Silane Agent Research Articles

Organosilane-functionalized graphene oxide-epoxy nanocomposite coating: corrosion performance and self-healing properties

In this study, decorated GO nanosheets with 3-glycidyloxypropyl trimethoxysilane (GPTMS) evaluated with Fourier Transformation Infrared Spectroscopy (FT-IR), x-ray diffraction (XRD), Thermogravimetric analysis (TGA), field emission scanning electron microscopy (FE-SEM) and energy dispersive x-ray spectroscopy (EDAX). The corrosion performance and of self-healing effect of the nanocomposite coating were examined by electrochemical techniques, Salt Spray, Contact Angle and Scratch test. Corrosion resistance was improved by increasing the percentage of GO from 0.1 to 0.2 wt% for both cases without and with silane agent. Higher impedance resistance (1.12 × 1010 Ω.cm2) was obtained for the functionalized one (EPFG) in the early days of immersion. The results of electrochemical and salt spray tests of EPFG nanocomposite coatings were compared epoxy (EP) coatings during various immersion times in 3.5 wt% NaCl solution with and without scratches.Based on our results, after 99 days of immersion, the impedance resistance for EP coating decreased about five orders compared to the EPFG composite coating. The self-healing performance of hydrophobic nanofillers in the matrix of epoxy coating (EPFG) is considered as the reason for increasing resistance after 63 days. The time of reaching corrosive solution to the surface of the steel for the EPFG nanocomposite increased up to 78 days. At all immersion times of the scratched samples, the highest impedance of EPFG composite samples was observed and increasing the impedance of EPFG after 12 days of immersion is related to the formation of a protective film in the metal substrate-coating interface leads to the passive and protective behaviors.

MICROSTRUCTURAL CHANGES OF THE PEO COATING INDUCED BY SILANE-BASED SOL–GEL TREATMENT

In this paper, the silane-based sol–gel treatment process was applied to the plasma electrolytic oxidation (PEO) ZM6 Mg-alloy. The microstructural characteristics and corrosion resistance of the PEO/organic composite coatings were studied by means of SEM and XRT in conjunction with electrochemical measurements. The results showed that the microdefects in the PEO coating could be effectively filled with the silane compounds, reducing the porosity of the PEO coating. The treated PEO coating had a hydrophobic property, which may be related to the siloxane network (Si–O–Si) formed on the PEO coating surface. The corrosiveness of the silane agent to the PEO coating and the generation of internal stress in the PEO coating resulted in the damage of microstructures of the PEO coating. The global and local electrochemical measurements showed that the corrosion-resistant performance of the PEO Mg-alloys after the silane-based sol–gel treatment was improved and its service life would be shortened by the balance of micropores without sealing and the damaged microstructure.

Improving water-resistance of inverted flexible perovskite solar cells via tailoring the top electron-selective layers

Inverted flexible perovskite solar cells (FPSCs) offer a promising route towards commercialization by using undoped inorganic hole transport layers and thermally-stable electron transport layers (ETLs), which deliver good environmental stability such as water resistance. But the power-conversion-efficiencies (PCEs) of inverted flexible perovskite cells are still far below those of FPSCs in regular configuration so far. One main challenge for achieving high-performance FPSCs lies in optimizing the ETLs and their adjacent buffering layers. Herein, we modify the fullerene derivatives (Phenyl-C61-butyric acid methyl ester, PCBM) ETLs by adding 3-aminopropyl triethoxysilane (APTS) molecules into the PCBM solutions. The addition of APTS results in smoother and denser PCBM layers via a physically steric-hindrance effect mechanism, which could benefit the electron collection between the PCBM layer and the perovskite layer. More importantly, APTS can offer nucleating sites, such as amine groups or hydroxy groups by partially hydrolyzing, to grow conformal tin oxide (SnO x ) layers by atomic layer deposition (ALD), which acts as robust buffer layers to replace traditional bathocuproine (BCP) layer. Finally, high-performance inverted FPSCs based on the optimized PCBM/SnO x electron-selective layers are fabricated, delivering a best PCE of 18.62%. The unencapsulated FPSC showed a slow decay and remained above 90% of its initial PCE after being stored for more than 600 h in a damp environment with a humidity of more than 85% R.H. The strategy is demonstrated to be applicable in the future large-scale production of stable FPSCs. • A flatter PCBM layer can reduce contact resistance and improve electron collection in inverted perovskite solar cells. • Modifying the PCBM layer with silane agents is helpful for the subsequent ALD growth of the inorganic buffer layer. • An optimized PCBM/SnO x electron selective layer endows flexible perovskite solar cells with outstanding water resistance.

New Method in Surface Treatment of Nanopipette for Interface between Two Immiscible Electrolyte Solutions (ITIES) Experiment

Interface between two immiscible electrolyte solutions (ITIES) is a powerful platform for chemical sensing and studying electron/ion transfer reactions and is typically formed between the interface of two immiscible solutions such as an oil phase and an aqueous phase. Micro/nano ITIES interface are generally formed at the tip of a borosilicate/quartz pipette, inner surface of which can be rendered hydrophobic to be filled with an organic solvent by a method called silanization. Nano/micrometer-sized electrodes are typically silanized by vapor silanization methods in which silanizing agent in vapor phase is exposed to nanopipettes. Micrometer-sized pipettes have been also silanized by directly filling liquid silanization agent, one type of liquid silanization methods, but this method has not been used at the nanoscale. Liquid silanization method allows to selectively silanize a single channel in a dual-channel pipette platform. Here, we developed the liquid silanization method for nanoscale ITIES and demonstrated that a stable cyclic voltammogram for tetrabutylammonium ion transfer across water/dichloroethane interface can be accomplished. We also presented challenges for liquid silanization at the nanoscale and strategies to overcome them. The liquid silanization methods presented here lay the foundation for future development of dual channel multi-functional probe where one channel is nanoITIES.

Influence of silane coupling agent and aging on the repair bond strength of dental composites

The objective of this work was to evaluate the effect of different protocols on the shear bond strength (SBS) of repairs made to aged composite resin substrates. Eighty cylindrical composite resin specimens (IPS Empress Direct, Ivoclar-Vivadent) were prepared, and divided into two main groups: in group 1 a silane agent was applied, while in group 2, the silane agent was not applied. Each group was then subdivided into four groups according to the adhesive system used: control, without any adhesive, Single Bond Universal, Tetric Bond Universal, and Clearfil SE Bond. As a reference group, the cohesive strength of the composite resin was determined. After applying the adhesive protocol, the treated surfaces were restored with composite resin cylinders. The specimens were stored in distilled water for 24 h or 6 months at 37 °C and subjected to a SBS test. The data were evaluated using a three-way ANOVA test followed by a Tukey test (α = 0.05). The previous application of silane did not significantly affect the SBS (p = 0.162), on the contrary, the type of adhesive protocol and aging impacted significantly (p < 0.001). The SBS was significantly higher when Clearfil SE Bond was used (p < 0.001), with the values achieved by this group being similar to those of the reference group (p ≥ 0.996). The use of a silane coupling agent before the application of an adhesive does not significantly affect the process of adhesion to an aged resin. The application of a solvent-free adhesive system was able to restore the cohesive strength values of the material.

Surface Modification of Cellulose Microfibrils with Silane Agent for Eco-Friendly Hydrophobic Coatings

Surface Modification of Cellulose Microfibrils with Silane Agent for Eco-Friendly Hydrophobic Coatings

An ion-imprinted imidazole-functionalized ordered mesoporous silica for selective removal of chromium(VI) from electroplating effluents.

In this work, ion imprinted technology incorporated with mesoporous silica materials (MCM-41) to obtain the novel specific adsorbent, ion imprinted mesoporous silica. Cr(VI) imprinted mesoporous silica (Cr(VI)IMS) was synthesized and used for adsorption studies and waste water application. A synthesized imidazolyl silane agent act as the functional monomer in the imprinted process to build up highly ordered functionalized imprinted materials. The chemical composition, porosity, and highly ordered morphology were characterized by Fourier transform infrared spectroscopy (FTIR), solid state nuclear magnetic resonance (NMR), Brunauer-Emmett-Teller (BET) method, X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM), respectively. The Brunauer-Emmett-Teller (BET) surface area was 1054.51 m2g-1 in this study. The Cr(VI)IMS showed great adsorption capacity to hexavalent chromium ions in acidic solution up to 45.6mgg-1. Cr(VI)IMS reached the adsorption equilibrium in a short time (10min) at acid and weak acid conditions, while most of adsorbents need more than 30min to achieve adsorption equilibrium. Cr(VI)IMS displayed much higher adsorption capacity to Cr(VI) ions than other negative ions. The relative selectivity coefficient was 2.56, higher than those of other anions (below 1.5). After eight adsorption-regeneration cycles, the adsorption efficiency of Cr(VI)IMS still reached 92.5%. The Cr(VI)IMS was found to exhibit equivalent property after multiple cycles of experiments, indicating good repeatability and reproducibility.

Additive manufacturing of complex-shaped and high-performance aluminum nitride-based components for thermal management

Improved heat dissipation performance, by way of thermal management, is critical in many engineering applications. In this study, three types of silane coupling agents were used to modify aluminum nitride (AlN) powder for vat photopolymerization. The effect of silane coupling agents on the rheology, stability, and curing behavior were systematically studied. The results showed that, compared with two other types of silane coupling agents, one silane agent (KH570) had a larger positive effect on the rheology and stability of the AlN suspension, and the absorbance of the AlN powder increased after surface modification. In addition, the effects of different solid loadings on the curing behavior and CC double-bond conversion rate were systematically investigated. It was found that a higher solid loading resulted in a lower curing depth, cure width, and CC double-bond conversion rate. For the sintered AlN components with increased solid loading, the shrinkage decreased while both the flexural strength and thermal conductivity increased. In addition, the shrinkage in the Z-direction was higher than that in the X- and Y-directions. Scanning electron microscopy analysis showed that the mean grain size decreased with increasing solid loading. Furthermore, a heat dissipation performance evaluation system was designed to illustrate the heat transmission capacity of AlN ceramics. Simulation and experimental results showed that AIN ceramic parts with complex shapes achieved better heat-dissipation performance than those with simple shapes.

Surface decoration of Halloysite nanotubes with POSS for fire-safe thermoplastic polyurethane nanocomposites

• POSS modified HNTs were synthesized successfully by using a silane agent as a chemical bridge. • The POSS in combination with HNTs endows TPU with excellent flame retardancy without scarifying the mechanical property. • The incorporation of 2 wt% HNTs-POSS into TPU could effectively reduce the peak of the peak of CO production rate and total smoke release during combustion. Halloysite nanotubes (HNTs) have been considered as a promising flame retardant fillers for polymers. In this work, the polyhedral oligomericsilsesquioxane (POSS) containing amino group was covalently grafted on the surface of HNTs with 3-(2,3-epoxypropoxy)propytrimethoxysilane as a chemical bridge. The POSS modified HNTs (HNTs-POSS) dispersed uniformly in the thermoplastic polyurethane (TPU) matrix and endowed TPU nanocomposites with enhanced tensile properties and fire safety. Cone calorimeter tests revealed that the introduction of 2 wt% HNTs-POSS to TPU matrix remarkably reduced the peak of heat release rate (PHRR) and total heat release (THR) by 60.0% and 18.3%, respectively. In addition, the peak CO production rate and total smoke release (TSR) could be significantly suppressed by the addition of HNTs-POSS. The well dispersed HNTs in combination with the ceramified silicon network from the thermal decomposition of POSS contributed to the formation of a continuous and compact char layer, exhibiting a tortuous effect by inhibiting heat diffusion and evaporation of volatile gaseous. In addition, the released crystal water from HNTs could dilute the combustible volatiles and then decline the combustion intensity. The tensile tests demonstrated that introduction of 2 wt% HNTs-POSS would enhance the maximum stress of TPU nanocomposite with a slight decrease of elongation at break. The combination of HNTs and POSS through the construction of effective interfacial interactions provides a feasible way to effectively enhance the fire safety of TPU nanocomposites without scarifying ductility.

Evaluation of corrosion inhibition capability of graphene modified epoxy coatings on reinforcing bars in concrete

Corrosion of reinforced concrete structures is the one of the biggest problems faced by the construction industry, with billions of dollars spent annually on corrosion control strategies. Epoxy Coated Rebars (ECRs) have been reported to mitigate corrosion in Reinforced Concrete (RC) structures, but due to the inherent brittle nature of epoxy, its usage is limited. In this study we have proposed modified epoxy coatings on rebars using reduced graphene oxide (rGO) and graphene oxide (GO) along with carbon nanotubes (CNTs) and silane agents for improved ductility and corrosion inhibition properties. Hybrid mixture of CNTs and rGO/GO enhances the mechanical strength of the coating matrix whereas silane agents improve dispersion and bonding characteristics of nano fillers. Differently coated mild steel rebars with rGO/GO based coatings were subjected to accelerated impressed current corrosion. Performance of the coatings was evaluated by visual inspection, corrosion current, ultrasonic guided wave measurements, mass loss and residual tensile strength. Our results indicate that compared to rGO, GO in small proportion (0.4 wt% of epoxy resin) performs superior in corrosion inhibition. The GO/CNT nano composites could have potential application in the field of modified ECR reinforced concrete structures.

Surface modification of the cellulose nanocrystals through vinyl silane grafting

Incompatibility of nanocellulose with non-polar polymer matrices disrupts the interfacial interaction and results in aggregation and phase separation. In this study a facile and environmentally friendly method was used to partially substitute the surface hydroxyl groups by attaching polysiloxane to impart hydrophobic properties. The silanization reaction proceeded with hydrolysis of triethoxyvinylsilane (TEVS) into reactive silanols followed by condensation to form the branched polymer. These polysiloxane oligomers were chemically grafted to form alkoxy silane bonds on the surface of CNCs. A suitable degree of hydrophilic-hydrophobic balance of the modified CNCs was achieved which improved their dispersion in hydrophobic matrix poly(butylene adipate-co-terephthalate) (PBAT). FTIR, NMR (13C and 29Si) and XPS demonstrated successful surface chemical modification and confirmed extent of silanization as a function of silane concentration. XRD showed successful grafting of the vinyl silane agent and confirmed polymorph structure of the nanocellulose was retained. The results from TEM and AFM demonstrated successful coating of nano whiskers at 5 wt% silane loading. The successful grafting of the silane agent with pendant vinyl groups improved surface hydrophobicity. These results show that this facile method produces adequately surface modified CNC which can be used as filler in hydrophobic matrices of bioplastics.

Surface treatment of lignocellulose biofiller for fabrication of sustainable polylactic acid biocomposite with high crystallinity and improved burning antidripping performance

In this work, we incorporated surface-treated coffee husks (CHs) into a polylactic acid matrix to fabricate environmentally friendly composites, with high crystallinity and satisfactory antidripping performance for flame retardancy. CHs are lignocelluloses that contain cellulose, hemicellulose, and lignin that are present as interlinked complex macromolecular structure. CH spectroscopic characterization confirmed that the phytic acid/amine silane agent was successfully attached and bonded with the cellulose portion of CHs. Morphological analysis of the composites revealed that the surface-treated CHs helped to improve the interfacial interaction between the filler and the matrix. Furthermore, the differential scanning calorimetry analysis showed that the crystallinity of the composites increased with CH loading. Flammability and combustion tests confirmed that the combined effect of P/Si/N on surface treatment improved the flame retardance behavior of the composites. The tensile strength and modulus of the composites exhibited a 28.7% and 34.4% increase compared with the corresponding composite with raw CHs.

Effect of organic-modified nickel phyllosilicate on the non-isothermal cure kinetics and flame retardancy properties of epoxy composites.

In this study, silane agents were employed as organic silicon to synthesize organic-modified nickel phyllosilicates (NiPS), which were then introduced into epoxy resin (EP) to yield composites. The effects of these organic-modified NiPS on the curing behavior and flammability of epoxy composites were then investigated carefully. Though the added NiPS resulted in the initial temperature shifts to high temperature, the whole curing temperature ranges for EP composites became narrow regarding pure EP. Simultaneously, the activation energy of curing was also decreased, implying the lowered energetic barrier during the whole curing process. For all investigated samples, the overall reaction orders varied negligibly, and the predicted curves fitted well with the DSC thermograms. Finally, the positive influence derived from the presence of these organic-modified NiPS on the enhancement of self-extinguishing ability and limited oxygen index were also discussed, and the solid phase flame retardant mechanism was proposed.

Influence of surface functionalization of ceramic nanofibers on morphological, physical and mechanical properties of unsaturated polyester nanocomposites

Alumina nanofibers at 0.25wt%, 0.5wt%, 0.75wt%, and 1wt% concentration were used to modify unsaturated polyester resin. Additionally, vinyl silane treated alumina nanofibers were used at the same concentrations and were compared to pristine alumina nanofibers. The SEM images showed a variation in the surface morphology when alumina nanofibers and the BET measurement showed surface area increase from 111 m2/g to 122 m2/g when nanofibers were treated with silane agent. The dispersion of alumina nanofibers into the host unsaturated polyester resin was successfully achieved by three roll mill dispersion. The TEM images showed good dispersion of alumina nanofibers in polyester resin. Although pristine nanofibers showed greater agglomeration at 1wt% concentration, the effect of agglomeration was reduced in the 1wt% concentration. The weight loss measurements from TGA showed that the thermal stability of nanocomposites increased with addition of nanofibers and the lower onset degradation temperature can be tailored to improve by a maximum of 5.5% for silane treated nanofiber. Viscosity and contact angle which are key factors affecting the processability has seen to be positively altered by silane treatment. Additional tensile, flexural, and Izod impact properties were evaluated for the nine material systems and the properties were summarized.

Silanization treatment for improve adhesion in Al-PP surfaces

In this work, a wide range of different silane based compounds has been studied with the aim of preparing the surfaces of the Al2024 and the polypropylene (PP). Afterwards, these materials have been joined with two kinds of adhesives: two-component structural adhesive DP8005 and double-sided adhesive tape RP45 (due to its interest in fast assembling operations). The compounds used for surface treatments are based on silane agents. Likewise, same authors have presented non-silane based treatments in other work (1). Both works, complement each other and provide the basis for a third one where the experimental design of measuring properties, mechanical properties in particular, is discussed (3).

Color stability of a resin nanoceramic after surface treatments, adhesive cementation, and thermal aging

Statement of problemWhether color changes in resin nanoceramic (RNC) restorations can occur because of material and adhesive interface degradation is unclear. PurposeThe purpose of this in vitro study was to evaluate the color of RNCs submitted to surface treatments, cementation, and aging. Material and methodsRNC specimens (N=120) were produced with a thickness of 0.5 mm. The No Treatment-High/Low Translucency (NT-HT/LT) groups did not receive treatments; the Airborne-particle Abrasion-High/Low Translucency (AA-HT/LT) groups were airborne-particle abraded, and the Airborne-particle Abrasion Silane-High/Low Translucency (AASIL-HT/LT) groups received airborne-particle abrasion and a silane agent. Single specimens (n=60) were measured on a spectrophotometer before and after aging (50 000 cycles). The other half was mounted on composite resin bases and measured. The cleaned specimens were cemented (C) on the bases and measured (T0 and T1). ΔE00, ΔL′, ΔC′, and ΔH′ were obtained by using the CIEDE2000 formula and analyzed by using ANOVA and repeated-measures ANOVA. Multiple comparisons were made by using the Tukey HSD test (α=.05). ResultsFor single specimens, the greatest ΔE00 values were observed in the AA-T1-LT resin (5.87). For mounted and cemented conditions, the greatest ΔE00 values were found in the AA-C-T1-LT resin (1.74), and the ΔE00 ranged from 0.75 (NT-OL) to 1.44 (AASIL-C-T1) for the HT resin (P<.001). The mounted and cemented specimens tended toward red and yellow, whereas lighter specimens were observed after cementation. ConclusionsAging affected the color of the RNCs evaluated. The single specimens showed greater color differences than the cemented specimens, reinforcing the importance of the adhesive cement in the optical behavior of thin restorations.

Graphene oxide and silane-modified graphene oxide/unsaturated polyester resin nanocomposites: A comparative cure kinetic and diffusion study

The curing behavior of pure unsaturated polyester resin (Neat UP), resin containing 0.5 wt% graphene oxide (UPGO) and resin containing 0.5 wt% graphene oxide modified by silane agent (UPMGO) was studied. The kinetic parameters of the systems were calculated using the advanced isoconversional method. The cure index was used to evaluate the curing quality of the systems. The results showed that the functional groups on the surfaces of graphene oxide and modified graphene oxide caused significant changes in the activation energies of different regions of resin curing. The formation of radical traps and stabilization of cobalt complexes by the added particles were other factors affecting the activation energy of the systems. The diffusion phenomenon was investigated in all three systems Neat UP, UPGO and UPMGO. The presence of attraction interactions between particles and alkyd resin chains are among the factors affecting the diffusion region of UPGO and UPMGO systems.

Improved adhesion of polyurethane-based nanocomposite coatings to tin surface through silane coupling agents

Conformal coatings with higher adhesion strength is crucial for mitigating the growth of whiskers from the pure tin (Sn) or Sn-rich surfaces of the Pb-free electronics. Silane coupling agents have the ability to form a durable bond between polymeric coatings and metallic materials. The main goal of this paper is to investigate the effect of silane agents on the adhesion behavior of polyurethane (PU), polyurethane acrylate (PUA) and both coatings filled with silicone rubber (SR) nanoparticles on the tin solder pads. It was found that an isocyanate-based silane provided excellent adhesion for PU and PU + SR coatings and an acrylic-based silane for PUA and PUA + SR coatings on the tin surface. This was due to the reaction bond formation between the silane coupling agent and the coating. Hence, the selection of silane coupling agents with the organofunctional group similar to the coating material is crucial to improve the adhesion properties of the coating.

Effect of methyl orange as the modifier on the mechanical, thermal, and thermo‐mechanical properties of clay/epoxy composites

AbstractIn this study, bentonite clay/epoxy composites were simply and successfully produced via conventional casting method for 0.5, 1, and 2 wt% filler content. Previously modified clay (surfactant and silane agent applied) was treated with methyl orange (MO) and its effects on composites were investigated in terms of crystallographic, thermal, thermo‐mechanical, morphologic, and topographic aspects as well as quasi‐static characteristics. According to XRD graphs, MO presence led to the increase of interlayer distance and resulted in partial intercalation for modified clay (MC) based mixture, while an opposite case was seen in neat clay (NC) blend. The 2 wt% MO/MC loaded composite achieved the highest tensile modulus, flexural stiffness, and hardness values among all samples—increase of 14%, 40%, and 3%, respectively. Same composite system exhibited improved results for both glass transition temperature (~7%↑) and storage modulus (~35%↑), in spite of insufficient thermal characteristics. Irregular particles/tactoids were present in the fracture images, which probably promoted the stress concentration and caused the reduction of strength parameter for all composites. Furthermore, independent of clay type (MC or NC) whole structures showed similar surface roughness values but different topographic textures in terms of surface profiles.

Development of stable water-resistant Cu-based catalyst for methanol synthesis

Improving the stability of Cu-based catalysts, especially in the presence of water, has always been a great challenge. The hydrophobization strategy and effects on the catalyst surface property and catalytic performance deserve rigorous investigations. Herein, the hydrophobic modified silica was introduced as a support for CuZn catalyst to hinder the adsorption of water on active sites of Cu-based catalysts, thereby improving its stability. And silane agents (methyltrimethoxysilane, ethyltrimethoxysilane, propyltrimethoxysilane) were selected to modify the SiO2 surface by a reaction between the silane agent and the hydroxyl groups on the silica surface. After modification, the catalysts exhibited the better stability for methanol synthesis in the presence of water. FT-IR, BET, H2-TPR, XRD, TEM, XPS characterization were employed to determine the surface physical properties, reduction properties, crystal structure and particle size of the catalysts before and after the reaction. The results showed that water can simultaneously cause the oxidation and growth of Cu species resulting in the deactivation of Cu-based catalyst. However, the introduction of hydrophobic groups reduced the contact time between water and the active center, which prevented the growth and oxidation of Cu species, thus improving the catalyst stability.