Silane Coatings Research Articles

Investigation of chemical, physical and mechanical properties of hybrid chitosan-silica based coatings for aluminium substrate

This paper describes the development and characterization of eco-friendly hybrid coatings using chitosan and tetraethoxysilane (TEOS) through sol-gel processing onto aluminium substrates.Firstly, we investigated the impact of curing temperatures and the addition of a coupling agent (VTMS) on various physical and chemical properties to determine the optimal composition, to achieve crack-free and uniform films.Chemical and physical properties were assessed via FTIR spectroscopy and SEM imaging, while surface wettability was analyzed through water contact angle measurements, and hydrolitic degradation tests were also performed. Since the mechanical strength of bonding is important for protective coatings, the mechanical characterization of optimized films was conducted by pin-on-disk and scratch tests to understand their elastic-plastic and adhesive behaviour. Finally, the antibacterial properties were also studied and discussed.The results indicate that an annealing temperature of 100 °C and the incorporation of vinyltrimethoxysilane (VTMS) as a coupling agent are essential for producing homogeneous, stable coatings with excellent hydrolytic degradation resistance. The addition of VTMS effectively addresses common challenges associated with hybrid sol-gel coatings, including cracking, porosity, and poor substrate adhesion. Subsequent investigations revealed that both the presence and concentration of chitosan within the hybrid sol-gel coatings significantly enhance mechanical resistance, water resistance, and friction reduction. A strong correlation between increased coating hydrophobicity and decreased coefficient of friction confirms the intrinsic lubricity of chitosan-silica sol-gel coatings. These coatings also exhibit antibacterial properties compared to both the uncoated aluminium substrate and pure silane coatings. Overall, these findings underscore the multifunctional benefits of chitosan-containing hybrid coatings, positioning them as a promising sustainable, transparent, self-lubricating, and water-resistant coating solution for anodized aluminium substrates.

Evaluation of nanoparticle-enhanced silane and vinyl ester coatings for protecting concrete from ammonium sulfate

Inferior quality of concrete surface layers can lead to significant deterioration of concrete infrastructure due to the infiltration of fluids and deleterious substances from the surrounding environment. Concrete structures such as foundations, abutments, flatwork, and underground tanks in agricultural and mining zones, as well as slabs in factories producing ammonium-based fertilizers, are highly susceptible to ammonium sulfate attack, which is known as the most aggressive sulfate deterioration driven by acid-sulfate reactions. Coatings are an effective strategy for protecting such concrete structures to restore its performance and prolong its service life. Therefore, this study aimed at investigating the performance of nano-based coatings as superficial treatments for concrete elements exposed to aggravated exposures of ammonium sulfate. Silane (hydrophobic agent) and vinyl ester (membrane-forming polymer) were used as base resins, in which nano-clay and nano-calcium carbonate particulates were dispersed at different dosages (0, 2.5, and 5 %). In addition, a colloidal silica solution was used as a surface treatment. The durability of coated concrete specimens was evaluated under two ammonium sulfate exposures: full immersion and combined with cyclic environmental conditions (freezing-thawing and wetting-drying cycles). Degradation of concrete specimens was monitored by visual assessment and quantified in terms of mass and length changes over time. In addition, the deterioration mechanisms and coatings’ performance were studied by thermal, mineralogical, and microstructural tests. The results showed that colloidal silica could not adequately protect concrete specimens from these exposures. Conversely, silane nanocomposites improved the durability of concrete under both exposures and superior performance was generally observed for concrete specimens coated with vinyl ester nanocomposites.

Predicted Corrosion Performance of Organofunctional Silane Coated Steel Reinforcement for Concrete Structures: An Overview

This article provides a comprehensive overview of the potential use of organofunctional silane coatings in the corrosion protection of concrete reinforcement in close relation to other commercially used coating technologies—i.e., epoxy coatings and bath hot-dip galvanizing coatings. The application technology of the steel surface is described in detail, and the corrosion performance and bond strength in concrete are compared. The paper also points out the possibility of improving the durability of epoxy coatings by the addition of silanes and, in the case of application to the surface of hot-dip galvanized steel, they can prevent corrosion of the coating by hydrogen evolution. The application potential of organofunctional silanes is also presented in the form of hydrophobic coatings on concrete surfaces or as corrosion inhibitors in simulated concrete pore solutions. The use of a suitable type of modified silane coating on the surface of carbon steel reinforcement can increase the corrosion performance and can also increase the bond strength in concrete. However, these facts need to be experimentally verified.

Corrosion Properties and Bond Strength in Normal Strength Concrete of Al2O3 Plasma-Sprayed Plain Bars with ZrCC/Organofunctional Silane Coating

Corrosion Properties and Bond Strength in Normal Strength Concrete of Al2O3 Plasma-Sprayed Plain Bars with ZrCC/Organofunctional Silane Coating

Adsorption behaviors of ethyltriethoxysilane on the calcium silicate hydrate surface: Effect of Ca/Si ratio and adsorption sites

Silane coupling agents (SCAs) are utilized to enhance the impermeability of concrete surfaces, whose adhesion force is affected by the interfacial interactions in between that remain unclear. In this study, we probe the adsorption tendencies of ethyltriethoxysilane (ETES) onto C-S-H surfaces by employing density functional theory (DFT) calculations and Born-Oppenheimer molecular dynamics (BOMD) simulations. Results suggest that significant chemisorption occurs at the CaOH(1.5), SiOH(1.0), Ca(1.0) sites C-S-H surfaces. Electronic structures analysis proved that the chemisorption of hydroxyl sites arises from the overlap of H and O atomic orbitals, resulting in the formation of hydrogen bonds. The chemisorption of the Ca(1.0) site is caused by electrostatic adsorption between calcium and oxygen. Adsorption energy results show: ECaOH(1.5) > ECa(1.0) > ESiOH(1.0). Moreover, ETES remains transverse adsorption on low Ca/Si C-S-H surfaces, while displaying longitudinal adsorption on high. Interaction analysis illustrates the configuration discrepancy arising from the absence of bridge silicon-oxygen tetrahedrons which possess vdW interactions with ethyl. Notably, transverse adsorption covers a wider area on the C-S-H surface thereby enhancing the hydrophobic effect. In summary, the utilization of ETES presents notable advantages within the context of low Ca/Si ratio cement. This study contributes valuable insights into the design and application of silane coatings.

Enhancement of ammonia corrosion resistance of coatings through improving dispersion and binding site of graphene oxide in silane coatings

Copper metal is essential to our production process, but it is highly corrosive in an ammonia environment and must be highly valued. Anti-corrosion coating is a simple and cost-effective method of preventing metal corrosion. In this study, a composite silane coating was prepared on copper using an impregnation method with mercaptopropyltriethoxysilane (TPTES) as the silane substrate and graphene oxide (GO) modified with isophorone diisocyanate (IPDI) or isocyanatopropyltriethoxysilane (IPTS) as filler to protect the copper from ammonia corrosion. The coating samples were hanging tested against ammonia corrosion by setting up two corrosive environments: ammonia gas and ammonia water. After 20 days of corrosion, the surfaces of the TPTES/IPDI-GO and TPTES/IPTS-GO coatings remained unchanged under both ammonia environments and the corrosion rate was consistently low at 2–3 μm/y. Additionally, the coating exhibited high protective qualities according to the electrochemical impedance spectroscopy (EIS) test in a 3.5% NaCl solution, which is attributed to the good dispersion that improves the densification and regularity of the coating. Meanwhile, IPTS-GO has a greater binding force with the coating matrix due to the increased number of reactive sites, resulting in further improved corrosion protection. This study provides an idea for research on ammonia-resistant coatings.

Novel Antifouling Coatings by Zwitterionic Silica Grafting on Glass Substrates.

Zwitterionic silica coatings for surface functionalization are greatly prominent because of their simple and fast preparation, high availability, and effective antifouling properties. In this work, two zwitterionic sulfobetaine silane coatings, i.e., mono-SBSi and tris-SBSi, were deposited on glass surfaces and tested for antifouling of biological material and biofilm using human cancer cell and seawater, respectively. The used zwitterionic precursors mono-SBSi and tris-SBSi differ by the number of hydrolyzable silane groups: mono-SBSi contains one trimethoxysilane group, whereas tris-SBSi contains three of these functions. First, X-ray photoelectron spectroscopy indicates the successful grafting of zwitterionic coatings onto a glass surface. Characterization using atomic force microscopy shows the different morphologies and roughness of the two coatings. The glass surface became more hydrophilic after the grafting of zwitterionic coatings than the bare glass substrate. The antifouling properties of two coatings were evaluated via human cancer cell adsorption. Interestingly, the tris-SBSi coating displays a significantly lower level of cell adsorption compared to that of both mono-SBSi coating and the non-modified control surface. The same trend was observed for biofilm formation in seawater. Finally, the toxicity of mono-SBSi and tris-SBSi coatings was evaluated on zebrafish embryos, indicating the good biocompatibility of both coatings. Our results indicate interesting antifouling properties of zwitterionic coatings. The chemical constitution of the used precursor has an impact on the antifouling properties of the formed coating: the tris-SBSi-based zwitterionic silica coatings display improved antifouling properties compared to those of the mono-SBSi-based coating. Besides, the use of trisilylated precursors should result in the formation of more resistant and robust coatings due to the higher number of grafting functions. For all these reasons, we anticipate that tris-SBSi coatings will open new perspectives for antifouling applications for biological environments and implants.

Removal and measurement of trace amounts of rhodamine B in aqueous samples based on the synthesis of a nanosorbent composed of Fe3O4 nanoparticles modified with SiO2 and polydopamine by magnetic solid phase extraction.

Rhodamine B (RDB) dye is generally toxic and causes problems such as carcinogenic activities, neurological disorders, and respiratory tract irritations. However, some individuals still illegally use RDB as a food additive. Therefore, a simple and accurate method is needed to determine RDB in real samples such as food or cosmetic products. In this study, the magnetic solid phase extraction (MSPE) method was used to measure very low amounts of RDB dye in water samples. The advantages of this method include simplicity, good repeatability, high preconcentration factor, higher extraction efficiency, low organic solvent volume requirement, rapid separation, low cost, high sensitivity, and interference removal compared to other methods. Within this approach, iron oxide nanoparticles were synthesised, followed by the application of tetra ethoxy silane (TEOS) and polydopamine (PDA) coatings on the nanoparticle surface, resulting in the creation of the Fe3O4@SiO2@PDA nano-sorbent. This nano-sorbent was then utilized as the magnetic solid phase in MSPE. The characteristics of the synthesized compounds were investigated by various methods such as infrared Fourier transform spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction spectroscopy (XRD), and vibrating sample magnetometry (VSM). Response surface methodology (RSM) and Box-Behnken (BB) design were used to optimize the variables affecting the adsorption process and achieved high recovery percentages. Under optimal experimental conditions, the detection limit and quantification limit of the method were found to be 0.73 and 2.42 μg L-1 for RDB, respectively, with RSDs of ±0.32% and ±0.67%. Furthermore, the linear concentration range of the proposed method for solid phase extraction of RDB was determined to be 10.0-900.0 μg L-1. Moreover, the recovery rates for tap water, lake water, and well water samples ranged from 96.9% to 98.6%.

AgNWs–Silane Coatings for the Functionalization of Aramid Woven Fabrics

Aramid woven fabrics are widely used to provide protection in extreme conditions, especially in high temperatures. Multifunctional aramid fabrics with no deteriorated thermal resistance and antibacterial properties are needed for high-risk professions. In this study, silver nanowires (AgNWs) and silanes (S) were used for the functionalization of meta- (mAr) and para-aramid (pAr) woven fabrics by mixture (Ag + S) or by the layer-by-layer (Ag/S) method. Antibacterial properties, thermal management, and stability were studied to select the functionalization method which provided the highest thermal performance, comfort, and bioactivity. Both methods decreased the fabric’s surface temperature during heating in the range of 35–40 °C by 3 °C and 2 °C, respectively, for mAr and pAr, in comparison to unmodified fabrics. After Ag + S and Ag/S modifications, the thermal degradation initial temperature increased from 554 °C to 560 °C (TG/DTG) and from 525 °C to 533 °C (DSC) for pAr fabrics, and decreased from 417 °C to 403 °C (TG/DTG) and from 411 °C to 406 °C (DSC) for mAr fabrics. The reduction in Gram− (Klebsiella pneumonia) and Gram+ (Staphylococcus aureus) bacterial growth for all modified samples was above 90%. The bactericidal and bacteriostatic coefficients were slightly higher for Ag/S functionalization. The highest thermal performance and antimicrobial activity were noted for pAr fabric modified using the Ag/S method.

Fabrication of silane-based surface coating with Ag/TiO2 hybridization and its anti-corrosion performance on metal surface

Surface coating technology is an effective anti-corrosion strategy which can form a layer of anti-corrosion film on metal surface, effectively preventing it from oxidation and corrosion. Among various strategies, silanization treatment of metals is the most commonly used one. However, using silane-based coatings alone often leads to poor anti-corrosion performance due to insufficient mechanical strength and presence of surface defects. In order to improve the corrosion resistance of silane coatings, a hybrid surface coating has been constructed by introducing epoxy resin and Ag/TiO2 nanoparticles into the silane film in this work. After adding epoxy resin, the thickness of the silane film greatly increases, which improves its mechanical properties. Ag/TiO2 nanoparticles can enhance the cross-linking between silane molecules and epoxy resin, thereby preventing formation of surface defects. The epoxy resin-silane-Ag/TiO2 composite surface coating is coated on the surface of AA2024 aluminum alloy using spin coating method. Electrochemical and salt spray tests indicate excellent corrosion resistance performance of the composite coating. This composite coating technology may have potential applications on the surfaces of various metal products such as medical devices and aerospace materials, and will shed light on the development of new surface coating technologies.

Acid Radical Tolerance of Silane Coatings on Calcium Silicate Hydrate Surfaces in Aggressive Environments: The Role of Nitrate/Sulfate Ratio.

Silane is known as an effective coating for enhancing the resistance of concrete to harmful acids and radicals that are usually produced by the metabolism of microorganisms. However, the mechanism of silane protection is still unclear due to its nanoscale attributes. Here, the protective behavior of silane on the calcium silicate hydrate (C-S-H) surface is examined under the attack environment of nitrate/sulfate ions using molecular dynamics simulations. The findings revealed that silane coating improved the resistance of C-S-H to nitrate/sulfate ions. This resistance is considered the origin of silane protection against harmful ion attacks. Further research on the details of molecular structures suggests that the interaction between the oxygen in the silane molecule and the calcium in C-S-H, which can prevent the coordination of sulfate and nitrate to calcium on the C-S-H surface, is the cause of the silane molecules' strong adsorption. These results are also proved in terms of free energy, which found that the adsorption free energy on the C-S-H surface followed the order silane > sulfate > nitrate. This research confirms the excellent protection performance of silane on the nanoscale. The revealed mechanism can be further used to help the development of high-performance composite coatings.

The Wetting Behavior of Water Droplets on Silane and Silane/GO-Modified Ettringite Surfaces: Insights into Molecular Dynamics Simulations

The use of rapid-hardening cementitious materials for the emergency repair of critical infrastructure in coastal environments is becoming increasingly widespread, and concrete surface hydrophobic protection treatment is equally necessary to improve the durability of both new and old concrete. Among them, silane-based hydrophobic materials play an important role in concrete hydrophobic protection. Graphene oxide (GO)-modified silane materials can significantly improve the hydrophobic performance of coatings, but the hydrophobic mechanism of coatings modifying the sulfoaluminate cement’s main hydration product ettringite (AFt) has not yet been explored. In this study, molecular dynamics simulations were conducted to investigate the wetting properties of water droplets on the surface of AFt, isobutyltriethoxy silane (IBTS)-modified AFt, and IBTS/GO-modified AFt. It was found that the AFt substrate had good hydrophilicity, and the droplets could wet the interface through Ca-O ionic bonds and H-bonds. The IBTS coating initially impeded droplet wetting, but the adsorption stability of IBTS on the AFt substrate surface was poor under droplet action, leading to droplet penetration and dispersion of the IBTS coating on the AFt surface. However, the IBTS/GO coating significantly restricted droplet wetting due to the stable adsorption of GO on the AFt surface and the strong stability of hydrogen bonds between IBTS and GO. In conclusion, selecting a suitable bridging material between AFt and silane is crucial for improving the hydrophobic stability of silane coatings on sulfoaluminate cement materials.

Evaluation of acrylic and silane coatings on limestone through macroscopic and microscopic analyses

The aim of this study was to obtain useful information about the behavior of a coating when it interacts with a stone substrate, to allow the choice of the most suitable protective agent to preserve stone artworks from deterioration phenomena in their environmental conditions. The effect of some commercially available silane-based polymers on Lecce stone was compared with that of two new acrylic ones not yet available for sale. The performance of each protective treatment was evaluated by colorimetry, contact angle measurements and NMR relaxometry, which allows to estimate the hygroscopic properties of the stone in terms of open porosity and water-uptake. The microscopic observations combined with micro-FTIR and SEM-EDS analyses were performed to investigate the distribution of the protectives on the stone surface and their depth of penetration. The results showed that the water repellency of the two acrylic products and of one of the silane-based protectives was mainly due to a surface effect, just slowing down water adsorption. On the contrary, the other two silane-based products turned out distributed throughout most of the sample volume, completely hindering water absorption.

Mono and bilayer coatings of alkanethiol and silane on copper: Prevents corrosion and regulate bacterial adhesion

Self-assembling molecules (SAMs) provide a flexible system for surface modification of materials by forming films of molecular thickness. SAMs protect materials from corrosion and modify surface properties such as adhesion, adsorption and wetting due to their molecular composition and orientation. In this investigation, polished copper specimens were dip coated to form SAMs of alkanethiol and silane to study bacterial adhesion as well as for corrosion prevention. The SAM coated specimens were exposed to the log phase cultures of Pseudomonas aeruginosa (aerobic bacteria) and Desulfovibrio vulgaris (anaerobic bacteria) for 12, 24 and 48 hrs, to monitor cell adhesion and biofilm thickness by microscopy. The results showed that alkanethiols SAM promoted adhesion and biofilm formation. The biofilm thickness ranged from 10 to 38 µm for Pseudomonas and 9 – 25 µm for Desulfovibrio sp. Among the SAM coatings tested, octadecyl-trichlorosilane (ODTCS), alkane-thiol and ODTCS (bilayer SAM) showed no bacterial adhesion, however, solitary alkane-thiol SAM showed significant bacterial adhesion. The high hydrophobicity (contact angle ∼140°), antibacterial and anti-biofilm property of the ODTCS coating could have regulated bacterial adhesion. The constant climate test results showed that silane SAM prevented copper corrosion up to ∼160 days (3480 hrs), while the alkanethiol coating could protect up to 10 days (240 hrs). Confocal laser scanning microscopic images of the silane coated copper specimens showed initiation of the corrosion after 160 days of exposure, while at the end of 200 days significant copper corrosion was observed. Surface modification leads to specific biochemical interactions that regulate bacterial adhesion and prevent biofilm formation and corrosion of copper.

Hybrid Silane Coatings Based on Benzotriazole Loaded Aluminosilicate Nanotubes for Corrosion Protection of Mild Steel

Hybrid Silane Coatings Based on Benzotriazole Loaded Aluminosilicate Nanotubes for Corrosion Protection of Mild Steel

Compartmentalized Quantitative Analysis of Concrete Sulfate-Damaged Area Based on Ultrasonic Velocity

The corrosion of concrete in sulfate environments is a difficult problem in the durability of civil engineering structures. To investigate the variability of deterioration damage to concrete structures by sulfate erosion under non-destructive testing and quantify the protective effect of silane coatings on concrete under the action of sulfate erosion, an accelerated erosion experiment was carried out using field sampling in a tunnel project under a sulfate erosion environment. By means of ultrasonic velocity measurement and CT scanning, the samples protected by a silane coating under the sulfate attack environment were compared with those not protected. The deterioration characteristics of concrete under the sulfate attack environment and the protective effect of silane coating on the concrete structure were analyzed. In addition, a method for evaluating the sulfate damage to concrete based on CT images and ultrasonic velocity analysis was proposed. The results show that the samples prepared in the field show a significant difference in ultrasonic velocity in the process of erosion and deterioration according to the material difference at the measuring point interface. Through the overall damage evaluation analysis of the sample, it is concluded that the damage degree of the protected group sample is light and the heterogeneity is weak, whereas the local damage to the exposed group is serious. Combined with the CT image analysis of concrete before and after loading, the distribution characteristics of the damaged area divided by the concrete sulfate damage evaluation method proposed in this paper are highly similar to the real situation. The results of the study can provide a reference for similar projects for the detection, analysis, protection and evaluation of sulfate-attacked concrete.

Utilization of functionalized silane coatings for enhanced mechanical properties of hydroxyapatite filler

Utilization of functionalized silane coatings for enhanced mechanical properties of hydroxyapatite filler

Interphase characterization of glass/epoxy composite using peridynamic method and micro tensile test

ABSTRACT In this paper, a novel procedure is developed to characterize the interphase region using the nonlocal peridynamic method and micro tensile tests of glass/epoxy specimens with a single fiber of glass. For this purpose, micro tensile tests are performed by an accurate tensile test device and high-quality camera imaging for data sampling. The obtained displacements are analysed by the image processing method and used as target values in the peridynamic analyses. Multiscale mass points from macro to micro scale are generated to model the interphase region in single fiber specimens using the state-based peridynamic method. With the coupling of peridynamic and multivariate optimization codes, the program is automatically executed by the prediction of thickness and elastic modulus of interphase to achieve the desired displacements similar to micro tensile test results. In this innovative method, unlike nanoindentation tests, where the results are limited to a specific section or point, the interphase characterization gives an overall elastic modulus value along the examined length of the sample. The obtained results from the presented procedure show that the interphase elastic modulus is between 20.8 and 28.86 GPa and the interphase thickness is between 1.149 and 1.986 microns. The obtained results are in the range of nanoindentation tests results presented in the literature, and the difference could be due to the manufacturing conditions, epoxy properties, and quality of the fiber silane coatings.

Enhancement of corrosion resistance of stainless steel with Zn doped silane coatings

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Research on Hard, Transparent and Hydrophobic Coating on PMMA Sheet

In this paper, nano SiO2 particles modified organic silane coatings were successfully prepared to aim at the application of the self-cleaning coating on PMMA substrate for deep-sea optical windows. The chemicals, surface microstructure, wettability, hardness, adhesion, transparency, water scouring resistance as well as microorganism attachment rate of the coatings were investigated. The results showed that adding SiO2 nanoparticles into the organic silicon coating can effectively improve the hydrophobicity due to generating a micro-nano structure surface. However, excessive addition would result in a decrease in hydrophobicity, adhesion, as well as transparency, due to the inorganic SiO2 particle destroying the integrity of the organic coating. The optimal coating was obtained by adding 0.5 wt% nano SiO2 particles, which possessed a water contact angle of 114.2°, hardness of 4H, adhesion level of 0, and visible light transmittance of 0.886. After 40-h water scouring, the water contact angle decreased to 108.3° and the visible light transmittance decreased to 0.839, suggesting good water scouring resistance. The microorganism attachment rate of the S05 coating was 0.17% after a 6 h immersion test, which was about half that of the PMMA substrate.