No presente trabalho, fizemos um estudo espectroscópico do vidro sódio aluminofosfato, cuja composição é (100-x) (NaPO3)3 - xAI(NaPO3)3visando utilizar a referida matriz como possível meio ativo para laser. Para isso, caracterizamos matrizes vítreas não dopadas e dopadas com o íon terra-rara Eu3+ e Nd3+. Nas matrizes não dopadas, procurou-se avaliar como algumas propriedades ópticas, como por exemplo, transmissão e alguns parâmetros estruturais (energia de fônon) se comportavam mediante a substituição sistemática do (NaPO3)3 pelo AI(PO3)3. O uso do Nd3+ como íon opticamente ativo nesta matriz vítrea, se deve ás suas excelentes características como elemento de prova. Para a caracterização destas amostras utilizamos diferentes técnicas, como por exemplo, excitação, luminescência sob excitação seletiva, absorção luminescência e tempo de vida. Os resultados obtidos, mostraram que com o aumento do alumínio a energia de fônon do vidro aumenta, o tempo de vida do nível 5D0 diminui e as bandas de emissão se alargam, o que indica que o alumínio causa uma desordem estrutural. O íon Nd3+, por ser um dos mais eficientes íons laseres, teve suas emissões avaliadas em função da composição, buscando uma matriz que otimizasse os parâmetros referentes à emissão laser. Devido a presença do grupo OH- na estrutura do vidro, o tempo de vida do nível laser 4F3/2 era menor que o calculado pela teoria de Judd¬-Ofelt, provocando então, uma baixa eficiência quântica de emissão (da ordem de 0.75). Então, a fim de evitar a presença dos referidos grupos, preparamos algumas amostras em atmosfera de nitrogênio (N2) dopadas com Nd3+, conseguindo assim, aumentar a eficiência quântica de emissão para 0.98 / In this work we have done a spectroscopic study on sodium aluminophosphate glasses of composition (NaPO3)- xAI(NaPO3)3 aiming to investigate the potential use of this glass host as laser active media when doped with Nd3+. Undoped samples were characterized to evaluate on what extent some optical properties, as transmission, and structural parameters (phonon energies), would be affected by systematic substitution of (NaPO3)3- AI(PO3)3. Since Eu3+ present excellent characteristics as a probe element, samples doped with this ion were characterized by excitation, luminescence with or without selective excitation, absorption and lifetime measurements. The results indicated that the phonon energy of the glass increases with increasing aluminum content, the lifetime of excited 5D0 state of Eu3+ decreases, and the emission bands are broadened. Such observations are evidences of an increase in structural disorder. Since Nd3+ is one of the most efficient laser ions, samples doped with it were also studied as a function of host compositional changes, aiming to optimize laser emission at 1.06 μm. Due to the presence of OH- groups in primarily prepared matrices, the experimental lifetime of laser level 4F3/2 was shorter than the one calculated by the Judd-Ofelt theory, resulting in a small quantum efficiency (≈0.75). To solve this inconvenience, Nd3+ doped samples were prepared under N2 atmosphere and that way, the quantum efficiency raised to a value of 0.97

Este trabalho consiste na caracterização óptica de vidros fluoretos (fluoreto de gálio e chumbo) e de vidros óxidos (aluminato de cálcio), dopados com os íons terras raras Er+3 visando à aplicação destas matrizes como meios ativos para lasers nas regiões do infravermelho e visível. Para isto foram utilizadas as técnicas espectroscópicas de absorção óptica, luminescência, tempo de decaimento e conversão ascendente de luz. O estudo é baseado nas seguintes emissões do Er+3: 4I11/2→ 4I13/2 (2800nm), 4I13/2 →4I15/2(1550nm) e 4S3/2→4I15/2(550nm). As melhores amostras óxidas para as três emissões foram aquelas codopadas com Er+3 e Yb+3. No caso dos vidros fluoretos, as amostras codopadas são mais eficientes para emissão no visível (conversão ascendente de luz) e as amostras dopadas apenas com Er+3 se mostram mais eficientes para as emissões no infravermelho. Os vidros fluoretos apresentam as maiores eficiências quânticas para as emissões de interesse devido os mesmos possuírem maior transparência e menor energia de fônons que os vidros óxidos. Porém, estes últimos apresentam maior resistência mecânica, maior condutividade e difusividade térmica o que os tornam interessantes para aplicações de alta potência. . / This work cansists in the optical characterization of Er+3 e Yb+3 doped fluoride, (galium and lead fluoride), and oxide, (calcium aluminate), glasses , aiming the application of theses hosts as an active media for laser in the infrared and visible regions. With this purpose we employed the spectroscopic technique of absorption and luminescence, and measurementes of excited state lifetimes and upconversion were performed. The study is based on the following Er+3: 4I11/2→ 4I13/2 (2800nm), 4I13/2 →4I15/2(1550nm) and 4S3/2→4I15/2(550nm). The best oxide samples were those codoped with Er+3 e Yb+3. For the fluoride glasses, the codoped samples showed to be more eficient for emission in the visible region, (upconversion), whereas the single doped samples are more eficient for emission in the infrared region. The fluoride glasses presented larger quantic efficiency for the emissions in which we were interested, due to the fact that these glasses are more transparent and have smaller phonon energies than the oxide glasses. However, the latter have better mechanical strength, larger thermal conductivity and difusivity, which enables them to be applied in high power systems.

Neodymium (Nd) isotopes have been increasingly used to trace the modern and past ocean circulation. This assumes that seawater Nd isotope ratios (εNd) effectively fingerprint different water masses and approximate expected values from water mass mixing. However, the decoupling of Nd isotopes and Nd concentration (the “Nd paradox”) in the water column, and the lack of understanding of sources and sinks of Nd, restrain our understanding of the “quasi-conservative” behavior of εNd in seawater. Nd is one of the lanthanide rare earth elements (REEs) with similar chemical characteristics that undergo some degree of fractionation. The shale-normalized REE patterns and REE ratios can be used to investigate potential sources/sinks of REEs. Combining REEs with εNd will provide additional information to study REE cycling in the ocean. To better understand the reliability of εNd as a water mass tracer, 17 high-resolution seawater profiles were sampled meridionally in the Southwest Atlantic (GEOTRACES GA02 Leg 3; RRS James Cook 057) and measured for εNd. This region involves the major water masses in the Atlantic Meridional Overturning Circulation: southward flowing North Atlantic Deep Water (NADW), northward flowing Antarctic Intermediate Water (AAIW) and Antarctic Bottom Water (AABW). Along the cruise track, there are potential sources (eolian dusts, marginal sediments, oceanic volcanism, and nepheloid layer) that could add external Nd to seawater and disturb the “quasi-conservative” behavior of εNd. Our results show strikingly that the Southwest Atlantic transect confirms “quasi-conservative” behavior of εNd in intermediate and deep water. Our evaluations of Nd isotopic deviations (ΔεNd) from conservative behavior show that out of 198 intermediate and deep samples, 49% of ΔεNd-values are within ± 0.25 εNd units (< analytical error: ± 0.30 εNd units) and 84% of ΔεNd-values are within ± 0.75 εNd units. Potential sources that could add external Nd to seawater from oceanic volcanism and the nepheloid layer do not show impact on seawater εNd. Terrigenous sources of Nd (e.g. eolian dusts from Africa and Patagonia, marginal sediments from South America) show influence on surface/subsurface water εNd but this εNd signature is not transferred to intermediate and deep water. To better understand the conservative vs. non-conservative behavior of REEs in the ocean, the dissolved REE concentrations were analyzed for the 17 seawater profiles in the Southwest Meridional Atlantic Transect (GEOTRACES GA02 Leg 3). The shale-normalized REE patterns are consistent with typical seawater patterns. To investigate whether and how much REE concentrations deviate from conservative water mass mixing, the REE concentration deviations were calculated for the intermediate and deep water. It is shown that within the SAMT, the intermediate and deep water REEs generally reflect water mass mixing and nearly conservative behavior. Along this transect, the potential sources that could add external REEs to seawater are dissolution of REEs from eolian dust to the surface/subsurface water, REEs released from dissolution of Fe-Mn oxides in the oxygen depleted zone, REEs from sediments near the continental margin, and dissolution of REEs from deep sea sediments. REEs and Nd isotopes of most intermediate and deep water masses passing the volcanic Rio Grande Rise (RGR) and Vitória-Trindade Ridge (VTR) do not show influence from RGR and VTR. REEs and Nd isotopes of the bottom water Lower Circumpolar Deep Water (LCDW) and AABW passing the RGR are influenced by dissolved REEs from the deep sea sediments. LCDW and AABW passing the VTR are influenced by dissolved REEs from the deep sea sediments as well as the volcanic VTR. In order to better understand the oceanic Nd cycling in the North Pacific, its sources and sinks in seawater must be better characterized. The high εNd of North Pacific Deep Water (NPDW, ~ −4) has been difficult to reconcile with the eolian inputs as reflected in surface waters (e.g. Jones et al., 2008), which have much lower εNd (~ −10), indicating potential addition of a component from Pacific volcanism. In order to constrain the REE sources in the North Pacific, we measured εNd and REEs of seawater from five stations across the subarctic North Pacific sampled by the Innovative North Pacific Experiment (INOPEX) Cruise SO202 (2009). In the surface water (~10 m), the highest εNd is observed at the station closest to the Aleutian-Kamchatka volcanic margin (Northwest station SO202-5), suggesting higher contribution of external REEs from volcanic ashes compared to the other stations. In the shallow water (100-400 m, depending on location), remineralization of REEs from volcanic ashes prevails over Asian dusts at Northwest station SO202-5 and near Japan stations SO202-44, 41, and 39, whereas remineralization of REEs from Asian dusts prevails over volcanic ashes at the Northeast station SO202-32 in the open ocean of the Alaska Peninsula. From the depths of North Pacific Intermediate Water (NPIW) to NPDW, seawater εNd and REEs show conservative water mass mixing of NPIW-NPDW. They also show conservative behavior along the water mass transport paths of NPIW and NPDW. Below the depths of NPDW, addition of external REEs is observed in the vertical profiles of εNd and REEs as well as along the transport path of LCDW. The potential sources that add external REEs to the bottom water are (1) sediments on the Kuril-Kamchatka-Aleutian volcanic margin along the LCDW transport path, and (2) sediments on the seafloor, both of which could interact with seawater and modify the seawater εNd and REE signatures.

No description available.

Chapter 1 gives a brief introduction to metal complexes supported by anionic nitrogen-based ligands. / Chapter 2 describes the synthesis, structural characterization and reactivity of Mn(II), Fe(II) and Co(II) amides derived from the strongly electron-withdrawing [N(C6F5)(C6H3Pr i2-2,6)]- ligand (L 1). Twelve new compounds, including the ligand precursor HL 1, and three alkali-metal and eight late transition metal derivatives of L1, were prepared. Reactions of MCl2 (M = Mn, Fe, Co) with [Li(L1)(TMEDA)] (2) yielded the monoamido complexes [M(L1)Cl(TMEDA)] [M = Mn (5), Fe ( 6), Co (7)]. Treatment of [Li(L1)(THF) 3] with MCl2 (M = Fe, Co) afforded the diamido complexes [M(L1)2(mu-Cl)Li(THF)3] [M = Fe ( 8), Co(9)]. The reaction chemistry of the Co(II) complex 7 was investigated. Treatment of the Co(II) derivative 7 with LiMe, NaN3 and NaOMe gave the corresponding methyl-, azido- and methoxide-amide complexes, namely [Co(L1)(Me)(TMEDA)] ( 10), [Co(L1)(N3)(TMEDA)] (11) and [Co(L1)2(mu-OMe)Na(TMEDA)] (12), respectively. The solid-state structures of complexes 5--12 were determined by X-ray crystallography. / Chapter 3 reports on the synthesis and catalytic properties of lanthanide(III) complexes derived from the unsymmetrical [PhC(NSiMe3)(NC6 H3Pri2-2,6)] - ligand (L2). The lithium and potassium salts of L2, and eight lanthanide(III) derivatives of L2 were synthesized. A series of Ln(III) complexes of the general formula [Ln(L 2)2(mu-Cl)2Li(TMEDA)] [Ln = Y (17), Eu (18), Er (19), Lu (20)] and [Li(THF) 4][Ln(L2)2Cl2] [Ln = Ce ( 21), Nd (22), Sm (23)] were synthesized by the reactions of anhydrous LnCl3 with two molar equivalents of [Li(L2)(TMEDA)] (15). In addition, the neutral dimeric yttrium(III) complex [Y(L2)2(mu-Cl)] 2 (24) was also prepared by the reaction of anhydrous YCl 3 with the potassium amidinate [K(L2)]n (16). The catalytic properties of complexes 20--22 towards the ring-opening polymerization of epsilon-caprolactone were also studied in this work. / Chapter 4 reports on the coordination chemistry of L2 towards divalent lanthanide metal ions. Three neutral divalent lanthanide complexes, [Ln(L2)2(THF)n] [Ln = Sm, n = 2 (25); Ln = Eu, n = 2, (26); Ln = Yb, n = 1 (27)], were prepared by treatment of LnI2(THF) 2 with the potassium amidinate [K(L2)]n . The reaction chemistry of 25--27 as one-electron transfer reagents has been examined. This led to the isolation of six lanthanide(III) complexes (28--33). Treatment of 25--27 with PhEEPh (E = Se, Te) gave the corresponding Ln(III) chalcogenolate complexes [Ln(L2)2(mu-EPh)]2 [Ln = Sm, E = Se (28); Ln = Eu, E = Se (29); Ln = Sm, E = Te ( 31)] and [Yb(L2)2(SePh)(THF)] (30). Besides, the reaction of 27 with iodine resulted in the isolation of the iodide complex [Yb(L2)2(I)(THF)] ( 32), whilst treatment of 25 with dicyclohexylcarbodiimide led to [Sm(L2)2{CyNC(H)NCy}] (33). / Chapter 5 summarizes the results of this research work. A brief suggestion on future directions of this research project is also discussed. / The present research work was focused on the coordination chemistry of the highly electron-withdrawing [N(C6F5)(C6H 3Pri2-2,6)]- ligand and the unsymmetrical [PhC(NSiMe3)(NC6H 3Pri2-2,6)- ligand. The first part of this work was centered on the synthesis, structure and reactivity of late transition metal complexes supported by the [N(C6F5)(C6H3Pr i2-2,6)]- ligand (L 1). The second part of this work dealed with the chemistry of trivalent and divalent lanthanide complexes derived from the bulky [PhC(NSiMe3 )(NC6H3Pri 2-2,6)]- ligand (L2). / Yao, Shuang. / Adviser: Hung Kay Lee. / Source: Dissertation Abstracts International, Volume: 71-01, Section: B, page: 0317. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese.

Alkylation of [eta5:sigma-Me2C(C5 H4)(C2B10H10)]TiCl(NMe 2) generates [eta5:sigma-Me2C(C5 H4)(C2B10H10)]Ti(R)(NMe 2) (R = Me, CH2TMS), which offers a unique opportunity to observe the direct competition among Ti-C(alkyl), Ti-N and Ti-C(cage) bonds in the insertion reactions with unsaturated molecules. The results indicate that unsaturated molecules insert preferably into the Ti-C (alkyl) bond over the Ti-N bond, while the Ti-C (cage) bond remains intact in all reactions. Several imido-titanium complexes [eta5:sigma-Me2C(C 5H4)(C2B10H10)]Ti(=NR)(Py) and [eta5:sigma-Me2C(C9H6)(C 2B10H10)]Ti(=NtBu)(Py) have been prepared by salt metathesis reactions or imido exchange reactions. These imido complexes can react with a variety of unsaturated molecules to give imido exchange products or [2+2] cycloaddition species. The imido complex [eta5:sigma-Me2C(C5H4)(C 2B10H10)]Ti(=NtBu)(Py) can also catalyze the hydroamination of phenyl acetylene. The key intermediate metallacyclic complex has been isolated and structurally characterized. / By taking the advantage of a cyclic organic group and an icosahedral carborane as well as the bridging ligand, trivalent phosphorus-bridged ligand iPr2NP(C9H7)(C2B 10H11) is designed and successfully synthesized. It is readily converted into the corresponding mono- and di-lithium salts, which have found many applications in transition metal chemistry. A series of organolanthanide and group 4 metal complexes derived from this new ligand have been prepared and structurally characterized. It is found that this ligand can effectively prevent lanthanocene chlorides from ligand redistribution reactions. [eta 5:sigma-iPr2NP(C 9H6)(C2B10H10)]Zr(NMe 2)2 can catalyze ethylene polymerization upon activation with MMAO and initiate the polymerization of epsilon-caprolactone. / iPr2NP(C9H 7)(C2B10H11) can be converted into the pentavalent derivative iPr2NP(O)(C9H 7)(C2B10H11) by treatment with H 2O2. Interactions of M(NMe2)4 with iPr2NP(O)(C9H7)(C2 B10H11) give unexpected products [sigma.sigma- iPr2NP(O)(C9H6)(C2 B10H11)]M(NR2)2. To investigate the similarities and differences between iPr2NP(O)(C 9H7)(C2B10H11) and its fluorenyl derivative in chemical properties, iPr 2NP(O)(C13H9)(C2B10H 11) is also prepared in a similar manner. It reacts easily with Zr(NMe 2)4 to give the amine elimination product [sigma.sigma- iPr2NP(O)(C13H8)(C 2B10H10)]Zr(NMe2)2(THF). However, treatment of iPr2NP(O)(C 2B10B11)(C2B10H11) with Ti(NMe2)4 affords amine elimination/deboration complex [sigma:eta5-iPr 2NP(O)(C13H9)(C2B9H 10)]Ti(NMe2)2. / Wang Hong. / "February 2005." / Adviser: Xie Zuomei. / Source: Dissertation Abstracts International, Volume: 67-01, Section: B, page: 0265. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. 168-180). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

by Ka-yue Chiu. / The "3" in the title is subscript. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1996. / Includes bibliographical references (leaves 103-110). / ACKNOWLEDGEMENTS --- p.3 / ABBREVIATIONS --- p.4 / ABSTRACT --- p.5 / Chapter I. --- COORDINATION CHEMISTRY OF SmI3 WITH DONOR SOLVENTS --- p.7 / Chapter 1.1. --- Introduction --- p.7 / Chapter 1.2 --- Results and Discussion --- p.21 / Chapter 1.2.A --- Synthesis and Structural Characterization of [trans-SmI2(THF)5][trans- SmI4(THF)2] (1) --- p.21 / Chapter 1.2.B --- Synthesis and Structural Characterization of SmI3(DME)2 (2) --- p.26 / Chapter 1.2.C --- Synthesis and Structural Characterization of [{Sm(H20)3}2{Sm(CH3CN) (H20)3}2{Sm(CH3CN)3(H20)}2(μ3-OH)8(μ6-0)]I8-2H20 (3) --- p.30 / Chapter 1.3 --- Conclusion --- p.38 / Chapter 1.4 --- Experimental Section --- p.39 / Chapter II. --- SYNTHESIS AND STRUCTURAL CHARACTERIZATION OF LANTHANACARBORANES --- p.45 / Chapter II.1 --- Introduction --- p.45 / Chapter II.2 --- Results and Discussion --- p.51 / Chapter II.2.A --- Synthesis and Characterization of closo-Lanthanacarboranes --- p.51 / Chapter II.2.A.i --- Sandwich Type Complexes --- p.51 / Chapter II.2.A.ii. --- Half-Sandwich Type Complexes --- p.62 / Chapter II.2.B --- Synthesis and Characterization of an exo-nido-Samaracarborane --- p.71 / Chapter II.2.B.i. --- Synthesis and Characterization of an exo-nido-[{(C6H5CH2)2C2B9H9} Sm(DME)2]2.DME(18) --- p.77 / Chapter II.3 --- Conclusion --- p.84 / Chapter II.4 --- Experimental Section --- p.85 / REFERENCES --- p.99

Made available in DSpace on 2014-06-11T19:31:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-03-25Bitstream added on 2014-06-13T21:01:53Z : No. of bitstreams: 1 oliveira_rc_dr_araiq.pdf: 2354887 bytes, checksum: 89c5b192793995d9542d4827f06031b1 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O processo de biossorção tem sido reconhecido como alternativa potencial na concentração de metais pesados e radioisótopos a partir de corpos d’água que recebem ação antropogênica (indústria, mineração, etc.). A biossorção é um processo que se baseia na remoção de íons metálicos em solução aquosa através de interações entre o metal e determinados sítios ativos presentes em revestimentos celulares, provenientes de biomassas como algas, bactérias e fungos. Na última década, há na literatura um crescente interesse na aplicação deste processo para concentração, recuperação e separação de metais de alto valor agregado e/ou de grande demanda tecnológica, tais como as terras-raras (TR) – essenciais para fabricação de um sem-número de produtos, a citar: laseres, supercondutores, equipamentos miniaturizados, etc. Apesar de apresentarem uma considerável disponibilidade na natureza, as TR possuem alto valor agregado devido aos dispendiosos e complexos processos de separação e purificação de misturas de TR, resultado da alta similaridade química entre os elementos do grupo. Poucos países detêm processos industriais completos de separação destes metais, dessa forma, o domínio dessa tecnologia determina uma importância considerável nos aspectos geopolíticos, estratégicos e econômicos, visto a extensão de investimentos em P&D envolvidos e as descobertas geológicas nas últimas décadas das jazidas chinesas, que abrangem 80% das reservas mundiais. Este trabalho consiste em uma avaliação preliminar da utilização do processo de biossorção na biomassa Sargassum sp. para a concentração, recuperação e separação de misturas de metais TR a partir de soluções sintéticas. As interações metal-biomassa seguem uma cinética de pseudo-segunda ordem e são descritas pelo modelo de adsorção de Langmuir... / The biosorption process has been recognized as potential alternative to concentrate heavy metal and radioisotopes from wastewaters of the anthropogenic activities (industry, mining, etc.). The biosorption is a process based on removal of metallic ions in aqueous solution from interactions among the metal and determined active sites on cellular envelope of biomasses as such algae, bacteria, and fungus. In last decade, there are in the literature a crescent interest to apply this process for the concentration, recovery, and separation of metals of high aggregated value and/or high technologic demand as the rare earth metal (RE), which are essential for the manufacturing of a great number of products; e.g. lasers, superconductors, miniaturized equipments, etc. Despite of the RE present a relevant availability, they have high aggregated value due to expansive and complicate processes of separation and purification of RE mixtures, which is resulted of the high chemical similarities of the group. Few countries have complete industrial processes of separation of these metals, so the domain of this technology determines a considerable importance in geopolitical, economic, and strategic aspects because the extension of R&D investments involved and the geological discoveries of the Chinese ore deposits in the last decades, which comprise 80 % of world reserves. This work consists on evaluation of the biosorption process by Sargassum sp. biomass for the concentration, recovery, and separation of RE metals from synthetic solutions. The metalbiomass interactions follow the pseudo-second-order kinetics and they are described by the Langmuir adsorption model. Potentiometric and spectroscopic (SEM/EDX, FTIR e XPS) analyses indicate that the biomass is bounded to the RE by oxygenated groups via ionexchange and complexation mechanisms... (Complete abstract click electronic access below)

Neste trabalho foram preparadas as amostras Al2O3:TR3+ (TR3+=Eu, Gd) pelos métodos cerâmico, combustão e Pechini, calcinadas de 400 - 1400 ºC. Os difratogramas de raios X sugerem que as amostras calcinadas em menores temperaturas apresentam-se como sistemas amorfos, que com a elevação da temperatura de calcinação transformam-se na fase cúbica das aluminas ativadas (&#947;-Al2O3). A partir de 1200 ºC forma-se a fase hexagonal de &#945;-Al2O3, altamente cristalina e termoestável. O tamanho dos cristalitos foi determinado pelo método de Scherrer a partir dos respectivos difratogramas. Em geral, os espectros no infravermelho de Al2O3:Eu3+ apresentaram estiramentos relativos aos grupos tetraédricos [AlO4] condensados e/ou isolados indicando a presença de fase &#947;-alumina. Foi também observada a existência de bandas em regiões de menores energias atribuídas às freqüências de estiramento de grupos octaédricos [AlO6] relativas à fase &#945;-alumina (coríndon). A Microscopia Eletrônica de Varredura (MEV) indicou que as partículas obtidas pelo método cerâmico apresentam menor tamanho e uma morfologia mais uniforme comparados com aquelas obtidas pelos métodos de combustão e Pechini. Os espectros de emissão (&#955; exc. = 320 nm) do sistema Al2O3:Gd3+ não apresentam as bandas finas oriundas dos íons Cr3+ observadas nos espectros da alumina não dopada, indicando que íon Gd3+ suprime a luminescência destes íons. Os espectros de excitação das amostras Al2O3:Eu3+ preparadas pelo três métodos apresentam uma banda larga atribuída aos defeitos da matriz Al2O3 e à banda LMCT do O&#8594;Eu3+, enquanto que as bandas finas são atribuídas às transições 7F0#&8594;5DJ, 5HJ e 5LJ oriundas do íon Eu3+. Os espectros de emissão dos sistemas Al2O3:Eu3+ (1%), obtidos pelos métodos de combustão, cerâmico e Pechini, e calcinados de 400 - 1100 ºC (&#955;exc. = 394 nm) apresentam bandas alargadas atribuídas às transições 5D0&#8594;7FJ do íon Eu3+, sugerindo a ocupação de diferentes sítios de simetria neste sistema evidenciado através do alargamento inomogêneo das bandas atribuídas às transições 4f-4f do íon terra rara. A presença da inomogeneidade das transições eletrônicas 5D0&#8594;7FJ para Al2O3:Eu3+ (1%) calcinada de 400 a 1000 ºC sugere que este sistema apresenta predominância da fase gama (&#947;-Al2O3:Eu3+). A conversão da &#947;-Al2O3 (fase metaestável) em &#945;-Al2O3 (fase estável - coríndon) promove alterações significativas nos espectros de emissão (&#955;exc. = 394 nm). As amostras calcinadas de 1100 a 1400 ºC exibem um pico fino de alta intensidade (695 nm) atribuídas à linha R do íon Cr3+. A curva de decaimento luminescente do nível emissor 5D0 apresentou um comportamento bi-exponencial indicando que o íon Eu3+ encontra-se em um ambiente químico com diferentes sítios de simetria. O sistema Al2O3:Eu3+ preparado pelo método de combustão (400 - 1100 ºC) apresenta um aumento nos valores dos parâmetros de intensidades &#937;2 com o aumento da temperatura de calcinação promovendo uma elevação do caráter covalente da interação metal-doador. Os valores da eficiência quântica de emissão (&#951;) dos sistemas Al2O3:Eu3+ apresentam-se maiores comparados com outros sistemas vítreos. Observa-se que as coordenadas CIE dos compostos Al2O3:Eu3+ localizam-se próximas ao vértice correspondente à cor vermelha sugerindo uma grande contribuição desta cor. / In this work, Al2O3:TR3+ (TR3+=Eu, Gd) samples were prepared by ceramic, combustion and Pechini methods annealed at the temperature range of 400 - 1400 ºC. X-Ray diffraction -XRD patterns suggest that samples heated at lower temperatures are amorphous systems, but when the temperature increases, a change in the cubic phase of activated alumina (&#947;-Al2O3) is observed. The &#945;-Al2O3 phase showed high crystallinity and thermostability annealed at 1200 ºC. Crystallite size was determined by Scherrer\'s method using XRDs. In general, infrared spectra of Al2O3:Eu3+ show stretching frequencies related to condensed and/or isolated tetrahedral groups [AlO4] indicating the presence of &#947;-alumina phase. It was observed the existence of bands in lower energies attributed to stretching frequencies of octahedral groups [AlO6] from &#945;-alumina phase (corundum). The scanning electron microscopy (SEM) suggests that particles obtained by ceramic method show the smallest size and the most uniform morphology compared to those prepared by combustion and Pechini methods. Emission spectra (&#955; exc. = 320 nm) of AlAl2O3:Gd3+ system present no narrow bands arising from Cr3+ ions observed in the spectra of non-doped alumina indicating luminescence quenching by Gd3+ ion. Excitation spectra of Al2O3:Eu3+ samples prepared by three methods present a broad band attributed to defects of Al2O3 matrice and to LMCT state of O&#8594;Eu3+, on the other hand, the narrow bands are assigned to 7F0&#8594;5DJ, 5HJ and 5LJ transitions arising from Eu3+ ion. Emission spectra of Al2O3:Eu3+ (1%) system prepared by combustion, ceramic and Pechini methods, annealed from 400 to 1100 ºC (&#955;exc. = 394 nm) show broad bands for 5D0&#8594;7FJ transitions of Eu3+ ion suggesting that this ion is in different symmetry sites indicated by inhomogeneous line broadening of bands attributed to 4f-4f transition from rare earth ion. The presence of inhomogeneity of 5D0&#8594;7FJ transitions for Al2O3:Eu3+ (1%) annealed from 400 to 1000 ºC suggests that this system presents predominantly the &#947;-alumina phase. The conversion of &#947;-Al2O3 (metastable phase) to &#945;-Al2O3 (stable phase - corundum) changes significantly their emission spectra (&#955;exc. = 394 nm). The samples annealed from 1100 to 1400 ºC, exhibited a high intensity narrow peak around 695 nm assigned to R lines of Cr3+ ion. Luminescence decay curves of 5D0 emitter level have a bi-exponential behavior indicating that Eu3+ ion is found in a chemical environment with different symmetry sites. The Al2O3:Eu3+ system prepared by combustion method at 400 -1100 ºC presents an increase in the &#937;2 intensity parameter values with the increase of annealing temperatures enhancing the covalent character of metal-donator interaction. The values of emission quantum efficiencies (&#951;) of Al2O3:Eu3+ are higher than those for vitreous systems. CIE coordinates of Al2O3:Eu3+ are located near the corner corresponding to monochromatic red color.

Zeólitas tipo Y contendo terras raras, RE,Ca/NaY (RE = La, Ce, Nd, Eu, Gd), foram preparadas a partir da forma NaY (razão Si/Al = 2,4 ) por trocas iônicas sucessivas com soluções de cloreto de cálcio e cloreto de terras raras, -através de refluxo; e subseqüente filtragem a vácuo, secagem e tratamento térmico sob fluxo de nitrogênio. Após o tratamento térmico, os Íons aquosos trivalentes de terras raras sofrem hidrólise, formando hidroxilas catiônicas do tipo [RE. OH]2+ e prótons H+, tornando-se localizados nas cavidades e canais da zeólita. O próton reage com o oxigênio da rede cristalina, originando centros ácidos muito fortes. O tipo específico de terra rara trocado ionicamente influencia a acidez total, força e distribuição dos sítios ativos na zeólita. As composições químicas das celas unitárias das amostras foram determinadas por espectrometria de emissão atômica por plasma de argônio induzido (ICP-AES). A cristalinidade, após troca iônica e tratamento térmico, foi confirmada por espectroscopia na região do infravermelho (FT-IR) e difração de raios-X. A microssimetria do íon európio na zeólita Eu,Ca/NaY foi investigada por espectroscopia eletrônica de emissão na região do visível, sob excitação de radiação ultravioleta (396 nm). As propriedades ácidas das amostras RE, Ca/NaY foram estudadas por termogravimetria (TG) e calorimetria exploratória diferencial (DSC), usando n-butilamina como molécula sonda. Por TG, foi investigada a acidez total das amostras; enquanto que por DSC, utilizando o modelo cinético de Borchardt & Daniels, foi investigada a força ácida relativa das amostras. A presença dos centros ácidos de Brönsted e Lewis foi determinada por espectroscopia na região do infravermelho (1700-1300 cm-1) , usando piridina como molécula sonda. A atividade catalítica e seletividade das amostras foram avaliadas na reação química modelo de alquilação de benzeno com a olefina linear 1-dodeceno para formação de alquilbenzeno linear. A reação foi estudada na fase líquida, em um microrreator de batelada, à temperatura de 80°C. 0s produtos monoalquilados e os isômeros lineares de 1-dodeceno foram determinados por cromatografia em fase gasosa e espectrometria de massa (GC-MS). / The Y zeolites containing calcium and rare earth polivalent cations, RE,Ca/NaY (RE = La, Ce, Nd, Eu, Gd), were prepared by ion exchange, refluxing the NaY zeolite (Si/Al = 2,4) with calcium chloride and rare earth chloride solutions, followed by thermal treatment under nitrogen flow. The trivalent hydrated rare earth ions undergo hydrolysis, forming [RE.OH]2+ cation hydroxyls and protons H+, which react with oxygen in the lattice, generating strong acid sites. The rare earth elements influence the total acidity, strength and distribution of the active sites in the zeolite. The unit cell chemical compositions of the samples were determined by Inductively Coupled Plasma / Atomic Emission spectroscopy (ICP/AES). The crystallinity was confirmed by Fourier Transform Infrared Spectroscopy (FT-IR) and X-ray diffraction. The europium microsimetry in the Eu,Ca/NaY zeolite was investigated by emission electronic spectroscopy in the visible region, under ultra-violet excitation (396 nm). The acid properties of the RE,Ca/NaY samples were studied by Thermogravimetry (TG) and Differential Scanning Calorimetry (DSC), using n-butilamine as molecular probe. From TG curves, the total acidity was calculated, whereas the relative acid strength was determinated by DSC curves, using the Borchardt-Daniels kinetic model. The nature of Brönsted and Lewis acid sites was investigated by FT-IR, in the 1700 - 1300 cm-1 region, using pyridine as molecular probe. The catalytic activity and selectivity of the samples were evaluated on the alkylation of benzene with 1-dodecene model reaction, to form linear alkylbenzenes, in liquid phase, at 80°C using a bath reactor. The reactant conversion, extent of isomerization and product distribution were monitored by Gas Chromatography and Mass Spectrometry techniques (GC-MS).