In iron oxide powders positrons are trapped in the surface layers and the value of the S-parameter is an indicator of the total specific surface, including external surface and internal surfaces of micropores. The evolution of micropores is followed when α-FeOOH is thermally decomposed into α-Fe_{2}O_{3}. It is shown that the micropore formation is not linked to the decomposition process, but that they also form in hematite synthesized from a ferrihydrite precursor in aqueous solution.
Plasma ion immersion implantation is a promising technique for nitriding. A case study of the characterization of the plasma ion immersion implantation nitriding of iron alloys is the plasma ion immersion implantation nitriding of pure Fe. A set of Fe samples of 99.98% purity and with different defect structure was plasma ion immersion implantation nitrided at different temperatures. Depth profiling of the samples was achieved using positron annihilation spectroscopy with a slow positron beam and nanoindentation. A correspondence was found between the line shape parameter S and the hardness of the plasma ion immersion implantation treated samples.
A set of Fe-Si samples with different Si content, varying from 0 to 7.6 wt.%, was investigated using positron annihilation spectroscopy. Different deformations were performed on these samples and the lineshape parameters of the annihilation line were measured in order to investigate the defects in the alloys. An exponential decay of the S-parameter in function of the time can be observed after deformation of the samples. The decay constant increases with increasing Si content. During the measurements of the samples with increasing Si content, the initiation of DO_3 structure can be seen above 5 wt.% of Si, as well as the decoration by impurities.
Defects in different iron based alloys were studied at room temperature using positron annihilation techniques. In FeSi alloys, it was found that the Si content and the deformation temperature affect the positron annihilation parameters. In Fe-Mn-Si-Cr-Ni-C samples with different deformations, positron lifetime measurements were carried out before and after isochronal annealing. X-ray diffraction gave information about the different microstructural phases that exist in the deformed alloys before and after annealing. During deformation a martensiticεphase is induced. At 500°C, defects and theεmartensite phase were almost annealed out from the low deformed samples.
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