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1
Oliveira, Rhuiago Mendes de. "Cálculo das propriedades dinâmicas dos sistemas moleculares H2O-He, H2O-Ne, H2O-Ar, H2O-Kr, H2O-Xe, CCl4-He, CCl4-Ar, CCl4-Ne, CCl4-O2, CCl4-D2O e CCl4-ND3." reponame:Repositório Institucional da UnB, 2014. http://repositorio.unb.br/handle/10482/17399.
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Dissertação (mestrado)—Universidade de Brasília, Pós-Graduação em Física, 2014.Submitted by Larissa Stefane Vieira Rodrigues (larissarodrigues@bce.unb.br) on 2014-12-09T17:05:57Z No. of bitstreams: 1 2014_RhuiagoMendesDeOliveira.pdf: 701976 bytes, checksum: 06685f90f88a213c31bd9179de2b0a31 (MD5)
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O objetivo principal deste trabalho foi o c´alculo das energias e constantes espectroscópicas rovibracionais de dois conjuntos de sistemas moleculares: água com os gases nobres (H2O-He, H2O-Ne, H2O-Ar, H2O-Kr e H2O-Xe) e moléculas envolvendo o tetracloreto (CCl4-He, CCl4- Ne, CCl4-Ar, CCl4-O2, CCl4-D2O e CCl4-ND3). Todos estes cálculos foram realizados usando duas metodologias diferentes (Método das variáveis discretas e método de Dunham) e curvas de energias potenciais analíticas do tipo ILJ (do inglês ”Improved Lennard-Jones) com parâmetros ajustáveis obtidos experimentalmente. Os resultados obtidos pelas duas metodologias estão em um excelente acordo e os mesmos podem ser utilizados como referência para futuros experimentos de espectroscopia. ______________________________________________________________________________ ABSTRACT
The goal of this work was the calculation of the rovibrational energies and rovibrational spectroscopy constants of two sets of molecular systems: water with noble gas (H2O-He, H2ONe, H2O-Ar, H2O-Kr and H2O-Xe) and molecules composed by tetrachloride (CCl4-He, CCl4- Ne, CCl4-Ar, CCl4-O2, CCl4-D2O and CCl4-ND3). These calculations were determined using two different methodologies (discrete variable method and Dunham method) and Improved Lennard-Jones analytical potential energy curves with experimentally adjusted parameters. The discrete variable method and Dunham results are in an excellent agreement and they can be used as a standard for spectroscopic experiments.
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Norval, Mary. "UV laser multiphoton dissociation studies of H2O, NO2 and H2O2." Thesis, University of Edinburgh, 1987. http://hdl.handle.net/1842/19199.
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McKendrick, Colin Bruce. "UV laser multiphoton dissociation studies of H2O, NO2 and H2O2." Thesis, University of Edinburgh, 1986. http://hdl.handle.net/1842/12630.
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Bryce, Christine. "A kinetic study of gallium arsenide etching in H2O2-NH4OH-H2O solutions /." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41991.
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Gallium arsenide, a compound semiconductor commonly used in optoelectronic devices, is often subjected to wet etching techniques during microelectronic device manufacture. In this work, the wet chemical etching of gallium arsenide in $ rm H sb2O sb2$-$ rm NH sb4OH$-H$ sb2$O solutions was studied using a batch stirred-tank reactor. A kinetic control regime was established and the influence of each component's concentration on the intrinsic etch rate was determined. The reaction rate was found, in the presence of excess NH$ sb4$OH, to fit a rate equation, r = k (H$ rm sb2O sb2 rbrack sp{0.75}$ at 15, 25, and 40$ sp circ$C with an activation energy of 33.7 kJ/mol. Using NaOH instead of NH$ sb4$OH resulted in greatly reduced reaction rates, and it was concluded that the presence of the ammonium ion increases the rate by forming soluble compounds with oxidized species of Ga and As. When mass transfer resistances are introduced, using a flow reactor to simulate an industrial etching apparatus, the reaction rates are considerably reduced and the rate's dependence on $ rm H sb2O sb2$ concentration is shifted closer to linear. Convective mass transfer expressions for flow past a flat plate were successfully used to predict the etch rate. The two reactors were used to etch samples masked by a circuit pattern, and the crystallography of GaAs dictated the shape of the etch profiles rather than the mass transfer limitations of the system.
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Thibert, Emmanuel. "Thermodynamique et cinétique des solutions solides HCl-H2O et HNO3-H2O : implications atmosphériques." Phd thesis, Université Joseph Fourier (Grenoble), 1996. http://tel.archives-ouvertes.fr/tel-00755697.
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Le but de notre travail est de contribuer à la compréhension des interactions entre les gaz acides et la glace, à la fois pendant la phase atmosphérique de la glace, c'est à dire dans les nuages, et dans la neige après dépôt au sol. Les gaz polaires en général, et les acides en particulier, interagissent fortement avec la glace dans la quelle ils peuvent se dissoudre. Dans les nuages, ces interactions peuvent modifier fortement la composition de l'air, et ce point reste une inconnue majeure en chimie atmosphérique. La compréhension de la relation entre la composition de l'air et celle de la glace, appelée fonction de transfert air-neige, est également indispensable pour reconstituer la composition des paléoatmosphères à partir des carottes de glace. Afin de contribuer à élucider ces problèmes, nous avons étudié l'incorporation dans la glace des composés gazeux HCI et HN03. Les compositions à l'équilibre thermodynamique des solutions solides HCl-glace et HN03-glace, en fonction de la température et de la pression partielle du gaz, ont été obtenues expérimentalement en mesurant les profils de diffusion du gaz dans des monocristaux de glace. A -15 °C, le coefficient de diffusion est de l'ordre de 10-12 cm2/s pour HCI et de 10-10 cm2/s pour HN03. A la même température, sous une pression de 6 x 10-3 Pa, HN03 est environ 25 fois moins soluble que HCI avec pour solubilité respectives de 2,2 x 10-7 et 5 x 10-6 fraction molaire. Ces données ont été appliquées à différents phénomènes d'intérêt atmosphérique. Dans le cadre de la fonction de transfert air-neige, nos résultats ont été comparés à des données de terrain obtenues au Groenland. Il apparaît que, dans les flocons de neige, HCI en solution solide n'est pas en équilibre avec HCI en phase gazeuse. La teneur en HCI dans la neige est déterminée par des facteurs cinétiques lors de la formation des cristaux. Les résultats concernant HN03 suggèrent en revanche que, dans les flocons analysés, HN03 est en équilibre avec la phase gazeuse sans doute grâce à sa cinétique de diffusion plus rapide. Suite à ces résultats, nous avons proposé un mécanisme d'incorporation des gaz dans la glace lors de la croissance des cristaux. Celui-ci suggère que la relation liant la composition atmosphérique à la composition de la glace des nuages est fortement influencée par la dynamique atmosphérique et, en particulier, par les paramètres température et vitesse de refroidissement lors de la phase de formation du nuage. Les données obtenues au laboratoire intéressent aussi le domaine de l'hydrologie appliqué à la composition des eaux de fonte des neiges. Les résultats sur les solubilités de HCI et de HN03 et leur localisation probable dans le névé en cas de sursaturation expliquent semi quantitativement le phénomène observé d'élution préférentielle de l'ion nitrate par rapport à l'ion chlorure.
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Timofejeva, Oksana. "Nuosėdų formavimosi sistemose CuSO4 – K4P2O7 – H2O ir CuSO4 – (NH4)4P2O7 – H2O mechanizmo tyrimas." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2009. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2009~D_20090526_111134-61644.
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Disertaciniame darbe naudojant IR-spektrometrijos, rentgenofazinės analizės, atominės absorbcinės spektroskopijos, kolorimetrijos analizės metodus buvo ištirta sistemose CuSO4 – K4P2O7 – H2O ir CuSO4 – (NH4)4P2O7 – H2O susidarančių mažai tirpių junginių sudėtis, jų susidarymo dėsningumai ir vykstančios reakcijos, įvairių veiksnių įtaka nuosėdų sudėčiai ir struktūrai. Nustatyta, kad sistemoje CuSO4 – K4P2O7 – H2O, be jau žinomų mažai tirpių junginių (paprastosios druskos Cu2P2O7 5H2O ir dvigubosios druskos Cu3K2(P2O7)2 H2O, susidaro ir naujas mokslinėje literatūroje neaprašytas junginys (Dimorfas B), dvigubajai druskai patiriant polimorfinį perėjimą. Polimorfinio perėjimo trukmė labai priklauso nuo pH ir reaguojančių jonų koncentracijų. FTIR duomenų analizė parodė, kad difosfato jonų energetinė būsena Cu – K ir Cu – NH4 Dimorfuose B panaši. Jų rentgenogramos yra panašios, tikėtina, kad šie junginiai – izostruktūriniai, jų kristalinės gardelės tipas – monoklininis. Naudojant Lazarevo lygtį bei Rulmonto priklausomybę buvo apskaičiuoti Cu – K ir Cu – NH4 Dimorfų A ir B bei paprastosios druskos P – O – P kampai, gauta, kad jie mažai keičiasi siaurame 123,1 – 127,1 º intervale.
Nustatyta, kad dviguboji druska susidaro iš paprastosios, vykstant heterogeninei reakcijai:
3Cu2P2O7 5H2O↓ + H2P2O72– + 4K+ → 2Cu3K2(P2O7)2∙3H2O↓ + 2H++ 9H2O.
Mokslinėje literatūroje tokia reakcija neaprašyta jokiai polifosfatų sistemai, jos tyrimo duomenys yra nauji. Taip pat nustatyta, kad heterogeninės... [toliau žr. visą tekstą]At least three poorly soluble compounds can be formed in the CuSO4 – K4P2O7 – H2O system: a single salt Cu2P2O7.5H2O and two dimorph’s both having chemical formula Cu3K2(P2O7)2.3H2O. A previously known form of Cu3K2(P2O7)2.3H2O (we named it Dimorph A) transforms into a novel Dimorph B, which has a different structure. The similarities between the XRD patterns and vibrations spectra of copper–ammonium and copper–potassium Dimorph’s B imply that they are isostructural. The values of the angle for copper–potassium and copper–ammonium salts and Cu2P2O7.5H2O are relatively low and vary within a narrow range (123.1 – 127.1°). The formation of the compounds significantly depends on the conditions of the experiment. A double salt in the CuSO4 – K4P2O7 – H2O system may be formed after some time in the reaction mixture as a result of the following heterogeneous reaction: 3Cu2P2O7∙5H2O↓ + H2P2O72– + 4K+ → 2Cu3K2(P2O7)2∙3H2O↓ + 2H+ + 9H2O This reaction has not been previously described for any polyphosphate system. Therefore, novel results of scientific investigation are presented. The rate, duration and yield of heterogeneous reaction substantially depend on pH of the solution, [Cu2+ + P2O74–] and n ([P2O74–] / [Cu2+]). At a relatively low pH the induction time is high, the reaction rate is low and duration is long. The maximal yields close to 100% can be achieved when [Cu2+ + P2O74–] = 0.1 M. At increased pH values, the induction time, the yield and duration of the reaction diminish... [to full text]
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Zakharchuk, Vitaly. "Löslichkeit von Spinell und Korund in reinem H2O und in KOH-H2O-Lösung." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=983022410.
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Salavera, Muñoz Daniel. "Propiedades Termofísicas de nuevos fluidos de trabajo (H2O+LiBr+LiNO3+LiC1, NH3+H2O y NH3+H2O+KOH) para sistemas de refrigeración por absorción." Doctoral thesis, Universitat Rovira i Virgili, 2005. http://hdl.handle.net/10803/8530.
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El incremento de la demanda energética, que acompaña al crecimiento experimentado por la economía mundial en las últimas décadas, obliga a la búsqueda de tecnologías más eficientes que permitan mitigar los efectos negativos que sobre el medio ambiente causa este crecimiento.En España, una de las principales demandas energéticas se produce en los meses estivales, debido al aumento de aparatos de aire acondicionado. Para reducir esta demanda, la refrigeración por absorción activada por energía solar o calor residual se presenta como una de las opciones más interesantes de cara al futuro.
Los fluidos de trabajo convencionales (agua + bromuro de litio y amoniaco + agua) presentan una serie de inconvenientes: la limitada solubilidad y elevada corrosividad del bromuro de litio, y la necesidad de rectificación para la separación de la mezcla amoniaco + agua que determinan las propias limitaciones del uso de estos sistemas.
La adición de otros componentes puede paliar estos inconvenientes y mejorar así las prestaciones del ciclo. Así, el uso de sales de litio (cloruro, nitrato y ioduro) pueden reducir la corrosividad y aumentar la solubilidad del bromuro de litio, y el uso de hidróxidos alcalinos (de sodio y de potasio) aumentan la volatilidad relativa de la mezcla NH3+H2O y facilitar así la separación de ambos a la salida del generador.
La información existente respecto a las propiedades termofísicas de estas nuevas mezclas es insuficiente para una precisa simulación del ciclo de absorción, por lo que el objetivo de este trabajo ha sido completar el estudio de las propiedades termofísicas más características de cada mezcla, así como la adaptación y puesta en marcha de los dispositivos y técnicas experimentales para realizar dicho trabajo.
Para la mezcla H2O + (LiBr + LiNO3 + LiCl + LiI) se ha determinado experimentalmente la solubilidad, la capacidad calorífica y la densidad. La primera se ha llevado a cabo por medio de dos métodos politérmicos, uno visual y otro calorimétrico, este último por medio de un calorímetro Calvet. Este mismo calorímetro fue utilizado para la determinación experimental de las capacidades caloríficas a presión constante de las disoluciones acuosas por medio de un método incremental. Finalmente, las densidades de las disoluciones fueron determinadas por medio de un densímetro de precisión de tubo vibrante.
Para las mezclas NH3 + H2O + NaOH y NH3 + H2O + KOH se ha realizado un estudio teórico-experimental del equilibrio líquido-vapor, a partir de las medidas de presión de vapor por el método estático a distintas composiciones y temperaturas de diferentes mezclas, determinandose la composición de las fases en equilibrio a través del método de Barker adaptado para sistemas ternarios. Además, los resultados se han correlacionado mediante el método Electrolyte-NRTL. Asimismo, se han determinado experimentalmente y correlacionado en función de la temperatura y composición las capacidades caloríficas a presión constante y las densidades de las disoluciones por el método calorimétrico y de tubo vibrante, respectivamente.
The increase of the power demand, that accompanies to the experienced growth by the world economy in the last decades, forces the search of more efficient technologies which allow to mitigate the negative effects that on the environment this growth causes.
In Spain, one of the main power demands happen in the summer months, due to the increase of air conditioning apparatuses. In order to reduce this demand, absorption refrigeration systems driven by solar energy or waste heat comes up as one of the most interesting options with the view to the future.
The conventional working fluids (water + lithium bromide and ammonia + water) show some disadvantages: limited solubility and high corrosivity of the lithium bromide, and the necessity of rectification for the separation of the mixture ammonia + water that determine the own limitations of the use of these systems.
The addition of other components can to alleviate these disadvantages and improving like this the performance of the cycle. Thus, the use of lithium salts (chloride, nitrate and iodide) can to reduce the corrosivity and increasing the solubility of the lithium bromide, and the use of alkaline hydroxides (of sodium and potassium) increasing the volatileness relative of mixture NH3+H2O and to facilitate the separation of both in the exit of the generator.
The information with respect to the thermophysical properties of these new mixtures is insufficient for one precise simulation of the absorption cycle, reason why the objective of this work has been to complete the study of the more characteristic thermophysical properties of each mixture, as well as the adaptation and experimental beginning of the devices and techniques to make this work.
For the mixture H2O + (LiBr + LiNO3 + LiCl + LiI) solubility, heat capacity and density have been determined experimentally. The first has been carried out by means of two polythermal methods, one visual and another calorimetric, this last one by means of a Calvet calorimeter. This same calorimeter was used for the experimental determination of the heat capacities to constant pressure of the watery dissolutions by means of an incremental method. Finally, the densities of the dissolutions were determined by means of an accurate vibrating tube densimeter.
For the mixtures NH3 + H2O + NaOH and NH3 + H2O + KOH a theoretical-experimental study of the liquid-vapor equilibrium has been made, from the measures of vapor pressure by the static method to different compositions and temperatures from different mixtures, determining the composition of the equilibrium phases through the method of Barker adapted for ternary systems.
In addition, results have been correlated by means of the Electrolyte-NRTL method. Also, heat capacities to constant pressure and densities have been determined experimentally and correlated based on the temperature and composition of the dissolutions, by the calorimetric method and of vibrating tube, respectively.
L'increment de la demanda energètica, que ha acompanyat el creixement experimentat per l'economia mundial en les últimes dècades, fa necessària la recerca de tecnologies més eficients que permetin reduir els efectes negatius que aquest creixement efectua sobre el medi ambient.
A l'estat espanyol, les puntes més elevades de demanda energètica es produeix durant l'estiu, degut a l'augment d'aparells d'aire condicionat. Per a reduir aquesta demanda, la refrigeració per absorció activada per energia solar o calor residual es presenta com una de les opcions més interessants de cara al futur.
Els fluids de treball convencionals (aigua + bromur de liti i amoníac + aigua) presenten una sèrie d'inconvenients: la limitada solubilitat i elevada corrosivitat del bromur de liti, y la necessitat de rectificació per a la separació de la mescla amoníac + aigua que determinen les pròpies limitacions de l'ús de aquests sistemes.
L'addició d'altres components pot minorar aquests inconvenients i millorar així les prestacions del cicle. Així, l'ús de sales de liti (clorur, nitrat i iodur) poden reduir la corrosivitat i augmentar la solubilitat del bromur de liti, i la utilització d'hidròxids alcalins (de sodi i de potassi) augmenten la volatilitat relativa de la sistema NH3+H2O i faciliten la separació de ambdós a la sortida del generador.
La informació existent respecte a les propietats termofísiques d'aquests nous sistemes és insuficient per una precisa simulació del cicle d'absorció, per la qual cosa l'objectiu d'aquest treball ha estat completar l'estudi experimental de les propietats termofísiques més característiques de cada mescla, així com l'adaptació i posada en marxa dels dispositius i tècniques experimentals per a realitzar aquest treball.
Per al sistema H2O + (LiBr + LiNO3 + LiCl + LiI) s'han determinat experimentalment la solubilitat, la capacitat calorífica i la densitat. La primera d'aquestes propietats s'ha mesurat fent servir dos mètodes politèrmics, un de visual i l'altre calorimètric, aquest últim por medi de un calorímetre Calvet. Aquest calorímetre també va ser utilitzat per la determinació experimental de les capacitats calorífiques a pressió constant de les dissolucions aquoses fent servir un mètode incremental. Finalment, les densitats de les dissolucions es van determinar fent servir un densímetre de precisió de tub vibrant.
Pels sistemes NH3 + H2O + NaOH y NH3 + H2O + KOH s'ha realitzat un estudi teòric-experimental de l'equilibri líquid-vapor. A partir de les mesures de pressió de vapor pel mètode estàtic a distintes composicions i temperatures dels diferents sistemes s'ha determinat la composició de les fases en equilibri a través del mètode de Barker adaptat per a sistemes ternaris. A més a més, els resultats s'han correlacionat fent servir el mètode Electrolyte-NRTL. Tanmateix s'han determinat experimentalment i correlacionat en funció de la temperatura i composició les capacitats calorífiques a pressió constant i las densitats de les dissolucions emprant el mètode calorimètric i de tub vibrant, respectivament.
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Ermatchkov, Viktor. "Phasengleichgewichte in komplexen, chemisch reagierenden Systemen NH3 + SO2 + H2O + Salze und CO2 + H2O + MDEA, Piperazin /." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=980777488.
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Pereira, Carmen Ines Feltrin. "Elaboração e analise de diagramas de fases dos sistemas SDS+H2O, (SDS+H2O)+DeOH e (SDS+H2O+DeOH)+Na2SO4, com auxilio de microscopia petrografica e refratometria." reponame:Repositório Institucional da UFSC, 1991. http://repositorio.ufsc.br/xmlui/handle/123456789/75807.
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Dissertação (mestrado) Universidade Federal de Santa Catarina. Centro de Ciencias Fisicas e MatematicasMade available in DSpace on 2012-10-16T04:35:54Z (GMT). No. of bitstreams: 0Bitstream added on 2016-01-08T17:10:15Z : No. of bitstreams: 1 82128.pdf: 1863688 bytes, checksum: 59152695215c6c861fa76c5071a36a9d (MD5)
No presente trabalho elaboramos diagramas de fases de sistem liotrópicos, usando como surfactante Decilsulfato de Sódio (SDS). Partindo da concentração de 50%, em peso, de SDS e água tridestilada, determinamos uma concentração particular de existência de liomesofases (42,5% de SDS e 57,5% de H2O). Mantendo a razão da concentração para a formação do sistema ternário. Com base no diagrama de fase do sistema ternário, na região de maior estabilidade do nemático exibido pelo sistema, em temperatura, a razão (SDS + H2O) / DeOH foi escolhida para ser mantida constante quando da adição de Na2SO4, para a formação do sistema quaternário.
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Timofejeva, Oksana. "Formation of Barely Soluble Compounds in the CuSO4 – K4P2O7 – H2O and CuSO4 – (NH4)4P2O7 – H2O Systems." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2009. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2009~D_20090526_111121-30909.
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At least three poorly soluble compounds can be formed in the CuSO4 – K4P2O7 – H2O system: a single salt Cu2P2O7.5H2O and two dimorph’s both having chemical formula Cu3K2(P2O7)2.3H2O. A previously known form of Cu3K2(P2O7)2.3H2O (we named it Dimorph A) transforms into a novel Dimorph B, which has a different structure. The similarities between the XRD patterns and vibrations spectra of copper–ammonium and copper–potassium Dimorph’s B imply that they are isostructural. The values of the angle for copper–potassium and copper–ammonium salts and Cu2P2O7.5H2O are relatively low and vary within a narrow range (123.1 – 127.1°).
The formation of the compounds significantly depends on the conditions of the experiment. A double salt in the CuSO4 – K4P2O7 – H2O system may be formed after some time in the reaction mixture as a result of the following heterogeneous reaction:
3Cu2P2O7∙5H2O↓ + H2P2O72– + 4K+ → 2Cu3K2(P2O7)2∙3H2O↓ + 2H+ + 9H2O
This reaction has not been previously described for any polyphosphate system. Therefore, novel results of scientific investigation are presented.
The rate, duration and yield of heterogeneous reaction substantially depend on pH of the solution, [Cu2+ + P2O74–] and n ([P2O74–] / [Cu2+]). At a relatively low pH the induction time is high, the reaction rate is low and duration is long. The maximal yields close to 100% can be achieved when [Cu2+ + P2O74–] = 0.1 M. At increased pH values, the induction time, the yield and duration of the reaction diminish... [to full text]Naudojant IR-spektrometrijos, rentgenofazinės analizės, atominės absorbcinės spektroskopijos, kolorimetrijos analizės metodus buvo ištirta sistemose CuSO4 – K4P2O7 – H2O ir CuSO4 – (NH4)4P2O7 – H2O susidarančių mažai tirpių junginių sudėtis, jų susidarymo dėsningumai ir vykstančios reakcijos, įvairių veiksnių įtaką nuosėdų sudėčiai ir struktūrai. Nustatyta, kad sistemoje CuSO4 – K4P2O7 – H2O, be jau žinomų mažai tirpių junginių (paprastosios druskos Cu2P2O7 ∙ 5H2O ir dvigubosios druskos Cu3K2(P2O7)2 ∙ 3H2O), susidaro ir naujas mokslinėje literatūroje neaprašytas junginys (Dimorfas B), dvigubajai druskai patiriant polimorfinį perėjimą. Polimorfinio perėjimo trukmė labai priklauso nuo pH ir reaguojančių jonų koncentracijų. FTIR duomenų analizė parodė, kad difosfato jonų energetinė būsena Cu – K ir Cu – NH4 Dimorfuose B panaši. Jų rentgenogramos yra panašios, tikėtina, kad šie junginiai – izostruktūriniai, jų kristalinės gardelės tipas – monoklininis. Naudojant Lazarevo lygtį, bei Rulmonto priklausomybę buvo apskaičiuoti Cu – K ir Cu – NH4 Dimorfų A ir B bei paprastosios druskos P – O – P kampai, gauta, kad jie mažai keičiasi siaurame 123,1 – 127,1 º intervale. Nustatyta, kad dviguboji druska susidaro iš paprastosios, vykstant heterogeninei reakcijai: 3Cu2P2O7 ∙ 5H2O↓ + H2P2O72– + 4K+ → 2Cu3K2(P2O7)2∙ 3H2O↓ + 2H++ 9H2O. Mokslinėje literatūroje tokia reakcija neaprašyta jokiai difosfatų sistemai, jos tyrimo duomenys yra nauji. Taip pat nustatyta, kad heterogeninės reakcijos... [toliau žr. visą tekstą]
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Velková, Zorka. "H2O - bezbarvá čirá kapalina bez zápachu." Master's thesis, Akademie múzických umění v Praze. Divadelní fakulta AMU. Knihovna, 2008. http://www.nusl.cz/ntk/nusl-78078.
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Presented diploma theses H2O is about the water and deals with element as such. It describes first contact, thinking about it and kind of fascination with the water as a living substance. Finally it brings under attention the description of the performance Zahrada mrtvých zón, which took several volunteers into the process of the communication with the liquid in order to let them to be confronted with the phenomenon of the water through an extraordinary experience. This represents the core issue of the presented project.
In my opinion, generalization in the Fine Arts is pointless; therefore, I present my own perspective as more valid approach, rather than using any abstract description as such. Simply put my point of view judges the whole project better.
Theses H2O is not scientific analysis of the water phenomenon. As an Artistic discipline stage design posses the exclusive advantage comparing to other approaches that it is not build on the exact knowledge but accepts all the possible information.
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Cares, Cuevas German Enrique. "Estudo vibracional infravermelho de compostos isomorficos : M2C2O4.X CM=K, Rb, Cs; X=H2O, H2O2)." [s.n.], 1992. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249721.
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Orientador : Yoshiyuki HaseTese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
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Doutorado
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Lima, Larissa Lavorato. "Análise estrutural e termodinâmica do composto {[Zn(2,5-pdc)(H2O)2].H2O}n nas formas desidratada e delaminada." Universidade Federal de Juiz de Fora (UFJF), 2017. https://repositorio.ufjf.br/jspui/handle/ufjf/4681.
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As redes metalorgânicas (ou MOF, do inglês Metal-Organic Frameworks) pertencem à classe dos polímeros de coordenação (ou CP, do inglês coordination polymers) e exibem características como porosidade e cristalinidade. Em particular, as MOF bidimensionais têm despertado o interesse no desenvolvimento de uma nova geração de dispositivos ópticos e eletrônicos. A capacidade de formação de filmes finos de algumas dessas MOF as tornam materiais mais atraentes. A MOF bidimensional estudada neste trabalho foi a rede {[Zn(2,5-pdc)(H2O)2].H2O}n (2,5-pdc = 2,5-piridinodicarboxilato), ZnPDC2D. A MOF 2D foi sintetizada e caracterizada por diferentes técnicas experimentais e também foi estudada por simulação computacional. O modelo do ZnPDC2D foi otimizado por dois métodos (PBE e PBE-D2), os quais descreveram bem os parâmetros estruturais. A partir do modelo do ZnPDC2D, foi elaborada uma proposta para o processo de desidratação e assim, sugerindo a formação de três novas fases (d1-ZnPDC2D, d2-ZnPDC2D e d3-ZnPDC2D). A temperatura em que o ZnPDC2D sofre amorfização foi determinada através da medida de difração de raios X com aumento de temperatura in situ e pôdese inferir que a fase amorfa sofre uma transformação reversível após ser exposta ao ambiente. A termodinâmica da primeira etapa da desidratação mostra que o funcional PBE é mais adequado para descrever a espontaneidade da reação. Esperase obter as estruturas por meio de análises de difração de raios X por policritais e refinamento pelo método de Rietveld. O trabalho também reporta a simulação da energia de formação do monofilme pelos métodos PBE e PBE-D2. As análises de propriedades eletrônicas para todas as estruturas citadas foram executadas e discutidas conforme os processos e mudanças envolvidas.
Metal-organic frameworks (MOFs) belong to the class of coordination polymers (CPs) and exhibit properties such as porosity and crystallinity. In particular, twodimensional MOFs have attracted interest in the development of a new generation of optical and electronic devices. The possibility of thin film formation of some of these MOFs makes them more attractive materials. The twodimensional MOF studied in this work was the network {[Zn(2,5-pdc)(H2O)2].H2O}n (2,5-pdc = 2,5-pyridinedicarboxylate), ZnPDC2D. The MOF 2D was synthesized and characterized by different experimental techniques and was also studied by computer simulation. Two optimized ZnPDC2D structures were obtained by distinct methods (PBE and PBE-D2) with a good description of their parameters. The structure obtained from the simulation of the dehydration process suggest the formation of three new phases (d1-ZnPDC2D, d2-ZnPDC2D and d3-ZnPDC2D). The temperature at which ZnPDC2D undergoes amorphization was determined by Xray podwer diffraction measurement with in situ temperature rise and it could be inferred that the amorphous phase undergoes a reversible transformation after being exposed to the environment. The thermodynamics of the first stage of dehydration shows that the PBE functional is adequate to describe the spontaneity of the reaction. The structures are expected to be obtained by Xray podwer diffraction analysis and refinement by the Rietveld method. Thise work also reports the simulation of the monofilm by the PBE and PBE-D2 methods. The analyses of electronic properties for all th cited structures were performed and discussed according to the processes and changes involved.
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Dickens, Dustin. "Supercooling and Freezing of HNO3/H2O Aerosols." Thesis, University of Waterloo, 2000. http://hdl.handle.net/10012/1225.
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The freezing kinetics of binary nitric acid/water aerosols is of fundamental importance to the modelling of polar stratospheric clouds and the role they in ozone depletion over the Arctic/Antarctic regions. Cirrus clouds are also often composed of nitric acid solutions, hence an understanding of freezing process in these aerosols also aids in modelling the earth's radiation budget and global warming. This thesis explores the kinetic phase diagram of nitric acid/water aerosols with sizes ranging between 0. 2 and 1. 5 mm in radius and concentrations ranging between pure water and 0. 45 mole fraction HNO3. Although the kinetic phase diagram has now been studied between 0. 46 mole fraction HNO3 and pure water, more data is needed in the region between 0. 18 and 0. 25 mole fraction HNO3 to confirm the results reported.
The project described in this thesis are a continuation of a project begun by Allan Bertram. The measurements involving aerosols with compositions greater than 0. 25 mole fraction HNO3 were carried out as part of Allan Bertram's Ph. D. thesis (see ref. 20) These data were later examined using a more comprehensive data analysis method (as presented in this thesis) in an effort to obtain a more complete understanding of this system.
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Steiu, Marieta Simona. "Refrigeración por absorción con nh3/h2o/hidróxidos." Doctoral thesis, Universitat Rovira i Virgili, 2010. http://hdl.handle.net/10803/8497.
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En esta tesis doctoral se estudia el uso de las mezclas ternarias NH3/H2O/XOH (X: NaOH, KOH, LiOH) en ciclos de refrigeración por absorción activados con energía solar térmica o calor residual. La adición de hidróxidos alcalinos NaOH, KOH o LiOH a la mezcla amoníaco/agua disminuye la temperatura de ebullición de la mezcla y favorece la separación del amoniaco al desplazar el equilibrio de disolución del amoniaco en agua hacia la separación del amoniaco en fase gas, con la consiguiente reducción de las etapas de rectificación y un aumento del COP y de la capacidad frigorífica del equipo. Sin embargo, la presencia del hidróxido en el absorbedor es perjudicial ya que reduce la capacidad de absorción del amoníaco por el absorbente. Este efecto puede contrarrestarse limitando la presencia del OH- en el absorbedor para lo cual el ciclo básico ha de modificarse incluyendo una etapa de separación que confine el OH- en el generador.The use of ammonia-water absorption refrigeration cycles driven by low temperature heat sources such as thermal solar energy or waste heat from some new energy distributed generation technologies is so far not feasible due to the low temperature of some of these heat sources. To overcome this problem over the past several years, it has been proposed the addition of hydroxides to the ammonia-water mixture.
The objective of this thesis is to study the effect of the NaOH, KOH and LiOH in the liquid vapour equilibrium of NH3/H2O mixture in order to reduce the boiling temperature, to select the hydroxide that presents more advantages for the operation of the absorption cycle and perform several simulations with the selected hydroxide to evaluate the overall performance of the cycle using the new ternary mixture.
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Fritsch, Marco. "Heissgaskorrosion keramischer Werkstoffe in H2O-haltigen Rauchgasatmosphären." Stuttgart Fraunhofer-IRB-Verl, 2007. http://d-nb.info/989259420/04.
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Fritsch, Marco. "Heißgaskorrosion keramischer Werkstoffe in H2O-haltigen Rauchgasatmosphären /." Stuttgart : Fraunhofer-IRB-Verl, 2008. http://deposit.d-nb.de/cgi-bin/dokserv?id=3127298&prov=M&dok_var=1&dok_ext=htm.
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Longo, Claudia. "Estudos de adsorção em interfaces SnO2|H2O." Universidade de São Paulo, 1994. http://www.teses.usp.br/teses/disponiveis/46/46132/tde-29102014-125817/.
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Estudos da adsorção de prótons e hidroxilas, considerados os íons determinantes de potencial para interfases óxido|H2O, e de surfactantes iônicos e não iônicos foram realizados para duas amostras de SnO2 obtidas através de métodos de preparação distintos. Uma amostra foi obtida pela oxidação de Sn metálico com HNO3 (conc.) e calcinação (amostra I) e a outra pela oxidação de Sn metálico com HCl (conc.), precipitação com ácido oxálico e calcinação (amostra II). A caracterização física das amostras identificou-as como sendo cristalinas, com estrutura de cassiterita e áreas específicas de 11,9 e 8,57 m2/g para as amostras I e II, respectivamente. A adsorção dos íons H+ e OH- foi determinada através de titulações potenciométricas ácido-base de suspensões do óxido em meio de KNO3 10-3 a 0,5 M. Através dos excessos superficiais destes íons, determinaram-se as curvas da variação da densidade de carga superficial (δo) em função do pH e da força iônica das suspensões. O ponto de carga zero da interfase foi determinado através do ponto de intersecção comum das curvas obtidas em diferentes concentrações do eletrólito suporte. Os valores obtidos foram pH (7,9 ± 0,3) para a amostra I e (7,0 ± 0,1) para a amostra II. A comparação das curvas mostrou que a amostra I apresenta valores de δo maiores que os correspondentes da amostra II, para condições de pH inferiores ao pcz. O estudo da adsorção de surfactantes consistiu na obtenção e análise de isotermas de adsorção de dodecilbenzenosulfonato de sódio (DBS), cloreto de benzil-hexadecildimetilamônio (CBz) e Triton X-100 (TX100). As isotermas foram determinadas a 25 °C em três condições nas quais a interfase apresenta valores distintos de δo. Para os surfactantes iônicos, o estudo foi realizado em condições nas quais a interfase apresenta densidades de carga opostas às dos tensoativos; para o TXI00, foram escolhidas condições nas quais a interfase apresenta carga aproximadamente nula. O comportamento apresentado pelas isotermas foi discutido em função das interações eletrostáticas e hidrofóbicas que ocorrem no sistema. A análise das isotermas obtidas para o DBS mostrou que a adsorção é favorecida quanto maiores a acidez e a concentração do eletrólito suporte, ou seja, para valores crescentes de δo. Para o TX100, as variáveis de pH e força iônica não exercem influência significativa na adsorção. Para o CBz, os resultados obtidos não permitiram avaliar a influência das forças de atração eletrostática no processo de adsorção deste sulfactante no sistema estudado. Através dos resultados obtidos, observou-se que a amostra I apresenta maior afinidade por prótons que a amostra II e que ambas as amostras apresentam afinidade aproximadamente equivalente por hidroxilas. No estudo referente à adsorção de sulfactantes, obteve-se que a amostra II apresenta maior capacidade de adsorção que a amostra I, comportamento oposto ao esperado considerando os valores de densidade de carga superficial e área específica determinados para as duas amostras.The adsorption of H+ and OH- ions, the potential determining ions for the oxide isoIution interface, and the adsorption of ionic surfactants were studied for two distinct SnO2 samples, prepared via two different routes. Sample I was obtained by oxidizing metallic tin with HNO3 (conc) and calcination, while the other one, sample II, was prepared via the oxidation of metallic tin by HCl (conc), precipitation with oxalic acid and calcination. The resulting materials were characterized as cristalline SnO2 with cassiterite structure having specific surface areas equal to 11,9 and 8,57 m2g-1, for samples I and II, respectively. The adsorption of the H+ and OH- ions was studied by means of the potentiometric titration method of SnO2 suspensions in KNO3 aqueous solutions. The resulting point of zero charge were pH (7,9 ± 0,3) for sample I and (7,0 ± 0,1) for sample II. Adsorption isotherms of three different surlfactants: sodium dodecylbenzenesulfonate, benzylcetyldimethylanunonium chloride and Triton X-100 were obtained at 25°C for three different surface charge conditions. The adsorption isotherms were interpreted as a function of electrostatic and hidrophobic interactions. It was observed that Sample I presents a higher affinity for H+ ions while both SnO2 samples show the same extension for affinity for OH- ions. In spite of this, analysis of the surfactant adsorption isotherms showed that Sample II has a higher adsorption ability that Sample I. This behavior is just the opposite than the expected considering the values of the surface charge density and surface area of the samples.
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Okhrimenko, Larysa Mikolaivna. "Stockage d'énergie thermique par un composite zéolite/MgSO4-H2O : étude thermocinétique du système MgSO4 – H2O et étude expérimentale des composites." Thesis, Lyon, 2018. http://www.theses.fr/2018LYSEM001/document.
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L’épuisement des combustibles fossiles et l’augmentation de la demande d’énergie, entrainent l’intérêt croissant du développement des énergies renouvelables et des systèmes efficaces énergétiquement. Néanmoins, le décalage entre le besoin en énergie et la fourniture de celle-ci par les énergies renouvelables rend nécessaire l’utilisation d’un système de stockage. Parmi les différentes technologies de stockage d’énergie thermique, les composites formés d’une matrice poreuse et d’un sel hygroscopique, permettent de profiter à la fois des capacités d’adsorption/désorption de la matrice et des réactions chimiques du sel. La difficulté principale du développement d’un tel système est la compréhension incomplète des phénomènes physico-chimiques mis en jeu.Le premier objectif de cette thèse est d’étudier les réactions d’hydratation et de déshydratation du sel MgSO4. La caractérisation physico-chimique des solides ainsi que des expériences de thermogravimétrie isotherme et isobare ont été réalisées. Il a été montré que le système est divariant et que les hydrates obtenus sont non-stœchiométriques. Un modèle thermodynamique a été développé et appliqué aux données expérimentales. Les études cinétiques des réactions de déshydratation et d’hydratation ont été réalisées ce qui a permis de définir les étapes limitantes ainsi que d’écrire deux modèles et d’appliquer aux résultats expérimentaux. Enfin différents matériaux composites zéolite/ MgSO4 ont été synthétisés. Ces matériaux ont été caractérisés et leur capacité de sorption a été mesurée. Les résultats mettent en évidence une augmentation de la capacité de sorption, mais uniquement pour des pressions de vapeur d’eau importantesExhaustion of fossil fuels and increase of energy demand, lead to growing interest in the development of renewable energies and energy efficient systems. Nevertheless, the gap between the supply and the demand of energy by renewable energies makes necessary the using a storage system. Among various thermals energy storage technologies, the composites formed by a porous matrix and a hygroscopic salt, allow to benefit advantage of both the adsorption/desorption capacities of the matrix and the chemical reactions of salt. The main difficulty to develop of such a system is the incomplete understanding of the involved physicochemical phenomena.The first objective of this thesis is to study the hydration and dehydration reactions of MgSO4 salt in presence of water vapor. Firstly, the physicochemical characterization of solids and isothermal and isobaric thermogravimetry experiments were carried out. It has been shown that the system is divariant and that the hydrates obtained are non-stoichiometric with localized water molecules. A thermodynamic model was developed and applied to the experimental data. In a second step, the kinetic studies of both the dehydration and hydration reactions were carried out. The rate limiting steps were defined, two kinetic models have been written and applied to the experimental results. Finally, various zeolite/MgSO4 composite materials have been synthesized. These materials have been characterized and their sorption capacity has been measured. The results show an increased sorption capacity, but only for water vapor pressures different from those used for thermal energy storage
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Jung, Mi-Hee. "Solubility Studies on the NaAlO2-NaNO3-H2O System." MSSTATE, 2005. http://sun.library.msstate.edu/ETD-db/theses/available/etd-08032005-140710/.
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An investigation of the sodium aluminate-sodium nitrate system was conducted. The effect of sodium nitrate on the solubility of aluminum is important to the retrieval of waste from the tanks at the Hanford nuclear facility located in the state of Washington. Experiments were performed on the NaAlO2 - NaNO3 - H2O system at 25?aC and 50?aC. The results obtained from these experiments were then compared to predictions from the Environmental Simulation Program (ESP, OLI Systems, Inc.) and available literature data. The presence of sodium nitrate increased the solubility of sodium aluminate in water. Sodium nitrate exhibited a greater effect on the solubility of sodium aluminate at higher temperature. Error analysis of the experimental data was performed and indicated that the experimental molalities were accurate to within an average of +3%. The measured data will be used to improve existing databases for ESP.
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Parmar, Dixit. "Reductive cyclisations of lactones using SmI2 and H2O." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/reductive-cyclisations-of-lactones-using-smi2-and-h2o(533c0430-fd14-4a24-93f2-18a7fb27232f).html.
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Carbonyl reduction is a fundamental transformation that underpins synthetic chemistry. The re-routing of carbonyl reduction through less-conventional intermediates allows new selectivity and reactivity to be found in the resulting reaction space. We have shown for the first time that the unusual radical anions formed by electron transfer to the ester carbonyl group can be exploited in additions to alkenes. We have demonstrated that the reductive cyclisations of lactones, triggered by electron-transfer from SmI2-H2O, allow for highly decorated cyclopentane and cycloheptane ring systems to be constructed. Futhermore, the reductive cyclisations of lactones can be exploited in cyclisation cascades. The cascade sequences involve the generation and trapping of unusual radical anions formed from the ester carbonyl followed by the trapping of more conventional radical anions from the carbonyl groups of ketone intermediates.
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Bernadet, Lucile. "Étude de l'effet de la pression sur l'électrolyse de H2O et la co-électrolyse de H2O et CO2 à haute température." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0312/document.
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Ces travaux de thèse portent sur l’étude du comportement sous pression d’une cellule à oxydes solides fonctionnant à haute température en mode électrolyse de H2O et en mode co-électrolyse de H2O et CO2. Une étude expérimentale sur mono-cellule associée au développement de modèles multi-physiques a été mise en place. Les essais, réalisés à partir d’une installation unique présente au CEA-Grenoble, sur deux types de cellules entre 1 et 10 bar et de 700 à 800 °C, ont permis d’identifier dans les deux modes de fonctionnement, que la pression a un effet positif ou négatif sur les performances selon le point de fonctionnement (courant, tension) de la cellule. De plus, des analyses de gaz conduites en mode co-électrolyse ont permis de détecter une production de CH4 in-situ sous pression. Ces effets de la pression ont été correctement simulés par les modèles calibrés à pression atmosphérique. L’analyse des simulations a ensuite permis l’identification des mécanismes impactés par la pression et la proposition de conditions opératoires de fonctionnement grâce à l’établissement de cartographies de fonctionnementThis thesis work investigates the behavior of a solid oxide cell operating under pressure in high temperature steam electrolysis and co-electrolysis mode (H2O and CO2). The experimental study of single cell associated with the development of multi-physical models have been set up. The experiments, carried out using an original test bench developed by the CEA-Grenoble on two types of cells between 1 and 10 bar and 700 to 800 °C, allowed to identify in both operating modes that the pressure has a positive or negative effect on performance depending on the cell operating point (current, voltage). In addition, gas analyzes performed in co-electrolysis led to detect in situ CH4 production under pressure. These pressure effects were simulated by models calibrated at atmospheric pressure. Simulations analysis helped identify the pressure dependent mechanisms and propose operating conditions thanks to the establishment of operating maps
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Galtayries, Anouk. "Etude de l'adsorption et de la réactivité de H2O, H2S et SO2 sur le cuivre et ses oxydes." Lille 1, 1996. http://www.theses.fr/1996LIL10020.
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Dans le cadre d'une meilleure compréhension des phénomènes liés à la corrosion de surfaces métalliques et d'empoisonnement de catalyseurs à base de cuivre, nous avons mené une étude des étapes initiales de l'interaction de molécules réactives avec des substrats en cuivre poly cristallin ou ses oxydes. Deux méthodes d'analyse complémentaires ont été utilisées: la spectroscopie de photoélectrons induits par rayons x qui nécessite un conditionnement sous ultra-haut vide et la mesure de variation de potentiel de surface par la méthode de kelvin, qui permet de mener des séquences réactionnelles sous flux gazeux, a pression atmosphérique jusqu'à 400c. Les adsorptions d'eau ou de méthanol, pratiquement entièrement réversibles à température ambiante sur Cu, conduisent à des variations de potentiel opposées. Elles résultent d'une répartition électronique totalement différente. Des cycles d'interaction de h2/o2 sur le métal prétraite par l'hydrogène permettent de suivre les cinétiques d'adsorption: ordre 1 ou cinétique d'elovich pour h2. Les interactions avec h2s et so2 conduisent à une dissociation des molécules sur les différents substrats, laissant des espèces s (a) de type sulfure. Pour h#2s, le métal est le substrat le plus réactif alors que c'est cou qui présente la plus forte affinité pour so2. Cependant, les solides évoluent tous vers la formation en surface de Cu+ quel que soit le degré d'oxydation initial. Avec so2, outre s(a), sont également détectées des espèces so2(a), so3(a) et so4(a) selon la température, l'exposition et la nature de la surface. Les résultats de ce travail et la méthodologie adoptée se révèlent très intéressants dans le contexte de la corrosion du cuivre. Une extension vers l'étude de la réactivité d'autres métaux, de films d'oxydes ou de sulfures, modelés de catalyseurs, est actuellement en cours.
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Freyer, Daniela. "Zur Phasenbildung und -stabilität im System Na2SO4-CaSO4-H2O." Doctoral thesis, Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola", 2009. http://nbn-resolving.de/urn:nbn:de:swb:105-7606881.
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In den Untersuchungen zur Phasenbildung und -stabilität im System Na2SO4 - CaSO4 - H2O wurden die bisher existierenden Phasendiagramme für das wasserfreie System Na2SO4 - CaSO4 korrigiert. Metastabile Mischkristalle wurden bezüglich ihrer Existenzgebiete und Zusammensetzungen charakterisiert. Für den im wässrigen System stabil auftretenden Glauberit, Na2SO4 . CaSO4, wurde die Löslichkeitskonstante bis 250°C bestimmt und ist ab 100°C kleiner als bisher angenommen wurde. Zur Bestimmung der Löslichkeitskonstante wurde die Temperaturabhängigkeit der Freien Standardreaktionsenthalpie für die Zersetzung des Glauberits ermittelt. Dazu wurden die Cp-Funktionen für die an der Reaktion beteiligten Phasen Glauberit und Anhydrit, CaSO4, über Wärmekapazitätsmessungen bis 510°C bestimmt. Eine weitere Möglichkeit zur Bestimmung der Freien Standardreaktionsenthalpie durch die Ermittlung der thermodynamischen Aktivität von Na2SO4 in der Hochtemperaturmischkristallphase mit EMK-Messungen an Festkörperelektroden wurde aufgezeigt. Für das im System Na2SO4 - CaSO4 - H2O metastabile auftretende Natriumpentasalz, Na2SO4 . 5 CaSO4 . 3 H2O, wurde eine Einkristallstrukturanalyse durchgeführt und die strukturelle Verwandtschaft zum Calciumsulfat-Halbhydrtat, CaSO4 . 0,5 H2O, aufgeklärt, sowie die Bildungsbedingungen charakterisiert.
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Freyer, Daniela. "Zur Phasenbildung und -stabilität im System Na2SO4-CaSO4-H2O." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=965898660.
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Postma, Johannes Petrus Maria. "MD of H2O : a molecular dynamics study of water /." [S.l. : s.n.], 1985. http://bibpurl.oclc.org/web/32873.
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Ellis, Daniel Jared. "Temperature Measurement Using Infrared Spectral Band Emissions From H2O." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5488.
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Currently there is no known method for accurately measuring the temperature of the gas phase of combustion products within a solid fuel flame. The industry standard is a suction pyrometer and thermocouple which is intrusive, both spatially and temporally averaging, and difficult to use. In this work a new method utilizing the spectral emission from water vapor is investigated through modeling and experimental measurements. This method was demonstrated along a 0.75m line of sight, averaged over 1 minute in the products of a natural gas flame but has the potential to produce a spatial resolution on the order of 5 cm and a temporal resolution of less than 1 millisecond. The method employs the collection of infrared emission from water vapor over discrete wavelength bands and then uses the ratio of those emissions to infer temperature. A 12.5 mm lens has been positioned within a water cooled probe to focus flame product gas emission into an optical fiber where the light is transmitted to a Fourier Transform Infrared Spectrometer (FTIR). The same optical setup was also used to collect light from a black body cavity at a known temperature in order to calibrate the spectral sensitivity of the optical system and FTIR detector. Experiments were conducted in the product gas of a 150 kWth methane flame comparing the optical emission results to a suction pyrometer with type K thermocouple. The optical measurement produced gas temperatures approximately 1 - 4% higher than the suction pyrometer. Broadband background emission was also seen by the optical measurement and was removed assuming grey body radiation. This background emission can be used to determine particle emission temperature and intensity. Additional work will be needed to demonstrate the method under conditions with significant particle emission. Additional work is also needed to demonstrate the work over a smaller path length and shorter time scale.
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Metchueng, Kamdem Syntia. "Stockage de chaleur dans l'habitat par sorption zéolite/H2O." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI059/document.
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Le couple zéolite/H2O, qui présente une densité énergétique importante et remplit les conditions d’innocuité requises pour un système de stockage de chaleur pour l’habitat, est mis en œuvre dans réacteur modulaire à lit fixe. Un modèle monodimensionnel de transferts couplés de masse et de chaleur dans un lit fixe de grains de zéolite parcourus par un flux d'air humide été élaboré. Ce dernier a été conçu de façon à pouvoir intégrer rapidement des données sur de nouvelles générations de matériaux et coupler le réacteur à d’autres modèles : bâtiment/sous-station/quartier. L'étape de validation expérimentale montre que le modèle permet une estimation satisfaisante de l'autonomie, la durée d'amorçage et la puissance moyenne fournie en phase de décharge ainsi que la durée de charge. Ce modèle est donc un bon outil de dimensionnement et de pilotage du réacteur. L'analyse de sensibilité a montré que l'amélioration des prévisions du modèle requiert une évaluation plus précise de la chaleur complémentaire de sorption et de la porosité du lit. Après avoir estimé les besoins de chauffage d'une maison BBC deux dimensionnements ont été proposés afin d'effacer soit l'hyper-pointe de 18h - 20h soit la semaine la plus froide. Si la première stratégie aboutit à un système de stockage plus compact, la seconde permet de réduire le nombre de cycles marche/arrêt. Pour un îlot de 50 maisons BBC, la notion de foisonnement est considérée lors de l'estimation des besoins en chauffage pendant la semaine la plus froide. La phase de charge du système de stockage se ferait par le biais de la chaleur fatale récupérée dans l'industrie. Pour des stratégies d'effacement similaires (semaine la plus froide en hiver), un volume équivalent de 544 litres par maison dans l'îlot suffit pour répondre aux besoins de chauffage à Nancy contre 580 litres pour une maison BBC seuleHeat storage systems for residential house heating could contribute to smoothing the load curve and would help prevent the use of the most polluting power plants or electricity imports during consumption peaks. Thermochemical heat storage systems are suitable for the intended application since they have high energy densities and low thermal losses. This thesis focuses on the design of an adsorption heat storage system that would be used to shed the load curve of the heating device of a house or residential district during the winter peak consumption periods. The zeolite/H2O pair, which has interesting features such as a high energy density and meets the conditions of safety required for a heat storage system for housing, is implemented in a modular fixed bed reactor. A 1D pseudo-homogeneous model was developed in order to simulate the performance of a fixed bed of zeolite during the adsorption and desorption of water. The latter was designed so as to facilitate the integration of data on new generations of materials and model couplings. The need to obtain data on the sorption properties of the zeolite/H2O pair to have reliable simulation results has been demonstrated, particularly at low partial pressures of water vapor and under the operating conditions selected. The experimental validation phase shows that the pseudo-homogeneous model provides a satisfactory estimate of criteria such as the autonomy, the responsiveness and the average power delivered during the discharging phase and the charging time. The model is thus a good sizing and management tool of the reactor. A sensitivity analysis, with the method of Morris, showed that improved model estimates require a more accurate assessment of the additional heat of sorption and porosity of the bed. After assessing the heating needs of the LEB house with a thermal model of the latter in cold climate conditions, two heat storage reactors were sized in order to shed the heating system's load curve either between 6 and 8pm or during the coldest week of the year. While the first strategy results in a more compact storage system, the second makes it possible to reduce the number of on/off cycles. The need for predictive control for monitoring the storage system was highlighted. As for the residential district of 50 LEB houses, diversity is considered when estimating the heating needs of the latter during the coldest week in Nancy. The heat source during the charging phase of the container would be industrial waste heat. During the coldest week, two sizings are suggested. For similar load shedding strategies, the comparison of the equivalent storage volume per house in the district with the storage volume for a single house serves highlights the importance of taking into account diversity. In order to meet the heating needs in Nancy, an equivalent volume of 544 liters per house in the district is sufficient whereas 580 liters are needed for a LEB house
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Penha, Frederico Marques. "Comportamento do sistema NaCI-KCI-H2O em cristalização simultânea." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-19092018-074356/.
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No que diz respeito às águas residuais industriais, além da elevada frequência direta de efluentes salinos, o tratamento convencional de efluentes aquosos de diferentes tipos de indústria quase sempre resulta em uma solução contendo sais solúveis e insolúveis que podem ter qualidade suficiente para serem descartados em corpos aquosos, mas qualidade insuficiente para permitir a reutilização da água em processos industriais. Para reutilizar a água, visando o descarte zero de líquido, a cristalização se mostrou tecnicamente viável e tem sido utilizada nesta separação. Simultaneamente com a evaporação da água, os sais dissolvidos tornam-se materiais particulados que são subsequentemente separados por filtração ou centrifugação. Contudo, para atender às necessidades modernas da indústria em relação aos tratamentos com efluentes salinos, o processo de cristalização deve mostrar melhorias, especialmente devido à sua importância para atingir as metas de descarga de líquidos. Neste sentido, a cristalização simultânea representa a possibilidade de remover vários compostos em uma única operação de cristalização a partir de uma solução multicomponente. Isso significa que além da purificação da água, essa operação também pode permitir a recuperação dos compostos nos efluentes, que podem ser considerados como matéria-prima, eliminando resíduos - ou dando-lhes a destinação mais adequada. Para isso, é necessário projetar processos para separar os diferentes componentes que compõem as correntes de efluentes salinos e produzir produtos cristalinos com características morfológicas conhecidas. Dessa forma, o presente trabalho visou investigar o comportamento de sistemas ternários em cristalização, utilizando como modelo o sistema NaCl-KCl-H2O no processo de cristalização evaporativa em batelada, no intuito de avaliar a influência dos parâmetros de processo nos cristais formados e de traçar estratégias que possibilitassem o aproveitamento dos sais contidos nos efluentes. Três diferentes rotas de operação foram testadas para avaliar o comportamento dos cristais: uma inicialmente saturada apenas em NaCl, uma inicialmente saturada apenas em KCl e uma já de início saturada em ambos sais. Diferentes taxas de evaporação, tamanhos e teores de sementes foram testados. Verificou-se, de maneira geral, que o controle de dois fenômenos elementares é a chave para contornar os principais obstáculos desse processo: crescimento epitaxial e nucleação secundária. Em determinadas condições foi possível obter o produto das bateladas em distribuições bimodais, com cada pico rico em um dos sais, com purezas superiores a 90 %. Estes produtos, passíveis de separação simultânea dos cristais por composição e tamanho, foram obtidos em condições de supersaturações mais baixas e semeadura de cristais grandes de KCl e pequenos de NaCl. A partir destes resultados, considerando-se a necessidade de desenvolver técnicas de purificação de água menos intensivas em energia e mais favoráveis ao meio ambiente, um sistema de cristalização por membranas (MC) foi testado, utilizando-se o mesmo sistema modelo. O design proposto para MC possibilitou operar com este sistema por tempos superiores a 6 horas, com decaimento do fluxo em torno de 20 %. Contudo, o produto da cristalização simultânea por membranas não apresentou melhorias quanto à segregação.In the industrial wastewater treatment, besides high direct frequency of saline effluents, conventional treatment of aqueous effluents of different types of industry usually results in a solution containing soluble and insoluble salts that may be of sufficient quality to be disposed in aqueous bodies, but insufficient quality for water reuse in industrial processes. In order to reuse the water, aiming at zero liquid discharge, crystallization has proved to be technically feasible and has been used in this separation. At the same time, with the evaporation of the water, the dissolved salts become particulate materials which are subsequently separated by filtration or centrifugation. However, to meet the industry\'s modern needs for saline effluent treatments, the crystallization process should show improvements, especially because of its importance in achieving liquid discharge goals. In this sense, simultaneous crystallization represents the possibility of removing several compounds in a single crystallization step from a multicomponent solution. This means that in addition to the purification of the water, this operation can also allow the recovery of the compounds in the effluents. In addition, particulate materials can be considered as raw material, eliminating waste - or disposing the residues appropriately. To this end, research is still needed to design processes to separate the different components that compose saline effluent streams and produce crystalline products with known morphological characteristics. Thus, the present work aimed to investigate the behaviour of ternary systems in crystallization, using as model the NaCl-KCl-H2O system in the batch evaporative crystallization process, in order to evaluate the influence of the process parameters on the crystals formed and to trace strategies to enable the use of the salts contained in the effluents. Three different routes of operation were tested to evaluate the behaviour of the crystals: one initially saturated only in NaCl, one initially saturated only in KCl and one initially saturated in both salts. Different evaporation rates, seed sizes and contents were tested. It was generally verified that control of two elementary phenomena is the key to overcome the main obstacles of this process: epitaxial growth and secondary nucleation. Some experimental conditions enablesd the obtaining of the batch product in bimodal distributions, where each peak was rich in one salt, with purities higher than 90 %. These fractions of the yield, that can be simultaneously separated by composition and size, were achieve mainly at lower supersaturations and using big KCl and small NaCl seeds. From these results, considering the need to develop energy-less and more environmentally friendly water purification techniques, a membrane crystallization (MC) system was tested using the same model system. The proposed design for the MC enable the operation for over 6 hours with a flux decay around 20 %. Yet, the proposed the yield of simultaneous membrane crystallization has not shown improvements in composition segregation.
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Atkinson, Allen Bradley Jr. "A Model for the PTX Properties of H2O-NaCl." Thesis, Virginia Tech, 2002. http://hdl.handle.net/10919/34376.
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In many geologic environments, fluids have compositions that are approximated by the H2O-NaCl system. When minerals grow in the presence of such fluids, some of the solution is trapped in the growing mineral as fluid inclusions. The salinity, temperature of homogenization, and pressure of homogenization are required to predict the trapping conditions of the fluid inclusion. In the laboratory the salinity and the temperature of homogenization of the trapped fluid are easily determined however, the pressure of homogenization cannot be determined directly, and must be calculated from an equation of state.A statistical model that relates the vapor pressure of H2O-NaCl to the fluid temperature and composition has been developed. The model consists of equations that predict the vapor pressure of H2O-NaCl from the eutectic temperature (-21.2°C) to 1500°C and for all compositions between the pure end-members. The model calculates the vapor pressure based on the composition (wt% NaCl) and the temperature of homogenization, which can be directly obtained from laboratory studies of fluid inclusions. This information in turn can be used to construct the isochore, or line of constant volume, along which the fluid inclusion was trapped. Finally the isochore can be used to determine the temperature and pressure at which the host mineral of the fluid inclusion was trapped.
Master of Science
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Xiao, Ruiyang. "The Freezing of Highly Sub-cooled H2O/D2O Droplets." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1211567463.
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Myers, Rupert J. "Thermodynamic modelling of CaO-Al2O3-SiO2-H2O-based cements." Thesis, University of Sheffield, 2015. http://etheses.whiterose.ac.uk/9175/.
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Most concrete is produced using calcium (alkali) aluminosilicate hydrate (C-(N-)A-S-H)-based cement. However, the chemistry of this phase in many cement-based materials is still not fully understood. This thesis presents a structural and thermodynamic investigation of C-(N-)A-S-H and C-(N-)A-S-H-based cements to provide insight into the chemistry of these materials. A mixed cross-linked and non-cross-linked tobermorite-like structural model for C-(N)-A-S-H is developed (the CSTM), which more appropriately describes the spectroscopic information available for this phase. Application of the CSTM to a Na2SiO3-activated slag cement cured for 56 and 180 days indicates the presence of a poorly-crystalline zeolite-like phase. The role of Al in cross-linking of C-(N-)A-S-H is also studied, which provides a more advanced description of the chemistry and structure of C-(N-)A-S-H than previously reported. A thermodynamic model for C-(N-)A-S-H (CNASH_ss) is derived, which greatly advances the utility of thermodynamic modelling of C-(N-)A-S-H-based cements by explicitly defining Al and alkali uptake in this phase. The chemistry of alkali-activated slag (AAS)-based cements is simulated using CNASH_ss and an ideal solid solution thermodynamic model for MgAl-OH-LDH that is also developed in the thesis. This analysis provides a good description of Na2SiO3-activated slag cement chemistry and accurately predicts chemical shrinkage in this material. Phase diagrams for NaOH, Na2SiO3, Na2Si2O5 and Na2CO3-activated slag-based cements are also simulated. These results can be used to design the chemistry of AAS-based materials. A detailed analysis of C-(N-)A-S-H solubility is presented, for Ca, Al, Si and alkali concentrations most relevant to C-(N-)A-S-H-based cements and at temperatures of 7-80°C. Solubility products for alkali-free C-(N-)A-S-H change slightly between 7°C and 80°C and as a function of Al/Si ratio. However, less soluble C-(N-)A-S-H is formed at higher Ca and alkali content. These results are important for understanding the stability of C-(N-)A-S-H in the majority of cement-based materials used worldwide.
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Vosper, Matthew E. "IR measurements of H2O solubility in CO2-rich mixtures." Thesis, University of Nottingham, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.727121.
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This study arises from the development of carbon capture and storage technology (CCS) as a means of disposing of the large quantities of CO2 emitted by industry. In particular the need is identified to measure the impact of impurities such as N2 and H2 on solubility of H2O in dense phase CO2 since the formation of an aqueous phase in CO2 bearing carbon steel pipelines presents a risk of corrosion or blockage. Chapter 1 describes this background, paying attention to the current state of affairs with regard to the development and deployment of CCS. An historical review is undertaken of the significant body of literature reporting the maximum H2O content of pure CO2. Analytical sampling methods are found to predominate in this literature, but particular attention is paid to several in situ infra-red methods upon which this thesis builds. The significant mathematical model of Spycher et al. is described along with equations of state relevant to the thesis. A discussion is presented of the limited literature concerning the effect of impurities on the H2O content of CO2. The aims of the thesis are then clearly set out: they pertain to the accurate measurement of H2O solubility in pure and impure CO2 at conditions relevant to CCS pipelines by an in situ infra-red method.
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Sundberg, Sara Nanna Kristina. "Optical and Raman Spectroscopic Studies on H2O at High Pressure." Doctoral thesis, Uppsala universitet, Institutionen för geovetenskaper, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5934.
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In this thesis, volumetric, optical and vibrational properties of H2O were studied at high pressures by combining techniques of Raman spectroscopy, interferometry and optical imaging. Pressures up to 7 GPa were generated in the diamond anvil cell (DAC), entering the stability fields of liquid water and ices VI, VII and VIII. A new integrated system for Raman, interferometric and optical-imaging studies has been built up. Utilizing the interferometric patterns formed between closely-spaced diamond anvils, the system allowed the complete monitoring and control of pVT-conditions of studied ices, as well as the determination of their dispersive properties in the visible range using the Airy equation and Cauchy formulation. This setup and technique thus represent a novel tool for the precise determination of equations of state (EOSs) of transparent materials, including fluids and low-Z materials. Data-sets on thermal pressure were obtained from heating/cooling experiments carried out on the liquid water and used for checking the mutual consistency between published EOSs. A pVT-EOS for ice VIII and room temperature isotherms for ices VI and VII at 300 K were derived by combined methods of interferometry and imaging. While the agreement with the available EOSs of ices VII and VIII is very good, some inconsistent EOSs of ice VI were identified in the present study. The technique of micro-Raman spectroscopy was applied for the monitoring of phase transformations, identification of various ice phases and for studying the response of vibrational symmetry modes to varying conditions. Analysis based on the combination of the pT-dependencies of the vibrational frequencies with the pVT-EOSs showed that, in the studied ices, the implicit volume-driven contributions dominate over the explicit phonon effects in the total temperature-induced changes in vibrational frequencies. The results provide valuable insight on the anharmonic effects and interactions in these molecular solids.
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Kamali, Fateme [Verfasser]. "Radio Continuum of Galaxies with H2O-Megamaser-Disks / Fateme Kamali." Bonn : Universitäts- und Landesbibliothek Bonn, 2019. http://d-nb.info/1200019857/34.
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Angarten, Rodrigo Giatte. "Termodinamica de micelização de alquilglicosideos em H2O e em D2O." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249588.
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Orientador: Watson LohDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica
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Resumo: Alquilglicosídeos (AG) são surfatantes não-iônicos totalmente provenientes de fontes naturais e renováveis, além de serem totalmente biodegradáveis e atóxicos. Neste trabalho estudou-se a termodinâmica de micelização desta classe de surfatantes através das técnicas de calorimetria diferencial de varredura (DSC) e titulação calorimétrica isotérmica (ITC), em função do número de átomos de carbono presentes em sua cadeia hidrofóbica e do número de unidades glicosídicas em sua parte polar. Estas propriedades foram determinadas em H2O e em D2O. Para um mesmo AG, o aumento de temperatura implica em uma energia de Gibbs, DmicG, mais favorável à micelização. Com o aumento de temperatura, a variação de entalpia, DmicH, passa de positiva para negativa e o termo entrópico, TDmicS, perde sua contribuição para a micelização. Quando comparados surfatantes de mesmo número de átomos de carbono na cadeia alquílica, mono e di-glicosídeos apresentam estritamente o mesmo comportamento termodinâmico. Heptilglicosídeo apresentou comportamento distinto dos demais surfatantes estudados, indicando que o ambiente químico no interior de sua micela é diferente. Estudos da micelização nos dois solventes mostraram que a maior energia coesiva de D2O, comparada a H2O, implica numa maior contribuição entrópica ao processo de micelização, mas não altera significativamente a energia de Gibbs
Abstract: Alkylglucosides (AG) are non-ionic surfactants obtained from natural raw materials, which are also totally biodegradable and non-toxic. This study investigated the thermodynamics of their micellization using the techniques of differential scanning calorimetry (DSC) and isothermal titration calorimetry (ITC), for a series of homologues varying their alkyl chain lengths and number of glucoside units (one or two). Some studies were conducted in D2O too, and compared with the results in H2O. As temperature increases, the micellization process becomes more favorable, as measured by a more negative DmicG. In parallel, the enthalpic contribution, DmicH, changes from positive to negative and the entropic term, TDmicS, reduces it positive value. These trends agree well with those reported for other families of surfactants. When AGs of the with the same alkyl chain length are compared, mono and diglucosides display the same thermodynamic functions for micellization. Only for the heptyl homologue of the monoglucoside family, results are slightly out of the general trend observed for the other AG, possibly due to different micelle structure being formed by this smaller surfactant. Comparison of results obtained in D2O with H2O confirmed that the greater cohesive energy of the former leads to a larger entropic contribution to micellization, but with no significant change in the Gibbs energy values
Mestrado
Físico-Química
Mestre em Química
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Monfredini, Thiago. "Estudo da emissão maser de H2O em IRAS 16293-2422." Instituto Nacional de Pesquisas Espaciais, 2010. http://urlib.net/sid.inpe.br/mtc-m19@80/2010/05.24.14.23.
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A formação da água em nuvens moleculares é uma questão importante pois remonta a estágios anteriores à formação estelar e o conjunto de modelos de evolução química e observações procuram inferir o papel dessa molécula ao longo de todo esse processo. Observações da emissão maser de água, resultada de choques associados a essas regiões, têm sido motivo de estudos e monitoramento no sentido de entender sua origem, estrutura de velocidade e variabilidade. IRAS 16293-2422, uma protoestrela de Classe 0, é um objeto muito estudado por causa de sua rica diversidade química e no qual já se detectou a molécula de água. Neste trabalho, apresentamos os resultados do monitoramento da transição maser 6$_{16}$-5$_{23}$ de água em 22,235 GHz, na direção dessa fonte, com a antena de 13,7 m do Rádio Observatório de Itapetinga, assim como uma compilação da literatura mais recente a respeito da formação de água no meio interestelar, para compreender a origem da molécula nesse tipo de emissão. Os resultados das observações mostram grandes variações na largura do perfil da componente principal e o surgimento de outras componentes de curta duração e/ou alta velocidade. Componentes com essas características ainda não haviam sido observadas e a investigação do regime de excitação do maser deve se dar através de modelos numéricos detalhados, incluindo a formação da água nesses ambientes.The formation of water in molecular clouds is an important issue because it goes back to earlier stages of star formation and the set of chemical evolution models and observations seek to infer the role of this molecule throughout this process. Observations of water maser emission, resulted from shocks associated with these regions, have been subject of studies and monitoring in order to understand its origin, structure and speed variability. IRAS 16293-2422, a Class 0 protostar, is a much studied object because of its rich chemistry in which it has detected the molecule of water. We present the results of the monitoring of maser transition 6$_{16}$-5$_{23}$ of water at 22.235 GHz toward this source, with the 13.7 m antenna of Radio Observatory Itapetinga as well as a compilation of recent literature regarding the formation of water in the interstellar medium, to understand the origin of the molecule in this type of emisson. The results of the observations show large variations in the linewidth of the profile of the main component and the appearance of other components of short duration and/or high speed. Components with these characteristics had not been observed and investigation of the maser excitation scheme should be done through detailed numerical models, including the formation of water in these environments.
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Hoxsie, Erin. "Ash Sintering in the Presence of a CO2-H2O Vapor." Thesis, University of Oregon, 2018. http://hdl.handle.net/1794/23715.
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We carried out rhyolite ash sintering experiments in the presence of a mixed CO2-H2O vapor using both fine and coarse ash. Fine ash is barely sintered after 7 minutes and fully densified after about 30 minutes. Coarse ash is barely sintered after 45 minutes and fully densified after a few hours. Vesicle relaxation from initially angular shapes to spherical shapes takes longer than estimated from scaling relations. The experimental sintering and vesicle relaxation timescales substantiate the hypothesis that natural obsidian pyroclasts from Mono Craters, California (USA) form by ash sintering. Two observations are interpreted as the most direct evidence yet that CO2 flushing from a deeper magmatic was involved in the eruption: (1) the preservation of sharp-tipped vesicles in domains of clasts that have high dissolved CO2 concentrations, and (2) the anticorrelation between H2O and CO2 observed in multiple clasts.
This thesis includes previously unpublished co-authored material.
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Yu, Xiang. "Photocatalytic conversion of methane and reduction of CO2 with H2O." Thesis, Lille 1, 2019. http://www.theses.fr/2019LIL1R022/document.
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La photocatalyse est l'une des technologies clés pour les applications liées à l'énergie propre et à l'environnement. Le nombre d'applications basées sur la photocatalyse a considérablement augmenté au cours des deux dernières décennies.L'activation photocatalytique des liaisons C-H est un domaine émergent. Cependant, en raison de sa grande stabilité, une grande quantité d’énergie est habituellement consommée pour sa conversion, ce qui reste un problème à résoudre. La conversion du méthane et le mécanisme réactionnel qui se produisent sur les nanocomposites métal-hétéropolyacide-oxyde de titane ont été étudiés aux chapitres 3 et 4. L'oxydation du méthane est effectuée depuis plus d'un siècle. Étant donné que l'oxygène est une molécule très réactive, le méthane peut réagir très rapidement avec l'oxygène moléculaire en produisant le CO2. Par conséquent, il est difficile d'obtenir un produit souhaité avec un rendement élevé et une sélectivité importante. Nous avons observé l'oxydation photocatalytique directe et très sélective du méthane en monoxyde de carbone dans les conditions ambiantes. Les catalyseurs composites à base de zinc, d'acide tungstophosphorique et d'oxyde de titane présentent des performances exceptionnelles dans cette réaction, une sélectivité élevée en monoxyde de carbone et un rendement quantique de 7.1% à 362 nm. La réaction se réalise selon le mécanisme de type Mars-Van Krevelen et implique la formation de méthoxy-carbonates de surface en tant qu'intermédiaires et un cycle d'oxydation et de réduction du zinc. Au cours des dernières décennies, des recherches approfondies ont été dédiées à la conversion directe du méthane en alcools ou en hydrocarbures supérieurs. Bien que la conversion directe du méthane en produits à haute valeur ajoutée ait un potentiel environnemental et commercial important, il n’existe aucun procédé à l’échelle commerciale. Nous avons découvert une conversion photochimique directe quantitative hautement sélective (>90%) du méthane en éthane à température ambiante sur un nanocomposite argent-hétéropolyacide-oxyde de titane. Le rendement en éthane atteint 9% sur les matériaux optimisés. Une efficacité quantique élevée, une sélectivité élevée et un rendement significatif en éthane, associés à une excellente stabilité, sont les principaux avantages de la synthèse quantitative de méthane à partir de méthane en utilisant l'approche de boucle photochimique. L'augmentation du taux de dioxyde de carbone dans l’atmosphère et l'épuisement des réserves de combustibles fossiles ont suscité de vives inquiétudes quant à l'impact ultérieur sur le climat mondial et l'approvisionnement futur en énergie. Le chapitre 5 porte sur l’efficacité du nouveau catalyseur pour la conversion sélective de CO2 en CO. Les nanocomposites acide de phosphotungstique-oxyde de titane contenant du zinc ont présenté une activité exceptionnelle atteignant 50 µmol CO/g·h et une sélectivité (73%) dans la réduction photocatalytique du CO2 en CO en présence d'eau. Les expériences infrarouges in situ suggèrent que la réaction implique des bicarbonates de zinc contenant des groupes hydroxyle. La décomposition sous irradiation de ces espèces de bicarbonate de zinc conduit à la production sélective de monoxyde de carbone et d'oxygène. Lors des réactions photocatalytiques, la différence de morphologie du catalyseur a généralement un effet significatif sur les performances photocatalytiques. Le chapitre 6 a étudié l'effet des cristaux monocliniques de vanadate de bismuth (BiVO4) avec un rapport contrôlé de facettes {010} et {110} sur la réduction photocatalytique de CO2 par H2O. La réaction sous irradiation est considérablement améliorée par la photodéposition sélective de co-catalyseurs de Cu et Co sur différentes facettes, fournissant un flux de charge selon le Z-schémaPhotocatalysis is one of the key technologies for clean energy and environmental applications. The number of applications based on photocatalysis has increased dramatically for the past two decades. Photocatalytic activation of C-H bonds is an emerging field. Methane is a promising source of energy with a huge reserve and is considered to be one of the alternatives to non-renewable petroleum resources because it can be converted to valuable hydrocarbon feedstocks and hydrogen through appropriate reactions. However, due to its high stability, high energy is usually consumed for its conversion, which remains a problem to be solved. Methane conversion and reaction mechanism occurring on metal-heteropolyacid-titania nanocomposites were investigated in Chapters 3 and 4. Oxidation of methane has been carried out for more than a century. Since oxygen is a very reactive molecule, methane can react very rapidly with molecular oxygen and is prone to total oxidation till CO2. Therefore, it is difficult to obtain a desired product with high yield and high selectivity. We report here direct and selective photocatalytic highly-selective oxidation of methane to carbon monoxide under ambient conditions. The composite catalysts on the basis of zinc, tungstophosphoric acid and titania exhibit exceptional performance in this reaction, high carbon monoxide selectivity and quantum efficiency of 7.1% at 362 nm. The reaction is consistent with the Mars-Van Krevelen type sequence and involves formation of the surface methoxy-carbonates as intermediates and zinc oxidation-reduction cycling. In the past few decades, extensive research has focused on the direct conversion of methane to alcohols or higher hydrocarbons. The current processes of converting methane to alcohols or olefins are complex and expensive, because they require an intermediate step of reforming methane to syngas. Although the direct conversion of methane to more valuable products has significant environmental and potential commercial value, there is no commercial scale process available. We uncovered highly selective (>90%) quantitative photochemical direct conversion of methane to ethane at ambient temperature over silver-heteropolyacid-titania nanocomposites. The ethane yield from methane reaches 9 % on the optimized materials. High quantum efficiency, high selectivity and significant yield of ethane combined with excellent stability are major advantages of methane quantitative synthesis from methane using the photochemical looping approach. The rise in atmospheric carbon dioxide and the depletion of fossil fuel reserves have raised serious concerns about the subsequent impact of CO2 on the global climate and future energy supply. The use of abundant solar energy to convert carbon dioxide into fuel, such as carbon monoxide, methane or methanol, solves both problems simultaneously and provides a convenient method of energy storage. Chapter 5 addresses a new efficient catalyst for selective CO2 to CO conversion. The zinc containing phosphotungstic acid-titania nanocomposites exhibited exceptional high activity reaching 50 µmol CO/g·h and selectivity (73%) in the CO2 photocatalytic reduction to CO in the presence of water. The in-situ IR experiments suggest that reaction involves zinc bicarbonates containing hydroxyl groups. The decomposition of these zinc bicarbonate species under irradiation leads to the selective production of carbon monoxide and oxygen. In photocatalytic reactions, the difference in catalyst morphology usually has a significant effect on the photocatalytic performance. Chapter 6 studied the effect of monoclinic bismuth vanadate (BiVO4) crystals with controlled ratio of {010} and {110} facets for photocatalytic reduction of CO2 by H2O. The reaction under irradiation is significantly enhanced by selective photo-deposition of Cu and Co co-catalysts over different facets providing Z-scheme charge flow
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Capobianco, Ryan Michael. "Ionization in H2O -- bearing carbon dioxide determined by conductivity measurements." Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/23283.
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Recent studies report rapid corrosion of metals and carbonation of minerals in contact with H2O-saturated (or nearly saturated) CO2. One explanation for this behavior is that addition of small amounts of H2O to CO2 leads to significant ionization within the fluid (analogous to corrosion in aqueous fluids). The extent of ionization in the bulk CO2 fluid was determined using a flow-through conductivity cell capable of analyzing very dilute solutions. Experiments were conducted from 25 to 200"C and 25 to 200 bar with H2O concentrations up to ~1650 ppmw. In all experiments, conductivities <10 nS/cm were obtained, indicating that the solution is essentially ion-free. This observation suggests that mobile ions are not present in the bulk CO2--rich fluid, and that the observed corrosion and carbonation reactions are not the result of ionization in the bulk fluid.Master of Science
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Baldassaro, Paige Marie. "Low Temperature Phase Relations in the System H2O-NaCl-FeCl2." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/31155.
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The low temperature phase behavior of the system H2O-NaCl-FeCl2 was examined using synthetic fluid inclusions. Experiments were conducted along the 5 wt% NaCl (relative to the total solution) pseudobinary, with FeCl2 concentrations varying from 2 to 33 wt%, and along the pseudobinary defined by mixing known amounts of FeCl2-4H2O with a 5 wt% NaCl solution, with final FeCl2 concentrations varying from 0 to 29 wt%. Synthetic fluid inclusions in quartz were prepared in cold-seal pressure vessels at 500 degrees C - 800 degrees C and 2 or 3 kilobars. The fO2 conditions were controlled by the Ni-NiO equilibrium curve. The liquid released from the capsule upon opening was initially colorless, but turned yellow-orange after contact with atmospheric O2. The clear color is characteristic of ferrous iron solutions, whereas the yellow-orange color is consistent with the presence of Fe3+ in solution. This color change suggested that the unopened capsules initially contained ferrous iron in solution, which oxidized to ferric iron when exposed to the atmosphere.
Borisenko (1977) reported a eutectic temperature of -37 degrees C for the system H2O-NaCl-FeCl2. In this study, it was not possible to verify this temperature due to the persistence of a metastable liquid down to liquid N2 temperatures (~-196 degrees C).
Final ice melting temperatures were obtained for concentrations less than 24 wt% FeCl2 and show a decrease in temperature with increase in FeCl2 concentration. For more concentrated solutions, final melting temperatures could not be obtained because the samples could not be frozen.Master of Science
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Barber, Robert John. "A high-accuracy synthetic H2O line list : computation and applications." Thesis, University College London (University of London), 2006. http://discovery.ucl.ac.uk/1445308/.
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The subject matter of this Ph.D. thesis is the production and application of the Barber-Tennyson line list, BT2, a computed list of H2160 transition frequencies and intensities. BT2 was produced using a discrete variable representation two-step approach for solving the rotation-vibration nuclear motions (Tennyson et al., 2004, Comp. Phys. Comm., 163, 85). It is the most complete water line list in existence, comprising over 500 million transitions ( 65% more than any other list) and it is also the most accurate (over 90% of all known experimental energy levels are within 0.3 cm-1 of the BT2 values). Its accuracy has been confirmed by extensive testing against astronomical and laboratory data. The line list has already found application in a wide range of astrophysical en vironments. It has been used to identify individual water lines in: the spectra of comets, sunspots, cool stars, brown dwarfs and the enigmatic object V838 Mon, and in a number of cases physical parameters have been derived from the intensities of the lines. The line list has also been used to model the atmospheres of cool stars and brown dwarfs and the chemistry of the circumstellar molecular shell ejected by V838 Mon. In addition to our own work with BT2, we have supplied various data, de rived from BT2, to other astrophysical research groups including: N. Dello Russo and co-workers for cometary applications J.M.C. Rawlings for modelling the time- dependent chemistry of the shell ejected by V838 Mon and P. Hauschildt's stellar atmospheric modelling group, which has included the complete BT2 line list in its 'PHOENIX' database. Practical applications of BT2 are not confined to the field of astronomy. The line list is now the preferred reference tool for many groups engaged in the identification of water lines in high temperature laboratory torch spectra, and we have been pleased to supply them with appropriate BT2 spectral data. The final chapter of the thesis looks to the future, which includes further appli cations of BT2 and the production of an NH3 line list.
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Rizk, Charles [Verfasser], Eckhard [Gutachter] Weidner, and Peter [Gutachter] Awakowicz. "Investigations and characterization of a subatmospheric disinfection process using H2O2/H2O vapor condensation / Charles Rizk ; Gutachter: Eckhard Weidner, Peter Awakowicz." Bochum : Ruhr-Universität Bochum, 2017. http://d-nb.info/1142001490/34.
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Baudu, Sylvain. "Etude expérimentale et modélisation des équilibres entre phases dans le système quaternaire réciproque H2O-UO2(NO3)2, H2O2-2HNO3, UO4." Lyon 1, 1997. http://www.theses.fr/1997LYO10350.
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Le peroxyde d'uranium est un compose intermediaire utilise dans l'elaboration du combustible des centrales nucleaires. Obtenu par oxydation des ions uranyle en solution aqueuse de peroxyde d'hydrogene, il peut presenter plusieurs degres d'hydratation. Afin de definir precisement les conditions optimales de cristallisation des peroxydes d'uranium hydrates, l'etude des equilibres solide-liquide du systeme quaternaire reciproque h#2o - uo#2(no#3)#2, h#2o#2 / 2hno#3, uo#4 a ete entreprise a deux temperatures : 25 et 70c. L'experimentation a ete conduite en utilisant une methode synthetique d'analyse des systemes complexes developpee au laboratoire : l'analyse thermique isoplethique. Par suite de la decomposition du peroxyde d'hydrogene, elle a necessite la mise au point d'un protocole operatoire et d'un mode de representation appropries. La caracterisation des phases solides a ete effectuee par diffraction des rayons x, atg et calorimetrie. Les teneurs en acide et en peroxyde d'hydrogene ont ete controlees systematiquement par dosage et les masses volumiques des solutions saturees ont ete determinees en vue d'une exploitation industrielle. A 25c, les resultats mettent en evidence la precipitation du tetrahydrate du peroxyde d'uranium mais l'existence d'un domaine restreint de cristallisation d'un hydrate superieur n'est pas ecartee. A 70c, la decomposition du peroxyde d'hydrogene est telle que les equilibres ne sont plus observables. Nous avons cependant montre la coexistence des di- et tetrahydrate a cette temperature. A partir du modele quasi ideal developpe au laboratoire une etude thermodynamique des equilibres solide-liquide-vapeur a ete entreprise dans les systemes de base h#2o-h#2o#2, h#2o-hno#3 et h#2o-uo#2(no#3)#2. Outre une excellente representation des courbes d'equilibre, le modele autorise une large extrapolation et permet de preciser la structure et les proprietes thermodynamiques de ces solutions.
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Peres, Durand Sylvie. "Etude physico-chimique de l'élaboration de gels de titane par le procédé PEM en milieu micellaire inverse decane/TX35/H2O-H2O2." Montpellier 2, 1993. http://www.theses.fr/1993MON20207.
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Nous avons caracterise les gels de titane formes par le procede sol-gel, en milieu micellaire inverse decane/tx35/h(2)o-h(2)o(2). L'isopropoxyde de titane, solubilise dans le decane, polymerise par un mecanisme d'hydrolyse et de condensation avec une vitesse qui est controlee par la frequence des echanges inter-micellaires, et par la quantite d'eau oxygenee contenue dans les micelles inverses. L'etude physico-chimique de la solution micellaire inverse par viscosite et par diffusion de la lumiere montre qu'elle est constituee de petits agregats de forme allongee, qui ne solubilisent que 8 molecules d'eau oxygenee par molecule de tensioactif (tx35). Nous avons determine les cinetiques de gelification de l'oxyde de titane en fonction de 3 parametres experimentaux, le taux d'hydratation de la micelle, n, le taux d'hydrolyse de l'alcoxyde, h, et la molalite de l'alcoxyde, m. La formation des gels, en presence d'eau oxygenee, est plus rapide que lorsqu'on utilise l'eau, dans les memes conditions de h, n et m. L'etude physico-chimique des gels par differentes techniques comme l'analyse thermique, la diffraction des rayons x et des electrons, les isothermes d'adsorption, la microscopie electronique, la thermoporometrie et la diffusion centrale des rayons x, montrent que les gels fabriques en presence d'eau oxygenee ont une meilleure resistance mecanique que ceux formes en presence d'eau; ce sont des solides mesoporeux dont les pores, en forme de bouteille, ont un diametre de 4 nm. Les agregats primaires (dont la taille est d'environ 100 nm) sont constitues de barreaux interconnectes de 2 nm de longueur. Ils ont une structure fractale, et sont formes par un processus d'agregation amas-amas controle par la reaction chimique
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Haas, Jérémy. "Etude expérimentale et modélisation thermodynamique du système CaO-SiO2-(Al2O3)-H2O." Phd thesis, Université de Bourgogne, 2012. http://tel.archives-ouvertes.fr/tel-00845956.
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L'objectif de ce travail est de proposer un modèle thermodynamique à 25°C qui permette de décrire les principaux produits d'hydratation d'un ciment Portland ordinaire avec et sans matériaux cimentaires secondaires : les hydrosilicates de calcium. La composition riche en aluminium de ces produits de substitution modifie la nature et la composition des hydrates de la pâte de ciment.Nous avons donc étudié le système simplifié CaO-SiO2-H2O, pour lequel nous avons réalisé différentes synthèses de C-S-H dans des conditions de synthèse et d'analyse identiques. Nous avons distingué le cas où la solution d'hydratation est sous-saturée de celui où elle est sursaturée par rapport à la Portlandite.Nous avons ensuite étendu le système simplifié précédent au système CaO-Al2O3-SiO2-H2O, pour lequel nous avons réalisé différentes synthèses de C-A-S-H et déterminé le protocole le plus adéquat pour obtenir des hydrates purs.La nature nanoparticulaire et la surface spécifique importante des C-S-H nous ont conduit à développer un modèle thermodynamique qui tiennent compte de réactions de surface. Ainsi, le modèle thermodynamique proposé dans ce travail, inspiré de différents travaux antérieurs du laboratoire, permet de décrire la composition de la solution, la stoechiométrie, et les propriétés de surface des C-S-H à l'équilibre. Ce premier modèle a été étendu aux C-A-S-H, en implémentant dans le modèle précédent des réactions de surface qui permettent de décrire l'incorporation de l'aluminium dans les différents sites possibles.Ce modèle a été appliqué à des cas simples tels que l'étude de la rétention d'alcalins par les C-S-H, et l'évaluation de l'impact de l'incorporation d'aluminium dans les C-S-H sur la répartition minéralogique des hydrates à l'équilibre pour un mélange cimentaire avec une forte teneur en aluminium
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Stöckel, Peter. "Homogene Nukleation in levitierten Tröpfchen aus stark unterkühltem H2O und D2O." [S.l.] : [s.n.], 2001. http://www.diss.fu-berlin.de/2002/23/index.html.
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Cote, Alexander Stephen. "Ab initio studies on the structure and dynamics of H2O ice." Thesis, University of Salford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.401985.
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Yalavac, Irem. "Assessing the scope of reductive cyclisations of lactones using SmI2-H2O." Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/assessing-the-scope-of-reductive-cyclisations-of-lactones-using-smi2h2o(7a7988bd-609c-4ab2-b541-6106bb7a3fb7).html.
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This report firstly describes the 5-exo-dig,6-exo-trig cascade cyclisation of 6-membered allenyl lactones for the formation of highly decorated 7,6-fused bicycles using the SmI2-H2O reducing system. Preliminary studies showed that 5-exo-dig,5-exo-trig cascade reactions successfully yield 7,5-fused bicycles. However, performance of 6-exo-trig reactions of this type with SmI2 has little literature precedent and was not known to proceed with SmI2 in combination with H2O.In order to investigate the cascade cyclisations, cis and trans allenyl lactones with alkene or alkyne chains tethered at the 2-position were successfully synthesised using a Barbier-type lactonisation reaction. Initial results using trans lactones with terminal alkene tethers yielded 5-exo-dig monocyclisation products as the major product and the corresponding 7,6-fused cascade cyclisation product as a minor component of the reaction. 5-exo-dig,6-exo-dig cascade cyclisation, as well as 5-exo-trig,6-exo-trig cyclisation attempts were not successful. Allenyl lactones containing alkene chains with a radical stabilising aryl group underwent cascade cyclisation to give the 7,6-fused ring systems as the major products. Secondly, the effect of a leaving group allowing for a beta-elimination upon reductive radical cyclisations of lactones, Meldrum's acids and barbituric acids was investigated. Using SmI2-H2O, 5-, 6-, and 7-membered lactones substituted with alkenyl radical accepting tethers containing an allylic pivalate as a leaving group successfully underwent monocyclisation to yield vinylic products. Allenyl lactones, as well as lactones with alkenyl radical acceptors at the 5-position also yielded 5-exo-dig,5-exo-trig/elimination, 5-exo-dig,6-exo-trig/elimination and 5-exo-trig,5-exo-trig/elimination products, respectively. A Meldrum's acid derivative, as well as a barbituric acid derivative decorated with the same allyl pivalate tether also gave desired vinylic cyclisation products. Manipulation of the vinyl moiety of a monocyclisation product, involving hydroboration/oxidation and Wacker oxidation, were also successfully performed.