Janice K. Lomness

Hydrogen uptake characteristics of mechanically alloyed mixtures of Ti-Mg-Ni

Abstract It has been well established that hydrogen will react directly and reversibly with a large number of metals and alloys to form metallic hydrides. Extensive research has been done over the years to improve properties of these hydrogen storage media and in developing new compounds to use as hydrogen storage media. In the present study, the hydrogen uptake characteristics of mechanically alloyed titanium–magnesium–nickel have been studied. Thermal and composition data obtained for studies carried out using three different ball-to-powder ratios by mass are presented in a discussion of the hydriding properties of mechanically alloyed Ti–Mg–Ni. It was found that up to 11 wt % hydrogen was obtained for a Ti–Mg–Ni mixture that was ball milled at a ball-to-powder ratio by mass of 70:1.

Site-specific Transmission Electron Microscope Characterization of Micrometer-sized Particles Using the Focused Ion Beam Lift-out Technique

Micrometer sized particles have been studied to show that a high-quality transmission electron microscope (TEM) specimen can be produced, without the use of embedding media, from a site-specific region of chosen particles using the focused ion beam (FIB) lift-out (LO) technique. The uniqueness of this technique is that site-specific TEM LO specimens may be obtained from particles and from regions which are smaller than the conventional approximately 10-20 &mgr;m x 5 &mgr;m x approximately 0.1 &mgr;m dimensions of the LO specimen. The innovative FIB LO procedures are described in detail and TEM images of electron transparent specimens obtained from specific micrometer-sized particles are presented.

Surface study of liquid water treated and water vapor treated Mg2.35Ni alloy

Abstract Magnesium nickel alloy (Mg2.35Ni) has been considered an excellent hydrogen storage medium because it has a high hydrogen capacity, forms a very stable hydride, is inexpensive, and it presents no environmental hazards. One of the major problems associated with the use of Mg2.35Ni alloy for hydrogen storage is its initial activation for hydrogen uptake. Earlier work in this laboratory showed that treatment of Mg2.35Ni with either liquid water or water vapor, activates the alloy for hydrogen up-take. In the present study, the surface modification of Mg2.35Ni by liquid water and water vapor is characterized. X-ray photoelectron spectroscopy, and transmission electron microscopy suggest the presence of Mg(OH)2 on the surface. It is believed that this is the first report showing the presence of hydroxides on the surface of an active hydrogen storage alloy.

Water activation of Mg2Ni for hydrogenuptake

Abstract Though the alloy, Mg 2 Ni, has desirable properties for storageof hydrogen, its application has been hindered by the difficulty of its initial activation for hydrogenuptake. A number of methods have been reported for activation of Mg 2 Ni. While someof these methods utilize aqueous solutions, there has been no report of activation with pure water.It has been demonstrated in this laboratory that magnesium nickel alloy can be activated forhydrogen uptake by treatment with water for as little as 2 min. Increasing the treatment time withwater increases the amount of hydrogen absorbed and increases the longevity of the activation.Thermal data, scanning electron microscopic data, and x-ray photoelectron spectroscopic data arepresented in a discussion of the activation of magnesium nickel alloy with water.

The activation of Mg2Ni for initial hydrogen uptake by treatment with water vapor

Abstract The alloy, Mg2Ni, is a good candidate for the storage of hydrogen. One problem associated with the use of this alloy for hydrogen storage is the difficulty of its activation for initial hydrogen uptake. A great deal of research has been done in this area. However, the resulting methods require hazardous conditions and reagents and⧸or prohibitively long periods of time. It has been found in this laboratory that water vapor can be used to activate Mg2Ni for hydrogen uptake in as little as 1 h at ambient temperature and pressure. This finding is particularly interesting considering the long-held view of water acting as a poison in metallic hydrogen storage systems.

Hydrogen Storage in Titanium-Magnesium-Nickel Mixtures

The hydrogen interaction properties of mechanically alloyed mixtures of Ti, Mg, and Ni have been shown to be strongly dependent on the time and energy of ball milling. Mixtures ball milled at a ball to powder ratio (by mass) of 20:1 were able to absorb 3-4 wt% hydrogen. Mixtures ball milled at a ball to powder ratio of 70:1 were able to absorb up to 11 wt% hydrogen. The dependence of hydrogen uptake on ball milling time and energy is shown to be related to the microstructural morphology of the ball milled powders. The original Mg powder particles were heavily deformed by the ball milling process and contained nano-sized inclusions of both Ti and Ni at the surface. The higher energy ball milled samples showed a more refined microstructure and a greater hydrogen capacity. In addition, there was an inverse relationship between the amount of hydrogen uptake and the size of inclusions at the surface of the particles.