This article aims to address the formation and the structural disordering/ordering phenomena of PtNi nanoalloys supported on hollow graphitic spheres (HGSs) using pair distribution function (PDF) analysis under ex situ/in situ data collection conditions. Starting from small nanoparticles (10-15 Å in diameter) embedded in HGSs, structural changes were monitored during stepwise heating and cooling of the sample using in situ PDF analysis. In order to evaluate the conventional synthesis route for the production of PtNi nanoalloys supported on HGSs, ex situ PDF experiments were performed before and after heat treatment in a furnace. The studies demonstrate that the local structure of the in situ synthesised PtNi nanoalloy differs from its ex situ synthesised counterpart. A partially ordered PtNi nanoalloy was obtained during the stepwise in situ cooling of the precursor, whereas the conventional ex situ synthesis route did not lead to the formation of an ordered crystal structure. In this study we could show that rapid heating and cooling results in a disordered PtNi alloy whereas slow heating and cooling leads to disorder-order transitions in PtNi.
In this contribution low temperature formation of Ruddlesden-Popper (RP)-type layered La 2 CoO 4±δ perovskite was optimized via in situ X-ray powder diffraction (XRPD). Starting from LaCoO 3 a stoichiometric transformation to La 2 CoO 4±δ and CoO can be achieved by controlled reduction with H 2 . The challenge of this reaction is the use of appropriate amounts of H 2 in a defined temperature region. If the amount of H 2 is too high, complete reduction of the perovskite occurs. If temperatures are not appropriate, intermediate phases seem to hinder [a]
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