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

摘要

Multi-component composite particles centered by polyethylene covered with the outer shell layers comprising Mg(OH)_2 and TiO_2 were prepared with 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 noticeable boundary of two different layers. According to the EPMA mapping and EDX local elemental analyses, concentration of Mg and Ti are either almost constant everywhere in the shell, or with a slight radial gradient, depending on the preparation condition. Chemical interactions within the shell are found by XPS,where profiles indicate the shift is observed toward higher binding energy side for Mg2p and lower energy for Ti2p. When the composite particles are calcined at 1000°C after burnout of the core polymer particle, composite hollow shells containing MgTiO_3 (MT) is formed. The relative amount of MT in the calcined product is different, depending on the titania source. The largest MT fraction is recorded when starting from TiO_2 anatase. The change in the microhomogeneity of the shell layer is not parallel to the MT fraction after calcinationPhysical homogenization and chemical interaction are shown to take place simultaneously within a shell layer during mechanical double coating.