Authors:E. Milaré, J. Turquetti, G. Souza, A. Benedetti, and F. Fertonani
Thermogravimetry (TG), cyclic
voltammetry (CV) and other analytical techniques were used to study the reactions
of mercury with Pt–30% Ir alloy. The results allowed to suggest that
an electrodeposited mercury film interacts with the substrate and when subjected
to heat or electrochemical removal at least four mass loss steps or five peaks
appeared during the mercury desorption process. The first two steps were attributed
to Hg(0) removal probably from the bulk and from the adsorbed monolayer which
wets the electrode surface. These two processes are responsible for peaks
D and F in the cyclic voltammograms. The last two peaks (G, H) in CV were
ascribed to the intermetallic compound decomposition. In TG curves, the last
two steps were attributed to the PtHg4 (third step),
and PtHg2 decomposition followed by Hg removal from
the subsurface. The PtHg2 was formed by an eutectoide
reaction: PtHg→PtHg2+Hg(Pt–Ir). The Hg diffused
to the subsurface was not detectable by cyclic voltammetry.
Authors:F. Fertonani, E. Milaré, A. Benedetti, and M. Ionashiro
Thermogravimetry, cyclic voltammetry and other analytical techniques were used to study the reactions of mercury with pure
iridium. The results allowed to suggest when subjected to heat or anodic stripping voltammetry an electrodeposited mercury
film reacts with Ir substrate and at least three mass loss steps and three peaks appear in the mercury desorption process.
The first two were attributed to Hg(0)species removal like a mercury bulk and a mercury monolayer. The last can be ascribed
to the mercury removal from a solid solution with iridium.
Authors:E. Milaré, F. Fertonani, A. Benedetti, and M. Ionashiro
Thermogravimetry (TG) and other analysis techniques (EDX, SEM, Mapping surface, X-ray diffraction, inductively coupled argon
plasma emission spectroscopy and atomic spectrometry with cold vapor generation) were used to study the reaction of Hg with
Rh. The results permitted the suggestion that, when subjected to heat, an electrodeposited Hg film reacts with Rh to form
intermetallic products with different stabilities, as indicated by at least three mass loss steps. In the first step, between
room temperature and 160C, only the bulk Hg is removed. From this temperature up to about 175C, the mass loss can be attributed
to the desorption of a film of metallic Hg. The last step, from 175 to 240C, can be ascribed to the removal of Hg from a
thin dark film of RhHg2 .
Authors:G. Souza, I. Pastre, A. Benedetti, C. Ribeiro, and F. Fertonani
Thermogravimetry, Differential Scanning Calorimetry and other analytical
techniques (Energy Dispersive X-ray Analysis; Scanning Electron Microscopy;
Mapping Surface; X-ray Diffraction; Inductively Coupled Plasma Atomic Emission
Spectroscopy and Cold Vapor Generation Atomic Absorption Spectroscopy) have
been used to study the reaction of mercury with platinum foils. The results
suggest that, when heated, the electrodeposited Hg film reacts with Pt to
form intermetallic compounds each having a different stability, indicated
by at least three mass loss steps. Intermetallic compounds such as PtHg4,
PtHg and PtHg2 were characterized by XRD. These intermetallic
compounds were the main products formed on the surface of the samples after
partial removal of bulk mercury via thermal desorption. The Pt(Hg) solid solution
formation caused great surface instability, attributed to the atomic size
factor between Hg and Pt, facilitating the acid solution’s attack to
Authors:A. Moitinho, E. Ionashiro, G. de Souza, and F. Fertonani
Solid-state M-EDTA chelates, where M represents the divalent ions Mg(II), Ca(II), Sr(II) or Ba(II) and EDTA is ethylenediaminetetraacetate
anion, were synthesized. Thermogravimetry, derivative thermogravimetry (TG, DTG), differential scanning calorimetry (DSC)
and X-ray diffraction powder patterns have been used to characterize and to study the thermal behaviour of these chelates.
The results provided information concerning the stoichiometry, crystallinity, thermal stability and thermal decomposition.
Authors:M. Kobelnik, Giseli Bernabé, C. Ribeiro, J. Capela, and F. Fertonani
Non-isothermal decomposition of iron (III)-diclofenac anhydrous salt was investigated by thermogravimetry (TG) under different
conditions in opened and closed α-alumina pans under nitrogen atmosphere. To estimate the activation energy of decomposition,
the Capela and Ribeiro isoconversional method was applied. The results show that due to the lid cover different activation
energies were obtained. From these curves a tendency can be seen where the plots maintain the same profile for closed lids
and almost run parallel to each other. Independently of the different experimental conditions no remarkably different results
have been obtained.
Authors:G. Fontanari, J. Batistuti, G. Bannach, I. Pastre, E. Ionashiro, and F. Fertonani
The guava seed protein isolate (PI) was obtained
from the protein precipitation belonging to the class of the gluteline (Ip
4.5). The conditions for the preparation of the PI were determined by both
the solubility curve and simultaneous thermogravimetry-differential thermal
analysis (TG-DTA): pH 11.5, absence of NaCl and whiteners and T=(253)C.
Under these conditions a yield of 77.00.4%, protein content of 94.20.3,
ashes 0.500.05% and thermal stability, T=200C,
were obtained. The TG-DTA curves and the PI emulsification capacity study
showed the presence of hydrophobic microdomains at pH 11.5 and 3.0 suggesting
a random coil protein conformation and, to pH 10.0, an open protein conformation.
The capacity of emulsification (CE), in the absence of NaCl, was verified
for: 1 – pH 3.0 and 8.5, using the IP extracted at pH 10.0 and 11.5,
CE≥3435 g of emulsified oil/g of protein; 2 – pH 6.60 just
for the PI obtained at pH 11.5, CE≥1408 g of emulsified oil/g of
Authors:I. Pastre, I. do Nascimento Oliveira, A. Moitinho, G. de Souza, E. Ionashiro, and F. Fertonani
The composite montmorillonite-8-hydroxyquinoline (Swy-1-8-HQ) was prepared by two different processes and studied by using
thermogravimetric analysis (TG/DTG and DSC), as well as helpful techniques as fluorescence in the UV-visible region and X-ray
diffraction. The composites developed fluorescent appearance, however with quantum poor efficiency and they exhibited distinct
TG and DSC thermal behavior. The fluorescence data of spectra associated to the TG/DT curves allowed to suggest that the 8-HQ
was present in the composites in two different circumstances: 1 - intercalated in the interlayer spaces (Swy-1-8-HQ2), rigidly
associated to the substrate feasible as a monolayer with the aromatic rings parallel to the silica layer; and/or, 2 - adsorbed
on the surface (Swy-1-8-HQ1), either as a bilayer formation or tilting of the molecules to the silicate layer sheet. All results
confirmed above are in agreement with X-ray diffraction patterns, once the interlayer space increases when 8-HQ is incorporated.
The experimental results confirm the formation of the composites in agreement with the method used in the preparation.
Authors:G. Fontanari, G. Souza, J. Batistuti, V. Neves, I. Pastre, and F. Fertonani
Glutelin, the major protein fraction from guava seed, was obtained by fractioning as described by Osborne. The total proteins
were extracted and the isolates obtained by isoelectric precipitation presented similar DSC curves, concordant with the results
obtained by gel filtration chromatography and electrophoresis in polyacrylamide gel (PAGE-SDS). However, the DSC curves showed
a higher enthalpy with regard to the denaturing protein isolate (PI) extracted at pH 10.0 when compared to a PI at pH 11.5.
Such results are in accordance with those obtained for PI extracted at pH 10.0 using chromatography, this one being present
in the form of molecular aggregates of greater molecular mass. The glutelin fraction, however, did not present a denaturation
peak in the DSC curve, showing that the process for obtaining the same significantly altered its conformation.