Development of Certified Reference Materials of Aluminum Oxide Porosity for Mercury Porosimetry Method

Egor P. Sobina, Ural Research Institute for Metrology (UNIIM), Ekaterinburg, Russian Federation

Creation of new porous materials, the quality of which should be controlled, requires the use of a wide range of instruments for measuring porosity characteristics. The most accurate method for measuring pore size in the range from 100 nm to 0.9 mm is the mercury porosimetry method. The objects of application of mercury porosimetry are rocks and ores, pigments, carbon and graphite, catalysts and minerals, glass, coatings, adsorbents, fertilizers, coal, filters, fillers, fabrics and fibers, gaskets, fibrous plates, refractories, paper, nuclear fuel, metal slags and composite materials. The method of mercury porosimetry is based on the fact that mercury, which does not wet a solid, penetrates into its pores only when exposed to external pressure.
Different materials of aluminum oxide with pore sizes from 12 nm to 60 000 nm were selected. Homogeneity and stability of granular alumina material with the pore size of 12 nm have been studied earlier using the gas adsorption method. The aim of the present work was the estimation of uncertainty of the following properties of such materials measured based on the mercury porosimetry: specific pore volume, specific surface area, the predominant and average pore size; as well as pressures, which correspond to 25 %, 57.5 % and 87.5 % of the specific saturation volume. Since the membranes of α-phase aluminum oxide are a new material, the full cycle of homogeneity and stability study was carried out with them. The obtained average pore sizes of the membranes under study were ~ 1000 nm, ~ 8000 nm, 58000 nm.
Development of the reference materials will provide a traceability chain for realization of SI in measurements of properties of solids and materials with the method of mercury porosimetry in various industries.

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