微纳结构对硅基超疏水表面冷凝特性的影响

Effect of Micro/Nano Structure on Condensation Characteristics of Hierarchical Superhydrophobic Silicon Surface

目的研究微米结构中心距对微纳二级结构超疏水硅表面热交换效率的影响。方法首先采用湿法腐蚀在硅表面构建中心距分别为22、24、26、28、30μm的微米四棱台结构,然后采用溶胶-凝胶法在表面涂覆疏水的纳米二氧化硅颗粒,获得微纳二级结构超疏水表面。通过表面接触角测量仪分析表面的湿润性,通过扫描电镜观察表面的微观形貌特征,使用光学显微镜观察冷凝小液滴自迁移现象,使用电子天平称量表面的冷凝集水质量。结果当纳米结构相同时,随着微米结构中心距的增加,液滴静态接触角减小,冷凝小液滴的自迁移频率变慢,相同时间段内,平均集水效率下降。当相对湿度大于90%时,会出现表面“淹没”现象。微纳二级结构超疏水硅表面(微米结构间距22μm)的集水效率是单独微米结构硅表面的1.38倍、单独纳米结构疏水表面的1.27倍、疏水硅光片表面的1.75倍、光二氧化硅亲水表面的3.6倍。结论当纳米结构相同时,在一定范围内适当减小微米结构的中心距,有助于增强微纳二级结构超疏水硅表面热交换效率。

The work aims to study the influence of microstructure center distance on heat transfer performance of micronano hierarchical superhydrophobic silicon surface.The wet etching was applied to construct micro-nano pyramid structures with center distance of 22,24,26,28 and 30 μm on the silicon surface and then sol-gel method was used to coat hydrophobic nano silica particles to obtain micro-nano hierarchical superhydrophobic surface.The wettability and microtopography characteristics of the superhydrophobic silicon surface were analyzed by contact angle meter and scanning electron microscope. Spontaneous migration of small condensate droplets was observed by optical microscope.The electronic balance was used to measure the mass of the collected condensation water.For the same nanostructure,with the increase of microstructure center distance,the static contact angle of droplets became smaller,the spontaneous migration of small condensate droplets became slower and the average water collection efficiency decreased within the same period.Flooding was observed when relative humidity was larger than 90%.The water collection efficiency of the micro-nano structured hierarchical superhydrophobic silicon surface (22 μm micro-distance) was 1.38 times as large as that of the monolayer microstructure Si surface,1.27 times as large as that of the monolayer nanostructure hydrophobic surface,1.75 times as large as that of the hydrophobic smooth Si surface and 3.6 times as large as that of the hydrophilic smooth SiO2 surface.For the same nanostructure,reducing the microstructure spacing is helpful to enhance the surface heat exchange efficiency of hierarchical superhydrophobic silicon surface.