Zircon and carbon is heated in an
electric arc furnace to around 2000°C. Here the SiO2 is reduced to SiO
where it evaporates off leaving behind zirconia. With further treatment, as an
option, a zirconia containing > 0.2% SiO2 can be formed.
Zircon is heated (600-1000°C)
with either sodium hydroxide or calcium oxide (lime) to form a silicate.
Subsequent leaching to remove the silicate, then either drying or calcining,
will produce zirconias at ~ 0.10 % SiO2.
|| Plasma Process
Zircon is continuously fed through a
very high temperature (15,000°C) plasma arc reactor wherein it is
dissociated into the zirconia (ZrO2) and silica (SiO2) constituents. Chemical
processing is then used to remove the silica yielding a zirconia in grades down
to < 0.10 % SiO2.
||Chemically Precipitated Process
thermo-chemically dissolved & taken into solution. A number of zirconium
compounds can then be precipitated out of solution, such as zirconium
oxychloride or zirconium hydroxide. These, in turn, can be calcined to form
zirconias with purity levels up to 99.9 %.