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.