Inorganic Microporous Membranes for Gas Separation in Fossil Fuel ...

4 Results and discussion
(Saito-Foley 137 ) for the microporous materials (HK-SF). A material is considered to be
microporous when the relative microporous adsorbed volume Vmicro/Vtotal is large in
combination with type I N2-sorption isotherm. The Barret, Joyner and Halenda (BJH)
algorithm 130 is selected for estimating the pore size in diameter of mesoporous material
that presents type IV isotherms.
Table 22 Microstructure properties of 8YSZ powders prepared from sols that are extracted or sols that are
dried and calcined at 450 and 500ºC.
Surfactant Temp. in ºC Crystal size
nm
76
SBET
m 2 /g
Vtotal *
cm 3 /g
Vmicro *
cm 3 /g
BJH Ø
nm
HK-SF
Ø nm
C10 450 - 77 0.096 0.021 3.4
C16 450 - 35 0.410 0.009 2.6
CTAB 450 - 67 0.114 0.017 3.5
F127 450 6.5 106 0.106 0.027 3.6
F127 Extracted Amorphous 106 0.260 0.034 7.4
F127 500 8.5 70
Acetyl acetone and caproic acid added to the 8YSZ sol
F127 500 7.0 49 0.037 0.013 3.5
- 500 5.7 57 0.028 0.015 1.0
* Vtotal = Absorbed pore volume at P/P0 of 0.95 128 and the Vmicro= Absorbed pore volume at P/P0 of 0.02
Sols that contained F127 as SDA result in powders with the largest specific surface area.
No clear trend could be observed on the microstructural properties as function of the
SDA type. The addition of the SDA C16 to the 8YSZ sols results in powders with the
lowest specific surface area and the lowest relative absorped microporous volume (ratio
between Vmicro and Vtotal). The microstructural properties of the C16 sample indicate a
more dense material compared to the others. The N2 sorption isotherms of the samples
with C10, C16 and CTA and F127 added to the 8YSZ sols are outlined in Figure 45-B.
8YSZ sol with F127 added as SDA were extracted or calcined at 450 and 500ºC after
drying. A lower specific surface area (106 to 70 m 2 /g) was observed for 8YSZ sols with
F127 when the calcination temperature was increased from 450 to 500ºC. This indicates
that the material is densifying above 450ºC.