One-step electrochemical machining of superhydrophobic surfaces on aluminum substrates

A superhydrophobic surface on an aluminum substrate was fabricated by one-step electrochemical machining using the sodium chloride (NaCl) aqueous solution containing fluoroalkylsilane as the electrolyte. The resulting superhydrophobic surfaces showed a static water contact angle of 166° and a tilting angle of about 1°. The morphological features and chemical compositions were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), electron probe micro-analyzer (EPMA), and Fourier-transform infrared spectrometer (FTIR). It shows that the binary micrometer–nanometer-scale rough structures and the low surface energy coating were present on the aluminum surfaces. The resulting surfaces have good properties of anti-adhesion and self-cleaning. The durability of the superhydrophobic surfaces on aluminum substrates was also investigated. This preparation method is advantageous as it does not require acid electrolyte or a separate process to lower the surface energy, uses simple steps, and is environmental friendly and highly efficient.     

Chemical nature of superhydrophobic aluminum alloy surfaces produced via a one-step process using fluoroalkyl-silane in a base medium

Various surface characterization techniques were used to study the modified surface chemistry of superhydrophobic aluminum alloy surfaces prepared by immersing the substrates in an aqueous solution containing sodium hydroxide and fluoroalkyl-silane (FAS-17) molecules. The creation of a rough micronanostructure on the treated surfaces was revealed by scanning electron microscopy (SEM). X-ray photoelectron spectroscopy (XPS) and infrared reflection absorption spectroscopy (IRRAS) confirmed the presence of low surface energy functional groups of fluorinated carbon on the superhydrophobic surfaces. IRRAS also revealed the presence of a large number of OH groups on the hydrophilic surfaces. A possible bonding mechanism of the FAS-17 molecules with the aluminum alloy surfaces has been suggested based on the IRRAS and XPS studies. The resulting surfaces demonstrated water contact angles as high as ~166° and contact angle hystereses as low as ~4.5°. A correlation between the contact angle, rms roughnesses, and the chemical nature of the surface has been elucidated.     

Micro/nano engineering on stainless steel substrates to produce superhydrophobic surfaces

Creating micro-/nano-scale topography on material surfaces to change their wetting properties has been a subject of much interest in recent years. Wenzel in 1936 and Cassie and Baxter in 1944 proposed that by microscopically increasing the surface roughness of a substrate, it is possible to increase its hydrophobicity. This paper reports the fabrication of micro-textured surfaces and nano-textured surfaces, and the combination of both on stainless steel substrates by sandblasting, thermal evaporation of aluminum, and aluminum-induced crystallization (AIC) of amorphous silicon (a-Si). Meanwhile, fluorinated carbon films were used to change the chemical composition of the surfaces to render the surfaces more hydrophobic. These surface modifications were investigated to create superhydrophobic surfaces on stainless steel substrates. The topography resulting from these surface modifications was analyzed by scanning electron microscopy and surface profilometry. The wetting properties of these surfaces were characterized by water contact angle measurement. The results of this study show that superhydrophobic surfaces can be produced by either micro-scale surface texturing or nano-scale surface texturing, or the combination of both, after fluorinated carbon film deposition.     

The preparation and characterization of preferred (110) orientation aluminum nitride thin films on Si (100) substrates by pulsed laser deposition

The preferred (110) oriented aluminum nitride (AlN) thin films have been prepared by pulsed laser deposition on p-Si (100) substrates. The films were characterized with X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and atomic force microscope (AFM). The results indicate that the AlN thin films are well-crystallized when laser energy is higher than 300 mJ/puls. The AFM images show that the surface roughness of the deposited AlN thin films gradually increases with increasing laser energy, but the surface morphologies are still very smooth. The crystallinity and morphology of the thin films are found to be strongly dependent on the laser energy.     

Superhydrophobic polymer films via aerosol assisted deposition — Taking a leaf out of nature's book

Aerosol assisted deposition of three sets of polymer films based on commercially available resins was achieved on various substrates. The films were characterised using a range of methods, including water contact and slip angle to determine water repellent properties. The aerosol assisted deposition inside the chemical vapour deposition reactor was unique in generating a highly rough superhydrophobic surface with water contact angles up to 170°. During the deposition process, two of the polymers were cured resulting in the development of high surface morphology. It was observed that the polymer that did not cure did not develop such a rough surface resulting in a lower water contact angle (∼ 99°). The superhydrophobic films had a Cassie-Baxter type wetting with water failing to penetrate the surface porosity, water spraying on the surface would bounce off. These films had exceptionally low slide angles of ca 1-2° from the horizontal.     

Wettability control of ZnO nanoparticles for universal applications

Herein, a facile approach for the fabrication of a superhydrophobic nanocoating through a simple spin-coating and chemical modification is demonstrated. The resulting coated surface displayed a static water contact angle of 158° and contact angle hysteresis of 1°, showing excellent superhydrophobicity. The surface wettability could be modulated by the number of ZnO nanoparticle coating cycles, which in turn affected surface roughness. Because of its surface-independent characteristics, this method could be applicable to a wide range of substrates including metals, semiconductors, papers, cotton fabrics, and even flexible polymer substrates. This superhydrophobic surface showed high stability in thermal and dynamic conditions, which are essential elements for practical applications. Furthermore, the reversible switching of wetting behaviors from the superhydrophilic state to the superhydrophobic state was demonstrated using repeated chemical modification/heat treatment cycles of the coating films.     

射频磁控反应溅射制备Al2O3薄膜的工艺研究

采用射频磁控反应溅射法,以高纯Al为靶材,高纯O2为反应气体,在不锈钢和单晶Si基片上成功地制备了氧化铝(Al2O3)薄膜,并对氧化铝薄膜的沉积速率、结构和表面形貌进行了研究.结果表明,沉积速率随着射频功率的增大先几乎呈线性增大而后缓慢增大;随着溅射气压的增加,沉积速率先增大,在一定气压时达到峰值后继续随气压增大而减小,同时随着靶基距的增大而减小;随着氧气流量的不断增加,靶面溅射的物质从金属态过渡到氧化物态,沉积速率也随之不断降低.X射线衍射图谱表明薄膜结构为非晶态;用原子力显微镜对薄膜表面形貌观察,薄膜微结构为柱状.     

草酸阳极氧化法制备铝合金氧化膜及其防腐蚀性能

为了改进铝合金的防护性能,扩展铝合金应用范围,需要对铝合金进行表面处理。利用草酸电解液阳极氧化法在2A12铝合金表面制备了一层氧化膜,通过扫描电子显微镜(SEM)、X射线光电子能谱(XPS)、X射线衍射仪(XRD)、原子力显微镜(AFM)等手段分析其表面形貌、组织结构、物相和表面粗糙度。微观表征结果表明,阳极氧化法能使铝基体表面生成非晶态的氧化铝薄膜,并且该薄膜是多孔结构,具有优异的屏蔽作用。利用电化学方法、中性盐雾试验评价了阳极氧化膜的防腐蚀性能,证实了阳极氧化后铝合金的防腐蚀性能优于铝合金基体。     

铝合金表面超疏水涂层的火焰喷雾热解法制备及其耐蚀性能

采用火焰喷雾热解与表面修饰相结合的方法在铝合金表面制备了具有一定耐蚀性能的超疏水表面。以六甲基二硅氧烷溶液为前驱液,通过火焰喷雾热解方法,首先在铝合金表面沉积SiO2纳米颗粒构建粗糙结构,再以氟硅烷溶液进行表面修饰,获得了具有154.9°静态接触角,滚动角<2°的超疏水表面。通过电化学测试,对比了构筑超疏水表面前后的铝合金样品的耐蚀性能。结果表明沉积层与低表面能物质协同作用,通过对腐蚀性离子的有效隔离,提高了铝合金基体的耐蚀性能。     

具有不同黏附力Al-Mg-Si合金超疏水表面的制备与表征

基于位错刻蚀理论利用溶液浸泡处理A1-Mg-Si合金在其表面形成微观粗糙表面结构,采用自组装技术在此表面制备FDTS自组装分子膜.采用X射线衍射仪、扫描电子显微镜和表面粗糙度仪对试样表面形貌进行了表征;采用接触角测量仪对试样表面接触角进行了测量.结果表明,试样经溶液浸泡处理和沉积自组装分子膜后,其表面润湿性实现了由亲水到超亲水再到超疏水的转变;改变溶液浸泡时间得到具有不同微观结构的表面,沉积自组装分子膜后得到的超疏水表面具有不同的滚动接触角,其表面黏附力具有明显差异.分析认为,超疏水表面的获得是溶液浸泡处理得到的粗糙表面结构和低表面能物质FDTS自组装分子膜共同作用的结果;表面黏附力的差异是试样表面微观形貌的不同造成水滴在其表面所处状态的差异引发的.     

Highly transparent, flexible, and thermally stable superhydrophobic ORMOSIL aerogel thin films

We report preparation of highly transparent, flexible, and thermally stable superhydrophobic organically modified silica (ORMOSIL) aerogel thin films from colloidal dispersions at ambient conditions. The prepared dispersions are suitable for large area processing with ease of coating and being directly applicable without requiring any pre- or post-treatment on a variety of surfaces including glass, wood, and plastics. ORMOSIL films exhibit and retain superhydrophobic behavior up to 500 °C and even on bent flexible substrates. The surface of the films can be converted from superhydrophobic (contact angle of 179.9°) to superhydrophilic (contact angle of <5°) by calcination at high temperatures. The wettability of the coatings can be changed by tuning the calcination temperature and duration. The prepared films also exhibit low refractive index and high porosity making them suitable as multifunctional coatings for many application fields including solar cells, flexible electronics, and lab on papers.     

氧化锌超疏水薄膜的制备及其耐久性

为了提高氧化锌(ZnO)纳米疏水膜层在实际应用中的耐久性能,采用水热法在铝基底表面制备出微纳米结构的ZnO超疏水薄膜,利用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和接触角测量仪对所得ZnO薄膜的成分、微观结构及润湿性能进行分析;利用UMT摩擦磨损试验机对薄膜的摩擦性能和机械疏水耐久度进行研究;并用CHI660E电化学工作站对超疏水试样在海水中的耐腐蚀性能进行测量分析。结果表明:制备的微纳米结构ZnO薄膜具有超疏水性,在未经低表面能物质改性的情况下,对水的静态接触角高达152°,滚动角仅为2°;摩擦磨损测试表明该薄膜在经过2 400磨损周期后仍能保持较高的静态接触角;电化学阻抗谱和Tafel曲线测试表明,该薄膜的确降低了铝在海水中的腐蚀速率,缓蚀率高达93.8%。     

Hydrophobic properties of polytetrafluoroethylene thin films fabricated at various catalyzer temperatures through catalytic chemical vapor deposition using a tungsten catalyzer

Using the catalytic chemical vapor deposition (Cat-CVD) method, polytetrafluoroethylene (PTFE) thin films were fabricated on Si(100) substrates at various catalyzer temperatures, using a tungsten catalyzer, and Fourier transform infrared (FTIR) spectroscopy and X-ray photoemission spectroscopy (XPS) were used to confirm the fabrication of the films. An atomic-force microscope (AFM) and a scanning electron microscope (SEM) were employed to study the correlation between the wettability and surface morphology of the samples. It was found that the wettability of the PTFE thin films fabricated via Cat-CVD is strongly correlated with the sizes of the film surfaces' nanoprotrusions, and that superhydrophobic PTFE thin-film surfaces can be easily achieved by controlling the sizes of the nanoprotrusions through the catalyzer temperature. The comparison of the wettability values and surface morphologies of the films confirmed that nanoscale surface roughness enhances the hydrophobic properties of PTFE thin films. Further, the detailed analysis of the films' surface morphologies from their AFM images with the use of the Wenzel and Cassie models confirmed that the nanoscale surface roughness enhanced the hydrophobic property of the PTFE films. Further, the variations of the wettability of the PTFE thin films prepared via Cat-CVD are well explained by the Cassie model. It seems that the increase in the trapping air and the reduction of the liquid-solid contact area are responsible for the superhydrophobicity of the PTFE thin films prepared via Cat-CVD.     

2A12铝合金基体超疏水表面制备及性能研究

铝合金在使用过程中极易引发基体腐蚀现象,如点蚀、晶间腐蚀等,为保障铝合金在腐蚀环境中的应用,可通过建立超疏水表面改变铝合金表面的润湿性,从而在一定程度上减少腐蚀液与铝合金表面的接触,进而改善耐蚀性。本文通过酸刻蚀和沸水刻蚀两种方法在铝合金表面构筑微纳米结构,并使用低表面能物质硬脂酸进行表面处理得到超疏水表面。采用扫描电子显微镜、接触角测试仪、原子力显微镜分别对铝合金表面形貌、疏水性和粗糙度进行测试,得到两种方法的最佳制备时间,而后通过极化曲线对两种方法制备的铝合金表面耐蚀性能进行对比,进而研究两种刻蚀方法对铝合金耐蚀性的影响。实验结果表明：酸刻蚀时间为15 s时,铝合金表面接触角达到峰值163.9°,呈现超疏水状态,相对于空白样品,表面粗糙度增加了24倍,电化学自腐蚀电位正向移动0.362 8 V;沸水刻蚀时间为1 min时,其表面接触角达到峰值109.6°,比空白样品疏水性强但未呈现超疏水状态,相对于空白样品,经沸水刻蚀的铝合金表面粗糙度增加了4.4倍,电化学自腐蚀电位正向移动0.074 8 V。两种方法处理得到的铝合金表面的耐蚀性与空白铝合金试样相比均有显著提高,而酸刻蚀法的缓蚀效...     

金属基超疏水表面的制备及性能研究进展

本文综述了金属基超疏水材料的研究进展,重点讨论了金属基超疏水表面的主要制备方法,比较了不同制备方法的优缺点。同时,探讨了金属基超疏水表面的各种功能特性,并分析了金属基超疏水表面目前在制备和应用中存在的主要问题。指出金属基超疏水表面未来的重点发展方向是简化制备工艺、降低成本、提高超疏水表面的耐久性和稳定性以及制备具有自修复性能的金属超疏水表面。     

Effect of substrates on the chemical characteristics and evolving structures of an organic superhydrophobic coating

While recent research has used organic coatings to replace chromium-based coatings, the ability of a coating material to repeat its chemical properties on different substrates is still under investigation. The Repellix superhydrophobic compound was developed and deposited on three different substrates using the atomic layer deposition method under the same condition. The films were characterized using the scanning electron microscope, atomic force microscope, water contact angle, attenuated Fourier transform infrared, and x-ray diffractometer. The surface morphology revealed that microstructural evolutions and topologies are different. The roughness of the coating deposited on stainless steel is the highest at 38.39 nanometers, while mild steel substrate showed the least surface roughness at 28.66 nanometers. From observations, the roughness also contributed to the degree of superhydrophobicity of the films deposited on substrates. The multiple hydroxyl functional groups observed in the Fourier transform spectroscopy in the range 3200 cm⁻¹ to 4000 cm⁻¹ would aid the adhesion of deposited films to the substrates. The x-ray diffraction results showed that all substrates had chemical stability, and the Repellix compound is amorphous on all substrates. Stainless steel showed to be the most robust among the substrates considered.     

Plasma polymer films rf sputtered from PTFE under various argon pressures

Fluorocarbon plasma polymer films were prepared by radio-frequency (rf) sputtering of polytetrafluoroethylene (PTFE). Their wettability decreased with the increase in pressure of argon working gas. The films deposited at 70 Pa were found to be superhydrophobic plasma polymers with a static contact angle 146° for water. Sputtered fluorocarbon plasma polymer films were characterized by atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS) and infrared (IR) spectroscopy. The paper shows that the surface composition and chemical structure of the films vary with altering the argon gas pressure.     

Al-Mg-B thin films prepared by magnetron sputtering

Hard, nanocomposite aluminum magnesium boride thin films were prepared on Si (100) substrates with a three target magnetron sputtering system. The films were characterized by X-ray diffraction, atomic force microscope, electron micro-probe, Fourier transform infrared spectroscopy and nanoindentation. The results show that the maximum hardness of the as-deposited films is about 30.7 GPa and these films are all X-ray amorphous with smooth surfaces. The influences of substrate temperature and boron sputtering power on the quality of the films are discussed. From the results of this work, magnetron sputtering is a promising method to deposit Al-Mg-B thin films.     

仿生超疏水棉织物的制备与表面分析

以荷叶表面微/纳米结构为参考模型,先用硅溶胶处理天然棉织物,再用N-β-氨乙基-γ-氨丙基聚二甲基硅氧烷(ASO-1)对其进行修饰,获得了微/纳米二元粗糙的超疏水织物,水滴在该织物表面接触角可达160.5°。场发射扫描电子显微镜(FE-SEM)观察发现超疏水纤维表面存在大量均匀分布的纳米微凸体。接触角分析表明织物织造过程中形成的微米级粗糙度和ASO-1膜的存在是织物疏水的主要原因,纳米微凸体能减少纤维与水的接触面积,提高水在纤维表面的接触角,使织物由疏水转变为超疏水。最后用X射线光电子能谱仪(XPS)证实了纤维表面SiO2粒子和ASO-1膜的存在。     

Dewetting behavior of Au films on porous substrates

Understanding the stability of thin films and their spontaneous pattern formation upon dewetting is essential to a host of physical phenomena. In this paper, we study the dewetting phenomena of Au thin films deposited on anodic aluminum oxide (AAO) membranes to analyze the stability of the metal film on porous substrates. AAO membranes, as-sputtered and dewetted Au films are all characterized by scanning electronic microscopy and X-ray diffraction. We found that both the roughness of AAO surface and modification of AAO pores exhibit remarkable influences on the dewetting behavior of Au films. The observed dewetting phenomena are explained from an energetic point of view since dewetting is a process of minimization of the system free energy.