BH4− self-diffusion in liquid LiBH4.
The hydrogen dynamics in solid and in liquid LiBH4 was studied by means of incoherent quasielastic neutron scattering. Rotational jump diffusion of the BH4- subunits on the picosecond scale was observed in solid LiBH4. The characteristic time constant is significantly shortened when the system transforms from the low-temperature phase to the high-temperature phase at 383 K. In the molten phase of LiBH4 above 553 K, translational diffusion of the BH4- units is found. The measured diffusion coefficients are in the 10(-5)cm2/s range at temperatures around 700 K, which is in the same order of magnitude as the self-diffusion of liquid lithium or the diffusion of ions in molten alkali halides. The temperature dependence of the diffusion coefficient shows an Arrhenius behavior, with an activation energy of Ea = 88 meV and a prefactor of D0 = 3.1 × 10(-4)cm2/s.
Martelli
Pascal
P
Empa Swiss Federal Laboratories for Materials Science and Technology, Hydrogen & Energy, Dübendorf, Switzerland. pascal.martelli@empa.ch
Remhof
Arndt
A
Borgschulte
Andreas
A
Mauron
Philippe
P
Wallacher
Dirk
D
Kemner
Ewout
E
Russina
Margarita
M
Pendolino
Flavio
F
Züttel
Andreas
A
D001894:Borohydrides / Q000737:chemistry*; D001895:Boron / Q000737:chemistry; D004058:Diffusion; D006859:Hydrogen / Q000737:chemistry; D018020:Lithium Compounds / Q000737:chemistry*; D013696:Temperature
D001894:Borohydrides; D018020:Lithium Compounds; D006859:Hydrogen; C040936:lithium borohydride; D001895:Boron