Silane solution stability and film morphology of water-based bis-1,2-(triethoxysilyl)ethane for thin-film deposition on aluminium

Thin-film silane coating (<1 μm) has been introduced as a chromium free multi-metal surface pre-treatment for corrosion protection, adhesion promotion and surface passivation of metals such as aluminium, steel, zinc, magnesium and others. Bis-1,2-(triethoxysilyl)ethane (BTSE) has received much attention as it is, after hydrolysis, highly reactive towards (covalent) metal/film bonding and cross-link formation for the creation of barrier properties. Much of the past work on BTSE was performed on methanol-based laboratory solutions due to the low solubility of BTSE in water. For industrial applications these solutions are not considered suitable anymore because of the high process cost as well as ecological and health issues associated with methanol and the high monomer content of such solutions. For industrial practice water-based silane solutions are being considered. In the present work water-based BTSE solution is compared to a reference methanol-based solution. The silane solution is analysed using ²⁹Si NMR spectroscopy, and the deposited silane films are morphologically characterised using infra-red spectroscopic ellipsometry and field-emission gun-scanning electron microscopy.     

Electrochemical impedance spectroscopic investigation of the role of alkaline pre-treatment in corrosion resistance of a silane coating on magnesium alloy, ZE41

The protective performance of the coatings of bis-1,2-(triethoxysilyl) ethane (BTSE) on ZE41 magnesium alloy with different surface pre-treatments were evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) in 0.1 M sodium chloride solution. Electrical equivalent circuits were developed based upon hypothetical corrosion mechanisms and simulated to correspond to the experimental data. The morphology and cross section of the alloy subjected to different pre-treatments and coatings were characterized using scanning electron microscope. A specific alkaline pre-treatment of the substrate prior to the coating has been found to improve the corrosion resistance of the alloy.     

Effect of bath concentration and curing time on the structure of non-functional thin organosilane layers on aluminium

The corrosion resistance of aluminium alloys can be improved by different surface treatments such as painting. A pre-treatment based on chromate is the current method used to increase the corrosion resistance and the adhesion of the organic layer. Silane films seem to be an interesting alternative system to replace the toxic chromates. In this paper, the characterisation of bis-1,2-(triethoxysilyl)ethane (BTSE) thin layers has been evaluated by coupling optical techniques like spectroscopic ellipsometry (SE) and infra-red spectroscopic ellipsometry (IRSE) along with electrochemical methods (electrochemical impedance spectroscopy (EIS)). This approach has been chosen to have a better understanding of the protection provided by these organosilane thin films. It will be demonstrated that the BTSE bath concentration modifies the thickness of the layers and that the curing of this thin film can also improve the barrier properties by forming a denser layer.     

Reel-to-reel inline atmospheric plasma deposition of hydrophobic coatings

Plasma deposition equipment was developed and installed at a pilot extrusion coating line for reel-to-reel substrates. Hexamethyldisiloxane was used as a siloxane precursor for the atmospheric plasma deposition of siloxane coatings on substrates of three different categories: paper, polyethylene-coated paper, and textile materials (woven cotton fabric and polypropylene nonwoven). SEM, H₂O contact angle measurements, heat sealability, and water vapor barrier measurements were carried out to characterize the composition and surface structure of the samples. The potential of the method and the equipment was shown by the coatings, ranging to micrometer scale. With selected samples, hydrophobic coating was shown to form at speeds up to 100 m/min.     

Bonding and corrosion protection mechanisms of γ-APS and BTSE silane films on aluminum substrates

Films of γ-aminopropyltriethoxysilane (γ-APS), 1,2-bis[triethoxysilyl] ethane (BTSE) and their mixtures adsorbed onto pure aluminum from aqueous solutions were characterized by means of ellipsometry, infrared spectroscopy (IR) and X-ray photoelectron spectroscopy (XPS). It was found that after hydrolysis in water the silanes were readily adsorbed onto aluminum oxide surfaces initially forming hydrogen bonds. Upon curing, such bonds are replaced by metallosiloxane bonds, Si - O - Al. The remaining silanol groups in the film condense and form Si - O - Si bonds. As the Si - O - Al bonds are known to hydrolyze, the corrosion protection is related to the hydrophobicity of the siloxane films formed on the metal substrate. BTSE films are acidic as they contain free silanol groups, therefore these are compatible with some paints but not with others. Electrochemical impedance spectroscopy (EIS) results, salt spray test results and filiform corrosion test results showed that some silane treatments, such as two-step γ-APS/BTSE and BTSE only, provided better corrosion protection on aluminum substrates as compared with a chromate treatment. Mechanisms of adhesion and corrosion protection of these silane films on aluminum substrates are proposed.     

Plasma enhanced aerosol–gel deposition of Al2O3 coatings

The new plasma enhanced aerosol–gel technique has been used for alumina films preparation, in this work. This process integrates aerosol–gel deposition of films and their plasma treatment in one reactor. The alumina films deposited by aerosol–gel method on Si substrate were plasma or thermally treated. The influence of deposition and condensation conditions on properties of the films was studied. Produced coatings were characterized in terms of surface morphology (SEM, AFM) as well as crystalline and chemical structure (FTIR, XRD). Plasma discharge used for modification of the substrates prior to the deposition process improved homogeneity of produced coatings. Coatings obtained at room temperature exhibit boehmite structure which was transformed into γ-Al₂O₃ after annealing. A similar transformation was induced by low temperature oxide plasma discharge treatment for sufficiently thin coatings.     

Surface tailoring of an ethylene propylene diene elastomeric terpolymer via plasma‐polymerized coating of tetramethyldisiloxane

In the research presented here, we explore the use of a low‐energy plasma to deposit thin silicone polymer films using tetramethyldisiloxane (TMDSO) (H(CH₃)₂? Si? O? Si? (CH₃)₂H) on the surface of an ethylene propylene diene elastomeric terpolymer (EPDM) in order to enhance the surface hydrophobicity, lower the surface energy and improve the degradation/wear characteristics. The processing conditions were varied over a wide range of treatment times and discharge powers to control the physical characteristics, thickness, morphology and chemical structure of the plasma polymer films. Scanning electron microscopy (SEM) shows that pore‐free homogeneous plasma polymer thin films of granular microstructure composed of small grains are formed and that the morphology of the granular structure depends on the plasma processing conditions, such as plasma power and time of deposition. The thicknesses of the coatings were determined using SEM, which confirmed that the thicknesses of the deposited plasma‐polymer films could be precisely controlled by the plasma parameters. The kinetics of plasma‐polymer film deposition were also evaluated. Contact angle measurements of different solvent droplets on the coatings were used to calculate the surface energies of the coatings. These coatings appeared to be hydrophobic and had low surface energies. X‐ray photoelectron spectroscopy (XPS) and photoacoustic Fourier‐transform infrared (PA‐FT‐IR) spectroscopy were used to investigate the detailed chemical structures of the deposited films. The optimum plasma processing conditions to achieve the desired thin plasma polymer coatings are discussed in the light of the chemistry that takes place at the interfaces. Copyright © 2004 Society of Chemical Industry     

基于电泳沉积工艺的低粘附抗菌涂层的制备

低表面能涂层因其优异的防污自清洁能力而受到广泛关注,但现有涂层存在易被细菌和真菌等微生物破坏而导致防污效果下降的问题,因此构建防污抗菌涂层具有深远的意义。本文基于电泳沉积工艺,将乙烯基硅油改性聚丙烯酸酯和固化剂沉积到导电基底,进一步负载纳米银杀菌剂,经过交联固化后获得了兼具抗细菌粘附与杀菌功能的涂层。采用傅里叶变换红外光谱仪(FT-IR)、核磁共振波谱仪(NMR)和扫描电子显微镜(SEM)等对涂层的结构和形貌进行了系统的表征,结果表明,成功合成了兼具低粘附与杀菌功能涂层。涂层表面具有优异的防油污、细菌及血液粘附的能力,涂层对大肠杆菌和金黄色葡萄球菌的抗细菌粘附效果达到99.9%以上。即使经过强酸、强碱等极端环境以及摩擦3000次后,涂层表面仍具有优异的防液体粘附效果。     

Electron‐beam deposition of polyethylene composite coatings at various initiators and inhibitors

Polyethylene (PE) composite coatings were prepared on silicon substrate by electron‐beam deposition (EBD) using mixed powders of low‐density polyethylene and various dopants (i.e., initiator and inhibitor) as evaporated target. The structural and morphological behaviors of PE composite coatings were investigated in dependence of initiator and inhibitor by attenuated total reflectance‐Fourier transform infrared spectroscopy and atomic force microscope. Free‐radical polymerization and cationic polymerization could be observed in the formation process of PE composite coatings by EBD. The initiating system of AlCl₃ and benzoyl peroxide as well as the inhibiting system of diphenylamine and hydroquinone used in EBD, in comparison with conventional synthesis methods, exhibited different effect on reaction mechanism of PE composite coatings. These results might contribute to the synthesis of polymer coatings with expectant molecule structure and controllable surface morphology. POLYM. ENG. SCI., 2012. © 2012 Society of Plastics Engineers     

Covalent functionalization of boron nitride nanotubes through photo-initiated chemical vapour deposition

Boron nitride nanotubes (BNNTs) are analogous nanostructures to carbon nanotubes (CNTs), possessing similar properties such as Young's modulus and thermal conductivity, but superior resistance to oxidation and thermal stability. In addition, BNNTs are insulating materials, whereas CNTs are electrically conductive. They could be used as reinforcements in polymeric matrices as heat dissipators or as protective coatings in harsh environments. However, when incorporating them into polymers, one main drawback is their tendency to agglomerate. To improve their dispersion, covalent surface modification can be applied, with solvent-free approaches being preferred. Herein, we used syngas photo-initiated chemical vapour deposition (PICVD) to incorporate oxygen functionalities on the surface of BNNT. X-ray photoelectron spectroscopy analysis showed a highly oxidized BNNT surface after treatment. In addition, a decrease in water contact angle and an increase in surface energy were observed for the treated material. These results open new possibilities to incorporate hydrophilic BNNTs surfaces into polar polymers or other matrices of interest.     

A comparative study on the corrosion resistance of AA2024-T3 substrates pre-treated with different silane solutions: Composition of the films formed

This work reports a comparative study on the corrosion resistance of AA2024-T3 pre-treated with three different silane solutions. The silanes used for the pre-treatments of the AA2024-T3 panels were: 1,2-bis(triethoxysilyl)ethane (BTSE), bis-[triethoxysilylpropyl]tetrasulfide (BTESPT) and γ-mercaptopropyltrimethoxysilane (γ-MPS). The analytical characterisation of the silane films was performed by Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). The corrosion performance of the pre-treated substrates was evaluated by electrochemical impedance spectroscopy (EIS). The results show that the pre-treatments based on silanes provide good corrosion protection of unpainted AA2024-T3. Painted substrates, previously pre-treated with the silane solutions also revealed improved corrosion resistance and good adhesion properties. Fatigue tests show that the silane pre-treatments do not affect the fatigue behaviour of the AA2024-T3. The work also discusses the formation of the protective silane films.     

Influences of bias voltage on properties of TiAl-doped DLC coatings synthesized by cathodic arc evaporation

In this work, the combinations of TiAl-doped DLC (Diamond-like Carbon) and TiAlN/TiN double-layered films were designed to deposit on the tool steels using cathodic arc evaporation in a single process. The economic advantage in depositing the combined coating in one production scale PVD coating system is of practical importance. The TiAl-doped DLC as lubricant coatings were synthesized with TiAl-target arc sources to emit ion plasma to activate acetylene reactive gases. Scanning electron microscopy (SEM), Auger electron spectroscopy (AES), micro-Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) techniques were employed to analysis the microstructure properties of TiAl-doped DLC coatings. Vicker's and tribometer tester were used to measure the mechanical properties of TiAl-doped DLC coatings. The results show that the TiAl-doped DLC coatings retained lower friction coefficient at approximately 0.15 during the steady state sliding. The lubricity and wear resistance of TiAl-doped DLC coatings is then demonstrated to potentially be applied to the cutting tools with no lubricants.     

Investigation of surface pre-treatments for the structural bonding of titanium

This paper evaluates wet-chemical pre-treatments (alkaline etching, anodising) and a plasma treatment for structural bonding of titanium (Ti₆Al₄V). The main objective of this study is the comparison of the applicability of the plasma pre-treatment to wet-chemical treatments on titanium for structural bonding. In this context, an atmospheric pressure plasma device was used to deposit thin functional films from hexamethyldisiloxane (HMDSO) precursor on titanium.X-ray photoelectron spectroscopy (XPS) was employed to assess the chemical composition of the surface after different pre-treatments on the titanium substrate, while the morphology and the film thickness were investigated with scanning electron microscopy (SEM). The adhesion properties on titanium were evaluated by means of a wedge test in hot/wet conditions. After bonding tests the fracture surface and the failure loci were analysed.Using a long arc plasma generator and HMDSO precursor almost stoichiometric SiO₂ coatings were obtained on the titanium substrate. These coatings exhibit good long-term durability and bond strength compared to an alkaline etching in the wedge test. The investigated anodising process leads to oxide layers revealing a highly porous nanostructure. In contrast to the alkaline etching, the plasma derived coatings and the oxide layer produced by the anodising process exhibit a higher micro, respectively nano roughness, and hence a better long-term durability.     

Plasma-polymerized coatings of trimethylsilane deposited on cold-rolled steel substrates Part 2. Effect of deposition conditions on corrosion performance

Trimethyl silane (TMS) plasma-polymerized films were deposited on cold-rolled steel (CRS) under different conditions. The films were characterized by angular-dependent X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and time-of flight secondary ion mass spectrometry (TOFSIMS). The complementary information generated by these surface techniques gave detailed information on the film composition. The corrosion performance of the plasma films was estimated by electrochemical impedance spectroscopy (EIS) and by exposure in a humidity test. All films were Si-based and their composition was a function of the deposition conditions and the plasma cleaning of substrate prior to deposition. A reducing plasma for metal surface treatment resulted in a film with the highest impedance. The plasma film surfaces were highly oxidized. The contact angle was the lowest for plasma films deposited from a mixture of TMS and oxygen and their corrosion performance was the poorest.     

Ethylene/ ammonia plasma polymer deposition for controlled adhesion of graphite fibers to PEEK

Plasma polymerization of ethylene and ammonia gas mixtures is used to obtain uniform polymer coatings on the surface of AS4 graphite fibers. The polymer deposition rates were determined for processing parameters such as composition of the monomer mix, monomer flow rate, chamber pressure, and power input of the radio frequency field. Plasma formed polymers were characterized using Fourier Transform Infrared (FTIR) and X-ray Photoelectron Spectroscopy (XPS). XPS spectra were collected at 75° and 30° takeoff angles to obtain elemental composition and functional group populations at different sampling depths. Plasma deposition rate was the smallest for 100% ethylene and increased by three to four fold when ammonia was added to the monomer mixture. The polymer coatings were of uniform thickness and exhibited a complex crosslinked structure. The 100% ethylene plasma polymer was strongly hydrocarbon in nature but had some oxygen and nitrogen containing groups. Plasma polymers from ethylene/ammonia mixture were much more polar and contained reactive and polar group constituents, including carbonyl, ether, primary and secondary amines, and hydroxyl groups. The presence of oxygen and nitrogen functionalities is presumed to arise primarily from the reaction of trapped radicals with oxygen and nitrogen when exposed to air. Small amounts of silicon were also detected in the plasma formed films.     

Nanostructured mullite steam oxidation resistant coatings for silicon carbide deposited via atomic layer deposition

Oxidation resistant, thin, pinhole‐free, crystalline mullite coatings were deposited on zirconia and silicon carbide particles using atomic layer deposition (ALD). The composition of the films was confirmed with inductively coupled plasma optical emission spectroscopy (ICP OES), and the conformality and elemental dispersion of the films were characterized with transmission electron microscopy (TEM) and energy dispersive X‐ray spectroscopy (EDS), respectively. The films are deposited on the particle surface with a deposition rate of ~1 Å/cycle. The elemental concentration of aluminum relative to silicon in the film was determined to be 2.68:1 which agrees closely with the ratio of stable 3:2 mullite (2.88:1). A high‐temperature anneal for 5 hours at 1500°C was used to crystallize the films into the mullite phase. This work represents the first deposition of mullite films by ALD. The mullite and alumina‐coated particles were exposed to high‐temperature steam for 20 hours at 1000°C to assess the oxidation resistance of the films, which reduced the oxidation of silicon carbide by up to 62% relative to uncoated particles under these conditions. The activation energy of oxygen diffusion in the films was determined with density functional theory, and the computational results aligned well with the experimental outcomes.     

Microwave plasma enhanced chemical vapor deposition of diamond in silicon pores

In this work, the feasibility of growing boron-doped diamond coatings, approximately 0.3 μm thick, on thin silicon substrates that have 50-μm diameter pores etched 125 μm deep has been demonstrated using deep reactive ion etching (DRIE) in combination with chemical–mechanical polishing (CMP). Using a microwave plasma enhanced chemical vapor deposition (MPECVD) cyclic growth process consisting of carburization, bias-enhanced nucleation, diamond growth and boron-doped diamond growth, uniform diamond coatings throughout the pores have been obtained. The coatings were characterized by Raman spectroscopy and scanning electron microscopy and the secondary electron emission coefficients were found to increase from 4 to 10 between 200 and 1000 V, in agreement with reported values for thicker polycrystalline diamond films grown under similar conditions.     

Analysis of corrosion protection behavior of Al2O3-TiO2 oxide ceramic coating on carbon steel pipes for petroleum industry

Corrosion is the deterioration of materials by chemical interaction with their environment. In the oil and gas industry, corrosion of the pipelines and other equipment is one of the leading causes of failure and the corrosion-related costs are very high. Hence, corrosion protection is an essential requirement. In this study, the objective is to analysis of the corrosion protection behavior of spray Alumina-Titania (Al₂O₃-TiO₂) oxide ceramic coating on carbon steel pipes C45 using two different thermal spray coatings processes. These two different thermal spraying coating, High velocity oxy-fuel (HVOF) and plasma thermal spraying techniques can be used instead of extensive treatment by expensive chemical formation of coatings on pipelines and equipment to improve or restore a component's surface properties or dimensions and to protect them from corrosion. Molten or semi-molten ceramic composite powders are sprayed on the surface in order to produce a dense coating layer. FESEM of coated samples showed that a high temperature of plasma coating method end in melting the ceramic powders and creation of completely melted regions on the coated samples’ surface compared to HVOF coating techniques. Corrosion testing of coated samples in seawater (3.5% NaCl) was conducted within 30 days. Electrochemical impedance spectroscopy (EIS) as well as potentiodynamic polarization outcomes represented that the corrosion resistivity of plasma coating technique for this type of ceramic composite is better than HVOF coating technique. However, both types of coating techniques are protecting the substrate against seawater.     

Diamond deposition on copper treated hardmetal substrates

The adhesion of diamond coatings onto hardmetal substrates is improved by a copper deposition produced by a cementation from aqueous CuSO₄ solutions. During this reaction Co is dissolved from the substrate surface and copper is deposited. To obtain homogeneous Cu deposits, the influence of CuSO₄ concentration and reaction time on cementation were investigated.During diamond deposition, Cu reduces the surface mobility of Co, which is necessary to decrease deposition of non-diamond carbon and therefore increase adhesion. Indentation tests showed the good adhesion of the diamond coatings qualitatively.Cu precipitation and diamond deposition were examined by scanning electron microscopy (SEM). The diamond quality was detected by Raman spectroscopy. Using secondary ion mass spectroscopy (SIMS) depth profiles the interface and the Cu distribution were characterized indicating that during diamond deposition Cu is dissolved and forms an intermetallic Co–Cu mixed crystal.     

类金刚石薄膜在模拟体液中的电化学阻抗

利用双放电腔微波等离子体源全方位离子注入设备,分别采用等离子体增强化学气相沉积技术、等离子体源离子注入和等离子体增强化学气相沉积复合技术两种工艺对医用3161,不锈钢进行类会刚石薄膜表面改性。利用电化学阻抗谱法考察了两种工艺制备的类金刚石薄膜在模拟体液中的抗腐蚀性能。结果表明：与采用等离子体增强化学气相沉积技术制备的类金刚石薄膜相比,在72h的浸泡时间内,采用等离子体源离子注入和等离子体增强化学气相沉积复合技术制备的类金刚石薄膜防腐蚀性能明显增高,腐蚀阻抗较高,碳注入层可有效抑制溶液渗入薄膜和基体之间的界面,起到了腐蚀防护层的作用。动电位极化测试表明：采用复合技术制备的类金刚石薄膜在模拟体液中的腐蚀倾向性更低,钝态稳定性更好。