Segregation of Components in Freeze Dry Processing for Ceramics Raw Powder

Abstract

In the freeze dry processing of a multicomponent aqueous solution to produce a uniformly mixed powder, segregation of components may occur under certain conditions of freezing operation. In this study, experimental investigation showed how much segregation occurred in an aluminum-magnesium two-component powder produced at various freezing rates. As the result, a freezing bath with sufficiently cooled n-hexane liquid produced powder with little segregation. But using a freezing bath with liquid nitrogen had no advantage in producing low-segregation powder because a droplet of aqueous solution in the bath was enveloped in a layer of gaseous nitrogen and this insulating layer might impede the freezing rate and allow segregation of the components.