Sunteti invitati sa participati la seminarului stiintific de miercuri, 16.03.2016, ora 11:00 din Sectia Laseri care va cuprinde prezentarea D-lui Andrei Rotaru cu titlul:“ Kinetics of Heterogeneous Processes of Materials: Fundaments and Advances ”
Abstract
Kinetics of heterogeneous processes is a useful tool for bringing a better understanding to the complexity of materials coming backwords from their behaviour towards their structure and composition. Generally, complex/composite materials are composed of more chemical groups or compounds which undergo parallel processes when subjected to a certain temperature regime; therefore understanding their thermal behaviour is not a simple task. We have designed a software package, TKS-SP, which contains a multitude of possibilities for performing the kinetic analysis of various thermally induced processes that are monitored by thermal analysis equipment. Recently reported, the advanced linear local kinetic methods of Tang&Chen and Ortega consider the activation energy to be constant on a restricted range of conversion degree (the temperature integral is defined on a fixed interval of conversion degree).
However, the first model-free kinetic method of this type was proposed by Popescu, but is an isothermic linear method rather than an isoconversional linear one; later, Vyazovkin has proposed the same procedure for an isoconversional method, but this time of non-linear type. By using this approach, the values obtained by these methods will describe a continuous curve when they will be defined on conversion ranges that are big enough to avoid local experimental fluctuations; in particular, the case of biomass and coals is discussed, eventual fluctuations relating to the chosen Δα chosen value and to the complexity of the local environment at the “moment” of the investigation. Precise values for the kinetic parameters, even though in some cases regarded as global ones, are useful for comparing origin of various fuels and for designing burning reactors. When employing precursors for thin films, the kinetic analysis enhances the understanding of decomposition mechanisms for obtaining functional materials and inspires the thermal processing of the films. A combined methodology for discriminating the true kinetic model is proposed. The historical purpose of kinetics was not forgotten: predicting the behaviour of materials in other conditions than the experimental ones (short or long) and ultimately, characterising the lifetime of materials.
