黒鉛への窒素およびアルゴンの吸着(第4報) -等温線の種々の異常について-

Several adsorption anomalies have occurred during the process of adsorption-desorption of N2 and Ar at 77K on graphite samples: the appearance of a distinct step around a relative pressure of 0.4, a prominent hysteresis over almost the whole range of pressure, and a breakpoint in the BET plot for N2. It is known that the step stems from the\ud process of a second layer adsorptio. Applying the same method for determination of point B, we read an adsorbed amount up to eompletion of a second layer from the isotherm. The observed hysteresis is probably due to the presence of slit-shaped pores on graphite samples. From both the height of the step and the amount of surface oxygen, the relationship between surface area in pores and an amount of surface oxygen is obtained. Furthermore, the cause of the appearance of a breakpoint in a BET plot is briefly discussed in terms of difference in the characterristics of the gas adsorbates