The influence of thermal process for indium hydroxoformate, In(OH)(HCO2)2, used as one of the precursor material of ITO transparent conducting films, has been successfully investigated in some controlled
atmospheres by unique thermal analyses equipped with a humidity generator, which are thermogravimetry - differential thermal
analysis (TG-DTA), thermogravimetry in conjunction with evolved gas analysis using mass spectrometry (TG-MS) and simultaneous
measurement of differential scanning calorimetry and X-ray diffractometry (XRD-DSC). The thermal process in dry gas atmosphere
by linear heating experiment was indicated through a single-step reaction between 200 and 300C, while the thermal process
in the atmosphere of controlled humidity proceeded through two-step reactions and the formation of crystalline indium oxide
(In2O3) was effectively promoted and completed at the lower temperatures with introducing water vapor in the atmosphere. The thermal
process changed dramatically by introducing water vapor and was quite different from that in dry gas atmosphere. Pure In2O3 was synthesized in inert atmosphere of controlled humidity and could be easily formed at temperatures below 260C. The XRD-DSC
equipped with a humidity generator revealed directly the crystalline change from In(OH)(HCO2)2 to In2O3 and the formation of the intermediate during the thermal decomposition. A detailed thermal process of In(OH)(HCO2)2 and the effect of heating atmosphere are discussed.
The emanation method and the method of surface labelling have been applied to study thermal processes. Using these methods,
processes which are not connected with thermal effects can be analysed. In certain cases, for example in the study of poorly
crystalline, or amorphous phases, these methods are even more sensitive than thermographic and X-ray techniques. The method
of surface labelling is advantageous in cases when it is impossible to activate the samples by the parent isotope of the gas
during the process of their preparation.
Solid-state thermal processes have their own specificity, distinguishing them from the processes in gases and liquids. This specificity includes, among others, their limited reversibility and the limited or modified role of chemical affinity as the main driving force indicating the direction of real solid-state processes. The consequency is the formation of metastable compounds or phases during heating, as intermediate steps towards the state of thermodynamic equilibrium. They are a results of the particular properties of the rigid internal structure of minerals and materials as the thermal reaction medium. The peculiarities of thermal reactions of solids are presented on the example of those of oxides (silicates and borates) with polymeric structures. The significance of crystal-chemical factors for the prediction or explanation of the course of high-temperature processes, as complementing the thermodynamic factors, is discussed.
The thermal stability of a polypropylene copolymer has been examined at several stages during the processing of the material
into its final product in order to obtain information on the influence of processing steps such as grinding and thermal heating
on the expected lifetime of the material. Mass loss kinetics in an inert atmosphere were able to detect differences in thermal
stability, but oxidative differential scanning calorimetry studies proved to be a more sensitive techiique. A comparative
study of a specially prepared series of samples revealed the importance of additives on measured thermal stability and indicated
that both mechanical and thermal processing can cause reduction in measured thermal stability.
Authors:E. Araújo, Renata Barbosa, Crislene Morais, L. Soledade, A. Souza, and Moema Vieira
Nanocomposites containing both polyethylene and montmorillonite clay organically modified with four different types of quaternary
ammonium salts were obtained via direct melt intercalation. Thus, the main purpose of this work was to evaluate the effect
of the organoclay on the thermal stability of polyethylene. The organoclays were characterized by XRD, FTIR, DSC and TG. The
polyethylene/organoclay nanocomposites were studied by XRD, TEM, TG, besides an evaluation of their mechanical properties.
The results showed that the salts were incorporated by intercalation between the layers of the organoclay and, apparently
that the nanocomposites were more thermally stable than pure polyethylene.