Investigation On Preparation Of Thin-walled Polymer Hollow Microspheres For Inertial Confinement Fusion

Laser inertial confinement fusion(ICF)is an effective way to explore controlled nuclear fusion,promising clean and non-polluting energy,and thin-walled polymer hollow microspheres are a much-needed class of microspheres for ICF physics experiments.To address the problem that thin-walled hollow microspheres are prone to cracking during drying and use due to the increase in diameter-to-thickness ratio(diameter/wall thickness),the effects of polymer raw materials and fillers on the quality of thin-walled microspheres were investigated,the preparation process of polymer microspheres was optimised,and the mechanism of the effects was explored.The study has implications for improving the yield of thin-walled polymer microspheres.The paper is divided into three main parts:(1)Influence of feedstock on the quality of thin-walled polymer microspheres:In the range of PS relative molecular weight 206-357 kg/mol,the PS relative molecular weight increases and the droplet stability of the W1/O/W2 compound increases when the oil phase concentration is low(4 wt%).The droplet stability of the compounds was good when the oil phase concentration was not lower than 8 wt%.the effect of PS relative molecular weight on the surface roughness of the microspheres was small,the sphericity and wall thickness uniformity of the microspheres decreased with increasing PS molecular weight,while the cracking rate of the microspheres decreased with increasing PS molecular weight during the drying process.The effect of two feedstocks,PS-4 and PAMS,on the quality of thin-walled microspheres was investigated and the size relationship between the initial W1/O/W2 compound droplets and the polymer hollow microspheres was revealed.The PS-4 hollow microspheres have better sphericity and wall thickness uniformity compared to the PAMS microspheres due to the oil phase viscosity.PS-4 microspheres also have a brighter surface and lower microsphere cracking rates than PAMS microspheres.(2)Optimisation of the process parameters for the preparation of thin-walled PS-4microspheres:The introduction of fluorobenzene(FB)in the external aqueous phase,which slows down the curing rate,can compensate for the negative effects of increasing PS molecular weight on the sphericity and wall thickness uniformity of the microspheres.The best stability of the emulsions during curing was achieved with L/D ratio of 1.There were almost no solid spheres in the thin-walled PS-4 microspheres,and the sphericity and wall thickness uniformity of the microspheres were better.Drying the cured microspheres after ethanol replacement avoids the effect of initial defects on the quality of the microspheres and reduces the cracking rate of the PS-4 microspheres during the drying process.By heat treating the cured PS-4microspheres closer to the glass transition temperature,molecular chain linkage rearrangement can reduce or even eliminate residual internal stresses,leading to a reduction in the cracking rate and an increase in sphericity and wall thickness uniformity.(3)Influence of fillers on the quality of thin-walled PS-4 microspheres:The introduction of0.3%C60 or a mass fraction of up to 0.2%C61 has no negative effect on the sphericity and wall thickness uniformity of the microspheres and even has an improvement effect.The introduction of C60 and C61 can increase the glass transition temperature and thermal degradation temperature of PS-4 microspheres and improve the thermal properties of the microspheres.The introduction of fillers also reduces the cracking rate of PS-4 microspheres to around 10%,due to the unique honeycomb structure and SP~2 hybridisation of CNT,C60and C61 materials,which can improve the strength of thin-walled PS-4 microspheres.0.025%CNT and 0.25%C61 fillers lead to a significant increase in the surface roughness of PS-4microspheres;0.3%C60 or a mass fraction of up to 0.2%C61 has a significant effect on the surface roughness of PS-4 microspheres.The introduction of C61 has almost no effect on the surface roughness of the microspheres and even improves the maximum height roughness of the microspheres.