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Membrane Processes 359

TABLE 9.5 Representative Conductivities of Oxide Membranes and
®
Nafion Compared with Preliminary Results for Ferroxane-Derived
Membrane. Conductivity is Reported at 100% Humidity and at 20 C
Material/Study Conductivity
(S/cm)
Nafion 117
(Sumner, 1998) 0.06
(Sone, 1997) 0.09
(Kopitzke, 2000) 0.09
SiO 2 glasses
(Nogami, 1998) 10 6 10 3
(SiO 2 -P 2 ) 5 glass
(Tung and Hwang, 2004) 9.43E-3
Sol-gel Al 2 O 3
(Vichi, 1999) 6.0E-4
Alumoxane-derived Al 2 0 3
(Tsui et al.) 6.7E-4
Ferroxane-derived membranes
(Tsui et al.) 0.03

higher conductivity (~0.03 S/cm) at all values of relative humidity com-
pared with the green body and with the ferroxane sintered at 400ºC
(Figure 9.5). Sintering at higher temperatures likely results in the sac-
rifice of the small pores in the ceramic as it forms and a resulting
decrease in conductivity. Under the conditions examined to date, proton
conductivity of these membranes appears to be relatively insensitive to
the relative humidity within the membrane. A membrane with high

1.0E+00
Green body (no sintering)
300°C
1.0E–01 400°C

σ (S/cm) 1.0E–02

log 1.0E–03

1.0E–04

1.0E–05
50% 60% 70% 80% 90% 100%
Relative humidity
Figure 9.5 Conductivity of ferroxane green body and ferroxane-derived
ceramics as a function of humidity.