Photoacoustic Spectroscopy Applied To The Study Of Clay Soils

The study of clay soils using photoacoustic spectroscopy was presented. The observation of the photoacoustic spectra showed the transition bands associated with Fe3+ ions in octahedral or tetrahedral symmetry. Rietveld refinements showed that the Al3+ cations were partially substituted by the Fe3+ cations in the octahedral states of kaolinite structure.741 II355357Alexandre, J., Saboya, F., Marques, B.C., Ribeiro, M.L.P., Salles, C., Da Silva, M.G., Sthel, M.S., Vargas, H., (1999) Analyst, 124, p. 1209Ambikadevi, V.R., Lalithambika, M., (2000) Appl. Clay Sci., 16, p. 133Mehra, O.P., Jackson, M.L., (1960) Clays Clay Miner., 7, p. 317Young, R.A., Sakthivel, A., Moss, T.S., Paiva-Santos, C.O., (1995) J. Appl. Crystallogr., 28, p. 366Sugano, S., Tunabe, Y., Kamimura, H., (1970) Multiplets of Transition-Metal Ions in Crystals, , Academic, New YorkAbritta, T., De Souza Barros, F., (1988) J. Lumin., 40, p. 187Abritta, T., Cella, N., Vargas, H., (1989) Chem. Phys. Lett., 161, p. 12Lima, G.A.R., Baesso, M.L., Arguello, Z.P., Da Silva, E.C., Vargas, H., (1987) Phys. Rev. B, 36, p. 9812Rosencwaig, A., Gersho, A., (1976) J. Appl. Phys., 47, p. 64Baesso, M.L., Mansanares, A.M., Da Silva, E.C., Vargas, H., (1989) Phys. Rev. B, 40, p. 188

Crystallinity evolution in ceramic materials monitored by thermal diffusivity

In this work, we present a detailed analysis of the thermal and crystalline evolution in ceramic samples produced from natural soil and heated at different temperatures, ranging from 300 to 1200ºC. The crystalline and amorphous volumetric fractions, as well as the crystalline phases evolution as a function of the applied temperature were determined from X-ray diffraction data. The structural modifications are responsible for drastic changes in the properties related to the ceramic performance. The thermal diffusivity results were correlated to the structural properties of the ceramic pieces, showing that this important thermal property can be used as a monitoring parameter of the quality of the final product