Browsing by Author "Han, YS"

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    Characterization of nano sized microstructures in Ni base ODS alloys using SANS and SAXS
    (International Conference on Neutron Scattering, 2017-07-12) Han, YS; Jang, J; Sokolova, AV
    The effects of thermo-mechanical treatment on microstructure of Ni base ODS(Oxide Dispersion Strengthened)alloys for future nuclear application were studied by SANS(Small Angle Neutron Scattering) and SAXS(Small Angle X-ray Scattering). Ni base ODS alloys were manufactured by MA(Mechanical Alloying) and hot extrusion process. The SANS experiments were performed by the 40 meter SANS instrument at HANARO and the Bilby SANS instrument at ANSTO. The SAXS experiments were performed by 9A SAXS beam line at Pohang Light Source. The existing phases were identified by the electron microscope and the X-ray diffractometer. The tensile test for the ODS alloys was performed at room temperature and 700?. The nano sized microstructures such as yttrium oxides, gamma prime phase and carbides were quantitatively analyzed by SANS. Based on the difference of the SANS and SAXS intensity in absolute units, the alloy contrast variation (ACV) method were used to determine the type of nano-sized precipitates. The relationship between microstructures and mechanical properties were analyzed and the effects of thermomechanical treatments on microstructure was discussed according to the quantitative microstructural analysis results by SANS and SAXS.
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    Characterization of porosity in sulfide ore minerals: a USANS/SANS study
    (GeoScience World, 2014-11-18) Xia, F; Zhao, J; Etschmann, BE; Brugger, J; Garvey, CJ; Rehm, C; Lemmel, H; Ilavsky, J; Han, YS; Pring, A
    Porosity plays a key role in the formation and alteration of sulfide ore minerals, yet our knowledge of the nature and formation of the residual pores is very limited. Herein, we report the application of ultra-small-angle neutron scattering and small-angle neutron scattering (USANS/SANS) to assess the porosity in five natural sulfide minerals (violarite, marcasite, pyrite, chalcopyrite, and bornite) possibly formed by hydrothermal mineral replacement reactions and two synthetic sulfide minerals (violarite and marcasite) prepared experimentally by mimicking natural hydrothermal conditions. USANS/SANS data showed very different pore size distributions for these minerals. Natural violarite and marcasite tend to possess less pores in the small size range (<100 nm) compared with their synthetic counterparts. This phenomenon is consistent with a higher degree of pore healing or diagenetic compaction experienced by the natural violarite and marcasite. Surprisingly, nanometer-sized (<20 nm) pores were revealed for a natural pyrite cube from La Rioga, Spain, and the sample has a pore volume fraction of ~7.7%. Both chalcopyrite and bornite from the massive sulfide assemblage of the Olympic Dam deposit in Roxby Downs, South Australia, were found to be porous with a similar pore volume fraction (~15%), but chalcopyrite tends to have a higher proportion of nanometer-size pores centered at ~4 nm while bornite tends to have a broader pore size distribution. The specific surface area is generally low for these minerals ranging from 0.94 to 6.28 m2/g, and the surfaces are generally rough as surface fractal behavior was observed for all these minerals. This investigation has demonstrated that USANS/SANS is a very useful tool for analyzing porosity in ore minerals. We believe that with this quantified porosity information a deeper understanding of the complex fluid flow behavior within the porous minerals can be expected. © 2014, Mineralogical Society of America.