AFM-Porosimetry: Density and Pore Volume Measurements of Particulate Materials

Abstract

We introduced the novel technique of AFM-porosimetry and applied it to measure the total pore volume of porous particles with a spherical geometry. The methodology is based on using an atomic force microscope as a balance to measure masses of individual particles. Several particles within the same batch were measured, and by plotting particle mass versus particle volume, the bulk density of the sample can be extracted from the slope of the linear fit. The pore volume is then calculated from the densities of the bulk and matrix materials, respectively. In contrast to nitrogen sorption and mercury porosimetry, this method is capable of measuring the total pore volume regardless of pore size distribution and pore connectivity. In this study, three porous samples were investigated by AFM-porosimetry: one ordered mesoporous sample and two disordered foam structures. All samples were based on a matrix of amorphous silica templated by a block copolymer, Pluronic F127, swollen to various degrees with poly(propylene glycol). In addition, the density of silica spheres without a template was measured by two independent techniques: AFM and the Archimedes principle.

Effects of Polypropylene Glycol 400 (PPG400) on the Micellization and Gelation of Pluronic F127

“…Our interest in the F127/PPG 400/water system arose because it could be used as a structure directing agent in the synthesis of mesoporous materials. Recent publications − have indicated advantages in expansion of mesoporous structure using polypropylene glycol (PPG3000) as a swelling agent. TEOS was used as the silica source, and F127 was used as the template.…”

Polarization Characterization of Porous Particles Based on DDA Simulation and Multi-Angle Polarization Measurements

“…(2) Based on the pore size obtained in step 1, we further extract the theoretical values of the polarization index S T (θ, p) corresponding to different porosities p that change from 0 to 100% with a step of 0.1%. The polarization indexes contain P-Hdop(30 (10) The measured data of the three porous particles (Unips5-100Å, Unips5-300Å, and Unips5-1000Å) are used to assess the feasibility of the inversion algorithm, and the results are shown in Table 2. The deviations of inversion pore size for Unips-300Å and Unips-1000Å are less than 4%, and the errors of inversion porosity are less than 6%.…”

“…Electron microscopy [6,7], N2 absorption isotherms [8], and mercury instruction proximity [9] are considered the typical methods to characterize pore structure at the microscale, but suffer from long sampling time, complex operation and potentially altered particle properties. AFM [10] and NMR cytophotometry [11] have high measurement accuracy but a limited pore size measurement range. Small-angle X-ray [12] scattering can obtain abundant structural information; however, it requires complex numerical analysis methods and eliminating interference effects.…”