Mechanical alloying (MA) is a solid-state powder processng technique involving repeated welding, fracturing, and rewelding of powder particles in a high-energy ball mill. Originally developed to produce oxide-dispersion strengthened (ODS) nickel- and iron-base superalloys for applications in the aerospace industry, MA has now been shown to be capable of synthesizing a variety of equilibrium and non-equilibrium alloy phases starting from blended elemental or prealloyed powders. The non-equilibrium phases synthesized include supersaturated solid solutions, metastable crystalline and quasicrystalline phases, nanostructures, and amorphous alloys. Recent advances in these areas and also on disordering of ordered intermetallics and mechanochemical synthesis of materials have been critically reviewed after discussing the process and process variables involved in MA. The often vexing problem of powder contamination has been analyzed and methods have been suggested to avoid/minimize it. The present understanding of the modeling of the MA process has also been discussed. The present and potential applications of MA are described. Wherever possible, comparisons have been made on the product phases obtained by MA with those of rapid solidification processing, another non-equilibrium processing technique.

Mechanical Alloying And Milling

Metal hydride materials for solid hydrogen storage: a review

Recent progress in alkaline water electrolysis for hydrogen production and applications

Note: Times Cited: 875 Reference EPFL-ARTICLE-206025doi:10.1021/cr0501846View record in Web of Science URL: ://WOS:000249839900009 Record created on 2015-03-03, modified on 2017-05-12

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Complex hydrides for hydrogen storage.

Complex Hydrides for Hydrogen Storage

Properties and Electrode Performances of (Zr, A)V 0.5 Ni 1.1 Mn 0.2 Fe 0.2 (A=Ti,Nb, and Hf) for Nickel-Hydrogen Rechargeable Batteries

In this paper, we report the first hydrogenation (activation) of a 1.2Ti-0.8Fe alloy synthesized by induction melting (9 kg ingot). The alloy presented a three-phase structure composed of a main TiFe phase, a secondary Ti2Fe phase and a Ti-rich BCC phase. The alloy required cold rolling to achieve activation at room temperature. However, it did so with good kinetics, reaching saturation (2.6 wt.% H) in about 6 h. After activation, the phases identified were TiFe, Ti2FeHx and an FCC phase. The Ti2FeHx and FCC are the stable hydrides formed by the secondary Ti2Fe and BCC phases, respectively. The stoichiometry of the Ti2FeHx was calculated to be between x = 3.2–4.75. As the microstructure obtained by an industrial-scale synthesis method (induction melting) may be different than the one obtained by laboratory-scale method (arc melting), a small 3 g sample of Ti1.2Fe0.8 was synthesized by arc melting. The lab-scale sample activated (2 wt.% H in ~12 h) without the need for cold rolling. The phases identified for the lab-scale sample matched those found for the induction-melted sample. The phase fractions differed between the samples; the lab-scale sample presented a lower abundance and a finer distribution of the secondary phases. This explains the difference in the kinetics and H capacity. Based on these results it can be concluded that the alloy of composition, 1.2Ti-0.8Fe, can absorb hydrogen without the need for a heat treatment, and that finer microstructures have a strong influence on the activation kinetics regardless of the secondary phases’ phase fractions.

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First Hydrogenation of TiFe with Addition of 20 wt.% Ti

Ball-milled nanocrystalline Ti3RuFe powders were mixed with 1, 2, 4, 10 and 20 equivalents of Al and the mixtures were milled again for 20 h. The amount of Al atoms dissolved into the B2 structure of Ti3RuFe does not exceed 8–9 at %, the remaining being present as elemental Al into the powder mixture. During a subsequent treatment of the composite powder in alkaline solutions, the elemental Al is leached out, while Al solutes in the B2 structure are not affected. An examination of the surface by scanning electron microscopy reveals that the leached powder has a highly porous surface structure. Surface area measurements performed by BET measurements show that there is a tenfold increase in the effective surface area. Activated electrodes made from these porous materials show a significant decrease of the cathodic overpotential for hydrogen evolution in typical chlorate electrolysis conditions of about 80 mV.

Large specific surface area nanocrystalline Ti-Ru-Fe cathode materials for sodium chlorate

Hydrogenation of TixFe2-x-based alloys with overstoichiometric Ti ratio (x = 1.1, 1.15 and 1.2)

The effect of heat treatment at 1273 K for 1 week on the first hydrogenation of body-centered cubic (BCC) 52Ti-12V-36Cr alloy with 4 wt pct Zr7Ni10, 4 wt pct Zr, and 2.2 wt pct Zr additives was investigated. Upon heat treatment, the relative abundances of BCC, C15-type Laves phase, and α-Ti drastically changed. Their chemical composition also changed. This resulted in the elimination of incubation time and faster first hydrogenation kinetics but also an important reduction of total hydrogen capacity by 40 pct.

Jacques Huot

Papers

Properties and Electrode Performances of (Zr, A)V 0.5 Ni 1.1 Mn 0.2 Fe 0.2 (A=Ti,Nb, and Hf) for Nickel-Hydrogen Rechargeable Batteries

First Hydrogenation of TiFe with Addition of 20 wt.% Ti

Large specific surface area nanocrystalline Ti-Ru-Fe cathode materials for sodium chlorate

Hydrogenation of TixFe2-x-based alloys with overstoichiometric Ti ratio (x = 1.1, 1.15 and 1.2)

Effect of Heat Treatment on Crystal Structure, Microstructure, and Hydrogenation Behavior of BCC 52Ti-12V-36Cr Alloys with Zr and Zr-Ni Additives