A utilização de novas rotas de síntese de materiais nanoestruturados tem levado à obtenção de materiais apresentando novas propriedades e aplicações. O presente trabalho teve como principal objetivo realizar a síntese e a caracterização de nanopartículas de óxido de vanádio obtidas pelo método da decomposição de peróxido utilizando o tratamento hidrotermal. Por meio do controle do tempo e da temperatura de síntese, foi possível obter nanoestruturas de pentóxido de vanádio com diferentes fases cristalinas e morfologias. Os resultados de espectroscopia Raman e difração de raios X (DRX) mostraram que o tratamento hidrotermal da solução em temperaturas de até 180oC, durante 2 horas, leva à formação da fase V2O5nH2O monoclínica, apresentando uma orientação preferencial na direção 00l. A partir desta temperatura, o material obtido passou a ter a fase ortorrômbica perdendo sua orientação preferencial. Através das medidas de termogravimetria (TG) foi observado que, dependendo da condição de síntese, as amostras apresentam diferentes quantidades de moléculas de água (H2O) intercaladas em sua estrutura. Imagens de microscopia eletrônica mostraram que as nanoestruturas obtidas podem possuir a forma de fitas, fios ou bastões. Utilizando a técnica de espectroscopia de absorção de raios X (XAS), foi possível verificar a presença de íons de V4+ nas amostras de fase monoclínica, o que não foi observado naquelas que possuem estrutura ortorrômbica. Pela técnica de XAS também foi possível constatar que as amostras de estrutura ortorrômbica possuem menor grau de desordem ao redor do átomo de vanádio. O estudo do mecanismo de crescimento da nanoestrutura de V2O5nH2O mostrou que ocorre um crescimento lateral, o qual pode ser descrito pelo mecanismo denominado Coalescência Orientada ou Oriented attachment (OA). Finalmente, através da decomposição do peróxido de vanádio, foi possível obter compostos vanadatos contendo cátions de Na+ em sua estrutura. / The use of new routes for nanostructured materials synthesis has lead to materials with new properties and applications. This PhD project aimed to realize the synthesis and the characterization of vanadium pentoxide nanoparticles obtained by peroxide decomposition using the hydrothermal treatment. By controlling synthesis time and temperature it was possible to achieve vanadium pentoxide nanoparticles with different crystalline phases and orphologies. The results of Raman spectroscopy and X-ray diffraction (XRD) showed that the hydrothermal treatment of the solution at temperatures up to 180oC for two hours leads to formation of the V2O5nH2O monoclinic phase with a preferential orientation on 00l direction. From this temperature on the material obtained began to present the orthorhombic phase misleading its preferential orientation. Through thermogravimetry (TG) measurements it was seen that depending on the synthesis condition the samples contains different amounts of water molecules (H2O) interleaved in their structure. Images of transmission electron microscopy (TEM) showed that the V2O5nH2O compound could have different morphologies such as ribbons, wires and rods. From X-Ray Absorption spectroscopy (XAS) measurements, it was observed the presence of V4+ ions in the monoclinic phase samples, which was not observed on orthorhombic structure samples. Through the XAS technique was also observed that the orthorhombic structure samples have a lower degree of disorder around the vanadium atom. Regarding the growth mechanism of these nanostructures, it was possible to verify that has been a wide growth which can be explained by the mechanism denominated Oriented Attachment (OA). Finally, through vanadium peroxide decomposition vanadates compounds containing Na+ cation in its structure were carried out.

Orientadores: Italo Odone Mazali, Talita Mazon / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-21T15:25:01Z (GMT). No. of bitstreams: 1 Madalossi_NatiaraVaughn_M.pdf: 3988977 bytes, checksum: 5fd028b4052bd1c0173b1e06a840ab1b (MD5) Previous issue date: 2012 / Resumo: Este trabalho reporta a síntese e caracterização de nanoestruturas de ZnO com morfologia de nanobastões hexagonais, crescidas verticalmente ao substrato de silício. Para o crescimento vertical dos nanobastões foi depositado um filme constituído por grãos de ZnO para atuar como camada de nucleação. Neste trabalho, as sínteses dos nanobastões e das camadas de nucleação foram preparadas por métodos químicos. As camadas de nucleação foram obtidas com a calcinação do filme de precursor polimérico e de 2-etilhexanoato de zinco, os quais foram depositados sobre o substrato de silício com o uso da técnica de spin coating e tratados termicamente em diferentes temperaturas para a formação dos grãos cristalinos de ZnO. Os nanobastões crescidos sobre as camadas de nucleação foram obtidos via síntese hidrotermal e síntese de deposição por banho químico (CBD). As camadas de nucleação e os nanobastões apresentaram estrutura cristalina tipo wurtzita com crescimento preferencial na direção [002] na qual a propriedade piezoelétrica se manifesta. As análises de espectroscopia Raman corroboraram com as análises de difração de raios X, sendo que não houve os deslocamentos das bandas do ZnO, indicando que os nanobastões não estavam no modo de confinamento quântico. Os nanobastões apresentam vários tipos de defeitos cristalinos, provocando a formação de defeitos eletrônicos na região da banda proibida, promovendo uma emissão centrada em 600 nm nas análises de espectroscopia de fotoluminescência. Para o estudo da resposta piezoelétrica dos nanobastões foi utilizado um substrato condutor de silício com um filme de platina para o crescimento dos nanobastões. O dispositivo constituiu-se de um eletrodo, formado pelo substrato condutor com as nanoestruturas e um contraeletrodo, formado pelo substrato condutor. Verificou-se que o dispositivo tem um comportamento de diodo tipo Schottky, sendo que a resposta piezoelétrica frente a uma deformação física foi de até 7 mV, indicando que os nanobastões podem ser utilizados como conversores de energia mecânica em energia elétrica / Abstract: This work reports the synthesis and characterization of nanostructures of ZnO with hexagonal nanorods morphology, growth vertically on silicon substrate. For the vertical growth a film constituted for ZnO grain was deposited over the substrate to act as nucleation layer. In this work, the synthesis of nanorods and nucleation layer was made by chemical methods. The nucleation layers were obtained by calcination of the polymeric precursor and 2-ethylhexanoate, being deposited on the silicon substrate by spin coating technique and annealed at different temperatures to promote the formation of ZnO crystalline grains. The growth of the nanorods on the nucleation layers were obtained by hydrothermal and chemical bath deposition (CBD) synthesis. The nucleation layers and the nanorods have wurtzite structure with preferential growth along the [002] axis, where the piezoelectric properties show up. Raman spectroscopy analyzes corroborate the x-ray diffraction, and there was no ZnO band shift, indicating that the nanorods would not be in quantum confinement. The nanorods showed different types of crystal defects, inducing the formation of electronic defects in the band gap. These defects showed an emission centered at 600 nm in photoluminescence spectroscopy. To study the piezoelectric response of the nanorods, a silicon substrate with a platinum film was used to grow the nanorods. The device consists of electrode formed by the conductive substrate with the nanorods and a contra-electrode, formed by the conductor substrate. It was found that the device is a Schottky type diode and the piezoelectric response was to 7 mV by physical deformation. Therefore, ZnO nanorods can be used as converter mechanical energy into electricity / Mestrado / Quimica Inorganica / Mestra em Química

Borophosphates are intermediate compounds of systems MxOy–B2O3–P2O5–(H2O) (M = main group or transition metal) which contain complex anionic structures built of interconnected trigonal–planar BO3 and / or BO4 and PO4 groups and their partially protonated species. The main objective of the present work was to synthesize, characterize and to study the properties of new selected 3d transition metal borophosphates. The selected four elements are scandium (Sc), iron (Fe), cobalt (Co) and nickel (Ni) due to their interesting contributions to borophosphate structural chemistry. The mild hydrothermal method was employed for the syntheses. During the investigation of borophosphates containing alkali–metals and scandium, the following three compounds were prepared and structurally characterized: MISc[BP2O8(OH)] (MI = K, Rb), CsSc[B2P3O11(OH)3] The anionic partial structure of MISc[BP2O8(OH)] (MI = K, Rb) consists of the well known open–branched four–membered rings of alternating borate and phosphate tetrahedra (a loop–branched hexamer with B : P = 1 : 2). The anionic partial structure of CsSc[B2P3O11(OH)3] represents the new type of oligomer containing boron in three– and four– fold coordination (B : P = 2 : 3). This is also the first time that a BO3 group is not only linked to borate species but also to a phosphate tetrahedron. This kind of oligomer was already predicted for borates but was never observed. By this, CsSc[B2P3O11(OH)3] is a special compound with regard to the structural building principles of borates and borophosphates. The significant differences in the crystal structures of MISc[BP2O8(OH)] (MI = K, Rb) and CsSc[B2P3O11(OH)3] may be due to the higher coordination number of cesium. Thermal treatment (up to 1000 ºC) of these compounds resulted in white crystalline products containing new phases with unknown crystal structures. Besides the discovery of alkali–metal scandium borophosphates, five new alkali metal scandium hydrogenphosphates were synthesized and structurally characterized: Li2Sc[(PO4)(HPO4)], MISc(HPO4)2 (MI = K, Rb, Cs, NH4) It was already predicted that open framework scandium phosphates should be isotypes of the respective indium phosphates. It was also stated that there should be a whole family of scandium hydrogenphosphates as we were able to confirm with the five novel compounds. Our systematic study reveals the structural changes of the anionic partial frameworks with increasing ionic radii of the alkali–metal ion. With respect to the M―T connections (M = six coordinated central metal atom, T = four coordinated phosphorous atom) the channel size increases from 8–membered rings in Li2Sc[(PO4)(HPO4)] to 12–membered rings in MISc(HPO4)2 (MI = K, Rb, Cs, NH4). KSc(HPO4)2 exhibits a new structure type in the family of monohydrogenphosphates with the general formula MIMIII(HPO4)2. This provides further evidence that scandium is a suitable element for the synthesis of framework structures with different channel sizes. The observation that in analogy to MISc(HPO4)2 (MI = Rb, Cs, NH4) a compound exists where the MI site is replaced by H3O+ gives rise to the hope that ion exchange properties could be of interest in this class of compounds. In addition, the possible existence of further modifications (as reported for the element–combinations RbV, NH4V, RbFe, and CsIn) shoud be investigated by thermoanalytical and X–ray methods. The extensive studies on borophosphate containing the transition metals Fe, Co, Ni together with alkaline earth–metals (Mg, Ca, Sr, Ba) led to the preparation of 13 compounds containing the combination of two different divalent M1IIM2II ions: CaM2II[BP2O7(OH)3] (M2II = Fe, Ni), BaM2II[BP2O8(OH)] (M2II = Fe, Co), SrFe[BP2O8(OH)2], CaCo(H2O)[BP2O8(OH)]•H2O, M1II0.5M2II(H2O)2[BP2O8]•H2O (M1II0.5 = Ca, Sr, Ba; M2II = Fe, Co, Ni) The anionic partial structure of CaM2II[BP2O7(OH)3] (M2II = Fe, Ni) consists of a tetrahedral triple [BP2O7(OH)3]4-, built from a central (HO)2BO2 tetrahedron sharing common vertices with two (H0.5)OPO3 tetrahedra. The complex anions in the crystal structure of BaM2II[BP2O8(OH)] (M2II = Fe, Co) comprises open–branched four–membered rings, [B2P4O16(OH)2]8-, which are formed by alternating (HO)BO3 and PO4 tetrahedra sharing common corners with two additional PO4 branches. The interconnection of these complex anions with M2II coordination octahedra (M2II = Fe, Co, Ni) by sharing common corners results in overall three–dimensional frameworks which contain channels filled with the M1II ions (M1II = Ca, Ba). The anionic partial structure of SrFe[BP2O8(OH)2] is built from a central (HO)2BO2 tetrahedron sharing common vertices with two PO4 tetrahedra. Surprisingly, SrFe[BP2O8(OH)2] represents the first example in the structural chemistry of borophosphates where the charge of the anionic partial structure is balanced by a divalent and a trivalent species (MIIMIII). Although being a member of the M1IIM2II[BP2O8(OH)] family the crystal structure of CaCo(H2O)[BP2O8(OH)]•H2O is different. Interestingly, this is the first case in the borophosphate structural chemistry where dimers of cobalt coordination octahedra together with borophosphate oligomers form a (two–dimensional) layered structure. The helical borophosphates M1II0.5M2II(H2O)2[BP2O8]•H2O (M1II0.5 = Ca, Sr, Ba; M2II = Fe, Co, Ni) contain one–dimensional infinite loop–branched borophosphate helices built of alternatively distorted borate and phosphate tetrahedra. Up to now, the group of compounds with 1[BP2O8]3– helical chain anions has been synthesized only in combination with different cations MIMII and MIII (MI = Li, Na, K; MII = Mg, Mn, Fe, Co, Ni, Zn; MIII = Sc, In, Fe). The systematic investigation on helical borophosphates of transition metals (Fe, Co, Ni) and alkaline–earth metals showed that it is also possible to accommodate divalent metal cations within the structure without disturbing the anionic partial structure. It was not possible to find the completely ordered structural model for the compounds M1II0.5M2II(H2O)2[BP2O8]•H2O (M1II0.5 = Ca, Sr, Ba; M2II = Co) but the substructure presented shows good agreement with the ordered known helical borophosphate compounds. Interestingly, it was also possible to judge the “kind of superstructure” against the crystal morphology. Syntheses of one of the few examples of borophosphates containing layered anionic partial structures (63 net topology) containing transition metal cations (Fe, Co, Ni) was realized with 6 isotypic compounds: MII(H2O)2[B2P2O8(OH)2]•H2O (MII = Fe, Co, Ni, Ni0.5Co0.5, Ni0.8Zn0.2, Ni0.5Mg0.5) The compounds MII(H2O)2[B2P2O8(OH)2]•H2O (MII = Fe, Co, Ni) adopt the structure type of Mg(H2O)2[B2P2O8(OH)2]•H2O characterized by a two–dimensional borophosphate anion. Substitution on the transition metal sites was shown to be possible (Ni0.5Co0.5) realized for this structure type. With the synthesis of Ni0.8Zn0.2(H2O)2[B2P2O8(OH)2]•H2O and Ni0.5Mg0.5(H2O)2[B2P2O8(OH)2]•H2O it was also proved that magnetically diluted samples can be prepared in analogy to Mg1–x Cox(H2O)2[B2P2O8(OH)2]•H2O (x = 0.25). The thermal stability of these compounds is very similar with a slight shift to higher decomposition temperatures for the Ni0.5Mg0.5(H2O)2[B2P2O8(OH)2]•H2O. In contrast to other borophosphates such as MIMII(H2O)2[BP2O8]∙H2O and MIII(H2O)2[BP2O8]∙H2O, it is not possible to rehydrate partially dehydrated samples even though the crystal structure may suggest this property. This shows that the aqua–ligands significantly contribute to the stability of the structure. The magnetic behavior of MII(H2O)2[B2P2O8(OH)2]•H2O (MII = Fe, Ni) corresponds well with separated 3d ions without strong magnetic interactions down to 1.8 K. Quite surprising was the remarkable change in the crystal habit that was observed during the synthesis upon addition of alkali–metal cations. Syntheses with the absence of alkali–metals lead to a change in the crystal habit by reducing of the number of faces in direction of the more simple prismatic morphology. Our research on borophosphates containing mixed transition metals led to the preparation of a borophosphate and a phosphate: FeCo(H2O)[BP3O9(OH)4], Fe1.3Co0.7[P2O7]∙2H2O The anionic partial structure of FeCo(H2O)[BP3O9(OH)4] is an open–branched tetramer built from (HO)BO3 sharing common O–corners with one (HO)PO3, one (HO)2PO2 and one PO4 group. The crystal structure is an isotype to Mg2(H2O)[BP3O9(OH)4]. Fe1.3Co0.7[P2O7]∙2H2O contains the diphosphate composed of two corner–sharing tetrahedra (isotypic to MII[X2O7]∙2H2O (MII = Mg, Mn, Co, Fe and X = P, As). However, the crystal structure of both, FeCo(H2O)[BP3O9(OH)4] and Fe1.3Co0.7[P2O7]∙2H2O, contains octahedral zigzag chains, which are interconnected by the respective tetrahedral anions. The octahedral chains in these crystal structures are closely related to the octahedral arrangements in MIIH2P2O7 (MII = Co, Ni) which exhibit a field-induced metamagnetic behavior from an antiferromagnetic state to a ferromagnetic state and to MII[BPO4(OH)2] (MII = Mn, Fe, Co) which indicate a low-dimensional antiferromagnetic correlation of the MII ions by dominant exchange interactions within the one–dimensional octahedral chain structure. Therefore, due to the similar structural features, FeCo(H2O)[BP3O9(OH)4] and Fe1.3Co0.7[P2O7]∙2H2O may exhibit interesting magnetic properties. Thermal investigation revealed that both compounds are stable until 300 ºC and transform into pyrophosphates at higher temperatures. Fe1.3Co0.7[P2O7]∙2H2O represents the first hydrated mixed divalent cation diphosphate.

Dans le cadre d’un stockage direct en milieu géologique, les actinides, et en premier lieu le plutonium, représentent l’essentiel de la radiotoxicité à long terme des combustibles nucléaires usagés. En conditions de stockage, les interactions entre les espèces silicatées présentes au sein de l’environnement et ces radioéléments pourraient fortement en impacter la mobilité et donc l’empreinte environnementale du stockage. La formation de AnSiO4 pourrait notamment jouer un rôle important, eu égard à la formation de telles phases pour le thorium et l’uranium en milieux naturels réducteurs et riches en ions silicate. La chimie associée aux phases de type AnSiO4 étant peu renseignée à ce jour, leur préparation et l’étude de leur propriétés thermodynamiques constitue un préalable essentiel afin d’évaluer leur potentielle formation en conditions de stockage.La première partie de ce travail est donc été consacrée à la préparation, en conditions hydrothermales, de ThSiO4, de USiO4 et de CeSiO4 en tant que phases analogues de PuSiO4. Cette étude a permis d’identifier les principaux paramètres expérimentaux contrôlant la formation de ces phases, d’optimiser les conditions d’obtention de solides purs et de proposer des mécanismes de formation pour chacune d’entre elles. Il est apparu que, pour l’ensemble de ces phases, la compétition entre la complexation des cations métalliques par les ions silicate et leur hydrolyse joue un rôle prédominant lors de la synthèse.Trois stratégies de synthèse ont été finalement retenues : la première a consisté à travailler en milieu faiblement acide lorsque cela s’est avéré possible, la seconde à se placer en présence d’ions complexants permettant de stabiliser les actinides à des pH favorables à la réactivité des ions silicate et la troisième à jouer sur le degré redox des ions métalliques, en se plaçant à un degré d’oxydation moins sensible à l’hydrolyse permettant de favoriser les interactions avec les ions silicate. La transposition de ces voies de synthèse à la préparation de PuSiO4 a ensuite été réalisée afin de de comparer la réactivité de Pu(IV) en milieu silicaté avec celles des différents éléments analogues considérés. / Actinides, and mainly plutonium, are the main contributors to the long-term radiotoxicity of spent nuclear fuel. In conditions representative for geological repository, the interactions between such radioelements and silicate species could influence the mobility of the actinides in the environment and thus, could affect the safety of the storage facilities. Especially, the formation of actinide silicate, AnSiO4, has to be considered carefully, since thorium and uranium silicate are ubiquitous in environmental silicate rich media and under reductive conditions. Because the chemistry of AnSiO4 is poorly known, their preparation is a prerequisite in order to determine thermodynamic data associated to their formation and to evaluate their stability under geological repository conditions.The first part of this work consisted in the preparation, under hydrothermal conditions, of ThSiO4, USiO4 and CeSiO4 as surrogates of PuSiO4. This study allowed us to determine the preponderant parameters which impact the formation of silicate phases, to establish optimized conditions for their synthesis as pure phases and then to propose potential mechanisms of formation. For all of these syntheses, the competition between the complexation of metal cations by silicate ions and their hydrolysis played a predominant role. Three different and efficient strategies have been identified for the formation of actinide silicates. The first one was characterized by the use of weakly acid reactive media to limit the hydrolysis of actinide in solution. The second involved the use of strong ligands to maintain the actinide in solution in weakly basic media. The third was developed with element oxidation states that also protected it against hydrolysis. The transposition of these strategies to the preparation of PuSiO4 allowed to determine the suitable synthesis conditions to form PuSiO4 and then to identify the differences in terms of reactivity between Pu(IV) and surrogate elements.

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Ce travail de thèse s’inscrit dans le cadre de la contribution au programme de valorisation des matériaux phosphatés et plus particulièrement, les phosphates de type alluaudite ou α-CrPO₄. Ces composés se distinguent par leurs propriétés physico-chimiques aussi variées qu’importantes et sont très convoités dans plusieurs domaines d’applications comme la catalyse et l’électrochimie.Nous avons pu isoler onze nouveaux phosphates et déterminer leur structure par la diffraction des rayons X sur monocristal.Le phosphate PbMg₃(HPO₄)(PO₄)₂ a été préparé par la méthode hydrothermale. Sa structure cristalline a été résolue dans le système monoclinique I2/m.La substitution d’un cation Mg²⁺ par un fer trivalent (Fe³) dans le composé PbMg₃(HPO₄)(PO₄)₂ a permis d’isoler cinq nouveaux composés par voie solide. Quatre phosphates de formule MMg₂Fe(PO₄)₃ (M = Ba, Sr, Pb, Ca) s’apparentent à deux types structuraux différents. Les composés contenant Sr et Ba sont de type α-CrPO₄ et cristallisent dans une maille orthorhombique de groupe d’espace Imma. Quant à ceux contenant Ca ou Pb, leur structure s’affine dans le groupe d’espace P21/n du système monoclinique. Le cinquième phosphate est de formule Ca₂MgFe₂(PO₄)₄ cristallisant dans le système monoclinique avec un groupe d’espace Pbca.Enfin, nous avons synthétisé cinq nouveaux phosphates à base de Mg, de Fe et d’élément monovalents : NaMg₃(HPO₄)2(PO₄), Na₂Mg₂Fe(PO₄)₃, Ag₁,₆₇Mg₂,₃₃Fe₀,₈₉(PO₄)₃, Na₁,₈₅Mg₁,₈₅In₁,₁₅(PO₄)₃ et Ag₁,₆₉Mg₁,₆₉In₁,₃₁(PO₄)₃, en utilisant aussi bien la méthode hydrothermale que la synthèse par voie solide. Ces phosphates cristallisent dans le système monoclinique de groupe d’espace C2/c et s’apparentent au type structural alluaudite. La poudre cristalline des phases stoechiométriques A₂Mg₂Fe(PO₄)₃ (A = Na, Ag) a été synthétisée par voie solide et caractérisée par la diffraction de rayons X sur poudre. L’étude de la conductivité en fonction de la température de ces deux composés conduit à σ = 0,12x10⁻⁴ S.cm⁻¹ pour Na₂Mg₂Fe(PO₄)₃ et à σ = 4x10⁻³ S.cm⁻¹ pour Ag₂Mg₂Fe(PO₄)₃ à 500°C. / This study is a part of contribution to the investigation program aiming to elaborate and to characterize new phosphate-based materials, particularly, with the alluaudite and/or α- CrPO₄ type structure. These compounds are characterized by their wide physico-chemical properties that they can exhibit in several fields of application such as catalysis and electrochemistry.We have isolated and determined the structure of eleven new phosphates by means of single crystal X-ray diffraction.The phosphate PbMg₃(HPO₄)(PO₄)₂ was synthesized by hydrothermal method. Its structure was resolved in monoclinic system with space group I2/m.The substitution of one cation Mg²⁺ by Fe³⁺ has allowed us to isolate five new compounds using solid-state diffusion method. Four compounds of general formula MMg₂Fe(PO₄)₃ (M = Ba, Sr, Pb, Ca) exhibit two different structural types. The Sr or Ba based compounds are related to the α-CrPO₄ type structure and crystallize with the space group Imma of the orthorhombic system. Besides, the Ca or Pb based phosphates crystallize with the P21/n space group of the monoclinic system. The fifth phase, namely Ca₂MgFe₂(PO₄)₄, crystallizes in orthorhombic system with a Pbca space group.Finally, we have succeeded to synthesize five new Mg, Fe and monovalent elements based phosphates, namely NaMg₃(HPO₄)₂(PO₄), Na₂Mg₂Fe(PO₄)₃, Ag₁,₆₇Mg₂,₃₃Fe₀,₈₉(PO₄)₃, Na₁,₈₅Mg₁,₈₅In₁,₁₅(PO₄)₃ and Ag₁,₆₉Mg₁,₆₉In₁,₃₁(PO₄)₃, using both the hydrothermal and the solid-state diffusion methods. All these phosphates crystallize in the monoclinic system with C2/c space group and are similar to the alluaudite type structural. The powder of stoichiometric compounds A₂Mg₂Fe(PO₄)₃ (A = Na, Ag) were synthesized by solid-state method and characterized by X-Ray powder diffraction. Conductivity’s studies by impedance spectroscopic method have allowed determining values for Na₂Mg₂Fe(PO₄)₃ (σ = 0.12.10⁻⁴ S.cm⁻¹ at 500°C) and for Ag₂Mg₂Fe(PO₄)₃ (σ = 4.10⁻³ S.cm⁻¹ at 500°C) due to cations migration in the channels of the structure.

Made available in DSpace on 2014-12-17T15:41:53Z (GMT). No. of bitstreams: 1 JoseABLRA_DISSERT.pdf: 2347923 bytes, checksum: 6e0dcb6d004a500ef5b9305459cc4e95 (MD5) Previous issue date: 2010-05-27 / Mesoporous molecular sieves of MCM-41 type are considered as promising support for metal in the refining processes of petroleum-based materials as catalysts and adsorbents for environmental protection. In this work, mesoporous molecular sieves MCM-41 were modified with different rare earth ions (La, Eu e Yb) for the obtaining nanostrutured materials with catalytic properties. The catalysts were synthesized by the hydrothermal method at 100oC for 120 h, presenting, all the samples, in the gel of synthesis molar ratio Si/Ln = 50. The obtained materials after calcination at 500oC for 2 h were characterized by XRD, surface area BET, TG/DTG, FTIR, and hydrothermal stability at 700?C. The XRD analysis of the catalysts indicated that the materials containing rare earth presented characteristic hexagonal structure of the mesoporous materials of the type MCM-41. The TG curves showed that the decomposition of the structural template occurs in the materials at temperatures lower than 500oC. The samples presented variations as the specific superficial area, average diameter of pores and thickness of the silica wall, as a function of the nature of the rare earth impregnated in the mesoporous material. Hydrotermal stability was evaluated through the exposition of the materials to water vapour at 700?C. The thiophene adsorptions reach a maximum at 80% of conversion and incorporation of the rare earths showed influence in the process. Adsorption capacity followed the sequence: Yb-MCM-41 < La-MCM-41 < Eu-MCM-41 < MCM-41 / As peneiras moleculares mesoporosas do tipo MCM-41 s?o consideradas promissoras como suporte para metais em processos de refino de materiais a base de petr?leo, como catalisadores e como adsorventes para prote??o ambiental. Neste trabalho a peneira molecular mesoporosa tipo MCM-41 foi modificada com diferentes terras raras (La, Eu e Yb) para a obten??o de materiais nanoestruturados com propriedades catal?ticas. Os catalisadores foram sintetizados pelo m?todo hidrot?rmico a 100 oC por 120 horas, apresentando, todas as amostras, no gel de s?ntese raz?o molar Si/Ln = 50. Os materiais resultantes, ap?s calcina??o a 500 oC por 2 horas, foram caracterizados por: DRX, ?rea superficial pelo m?todo de BET, TG/DTG, FTIR e testes hidrot?rmicos a 700oC. As an?lises de DRX dos catalisadores indicaram que os materiais contendo as terras raras apresentaram estrutura hexagonal caracter?stica do material mesoporoso tipo MCM-41. As curvas TG mostraram que a decomposi??o do direcionador estrutural ocorre nos materiais em temperaturas inferiores a 500oC. As amostras apresentaram varia??es quanto ? ?rea superficial espec?fica, di?metro m?dio de poros e espessura da parede de s?lica, em fun??o da natureza da terra rara impregnada no material mesoporoso. A estabilidade hidrot?rmica foi avaliada atrav?s da exposi??o dos materiais a vapor d ?gua a 700oC. A adsor??o de tiofeno atingiu valores m?ximos de 80% e a incorpora??o das terras raras influenciaram no processo. A ordem crescente de capacidade de adsor??o seguiu a seguinte seq??ncia: Yb-MCM-41 < La-MCM-41 < Eu-MCM-41 < MCM-41

Made available in DSpace on 2014-12-17T15:42:17Z (GMT). No. of bitstreams: 1 EdjaneFBS_TESE.pdf: 3916289 bytes, checksum: c86ba6653bacd96524384f5ddbd3741b (MD5) Previous issue date: 2012-08-03 / Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico / Nanostructured materials have been spreading successfully over past years due its size and unusual properties, resulting in an exponential growth of research activities devoted to nanoscience and nanotechnology, which has stimulated the search for different methods to control main properties of nanomaterials and make them suitable for applications with high added value. In the late 90 s an alternative and low cost method was proposed from alkaline hydrothermal synthesis of nanotubes. Based on this context, the objective of this work was to prepare different materials based on TiO2 anatase using hydrothermal synthesis method proposed by Kasuga and submit them to an acid wash treatment, in order to check the structural behavior of final samples. They were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), adsorption/desorption of N2, thermal analysis (TG/DTA) and various spectroscopic methods such as absorption spectroscopy in the infrared (FT-IR), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). All the information of characterizations confirmed the complete conversion of anatase TiO2 in nanotubes titanates (TTNT). Observing the influence of acid washing treatment in titanates structure, it was concluded that the nanotubes are formed during heat treatment, the sample which was not subjected to this process also achieved a complete phase transformation, as showed in crystallography and morphology results, however the surface area of them practically doubled after the acid washing. By spectroscopy was performed a discussion about chemical composition of these titanates, obtaining relevant results. Finally, it was observed that the products obtained in this work are potential materials for various applications in adsorption, catalysis and photocatalysis, showing great promise in CO2 capture / Materiais nanoestruturados t?m se difundido com sucesso ao longo dos ?ltimos anos, isso devido ao seu tamanho e propriedades incomuns, resultando em um crescimento exponencial das atividades de investiga??o dedicadas ? nanoci?ncia e nanotecnologia, o que tem estimulado a procura por diferentes m?todos que possam controlar as principais propriedades dos nanomateriais a fim de adequ?-los para aplica??es de alto valor agregado. No final da d?cada de 90 um m?todo alternativo e de baixo custo foi proposto a partir da s?ntese hidrot?rmica alcalina de nanotubos. Baseando-se nesse contexto, o objetivo deste trabalho foi preparar diferentes materiais ? base de TiO2 anatase utilizando o m?todo de s?ntese hidrot?rmica proposto por Kasuga e submet?-los em seguida a um tratamento de lavagem ?cida, com o prop?sito de verificar o comportamento estrutural das amostras finais. Essas foram caracterizadas por difratometria de raios X (DRX), microscopia eletr?nica de varredura (MEV), microscopia eletr?nica de transmiss?o (MET), adsor??o/dessor??o de N2, an?lise t?rmica (ATG/ATD) e diferentes m?todos espectrosc?picos como, espectroscopia de absor??o na regi?o do infravermelho (FT-IR), espectroscopia Raman e espectroscopia fotoeletr?nica de raios X (XPS). O conjunto de caracteriza??es se complementou, confirmando a transforma??o completa do TiO2 anatase de partida em titanatos nanotubulares (TTNT). Ao observar a influ?ncia que o tratamento de lavagem ?cida exerce na estrutura do mesmo, conclui-se que os nanotubos s?o formados durante o tratamento t?rmico, pois a amostra que n?o foi submetida ao processo tamb?m alcan?ou uma transforma??o completa de fase, conforme os resultados de cristalografia e morfologia, entretanto a ?rea espec?fica deles ? praticamente dobrada ap?s a lavagem ?cida. Por espectroscopia foi realizada uma minusiosa discuss?o acerca da composi??o qu?mica desses titanatos, obtendo resultados relevantes. Por fim, ressalta-se que os produtos obtidos nesse trabalho s?o materiais com potencial para diferentes aplica??es em adsor??o, cat?lise e fotocat?lise, se mostrando promissores na captura do CO2

Novel open-framework germanates and vanadoborates, which are constructed from typical types of clusters, have been synthesized based on different strategies. The crystal structures are solved by using single crystal X-ray diffraction (SXRD) technique or by combined techniques. Additionally, the structures of two open-framework materials, PKU-3 and PKU-16, are determined from nano-sized crystals by rotation electron diffraction (RED) combined with powder X-ray diffraction (PXRD). This thesis serves as an introduction to synthesis of open-framework germanates and vanadoborates based on different design strategies. Two germanates are obtained; SU-74 is achieved by employing a novel structure directing agent (SDA), SUT-8 is achieved by assembling the novel structure building units (SBUs) of Co@Ge14 with the introduction of cobalt ions in the synthesis. Four strategies are successfully used in construction of open-framework vanadoborates: using metal-oxo polyhedra as the linkages in SUT-6; applying the scale chemistry approach in SUT-7; employing metal-organic complexes as the linkages in SUT-12, SUT-13, SUT-14; and introducing covalent bond organic linkages into SUT-10 and SUT-11. Single crystal X-ray diffraction is used to conduct the structure determination in combination with other techniques. Furthermore, the structures of two open-framework materials, an aluminoborate PKU-3 and a germanosilicate PKU-16, are solved from nano-sized crystals using RED data. The structures are further confirmed by Rietveld refinement against PXRD data. The advantages of the RED techniques are demonstrated in two aspects. In PKU-3, the presence of seriously preferred orientation and light elements in the structure makes it difficult for structure determination by PXRD, but it is easier by RED. In PKU-16, the RED technique is used to determine its structure from the as-synthesized multi-phasic sample containing nano-sized crystals. After the structure of PKU-16 has been solved, the synthesis of this interesting phase can be optimized and pure PKU-16 can be obtained. Keywords: Open-framework, germanates, vanadoborates, aluminoborates, germanosilicates, crystal structure, hydrothermal synthesis, single crystal X-ray diffraction, rotation electron diffraction, powder X-ray diffraction