HYDROGEN JUMP DYNAMICS OF TWO ALKALI BOROHYDRIDES

 

Nina Verdal1, Michael Hartman2, Timothy Jenkins1, John J. Rush3,

Terrence J. Udovic1

 

1NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, MD 20899-6102;

2Nuclear Engineering and Radiological Sciences, University of Michigan, Ann Arbor, MI 48109-2104

3Department of Materials Science and Engineering, University of Maryland,
College Park, MD 20742-2115;

 

Quasi-elastic neutron scattering studies have been performed on potassium borohydride (KBH4) and sodium borohydride (NaBH4), two potential hydrogen storage materials.† The data were collected at temperatures near a phase transition that is characterized by a change in the orientation of the borohydride anions:† At low temperatures below the phase transition, the BH4- anions are ordered.† At high temperatures above the phase transition, the BH4- anions are disordered with the hydrogen atoms of the borohydride tetrahedra in half-occupancy positions, in a cube surrounding the boron.† So far, data has been collected on the KBH4 in the high-temperature, disordered phase, and on the NaBH4 in the low-temperature, ordered phase.† From the analysis of these results, it has been determined that the BH4- anions rotate via twofold and threefold reorientational jumps, in an uncorrelated manner, within the timescale of the measurement.† The barriers to this hydrogen motion have been determined from the analysis of data collected over a range of temperatures.

 

 

 

 

 


 

CATEGORY: Materials

Mentorís Name: Terrence J. Udovic

NCNR Neutron Condensed Matter Science

Bldg 235, room A121, mailstop 6102

Phone:† 301 975 6027

Fax:† 301 921 9847

Email:† nina.verdal@nist.gov

Not a Sigma Xi member