Papers by Keyword: Mechanical Milling

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Authors: B. Anandan, S. Gopalakannan
Abstract: A high density nanoscale clusters of Y–Ti–O exhibit superior creep strength and potential for high resistance to radiation damage. X-Ray Diffraction is used to determine the formation of the complex nanoclusters (NCs). The formation of Y2TiO5 NCs takes place during heat treatment of mechanically milled (MM) titanium and Yttria, and also it forms the mixture of Y2Ti2O5 and Y2Ti2O7 NCs during the high temperature soaking of MM iron, MM titanium and yttria. The microstructure of the hot consolidated mixture of MM iron, MM titanium and yttria were obtained through scanning electron microscopy (SEM). The back scattered electron mode is used to show the contrast between different elements in the microstructure. The increase in soaking temperature increases the size of the nanocluster, which decrease the volume fraction and number densities. A large population of nanoclusters precipitates during the heat treatment at high soaking temperature.
Authors: C. Deidda, S. Doppiu, M. Monagheddu, Giorgio Cocco
Authors: Yong Gang Xu, Li Ming Yuan, Jun Cai, De Yuan Zhang
Abstract: Graphite-FeSi absorbents were fabricated by mechanical milling method. The complex permittivity and permeability were measured in frequency 1-4 GHz, and then reflection loss (RL) and shielding effectiveness (SE) were calculated. It was obtained that the graphite was bonded to the surface of FeSi by X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images. The permittivity and permeability could be enlarged as graphite added in the milling process. It was attributed to the excellent conductivity of graphite and interactions of the two particles. The graphite-FeSi composites had a better shielding property (maximum 25.93 dB) in 1-4 GHz as well as the absorbing property at 1GHz than FeSi composites.
Authors: Masahiro Kubota, Xiao Lin Wu, Wei Xu, Kenong Xia
Abstract: Mechanically milled pure aluminium powders were fabricated into bulk materials using back pressure equal channel angular consolidation (BP-ECAC) for four or eight passes at 373K. The bulk materials consolidated from 0 h and 4 h mechanically milled powders were characterised by Vickers hardness tests and density measurements. Thermal stability of the consolidated bulk materials was evaluated by isothermal heat treatments at 673K. The as-consolidated bulk material from the 0 h milled (i.e. unmilled) powder showed nearly full density. However, full density was not obtained with the 4 h milled powder even after eight passes. The HV values for the as-consolidated materials fabricated from the 0 h and 4 h milled powders after four passes and from the 4 h milled powder after eight passes were 57, 121 and 136, respectively. Softening was observed in the bulk material consolidated from the 0 h milled powder during the isothermal heat treatment. However, the hardness of the bulk materials consolidated from the 4 h milled powders after four and eight passes increased to maximum values of 137 and 141 after heat treatment for 28 h and 8 h at 673K, respectively. The maximum hardness was maintained for up to 100 h at 673K in both materials. The hardening and thermal stability in the bulk materials from the milled powders are attributable to dispersion strengthening of Al4C3 particles formed by solid-state reaction during the isothermal heat treatment.
Authors: Yan Wang
Abstract: We report on the preparation and hydrogen desorption/absorption kinetics of nanocrystalline magnesium hydride (MgH2) added commercial Ti by high-energy ball milling. The phase and composition of the as-milled powders are characterized by X-ray diffraction (XRD). The results show that the milled sample contained MgH2 phase, Ti phase and small amount of MgO phase. When the milling time is 30 h, the hydrogen desorption property of MgH2 has been investigated and found that the sample releases 0.43, 0.86 and 0.90 wt% H2 in 200 minutes at 280, 290 and 300 oC , respectively. Moreover, the sample absorbs 0.48, 0.0.58 and 0.61 wt% H2 in 15 minutes at 280, 290 and 300 oC , respectively. It can be seen that the kinetics of hydrogen desorption/absorption of MgH2-Ti composite has been greatly enhanced compared to the pure MgH2.
Authors: Gil Jae Lee, Jae Hyeok Shim, Young Whan Cho, Kyung Sub Lee
Abstract: Fine Ti5Si3 powder has been synthesized from a mixture of elemental Ti and Si powders using a mechanochemical method. It shows a good catalytic effect on NaAlH4 by reducing the dehydrogenation temperature and improving the dehydrogenation kinetics. Although the catalytic effect of Ti5Si3 is not better than that of TiCl3, the Ti5Si3 catalyst has an advantage over TiCl3 in terms of hydrogen capacity by releasing more hydrogen than TiCl3 during dehydrogenation. NaAlH4 catalyzed with Ti5Si3 shows reversible hydrogen storage by being hydrogenated at moderate conditions, although the hydrogenation kinetics is rather slow.
Authors: C. Díaz-Guerra, Amelia Montone, J. Piqueras, Francsco Cardellini
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