Lamellar structure versus pyrochlore structure: preparation of the compounds 'H IND.1-x' 'Ag IND.x' 'Ta' W'O IND.6' and intercalation/insertion reactions of linear amines

Author(s)

Marco Aurelio Culhari De Santis

• Document type: Master's Dissertation
• Press: Campinas, SP.
• Institution: Universidade Estadual de Campinas (UNICAMP). Instituto de Química
• Defense date: 2006-05-29

Examining board members

Oswaldo Luiz Alves; Jivaldo do Rosario Matos; Ricardo Aparicio

• Advisor: Oswaldo Luiz Alves

Abstract

The present work is about the preparation of the HTaWO6.H2O oxide with bidimensional (trirutile) and tridimensional (pyrochlore) structures. These compounds were prepared by ion-exchange reactions of the alkaline metal by the proton, starting from precursor (Li or K)TaWO6. The synthesis of the precursors compounds involved typical solid state reactions. In the process, the structural evolution of the materials was evaluated related to the temperature (350 ¿ 850 ºC) and time of synthesis. Trirutile and pyrochlore crystalline phases present structural and electronic properties that make technological applications become possible, such as host matrices for the preparation of organic/inorganic nanocomposites and as solid electrolytes. Both solids, obtained as powders, were functionalized by ion exchange reactions of the proton by Ag ions, leading to the formation of compounds H1-xAgxTaWO6.H2O, with bi- and tridimensional structure. In addition, the solid presenting trirutile (lamellar) structure was used as a host matrix for intercalation of two linear amines (n-butylamine and n-dodecylamine). Reactions yielded the following intercalation products: HTaWO6.H2O@C4H11N and HTaWO6.H2O@C12H27N. The ¿as prepared¿ materials were characterized by different techniques, such as X-ray difratometry (XRD), X-ray fluorescence (XRF), Raman spectroscopy, infrared spectroscopy (FTIR) and thermogravimetry (TG). The results revealed different behavior of the structures towards ion exchange and intercalation/insertion reactions. In the study of structural evolution of the precursors materials, results revealed the possibility of preparation of the compounds (Li or K)TaWO6 via solid state reactions, with substantial reduction of time and temperature of synthesis related to the procedures described in the literature (AU)