Caracterização da microestrutura de materiais porosos por microtomografia de raios x e transmissão de raios gama

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

This work presents the application of the X-Ray Microtomography and Gamma Ray Transmission techniques for the microstructure characterization of different kinds of materials. Total porosity, pore size distribution and the two point correlation functions were measured. The two point correlation function, which allows the reconstruction of 3D models, was carried out for two samples. Seven ceramic tablets of Alumina (Al2O3), seven tablets of Boron Carbide (B4C), three samples of sedimentary rocks and one sample of Titanium foam were analyzed. The experimental set up for the Gamma Ray Transmission technique consisted of: a 2" x 2" crystal NaI(Tl) detector, an 241Am radioactive source (59,53keV, 100mCi), an automatic micrometric table for the sample XZ movement and standard gamma spectrometry electronics. Two microtomography systems were used: a Fein Focus system, constituted by an X-ray tube, operated at 160kV and 0.3 to 1.1mA, a CCD camera and the movement sample system, and a Skyscan system, model 1072, with a X-ray tube operated at 100kV and 100µA, and a CCD camera. The ceramic tablets, analyzed by the gamma ray transmission technique presented results for most of the porosities data with smaller confidence intervals and inside the intervals supplied by the tablets manufacturer. The Titanium porous sample was analyzed by the two techniques, its microtomography images achieved a resolution of 17µm, obtained employing the Fein Focus system. For both techniques, this sample showed high porosity, which allows its application for this purpose. The sandstones samples were analyzed by the Skyscan system, achieving resolutions of 19µm, 11µm and 3.8µm for each sample, respectively. The resolutions of 11µm and 3.8µm were the ones that generated better 2D sections for the respective samples and, consequently, more reliable porosities. The 3.8µm resolution was the one that best quantified the pore size distribution data, showing information not shown by the 11µm resolution, showing that pores with 15 to 45µm radius are predominant, constituting 57% of the porous phase of this sample, and 1% are just constituted by pores with radius up to 3.8µm. These results show that resolution better than 3.8µm could be necessary only for specific cases.

ASSUNTO(S)

porosidade (física) microtomografia de raios x - física transmissão de raios gama - física gamma rays - industrial applications x-ray microanalysis porosity

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