Verification of the Condensation Model for Cylindrical Nanopores. Analysis of the Nitrogen Isotherm for FSM-16

An improved condensation model for the estimation of pore-size distribution in the range of nanometers is examined. In the authors' previous paper, the model proved its reliability in computer experiments employing the molecular dynamics technique. The model is tested here in a real experimental system with a MCM-41-like ordered mesoporous silicate, FSM-16. The study includes how to find the adsorbate−solid interaction strength, which is taken into account as an additional contribution for condensation other than the Kelvin effect. The true pore size of the material is separately determined to be 3.2 ± 0.2 nm by high-resolution transmission electron microscopy observation, and by a “colloidal particle adsorption method”. The conventional model for condensation, the Kelvin model, underestimates the pore size of FSM-16 to be 2.5 nm from the nitrogen isotherm. The present model successfully predicts the pore size to be 3.4 nm, and proves its reliability in the real experimental system. The effect of the pore wall's potential on the capillary coexistence relation is further discussed comparing ordered mesoporous silicates and the usual silica materials.