Synthesis, thermal behavior and spectroscopic study of trivalentlanthanide and yttrium(III) α-hydroxyisobutyrates, in solid state

Thermal and spectroscopic studies on solid trivalent lanthanides and yttrium(III) α-hydroxyisobutyrates, Ln(C4H7O 3)3·nH2O were investigated employing simultaneous thermogravimetry and differential thermal analysis (TG-DTA), elemental analysis, X-ray diffractometry, complexometry, experimental and theoretical infrared spectroscopy and TG-DSC coupled to FTIR. The dehydration of lanthanum to neodymium and terbium to thulium and yttrium compounds occurs in a single step while for samarium, europium and gadolinium ones it occurs in three consecutives steps. Ytterbium and lutetium compounds were obtained in the anhydrous state. The thermal decomposition of the anhydrous compounds occursin two consecutives steps, except lanthanum (five steps) and cerium (single step), with formation of the respective oxides CeO2, Pr6O 11, Tb4O7 and Ln2O3 (Ln = La, Nd to Lu and Y), as final residue. The resultsalso provided information concerning the composition, thermal behavior, crystallinity and gaseous products evolved during the thermal decomposition. The theoretical and experimental spectroscopic data suggested the possible modes of coordination of the ligand with the lanthanides.© 2013 Elsevier B.V.

Synthesis, structural characterization and photophysical properties of highly photoluminescent crystals of Eu(III), Tb(III) and Dy(III) with 2,5-thiophenedicarboxylate

Lanthanide compounds of general formula [Ln2(2,5-tdc) 3(dmf)2(H2O)2] ·2dmf·H2O (Ln = Eu(III) (1), Tb(III) (2), Gd(III) (3) and Dy(III) (4), dmf = N,N′-dimethylformamide and 2,5-tdc2- = 2,5-thiophedicarboxylate anion) were synthesized and characterized by elemental analysis, X-ray powder diffraction patterns, thermogravimetric analysis and infrared spectroscopy. Phosphorescence data of Gd(III) complex showed that the triplet states (T1) of 2,5-tdc2- ligand have higher energy than the main emitting states of Eu(III), Tb(III) and Dy(III), indicating that 2,5-tdc2- ligand can act as intramolecular energy donor for these metal ions. An energy level diagram was used to establish the most relevant channels involved in the ligand-to-metal energy transfer. The high value of experimental intensity parameter Ω2 for the Eu(III) complex indicate that the europium ion is in a highly polarizable chemical environment. The emission quantum efficiency (η) of the 5D0 emitting level of Eu(III) was also determined. The complexes act as possible light conversion molecular devices (LCMDs). © 2013 Elsevier B.V. All rights reserved.

Studies on thermal-oxidative degradation behaviours of raw natural rubber: PRI and thermogravimetry analysis

Thermal-oxidative degradation behaviours of raw natural rubber (NR) have been investigated by using thermogravimetry analysis in inert and oxidative atmospheres and the plasticity retention index (PRI). The activation energy E a, was calculated using Horowitz-Metzger and Coats-Redfern methods and compared with PRI. The E a values obtained by each method were in good agreement with each other. The June samples are the least stable rubbers among the studied ones, whereas February samples exhibited the highest values of activation energy, therefore in agreement with the PRI behaviour, which indicates that the thermo-oxidative stability of the June samples are the poorest during the thermo-oxidative degradation reaction. Natural rubber is a product of biological origin, and thus these variations in the values of thermal behaviour and PRI might be related to the genetic differences and alterations of climatic conditions that act directly on the synthesis of non-rubber constituents, which are generally reflected in latex and rubber properties. © 2013 Institute of Materials, Minerals and Mining.

Characterization of natural rubber/gold nanoparticles SERS-active substrate

Natural rubber/gold nanoparticles membranes (NR/Au) were studied by ultrasensitive detection and chemical analysis through surface-enhanced Raman scattering and surface-enhanced resonance Raman scattering in our previous work (Cabrera et al., J. Raman Spectrosc. 2012, 43, 474). This article describes the studies of thermal stability and mechanical properties of SERS-active substrate sensors. The composites were prepared using NR membranes obtained by casting the latex solution as an active support (reducing/establishing agents) for the incorporation of colloidal gold nanoparticles (AuNPs). The nanoparticles were synthesized by in situ reduction at different times. The characterization of these sensors was carried out by thermogravimetry, differential scanning calorimetry, scanning electron microscopy (SEM) microscopy, and tensile tests. It is suggested an influence of nanoparticles reduction time on the thermal degradation of NR. There is an increase in thermal stability without changing the chemical properties of the polymer. For the mechanical properties, the tensile rupture was enhanced with the increase in the amount of nanoparticles incorporated in the material. © 2013 Wiley Periodicals, Inc.

Pesquisa e desenvovimento de novos materiais microporosos e mesoporosos para uso em ressonância magnética nuclear por imagem como agentes de contraste

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Otimização das condições de síntese de amostras cerâmicas do composto Y'Ba IND. 2''Cu IND. 3''O IND. 7'-δ através do Método Pechini

Pós-graduação em Ciência e Tecnologia de Materiais - FC

Avaliação das propriedades mecânicas e químicas em função de diferentes cimentos resinosos e pinos não-metálicos

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Propriedades analíticas de materiais a base de sílica e óxido de titânio modificados

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Síntese e caracterização de blendas de polianilina com látex de borracha natural

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Propriedades de materiais nanoestruturados do sistema epoxídico DGEBA/TETA modificado com um éster de silsesquioxano

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Desenvolvimento de revestimentos híbridos do sistema siloxano-PMMA com aplicações anticorrosivas

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Preparação de espuma cerâmica à base de zircônia pelo processo sol-emulsão-gel

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Impactos no meio físico da bacia hidrográfica do Córrego das Almas, Pouso alegre (MG): subsídios para a educação ambiental

Pós-graduação em Geociências e Meio Ambiente - IGCE

Caracterização de compositos de matrizes poliméricas reforçadas com fibra de sisal e de vidro

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Caracterização química, física e térmica de pellets de madeira produzidos no Brasil

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)