 0.036 °R/(BTU/hr), respectively.

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6

Mahasaranon, Sararat. "Acoustic and thermal properties of recycled porous media." Thesis, University of Bradford, 2011. http://hdl.handle.net/10454/5516.

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This thesis is concerned with developing porous materials from tyre shred residue and polyurethane binder for acoustic absorption and thermal insulation applications. The resultant materials contains a high proportion of open, interconnected cells that are able to absorb incident sound waves through viscous friction, inertia effects and thermal energy exchanges. The materials developed are also able to insulate against heat by suppressing the convection of heat and reduced conductivity of the fluid locked in the large proportion of close-cell pores. The acoustic absorption performance of a porous media is controlled by the number of open cells and pore size distribution. Therefore, this work also investigates the use of catalysts and surfactants to modify the pore structure and studies the influence of the various components in the chemical formulations used to produce these porous materials. An optimum type and amounts of catalyst are selected to obtain a high chemical conversion and a short expanding time for the bubble growth phase. The surfactant is used to reduce the surface tension and achieve a homogenous mixing between the solid particulates tyre shred residue, the water, the catalyst and the binder. It is found that all of the components significantly affect the resultant materials structure and its morphology. The results show that the catalyst has a particularly strong effect on the pore structure and the ensuing thermal and acoustical properties. In this research, the properties of the porous materials developed are characterized using standard experimental techniques and the acoustic and thermal insulation performance underpinned using theoretical models. The important observation from this research is that a new class of recycled materials with pore stratification has been developed. It is shown that the pore stratification can have a positive effect on the acoustic absorption in a broadband frequency range. The control of reaction time in the foaming process is a key function that leads to a gradual change in the pore size distribution, porosity, flow resistivity and tortuosity which vary as a function of sample depth. It is shown that the Pade approximation is a suitable model to study the acoustic behaviour of these materials. A good agreement between the measured data and the model was attained.

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7

Mueller, Jennifer Elizabeth. "Determining the Role of Porosity on the Thermal Properties of Graphite Foam." Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/34110.

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Graphite foams have high bulk thermal conductivity and low density, making them an excellent material for heat exchanger applications. This research focused on the characterization of graphite foams under various processing conditions (different foaming pressures and particle additions), specifically studying the effects of porosity on the thermal properties. The characterization of the foams included measuring cell sizes, percent open porosity, number of cells per square inch, bulk density, Archimedes density, compression strength, thermal conductivity, thermal resistance, and permeability. Several relationships between the structure and properties were established, and a recommendation for the processing conditions of graphite foams for the use in heat exchangers was determined.
Master of Science

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8

Bai, Chengying. "Highly porous geopolymer components." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3427257.

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The geopolymers, semi-crystalline three-dimensional silico-aluminate inorganic polymers, have attracted increasing attention from a wide range of scientific interests. The topic of this study deals with the synthesis, the characterization and the potential applications of porous geopolymers (PGs) or geopolymer foams (GFs, total porosity > 70 vol%), realized through different processing routes. Firstly, the processes are divided into five categories: (i) direct foaming, (ii) replica method, (iii) sacrificial template, (iv) the 3D printing, and (v) others. The microstructure, porosity, and properties of porous geopolymers also compared and discussed. Secondly, K-based porous geopolymers were produced by direct foaming using hydrogen peroxide as chemical pore-forming agent (PFA) combined with three types of stabilizing agent (SA, egg white, Tween 80, vegetable oils), and by direct foaming plus reactive emulsion templating. Furthermore, open-celled phosphate-based porous geopolymers were obtained by a simple direct foaming method (using Triton X-100 as physical pore-forming agent). The porosity, pore morphology, high temperature performance, adsorption, mechanical, and insulating properties of PGs were investigated. High strength PGs with tailored porosity and controlled macro-porous structure were fabricated by different processes. The results suggest that the porous geopolymers are promising low-cost highly porous candidates for potential applications such as catalyst or membrane supports (high open porosity and high strength), adsorption (high removal efficiency and adsorption capacity with high open porosity) and insulating (low thermal conductivity, high porosity, and acceptable strength) materials.
I geopolimeri, polimeri inorganici silicoalluminati tridimensionali semi-cristallini, hanno attirato crescente attenzione da una vasta gamma di interessi scientifici. L'argomento di questo studio riguarda la sintesi, la caratterizzazione e le potenziali applicazioni di geopolimeri porosi (PG) o schiume di geopolimeri (GF, porosità totale> 70% vol), realizzati attraverso diversi percorsi di lavorazione. In primo luogo, i processi sono suddivisi in cinque categorie: (i) schiumatura diretta, (ii) metodo di replica, (iii) modello sacrificale, (iv) stampa 3D e (v) altri. Anche la microstruttura, la porosità e le proprietà dei geopolimeri porosi sono state confrontate e discusse. In secondo luogo, i geopolimeri porosi basati su K sono stati prodotti mediante schiumatura diretta utilizzando perossido di idrogeno come agente chimico di formazione dei pori (PFA) combinato con tre tipi di agente stabilizzante (SA, bianco d'uovo, Tween 80, oli vegetali) e mediante schiumatura diretta più reattivo emulsione che modella. Inoltre, geopolimeri porosi a base di fosfato a cellule aperte sono stati ottenuti con un semplice metodo di schiumatura diretta (usando Triton X-100 come agente fisico di formazione dei pori). Sono state studiate la porosità, la morfologia dei pori, le prestazioni ad alte temperature, l'adsorbimento, le proprietà meccaniche e isolanti delle PG. I PG ad alta resistenza con porosità adattata e struttura macroporosa controllata sono stati fabbricati con diversi processi. I risultati suggeriscono che i geopolimeri porosi promettono candidati altamente porosi a basso costo per potenziali applicazioni come catalizzatori o supporti a membrana (elevata porosità aperta e alta resistenza), adsorbimento (alta efficienza di rimozione e capacità di adsorbimento con elevata porosità aperta) e isolanti (basso materiali di conducibilità termica, elevata porosità e resistenza accettabile).

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9

Zahedi, Maryam. "Meshfree Method for Prediction of Thermal Properties of Porous Ceramic Materials." FIU Digital Commons, 2013. http://digitalcommons.fiu.edu/etd/954.

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In the presented thesis work, meshfree method with distance fields is applied to create a novel computational approach which enables inclusion of the realistic geometric models of the microstructure and liberates Finite Element Analysis(FEA) from thedependance on and limitations of meshing of fine microstructural feature such as splats and porosity.Manufacturing processes of ceramics produce materials with complex porosity microstructure.Geometry of pores, their size and location substantially affect macro scale physical properties of the material. Complex structure and geometry of the pores severely limit application of modern Finite Element Analysis methods because they require construction of spatial grids (meshes) that conform to the geometric shape of the structure. As a result, there are virtually no effective tools available for predicting overall mechanical and thermal properties of porous materials based on their microstructure. This thesis is a separate handling and controls of geometric and physical computational models that are seamlessly combined at solution run time. Using the proposedapproach we will determine the effective thermal conductivity tensor of real porous ceramic materials featuring both isotropic and anisotropic thermal properties. This work involved development and implementation of numerical algorithms, data structure, and software.

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10

Zihms, Stephanie Gabriele. "Smouldering and thermal remediation effects on properties and behaviour of porous media." Thesis, University of Strathclyde, 2013. http://oleg.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=23194.

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Smouldering and thermal remediation processes can achieve rapid removal of organic contaminants from soils but these processes expose soils to high temperatures for extended periods of time. Wild fire research shows changes in soil properties, when exposed to temperatures up to 850°C. Based on temperatures achieved during smouldering, this work aims to investigate how high temperature thermal and smouldering treatments affect soils. Laboratory experiments on simple soils prepared from silica sand and silica sandkaolin show that thermal treatments affect soil particle size distribution, mass, pH, mineralogy, liquid limits, and plastic limits. Properties such as particle density and bulk density remain unchanged after exposure to elevated temperatures. In silica sand, shear strength decreases with increasing temperature and smouldering whereas it increases with increasing temperature in the sand-kaolin soil. High temperatures and smouldering may smooth the sand particle surfaces and reduce interparticle friction. The presence of kaolin may protect the sand grains from this effect and affect the shear strength through mineralogical changes. Kaolin addition has similar effects on hydraulic conductivity. Samples containing 10% kaolin show a relationship between hydraulic history, microstructure and hydraulic conductivity. Samples treated by smouldering have lower saturated hydraulic conductivities compared to furnace treatments. For silica sand no changes in hydraulic conductivity were observed. These changes in dynamic response were linked to changes on a particle scale such as chemistry, mineralogy, and composition.

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11

Zhang, Lizhong. "Physical, mechanical, thermal, and viscoelastic properties of water-blown rigid polyurethane foam containing soy flours /." free to MU campus, to others for purchase, 1998. http://wwwlib.umi.com/cr/mo/fullcit?p9924871.

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12

Santhosh, Balanand. "Thermal properties of polymer derived Si-O-C-N ceramics." Doctoral thesis, Università degli studi di Trento, 2020. http://hdl.handle.net/11572/267913.

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The main objective of the thesis is to study the thermal properties of Si-based polymer derived ceramics (PDCs) at elevated temperatures and to classify the main factors affecting the thermal transport through these ceramics. The polymer derived ceramics with the chemistry Si- O-C-N were prepared starting from commercial polycarbosilane, polysiloxane, and polysilazane precursors. These precursors are cross-linked at room temperature to obtain the preceramic, followed by controlled pyrolysis (at different temperatures ranging from 1200 oC to 1800 oC in argon, nitrogen or carbon-di-oxide atmospheres), to get the final ceramic. The first part of the thesis discusses on development and studies of dense polymer derived thin disks having a basic chemistry, Si-C, Si-O- C, and, Si-C-N-O, developed via a casting technique followed by specific pyrolysis cycles. Having a thickness in the range of 100 μm- 300 μm, these ceramic disks were studied to be nanocrystalline/amorphous at least up to a temperature of 1400 oC and were found to have a significant amount of Cfree phase existing in them along with the intended chemistry. The high-temperature thermal properties were primarily investigated on ceramics prepared at a pyrolysis temperature of 1200 oC (ceramic still in nanocrystalline/amorphous glassy phase). The disks were found to have very low expansion coefficients (CTE) measured up to ~900 oC and the thermal diffusivity (k) and thermal conductivity (l) of these disks were also measured. An attempt to understand the influence of the different phases in a SiOC ceramic (mainly the Cfree phase, studied by enriching the carbon percentages using DVB) in determining the final thermal properties was also conducted. The influence of carbon enrichment on the mechanical properties of these disks is also studied as a sub-part of this work. The second part of the work deals with testing the possibility to use these ceramics for high-temperature insulation applications. ‘Reticulated’ ceramic foams of relatively same chemistries as that of the disks were prepared by a template replica approach, using polyurethane (PU) foams (more open-celled to more closed-celled types of PU foams were used in the study) as the template. Porous structures having densities ranging from as low as 0.02 g.cm-3 to 0.56 g.cm-3 and with a porosity ~ 80 % to ~99% were prepared and tested. The developed foams showed excellent thermal stability up to a temperature of 1400 oC and possessed very low thermal expansion. The thermal conductivity measured on them at RT gave values in the range 0.03 W.m-1.K-1- 0.25 W.m-1.K-1. A Gibson-Ashby modeling approach to explain the thermal conductivity of the porous ceramics was also attempted. The developed foams were also found to be mechanically rigid. In a nutshell, the thesis work studies the thermal properties of Si-O-C- N ceramics in detail and probes into the possibility to develop these class of Si-O-C-N ceramics into promising high-temperature insulation material.

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13

Santhosh, Balanand. "Thermal properties of polymer derived Si-O-C-N ceramics." Doctoral thesis, Università degli studi di Trento, 2020. http://hdl.handle.net/11572/267913.

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Анотація:

The main objective of the thesis is to study the thermal properties of Si-based polymer derived ceramics (PDCs) at elevated temperatures and to classify the main factors affecting the thermal transport through these ceramics. The polymer derived ceramics with the chemistry Si- O-C-N were prepared starting from commercial polycarbosilane, polysiloxane, and polysilazane precursors. These precursors are cross-linked at room temperature to obtain the preceramic, followed by controlled pyrolysis (at different temperatures ranging from 1200 oC to 1800 oC in argon, nitrogen or carbon-di-oxide atmospheres), to get the final ceramic. The first part of the thesis discusses on development and studies of dense polymer derived thin disks having a basic chemistry, Si-C, Si-O- C, and, Si-C-N-O, developed via a casting technique followed by specific pyrolysis cycles. Having a thickness in the range of 100 μm- 300 μm, these ceramic disks were studied to be nanocrystalline/amorphous at least up to a temperature of 1400 oC and were found to have a significant amount of Cfree phase existing in them along with the intended chemistry. The high-temperature thermal properties were primarily investigated on ceramics prepared at a pyrolysis temperature of 1200 oC (ceramic still in nanocrystalline/amorphous glassy phase). The disks were found to have very low expansion coefficients (CTE) measured up to ~900 oC and the thermal diffusivity (k) and thermal conductivity (l) of these disks were also measured. An attempt to understand the influence of the different phases in a SiOC ceramic (mainly the Cfree phase, studied by enriching the carbon percentages using DVB) in determining the final thermal properties was also conducted. The influence of carbon enrichment on the mechanical properties of these disks is also studied as a sub-part of this work. The second part of the work deals with testing the possibility to use these ceramics for high-temperature insulation applications. ‘Reticulated’ ceramic foams of relatively same chemistries as that of the disks were prepared by a template replica approach, using polyurethane (PU) foams (more open-celled to more closed-celled types of PU foams were used in the study) as the template. Porous structures having densities ranging from as low as 0.02 g.cm-3 to 0.56 g.cm-3 and with a porosity ~ 80 % to ~99% were prepared and tested. The developed foams showed excellent thermal stability up to a temperature of 1400 oC and possessed very low thermal expansion. The thermal conductivity measured on them at RT gave values in the range 0.03 W.m-1.K-1- 0.25 W.m-1.K-1. A Gibson-Ashby modeling approach to explain the thermal conductivity of the porous ceramics was also attempted. The developed foams were also found to be mechanically rigid. In a nutshell, the thesis work studies the thermal properties of Si-O-C- N ceramics in detail and probes into the possibility to develop these class of Si-O-C-N ceramics into promising high-temperature insulation material.

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14

Hudiono, Yeny C. "Thermal transport properties of nanoporous zeolite thin films." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24748.

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Thesis (Ph.D.)--Chemical Engineering, Georgia Institute of Technology, 2009.
Committee Chair: Prof. Sankar Nair; Committee Co-Chair: Prof. Samuel Graham; Committee Member: Prof. Amyn S. Teja; Committee Member: Prof. Mo Li; Committee Member: Prof. Peter Ludovice.

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15

Guynn, Jerome Hamilton. "Estimation of thermal properties in a medium with conduction and radiation heat transfer." Diss., Virginia Tech, 1996. http://hdl.handle.net/10919/39292.

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The simultaneous estimation of multi-mode heat transfer properties, conductive and radiative, is investigated for materials that include significant heat transfer by radiation. The focus is on insulative type materials with a relatively large optical thickness. Two basic models were developed for the combined conduction and radiation heat transfer: a diffusion solution and a more exact absorbing and isotropically scattering solution. Both solutions were written for one-dimensional heat transfer in gray, isotropically scattering materials. Different experimental setups were compared through a sensitivity analysis of the parameters to determine the best experiment for estimating the properties. An experiment was performed to collect real data to verify estimation procedures. The material used for the experiment was Styrofoam and the experiment consisted of a heat flux supplied by a thin film heater on one boundary and a constant temperature on the other boundary. The thermal capacitance of the heater proved to have an effect on the temperature measurements at the heated surface and had to be incorporated into the model. The estimation procedure involved the use of two methods, the modified Box Kanemasu algorithm and a genetic algorithm. Difficulties were encountered in simultaneously estimating all the properties due to correlation between the thermal conductivity and the radiation parameters, as well as some correlation between the heat capacity of the Styrofoam and the heat capacity of the heater. However, the genetic algorithm did provide fairly narrow and well-defined property ranges and confirmed that radiation transfer was significant in the Styrofoam.
Ph. D.

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16

Morgan, Nathaniel Ray. "A porous medium for structural support and multiphase cooling of high-frequency conductors." Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/16335.

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17

Esen, Ziya. "Production And Characterization Of Porous Titanium Alloys." Phd thesis, METU, 2007. http://etd.lib.metu.edu.tr/upload/3/12608964/index.pdf.

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In the present study, production of titanium and Ti6Al4V alloy foams has been investigated using powder metallurgical space holder technique in which magnesium powder were utilized to generate porosities in the range 30 to 90 vol. %. Also, sintering of titanium and Ti-6Al-4V alloy powders in loose and compacted condition at various temperatures (850-1250oC) and compaction pressures (120-1125 MPa), respectively, were investigated to elucidate the structure and mechanical properties of the porous cell walls present due to partial sintering of powders in the specimens prepared by space holder technique. In addition, microstructure and mechanical response of the porous alloys were compared with the furnace cooled bulk samples of Ti-6Al-4V-ELI alloy subsequent to betatizing. It has been observed that the magnesium also acts as a deoxidizer during foaming experiments, and its content and removal temperature is critical in determining the sample collapse. Stress-strain curves of the foams exhibited a linear elastic region
a long plateau stage
and a densification stage. Whereas, curves of loose powder sintered samples were similar to that of bulk alloy. Shearing failure in foam samples occurred as series of deformation bands formed in the direction normal to the applied load and cell collapsing occured in discrete bands. Average neck size of samples sintered in loose or compacted condition were found to be different even when they had the same porosity, and the strength was observed to change linearly with the square of neck size ratio. The relation between mechanical properties of the foam and its relative density, which is calculated considering the micro porous cell wall, was observed to obey power law. The proportionality constant and the exponent reflect the structure and properties of cell walls and edges and macro pore character.

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18

Wilson, Scott E. "Investigation of Copper Foam Coldplates as a High Heat Flux Electronics Cooling Solution." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/6944.

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Compact heat exchangers such as porous foam coldplates have great potential as a high heat flux cooling solution for electronics due to their large surface area to volume ratio and tortuous coolant path. The focus of this work was the development of unit cell modeling techniques for predicting the performance of coldplates with porous foam in the coolant path. Multiple computational fluid dynamics (CFD) models which predict porous foam coldplate pressure drop and heat transfer performance were constructed and compared to gain insight into how to best translate the foam microstructure into unit cell model geometry. Unit cell modeling in this study was realized by applying periodic boundary conditions to the coolant entrance and exit faces of a representative unit cell. A parametric study was also undertaken which evaluated dissimilar geometry translation recommendations from the literature. The use of an effective thermal conductivity for a representative orthogonal lattice of rectangular ligaments was compared to a porosity-matching technique of a similar lattice. Model accuracy was evaluated using experimental test data collected from a porous copper foam coldplate using deionized water as coolant. The compact heat exchanger testing facility which was designed and constructed for this investigation was shown to be capable of performing tests with coolant flow rates up to 300 mL/min and heat fluxes up to 290 W/cm2. The greatest technical challenge of the testing facility design proved to be the method of applying the heat flux across a 1 cm2 contact area. Based on the computational modeling results and experimental test data, porous foam modeling recommendations and porous foam coldplate design suggestions were generated.

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19

Cunsolo, Salvatore. "Radiative properties computational modeling of porous cellular materials." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEI005/document.

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Les transferts thermiques par rayonnement dans des mousses sont modélisés à partir de la morphologie du matériau et des propriétés de sa phase solide. Dans ce travail de thèse, une attention particulière est portée sur les modèles radiatifs de Monte Carlo. Les différentes approches d’homogénéisation telles que « Homogeneous Phase » (HPA) and « Multi Phase » (MPA) sont discutées et comparées. Des développements novateurs sont proposés pour améliorer la précision des résultats. Nos avancées permettent de générer numériquement trois types de mousses périodiques couvrant un large domaine de matériaux cellulaires: mousse à pores fermés à haute porosité, mousse à cellules ouvertes à basse et haute porosité. Pour ces dernières, des comparaisons morphologiques avec des données expérimentales tomographiques, montrent des résultats satisfaisants et tendent à valider nos modèles de génération. Des mousses dont la phase solide est opaque ont tout d’abord été étudiées. Nos simulations ont permis de trouver de nouvelles lois analytiques précises permettant d’estimer les propriétés radiatives de ces matériaux à partir de données morphologiques. Ensuite, nous avons considéré des mousses, dont la phase solide est semi transparente. La modélisation du transfert radiatif au sein de ces milieux cellulaires est plus complexe. Les méthodes de modélisation des propriétés radiatives de la littérature, HPA et MPA, sont testées. Des simulations de Monte carlo directes dans les matériaux ont permis de mettre en exergue les limites de ces modèles. Des modèles novateurs ont été proposés afin d’ améliorer la précision des simulations. Ils sont basés sur une méthode hybride directe-inverse et une modification de l’équation de transfert radiatif classique. Ces nouveaux modèles (HPA+ et MPA+) ont été testés sur un ensemble varié de morphologies générées numériquement. Les modèles améliorés sont systématiquement plus précis que les modèles existants
Cellular media such as plastic, ceramic and metal foams present specific characteristics that make them interesting for a number of applications related to thermal engineering. Their ability to minimize natural convection makes them ideal candidates for insulation applications, while the high specific surface and permeability to fluid of open cell foams makes them interesting heat transfer enhancers. In addition, their permeability to light makes them an ideal candidate for thermal radiation based applications, such as porous burners or solar energy collectors. In many of these application, thermal radiation heat transfer can have a significant influence on the heat transfer process. Both accurate radiation models and accurate morphological models of the structure of the foam are required. This work provides an original contribution on both these accounts. A discussion of the literature on numerical methods for radiation heat transfer in cellular media is presented, with focus on Monte Carlo methods. Homogeneous Phase (HPA) and Multi Phase (MPA) methods are discussed. Further efforts are required to accurately model and digitally replicate of foam morphologies. Our goal is to digitally generate three commonly occurring types of foam structures, covering a large range of real materials: high-porosity open cell foams, high-porosity closed cell foams, low-porosity open-cell structures. For high-porosity open cell foams, the automated parametric digital generation technique was validated against a dataset consisting of raw morphological data obtained by tomographic analysis. The generation capabilities were then applied to parametrically investigate the influence of morphological parameters on the radiative properties (namely, the extinction coefficient) of an opaque open-cell foam. Highly accurate analytical relationships were subsequently deduced and validated by comparison with results obtained from tomography samples. Modeling radiation in foams with a semi-transparent solid phase is substantially more complex. A Direct Monte-Carlo Homogenization reference technique is proposed, that allows to simulate radiation within arbitrary cavities and calculate macroscopic radiative quantities based on a Representative Elementary Volume (REV) of cellular material. The technique is validated against full scale Monte Carlo simulations. Improvements of the existing Homogeneous Phase and Multi Phase approach are proposed, through extensive use of inverse methods and the addition of one equation to take into account specific phenomena taking place in the semi-transparent solid phase. The resulting Improved Homogenized Approaches are extensively tested by comparing them with Direct Monte Carlo Homogenization simulations and existing homogenized models, on a varied set of morphologies making full use of the previously developed digital generation techniques. The improved models consistently outperform existing homogenized models

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20

Mohiti, Asli Ali. "Analyze and Rebuild an Apparatus to Gauge Evaporative Cooling Effectiveness of Micro-Porous Barriers." Thesis, University of North Texas, 2008. https://digital.library.unt.edu/ark:/67531/metadc9750/.

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The sample used for evaporative cooling system is Fabric defender 750 with Shelltite finish. From the experimental data and equations we have diffusion coefficient of 20.9 ± 3.71 x 10-6 m2/s for fabric with one layer with 17%-20% fluctuations from the theory, 27.8 ± 4.5 x 10-6 m2/s for fabric with two layers with 6%-14% fluctuations from the theory and 24.9 ± 4.1 x 10-6 m2/s for fabric with three layers with 13%-16% fluctuations from the theory. Since the thickness of the fabric increases so the mass transport rate decreases so the mass transport resistance should be increases. The intrinsic mass resistances of Fabri-1L, Fabri-2L and Fabri-3L are respectively 104 ± 10.2 s/m, 154 ± 23 s/m and 206 ± 26 s/m from the experiment.

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21

Crimm, Robert Prentiss. "Experimental apparatus for measuring moisture transfer in porous materials subject to relative humidity and temperature differences." Thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-01122010-020146/.

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22

Xu, Wenyue. "Towards numerical modeling of two-phase flow in seafloor hydrothermal systems." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/26014.

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23

Li, Yang. "Application of cellulose nanowhisker and lignin in preparation of rigid polyurethane nanocomposite foams." Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/44746.

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Cellulose nanowhisker (CNW) prepared by acid hydrolysis of softwood Kraft pulp was incorporated as nanofiller in rigid polyurethane (PU) foam synthesis. The density, morphology, chemical structure, mechanical properties and thermal behavior of the products were characterized. The nanocomposites exhibited better performance especially at high CNW¡¯s content which was probably due to the high specific strength and aspect ratio of CNW, the hydrogen bonding and crosslinking between CNW and polymer matrix, a higher crosslinking density compared to the control, and the function of CNW as an insulator and mass transfer insulator. Lignin polyol was synthesized through oxypropylation and used for rigid PU foam preparation. The density, morphology, chemical structure, compressive property and thermal behavior of the product were characterized. Lingin-based rigid PU foam showed improved compressive property compared to its commercial counterpart. Ethanol organosolv lignin-based PU showed a slightly stronger compressive property than Kraft lignin-based PU. The enhancement was primarily attributed to the rigid phenolic structure and the high hydroxyl functionality of lignin. Lignin-based PU generated more char than common PUs which was possibly related to the better flame retardant property. This study provided an alternative way to valorize the two most abundant biopolymers and resulted in relatively environmentally benign rigid PU nanocomposite foam.

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24

Kong, Lingjun. "Characterization of Mineral Oil, Coal Tar and Soil Properties and Investigation of Mechanisms That Affect Coal Tar Entrapment in and Removal from Porous Media." Diss., Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/5093.

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Mineral oils and coal tars are complex nonaqueous phase liquids (NAPLs), which can serve as long-term sources of ground water contamination. Very limited data are available on mineral oil and coal tar entrapment in and removal from porous media. Thus, the objectives of this research were to evaluate the behavior of these NAPLs in porous media, and investigate the mechanisms governing NAPL entrapment in and recovery from porous media. Quantification of properties of three commercial mineral oils and six MGP coal tars reveals that mineral oils are slightly viscous LNAPLs (density: ~0.88 g/cm3; viscosity: 10-20 cP), whereas coal tars are highly viscous DNAPLs (density: 1.052-1.104 g/cm3; viscosity: 32-425 cP). Measured oil (tar)-water interfacial tensions (IFT) were lower than that of pure NAPLs. Properties of 16 field soil samples (soil particle size distribution, specific surface area, total carbon content, cationic exchange capacity and soil moisture release curves) were characterized. Correlations between residual NAPL saturation and NAPL and soil properties were developed, and show that the entrapment of NAPL dependent upon soil particle size distribution, total carbon content, NAPL viscosity and NAPL-water IFT. Aqueous pH and ionic strength were found to influence the interfacial properties in tar-water-silica systems. At pHs greater than 7.0, observed reduction in contact angle were attributed to the repulsive electrostatic force between coal tar and solid surface. When pH less than 4, hydration forces played a role on the contact angle decrease. The IFT reduction was resulted from the accumulation of surface-active molecules at the tar-water interface. The effect of ionic strength on interfacial properties was not significant below 0.5 M. The effects of temperature and surfactant or surfactant/polymer addition on coal tar removal was investigated by conducting coal tar displacement experiments at three different temperatures (22, 35, and 50??with sequential flushing of water, surfactant and surfactant/polymer. Coal tar removal from porous media was enhanced by elevating temperature and surfactant flushing due to the viscosity and IFT reduction, respectively. Xanthan gum was used as the polymer to increase the viscosity of the displacing fluid. In summary, these results provide tools for the prediction of NAPL entrapment in porous media, and for the selection of remediation strategies for coal tar contaminated source zone.

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25

Grosu, Yaroslav G. "Thermodynamics and operational properties of nanoporous heterogeneous lyophobic systems for mechanical and thermal energy storage/dissipation." Thesis, Clermont-Ferrand 2, 2015. http://www.theses.fr/2015CLF22579/document.

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La thèse est consacrée à l’étude théorique et expérimentale des propriétés thermodynamiques et d'usage de Systèmes Hétérogènes de Lyophobes nanoporeux (SHL) et leurs dépendances en fonction de la température afin de déterminer les conditions optimales et accroître l'efficacité des dispositifs énergétiques à base de SHL. La thèse présente les résultats obtenus dans trois directions principales de recherche: 1. Analyse thermodynamique; 2. Caractéristiques des SHL dans une large plage de température; 3. Stabilité de SHL dans différentes conditions opérationnelles. La gamme maximale de température étudiée est à 2 - 150 °C et 0.1 - 120 MPa pour la pression. En particulier, les résultats comprennent une équation d'état pour décrire des SHL réels qui prend en compte la distribution de taille des pores; les caractéristiques énergétiques de quatre (deux mésoporeux et deux microporeux) SHLs mesurées dans une large plage de température; certains nouveaux régimes de fonctionnement de SHLs ont été étudiés dans des conditions isobares contrôlées; enfin le concept d'utilisation de SHL comme système avec dilatation thermique négative prononcée est proposé
The thesis is devoted to the theoretical and experimental investigations of thermodynamic and operational properties of nanoporous Heterogeneous Lyophobic Systems (HLS) and their temperature dependences in order to determine optimal conditions and increase efficiency of HLS-based energetical devices. The thesis reflects results obtained in three main directions of research: 1. Thermodynamic analysis; 2. Characteristics of HLS in a wide temperature range; 3. Stability of HLS under different operational conditions. Maximum temperature range investigated is to 2 - 150 ° C. Pressure range is 0.1 - 120 MPa. Particularly, results include proposed equation of state for real HLS, which takes into account pore size distribution function; the energetic characteristics of four (two mesoporous and two microporous) HLSs collected in a wide temperature range; some new operation regimes of HLSs were investigated under controlled isobaric conditions; proposed concept of usage of HLS as a system with pronounced negative thermal expansion

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26

SANTOS, WILSON N. dos. "Contribuicao ao estudo da condutividade termica do material ceramico concreto refratario utilizando a tecnica de fio quente com ajustes por regressao nao linear." reponame:Repositório Institucional do IPEN, 1988. http://repositorio.ipen.br:8080/xmlui/handle/123456789/9901.

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Анотація:

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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

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27

Pathak, Mihir Gaurang. "Periodic flow physics in porous media of regenerative cryocoolers." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/49056.

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Pulse tube cryocoolers (PTC) are a class of rugged and high-endurance refrigeration systems that operate without moving parts at their low temperature ends, and are capable of reaching temperatures down to and below 123 K. PTCs are particularly suitable for applications in space, guiding systems, cryosurgery, medicine preservation, superconducting electronics, magnetic resonance imaging, weather observation, and liquefaction of gases. Applications of these cryocoolers span across many industries including defense, aerospace, biomedical, energy, and high tech. Among the challenges facing the PTC research community is the improvement of system efficiency, which is a direct function of the regenerator component performance. A PTC implements the theory of oscillatory compression and expansion of the gas within a closed volume to achieve desired refrigeration. An important deficiency with respect to the state of art models dealing with PTCs is the limited understanding of the hydrodynamic and thermal transport parameters associated with periodic flow of a cryogenic fluid in micro-porous structures. In view of the above, the goals of this investigation include: 1) experimentally measuring and correlating the steady and periodic flow Darcy permeability and Forchheimer’s inertial hydrodynamic parameters for available rare-Earth ErPr regenerator filler; 2) employing a CFD-assisted methodology for the unambiguous quantification of the Darcy permeability and Forchheimer’s inertial hydrodynamic parameters, based on experimentally measured steady and periodic flow pressure drops in porous structures representing recently developed regenerator fillers; and 3) performing a direct numerical pore-level investigation for steady and periodic flows in a generic porous medium in order to elucidate the flow and transport processes, and quantify the solid-fluid hydrodynamic and heat transfer parameters. These hydrodynamic resistances parameters were found to be significantly different for steady and oscillatory flows.

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28

Kumar, Prashant. "Investigation of Kelvin-like solid foams for potential engineering applications : an attractive set of geometrical and thermo-hydraulic properties." Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4730/document.

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Анотація:

Les mousses à cellules ouvertes ont diverses applications industrielles, par exemple pour des échangeurs de chaleur, des réacteurs structurés, la filtration, la catalyse, récepteurs solaires volumétriques en raison de leurs propriétés uniques telles qu'une importante porosité et une surface spécifique élevée. Pour déterminer théoriquement la surface spécifique géométrique et les relations entre les paramètres géométriques de mousses, une corrélation mathématique généralisée a été développée. A cet effet, la géométrie de la tetrakaidecahedron a été utilisé et différentes formes de sections transversales de brins de structures en mousse ont été pris en compte de façon explicite. La corrélation dérivée pour prédire les propriétés géométriques peut facilement être étendue à des formes différentes. Des simulations numériques 3-D à l'échelle des pores ont été réalisées pour étudier la perte de charge et la conductivité effective thermique. L'écoulement du fluide à travers la mousse à cellule ouverte a été réalisé dans trois régimes différents: les régimes de Darcy, transitoire et inertiel. L'importance des propriétés géométriques sur les caractéristiques d'écoulement de fluide et leurs inclusions dans les corrélations proposées pour prédire la perte de charge est discutée. La question « Les paramètres d'Ergun peuvent-ils avoir des valeurs numériques constantes ou non ? » est discutée. Trois différentes corrélations étaient dérivées pour prédire la conductivité thermique effective à la fois isotrope et anisotrope des mousses. Les paramètres géométriques de la matrice de mousse étaient introduits dans les corrélations pour prédire la conductivité thermique effective
Open cell foams have diverse industrial applications e.g. heat exchangers, structured reactors, filtration due to their unique properties such as high porosity and high specific surface area. In order to theoretically determine the geometric specific surface area and relationships between geometrical parameters of isotropic open cell foams, a generalized mathematical correlation was developed. For this purpose the tetrakaidecahedron geometry was used and different shapes of strut cross-sections of foam structures were taken explicitly into account. The derived correlation to predict geometrical properties can be easily extended to different strut shapes. 3-D numerical simulations at pore scale were performed to study the pressure drop characteristics and effective thermal conductivity. Fluid flow through open cell foam was performed in three different regimes: Darcy regime, transition regime and inertia regime. Importance of geometrical properties on fluid flow characteristics and their inclusion in the proposed correlations for predicting pressure drop is discussed. "Can Ergun parameters have constant numerical values or not" is also extensively discussed. Three different correlations were derived to predict the effective thermal conductivity for both, isotropic and anisotropic open cell foams. Geometrical parameters of foam matrix were introduced in the correlations to predict effective thermal conductivity

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29

Jorge, Alexandre Fonseca. "Fabricação, por tixo-infiltração, de materiais de baixa densidade a partir da liga AA7075 e caracterizacao de suas propriedades físicas e mecânicas." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263689.

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Анотація:

Orientadores: Maria Helena Robert, Antonio Celso Fonseca de Arruda.
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: Este trabalho teve como objetivo estudar o processo de produção de esponjas metálicas e compósitos de baixa densidade por tixoinfiltracao. A liga metálica AA7075 foi submetida a uma analise de tixohabilidade, na qual foi observada sua adequação ao processo e foi definida a temperatura de trabalho para a infiltração. A produção das amostras consistiu em infiltrar a pasta tixotropica da liga AA7075 sobre bloqueadores removíveis (partículas de NaCl), para a produção das esponjas, e sobre bloqueadores não-removíveis de materiais cerâmicos porosos (vermiculita e cinasita), para a produção dos compósitos. Todas as esponjas metálicas e compósitos produzidos foram caracterizados quanto a sua arquitetura interna, propriedades físicas, térmicas e mecânicas. Os resultados mostraram em todos os casos uma boa qualidade geral dos produtos e uma boa repetibilidade do processo. O comportamento de todos os materiais produzidos em compressão estática ou dinâmica se mostrou próximo do comportamento típico de materiais celulares, com grande platô de deformação plástica ocorrendo com valores relativamente baixos de tensão. A analise das curvas obtidas nos ensaios de compressão semi-estática e compressão dinâmica, em conjunto com imagens de amostras parcialmente comprimidas, forneceu informações sobre os prováveis mecanismos de deformação envolvidos, incluindo o papel dos materiais de reforço. Adicionalmente, foi proposto um equacionamento para a condutividade térmica, dos compósitos, cujos resultados se mostraram satisfatoriamente correlacionados com os experimentais
Abstract: This work had the objective to study the process of production of open-cell metallic foams and low-density composites by thixoinfiltration. The AA7075 alloy underwent a thixoability analysis, in which it was observed its adequation to the process, and the working temperature for the infiltration was defined. The samples production consisted in infiltrating the thixotropic slurry of AA7075 alloy into removable space-holders (NaCl particles) for the production of the foams, and into non-removable space-holders of porous ceramic materials (vermiculite and expanded clay) for the production of the composites. All the foams and composites produced were characterized according to their internal architecture, physical, thermal, and mechanical properties. The results in all cases showed a good quality of the products in general, and a good repeatability of the process. The behavior of all the produced materials under semi-static and dynamic compression remained similar to the typical behavior of cellular materials, with a large plastic deformation plateau occurring with relatively low stress levels. The analysis of the obtained curves from the semi-static and dynamic tests, together with images from partially compressed samples, gave information about the possible deformation mechanisms involved, including the role of the reinforcement materials. Furthermore, a calculation for the thermal conductivity of the composites was proposed, with their results satisfactorily correlated to experimental data
Doutorado
Materiais e Processos de Fabricação
Doutor em Engenharia Mecânica

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30

Imbert, Claire. "Matériaux à propriétés mécaniques et thermiques améliorées sous pression hydrostatique en utilisation aquatique." Thesis, Montpellier 2, 2010. http://www.theses.fr/2010MON20019.

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Les matériaux aujourd'hui utilisés pour l'isolation thermique en milieu aquatique sous pression hydrostatique sont soit des mousses souples à base de caoutchoucs, soit des mousses rigides, notamment syntactiques, selon la profondeur. Ces matériaux souples ont été analysés par des tests mécaniques et thermiques classiques. Cependant, les protocoles et valeurs relevées ont été adaptés à l'usage final du produit, et plus particulièrement à l'environnement aquatique en surface et en profondeur. Les relations entre les différentes caractéristiques (structures et propriétés) de ces matériaux ont été étudiées afin de définir les propriétés adéquates selon des critères pertinents. Pour mettre en évidence les propriétés thermiques sous pression hydrostatique, un outil de test a de plus été développé : une enceinte de test hyperbare innovante, pour l'évaluation de la résistance thermique et de l'épaisseur sous pression d'eau entre 0 et 50 m de profondeur. Les points forts et faibles des matières classiquement utilisées ont été clairement établis. L'analyse de ces résultats a permis d'identifier un concept de matériau composite propre à l'usage défini. Une matière innovante a été conçue en fonction : une mousse syntactique. En variant le type de particules additionnées à une matrice thermoplastique élastomère, la structure cellulaire a été affinée pour obtenir un comportement identique en milieu aquatique, en surface comme en profondeur. En parallèle de sa production industrielle, cette matière a été testée afin d'identifier les relations entre structures et propriétés
Materials nowadays used for thermal insulation in aquatic environment under hydrostatic pressure are either rubber flexible foams or rigid foams, especially syntactic foams, depending on depth. These flexible materials were analyzed through classical mechanical and thermal tests. However, methods and results were adapted to the final usage of the product, particularly to the aquatic environment at the surface and under depth. Relationships between structures and properties characteristics were studied to define appropriate properties within relevant criteria. Moreover, to underline thermal properties under hydrostatic pressure, a testing instrument has been developed: an innovating hyperbaric test chamber, dedicated to under water pressure thermal resistance and thickness measurements, from 0 to 50 m depth. Strengths and weak points of these classical materials have been clearly established. Results analysis lead to a new concept of composite material for the defined usage. This innovating material, a syntactic foam, has been developed. By varying the particle type added to a thermoplastic elastomer matrix, the cellular structure has been refined in order to obtain a similar behaviour in aquatic environment, at the surface like in depth. This material has been tested, parallel to its industrial production, to identify relationships between structures and properties

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31

Khan, Amir. "Vibro-acoustic products from re-cycled raw materials using a cold extrusion process : a continuous cold extrusion process has been developed to tailor a porous structure from polymeric waste, so that the final material possesses particular vibro-acoustic properties." Thesis, University of Bradford, 2008. http://hdl.handle.net/10454/4289.

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A cold extrusion process has been developed to tailor a porous structure from polymeric waste. The use of an extruder to manufacture acoustic materials from recycled waste is a novel idea and the author is not aware of any similar attempts. The extruder conveys and mixes the particulates with a reacting binder. The end result is the continuous production of bound particulates through which a controlled amount of carbon dioxide gas that is evolved during the reaction is used to give the desired acoustic properties. The cold extrusion process is a low energy consuming process that reprocesses the post manufacturing waste into new vibro-acoustic products that can be used to meet the growing public expectations for a quieter environment. The acoustical properties of the developed products are modelled using Pade approximation and Johnson-Champoux-Allard models. Applications for the developed products are widespread and include acoustic underlay, insulation and panels in buildings, noise barriers for motorways and railway tracks, acoustic insulation in commercial appliances and transport vehicles.

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32

Vaněk, Lukáš. "Vývoj pokročilých tepelně izolačních omítek s možností uplatnění jako sanační omítky dle WTA." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2014. http://www.nusl.cz/ntk/nusl-226722.

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The theoretical part of the thesis is devoted to the issue thermal insulation plasters which can be applied in the remediation of buildings. The practical part deals with optimizing the composition of thermal insulation plaster-based lightweight aggregate of the foam glass and with possible substitution of cement for other binders with latent hydraulic properties. The resultant plaster should meet the best ratio of mechanical and thermal insulating properties.

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33

RAMBO, CARLOS R. "Sintese e caracterizacao de ceramicas biomorficas." reponame:Repositório Institucional do IPEN, 2001. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10973.

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Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

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34

Perret, Anouk. "Méthodologie de caractérisation microstructurale 3D de matériaux poreux structurés pour la thermique." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0042/document.

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Depuis 30 ans, les exigences règlementaires en matière d’isolation thermique des bâtiments augmentent sans cesse. Pour mieux isoler, et conserver la surface habitable et la valeur patrimoniale, il est nécessaire d’augmenter les performances des isolants thermiques. Si les meilleurs systèmes classiques d’isolant atteignent désormais des conductivités thermiques proches de 30 mW/(m.K), les matériaux supers isolants à pression atmosphérique affichent moins de 18 mW/(m.K) et sont à base d’aérogels de silice. Cette matière première doit ses excellentes performances thermiques, à d’une part la taille de ces nanopores inférieure à 70nm, et d’autre part leur très forte quantité. Ceci induit par contre de très faibles propriétés mécaniques, les systèmes super isolants formulés avec des aérogels sont donc toujours des composites : empilement granulaire faiblement lianté. Pour développer l’optimisation de ces formulations, il est nécessaire de disposer d’outils de caractérisation microstructurales multiéchelles dédiés aux aérogels et au suivi pas à pas des étapes d’élaboration post synthèse. Ce travail de thèse a pour objectif de les mettre en place et de les valider. Les matériaux supports de cette thèse, sont des aérogels de silice hydrophobes granulaires et deux formulations liantées en phase aqueuse. Ces formulations architecturées, par une faible fraction volumique de liant organique de taille nanométrique, se distinguent par la taille et le type de surfactant employé, et les performances tant thermiques que mécaniques obtenues. Tout d’abord, le réseau poreux de silice à l’échelle nanométrique a été imagé et caractérisé par tomographie électronique. Cette partie vise à fournir une distribution en taille de pores, particules et agrégats, destinée à alimenter des modèles thermo-mécaniques. Dans un second temps, l’empilement granulaire des aérogels non liantés a été étudié par tomographie aux rayons X. Les résultats de compacité, les morphologies des réseaux de pores, et de grains ont été couplés aux mesures de masse volumique et de porosité inter-granulaire afin de dégager un lien entre microstructure de l’empilement granulaire et conductivité thermique mesurée. Enfin, les interactions aérogels de silice/liant sont imagées en utilisant l’ESEM wet-stem. Une méthodologie quantitative permet ensuite de s’assurer que le surfactant employé induit bien d’une part une dispersion homogène des aérogels, et d’autre part un réseau texturé de liant. Pour conclure, les propriétés thermiques et mécaniques sont mesurées sur les composites référence et des composites innovants avec une étude détaillée des microstructures formées en synergie. Des pistes d’optimisation matériau par opacification intra-granulaire des aérogels sont proposées, un nouveau surfactant est infirmé. Les outils développés valident ainsi leur pertinence pour assurer la qualification des futures formulations de matériaux super isolants
The national objectives on the reduction of the rejections of greenhouse gases bring to the necessity of a thermal renovation for 75 % of the French buildings. As the requirements for old and new buildings increase their standards, design thinner and more efficient insulation materials is of great and increasing interest. New insulating materials with thermal conductivities lower than the still dry air (25 mW / (m. K)), such as based silica xerogel products (15 mW / ( m.K )), recently developed, are an interesting choice to answer those new fonctionnalities. In our study, silica xerogels (porosity > 80 %, specific surface > 600 m ²/g) are available as granular materials and binded stiff composite boards (xerogels / latex). The optimization of these materials requires to understand the link between their microstructure, their thermal conductivity and their mechanical behaviour

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35

Hannaoui, Rachid. "Simulation par Dynamique Moléculaire des Propriétés de Transport (Masse et Chaleur) de Fluides Confinés." Thesis, Pau, 2012. http://www.theses.fr/2012PAUU3010/document.

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Le comportement d’un fluide confiné dans un milieu poreux peu perméable (micro- and méso-pores) a été étudié en ce qui concerne ses propriétés de diffusion de masse, de conductivité thermique et de thermodiffusion. Pour ce faire des simulations de dynamique moléculaire hors équilibre ont été réalisées sur des mélanges binaires modèles placés dans des conditions thermodynamiques diverses, confinés dans des milieux poreux de géométrie lamellaire de différentes natures (lisse ou atomique, plus ou moins adsorbant) en utilisant l’ensemble __//_ et l’ensemble grand canonique. Les résultats ont montré que les effets du milieu poreux sur les propriétés de transport sont d’autant plus marqués que lataille de pore est petite, que l’adsorption est forte et que la température est basse. Les résultats ont permis d’évaluer quantitativement ces effets. Il a aussi été montré que la rugosité des murs a un impact très important sur le coefficient de diffusion de masse et non négligeable sur celui de thermodiffusion
The aim of this work was to study how a fluid confined in a low permeability porous medium (micro- and meso-porous) behaves concerning its properties of mass diffusion, thermal conductivity and thermal diffusion. For this purpose, non-equilibrium molecular dynamics simulations have been performed on simple binary mixtures placed in various thermodynamic conditions, confined in a porous medium of lamellar geometry of different types (structure-less or atomistic, more or less adsorbent) in __//_ and grand canonical ensembles. The results show that the effects of porous medium on transport properties are more pronounced when the pore size is small, the adsorption is strong and the temperature is low. The results allowed to evaluate these effects quantitatively. In addition, it has been found that the wall roughness has a major impact on the mass diffusion coefficient and a non negligible one on the thermal diffusion coefficient

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36

Juvenal, Frank. "Polymères de coordination luminescents 1D et 2D avec des ligands rigides contenant du Pt(II) montrants des propriétés d’adsorption du CO2." Mémoire, Université de Sherbrooke, 2017. http://hdl.handle.net/11143/10578.

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La conception de nouveaux matériaux fonctionnels a une longue histoire. Durant les deux dernières décennies, le domaine des polymères organiques et inorganiques a attiré l'attention des chercheurs. Plus important encore, les matériaux poreux tels que les Metal Organic Frameworks (MOFs), en anglais, Covalent Organic Frameworks (COFs), en anglais, ainsi que des polymères de coordination poreux sont maintenant étudiés de manière intensive en raison de leurs applications potentielles, comprenant le stockage de gaz, la séparation de gaz, la catalyse et la détection. D'un autre côté, les polymères contenant du Pt ont montré l'application potentielle dans les cellules solaires et les diodes électroluminescentes. Le mémoire est divisé en trois sections principales présentant des résultats nouveaux. Dans la première section, le chapitre 2 traite essentiellement de la formation de polymères de coordination (CP) avec des sels CuX (X = Cl, Br, I) et trans-[p-MeSC6H4C≡C-Pt(PMe3)2-C≡CC6H4SMe] (L1), soit dans le PrCN ou PhCN. Les polymères résultants sont soit 2D (bidimensionel) ou 1D (unidimensionel). Cependant, en presence de PrCN ou de PhCN, le CP 2D obtenu avec le CuBr n'a pas incorporé de solvant dans ses espaces vides. D'autre part, le CP 2D et le reste des CP 1D obtenus avaient soit des molécules de solvant de cristallisation dans leurs cavités ou coordonnés au cuivre sur la chaîne. Les unités cuivre-halogénures étaient soit des rhomboïdes Cu2X2 ou le cubane Cu4I4. Leurs mesures photophysiques en présence et en l'absence de molécules de solvant de cristallisation ont été effectuées. En outre, la porosité du CP a été évaluée par BET (N2 à 77 K). Le vapochromisme du CP 2D sans solvant et des CP 1D ont été étudiés, ainsi que les mesures de sorption du CO2 ont été effectuées. De plus, nous avons utilisé CuCN et L1 dans MeCN pour former de nouveaux CP’s. Ceci est rapporté dans la deuxième section, le chapitre 3. Le CP obtenu était inattendu : L1 s’est rompu et du cyanure CN‾ s’est coordonné sur le Pt. Ceci a conduit à la formation d’un CP 1D zigzag. Généralement, les CP sont formés avec L1 via des liens Cu-S ou/et Cu([éta]2-C≡C), mais pas dans le cas du CuCN qui lui forme une chaîne 1D (CuCN)n où le L1 rompu se lie avec cette chaîne via un lien Cu-N. Les propriétés photophysiques et de stabilité thermique ont été étudiées. La troisième section (Chapitre 4) traite d'une exploration des CP formés par la reaction des sels CuX (X = Cl, Br, I) et le trans-[p-MeSC6H4C≡C-Pt(PMe3)2-C≡CC6H4SMe] (L1) ou le trans-[p-MeSC6H4C≡C-Pt(PEt3)2-C≡CC6H4SMe] (L2) dans du MeCN afin de trouver des tendances. L'utilisation de L1 a donné lieu à un CP 2D ou 1D CPs avec le MeCN piégé à l'intérieur des cavités, il y a de l’espace vide. L2 a conduit uniquement à des CP 1D sans molecules de solvant de cristallisation. Des analyses thermogravimétriques, photophysique et des mesures d’adsorption de gaz (uniquement pour ceux avec du solvant) ont été étudiées.
Abstract: The design of new functional materials has a long history. For the past two decades, the field of organic and inorganic polymers has attracted attention of researchers. More importantly, porous materials such as Metal Organic Frameworks (MOFs), Covalent Organic Frameworks (COFs) as well as porous coordination polymers are now being intensively studied due to their potential applications including gas storage, gas separations, catalyst and sensing. On another hand, Pt-containing polymers have shown potential applications in solar cells and light emitting diodes. The masters’ thesis is mainly divided into three main sections presenting new results. In the first section; Chapter 2 mainly discusses the formation of coordination polymers with CuX salts (X= Cl, Br, I) and trans-[p-MeSC6H4C≡C-Pt(PMe3)2-C≡CC6H4SMe] (L1), in either PrCN or PhCN. The resulting polymers obtained were 2D (bidimensional) CPs or 1D (unidimensional) CPs in all cases. However, 2D CPs obtained when CuBr salt is used by either using PrCN or PhCN did not incorporate the solvents in their cavities. On the other hand, the 2D CP and the rest of 1D CPs obtained had either the crystallization molecules in the cavities or coordinated to the copper cluster. The copper-halide clusters were either the rhomboids Cu2X2 fragments or the step cubane Cu4I4. The photophysical measurements in the presence and absence of solvent crystallization molecules were performed. In addition, the porosity of the CPs was evaluated by adsorption isotherms. The vapochromism of the solvent-free 2D and 1D CPs were investigated as well as CO2 sorption measurements were perfomed. Furthermore, we then attempted to use CuCN and L1 in MeCN which is reported in the second section as Chapter 3. The obtained CP was unexpected as L1 broke and a cyanide (CN‾) ion coordinated to the Pt atom leading to the formation of zigzag 1D CP. The coordination bonds Cu-S or/and Cu([eta]2-C≡C) were generally observed with L1, but not in the CuCN case. Instead a 1D chain of (CuCN)n was made and the broken L1 now binds the chain via a Cu-N bond. The photophysical and thermal stability properties were studied. Lastly, the third section, Chapter 4 deals with a potential predictability of CP formation by using CuX salts (X= Cl, Br, I) and either trans-[p-MeSC6H4C≡C-Pt(PMe3)2-C≡CC6H4SMe] (L1) or trans-[p-MeSC6H4C≡C-Pt(PEt3)2-C≡CC6H4SMe] (L2) in MeCN as the solvent. The use of L1 resulted in either 2D or 1D CPs with the MeCN trapped inside of the cavities while L2 resulted in 1D CPs without MeCN being present in their cavities. The thermogravimetric, photophysical as well as gas sorption measurements (only for those with crystalisation molecules) were perfomed.

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37

Fedosse, Zornio Clarice. "Ionic liquids as multifuncional additives for poly(methyl methacrylate)-based materials." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI041/document.

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La vaste gamme de combinaisons possibles de cations et anions, ainsi que les excellentes propriétés intrinsèques des liquides ioniques (LIs) peuvent être considérées comme les principaux facteurs qui ont conduit au développement d’une recherche utilisant des LIs comme additifs des matériaux polymère. Ainsi, l'objectif principal de ce travail est d'explorer le rôle de la nature du cation et/ou du anion du LI sur les propriétés des matériaux basées de poly (méthacrylate de méthyle) (PMMA). Dans une première partie, des LIs de type imidazolium et ammonium ont été incorporés au PMMA et des caractérisations morphologiques et structurales ont été effectuées afin de comprendre leur impact sur les propriétés thermiques, viscoélastiques et mécaniques des matériaux résultants. Dans la section suivante, la capacité de ces LIs à base d'imidazolium et d'ammonium en tant qu’agents interfaciaux à la surface de la silice a été évaluée. Sub-micro et nanoparticules de silice, ainsi que les LIs, ont été incorporées dans une matrice de PMMA afin de préparer des composites. L'amélioration des propriétés des matériaux ont été discutées en fonction du degré auquel chaque LI influence la compatibilité entre les particules et la matrice polymère. De plus, ces composites ont été exposés au dioxyde de carbone en état supercritique (scCO2) pour utiliser celui-ci comme agent moussant et ainsi produire des matériaux expansés. Le rôle du LI et des particules de silice pour structurer les matériaux expansés a été analysé. Dans la dernière partie de cette étude, le scCO2 est utilisé comme milieu de réaction pour la modification chimique par greffage de la surface des nanoparticules de silice par des LIs de type imidazolium, contenant également des groupes hydrolysables et différentes chaînes alkyles. Le rôle de la pression et la quantité de LI ajoutées au milieu de réaction, ainsi que la longueur de la chaîne alkyle des LIs se sont avérées essentielles pour contrôler le degré de fonctionnalisation des nanoparticules. Enfin, ces nanoparticules modifiées ont été incorporées dans une matrice PMMA. Des analyses de morphologie ont été utilisées pour évaluer la dispersion des particules dans la matrice et les propriétés physico-chimiques de ces matériaux ont été également étudiées
The large array of cation/anion combinations, and the excellent intrinsic properties of ionic liquids (ILs) open a large range of possibilities in their use as additives to polymer materials. Thus, the main objective of this work is to explore the role of both the cation and anion of a series of ILs on the properties of poly(methyl methacrylate) (PMMA)-based materials. In a first approach, low amounts of imidazolium and ammonium-based ILs were incorporated as additives to PMMA in the molten state. Morphological and structural characterizations were developed in order to understand the impact of the presence of such ILs on the thermal and mechanical properties of the resulting materials. Then, in the following section, the ability of the same imidazolium and ammonium-based ILs as physical modifiers of silica surface was evaluated. In such an approach, ILs were supposed to act as interfacial agents. Sub-micron and nanosize silica particles were used to prepare PMMA composites. Thus, the extents of each IL improve the interfacial interaction between PMMA and silica particles were discussed. In addition, supercritical carbon dioxide (scCO2) was used as foaming agent to produce foamed PMMA-based composites. In such a case, the combined effect of the presence of ILs and silica particles was analyzed regarding the morphology of the foamed structures. In the last section, scCO2 was used as reaction medium, in an environmental friendly approach, to chemically modify silica nanoparticles using a series of imidazolium IL-functionalized silanes (with different alkyl chain lengths). Thermogravimetric analysis (TGA) was used to highlight the effect of the working pressure and the content of such ILs in the reaction medium. The effect of the alkyl chain length on the grafting density of the resulting nanoparticles was also discussed. Finally, novel PMMA-based nanocomposites were prepared by the incorporation of such grafted nanoparticles. Transmission electron microscopy (TEM) and small-angle neutron scattering (SANS) analyses were used to evaluate the state of dispersion of the particles into the polymer matrix. Moreover, the thermal, rheological and mechanical properties of the materials were studied

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38

Abuaisha, Murad S. "Géothermie profonde : stimulation de la perméabilité par fracturation hydraulique dans un cadre thermo-poroélastique." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENI016/document.

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Ce travail concerne l'utilisation de la technique de Fracturation Hydraulique (FH) pour exploiter l'énergie géothermique des réservoirs profonds de roches sèches chaudes (HDR). La fracturation hydraulique est réalisée par injection de fluides géothermiques dans des réservoirs partiellement fracturés de faible perméabilité. Les fluides à haute pression sont destinés à faire évoluer les fissures et leur connectivité. Les valeurs de débit/pression auxquelles les fluides géothermiques doivent être pompés, ainsi que le calendrier de pompage pour initier la fracturation hydraulique, dépendent principalement des conditions géostatiques existantes (contraintes géostatiques, pression fluide et température initiales de l'HDR) ainsi que des propriétés des fissures de l'HDR (longueur, épaisseur, densité et distribution directionnelle initiales moyennes de fissures). Tous ces éléments, en sus de leurs effets sur la stabilité des forages, sont analysés dans cette recherche. Des modèles de fracturation, qui sont capables de suivre l'évolution des fissures dans toutes les orientations spatiales possibles, sont utilisés pour obtenir le tenseur anisotrope de perméabilité. Ces modèles sont intégrés dans un code domestique d'éléments finis qui est développé pour résoudre des problèmes aux limites thermo-poroélastiques. Pour supprimer/diminuer les oscillations qui accompagnent les solutions paraboliques et/ou hyperboliques lors de la convection forcée, plusieurs techniques de stabilisation ont dû être implémentées
The application of the Hydraulic Fracturing (HF) technology to exploit geothermal energy from Hot Dry Rocks (HDR) reservoirs is addressed. HF is achieved by extensively pumping geothermal fluids to already existing fractured HDR reservoirs of low permeability. High fluid pressures are expected to drive cracks to evolve and connect. The newly created burgeoning hydraulic conduits should supposedly enhance the permeability of the existing HDR reservoirs. The flow rate/pressure values at which geothermal fluids should be pumped, as well as the pumping schedule to initiate HF, depend primarily on the existing geostatic conditions (geostatic stresses, initial HDR pressure and temperature) as well as on HDR fracture properties (initial mean fracture length, mean fracture aperture, density and orientational distribution of fractures). While these components, in addition to their effects on borehole stability, are scrutinized in this research, focus is on the evolution during circulation processes of the fracture properties. A fracturing model that is capable of tracking fracture evolution in all possible spatial orientations is used to obtain the time course of the anisotropic permeability tensor. This evolving property is integrated into a domestic finite element code which is developed to solve thermo–poroelastic BVPs: emphasis is laid on the efficiency of the doublet flow technique where a fluid gains thermal energy by circulating through the HDR reservoir from the injection well to the production well. The spurious oscillations in the hyperbolic solutions of the approximated finite element approach that are commensal with the phenomenon of forced heat convection are healed/mitigated through several stabilization approaches

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39

Sulong, Mohd Ayub. "Characterisation of advanced porous materials." Thesis, 2015. http://hdl.handle.net/1959.13/1309835.

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Research Doctorate - Doctor of Philosophy (PhD)
Advanced porous materials are a new group of materials where the desired properties can be controlled and even tailored. These interesting materials offer a vast field of applications, thanks to their multi-functional abilities. Several types of advanced porous structures including cellular metals and ceramic porous materials are the focus of the present investigation. Corevo® foam and perlite metallic syntactic foam are investigated in this thesis and manufactured from infiltration casting. In addition, advanced pore morphology foam elements are addressed that are fabricated using thermal expansion of a thin wire-shaped precursor. Ceramic porous structures specially developed (via foam replication) for tissue engineering scaffolds are also studied within the scope of this work. Given the similarity of the geometrical structure of all these materials, the same mechanical characterisation approaches are adopted to assess their mechanical properties. The materials properties are determined for quasi-static and dynamic compression for both small and large strain deformation. Numerical simulations are performed by making use of the highly accurate models obtained from micro-computed tomography data. Where possible, numerical results are verified by the findings of experimental testing. Detailed analysis is included in each chapter elaborating the result from the numerical simulations and the compressive loading test. Versatile tools such as electron microscopy, image based geometry analyser software and IR-thermal imaging are utilised to assist the study. The results show that all cellular metals investigated in this thesis exhibit the characteristic stress-strain curve of metallic foams. This means that a linear slope is found in the beginning of the compression loading, this is followed by a long plateau region indicating energy absorption capability and ends with a steep slope at the end representing the densification. Corevo® foam exhibits a significant amount of mechanical anisotropy in casting direction under quasi-static compressive loading. The degree of mechanical anisotropy is considered mild for perlite metallic syntactic foam in the casting direction under the same loading condition. Foam materials (Corevo® and advanced pore morphology foam element) characterised under dynamic loading show a strain-rate dependence property. Last, but not least, a possible extension of the present research is proposed at the end of this thesis in the Conclusions and Outlook section.

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40

Vijay, Dig. "Forced convective heat transfer through open cell foams." Doctoral thesis, 2016. https://tubaf.qucosa.de/id/qucosa%3A23120.

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The purpose of this study is to investigate forced convection of air through open cell foams. It can be numerically investigated either by implementing the time efficient macroscopic models or computationally expensive microscopic models. However, during the course of this study, it was observed that the macroscopic models are not sufficient for determining the desired key parameters. Nevertheless, it is still possible that these macroscopic models can be used to design an application accurately with minimum time efforts if the concerned key parameters are already known through other means. Accordingly, in this work, a methodology is developed to determine the desired key parameters by implementing the microscopic models, which are further used into the macroscopic models for designing different applications. To validate the proposed methodology, a set of steady state and transient forced convection experiments were performed for a set of ceramic foams having different pore diameter (10−30 PPI) and porosity (0.79−0.87) for a superficial velocity in the range of 0.5−10 m/s.

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41

LIhsing-Lee and 李力行. "Thermal properties of porous silicon and metal membranes." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/85340930466279658590.

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碩士
中國文化大學
材料科學與奈米科技研究所
95
Present day, many of the 3C product become more and more small and powerful so that the plenty of heat will be bring out from computer or other 3C products as we use. In this study, using chemical etching wafer to produce porous silicon and to determine their thermal properties was main idea. There are four part of this essay. There were different kinds of subject to discuss in first part which was discussed different structures from using lighting or heating to etching wafer. In the second part, by using super crystal fluid (SCF), the reduction of particle of silver would be put into pore of porous silicon. And then, there was discussed annealing porous silicon after SCF in the third part. The last step, it was determined structure, thermal properties, and relation of voltage-current. Finally, the specimen which was decided that thermolysis property was better than others was prepared by heating chemical etching for 1hr at 65℃.And specimen was improved thermolysis property and relation of voltage-current by filled in nano-silver though SCF.

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42

Huang, Szu-Yao, and 黃思瑤. "Thermal properties of thermoplastic polyurethanes foam composed with different soft segments." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/c97cjv.

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碩士
國立臺灣科技大學
材料科學與工程系
106
Thermoplastic polyurethanes (TPU) are linear segment block coploymers composed of soft and hard segments, the thermodynamic incompatibility between the soft and hard segments causes microphase separation. Such a microstructure provides TPU various properties. In recent years, expanded TPU (ETPU) bead foam appeared on the market, which has the advantages of lightweight, wear resistance, high elasticity and recyclable. The most important advantage of bead foam material is that it can prepare 3D foaming material with high expansion ratio. The foam beads are sintered using high temperature steam. The double melting peaks is the important feature for elastomeric or crystalline polymers to be sintered. In this experiment, three different soft segments of TPUs were synthesized to prepare low-density foam materials. TPU was synthesized by the two-step method using PTMEG, PPG and PBA three different polyols as soft segments. MDI and BD were applied as hard segments. The synthesized TPUs were foamed by the one-step batch foaming using CO2 as the blowing agent. TPU was saturated at high temperature for a certain period of time before foaming. It is known that thermal processing has a great influence on the TPU structure. Therefore, series heat treatments were performed on the solid and foamed TPU and then analyzed by DSC. The results showed that the three TPUs has almost the same trend with saturation temperature. The relationship between different saturation temperature and saturation time and cell morphology is discussed. After foaming, two distinct endothermic peaks were observed on DSC graph, which is suitable for bead foam sintering.

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43

Benkreira, Hadj, Amir Khan, and Kirill V. Horoshenkov. "Sustainable acoustic and thermal insulation materials from elastomeric waste residues." 2011. http://hdl.handle.net/10454/9042.

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Анотація:

No
This study presents the data elements to develop a new processing route to transform elastomeric waste residue (particulates) into acoustic and thermal insulation materials that can compete with commercial products. The approach is to bind these grain and fibre particulates with a foaming polyurethane or a similar polymer, the chemistry of which can be manipulated to control the structure stiffness and the evolution of the foaming gas into open or closed cells. Here the study uses two examples of such residues, tyre and carpet shreds both composed of fibres trapping grains of either rubber or PVC. Compounds were made from these systems with different PU binders and the structural properties (density, porosity, air flow resistivity, tortuosity and stiffness) and performance properties (sound absorption, sound transmission, impact sound insulation and thermal conductivity) were measured as a function of binder loading and chemistry. The data obtained show clearly that performance can be tailored by tailoring structural properties resulting with materials that match or even outperform commercial products. The data set obtained here can be usefully exploited with available acoustic and thermal insulation materials model to take the approach further and extended to other waste systems.

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44

Zhang, Zhong Xing, and 張中興. "Investigation of flow and thermal properties of porous medium flow." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/57570842203612560959.

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45

Chen, Shin-Liang, and 陳信良. "Thermal Properties of Porous Aluminum Plates Fabriced by Recycled Aluminum Alloy." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/12306505536661647406.

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46

Lin, Shing-An, and 林信安. "Analysis on the thermal properties of asymmetric porous silicon using phonon Boltzmann equation." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/48408959424408511327.

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碩士
國立中央大學
機械工程學系
104
Porous silicon has tremendous applications in different engineering fields, especially its low thermal conductivity property which can be used as insulated materials. Besides, such low thermal conductivity also has potential applications in thermoelectric materials and thermal rectification. When it comes to small size scale, that is, when the characteristic length is smaller than the mean free path of the heat carrier, the description of conventional heat conduction is no longer applied due to the size effects and the quantum effects. Heat conduction in solids can be considered as the propagation of quantized energy due to lattice vibration called phonons. The transport behavior of phonons can be described using the Boltzmann Transport equation. In our study, the phonon Boltzmann transport equation is solved using Finite Element Method and Discrete Ordinates Method to simulate the thermal behavior of nano porous silicon films. First, we study the two dimensional thin film and unit cell structure of silicon and discover a transition zone between the porous structure and the bulk material where the heat transport is affected by the pores. The numerical results show that the length of transition zone is independent of porous structure length and bulk material length. Then, we consider symmetric porous silicon with aligned and staggered pores. The simulated thermal conductivities are compared with the results from theoretical models for different porosities. The deviations are less than 20% . Finally, we discuss the thermal properties of asymmetric porous silicon with different porous density distributions. Consider that the porosity and pore diameter are constants, the numerical results show that as the porous density increases, the thermal conductivity will decline. As the separation between pores becomes smaller than 50 nm, pores will have increasingly impact on the propagation of phonon scattering. Using the thermal circuit concept, the thermal conductivities of asymmetric porous materials can be modeled by thermal resistance in series connection, but the results will have large deviation for large asymmetric cases.

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47

Kusumawardani, Dana Mutiara, and 古貝華. "Evaluations of Performance and Thermal Properties in Porous Asphalt Concrete Containing Steel Slag." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/22313211576137486539.

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碩士
國立中央大學
土木工程學系
102
Porous asphalt concrete (PAC) is one alternative solution to the problem of stormwater drainage from parking and other low traffic density areas. The overall benefits of porous asphalt concrete may include both environmental and safety benefits including improved stormwater management, improved skid resistance, reduction of spray to drivers and pedestrians, reduction in light reflection and headlight glare, as well as a potential for noise reduction. However, there are disadvantages of this pavement type such as has lower service life than dense mixes. Steel slag is the material generated from purifying metal, their casting and alloying. It is steel slag that can be used as an aggregate substitution. The objective of this study was to evaluate the performance and thermal properties of porous asphalt concrete containing steel slag. Two types of steel slag were used to subtitute coarse aggregate, including Basic Oxygen Furnace (BOF) and Baoshan Slag Short Flow (BSSF). Three different percentages of steel slag, namely 0%, 30%, and 50%, were mixed. Two main aspects are investigated in this study. One is mixture performance, including resilient modulus, rutting potential, skid resistance, and moisture susceptibility test. The other is thermal properties characteristic, including thermal conductivity, thermal heat capacity, and thermal diffusivity. Statistical were utilized to determine which treatment has the best performance result. The test results show that steel slag has higher specific gravity, high absorption, but lower L.A. abrasion, and soundness compared with natural aggregate. PAC containing steel slag may enhance the resilient modulus, skid resistance, rutting potential, and moisture susceptibility. However the application of high percentage of steel slag may decrease the performance of PAC, such as decrease skid resistance, rutting potential, and moisture susceptibility. The statistical analysis results show that PAC containing 30% of BOF slag has the best performance results, however this kind of pavement had the highest thermal conductivity and thermal diffusivity compared with others. The conclusions indicate that both BOF and BSSF slag are suitable to used as coarse aggregate substitution in PAC.

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48

Hsu, Hung-Che, and 許宏哲. "The Studies of Physical Properties and Model of Thermal Conductivity of Open Cell Rigid Polyurethane Foam." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/08151362582502812722.

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碩士
中國文化大學
材料科學與製造研究所
88
The objectives of this research are to identify the factors which influence the physical properties of open cell rigid polyurethane foam and find the model of thermal conductivity of PU foam. The physical properties performances of the open cell rigid PU foam were experimently inuestigated. The effect factors for the physical properties of PU foam include the ratio of isocynate , polyether and water mixing temperature, and the additives. The model of thermal conductivity of PU foam is fowrd as below： The thermal conductivities data between the thereotical caculation of model and experinently inuertigated are within 12%.

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49

Chen, Po-Ting, and 陳柏廷. "Effect of Nanoclay Addition on the Thermal and Fire Properties of LDPE foam and EVA Copolymer." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/zmb8n2.

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碩士
國立臺北科技大學
化學工程研究所
95
The main objective of this study was to investigate the effect of organoclay addition on thermal and fire properties of low density polyethylene (LDPE) foam and Ethylene Vinyl Acetate copolymer (EVA). Nanoclay、P-N type intumescent flame retardant、cross-linking agent and blow agent have been mixed with LDPE to prepare flame-retarded LDPE foam. LOI and cone calorimeter (CONE) experiments showed that the presence of organoclay in the flame-retarded LDPE foam was not only improve its thermal stability but also reduce its maximum heat release rate and extinction coefficient. EVA/CLAY hybrids have been prepared by melt-blending. The exfoliated structures of clay in the hybrid were characterized by XRD and TEM. TGA and cone calorimeter data shown that nanoclay improve the degradation pathway and also improve its thermal stability.

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50

Lee, Ying-Kuan, and 李盈寬. "A Study of Sn-Based Solders on the Bonding and Thermal Properties of Graphite Foam/Copper." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/jthy47.

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Анотація:

碩士
國立臺北科技大學
製造科技研究所
95
Graphite foam has high heat transfer specific areas and lightweight and it’s suitable for the micro-processes heat sink. However, the graphite foam is brittle and its surface is rough. To enhance the thermal contact between the bottom of the heat sink and heat source, the bonding of the graphite-foam and copper is good for the demand. However, the thermal resistance of the solder layers will affect the cooling performance of the graphite-foam heat sink. The aim of the research is to investigate the effects of different Sn-based solders （Sn-Ag、Sn-Ag-Cu、Sn-Bi and S-Bond）with 1wt％ copper powders for 240℃,260℃ and 5~30min on the bonding quality of graphite foam/copper and thermal property. The results show that the contact angles and extending index of Sn-based solders are higher than those of Sn-based solders with 1wt% copper powders. The EPMA data also indicate that the intermetallic phase (Cu3Sn is close to the copper substrate; Cu6Sn5 is closer to interface of solders) exists between Sn-based solders and copper substrates. In addition, the intermetallic layer is increasing with higher temperature and time. The order of the thickness of the intermetallics is as following Sn-Bi＞Sn-Ag-Cu＞Sn-Ag. The thermal resistance test of the heat sink composed of graphite foam and copper shows that the thermal resistance of Sn-Bi layers is higher and the thermal resistance can be reduced by adding 1wt% copper powders. The thermal resistance of graphite foam/copper powders is lower than that of Al and Copper heat sink identified by natural convention test. Due to the folw resistance accrue, the thermal resistance of graphite-foam is higher than that of heat sink identified by force test.

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