Surface area investigation of materials with transition layers of continuously changing electron density

The paper examines the comparison of the surface areas of siliceous materia ls with the surface polymer layer, measured by means of SAXS and BET method s. The investigated materials possessed the transition layer at the air-sur face polymer layer interface border in which the electron density changes i n a continuous manner. The results show that the equation [I(q)= k(1)/q + k (2)/q(3)] gives SAXS surface areas comparable with those from BET measureme nts. However, the former are lower. In addition, the difference between the m depends on the transition layer thickness, as well as on the composition of the surface polymer layer. In case of the surface area investigation of rigid materials with soft surface polymer layer and not sharply defined int erface border, the SAXS method seems to be more convenient than the BET one due to the low temperature (-196 degrees C) during BET measurements. (C) 1 999 Elsevier Science B.V. All rights reserved.