Some approaches to producing microporous materials and coatings by EB PVD

Abstract

Techniques to produce bulk microporous structures as well as coatings, are examined in metal and ceramic systems based on the role of second source additives to the main component during their simultaneous evaporation and condensation in an electron beam apparatus. An arbitrary grouping of additives is proposed to differentiate the extent of their interaction in the vapor and solid phases of the main component. Additives are chosen from components that essentially do not interact (group 1), that are essentially removed (group 2), and those that react and are accompanied by the creation and removal of gaseous products during formation of the main condensate phase (group 3). These additives are shown to have a marked influence on the vapor solid interface shape and the dimensions of the deposited columnar crystals, their boundary zones and their internal porous structure. The chemical nature and content of the additives to the vapor phase opens up a broad spectrum of possibilities for construction of stable porous materials with micron and sub-micron size pores and large percentages (30–40%) of voids. Three characteristic shapes of microporous structures were distinguished within columnar and dendritic crystallites containing additives: gaps between dense and porous columns, micropores inside columnar cells and interdendritic (branch) porosity.