Physical and chemical interactions in multi-component composite particles prepared by mechanical stressing

Multi-component composite particles containing polyethylene in the center with shell layers of Mg(OH)₂ and TiO₂ were prepared in a shear-compression type machine by a stepwise double-coating method. Whether and to what extent physical and chemical interactions occur between particles in the shell layer during preparation were examined. The composite shell layer is well mixed, without a noticeable boundary between the two different layers. According to the EPMA mapping and EDX local elemental analyses, the concentrations of Mg and Ti are almost constant everywhere in the shell, with an appreciable fluctuation on a higher resolution. Chemical interaction within the shell was detected by X-ray photoelectron spectroscopy (XPS), i.e., as a chemical shift toward the lower energy side for Ti_2p. When the composite particles are calcined at 1000°C after burnout of the core polymer particle, composite hollow shells containing MgTiO₃ (MT) are formed. The relative amount of MT in the calcined product is different, depending on the titania source and is the highest, 0.73, by starting from anatase as a source of titania.