Preparation and thermal decomposition of solid state lanthanide(III) and yttrium(III) chelates of ethylenediaminetetraacetic acid

Solid state chelates of general formula H[Ln(EDTA)] · nH2O (Ln = trivalent lanthanide (except for promethium) or yttrium; EDTA = ethylenediaminetetraacetate) were prepared. Thermogravimetry, differential thermal analysis. X-ray diffraction and complexometry were used to characterize and study the thermal stability and thermal decomposition of these compounds. © 1993.

Production and Characterization of β-glucosidase Obtained by the Solid-State Cultivation of the Thermophilic Fungus Thermomucor indicae-seudaticae N31

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

The preparation and thermal decomposition of some metal compounds of 4-dimethylaminobenzylidenepyruvate in the solid state

Solid M-DMBP compounds, where M represents Mg(II), Ca(II), Sr(II), Ba(II), Ni(II), Cu(II), Zn(II), Fe(III), La(III), Th(IV), and DMBP is 4-dimethylaminobenzylidenepyruvate, have been prepared. Thermogravimetry-derivative thermogravimetry (TG-DTG), differential scanning calorimetry (DSC) and other methods of analysis have been used to characterize and to study the thermal stability and thermal decomposition of these compounds. © 1995.

Solid-state compounds of 2-methoxybenzylidenepyruvate with some bivalent metal ions - Synthesis, characterization and thermal behavior studies

Solid-state M-2-MeO-BP compounds, where M represents bivalent Mn, Fe, Co, Ni, Cu, Zn and 2-MeO-BP is 2-methoxybenzylidenepyruvate have been synthesized. Simultaneous thermogravinietry-differential thermal analysis (TG-DTA), differential scanning calorimetry (DSC), X-ray powder diffractometry, infrared spectroscopy, elemental analysis and complexometry were used to characterize and to study the thermal stability and thermal decomposition of these compounds. The results led to information about the composition, dehydration, crystallinity and thermal decomposition of the isolated compounds.

The preparation and thermal decomposition of solid state compounds of 4-dimethylaminobenzylidenepyruvate and trivalent lanthanides and yttrium

Solid state Ln-DMBP compounds, where Ln represents trivalent lanthanides (except for promethium) and yttrium, and DMBP is 4-dimethylaminobenzylidenepyruvate, were prepared. Thermogravimetry (TG), differential thermal analysis (DTA), and other methods of analysis were used to characterize and to study the thermal stability and thermal decomposition of these compounds. © 1993.

Production of α-amilase by solid state fermentation by Rhizopus oryzae

A thermotolerant strain of Rhizopus oryzae was grown in three agro-industrial by-products: brewers’ rice, corn grits and wheat bran. Different substrates, cultivation time, moisture content, additional nitrogen sources, pH and temperature of incubation were evaluated aiming to optimize growing conditions. The highest enzymatic activity was observed after 24 h of cultivation using wheat bran as substrate with the following salt solutions: NH4NO3, MgSO4.7H2O and (NH4)2SO4 0.1% at temperature of 35°C. It was observed that changes in the pH range 4.0-6.0 did not significantly affect α-amylase activity. The optimum operation conditions were 75°C and pH 4.5. The enzymes remained stable at 75°C in the absence of substrate for 25 min.

Análise da resposta dielétrica e varistora de compostos cerâmicos multifásicos à base de Ca2CU2Ti4-xSnxO12 (0,0 < x< 4,0)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Estabilização da fase perovskita e propriedades estruturais de filmes finos relaxores do sistema PLZT

Pós-graduação em Ciência dos Materiais - FEIS

Estudo das propriedades ópticas de pós cerâmicos à base de Zn3Ga2Ge2O10: X% Cr3+ (X = 0 ; 0,5 ; 0,75 ; 1,0)

Ceramic powders based on Zn3Ga2Ge2O10: Cr3+ X% (X = 0.0; 0.5; 0.75; 1.0) were synthesized by solid-state reaction method. The gallium-zinc germanate doped with chromium presents an interesting property of phosphorescence, that means, it is capable of emitting light when excited by a source of radiation, and such emission remains for some time after stopping the source. For this reason, these materials can be widely applied in night-vision surveillance, (through the use of solar energy, for example), electronic devices screen, emergency routes signals, control panels indicators in dark environments, etc. In this job were considered different amounts of dopant in order to perform a comparison of structural and photoluminescent properties. For that, some analyses were performed on samples, such as XRD, FT-Raman, SEM, UV-vis and photoluminescence measurements (PL). Such analysis allowed to infer that the presence of chromium results in no phase transformation, so that the four compositions have the same set of phases: cubic, rhombohedral and hexagonal. Although the structure was not changed, chromium influences other properties / characteristics of these materials. Examples are: increase of band-gap, decrease of average particle size, small changes in binding energy checked by Raman and especially the increase of photoluminescent property. The chromium ions have great ease in replacing gallium ions in octahedral sites, resulting in emission of light with a wavelength of about 700 nm (infrared region), which is justified by the spin-forbidden 2E 4A2 transition. In other words, chromium is a favorable luminescent center, acting as a trap in the crystal structure, since it imprisons the excitation energy easily and releases it gradually, allowing the phosphorescence. It was observed that the composition ... (Complete abastract click electronic access below)

Dielectric and impedance properties of Nd3/2Bi3/2Fe5O12 ceramics

The polycrystalline sample of Nd3/2Bi3/2Fe5O12 was prepared by a high- temperature solid-state reaction technique. Preliminary X-ray structural analysis exhibits the formation of a single-phase tetragonal structure at room temperature. Microstructural analysis by scanning electron microscopy shows that the sintered sample has well defined grains. These grains are distributed uniformly throughout the surface of the sample. Detailed studies of dielectric response at various frequencies and temperatures exhibit a dielectric anomaly at 400 A degrees C. The electrical properties (impedance, modulus and conductivity) of the material were studied using a complex impedance spectroscopy technique. These studies reveal a significant contribution of grain and grain boundary effects in the material. The frequency dependent plots of modulus and the impedance loss show that the conductivity relaxation is of non-Debye type. Studies of electrical conductivity with temperature demonstrate that the compound exhibits Arrhenius-type of electrical conductivity. Study of ac conductivity with frequency suggests that the material obeys Jonscher's universal power law.

IMPEDANCE CHARACTERISTICS of La3/2Bi3/2Fe5O12 CERAMICS

Polycrystalline La3/2Bi3/2Fe5O12 (LBIO) compound was prepared by a high-temperature solid-state reaction technique. The complex impedance of LBIO was measured over a wide temperature (i.e., room temperature to 500 C) and frequencies (i.e., 10(2)-10(6) Hz) ranges. This study takes advantage of plotting ac data simultaneously in the form of impedance and modulus spectroscopic plots and obey non-Debye type of relaxation process. The Nyquist's plot showed the presence of grain effects in the material at high temperature. The ac conductivity spectrum was found to obey Jonscher's universal power law. The dc conductivity was found to increase with rise in temperature. The activation energy of the compound was found to be 0.24 and 0.51 eV in the low and high-temperature region, respectively, for conduction process.

Structural and dielectric properties of relaxor Sr0.5Ba0.5Bi2Nb2O9 ceramic

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

Microwave-hydrothermal synthesis of perovskite bismuth ferrite nanoparticles

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Schottky-type grain boundaries in CCTO ceramics

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