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.
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.
In this work the influence of Ag additions on the thermal behavior of the Cu-11 mass% Al alloy was studied using differential
scanning calorimetry, in situ X-ray diffractometry and scanning electron microscopy. The results indicated that changes in
the heating rate shift the peak attributed to α phase formation to higher temperatures, evidencing the diffusive character
of this reaction. The activation energy value for the α phase formation reaction, obtained from a non-isotherm kinetic model,
is close to that corresponding to Cu atoms self diffusion, thus confirming that this reaction is dominated by Cu atoms diffusion
through the martensite matrix.
Authors:S. Sajadi, A. Alamolhoda, and S. Hashemian
Using two techniques of thermogravimetry and differential scanning calorimetry under O2 gas atmosphere from 25 to 600°C, the thermal behavior of laboratory-produced compound lead(IV) oxide α-PbO2 was investigated. The identity of products at different stages were confirmed by XRD technique. Both techniques produced
similar results supporting the same decomposition stages for the compound. Three distinct energy changes were observed, namely,
two endothermic and one exothermic in DSC. The amount of ΔH for each peak is also reported.
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.
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: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.
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: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.