Search

Kinetic data, for example, activation energy and reaction order, are crucial for the understanding of chemical reactions and processes. Here, we describe a novel method for obtaining kinetic data based on thermogravimetric measurements (TGA) that exploits in each measurement multiple successive isothermal steps (SIS). We applied this method to the notoriously challenging carbon combustion process for vastly different carbons for oxygen molar fractions between 1.4 % and 90 %. Our obtained apparent EA values are within the wide range of results in the literature and vary in a systematic way with the oxygen partial pressure. The improved accuracy and large amount of obtainable data allowed us to show that the majority of experimentally obtained apparent data for apparent EA are neither in a kinetic regime nor in a diffusion‐controlled one but rather in a transition regime. [ABSTRACT FROM AUTHOR]

Abstract: Nanocrystallized ceria-based coatings were prepared on TA6V titanium alloy by using a three-step procedure: substrate pre-treatment, electrochemical impregnation and final heat treatment. UV–vis and Raman in situ spectroscopies performed at the substrate interface during the electrochemical impregnation, showed experimentally for the first time that the interfacial deposit is made up of cerium hydroxide, incorporating also water molecules and nitrate ions coming from the electrolyte. Thermogravimetric analysis indicated also that the composition of the coating after the impregnation is given by the global formula CeO2·3.4H2O, while XRD analysis revealed that ceria with cubic fluorite crystalline structure is finally produced. Different preparation conditions were studied in view to control the nanosize of the supported ceria crystallites. It appeared that the final heat treatment is the most efficient operational parameter for the tuning of the particle size, that it can be thus well controlled from 5 to 30nm between 300 and 700°C. [Copyright &y& Elsevier]

Titelbild: Thermal Oxidation of Carbonaceous Nanomaterials Revisited: Evidence of Mechanism Changes (Angew. Die Ergebnisse deuten darauf hin, dass die chemische Reaktion bei der Kohlenstoffverbrennung noch lange nicht verstanden wurde, was auf spannende weitere Studien hindeutet. Die Ergebnisse deuten darauf hin, dass die chemische Reaktion bei der Kohlenstoffverbrennung noch lange nicht verstanden wurde, was auf spannende weitere Studien hindeutet. [Extracted from the article]