Geoscience Reference
In-Depth Information
Figure 10.34 Schematic of the nozzle
mixer.
Source: Courtesy of E. Lester.
Supercritical
water
Stainless
steel tube
Union cross
Reactor
outlet
Thermocouple T2
Heater
Stainless steel tube
T-piece
Thermocouple T1
Water cooling
Aqueous
metal
salt
its infancy and far beyond its maturity even though this hydrothermal method has
been studied for many years. Yu and coworkers have reported the hydrothermal
synthesis of such nanostructures of ZnO, CuO, VO
2
, MnO
2
, MoO
3
, h-WO
3
,Fe
2
O
3
,
SnO
2
, and oxides and hydroxides of rare earths
[153]
.
10.6.7 Hydrothermal Processing of Mixed Oxides
Several mixed oxide nanoparticles like CoFe
2
O
4
, ZnFe
2
O
4
, ZnAl
2
O
4
,Fe
2
CoO
4
,
BaFe
12
O
19
, LiMn
2
O
4
, and LiCoO
2
have been synthesized using hydrothermal and
supercritical hydrothermal methods. Similarly, MgFe
2
O
4
nanoparticles in the size
range 20
50 nm have been prepared under supercritical hydrothermal conditions
600
C; P
(T
10 min)
showing greater capability for magnetic hyperthermia. The coercivity force and
saturation magnetization at room temperature of these nanoparticles are 61.3 Oe
and 15.3 emu/g, respectively.
Figure 10.35
shows nanoparticles of LiMn
2
O
4
with a
particle size ranging from 10 to 20 nm synthesized from LiOH, Mn(NO
3
)
2
, and
H
2
O
2
at 400
C and 30 MPa. These particles do not show the decay of its capacity
even after the charge
30 MPa; Mg/Fe mole ratio
1.5; experimental duration
5
5
5
5
discharge cycles, which has been considered as a major
breakthrough point of these solid electrolyte materials
[154,155]
. Kanamura et al.
[156]
have discussed this mechanism in detail and concluded that these particles
are single crystals of LiMn
2
O
4
and are totally different from those obtained by
