Silicate Coatings Research Articles

Preparation of ester-modified nano-SiO2/silicate coatings and its application in the impermeability of concrete

Surface treatment protective technology is a cost-effective approach to prevent harmful ions from infiltrating concrete, avoiding the deterioration of performance and increasing longevity. Here, a novel coupling agent with ester group (MA-KH-550) is synthesized from γ-aminopropyltriethoxysilane (KH-550) and methyl acrylate (MA) to modify nano-SiO2 particles. Subsequently, the ester-modified nano-SiO2 can be successfully dispersed in alkaline composite silicate solutions to fabricate nano-SiO2/silicate coatings, improving the impermeability of concrete. The incorporation of nano-SiO2 particles can fill microscopic pores in cementitious materials, which improves the compactness of the concrete. Furthermore, nano-SiO2 particles can also accelerate secondary hydration of cement and synergistically generate more calcium silicate hydrate gel with silicates to further boost the compactness of the concrete. High-compactness coatings reduce the penetration of the medium, thereby enhancing the impermeability performance of the concrete. When the nano-SiO2 particle content is 1.0 wt%, the optimal performance of concrete is achieved. Compared with the original C30 concrete, the C30 concrete treated with the nano-SiO2/composite silicate (nano-SiO2/CSC) shows a 31.1 % decrease in chloride ion resistance, a 35.5 % reduction in carbonization resistance, a loss rate of 1.08 % for anti-freezing quality. This work charts a new course for designing and developing high-performance composite silicate coatings for concrete.

Enhanced osseointegration and antimicrobial properties of 3D-Printed porous titanium alloys with copper-strontium doped calcium silicate coatings.

The 3D printing of porous titanium scaffolds reduces the elastic modulus of titanium alloys and promotes osteogenic integration. However, due to the biological inertness of titanium alloy materials, the implant-bone tissue interface is weakly bonded. A calcium silicate (CS) coating doped with polymetallic ions can impart various biological properties to titanium alloy materials. In this study, CuO and SrO binary-doped CS coatings were prepared on the surface of 3D-printed porous titanium alloy scaffolds using atmospheric plasma spraying and characterized by SEM, EDS, and XRD. Both CuO and SrO were successfully incorporated into the CS coating. The in vivo osseointegration evaluation of the composite coating-modified 3D-printed porous titanium alloy scaffolds was conducted using a rabbit bone defect model, showing that the in vivo osseointegration of 2% CuO-10% SrO-CS-modified 3D-printed porous titanium alloy was improved. The in vitro antimicrobial properties of the 2% CuO-10% SrO-CS-modified 3D-printed porous titanium alloy were evaluated through bacterial platform coating, co-culture liquid absorbance detection, and crystal violet staining experiments, demonstrating that the composite coating exhibited good antimicrobial properties. In conclusion, the composite scaffold possesses both osteointegration-promoting and antimicrobial properties, indicating a broad potential for clinical applications.

Protection behavior of Ti-SiO2 modified potassium silicate coating on K447a alloy at 1000 °C

Potassium silicate coatings cured by calcium hydrogen phosphate and modified by fillers of Ti and SiO2 powders were prepared on K447A alloy at 120 °C. The influences of Ti, SiO2 and both powders on the oxidation behavior of the coated specimens were investigated at 1000 °C for 100 h in static air by thermogravimetry, SEM, XRD and EPMA. The bare K447A alloy suffered severe oxidation at 1000 °C, and the TGO was found to be composited of an outer layer of mixtures of NiCr2O4, CoAl2O4 and rutile TiO2, and an inner α-Al2O3 layer. The potassium silicate coating without filler showed local damages where formation and rapid rupture of bubbles occurred and consequently the local substrate was oxidized. The SiO2 powder in the coatings is more capable of reducing O diffusion thru the coatings than the Ti powder, while the latter is more effective in getting rid of bubble rupture than the former. Thus, the coating modified by 10 wt% Ti and 20 wt% SiO2 showed the best protective performance.

Temperature-responsive self-healing coating with excellent resistances to oxidation and thermal shock from core-shell B2O3@SiO2 microcapsule

Hierarchical design was applied to core-shell B2O3@SiO2 microcapsule, followed by fabrication of the SiC–B2O3@SiO2 coating by a combination of entrapping and hot dip processes. Among the C/C-SiC-BS2, C/C-SiC-BS4 and C/C-SiC-BS6 samples, the C/C-SiC-BS4 composite exhibits long-term antioxidant capabilities, with only a 2.30 % mass loss as oxidized at 973 K for 1500 h, and 2.35 % at 1073 K for 2600 h. Furthermore, after enduring 150 thermal shocks between 293 K and 1173 K, its mass loss is only 2.07 %. The XRD patterns detected the existence of B2O3 and SiO2 phases, and the SEM and EDS analysis proved the borosilicate glass, indicating the excellent performances came from the synergistic self-healing effects of the B2O3, SiO2 phases, and borosilicate glass. Thus, within the temperature ranges from 873 K to 1273 K, the oxygen penetration shifts from osmotic state to defect diffusion in coating. This research emphasizes the significance of hierarchical designs for core-shell sacrificial phase in silicate coatings, thereby enhancing their long-term applicability.

Corrosion behavior of low melting glass modified potassium silicate coating under the synergy of solid NaCl deposit and water vapor at 700 °C

The effects of LMG (SiO2–BaO–Al2O3–TiO2–Na2O–K2O–ZnO) modification on the performance of potassium silicate coatings on Ti–6Al–4V alloy during tests of either H2O/O2- or NaCl/H2O/O2- corrosion were investigated at 700 °C for 500 h using thermogravimetric, SEM, EPMA, and XRD. Adding 10-30 wt% LMG particles into the potassium silicate solution did not impair the intact and the surface roughness of the coatings and improved the resistance of the coatings against humid oxygen corrosion and NaCl/H2O/O2-induced corrosion. For the humid oxygen corrosion, the improvement was enhanced when the amounts of LMG was increased. However, the LMG10 coating with 30 vol% LMG had the most excellent corrosion resistance, the formation of titanate was prohibited; the coatings with more LMG additions were less protective than LMG10 though better than the coating without LMG.

Enhancement of interfacial corrosion resistance between aluminum powder–modified zinc silicate–potassium silicate coating and steel bars for sand-based autoclaved aerated concrete

Organic coatings cannot provide long-term corrosion protection to steel bars in sand-based autoclaved aerated concrete because they are prepared at high temperatures and pressures. Herein, potassium silicate, zinc silicate, and aluminum powder were used as the raw materials to prepare inorganic aluminum powder–modified zinc silicate–potassium silicate coatings with anticorrosive properties. The physical, mechanical, microscopic, and anticorrosion properties of the prepared inorganic coatings were investigated using X-ray diffraction, Fourier-transform infrared spectroscopy, Raman spectroscopy, thermogravimetry–differential scanning calorimetry, scanning electron microscopy, electrochemical impedance spectroscopy, and potentiodynamic polarization. The results showed that aluminum powder increased the density of the zinc silicate–potassium silicate coatings and significantly improved the corrosion resistance and mechanical properties of the coatings. The prepared coatings exhibited stable qualities with no heat absorption and release before 317°C. The adhesive strength and impact resistance of the coatings were as high as 1.65 MPa and 50 kg·cm, respectively. The electrochemical test results showed that the coating resistance (Rc), charge-transfer resistance (Rct), and polarization resistance (Rp) of the 5.5–50Zn2SiO4–40Al coating were 7835, 135,915, and 89,568 Ω·cm2, respectively, which exhibited the optimal corrosion resistance.

Phase and properties evolution of plasma sprayed rare earth silicate coatings

Rare-earth silicates have been pursued for many years as candidates for Environmental Barrier Coatings for the protection of silicon carbide (SiC) based components in the new generation of aero and power production turbine engines. The properties and behavior of these materials are usually reported based on theoretical studies or measurements done on bulk specimens, but their prospective use is in the form of coatings. One of the most extended ways of depositing these coatings is plasma spray which produces partially or totally amorphous deposit and changes towards SiO2 lean chemical composition. In this work is comparatively discussed the effect of plasma spray deposition on Yb2Si2O7, Y2Si2O7 and the mixed cation silicate (Y0.5Yb0.5)2Si2O7 coatings. The phase evolution with temperature and its impact on the coefficient of thermal expansion, microstructure and thermal conductivity are described. The stability of crystalline phases, properties and absence of cracks in its microstructure makes (Y0.5Yb0.5)2Si2O7 a more optimum candidate among the studied rare-earth silicates for environmental barrier applications.

Differences among SiO2, TiO2, and Ti in the anti-foaming mechanism of chemically bonded silicate coatings

Potassium silicate coating foams seriously at high temperature. SiO2, TiO2 and Ti particles were added to solve this problem. Micro-morphologies, phase composition, mass change kinetics were analyzed, porosity and volatilizable water contents (κ0) of coatings were calculated to reveal the effects of adding SiO2, TiO2, and Ti particles on the foaming behavior of potassium silicate coatings at 500 °C. The higher the κ0, the more severe the foaming becomes. Results shows that addition of fillers improved the anti-foaming resistance due to volume occupier effect. Among them, SiO2 particles did not alter κ0 of the as-prepared coatings due to similar tetrahedral structure with silica, addition of TiO2 particles increased κ0 because titania can form more -Ti-OH groups than silica, Ti particles decrease κ0 because dissolved Ti4+ ions can decrease the number of the pending -Si-OH bonds. Combined with the volume expansion occurred due to the oxidation of Ti particles during heat treatment, potassium silicate coating modified by 30 wt% Ti exhibited the best anti-foaming performance with the lowest porosity, at 1.8%.

Influence of chemistry and surface roughness of various thermal barrier coatings on the wettability of molten sand

High temperature wettability experiments were carried out to investigate how chemistry and surface roughness affect wetting characteristics of molten sand several promising thermal/environmental barrier coatings. Contact angle experiments were performed on varying as-sprayed and polished yttria-stabilized zirconia (YSZ), rare-earth oxide-YSZ (REO-YSZ), and rare-earth silicate coatings subjected to molten synthetic sand at 1260 °C. The results showed that the spreading rate of molten sand was higher on silicate-based environmental barrier coatings (~60°/min) than on Zr-based thermal barrier coatings (~25°/min). Increased surface roughness had opposite effects on the wettability depending on the reactivity of the coatings. Wettability decreased on coatings such as YSZ (which did not react with sand) but increased for REO-YSZ coatings (which formed reaction products with sand). It was found that while the REO-YSZ coatings were able to promote formation of the apatite that performed as a sealing layer to reduce further infiltration, molten sand wetting increased. YSZ was found to have greater wetting resistance in the roughened state while the REO-YSZ coatings had greater wetting resistance in the polished state. Surface energy, microstructure, and molten sand penetration also play a key role in the wetting kinetics and are discussed. This work reveals the dependency of chemistry and surface roughness on influencing the “sandphobicity” (analogous to hydrophobicity) of a material and provides insights for optimizing these variables to realize more “sandphobic” coatings.

The Effects of Various Silicate Coatings on the Durability of Concrete: Mechanisms and Implications

Silicate solutions can improve the durability of concrete conveniently and effectively. To horizontally compare the enhancement effects of different composite silicate solutions, three types of silicate surface treatment agents were prepared by using sodium silicate, potassium silicate, and lithium silicate as the main agents, along with urea, sodium polyacrylate, catalysts, and fluoro-carbon surfactants as the adjuvants. Furthermore, their effects on the durability of concrete were compared. The results showed that silicate surface treatment could reduce the content of Ca(OH)2, increase the content of hydrated calcium silicate (C-S-H), and improve the compactness and hydrophobicity of the hardened cement surface. Although the three surface treatments enhanced the durability of concrete, the effects differed based on the complexities and mixtures. The sodium silicate compounded with potassium silicate performed the best of all three, wherein the content of the C-S-H gel increased by 389.8%, the permeability decreased by 60.6%, the water contact angle improved to 83.5° and the chloride ion resistance and freeze–thaw resistance of concrete increased by 36.7% and 37.34%, respectively, compared with the control sample.

Corrosion behavior of Ti powder enhanced potassium silicate coating with solid NaCl deposit in wet oxygen at 500 °C

The potassium silicate coatings modified with various contents of Ti powders were prepared on the surfaces of Ti-6Al-4V alloy. The corrosion tests of NaCl coated specimens were conducted in wet oxygen at 500 °C for 50 h. The corrosion depth of the bare Ti-6Al-4V alloy was deeper than 60 μm while the mass gain reached to about 1.9 mg/cm2. All the coatings exhibited excellent protection against corrosion as corrosion products have been hardly detected. The main roles of the Ti powders in the coatings are believed to be prohibiting formation of micro-pores and oxygen permeation through the coatings.

One-step Preparation of Silicate Coatings on AZ91D Magnesium Alloy Surface for Boosting its Corrosion Resistance

One-step Preparation of Silicate Coatings on AZ91D Magnesium Alloy Surface for Boosting its Corrosion Resistance

INFLUENCE OF THERMAL STRESS ON THE FORMATION OF CRACKS IN THE SILICATE COATING OF THE HEAT EXCHANGE TUBE

The effect of temperature stress on the silicate coating of heating tubes has been considered. Deformation caused by temperature changes in silicate coating in heating tubes causes micro-macro cracks to appear on the surface of the coating. Taking these into account, the characteristics of temperature stress changes were studied. With this, a mathematical expression was obtained by the mathematical modeling of temperature stress. The theoretical and graphical dependencies of the distribution of temperature energy inside the tube? The coating in the external and internal systems is presented separately, and a wide explanation and analysis is given at the same time of expression with its analysis, it was interpreted on the basis of the works processed in the Matlab program. Currently, the results obtained as a result of the application of silica-coated pipes in various areas of SOCAR are being continued. The application of silica-coated pipes in various areas of SOCAR continues to give positive results. Based on the main data and results of the conducted research, a report on the efficiency of the operating condition was made, efficiency is increased by 2.0-2.5 times, and reliability and longevity are fully ensured. Keywords: silicate coatings, thermal conductivity, corrosion, temperature, resistance, durability.

Preparation and ablation resistance of carbon fiber with yttrium silicate coating

AbstractIn order to solve the shortcoming of fiber oxidation in a high‐temperature environment and improve the antiablative performance, yttrium silicate is coated on the carbon fibers’ surface by the sol‐gel process. In the present work, investigations of the ablation resistance of carbon fiber composites with yttrium silicate coatings (YS‐CFs) prepared by different sol contents and sintering temperatures are reported. The results show that YS‐CFs exhibit excellent ablation resistance in the oxyacetylene test with a heat flow of 1.5 MW/m2. The surface coating of carbon fiber is composed of a mixture of cristobalite, yttrium monosilicate, and yttrium disilicate. The best ceramic coating could be obtained by dipping 20% silica sol and 14% yttrium sol in turn and sintering at 1300°C. In this case, the linear and mass ablation rates reach the minimum values of .667 μm/s and 2.975 mg/s, respectively. YS‐CFs could be used as reinforcements for thermal protection materials in high‐temperature environments.

Ultrahigh impedance of potassium silicate coatings hardened by calcium hydrogen phosphate

The potassium silicate coatings cured by calcium hydrogen phosphate (CHP) at 25, 120 and 200 °C were investigated using electrochemical impedance spectroscopy, scanning electron microscope, X-ray diffraction, Raman spectra and Silicon-29 nuclear magnetic resonance spectra. The potassium silicate coating cured by 10 wt% CHP at 120 °C exhibited ultrahigh low-frequency impedance, represented by Z0.01, ∼61 GΩ cm2, which is 3 orders of magnitude higher than that of the reference coating which was cured by 15 wt% AlPO4 at 120 °C. It is revealed that the impedance is strongly dependent on the amounts of micron-sized defects rather than the polymerization degree. The lower density the defects, including those formed during testing, the higher the impedance. The formation of defects which has a significant impact on the adhesion and anti-corrosion properties of the coating is mainly correlated to the curing kinetics.

Mg-incorporated micro/nano-topographical calcium silicate coatings with enhanced osteogenic properties and reduced inflammatory reactions

Orthopedic implant coatings with optimized surface topography and chemistry can achieve favorable osteogenesis and inflammatory responses. In this work, to take advantage of micro/nano-topography and nutrient element Mg, atmosphere plasma spray and hydrothermal treatment were employed to fabricate two kinds of Mg-incorporated micro/nano-topographical calcium silicate coatings with 0.9 and 15.7 wt% Mg content (Mg1-CS and Mg2-CS). MgSiO3 microspheres composed of nano-flakes were formed on the CS coating surface. We investigated the effects of surface topography and released Mg ion on the protein adsorption and the behaviors of bone mesenchymal stem cells (BMSCs) and RAW264.7 macrophages. Compared with the CS coating, the Mg2-CS coating had 1.8-fold increase in specific surface area, which favored serum protein adsorption and BMSC adhesion. With higher Mg2+ release, the Mg1-CS coating exerted greater effect on enhancing fibronectin adsorption, integrin activation, and osteogenic behaviors of BMSCs. The gene expression profiles showed that the Mg-incorporated CS coatings could modulate macrophage polarization towards M2 phenotype with Mg2-CS showing greater effect. These results showed that the nanostructured Mg-containing surface can promote osteogenic responses and mitigate inflammatory reactions.

Regulation on electrochemical performance of LiNi0.5Mn1.5O4 cathode material via lithium silicate coating with different Li/Si ratio

Surface coating is regarded as an effective means to alleviate the rapid capacity fading of LiNi0.5Mn1.5O4 material. Lithium silicate, as an ideal coating material, combines the advantages of high ionic conductivity, chemical inertness, and HF capture. Considering the influence of Li/Si ratios on Li+ ions diffusion in lithium silicate, the effects of different Li/Si lithium silicate coatings on the structural and electrochemical performance of LiNi0.5Mn1.5O4 material are investigated. The results show that lithium silicate coatings increase the cation disordering degree, improve the crystallinity, stabilize the electrode/electrolyte interface, and improve Li+ diffusion kinetics. Li/Si ratio greatly affects the composition of lithium silicate coating, which changes from Li2Si2O5 + Li2SiO3 (1:1), Li2Si2O5 + Li4SiO4 (2:1, 3:1) to pure Li4SiO4 phase (4:1). First principles calculation manifests that Li+ migration energy barriers decrease with the increase of Li/Si ratio in lithium silicate. At Li/Si = 4:1, the coated sample shows the best electrochemical performance, with specific discharge capacity of 126.7 mAh g−1 at 10 C rate and capacity retention rate of 91.25% after 200 cycles at 1 C rate. The composition of lithium silicate coating can be controlled by changing Li/Si ratio, which in turn regulates the electrochemical performance of LiNi0.5Mn1.5O4 material.

Molecular Dynamics Simulation of Interface Properties between Water-Based Inorganic Zinc Silicate Coating Modified by Organosilicone and Iron Substrate

The interface properties of Fe(101)/zinc silicate modified by organo-siloxane (KH-570) was studied by using the method of molecular dynamics simulation. By calculating the temperature and energy fluctuation of equilibrium state, equilibrium concentration distribution, MSD of layer and different groups, and interaction energy of two interface models, the influencing mechanism on the interface properties of adding organosiloxane into coating system was studied at the atomic scale. It shows that the temperature and energy of interface oscillated in a small range and it was exited in a state of dynamic equilibrium within the initial simulation stage (t < 20 ps). It can be seen from the multiple peak states of concentration distribution that the iron substrate, organo-siloxane and zinc silicate are distributed in the form of a concentration gradient in the real environment. The rapid diffusion of free zinc powder in zinc silicate coating was the essential reason that affected the comprehensive properties of coating. The interface thickness decreased from 7.45 to 6.82 Å, the MSD of free zinc powder was effectively reduced, and the interfacial energy was increased from 104.667 to 347.158 kcal/mol after being modified by organo-siloxane.

SILICATE COATINGS FILLED WITH ZINC POWDER AND GRAPHENE NANOPLATES FOR STEEL CORROSION PROTECTION

The method is proposed to protect the carbon steel from corrosion by silicate coatings filled with powdered zinc and graphene nanoplates obtained by thermal splitting of graphite. The conditions for steel pre-treatment in an alkaline solution containing citrate ions and a nonionic surfactant, for the production of potassium liquid glass composition with the addition of zinc and graphene powders are selected. It is shown that coatings 70–80 µm thick, cured at room temperature for three days and containing 80–90 wt. % zinc, 7– 12 wt. % silicon dioxide and 0.2 wt. % carbon have the highest adhesion, water resistance and protective ability. The study of steel corrosion in 3.5% NaCl solution using methods of voltammetry and the dependence of open circuit potential on the test duration showed that silicate coatings filled with zinc and graphene provide cathodic polarization of steel and protect it from corrosion better than twice as thick coatings obtained by hot galvanizing. Graphene nanoplates enhance the contact of zinc particles with each other and with steel, promoting its cathodic polarization. Using scanning electron microscopy and X-ray spectral microanalysis, it has been shown that zinc corrosion products fill the pores of the near-surface layer of coatings, enhancing their protective ability.

Water Vapor Effects on the Oxidation Resistance of Potassium Silicate Coating at 630 ºC

Water Vapor Effects on the Oxidation Resistance of Potassium Silicate Coating at 630 ºC