Ammonium Perchlorate Surface Area

The effectiveness of all catalysts is related to the sizes of the particles of ammonium perchlorate and of the catalyst, i.e., to the surface-to-surface contact area. 

Iron compounds are common catalysts for ammonium perchlorate propellant systems, and burning-rate augmentation is a strong function of catalyst surface area and shape. 

Most surface area determinations are based on measurements of the low temperature adsorption of nitrogen or krypton on the solid and use of the BET theory. This procedure may not give reliable results because the products are chilled well below reaction temperature, possibly resulting in the sealing of internal pores. Volumes of gases adsorbed are sometimes small, as observed for dehydrated alums [37] and decomposed ammonium perchlorate [48], where the areas are consistent with product crystallites of linear dimensions between 1 and 3 pm. The results indicate, however, that little, if any, zeolitic material is formed [36]. The surface area of a solid may also be estimated from electron micrographs. Density measurements may be used to complement area measurements. 

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