CLAUDIO JOSE DA ROCHA

CLAUDIO JOSE DA ROCHA

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An alternative route to produce easily activated nanocrystalline TiFe powder
2018 - FALCAO, R.B.; DAMMANN, EDGAR D.C.C.; ROCHA, C.J.; DURAZZO, M.; ICHIKAWA, R.U.; MARTINEZ, L.G.; BOTTA, W.J.; LEAL NETO, R.M.
In this paper, an alternative process route to produce active nanocrystalline TiFe compound was investigated. First, TiH2 and Fe powders were dry co-milled in a planetary ball mill for 5e40 h. TiH2 was selected as precursor powder, instead of Ti powder, due its fragility, which has proved to be beneficial to decrease powders adherence on milling tools. In terms of loose powder mass, milling yields ranged from 90 to 95 wt.%. Next, milled powders were post-heated at 873 K under dynamic high-vacuum for TiFe synthesis reaction. First hydrogen absorption was verified in situ during the cooling process of samples (until the room temperature), being the amount of hydrogen absorbed and desorbed by this samples measured by automated Sievert's apparatus, under constant hydrogen flow rate of 9 cm3. min-1 (dynamic measurements). Besides to allowing the first absorption in situ, the investigated process route also allowed the production of the non-stoichiometric TiFe compound (rich in Ti) in samples milled for shorter times (5 and 10 h), both characteristics associated with maintaining the mechanical compound activity. Each sample absorbed hydrogen at 2 MPa during the cooling process, requiring no additional thermal activation cycles, since the samples milled for shorter times (mainly for 10 h) could absorb hydrogen for the first time more easily. However, the samples milled for longer times (25 and 40 h) shown better results in terms of reversible and storage capacities (0.73 and 0.94 wt.%, respectively).
An investigation on hydrogen absorption/desorption properties of nanostructured TiFe compound prepared by high-energy ball milling and post-heating
2015 - FALCAO, R.B.; DAMMANN, E.D.C.C.; ROCHA, C.J.; ICHIKAWA, R.U.; DURAZZO, M.; MARTINEZ, L.G.; LEAL NETO, R.M.
Easily hydridable nanostructured TiFe from ball milled TiHsub(2) and Fe powders mixtures
2015 - FALCAO, R.B.; DAMMANN, E.D.C.C.; ROCHA, C.J.; ICHIKAWA, R.U.; MARTINEZ, L.G.; DURAZZO, L.G.; LEAL NETO, R.M.
Ball milling of TiHsub(2) and Fe powders mixture: An alternative route to synthesize hydridable TiFe
2014 - FALCAO, R.B.; DAMMANN, E.D.C.C.; ROCHA, C.J.; ICHIKAWA, R.U.; MARTINEZ, L.G.; DURAZZO, M.; LEAL NETO, R.M.
Synthesis of TiFe compound from ball milled TiHsub(2) and Fe powders mixtures
2014 - FALCAO, RAILSON B.; DAMMANN, EDGAR D.C.C.; ROCHA, CLAUDIO J. da; ICHIKAWA, RODRIGO U.; DURAZZO, MICHELANGELO; MARTINEZ, LUIS G.; LEAL NETO, RICARDO M.
TiFe compound was produced by high-energy ball milling of TiH2 and Fe powders, followed by heating under vacuum. TiH2 was used instead of Ti in order to avoid the strong particles adhesion to grinding balls and vial walls. Mixtures of TiH2 and Fe powders were drymilled in a planetary mill for times ranging from 5 to 40 hours. The amount of sample, number and diameter of the balls were kept constant in all experiments. After milling, samples were heated under dynamic high-vacuum for the synthesis reaction. As-milled and heat-treated materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential thermal analysis (DTA). The mean crystallite sizes and microstrains were determined by XRD line profile analysis using the Warren-Averbach method. As-milled materials presented only Fe and TiH2 phases. Nanostructured TiFe compound was formed after heat treatment. TiH2 was effective for providing low adherence of the powders during milling.