Study On Fabrication Of Monodispersed Hollow Barium Ferrite Submicrospheres

As a hotspot and research foreland of nanomaterial science, micron or submicron hollow spheres with controllable structure and tunable properties have potential applications in such field as electromagnetic, optics, chemistry, pharmacy, biology, and so on. Due to the double difficulties in control of both impurity and ingredients, the study on fabrication of mono-dispersed hollow inorganic spheres of multi-metal-element systems still keeps a challenge to scientists. The fabrication of mono-dispersed M-type barium ferrite hollow submicrospheres, which may be used as high performance microwave absorbers, is exploringly studied in this thesis.Monodisperse poly (styrene-co-acrylic acid) latexes with carboxylic surface are synthesized by soap-free emulsion polymerization. The results show that during the soap-free emulsion polymerization of styrene, using hydrophilic acrylic acid as comonomer will enlarge the polymerization system stabilization and improve the monodisperse characteristic of the obtained latexes. The copolymerization parameters such as concentration of electrolyte and acrylic acid, the charging occasion of acrylic acid etc. have strong influence on the size and surface-bounded carboxyl content of poly (styrene-co-acrylic acid) particles.The technique of layer-by-layer electrostatic self-assembly templated on colloids to core-shell composites is explored. The results show that the particle size and surface properties of barium ferrite precursors have direct dependence on the electrostatic self-assembling behavior. When the barium ferrite precursors synthesized by chemical co-precipitations in polar solvent are used as building blocks, the polystyrene/barium ferrite precursor core-shell particles with loose shells and a mass of free "building blocks", which are difficultly to remove, will be obtained. When the ones synthesized in reverse microemulsion are used as building blocks, the core-shell particles containing dense shells are gained with rather low efficiency and expensive cost. When the ones synthesized in weak polar solvent are used as building blocks, the perfect core-shell particles of compact coatings and without free "building blocks" are obtained, but resulting in a hybrid hollow particles of BaFe₁₂O₁₉ and a-Fe₂O₃ after heat-treatment to the core-shell composites.The monodisperse poly(styrene-co-acrylic acid)/barium ferrite precursor core-shell particles are fabricated by means of the chemical interaction between the...