GRAZIELE CRISTIANE SECO COUTINHO
2 resultados
Resultados de Busca
Agora exibindo 1 - 2 de 2
Resumo IPEN-doc 24485 MgH2-TiFe composite for hydrogen storage2017 - 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.Artigo IPEN-doc 23231 Synthesis by high-energy ball milling of MgH2-TiFe composites for hydrogen storage2017 - LEAL NETO, RICARDO M.; SILVA, RAFAEL de A.; FLORIANO, RICARDO; COUTINHO, GRAZIELE C.S.; FALCAO, RAILSON B.; LEIVA, DANIEL R.; BOTTA, WALTER J.The aim of this work is to investigate the influence of some processes variables on the microstructure and hydrogen absorption kinetics of MgH2 - X wt.% TiFe composites. Samples were synthesized by high-energy ball milling in a planetary (X = 40, 50, 60) and shaker mill (X = 40) under high-purity argon atmosphere. Commercial MgH2 instead of Mg powder was used in order to reduce adherence on the vial and balls. TiFe powder was previously produced by ball milling a mixture of TiH2 and Fe powders followed by a reaction synthesis at 600ºC. Milled composites samples were characterized by XRD and SEM analysis. Milling time was preliminary investigated (X = 40) in the planetary ball mill (6 to 36h). TiFe particle size reduction was shown to be difficult since they are surrounded by MgH2 matrix. Strong particle reduction was obtained by using a shaker mill only for 2 hours and adding cyclohexane as process control agent. No reaction between MgH2 and TiFe compound was observed in any milled sample. Hydrogen absorption kinetics measurements of the as-milled samples were conducted on an Sieverts' type apparatus at room temperature after hydrogen desorption at 350ºC under vacuum. The best hydrogen kinetics (3 wt% at the first hour) was attained by the planetary milled sample (36 h). Higher hydrogen capacity was observed for the sample milled in the shaker mill (4.0 wt.%), but only after 13h.