Study On Preparation And Surface Modification Of BaFe₁₂O₁₉/PU Composite Microspheres

At present,magnetic microspheres have many defects,such as low content of magnetic substance,broad distribution of particles size,lack of active functional groups on surface,bad biocompatibility and so on.In this study,Ba-ferrite particles and PU were chosen to prepare BaFe₁₂O₁₉/PU magnetic composite microspheres combining with X-ray radioparency and high magnetic response of BaFe₁₂O₁₉ and excellent elasitisity,good biocompability of PU polymer.After surface modification, the microspheres obtained aminated surface,high magnetic contents and narrow size-distribution.The paper focused on preparation and surface modification of micro- and nano- BaFe₁₂O₁₉ particles,the optimal technological conditions for preparation,physic-chemical properties and adsorptive Capacities of the composite microspheres.An appropriate preparation technology for magnetic composite microspheres was established.BaFe₁₂O₁₉ powder with flake structure and 1μm of average size was prepared by self-combustion method.Spherical nano-BaFe₁₂O₁₉ particles were synthesized by using citrate sol-gel method combined with rapid warming and pre-heat treatment process,glycol and PVA were utilized as auxiliaries.The average size of nano-BaFe₁₂O₁₉ particles was 30-50 nm.Both of micro-BaFe₁₂O₁₉ and nano-BaFe₁₂O₁₉ had high saturation magnetization.In this paper,the influence of magnetic particles' size and stirring rate on the coating rate,magnetic properties and structure of microspheres were studied.The sutructure of microsphere was observed by SEM.The chemical constitution of microsphere was tested by FT-IR.The content of magnetic inorganic and magnetic properties of microspheres were analyzed by TG and VSM respectively.The adsorption quantity of microspheres was investigated by UV absorption spectra.The results showed that the coating rate of nano-BaFe₁₂O₁₉/PU magnetic composite microspheres was more than that of micro-BaFe₁₂O₁₉/PU ones.The magnetic properties and coating rate of microspheres increased with its particle size decreasing.When the size of magnetic particles kept in some range,coating rate of microspheres increased with its average size increasing.Magnetic microspheres had high purity,narrow particle size distribution and perfect sphere when medium stirring rate was adopted.Compared with micro-BaFe₁₂O₁₉/PU,nano-BaFe₁₂O₁₉/PU microspheres had high saturation magnetization.After surface modification,-NH₂ was grafted on the surface of microspheres.From adsoption experimet,we found that per gram microsphere could adsorb 95 mg lecithin,and the adsoption rate was 72.24%.