Thermal gravimetric (TG) and differential thermal (DTA) analyses were performed to characterize the thermal behavior and the
stoichiometry of uranyl bis-1,3-diketonate complexes (R1COCR2COR3)2 UO2x H2O, where R1,3=CH3; C2H5; C6H5; CF3; pNO2−C6H4; pCl−C6H4; pMe−C6H4; NH−C6H5; R2=H, C6H5 andx=1; 2. Based on the data obtained, a thermal degradation mechanism for each complex was proposed. The final degradation product
for all studied complexes was U3O8 oxide. The temperature of the first organic fragment rupture including the U-O (ligand) bond was taken as criterion for the
thermal stability of the metal-oxygen donor bond in these complexes. The observed stability order is in good agreement with
the IR determined constant force values,k, of the U-O (ligand) bond.
Vitreous solder glasses, such as Mansol #40 and FEG-2002, are commercialized solder glasses, which are compression sealing
glasses that can be used to solder materials with expansions between 55-68⊙10-7C-1, such as Al2O3.
In order to understand and tailor the thermal behaviour of solder glasses, cylindrical-like glasses were first carefully ground
with a stainless steel mortar and pestle. Initially, no exothermic or endothermic data were obtained from the DTA/DSC curves
except those relating to melting. However, exothermic peaks appeared after the glass samples were re-melted. In this work,
kinetic parameters such as the activation energy, and the morphology of the devitrification mechanisms for two kinds of solder
glasses were also investigated, using non-isothermal DTA techniques. The activation energies ranged from 220 to 235 kJ mol-1 and the devitrification mechanism parameters were close to 1. This indicates that the devitrification mechanisms of the two
kinds of solder glasses involve surface nuclei.
Authors:A. La Ginestra, P. Patrono, A. Frezza, C. Mancini, M. Massucci, and S. Vecchio
Pure and mixed Ge and Sn hydrogenphosphates, prepared either by refluxing in 8M H3PO4 or by hydrothermal treatment at 180° or 300°C, have been characterized in terms of chemical composition and thermal behaviour
and also tested as catalysts in the 1-butene isomerization, in order to correlate acidic properties with preparation method.
Solid solutions for every composition in this system are formed only when using the refluxing method, as proved by X-ray and
TG-DTA data. The hydrothermal treatments are strongly influenced by the hydrolysability of the Ge phosphate: in almost all
the samples, where Ge was present, GeOHPO4 was identified on TG-DTA curves by the endothermic H2O weight loss at 700°–800°C. The acidic properties of the various materials decrease as GeOHPO4 content increases.
Authors:M. Teodorovic, Lj. Majdanac, D. Cosic, and V. Nesovic
In this work the thermal characteristics of cellulose samples with different structure were investigated. The samples were prepared by reacting the cellulose with ethanolic hydroxide solution. Depending on the time of alkaline treatment, the intensity of cellulose transformation differed. Starting from cellulose I structure, with the highest degree of crystallinity, the other samples consisted of mixed structures of cellulose I and II, or were completely transformed to cellulose II structure with the lowest degree of crystallinity. The thermal behaviour of the samples was studied by using a Perkin Elmer TGS-2 and DSC-2 instruments. The kinetic parameters of dehydration and degradation were determined from non-isothermal TG-data (Nitrogen-inert atmosphere and a heating rate of 20 deg/min). The thermal effects of water evolution (heating rate of 80 deg/min) of the cellulose samples were found to depend on the structural characteristics and the crystallinity of the samples. The activation energy and frequency factor were in correlation with the structural changes.
The technique of heat flow calorimetry was used to study the thermal behaviour of different carbohydrates between 20°C and 270°C. The samples were analyzed by heating in sealed cells. The temperature range in which exothermic reactions, due to thermal decomposition, occurred varied widely depending on the type of carbohydrate investigated. Reaction enthalpies of 44 sugars and polysaccharides are given. Endothermic phenomena, such as fusion or vaporization of crystallized water, were also observed: fusion temperatures and enthalpies of 34 sugars and sugar alcohols are listed. Calorimetric curves showing crystallization of amorphous sucrose, cellobiose and lactose are also presented.
Authors:Ramón Piloto Rodríguez, Leonardo Goyos Pérez, Marlen Alfonso, Milagros Duarte, Rinaldo Caro, Jonas Galle, Roger Sierens, and Sebastian Verhelst
tested in this paper will be named as derived FAEE, as ethanol was used in the chemical synthesis.
The purpose of this study is to evaluate and compare the thermalbehavior and oxidative stability of two different species and plantations of
In the previous study, it was observed that the stability of nitrocellulose (NC) cannot be determined by thermal analyses
such as differential scanning calorimetry (DSC) at heating rates of 1–10 K/min. This was because the thermal curves of NC
samples with different stabilities could not be distinguished from one another. In this study, we explain why such thermal
analyses cannot be used to evaluate the thermal stability of NC and identify the conditions under which thermal analyses can
be used for this purpose. We investigated the effect of heating rate on the thermal behavior of pure NC and NC stabilized
with diphenylamine (DPA) or akarditeII (AKII), which is a conventional stabilizer, by using the heat flux calorimeter (C80).
At high heating rates (0.2–0.3 K/min), only single exothermic peak was observed in the thermal curves of both pure NC and
NC/DPA and the thermal curve of pure NC was practically similar to that of NC/DPA. At low heating rate (0.02 K/min), two exothermic
peaks were observed for both pure NC and NC/DPA. The heat amount of the first peak depended on the partial pressure of O2 in the atmosphere. The first peak in the thermal curve of NC/DPA was slightly suppressed as compared to that of pure NC.
These results indicate that the stability of NC probably depends on the first exothermic peak that represents oxidation of
NC by atmospheric O2. From this, on the thermal analyses at high heating rates, thermal curves of pure NC and NC/DPA could not be distinguished
from one another. This is because the decomposition of NC itself occurs in the second exothermic peak before the oxidation
of NC by atmospheric O2 in the first peak, which is attributed to the stability of NC. The results of the thermal analyses under isothermal conditions
at 393 K in an O2 atmosphere revealed that the induction period of NC/DPA and NC/AKII was longer than that of pure NC. From these results,
it is speculated that the stability of NC can be evaluated by thermal analyses carried out under O2-rich conditions at low heating rates.
Authors:Renato Vessecchi Lourenço, Marcelo Kobelnik, Clóvis Augusto Ribeiro, and Fernando L. Fernonani
biocatalyst and sludge material to be processed due in large bacterial activity, allows a greater organic load and higher conversion rates of organic matter into biogas [ 7 ].
In this study, we report on the thermalbehavior of the aerobic UASB and
Authors:Marcelo Kobelnik, Douglas Lopes Cassimiro, Diógenes dos Santos Dias, Clóvis Augusto Ribeiro, and Marisa Spirandeli Crespi
. Recently, we evaluated the thermal characterization of jerivá oil, but were not observed the similar thermalbehavior like here reported [ 9 ]. Nevertheless, the jerivá oil showed varied fatty acids composition, while the araça oil has predominantly only
Authors:Marisa S. Crespi, Quézia V. Martins, Sonia de Almeida, Hernane S. Barud, Marcelo Kobelnik, and Clóvis A. Ribeiro
]. Here, we studied the first five, since some of them have great economic value and possible use as an energy source, or because of the higher potential for environmental pollution from the large amounts produced. We evaluated the thermalbehavior of