High resolution N2 adsorption isotherms at 77.4 K and 87.3 K by carbon blacks and activated carbon fibers--analysis of porous texture of activated carbon fibers by αs-method.

The standard α(s)-data of N(2) at 87.3 K by graphitized and nongraphitized carbon black samples (GCB-I and NGCB) (cf.Figs. 3 and 4) have been determined on the basis of the high resolution adsorption isotherms of N(2) at 87.3 K, which were repeatedly measured in the pressure range of p/p(o)=5×10(-8)-0.4. The high resolution adsorption isotherms of N(2) by two kinds of activated carbon fibers (ACF-I and ACF-II) were measured from p/p(o)=10(-7) to p/p(o)=0.995 at 77.4 K and from p/p(o)=10(-7) to p/p(o)=0.4 at 87.3 K. Combination of the adsorption isotherms by ACF-I and ACF-II with the standard α(s)-data by NGCB at 77.4 K and 87.3 K make it possible to construct the high resolution α(s)-plots from very low filling (1%) to complete filling (100%). The high resolution α(s)-plots of N(2) at 77.4 K and 87.3 K were analyzed. On the basis of the analyzed result, the porous textures of ACF-I and ACF-II will be discussed.

High resolution N2 adsorption isotherms by graphitized carbon black and nongraphitized carbon black--αs-curves, adsorption enthalpies and entropies.

The high resolution N(2) adsorption isotherms (77.4 K) by graphitized carbon blacks (GCB-I: A(BET)=54.2 m(2) g(-1) and GCB-II: A(BET)=69.4 m(2) g(-1)) and nongraphitized carbon black (NGCB: A(BET)=18.87 m(2) g(-1)) have been measured at p/p°=5×10(-8)-0.99. α(s)-Curve of the N(2) adsorption isotherm by GCB-I is completely overlapped with that by GCB-II in the pressure range of p/p°=5×10(-6)-0.90, but the N(2)α(s)-curve by GCB-I is remarkably different from that by NGCB. The standard N(2)α(s)-data by GCB-I and NGCB have been determined in the range of α(s)=0.002-2.2. On the basis of the N(2) adsorption isotherms at the two temperatures (77.4 K, 87.3 K), the isosteric heat of adsorption (differential adsorption enthalpies), the differential adsorption entropies, and the integral adsorption entropies of N(2) molecules have been evaluated between θ (coverage)=0.05 and θ=1.50. The surface homogeneity/heterogeneity of carbon black samples has been discussed by the N(2) differential adsorption enthalpies. The adsorbed state of N(2) molecules on the carbon black surfaces has been considered by the differential and integral adsorption entropies.