Geoscience Reference
In-Depth Information
Process
Advantages
Disadvantages
Composites
Particle Size
Sol gel (hydrolysis of metal alkoxides),
precipitation, coprecipitation
High product purity and
homogeneity, crystal
symmetry;
metastable compounds
with unique properties;
narrow particle size
distribution; lower
sintering temperatures
May require
calcination,
sometimes milling;
mixed alkoxides can
cause
inhomogeneity,
nonstoichiometry;
sometimes
expensive raw
materials
Oxides; LAS, mullite,
spinel, cordierite
Down to 5 nm;
0.1
5
μ
m
Evaporative decomposition solids
Wide range of chemical
compositions; single-step
process; no separate
calcination or milling
required
Hollow aggregates
formed; precursor
must decompose at
low temperatures;
excess carbon
impurities may
require calcinations
Oxides, nonoxides,
composites, fibers
1
20
μ
m
Hydrothermal processing
High surface area; 99%
dense sintered powders;
submicron particles with
narrow size distribution;
simple equipment;
continuous; no milling or
calcination; short reaction
times; lower energy
requirements
Requires moderate
temperatures/
pressures; requires
additives (seed
crystals), surface
treatments
Y
2
O
3
PSZ, Eu
2
O
3
-
doped HfO
2
lead-
zirconate titanate,
other oxides
Down to 8 nm
(Continued)
