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.     

Influence of SHI irradiation on the structure and surface topography of CdTe thin films on flexible substrate

Impact of ion irradiation on thin films is an emerging area for materials modification. CdTe thin films grown by thermal evaporation on flexible molybdenum (Mo) substrate were irradiated with Swift (100 MeV) Ag⁺⁷ ions for various ion fluence in the range 10¹²–10¹³ ions/cm². The modifications in the composition, structure and surface morphology have been studied as a function of ion fluence. The Energy Dispersive X-ray Analysis (EDS) shows slightly Te-rich composition for both as-grown and irradiated films with no significant change after irradiation. X-ray diffraction (XRD) analysis indicates a consistent shift in the (111) peak position towards higher diffraction angle and an increase in the full width at half maximum (FWHM) with increase in ion fluence. The change in the residual stress during irradiation has been evaluated and is related to the corresponding microstructural changes in the films. The initial tensile stress is found to be relaxed after irradiation. Atomic Force Microscopy (AFM) studies revealed significant grain splitting after irradiation and formation of hillocks at higher ion fluence. The surface roughness was significantly increased at higher ion fluence.     

Swift heavy ion induced formation of nanocolumns of C clusters in a Si based polymer

The formation of nanocolumns of C clusters in thin films of a Si based inorganic polymer, allylhydridopolycarbosilane (HPCS), as a result of irradiation of the films with 100?MeV Au ions at fluences of 2 × 10(12) and 5 × 10(12)?ions?cm(-2) is demonstrated. The evolution and arrangement of the C?clusters while subjected to the irradiation fluence is investigated by energy filtered cross-sectional transmission electron microscopy. Irradiation results in evolution of C clusters of sizes ≤5?nm, and their alignment along channels of ～10?nm diameter, which are essentially the latent tracks created by the Au ions in the polymer. At the fluence of 5 × 10(12)?ions?cm(-2), these clusters become densely packed in the channels. The growth of such C cluster filled nanocolumns is shown to be a consequence of two simultaneous diffusion processes taking place during the transient molten phase of the latent tracks.     

Study of anti-corrosion and anti-wear properties on superhydrophobic aluminium alloy surfaces

To improve the wear and corrosion resistance of aluminium alloys in salt environments, we produced superhydrophobic surfaces via high-speed electrical discharge machining. The specimens were characterised using a scanning electron microscope and a laser scanning confocal microscope and through contact angle (CA) measurement, measurement of electrochemical corrosion at an electrochemical workstation and wear testing. Results showed that the superhydrophobic specimens had a water CA of 151.5°. The corrosion of the as-obtained superhydrophobic specimens was significantly reduced by more than 50%, indicating their excellent anti-corrosion properties. The wear of as-obtained superhydrophobic specimens were reduced by approximately 10–35% in dry conditions and by approximately 45–85% in 3.5% NaCl solution, revealing their excellent anti-wear properties in both dry and salt environments.     

Water-Repellent Approaches for 3-D Printed Internal Passages

In this work, two different manufacturing approaches are presented that create water-repellency (hydrophobicity and super-hydrophobicity) for acrylonitrile butadiene styrene (ABS) structures. In particular, this is the first study to render three-dimensional (3-D) printed ABS surfaces with internal flow paths to be superhydrophobic. The first approach uses standard wet-based chemical processing for surface preparation after which a fluorocarbon layer is deposited by dip coating or with vapor deposition. This first approach creates hydrophobic surfaces with roll-off angles of less than 30°. In the second approach, the ABS structures are dip-coated with a commercial rubber coating solution and subsequently surface-modified by reactive ion etching (RIE) with fluorinated gases to render the samples superhydrophobic, with roll-off angles as low as 6°. In order to further enhance their water-repellency, the dip-coating rubber solution is mixed with polytetrafluoroethylene (PTFE) colloidal dispersions to form a nanocomposite layer prior to the RIE process. The PTFE particles induce surface roughness as well as hydrophobicity. The modified surfaces created by the two approaches are further characterized by scanning electron microscopy and water drainage performance. Water drainage (prevention of water retention) is especially important for high thermal efficiency of 3-D printed heat exchangers. However, water-repellency for ABS is also interesting for a broader range of applications that use this material.     

Analysis of organometallics dispersed polymer composite irradiated with oxygen ions

Thin films of polymethyl methacrylate (PMMA) were synthesized. Ferric oxalate was dispersed in PMMA films. These films were irradiated with 80 MeV O⁶⁺ ions at a fluence of 1×10¹¹ ions/cm². The radiation induced changes in electrical conductivity, Mössbauer parameter, microhardness and surface roughness were investigated. It is observed that hardness and electrical conductivity of the film increases with the concentration of dispersed ferric oxalate and also with the fluence. It indicates that ion beam irradiation promotes (i) the metal to polymer bonding and (ii) convert the polymeric structure into hydrogen depleted carbon network. Thus irradiation makes the polymer harder and more conductive. Before irradiation, no Mössbauer absorption was observed. The irradiated sample showed Mössbauer absorption, which seems to indicate that there is significant interaction between the metalion and polymer matrix. Atomic force microscopy shows that the average roughness (R _a) of the irradiated film is lower than the unirradiated one.     

Surface Structures and Osteoblast Activity on Biomedical Polytetrafluoroethylene Treated by Long‐Pulse,High‐Frequency Oxygen Plasma Immersion Ion Implantation

Polytetrafluoroethylene (PTFE) is a biologically safe polymer used widely in clinical medicine including oral and orthopedic surgery. However, the high bio‐inertness of PTFE has hampered wider applications in the biomedical fields. In this work, we extend the treatment time in long‐pulse, high‐frequency oxygen plasma immersion ion implantation of PTFE and a more superhydrophobic surface with a water contact angle of 160° is created. X‐ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) reveal that the optimized long‐pulse, high‐frequency oxygen plasma immersion ion implantation process induces a rougher surface and to a lesser extent alters the surface oxygen concentration on the PTFE. Our data, especially long‐term contact angles, suggest that the superhydrophobility stems from surface roughness alteration. Furthermore, the activity of MC3T3‐E1 osteoblasts cultured on the treated surfaces is promoted in terms of quantities and morphology.     

Chemical surface modification of poly (ethylene terephthalate) by excimer irradiation of high and low intensities

Poly (ethylene terephthalate) (PET) was modified by a KrF 248 nm excimer laser with high- (above ablation threshold) and low- (below ablation threshold) fluence. The PET surface develops usually a periodic roughness or ripples with high fluence. The roughness size is in the micron range and the surface shows signs of global melting. However, the ripple size can be reduced to sub-micron level by an irradiation of the sample below the ablation threshold with a polarized beam. The morphology of the irradiated surfaces was examined by scanning electron microscopy (SEM). Chemical surface changes of the materials were characterized by X-ray photoelectron spectroscopy (XPS). The PET modification by high fluence will normally results in the deposition of some yellow to black materials (debris), on the treated surface. The debris are ionized and from carbon rich materials which finally condense forming higher aggregates, resulting in a reduction of O/C ratio. By contrast, modification of PET surfaces by low fluence leads to an oxidation and almost no ablation is detected. The increase of oxygen concentration on low fluence modified surfaces is probably due to a subsequent reaction with atmospheric O₂ during irradiation. Our work suggests that a careful selection of laser parameters for the surface modification of polymer is of primary importance. Received: 06 November 2000 / Reviewed and accepted: 07 November 2000     

Creatinine biomaterial thin films grown by laser techniques

Creatinine thin films were synthesised by matrix assisted pulsed laser deposition (PLD) techniques for enzyme-based biosensor applications. An UV KrF* (λ = 248 nm, τ∼10 ns) excimer laser source was used for the irradiation of the targets at incident fluence values in the 0.3–0.5 J/cm² range. For the matrix assisted PLD the targets consisted on a frozen composite obtained by dissolving the biomaterials in distilled water. The surface morphology, chemical composition and structure of the obtained biomaterial thin films were investigated by scanning electron microscopy, Fourier transform infrared spectroscopy, and electron dispersive X-ray spectroscopy as a function of the target preparation procedure and incident laser fluence.     

Effect of Enhanced Plasma Density on the Properties of Aluminium Doped Zinc Oxide Thin Films Produced by DC Magnetron Sputtering

Aluminum doped zinc oxide (AZO) thin films were prepared by DC magnetron sputtering at low substrate temperature. A coaxial solenoid coil was placed near the magnetron target to enhance the plasma density (Ji). The enhanced plasma density improved significantly the bulk resistivity (ρ) and its homogeneity in spatial distribution of AZO films. X-ray diffraction (XRD) analysis revealed that the increased Ji had inuenced the crystallinity, stress relaxation and other material properties. The AZO films deposited in low plasma density (LPD) mode showed marked variation in ρ (ranging from ～6.5×10?2 to 1.9×10-3 ·cm), whereas those deposited in high plasma density (HPD) mode showed a better homogeneity of films resistivity (ranging from ～1.3×10?3 to 3.3×10?3 ?·cm) at di?erent substrate positions. The average visible transmittance in the wavelength range of 500-800 nm was over 80%, irrespective of the deposition conditions. The atomic force microscopy (AFM) surface morphology showed that AZO films deposited in HPD mode were smoother than that in LPD mode. The high plasma density produced by the coaxial solenoid coil improved the electrical property, surface morphology and the homogeneity in spatial distribution of AZO films deposited at low substrate temperature.     

Transforming an intrinsically hydrophilic polymer to a robust self-cleaning superhydrophobic coating via carbon nanotube surface embedding

A single-step method, including surface embedding of nanoparticles into a polymer matrix, was employed to fabricate superhydrophobic thermoplastic polyurethane (TPU)/carbon nanotube (CNT) nanocomposite coatings. The main aim was to prove that surface roughness plays a more important role in designing superhydrophobic surfaces as compared with the surface energy. Therefore, TPU was used as the model hydrophilic polymer and CNTs were employed as non-hydrophobic nanoparticles. It was found that, at a certain pressing time, CNTs form an efficient hair-like morphology which is able to highly enclose air within its as-formed pores leading to superhydrophobic behavior. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and confocal microscopy were utilized for characterization of samples. SEM and confocal microscopy results proved that surface roughness played the key role in the final wettability behavior. Based on XPS results, it was also found that a very long pressing time led to partial migration of TPU macromolecules into the CNTs' pores, and hence, superhydrophobicity was reduced. The effects of mechanical abrasion and nanoparticle type on wettability behavior of samples were evaluated as well. In conclusion, it is suggested that surface roughness factor should be highly considered in designing superhydrophobic nanocomposite coatings rather than surface energy.     

Morphologies and Superhydrophobicity of Hybrid Film Surfaces Based on Silica and Fluoropolymer

Fluoropolymer and different kinds of silica particles were used for controlling surface chemistry and morphology, respectively. A superhydrophobic surface originated from strawberry-like or quincunx-shaped composite silica particles was obtained. The dual size particles are obtained by utilizing the graft of different modified silica particles with epoxy functional group and amine functional group, This makes the surface of film form a composite interface to have irregular binary structure which plays an essential role in trapping air between the substrate surface and the liquid droplets to be necessary for high contact angle and low contact angle hysteresis. The maximum contact angle for water on the hybrid film is about 174±2° and the contact angle hysteresis is less than 2°. The surface morphologies, roughness and the wettability on the surface of films containing different structural silica particles were compared. It was shown that the hierarchical irregularly structure with a low roughness factor and high air-trapped ratio is indispensable for superhydrophobic surface. Although this structural surfaces based on composite silica particles play a vital role in governing the surface wettability, it is necessary to combine with a low surface energy to make the surface superhydrophobic.     

绒面AZO干法制备及性能研究

利用射频溅射方法,制得AZO透明导电膜,并用离子束刻蚀制备绒面,得到绒面AZO透明导电膜。比较刻蚀前后光电性能及表面形貌,发现透过率稍有下降,在可见光波段透过率在80%以上;电阻率略有上升,但仍保持在10-3?·cm数量级,最低为2.91×10-3?·cm;刻蚀后薄膜表面形貌变化较大,大多数薄膜表面呈现"坑状"结构,横向尺寸在0.5?1.0μm,开口角在120°左右,表面粗糙度从7.29nm上升到36.64nm。薄膜具有较好的表面微结构,在作太阳能电池前电极方面有较好的应用前景。     

溶剂对FTO薄膜的结构和光电性能的影响

采用喷雾热解法(SPD),分别使用甲醇、乙醇、异丙醇、正丁醇和去离子水作为溶剂制备F掺杂的SnO₂(FTO)透明导电薄膜,使用X射线衍射仪、扫描电子显微镜、四点探针电阻仪、霍尔效应仪和紫外可见分光光度计等手段对薄膜进行测试和表征,研究了溶剂对FTO薄膜结构、形貌和光电性能的影响,研究了溶剂对FTO薄膜结构与光电性能的影响。结果表明：FTO薄膜具有四方相金红石结构;使用不同溶剂制备的薄膜,其表面形貌和颗粒尺寸明显不同;使用甲醇为溶剂制备的FTO薄膜呈现饱满的金字塔状,晶粒尺寸均匀,结构致密,具有最佳的综合光学和电学性能,其电阻率可达4.43×10^-4 Ω·cm,载流子浓度为9.922×10²⁰ cm^-3,品质因数为1.646×10^-2 Ω^-1,可见光区透射比均大于75%。     

氧化还原法制备超疏水表面及其防覆冰性能

使用化学氧化还原法制备出疏水性能优异的超疏水表面,使用接触角测量仪、扫描电镜对表面浸润性及形貌进行表征分析。制得的铝基体超疏水表面接触角高达163.31°,滚动角小于5°。探究不同反应时间对表面形貌和浸润性的影响,使用自制的结冰监测系统对制备出的超疏水表面的静态和动态水滴防覆冰性能进行探究,并结合一维传热理论和经典成核理论对实验结果进行分析。结果表明,反应80min时表面疏水效果最好,超疏水表面静态水滴延缓结冰时间约是普通样品的5倍,结冰温度也低了3.3℃,动态水滴撞击表面时,超疏水表面始终无积水和覆冰,表现出优异的静态和动态防覆冰性能。     

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.     

在线紫外辐照辅助沉积柔性ITO薄膜的研究

显示技术正朝着柔性化、超薄化方向发展,低温制备柔性ITO薄膜已经成为一大趋势.本文在射频磁控溅射过程中,引入在线紫外辐照,室温条件下在有机衬底上制备柔性ITO薄膜的工艺,其最低方块电阻为5Ω,电阻率为2.5×10 -4Ω·cm,透光率为92%,远远优于未采用紫外辐照制备的柔性ITO薄膜.我们用四探针测试仪、分光光度计、原子力显微镜、X射线衍射仪等测试仪器,对未采用和采用在线紫外辐照制备的薄膜进行测试,分析探讨了紫外线辐照对薄膜的光电性能、表面形貌和生长取向的影响.研究结果表明:在紫外线的照射下,ITO薄膜表面形貌得到改善,晶界缺陷减少,生长更均匀,致密度更好,在降低薄膜电阻率的同时,提高了薄膜在可见光区的透射率,在紫外辐照下,ITO薄膜更趋于〈222〉的择优取向,且平均晶粒尺寸变大,结晶度提高,宏观表现为薄膜的电阻率降低.     

Synthesis of nanoscale copper nitride thin film and modification of the surface under high electronic excitation

Nanoscale (approximately 90 nm) Copper nitride (Cu3N) films are deposited on borosilicate glass and Si substrates by RF sputtering technique in the reactive environment of nitrogen gas. These films are irradiated with 200 MeV Au15+ ions from Pelletron accelerator in order to modify the surface by high electronic energy deposition of heavy ions. Due to irradiation (i) at incident ion fluence of 1 x 10(12) ions/cm2 enhancement of grains, (ii) at 5 x 10912) ions/cm2 mass transport on the films surface, (iii) at 2 x 10(13) ions/cm2 line-like features on Cu3N/glass and nanometallic structures on Cu3N/Si surface are observed. The surface morphology is examined by atomic force microscope (AFM). All results are explained on the basis of a thermal spike model of ion-solid interaction.     

Fabrication of superhydrophobic copper by wet chemical reaction

A wet chemical reaction was employed herein to fabricate a stable superhydrophobic surface on a polished copper substrate at ambient temperature. The resulting surface showed superhydrophobic properties as evidenced by a water contact angle (CA) of about 154° and a water sliding angle (SA) of about 4°, which may be attributed to the combination of the roughened surface morphology by means of wet chemical reaction and the formed low surface free energy per chemical modification with poly (dimethysiloxane) vinyl terminated (PDMSVT). Scanning electron microscopy (SEM) images of the resulting surface reveal the resulted copper oxalate microscopic sizes with average diameter of about 0.5 μm and circular submicroscopic structures with diameter of about 100 nm, constructing a hierarchical structure consisted by micro- and nano-scale elements similar to that of lotus leaf in some extent. The elemental and chemical compositions of the resulting surface were also identified by Powder X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), respectively. This work provides improved understanding of the effect of surface roughness and surface energy on superhydrophobicity.     

Branched versus linear perfluorocarbon chains in the formation of superhydrophobic electrodeposited films with low bioaccumulative potential

This work concerns the replacing of long and linear perfluorocarbon chains by branched ones to reduce the bioaccumulative potentials of fluorinated materials. Here, novel 3,4-propylenedioxythiophene monomers containing a branched perfluorocarbon chain or a linear perfluorocarbon chain with the same number of C–F bonds are synthesized and used to produce superhydrophobic films by electropolymerization. The branching induces higher steric hindrance during electropolymerization, which reduces the mean polymer backbone length, decreases the polymer electrical conductivity, and changes the surface morphology. Here, we show that these changes can be beneficial in the case of super liquid-repellent properties. Indeed, superhydrophobic properties are obtained with linear and branched perfluorocarbon chains. However, while superoleophilic properties are obtained with both linear perfluorocarbon chains, much higher oleophobic properties are obtained with branched perfluorocarbon chains. Here, the differences are due to changes in the surface morphology and roughness. This work opens new strategies to obtain surfaces with high hydrophobicity and oleophobicity.