RESUMO Este trabalho verificou a dependência das propriedades físicas e mecânicas com a composição química de várias argilas vermelhas do Estado da Bahia. Preservou-se a granulometria dos materiais em peneiras de até 30 mesh. Para caracterização físico-química e mecânica foram realizados os ensaios: limite de plasticidade, limite de liquidez, índice de plasticidade, coloração subsequente à queima em 900/1000/1100 °C, retração linear, módulo de tensão de ruptura, determinação de água de absorção, distribuição granulométrica, umidade natural e perda de massa ao fogo (modo flamejante). Em paralelo empregou-se a técnica de Espectrometria de Emissão Óptica com Plasma Indutivamente Acoplado – ICP – OES, Modelo Perkin Elmer Optima 8300 para determinação da composição química das argilas. Os resultados evidenciaram a dependência das propriedades com a composição química das argilas de forma sinergética e conciliativa.

ABSTRACT This work verified the dependence of the physical and mechanical properties with the chemical composition of several red clays in the State of Bahia. The granulometry of the materials was preserved in screens up to 30 mesh. For physical-chemical and mechanical characterization, the following tests were performed: plasticity limit, liquidity limit, staining after burning at 900/1000/1100 °C, linear retraction, rupture stress module, determination of absorption water, particle size distribution, natural moisture, and loss of mass to fire (flaming mode). In parallel, the technique of Optical Emission Spectrometry with Inductively Coupled Plasma - ICP - OES, Model Perkin Elmer Optima 8300 was used to determine the chemical composition of the clays. The results showed the dependence of properties on the chemical composition of clays in a synergistic and conciliatory way.

In the last decade, many method has been developed to obtain oxysufides. However, theses materials were obtained by reaction involved gaseous toxics, CO, CS2, H2S and S. In the present work, the synthesis of lanthanum oxysufides actived by europium (III) through an alternative method has been made. This method involve the rare earth sulfate reduction under an atmosphere of argon contained 10% hydrogen using the thermogravimetric technique. The results showed the formation of the phase TR2O2S (TR = La and Eu) at temperatures which depend upon the heating rate, respectively 650 - 830ºC at 5ºC min-1 and 680 - 800ºC at 10ºC min-1. The oxysufides obtained are characterized by infrared spectroscopy. The method developed is more economic than the usual industrial methods and the environmental problems during the synthesis are also better controled.