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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.
1

Étude du mécanisme de la dissolution par oxydoréduction chimique et électrochimique des bioxydes d'actinides (UO, NpO, PuO, AmO) en milieu aqueux acide /

Berger, Pascal, January 1990 (has links)
Th. Univ.--Chimie analytique--Paris 6, 1988. / Résumé en anglais. Bibliogr. p. 208-223.
2

Estudo sobre a instabilidade dimensional do uranio metalico sujeito a alternancia termica

GENTILE, ERBERTO F. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:25:04Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:02:27Z (GMT). No. of bitstreams: 1 00013.pdf: 754062 bytes, checksum: 174c004fbaaabe5d0ec7236dfb024d78 (MD5) / Dissertacao (Mestrado) / IEA/D / Escola Politecnica, Universidade de Sao Paulo - POLI/USP
3

Estudo experimental da obtencao de torio metalico por reducao direta de oxido de torio por metais liquidos

CAPOCCHI, JOSE D.T. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:25:06Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:02:29Z (GMT). No. of bitstreams: 1 00921.pdf: 1219080 bytes, checksum: 2b2bfe4d60fb1d34626cd2f4bf24a4f1 (MD5) / Dissertacao (Mestrado) / IEA/D / Escola Politecnica, Universidade de Sao Paulo - POLI/USP
4

Estudo sobre a instabilidade dimensional do uranio metalico sujeito a alternancia termica

GENTILE, ERBERTO F. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:25:04Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:02:27Z (GMT). No. of bitstreams: 1 00013.pdf: 754062 bytes, checksum: 174c004fbaaabe5d0ec7236dfb024d78 (MD5) / Dissertacao (Mestrado) / IEA/D / Escola Politecnica, Universidade de Sao Paulo - POLI/USP
5

Estudo experimental da obtencao de torio metalico por reducao direta de oxido de torio por metais liquidos

CAPOCCHI, JOSE D.T. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:25:06Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:02:29Z (GMT). No. of bitstreams: 1 00921.pdf: 1219080 bytes, checksum: 2b2bfe4d60fb1d34626cd2f4bf24a4f1 (MD5) / Dissertacao (Mestrado) / IEA/D / Escola Politecnica, Universidade de Sao Paulo - POLI/USP
6

Etude du paramagnétisme des actinides en solution par RMN / Study of paramagnetism of actinides in solution by NMR

Jan, Steve 11 December 2012 (has links)
Le paramagnétisme des actinides en solution a été caractérisé par RMN selon deux approches, l'une macroscopique et l'autre moléculaire. Dans la première approche, les susceptibilités magnétiques des ions les plus stables en solution de l'uranium au californium, et ce pour différents degrés d'oxydation (U(IV)-U(VI), Np(IV)-Np(V)-Np(VI), Pu(III)-Pu(IV)-Pu(VI), Am(III), Cm(III) et Cf(III)), ont été mesurées par RMN à l'aide de la méthode d'Evans. En milieu perchlorique, l'étude ducomportement paramagnétique des cations actinide a montré des déviations significatives par rapport à celui des lanthanides, particulièrement pour les ions actinide aux degré d'oxydation +III et +IV. En milieux chlorhydrique et nitrique, il a été observé que les comportements magnétiques des actinides suivaient l'ordre M(IV) > M(VI) > M(III) > M(V), correspondant à l'ordre généralement admis concernant le pouvoir complexant des ions actinide en solution aqueuse. Il a été démontré que la présence d'ions chlorure et nitrate en solution pouvait avoir un impact important sur le comportement magnétique de ces cations. Dans la deuxième approche, les déplacements chimiques des complexes paramagnétiques actinide(IV)-dipicolinate ont été étudiés et analysés en milieu diméthylformamide. Dans ces conditions expérimentales, il a été vérifié que le degré d'oxydation +IV des actinides en solution était stable en présence ou non de ligand ainsi que sur l'échelle de temps des analyses RMN. Les déplacements chimiques paramagnétiques des complexes limites 1 : 3 ont été étudiés à différentes températures. Les méthodes de séparation des contributions de contact et dipolaire habituellement utilisées pour les complexes de lanthanide(III) se sont avérées inapplicables dans le cas des complexes d'actinide(IV). / Paramagnetism of actinides in solution was characterized by NMR according to two approaches, a macroscopic one and a molecular one. In the first approach, magnetic susceptibilities of the most stable ions in solution from uranium to californium, for various oxidation states (U(IV)-U(VI), Np(IV)-Np(V)-Np(VI), Pu(III)-Pu(IV)-Pu(VI), Am(III), Cm(III) et Cf(III)), were measured by NMR by using the Evans' method. In perchloric medium, the paramagnetic behavior of actinide cations showed significant deviations compared with lanthanides, particularly for cations at oxidation state +III and +IV. In hydrochloric and nitric media, it was observed that actinide magnetic behaviors followed the order M(IV) > M(VI) > M(III) > M(V), corresponding to the generally admitted order concerning the complexing power of actinide cations. It was demonstrated that the presence of chloride and nitrate in solution could have an large impact on the magnetic behavior of these cations. In the second approach, chemical shifts of actinide(IV)-dipicolinate paramagnetic complexes were studied and analyzed in dimethylformamide. In these experimental conditions, the only presence of the oxidation state +IV in solution as well as the stability of the latter on the NMR analysis timescale were verified, in presence or not of the ligand. Paramagneticchemical shifts of the 1 : 3 limit complex were studied at various temperatures. Themethod of separation of the contact and dipolar contributions usually used for lanthanide(III) complexes have proved not applicable in the case of actinide(IV) complexes.
7

Reduction and desymmetrisation of the uranyl dication in a macrocyclic framework

Patel, Dipti January 2009 (has links)
The transamination reaction between a Schiff base polypyrrolic macrocycle, H4Ltet/oct, where tet = tetramethyl (C38H36N8), oct = octamethyl (C42H44N8), and [UO2(THF)2{N(SiMe3)2}] results in the sole formation of mono uranyl complexes [UO2(THF)(H2Ltet)], 7, and [UO2(THF)(H2Loct)], 8. The molecular structure of 8 was confirmed by an X-ray diffraction study which shows that the macrocycle folds to form a Pac-man shape. The reaction between 7 and [M{N(SiMe3)2}2], where M = Mn, Fe, Co or Zn, results in the formation heterobimetallic complexes, [UO2(THF)M(THF)(Ltet)], 9, 10, 11, and 13, respectively. The structures of 9 and 11 have been confirmed by X-ray crystallography and show that there is a direct donor bond from one oxo ligand of the uranyl dication to the transition metal, and characterisation by vibrational spectroscopy suggests that the bonding of the uranyl dication has weakened. The double deprotonation of 8 with KN(SiMe2R)2, where R = Me, Ph, and subsequent salt elimination reaction with MX2, where M = Fe, X = I and M = Zn, X = I, Cl, results in the formation of the first discrete reductively functionalised pentavalent uranyl complexes [UO(OSiMe3)(THF)(FeI)2(Loct)], 17, [UO(OSiMe2Ph)(THF)(FeI)2(Loct)], 18, [UO(OSiMe3)(THF)(ZnI)2(Loct)], 19, and [UO(OSiMe3)(THF)(ZnCl)2(Loct)], 20, which contain a covalent Si–O bond to one oxo-group. Complexes 17 to 20 have been fully characterised and the solid state molecular structures of 17 and 19 were determined. Investigation into the mechanism of the functionalisation suggests that the intermediate complex [UO2(THF)(K2L)] is highly oxidising and reactive and promotes the single electron transfer reaction with trimethylsilyl reagents and results in the homolytic cleavage of bonds and concurrent reduction of the uranyl ion. The solution redox properties of 8 have been measured by cyclic voltammetry, and exhibits a single electron reduction at -1.17 V (vs. Fc/Fc+). The reaction of 8 with one equivalent of cobaltocene results in the formation of the pentavalent uranyl complex [CoCp2][UO2(THF)(H2Loct)], 26. The reaction of 8 with two or three equivalents of B(C6F5)3 results in the formation of [UO2(H2Loct)B(C6F5)3], 31, and [UO2(H2Loct)(B{C6F5}3)2], 34, respectively, which are examples of uranyl macrocyclic borane adducts. Reaction of complex 31 with an excess of PMe3 results in the formation of the THF-free uranyl macrocyclic complex [UO2(H2Loct)], 35.
8

Synthesis of f-block complexes in a polypyrrolic macrocyclic environment

Potter, Natalie Alison January 2011 (has links)
In this thesis, the chemistry of lanthanide and actinide complexes of Schiff-base, polypyrrolic macrocyclic ligands has been evaluated. Chapter one introduces some general chemistry of uranium before focussing on uranium(III) and (IV) coordination complexes of nitrogen donor ligands. The surface chemistry of uranium metal is also briefly discussed along with the synthesis of uranium borohydride, hydride and alkyl complexes. Chapter two describes the synthesis and characterisation of the monometallic complexes [M(L)] or [M(HL)], where M = Y, Ce, and U, of the octadentate Schiffbase pyrrole macrocycle H4L. In particular, these complexes display a new binding mode of the macrocycle which leads to the formation of the unique trinuclear supramolecular complexes [M(HL)]3, (M = Ce, Y). Reactions of these materials towards hydrolysis, oxygen sources and other metal reagents are also exemplified. Chapter three details the synthesis and characterisation of the bimetallic complexes, [(MX)2(L)], where M = Ce, U, and Np and X = I or Cl, and [(MX2)2(L)], where M = U, and the attempts to transform these complexes into metal hydrides via their borohydrides. The solid state variable temperature magnetism of the binuclear U(III) and Np(III) complexes was recorded and was found to be consistent with the formation of iodide-bridged, polymeric structures. Chapter four explores the synthesis and reactions of adducts between UI3 and neutral macrocyclic ligands that incorporate either oxygen or nitrogen donors such as crown ethers and cyclam, respectively. The new synthesis of the key starting material, unsolvated UI3 is also outlined, along with the full characterisation of UI4(OEt)2.
9

Metal complexes of trimethylsilyl substituted cyclooctatetraenes

O'Sullivan, Julie Ann January 1997 (has links)
No description available.
10

Contribution à l'étude de l'extraction d'acides minéraux et de cations actinides aux degrés d'oxydation (IV) et (VI) par des N,N-dialkylamides /

Condamines, Nicole. January 1990 (has links)
Th. Univ.--Chimie analytique--Paris 6, 1989. / Résumé en anglais. Bibliogr. p. 267-288.

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