磁场诱导取向碳纳米管强化凝固行为研究

Study on enhanced solidification behaviors by oriented carbon nanotubes under magnetic field

基于纳米材料相变储能的研究进程,采用化学共沉淀法制备了Fe 3O 4包覆多壁碳纳米管(MWCNT)水基纳米磁流体。在引入浓硝酸和分散剂两种功能化方法的基础上,对磁场诱导取向MWCNT磁流体的凝固特性进行了实验研究。结果表明,反应温度70℃和反应时间30min可以制备高饱和磁化强度的磁性MWCNT,添加表面活性剂十二烷基苯磺酸钠(SDBS)的MWNCT磁流体在磁场诱导取向下具有最佳的凝固特性,与水相比,过冷度降低68.6%,成核时间提前76.4%,总凝固时间缩短36.2%。此外,对凝固速率和热流密度进行研究,发现磁场诱导取向碳纳米管磁流体的凝固速率可达8mL/min,是水的1.60倍,前25%凝固时间内的平均凝固速率是总平均速率的2倍;且初始热流密度最高可达5500W/m^(2),为水的1.55倍。

Based on the study of phase change energy storage of nano materials,Fe 3O 4-coated multi-walled carbon nanotubes(MWCNT)water-based nanomagnetic fluid was prepared by chemical coprecipitation method.The solidification characteristics of oriented MWCNT magnetic fluid that functionalized by concentrated nitric acid and dispersant were experimentally studied under magnetic field.The results showed that the magnetic MWCNT with high saturation magnetization could be prepared at a reaction temperature of 70℃and a reaction time of 30 min.The MWCNT magnetic fluid with surfactant sodium dodecyl benzene sulfonate(SDBS)had the optimal solidification characteristics under the magnetic field.Compared with the pure water,the supercooling was reduced by 68.6%,the nucleation time was advanced by 76.4%,and the total solidification time was shortened by 36.2%.Furthermore,the investigation of the solidification rate and heat flow density revealed that the solidification rate of magnetic fluid could reach 8 mL/min,which was 1.60 times that of water.Moreover,the average solidification rate at 25%time of solidification was 2 times that of total average rate,and the initial heat flow density reached up to 5500W/m 2,which was 1.55 times that of water.