KENGO IMAKUMA
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Artigo IPEN-doc 27801 Disordered Gd6UO12-δ with the cation antisite defects prepared by a combined mechanochemical2021 - DARIN, G.; IMAKUMA, K.; SANTIAGO, R.T.; SILVA, K.L. da; COTICA, L.F.; FABIAN, M.; VALICEK, J.; HAHN, H.; SEPELAK, V.The synthesis of the rhombohedral Gd6UO12-δ is reported via mechanochemical processing of stoichiometric Gd2O3/UO2 mixtures and their subsequent annealing. Rietveld refinement of XRD data reveals that the as-prepared material exhibits a remarkable degree of cation antisite disorder and oxygen deficiency. The simulations of intensities of the selected XRD superlattice reflections are performed for limiting states of Gd6UO12-δ with its most extreme degrees of the cation antisite disorder. On the basis of the estimated bond lengths it can be stated that distorted geometry of structural units in the material is a consequence of its relatively large oxygen deficiency.Artigo IPEN-doc 27781 X-ray diffraction and thermoanalytical datasets of precursors of the Gd6UO12-δ phase processed by combined mechanochemical2021 - DARIN, GASPAR; IMAKUMA, KENGO; SANTIAGO, RAFAEL T.; SILVA, KLEBSON L. da; COTICA, LUIZ F.; FABIAN, MARTIN; VALICEK, JAN; HAHN, HORST; SEPELAK, VLADIMIRThe datasets presented here are related to the research paper entitled “Disordered Gd6UO12-δ with the cation antisite defects prepared by a combined mechanochemical−thermal method” [1]. The datasets complement the findings [1] on the effect of the combined mechanochemical−thermal processing of the stoichiometric mixture of solid precursors (3Gd2O3 + UO2) on the formation of Gd6UO12-δ phase. In this article, we provide (i) X-ray diffraction (XRD) data of the 3Gd2O3 + UO2 mixture milled for 12 h, (ii) the refined XRD data of the non-milled 3Gd2O3 + UO2 mixture after annealing at 1282 °C for 3 h in air, and (iii) the thermogravimetric and differential thermal analysis (TG-DTA) data for non-milled and mechanically preactivated 3Gd2O3 + UO2 mixture measured in air at a heat rate of 10 K/min.Artigo IPEN-doc 24172 Structural and microstructural analysis of the U-GD-O system using X-ray diffraction data2017 - DARIN, GASPAR; IMAKUMA, KENGO; MARTINEZ, LUIS G.; TURRILAS, XABIER M.; ICHIKAWA, RODRIGO U.; SILVA, ANDRE S.B.; DURAZZO, MICHELANGELO; RIELLA, HUMBERTO G.; URANO, ELITAGadolinium is one of the best neutron absorber materials and its usage can be considered as a burnable poison for Light Water Reactors (LWR) and as a sacrificial material in Sodium Fast Reactor (SFR). Most of the experiments in the literature focus on nuclear fuel with up to 12 wt% Gd2O3. Recently, the phase diagram and melting point has been investigated for high contents of Gd2O3 in the U-Gd-O system, that means a solid solution of the composition (U1-x, Gdx)O2 for 0