Particulate deposit core particles

The core and shell type of particulates are similar to one of the deposit morphologies formed on an Fe-Ni alloy from CO at temperatures above 500°C where the core consisted of a metal particle in the size range 0.09 to 0.2 pm, with a shell thickness typically of 0.04 jjm(23). The structure of the particles, i.e. a carbon layer on metal, is comparable to the laminar film on the metal, suggesting that the carbon in the shell has been precipitated. Free metal particles have not been observed on the iron foils that could serve as active centres for growth directly from the gas phase. Therefore, it must be concluded that a solution-precipitation process plays a part in determining the final morphology of the core / shell particles, but further details of the mechanism of growth cannot be established at present. 

The outer shape of the microcapsules depends on the type of material in the core and the method of depositing the wall material. Microcapsules may be smooth, spherical particles and grape-like conglomerates or irregular particulates with smooth or rough surfaces. 

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