Evaporation of volatile component from intermetallic granule with non-volatile component shell

A problem of evaporation of a volatile component A from a spherical granule with an intermetallic core A(n)B(m) and a protective shell of a nonvolatile component B has been studied. Solution of the given problem (which belongs to the so-called Stefan's-type problems with two moving boundaries) was obtained by asymptotic method. It is shown that, unlike for a liquid droplet of the same total content, for a solid granule with a shell there is a range of conditions under which a quasi-steady-state regime of evaporation is possible. The issue connected with the use of the A,B, granules as vapor sources in the production of film materials are dealt with. (C) 1999 Elsevier Science Ltd. All rights reserved.