Effects of scaling in metal hydride materials for hydrogen storage and compression

• Effect of scaling is reported for the first time.
• Scale effect is determined by elastic strains while phase transition of hydride.
• Scale effect does not influence the behaviour of pure hydride phase.
• The hydrogen chemical potential change ΔμsH is used to describe the scale effect.

For the first time the dependence of thermodynamic parameters of hydrogen desorption process on sample scale (weight) was discovered experimentally for the desorption isotherms of 100 g and 500 g samples of LaFe0.1Mn0.3Ni4.8. The scale effect leads to decreasing of the equilibrium pressure for the larger sample, the pressure difference is ΔPscale=-0.15±0.03MPa at 100 °С, and is in the range ΔPscale=-0.5to-0.3MPa at 150 °С. In our opinion the scale effect is determined by elastic strains due to the mutual influence of particles while phase transition from hydride to solid solution and back in large-scale fine–disperse beds of AB5-type compounds. Scale effect has no influence on the behaviour of pure hydride phase and is absent for small samples. The value of hydrogen chemical potential change is proposed for the description of scale effect, average values are equal ΔμHscale=-310±30J/mole H for 100 °C and ΔμHscale=-260±30J/mole H for at 150 °C.