Silica glasses with high surface area were prepared by the sol-gel method, the electrical conductivity of which was measured as a function of the content of adsorbed water. The glasses obtained by heating at 400-800°C had specific surface areas of 700-900 m 2 /g glass and exhibited room-temperature conductivities of 10 -6 -10 -3 S/cm by absorbing the water in pores. The activation energy for conduction linearly decreased with increasing logarithm of the product of proton and water concentration. On the other hand, the increase in conductivity was represented to be proportional to the logarithm of water concentration. Electrical conduction in glasses containing a large amount of water is related to the dissociation of protons from the SiOH bonds and the proton hopping through water molecules in pores. IntroductionProtons in glass are bound with oxygens to form hydroxyl groups attached to a network forming cations such as Si 4+ and P 5+ and are able to function as electrical charges when they are strongly hydrogen bonded in glasses. 1-3 Fast protonconducting glasses, if developed, have a high potential for use in clean energy fields, such as hydrogen gas sensors and hydrogen fuel cells. Recently, using a sol-gel technique, we succeeded in preparing P 2 O 5 -containing glasses with high conductivities of approximately 10 -4 -10 -2 S/cm at room temperature. 4-6 These high conductivities are considered to be achieved by fast proton mobility in the coexisting adsorbed molecular water in samples. The question how the adsorbed waters contribute to the high proton conductivity was not clear at that time.In the previous paper, we discussed the effect of molecular water on the proton conduction using sol-gel-derived porous silica glasses containing water molecules up to 2 wt %. 7 Since the water content is less than 2 wt %, all the water molecules are strongly hydrogen-bonded with SiOH on the pore surface. The activation energy for conduction linearly decreased with increasing logarithm of the product of proton and water concentration. We concluded that the proton conduction is associated with proton hopping between SiOH and water molecules and its activation energy is related to the energy necessary for the dissociation of the proton from SiOH and H 2 O. The dissociated proton from the hydroxyl groups moves between the SiOH and the H 2 O bound with SiOH. However, the effect of the molecular water adsorbed in excess of the number of SiOH groups still remains unknown. Molecular water acts sometimes in harmful ways to decrease the chemical durability of glasses. The search for the effect of water on proton conduction is necessary for both an understanding of the mechanism of proton conduction in glass and the development of fast proton conducting glasses.In this paper, we discuss how molecular water contributes to the proton conduction of water-containing glasses. Porous silica glasses with high specific surface areas were prepared by the sol-gel method, the conductivities of which were measured under a controlled water vapor...

High proton conducting P2O5−SiO2 glasses were prepared using the sol−gel method, the electrical conductivities of which were studied in relation to the pore structure and the adsorbed water. The pore properties of SiO2 and P2O5−SiO2 glasses were controlled by addition of formamide during the gel synthesis, the specific surface areas of which were changed from 200 to 900 m2/g-glass. These glasses absorb water molecules on exposure to a humid atmosphere. The conductivity increased with increasing logarithm of water concentration and reached a saturated value above the water vapor pressure of 0.8. The highest conductivity, 2 × 10-2 S/cm at room temperature, was achieved by 5P2O5−95SiO2 glass heated at 700 °C and absorbing the water molecules.

Pervious concrete is used as the material for drainage structure in roads, buildings, and water facilities due to its excellent permeability. Existing devices for testing the permeability of pervious concrete do not consider the fluid leakage through the specimen-container interface induced by the large numbers of open pores on the surface of molded specimen. This may significantly affect the precision of the results. In this study, a new permeability test device for pervious concrete was developed and a modified permeability testing method is described. The modified method and currently used test methods were employed to measure the permeability of molded specimens with different porosities, graded aggregates, and admixtures. In order to calibrate the modified method, the permeabilites of the cored specimens were measured using the method and currently used test methods. The comparisons show that the permeabilities of the molded specimens measured using the modified method are lower than the two existing methods, and are approximate to the results of cored specimens. This indicates that for the molded specimens, the modified method can give better precision and more accuracy than the two existing methods.

High Proton Conductivity in Porous P 2 O 5 -SiO 2 Glasses.-Porous silica glasses containing 2 or 5 mol% P 2 O 5 are prepared by a sol-gel process starting with the hydrolysis of Si(OEt) 4 and PO(OMe) 3 . The electrical conductivity of the glasses is studied as a function of the pore structure and the amount of adsorbed water. The pore structure is controlled by addition of formamide during gel syntheses and the specific surface area is varied over the range 200-900 m 2 /g. Exposure to humid atmosphere results in water absorption. The conductivity is found to increase linearly with increasing product of the surface area and the reciprocal number of the pore radius. The protons in P-OH bonds give conductivities 4 orders of magnitude higher than that of Si-OH bonds. The highest conductivity of 2·10 −2 S/cm is observed for the glass with 5 mol% P 2 O 5 after heating at 700 • C and water absorption. -(NOGAMI, MASAYUKI; NAGAO, RITSUKO; WONG, CONG; KASUGA, TOSHIHIRO; HAYAKAWA, TOMOKATSU;

Proton Conduction in Porous Silica Glasses with High Water Content.-Silica glasses with high surface area are prepared by the sol-gel method. The glasses obtained by heating at 400-800 • C have specific surface areas of 700-900 m 2 /g and exhibit room temp. conductivities of 10 −6 to 10 −3 S/cm by absorbing the water in pores. Electrical conduction in glasses containing H 2 O is related to the dissociation of protons from the SiOH bonds and the proton hopping through H 2 O molecules in pores. -(NOGAMI, M.; NAGAO, R.; WONG, C.; J.