Neutron scattering study of adsorption in porous MCM-41 silica

Adsorption of n-pentane on MCM-41 silica has been studied by neutron scattering on both the adsorption and desorption isotherms. Adsorption takes place without hysteresis in either the isotherm or the neutron scattering profile. Adsorption of contrast-matched pentane in porous MCM-41 silica at first increases the intensity of the (10) Bragg peak but reduces the (11) and (20) peaks, and as the pores are filled the intensities of all Bragg peaks are reduced to zero. The SANS background has a 1/Q dependence, typical of a material prepared with templates of one-dimensional character (cylinders). The initial increase of (10) intensity allows estimation of the cylindrical pore diameter to be 37 angstrom based on the variation of form factor as a function of the cylinder radius.