Si and CB powders pre-mixed in a molar ratio (Si/C) of
1/12–1/2 were ultrasonically dispersed in isopropyl alcohol
(IPA) for 2 h. After evaporation removal of IPA in an oven, the
dry mix obtained was ball milled with a single NaCl salt or a
NaCl–NaF binary salt containing 1.25, 2.5, 5 or 20 wt% NaF.The
powder mixture was then placed in a graphite crucible with a lid
and fired in a tube furnace under Ar protection to 900–1200 ◦C
and held for 6 h.