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The present study examined the microstructure and mechanical properties of ceramic composites based on a kaolin from Djebel Debbagh, northeast Algeria, composed mainly of kaolinite and halloysite with the addition of various amounts of BaCO3. The composites were prepared by high-energy ball milling and sintered at 1100°C and 1200°C for 3 h. The samples sintered at 1200°C without BaCO3were composed mainly of mullite, which disappeared with increasing BaCO3content. X-ray diffraction investigation showed the presence of hexacelsian (BaAl2SiO6and BaAl2Si2O8), which disappeared at BaCO3contents >50 wt.% in favour of barium aluminium and barium silicate phases. At 40 wt.% BaCO3content, the porosity of the composites decreased from 0.7% to 0.1% and the microhardness increased from 7 to 8 GPa, respectively, at 1100°C and 1200°C due to the amorphous phase.

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This paper describes a pulsed eddy current nondestructive evaluation of an annular groove dimensions using a simplex inversion method associated with a semianalytical direct model, in axisymmetric case. The proposed semianalytical formulation, used for direct calculations, is developed from coupled electric circuits modeling. It uses the current excitation allowing the determination of the sensor voltage. The feature of the variation of voltage provides information on the electromagnetic and geometrical properties of the device. The transient sensor voltage is then calculated, allowing the evaluation of the groove dimensions of the considered work piece. The peak's amplitude and the zero and peak crossing times are used to determine these properties.