A. Baruj

Equipment for hydrogen absorption-desorption cycling characterization of hydride forming materials.

Hydrogen storage materials suffer different degradation processes when they are cycled, forming and decomposing their associated hydride phases. In order to study these processes, we have designed and built an automated apparatus specifically developed for cycling samples of hydride forming materials by changing the external hydrogen pressure. Instead of the standard open configuration involving a high-pressure, high-quality gas bottle and a vacuum pump, the equipment uses another hydride forming material (in our case LaNi5) as a source and sink of hydrogen. The resulting closed-loop configuration eliminates hydrogen waste and ensures that extremely high purity gas is used during the whole experiment, thanks to the purifying properties of the selected hydride as source/sink. Hydrogen pressure is set by changing the source/sink temperature. Cycles can be performed as fast as one cycle every 5 min, a period comparable with typical good hydride forming material kinetics. An example of application of the apparatus is given for 1000 absorption/ desorption cycles on a Mm0.8Ca0.2Ni5 sample.

Novel device for simultaneous volumetric and x-ray diffraction measurements on metal-hydrogen systems.

Hydrogen storage materials can form more than one hydride phase. These different phases, in turn, display different hydrogen absorption/desorption capacities, kinetics, and stabilities. Studies aimed at characterizing and improving these materials usually need to correlate hydrogen intake with the precise determination of the hydride phase involved in the process. Here, we present a device designed to perform measurements of well known volumetric techniques with simultaneous x-ray diffraction on the material under study. The compact design can stand up to 6000 kPa of internal pressure while the sample can be heated up to 450 degrees C. The design process was assisted by finite element modeling and by the use of mock-up prototypes in order to optimize the thermal and under load behaviors. We provide two examples of use for this new device: (1) hydride decomposition in LaNi5 at 115 degrees C and (2) formation of MgCo during the programmed thermal desorption of the Mg2CoH5 hydride.

Characterization and Comparative Study of Pseudo-Elastic Cu-Zn-Al Foams Synthesized by Two Different Methods

Low cost Cu-Zn-Al foams present, in specific composition ranges, good pseudoelastic properties associated with interesting damping capacities, which establish these materials as attractive from the point of view of structural applications. These foams are manufactured by infiltration of small SiO2 spheres into the molten alloys. After alloy solidification the SiO2 spheres are removed by immersing the material in a solution of aqueous hydrofluoric acid. In this work, we have investigated the effect of two different foam preparation techniques: inductive and resistive melting. The paper details both the physico-chemical and mechanical characterization of the foams synthesized with the two different methods. The purpose of this study is to determine the quality of each synthesis method in order to identify the best alternative.