Neste trabalho, realizou-se o estudo que permitiu a otimização termodinâmica das seções binárias pertencentes ao diagrama de fase ternário do sistema LiF-GdF3-LuF3, para tanto o programa FactSage foi empregado na simulação computacional. Assim, o comportamento de fusão das misturas destes compostos foi elucidado, o que representa uma contribuição inovadora para o conhecimento das propriedades físicas e químicas destes materiais. Em particular, determinou-se a faixa de composições nas quais as soluções sólidas de LiGdxLu1-xF4 e GdxLu1-xF3 podem ser obtidas diretamente da fase líquida. Neste trabalho as três secções binárias, LiF-GdF3, LiF-LuF3 e GdF3-LuF3 foram reavaliadas experimentalmente utilizando a calorimetria exploratória diferencial para a obtenção de dados mais precisos de temperatura versus composição, uma vez que foi possível minimizar a contaminação das amostras com compostos de oxigênio. A capacidade calorífica e outros dados calorimétricos foram também determinados experimentalmente e comparados com os existentes na literatura. Os termos da energia livre de Gibbs de excesso para as fases representadas como soluções, os quais descrevem os efeitos de interação não ideal entre os dois fluoretos nestas fases, foram expressos com sucesso pela modelo polinomial Redlich-Kister. Finalmente, o caminho de solidificação no diagrama de fase ternário LiF-GdF3-LuF3 pôde ser extrapolado de acordo com o formalismo de Kohler-Toop. Assim, pela primeira vez, a interação ternária entre os compostos LiF, GdF3 e LuF3 foi determinada. / In this work, it was carried out the study that allowed the thermodynamic optimization of the binary sections belonging to the ternary phase diagram of the LiF-GdF3-LuF3 system, for this purpose the FactSage software was used in the computational simulation. Thus, the melting behavior of the mixture of these compounds has been elucidated, which represents an innovative contribution to the knowledge of the physical and chemical properties of these materials. In particular, it was determined the composition ranges in which the solid solutions of LiGdxLu1-xF4 and GdxLu1-xF3 can be obtained directly from the liquid phase. In this work the three binary sections, LiF-GdF3, LiF-LuF3 and GdF3-LuF3, were evaluated using differential scanning calorimetry to obtain more accurate data of temperature versus composition, since it was possible to minimize the contamination of the samples due to oxygen compounds. The heat capacity and other calorimetric data were experimentally determined and compared with those cited in the literature. The terms of the Gibbs free excess energy for the solution phases, which describe the non ideal interaction effects between the two fluorides at these phases, were expressed by the Redlich-Kister polynomial model. Finally, the solidification path in the ternary phase diagram LiF-GdF3-LuF3 could be extrapolated according to the Kohler-Toop formalism. Thus, for the first time, the interaction between the ternary compounds LiF, GdF3 and LuF3 was determined.

A crescente escassez de recursos energéticos renováveis bem como o aumento contínuo dos seus custos, tem requerido uma redução drástica no consumo de energia utilizada para o transporte de cargas e passageiros nas últimas décadas. Uma alternativa é a redução de peso com a utilização de ligas leves em substituição às ligas convencionais utilizadas no setor de transporte. Nesse conceito o uso de ligas de magnésio é justificado pela sua baixa densidade. Dentre as ligas de magnésio, a matriz ASTM série ZK é a que apresenta maior resistência mecânica e a adição de elementos de terras raras (RE) elevam a resistência à corrosão, a temperatura de trabalho e o limite de escoamento, devido à formação de filmes de óxidos finos e densos, além de intermetálicos de alto ponto de fusão e de maior dureza. A formação de intermetálicos do tipo MgZn de baixo ponto de fusão, torna as ligas de matriz do tipo ZK susceptíveis à formação de trinca à quente durante a soldagem, inviabilizando o uso de processos de soldagem convencionais. Uma alternativa é a solda por fricção e mistura mecânica (SFMM) realizada abaixo da temperatura de fusão. Neste trabalho, foram produzidas ligas ZK60, ZK60-1,5RE (liga ZK60 com adição de 1,5% em peso de mischmetal) por fundição convencional e ZK60-1,5RE tixofundidas com batimento mecânico no estado semissólido. Todas foram laminadas a quente em um laminador simétrico e soldadas por fricção e mistura mecânica. Os métodos de fundição e resfriamento apresentaram materiais isentos de defeitos e com homogeneidade química, além do batimento mecânico proporcionar uma microestrutura com grãos globulares homogêneos. A adição de Mischmetal deu origem a uma microestrutura com granulometria aproximadamente 22% menor. Quando comparado com o método de fundição, a liga fundida com batimento no estado semissólido apresentou uma diminuição no tamanho médio de grão de aproximadamente 26%. A laminação deu origem a uma microestrutura parcialmente recristalizada, com tamanho médio de grãos entre 3 e 4 μm. A rede de intermetálicos foi quebrada, porém, manteve-se contínua para as ligas com adição de Mm. Quanto à resistência mecânica, a liga ZK60 foi superior, devido à menor quantidade e redes intermitentes de intermetálicos, uma vez que tanto para as ligas fundidas quanto para as laminadas, as trincas foram originadas nas regiões de aglomeração de intermetálicos. As ligas com adição de Mm apresentaram melhor estabilidade térmica durante a soldagem e melhor acabamento superficial, sendo possível a soldagem com rotação de 1200 rpm e velocidade de avanço de 400 mm/min enquanto a liga ZK60 só foi possível a soldagem com 200 mm/min. As análises das tensões residuais apresentaram valores e perfis semelhantes e seguem o fluxo de material, bem como a textura dos cordões de solda. Os mapas de microdureza na secção transversal do cordão de solda revelaram maior dureza nas zonas de mistura, e valores ainda maiores e mais homogêneos para liga ZK60, pode-se afirmar que os intermetálicos do tipo MgZn tem maior dureza que os do tipo MgZnRE. / The growing scarcity of renewable energy resources, as well as the continued rise in costs has required in recent decades a dramatic reduction in energy used for transportation freight and passenger, which is increasing daily all over the world. An alternative is to weight reduction with the use of light alloys, this concept the use of magnesium alloys is justified by their low density, about 1/3 lower than that of aluminum. Among the magnesium alloy, the matrix is ZK type that has greater mechanical strength and the addition of rare earth elements (RE) to increase corrosion resistance, working temperature and yield strength due to the formation of thin films and density oxides, and intermetallic of the high melting point and higher hardness. The formation of intermetallic of the MgZn type, which has a low melting point, makes alloys with matrix of the ZK type susceptible to formation of hot crack during the welding, making impossible the use of conventional welding processes, an alternative is the friction stir welding (FSW) that the union is made below the melting point. This work shows the studies the addition of 1.5% wt. of mischmetal (Mm) in the ZK60 alloy and effects of the casting process with mechanical mixing in the semi-solid state. Were produced the alloys: ZK60, ZK60-1.5RE with conventional casting and ZK60-1.5RE Tixo with mechanical mixing in the semi-solid state, all were hot-rolled in a symmetrical laminator and welded with friction stir welding (FSW) process. The methods of casting and cooling gave resulted in materials free of defects and chemical homogeneity, and the mechanical mixing provides homogeneous microstructure with globular grains. The alloy with mischmetal addition had an average grain size of about 22% lower than ZK60 alloy, when compared to the casting method the ZK60- 1.5RE Tixo alloy had an average grain size of about 26% lower than ZK60-1.5RE alloy. The rolling process gave rise to a partially recrystallized microstructure with average grain size of between 3.3 and 4.23 μm, the intermetallic network were broken, however, kept continuous for alloys with Mm addition. As for mechanical strength was higher for ZK60 alloy, due smaller amount and intermittent network of the intermetallic. The alloys with Mm addition had better thermal stability during welding and showed better surface quality, being possible to do a welding with rotation of 1200 rpm and advancing speed of 400 mm/min while the ZK60 alloy only was possible the welding with advancing speed of 200 mm/min. The analyzes of residual stresses had similar values and profiles and follow the flow of material as well as the texture of the weld beads. The micro hardness maps in the cross section of the weld bead showed a higher hardness in the mixing zones, and higher and more homogeneous values for ZK60 alloy, and can thus affirm that the intermetallic MgZn type has higher hardness than the MgZnRE type.

The present research work focuses on the coordination chemistry of two different types of monoanionic nitrogen-coordinating ligands, namely the bidentate triazenide ligand [(DippN)N(NDipp)]⁻ (Dipp = Prⁱ₂C₆H₃−2,6) (L¹) and monodentate arylamido ligands [N(R)(Ar)]⁻ (R = SiMe₃., Ar = C₆H₃Me₂-2,6 (L²), C₆H₂Me₃-2,4,6 (L³) or C₆H₃Prⁱ₂-2,6 (L⁴); R = SiBuᵗMe₂, Ar = C₆H₃Prⁱ₂-2,6 (L⁵)). The first part of this work was centred on the synthesis, structural characterization and reactivity of divalent lanthanide metal complexes derived from the triazenide ligand L¹. The second part of this work dealt with the chemistry of low valent and low-coordinate first row transition metal complexes supported by arylamido ligands Lⁿ (n = 2-5). The last part of this work focused on the synthesis and structures of divalent chromium complexes derived from the L¹, L⁴ and L⁵ ligands. / Chapter 1 presents an overview on divalent lanthanide complexes derived from nitrogen-coordinating ligands. The coordination chemistry of low valent and low-coordinate first-row transition metal complexes was also reviewed. / Chapter 2 describes the preparation and characterization of samarium(II) triazenide complex [Sm(L¹)₂(THF)₂] (2). Complex 2 was prepared by the reaction of SmI₂(THF)₂ with 2 equivalents of potassium triazenide [KL¹(THF)₀.₅] (1). The electrochemistry of 2 in THF was studied with cyclic voltammetry. Complex 2 is a strong reducing reagent. Its reactions with various inorganic/organic substrates have been examined. Treatment of 2 with AgCl or PhCH₂Cl gave Sm(III) bis(triazenide) chloride complex [Sm(L¹)₂Cl(THF)₂] (3), whilst reaction of 2 with I₂ led to the isolation of the iodide complex [Sm(L¹)I₂(THF)₃] (4). Reactions of 2 with PhEEPh (E = S, Se) afforded the corresponding Sm(III) chalcogenolate complexes [Sm(L¹)₂(EPh)(THF)] (E = S (5), Se (6)). On the other hands, addition of 2 to ArEEAr (Ar = Buᵗ₂C₆H₃−2,6, E = S, Se and Te) yielded the homoleptic Sm(III) tris(triazenide) complex [Sm(L¹)₃] (7) as the only isolable product. Besides, reactions of 2 with O₂, S₈, Se, Ph₃P=Se and BuᵗOOBuᵗ also yielded complex 7. Complex 2 reacted with PhNHNH₂ and PhNHNHPh, leading to the isolation of the corresponding Sm(III) phenylhydrazido complexes [Sm(L¹)₂(DMAP)₂(NH₂NPh)] (8) and [Sm(L¹)(THF)(μ-η²:η²-PhNNPh)]₂ (9). Reactions of 2 with azobenzene, benzophenone, 9-fluorenone, adamantyl azide, N, N’-dicyclohexylcarbodiimide, N, N’-diisopropylcarbodiimide, and CS₂ were examined as well. / Chapter 3 reports on the coordination chemistry of the triazenide ligand L¹ with divalent ytterbium and europium ions. Metathetical reaction of LnI₂(THF)₂ (Ln = Yb, Eu) with two molar equivalents of [Na(L¹)(THF)₃] (10) led to the corresponding divalent lanthanide(II) bis(triazenide) complexes [Eu(L¹)₂(THF)₂] (11) and [Yb(L¹)₂(THF)₂] (12). The heteroleptic ytterbium(II) complex [Yb(L¹)(μ-I)(THF)₂]₂.(C₆H₁₄) (13.C₆H₁₄) was also isolated along with 12. Oxidation of 12 with CuCl afforded Yb(III) triazenide−chloride complex [Yb(L¹)₂Cl(THF)₂] (14). Treatment of 12 with PhEEPh (E = S, Se) afforded the corresponding Yb(III) chalcogenolate complexes [Yb(L¹)₂(EPh)(THF)] (E = S (15), Se (16)). Nevertheless, reactions of 12 with elemental sulfur and selenium yielded the homoleptic Yb(III) complex [Yb(L¹)₃] (17) as the only isolable product. / Chapter 4 deals with the synthesis and characterization of low valent and low-coordinate first row transition metal complexes derived from arylamido ligands L²-L⁵. Reaction of MCl₂ (M = Fe, Co) with one molar equivalent of lithium amide [Li(L³)(TMEDA)] (TMEDA = Me₂NCH₂CH₂NMe₂) yielded the corresponding monoamido complexes [M(L³)Cl(TMEDA)] (M = Fe (20) and Co (22)). Reduction of [Co(L²)Cl(TMEDA)] (21), 22 and [Co(L³)Cl(TMEDA)] (23) with potassium metal gave the corresponding cobalt(I) amido complexes [CoL²]₂ (24), [CoL₃]₂ (25) and [CoL⁴]₂ (26), respectively. Meanwhile, treatment of [Fe(L⁴)Cl(TMEDA)] (23) with potassium metal yielded iron(I)-dinitrogen complex [{FeL⁴(TMEDA)}₂(μ-η¹:η¹-N₂)] (27). Complexes 24-27 were fully characterized by X-ray crystallography, various spectroscopic techniques and cyclic voltammetry. DFT calculations were carried out in order to understand the electronic structures of these complexes. / Chapter 5 describes the preparation and characterization of three neutral two-coordinate first row transition metal complexes of the general formula [M(L⁵)₂] (M = Fe (29), Co (30), Ni (31)). They were prepared by the reactions of anhydrous MCl₂ (M = Fe, Co) or NiBr₂(DME) with [LiL⁵(Et₂O)₂] (28). The solid-state structures of complexes 29-31 were determined by X-ray diffraction analysis. They were also characterized by spectroscopic methods (UV/Vis, I.R.) and electrochemistry. TD-DFT computational analysis was carried out in order to assign UV/Vis spectra features of these two-coordinate late transition metal (Fe->Ni) complexes. / Chapter 6 reports on the coordination chemistry of L¹, L⁴ and L⁵ with chromium ions. Treatment of CrCl₂ or CrCl₃ with one molar equivalent of [Li(L¹)(Et₂O)₂] (32) yielded heteroleptic Cr(II) complex [Cr(L¹)(μ-Cl)(THF)]₂ (33) and Cr(III) complex [Cr(L¹)Cl₂(THF)₂] (34), respectively. Attempts to reduce 33 and 34 with potassium metal, potassium graphite or magnesium were unsuccessful, yielding [Cr(L¹)₂] (35). Reaction chemistry of 35 was also studied in our research work. No reaction was observed in the reaction of 35 with PhEEPh (E = S, Se). Treatment of 35 with iodine led to the isolation of iodide bridged heteroleptic Cr(II) complex [Cr(L¹)(μ-I)(THF)]₂ (36). Simple monodentate amido ligands L⁴ and L⁵ were also used to prepare Cr(I) complexes. Treatment of anhydrous CrCl₂ with [LiL⁴(Et₂O)₀.₅] and [LiL⁵(Et₂O)₂] (28) afforded oxidative deprotonation products [Cr{N(C₆H₃Prⁱ₂-2,6)(SiMe₂CH₂)}₂Cr(L⁴)] (37) and [Cr(L⁵){N(C₆H₃Prⁱ₂-2,6)(SiBuᵗMeCH₂)}] (38). Attempts to synthesize monovalent chromium complexes supported by the L¹, L⁴ and L⁵ ligands were still in progress during the submission of this thesis. / Chapter 7 summarizes the results of the present studies. A brief description on the future direction of this research work is also presented. / 本項研究工作主要針對兩類負一价含氮配体，即雙齒叠氮基配体[(DippN)N(NDipp)]⁻ (Dipp = Prⁱ₂C₆H₃−2,6) (L¹)和單齒苯胺基配体[N(R)(Ar)]⁻ (R = SiMe₃, Ar = C₆H₃Me₂-2,6 (L²), C₆H₂Me₃-2,4,6 (L³) or C₆H₃Prⁱ₂-2,6 (L⁴); R = SiBuᵗMe₂, Ar = C₆H₃Prⁱ₂-2,6 (L⁵))的配位化學進行研究。本研究工作的第一部分致力於研究二價鑭系叠氮基配合物的合成，結構及其化學反應性。第二部分研究工作主要集中于由苯胺基構築的低價態，低配位數的第一周期后過渡金属的配位化學研究。最後一部分工作闡述了二價鉻叠氮基配合物和苯胺基配合物的合成，結構和表徵。 / 第一章概述了二價鑭系含氮配合物的發展。同時，也簡要闡述低價態，低配位數過鍍金属含氮配合物的研究工作。 / 第二章描述了二價釤叠氮基配合物[Sm(L¹)₂(THF)₂] (2)的製備，結構及其化學反應性。配合物2是由SmI₂(THF)₂與兩當量的鉀叠氮基化合物[KL¹(THF)₀.₅] (1) 反應製得。配合物2的電化學性質採用了循環伏安法進行了研究。介於配合物2為強還原劑，它與一系列無機/有機化合物的反應也予以探索。配合物2與AgCl或PhCH₂Cl反應得到了三價釤雙叠氮基氯化物[Sm(L¹)₂Cl(THF)₂](3)，同時配合物2與單質碘I₂反應得到了碘化物[Sm(L¹)I₂(THF)₃] (4)。配合物2與二苯基硫族化合物PhSSPh及PhSeSePh反應得到了相應的三價釤硫族配合物[Sm(L¹)₂(EPh)(THF)](E = S (5), Se (6))。與之相反，配合物2與位阻較大的二苯基硫族化合物ArEEAr (Ar = Buᵗ₂C₆H₃−2,6, E = S, Se和Te)反應得到了均配的三價釤三叠氮基配合物[Sm(L¹)₃] (7)。此外，配合物2與O₂, S₈, Se, Ph₃P=Se和BuᵗOOBuᵗ反應都生成了配合物7。配合物2與苯肼化合物PhNHNH₂和PhNHNHPh反應得到了相應的三價釤苯肼配合物[Sm(L¹)₂(DMAP)₂(NH₂NPh)] (8) (DMAP = 對二甲基胺吡啶)以及[Sm(L¹)(THF)(μ-η²:η²-PhNNPh)]₂(9)。另外，本章對配合物2與偶氮苯;二苯基酮;9-芴酮;金剛烷叠氮化物;二環已基碳二亞胺;二異丙基碳二亞胺以及二硫化碳的反應性也進行了研究。 / 第三章講述了對該叠氮基配体L¹所衍生出的二價鐿和銪配合物的配位化學研究工作。二價鑭系碘化物LnI₂(THF)₂(Ln = Yb, Eu)與兩當量的鈉叠氮基化合物[Na(L¹)(THF)₃] (10)的複分解反應得到相應的二價鑭系雙叠氮基配合物[Eu(L¹)₂(THF)₂] (11)以及[Yb(L¹)₂(THF)₂] (12)。在製備二價鐿雙叠氮基配合物[Yb(L¹)₂(THF)₂] (12)的過程中同時得到了異配的二價鐿碘橋連單叠氮基配合物[Yb(L¹)(μ-I)(THF)₂]₂.(C₆H₁₄) (13.C₆H₁₄)。配合物12與CuCl的氧化反應得到三價鐿叠氮基氯化物[Yb(L¹)₂Cl(THF)₂] (14)。此外，配合物12與二苯基硫族化合物PhSSPh及PhSeSePh反應得到了相應的三價鐿硫族配合物[Yb(L¹)₂(EPh)(THF)] (E = S (15), Se (16))。然而，配合物12與單質硫和單質硒的反應生成唯一的產物，即均配的三價鐿三叠氮基配合物[Yb(L¹)₃] (17)。 / 第四章闡述了由苯胺基配体L²-L⁵所衍生的低價態，低配位數第一周期后過渡金屬的製備以及結構表徵。通過金屬氯化物MCl₂(M = Fe, Co)和一當量的鋰苯胺基化合物反應得到相應的二價鐡和鈷的單苯胺基配合物[M(L³)Cl(TMEDA)] (M = Fe (20) 和 Co (22))。配合物[Co(L²)Cl(TMEDA)] (21), 22和[Co(L³)Cl(TMEDA)] (23) 與金屬鉀的還原反應分別得到相應的一價鈷苯胺基配合物[CoL²]₂ (24), [CoL³]₂ (25) 和 [CoL⁴]₂ (26)。與此同時，二價鐡單苯胺基配合物[Fe(L⁴)Cl(TMEDA)] (23)與金屬鉀反應得到了一價鐡-偶氮配合物[{FeL⁴(TMEDA)}₂(μ-η¹:η¹-N₂)] (27)。配合物24-27的分子結構及其物理性質分別以X射綫衍射晶体學，波譜學以及循環伏安法表徵。密度泛函(DFT)這一理論計算方法也被用來瞭解這些配合物的電子結構。 / 第五章描述了三個二配位的第一周期后過渡金屬配合物[M(L⁵)₂] (M = Fe (29), Co (30), Ni (31))的製備和表徵。它們由相應的無水金屬鹵化物MCl₂ (M = Fe, Co)或NiBr₂(DME)與[LiL⁵(Et₂O)₂] (28)反應製得。配合物29-31的固體結構由X射綫衍射分析獲得。它們的光學性質和電學性質也分別由波譜方法（紫外可見光光譜，紅外光譜）以及循環伏安法表徵得到。含時密度泛函(TD-DFT)這一計算分析方法也被用來瞭解這些化合物紫外可見光光譜性質。此外，配合物31在有機烯烴與苯硅烷PhSiH3的硅氫化反應中被證實為有效的催化劑。 / 第六章講述了由配体L¹, L⁴與L⁵所構築的二價鉻的配位化學的研究。通過無水二氯化鉻CrCl₂或三氯化鉻CrCl₃與一當量的鋰叠氮基配合物[Li(L¹)(Et₂O)₂] (32)反應分別成功製備了相應的異配的二價鉻配合物[Cr(L¹)(μ-Cl)(THF)]₂ (33) 以及三价鉻配合物[Cr(L¹)Cl₂(THF)₂] (34)。利用金屬鉀，鉀碳以及單質鎂來還原配合物33和34生成了二價鉻雙叠氮基配合物[Cr(L¹)₂] (35)。此外，配合物35的反應性能也在本項工作得以研究。然而，在配合物35與二苯基硫族化合物PhSSPh及PhSeSePh反應中並沒有觀察到明顯的反應變化，依舊得到了原料配合物35。配合物35與單質碘I₂反應得到了異配碘橋連二價鉻配合物[Cr(L¹)(μ-I)(THF)]₂ (36)。單齒苯胺基配体L⁴和L⁵也被嘗試用來合成一價鉻配合物。無水二氯化鉻CrCl2與鋰苯胺基化合物[LiL⁴(Et₂O)₀.₅]和[LiL⁵(Et₂O)₂] (28)反應分別生成了氧化脫質子產物[Cr{N(C₆H₃Prⁱ₂-2,6)(SiMe₂CH₂)}₂Cr(L⁴)] (37) and [Cr(L⁵){N(C₆H₃Prⁱ₂-2,6)(SiBuᵗMeCH₂)}] (38)。關於利用叠氮基配体L¹，以及苯胺基配体L⁴和L⁵來製備一價鉻配合物的相關工作在遞交本論文的過程中还在進行中。 / 第七章總結了本論文的研究成果，並對本項工作未來的發展作出了簡要的描述。 / Yun, Lei. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2015. / Includes bibliographical references. / Abstracts also in Chinese.80-30|aDetailed summary in vernacular field only. / Title from PDF title page (viewed on 21, December, 2016). / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.

by Chan Hoi Shan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references (leaves 111-119). / Abstracts in English and Chinese. / Acknowledgement --- p.iii / Abbreviation --- p.iv / List of Compounds --- p.vi / Abstract --- p.vii / Abstract (Chinese) --- p.ix / Chapter Chapter 1. --- Introduction / Chapter 1.1 --- Lanthanide-Amine Compounds --- p.1 / Chapter 1.2 --- Lanthanide-Amide Compounds --- p.3 / Chapter 1.3 --- Lanthanide-Imide Compounds --- p.11 / Chapter 1.4 --- Some Applications of Lanthanide-Amide Compounds in Organic Synthesis --- p.15 / Chapter 1.5 --- Aims --- p.19 / Chapter Chapter 2. --- Synthesis and Structural Characterization of Anionic and Neutral Dichlorolanthanocene Compounds / Chapter 2.1 --- Synthesis --- p.20 / Chapter 2.2 --- Structural Characterization --- p.22 / Chapter 2.3 --- Conclusion --- p.23 / Chapter Chapter 3. --- Synthesis and Structural Characterization of Amido-Lanthanide Compounds / Chapter 3.1 --- Synthesis and Structural Characterization of Yb(NHAr)3(THF)n --- p.26 / Chapter 3.2 --- "Synthesis and Structural Characterization of Yb(NHC6H3iPr2- 2,6)4Na(THF)" --- p.38 / Chapter 3.3 --- "Synthesis and Structural Characterization of Yb(Cp"")(NHAr)2(L)" --- p.45 / Chapter 3.4 --- "Synthesis and Structural Characterization of Yb(Cp"")(NHC6H3iPr2- 2,6)3M(L)" --- p.54 / Chapter 3.5 --- Synthesis and Structural Characterization of Yb(NHAr)3(NH2Ar)(L) --- p.74 / Chapter 3.6 --- Conclusion --- p.76 / Chapter Chapter 4. --- Synthesis and Structural Characterization of Imido-Lanthanide Compounds / Chapter 4.1 --- Synthesis --- p.81 / Chapter 4.2 --- Structural Characterization --- p.82 / Chapter 4.3 --- Conclusion --- p.85 / Chapter Chapter 5. --- Summary and Remarks / Chapter 5.1 --- Summary --- p.96 / Chapter 5.2 --- Remarks --- p.97 / Chapter Chapter 6. --- Experimental Section --- p.98 / References --- p.111 / Appendix --- p.120

Neste trabalho são investigados o designer e a fabricação nanomateriais magnéticos e luminescentes sofisticados bifuncionais baseados em Fe3O4 e complexos de RE3+. Portanto, novos nanomateriais Fe3O4@calix-Eu(TTA) e Fe3O4@calix-Tb(ACAC) emissores vermelho e verde superparamagnéticos foram preparados pelo método one-pot. Neste caso, o ligante calixareno quimicamente modicado como surfactantes para estabilizar as nanopartículas de Fe3O4. O ligante calixareno proporciona uma superfície quimicamente modificada e estabilidade coloidal das nanopartículas magnetitas. Consequentemente, as nanopartículas funcionalizadas (Fe3O4@calix) foram coordenadas aos íons TR3+ por meio da síntese one-pot, usando ligantes TTA e ACAC como sensibilizadores (efeito antena) para produzir nanofósforos altamente luminescentes. Além do mais, nanocompósitos bifuncionais óptico e magnético Fe3O4@SiO2-TTA-Eu(L), L: TTA, TC, AB e AMB bem como Fe3O4@SiO2-TTA-Tb(AB ou AMB) foram também preparados por meio de um protocolo de múltiplas etapas, utilizando as nanopartículas Fe3O4 como precursoras. Elas foram modificas com camadas de sílica, usando o método Stöber modificado e ligados com complexos de TR3+ para produzir nanocompósitos luminescentes e magnéticos. As técnicas de difração de raios X pelo método do pó (XPD), Espalhamento de Raios-X a baixo ângulo (SAXS), microscopia eletrônica de transmissão (TEM) e microscopia de eletrônica de varredura (MEV) foram utilizas para determinar as estruturas, morfologias, distribuições de tamanhos e monodispersividade dos materiais sintetizados. Estes novos nanomateriais bifuncionais Fe3O4@calix-Eu(TTA), Fe3O4@calix-Tb(ACAC), Fe3O4@SiO2-TTA-Eu(L) e Fe3O4@SiO2-TTA-Tb(AB ou AMB) apresentam propriedades fotônicas e superparamagnéticas muito interessantes. As propriedades magnéticas (ZFC/FC e M-H) obtidas nas temperaturas de 2, 5 e 300 K foram investigadas a fim de obter informações sobre o efeito da cristalinidade na magnetização de saturação e das temperaturas de bloqueios. Também foram estudadas a influência dos íons TR3+ sobre a magnetização dos nanomateriais. Apesar da magnetita atuar como um forte supressor de luminescência, as camadas do ligante calixareno modificado e da sílica sobre as nanopartículas de Fe3O4 compensam esta desvantagem. Do mesmo modo foi considerada a discussão sobre a transferência de energia intramolecular do estado tripleto T1 dos ligantes TTA e ACAC para os níveis excitados dos íons Eu3+ e Tb3+ nos nanomateriais Fe3O4@calix-Eu(TTA) e Fe3O4@calix-Tb(ACAC). As eficiências quânticas de emissão (η) dos compostos Fe3O4@calix-Eu(TTA) e Fe3O4@SiO2-TTA-Eu(L) foram calculadas e discutidas, bem como suas características estruturais baseadas nos níveis de energia e parâmetros de intensidades experimentais dos sistemas contendo o íon Eu3+. Estes novos nanomateriais podem atuar como camadas emissores vermelha e verde para dispositivos moleculares conversores de luz e magnéticos (MLCMDs). / The design and fabrication of sophisticated bifunctional luminescent and magnetic nanomaterials based on Fe3O4 and RE3+ complexes are sought for. Accordingly, novel red-green emitting superparamagnetic Fe3O4@calix-Eu(TTA) and Fe3O4@calix-Tb(ACAC) nanomaterials were prepared through on-pot method. In this regard, the chemically modified calixarene ligand was used as a surfactant to stabilize the Fe3O4 nanoparticles. The calixarene ligand provides colloidal stability and chemically modifiable surface to the magnetite nanoparticles. Thus, this ligand functionalized Fe3O4@calix nanoparticles were further coordinated to the RE3+ ions via one-pot synthesis, using TTA and ACAC ligands as sensitizers (antenna effect) to produce highly luminescent nanophosphors. In addition, bifunctional optical and magnetic Fe3O4@SiO2-TTA-Eu(L), L: TTA, TC, AB and AMB as well as Fe3O4@SiO2-TTA-Tb(AB or AMB) nanocomposites were also synthesized through multistep synthetic protocol, utilizing Fe3O4 nanoparticles as precursors. They were modified with silica shell, using modified Stöber method and further grafted with RE3+ complexes to produce the luminescent and magnetic nanocomposites. The X-ray powder diffraction (XPD), small angle x-ray scattering (SAXS), transmission electron microscopy (TEM) and scanning electron microscopy (SEM) techniques were used to determine the structures, morphologies, size distribution and monodispersity of the synthesized materials. These novel Fe3O4@calix-Eu(TTA) and Fe3O4@calix-Tb(ACAC) as well as Fe3O4@SiO2-TTA-Eu(L) and Fe3O4@SiO2-TTA-Tb(AB or AMB) magnetic luminescent nanomaterials show interesting superparamagnetic and photonic properties. The magnetic properties (M-H and ZFC/FC measurements) at temperatures of 2, 5 and 300 K were explored in order to investigate the extent of coating and crystalinity effect on the saturation magnetization and blocking temperatures. The influence of the RE3+ ions on the magnetization of the optical and magnetic nanomaterials was also studied. Even though magnetite is a strong luminescence quencher, the coating of the Fe3O4 nanoparticles with synthetically modified calixarene ligand (calix) and silica shell have overcome this difficulty. Moreover, the intramolecular energy transfer from the T1 excited triplet states of TTA and ACAC ligands to the emitting levels of Eu3+ and Tb3+ in the Fe3O4@calix-Eu(TTA) and Fe3O4@calix-Tb(ACAC) nanomaterials are discussed. The emission quantum efficiencies (η) for the Fe3O4@calix-Eu(TTA) and Fe3O4@SiO2-TTA-Eu(L) nanomaterials are also calculated and discussed, as well as the structural features based on the energy levels and experimental intensity parameters, in the case of the Eu3+ ion. These novel nanomaterials may act as the emitting layer for the red and green light for magnetic and light converting molecular devices (MLCMDs).

The structure of molten Au0.81Si0.19, Au0.72Ge0.28 and Ag0.74Ge0.26 alloys with a composition at or near to the eutectic was investigated by using neutron diffraction (ND). The results suggest that the Au-Au distance in the alloys is similar to that of liquid Au, there is a preference for Au-Si bonds and show that there are pre-peaks in the total structure factors for Au0.72Ge0.28 and Ag0.74Ge0.26 at 1.3(2) and 1.6(3) ˚, A−1 respectively. The asymptotic decay of the pair correlation functions was found to agree both with a theoretical prediction based on simple pair potentials and a fractal model for metallic glasses. The structure of glassy (R2O3)0.2(Al2O3)0.2(SiO2)0.6, where R denotes Dy, Ho or a 50:50 mixture of Dy and Ho, was investigated by using the method of isomorphic substitution in ND, x-ray diffraction (XRD) and extended x-ray absorption fine structure (EXAFS) spectroscopy. The network is made from SiO4 tetrahedral units with a distribution of AlO4, AlO5 and AlO6 units giving an average coordination number of 4.5(1). There is a distribution of RO5, RO6, RO7, RO8 and RO9 units with an average coordination number of 7.2(3) and an average R-O distance of 2.33(2) ˚ A. The EXAFS results confirmed that Dy and Ho are isomorphic and were used to refine an RMC model of the structure. R-Al and R-Si nearest neighbour shells with average distances of 3.15(3) and 3.6(1) ˚A were required to fit the EXAFS results. The structure of glassy and liquid ZnCl2 was studied by using ND and XRD. The material has a network structure made from ZnCl4 tetrahedra units which is retained in the liquid at temperatures near to the boiling point. An increase of temperature promotes edge sharing connectivity as inferred from a decrease of the Zn-Zn nearest neighbour distance and average Zn-Cl coordination number. An EXAFS study on crystalline ZnCl2 at room temperature shows that Zn remains 4fold coordinated at pressures less than 1 GPa, is 4+2-fold coordinated at 2-4 GPa, and is 6-fold coordinated above 4 GPa. For liquid ZnCl2, Zn is 4-fold coordinated by Cl at a pressure of about 1 GPa and could be 6-fold coordinated at 2-3 GPa.

"Hydroxyl ions are a common contaminant in optical fibers, and are responsible for strong absorption centered at 1380 nm that becomes significant over long optical path lengths. Recently, however, special fabrication methods have been developed that minimize the hydroxyl ion contamination, permitting use of the entire 1300-1700 nm spectral region for telecommunications. There is therefore interest in examining the Nd 4F3/2 to 4I13/2 transition for a potential optical amplifier at 1400 nm. In this thesis, the excited state absorption cross section and the overall gain/loss spectrum of neodymium in a silica glass fiber were determined for the 1200-1500 nm wavelength region using the pump-probe method. The ground state absorption cross section was also determined from transmission measurements, and the stimulated emission cross section was calculated using the fluorescence spectrum and the McCumber relation. Oscillator strengths for absorption and emission transitions were calculated in the 800-1600 nm wavelength range using the Judd-Ofelt method. The above procedures were followed for both the Nd-doped fiber, as well as an erbium-doped silica fiber. The shape of the Nd emission spectrum is also noteworthy, since the characteristic Nd peak at 1064 nm is not observed, although there is strong emission at 1092 nm. The pump-probe measurements revealed significant excited state absorption loss between 1200 and 1350 nm, due to excitation from the 4F3/2 to the higher 4G9/2 and 4G7/2 states. Between 1350 and 1475 nm, there was no net gain or loss that could be observed beyond the level of the noise. For the glass fibers studied, it appears that in the spectral region of interest for an optical amplifier, the stimulated emission and excited state absorption cancel one another out."

Os pegmatitos estudados estão associados à fácies albita granito do granito Madeira, a qual corresponde ao depósito de Sn-Nb-Ta (F, ETR, U, Th) Madeira, na mina Pitinga (AM) e estão associados a falhas de orientação N320/60SW. Estas rochas contêm minerais poucos comuns como gagarinita (NaCaYF6), genthelvita (Zn4Be3(SiO4)3S) e polilitionita (KLi2AlSi4O10(F, OH)2), além de grandes quantidades de criolita (Na3AlF6). Com base na composição química e mineralógica, estes pegmatitos foram classificados em três tipos: PEG ANF (teores médios de K e Na, com alta concentração de anfibólios), PEG POL (rico em K e com alta concentração de polilitionita) e PEG CRIO (rico em Na e com alta concentração de criolita). Estes pegmatitos contêm altos teores de ETR (especialmente ETRP) e Y, que estão concentrados principalmente na xenotima e na gagarinita. Estes elementos também ocorrem em elevados teores na grande parte dos demais minerais analisados. Também se destacam as concentrações anômalas de F, muito superiores às detectadas nos pegmatitos de outras localidades, e que promoveram o enriquecimento em Li, Na, K, Rb e Cs. A similaridade na composição química do AGN com os pegmatitos indica que eles possuem a mesma fonte. / The pegmatites studied are associated with the albite granite facies of the Madeira granite, which corresponds to the Sn-Nb-Ta (F, ETR, U, Th) Madeira deposit at the Pitinga mine (AM). They are associated with N320/60SW orientation faults. These rocks contain few common minerals such as gagarinite (NaCaYF6), genthelvite (Zn4Be3(SiO4)3S) and polylithionite (KLi2AlSi4O10(F,OH)2), as well as large amounts of cryolite (Na3AlF6). Based on the chemical and mineralogical composition, these pegmatites were classified into three groups: PEG ANF (medium K and Na, with high concentration of amphiboles), PEG POL (K rich and with high polylithionite concentration) and PEG CRIO (rich in Na and with high concentration of cryolite). These pegmatites contain high levels of REE (especially HREE) and Y, which are mainly concentrated in xenotime and gagarinite. These elements also occur at high levels in most of the other minerals analyzed. Anomalous concentrations of F, much higher than those detected in pegmatites from other localities, were also highlighted, and promoted enrichment in Li, Na, K, Rb and Cs. The similarity in the chemical composition of AGN with pegmatites indicates that they have the same source.

Rare earth elements (REE) are considered as critical and non-substitutable metals for electronics and green technology. A greater diversity of supply is needed and the REE occur in a wide range of REE- and REE-bearing minerals within different ore deposit types. The beneficiation processes for REE ores can vary widely based on their mineralogy and texture. It is, therefore, essential to understand the mineralogical characteristics when designing processing routes. Little research was carried out on this topic until the last few years, apart from bastnäsite, monazite, and xenotime, and most REE minerals in deposits currently under exploration are poorly understood in terms of processing characteristics. This geometallurgical study brings together the results of process mineralogy and minerals processing to recover synchysite-(Ce) and apatite from the carbonatite at Songwe Hill, Malawi. This deposit is unusual because it is a potential carbonatite source of both LREE and HREE. Results from previous flowsheet development studies on this deposit suggest that flotation is the most promising processing route and therefore this study concentrated on testing this hypothesis. It sought to understand the mineralogy better in order to predict processing response and carried out a series of flotation experiments to improve the processing efficiency. It also investigated the fundamental magnetic properties of the rare earth fluorcarbonate minerals (including synchysite) and established for the first time that there is a systematic variation in their properties that can be applied to minerals processing. Eight samples of REE carbonatite drill core, crushed to 1700 μm, and a composite sample ground to 53 μm and 38 μm were used throughout this research. Automated mineralogy (QEMSCAN®) was applied to determine the mineralogical characteristics of the ore deposit. This utilised a novel species identification protocol (SIP) for REE minerals in carbonatites, which was validated by electron microscopy (SEM-EDS), and electron probe microanalysis (EPMA). The principal REE minerals at Songwe are the REE fluorcarbonates, synchysite-(Ce) and also parisite-(Ce). These are challenging minerals for automated mineralogical techniques owing to their chemical similarity and common occurrence either as bladed (needle-like) crystals, which is the main textural type at Songwe Hill, or as syntaxial intergrowths. However, using the SIP developed in this study, the QEMSCAN® can distinguish between these minerals based on the Ca content and can also recognise syntaxial intergrowths on a scale of about > 20 μm. The Songwe Hill carbonatite hosts about 6 wt% to 10 wt% of REE- and REE-bearing minerals. Apatite hosts the more valuable HREE in addition to P2O5, followed by synchysite-(Ce)/parisite-(Ce) (mainly synchysite-(Ce)), and minor florencite-(Ce), which host the LREE. These minerals are commonly associated with the predominant gangue minerals, ankerite and calcite, and, to a lesser extent Fe- Ox/CO3 and K-feldspar, strontianite and baryte. Fundamental magnetic properties of pure REE fluorcarbonate single crystal minerals using a vibrating sample magnetometer (VSM) were determined. The magnetic susceptibility is highly dependent on the mineral composition. It is positive (paramagnetic) for bastnäsite-(Ce) and gradually decreases as the amount of Ca increases in parisite-(Ce), becoming negative (diamagnetic) for the Ca-rich member of the series, röntgenite. Synchysite-(Ce) in this deposit was experimentally determined by magnetic separation and behaved as a diamagnetic mineral. This can be explained by the layered structure common to the REE fluorcarbonate series minerals. Selected laboratory scale mineral processing experiments including magnetic separation and froth flotation were performed. Pre-concentration tests by magnetic separation showed a recovery of 84% for P2O5, 80% for Y2O3, and 76% for Ce2O3 in the non-magnetic product, with gangue minerals rejection of about 49% for ankerite and 48% for Fe-Ox/CO3 to the magnetic product. Apatite and synchysite-(Ce) loss to the magnetic product is mainly the result of their association with the paramagnetic minerals i.e. ankerite and Fe-Ox/CO3 as indicated by automated mineralogy. A spectrophotometer was utilised to measure the solubility of the organic chemical reagents including fatty acids and lignin sulphonate in different alkaline solutions and to determine the appropriate operating parameters for bench flotation tests. The results indicated that the solubility of fatty acids increased with increasing the pH value from 8.5 to 10.5, while the opposite was observed for lignin sulphonate. 35 bench-scale froth flotation tests under a wide range of chemical and operating conditions including pH modifiers and dosages, soluble and insoluble collectors, depressants, temperature, and conditioning time were performed. The results demonstrated that fatty acids and lignin sulphonate are sensitive to changes in pH, conditioning time, and temperature. These factors significantly affected flotation efficiency. A recovery of 86% for P2O5 and 74% for both of Y2O3 and Ce2O3 with TREO upgrading from 1.6 wt% to 3.8 wt% at a mass pull of 31% were achieved under a constant pulp pH of 9.5, elevated temperature, and long conditioning time. This study suggests that combining magnetic separation and froth flotation techniques to pre-concentrate and upgrade the REE- and REE-bearing minerals, should be considered further to minimise the cost of the chemical reagents used in froth flotation and gangue leaching.

Luz e oxigênio induzem reações de degradação (foto-oxidação) que modificam as propriedades físicas e químicas da matéria, efeitos nocivos da radiação ultravioleta (UV) podem causar descoloração de corantes e pigmentos, amarelamento de plásticos, perda de brilho e da propriedade mecânica (cracking) de materiais, queimaduras, câncer de pele, entre outros problemas relacionados à luz UV. A fim de reduzir os efeitos nocivos da radiação UV e alcançar uma adequada conservação das propriedades dos materiais surgem os absorvedores ou filtros UV. Uma vez que materiais nanométricos a base de cério apresentam atividade fotocatalítica menor e elevada absorção na região do UV tornam-se filtros solares com aplicabilidade em diversas áreas quando comparados aos óxidos utilizados atualmente com função de filtros solares (ZnO e TiO2). Fosfatos de cério (III) (CePO4) foram preparados por Pechini (modificado), síntese hidrotermal e microemulsão reversa; as amostras foram submetidas a tratamento térmico em distintas temperaturas com o intuito de averiguar a estrutura do CePO4 e influência desta na capacidade da absorção UV. Sistemas de óxidos metálicos contendo cério também foram estudados, sendo sintetizados por sol-gel não-alcoóxido e aplicados na forma de pó e filme fino sobre substrato de vidro. A preocupação com a morfologia e o tamanho dos materiais motivou a escolha pelas metodologias de síntese empregadas. Neste trabalho foram exploradas e elucidadas as propriedades dos materiais a base de cério em absorver luz UV, devido às transições 4f-5d dos íons Ce3+ e/ou às transições entre banda de condução e banda de valência. As amostras foram analisadas por espectroscopia de absorção no UV-Vis e na região do infravermelho (FTIR), difração de raios X (XRD), difração de elétrons, susceptibilidade magnética (MS), microscopia eletrônica de varredura (SEM), microscopia eletrônica de transmissão (TEM), espectroscopia de reflectância difusa (DRS), atividade fotocatalítica (AF) e ressonância paramagnética de elétrons (EPR). As excelentes propriedades morfológicas, ópticas e fotocatalíticas indicam a possível aplicação dos materiais à base de cério, foco de investigação do presente trabalho, como filtros solares em proteção cosmetológica (cremes, shampoos, sprays etc) ou de materiais (tintas, vernizes, vidros e outros). / Light and oxygen induce degradation reactions (photo-oxidation) that modify the physical and chemical properties of the matter. The damaging UV radiation is responsible for the discoloration of dyes and pigments, weathering, yellowing of plastics, loss of gloss and mechanical properties (cracking), sunburnt skin and other problems associated to UV light. UV absorbers or UV filters have been used in order to reduce these damaging effects and achieve an adequate conservation of the properties of the materials. In front of this problem, cerium based nanomaterials are promising inorganic UV absorbers for the substitution of zinc and titanium oxide, once it presents high UV absorptivity, a lower refraction index than TiO2 and ZnO, and a higher chemical inertia (and thus a lower photocatalytic activity). Nanostructured cerium phosphates (CePO4) were prepared by Pechini, hydrothermal and reverse microemulsion synthesis, and some parameters (calcinations temperature and reactants rate) employed in each synthesis were investigated. Cerium metal oxide systems synthesized by sol-gel (non-alcooxide) and applied as powder and thin films materials were investigated too. The methodology of the synthesis were chosen aiming ideal morphology and particles size. In this work we explored and elucidated the properties of UV absorber cerium based nanomaterials , due to 4f-5d transitions of Ce3+ ions, charge transference of Ce4+ and, a little portion is due to the contribution of valence and conduction band. The samples were characterized by UV-Vis absorption spectroscopy , Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), electron diffraction, magnetic susceptibility (MS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS), photocatalytic activity (PA) and electron paramagnetic resonance (EPR). The excellent morphological, optical and photocatalytic properties indicate the possible application of cerium based materials in solar protection for cosmetics (creams, shampoos, sprays etc.) or materials (paints, varnishes, glass and others).