Zircon sand was reacted with liquid caustic soda (50% NaOH) in open vessel at 600 oC for 2h. The effect of NaOH/ZrSiO4 reactant ratio on the yield of zirconia recovery was verified. Samples of fusion products water washed were characterized by X-ray diffraction (XRD) to identify the main compounds formed. Silica powders were obtained via acid catalyzed reaction and zirconia powders were resulted from crystallization of zirconium oxychoride. Both zirconia and silica powders were analyzed by XRF (X-ray fluorescence) and BET method. Laser Quasi Elastic Light Scattering (QLS) technique was used for agglomerate size distribution determination. High purity and fine zirconia and silica powders were obtained. The specific surface area of zirconia calcined at 550 oC reached ~ 70m2g-1. Silica powder calcined at 800 oC presented a high specific surface area ~ 500 m2g-1.
Revista Brasileira de GeociênciasMônica Mazzini Perrotta et al. 38(1): 153-166, março de 2008 Arquivo digital disponível on-line no site www.sbgeo.org.br 153Geobotânica por sensoriamento remoto e aerogamaespectrometria aplicados ao mapeamento geológico da Amazônia: um estudo comparativo no vale do Guaporé (MT) Resumo Em áreas de floresta tropical métodos indiretos de mapeamento baseados em sensoriamento remoto e em geofísica aeroportada são necessários para substanciar e expandir as informações geológicas de campo. A aerogamaespectrometria informa da radiação gama emitida pelas rochas e solos. As imagens de sensoriamento remoto óptico informam do comportamento espectral da vegetação, função da constituição química das folhas componentes do dossel da floresta e de sua arquitetura. O objetivo desse estudo é avaliar a correlação das variações da cobertura vegetal com a variação litológica em áreas na Amazônia brasileira através de dados do sensor multiespectral ASTER e dados gamaespectrométricos. Técnicas de processamento digital, visando o realce espectral de diferentes compostos foliares, e sua generalização através de filtro de convolução passabaixas, foram aplicados aos dados multiespectrais. Os dados gamaespectrométricos, após pré-processamento padrão, foram convertidos em imagens dos canais eU, eTh, K, distribuição ternária K-U-Th e razões. A comparação entre as imagens de sensoriamento remoto óptico e de gamaespectrometria mostrou uma importante correlação, em que pese as diferentes origens do sinal e dos comprimentos de onda envolvidos. Como a origem da radiação gama necessariamente é mineral demonstra-se tanto a importância da informação geológica presente no dossel florestal como a eficiência na estratégia de processamento digital utilizada.Palavras-chave: sensoriamento remoto, geobotânica, aerogamaespectrometria, mapeamento geológico, sensor ASTER. Abstract Remote sensing geobotany and airborne gamma-ray data applied to geological mapping of the Amazon: a comparative study in the Guaporé Valley (Mato Grosso State, Brazil) This papercomprises a comparison between the vegetation response in ASTER multispectral optical imagery and possibly equivalent bedrock/regolith/soil response in airborne gamma-ray spectrometry grids, employing two tropical rainforest areas in the Brazilian Amazon as controls. The applied technique comprised band ratios using a fixed near infrared band (numerator) divided by individual visible and shortwave infrared bands (denominator). These band ratios were subsequently submitted to principal component analysis, and the high frequency information smoothed by low pass filtering. The color compositions selected for interpretation were sharpened by the first principal component of the original ASTER bands through an IHS transform in order to add albedo/ texture information -lost by band rationing -back to the imagery. The products show a plausible coherence with airborne gamma-ray data and field observations, proving that the proposed processing strategy applied to low cost multispec...
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