Obtaining advanced oxide thin films at low temperatures by chemical methods. Thermal analysis of thin films

Abstract

L'objectiu d'aquest treball és analitzar mètodes químics de baix cost com a ruta per a sintetitzar òxids avançats a baixa temperatura. En particular, hem explorat l'SHS per a la síntesi d'un òxid catalitzador fent servir pólvores de ciano complexes heteronuclears. També hem explorat el transport de calor per a sintetitzar capes via VCS concloent que les capes primes rarament experimentaran una combustió. Per això hem analitzat la condició necessària per que tingui lloc una combustió volumètrica en una mostra sòlida que reacciona sense intercanvi de gasos amb el seu entorn. Per fer-ho, hem ampliat el criteri de Frank-Kaminetskii per a sistemes d'escalfament continu i per a reactors cilíndrics. Per la part experimental em fet servir tècniques l'anàlisi tèrmica (TA). Hem desenvolupat un mètode per a mesurar la conductivitat tèrmica en pólvores per DSC. Finalment, hem desenvolupat dos criteris per a comprovar la fiabilitat en la mesura de la temperatura als experiments de TA.

The aim of this work is to analyse chemical methods as a route to synthesise advanced oxides at low cost and low temperatures. In particular, we have explored the combustion synthesis of a catalytic perovskite-type oxide from heteronuclear cyano complex powders. We have also explored heat transfer to synthesise films via VCS and concluded that thin films will hardly experience combustion. In particular, we have analysed the conditions needed for a thermal explosion to occur in a solid sample reacting without any gas exchange with its surroundings. For that purpose, we have extended the Frank-Kamenetskii relationship to continuous heating systems and to cylindrical reactors. The experimental component of this work is based on thermal analysis methods (TA). We have developed a new method to measure thermal conductivity of powders by DSC. Finally, we have developed two analytical relationships to check the reliability of the sample temperature in TA experiments.