Crystal Structure and Morphology of Hydrogen Absorbing Alloys with BCC Structure
- PDF / 396,676 Bytes
- 8 Pages / 612 x 792 pts (letter) Page_size
- 75 Downloads / 199 Views
BB7.2.1
Crystal Structure and Morphology of Hydrogen Absorbing Alloys with BCC Structure Akiba E., Enoki H. and Nakamura Y. National Institute of Advanced Industrial Science and Technology AIST Central 5, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565 Japan ABSTRACT Hydrogen absorbing alloys with BCC (body centered cubic) structure such as Ti-V-Mn, Ti-V-Cr and Ti-V-Cr-Mn systems were proposed and named as “Laves phase related BCC solid solution” by Akiba in 1993. Since our reports, many researchers have developed BCC hydrogen absorbing alloys. These alloys have higher hydrogen capacity (about 2.8 mass% at present) than conventional intermetallic compounds. Many efforts have been made to increase hydrogen capacity of the alloys but fundamental studies were a few. Crystal structure and morphology of the BCC alloys that are keys to understand BCC hydrogen absorbing alloys are reviewed. INTRODUCTION Body centered cubic (BCC) metals and alloys intrinsically have a large hydrogen capacity but they have not been used for any applications so far. Even studies on hydride formation in BCC alloys were fewer than those of conventional intermetallics such as AB5 and AB2 alloys[1~7]. We will review new BCC alloys developed based on a new concept, "Laves phase related BCC solid solution", proposed by Akiba [8, 9]. Hydrogen absorbing alloys based on the concept of “Laves phase related BCC solid solution alloy” have been developed but only a few studies on fundamentals of the alloys such as crystal structure of both alloys and hydrides have been reported. In addition, morphology or “nano-order” structure of these alloys is key to understand hydrogen absorbing /desorbing properties of “Laves phase related BCC solid solution alloy”. EXPERIMENTAL DETAILS All the alloys were prepared by arc melting method. The alloys were hydrogenated as-cast unless the heat-treat conditions were shown. The as-cast alloys are enough active for hydrogenation. Therefore, as-cast alloys were used for most of measurements. Morphology of the alloys was observed by JEOL JEM-2000FX II transmission electron microscope (TEM). Deuteride samples of Ti1.0V1.1Mn0.9 were prepared by hydrogenation with D2 gas at 5MPa at room temperature. The average deuterium content determined by chemical analysis was 1.55±0.03 D/M and 1.56±0.03 D/M. The sample for neutron scattering is the same for every measurement. The Time-of-flight (TOF) powder diffraction data were collected by Vega at KENS, KEK (High-Energy Accelerator Research Organization, Japan) and the crystal structure was refined using RIETAN-98T3). The neutron scattering measurement was performed at room temperature using the high-intensity total scattering spectrometer, HIT-II at KENS. The sample of 2 cc was put into a vanadium cylindrical cell. Measurements were performed on the sample, the blank cell, background and a vanadium rod, respectively.
BB7.2.2
RESULTS AND DISCUSSION The concept of Laves phase related BCC solid solution Nominal AB2 multi-component alloys that have been developed for battery and heat pump appli
Data Loading...
