Accession Number : ADA538064


Title :   Low-pressure Structural Modification of Aluminum Hydride


Descriptive Note : Final rept. 1 Oct 2009-30 Sep 2010


Corporate Author : ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD WEAPONS AND MATERIALS RESEARCH DIRECTORATE


Personal Author(s) : Ciezak-Jenkins, Jennifer A


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a538064.pdf


Report Date : Feb 2011


Pagination or Media Count : 22


Abstract : In-situ isothermal high-pressure synchrotron x-ray diffraction and optical Raman spectroscopy were used to examine the structural properties, equation of state, and vibrational dynamics of alpha-aluminum hydride (AlH3). The x-ray measurements show that the pressure-volume relations remain smooth to near 50 GPa. Although there is no evidence for a first-order phase transition, the unit cell axial ratio (c/a) is anomalous near 2.5 GPa, which correspond to the onset of a monoclinic structural distortion. Infrared measurements conducted within a similar pressure range show a distinct discontinuity in the frequencies of the Al-H lattice modes. The combined data provide evidence for a monoclinic structural distortion beginning near 2.5 GPa. The results are consistent with recent synchrotron x-ray diffraction measurements and theoretical calculations. All structural changes are reversible upon pressure release.


Descriptors :   *LATTICE DYNAMICS , *ALUMINUM HYDRIDE , STRUCTURAL PROPERTIES , RAMAN SPECTROSCOPY , DIAMONDS , HIGH PRESSURE , MOLECULAR STRUCTURE , EQUATIONS OF STATE , POLYMORPHISM , PHASE TRANSFORMATIONS , OPTICAL PROPERTIES , LOW PRESSURE


Subject Categories : Physical Chemistry
      Properties of Metals and Alloys


Distribution Statement : APPROVED FOR PUBLIC RELEASE