Synthesis of nano grade ?-ferric oxide and evaluation of its catalytic properties

Abstract

Ferric oxide is a well–known catalyst for the thermal decomposition of ammonium perchlorate and hence it is extensively used as ballistic modifier for ammonium perchlorate based composite solid propellants. The particle size of conventional propellant grade ferric oxide was reduced to nano levels by continuous ball milling using a planetary ball mill employing zircon balls in isopropyl alcohol. The batches of nano ferric oxide prepared by varying the ball milling parameters viz., time and sample mass were characterised by particle size analyser, surface area analyser, XRD, etc. Lewis acid sites present in the catalyst were determined by butyl amine desorption technique. The catalytic activity of nano ferric oxide samples were evaluated from the thermal decomposition data of ammonium perchlorate mixed with ferric oxide using TG–DTA techniques. The catalytic activity of different batches of ferric oxide was correlated with their surface properties. It was found that continuous ball milling reduced particle size of ferric oxide particles to nano levels and the particle size of conventional ferric oxide was reduced from 138 nm to 72 nm after 40 h of wet ball milling in isopropyl alcohol. The overall decomposition of ammonium perchlorate is reduced from 133°C to 66°C by the addition of ferric oxide ball milled to nanolevels.