The Effect Of The Conditions Of The Treatment Of Gel On The Crystallinity Of The Layered Compound Zirconium (iv) Bis(phosphite)

The conditions of treatment of gels obtained by the reaction of Zr4+ and H3PO3 with the formation of layered compound Zr(HPO3)2. nH2O are analyzed. An increase of the degree of crystallinity with the molar ratio H3PO3/Zr4+ was observed. For conditions where the ratio is < 5:1 the X-ray patterns indicate that a non-crystalline material is formed. The FTIR spectra show that the P-H stretching mode (∼2460 cm-) is very sensitive to the organization of the layers. The temperature and time of gel treatment also increases the degree of crystallinity. The combination of these parameters allows us to modulate the crystallinity of this material. © 1990.1211-398103 IEEE Computer Society,West Virginia UniversityPublisher: IEEE Computer SocietyClearfield, (1984) J. Molec. Catal., 27, p. 251Alberti, Costantino, (1984) J. Molec. Catal., 27, p. 235Clearfield, (1982) Inorganic Ion Exchange Materials, , CRC Press, Boca Raton, FLWittingham, Jacobson, (1982) Intercalation Chemistry, , Academic Press, New YorkAvduevskaya, Mironova, (1970) Neorg. Mat., 6, p. 391Dines, DiGiacomo, (1981) Inorg. Chem., 20, p. 92Alberti, Costantino, Perego, (1986) J. Solid State Chem., 63, p. 455Elving, Olson, (1955) Anal. Chem., 27, p. 1817Bernhardt, Wreath, Colorimetric Determination of Phosphorus by Modified Phosphomolybdate Method (1955) Analytical Chemistry, 27, p. 440Clearfield, Thomas, (1969) Inorg. Nucl. Chem. Lett., 5, p. 775Clearfield, Smith, (1969) Inorg. Chem., 8, p. 431Tsuboi, (1957) J. Am. Chem. Soc., 79, p. 1351Garrido, (1989) MS thesis, , UNICAM

Preparation Of Zr(iv)/nb(v) Nasicon-like Phosphates By A Sol-gel Method - Code: Dp21

The NbZr(PO4)3 and Na0.5Nb0.5Zr1.5(PO4)3 Nasicon-like phases were prepared by the sol-gel method using (NH4)3 [NbO(C2O4)3]·1.5H2O, ZrOCl2·8H2O and NH4H2PO4 in oxalic or tartaric acid mediums. The thermal evolution of the xerogels prepared was followed by XRD and IR techniques. Depending on reaction conditions, such as, pH and Zr4+/organic acid ratio, pure Nasicon-like phases can be prepared at different temperatures. © 1994 Kluwer Academic Publishers.21-342142

Synthesis And Hyperfine Interactions Of The Amine Intercalates Of Feocl

Some amine derivatives were intercalated into the van der Waals gap of layered compound FeOCl. These compounds were characterized by X-ray powder diffraction and Mössbauer spectroscopy. The isomer shift and the quadrupole splitting are characteristic of the high-spin ferric iron. The magnetic structure of FeOCl was affected by intercalation of amine molecules in the interlayer region of FeOCl. The magnetic hyperfine field in the low temperature is larger in the intercalates than it is in unintercalated FeOCl. The sign of the EFG tensor at the iron atom is dependent of the type of amine intercalated. © 1991 J.C. Baltzer A.G. Scientific Publishing Company.661-427928

Ionic Conductivity And Structural Characterization Of Na1.5nb0.3zr1.5(po4)3 With Nasicon-type Structure

The NASICON-type Na1.5Nb0.3Zr1.5(PO4)3 was prepared by solid state reaction of Nb2O5 and the precursor γ-NaHZr(PO4)2 at 700°C. The EPR spectra showed a signal with a g factor of 1.984 assigned to Nb (IV) species in octahedral oxygen environments. The X-ray powder diffraction pattern obtained with monochromatic radiation was indexed on the basis of a rhombohedral cell, the hexagonal parameters being aH = 8.8061(2) and cH = 22.7638(7) Å. The Na+ ion conduction was measured by the complex impedance method (frequency range: 0.1-105 Hz; temperature range: 20-500°C) on four pellets previously sintered at 450, 750, 900 and 1000°C. The conductivity data are discussed in relation to the sintering temperature. An activation energy of 0.60 eV for the movement of Na+ ions in the NASICON framework has been found.10001/02/15127134Goodenough, J.B., Hong, H.Y.-P., Kafalas, J.A., (1976) Mat. Res. Bull., 11, p. 203Hagman, L., Kierkegaard, P., (1968) Acta Chem. 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Microbiologia do solo no ensino médio de Lavras, MG

Os microrganismos realizam processos imprescindíveis para a sustentabilidade dos ecossistemas e para a vida no planeta; apesar disso, a sociedade de modo geral ignora esse papel e os considera apenas do ponto de vista de patógenos. Este trabalho foi realizado com os objetivos de analisar o conteúdo sobre os microrganismos do solo nos livros didáticos de Biologia adotados nas escolas de ensino médio de Lavras, MG; caracterizar estudantes e professores de três escolas desta cidade; e avaliar a percepção sobre Microbiologia do Solo de 334 estudantes do ensino médio dessas escolas após a apresentação do assunto em diversos formatos atrativos (palestras, workshops e aulas práticas). A coleta de dados, a priori e posteriori, foi realizada por questionários; avaliou-se ainda a viabilidade de trabalhar esse conteúdo no ensino médio. Apesar da importância dos microrganismos do solo, os materiais didáticos para o ensino de Biologia no ensino médio os abordam superficialmente e não destacam sua relevância nos contextos agrícola e ambiental. Após apresentação do assunto, houve diferenças significativas na percepção por estudantes das escolas tanto públicas como privadas. Concluiu-se ser possível ensinar e melhorar esse conteúdo da disciplina de Biologia por meio de recursos acessíveis e constatou-se a necessidade de levar os avanços científicos conhecidos na universidade para atualizar o ensino médio