Preparation Of Inorganic Embolic Material

Aiming at the problem of existing embolic material, this thesis selected barium ferrite as study system. Magnetic microspheres were obtained by preparation of fine powders, pelleting and heat treatment. Their performance was also analyzed.Fine powders of barium ferrite were prepared by auto-combustion method. Under pH value of solution was 7⁹, pure barium ferrite could be produced after auto-combustion of gel and 600℃ heat treatment. Its magnetization and coercive force were higher than product under 700℃ by magnetism test. Study on reaction path: citric acid complexed metal ion through NH₄⁺ and NO₃^- participated gel formation as a whole; auto-combustion was a heterogeneous process, NO3^- and citric acid had oxidation -reduction, gel had certain autocatalysis and citric acid not complexed might be decarbonized; barium ferrite couldn't be obtained under lower temperature(500℃), medium grain size of fine powders under 600℃ was 110nm, product under 700℃ crystallized more completely but grain growth and agglomeration were observed. Analysis on effect factor: precipitate appeared if pH value was less than 7, which resulted in bad gelation; optimum heating temperature was 80℃, temperature blow 60℃ or above 100℃ was a disadvantage; auto-combustion phenomena were affected by proportion of citric acid; reaction space was too big or small to process auto-combustion. According to E-pH diagram, theories of propellant thermochemistry and thermodynamics and simple model, mechanism of auto-combustion was discussed preliminarily.Microsphere between 200μm and 300μm were obtained after pelleting of fine powders and heat treatment. The distribution was homogenous and there were plenty pores on surface. The mensuration of density and magnetism indicated: apparent density reduced and size distribution became wider with increase of bonder content; apparent density increased with increase of solid content in slurry but high solid content would be a disadvantage, general in 60⁶5%(mass ratio); higher atomizing pressure made size distribution narrow; apparent density increased with bigger diamond of nuzzle; With higher heating temperature, density of microsphere reduced, saturation magnetization increased and remanent magnetization increased initially then reduced; With longer heating time, saturation magnetization increased initially then reduced and remanent magnetization reduced.Microsphere had preferred magnetism response under magnetic field. Retained quantity reduced with higher medium velocity but increased with higher field intensity.Observation of cell morphology, anchorage-dependent rate and MTT colorimetry preliminarily indicated that microsphere had no cytotoxicity.