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Infrared emission imaging as a tool for characterization of hydrogen storage materials

Published

Author(s)

H. Oguchi, Edwin J. Heilweil, Daniel Josell, Leonid A. Bendersky

Abstract

Combinatorial thin films provide an opportunity for studying a variety of properties over a wide range of compositions and microstructures on a single substrate, allowing substantial acceleration of both the fabrication and study of materials and their properties. This paper details the use of infra-red (IR) emissivity imaging for studying the in-situ hydrogenation of Mg_{x}Ni_{1-x} films with hydrogen gas; the method is shown to be a powerful combinatorial screening tool for metal hydrides-base hydrogen storage materials. The 100 nm-thick Mg_{x}Ni_{1-x} composition gradient films (0.4<x<0.9) capped with a Pd layer of varying thickness were deposited in a combinatorial electron-beam deposition chamber using a shutter-controlled multilayer technique. Both as-deposited and 250 °C-annealed films were characterized by scanning electron microscopy (SEM), x-ray ffraction (XRD), and transmission electron microscopy (TEM). TEM study of the “x-ray amorphous” films shows that the microstructure consists of nanoscale grains of a metastable fcc phase as well as Mg_{2}Ni and MgNi_{2} phases over a broad range of higher Ni compositions. The metastable phase appears to be a Ni-stabilized fcc form of Mg. Hydrogenation differences between the studied films and bulk alloys are suggested to be associated primarily with crystallographic differences of the metallic and hydride phases. Hydrogen absorption and desorption of the films were monitored with an infrared camera capable of simultaneously imaging the entire composition spread. The observed changes in infrared intensity due to hydrogen absorption/desorption demonstrate the sensitivity of the method to differeces in composition and microstructure.
Citation
Journal of Alloys and Compounds

Keywords

combinatorial methods, hydrogen storage, infrared emissivity, Mg-Ni
Created December 6, 2008, Updated February 19, 2017