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Preparation And Properties Of Micro-nanometer Particles With Core/shell And Hollow Structure

Posted on:2010-07-15Degree:DoctorType:Dissertation
Country:ChinaCandidate:D SongFull Text:PDF
GTID:1101360275498846Subject:Materials science
Abstract/Summary:PDF Full Text Request
The capability of micro-nanometer particles with core/shell structure are different from or better than that of the core or shell single compounents. The preparation of core/shell particles can realize the design and optimization of the structure and properties of particles, and it is the attractive topic in material areas. Hollow particles obtained by removal of the core have widely potential applications in high-technology fields because they have large specific surface areas, low density and well permeability. The preparation and properties of core/shell micro-nanoparticles had been studied, but systemic researches on the core/shell micro-nanoparticles with polymer as core were fewer.In view of the great development potential of micro-nanometer particles with core/shell and hollow structure, we researched the preparation of polymer/metal core/shell particles in micrometer. Regarding this as cutting point, the preparation and properties of particles with these two novel structures are investigated. The research will provide the experimental and theoretical basis of the preparation and application of particles with novel structure. The main contents of the research are described as follows:(1) The preparation of polymer microspheresThe polymer microspheres have the merits of simple preparation process and controllable morphology, which are the good substrate used for the preparation of core/shell composite particles. The preparation methods of polymer microspheres with controllable morphology were discussed. The influencing factors of preparation process were studied, and the optimal technical conditions were determined. The polymer microspheres with narrow distribution and controllable morphology were obtained, which provided good substrate for the subsequent research.Firstly, the polymer microspheres were prepared by dispersion polymerization. The effects of the influencing factors on the morphology, particle size and size distribution of the polymer microsphere were discussed, such as the monomer concentration, the initiator dosage, the stabilizer dosage, the solvent polarity, the polymerization temperature, reaction time, and the proportion of monomers. The best experimental formulation were determined, and the polymer (PS and P(St-MMA)) microspheres with small particle size were prepared at the best experimental formulation. Then the PS microspheres prepared by dispersion polymerization were used as seed microspheres for seed swelling polymerization. The influencing factors in preparation process were analyzed, and the best technical conditions were determined. Then the PS microspheres with uniform particle size (7μm), slick surface and good monodispersity were obtained.(2) The preparation and properties of polymer/metal core/shell particlesElectroless plating is an important method for preparing particles with core/shell structure. The surface pretreatment is the key technique of electroless plating of inertia polymer microspheres. The surface pretreatment methods of polymer were studied, and a simple and effective method called "direct-activation" was put forward. The polymer microspheres were pretreated by sensitization-activation and direct-activation, respectively. The Pd catalytic active sites were adhibited on the surface of microspheres, which provided conditions for subsequent electroless plating. The influencing factors of electroless nickel plating of microspheres were analyzed, and PS/Ni core/shell microspheres with controllable coverage morphology and good dispersibility were prepared by controlling the experimental conditions.The application of polymer/metal core/shell microspheres was explored. The catalytic effects of PS/Ni microspheres on the thermal decomposition of AP, the conductive properties of Au/Ni-P/PS microspheres, the catalytic effects of the Pd/polymer microspheres on the Heck reaction, and the magnetic properties of Ni/PS microspheres were studied in this dissertation. The results showed that the composite microspheres with polymer as cores had good application prospects in the above-mentioned fields.(3) The preparation and properties of hollow particlesThe feasibility of using polymer as template to prepare hollow particles was studied. Hollow particles were prepared by calcining and dissolving the the polymer core of the PS/Ni core/shell microspheres, respectively.In view of the complicated process of the method mentioned above, a novel method named "hydroxide template method" was proposed to prepare hollow particles. In this method, using metal hydroxide (M(0H)2) colloids as templates, electroless plating was carried out on the surface of M(0H)2 colloids to prepare M(OH)2-M core/shell composite particles, and controllable Ni-P, Ni-B and Co-B hollow amorphous particles in micro-nanometer were obtained by adding complexing agent to dissolve the core. Compared with other methods, this method was simple and controllable, which could be extended to obtain other metal or alloy hollow particles. Then the catalytic properties of hollow particles on the thermal decomposition of AP were studied. The results showed that the hollow particles could decrease the high decomposition peak temperature evidently, showing good catalytic properties on the thermal decomposition of AP.
Keywords/Search Tags:micro-nano particles, polymer microspheres, electroless plating, core/shell structure, hollow structure
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