基于超支化聚合物的功能性高稳金属纳米流体及性能研究

As a new kind of working medium enhancing heat transfer, nanofluids have been a topic of great interest. The applications of metal nanoparticles are limited as the nanoparticles are easy to aggregate in fluids. A lot of dispersants are need in practical application, while the settling time of metal particles in fluids is short and the quantity of suspension is low. The hyperbranched polymer has special structure and can be used to modify metal nanoparticles with self-assembly technology to form an elastic superficial modification layer. The hydrophobic performance and stability of metal nanoparticles with the hyperbranched polymer as ligands in nanofluids can be enhanced. And then the nanofluids with high dispersion stability， high quantity of suspension and high heat transfer performance can be fabricated. The thermal stability of the nanofluids will be studied systematically. The coefficient of the thermal conductivity and thermal diffusivity of the fluids with metal nanoparticles with the hyperbranched polymer as ligands are compared with the nanofluids with bare metal nanoparticles. The influences of the structure, branching index and coating degree of the modification layer on the heat transfer performance of nanofluids will be analyzed. The interrelated mathematic model and heat transfer mechanism will be studied. The research results of this project will provide a theoretical and practical basis on the exploration of new heat transfer media with high efficiency.

纳米流体作为一类新型的高效换热工质，具有广阔的应用前景。金属纳米粒子易团聚，且在实际应用中多需添加大量分散剂，但金属纳米粒子稳定时间短且悬浮量低。本项目拟利用超支化聚合物分子的特殊结构结合自组装技术，在制备金属纳米粒子的同时实现对其表面的弹性修饰，以增强金属纳米粒子的亲油性和功能性，提高纳米流体中金属纳米粒子的稳定性，从而实现具有高分散稳定性、高悬浮量和高传热性能的纳米流体的研制。拟对纳米流体的热稳定性进行系统研究，对比超支化分子修饰的金属纳米粒子与裸露金属纳米粒子对基液的导热系数、热扩散系数等影响的差异，分析纳米粒子表面超支化分子修饰层的结构、支化度、包裹程度等对纳米流体性能尤其是传热性能的影响，建立相互关联的数学模型并揭示传热机理，以期望从理论和实际应用方面指导新型高效换热介质的研究和开发。

本项目针对金属纳米粒子稳定时间短且悬浮量低等问题，利用超支化聚合物分子的特殊结构结合自组装技术，实现对金属纳米粒子表面的弹性修饰，以增强金属纳米粒子的稳定性和功能性，实现具有高分散稳定性、高悬浮量和高传热性能的纳米流体的研制。课题主要围绕基于超支化分子修饰的纳米粒子制备及油基纳米流体性能尤其是导热能力开展了系统研究，以表面功能化设计修饰为基础，研究功能化对金属纳米粒子及纳米流体的影响，构筑新型功能性高稳金属纳米流体。项目研究了改性超支化聚缩水甘油和超支化聚乙烯亚胺等修饰材料对金属纳米粒子的性能调控，制备了可稳定分散于不同基液中的金属纳米粒子及功能性高稳金属纳米流体。制备的金属纳米粒子（Ag、Au、Pd和Cu等）可稳定分散于十氢萘等非极性基液或水等极性介质中，且具有良好的导热性能，对金属纳米流体的稳定性进行了系统研究，制备的金属纳米粒子在基液中的添加量较小时（0.01~0.5 %），纳米流体的稳定性和导热能力即可得到较好提升。对比超支化分子修饰的金属纳米粒子对基液的导热系等影响的差异，分析了种类、结构、加入量等对纳米粒子分散性、稳定性尤其传热性能的影响规律，研究拓宽了金属纳米流体的应用领域，为新型高效换热介质的研究和开发提供了指导；同时还研究了石墨烯二维材料对金属纳米粒子的修饰及性能的影响，该研究为设计功能性金属纳米材料提供了思路。