Significance and Use
5.1 Advanced ceramic powders and porous ceramic bodies often have a very fine particulate morphology and structure that are marked by high surface-to-volume (S-V) ratios. These ceramics with high S-V ratios commonly exhibit enhanced chemical reactivity and lower sintering temperatures. Results of many intermediate and final ceramic processing steps are controlled by, or related to, the specific surface area of the advanced ceramic. The functionality of ceramic adsorbents, separation filters and membranes, catalysts, chromatographic carriers, coatings, and pigments often depends on the amount and distribution of the porosity and its resulting effect on the specific surface area.
5.2 This test method determines the specific surface area of advanced ceramic powders and porous bodies. Both suppliers and users of advanced ceramics can use knowledge of the surface area of these ceramics for material development and comparison, product characterization, design data, quality control, and engineering/ production specifications.
Scope
1.1 This test method covers the determination of the surface area of advanced ceramic materials (in a solid form) based on multilayer physisorption of gas in accordance with the method of Brunauer, Emmett, and Teller (BET) (1)2 and based on IUPAC Recommendations (1984 and 1994) (2) and (3). This test method specifies general procedures that are applicable to many commercial physical adsorption instruments. This test method provides specific sample outgassing procedures for selected common ceramic materials, including: amorphous and crystalline silicas, TiO2, kaolin, silicon nitride, silicon carbide, zirconium oxide, etc. The multipoint BET (1) equation along with the single point approximation of the BET equation are the basis for all calculations. This test method is appropriate for measuring surface areas of advanced ceramic powders down to at least 0.05 m2  (if in addition to nitrogen, krypton at 77.35 K is utilized as an adsorptive).
1.2 This test method does not include all existing procedures appropriate for outgassing of advanced ceramic materials. However, it provides a comprehensive summary of procedures recommended in the literature for selected types of ceramic materials. The investigator shall determine the appropriateness of listed procedures.
1.3 The values stated in SI units are to be regarded as standard. State all numerical values in terms of SI units unless specific instrumentation software reports surface area using alternate units. In this case, provide both reported and equivalent SI units in the final written report. It is commonly accepted and customary (in physical adsorption and related fields) to report the (specific) surface area of solids as m2/g, and, as a convention, many instruments (as well as certificates of reference materials) report surface area as m2 g-1, instead of using SI units (m2 kg-1).
