Lanthanum oxide (La2O3) is of great interest as catalyst material. When La2O3 particles are prepared from lanthanum hydroxide (La(OH)3) by thermal processes under air, various oxycarbonate phases are formed which are resistant to thermal hydroxylation. This phenomenon has not yet been extensively investigated, even though oxycarbonate phases at the particle surfaces cause a change in lanthanum oxide's catalytic activity. The carbonate phases formed cannot be detected by means of XRD or REM-EDX investigations due to their detection limits. Thermal analysis, particularly TG-FT-IR, allows not only for the detection of the carbonate phases in La(OH)3, but also for the tracking of the entire dehydration process from La(OH)3 via LaOOH to La2O3 as well as the correct interpretation of mass changes during the thermal transformations. Pursuant to the investigations here carried out, it was determined that carbonate-free lanthanum hydroxide compounds can only be prepared and stored in a CO2-free protective gas atmosphere (e.g., argon).
Authors:Fatma I. Khattab, M. M. Amer, and Nagiba Y. M. Hassan
Some sulphonamides are evaluated by means of thermal analysis. Use is made of their characteristic endothermic DTA peaks (melting peaks), where the area changes linearly with variations in the amount of sulphonamides. The method is suitable for the determination of 30–100 mg of sulphathiazole, sulphisomidine, sulphaguanidine, sulphacetamide sodium and sulphamethoxypyridazine with reasonable accuracy. As for sulphisoxazole, two peaks are used for its determination: an endothermic one to determine 30–100 mg, and an exothermic one to determine 6–30 mg.
Arylazohydroxynaphthoic acids of general formula were subjected to thermal analysis. The decomposition temperatures of the compounds were found to be determined by the resonance and inductive interaction of substituent R with the benzene ring and the azo group of the arylazohydroxynaphthoic acid molecule. The results of DTG analysis correspond with the HammetσH constants. The mechanism of thermal splitting is briefly discussed.
reported to show that there is a reduction in Ca(OH) 2 content [ 14 ]. Little is known however, in terms of the effect thereafter and that no full investigation of the system have been found using both thermogravimetric and differential thermalanalysis
The thermal behaviour of some antiallergic drugs belonging to different groups of antihistaminics, such as phenyltoloxamine, chlorpromazine, clemizole and meclozine was examined. Thermogravimetry, derivative thermogravimetry and differential thermal analysis curves were used for the elucidation of the mechanisms of thermal decomposition. The melting temperatures of the compounds and their thermal stabilities were determined. The stability was found to decrease in the order: clemizole > chlorpromazine > meclozine > phenyltoloxamine.
Differential thermal analysis and thermogravimetry have been carried out on oligoamidophosphates with established plastifying and anti-ignition effects, which contained various amounts or bound phosphorus, had different molecular masses, and were obtained on the basis of epsilon-caprolactam, oligo- or polycaproamide. The ranges of thermal stability were determined and some differences between the combustion mechanisms of the starting polycaproamide and the oligoamidophosphates were shown. A probable mechanism of the anti-ignition action of the latter is proposed.
Authors:Elena Badea, Lucreţia Miu, P. Budrugeac, Maria Giurginca, A. Mašić, Nicoleta Badea, and G. Della Gatta
A comprehensive investigation has been made of a set of 14th to 16th-century parchment bookbindings from the Historical Archives of the City of Turin. Advanced physico-chemical techniques, such
as thermal analysis (DSC, TG and DTA), spectroscopy (FTIR and UV-Vis-NIR), scanning electron microscopy (SEM) and unilateral
nuclear magnetic resonance (NMR-ProFiler) were employed to assess specific deterioration processes occurring at different
levels in the hierarchical structure of parchment. Changes in the measured physical and chemical parameter values of parchment
due to interaction with the environment were used to identify possible deterioration pathways.
By using reactive atmospheres, the area of application of thermal analysis is expanded considerably to cover many aspects of high temperature research into fuels, extractive metallurgy, materials and catalysts. This article reviews the design of apparatus and its application in kinetic and thermodynamic studies involving atmospheres such as H2, CO, N2, NH3, CO2, H2O, SO2or3, H2S, S2, Cl2, HO, F2 and HF at low or high pressures and as low pressure plasmas. Apart from gas-solid reactions, the important influence of a controlled product gas atmosphere on decomposition reactions is discussed also. Gas-solid adsorption and solubility studies are not included.
Authors:A. d’Almeida, D. Barreto, V. Calado, and J. d’Almeida
The thermal behavior of four unusual lignocellulose fibers — namely Caroa, Curaua, Piassava and Sponge gourd — is described.
Caroa and Curaua fibers showed a more homogeneous thermal degradation, with a single peak dominating in the DTG curve. Piassava
and Sponge gourd showed two separated peaks, revealing the more pronounced amounts of hemicellulose present at these fibers.
All four fibers are, however, thermally stable up to temperatures of around 200°C. The activation energies for the thermal
degradation of the fibers were similar, except for the Caroa fiber. The lower activation energy associated to this fiber was
attributed to its higher hemicellulose to cellulose ratio.
Authors:J. J. H. Lancastre, F. M. A. Margaça, L. M. Ferreira, A. N. Falcão, I. M. Miranda Salvado, M. S. M. S. Nabiça, M. H. V. Fernandes, and L. Almásy
, the thermal behaviour of the prepared materials, as well as their microstructure, were studied by thermalanalysis, X-ray diffraction and small-angle neutron scattering (SANS) in the present work.