To see the other types of publications on this topic, follow the link: Lanthane ion.
Dissertations / Theses on the topic 'Lanthane ion'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Lanthane ion.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Vieira, Nunes Antonio Idivan. "Transport d'ions sous l'effet d'un champ électrique en milieu poreux : applications à la séparation de terres rares par électrophorèse à focalisation." Vandoeuvre-les-Nancy, INPL, 1999. http://docnum.univ-lorraine.fr/public/INPL_T_1999_VIEIRA_NUNES_A_I.pdf.
Full textAbstract:
Les ions trivalents de terre rare ont des propriétés très voisines et leurs séparation les uns des autres, généralement délicate, est souvent effectuée par extraction par solvant ou échange d'ions. L'électrophorèse à focalisation représente une alternative à ces techniques éprouvées et l'objet de ce travail était l'étude fondamentale des phénomènes de transport d'ions dans un tel procédé. L'électrophorèse dite à focalisation permet de séparer des espèces amphotères comme des cations de terres rares, M+3, en ayant recours à un gradient de pH dans la cellule et à l'ajout d'un complexant acide (EDTA) par exemple. Cette méthode repose sur la différence des points isoélectriques de ces espèces, présentés sous forme cationique prés de l'anode ou bien sous la forme complexé ionique, plus prés de la cathode. Les ions de terres rares sont soumis aux effets antagonistes de la diffusion et de la migration, ce qui permet leur focalisation au point isoélectrique, correspondant au pH pour lequel leur mobilité effective est nulle. Après une étude bibliographique sur les terres rares et les procédés de séparation par électrophorèse, ce mémoire décrit des approches théoriques et expérimentales des équilibres de complexation de quelques terres rares (lanthane, cérium, praséodyme et néodyme) en fonction du pH ainsi que l'estimation du point isoélectrique. Les phénomènes des transports et de focalisation en vie de la séparation de deux terres rares font l'objet du dernier chapitre: l'étude a été conduite tout d'abord en absence d'écoulement forcé de la solution et a permis de dégager des conditions opératoires permettant la focalisation d'une espèce. L'apport méthodologique a été utilisé pour la conception et la réalisation d'un cellule avec circulation continue de solution et dotée de 42 capteurs de températures et 42 de potentiels. Les résultats de premiers essais de focalisation et de séparation de deux terres rares sous la forme de profils des différentes grandeurs, sont présentés et discutés<br>Trivalent ions of rare earth elements have very similar properties and their difficult separation each from another is usually carried out by liquid-liquid extraction or ion exchange focalisation electrophoresis represehts an alternative route to the usual techniques. The purpose of this work consisted of the fundamental investigation of ion transport phenomena in electrophoretic processes. Focalisation electrophoresis is suitable for separation of amphoteric species such as rare earth ions, using a pH gradient in the cell and upon addition of a complexed agent e. G. EDTA. This technique relies upon the difference in isoelectrical points of the considered species, being under the form of free cation near the ano'de, and in the form of anionic complexed species doser to the cathode Rare earth species are submitted to the antagonist effects of diffusion and migration, enabling their focalisation to occur at the isoelectrial point, corresponding to nil value of their effective mobility. Following a literature survey on rare earth elements and electrophoresis processes, the document describes theoretical and experimental investigations of complexation equilibria of some rare earth elements, namely lanthanum, neodymium, praseodymium and cerium, depending on pH. Values for the isoelectrical points coulb be estimated. Transport and focalisation phenomena in view of rare earth separation, are dealt in the last chapter. Investigations were first carried out without forced circulation of the electrolyte solution and the transient behavior of the system allowed operating conditions to be design and built-up of a continuos device, more suitable to separation, and provided with 42 potential and 42 temperature sensors: the results of the preliminary runs, in form of variable profiles, are presented and discussed<br>Os fons trivalentes de terras raras apresentam propriedades muito proximas umas das outras, o que dificulta bastante a separaçao destes elementos, sendo a extraçao por solvente e troca de ions os unicos métodos mais usados na separaçao de terras raras. No entanto, a eletroforese à focalisaçao representa uma alternativa à separaçao de terras raras como mostra este trabalho que tem como objetivo fundamental estudar os fenomenos de transportes de ions num determinado processo. Através da técnica de eletroforese à focalizaçao, é possivel separar espécies ionicas anfotéricas, como por exemplo cations de terras raras, M+3, aplicando-se um gradiente de pH na célula de separaçao e utilizando um acido como agente complexante, como por exemplo o EDTA. 0 principio deste método é baseado na diferença dos pontos isoelétricos das espécies presentes sob a forma cationica proxima ao anodo ou sob a forma do complexo ionico proximo ao catodo. Os ions de terras raras estao sempre submetidos aos efeitos da diftisao e da migraçao o que os levam a focalizarem em seus pontos isoelétricos correspondentes a mobilidade efetiva nula. Apos um èstudo bibliognifico sobre as terras raras e os processos de separaçao por eletroforese, este relatorio de tese descreve as aproximaçoes teorico e experimental de equilfbrio de complexaçao de alguns elementos de terras raras, como por exemplo: lantanio, cério, praseodimio e neodimio, em funçao do pH, hem como a estimacao do ponto isoelétrico. Os fenomenos de transporte e de focalizaçao foram abordados no ultimo capftulo, o que nos permitiu de observar as condiçoes operacionais de focalizaçao de uma espécie sem o fluxo forçado de uma soluçao. A metodologia descrita anteriormente foi utilizada para a concepçao e a realizaçao de uma célula corn circulaçao continua da soluçao num sistema dotado de 42 captores de temperaturas e 42 de potenciais. Os resultados dos primeiros testes de focalizaçao e da separaçao de dois elementos de terras raras foram apresentados e discutidos sob a forma de perfis de diferentes parametros
2
AL-NEAMI, KADOM ANAM. "Mesure des sections efficaces de production des rayons x : :(l) des elements ::(56)ba, ::(57)la, ::(58)ce par des protons de 1 mev-3,5 mev." Université Louis Pasteur (Strasbourg) (1971-2008), 1988. http://www.theses.fr/1988STR13172.
Full textAbstract:
Mesures dans des cibles epaisses de sulfates et d'oxydes, dans des cibles minces d'oxydes disposees sur des couches minces de carbone et dans des cibles epaisses de tetraborate de li dope par equiv. A 1% de ba, la ou ce sous forme de sulfate ou d'oxyde. Bon accord avec les previsions theoriques et avec les valeurs experimentales trouvees pour des elements voisins
3
Mottot, Yves. "Propriétés chimiques et électrochimiques des chlorures de lanthanides cérides en milieux chlorures fondus : stabilité thermodynamique des alliages LA-NI et ND-FE à haute température." Paris 6, 1986. http://www.theses.fr/1986PA066127.
Full textAbstract:
Etude thermodynamique et cinétique de la réduction électrolytique de terres rares cériques, réalisée au sein de l'eutectique fondu LICL-KCL. Comportement singulier du néodyme étudié dans l'eutectique BACL::(2)-KCL jusqu'à 1300k; on montre que la stabilité de ND(II) croit avec la température. Etude des alliages entre les métaux des terres rares et les métaux de transition de composition générale LNM::(X), dont les propriétés thermodynamiques ont été déterminées par mesure de la F. E. M. De la pile LN/LNCL::(3), LICL+KCL/LNM::(X); application aux alliages LA-NI ET ND-FE entre 700 et 800K.
4
Lefebvre, Dominique. "Hexagallates de lanthanide pour matrices laser et substrats d'épitaxie : élaboration, étude cristallographique et spectroscopique." Paris 6, 1986. http://www.theses.fr/1986PA066415.
Full textAbstract:
Différentes méthodes de cristallogenèse de la MgGa 11O 19 sont testées, notamment l'élaboration par tirage Czochralski. Affinement structural confirmant la structure de type magnétoplombite du composé. Substitution ionique permettant d'accroitre les paramètres cristallins du composé étudié en vue de son utilisation comme support pour la croissance d'hexaferrites alcalinoterreux. Détermination du domaine schématique de composition des aluminogallates La1-xNdxMgGa11O19. Étude des propriétés optiques du néodyme par réflexion diffuse, RPE et fluorescence.
5
Martin, Philippe. "Etude des mécanismes de diffusion thermique et de diffusion sous irradiation alpha des terres rares dans les apatites." Lyon 1, 1999. http://www.theses.fr/1999LYO10026.
Full textAbstract:
A l'heure actuelle, le probleme du stockage des dechets nucleaires doit etre resolu. Une des solutions envisagees est de creer des sites de stockage en profondeur et d'assurer leur securite, c'est a dire d'empecher la migration des radionucleides dans la biosphere. Parmi les materiaux susceptibles de freiner cette diffusion, les apatites sont envisagees en raison de leur faible cout (mineral present dans les phosphates sedimentaires ou dans le roches) et de leurs proprietes de retention vis a vis des elements lourds tels que les actinides et les lanthanides. Le but de ce travail a ete d'etudier la diffusion dans les apatites des radionucleides en fonction de la temperature et de la radioactivite ambiante. Pour limiter les problemes de radioprotection nous avons choisi de travailler sur des elements stables suivants : le lanthane et l'europium. Leurs masses et leurs proprietes chimiques permettent de simuler les produits de fission et les actinides. Dans un premier temps, nous avons mesure a l'aide des techniques d'analyse par faisceaux d'ions la diffusion thermique dans deux types d'apatite : la fluorapatite et l'hydroxyapatite. Les valeurs de coefficients de diffusion etant tres faibles des etudes de localisation par luminescence laser et spectroscopie d'absorption x (exafs) ont ete menees. Dans un second temps, la diffusion sous irradiation d'ions bismuth simulant les noyaux de recul de la radioactivite alpha a ete etudiee, mettant en evidence un mecanisme de diffusion par annihilation vers la surface des defauts crees lors de l'irradiation.
6
Congreve, Aileen. "Responsive lanthanide complexes for metal ion sensing." Thesis, Durham University, 2004. http://etheses.dur.ac.uk/3668/.
Full textAbstract:
The speciation and distribution of zinc (II) within cells is not well established and the range of zinc (II) probes available are of limited use. The quest was to develop responsive lanthanide complexes to bind selectively and respond (by change in hydration state) to biologically relevant concentrations of zinc at physiological pH for possible application in MRI and luminescence. A pyridyl sulfonamide ligand with an a-CH(_2)NHSO(_2)CF(_3) substituent was found to have the desired properties for strong zinc (II) coordination. The presence of a methyl group at 6', inhibited the formation of related square planar copper (II) complexes. Pyridyl amide appended europium and gadolinium (III) complexes, based on cyclen were developed with C(_2) and (C_3) spacers separating the macrocyclic ring and the amide. The mono-aqua C(_2) complex exhibited fast water exchange, due to the steric hindrance of the seven-membered chelate between the amide carbonyl and the lanthanide centre. The increase in steric hindrance caused by the eight-ring chelate in the C(_3) analogue rendered it q = 0. A trifluoromethanesulfonamide moiety at the 6' position of the pyridine group resulted in a mono-aqua complex for the C(_2) and C(_3) appended systems. This system showed no change in hydration state on addition of Zn(^2+). The addition of a-N- carboxyalkyl groups to give a GdaD03A system resulted in the formation of q = 2 complexes which showed no zinc (II) responsive properties. However, the C(_2)- linked species exhibited a high binding affinity to HSA which resulted m a dramatic increase in the relaxivity. Eu and Gd complexes of an octadentate N(_5)O(_3) pyridyl sulfonamide containing ligand were developed as pH and pZn responsive probes. The pyridyl nitrogen bound irreversibly to the lanthanide centre, resisting protonation even in the presence of zinc and copper ions, for which the pyridyl sulfonamide group has an establiblished high affinity.
7
Abram, Edward John. "Synthesis and characterisation of doped lanthanum gallate and lanthanum silicate oxide-ion conductors." Thesis, University of Sheffield, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.251374.
Full text
8
COURANT-DENIARD, SYLVIE. "Les acides phosphatoantimoniques h::(n)sb::(n)p::(2)o::(3n+5),xh::(2)o (n = 1,3,5) : synthese, caracterisation, proprietes d'echange, de conductivite protonique et de catalyse." Nantes, 1988. http://www.theses.fr/1988NANT2002.
Full textAbstract:
Les acides sont prepares par echange k**(+)-h**(+) a partir des phosphoantimonates de potassium. Les composes correspondant a n=1 et 3 ont une structure en couche alors que le troisieme presente une charpente covalente tridimensionnelle. Pour chacun d'eux, ont ete precisees l'isotherme d'hydratation a 20**(o)c, la variation des parametres de mailles avec l'humidite relative a 20**(o)c et l'evolution de la teneur en eau et des parametres de maille en fonction de la temperature
9
Aull, Brian Francis. "The impact of ion-host interactions on the 5d-to-4f spectra of lanthanide rare earth ions." Thesis, Massachusetts Institute of Technology, 1985. http://hdl.handle.net/1721.1/40343.
Full textAbstract:
Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1985.<br>MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.<br>Includes bibliographical references.<br>by Brian Francis Aull.<br>Ph.D.
10
White, Gaye Francine. "Lanthanide ion binding proteins as in vivo luminescent labels." Thesis, University of East Anglia, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247225.
Full text
11
Felix, Olivia. "Etude thermodynamique de la sorption de l'uranyle sur la monazite et la magnétite." Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00737326.
Full textAbstract:
Les phénomènes d'adsorption interviennent dans les processus géochimiques gouvernant ainsi le transport des contaminants. Par ailleurs, les variations de température sont susceptibles d'influencer significativement leur comportement vis-à-vis de la surface des minéraux. Aussi, l'influence de la température sur la sorption doit être étudiée afin de mieux appréhender le devenir des éléments dans l'environnement. Dans cette optique, l'interaction entre un ion modèle, l'uranyle et deux minéraux a été étudiée. Dans un premier temps, un composé méthodologique, la monazite, a été choisi afin de déterminer la démarche à suivre pour étudier l'influence de la température sur la sorption de l'uranyle dans trois milieux plus ou moins complexants. Puis, des tests préliminaires ont été réalisés pour étudier la sorption de l'uranyle sur un composé d'intérêt industriel, la magnétite, en appliquant la démarche mise en place. Le solide a d'abord été caractérisé d'un point de vue massif puis les caractéristiques acido-basiques de sa mise en suspension dans les trois électrolytes (NaClO4, NaNO3 et Na2SO4) ont été étudiées en fonction de la température. Les constantes d'équilibre associées aux réactions de déprotonation des sites de surface ont été déterminées entre 25°C et 95°C par modélisation de courbes de titrages potentiométriques. Les simulations ont été effectuées en limitant au maximum le nombre de degrés de liberté du système. Le modèle 1-pK a donc été préféré au modèle 2-pK en raison du nombre de paramètres ajustables plus limité dans ce modèle. Des contraintes expérimentales telles que le pH de point de charge nulle ou les enthalpies déterminées par mesure directe des chaleurs associées par microcalorimétrie de mélange ont été imposées pour déterminer les constantes d'équilibre acido-basiques. La sorption de l'uranyle en fonction du pH sur le même intervalle de température a été étudiée en alliant l'acquisition de données macroscopiques telles que les sauts de sorption et la spéciation en solution à une étude structurale menée par analyse par spectrofluorimétrie laser permettant l'identification des espèces sorbées. La simulation des sauts de sorption permettant d'accéder aux constantes associées aux réactions de sorption a été réalisée en imposant les caractéristiques acido-basiques préalablement déterminées. Des mesures directes, par microcalorimétrie de mélange, des chaleurs mises en jeu lors de la sorption de l'uranyle ont permis de tester la validité de la loi de Van't Hoff sur ce phénomène. La même démarche a été suivie pour étudier l'influence de la température sur la sorption de l'uranyle sur la magnétite en milieu NaClO4 et NaNO3. Cependant, l'étude structurale par spectrofluorimétrie laser n'a pu être réalisée en raison de la couloration noire de la magnétite.
12
Cullen, Thomas Donovan. "Hydroxyl radical reaction and lanthanide ion complexation kinetics of DTPA." Thesis, California State University, Long Beach, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=1524188.
Full text
13
Sudhakaran, Pillai S. "Luminescent materials based on Lanthanide ions." Thesis, Kingston University, 2010. http://eprints.kingston.ac.uk/20413/.
Full textAbstract:
The inclusion of lanthanide (III) (Ln[sup]3+) ions into polymers by “covalent” bonding has applications. Heteroleptic hydrotris(pyrazolyl)borate crotonate and cinnamate complexes were synthesised for reasons that, firstly, knowledge of the polymerisable double bond was helpful in establishing the conditions of any copolymerisation reaction; secondly, the chosen ligands are very good at receiving energy in the UV region; and thirdly, lanthanide complexes might undergo changes in properties, on moving between adjacent lanthanide ions, allowing potentially convenient isolations of pure materials at the monomer production stage, or even at the polymerisation stage. For both complexes, two classes of target complex were identified: the mononuclear (Er-Lu) and dinuclear (La-Ho). Mononuclear forms were identified by MS, [sup]1H NMR and elemental analysis and dinuclear forms were characterised by X-ray crystallography. For heteroleptic hydrotris(pyrazolyl)borate crotonate and cinnamate complexes, the ligands act as antennae for receiving and then transferring energy to metal ions and these complexes were studied in several homogeneous and heterogeneous copolymers as well as in rigid PMMA or polystyrene matrices. Luminescence decay of these complexes depends on the distance between the metal and C-H oscillators so the cinnamate complexes showed better luminescence life-times compared to crotonate complexes. The copolymer system helped to reduce the concentration quenching compared to corresponding metal complex / polymer blend systems. The thermal stabilities of the complex monomers were increased by incorporating them into polymer chains. Europium crotonate and cinnamate complexes in the poly(p-phenylenevinylene) (PPV) precursor blends showed the characteristic emission of europium, and the emission from PPV was quenched by increasing the europium content in the PPV precursor blends.
14
Accorsi, Gianluca <1973>. "Trivalent lanthanide ions: luminescence and applications." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/472/.
Full text
15
Moscrop, R. "Experimental techniques for the study of nuclei in the light Lanthanide region." Thesis, University of Manchester, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383186.
Full text
16
Pereao, Omoniyi Kolawole. "Functionalisation of electrospun nanofibre for lanthanide ion adsorption from aqueous solution." University of the Western Cape, 2018. http://hdl.handle.net/11394/6393.
Full textAbstract:
Philosophiae Doctor - PhD (Chemistry)<br>Rare earth elements (REEs) have widespread use and importance for industrial
applications due to their metallurgical, optical and electronic properties. Several
typical hydrometallurgical techniques such as adsorption, chemical precipitation,
filtration, ion exchange and solvent extraction techniques have been used for
separation and recovery of the rare earth metals from aqueous solutions. Adsorption
was recognised as one of the most promising methods due to its simplicity, high
efficiency and availability. Many adsorbents are being investigated but there are few
adsorbents containing specific functional groups in practical use for REEs recovery.
This aim of this study was to develop a nanofibre based adsorbent containing
glycolic acid functional groups for the recovery of rare earth metals. Polystyrene (PS)
and polyethylene terephthalate (PET) nanofibres were prepared by the
electrospinning technique, glycolic acid functional groups were grafted onto the PS
or PET nanofibres and the potential of the two modified nanofibre adsorbents for
adsorption of Ce3+ or Nd3+ from aqueous solution were investigated and compared.
The adsorption experiments were carried out to investigate the effect of different
adsorption parameters such as pH, contact time and initial concentration in a batch
system in order to achieve the objectives of this research.
17
Lisowski, Carmen Ellen 1978. "Hybrid organic/inorganic nanomaterials: Development of malonamide-functionalized nanoparticles designed for lanthanide ion detection." Thesis, University of Oregon, 2010. http://hdl.handle.net/1794/10523.
Full textAbstract:
xviii, 174 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number.<br>Hybrid nanoscale complexes incorporate the attributes of organic and inorganic components to yield novel multifunctional materials. Because the individual components themselves and the combinations used can be widely varied to tune the properties of the resulting complex, the potential for new properties and practical applications is nearly limitless. However, widespread use of these materials relies on appropriate design, synthesis and characterization strategies to ensure proper function and compositional integrity. This dissertation describes the chemistry of these hybrids, made possible by combining organic ligands, inorganic nanoparticles, and metal ions, and the interesting optical and spectroscopic properties associated with the hybrid nanomaterials.
Organic ligands containing Bunte salt and acyclic malonamide functionalities were attached to gold nanoparticles to produce colorimetric sensors for lanthanide ion detection. Bunte salt functionality stabilizes the gold core and malonamide functionality offers selective and sensitive lanthanide ion binding. The binding interaction controls a nanoparticle cross-linking event that changes the color of the nanoparticle solution, resulting in visual, colorimetric lanthanide ion detection. Next, the concentration of malonamide ligand was diluted and replaced with a diluent ligand yielding nanoparticles stabilized with a mixed ligand composition. The mixed ligand environment makes the optical response of the colorimetric sensor reversible. Furthermore, the use of Bunte salt ligands during nanoparticle synthesis has allowed the investigation of the role of reducing agent on nanoparticle stability.
In addition to exploring interactions pertaining to gold nanoparticle complexes, a new approach to sensitize europium ion luminescence was developed by fabricating a zinc oxide/europium complex. A molecular linker permits simultaneous zinc oxide nanoparticle functionalization and trivalent europium binding in order to tether the europium ion close to the nanoparticle surface. The zinc oxide nanoparticle can then act as an inorganic antenna, transferring energy to the europium ion and enhancing its luminescence.
Finally, a strategy was developed to synthesize bifunctional bicyclic malonamides. Synthesis of these ligands allows the enhanced f-block ion binding affinity of bicyclic malonamides to be incorporated into functional materials to compare their performance to our previously prepared acyclic malonamide hybrid complexes.
This dissertation includes my previously published and co-authored materials.<br>Committee in charge: Darren Johnson, Chairperson, Chemistry;
James Hutchison, Advisor, Chemistry;
Catherine Page, Member, Chemistry;
Michael Haley, Member, Chemistry;
Barbara Roy, Outside Member, Biology
18
Farkas, Ildiko. "Coordination Chemistry of Actinide and Lanthanide Ions." Doctoral thesis, KTH, Chemistry, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3236.
Full text
19
Farkas, Ildikó. "Coordination chemistry of actinide and lanthanide ions /." Stockholm, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3236.
Full text
20
McCaw, Charles Stuart. "Electronic structure of lanthanide ions in crystals." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298628.
Full text
21
Shehu, Ali. "Structural analysis and its implications for oxide ion conductivity of lanthanide zirconate pyrochlores." Thesis, Queen Mary, University of London, 2018. http://qmro.qmul.ac.uk/xmlui/handle/123456789/36699.
Full textAbstract:
The local structure evolution as a function of composition and temperature, and the resulting electrical conductivities were studied in samples with general composition (Yb1-xNdx)2Zr2O7, using Reverse Monte Carlo (RMC) modelling of total neutron scattering data and Impedance Spectroscopy. At low neodymium content (0.00 ≤ x ≤ 0.50), this system crystallizes in the fluorite structure with space group Fm3̄m, where-as at high neodymium content (0.75 ≤ x ≤ 1.00), a pyrochlore structure with space group Fd3̄m is observed. For compositions with high neodymium content prepared at lower temperatures, a fluorite structure is seen, which shows gradual evolution of pyrochlore ordering with increasing calcination temperature. Cation anti-site disorder was present throughout the compositional range. Total conductivity increases with increasing Nd content, up to a maximum at x = 0.75 and then decreases. The conductivity of these oxides is of the order of 10-4 S cm−1 at 700 °C. Variable temperature neutron powder diffraction experiments were carried out on the (Nd1-xCax)2Zr2O7-x (0.10 ≤ x ≤ 0.50) system, to investigate the local structural evolution as a function of composition and temperature. The entire compositional range studied exhibits a single phase with a pyrochlore-type structure. The variable temperature study showed that the pyrochlore structure is maintained throughout the temperature range studied. No cation anti-site disorder was present in any of the compositions, over the temperature range studied. Total conductivity increases with increasing Ca content, up to a maximum at x = 0.30 and then decreases. The conductivity of these oxides is of the order of 10-3 S cm−1 at 700 °C. Structural evolution in oxidising and reducing atmospheres was investigated in cerium zirconate, Ce2Zr2O7+δ. A number of transformations were revealed, depending on the atmosphere (O2 vs CO) and temperature. Upon heating the pyrochlore phase in flowing O2, three distinct phases were observed, with transitions at ca. 140 C and 410 C. At around 140 C, a previously un-identified phase formed, which was fitted with a triclinic model that contained 10 Ce and 10 Zr sites, each with a distorted cubic coordination. Above 410 C, the triclinic phase transformed to a cubic phase, corresponding to the κ-phase (space group P213). RMC modelling of the local structure of the -phase, revealed an ordered, pyrochlore-like cation sub-lattice, with a disordered anion sub-lattice. Upon re-heating the κ-phase in CO, the pyrochlore phase re-appeared at around 260 °C. At 290 °C, the pyrochlore phase was phase pure.
22
Takasaki, Bryan K. "Lanthanide ions in the development of artificial nucleases." Thesis, McGill University, 1994. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=28535.
Full textAbstract:
The kinetics and mechanism of hydrolysis of both activated and unactivated phosphate diesters in the presence of aqueous solutions of Ce(III) salts are studied in detail. In the presence of 20 mM Ce$ rm (ClO sb4) sb3 (pH 8, 37 sp circ C)$ a DNA dinucleotide (dApdA) is converted to the nucleoside (dA) and inorganic phosphate with a half-life of approximately 100 minutes. This reaction is oxygen dependent and a mechanism involving the activation of oxygen by Ce(III) to give a Ce(IV) coordinated peroxide dianion as the active species is proposed.<br>The addition of 20 mM hydrogen peroxide to 2mM La(III) (pH 7.0, 25$ sp circ$C) results in a 34,000 fold increase in the rate of BNPP hydrolysis over that observed in the presence of 2mM La(III) alone and an overall 5 x l0$ sp8$ fold rate increase over the uncatalyzed rate. Incorporation of $ sp{18}$O from hydrogen peroxide into the inorganic phosphate product and evidence from the reaction kinetics and potentiometric titrations indicate that the mechanism involves nucleophilic attack of a La(III) coordinated peroxide dianion upon the substrate.<br>La(III) hydroxide clusters formed from the combination of La(III) (20 mM) and NaOM (40 mM) rapidly converts an RNA dinucleotide (ApA) to the monophosphates (2$ sp prime$-AMP and 3$ sp prime$-AMP) (t$ sb{1/2}$ = 8 sec at pH 8.7, 20$ sp circ$C). The presence of molecular oxygen does not improve the efficiency of Ce(III) in cleaving ApA; however, it does assist in the cleavage of the monophosphates which are not cleaved by Ce(III) in the absence of O$ sb2$ or La(III).
23
楊友源 and Yau-yuen Yeung. "Alternative parametrization schemes in lanthanide crystal fieldtheory." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1986. http://hub.hku.hk/bib/B31231044.
Full text
24
Crooks, Steven M. "Analysis of the spectra of compounds containing lanthanide ions." Thesis, University of Canterbury. Physics, 1998. http://hdl.handle.net/10092/8144.
Full textAbstract:
This thesis is concerned with the mechanics of transforming between observational data of lanthanide ion transition intensities and the parameters which model the observed intensities. The accuracy of intensity measurements and the underlying accuracy of the model used to predict the observables is investigated. Investigation is made of the effect of uncertainties for the fitting of transition intensities and rotatory strengths.
In this thesis it is shown that the parameterisation of the transition intensity operator using the Reid-Richardson Aλtp intensity parameters is inherently, multi-valued. When the superposition model is not explicitly assumed,, distinct sets of Aλtp parameters can exist which produce identical calculated spectra. In this thesis, a new parameterisation was developed which allows the easy identification of the multiple solutions of the electric-dipole transition parameters. It is possible to transform between the different Aλtp solutions by a matrix transformation. Additionally, this new parameterisation allows the different polarisations that can be observed in the symmetry to be treated separately. For example, in most high symmetry systems it is possible to write a parameterisation for the π polarisation and fit the resulting parameters independently of the parameters for the σ polarisation.
With only a single polarisation for the intensities or circular dichroism it is not possible to determine all of the Aλtp parameters, both σ and π are required. Published analyses of circular dichroism are repeated using the new parameterisation scheme showing the effect of this polarisation dependence, and the improvement over previous work.
The intensities for low symmetry systems, or the π polarised intensities for most symmetries, can be written as a linear matrix equation.
The possible use of Stark effect splittings to determine the intensity parameters is investigated. The use of the Stark effect in the investigation of transition intensities appears to have been previously unexplored by other researchers. It is found that such Stark splittings are expected to be resolvable and have magnitudes of the order of 0.1cm-¹. It may be possible to utilise splittings of hyperfine lines to determine parameters which describe the transition intensities.
Intensity parameters are presented for a variety of systems that have been analysed for the first time in this thesis. Intensity parameters for the C4v symmetry centre of Pr³⁺:CaF₂ and Pr³⁺:SrF₂ systems are presented. The vibronic transitions for the Cs₂NaEr³⁺Cl₆ system were analysed and the vibronic intensity parameters were determined. Re-analysis of the previous results was carried out uising the new parameterisation and a new set of intensity parameters is presented.
The level of statistical significance that can be assigned to distinct parameter sets is examined. It is found that quite small variations in the χ² value for fitting intensities can be resolved. Using Monte-Carlo methods it is possible to derive levels of confidence for the distinguishability of the resolveability of two minima into distinct sets.
25
Zouad, Sélim. "Etude de la fixation des ions strontium et lanthane sur les acides antimonique et phosphatoantimonique." Grenoble 2 : ANRT, 1988. http://catalogue.bnf.fr/ark:/12148/cb37619334w.
Full text
26
Zouad, Sélim. "Etude de la fixation des ions strontium et lanthane sur les acides polyantimonique et phosphatoantimonique." Paris 6, 1988. http://www.theses.fr/1988PA066620.
Full textAbstract:
Etude des mecanisme et cinetique de la fixation d'ions lanthane et strontium sur le pentoxyde d'antimoine hydrate et sur les aides h#3sb#3p#2o#1#4?xh#2o et h#5sb#5p#2 o#2#0?xh#2o. Mise en evidence de l'echange cationique h#+/sr#2#+
27
Yeung, Yau-yuen. "Alternative parametrization schemes in lanthanide crystal field theory /." [Hong Kong : University of Hong Kong], 1986. http://sunzi.lib.hku.hk/hkuto/record.jsp?B12324863.
Full text
28
Guillot, Stéphanie. "Étude des paramètres principaux gouvernant les propriétés de conduction dans les apatites, électrolytes pour piles SOFC." Thesis, Lille 1, 2009. http://www.theses.fr/2009LIL10052/document.
Full textAbstract:
Cette thèse a pour objet l’élaboration et la caractérisation d’oxyapatite silicatées de lanthane, matériaux potentiellement utilisables comme électrolyte pour piles à combustible à oxyde solide. Des poudres et céramiques denses d’apatite de stœchiométries en oxygène et de compositions (substitutions) différentes ont été élaborées par réaction à l’état solide à haute température. Il ressort que quelque soit la composition, le paramètre principal qui gouverne les propriétés de conduction est la stœchiométrie en oxygène. La conductivité atteint 1,7 x 10-2 S.cm-1 à 700°C pour la composition La10Si5,5Mg0,5O26,5. La combinaison d’analyses spectroscopiques (Diffusion Raman, Résonance Magnétique Nucléaire) et de diffraction des neutrons a permis de définir un mécanisme de conduction des ions oxydes dans la structure. L’existence d’un site interstitiel localisé dans les canaux de la structure apatite en (-0,01, 0,04, 0,06) est confirmée. Un chemin de diffusion des ions oxyde de type « lacune sur le site 2a – atome interstitiel » est proposé le long de l’axe c. Ce mécanisme semble facilité par le déplacement des tétraèdres situés à la périphérie du canal<br>This work is devoted to the elaboration and the characterisation of apatite type lanthanum silicates as new electrolyte for SOFC fuel cells. Apatite powders and dense ceramics with different oxygen stoichiometries and compositions (substitutions) were prepared by high temperature solid state reaction. Whatever the composition, we can conclude that the key parameter which governs the conduction properties is the oxygen stoichiometry. The conductivity reaches 1.7 x 10-2 S.cm-1 at 700°C for the La10Si5,5Mg0,5O26,5 composition. By combining Raman spectroscopy, NMR and neutron diffraction, an oxide ion conduction mechanism was deduced. The existence of an interstitial site located at (-0.01, 0.04, 0.06) was confirmed. This allows to proposed a realistic oxygen diffusion pathway through this interstitial site along the c axis. Moreover, this mechanism seems to be facilitated by the displacement of tetrahedral located at the periphery of the oxide channels
29
Smith, Charlene Amanda. "The synthesis and magnetochemistry of transition and lanthanide metal compounds." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/the-synthesis-and-magnetochemistry-of-transition-and-lanthanide-metal-compounds(1f50bd6e-19e2-4cf6-9211-e22fcef578f9).html.
Full textAbstract:
The introductory Chapter to this thesis outlines fundamental aspects of 4f lanthanide(III) coordination chemistry, in particular compounds that possess the intriguing properties of slow relaxation of magnetisation, (or the ability to behave as single-molecule magnets, SMMs). The recent renaissance into the study of the magnetic behaviour of 4f-coordination complexes has led to the consideration of utilising organometallic precursors for the development of novel lanthanide containing compounds, which may possess interesting magnetic properties, subsequently forming the basis of Chapter Two. In Chapter Two, the syntheses and structures of the novel lithiated thiolate ligand, lithium triphenylsilylthiolate, (Ph3SiS-Li) (2.1), and the sulfur-bridged, dimetallic dysprosium(III) and gadolinium(III) complexes [(MeCp)2Dy(µ-SSiPh3)]2 (2.2) and [(MeCp)2Gd(µ-SSiPh3)]2 (2.3), are described in detail. The structural and physical properties of these compounds are analysed through NMR, elemental analysis and SQUID magnetometry, alongside supporting theoretical calculations to reveal that compound 2.2 is the first dimetallic, sulfur-bridged SMM reported, giving an energy barrier to the reversal of magnetisation of Ueff = 192 ± 5 K.56bChapter Three reports on the structural development of a series of lanthanide monomers, exhibiting the general motif [Ln(OSiPh3)3(THF)3] (where Ln = Dy(3.4), Er(3.5), Ho(3.6), Gd(3.7), Tb(3.8)), exploiting the siloxide ligand Ph3SiOH through two novel synthetic routes. This Chapter also provides new analytical insight to these complexes by exploring their magnetic properties through a series of SQUID measurements and through the analysis of their electronic properties using air sensitive, variable temperature optical absorption spectroscopy. Compounds 3.4 and 3.5 were revealed to be SMMs, with 3.5 having a much higher thermal barrier to the reversal of magnetisation, Ueff = ~ 28 K, than 3.4, which are supported by theoretical analysis. Chapter Four describes the utility of ligand 2.1 and Ph3SiOH in the context of 3d transition metal cyclopentadienyl chemistry, outlining the syntheses and structures of three distinct compounds; the trimetallic, [Cp2Mn3(µ-OSiPh3)4](4.7), the hetero-cubane tetramer [CpMn(µ-SSiPh3)]4 (4.8) and the dimetallic thiolate-bridged [CpCr(µ-SSiPh3)]2 (4.9) compound. These compounds were formed in reactions exploiting organometallic manganocene and chromocene precursors. Magnetic susceptibility measurements were conducted on these compounds to gain further insight into their structural properties. The magnetic exchange coupling constants for Mn(II) compounds 4.7 and 4.8 were J = - 4.4 cm-1 and J = - 3.0 cm-1 respectively. Furthermore, having demonstrated the use of metal-cyclopentadienyl building blocks in the synthesis of novel SMMs, Chapter Five discusses the possibility of further advancement on the development of this class of magnetic molecules.
30
蔡慶銘 and Hing-ming Michael Chua. "Transition intensities and energy transfer of lanthanide ions in crystals." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1994. http://hub.hku.hk/bib/B31211409.
Full text
31
Chua, Hing-ming Michael. "Transition intensities and energy transfer of lanthanide ions in crystals /." [Hong Kong : University of Hong Kong], 1994. http://sunzi.lib.hku.hk/hkuto/record.jsp?B13692689.
Full text
32
Ritt, Marie-Claude. "Thermodynamics of interaction of macrocyclic ligands with multivalent ions and organic molecules of biological importance." Thesis, University of Surrey, 1991. http://epubs.surrey.ac.uk/843105/.
Full textAbstract:
The first part of this work deals with the determination of the thermodynamic parameters for the complexation of lanthanide cations (La3+, Pr3+ and Nd3+) with Cryptand-221 and Cryptand-222 in acetonitrile and propylene carbonate at 298.15 K. The complexation process between these cations and these ligands in these solvents is enthalpy-controlled. The higher stability observed for these cations and these ligands in propylene carbonate with respect to acetonitrile is attributed to the increase in entropy observed for the complexation reaction in propylene carbonate. Enthalpies of solution of lanthanide and lanthanide cryptates are reported. These data are used to derive single-ion enthalpies of transfer of La3+, Pr3+ and Nd3+ from propylene carbonate to acetonitrile based on the Ph4AsPh4B convention. The results show that the cryptate conventions are not valid for the calculation of single-ion values for the transfer of tervalent lanthanide cations among dipolar aprotic media. Enthalpies of coordination of lanthanide(III) cryptates in the solid state are calculated. The second part of this study aims to investigate the properties of the synthetic macrocyclic ligands such as Cryptand-222 and 18-Crown-6 towards molecules of biological importance. Stability constants (hence free energies), enthalpies and entropies of complexation of a series of DL-amino acids with 18-Crown-6 and Cryptand-222 in methanol and ethanol, as obtained from titration calorimetry, are reported. No significant variations are found in the free energies of complexation of the different amino acids and these two ligands in these solvents as a result of an enthalpy-entropy compensation effect. This effect is for the first time shown in complexation reactions involving crown ethers and cryptands. The thermodynamic parameters of transfer of amino acids and their complexes with 18-Crown-6 and Cryptand-222 from methanol to ethanol have been calculated. Possible correlations between complexation and transfer data for the amino acids, the ligands and the amino acid-macrocyclic ligand complexes are investigated. The implications of these results to processes of biological importance are discussed. As a continuation of this study, the possibility of selectively extracting amino acids from methanol by polymeric resins containing crown ethers as anchor groups is investigated.
33
Chen, Chao-Hsu. "Atomistic Computer Simulations of Diffusion Mechanisms in Lithium Lanthanum Titanate Solid State Electrolytes for Lithium Ion Batteries." Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc700110/.
Full textAbstract:
Solid state lithium ion electrolytes are important to the development of next generation safer and high power density lithium ion batteries. Perovskite-structured LLT is a promising solid electrolyte with high lithium ion conductivity. LLT also serves as a good model system to understand lithium ion diffusion behaviors in solids. In this thesis, molecular dynamics and related atomistic computer simulations were used to study the diffusion behavior and diffusion mechanism in bulk crystal and grain boundary in lithium lanthanum titanate (LLT) solid state electrolytes. The effects of defect concentration on the structure and lithium ion diffusion behaviors in LLT were systematically studied and the lithium ion self-diffusion and diffusion energy barrier were investigated by both dynamic simulations and static calculations using the nudged elastic band (NEB) method. The simulation results show that there exist an optimal vacancy concentration at around x=0.067 at which lithium ions have the highest diffusion coefficient and the lowest diffusion energy barrier. The lowest energy barrier from dynamics simulations was found to be around 0.22 eV, which compared favorably with 0.19 eV from static NEB calculations. It was also found that lithium ions diffuse through bottleneck structures made of oxygen ions, which expand in dimension by 8-10% when lithium ions pass through. By designing perovskite structures with large bottleneck sizes can lead to materials with higher lithium ion conductivities. The structure and diffusion behavior of lithium silicate glasses and their interfaces, due to their importance as a grain boundary phase, with LLT crystals were also investigated by using molecular dynamics simulations. The short and medium range structures of the lithium silicate glasses were characterized and the ceramic/glass interface models were obtained using MD simulations. Lithium ion diffusion behaviors in the glass and across the glass/ceramic interfaces were investigated. It was found that there existed a minor segregation of lithium ions at the glass/crystal interface. Lithium ion diffusion energy barrier at the interface was found to be dominated by the glass phase.
34
Sharples, Joseph William. "Cooling rapidly and relaxing slowly with 4f ions." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/cooling-rapidly-and-relaxing-slowly-with-4f-ions(fab0aa0f-1ab7-4016-9d97-5edf6a629fa8).html.
Full textAbstract:
Anisotropic magnetic materials have been proposed over the past twenty years or so as candidates for high density storage, so-called Single-Molecule Magnets (SMMs). These may in future be used to store data at the level of an individual molecule. Separately, isotropic materials may be harnessed for their large magnetocaloric effect which enables them to be used as refrigerants. This can potentially replace the increasingly rare and therefore expensive 3He and 4He currently employed either separately or in 3He-4He dilution refrigerators. This thesis examines the use of lanthanide(III) ions for these applications, by detailing the synthesis, characterisation and performance of three new classes of zero-dimensional compounds, {LnIII2}, {LnIII2ZnII4} and {LnIII7}. These are assessed by several techniques including SQUID magnetometry, heat capacity measurements luminescence spectroscopy, Electron Paramagnetic Resonance and ab initio calculations. In doing so we extended the use of a tripodal ligand widely employed in 3d chemistry to 4f ions, and found only the second 3d-4f phosphonate SMM. Investigating several members of a known three-dimensional lanthanide(III) polymer, {LnIII}n, showed the isotropic gadolinium(III) analogue is one of the very best of all known magnetic refrigerants in the low-temperature regime.
35
Santos, Marina. "ANALYTICAL POTENTIAL OF POLYMERIZED LIPOSOMES BOUND TO LANTHANIDE IONS FOR QUALITATIVE AND QUANTITATIVE ANALYSIS OF PROTEINS." Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2587.
Full textAbstract:
One of the intriguing features of biological systems is the prevalence of highly selective and often very strong interactions among different cellular components. Such interactions play a variety of organizational, mechanical, and physiological roles at the cellular and organism levels. Antigen-antibody complexes are representative examples of highly selective and potent interactions involving proteins. The marked specificity of protein-antibody complexes have led to a wide range of applications in cellular and molecular biology related research. They have become an integral research tool in the present genomic and proteomic era. Unfortunately, the production of selective tools based on antigen-antibody interactions requires cumbersome protocols. The long term goal of this project explores the possibility of manipulating liposomes to serve as the chemical receptors ("artificial antibodies") against selected proteins. Cellular lipids (e.g., lipid rafts) are known to facilitate highly selective binding of proteins on cell membranes. The binding of proteins to cell membranes can be envisaged to be modulated via interactions between polar (charged) and non-polar head groups of lipids and the complementary amino acid residues of proteins. Their interaction is facilitated by a combination of van der Waals, electrostatic, hydrogen bonding and hydrophobic forces. A further interesting aspect of the above interaction is the "fluidity" of the membrane resident lipids, which can migrate from other regions to further enhance the complementary interactions of proteins on the initially "docked" membrane surface. With these features in mind, the end goal of this project is expected to deliver lipid-based chemical receptors "synthetically" designed against proteins to function as "artificial antibodies". Protein sensing will be accomplished with lipid receptors assembled in templated polymerized liposomes. The research presented here specifically focus on the analytical aspects of protein sensing via polymerized liposome vesicles. Lanthanide ions (Eu(III) and Tb(III)) are incorporated into polymerized liposome with the expectation to "report" quantitative and qualitative information on the interacting protein. Our proposition is to extract quantitative and qualitative information from the luminescence intensity and the luminescence lifetime of the lanthanide ion, respectively. A thorough investigation is presented regarding the analytical potential of these two parameters for protein sensing. Two chemometic approaches - namely partial least squares (PLS-1) and artificial neural networks (ANN) - are compared towards quantitative and qualitative analysis of proteins in binary mixtures.<br>Ph.D.<br>Department of Chemistry<br>Sciences<br>Chemistry: Ph.D.
36
Santos, Marina. "ANALYTICAL POTENTIAL OF POLYMERIZED LIPOSOMES BOUND TO LANTHANIDE IONS FOR QUALITATIVE AND QUANTITATIVE ANALYSIS OF PROTEINS." Doctoral diss., University of Central Florida, 2007. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2588.
Full textAbstract:
One of the intriguing features of biological systems is the prevalence of highly selective and often very strong interactions among different cellular components. Such interactions play a variety of organizational, mechanical, and physiological roles at the cellular and organism levels. Antigen-antibody complexes are representative examples of highly selective and potent interactions involving proteins. The marked specificity of protein-antibody complexes have led to a wide range of applications in cellular and molecular biology related research. They have become an integral research tool in the present genomic and proteomic era. Unfortunately, the production of selective tools based on antigen-antibody interactions requires cumbersome protocols. The long term goal of this project explores the possibility of manipulating liposomes to serve as the chemical receptors ("artificial antibodies") against selected proteins. Cellular lipids (e.g., lipid rafts) are known to facilitate highly selective binding of proteins on cell membranes. The binding of proteins to cell membranes can be envisaged to be modulated via interactions between polar (charged) and non-polar head groups of lipids and the complementary amino acid residues of proteins. Their interaction is facilitated by a combination of van der Waals, electrostatic, hydrogen bonding and hydrophobic forces. A further interesting aspect of the above interaction is the "fluidity" of the membrane resident lipids, which can migrate from other regions to further enhance the complementary interactions of proteins on the initially "docked" membrane surface. With these features in mind, the end goal of this project is expected to deliver lipid-based chemical receptors "synthetically" designed against proteins to function as "artificial antibodies". Protein sensing will be accomplished with lipid receptors assembled in templated polymerized liposomes. The research presented here specifically focus on the analytical aspects of protein sensing via polymerized liposome vesicles. Lanthanide ions (Eu3+ and Tb3+) are incorporated into polymerized liposome with the expectation to "report" quantitative and qualitative information on the interacting protein. Our proposition is to extract quantitative and qualitative information from the luminescence intensity and the luminescence lifetime of the lanthanide ion, respectively. A thorough investigation is presented regarding the analytical potential of these two parameters for protein sensing. Two chemometic approaches - namely partial least squares (PLS-1) and artificial neural networks (ANN) - are compared towards quantitative and qualitative analysis of proteins in binary mixtures.<br>Ph.D.<br>Department of Chemistry<br>Sciences<br>Chemistry: Ph.D.
37
Couchman, Samantha M. "Syntheses and structural studies of complexes of mixed donor pyridine/phenol and pyridine/pyrazole ligands." Thesis, University of Bristol, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299312.
Full text
38
Lontsi, Fomena Mireille Doumerc Jean-Pierre Villesuzanne Antoine. "Etude théorique de la diffusion de l'oxygène dans des oxydes diélectriques." S. l. : Bordeaux 1, 2008. http://tel.archives-ouvertes.fr/tel-00402631.
Full text
39
Viguier, Romain. "Synthèse de nouveaux ligands polypodes : complexation des ions lanthanide en solution aqueuse." Grenoble 1, 1999. http://www.theses.fr/1999GRE10277.
Full textAbstract:
Dans ce travail les syntheses de ligands tripodes a sous unites methyloxyacetates : hexadentes, nonadentes et dodecadentes, a espaceur tris (oxymethyl) alkyle, ont ete realisees. La synthese de nouveaux ligands hexapodes triaminehexaacetates : nonadentes a espaceur tris (aminomethyl) alkyle est egalement decrite. Les constantes de stabilite ainsi que les constantes de protonation des complexes d'ions lanthanide de ces ligands sont determinees ainsi que celles d'une serie de ligands tripodes a sous unites methyloxypropionates. Les valeurs des constantes de stabilite des complexes d'ions lanthanide en solution aqueuse sont de l'ordre de 10 4 pour les tripodes tripropionates, 10 8 pour les triacetates hexadentes, 10 5 pour des triacetates nonadentes, 10 4 pour les triacetates dodecadentes et 10 1 4 pour les hexaacetates nonadentes. Une approche par rmn de l'oxygene-17, denombre les molecules d'eau presentes dans la sphere interne de coordination du cation dysprosium complexe et permet de suivre la complexation en fonction du ph. Nous n'avons observe aucune participation particuliere des oxygenes donneurs neutres des fonctions ethers. Que ce soit dans les systemes a chaines courtes (tota et totp) ou les systemes a chaines plus longues (to(eo)ta et to(eo) 2ta), l'augmentation du nombre d'oxygenes donneurs neutres dans la structure des ligands a ete sans effet sur la stabilite. Par contre nous avons remarque que l'augmentation de la taille des branches du tripode etait un facteur destabilisant. Le taha forme des complexes sur toute la gamme de ph etudie (1 a 9,5), le nombre des molecules d'eau liees au centre metallique (entre un et deux) en milieu physiologique pourrait permettre l'utilisation de ce complexe comme agent de contraste. De plus sa charge globale negative lui permettrait une elimination rapide par voie urinaire et pourrait autoriser des tests de biodistribution en vue de son utilisation comme agent chelatant pour la radiotherapie.
40
Huber, Anne-Katrin, Sven Ole Steinmüller, Eva Mutoro, Bjoern Luerßen, and Jürgen Janek. "In situ examination of Lanthanum Strontium Manganate (LSM) with Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS)." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-186860.
Full text
41
Huber, Anne-Katrin, Sven Ole Steinmüller, Eva Mutoro, Bjoern Luerßen, and Jürgen Janek. "In situ examination of Lanthanum Strontium Manganate (LSM) with Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS)." Diffusion fundamentals 12 (2010) 52, 2010. https://ul.qucosa.de/id/qucosa%3A13889.
Full text
42
BOREL, CORINNE. "Cristallogenese et caracterisation d'hexaaluminates de lanthane dopes aux ions chrome et titane pour la realisation de nouveaux lasers accordables." Paris 6, 1990. http://www.theses.fr/1990PA066732.
Full textAbstract:
L'etude des monocristaux d'hexaaluminates mixtes de lanthane et magnesium, de formule lamgal11019 (lma), dopes aux ions cr3+ et ti3+, pour la realisation de nouveaux materiaux laser accordables dans le visible et proche infra-rouge (600-1200 nm), s'est deroulees en trois etapes: cristallogenese et amelioration de la qualite cristalline, etude des proprietes spectroscopiques d'absorption et d'emission et essais laser en cavite. Aucun des deux materiaux n'a donne lieu a une emission laser: le lma:cr de bonne qualite cristalline possede des proprietes d'emission mediocres, principalement dues a l'existence de plusieurs sites emetteurs de sections efficaces d'emission stimulee faible et de transferts d'energie entre ces sites. Le lma:ti presente de nombreux defauts cristallins, lies a une forte segregation du titane. De plus il presente des bandes d'absorption parasites dans la zone d'absorption et d'emission de l'ion ti#3#+, liees sans doute a la presence d'ions ti#4#+, ti#2#+ et/ou de lacunes cationiques. Des recherches pour diminuer ces bandes parasites ont ete entreprises (codopages, recuits. . . )
43
Bortolus, Sophie. "Etude comportementale des acides humiques en solution et de leur interaction avec les ions cuivre (II) et lanthane (III)." Paris 6, 2004. http://www.theses.fr/2004PA066516.
Full text
44
Henneberg, Eva. "Thermodynamische und kinetische Untersuchungen im System La-Si-H-(Cl)." Doctoral thesis, [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=969828241.
Full text
45
Zheng, Zhangfeng. "Sol-Gel Processed Amorphous LiLaTiO3 as Solid Electrolyte for Lithium Ion Batteries." Digital WPI, 2015. https://digitalcommons.wpi.edu/etd-dissertations/547.
Full textAbstract:
Rechargeable lithium ion batteries have been widely used in portable consumer electronic devices, hybrid and full electric vehicles, and emergency power supply systems, because of their high energy density and long lifespan. The lithium ion battery market was approximately $11.8 billion in 2010 and is expected to grow to $53.7 billion in 2020. However, there is an intrinsic safety issue in these batteries because electrolyte contains a flammable organic solvent which may cause fire and/or even explosion. All solid-state lithium ion battery is recognized as next-generation technology for rechargeable power sources due to improved safety, high energy density, and long cycle life. Inorganic solid electrolyte replace liquid one to eliminate flammable components. The major challenge for all solid-state lithium ion batteries is to develop solid electrolytes with high ionic conductivity and good stability against both electrodes. Amorphous lithium lanthanum titanium oxide (LLTO) is very promising as solid electrolyte owing to its high ionic conductivity, good stability, and wide electrochemical stability window. In this work, amorphous LLTO thin films (or powders) were successfully prepared by sol-gel process. The thin films are smooth and crack-free. The microstructure evolution from dried gel film to fired film to annealed film was examined. The microstructure of the annealed film, either amorphous or crystalline, depends on the annealing temperature and time. Theoretical analysis was conducted to understand the microstructure evolution. Induction time determines the longest annealing time without transformation from amorphous to crystalline state. The induction time decreases with annealing temperature until the time approaches a minimum, and after that, the time increases with the temperature. Ion transport properties were investigated by Electrochemical Impedance Spectroscopy (EIS). The plateau at low frequencies results from lithium ion long-range diffusion which contributes to dc conductivity, while the observed frequency dispersion at high frequencies is attributed to short-range forward¨Cbackward hopping motion of lithium ions. The relaxation processes are non-Debye in nature. Amorphous LLTO is compatible with Li metal due to its disordered atomic configuration. Finally, a 3D structure of electrode with amorphous LLTO was successfully prepared. This electrode displays promising electrochemical performance.
46
DIAS, CRISTIANE. "O Estudo do comportamento eletroquimico do ion La sup(3+) em meio a cloretos fundidos. A formacao de LaNi sub(5)." reponame:Repositório Institucional do IPEN, 2002. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11062.
Full textAbstract:
Made available in DSpace on 2014-10-09T12:47:41Z (GMT). No. of bitstreams: 0<br>Made available in DSpace on 2014-10-09T14:08:15Z (GMT). No. of bitstreams: 1
08318.pdf: 5216839 bytes, checksum: a5aa91f30daca6826d66086676357dd7 (MD5)<br>Dissertacao (Mestrado)<br>IPEN/D<br>Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
47
Gömann, Anissa. "Das Verhalten von donatordotierten SrTiO3-Oberflächen unter Hochtemperaturbehandlung." Clausthal-Zellerfeld : Papierflieger, 2005. http://deposit.d-nb.de/cgi-bin/dokserv?idn=974496510.
Full text
48
Hatscher, Stephan Tobias. "Thiosilicate der Lanthanide Synthesen, Kristallstrukturen und magnetische Eigenschaften /." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=968692176.
Full text
49
Waiter, Gordon David. "The NMR proton relaxation effectiveness of paramagnetic metal ions and their potential as MRI contrast agents." Thesis, University of Aberdeen, 1995. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU077829.
Full textAbstract:
Paramagnetic lanthanide ions have been investigated as possible MIR phantom materials and contrast agents. The aim of this study is to determine if it is possible to apply the well known Solomon-Bloembergen equations to solutions of paramagnetic lanthanide ions that have fast electron spin relaxation times, compared to Gadolinium, the most widely used ion for NMR. Studies of the relaxivity, frequency and temperature dependence, show that there is a considerable difference in those properties over the series. Chelation of the ions to EDTA and DTPA resulted in a decrease in the relaxivity which was directly proportional to the decrease in the number of water molecules in the inner co-ordination sphere. The fit of the Solomon-Bloembergen equations to the variable frequency and temperature relaxation times showed that theory is valid for the fast electron spin ions and allowed the calculation of the electron spin relaxation times. This showed that there is a difference of 5 orders of magnitude between Gadolinium, the ion demonstrated to have a slow electron spin relaxation time, and the remaining ions. The addition of EDTA chelated forms of these ions to agarose gels produced NMR phantom materials with relaxation time characteristics that could be chosen to fulfil a desired application. The biodistribution of Gd-DTPA was investigated using ESR and NMR. The concentration of Gd-DTPA in excised rat tissue, 20 minutes after intraperitoneal injection, was determined, by the change in NMR water proton relaxation time from that of a control tissue, and by ESR from direct measurement of the microwave power absorbed by the sample, which is directly proportional to the number of unpaired electron spins in the sample. The results from these two methods of determining contrast agent concentration agree well with each other both in the order of biodistribution and on the absolute concentrations.
50
Bentz, Dirk. "Komplexe von Zink, Cadmium, Lanthan, Cer und Samarium mit sperrigen Alkylcyclopentadienyl-Liganden." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=977288579.
Full text