化学/电化学腐蚀法快速制备超疏水金属铝

提出一种金属铝超疏水表面的快速制作方法. 先以化学腐蚀在铝表面形成微米级粗糙结构, 再通过电化学腐蚀构筑纳米结构, 在20 min内完成了超疏水表面所需粗糙结构的制备. 这种化学腐蚀/电化学腐蚀两步法比单独化学或电化学腐蚀方法在时间上缩短了1~2个数量级, 且不受铝材晶形限制, 同时电化学腐蚀所用电流密度也降低了1个数量级, 降低了对电源设备的要求, 可望大规模应用于工业生产和其它金属的超疏水表面制备.     

热处理对超疏水性含氟丙烯酸酯共聚物膜表面性能的影响

以微乳液聚合法和溶液聚合法制备丙烯酸全氟烷基乙基酯和甲基丙烯酸甲酯的共聚物, 以1,1,2-三氟三氯乙烷为溶剂, 采用溶剂挥发成膜法直接制备出超疏水膜, 并研究120 ℃热处理对超疏水膜表面性能的影响. 对于用乳液聚合方法制备的超疏水膜, 随着热处理时间的延长, 滚动角表现出先逐渐增大直至完全不能滚动, 然后重新回复到极小滚动角的特殊变化过程, 而静态接触角只是略微减小, 完全不同于热处理对平滑的含氟聚合物表面接触角的影响. 扫描电镜结果显示, 聚合物膜表面形貌对应出现从微/纳复合粗糙结构到微孔粗化并重新形成微/纳复合多层粗糙结构的变化.     

On the onset of instability in the wake of super-hydrophobic spheres

We report an experimental investigation of free falling super-hydrophobic (SH) spheres in glycerine-water mixtures over a wide range of Reynolds number. SH coatings have the ability to reduce the contact area between the surrounding liquid and the solid surface by entrapping an air layer in the surface roughness. We investigate the effect of this air plastron on the hydrodynamic performance of spheres, focusing our attention on the onset of wake instabilities. Our results emphasise the key role of the surface roughness properties on the triggering of wake instabilities. It is shown that, unlike what was reported in previous numerical studies on SH bluff-bodies, local deformation of the interface may act as a by-pass mechanism promoting earlier transition, yielding a decrease of the critical Reynolds number at which the wake becomes unstable. A scenario coupling the hydrodynamic instabilities (scaling with the Reynolds number) and the interface deformation (scaling with the roughness-based Weber number) is proposed to describe the different transition mechanisms in presence of SH surfaces. It is found that the promotion of wake instabilities over SH surfaces occurs when the roughness-based Weber number is larger than a critical threshold. These findings are of primary importance for guiding the design of resilient and efficient SH surfaces.     

Fabrication and tribological properties of super-hydrophobic surfaces based on porous silicon

In the present work, super-hydrophobic surfaces based on porous silicon (PS) were constructed by the self-assembled molecular films and their tribological properties were investigated. A simple chemical etching approach was developed to fabricate PS with the certain rough microstructure surface, which can be observed by the environmental scanning electron microscopy (ESEM). The hydrocarbon and fluorocarbon alkylsilane molecular films were self-assembled on PS, which was confirmed by the X-ray photoelectron spectroscopy (XPS) measurement. In contrast to PS, the alkylsilane molecular films modified PS (mPS) were super-hydrophobic since the apparent water contact angle (CA) exceeded 160°. The tribological properties of PS and the mPS were investigated by a ball-on-disk tribometer during the processes of different sliding velocities and normal loads. The experimental results showed that the alkylsilane molecular films could decrease the friction coefficient. Due to the difference of chain structure and functional groups, the fluorinated alkylsilane films are better candidates for improving the hydrophobicity and lubricating characteristics of PS comparing to the non-fluorinated ones. The carbon chain length of alkylsilane molecules self-assembling on the Si or PS substrates could have little effects on the hydrophobic properties and the tribology performances.     

用含氟丙烯酸酯无规共聚物制备超疏水膜

用微乳液聚合法制备了丙烯酸全氟烷基乙酯和甲基丙烯酸甲酯的无规共聚物,并对其进行了表征.采用溶剂挥发成膜法一步制备了具有超疏水性的该聚合物膜,水滴在该聚合物膜上的静态接触角可达151°~160°,滚动角小于3°.通过扫描电子显微镜观察发现该聚合物膜表面分布了许多乳突状突起和微孔洞,并具有微米和纳米尺度相结合的复合杂化结构.该类超疏水表面的形成是由适度粗糙的表面和低表面能相互结合引起的.探讨了该类超疏水膜的形成机理.     

Investigation on Preparation and Anti-icing Performance of Superhydrophobic Surface on Aluminum Conductor

Aluminum is widely used in transmission lines, and the accumulation of ice on aluminum conductor may inflict serious damage such as tower collapse and power failure.In this study, super-hydrophobic surface (SHS) on aluminum conductor with micro-nanostructure was fabricated using the preferential etching principle of crystal defects.The surface microstructure and wettability were investigated by scanning electron microscope and contact angle measurement, respectively.The icing progress was observed with a self-made icing experiment platform at different environment temperature.The results showed that, due to jumping and rolling down of coalesced droplets from SHS of aluminum conductor at low temperature, the formation of icing on SHS could be delayed.Dynamic icing experiment indicated that SHS on aluminum conductor could restrain the formation of icing in certain temperature range, but could not exert influence on the accumulation of icing.This study offers new insight into understanding the anti-icing performance of actual aluminum conductor.     

PVDF and HYFLON AD membranes: Ideal interfaces for contactor applications

Super-hydrophobic fluorinated membranes were tailored by combining traditional dry-wet phase inversion and wet chemical treatment techniques. PVDF and HYFLON AD 60X were selected as raw polymers for their chemical and mechanical resistance as well as hydrophobic and solvophobic properties. Membranes with modulated pore size, narrow distribution and high overall porosity were manufactured without using additional additives or modifiers. High resistance to liquid water entry pressure (LEPw), high mass transfer and low surface free energy of the membrane surfaces were fully achieved. The combination of these two fluorinated polymers improved dramatically the mechanical resistance and the water repellence of the PVDF membranes. Well-controlled structure combined with aimed supra-molecular chemistry makes these porous layers ideal interfaces to be processed in membrane contactor devices.     

Self-cleaning and Oil/Water Separation of 3D Network Super-hydrophobic Bead-like Fluorinated Silica Pellets/Poly(aryl ether ketone) Composite Membrane Fabricated via a Facile One-step Electrospinning

Novel super-hydrophobic fluorinated silica pellets/poly(aryl ether ketone) composite membranes with controllable structure have been prepared through incorporating poly(aryl ether ketone)s with (3-trifluoromethyl)-phenyl side groups and fluorinated silica pellets(F-SiO₂) by a facile one-step electrospinning. Under the condition of adding 50%(mass fraction) F-SiO₂ in the composite membrane, the water contact angle(WCA) reached its maximum (157°±4.3°). The controllable micro/nano-structures grown on the electrospun fibers could be regulated by the F-SiO₂ loading, which was illustrated by scanning electron microscopy(SEM). Moreover, these super-hydrophobic membranes also demonstrated excellent durability, anti-fouling property and oil-water separation ability after 200 h of water flushing. These promising PAEK composite membranes with controllable structure have the potential values in large-scale application of filtration, oil-water separation and antifouling.     

Super-hydrophobic surface on pure magnesium substrate by wet chemical method

A layer of flower-like super-hydrophobic film was fabricated on pure Mg surface by chemical etching in H₂SO₄, H₂O₂ and subsequent immersion in stearic acid (CH₃(CH₂)₁₆COOH) ethanol solution. The super-hydrophobic surface showed a static water contact angle of 154° with the sliding angle of about 3°. With scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and Fourier-transform infrared (FT-IR) spectrometer, the microstructure and composition of the sample were analyzed. Results showed that the flower-like structure and the bonding of the CH₃(CH₂)₁₆COO⁻ on Mg surface can be responsible for the superior water-repellent property. Electrochemical impedance spectroscopy revealed that the transfer resistance of super-hydrophobic surface was increased about four times than bare Mg after one-hour immersion in 0.1 mol/L NaCl solution.     

铝合金表面原位自组装超疏水膜层的制备及耐蚀性能

采用阳极氧化法在铝合金表面原位构造粗糙结构, 经表面自组装硅氧烷后得到超疏水自清洁表面, 与水滴的接触角最大可达157.5°±2.0°, 接触角滞后小于3°. 通过傅立叶变换红外(FT-IR)光谱分析仪、场发射扫描电子显微镜(FE-SEM)、能谱仪(EDS)、原子力显微镜(AFM)和接触角测试对阳极氧化电流密度、硅氧烷溶液中水的含量和自组装时间等参数进行了分析, 并得到制备超疏水自清洁表面的最优工艺参数. FE-SEM及AFM的测试结果表明, 由自组装硅氧烷膜层的无序性形成的纳米结构和阳极氧化构造的微米级粗糙结构与硅氧烷膜层的低表面能的协同作用构成了稳定的超疏水表面. 电化学测试(动电位极化)的结果表明, 原位自组装超疏水膜层极大地提高了铝合金的耐蚀性.