CLAUDIO JOSE DA ROCHA

CLAUDIO JOSE DA ROCHA

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Mechanical activation of TiFe for hydrogen storage
2019 - LEAL NETO, RICARDO M.; VEGA, LUIS E.R.; FALCÃO, RAILSON B.; LEIVA, DANIEL R.; ROCHA, CLAUDIO J.; ISHIKAWA, TOMAZ T.; KIMINAMI, CLAUDIO S.; BOTTA, WALTER J.
The aim of this work is to report some recent developments on the synthesis of TiFe by high energy ball milling and cold rolling, concerning hydrogen storage. Ball-milled TiFe was produced by two procedures, both under inert atmosphere and with various milling times. In the first one a powder mixture of TiH2 an Fe was milled, followed by a vacuum heat treatment to promote the reaction synthesis of TiFe compound [1]. Second procedure consisted of milling Ti and Fe powders with stearic acid (as a process control agent) after a pre-milling operation (with the same powders and without PCA) to prepare the surface of milling media. Both methods were conceived for avoiding strong adherence of the powders to the milling balls and vial, impairing the mechanical alloying. Cold rolling was performed on a ground TiFe ingot produced by arc melting [2]. After 20 to 40 passes under inert atmosphere, powder particles and thin cracked flakes were produced. Results showed that both milling procedures succeeded in avoiding unacceptable adherence to the milling media, with high loose powder yields. Whatever the route, nanostructured TiFe was obtained with no need of further thermal activation for the first hydrogenation. Hydrogen absorption capacities of about 1.0 wt% at room temperature was obtained with both milling procedures. Higher capacity (1.4wt%) was obtained with cold rolled TiFe (powder and flakes) after 40 passes. Some possible explanations for this difference are presented and discussed.
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).
MgH2-TiFe composite for hydrogen storage
2017 - COUTINHO, G.C.S.; FALCAO, R.B.; SILVA, R.A.; ROCHA, C.J.; LEIVA, D.R.; ISHIKAWA, T.T.; BOTTA, W.J.; LEAL NETO, R.M.
MgH2 - 40wt.% TiFe composites were mechanical alloyed by high-energy ball milling, starting from both compounds, under high-purity argon atmosphere. In this case, the aim was to combine TiFe compound, which absorbs and desorbs hydrogen at or very near room temperature, with Mg, which has higher storage capacity. To avoid or reduce adherence on the vial and balls commercial MgH2 powder, instead of Mg, was used. TiFe was synthesized following a route described previously [1]. Three sets of experiments were done. In the first and second sets, MgH2 and TiFe powders were individually pre-milled in a shaker mill for 0.5 and 1 hour, respectively. Both milled powders were further mechanical alloyed in a planetary mill for 6 hours with ball-to-powder weight ratio (BPWR) of 40:1 (first set), or in a shaker mill for 2 hours, with BPWR of 30:1 (second set). In the third set, milling of both powders was conducted only in the shaker mill for 2 and 4 hours. Cyclohexane was used as process control agent in all experiments. DRX analysis showed no reaction between MgH2 and TiFe compound in all milled samples. Microstructural analysis by SEM revealed that TiFe particle size was 15% lower when pre-milling stage was performed (first and second sets of experiments). In the third set of experiments, TiFe particle size was reduced about 35% comparing milled samples for 2 and 4 hours (shaker mill). PCT and kinetics measurements were carried out in a Sieverts' type apparatus (under constant hydrogen flow) after heating the samples at 623K under vacuum for hydrogen desorption from MgH2. Results showed a increased hydrogen absorption capacity (about 4 wt % H2) for samples with lower TiFe particle size, which is accomplished after milling for 4 hours in the shaker mill.
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.
Fabrication of powder from ductile uranium alloys for use as nuclear dispersion
2014 - DURAZZO, M.; LEAL NETO, R.M.; ROCHA, C.J.; CARVALHO, E.U. de; RIELLA, H.G.
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.
An investigation on the mechanical alloying of TiF e compound by high-energy ball milling
2009 - FALCÃO, R.B.; DAMMANN, E.D.C.C.; ROCHA, C.J.; LEAL NETO, R.M.
Effect of vibratory and planetary ball milling on combustion synthesis of NbAl3
2003 - ROCHA, C.J.; GONCALVES, V.S.; BURACOVAS, F.; LEAL NETO, R.M.