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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
201

Sorption behaviour of metal contaminants in clay minerals, soils and matrices : understanding the influence of organic matter, pH, ionic strength and mineralogy

Anjolaiya, Olanrewaju January 2015 (has links)
Many chemical and physical factors govern the mobility of metal contaminants in soils and clay systems; some of these chemical factors include mineralogical composition, cation exchange capacity, organic matter content, pH and the ionic strength of soil water. This makes understanding and therefore predicting the fate of metal contaminants in soils a complex undertaking. There were two broad objectives in this study. The first was to investigate binary and ternary sorption systems, with the aim to understand the effects that factors such as pH, ionic strength, organic matter and metal concentrations, have on sorption of simple clay minerals (bentonite and kaolinite) with metals (cadmium, caesium, nickel and strontium). The second was to investigate the retention of heavy metals and radionuclides by well characterised organic-rich and organic-poor clay soils, breaking them down to their individual components to help understand the effects of each component separately, the study also tested to see if the additivity principle holds for these heavy metals and radionuclides, the additivity principle presumes that the overall sorption behaviour of a complex mixture is a summation of the weighted individual sorption behaviours of its constituents. The study also determined the relationship between the natural organic matter (NOM) content and cation exchange capacity (CEC) of the soils and how these affect the mobility of the metals, while also considering the relative importance of the speciation of the metals. Two British clay soils (Mercia Mudstone and London Clay) and two Nigerian soils (an organic-rich Ikeja Loam and the other organic-poor Magodo Laterite) were characterised by X-ray diffraction (XRD) analysis. Batch techniques were employed for the sorption studies, and radiometric techniques, ICP-OES and ICP-MS were used to quantify metal distribution between phases. The sorption of dissolved organic matter to clay minerals is very dependent on pH; this dependence is greater with increasing concentration of organic matter. The formation of metal-humate complexes is dependent on the nature of the metal and pH. Caesium exhibits no discernible sorption to humic acid, cadmium sorption is enhanced by increasing alkalinity but this enhancement is slightly reduced in higher concentrations of humic acid, nickel sorption is mostly unaffected by pH except in higher concentrations of humic acid and enhanced only under very low concentrations of humic acid, while strontium sorption to humic acid is reduced with increasing alkalinity. The nature and preference of humic acid sorption for these metals are vital to understanding the role played by humic acid in the ternary sorption studies of metals, humic acid and clay minerals. Strongly acidic conditions dominate other factors affecting sorption such as ionic strength in sorption of metals to clay minerals. Caesium sorption to bentonite at pH 4 is poor and almost unaffected by ionic strength of the electrolyte solution; saturation of sorption sites is reached with low amounts of adsorbed caesium. Strontium also binds poorly to bentonite at pH 4, more so than caesium, but an ionic strength effect on sorption still exists and is discernible even under these conditions. Increasing alkalinity has the expected effect of increasing sorption capacity of bentonite for both metals. Bentonite has poor sorption properties, having low affinity for caesium and strontium, but has greater affinity for caesium than strontium. The presence of humic acid can enhance or suppresses sorption, this varies from metal to metal and from solid to solid, the degree of enhancement or suppression also depends on humic acid concentration. Kaolinite has better sorption properties than bentonie. Cadmium has greater sorption affinity for kaolinite in the absence of humic acid, but nickel sorption is more enhanced in the presence of humic acid. Although the presence of humic acid enhances cadmium and nickel sorption to kaolinite, low humic acid concentration provides the best conditions for maximum sorption of both metals. High concentrations of humic acid lead to colloid formation which block access of metals with larger hydration radii to sorption sites while also encouraging the formation of humic acid-metal complexes. As with bentonite, caesium and strontium are both poorly sorbed by kaolinite. Unlike with cadmium and nickel however, the enhancement of strontium sorption is supported by higher concentrations of humic acid, these confirm a greater preference for the formation of S-HA-Sr ternary and lower preference for the formation HA-Sr binary complexes. The presence of humic acid inhibits caesium binding, and retention but this reduces with increasing alkalinity, while the reverse is the case with strontium whose retention is very poor and improved in the presence of humic acid and increasing alkalinity. Both caesium and strontium are poorly sorbed and retained by kaolinite but their retention improves with increasing humic acid concentration and pH. Cadmium and nickel also exhibit poor retention to kaolinite but their retentions are more improved under alkaline conditions and higher humic acid concentrations, nickel more so than cadmium. Similar sorption affinities were exhibited by the British (London Clay and Mercia Mudstone) and Nigerian soils (Magodo Laterite and Ikeja Loam) for the metals studied, showing the significance of soil constituent contribution to sorption behaviour. Both British clay matrices have affinity for the metals in the order Cs >> Cd ≈ Ni >> Sr, London Clay has the greater sorption capacity for all the metals, the clay mineral content of Mercia Mudstone is almost entirely made up of Illite while London Clay contains a mixture of smectite, illite and kaolinite with smectite being the most prevalent clay mineral phase. These confirm that smectite-rich clay systems will exhibit better sorption and retention capacities for metal contaminants. Both Nigerian soils showed the same order of affinity for all the metals Cd >> Ni >> Cs >> Sr, cadmium s preferential sorption to kaolinite was observed in its greater sorption and retention by the Nigerian soils which are kaolinite-rich. This preferential sorption of cadmium by kaolinite is confirmed by the Standard Addition experiment where its contribution to cadmium sorption is clearly evident, a trend not replicated with nickel as the sorbing metal. The presence of organic matter in soils or clay systems improves their metal sorption capacity significantly, especially true for insoluble organic matter, however its significance is reduced as pH increases. The contribution of organic matter also depends on the sorption affinity of the metal for organic matter; metals such like strontium are more affected by organic matter presence. The overall sorption behaviour of complex systems such as soils is difficult to attribute to their individual constituents. The laterite soils can be considered a relatively simple soil system containing only four constituents in significant quantities, yet it is difficult to replicate its sorption behaviour using a replicate proportioned mixture of its constituent phases. The additively calculated sorption profiles for the synthetic laterite were different from those obtained experimentally, the reason for this is that the existence of significant particle size differences between the natural and synthetic soils give rise to differences in the availability of sorption sites which is evident from the different CEC values measured for both systems.
202

QM/MM výpočty a klasické molekulárně-dynamické simulace biomolekul / QM/MM výpočty a klasické molekulárně-dynamické simulace biomolekul

Melcr, Josef January 2013 (has links)
Systematic calculations were performed to uncover the free energy surfaces for hydrolytic reactions of methyl-diphosphate (in vacuum and implicit solvents) and GTP in EF-Tu active site. Density functional theory and ONIOM extrapolative QM/MM scheme were adopted for the assay. In accordance with experiments, the catalytic effect of the sodium cation was mild. It changes the conformation of GTP attracting its negatively charged oxygen atoms. hydrolýze GTP. The Na+ also equilibrates the charges of all phosphate groups of the GTP mostly by transferring electrons from gamma to beta-phosphate group, which is characteristic for the intermediate states during the hydrolytic reaction.
203

Nanoparticules mono- et bimétalliques pour la métallisation de microvias par un procédé innovant utilisant les liquides ioniques / Mono- and bimetallic nanoparticles for the metallization of microvias using an innovative process in ionic liquids

Arquillière, Philippe 24 October 2012 (has links)
De nos jours, nous sommes entourés de dispositifs microélectroniques de plus en plus petits et performants. Pour poursuivre cette évolution, une nouvelle technologie est en cours de développement qui consiste à empiler plusieurs circuits intégrés. L’une des clefs pour aboutir à ce type d’architecture est la formation de microvias entre les différentes couches. Ce travail s’inscrit dans un à objectif à long terme qui vise à la mise au point d'un procédé innovant à coût réduit pour la métallisation de ces microvias, à partir de nanoparticules (NPs) métalliques de taille parfaitement calibrée. En particulier, des NPs bimétalliques de Mn et Cu pourraient être des précurseurs intéressants pour l'élaboration de barrières dites auto-formées et de couches d’accroches dans les microvias. Les liquides ioniques sont des milieux intéressants pour la synthèse de telles NPs, notamment à partir de précurseurs organométalliques. Il a été démontré que leur structure tridimensionnelle spécifique « guide » la croissance de NPs de Ru et les stabilise tout en les laissant libres de toute contamination de surface. Dans ce travail, ce concept a été enrichi par la synthèse de NPs d’autres métaux tels que Cu et Mn, et étendu à la formation de NPs constituées de deux métaux (M-M’NPs bimétalliques). De façon remarquable, les M-M’NPs obtenues ont toujours une taille inférieure aux MNPs et M’NPs prises séparément. Ces suspensions homogènes, très stables dans le temps, ont été directement déposées et frittées sur des substrats technologiques dans le but de former des films métalliques uniformes et adhérents. / Nowadays, microelectronic devices are omnipresent in our everyday life. To make them smaller and smaller as well as smarter and smarter, a new process which consists in stacking integrated circuits is being studied. In order to build this type of structures, the fabrication of microvias between layers is key. This work ultimately aims at developing an innovative process with reduced cost for the efficient metallization of these microvias. This can be achieved using perfectly calibrated metallic nanoparticles (NPs). In particular, bimetallic Mn-CuNPs could be interesting precursors to grow “self-formed” barriers and seed layers in microvias. Ionic liquids (ILs) are extremely well adapted media for the synthesis of such nano-objects, especially when organometallic precursors are used. It has been shown that theirspecific 3D structure provides a template to grow RuNPs of controlled size. The IL also acts as stabilizer, eliminating the need to use ligands that contaminate the metallic surface. In this work, this concept have been extended to the synthesis of other metallic NPs, such as Cu and Mn, as well as synthesis of NPs containing the two metals (bimetallic M-M’NPs). Remarkably, these M-M’NPs always exhibit a smaller size than the MNPs and M’NPs separately. These homogeneous and stable suspensions have been directly applied and sintered onto technological substrates in order to form uniform and adherent metallic layers.
204

Fundamental research of the solvent role in the ionothermal synthesis of microporous materials

Sun, Xin January 1900 (has links)
Doctor of Philosophy / Department of Chemical Engineering / Jennifer L. Anthony / Zeolites and zeolite-like materials are a group of porous materials with many applications in industry including but not limited to detergent builders and catalyst in the oil refining and petrochemical industry, due to their unique properties such as uniform pore size, large surface area and ion-exchange capacity. Researchers are constantly seeking new methods to synthesize zeolites. Zeolites are commonly synthesized in water. Then in 2004, a new method called ionothermal synthesis was invented by Dr. Morris and his colleagues, using ionic liquids (ILs) and eutectic mixtures as the solvent. In contrast to water, ILs and eutectic mixtures have negligible vapor pressure, thus making the use of high-pressure vessel unnecessary. In addition, they have various structures which could render new structures to frameworks of zeolite. Furthermore, since the cations of some ILs have structures which are similar to common structure directing agents, they theoretically could be used both as solvent and structure directing agent in ionothermal synthesis, possibly simplifying the synthesis process. This project is aimed at investigating the behavior of precursors of zeolites in ionic liquids and the interaction between precursors and ionic liquids in ionothermal synthesis because these fundamental properties could be useful in the current and future synthesis of zeolites. First, solubilities of different precursors, including Syloid 63 silica particles, aluminium isopropoxide (Al(OiPr)3) and phosphoric acid (H3PO4) in ILs with different structures are reported. Parameters such as activity coefficient and Henry’s constant are calculated from the solubility result. Second, interaction between precursors and ILs are studied. It is found that the addition of ILs in Al(OiPr)3 could change the structure of Al(OiPr)3, especially with the presence of H3PO4. Both ILs’ structures and temperature are capable of influencing the structure change of Al(OiPr)3. Third, hydrochloric acid is used for the first time as the mineralizer to synthesize aluminophosphates in ILs and it could lead to both dense and porous materials. Regardless of the acid used, frameworks synthesized after several hours always undergo a dramatic change after further heating. A slightly longer alkyl chain of ILs could accelerate the formation of crystalline materials. Increasing concentration of precursors in the reaction gel could increase the yield, but the same framework is not retained. Researches have also been done on stability of ILs in the synthesis process and it is found that heat and the presence of H3PO4 could decompose ILs, but the decomposed amount is extremely small.
205

Incorporation of Charge Transfer into Classical Molecular Dynamics Force Fields with Applications in Physical Chemistry.

Soniat, Marielle 18 December 2014 (has links)
The presence of charge transfer (CT) interactions is clear in a variety of systems. In CT, some electron density is shifted from one molecule to another (non-bonded) molecule. The importance of this CT interaction is unclear. Previous attempts to look at the conse- quences of CT required the use of ab initio molecular dynamics (AIMD), a computationally intensive method. Herein, a method for including CT in force field (FF) simulations is described. It is efficient, produces charges in agreement with AIMD, and prevents long- ranged CT. This CT MD method has been applied to monatomic ions in water. When solvated, ions do not have an integer charge. Anions give up some electron density to their ligands, and cations receive some electron density from their ligands. In bulk, the first solvation shell does not compensate for all CT, i.e. the charge is not smeared out over the first solvation shell. Rather, some charge is also found in the second solvation shell and further into the bulk. The charge of the first solvation shell depends on the balance between ion-water and water-water CT. When an interface is present, the charge outside of the second solvation shell will reside at the interface. This occurs even when the ion is over 15 Å away from the surface. The effect of long-ranged CT is mediated by changes in the hydrogen bonding patterns in water induced by the ions (not direct CT from the ions to distant waters). The model has also been applied to water’s ‘‘self-ions’’ hydronium and hydroxide. Trajectories from the multi-state empirical valence bond model (MS-EVB3) are analyzed. The differences between monatomic and molecular ions are explored. The direction of CT and the effect of hydrogen bonding with the ion are considered. The damping of CT as ligands are added is discussed and a method to improve the MD model, in order to account for damping, is proposed.
206

Study of new exchangers for boron removal from water containing high concentration of boron

Nguyen, Thi Thu Hien 12 July 2017 (has links) (PDF)
Boron is an element, which is necessary as essential nutrient for living organisms, especially for plants where it is involved in cell wall composition. But boron excess can cause some problems on the development of plants (defoliation, decay and fall unripe fruits), of humans and animals such as nausea, diarrhoea, dermatitis, lethargy. Boron toxicity also changes blood composition, caused disorder in neurological, physical, intellectual development. Nowadays, due to the shortage of fresh water sources, seawater desalination has been becoming an alternative fresh water supply. However, the presence of boron in seawater is quite high (4.5 mg L–1, around 4.5 mM). Moreover, the increasing use of boron in industries and its discharge to the environment has led to the contamination of surface and ground waters. As the result, boron removal, in production of drinking water becomes very important. Therefore, the World health organization has recommended a guideline of 0.5 mg L–1 B in drinking water and a maximum limit of 0.3 mg L–1 B in fresh water used for irrigation. The objective of this thesis is to study the mechanisms of boron surface exchange on different materials versus time and at equilibrium depending on some physicochemical parameters such as pH, initial boron concentration, reaction time in order to find a new exchanger for boron removal. Boron removal was carried out by ion exchange process using 2 types of resins: Amberlite IRA 743, Diaion CRB 03 as boron selective resins with methylglucamine functions, and Ambersep 900-OH and Amberlite IRA 402 Cl as anionic exchange resins with ammonium functions. From batch studies, fast exchange between resin surface and liquid phase was observed with boron removal up to at least 96 % within 30 min for Amberlite IRA 743, Diaion CRB 03 and Ambersep 900- OH. The reaction between resin surface and boron solution reached equilibrium after 2 h for all the resins. The pseudo-second order kinetic model was used to well describe the sorption kinetic process of the resins. At equilibrium, the experimental results showed that the maximum adsorption was observed to be achieved at pH 8 for Ambersep 900- OH, pH 10 for Amberlite IRA 402 Cl and independent on pH range from 6 to 12 for the 2 boron selective resins Amberlite IRA 743 and Diaion CRB 03. At pH 8 and for boron concentrations < 20 mM, the Langmuir-type relationship was used to fit the experimental data for Amberlite IRA 743, Ambersep 900- OH and resin Diaion CRB 03. In the range of studied boron concentration, the boron sorption onto Amberlite IRA 402 Cl followed linear-type behaviour. At pH 8 and for boron concentrations < 20 mM, the sorption capacities are: 1, 0,7, 0,3 et 0,05 mmol g–1 for Diaion CRB 03, Amberlite IRA 743, Ambersep 900- OH and Amberlite IRA 402 Cl, respectively. Column experiments were performed with the anionic resin Ambersep 900-OH and the selective one Amberlite IRA 743 by studying both the influence of boron concentration and the residence time. For the selective resin, if the residence time decreases, the boron breakthrough is fast followed by a long tail. For larger residence time, local equilibrium seems to be assumed. Results are thus consistent with batch experimental data. For the anionic resin, the nonlinear behaviour is also confirmed. Moreover, column experiments showed a strong difference during desorption. To regenerate resins, acid and basic treatments are necessary for the selective resin although a basic solution is enough for the anionic resin. A more detailed study of mechanisms is in progress in order to build a exchange model for predicting boron fate. Finally, characterization of pectins was also performed. Its composition (sugar and boron content) and the viscosity of pectin solutions were quantified. Filtration experiments allowed testing the efficiency of such material to remove boron too
207

Studies of interactions between ions in ionics liquids electrolytes by nuclear magnetic resonance / Etude de l’interaction entre les ions dans des électrolytes à base de liquides ionique par résonance magnétique nucléaire

Martin, Pierre 12 December 2018 (has links)
Ce travail de thèse porte sur l’étude d’électrolytes pour utilisation dans des systèmes de stockage énergétiques tels que les batteries lithium-ions. Les matériaux spécifiques à cette étude sont des liquides ioniques à base de pyrrolidinium avec le fluorosulfonylimide (FSI) en tant que contre-ion, le tout dopé au lithium.La méthode de caractérisation principale est la spectroscopie par Résonance Magnétique Nucléaire (RMN) qui peut être utilisée pour résoudre la structure, la dynamique ou encore l’arrangement spatial entre les anions et les cations. Des mesures de diffusion et des expériences de relaxation réseau-spin, utilisant 1H pour les cations, 19F pour les anions et 7Li, sont effectuées pour étudier le transport ionique dans le liquide ainsi que la rotation moléculaire respective des différents ions.Toutefois, dans le but de mieux comprendre le mécanisme de transport des ions à un niveau moléculaire dans ces liquides ioniques, l’expérience Heteronuclear Overhauser Effect SpectroscopY (HOESY) a été employée. Cette technique est basée sur le transfert d’aimantation entre deux isotopes nucléaires dans l’espace. Puisque le transfert est généralement dû à des interactions de courtes portées, des informations concernant les différentes proximités des espèces dans le liquide sont obtenues.Une grande partie de cette étude est concentrée sur le développement de la technique HOESY elle-même, avec l’amélioration de la séquence d’impulsion RMN mais aussi de l’analyse du signal, dans l’optique d’une étude quantitative et du développement d’une procédure automatique et systématique d’ajustement des données théoriques aux données expérimentales. Des simulations par Dynamique Moléculaire (DM) et des mesures de relaxation RMN sont utilisées pour permettre l’analyse des expériences OESY, permettant alors d’accéder à la corrélation des distances entre les noyaux et des paramètres de relaxation tels que les temps de corrélation, pouvant permettre une meilleure compréhension du transport ionique. En plus du développement de cette technique, de nouveaux liquides ioniques incluant des chaînes alkyles plus longues, des cycles plus longs ou encore un groupe ethero-alkyle sur la chaine alkyle sont étudiés par HOESY dans le ut d’observer l’impact de la structure du cation sur les interactions ioniques. Une autre technique complémentaire, la polarisation dynamique nucléaire, est aussi adoptée afin d’étudier les liquides ioniques dans un état vitreux imitant leur structure à l’état liquide. / This work is focused on the study of electrolytes for energy storage devices such as lithium ion batteries. The specific materials are pyrrolidinium-based ionic liquid electrolytes with bis-fluorosulfonylimide (FSI) as the counter anion, and also containing lithium.The main experimental method of characterization is Nuclear Magnetic Resonance (NMR) spectroscopy, which can be used to probe structure, dynamics and spatial arrangements between anions and cations. NMR-based diffusion measurements or spin lattice relaxation experiments, using 1H for cations, 19F for anions and 7Li, are used to study the ionic transport in the liquid and the molecular tumbling of the different ions respectively.However, in order to attempt to better understand the ion transport mechanism at the molecular level in these ionic liquids, the HOESY (Heteronuclear Overhauser Effect SpectroscopY) experiment is used. This technique is based on a transfer of magnetization through space between two different nuclear isotopes. As this transfer is generally mediated by short-range interactions, it provides information on which species are close together in the liquid.A large part of this work is based on the development of the HOESY technique itself, both improving the implementation of the NMR pulse sequence to reduce the experimental time, but also improving ways to analyze the resulting data in a quantitative way and developing an automatic and systematic data fitting procedure. Molecular Dynamics (MD) simulations and NMR relaxation measurements are also used to assist the HOESY analysis, allowing correlations with distances between nuclei and motional parameters such as correlation times to be established, which will lead to a better understanding of the ion interactions. In addition to this technique development, others ionic liquids including longer alkyl, longer cycle or even an ether-o-alkyl group on the alkyl chain, are studied by HOESY in order to observe the impact of the cation structure on the ionic interactions. Another complementary technique, dynamic nuclear polarization, is also used in order to study the ionic liquid in the glassy state structure which mimics the liquid state.
208

Mecanismos de relaxação spin-nuclear-rede em CaF2:U3+. / Nuclear-spin-lattice relaxation mechanics for CaF2:U3+.

Delben, José Renato Jurkevicz 20 October 1983 (has links)
Neste trabalho descreve-se a construção de dois equipamentos controladores da temperatura da amostra, que operam entre 77K e 300K e entre 300K e 700K. Apresenta-se os resultados de medidas de T1 e T2, no intervalo de 77K e 700K, realizadas com o campo estático Ho paralelo à direção [111] e uma radiofreqüência de 24MHz. Discutem-se os comportamentos de T1 e T2 neste intervalo de temperaturas e os possíveis mecanismos de relaxação, spin nu clear-rede e spin eletrônico de impureza-rede, atuantes. / In this work we describe the construction of two sample temperature controlled equipments that operate between 77K and 300K and between 300K and 700K. We show the results of T1 and T2 measurements over the temperature range of 77K to 700K with the static field Ho parallel to [111] direction and 24MHz. We discuss the T1 and T2 behavior in this range temperature and the possible relaxation mechanisms of spin nuclear and spin electronic of impurity to lattice that are present.
209

Novos líquidos iônicos para aplicações como eletrólitos / New ionic liquids for applications as electrolytes

Sánchez Ramirez, Nedher 21 August 2014 (has links)
Os líquidos iônicos (LIs) são eletrólitos promissores para uso em baterias de lítio e outros dispositivos eletroquímicos, devido às suas propriedades físico-químicas únicas como, por exemplo, ampla faixa de temperatura como liquido, boa condutividade, baixa pressão de vapor e estabilidade térmica, química e eletroquímica. Um LI é composto normalmente por um cátion orgânico e um ânion orgânico ou inorgânico. Neste trabalho, foram sintetizados novos líquidos tanto modificando o ânion como o cátion. Em ambos os casos procurou-se LIs com ótimas propriedades de transporte e que melhorassem a condutividade do lítio em relação condutividade total da mistura LI - sal de lítio. Em primeira instância, foram sintetizados e caracterizados os seguintes líquidos iônicos derivados do ânion [B(CN)4]-: [BMPYR][B(CN)4] (N-butil-N-metilpirrolidínio tetracianoborato), [BMP][B(CN)4] (N-nbutil- N-metilpiperidínio tetracianoborato) e [BMMI][B(CN)4] (1-n-butil-2,3-dimetilimidazólio tetracianoborato), sendo os dois primeiros são líquidos na temperatura ambiente. Quando comparados com os derivados de bis(trifluorometanosulfonil)imideto, [Tf2N]-, os líquidos iônicos derivados de tetracianoborato apresentam melhores valores de condutividade e viscosidade, sendo isto refletidos em um maior valor do parâmetro condutividade do lítio (&#963;Li). Além disso, estes LI possuem maior estabilidade química e eletroquímica. Utilizou-se a técnica de espectroscopia Raman para estudar os líquidos [BMPYR][B(CN)4] e [BMP][B(CN)4] e suas misturas com sal de lítio (0,1 molL-1 de LiB(CN)4), demostrando-se que a interação entre o íon lítio e o ânion tetracianoborato é muito baixa, o que explica o altos valores do número de transporte e condutividade do lítio nestes sistemas. já através da Modificação do cátion, foram sintetizados cinco líquidos iônicos derivados de fosfônio, usando sempre o ânion [Tf2N]-. Entre eles são líquidos na temperatura unicamente os LIs [P2225][Tf2N] (Bis(trifluormetilsulfonil)imideto de trieltilpentilfosfônio) e [P222(201)][Tf2N] (Bis(trifluormetilsulfonil)imideto de trietil(2-metoxietil)fosfônio). Estes líquidos apresentaram excelentes propriedades de transporte e estabilidade eletroquímica quando comparados com seus equivalentes derivados de nitrogênio. Quando se adicionou o sal de lítio, LiTf2N, em concentrações de 1 e 2 molL-1 , os líquidos apresentaram um decréscimo das propriedades de transporte, embora demostrarem efeito menor em comparação com os líquidos iônicos derivados de nitrogênio, apresentando inclusive maiores valores nos números de transporte e de condutividade do lítio nas misturas estudadas. / Ionic liquids (ILs), are of great interest nowadays as electrolytes for lithium ion batteries due their unique characteristics, which include: liquid state over a wide temperature range; nonvolatility, which assures thermal stability and nonflammability; high ion content, which results in high ionic conductivity; and excellent chemical and electrochemical stability. ILs consists of an organic cation and an inorganic or organic anion. In order to improve the transport properties, the cation and anion of the ionic liquid were changed. Three ionic liquids derived from the anion [B(CN)4]- were synthetized and chararacterized: [BMPYR][B(CN)4] (N-n-butyl-N-methylpyrrolidinium tetracyanoborate) [BMP][B(CN)4] (N-n-butyl-Nmethylpiperidinium tetracyanoborate) and [BMMI][B(CN)4] (1-n-butyl-2,3-dimethylimidazolium tetracyanoborate). The first two are liquid at room temperature. When comparing these ionic liquid with the analogous ones containing the anion Tf2N, it was found that ILs derivates from tetracyanoborate have better transport properties which is reflected in a larger value of parameter conductivity of lithium (&#963;Li). Moreover these ILs have higher chemical and electrochemical stability. The Raman spectroscopy was employed to study the BMPYRB(CN)4 and BMPB(CN)4 liquids and their mixtures with lithium salt (0.1 mol L-1 of LiB(CN)4); it was demonstrated that the interaction between the lithium ion and anion tetracyanoborate is very low, which explains the high values of conductivity and transport numbers of lithium in these systems. Furthermore five ionic liquids from the phosphonium cation was synthesized always using the anion [Tf2N]-; being liquid at room temperature only the ILs [P2225][Tf2N] (triethyln-pentylphosphonium bis(trifluoromethylsulfonyl)imide) and [P222(201)][Tf2N] (triethyl (2- methoxyethyl) phosphonium bis(trifluoromethylsulfonyl imide) imide). It was found that these liquids have excellent transport properties and electrochemical stability when compared with their counterparts derived from nitrogen; furthermore, when lithium salt LiTf2N, was added at concentrations of 1 and 2 mol L-1, the ILs containing the phosphonium cations have also shown a decrease in the transport properties, however, the effect is less pronounced when compared to ionic liquids derived from nitrogen, presenting higher transport number and lithium ion conductivity.
210

Desenvolvimento de um fotoelasticímetro e algumas aplicações. / Construction of a photoelasticimeter and some applications

Barboza, Ruy 15 June 1978 (has links)
Descreve-se detalhadamente a teoria e construção de um fotoelasticímetro, destinado ao estudo da estrutura de cristais iônicos deformados pela adição de impurezas. No método utilizado, a modificação do estado de polarização da luz pela amostra é investigada com o auxílio da modulação do feixe por uma placa fotoelástica. Exemplos de aplicação são apresentados. / The theory and construction of a photoelasticimeter are described in detail. The main use of the instrument will be in the study of the structure of ionic crystals deformed by the addition of impurities. In the employed method, the modification of the state of polarization of the light by the sample is investigated with the aid of a photoelastic board. Some examples of use are presented.

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