Silicone Coatings Research Articles

Corrosion resistance and biocompatibility of silica coatings on AZ31 magnesium alloy via magnetron sputtering

Magnesium alloys have promising prospects in biodegradable implants, but premature degradation is the main factor limiting their application. We prepared silicon coatings of different thicknesses on the surface of AZ31 magnesium alloy using the RF magnetron sputtering method. The phase, microstructure, and elemental composition of the coatings were characterized by XRD, SEM, and EDS, respectively. The corrosion resistance of the coatings in simulated body fluids was tested using immersion corrosion and electrochemical corrosion tests. Results showed that the silicon coating sputtered for 3 hours had the best corrosion potential and current, with a corrosion current density of 6.5614E-6 (A/cm2), which is two orders of magnitude lower than that of the AZ31 substrate. The extract of the sample in RPMI-1640 medium was co-cultured with human umbilical vein endothelial cells (HUVEC), and its cytotoxicity was evaluated by the CCK-8 assay. It was found that the silicon coating sputtered for 3 hours had the least toxicity, and the endothelial cells had a high proliferation rate. Therefore, the magnetron sputtered Si coating on AZ31 magnesium alloy exhibits good corrosion resistance and biocompatibility.

Highly dispersed nanocomposite based on magnesium ion modified and silver nanoparticles loaded graphene oxide for enhanced antibacterial activity of silicone coatings

Silver nanoparticles (Ag NPs) possess excellent antibacterial properties and have received widespread attention. However, the poor dispersion and easy aggregation of Ag NPs can severely diminish their antibacterial efficacy, limiting their practical applications. In this work, we report a simple method for preparing graphene oxide (GO) nanocomposites (Mg-GO/Ag NPs), in which GO is modified by Mg2+ and uniformly loaded with Ag NPs. The Ag NPs have an average diameter of approximately 11.14 nm, and uniformly are deposited on the surface of the GO. Compared with GO, the dispersion of Mg-GO/Ag NPs in deionized water (DW) and N, N-dimethylformamide (DMF) is significantly improved. The reaction principle of preparing Mg-GO/Ag NPs was revealed by gas chromatography–mass spectrometry (GC–MS). Additionally, we studied the antibacterial properties of Mg-GO/Ag NPs coatings against marine bacteria and Navicula tenera. This study introduces a novel approach for the preparation of high-efficiency silver-based antifouling coatings, with promising potential for a wide range of marine antifouling applications.

Electrodeposition of Silicon in the Low-Temperature LiCl-KCl-CsCl-K2SiF6 Melt Under Direct and Pulse Current

In this work, the effect of electrolysis modes and their parameters on the morphology of the silicon deposits on glassy carbon were studied. In direct current mode it was found that an increase in current density and deposition time changes the morphology of the silicon from a coating to a deposit with a complex surface. Scanning electron microscopy showed that silicon films produced at low current densities and a short deposition time are represented by spherical particles with a diameter of less than 1 μm. The pulse current mode made it possible to increase the cathode density of the deposition current, and the pulse current density to an average of ≈250 mA cm−2 does not lead to the formation of a large amount of dendritic deposit. It was found that a low frequency makes it possible to obtain higher-quality silicon coatings, because when the frequency increases, the coating most often does not cover the entire electrode. The high value of the duty cycle, even at low pulse current densities, always leads to the formation of dendrites. An increase in the total deposition time also leads to an increase in the amount of deposit and the formation of dendrites.

Self-growing composite photocatalytic materials for surface self-renewal of marine antifouling coatings

The attachment of marine organisms leads to the problem of marine biofouling. Biofouling can be prevented by using antifouling coatings this provided a low surface energy surface to inhibit the attachment of marine organisms. However, microorganisms inevitably attach during their use, leading to failure of the fouling release coating. To address this problem, we report an innovative strategy of doping photocatalytic materials into silicone coatings. This approach enables the degradation of bacterial carcasses and their secretions, leading to surface self-renewal and extended fouling protection. In this work, we report the controlled crystallisation of Ag-TiO2 nanomaterials (APTES-Ag@TiO2) using various methods influenced by aminopropylsilane. This strategy ensures the full utilisation of sunlight and strong interfacial adhesion, thereby preventing the degradation of photocatalytic performance. APTES-Ag@TiO2 not only has a self-growth effect and excellent photocatalytic performance but also facilitates the degradation of bacterial carcasses, thereby renewing the surface in organosilicon coatings.

Transparent, robust, and anti-fingerprint silicone coating with a three-dimensional cross-linked network enabled by hydrosilylation reaction

Silicone coatings with anti-smudge, anti-fingerprint, abrasion resistance, and ultraviolet (UV) resistance properties are increasingly demanded for touch screens as the development of artificial intelligence and human-computer interaction interfaces. Herein, a transparent, robust, and self-cleaning silicone coating was developed by incorporating cage-like structures and long carbon chains into a 3D cross-linked network via the rational combination of polymethylhydrosiloxane (PMHS), PSS-Octavinyl substituted (VPOSS), lauryl acrylate (LA), and 1,2-epoxy-4-vinylcyclohexane (EVCH) through hydrosilylation reaction with the presence of Karstedt catalysts. After introducing sealed diphenyliodonium phosphate (I-200), the silicone coating (PVLE-I-200) demonstrated excellent pencil hardness, anti-smudge, and abrasion resistance, and its average transmittance of visible light reached about 92 %. Owing to the low surface energy carbon chains, the coating showed amphiphobic properties and excellent anti-fingerprint property. The binding between cyclohexyl epoxy and glass substrate contributed to the high adhesion of the coating, which remained nearly intact and slightly reduced surface wettability after 500 friction cycles of sandpaper. In addition, the PVLE-I-200 coating demonstrated UV resistance which could withstand 200 h of UV irradiation attributed to the cage-like structure of VPOSS. The functional silicone coating provides insights into the development of environmentally friendly coatings for touch screens with high transparency, abrasion resistance, anti-smudge, and anti-fingerprint properties.

Experiment on Freeze–Thaw Resistance of Tunnel Portal-Lining Concrete with Silicone Coating in Cold Regions

Experiment on Freeze–Thaw Resistance of Tunnel Portal-Lining Concrete with Silicone Coating in Cold Regions

Preparation of Silicone Coating and Its Anti-Ice and Anti-Corrosion Properties

To enhance protection against corrosion and ice on iron metal material in frigid zones, an organic silicone resin coating was prepared using four monomers. Its structure and performance was analyzed via infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), and thermal analysis (TG). Corrosion resistance of coating was tested by saltwater resistance and salt spray resistance and assessed using an electrochemical workstation, alongside anti-icing tests. The results showed that the organic silicone resin was successfully synthesized. The coatings could delay freezing onset by one-third compared to controls in low temperatures, with a detachment time also reduced by one-third, indicating excellent corrosion and ice resistance. The methylphenyl silicone resin had good anti-corrosion and anti-ice properties, with a low corrosion current density (icorr) of 0.8793 μA/cm2 and a high charge transfer resistance (Rct) of 24,930 Ω·cm2 in saline.

One step synthesis of durable slippery, oil/water selective, corrosion-resistant silicone coatings with grafted flexible sidechains

Slippery liquid-infused porous surfaces (SLIPSs) based on polymer matrices impregnated with liquid lubricants are multifunctional and provide a wide range of useful properties such as low adhesion of water and other liquids, selectivity, high corrosion resistance, etc. However, these properties vanish quickly due to the gradual depletion of lubricant from the matrix. This issue could be resolved by attaching lubricant molecules to the matrix as flexible, liquid-like sidechains. In the present work, thin silicone films with grafted sidechains are fabricated. The uniform coatings are obtained in “eco-friendly” pressurized (subcritical) CO2 on smooth silicon wafers as well as on rough porous substrates such as carbon aerogels. The possibility of applying films by the traditional dip-coating method is also demonstrated on titanium slides. The coatings demonstrate low sliding angles for water and water/alcohol solution droplets. Coated aerogels preserve high porosity. It is demonstrated that initially hydrophilic aerogels become highly hydrophobic after coating and selectively absorb oil from water/oil mixtures. The tests of obtained coatings on titanium substrates demonstrate a significant increase in corrosion resistance. The proposed technique has a wide range of potential applications where such slippery coatings should be applied on complex rough substrates: from filtration materials production to textile finishing.

Branching and Cross-Linking of Siloxane Copolymers Containing Hydromethyl-Siloxane Units by the Hydride Transfer Restructuring Reaction. Possible Route to Silicone Coatings

Branching and Cross-Linking of Siloxane Copolymers Containing Hydromethyl-Siloxane Units by the Hydride Transfer Restructuring Reaction. Possible Route to Silicone Coatings

Effects of Annealing and Oxidation on the Microstructure of Hot-Dipped Aluminum–Silicon Coating of 316L Stainless Steel

Effects of Annealing and Oxidation on the Microstructure of Hot-Dipped Aluminum–Silicon Coating of 316L Stainless Steel

Controllable preparation of VO2@m-SiO2 and its light transmittance and thermal insulation properties of PVB composite films

In this study, a hybrid approach using the Stöber and solvent extraction techniques was employed to synthesize mesoporous silicon-coated VO2 nanomaterials (VO2@m-SiO2, VmS) with controllable pore sizes and shell thicknesses. This synthesis was aimed at elucidating the influence of mesoporous silicon coatings on the thermochromic effect and optical properties of VO2. Experimental findings reveal that the mesoporous silica architecture markedly improve the phase-transition hysteresis of VO2 while mitigating the Mie effects attributable to particle coarsening, under the appropriate shell thickness. Furthermore, concomitant with the enlargement of the mesoporous aperture, the Tlum and ΔTsol of the VmS/PVB films also exhibit upward trends. Tlum reaches 73.33% and 62.24% in VmS3/PVB and VmS5/PVB, peak ΔTsol reaches 5.16% in VmS5/PVB. The facile synthesis procedure of VmS, in conjunction with its superior performance across phase transition, optics, and thermal insulation metrics, offers a viable pathway for industrial-scale deployment of VO2(M) in smart window applications.

Effect of silicon content on microstructure and mechanical properties of AlSi alloy coating obtained by physical vapour deposition

ABSTRACT Several contents of silicon in AlSi coatings, and substrate nature, were investigated in this present research. For this purpose, thin films were deposited by Physical Vapour Deposition onto three substrates: The effect of silicon content on the microstructure and mechanical properties of the coatings was studied. The microstructural observations showed that the coating carried out with 7 wt-%. silicon reduced the porosities by making the microstructures more homogeneous and denser. Also, the influence of substrate characteristics on the evolution and distribution of the microstructure formed during coating is important. Content of 13 wt-% eutectic enhanced the mechanical properties. The crystallite size evolves in a completely opposite way to that of the dislocation density and micro-deformation, with a minimum for the same values of silicon content (10–12 wt-%). The microstructural analysis allowed us to highlight the importance of silicon in the formation of intermetallic compounds.

Hierarchical biocide-free silicone/graphene-silicon carbide nanocomposite coatings for marine antifouling and superhydrophobicity of ship hulls

A new series of fluorine-free, nonbiocidal, and hierarchical superhydrophobic silicone coatings filled with reduced graphene oxide (RGO)/β-SiC bamboo-like nanocomposites was successfully fabricated as durable ternary marine fouling release (FR) surfaces. RGO/β-SiC hybrid was used as coating nanofiller that would release fouling and confer surface robustness. It was facilely created using a straightforward one-phase ultrasonication technique. The dispersion of different concentrations of RGO sheets decorated with β-SiC bamboo-like fillers was determined to study the superhydrophobicity and antifouling behaviors of polysiloxane nanocomposites. RGO was prepared through a simple hydrothermal technique. Solution casting was used to distribute the RGO/β-SiC nanofillers throughout a silicone matrix. Atomic force microscopy, surface free energy, and water contact angle (WCA) were employed to examine the superhydrophobicity and micro/nanoroughness of the coatings. The mechanical, anticorrosive, and durability characteristics of the silicone-RGO/β-SiC-filled composites were also investigated. The antifouling effects of the coating systems were evaluated in the laboratory for 30 days with specific bacteria. The silicone-RGO/β-SiC (3 wt%) composite with the best dispersion, highest WCA (156°), and lowest surface free energy (12.7 mN/m) among the composites exhibited favorable FR characteristics. The well-dispersed PDMS-RGO/β-SiC (3 wt% nanofiller) composite presented the minimum degradation and cell viability percentages against Gram-positive and Gram-negative bacteria as well as diatoms. Therefore, this study produced a series of nonstick and fluorine-free ternary FR nanocomposites for maritime coatings with surface durability, superhydrophobicity, and fouling retardancy. This work highlights the design and preparation of multifunctional marine nanocoatings with excellent antifouling performance, easy applicability, and superhydrophobicity properties.

Transmittance of PDMS film on the fluorescent performance and synergistic antifouling effect of SWLAP/PDMS composite coatings

The film-forming substances in waterborne silicone coatings play a crucial role in the properties of coatings. A novel waterborne fluorescent antifouling coating inspired by fluorescent coral was reported in this paper. A series of sky-blue waterproof long afterglow phosphor (SWLAP)/polydimethylsiloxane (PDMS) composite coatings were prepared with different properties of hydroxy‑terminated silicone oil emulsion (HT-SOE). SWLAP is irradiated by sunlight during the day and emits fluorescence at night to interfere with the normal physiological activities of marine organisms. The high transmittance of PDMS films formed by HT-SOE contributes to the high fluorescence intensity of coatings. The adhesion behavior of marine bacteria and Navicula sp. on the coatings was studied under simulated alternative day-night, continuous light, and constant dark conditions. The results showed that the bacterial adhesion rate (BAR) and diatom removal rate (DRR) under simulated alternative day-night conditions of coatings was significantly decreased and increased, respectively. C-S20/5011 had the best static and dynamic antifouling performance. The BAR was only 2.46 % after 24 h and DRR reached 39.9 % after 48 h. Under continuous light or dark conditions, the antifouling abilities of coatings mainly depend on their surface performance and mechanical properties. The fluorescence effect played an important role in the synergistic antifouling mechanism. This study provides a new idea for environmentally friendly antifouling coatings and becomes an important step in the development of green and long-acting marine antifouling coatings.

Nature-Inspired Regenerative Fine-Dust-Catching Coatings to Improve Air Quality.

Increased particulate matter (PM) concentrations in our ambient air are the cause of various life-threatening diseases and consequently need to be reduced to nonhazardous levels. The natural PM removal capabilities of leaves inspired the development of a low-cost coating technology that exploits natural weather phenomena for its PM catching and removal processes. The herein presented coating is based on microparticle-filled silicone with optimized chemical and physical surface properties. Its surface roughness was tuned using differently sized spray-dried particles, and its surface contact angle was adjusted through silicone tensides, polar ether groups incorporated in the silicon backbone, and the used amount of spray-dried particles. In such a way, optimized silicone coatings showed in laboratory experiments improved catching abilities (>300% relative to glass surfaces), a full retention of adsorbed PM during wind events, and the formation of large PM aggregates. Upon (simulated) rain events, these coatings were regenerated, and the content of harmful PM of various sizes dispersed in water was reduced between ∼73 and 100%. Furthermore, an outdoor test over 100 days showed the functioning of the coating under real-world conditions. These regenerative coatings are readily applicable on diverse surfaces and do not require any further technical infrastructure. Thus, they present an extension of the toolbox for PM reduction technologies.

Impact of Molecular Weight on Anti-Bioadhesion Efficiency of PDMS-Based Coatings

Silicone elastomer coatings have shown successful fouling release ability in recent years. To further enhance the design of silicone coatings, it is necessary to fully understand the mechanisms that contribute to their performance. The objective of this study was to examine the relationship between the molecular weight of polydimethylsiloxane (PDMS) and antibioadhesion efficiency. PDMS-based coatings were prepared via a condensation reaction, with a controlled molecular weight ranging from 0.8 to 10 kg·mol−1. To evaluate changes in surface wettability and morphology, contact angle experiments and atomic force microscopy (AFM) were performed. Finally, the antibioadhesion and self-cleaning performance of PDMS coatings was carried out during in situ immersion in Lorient harbor for 12 months. Despite small variations in surface properties depending on the molecular weight, strong differences in the antibioadhesion performance were observed. According to the results, the best antibioadhesion efficiency was obtained for coatings with an Mn between 2 and 4 kg·mol−1 after 12 months. This paper provides for the first time the impact of the molecular weight of PDMS on antibioadhesion efficiency in a real marine environment.

Design of a soft sensor based on silver-coated polyamide threads and stress-strain modeling via Gaussian processes

The demand for reliable and efficient soft sensors has grown exponentially with the evolution of wearable devices and smart textiles. However, existing soft sensors often face challenges related to hysteresis, noise, and accuracy, hindering their seamless integration into practical applications. Our research presents a pioneering stress–strain soft sensor model based on silver-coated polyamide threads, augmented with additional silicone and graphite coatings for enhanced properties. Specifically, the silicone coating proves instrumental in elevating the sensor’s gauge factor and reducing noise, resulting in heightened accuracy. The extensive data analysis reveals the presence of hysteresis and non-linearities; however, our data exhibits remarkable robustness, as indicated by the high Spearman correlation coefficient values. In the context of system identification, a comparative analysis between traditional regression methods and Gaussian Process (GPs) Regression demonstrates the superior performance of GPs: this technique outperforms conventional regression techniques, obtaining 8.75 ± 4.06% Root Mean Square Error (RMSE) compared to the 12.70 ± 7.04% error observed in traditional methods. This research not only advances the field of soft sensor technology by developing an accurate, affordable and adaptable device, but also offers valuable insights into highly effective system identification techniques tailored for wearable devices.

Quantitative thermodynamic exposure assessment of PCBs available to sandworms (Alitta virens) in activated carbon remediated sediment during ongoing sediment deposition.

Marine mesoscale studies with sandworms (Alitta virens) were conducted to isolate important processes governing the exposure and bioaccumulation of polychlorinated biphenyls (PCBs) at contaminated sediment sites. Ex situ equilibrium sampling with silicone-coated jars, and in situ passive sampling with low-density polyethylene (LDPE) were used to determine the performance of an activated carbon (AC) amendment remedy applied to the bed sediment. A quantitative thermodynamic exposure assessment ('QTEA') was performed, showing that PCB concentrations in polymers at equilibrium with the surficial sediment were suited to measure and assess the remedy effectiveness with regard to PCB bioaccumulation in worms. In practice, monitoring the performance of sediment remedies should utilize a consistent and predictive form of polymeric sampling of the sediment. The present study found that ex situ equilibrium sampling of the surficial sediment was the most useful for understanding changes in bioaccumulation potential as a result of the applied remedy, during bioturbation and ongoing sediment and contaminant influx processes. The ultrathin silicone coatings of the ex situ sampling provided fast equilibration of PCBs between the sediment interstitial water and the polymer, and the multiple coating thicknesses were applied to confirm equilibrium and the absence of surface sorption artifacts. Overall, ex situ equilibrium sampling of surficial sediment could fit into existing frameworks as a robust and cost-effective tool for contaminated sediment site assessment.

The influence of silicon content on the microstructure and high‐temperature oxidation behavior of aluminum‐silicon coatings on Ti‐6Al‐4 V alloy by hot dipping route

AbstractThe poor high‐temperature oxidation properties of Ti‐6Al‐4 V (titanium‐aluminum‐vanadium) alloy limit its applications under high‐temperature components of aero‐engines. In this study, the aluminum‐silicon coatings with different silicon content were fabricated on titanium‐aluminum‐vanadium alloy via the hot dipping route. A metallurgical bond was established at the interface between aluminum‐silicon coatings and substrates following the hot dipping. The results showed that three different coatings were formed: titanium(aluminum, silicon)3+ liquid‐(aluminum, silicon), titanium(aluminum, silicon)3+ τ2+ liquid‐(aluminum, silicon) and τ1+ τ2+ liquid‐(aluminum, silicon). Furthermore, the formation of aluminum‐silicon coatings was analyzed by diffusion path theory. The coated alloy was subjected to a high‐temperature oxidation test at 850 °C, and the weight gains were only 5.1 % to 22.4 % of the bare alloy. The coatings improved the high‐temperature oxidation resistance of titanium‐aluminum‐vanadium alloy. The most favorable oxidation behavior was noticed for the titanium(aluminum, silicon)3+liquid‐(aluminum, silicon) coatings. The higher the silicon content in titanium(aluminum, silicon)3+liquid‐(aluminum, silicon) coatings, the more excellent high‐temperature oxidation resistance was achieved.

Influence of multi-walled carbon nanotubes/N, N-dimethylformamide slurry amount on fouling release performance of silicone coatings

MWCNTs reinforced silicone coatings were prepared by mechanically mixing hydroxyl-capped polydimethylsiloxane (PDMS) and multi-walled carbon nanotubes/N, N-dimethylformamide (MWCNTs/DMF) slurries. The effects of MWCNTs/DMF slurry amount on the fouling release performance of silicone coatings were investigated. Incorporation of 5 wt% MWCNTs/DMF slurry increased the elongation and reduced Young's modulus, Shore's hardness, and roughness observed. As a result, an excellent silicone coating was fabricated with stable surface properties, fouling release performance, economic savings, and prolonged longevity for marine applications. Silicone coatings reinforced by MWCNTs were prepared by mechanical blending. MWCNTs are tubular crystals 30–80 nm in diameter and less than 10 μm long. The effects of MWCNTs/DMF slurry amount on the coating properties were investigated by dispersion properties, surface properties, mechanical properties, marine bacteria adhesion, and Navicula tenera adhesion test. The most favorable fouling release performance with the lowest roughness (0.168 ± 0.008 μm), the minimum Shore's hardness (18.47 HA), and the minimum relative adhesion factor (5.88 RAF) were shown for the silicone coatings prepared with 5 wt% MWCNTs/DMF slurry.