Dissertations / Theses: 'Chemical and fuel properties'

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Goldsmith, Claude Franklin III. "Predicting combustion properties of hydrocarbon fuel mixtures." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/59876.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 189-201).
In this thesis, I applied computational quantum chemistry to improve the accuracy of kinetic mechanisms that are used to model combustion chemistry. I performed transition state theory calculations for several reactions that are critical in combustion, including a detailed analysis of the pressure dependence of these rate coefficients. I developed a new method for rapidly estimating the vibrational modes and hindered rotor parameters for molecules. This new method has been implemented in an automatic reaction mechanism generation software, RMG, and has improved the accuracy of the density of states computed in RMG, which in turn has improved RMG's ability to predict the pressure-dependence of rate coefficients for complex reaction networks. I used statistical mechanics to compute the thermochemistry for over 170 of the most important species in combustion. These calculations form a new library of thermodynamic parameters, and this library will improve the accuracy of kinetic models, particularly for fuel lean conditions. I measured reaction rate coefficients using both laser flash-photolysis absorption spectroscopy in a slow-flow reactor and time-of-flight mass spectrometry and laser Schlieren densitometry in a shock tube. Based upon these experimental projects, I helped design a one-of-a-kind instrument for measuring rate coefficients for combustion-relevant reactions. The new reactor combines photoionization time-of-flight mass spectrometry with multi-pass absorption spectroscopy in a laser-flash photolysis cell. The cumulative effect of these efforts should advance our understanding of combustion chemistry and allow us to make more accurate predictions of how hydrocarbons burn.
by Claude Franklin Goldsmith, III.
Ph.D.

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Ashcraft, James Nathan. "Tuning the transport properties of layer-by-layer thin films for fuel cell applications." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/54207.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2009.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student submitted PDF version of thesis.
Includes bibliographical references (p. 138-148).
The increasing global focus on alternative energy sources has led to a renewed interest in fuel cells. For low power, portable applications, direct methanol fuel cells (DMFCs) are the most promising type of fuel cell. DMFCs can operate at ambient conditions and only require dilute methanol solutions and air to be input to the devices. At the core of these devices is a proton exchange membrane (PEM) that allows rapid proton transport through the polymer matrix while preventing fuel from permeating across. Additionally, PEMs must have long-term stability in the fuel cell environment, the ability to operate over a wide range of conditions (temperature and humidity), and be cost effective. A promising, robust method for fabricating polymer films with tunable properties is layer-by-layer (LbL) assembly. This technique consists of building a polymer film by sequential dipping into polymer solutions with complementary interactions, such as opposite electrostatic charges. The LbL method allows the formation of thin films that have perm-selective properties and high ionic conductivity values. This work describes the optimization of multilayer systems for use as the PEM in DMFCs. First, LbL assembled films of poly[bis(methoxyethoxyethoxy)-phosphazene] (MEEP) and poly (acrylic acid) (PAA) are demonstrated by utilizing the hydrogen bonding between these two polymers. These films show controlled thickness growth, high ionic conductivity, and excellent hydrolytic stability. The ionic conductivity of these films is optimized by tuning the assembly pH of initial polymer solutions and thereby controlling the hydrogen bonding characteristics.
(cont.) Despite similar film composition, MEEP/PAA LbL films assembled at higher pH values have enhanced water uptake and transport properties, which play a key role in increasing ion transport within the films. At fully humidified conditions, the ionic conductivity of MEEP/PAA is over one order of magnitude higher than previously studied hydrogen bonded LbL systems. The next LbL systems studied consist of a highly sulfonated aromatic polyether (sPPO) paired with amine containing polycations. The best performing sPPO system has ionic conductivity values which are the same order of magnitude as commercially relevant PEMs and has the highest ionic conductivity ever obtained from a LbL assembled film. Additionally, these LbL systems have methanol permeability values over two orders of magnitude lower than traditional PEMs. Incorporating the sPPO systems into DMFCs results in a 53% improvement in power output as compared with DMFCs using traditional PEMs. In-depth structure property studies are performed to understand the nature of the high ionic conductivity of the sPPO LbL systems with respect to film growth, composition, water uptake, and ionic crosslink density. Lastly, the mechanical properties of highly conducting LbL films are improved by forming the LbL matrix on highly tunable electrospun fiber mat (EFM) supports. Free-standing LbL films have moderate mechanical properties when dry, but are mechanically deficient when hydrated. Coating an EFM with the LbL dipping process produces composite membranes with interesting "bridged" morphologies, while still maintaining high ionic conductivity values.
(cont.) The spray LbL assembly is studied as a means for the rapid formation of LbL films on EFMs. At optimized conditions, the LbL materials conformally coat the individual fibers throughout the bulk of the EFM and have uniform surface coatings. The mechanical properties of the spray coated EMFs are shown to be superior to the pristine LbL systems.
by James Nathan Ashcraft.
Ph.D.

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El-Kharouf, Ahmad. "Understanding GDL properties and performance in polymer electrolyte fuel cells." Thesis, University of Birmingham, 2014. http://etheses.bham.ac.uk//id/eprint/5211/.

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The Gas Diffusion Layer (GDL) has the important role of transporting the reactants into, and products out of the cell. This study aims to provide insights for understanding the relationship between GDL properties and the performance of PEFCs. Ex-situ characterisation techniques were employed to study the mechanical, physical and electrical properties of the GDL. The relationship between the various properties of GDL was investigated and discussed in this work. The study shows that characteristics such as GDL thickness, bulk density, PTFE and MPL content, porosity, hydrophobicity, permeability and electrical conductivity are closely connected. The effect of compression on the cathode GDL performance in PEFC membrane electrode assembly (MEA) is discussed using Polarisation (IV) curve and electrochemical Impedance Spectroscopy (EIS). Compression affects the electrical and mass transport properties of the GDL and therefore needs to be optimised. The results show that there is an optimum compression point, at which; a minimum contact resistance and optimum water transport are achieved. The optimum compression level is dependent on the GDL properties. The optimum compression ratio varies for the different GDLs according to the difference in the material properties. At optimum compression, the performance of the different GDL materials was compared to understand the effect of the GDL properties on the performance. GDL characteristics such as structure, thickness, bulk density, PTFE loading, and MPL presence have a direct effect on the MEA performance and need to be optimized for the different PEFC applications.

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Taylor, Kevin Brian. "Comparative Study of Alternative Fuel Icing Inhibitor Additive Properties and Chemical Analysis of Metal Speciation in Aviation Fuels." University of Dayton / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1280850044.

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Zhang, Lipeng. "Theoretical study of oxygen reduction reaction catalytic properties of defective graphene in fuel cells." Thesis, The University of Akron, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3718274.

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In this dissertation density functional theory (DFT) was applied to study the electronic structure and catalytic properties of graphene containing different types of defects. These defects includes hetero-atoms such as nitrogen, sulfur doped graphene, point defects such as Stone-Wales defects, single vacancy, double vacancies and substituting pentagon ring at zigzag edge, line defects such as pentagon-heptagon carbon ring chains, pentagon-pentagon-octagon carbon ring chains locating at the middle of graphene. The mechanisms of oxygen reduction reaction (ORR) were studied on these defective graphene, and electron transfer processes were simulated. Using DFT methods, we also explored the effect of strains to ORR electronic catalytic properties on pure and nitrogen doped graphene.

Our simulaltion results show that nitrogen, sulfur doped graphene, graphene containing point defects, substituting pentagon ring at zigzag edge, graphene containing line defects, pentagon-heptagon chain or pentagon-pentagon-octagon chains which have odd number of heptagon or octagon carbon ring perform high catalytic properties for ORR. Four electron transfer reactions could occur, and there are also two electrons transfer occuring on these defective graphene. The Stone-Wales defect itself cannot generate the catalytic activity on the graphene, but can facilitate the formation of hetero atom doping on graphene, which could show high catalytic activities to ORR. The catalytic active sites on defective graphene are atoms possessing high spin or charge density, where the spin density plays more important effect on the catalytic properties. For the N-doped graphene, the identified active sites are closely related to doping cluster size and dopant-defect interactions. Generally speaking, a large doping cluster size (number of N atoms >2) reduces the number of catalytic active sites per N atom. In combination with N clustering, Stone-Wales defects can strongly promote ORR. For four-electron transfer, the effective reversible potential ranges from 1.04 to 1.15 V/SHE, depending on the defects and cluster size. The catalytic properties of graphene could be optimized by introducing small N clusters in combination with material defects. For S-doped graphene, sulfur atoms could be adsorbed on the graphene surface, substitute carbon atoms at the graphene edges in the form of sulfur/sulfur oxide, or connect two graphene sheets by forming a sulfur cluster ring. Catalytic active sites distribute at the zigzag edge or the neighboring carbon atoms of doped sulfur oxide atoms, which possess large spin or charge density. For those being the active catalytic sites, sulfur atoms with the highest charge density take two-electron transfer pathway while the carbon atoms with high spin or charge density follow four-electron transfer pathway. Stone-Wales defects not only promote the formation of sulfur-doped graphenes, but also facilitate the catalytic activity of these graphenes. The ORR catalytic capabilities of the graphene containing point or line defects denpend on whether the defects could introduce spin density into the system or not. The axial strain field applied on the graphene could change its electronic properties. Neither the compressive nor the tensile strain along the zigzag or armchair direction could facinitate the catalytic activities of perfect graphene without any defects. Tensile strain along zigzag direction could change the electronic properties of nitrogen doped graphene, which are favorable to its ORR catalytic property.

Our simulation results explored the ORR on defective graphene in essence and provide the theoretical base for searching and fabricating new high efficient catalysts using the carbon based materials for fuel cells.

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Nerva, Jean-Guillaume. "An Assessment of fuel physical and chemical properties in the combustion of a Diesel spray." Doctoral thesis, Universitat Politècnica de València, 2013. http://hdl.handle.net/10251/29767.

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With the slow but ineluctable depletion of fossil fuels, several avenues are currently being explored in order to define the strategic boundaries for a clean and sustainable energetic future, while accounting for the specificities of each sectors involved. In regard to transport applications, alternative fuels may represent a promising solution, at least at short or middle term, such as the International Energy Agency foresees that their share could account for 9% of the road transport fuel needs by 2030 and 27 % by 2050, with the potential resources to reach 48% beyond. If they have already been included in significant blending proportions with conventional fossil fuel in most of the occidental countries, their introduction also coincides with a long-time established program of continuously more drastic standards for engine emissions of NOX and PM, now even further demanding by the seek for combustion efficiency aiming at reducing CO2 emissions. While several works discuss the alternative fuels effect on exhaust emissions when used directly in production Diesel engines, results and analysis are sometimes contradictory, depending sometimes on the conditions in which they were obtained, and the causes of these results remain unclear. Therefore, in order to better understand their effect on the combustion processes, and thus extract the maximum benefits from these fuels in the optimization of engine design and calibration, a detailed comprehension of their spray and combustion characteristics is essential. The approach of this study is mostly experimental and based on an incremental methodology of tests aiming at isolating injection and combustion processes with the objective to identify and quantify the role of both fuel physical and chemical properties at some key stages of the Diesel combustion process. After obtaining a detailed characterization of their properties, five fuels have been injected in an optical engine enabling a sharp control of the thermodynamic e
Nerva, J. (2013). An Assessment of fuel physical and chemical properties in the combustion of a Diesel spray [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/29767
Palancia

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Liu, David ShinRen. "Controlling the mechanical and transport properties of layer-by-layer films and electrospun mat composite membranes for fuel cell applications." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/91061.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2014.
Cataloged from PDF version of thesis.
Includes bibliographical references.
There is an ever increasing need for clean, portable energy devices, such as fuel cells and high energy batteries to replace or reduce the world's dependence on fossil fuels. The continued development of thin-film solid polymer electrolytes with improved mechanical and ion transport properties is critical for the further advancement of such electrochemical energy devices. For hydrogen and methanol fuel cells, the proton exchange membrane (PEM) has to have high protonic conductivity, low fuel crossover, and be mechanically and chemically stable. In particular, for direct methanol fuel cells and for high temperature (>100 °C), low relative humidity (< 60% RH) hydrogen fuel cells, the current industrial standard PEM, Nafion®, does not have all the required attributes. Layer-by-Layer (LbL) assembly allows for the controlled deposition of alternating polyelectrolytes at the nanometer scale. This technique can be used with highly proton conductive water soluble polymers as well as doped polymers. In addition, LbL assembly can be used to coat a variety of substrates of various shapes and sizes. An LbL system composed of poly(diallyl dimethyl ammonium chloride) (PDAC) and sulfonated poly(2,6-dimethyl 1,4- phenylene oxide) (sPPO) has shown to have relatively high proton conductivity and very low methanol permeability compared to that of Nafion@, but lacking in mechanical strength when hydrated and losing significant proton conductivity at lower RH conditions. Herein this thesis work describes the selection, optimization, and utilization of multilayer systems and system composites as the PEM in hydrogen and methanol fuel cells, focusing on improving and understanding the improvements to the properties of layer-by-layer films and composite membranes for fuel cell applications by targeting two main areas: the mechanical properties and the conductive properties. In addition, characterization and film analysis work was done to correlate and explain how the changing of the LbL system and fabrication techniques impacted the membrane's mechanical and conductive properties. First, the mechanical strength and stability were greatly improved by spray-assembling the films on an electrospun fiber mat to form a composite membrane. Spray-LbL assembly was performed both with and without vacuum assistance, which had complementary effects on the film properties. By combining these techniques, composite membranes with methanol permeability twenty times lower than Nafion® and through-plane proton selectivity five times greater than Nafion@ were fabricated. In addition, the planar swelling of the composite membranes in water was significantly reduced. This large reduction in swelling is hypothesized to be due to the electrostatic interaction of the LbL system with the underlying electrospun fibers and would not occur in a typical polymer blend. Second, to improve the conductivity of the LbL films overall and specifically at lower RH conditions, two approaches were used. In the first approach, divalent salts were added to the polyanion solution to provide a stronger shielding effect than monovalent salts. The divalent salts allowed for ion bridging and increased both the number and the mobility of protons associated with sulfonic acid groups in the LbL film; thus increasing the film's conductivity. Through optimization of salt type and concentration, the protonic conductivity of PDAC/sPPO films was increased fourfold, and the humidity dependence of the conductivity was decreased. In the second approach, PDAC was replaced with a phosphoric-acid-doped polymer, poly(2- vinyl pyridine) (P2VP). The phosphoric acid concentration in the LbL film and the number of free sulfonic acid groups could be controlled post film fabrication by changing the concentration of the phosphoric acid dopant. The resulting P2VP/sPPO films exhibited greater conductivity than similarly doped P2VP films and under stronger doping conditions (0.4 M - 1.0 M phosphoric acid), the film's conductivity increases seventy-fivefold (110 mS/cm at 50% RH at room temperature), resulting in a conductivity an order of magnitude greater than Nafion®. The large increases in conductivity, particularly at low RH conditions further support a recently reported and very promising proton transport mechanism that utilizes both phosphoric and sulfonic acid groups.
by David ShinRen Liu.
Ph. D.

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Zhang, Lipeng. "Theoretical Study of Oxygen Reduction Reaction Catalytic Properties of Defective Graphene in Fuel Cells." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1374245184.

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Cheng, Xinwei. "Development of reduced reaction kinetics and fuel physical properties models for in-cylinder simulation of biodiesel combustion." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/33397/.

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The analyses of spray, combustion and emission characteristics for two types of biodiesel fuels, namely coconut methyl ester (CME) and soybean methyl ester (SME) are reported in this thesis. In order to produce high fidelity numerical spray and combustion representation for CME and SME, accurately developed thermo-physical properties and chemical kinetics were integrated with open-source computational fluid dynamics codes. First, the thermo-physical properties of CME and SME which include liquid and vapour properties were calculated using temperature-dependent correlations that were found in the literature. These calculated thermo-physical properties were then incorporated into Open Field Operation and Manipulation (OpenFOAM) to determine the sensitivities of the fuel properties on the spray development. Based on the sensitivity analyses, 5 of 12 thermo-physical properties, including latent heat of vaporisation, liquid density, liquid heat capacity, liquid surface tension and vapour pressure, gave the largest fluctuation to the spray development. Besides, coupled effects among the thermo-physical properties were discovered. The effects of thermo-physical properties were also varied according to the addition of unsaturation levels and combustion chemistries. Next, a generic reduced chemical kinetic mechanism, with components of methyl decanoate, methyl-9-decenoate and n-heptane was developed to represent the biodiesel fuels. The reduced mechanism with 92 species and 360 elementary reactions was validated under 72 shock tube conditions against experimental measurements in the literature and detailed mechanism predictions, for each zero-dimensional auto-ignition and extinction process using CHEMKIN-PRO. Maximum percentage errors of less than 40.0% were recorded when the ignition delay (ID) period predictions of the reduced mechanism were compared to those of detailed mechanism. Satisfactory agreement was attained when the predictions of the reduced mechanism were validated against the measured species profiles of rapeseed methyl ester oxidation in jet stirred reactor, which were obtained from the literature. Besides, the ID periods and lift-off lengths (LOL) predicted for the reacting spray at initial temperatures of 900 K and 1000 K achieved a maximum deviation of 29.8% and 43.4%, respectively, as compared to those of the experimental measurements in the literature. CME and SME were then numerically analysed under both the conditions of constant volume bomb and diesel engine, using the validated thermo-physical properties and reduced mechanism. The ambient oxygen level of the constant volume bomb was raised from 15.0 to 21.0% to emulate the intake air composition in the diesel engine. As such, the spray development was changed from radial to forward propagation, where LOL was reduced by 24.3%. Higher levels of carbon monoxide (CO), carbon dioxide (CO2) and soot mass concentrations were also obtained. When the unsaturation level was increased from 20.0% (CME) to 80.0% (SME), retarded spray and combustion developments were found in both the constant volume bomb and diesel engine. Besides, the CO, soot and nitric oxide (NO) emissions, including the tailpipe predictions were maximally increased by 32.0%. In overall, CME performs better than SME does because of the improved air-fuel mixing and decreased tailpipe NO, CO and CO2 emissions. Based on these, it is sufficient to deduce that the phenomena predicted in the constant volume bomb are adequate to replicate those in the diesel engine.

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Shen, Chen. "Application of Fuel Element Combustion Properties to a Semi-Empirical Flame Propagation Model for Live Wildland Utah Shrubs." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3550.

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Current field models for wildfire prediction are mostly based on dry or low-moisture fuel combustion research. To better study live fuel combustion behavior and develop the current semi-empirical bush combustion model, a laminar flow flat-flame burner was used to provide a convection heating source to ignite individual live fuel samples. In this research project, four Utah species were studied: Gambel oak (Quercus gambelii), canyon maple (Acer grandidentatum), big sagebrush (Artemisia tridentata) and Utah juniper (Juniperus osteosperma). Leaf geometrical parameters and time-dependent combustion behavior were recorded. Qualitative results included various combustion phenomena like bursting, brand formation and bending. Quantitative results included determination of best correlations for (a) leaf geometrical properties (individual leaf dry mass (mdry), thickness (Δx), leaf width (W) and leaf length (L)) and (b) combustion characteristics (e.g., time to ignition (tig), time of flame duration (tfd), time to maximum flame height (tfh), time to burnout (tbrn), and maximum flame height (hf,max)). A semi-empirical bush model was expanded to describe the combustion behavior of the three Utah species (Gambel oak, canyon maple and Utah juniper). Leaf placement and bush structure were determined from the statistical model. A new flame area simulation was explored in the semi-empirical bush model in order to improve the bush burning predictions.

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Zysman-Colman, Eli. "The chemical and physical properties of polychalcogens." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84864.

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The optimized synthesis of acyclic dialkoxy disulfides and aromatic polysulfides is described and their physical properties probed. A theoretical survey of dialkoxy disulfides and thionosulfites was undertaken in order to determine the most efficacious method for accurately modeling these compounds. In particular, the origin of the high barrier to rotation in the dialkoxy disulfides was determined to be due to a generalized anomeric effect resulting from two lone pair donations of each sulfur atom into each of their respective sulfur-oxygen antibonding orbitals. The origin of the high rotational barrier was also verified experimentally, in particular with respect to solvent and substituent effects. Complimentary to this thermal process, the decomposition of dialkoxy disulfides was also investigated. It was determined that these compounds decompose under first order kinetics via an initial asymmetric S-O homolytic cleavage. Activation parameters for both of these processes were determined.
Theoretical modeling on the relative ground state energies of dialkoxy disulfides is also described. It has been ascertained that the equilibrium position between the two isomers can be influenced by the ring size of the molecule; larger rings promote the dialkoxy disulfide isomer. These modeling studies were successfully corroborated experimentally. Of note is the synthesis of a new 8-membered ring dialkoxy disulfides as well as novel 7-membered ring thionosulfites. These compounds were also confirmed by single X-ray crystallography.
The kinetics of desulfurization of acyclic aromatic tri- and tetrasulfides is described. Tetrasulfides were found to transfer a sulfur atom to triphenylphosphine over ten times faster than their trisulfide analogues.

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Young, Dominique Emma. "Characterisation of the chemical properties and behaviour of aerosols in the urban environment." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/characterisation-of-the-chemical-properties-and-behaviour-of-aerosols-in-the-urban-environment(27de7e50-5069-40a0-b5cd-1370747f646a).html.

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Atmospheric aerosols have adverse effects on human health, air quality, and visibility and frequently result in severe pollution events, particularly in urban areas. However, the sources of aerosols and the processes governing their behaviour in the atmosphere, including those which lead to high concentrations, are not well understood thus limit our ability to accurately assess and forecast air quality. Presented here are the first long-term chemical composition measurements from an urban environment using an Aerodyne compact Time-of-Flight Aerosol Mass Spectrometer (cToF-AMS). Organic aerosols (OA) were observed to account for a significant fraction (44%) of the total non-refractory submicron mass during 2012 at the urban background site in North Kensington, London, followed by nitrate (28%), sulphate (14%), ammonium (13%), and chloride (1%). The sources and components of OA were determined using Positive Matrix Factorisation (PMF) and attributed as hydrocarbon-like OA (HOA), cooking OA (COA), solid fuel OA (SFOA), type 1 oxygenated OA (OOA1), and type 2 oxygenated OA (OOA2), where HOA, COA, and SFOA were observed to be of equal importance across the year. The concentration of secondary OA increased during the summer yet the extent of oxidation, as defined by the oxygen content, showed no variability during the year. The main factors governing the diurnal, monthly, and seasonal trends observed in all organic and inorganic species were meteorological conditions, specific nature of the sources, and availability of precursors. Regional and transboundary pollution influenced total aerosol concentrations and high concentration events were observed to be governed by different factors depending on season. High-Resolution ToF-AMS measurements were used to further probe OA behaviour, where two SFOA factors were derived from PMF analysis in winter, which likely represent differences in burn conditions. In the summer an OA factor was identified, likely of primary origin, which was observed to be strongly associated with organic nitrates and anthropogenic emissions. This work uses instruments and techniques that have not previously been used in this way in an urban environment, where the results further the understanding of the chemical components of urban aerosols. Aerosol sources are likely to change in the future with increases in solid fuel burning as vehicular emissions decrease, with significant implications on air quality and health. Thus it is important to understand aerosol sources and behaviour in order to develop effective pollution abatement strategies.

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Schollin, Mårten. "Formulation and Assessment of Hexamethylene-tetramine Filled Solid Fuel Grains." Thesis, KTH, Fiber- och polymerteknologi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-297507.

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Hybridraketer har inte sett så mycket användning som dess motsvarigheter som använder flytande eller fasta drivmedel. De främsta orsakerna kan förklaras med att hybridraketer historiskt sett haft lägre regressionshastighet och bränsletäthet. Inverkan av nackdelarna har dock minskat tack vare fortsatt forskning rörande hybridraketer. Tillsammans med de säkerhetsoch ekonomiska fördelar som kommer med hybridraketer har gjort hybridraketer ett mer konkurrenskraftiga. Hexaminbaserade fasta bränslen har formulerats och utvärderats med betoning att förbättra härdningstid och mekaniska egenskaper. Genom att inkludera mjukgörare och ändra NCO/OH-förhållandet har ett fast bränsle med lovande mekaniska egenskaperoch god härdningstid framställts.
Hybrid propellant rockets has not seen as much use as its liquid and solid propellant counterparts. The main reasons for this can be attributed to hybrid propellant rockets historically having lower regression rate and fuel density. However, the impact of these disadvantages have been diminished over the years as a result of increased research. This together with the safety and economic advantages of hybrid propellant rockets, the hybrid system have become a more competitive system to use. Hexamine basedsolid fuel grains have been formulated and evaluated with emphasis on enhancing pot-life and tensile proprieties. By including plasticisers and altering the NCO/OH ratio, a solid fuel grain was successfully produced, overcoming earlier encountered problems with short pot-life as well as having promising tensile properties.

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Demarquette, Nicole Raymonde. "Nonlinear viscoelastic properties of polystyrene solutions." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60004.

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In this work the nonlinear behavior of concentrated polystyrene solution was examined using sliding plate rheometer developed at McGill University. In this rheometer a novel transducer is used to measure the shear stress and an optical system is used to measure birefringence during flows involving high shear rates.
The steady shear stress was found to be independent of shear rate at high shear rates. The Cox-Merz rule was found to be valid for concentrations less than 0.199 g.cm$ sp{-3}$, but a deviation from the rule was observed for higher concentrations. Sigmoidal damping functions, based on both the shear stress measurements and the birefringence measurements, were determined. The exponential stress coefficient and the third normal stress difference were calculated from experimental data for different values of exponential rate constant and different strain scale factor. The exponential rate constant was shown to have a strong influence on both the exponential stress coefficient and the third normal stress difference.

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Robert, Mylène. "Impact of degradation and aging on properties of PFSA membranes for fuel cells." Electronic Thesis or Diss., Université de Lorraine, 2021. http://www.theses.fr/2021LORR0004.

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Bien que déjà présentées comme une technologie sûre et propre, les piles à combustible à membrane échangeuse de protons (PEMFC) restent confrontées à de solides verrous en termes de durabilité et de fiabilité, limitant leur commercialisation à large échelle. De nombreuses études ont déjà permis d’affiner la compréhension des phénomènes de vieillissement et ont permis de désigner la dégradation de la membrane comme l’un des principaux facteurs limitant la durée de vie des PEMFC. Cette étude vise à apporter des éléments de compréhension sur les mécanismes de dégradations chimique et mécanique par l’intermédiaire de protocoles de vieillissement ex-situ, ainsi qu’à comprendre l’impact de ces dégradations sur la structure et les propriétés fonctionnelles des membranes. Dans un premier temps, il a été nécessaire de clarifier l’influence de la réaction de Fenton, un protocole de vieillissement ex-situ largement reconnu dans la littérature, sur la dégradation chimique des membranes Nafion™. Les résultats ont confirmé que la concentration en réactifs de Fenton influençait significativement la décomposition chimique du polymère, à la fois d’un point de vue chimique et morphologique. Par la suite, nous avons choisi de suivre l’évolution de la dégradation chimique des membranes Nafion™ en fonction du temps et d’étudier son impact sur la structure de la membrane, ses propriétés de sorption et de diffusion de l’eau ainsi que son fonctionnement en pile. À cet égard, différentes techniques de caractérisation telles que la spectroscopie RMN 19F ou 1H ainsi que la spectroscopie FTIR ont permis de corréler les propriétés physico-chimiques de la membrane à ses caractéristiques structurelles et de mettre ainsi en évidence plusieurs marqueurs de la dégradation chimique. Enfin, un dispositif sur-mesure a été conçu afin d’étudier l’impact des contraintes mécanique et chimique conjointes sur les membranes Nafion™. L’objectif de ce dispositif était de reproduire des conditions de vieillissement proches de celles rencontrées lors du fonctionnement en pile
Although proton-exchange membrane fuel cells (PEMFC) are nowadays considered as a safe and clean energy technology, they still suffer from durability and reliability issues restricting their widespread commercialization. Innumerable studies have already led to a better understanding of aging phenomena and highlighted membrane degradation as one of the main factors limiting PEMFC lifetime. This study aims at bringing some clarifications on the chemical and mechanical degradation mechanisms of membranes through ex-situ aging protocols as well as understanding the impact of these degradations on the membrane structure and functional properties. First, it was necessary to clarify the influence of Fenton’s reaction, an ex-situ aging protocol widely recognized in the literature, on the chemical degradation of Nafion™ membranes. The results confirmed that Fenton’s reagents concentration significantly influenced polymer chemical decomposition, both from a chemical and morphological point of view. Subsequently, we chose to monitor the evolution of pure chemical degradation of Nafion™ membranes as a function of time and to study its impact on the membrane structure, water sorption and diffusion properties, as well as operability in fuel cells. In that respect, various characterization techniques such as 19F or 1H-NMR as well as FTIR spectroscopies allowed us to correlate physico-chemical properties of the membrane to its structural characteristics and to thus highlight several indicators of chemical degradation. Finally, a custom-made device has been developed to study the impact of conjoint mechanical and chemical stress on Nafion™ membranes. The objective of this device was to replicate aging conditions close to those encountered during fuel cell operation

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16

Imafidon, Gilbert Idolo. "Genetic polymorphism and physico-chemical properties of milk proteins." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74578.

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The properties of genetic variants of $ alpha sb{ rm s1}$-casein (BB, AB), $ beta$-casein (A$ sp1$A$ sp1$, A$ sp2$A$ sp2$, A$ sp1$A$ sp2$, A$ sp1$A$ sp3$, A$ sp2$A$ sp3$, A$ sp1$B, A$ sp2$B, BB), $ kappa$-cn (AA, AB, BB) and $ beta$-lactoglobulin (AA, AB, BB) were compared. The caseins and $ beta$-lactoglobulin were purified by mass ion exchange chomatography. Model systems of $ alpha sb{ rm s1}$- and $ kappa$-caseins were compared with respect to their stability towards calcium ions and other major milk salts precipitation. $ beta$-Casein, $ alpha sb{ rm s1}$-casein BB + $ beta$-caseins and $ kappa$-casein were also compared in their ability to resist calcium ion precipitation. $ kappa$-casein AB was a better stabilizer of $ alpha sb{ rm s1}$-casein than the BB and AA variants. $ alpha sb{ rm s1}$-Casein BB resisted calcium ion precipitation more than the AB variant in presence of $ alpha$-lactose, citrate, chloride and magnesium ions. $ kappa$-Casein BB stabilized $ alpha sb{ rm s1}$-casein AB more than the BB variant in presence of calcium and phosphate ions. Solubility of $ kappa$-casein AA, however, was greater than that of $ kappa$-cn BB and $ kappa$-cn AB variants in calcium and phosphate solutions. As in $ alpha sb{ rm s1}$-casein, significant differences were also found among $ kappa$-casein variants in stabilizing $ beta$-casein against calcium ion precipitation. $ beta$-Caseins A$ sp1$A$ sp1$, A$ sp2$A$ sp2$ and A$ sp1$B produced the most stable micelles while those of A$ sp2$B and B variants the least at 0.03-0.25 $ kappa$-cn/$ beta$-casein ratios and 20 mM Ca$ sp{2+}$. However, stability of micelles formed from $ alpha sb{ rm s1}$-cn + $ beta$-cn A$ sp2$A$ sp3$, $ alpha sb{ rm s1}$-cn + $ beta$-cn A$ sp1$A$ sp3$, and $ alpha sb{ rm s1}$-cn + $ beta$-cn A$ sp2$A$ sp2$ caseins were higher than those of $ alpha sb{ rm s1}$-cn + $ beta$-cn A$ sp1$A$ sp2$, $ alpha sb{ rm s1}$-cn + $ beta$-cn A$ sp1$B and $ alpha sb{ rm s1}$-cn + $ beta$-cn A$ sp1$A$ sp1$.

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17

Pulido-Cejudo, Gabriel. "Chemical and biological properties of iron-pyruvate-transferrin complexes." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74529.

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The preparation of a novel complex, ferric bromopyruvate, is described. In solutions from which most of the carbonate has been removed, ferric bromopyruvate can be used both as an iron and pyruvate source for the full iron saturation of apotransferrin. Using ferric bromopyruvate as an iron donor, iron incorporation into human apotransferrin is biphasic; the N-terminal domain is saturated three times faster than its homologous C-terminal iron binding site. Following the reaction of apotransferrin with ferric bromopyruvate, 4 moles of pyruvate per mole of transferrin are covalently bound. Based on the effect of acetylation on pyruvate and iron binding, it is suggested that lysyl residues could be the target of pyruvate bonding. However, the reaction of pyruvate with other positively charged amino acid residues cannot be excluded. The possible sites of pyruvate binding within the N-terminal domain of human serum transferrin are discussed. Covalent attachment of pyruvate to cationic amino acid residues decreased both in vitro and in vivo iron release, preferentially from the N-terminal domain of transferrin. The decreased rate of iron incorporation from iron-pyruvate-transferrin complexes by rabbit reticulocytes caused a lower iron incorporation into heme. It is suggested that an impairment of iron release from transferrin may decrease the rate of heme synthesis in reticulocytes. In vitro studies on the iron removal from iron-pyruvate-transferrin complexes showed that pyrophosphate can remove iron from this complex at an acid pH to a similar extent to the cellular mediated iron release from this complex. Based on this data, a model for the intravesicular iron release from transferrin is proposed.

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18

Glenns, Robert N. "Structures and properties of Sophorolipids from Candida bombicola." Thesis, McGill University, 2003. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=80015.

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The production of sophorolipids from the yeast Candida bombicola (ATCC 22214) was studied. Heptadecane resulted in the highest percentage of direct incorporation into the sophorolipid products of all the hydrocarbon substrates used. The diacetylated lactone form of the sophorolipid product was favoured when the hydroxycarboxylic acid was sixteen or seventeen carbon atoms long. Crystalline product was only obtained when a high degree of uniformity of both the type of sophorolipid and the number of carbon atoms in the fatty acid part of this lipid was achieved. These conditions were only met when the hydrocarbon substrate was hexadecane or heptadecane and the specific products in these cases were diacetylated lactones.
The surface properties of the sophorolipids were analyzed using a modified evaporating drop technique. The lactone sophorolipids were more effective at reducing the surface tension of water than the acid sophorolipids. This could be part of the explanation for the fact that the lactones have been shown to be more effective than the acid form of the sophorolipids for several different applications.

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19

COSTA, GUSTAVO C. C. da. "Sintese, caracterizacao estrutural, termoquimica e eletrica de materiais ceramicos para celulas a combustivel de oxido solido." reponame:Repositório Institucional do IPEN, 2008. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11784.

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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP
FAPESP:05/54171-4

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20

Dionne, Jean-Philippe. "Chapman-Jouguet properties of heterogeneous explosives." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=24055.

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The role of inert additives in the detonation characteristics of nitromethane-based heterogeneous explosives is investigated. Available experimental data on the detonation velocity are compared with theoretical CJ calculations using two different detonation codes (IDeX and Cheetah). IDeX uses the Theostar equation of state (EOS) for the fluid phase and the Murnaghan EOS for the solid phase while Cheetah uses the JCZ3-EOS for the fluid species and the OLD-EOS for the solid phase.
Large deviations are observed for heterogeneous explosives with a large mass fraction of inert material. This is credited to the different relaxation times of the various equilibration processes in the detonation zone, as well as the complex shock interactions between the fluid and solid phases. The equations of state used for the detonation products are found to have only a small effect on the equilibrium CJ state. A more realistic EOS for solids is proposed.

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21

Saban, Waheed. "Synthesis, characterization and physicochemical properties of platinum naboparticles on ordered mesoporous carbon." Thesis, University of the Western Cape, 2011. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_8474_1320738516.

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In this study SBA-15 mesoporous silica template was synthesized and used as a sacrificial template in the preparation of ordered mesoporous carbon material. A chemical vapour deposition (CVD) technique using LPG or alternatively sucrose, pyrolyzed upon a mesoporous Si matrix were used to produce nanostructured ordered mesoporous carbon (OMC) with graphitic character after removing the Si template. The sucrose method was found to be a suitable route for preparing OMC. The OMC was used as a conductive three dimensional porous support for depositing catalytic nanophase Pt metal. Deposition of Pt nanoparticles on OMC was accomplished using a CVD method with Pt(acac)2 as a precursor. The synthesized nano-composite materials were characterized by several techniques such as, HRTEM, HRSEM, EDS, XRD, BET, TGA, FT-IR and CV.

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22

Porubská, Jana. "Microstructure and properties of TMP papers." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33343.

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Paper is comprised of quasi-randomly distributed fibres, fines and different additives. The properties of paper depend on the type of fibres used, their uniformity of distribution, the amount and type of fines and fillers. It is difficult to predict how a particular component will behave in a mixture. This will depend on the form of material introduced (flocculated or dispersed) and on what kind of interactions will take place. These factors can be controlled by various wet-end strategies based on known colloidal behaviour of various additives. Thus, applying this knowledge to papermaking, one should be able to predict and control final structures of paper, which will be reflected in optical and mechanical properties.
A thorough understanding of the effects of different materials, such as fines and fillers, on optical and mechanical properties of paper can only be obtained from a systematic study. Therefore, this research focused on elucidating the relationship between the nature and amount of fines and fillers and paper properties. The studies were mainly limited to papers made from thermomechanical pulps (TMP), although occasionally comparisons with other pulps were made as well.

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23

Swanson, Edward. "Dual-plasma synthesis of coated metal nanoparticles with controlled surface properties." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=21906.

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There are many fluid based heat transfer processes that could benefit from an increase in efficiency. Recently a process has emerged that allows the improvement of the thermal conductivity of existing heat transfer fluids. This increase is achieved when particles with at least one dimension less than 100 nm (i.e. nanoparticles) are dispersed into the heat transfer fluid to create a so-called "nanofluid". Nanofluids are not free of problems, unfortunately. The dispersed nanoparticles are not stable and tend to form agglomerates that settle out of suspension. The conventional method for combating this involves the use of surfactants, but these tend to loose effectiveness at moderate temperatures. Another more permanent and reliable method for stabilizing these nanofluids is to functionalize their surface in an effort to create a more favorable interaction between the particle surface and the host fluid. In this work, a novel dual-plasma reactor using a low-pressure pulsed DC arc system for the synthesis of metal nanoparticles coupled with an in-flight RF plasma polymerization system was designed to synthesize coated and functionalized metal nanoparticles. The reactor geometry takes into account the initial nanoparticle trajectory in order to optimize the nanoparticle collection efficiency. It was found that microdroplets also produced in the pulsed DC arc system could be effectively filtered out through strategic collection of the nanoparticles. The plasma polymer coatings produced range from slightly non-polar to polar, based on contact angle measurements. The hydrophilicity of the surface depends strongly on the gas species present in the plasma environment.
Il existe plusieurs procédés de transfert de chaleur qui pourraient bénéficier d'une amélioration d'efficacité énergétique, particulièrement les procédés faisant usage d'un liquide pour le transport thermique. Récemment, il a été démontré qu'il est possible d'augmenter la conductivité thermique d'un liquide en y dispersant des particules ayant au moins une dimension spatiale inférieure à 100 nm (nanoparticules). Les suspensions résultantes sont appelées « nanofluides ». Les nanofluides présentent un problème important, soit la tendance des particules en suspension à former des agglomérats qui sédimentent rapidement. La méthode conventionnelle pour contrer ce phénomène est d'ajouter un surfactant à la suspension. Toutefois, plusieurs surfactants perdent leur efficacité à des températures moyennement élevées. Une solution plus permanente et davantage fiable serait de fonctionnaliser la surface des nanoparticules afin d'améliorer l'interaction de ces dernières avec le liquide hôte. Cette thèse présente un système innovateur à plasma hybride, faisant usage d'un procédé d'érosion par arcs électriques pulsés à basse pression pour la synthèse de nanoparticules métalliques et d'une décharge radio-fréquentielle pour assurer, par polymérisation plasma, le revêtement et la fonctionnalisation des nanoparticules en vol. La géométrie du réacteur est adaptée aux trajectoires des nanoparticules ainsi générées afin d'augmenter l'efficacité d'échantillonnage. De ce fait, il a été déterminé que la collecte stratégique des nanoparticules permet de filtrer les microgouttelettes engendrées par le procédé d'arcs pulsés. Le revêtement organique issu de la polymérisation par plasma a un comportement allant de légèrement non-polaire à polaire, selon des mesures d'angle de contact. Le comportement hydrophile ou hydrophobe de la surface dépend fortement des gaz plasmagènes utilisés.

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24

CASTANHEIRA, MYRTHES. "Analise dos mecanismos de degradacao de varetas combustiveis falhadas em reatores PWR." reponame:Repositório Institucional do IPEN, 2004. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11141.

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

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25

Liao, Xiangjun 1970. "Dielectric properties and their application in microwave-assisted organic chemical reactions." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=38220.

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This study was designed to develop some predictive models for the dielectric properties of the chemicals and chemical reactions and make use of dielectric properties and microwave irradiation in the chemical reactions. Specifically, the dielectric properties of the following systems were investigated at microwave frequencies of 2450 and 915 MHz: (1) C1--C5 alcohols, (2) glucose aqueous solutions, (3) lysine aqueous solutions, (4) mimicked esterification reaction model systems of parahydroxybenzoic acid with methanol, 1-propanol and 1-butanol in the presence of para-toluene sulfonic acid as a catalyst, (5) Maillard reaction model system consisting of glucose, lysine and water.
The dielectric properties of the model systems showed that they depended on the frequency applied, concentration of the material, and temperature. Most of the predictive models showed that there exists a linear or quadratic relationship between dielectric constant and concentration or temperature. However, the quadratic equation is better than the linear one to describe the variation of the loss factor with temperature or concentration.
Esterification showed great advantages for the use of microwave irradiation in chemical reaction. It included reduction in reaction time, and provided distinct temperature profiles due to microwave environment during chemical reactions. The reason for rate enhancement of this type of reaction was also demonstrated from the temperature profile.
Microwave-assisted solvent free Maillard reaction model system, consisting of glucose and lysine, demonstrated that the heating method applied was not one of the crucial factors, but the temperature level was important during the chemical reaction.
The relationship of loss factor with yield of reaction showed that it is possible to use dielectric data to analyze, and monitor the chemical reaction. It provided a new methodology to analyze the reaction.
The relationship between the loss factor, loss tangent and the reaction time, and concentration of the material showed that it is also possible to use dielectric data at microwave frequencies of 2450 and 915 MHz to study chemical reactions, especially the kinetics.

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26

Wang, Lei 1972. "Morphology and optical properties of polyolefin blown films." Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36728.

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Optical properties of polyethylene blown films are of great commercial and scientific interest. An understanding of the relationship between morphology and optical properties will have a significant impact on product and process optimization.
In this work, a number of linear low density polyethylene (LLDPE) resins of different molecular and structural characteristics were studied. Intrinsic properties such as refractive index and absorption coefficient were estimated from resin compositions using group contribution models. The refractive indices of sample films were also measured using the method of Transmission Spectrum.
The morphology of polyethylene films was investigated using Atomic Force Microscopy (AFM) and Near-field Scanning Optical Microscopy (NSOM). Both the surface and bulk morphologies were evaluated. The observation shows the dominant spherulitic structure on the surface as well as in the bulk, as the result of nucleation and crystallization during the film blowing process. In addition to qualitative observations and comparisons; quantitative characterization methods were employed to describe the features of the morphology.
Based on the morphology characterization, the surface reflection was described by the Beckmann-Davies theory of reflection of electro-magnetic waves by rough surface. The directional distribution of reflected intensity was computed according to the surface roughness information. The gloss values of sample films were computed accordingly and compared with experimental measurements. Furthermore, the problem of light transmission and scattering was investigated. A scattering geometry was proposed from the observations of the morphology of sample films. The light scattering by the surface of polymer films was analyzed using a model that is based on the Mie theory of scattering. The haze values of sample films were computed and compared with experimental measurements.

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27

Browne, Thomas 1955. "Viscoelastic properties of paper in a calender nip." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28698.

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Paper in a calender nip is subjected to a pressure pulse which reduces its thickness and roughness, thus improving the product quality. Strain recovery after the nip is time-dependent, and some permanent strain remains. The material behaviour is viscoelastic; recovery depends on the pulse magnitude and duration, and does not occur immediately on exiting the nip. An improved description of the viscoelastic response to a calender pulse would allow design of adaptive control systems using feedforward techniques.
Measurements of paper thickness in the nip, immediately after the nip and 24 hours after calendering were made with newsprint sheets running through an experimental calender operating at industrial conditions. The calculated strains were first related to the operating conditions using empirical curve-fitting methods, then using linear viscoelastic models. Empirical results describe the data well, and can be used to design improved control systems. Linear viscoelastic modeling was less successful since the material behaviour is not linear. Photomicrographs of sheet cross-sections were taken, and the observed non-linearities were discussed qualitatively in terms of paper and fibre properties.

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28

Park, Hee Eon 1972. "Effect of pressure on the rheological properties of three polyethylenes." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=31066.

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The effect of pressure on the viscosity of polyethylenes was studied using a newly developed high-pressure, sliding-plate rheometer. The rheometer subjects the sample to a homogeneous pressure and temperature at levels up to 70 MPa and 225°C. Simple shear is generated in the sample, and the resulting shear stress is measured locally in the center of the sample by means of a shear stress transducer. Viscosity curves were generated at four pressures from 0.1 to 70 MPa, and it was found that the pressure data could be shifted onto the ambient pressure curves by means of a pressure shift factor. The viscosity increases exponentially with pressure. Long chain branching increases the pressure sensitivity, but the polydispersity has little effect.
The effect of pressure on the creep behavior of polyethylenes was also studied. It was observed that pressure decreases the creep compliance. Careful tuning the controller is required to obtain reliable data when operating the rheometer in the creep mode.

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29

Tavares, Jason. "Dual plasma synthesis of functionalized metal nanoparticles: from enhanced surface properties to stable nanofluids." Thesis, McGill University, 2010. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=94917.

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This thesis presents a dual plasma process allowing for the single-step synthesis of surface functionalized metal nanoparticles. The process uses a pulsed cathodic arc discharge to erode a metal target and form nanoparticles. These nanoparticles are then coated in flight through plasma polymerization in a radio-frequency glow discharge. This discharge was sustained in a wide range of organic precursors to affect the resulting surface properties of the nanoparticles. Using ethane as the plasma polymerizing monomer, a super-hydrophobic surface is formed. Alternatively, the use of ethylene glycol to modify the particle results in the formation of a super-hydrophilic surface. This treatment is shown to improve dispersion of the nanoparticles into polar media. Surface-modified nanoparticles were collected in situ in a liquid flowing inside the dual plasma reactor to form a nanofluid. Suspensions formed via this process are shown to be stable over a wide temperature range, compared to suspensions stabilized using surfactants that can be thermally unstable. Moreover, the hydrophilic nature of the ethylene glycol-based plasma polymer coating (when deposited onto titanium nanoparticles) is demonstrated to reduce the expected thrombogenicity of blood-contacting stainless steel implants, without adversely affecting the implants' corrosion resistance. A detailed investigation into the gas phase reactions that lead to these hydrophilic surface properties is presented, along with an in-depth characterization of the morphology and surface chemistry of the nanoparticles.
Cette thèse présente un procédé à plasma hybride permettant la synthèse en une seule étape de nanoparticules métalliques fonctionnalisées en surface. Le procédé utilise une décharge pulsée par arc cathodique pour assurer la synthèse de nanoparticules à partir d'une cible métallique. Ces particules sont ensuite revêtues et fonctionnalisées en vol au moyen d'une polymérisation par plasma dans une décharge radio fréquentielle. Cette dernière décharge a été soutenue dans une variété de précurseurs organiques, le choix duquel affectera les propriétés de surface des particules. Lorsque l'éthane est utilisé comme gaz plasmagène, une surface super hydrophobe est engendrée. En contrepartie, lorsque l'éthylène glycol est utilisé comme monomère pour la polymérisation par plasma, une surface super hydrophile en résulte. Ce dernier traitement améliore notamment les propriétés de dispersion des particules dans des solvants polaires. De plus, les nanoparticules modifiées en surface à l'aide d'éthylène glycol peuvent être collectées dans un liquide à même le réacteur pour former un nanofluide. Les suspensions nanométriques formées de cette façon sont stables sur une plus grande plage de température que les suspensions de nanoparticules stabilisées au moyen d'un surfactant. Aussi, la nature hydrophile du revêtement organique à base d'éthylène glycol (lorsqu'il est déposé sur des nanoparticules de titane) peut aider à réduire le caractère thrombogénique d'implants en acier inoxydable, sans diminuer leur résistance à la corrosion. Une investigation détaillée de la production en phase gazeuse des radicaux utilisés pour la fonctionnalisation est présentée, ainsi qu'une caractérisation approfondie de la morphologie et de la chimie de surface des nanoparticules produites.

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30

Park, Hee Eon 1972. "Effects of pressure and dissolved carbon dioxide on the rheological properties of molten polymers." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=85949.

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Supercritical carbon dioxide (SC-CO2) is used as a physical blowing agent in the manufacture of plastic foam and as a plasticizer to reduce melt viscosity during processing. Pressure is also an important variable for processing, and the combined effects of dissolved SC-CO 2 and pressure on rheological properties must be known to achieve optimum processing conditions. However, until recently there was no method to measure these effects accurately. A high-pressure sliding plate rheometer in which the shear rate, temperature, pressure, and CO2 concentration are uniform, was used in the present study. The effects of CO2 and pressure on the viscosity, stress growth function, and creep compliance of a high density polyethylene (HDPE) were determined. To separate the effects of pressure and CO2, samples were first pressurized without CO 2, and then pressurized and saturated with CO2. It was possible to use shift factors for pressure and CO2 concentration to obtain a master curve. For the purpose of comparison, the effect of nitrogen on the viscosity is also determine. Another important concern in plastics processing is molecular structure, which has a strong effect on melt flow properties. The effects of long- and short-chain branching and side groups on the pressure sensitivity of viscosity were also determined in this project.

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31

Li, Ruonan. "Surface properties and pore structure of superheated steam dried paper." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=55414.

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Effects of superheated steam drying were determined for surface properties and pore structure of paper, properties which are important in the end use of paper. Two furnishes were investigated, thermomechanical pulp (TMP) and a TMP/kraft pulp blend. Drying of handsheets under matched conditions in air was used as the basis of comparison.
TMP paper dried in superheated steam has a slightly higher surface roughness, by about 0.5 $ mu$m at a roughness around 8 $ mu$m. This difference decreases with drying fluid temperature. It is also reduced by about half after a very light blade coating. Surface roughness of paper from 50/50 TMP/kraft blend is unaffected.
Superheated steam drying reduces substantially the linting propensity of TMP paper, by about 30%-60% depending on the criteria used. Improved lignin softening by higher web temperature from the beginning of drying in superheated steam drying is believed an important mechanism in improving bonding of surface fines and short fibre fragments.
The Z-direction bond strength of TMP paper after surface treatment with water is about 20% higher for sheets dried in steam. Time for water absorption is 100%-150% longer for superheated steam dried TMP paper and contact angle of water is also substantially increased.
Superheated steam drying substantially reduces the volume of micropores of diameter 0.2-0.6 $ mu$m while having no significant effect on larger pores. Thus superheated steam drying affects only the pore structure of the micronetwork. The decrease of micropore volume in superheated steam drying is associated with an increase of Z-direction bond strength and a decrease of light scattering coefficient.

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32

Addona, Tony. "The effect of quench conditions on the properties of fumed silica produced using an arc process." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=26108.

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The effect of quench conditions on the properties of fumed silica generated using an arc process was studied. The process consisted of vaporizing quartz particles in a batch transferred arc reactor using the radiative energy from an Ar/NH$ sb3$ thermal plasma. Ammonia was used to increase the vaporization rate of quartz. The hot gas stream exiting the reactor contained a mixture of the decomposition products of NH$ sb3$ and SiO$ sb2$. This included SiO$ sb{ rm (g)}$, O$ sb2$, H$ sb2$ and N$ sb2$. Rapid quenching of this gas stream with steam resulted in the production of a fumed silica aerosol. Collection of the product took place in a baghouse filter. The quench conditions studied included pre-quench temperature, T$ sb{ rm q}$, and supersaturation, P$ sb{ rm s}$, quench rate, R$ sb{ rm q}$, and quench stoichiometry, S$ sb{ rm q}$. P$ sb{ rm s}$ was defined as the molar ratio of SiO$ sb{ rm (g)}$ flow, calculated from the quartz weight loss during an experiment, to the SiO$ sb{ rm (g)}$ flow predicted at equilibrium. S$ sb{ rm q}$ was the molar ratio of steam to SiO$ sb{ rm (g)}$ flow.
In general, high pre-quench temperatures, high quench rates, and low pre-quench supersaturation ratios, produced high surface area powders. Quench stoichiometry did not have an effect here, but the use of a large excess of steam in the quench caused the degree of surface hydroxylation to be high. In all cases, the characteristic chain-like aggregate shape and an amorphous morphology were produced. The thickening and thixotropic ability of the powders was found to be significant compared to commercial brands of fumed silica. The best fumed silica produced during the study was found to be 46% as effective as Aerosil$ sp circler$ 200 and 60% as effective as Cab-O-Sil$ sp circler$ M-5. The experimentally generated powders were not equivalent to the commercial brands due to a lack of surface area. (Abstract shortened by UMI.)

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Poirier, Nicole A. "The effect of superheated steam drying on the properties of paper." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41057.

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The effect of drying paper by direct contact with superheated steam was determined with respect to the physical, optical and chemical properties of the dried sheet. The results were compared with those for paper dried in a similar fashion by direct contact with hot air.
It was found that the results depended on the type of pulp from which the sheet was made. For thermomechanical pulp sheets, superheated steam drying resulted in improved strength properties; burst index, tensile index and elastic modulus were 20-30% higher relative to the air dried sheets. The increase in strength was found to be due to an increase in bonded area, especially of the fine fraction, caused by the higher sheet temperatures occurring in the constant rate period of steam drying. As a result of the increased bonding but not due to any color change, brightness of the steam dried sheet decreased by 5 points. Steam drying of TMP sheets results in strength and optical properties more characteristic of paper made from CTMP.
Superheated steam drying of kraft pulp sheets had a smaller and opposite effect, as strength properties decreased and optical properties increased relative to the properties of sheets dried in air. Unlike mechanical pulp, no increase in bonded area was observed because of the already high bonding potential of kraft fibres; a thermally induced drying stress relaxation is thought to be the cause of the decreased strength properties.

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Carignan, Alain. "The influence of cofactors on the flocculation properties of polyethylene oxide." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=24053.

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Adding polyethylene oxide (PEO) at the wet end of a paper machine, can result in an increase in retention of the fine particles. The results obtained with PEO and the cofactors (SNS, MPR, and CAR), are discussed in terms of the association-induced polymer bridging mechanism.
Dynamic Light Scattering (DLS) of polymer solutions revealed that each of the three cofactors are forming complexes with PEO. CAR radically increased the apparent diameter of the PEO chains, and MPR seems to decrease it. In latex suspensions, the SNS was found very efficient in the sequence latex-polymer-cofactor (LPC), increasing the PEO hydrodynamic layer thickness (HLT).
Flocculation experiments with the help of a Photometric Dispersion Analyser (PDA), with PEO only (no cofactor) suggested that the fines are composed of more than one component. SNS was found to make all the fines alike by adsorbing on them. Adding the PEO after SNS gave homoflocculation. As a result, the specific surface of fines, calculated by PEO adsorption was found to be 0.223 m$ sp2$/g.
The association-induced polymer bridging mechanism can happen in three different manners depending if the cofactor and the polymer are adsorbing onto fines. When neither of PEO nor cofactor adsorb onto the collector, the PEO/cofactor association-complexes bridge the particles (van de Ven and Alince (1996)). When the cofactor (e.g. SNS) and the polymer adsorb onto the fines, in the sequence fines-cofactor-polymer (FCP), with a chemical ratio cofactor/PEO of 3/1, adsorption of the PEO chains onto cofactor-coated fines is likely to occur at the beginning followed by the flocculation of the fines. In the sequences fines-polymer-cofactor (FPC), when the polymer adsorbs onto the fines and the cofactor adsorbs (e.g. SNS) or not (e.g. MPR), a reenforcement of the bondstrength was noticed. (Abstract shortened by UMI.)

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Karczewska, Hanna. "The effects of acid leaching on some physico-chemical properties of Quebec soil /." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=64017.

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Li, Hailong. "Thermodynamic Properties of CO2 Mixtures and Their Applications in Advanced Power Cycles with CO2 Capture Processes." Doctoral thesis, KTH, Energiprocesser, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-9109.

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The thermodynamic properties of CO2-mixtures are essential for the design and operation of CO2 Capture and Storage (CCS) systems. A better understanding of the thermodynamic properties of CO2 mixtures could provide a scientific basis to define a proper guideline of CO2 purity and impure components for the CCS processes according to technical, safety and environmental requirements. However the available accurate experimental data cannot cover the whole operation conditions of CCS processes. In order to overcome the shortage of experimental data, theoretical estimation and modelling are used as a supplemental approach. In this thesis, the available experimental data on the thermodynamic properties of CO2 mixtures were first collected, and their applicability and gaps for theoretical model verification and calibration were also determined according to the required thermodynamic properties and operation conditions of CCS. Then in order to provide recommendations concerning calculation methods for engineering design of CCS, totally eight equations of state (EOS) were evaluated for the calculations about vapour liquid equilibrium (VLE) and density of CO2-mixtures, including N2, O2, SO2, Ar, H2S and CH4. With the identified equations of state, the preliminary assessment of impurity impacts was further conducted regarding the thermodynamic properties of CO2-mixtures and different processes involved in CCS system. Results show that the increment of the mole fraction of non-condensable gases would make purification, compression and condensation more difficult. Comparatively N2 can be separated more easily from the CO2-mixtures than O2 and Ar. And a lower CO2 recovery rate is expected for the physical separation of CO2/N2 under the same separation conditions. In addition, the evaluations about the acceptable concentration of non-condensable impurities show that the transport conditions in vessels are more sensitive to the non-condensable impurities and it requires very low concentration of non-condensable impurities in order to avoid two-phase problems. Meanwhile, the performances of evaporative gas turbine integrated with different CO2 capture technologies were investigated from both technical and economical aspects. It is concluded that the evaporative gas turbine (EvGT) cycle with chemical absorption capture has a smaller penalty on electrical efficiency, while a lower CO2 capture ratio than the EvGT cycle with O2/CO2 recycle combustion capture. Therefore, although EvGT + chemical absorption has a higher annual cost, it has a lower cost of electricity because of its higher efficiency. However considering its lower CO2 capture ratio, EvGT + chemical absorption has a higher cost to avoid 1 ton CO2. In addition the efficiency of EvGT + chemical absorption can be increased by optimizing Water/Air ratio, increasing the operating pressure of stripper and adding a flue gas condenser condensing out the excessive water.
QC 20100819

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Hossain, A. "Synthesis, crystal structure and properties of complex oxides with the perovskite structure based on neodymium, alkaline earth and 3d-transition metals : dissertation for the degree of candidate of chemical sciences : 02.00.04." Thesis, б. и, 2019. http://hdl.handle.net/10995/82032.

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Arghyris, Laurent. "Modification of the impact properties of blends of polypropylene and poly(ethylene-vinyl alcohol)." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=60574.

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The purpose of this research project has been to evaluate the feasibility of improving the impact properties of polypropylene (PP)/ethylene vinyl alcohol copolymer (EVOH) laminar blends by the incorporation of a rubber phase. The impact modifier was poly (ethylene-propylene) rubber (EPR). The study was conducted initially with a batch mixer, and then continued with an extruder. Furthermore, it was decided to evaluate the improvement in impact toughness of the blends upon addition of a polyethylene (PE) phase.
The batch mixing studies showed that it is possible to bring the impact properties of maleated PP (MAPP)-based blends to the range of those exhibited by MAPP, by incorporation of both EPR and PE. The sequence of addition of EPR and PE is very important. The products obtained exhibited good adhesion at the interface between the dispersed phase and the matrix. The presence of EPR and PE did not affect the final oxygen permeabilities of the blends.
The extrusion studies showed that the morphology of the blends, and therefore their final properties, depend on the method of compounding. Different MAPP resins were used as the major phase. The best impact properties were found in the case of addition of the EPR-PE phase in a twin screw extruder. The oxygen permeabilities were disappointing, and appeared to be only slightly influence by compositional or processing parameters. One possible explanation is that moisture might have contaminated the EVOH phase, inhibiting its effectiveness as an oxygen barrier.

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Mailhot, Hélène. "The use of some physico-chemical properties to predict algal uptake of ogranic compounds /." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65504.

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Weber, Mark 1964. "The processing and properties of electrically conductive fiber composites." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40279.

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The electrical and mechanical properties of electrically conductive fiber composites were measured and related to composite microstructure. Samples were manufactured by compression molding, extrusion, and injection molding to determine the effect of processing method on fiber length and orientation. A strong correlation between the processing-induced fiber-phase microstructure and the measured properties is found. The results are highly dependent on the type of conductive fiber. Computer-generated flow-field models are able to illustrate the thermal and flow processes which affect microstructure. A simple orientation model gives good qualitative agreement with experimental observations in injection molded composites.
Two models for predicting volume resistivity are proposed. One model assumes that the fibers are aligned end-to-end, and the effect of fiber orientation and concentration is obtained. The results agree qualitatively with experimental data, and give a lower bound or resistivity. More realistic fiber-fiber contacts are considered in the second model. The resistivity is expressed in terms of the area of contact, and orientation, length, and concentration of the fibers. Model predictions are in excellent agreement with experimental results.

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41

Chandran, Davannendran. "Experimental investigation into the physico-chemical properties changes of palm biodiesel under common rail diesel engine operation for the elucidation of metal corrosion and elastomer degradation in fuel delivery system." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/35228/.

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Compatibility of fuel delivery materials (FDM) with biodiesel fuel in the fuel delivery system (FDS) under real-life common rail diesel engine (CRDE) operation poses a challenge to researchers and engine manufacturers alike. Although standard methods such as ASTM G31 and ASTM D471 for metals and elastomers, respectively, are deemed suitable for evaluating the effects of water content, total acid number (TAN) and oxidation products in biodiesel on FDM degradation, they do not resemble the actual engine operation conditions such as varying fuel pressure/temperature as well as the presence of a wide range of materials in the FDS of a diesel engine. Hence, the current allowable maximum 20 vol% of biodiesel with 80 vol% of diesel (B20) for use in diesel engines to date is debatable. Additionally, biodiesel utilization beyond B20 is essential to combat declining air quality and to reduce the dependence on fuel imports. This thesis aims to elucidate the actual compatibility present between FDM and biodiesel in the FDS under real-life CRDE operation. This was achieved through multi-faceted experimentations which commenced with analyses on the deteriorated palm biodiesel samples collected during and after CRDE operation. Next, the fuel properties which should be emphasized based on the deteriorated fuel were determined. This was then followed by ascertaining the effects of the emphasized fuel properties towards FDM degradation. Ultimately, the actual compatibility of FDM with biodiesel under engine operation through modified immersion investigations was determined. FDM degradation acceleration factors such as oxidized biodiesel, TAN and water content were eliminated since these factors were not affected based on the analysed fuel samples collected after engine operation. No oxidation products such as aldehydes, ketones and carboxylic acids were detected while the TAN and water content were within 0.446% and 0.625% of their initial values, respectively. Instead, the biodiesel’s dissolved oxygen (DO) concentration and conductivity value were not only found to have changed during and after engine operation by -93% and 293%, respectively, but were also found to have influenced biodiesel deterioration under engine operation. These two properties were subsequently discovered to have adversely affected FDM degradation independently. The copper corrosion rate and nitrile rubber (NBR) volume change increased by 9% and 13%, respectively, due to 22% increase in the conductivity value. In contrast, the copper corrosion rate and NBR volume swelling reduced by 91% and 27%, respectively, due to 96% reduction in the DO concentration. Ultimately, copper corrosion and NBR degradation were determined to be lowered by up to 92% and 73%, respectively, under modified immersion as compared to typical immersion condition. These outcomes distinctly show that acceptable to good compatibility is present between FDM and biodiesel under CRDE operation. The good compatibility is strongly supported since only a maximum lifespan reduction of 1.5 years is predicted for metal exposed to biodiesel as compared to diesel for a typical component lifespan of 15 years. For the elastomers, acceptable compatibility is found present between elastomer and biodiesel based on the determined 11% volume change which conforms to the tolerance level of elastomer degradation as stated by the elastomer manufacturers. These are especially true for the evaluated metals and elastomers investigated under the modified laboratory immersion which replicates similar conditions to a real-life CRDE. Overall, this work has contributed to the advancement of knowledge and application of biodiesel use in diesel engines.

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Cheung, Mee Chu. "Comparative study of the structural, chemical and physical properties of activated sludge floc from different full-scale wastewater treatment systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape17/PQDD_0013/MQ33959.pdf.

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43

Sani, Rababe. "Étude des transformations microstructurales de mélanges argile/Combustibles Solides de Récupération (CSR) lors de la cuisson : relations entre propriétés physico-chimiques, mécaniques et thermiques." Thesis, Ecole nationale des Mines d'Albi-Carmaux, 2018. http://www.theses.fr/2018EMAC0005/document.

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La valorisation des co-produits riches en matières organiques et inorganiques comme additifs dans des formulations à base d’argile peut améliorer à la fois les performances mécaniques et thermiques des produits de terre cuite, de même que le bilan énergétique des procédés de fabrication de ces matériaux. Cette étude a porté sur l’incorporation de combustibles solides de récupération (CSR) dans un mélange de fabrication des produits de terre cuite pour le génie civil en étroite collaboration avec l’entreprise TERREAL dans le cadre du projet LabCom RESPECTc financé par l’ANR.Premièrement, deux CSR ont été sélectionnés et utilisés comme additifs pour améliorer les produits issus des deux gisements de mélange argileux nommés ML et MC de chez TERREAL. L’influence de la nature, du taux d’incorporation des CSR, de la granulométrie des CSR et de la nature de la matrice argileuse sur les propriétés physico-chimiques, mécaniques et thermiques des mélanges argileux/CSR a été étudiée entre 30°C et 1100°C. Dans tous les cas, l’ajout de CSR a permis d’améliorer le caractère isolant des produits de terre cuite, en diminuant leur conductivité thermique. L’ajout de CSR a aussi permis d’améliorer les propriétés mécaniques des produits, en fonction du type et du taux de CSR ajouté, du taux et de la nature (forme, taille et distribution) de la porosité créée. L’étude a démontré que les interactions entre les minéraux argileux et les éléments inorganiques des CSR avaient un impact important sur les propriétés mécaniques et thermiques. Les résultats ont montré que l’ajout de 4% en masse du CSR15-1 contenant un taux de cendres de 65,7% en masse a conduit à une augmentation de la résistance mécanique du matériau à base de la matrice argileuse ML de l’ordre de 32%. Ensuite, un modèle cinétique du frittage basé sur les variations dimensionnelles des matériaux entre 650°C et 1000°C a été développé à partir de l’analyse thermomécanique (ATM) des mélanges (avec ou sans CSR). L’objectif a été de mieux comprendre les mécanismes du frittage mis en jeu. Le modèle développé a montré une bonne adéquation avec les données expérimentales. Les résultats ont montré que l’étape du frittage thermique de ces mélanges se fait en présence d’une phase liquide et que l’ajout de CSR a permis d’accélérer la densification des matériaux. Cela a conduit à une diminution de la température usuelle de cuisson des produits de terre cuite permettant ainsi un gain énergétique non négligeable. Finalement, une étude environnementale a été réalisée lors de la cuisson des mélanges argileux/CSR. Cette étude a particulièrement été focalisée sur la contribution de CSR au bilan énergétique et à l’impact des émissions des gaz critiques tels que le CO2, le CO et l’HCl. Les résultats ont montré que les émissions de CO2 et de CO lors de la cuisson des mélanges argileux/CSR ont augmenté en raison de la décomposition thermique de la matière organique des CSR et que moins de 50% en masse du chlore a été transformé en HCl (18-31 ppm). Le bilan énergétique effectué a montré que l’ajout de CSR au sein des matrices argileuses ML ou MC compense une part non négligeable du gaz naturel usuellement utilisé comme combustible au cours de la cuisson de ces matériaux. Cela s’est traduit par une économie d’énergie thermique et une réduction des émissions de CO2 provenant de la décarbonatation de la matrice argileuse
The valorization of co-products rich in organic and inorganic materials as additives in formulations based on clay matrix can improve both the mechanical and thermal performances of ceramic materials as well as the energy balance of the manufacturing processes of these products. This study focused on the incorporation of Solid Recovered Fuels (SRF) into the clay ceramics for civil engineering in close collaboration with TERREAL as part of the ANR funded LabCom RESPECTc project. Firstly, two SRF were selected and used as additives to improve the properties of ceramic materials from to clay mixture deposits named ML and MC from TERREAL. The influence of the nature, the amount of SRF, the grain size of SRF and the nature of clay matrix on the physico-chemical, mechanical and thermal properties of the clay/SRF mixtures were studied between 30°C and 1100°C. In all cases, the addition of SRF into the clay mixture (ML or MC) has enhanced the insulating nature of the ceramic materials by reducing their thermal conductivity. The addition of SRF has also improved the mechanical properties of the ceramic materials, depending on the nature and the amount of SRF added, the rate and the nature (shape, size and distribution) of the porosity created. The study demonstrated that interactions between clay minerals and inorganic elements of SRF have a significant effect on mechanical and thermal properties. The results showed that the addition of 4 wt.% of SRF15-1 containing an ash content of 65.7 wt.% into clay matrix ML led to increase the mechanical strength of the material based on the clay matrix ML of the order of 32%. Then, a kinetic model of thermal sintering based on the dimensional variations of ceramic materials between 650°C and 1000°C was developed from thermomechanical analysis (TMA) of the clay mixtures (with or without SRF). The main objective is to better understand the mechanism of the thermal sintering involved. The model developed showed a good adequacy with the experimental data. The results showed that the thermal sintering step of these mixtures is carried out by the presence of a liquid phase and that the addition of SRF has accelerated the densification of ceramic materials. This has led to decrease the usual firing temperature of ceramic materials, allowing a significant energy savings. Finally, an environmental assessment was carried out during the firing of clay/SRF mixtures. This study was particularly focused on the contribution of SRF to the energy balance and impact of critical gas emissions such as CO2, CO and HCl. The results showed that CO2 and CO emissions during firing of clay/SRF mixtures increased due to the thermal decomposition of the organic matter of SRF and that less than 50 wt.% of chlorine was converted to HCl (18-31 ppm). The energy balance showed that the addition of SRF into the ML matrix compensates for a significant part of the natural gas usually used as fuel during firing of these ceramic materials. This was reflected by a thermal energy saving and reduction of CO2 emissions from the decarbonatation of the clay matrix

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USSUI, VALTER. "Preparacao e caracterizacao de ceramicas de ZrOsub(2)-Ysub(2)Osub(3)-TiOsub(2) para aplicacoes em celulas a combustivel do tipo oxido solido." reponame:Repositório Institucional do IPEN, 2003. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11081.

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Made available in DSpace on 2014-10-09T12:48:03Z (GMT). No. of bitstreams: 0
Made available in DSpace on 2014-10-09T14:07:33Z (GMT). No. of bitstreams: 1 09454.pdf: 6331407 bytes, checksum: 3ee8d9f10149c12100a0263857d5bcca (MD5)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

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Zenith, Federico. "Control of Fuel Cells." Doctoral thesis, Norwegian University of Science and Technology, Faculty of Natural Sciences and Technology, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1537.

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This thesis deals with control of fuel cells, focusing on high-temperature proton-exchange-membrane fuel cells.

Fuel cells are devices that convert the chemical energy of hydrogen, methanol or other chemical compounds directly into electricity, without combustion or thermal cycles. They are efficient, scalable and silent devices that can provide power to a wide variety of utilities, from portable electronics to vehicles, to nation-wide electric grids.

Whereas studies about the design of fuel cell systems and the electrochemical properties of their components abound in the open literature, there has been only a minor interest, albeit growing, in dynamics and control of fuel cells.

In the relatively small body of available literature, there are some apparently contradictory statements: sometimes the slow dynamics of fuel cells is claimed to present a control problem, whereas in other articles fuel cells are claimed to be easy to control and able to follow references that change very rapidly. These contradictions are mainly caused by differences in the sets of phenomena and dynamics that the authors decided to investigate, and also by how they formulated the control problem. For instance, there is little doubt that the temperature dynamics of a fuel cell can be slow, but users are not concerned with the cell’s temperature: power output is a much more important measure of performance.

Fuel cells are very multidisciplinary systems, where electrical engineering, electrochemistry, chemical engineering and materials science are all involved at various levels; it is therefore unsurprising that few researchers can master all of these branches, and that most of them will neglect or misinterpret phenomena they are unfamiliar with.

The ambition of this thesis is to consider the main phenomena influencing the dynamics of fuel cells, to properly define the control problem and suggest possible approaches and solutions to it.

This thesis will focus on a particular type of fuel cell, a variation of proton-exchange-membrane fuel cells with a membrane of polybenzimidazole instead of the usual, commercially available Nafion. The advantages of this particular type of fuel cells for control are particularly interesting, and stem from their operation at temperatures higher than those typical of Nafion-based cells: these new cells do not have any water-management issues, can remove more heat with their exhaust gases, and have better tolerance to poisons such as carbon monoxide.

The first part of this thesis will be concerned with defining and modelling the dynamic phenomena of interest. Indeed, a common mistake is to assume that fuel cells have a single dynamics: instead, many phenomena with radically different time scales concur to define a fuel-cell stack’s overall behaviour. The dynamics of interest are those of chemical engineering (heat and mass balances), of electrochemistry (diffusion in electrodes, electrochemical catalysis) and of electrical engineering (converters, inverters and electric motors). The first part of the thesis will first present some experimental results of importance for the electrochemical transient, and will then develop the equations required to model the four dynamic modes chosen to represent a fuel-cell system running on hydrogen and air at atmospheric pressure: cathodic overvoltage, hydrogen pressure in the anode, oxygen fraction in the cathode and stack temperature.

The second part will explore some of the possible approaches to control the power output from a fuel-cell stack. It has been attempted to produce a modularised set of controllers, one for each dynamics to control. It is a major point of the thesis, however, that the task of controlling a fuel cell is to be judged exclusively by its final result, that is power delivery: all other control loops, however independent, will have to be designed bearing that goal in mind.

The overvoltage, which corresponds nonlinearly to the rate of reaction, is controlled by operating a buck-boost DC/DC converter, which in turn is modelled and controlled with switching rules. Hydrogen pressure, being described by an unstable dynamic equation, requires feedback to be controlled. A controller with PI feedback and a feedforward part to improve performance is suggested. The oxygen fraction in the cathodic stream cannot be easily measured with a satisfactory bandwidth, but its dynamics is stable and disturbances can be measured quite precisely: it is therefore suggested to use a feedforward controller. Contrary to the most common approach for Nafion-based fuel cells, temperature is not controlled with a separate cooling loop: instead, the air flow is used to cool the fuel-cell stack. This significantly simplifies the stack design, operation and production cost. To control temperature, it is suggested to use a P controller, possibly with a feedforward component. Simulations show that this approach to stack cooling is feasible and poses no or few additional requirements on the air flow actuator that is necessary to control air composition in the cathode.

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Class, Caleb Andrew. "Predicting organosulfur chemistry in fuel sources." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98155.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references.
Desulfurization of fossil fuels with supercritical water (SCW) has been the topic of many studies over the past few decades. This process does not require the use of any catalyst, eliminates the need for a hydrogen feed, and minimizes coke formation. Previous research has shown that it has the potential to be a viable commercial process, and recent experimental studies have proven that water acts as one hydrogen source for sulfur removal in this process. However, the exact desulfurization mechanism is largely unknown, as are many other reaction mechanisms involving sulfur compounds. Recent work has greatly expanded our ability to build comprehensive reaction mechanisms automatically for the decomposition of organic sulfur compounds using the automated Reaction Mechanism Generator (RMG). This thesis presents the implementation of this and other tools to investigate chemical processes relevant to our use of fuel sources containing sulfur compounds, and it shows some steps that have been taken to improve our predictions for these mechanisms and those that will be generated in the future. Previous investigations had focused on the pyrolysis of small sulfur compounds containing less than six heavy atoms, so RMG is first used to study the pyrolysis of t-butyl sulfide. A detailed reaction mechanism is then presented for the SCW desulfurization of hexyl sulfide. Comprehensive kinetic mechanisms for these larger molecules are likely to include thousands of reactions, so RMG builds this model in a systematic and unbiased way using a database of ab initio data. This database is expanded with potentially relevant thermochemical and kinetic parameters using transition state theory and quantum chemical calculations at the CBS-QB3 and CCSD(T)-F12 levels of theory. With these data, as well as previously calculated rates for hydrocarbon and sulfur kinetics, RMG is used to build a reaction mechanism for the conversion of hexyl sulfide to hydrogen sulfide, pentane, and carbon monoxide in the presence of SCW. This mechanism is validated with results from batch and flow reactor experiments, and predictions are accurate within a factor of two for reactant and major product concentrations. Analysis of the proposed mechanism shows that the molecular addition of water to the carbonsulfur double-bond in hexanethial is a key step in the SCW process, as this not only leads to the desulfurization of the compound, but also prevents the thioaldehyde from undergoing addition reactions with other hydrocarbons in a process that could eventually form coke. Thus, this work not only has implications in the SCW desulfurization process, but in the overall crude oil upgrading process as well. The calculated kinetic and thermochemical parameters are used to generate predictive reaction mechanisms for other processes relevant in fuel chemistry, such as the geological formation of oil and gas from kerogen. This not only allows us to model experimental work investigating the effect sulfur compounds have on the oil-to-gas process, but we also explore how these effects differ at geological conditions and timescales. And as the possible applications of RMG grow, the need for accurate parameters in mechanism generation become even more critical. A thermochemical database is generated for a wide variety of sulfur compounds using the highaccuracy CCSD(T)-F12/cc-pVTZ-F12 method, and this provides a basis for the investigation of organosulfur chemistry with tighter uncertainty.
by Caleb Andrew Class.
Ph. D.

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Mlwilo, Nolasco Anton. "Radiometric characterisation of vineyard soils, Western Cape, South Africa." Thesis, University of the Western Cape, 2010. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_6358_1318594333.

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This study is aimed at investigating the feasibility of using the radiometric technique as an alternative to traditional methods for determining soil physico-chemical parameters which are important for terroir characterization. In-situ and ex-situ radiometric analyses of soil from three vineyard blocks of Simonsig Wine Estate in the Stellenbosch district (Western Cape, South Africa) were studied. A mobile MEDUSA gamma-ray detection system comprising a CsI(Na) crystal (length 15 cm, diameter 7 cm) and associated electronics mounted on a portable trolley were used for partial terroir characterisation. Thereafter activity concentrations of 40K, 232Th series and 238U series in soil (top ~30 cm) from the measured MEDUSA spectra (0 â 3 MeV) were extracted by means of the full-spectrum analysis (FSA) method. A lead-shielded HPGe detector was used for analyzing collected soil samples while soil physico-chemical parameters were analysed using standard methods at research and commercial laboratories.

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48

Tingelöf, Thomas. "Polymer Electrolyte Fuel Cells in Reformate Power Generators." Doctoral thesis, KTH, Skolan för kemivetenskap (CHE), 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-26938.

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The topic of this thesis is the generation of electricity from hydrocarbon fuels via polymer electrolyte fuel cells (PEFC). The aim has been to develop methods and hardware for experimental evaluation of process parameters and design variables in PEFC reformate cells and stacks. Reformate fuel cell systems have the potential to offer a way for utilizing fuels efficiently with low global and local emissions. Reforming of hydrocarbon fuels may also provide a way around the famous “chicken or egg” dilemma of hydrogen vehicles and infrastructure. In this thesis current distribution measurements are introduced as a tool for investigating the current distribution in a PEFC with Pt/C or PtRu/C anode catalyst as function of reformate fuel gas composition. It is shown that CO may induce a strong transient behavior, with respect to current density, on both Pt/C and PtRu/C catalysts, depending on mode of operation. Analysis of the exhaust fuel gas showed that the oxygen in the air bleed most likely reacts close to the anode inlet, but this is not visible in the measured current density plots. The time dependence of the CO poisoning reactions is studied more closely in a commercial fuel cell stack. The development of a test fuel cell system, called multisinglecell, that can multiply the capacity of a conventional test station is reported. The setup is successfully demonstrated with initial screening of the corrosion resistance of different stainless steel grades and coatings. Most of the iron originating from a stainless steel sample accumulates in the MEA and GDLs. These results were validated with a similar measurement in a commercial fuel cell stack. The experimental validation of a 3D FEM computer endplate model, which can accurately predict pressure distribution within any type of fuel cell at any temperature, is described. The model could reliably predict trends in changes in the compression pressure distribution. The PBI fuel cell competes with the PEFC in small-scale power applications. A high temperature break-in procedure for PBI fuel cells is developed, which can rapidly and reproducibly ensure stable cell behavior.
QC 20101130

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Nilsson, Frederik. "Alkylglucosides physical-chemical properties /." Lund : Physical Chemistry 1, Center for Chemistry and Chemical Engineering, Lund University, 1998. http://catalog.hathitrust.org/api/volumes/oclc/39761789.html.

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50

Girgis, Elisabeth. "Fuel devolatilization in packed bed wood combustion." Thesis, University of Ottawa (Canada), 2004. http://hdl.handle.net/10393/26645.

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Packed bed combustion is the burning of solid fuel particles supported by a grate with the combustion air supplied from below. The combustion process is divided into four main stages: drying, devolatilization, volatiles combustion and char combustion. Biomasses proposed as renewal energy sources, such as wood, have a very high volatile content (∼80%). Therefore mechanistic models developed for the prediction of bed characteristics during biomass combustion must include devolatilization and volatile combustion stages in order to correctly predict combustion behaviour for better emissions control and process efficiency. A novel in-situ sampling method for tar, a major pyrolysis product, was developed that allows its concentration to be measured at various heights within the packed bed and appears to work satisfactorily. A series of experiments on packed bed combustion were conducted in a laboratory 'pot' type combustor. Two different equivalent particle size diameters (2.8 cm and 3.2 cm) of untreated spruce wood and two different airflow rates (0.025 kg/m2s and 0.03 kg/m 2s) were tested at a 22 cm bed height. Although the experimental data show scatter, the measurements indicated that pyrolysis occurred primarily within two particle diameters of the top of the bed, with large amounts of tar and CO and somewhat less CO2 being produced. This research also expanded a numerical model for packed bed combustion of solid fuels with the addition of a simple first order pyrolysis reaction, in which fixed proportions of the products were set as light volatiles of CO and CO2 with the balance as tar. The model results compared well with bed temperature, particle size and density measurement throughout the bed and gas concentration (CO, CO2, O2, and CH4) measurements in the reduction and oxidation zone.

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Dissertations / Theses on the topic 'Chemical and fuel properties'

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