I have recently begun working with magnesium powder, looking at the de/hydrogenation thermodynamics and kinetics using a Hiden Isochema IGA-003 (Gravimetric gas sorption).
What I would like to know is what sequence of steps and what conditions are generally recommended for preparing a magnesium sample before conducting temperature-dependent dehydrogenation sweeps and hydrogenation/dehydrogenation kinetic cycling.
Naturally, I imagine its best practice to run experiments in this sequence after loading from an inert glovebox:
1) leak test (static vacuum, observe temperature for several minutes)
2) purge system (flush with helium and evacuate again)
3) determine dry mass at static vacuum
4) Buoyancy measurement to determine sample density (skeletal volume)
5) Initial hydrogenation
6) Other tests
Currently, I have attempted the initial hydrogenation at 450 deg C at 10 bar (pressure set to regulate to oppose increasing pressure from heating) H2, but during heating, I get an anomalous decrease in the sample weight (which doesn't align with the gas density changes aka. not a buoyancy effect).
Is something missing in my preparation stages? Could someone please suggest a robust standard operating procedure for magnesium?
Thank you
Charles Brewster