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Through the sol–gel process, using the so-called neutral amine route, spherical particles of 1:1 zirconia–titania were synthesized from zirconium(IV) and titanium(IV) butoxides as well as 1,12-diaminododecane as precursor species. The obtained product exhibited a hexagonal structure, as determinated by X-ray diffraction data. The obtained material was also characterized by thermogravimetry, differential scanning calorimetry, infrared spectroscopy, scanning electron microscopy, and surface area measurements. Despite the release of template molecules on heating, the spherical morphology was retained up to about 1200°C, at which the disruption of the spheres took place. 相似文献
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This communication reports the first intercalation into VOPO4·2H2O performed through a solid-state reaction at room temperature. Ethyleneurea, EU (2-imidazolidone) was intercalated into the oxovanadium phosphate by grinding in a mortar stoichiometric amounts of both reagents at room temperature for 30 min. C, H and N elemental analyses of the obtained intercalation compound gave the formula VOPO4·(EU)·H2O. The profile of the absorption bands due to the VOPO4 lattice vibration around 1000 cm−1 was retained after reaction, providing evidence that an intercalation compound and not merely a salt of V-P-O species was produced. For α-VOPO4·2H2O, the interlayer distance is 0.75 nm, whereas for the EU inter-calation compound it is 0.95 nm. The obtained SEM micrographs show that the microstructure of VOPO4·2H2O is changed after reaction, with a total exfoliation of the oxovanadium matrix. 相似文献
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Thermogravimetric (t.g.) and differential scanning calorimetric (d.s.c.) data have been used to study metal–amino acid interactions in adducts of general formula MnCl2 · ngly (gly = glycine, n = 0.7, 2.0, 4.0 and 5.0). All the prepared adducts exhibit only a one step mass loss associated with the release of glycine molecules, except for the 0.7gly adduct, which exhibits two glycine mass loss steps. From d.s.c. data, the enthalpy values associated with the glycine mass loss can be calculated: MnCl2 · 0.7gly = 409 and 399 kJ mol–1, MnCl2 · 2.0gly = 216 kJ mol–1, MnCl2 · 4.0gly = 326 kJ mol–1 and MnCl2 · 5.0gly = 423 kJ mol–1, respectively. The enthalpy associated with the ligand loss, plotted as function of the number of ligands for the n = 2.0, 4.0 and 5.0 adducts, gave a linear correlation, fitting the equation: H (ligand loss)/kJ mol–1 = 67 × (number of ligands, n) + 76. A similar result was achieved when the enthalpy associated with the ligand loss was plotted as a function of the
a(COO–) bands associated with the coordination through the carboxylate group, 1571, 1575 and 1577 cm–1, respectively, for the n = 2.0, 4.0 and 5.0 adducts, giving the equation H (ligand loss) /kJ mol–1 = 33.5 ×
a(COO–) /cm–1 – 52418.5. This simple equation provides evidence for the enthalpy associated with the ligand loss being very closely related to the electronic density associated with the metal–amino acid bonds. 相似文献
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de Farias Robson Fernandes Martínez Leandro Airoldi Claudio 《Transition Metal Chemistry》2002,27(7):748-750
This paper describes the synthesis, characterization and a thermogravimetric (t.g.) study of 11 adducts of general formula MCl2·nL (M = Cu, Co and Sn; n = 1 and 2 for Sn, and 2 for Cu and Co; L = ethyleneurea eu, ethylenethiourea etu, and propyleneurea pu). The i.r. results shows that the eu and pu adducts are coordinated through oxygen, whereas for etu nitrogen is the coordination site. The (C=O) or (C=S) trend is: Cu > Co > Sn. The t.g. curves show that the adducts release ligand molecules in a single mass loss step. As regards considering adducts with the same stoichiometry, the observed thermal stability trend is: etu > pu > eu. 相似文献
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de Farias RF de Souza JM de Melo JV Airoldi C 《Journal of colloid and interface science》1999,212(1):123-129
The effects exhibited by adsorbed conducting polyaniline on the redox process on a molybdenum oxide surface were studied. Thermogravimetric results indicate a 4% polyaniline deposition. Cyclic voltammograms of the adsorbed polymer on MoO3 show that polyaniline exerts remarkable effects on the molybdenum blue oxidation-reduction process, with oxidation and reduction potentials of 0.33 and 0.18 V, respectively. This effect strongly enhances the electrode response, and can be used as an important tool in qualitative and/or quantitative determinations of molybdenum in solution as well as in any substrate. Copyright 1999 Academic Press. 相似文献