Physisorption
The BET or Langmuir surface area of a material is determined from the measurement of N2-gas adsorption at different partial pressures. The Pore Size Distribution of a material may be assessed yet another part of the adsorption/desorption isotherm. The micro-, meso- and macroporosity of the investigated material is deduced from these isotherms. BET measurements comprise only 5 points of the entire isotherm.
We use a 100-point adsorption/desorption isotherm to quantify pores from 7Å to 0.35µm. Such an analysis allows to quantify small pores which are inaccessible by most other methods such as Hg-intrusion (MICP) or (electron-)microscopy.
Figure. Adsorption and desorption isotherms of a full physisorption analysis. The microporosity of the investigated material is deduced from these isotherms. BET measurements comprise 5 points of the entire isotherm.