Metal complexes of calcium with 5,7-dibromo, 7-iodo and 5-chloro-7-iodo-8-hydroxyquinolate were precipitated in aqueous ammonia
and acetone medium, except for the solid state compound with 5,7-dichloro-8-hydroxyquinoline which hasn"t been obtained under
these conditions. The complexes obtained through the mentioned precipitation are Ca[(C9H4ONBr2)2]3H2O, Ca[(C9H5ONI)2]2H2O and Ca[(C9H4ONICl)2]2.5H2O. Their intermediate from the thermal decomposition found through TG/DTA curves in air indicated the presence of different
kinds of calcium carbonates related to the reversibility and crystalline structure, depending on the original compounds. The
initial compounds and the intermediate from the thermal decomposition were also characterized through IR spectra and X-ray
Authors:C. Guerreiro, C. Ribeiro, M. Crespi, and C. Torres
Magnesium ion was reacted with 5,7-dibromo-, 5,7-dichloro-, 7-iodo-and 5-chloro-7-iodo-8-hydroxyquinoline, in acetone/ammonium
hydroxide medium under constant stirring to obtain (I) Mg[(C9H4ONBr2)2]2H2O; (II) Mg[(C9H4ONCl2)2]3H2O; (III) Mg[(C9H5ONI)2]2H2O and (IV)Mg[(C9H4ONICl)2]2.5H2O complexes. The compounds were characterized by elemental analysis, IR spectra, ICP, TG-DTA and DSC.
Through thermal decomposition residues were obtained and characterized, by X-ray diffractometry, as a mixture of hexagonal
MgBr2 and cubic MgO to the (I) compound at 850C; cubic MgO to the (II), (III) and (IV) compounds at750, 800 and 700C, respectively.
Authors:C. Guerreiro, C. Ribeiro, M. Crespi, and C. Torres
Strontium complexes of 5,7-dibromo-, 5,7-dichloro-, 7-iodo- and 5-chloro-7-iodo-8-hydroxyquinoline were precipitated from
an aqueous ammonia and acetone medium. The complexes obtained were Sr[(C9H4ONBr2)2]2.5H2O; Sr[(C9H4ONCl2)(OH)]1.5H2O; Sr[(C9H5ONI)2]5H2O and Sr[(C9H4ONICl)(OH)]1.25H2O. The residues of their thermal decomposition were SrBr2; a mixture of SrCl2, SrCO3 and SrO; SrCO3 and SrCO3, respectively. All were characterized by means of thermogravimetry, differential thermal analysis, complexometry with EDTA,
atomic absorption spectroscopy, IR spectroscopy and X-ray diffraction.
Crystalline PbTiO3 was obtained through the thermal decomposition of 8-hydroxyquinolinate of lead(II) and that of titanium(IV), which was monitored
by TG/DTG/DTA under different atmospheric conditions and with varying heating rates. The compound was prepared from adding
8-hydroxyquinoline solution in the solution of metallic ions Pb(II):Ti(IV) (1:1) under constant stirring at 3C, having the
pH adjusted to 10. The results of these investigations show that different thermal behavior related to the precursor occurred
and also the consequent formation of residues which have different crystallinities. No carbonate residues from the thermal
decomposition could be determined by XRD and IR. Only PbTiO3 was observed and confirmed by DSC at 470C, temperature lower than the tetragonal-cubic transition.
Fluoride glasses have been extensively studied due to their high transparency in the infrared wavelength. The crystallization
kinetics of these systems has been studied using DTA and DSC techniques. Most of the experimental data is frequently investigated
in terms of the Johnson-Mehl-Avrami (JMA) model in order to obtain kinetic parameters. In this work, DSC technique has been
used to study the crystallization of fluorozirconate glass under non-isothermal conditions. It was found that JMA model was
not fit to be applied directly to these systems, therefore, the method proposed by Mlek has been applied and the Šestk-Berggren
(SB) model seems to be adequate to describe the crystallization process.
Authors:C. Ribeiro, M. Crespi, C. Guerreiro, and L. Guinesi
In this present work, barium ion was reacted with different ligands which are 5,7-dibromo 5,7-dichloro, 7-iodo and 5-chloro-7-iodo-8-hydroxyquinoline,
in acetone/ammonium hydroxide medium under constant stirring and the obtained compounds were as follows: (I) Ba[(C9 H4 ONBr2 )2 ]⋅1.5H2 O; (II) Ba[(C9 H4 ONCl2 )(OH)]⋅1H2 O; (III) Ba[(C9 H5 ONI)2 ]⋅1H2 O and (IV) Ba[(C9 H4 ONICl)2 ]⋅5H2 O, respectively. The compounds were characterized by elemental analysis, infrared absorption spectrum (IR), inductively coupled
plasma spectrometry (ICP), simultaneous thermogravimetry-differential thermal analysis (TG-DTA) and differential scanning
The final residue of the thermal decomposition was characterized as orthorhombic BaBr2from (I); the intermediate residue, as a mixture of orthorhombic BaCO3 and BaCl2 and cubic BaO and the final residue, as a mixture of cubic and tetragonal BaO and orthorhombic BaCl2 (II); the intermediate residue, as orthorhombic BaCO3 and as a final residue, a mixture of cubic and tetragonal BaO from (III); and the intermediate residue, as a mixture of orthorhombic
BaCO3 and BaCl2 and as a final residue, a mixture of cubic and tetragonal BaO and orthorhombic BaCl2 from (IV).
Authors:C. Ribeiro, M. Crespi, L. Guinesi, C. Guerreiro, and H. Zorel
Tin(II) complexes with 8-hydroxyquinolinate in solid state have been obtained by adding aqueous ammonium to a solution containing
stannous chloride and 8-hydroxiquinoline in medium of HCl and acetone up to pH 5 and 9, respectively. The products obtained
show the same composition, Sn(C9H6ON)2; however there are some differences regarding both the thermal behaviour in an oxidant atmosphere and morphology. These products
were characterised by elemental and complexometric analysis, TG and DTA curves, infrared and X-ray diffractometry. TG curves
show, above 448 K, the partial oxidation on air atmosphere of Sn(II) complexes to Sn(IV) complexes, SnO(C9H6ON)2. This behaviour does not depend only on pH in which the compounds were obtained but also on the heating rate in TG curves.
Sn(II) complexes volatilise almost completely on nitrogen atmosphere and partially on air atmosphere depending on the oxidation
degree of the compound.
Authors:A. Adorno, M. Guerreiro, C. Ribeiro, and C. Guerreiro
The influence of additions of 2, 4, 6, 8, 10 and 12 mass% Ag on the thermal behavior of the Cu–8 mass% Al alloy was studied
using differential scanning calorimetry (DSC), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX)
and X-ray diffractometry (XRD). The results indicate that the presence of silver introduces new thermal events, due to the
formation of a silver-rich phase and, for additions of 10 and 12 mass% Ag, it is possible to verify the formation of the γ1 phase (Cu9Al4) and the metastable transitions which are only observed in alloys with a minimum of 9 mass% Al.
Authors:M. Ribeiro da Silva, C. Santos, M. Monte, and C. Sousa
MPa) molar enthalpies of formation, ΔfHm0, for
crystalline phthalimides: phthalimide, N-ethylphthalimide
and N-propylphthalimide were derived from
the standard molar enthalpies of combustion, in oxygen, at the temperature
298.15 K, measured by static bomb-combustion calorimetry, as, respectively,
– (318.01.7), – (350.12.7) and – (377.32.2)
kJ mol–1. The standard molar enthalpies of
sublimation, ΔcrgHm0, at T=298.15
K were derived by the Clausius-Clapeyron equation, from the temperature dependence
of the vapour pressures for phthalimide, as (106.91.2) kJ mol–1
and from high temperature Calvet microcalorimetry for phthalimide, N-ethylphthalimide and N-propylphthalimide
as, respectively, (106.31.3), (91.01.2) and (98.21.4)
The derived standard molar enthalpies of formation,
in the gaseous state, are analysed in terms of enthalpic increments and interpreted
in terms of molecular structure.