Sdílená laboratoř RP2


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    Non-aqueous template-assisted synthesis of mesoporous nanocrystalline silicon orthophosphate
    (Royal Society of Chemistry, 2015-01-01) Styskalik, Aleš; Škoda, David; Moravec, Zdeněk; Roupcová, Pavla; Barnes, Craig E.; Pinkas, Jiří
    The first synthesis of mesoporous nanocrystalline silicon orthophosphate Si5P6O25 is presented. The synthetic procedure is based on the non-hydrolytic sol-gel reaction in the presence of Pluronic P123 template and subsequent calcination in air. The condensation of silicon acetate, Si(OAc)(4), and tris(trimethylsilyl) phosphate, OP(OSiMe3)(3) (TTP), in non-aqueous solvents driven by elimination of trimethylsilyl acetate provides a homogeneous network with a high content of Si-O-P bonds and SiO6 moieties. After burning out the template, mesoporous silicon orthophosphate was obtained with surface areas up to 128 m(2) g(-1) and pore sizes around 20 nm. The nanocrystalline Si5P6O25 phase forms relatively easily (500 degrees C, 4 h) in comparison with other synthetic routes. All samples were characterized by SEM, TEM, elemental analysis, TGA, nitrogen adsorption, SAXS, H-1, C-13, Si-29, and P-31 solid-state NMR spectroscopy, and powder XRD. These xerogels showed superior catalytic activity and selectivity in methylstyrene dimerization.
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    Microstructural changes during deformation of AISI 300 grade austenitic stainless steels: Impact of chemical heterogeneity
    (Elsevier, 2016-06-24) Man, Jiří; Kuběna, Ivo; Man, Ondřej; Weidner, Anja; Chlup, Zdeněk; Polák, Jaroslav
    The present work points out the importance of chemical heterogeneity on the destabilization of austenitic structure and the formation of deformation induced martensite (DIM) in AISI 300 grade austenitic stainless steels (ASSs) of different level of austenite stability (316L, 304, 301LN). Color etching reveals that the structure of wrought Cr-Ni type steels is never fully chemically homogeneous. Confrontation of distribution and morphology of DIM formed in the volume of material after static and cyclic straining under well controlled different conditions with the characteristic local variations in chemical composition of diverse wrought semi-product forms (plates, sheets, bars) proved prominent and very important role of chemical banding in the destabilization of originally fully austenitic structure. This fact should be considered especially when interpreting the results of hydrogen embrittlement tensile testing of Cr-Ni ASSs with lowered Ni content. An impact of chemical heterogeneity on microstructural changes during production of UFG structure of 301LN and its cyclic straining is highlighted.