Authors:M. Badea, R. Olar, D. Marinescu, and G. Vasile
This paper reports the
investigation of the thermal stability of a series of new complexes with mixed
ligands of the type M(dipy)(C3H3O2)2(H2O)y ((1) M: Mn, y=1; (2) M: Ni, y=2; (3) M: Cu, y=1; (4) M: Zn, y=2; dipy: 2,2’-dipyridine and C3H3O2
is acrylate anion). The thermal behaviour steps were investigated. The thermal
transformations are complex processes according to TG and DTG curves including
dehydration, oxidative condensation of acrylate and thermolysis processes.
The final products of decomposition are the most stable metal oxides.
The thermal behaviour
of 2- and 4-biphenylmethanol were studied by differential scanning calorimetry
(DSC). It was found that the 2-isomer shows a relatively strong resistance
to crystallisation, and that it easily vitrifies on cooling. Oppositely, 4-biphenylmethanol
readily crystallizes on cooling. The slow molecular mobility of 2-biphenylmethanol
in the amorphous solid state was studied by DSC and by thermally stimulated
depolarisation currents (TSDC). Both techniques indicate that 2-biphenylmethanol
is a relatively strong glass-former, with a fragility index of ~50 in
the Angell's scale.
In order to obtain a better understanding of thermal substituent effects in 1,2,4-triazole-3-one (TO), the thermal behavior
of 1,2,4-triazole, TO, as well as urazole and the decomposition mechanism of TO were investigated. Thermal substituent effects
were considered using thermogravimetry/differential thermal analysis, sealed cell differential scanning calorimetry, and molecular
orbital calculations. The onset temperature of 1,2,4-triazole was higher than that of TO and urazole. Analyses of evolved
decomposition gases were carried out using thermogravimetry–infrared spectroscopy and thermogravimetry–mass spectrometry.
The gases evolved from TO were determined as HNCO, HCN, N2, NH3, CO2, and N2O.
Authors:D. Malferrari, Maria Franca Brigatti, Angela Laurora, L. Medici, and S. Pini
The thermal behavior
of montmorillonite and organically modified montmorillonite, both treated
with heavy metal cations [Cu(II), Cd(II) and Hg(II)], was characterized via
thermal analyses (TG, DTG and DTA) combined with evolved species gas mass
spectrometry (MS-EGA), and X-ray diffraction at in situ controlled temperature
(HTXRD). The reactions involving Cu(II)- and Cd(II)-montmorillonite samples
are mostly related to H2O and OH loss, unlike Hg(II)-montmorillonite,
where effects associated to Hg(II) loss are also present. Finally reactions
related to dehydration, dehydroxylation and to organic matter decomposition
can be observed in montmorillonite samples treated with cysteine.
The mono- and di-imines of some diaminonaphthalenes were prepared using a solid solid reaction technique. Their structures were studied using elemental analysis, infrared and electronic spectra. The thermal behaviour of the obtained compounds and their solid solid preparation reactions have also been studied. The energies of activation as well as the reaction orders of those reactions were determined.
Authors:G. Gusmano, P. Nunziante, E. Traversa, and G. Chiozzini
The thermal behaviour of hydroxide mixtures aimed at Mg-Al spinel preparation is reported. The mixtures of hydroxides were prepared by precipitation reaction from Mg and Al nitrate solutions, stoichiometric to the spinel formation. Hydroxide mixtures with different phase distributions were investigated, prepared by varying the precipitation procedure. The results were related to the thermal behaviour of mechanical mixtures of separately precipitated hydroxides. The spinel formation was identified performing XRD analysis on powder samples heated at different temperatures. The coprecipitated mixtures are completely decomposed to spinel at 400‡C. The presence of the Mg-Al mixed hydroxide phase in the mixture is of primary concern to get spinel at low temperatures.
Authors:I. Rudjak, T. Kaljuvee, A. Trikkel, and V. Mikli
The thermal behaviour of ammonium nitrate (AN) and its prills coated with limestone and dolomite powder was studied on the
basis of commercial fertilizer-grade AN and six Estonian limestone and dolomite samples. Coating of AN prills was carried
out on a plate granulator and a saturated solution of AN was used as a binding agent. The mass of AN prills and coating material
was calculated based on the mole ratio of AN/(CaO + MgO) = 2:1. Thermal behaviour of AN and its coated prills was studied
using combined TG-DTA-FTIR equipment. The experiments were carried out under dynamic heating conditions up to 900 °C at the
heating rate of 10 °C min−1 and for calculation of kinetic parameters, additionally, at 2, 5 and 20 °C min−1 in a stream of dry air. A model-free kinetic analysis approach based on the differential isoconversional method of Friedman
was used to calculate the kinetic parameters. The results of TG-DTA-FTIR analyses and the variation of the value of activation
energy E along the reaction progress α indicate the complex character of the decomposition of neat AN as well as of the interactions
occurring at thermal treatment of AN prills coated with limestone and dolomite powder.
Authors:V. Balek, H. Hamerská, L. Montanaro, and A. Negro
The results of the investigations of thermal behaviour of Li2ZrO3, prepared in the amorphous state by means of sol-gel technique are demonstrated. The thermal treatment was carried out in air under constant heating rate of 5 deg·min−1 and cooling rate of 2.5 deg·min−1. The methods of DTA, TG, Emanation Thermal Analysis (ETA) and dilatometry were used, for characterization of the thermal behaviour in dynamic conditions. The X-ray diffraction patterns were used for characterization of the phase changes observed by TA Methods.
Authors:Irina Catta Preta, Solange Sakata, G. Garcia, J. Zimmermann, F. Galembeck, and Claudia Giovedi
(PAN) polymers are used as precursors for carbon fiber production. This process
requires an oxidative stabilization step, which can be studied by differential
scanning calorimetry (DSC). In this sense, thermal behavior of PAN based terpolymers
by different polymerization processes, compositions and itaconic acid concentrations
in the reaction media were investigated. The obtained results showed that
the addition of itaconic acid and methyl acrylate as comonomers resulted a
lower heat flow during the process comparing to the PAN homopolymer. It suggested
that these comonomers aid the oxidative stabilization stage for all studied
process. The redox system polymerization at 40C resulted in a lower heat
flow. Itaconic acid decreases slightly initial and peak temperatures of the
terpolymer and heat flow until concentration of 3y. The cyclization temperature
decreases when MAis incorporated into the terpolymer compared to the MMA terpolymer
and increases when MAA is the acidic monomer. Among terpolymers the AN/MA/AA
polymer showed the best thermal behavior for carbon fiber producing.