Silane Coatings Research Articles

Assessing Stability, Durability, and Protein Adsorption Behavior of Hydrophilic Silane Coatings in Glass Microchannels

Microfluidics-based separation of biomolecules has numerous applications, including fundamental characterization of biomolecules, sequencing of genomes for biological functions, biometric fingerprinting, and identification of pathogens and genetic diseases. One of the main drawbacks, however, for making microfluidic based separations more commercially viable is the non-specific adsorption of biomolecules at the channel walls during separations. Herein, we compare five commonly employed surface coatings, and evaluate their performance in terms of successful silanization of channel surface walls, long term stability, and antifouling performance, using BSA or IgG as model proteins. We compare adsorption of fluorescently-tagged proteins on glass slides with those confined within channels, showing similar behavior with static measurements, but differences when incorporating electrokinetic flow. Based on these data, we find that MPEG is an effective surface coating for applications where long term stability is critical. However, for separation experiments, where the channel is used shortly after coating, a silanized zwitterionic sultone has superior anti-fouling characteristics.

Effectiveness of lanthanum triflate activated silica nanoparticles as fillers in silane films for corrosion protection of low carbon steel

Abstract The synergistic effects of lanthanum activated silica nanoparticle fillers in silane films on the corrosion behavior of low carbon steel have been investigated. The silane films were synthesized through hydrolysis and condensation reactions of 3-glycidoxy-propyl-trimethoxy-silane (3-GPTMS) and methyl-triethoxy-silane (MTES) in acid catalyzed condition. A new corrosion inhibitor, lanthanum triflate at 1000 ppm concentration, was used to activate silica nanoparticles before their impregnation into silane sol–gel mixtures. The morphological characteristics and elemental distribution of the coatings were investigated using scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectrometer (EDX), confirming crack-free coatings distributed with silica nanoparticles. The structural characteristics and adhesive properties of the silane coatings on steel substrates were analyzed using Fourier Transform Infrared Spectroscopy (FTIR) with the results suggesting the formation of Si O Si network and Si O Fe bonding. Furthermore, the wetting properties of the coatings were determined through contact angle measurements; the silane films doped with lanthanum and/or silica nanoparticles exhibited increased hydrophobicity of the coatings. The corrosion resistance of the coated steel was evaluated by using electrochemical impedance spectroscopy (EIS) fitted with electrical equivalent models (EEC). The EIS diagrams obtained for the coatings doped with fillers exhibited higher impedance values by at least an order of magnitude when compared with non-doped coatings, indicating improved barrier properties of the coatings. Moreover, the films doped with both lanthanum inhibitor and silica nanoparticles exhibited the most efficient corrosion resistance – by more than two orders of magnitude for more than 168 h – compared to the films doped with either La 3+ or silica nanoparticles alone. The overall system responses from EIS at high and low frequencies confirmed the benefits derived from synergistic roles of lanthanum-silica nanoparticles in silane films for a long term corrosion resistance performance of low carbon steel.

Studying various mixtures of 3-aminopropyltriethoxysilane (APS) and tetraethylorthosilicate (TEOS) silanes on the corrosion resistance of mild steel and adhesion properties of epoxy coating

Different mixtures of tetraethylorthosilicate (TEOS) and 3-aminopropyltriethoxysilane (APS), i.e. 100/0, 70/30, 50/50, 30/70 and 0/100, were applied on mild steel samples. The morphology and composition of the silane coatings were investigated by field emission scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS) and contact angle analysis. Open circuit potential (OCP) and electrochemical impedance measurements were performed on the bare steel and silane coated samples by electrochemical impedance spectroscopy (EIS). Results showed that a mixture of 70/30 of TEOS/APS resulted in a more consecutive and compact film formation on the steel surface. It was shown that the mixture of TEOS/APS provided better corrosion protection properties than the single ones. The film composed of APS decreased the contact angle more than TEOS. An epoxy coating was applied on the surface of steel samples treated by various mixtures of silanes. Pull-off and salt spray tests were performed on these samples to investigate the effects of surface treatment on the adhesion and corrosion protection properties of the epoxy coating. It was found that the mixture of silanes significantly enhanced the adhesion and corrosion protection properties of the epoxy coating.

Development of antibacterial quaternary ammonium silane coatings on polyurethane catheters

Polyurethene (PU) catheters were coated with 3-(trimethoxysilyl)-propyldimethyloctadecylammonium chloride (QAS) by means of a multistep process which involved a vapor phase plasma-induced graft-polymerization of acrylic acid (AAc). The AAc coating, whose stability in aqueous media was assessed by immersion in Phospate Buffer Saline (PBS), was characterized by means of Attenuated Total Reflectance Fourier Transform Infrared (ATR/FTIR) spectroscopy. Moreover, the COOH surface density was evaluated by a colorimetric assay with Methylene Blue. Carrying a negative charge at neutral pH, AAc coatings were proficient in positively charged molecules (like QAS) adsorption. ATR/FTIR spectroscopy and a colorimetric assay with Bromophenol Blue allowed us to verify the presence and the uniformity of the QAS coating on the PU catheters and the positive effect of the AAc graft-polymerization on the QAS adsorption. Morphological characterization of the QAS-modified catheters was performed by means of Atomic Force Microscopy (AFM). QAS-coated catheters displayed in vitro antimicrobial activity against Gram-negative Escherichia coli bacterial cells.

Silane and epoxy coatings: A bilayer system to protect AA2024 alloy

Abstract This work has proved that a good combination of a simple and fast metal pre-treatment, followed by the deposition of a thin layer of an organic–inorganic silane coating and further layer of epoxy coatings, are able to protect the aluminium alloy AA2024-T3 against corrosion in high concentrations of NaCl solution. The alloy AA2024 is one of the most employed aluminium alloy in structural applications due to its good mechanical properties. However, AA2024 alloy series commonly presents galvanic corrosion due to the rich content of copper element. The influence of different surface pre-treatments, the presence of a silane layer as pre-coating treatment and the influence of phosphonic acids combined with the silane layer on the corrosion protection and adhesion to the aluminium alloy have been examined using accelerated corrosion tests. High roughness and the presence of a pre-coating film between the metal surface and the organic coating were essential for a good protection and resistance to blistering appearance in the surface of AA2024-T3.

Corrosion Protection of Silane Coatings Modified by Carbon Nanotubes on Stainless Steel

Corrosion Protection of Silane Coatings Modified by Carbon Nanotubes on Stainless Steel

Adhesion and Friction Force on Various Smooth Hydrophobic Silane Coatings

Abstract Various smooth hydrophobic silane coatings were prepared on a Si substrate using CVD. Then adhesion and friction force for these coatings were evaluated using force curve measurements and friction force microscopy with Si3N4-coated Si cantilevers in the ambient atmosphere. The adhesion force depended on the cosine of the water contact angle, which suggests that it was governed by the capillary force. The water contact angle, packing density, rigidity, and molecular interaction contribute to the friction coefficient of the coatings.

Electrochemical Impedance Spectroscopy Behaviour of NdFeB Coated Magnets in Saliva Solution for Orthodontic Applications

In this work the assessment of the corrosion performances in saliva solution of NdFeB magnets coated with silane layers was studied for its application in orthodontic brackets. The silane film, deposited by dip coating technique, has been prepared with varying dipping steps, with the purpose to identify the number of layers able to achieve an optimal protective action. Corrosion protection performance, during immersion in Fusayama synthetic saliva solution, was evaluated by means electrochemical impedance spectroscopy (EIS). The silane coatings evidenced good barrier properties resulting in an improvement of the anti-corrosion performances of the magnets. Better results were observed for samples with at least 15 layers of silane, that evidenced still acceptable protective action after three days of immersion in a Fusayama synthetic saliva solution.

Effects of Activated Ceria and Zirconia Nanoparticles on the Protective Behaviour of Silane Coatings in Chloride Solutions

Effects of Activated Ceria and Zirconia Nanoparticles on the Protective Behaviour of Silane Coatings in Chloride Solutions

Silane-incorporated epoxy coatings on aluminum alloy (AA2024). Part 2: Mechanistic investigations

In the second part of this series work, the protection mechanism of epoxy–silane coatings was further investigated by combined use of sum frequency generation vibrational spectroscopy, FTIR mapping, XPS and AFM, from the microscopic point of view. Results showed that silane components, no matter γ-aminopropyltrimethoxy silane or bis-1,2-[triethoxysilyl] ethane, enhance the ordering of functional groups and exhibit healing effect and thus provide improved corrosion performance of superprimers. Phase separation was detected in epoxy coatings laced with immiscible bis-silane. Such phenomenon was gradually disappearing with prolonging the immersion, as a result of phase re-organization caused by the cross-linking reaction between silanes.

Effect of Anodized Oxide Layer Aging on Wettability of Alkyl Silane Coating Developed on Aerospace Aluminum Alloy

Incipient nanoporous texture was developed by phosphoric acid anodization (PAAO) process on AA2024 specimen. The developed oxide layer was modified with low surface energy material fluoroalkyl-silane (FAS-13) by simple immersion technique to improve the hydrophobic property of the surface. Atomic force microscopy results showed that there was a significant reduction (30 pct) in surface roughness due to the aging of PAAO. The water contact angle measurement revealed that there was a gradual increase in WCA from 130 to 160 deg due to the aging of PAAO. A systematic composition analysis was carried out to understand the interfacial chemical reaction and also to differentiate the coating formation mechanism between the natural and artificial aging processes. The potentiodynamic polarization results revealed that the superhydrophobic (SH) surface exhibited about 15 and 4 times improved corrosion resistance compared to bare specimen and PAAO, respectively. Electrochemical impedance spectroscopy results also showed the improved corrosion inhibition behavior of vacuum heat-treated and FAS-modified SH surface among the developed coatings.

A Facile and Fast Chemical Process to Manufacture Epoxy–Silane Coating on Plastic Substrate for Biomolecules Sensing Applications

Microarray is the most powerful technology in the field of molecular diagnostics and genomics. The manufacturing of microarray devices, based on traditional materials such as silicon and glass, is not easily adaptable to integration into microfluidics system. Recently, there was an increased interest in using polymers as substrates for microarray devices production, but fabrication of microarray on polymer surfaces requires complicated chemistry modification. In this paper we report a simple and effective chemical process to generate an epoxy–silane coating on cyclic olefin polymer surface for the grafting of single-stranded DNA (ssDNA) probes. We demonstrated the effectiveness of this process by direct hybridization of microarray probes with oligonucleotides perfect matches and PCR product. All hybridized probes showed high values for signal-to-noise ratio with a negligible noise level. In addition we propose the water contact angle as process control parameter to control the chemical process capability for industrialization purpose.

Analyses of the Protective Effect of Polyethylene-Triethoxysilane and Triethoxysilane Emulsion Coatings on Concrete Substrate

Water could transport aggressive substances such as carbon-dioxide, sulfates and chloride ions in reinforced concrete structures. By penetration, the stability of the whole structure is influenced. This paper deals about waterproof effect and chloride resistance of two kinds of silane coatings, polyethylene-triethoxysilane and triethoxysilane emulsions on concrete substrate along with the mechanism of the hydrophobic action. The results, in terms of visual observations, chloride test and water absorption test, showed that the two silane coatings could reduce the chloride penetration and the water absorption efficiently. The comparison between the two indicates that polyethylene-triethoxysilane penetrates little when applied on the substrate, but it performs better waterproof effect and is more efficient to chloride penetration.

Mechanical properties, tribological behavior, and biocompatibility of high-density polyethylene/carbon nanofibers nanocomposites

Carbon nanofibers (CNFs) with silane coatings were used as the reinforcement to enhance the mechanical and tribological properties of high-density polyethylene (HDPE) at different loading levels (0.5 wt% and 3 wt%). To improve the interfacial bonding between the CNFs and HDPE matrix, two types of silane coating thicknesses, 2.8 nm and 46 nm, were applied onto oxidized CNFs. Mechanical properties of the HDPE/CNF nanocomposites including Young’s modulus, ultimate stress, strain at fracture, as well as work of fracture, were investigated through tensile testing. The wear tests were performed on a pin-on-disk tribometer under the bovine serum lubricated condition. The coefficient of friction of the materials in contact with steel balls was monitored over the duration of the wear test. The addition of CNFs not only decreased the coefficients of friction of the nanocomposites, but also reduced their wear rates. The thicker silane-treated CNFs were found to be more effective in reducing the coefficients of friction and elongating the strain of fracture compared with the pristine CNFs and thinner silane-treated ones. The biocompatibility of the nanocomposites against a mouse osteoblast precursor cell line was also evaluated. Among the several types of nanocomposites, the one reinforced with the thicker silane-treated CNFs (46 nm) at 0.5 wt% loading level yielded the highest strain at fracture, the best wear resistance with a wear rate reduction of nearly 57.9% compared to the neat HDPE, and good biocompatibility, making it a promising material for biomedical applications.

Polymer-grafted Al2O3-nanoparticles for controlled dispersion in poly(ethylene-co-butyl acrylate) nanocomposites

We report a model system to control the dispersion and inter-particle distance of polymer-grafted Al2O3-nanoparticles in high molecular weight poly(ethylene-co-butyl acrylate). The proposed methods make it possible to extend the use of surface initiated atom transfer radical polymerization (SI-ATRP) in combination with more commercial grades of silanes and particles, showing the versatility of this polymerization process. The nanoparticles were surface-modified by an amine-terminated silane, forming multilayered silane coatings to which moieties capable of initiating ATRP were attached. Subsequently, “short” (DP: 117) and “long” (DP: 265) chains of poly(n-butyl acrylate) were grafted from the particles via SI-ATRP. The graft density was found to be in accordance with the density of the accessible amine groups and could therefore be assessed directly after the initial silanization step using UV–Vis spectrometry. From AFM micrographs, the grafted nanoparticles were found to be well-dispersed in the matrix. This observation was corroborated by a novel simulation method capable of transforming the inter-particle distances from 2D to 3D, for the closest and more distant neighbors. Further, we calculated the deviation ratios and concluded that the dispersions were homogeneous and that the inter-particle distances were related to the graft length. The homogeneous dispersions were explained by dominating enthalpic contributions of the polymer grafts to the nanocomposites in combination with shielding of the nanoparticle core–core attraction by the silane multilayer (similar to bimodal systems).

Thermal properties of carbon nanofiber reinforced high-density polyethylene nanocomposites

Reinforcing polymers with the appropriate nanofillers is an effective way to obtain a variety of enhanced material properties. In this paper, high-density polyethylene nanocomposites reinforced with either pristine or silane-treated carbon nanofibers at various weight percentages (0.5 wt%, 1 wt%, and 3 wt%) were fabricated through melt-mixing and compressive processing. Silane coatings with two thicknesses, 2.8 nm and 46 nm, were applied on the oxidized carbon nanofibers to improve the interfacial bonding between the carbon nanofibers and the matrix. Scanning electron microscopy and transmission electron microscopy demonstrated the dispersion of carbon nanofibers and the strongly improved interfacial adhesion between the carbon nanofibers and high-density polyethylene matrix due to the silane coating. The thermal properties of high-density polyethylene / carbon nanofiber nanocomposites were characterized and compared with those of the neat high-density polyethylene. The measurement results showed that the thermal conductivity of the high-density polyethylene /carbon nanofiber nanocomposites increased with the carbon nanofiber loading. The enhancement of thermal conductivity was not only due to the high thermal conductivity of carbon nanofibers but also due to the interfacial quality between the carbon nanofibers and the high-density polyethylene matrix. The interfacial thermal contact resistance between the carbon nanofibers and the matrix was determined to be in the range of [Formula: see text] to [Formula: see text]. Furthermore, the coefficient of thermal expansion of the nanocomposite was found to be reduced by the incorporation of carbon nanofibers.

Comparative study of the impact and sliding behavior of water droplets on two different hydrophobic silane coatings

Smooth hydrophobic silane coatings were prepared on a Si substrate using ODS (CH3(CH2)17Si(OCH3)3) and FAS17 (CF3(CF2)7(CH2)2Si(OCH3)3). Results obtained using ellipsometry and Kelvin force microscopy suggest that ODS molecules in the coating are tilting or inflected, whereas those of FAS17 are more normal to the substrate. Impact and sliding behaviors of water droplets on the respective surfaces were investigated using a 15μL water droplet by varying the droplet release height. Droplets on ODS slid down faster than on FAS17 when released from 0mm height (i.e. traditional dynamic hydrophobicity measurement). The order was reversed when providing the impact velocity. Comparison of energy dissipation during the impact process revealed that the droplet on ODS, because of its large deformation, loses more energy than that on FAS17. These results demonstrate that the order of droplet removal performance depends on the presence or absence of some initial velocity.

Effect of Different Surface Treatments on Push-Out Bond Strength of Zirconia Oxide Posts

To Investigate the Effect of Different Surface Treatments on Push-out Bond Strength of Zirconia Oxide Posts in Root Canals. Sixty Single Rooted Extracted Teeth were Collected and Divided into Two Groups. Custom Milled Zirconium Oxide Posts (Cercon, Degudent, Germany; Cosmopost, Ivoclar, Liechtenstein) were Fabricated. Post Specimens of each Group were Subjected to Different Surface Treatments (n=10): no Treatment (control), Sandblasting then Silane Coating and Silane Application (SB+SC+SI), Sandblasting and Silane Application (SB+SI). all Specimens were Bonded with Relyx Unicem and Horizontally Sectioned into Three Sections and Subjected to a Push-out Test. Data were Analyzed Using Two-way ANOVA. Cercon Recorded Significant Higher Bond Strength than Cosmopost (P＞0.05). Surface Treatments Recorded Higher Values than Control Group, and SB+SC+SI Presented Higher Bond Strength than SB+SI (P＞0.05). there was no Significant Difference among Different Root Regions (P＞0.05). Therefore Cercon May be more Suitable to be Used as Post Materials than Cosmopost. Surface Treatments have Significant Effect on Push-out Bond Strength of Zirconia Oxide Post and SB+SC+SI Group Presents Better Bond Strength than SB+SI Group.

Protection of Galvanized Steel with Silanes: Its Comparison with Chromium(VI)

The corrosion behavior of hot dip galvanized steel (HDGS) pre-treated with mercaptopropyltrimethoxysilane and a commercial sulfur-bearing silane was studied. Electrochemical polarization, electrochemical impedance spectroscopy, and electrochemical noise tests showed that silane coatings have a corrosion protection performance similar to the usual hexavalent chromium HDGS passivation treatments. It is also evident that the silane films protect the zinc surface through the formation of an isolating barrier. Through voltamperometric studies it was possible to define an electrochemical porosity of the protective coatings. Based on copper sulfate tests and electrochemical porosity results the films protection capability was evaluated, showing that silane treatments have similar or even better protection performance than standard chromium passivation.

Facile fabrication of core–shell Pr6O11-ZnO modified silane coatings for anti-corrosion applications

In this work, we have developed a facile and inexpensive method to fabricate anti-corrosive and hydrophobic surface with hierarchical micro and nano structures. We demonstrate for the first time the use of praseodymium oxide doped zinc oxide (Pr6O11-ZnO) nanocomposites loaded in a hybrid sol–gel (SiOx/ZrOx) layer, to effectively protect the underlying steel substrate from corrosion attack. The influence of Pr6O11-ZnO gives the surprising aspects based on active anti-corrosion and hydrophobic coatings. The spherical SiO2 particles have been successfully coated with Pr6O11-ZnO layer through sol–gel process. The resulted SiO2@Pr6O11-ZnO core–shell was characterized by Transmission Electron Microscopy (TEM), X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), and X-ray Photoelectron Spectroscopy (XPS). The barrier properties of the intact coatings were assessed by Electrochemical Impedance Spectroscopy (EIS). The fabrication of SiO2@Pr6O11-ZnO shows dual properties of hydrophobic and anti-corrosion micro/nanostructured sol–gel coatings follows a single/simple step coating procedure. This study has led to a better understanding factor influencing the anti-corrosion performance with embedded nanocomposites. These developments are particularly for silane network@ Pr6O11-ZnO for self-healing and self-cleaning behavior which can be designed for new protective coating system.