Page 87 - Book Hosokawa Nanoparticle Technology Handbook

2.2 PARTICLE SIZE FUNDAMENTALS

Electric furnace
3000 Benzene
Benzene heavy water Ethane
Naphthalene
Two phase o-
Toluene Xylene Reactor vessel
2000
Pressure (atm) Biphenyl Condenser

Cyclohexane
1000 Pump Inline
Homogeneous filter
phase
n- Butane
Back pressure
Critical point of water valve
0 Metal salt aqueous Distilled water
300 320 340 360 380 400 420
Temperature (°C) solution

Figure 2.2.12 Figure 2.2.13
Phase behavior of water–hydrocarbon two component Rapid temperature rise type reactor for hydrothermal
system. synthesis in supercritical fluid.

Table 2.2.2
Nanoparticles synthesized by the supercritical hydrothermal method.

Starting materials Products Particle size (nm) Morphology
Al(NO ) AlOOH 80~1,000 Hexagonal
3 3
Rhombus
Needle-like
Fe(NO ) -Fe O 3 ~50 Spherical
2
3 3
Fe (SO ) -Fe O 3 ~50 Spherical
4 3
2
2
FeCl 2 -Fe O 3 ~50 Spherical
2
Fe(NH )2H(C H O ) Fe O 4 ~50 Spherical
6
3
7 2
5
4
Co(NO ) Co O 4 ~100 Octahedral
3
3 2
Ni(NO ) NiO ~200 Octahedral
3 2
ZrOCl 2 ZrO (cubic) ~20 Spherical
2
Ti(SO ) TiO 2 ~20 Spherical
4 2
TiCl 4 TiO (anatase) ~20 Spherical
2
Ce(NO ) CeO 2 20~300 Octahedral
3 3
Fe(NO ) , Ba(NO ) BaO·6Fe O 3 50~1,000 Hexagonal
3 2
3 3
2
Al(NO ) , Y(NO ) , TbCl 3 Al (Y Tb) O 12 20~600 Dodecahedronal
3 3
5
3 3
3
synthesizing hydroxides or oxides making use of this To eliminate the effect of reaction during the tem-
shift of equilibrium is called the hydrothermal syn- perature rise, a flow-type rapid temperature rise reac-
thesis method. Supercritical hydrothermal synthesis tor [3] as shown in Fig. 2.2.13 has been developed.
applies supercritical water as the reaction zone for The metal salt solution is supplied by a high-pressure
the hydrothermal synthesis. In most cases, the liquid pump and contact is made with the supercriti-
hydrothermal synthesis tests are conducted using a cal water fed through a high-temperature furnace in
batch autoclave. After charging the feed material, the the other separated line.
hydrothermal synthesis is carried out by heating the In this method, the feed liquid is heated up rapidly
reaction vessel. However, since the hydrothermal syn- to the supercritical state and the hydrothermal
thesis takes place as the temperature increases by this synthesis reaction takes place in the supercritical
method, the final product includes the compounds water. The results obtained with this flow-type rapid
generated during the temperature rise, even when the temperature rise reactor are shown in Table 2.2.2. It
process finally reaches the critical point. suggests wide application of this method because of
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