the solidified
mass was washed repeatedly with distilled water to remove any
residual salt, and then dried in an oven for further characterization.
To assist verifying their core–shell structure (i.e., the
coating formation), as-prepared particles were heated to 600 ◦C
for 60 min in air to oxidise their carbon cores. In addition, to
examine the effect of NaF on the dissolution of Si in the salt and
assist understanding the MSS mechanism, Si powder was fired
alone at 1100 ◦C for 6 h in a single NaCl, a single NaF or a binary
salt containing 5 wt% NaF, and their morphology changes before
and after firing were examined using the techniques described
below (Section 2.2).