Preparing Polycarbosilane Nanoparticle Through GAS Annealing Crystallization

There are mainly four parts in this dissertation: solvent selection, theoretical calculation of solvent parameter, the study of nanoparticle size and dispersivity affected with different pressure, dissolve equilibrium time, solution concentration and molecular weight in the process of polycarbosilane preparation, nanoparticle's agglomeration property.When preparing nanoparticle through GAS annealing crystallization, we chose carbon dioxide with super critical state as anti-solvent gas. Thus we needed to find some kind of solvent with the capacity of dissolving polycarbosilane and carbon dioxide. Polycarbosilane's solvent parameter was 16.7 gained through the method of theoretical calculation. Basing on this value, we finally selected tetrahydrofuran as the solvent through the experiment of studying it's dissolvability with carbon dioxide.Calculating the solubility of tetrahydrofuran in super critical carbon dioxide, we got the interactive parameter () of this duality system as 0.037 and the eccentric factor () of tetrahydrofuran as -0.963. There were 3.4482 percent error between theoretical calculation and experiment.That polycarbosilane nanoparticle was produced by gas anti-solvent method was a good try for super critical fluid technique applying in nano field. By this technique, we made nanoparticles and their granularity and distribution had a close relationship with super critical fluid pressure, dissolve equilibrium time, solution concentration and molecular weight.Result of study show as follow.When pressure is increased,size of particles will be reduced and size distributing of particles will be tended to concentration;Molecular weight increasing,we test result show that size of particles will be increase and size distributing of particles will be tended to sepatation;Under short time of dissolve equilibrium time,there are dispersive size distributing of particles.When dissolve equilibrium time reach two hours there are very narrow size distributing of particles.Even though we increase the time of solution that the size of distributing keep a fix values;Original concentration of solution .Almost affect diameter size of particles.As low solution concentration there are concentrative size distributing of particles.Which is finally crented.In this paper, we analyzed a lot of samples with different granularity and tried to get some laws. It was certain that gas anti-solvent was an effective method for preparing nanoparticles. By this way, we could make nanoparticles with narrow granularity distribution and controllable particle size. Particle size between 15 nano-meters and 100 nano-meters .The agglomeration property of nanoparticle was reversible.