Silicate Electrolyte Research Articles

Fabrication and Characterization of Micro-Arc Oxidation Films on β-Titanium Alloy in Silicate and Silicate/Glycerin Electrolyte

Micro-arc oxidation (MAO) films were fabricated on the Ti-39Nb-6Zr alloy at different voltages in the silicate and silicate/glycerin electrolyte. Their morphology, phase structure and composition were characterized by scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). It was found that the glycerin additive in the silicate electrolyte improved the compactness of the MAO film. The corrosion resistance was evaluated, and the influence of glycerin additive in electrolyte on the growth of micro-arc oxidized film was revealed by optical emission spectra.

Self-Powered Machine-Learning-Assisted Material Identification Enabled by a Thermogalvanic Dual-Network Hydrogel with a High Thermopower.

Wearable devices equipped with high-performance flexible sensors that can identify diverse physical information free from batteries are playing an indispensable role in various fields. However, previous studies on flexible sensors have primarily focused on their elasticity and temperature-sensing capability, with few reports on material identification. In this paper, a thermogalvanic dual-network hydrogel is fabricated with [Fe(CN)6]3-/4- as a redox couple and lithium magnesium silicate, Gdm+ and lithium bromideas key electrolytes to optimize the interconnected porous structure of the gel, which shows excellent mechanical and thermoelectric properties with a thermopower as high as 4.01mV K-1. A self-powered material identification ring is developed based on the temperature-triggered thermoelectric response of the gel in conjunction with machine learning, which can actively infer materials without an external power connection by analyzing the voltage signals correlated with interfacial heat transfer produced upon contact with different materials. The proposed gel ring has important applications for future areas such as human-computer interaction and haptic-associated artificial intelligence.

A Breakthrough in the Application of Simonkolleite in All‐Solid‐State Zn‐Graphite Battery

ABSTRACTTo enhance the electrochemical performance of the Zn solid‐state battery, we introduce simonkolleite as a novel anode material. With oxygen vacancies on its surface, simonkolleite exhibits both electrical and chemical activity; these vacancies serve as n‐type donors, significantly improving the material's conductivity. In this research, simonkolleite is synthesized using a straightforward and cost‐effective method and employed as the anode. The all‐solid‐state Zn battery combines the simonkolleite anode, sodium silicate (SS) electrolyte, and graphite film (GF) cathode. Our battery configuration (simonkolleite/Ingot SS/GF) achieves a high 1280 mAh g−1 capacity and demonstrates improved cyclic stability. The large‐scale module battery can also power a motor‐fan unit for 1 h and 19 min.

Effect of electrolyte pH value on microstructure and corrosion resistance of black MAO coating on 6063 aluminum alloy

Black micro-arc oxidation (MAO) coatings were obtained on the surface of 6063 aluminum alloy by using the MAO technique in silicate electrolyte with colorant NH4VO3. The work aimed to study the effect of adjusting the electrolyte pH (pH10, pH11, pH12, and pH13) on the microstructure, mechanical properties, and corrosion resistance of black MAO coatings on 6063 aluminum alloy. The experimental results showed that the electrolyte pH had an important effect on the macroscopic morphology of the MAO coatings. As the electrolyte pH value increased, the process voltage of the sample decreased, the duration of the anodic oxidation stage and the spark discharge stage were shortened, while the duration of the micro arc oxidation stage was prolonged. Reasonable adjustment of the electrolyte pH could reduce the poriness and defects of the coatings, decrease the surface roughness of the coatings, and improve the quality and wear resistance of the coatings. The corrosion resistance of the black MAO coating obtained in the electrolyte with pH12 was superior and the corrosion current density was only 3.207×10−7 A/cm2. The immersion corrosion test further demonstrated the same results of corrosion resistance.

Growth mechanism of microarc oxide membrane under the distribution law of Si and Zr elements

This study investigated the growth mechanism of microarc oxidation ceramic coatings on AZ91D magnesium alloy by sequentially treating it in silicate and zirconate electrolyte systems. The distribution patterns of Si and Zr elements were examined to understand the growth mechanism. The results showed that the distribution of Si and Zr elements in the SZ ceramic coatings changed with increasing termination voltage of microarc oxidation. The growth mechanism of microarc oxidation ceramic coatings on magnesium alloys involved the reaction between Si and Zr elements from the electrolyte and Mg elements from the substrate to form molten oxides under the high-temperature and high-pressure conditions of microarc oxidation discharge. At lower termination voltages, some of the molten oxides remained near the discharge channels or the film/substrate interface, resulting in inward growth of the ceramic coating. As the termination voltage increased, some of the molten oxides were ejected outward through the discharge channels, facilitating outward growth of the ceramic coating. The inclusion of silicon elements compared to zirconium elements will significantly increase the concentration of oxygen vacancies in the ceramic membrane, enhancing the electrical conductivity of the ceramic membrane while reducing its corrosion resistance.

Study on the Optimization of the Preparation Process of ZM5 Magnesium Alloy Micro-Arc Oxidation Hard Ceramic Coatings and Coatings Properties

Hard ceramic coatings were successfully prepared on the surface of ZM5 magnesium alloy by micro-arc oxidation (MAO) technology in silicate and aluminate electrolytes, respectively. The optimization of hard ceramic coatings prepared in these electrolyte systems was investigated through an orthogonal experimental design. The microstructure, elemental composition, phase composition, and tribological properties of the coatings were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and tribological testing equipment. The results show that the growth of the hard ceramic coatings is significantly influenced by the different electrolyte systems. Coatings prepared from both systems have shown good wear resistance, with the aluminate electrolyte system being superior to the silicate system in performance. The optimized formulation for the silicate electrolyte solution has been determined to be sodium silicate at 8 g/L, sodium dihydrogen phosphate at 0.2 g/L, sodium tetraborate at 2 g/L, and potassium hydroxide at 1 g/L. The optimized formulation for the aluminate electrolyte solution consists of sodium aluminate at 5 g/L, sodium fluoride at 3 g/L, sodium citrate at 3 g/L, and sodium hydroxide at 0.5 g/L.

The growth behavior and performance of microarc oxidation coating on AZ91/Ti composite: Influence of Ti-reinforcement phase and electrolyte

Magnesium matrix composites with both high strength and ductility have been achieved by introducing pure Ti particles. However, the properties of the surfaces of the composites need to be improved by surface technology, such as micro-arc oxidation (MAO). In this study, we investigated the influence of the Ti-reinforcement phase on coating growth and evolution by subjecting both AZ91 alloy and AZ91/Ti composite to MAO treatment using silicate-based and phosphate-based electrolytes. Results revealed that the Ti-reinforcement phase influenced the MAO process, altering discharge behavior, and leading to a decreased cell voltage. The vigorous discharge of the Ti-reinforcement phase induced the formation of coating discharge channels, concurrently dissolving and oxidizing Ti-reinforcement to produce a composite ceramic coating with TiO2. The MAO coating on the AZ91/Ti composite exhibited a dark blue macromorphology and distinctive local micromorphological anomalies. In silicate electrolyte, a “volcano-like” localized morphology centered on the discharge channel emerged. In contrast, treatment in phosphate-based electrolyte resulted in a coating morphology similar to typical porous ceramic coatings, with visible radial discharge micropores at the reinforcement phase location. Compared to the AZ91 alloy, the coating on the AZ91/Ti composite exhibited lower thickness and higher porosity. MAO treatment reduced the self-corrosion current density of the AZ91/Ti surface by two orders of magnitude. The silicate coating demonstrated better corrosion resistance than the phosphate coating, attributed to its lower porosity. The formation mechanism of MAO coatings on AZ91/Ti composites in phosphate-based and silicate-based electrolytes was proposed.

Effects of graphene content in alkaline silicate electrolyte on AA1060 pure aluminum micro‐arc oxidation coating

AbstractCeramic coatings were obtained by micro‐arc oxidation (MAO) on the surface of AA1060 pure aluminum in alkaline silicate electrolyte with the addition of graphene. The effects of graphene contents in the range of 0–.30 g/L in the electrolyte on surface morphology, corrosion resistance, and wear resistance of the ceramic coatings were investigated. The outer surface structure, outer surface element content, coating cross‐section structure, coating cross‐section element content, coating/substrate interface structure, and coating phase were characterized by scanning electron microscope and X‐ray diffraction. Potentiodynamic polarization and electrochemical impedance spectroscopy were used to evaluate the corrosion behavior of MAO samples in a 3.5‐wt% NaCl solution. In addition, the resistance to sliding and abrasive wear of the oxide coating were studied experimentally. The results show that the alkaline silicate electrolyte with the addition of graphene has a significant effect on the characteristics of MAO coating. The performance of micro‐arc oxide coatings is best when the graphene content in the electrolyte is .15 g/L, the average thickness of the film is 7.24 μm, the average pore size is 6.07 μm, the impedance value is approximately 4.01 × 106 Ω, and its friction coefficient is .55.

Study of the wear resistance of composite coatings modified with h-BN particles on AZ31 magnesium alloy

A low wear resistance is a significant disadvantage of magnesium-based alloys widely used in industry. The results of plasma electrolytic oxidation (PEO) carried out in an aqueous-alkaline phosphate electrolyte with the addition of hexagonal boron nitride (h-BN) powder to obtain coatings with greater wear resistance on the surface of AZ31 magnesium alloy are presented. The PEO method is one of the most promising for surface treatment of magnesium alloys, since oxidation is carried out in alkaline aluminate, silicate or phosphate electrolytes with various functional additives. The addition of nanocrystalline hexagonal h-BN powder in the form of a suspension into the electrolyte volume does not affect the electrical parameters of PEO, and h-BN particles are incorporated into the structure of the formed composite coating, increasing the wear resistance. It is shown that the resulting coatings have a relief typical of PEO with developed morphology and porosity, which change depending on the oxidation time. In this case, the incorporation of h-BN particles into the coating occurs by an inert mechanism, since they do not undergo chemical transformations with the formation of new phases. Composite coatings obtained on the surface of the AZ31 magnesium alloy by the PEO method consist of crystalline phases of MgO and Mg3(PO4)2, regardless of the addition of h-BN particles to the electrolyte. The wear resistance of coatings is 6 – 8 times higher compared to the untreated alloy. The results obtained can be used to produce PEO coatings with increased wear resistance and use them in various sectors of the economy.

Improved Corrosion Properties of Mg-Gd-Zn-Zr Alloy by Micro-Arc Oxidation

In order to improve the corrosion resistance of Mg-3Gd-1Zn-0.4Zr (GZ31K) alloys for biomedical application, the alloy was micro-arc oxidation (MAO)-treated using silicate electrolyte system under various voltages (400 V, 425 V, 450 V, 475 V). The effects of voltage on the microstructure and corrosion properties of MAO coating were investigated via X-ray diffraction (XRD) and a scanning electron microscope (SEM) combined with an energy-dispersive spectrometer (EDS), X-ray photoelectron spectroscope (XPS), and electrochemical experiments. The results showed that, with the increase in voltage, the MAO coatings became thicker and the micropores on the MAO coating increased in diameter. The main phase compositions of the MAO coatings were MgO and Mg2SiO4. Potentiodynamic polarization curve results showed that MAO coatings could enhance corrosion resistances, where the corrosion current density decreased by six orders of magnitude and the corrosion potential of the specimens increased by 300 mV for the voltage of 450 V in the MAO treatment; nevertheless, the corrosion resistance rapidly deteriorated due to the creation of large micropores in the MAO coating, which provide a pathway for corrosive media when the voltage is 475 V. The electrochemical impedance spectroscopy results showed that MAO treatments could increase low-frequency modulus resistance and increase the corrosion resistance of Mg alloys. In addition, MAO-treated GZ31K alloys still exhibited uniform corrosion, which is desirable for biomedical applications.

Corrosion behavior of laser powder bed fusion additive manufacturing produced TiNi alloy by micro-arc oxidation

To improve the corrosion resistance of TiNi alloy fabricated by laser powder bed fusion (LPBF), a porous oxidation layer was synthesized by micro-arc oxidation in a sodium aluminate and sodium silicate electrolyte. The influences of the applied voltage and the processing time on the morphology of oxidation layer were investigated, and the corrosion behavior of the oxidation layer in artificial saliva was evaluated and compared with that of the as-fabricated LPBF alloy. The results indicate that, as increasing the applied voltage and the processing time, the oxidation layer becomes uniform and integrated. The optimum parameters are with an applied voltage of 450 V and processing time of 40 min. The oxidation layer primarily contains α-Al2O3 and consists of two layers, i.e., a thin, compact and uniform inner layer and a porous outer layer. The formation of stable α-Al2O3 phase in the coating and its almost non-porous dense structure reduce the channels for corrosion ions to penetrate into the substrate through coating, thereby improving the corrosion resistance of TiNi alloy.

Chlorination for all solid-state zinc-graphite battery: Investigate into the charge-discharge mechanism of zinc electrodes and sodium silicate electrolyte

Zn solid-state batteries offer a novel and environmentally friendly energy storage solution with excellent safety features. This study explores the material characteristics and electrochemical mechanisms of the Zn anode and sodium silicate solid electrolyte powder after HCl chlorination. Results reveal the formation of Zn chloride hydroxide monohydrate (Zn5OH8Cl2⋅H2O, known as Simonkolleite) in the zinc anode post HCl treatment. The compound's layered structure enhances ion transport. The sodium silicate electrolyte exhibits increased surface area after HCl treatment. In engineering applications, a solid-state battery assembled with Simonkolleite anode, electrolyte (HB), and graphite film (GF) cathode demonstrates a high capacity (>5000 mAh/g) in the first discharging cycle and impressive stability over 30–100 cycles, highlighting its promising potential for energy storage.

(Invited) Electrolytes for Next-Generation Sodium Metal Batteries

Developing reliable and cost-effective electrical energy storage systems (EESs) for portable electronics, electric vehicles, and grid storage applications is vital. Na-ion batteries are the most promising alternative technology owing to their natural abundance and low sodium cost.[1] Solid-state batteries (SSBs) have garnered extensive attention for their ability to suppress the safety hazards of organic liquid electrolytes by replacing them with solid electrolytes.[2] Among the various solid electrolytes being explored, our group mainly focuses on NASICON (Sodium superionic conductor) type silicate and solid polymer electrolytes. Sodium silicates are a class of materials with composition, NaxMxSixOx (M = rare-earth metals, x = integer (1-10)).[3] They have the advantage of low sintering temperature (~1050 °C) and 3D framework structure containing MO6 octahedra and SiO4 tetrahedra providing facile ionic movement.[4] Solid polymer electrolytes (SPE) are known for their flexibility and electrode compatibility. Highly conductive, filler-free composite solid polymer electrolyte films were prepared using poly(vinylidene fluoride), poly(vinyl pyrrolidone) (PVP), and NaPF6.[5] PVP binder played an essential role in improving Na ion conductivity and excellent plating−stripping performance. This talk will present an overview of these solid electrolytes for next-generation sodium metal batteries.

Antireflection Property and Corrosion Resistance of Black Ceramic Superhydrophobic Coatings on Aluminum Alloy

In this article, a black ceramic coating is produced on the surface of 7075 aluminum alloy by plasma electrolytic oxidation (PEO) in a silicate electrolyte containing ammonium metavanadate (NH4VO3). The PEO processed sample is further subjected to hydrothermal treatment (HT) and fluorination treatment (FT) to obtain a superhydrophobic PEO/HT/FT coating. The 21‐day air durability test and the tape stripping test show that the superhydrophobic surface shows excellent air durability and mechanical durability. The antireflection test study shows that the average antireflection of the PEO/HT/FT coating is as high as 96.6% in the wavelength range between 400 and 1000 nm. Furthermore, electrochemical test results show that the corrosion current density of the PEO/HT/FT coating decreases to 2.49 × 10−6 A cm−2, three orders of magnitude lower than the aluminum substrate, and the anticorrosion efficiency is as high as 99.87%. The preparation of PEO/HT/FT coating provides more methods for the wide application of Al alloy in aerospace field.

Comparison of plasma electrolytic oxidation coatings on Al alloy produced in diluted and concentrated silicate electrolytes for space thermal control application

In this work, a bright white oxide coating was successfully prepared on 6061 Al alloy by PEO process from an environmentally friendly and low-cost concentrated silicate electrolyte as an alternative for commonly used fluozirconate electrolyte. The characteristics of PEO processes and resulting coatings both in diluted and concentrated silicate electrolytes were investigated by using Optical Emission Spectrometer (OES), Scanning Electron Microscope (SEM), X-ray Energy Dispersive Spectrometer (EDS) and X-ray Diffraction Spectrometer (XRD). The thermal control properties of the coatings were evaluated by UV-VIS-NIR spectrophotometer and infrared emissivity spectrometer, respectively. The corrosion protection performances of the coatings were investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests. Results show that the discharges in diluted silicate electrolyte are more pronounced than those in concentrated silicate electrolyte. The more intensive discharges in diluted silicate electrolyte are related to plasma electrochemical reactions at the material surface or at the metal-oxide interface, facilitating to a relatively dense structure and complex oxides including α-Al2O3, γ-Al2O3 and mullite. The weaker discharges in concentrated silicate are associated with the fast silicate anions deposition process, resulting in the formation of amorphous SiO2 with a porous microstructure and high thickness. The coating prepared in concentrated silicate electrolyte is characterized by a bright white color in appearance and has much lower solar absorptance (αs) of 0.159 and higher emissivity (ε) of 0.90 than the coating prepared in diluted silicate electrolyte with αs of 0.429 and ε of 0.79. However, the coating prepared in concentrated silicate electrolyte has a little inferior corrosion protection performance compared with that prepared in diluted silicate electrolyte due to the more porous microstructure.

Evaluating the energy consumption, structural, and corrosion resistance properties of photocatalytic TiO2-based PEO coatings on pre-anodized AA2024-Al

In this work, a thorough investigation is carried out to develop plasma electrolytic oxidation (PEO) coatings on pre-anodized AA2024-Al at various concentrations of TiO2 dispersed in a water base electrolyte of sodium silicate, sodium phosphate dodecahydrate, and potassium hydroxide in order to determine the effect of TiO2 incorporation on energy consumption, coating growth, surface morphology, photocatalytic behavior, and associated long-term corrosion resistance properties. The pre-anodization time is controlled to develop a 20.0 ± 1.6 µm thick anodic film, where a reduction of ∼66 % in the energy consumption (kW h m2 µm−1) is observed compared to the PEO developed without pre-anodic precursors, while the addition of TiO2 nanoparticles (Degusa-P25) into the base electrolyte results in reductions of ∼68 %, 64 %, and 51 % for the PEO coatings developed at 2, 5 and 10 g/L TiO2-based electrolyte, respectively. TiO2-based PEO process is found to improve growth rate, coating microstructure with lower porosity and defects, and reduce energy consumption (for a coating of a given thickness). The photocatalytic activity of TiO2 was investigated by photodegrading phenol under simulated sunlight conditions, where the higher concentration of TiO2 nanoparticles affected the phenol photodegradation efficiency, whereas the effectiveness of TiO2 concentration on the corrosion resistance properties of PEO coatings was observed with nearly one-order higher impedance magnitude (after 336 h) than the PEO layer without TiO2.

Enhancing Dry Sliding Wear Resistance of Pure Mg by Plasma Electrolytic Oxidation Ceramic Coatings Using Silver Addition

This study investigated the wear effect on ceramic coated Mg by Plasma Electrolytic Oxidation. Three series of PEO coatings were prepared; one of was the effect of silicate electrolyte (5, 8, and 10 g/L) concentrations and the other was the effect of coating time (5, 10, 15 min), last one was the effect of AgNO3 (0.1, 0.2, 0.4 g/l) additive. The coatings were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray diffraction (XRD). The mechanical properties were analyzed by microhardness and linear wear test. The unlubricated wear resistance was observed by linear ball-on-disc tribometer. With increasing the silicate concentration, the average pore size and porosity percentage and the surface roughness increase. On the other hand, with increasing the coating time, the surface morphology gradually becomes flat. The coating time caused more compact and homogenous appearance. The surfaces coated with the addition of silver were obtained smoother and denser. The wear resistance of the high time coated Mg was significantly improved. The best wear resistance was obtained with silver-reinforced coatings.

Effect of TiO2 nanoparticles on the corrosion resistance, wear, and antibacterial properties of microarc oxidation coatings applied on AZ31 magnesium alloy

Microarc oxidation (MAO) is a surface modification process that is often adopted to produce a hard oxide layer on magnesium alloys to improve their corrosion resistance and wear resistance. However, under continual corrosion, the characteristic porous microstructure of MAO coatings provides diffusion paths that allow corrosive species to penetrate the coatings and react with the substrate underneath. Therefore, the present study investigated the modification of the microstructure of MAO coatings when adding TiO2 nanoparticles to a fluoride-containing silicate electrolyte system under the bipolar current mode. The results indicate that as the concentration of TiO2 nanoparticles increased, the quantity of rutile (TiO2) incorporated in the MAO coating increased, which led to the coating exhibiting an elevated hardness and a color change from white to gray-black. When the TiO2 concentration in the electrolyte was increased from 2.5 to 7.5 g/L, the total impedance of the MAO coating in electrochemical impedance spectroscopy analysis increased from 107 to >600 kΩcm2, which indicates that the corrosion resistance of the coating increased with the number of defects on it decreased. The addition of TiO2 enhances the photocatalytic properties of MAO coatings. However, excessive addition of TiO2 can lead to an adverse effect on the wear resistance of MAO coatings.

Preparation and corrosion resistance characterization of MAO coating on AZ31B magnesium alloy formed in the mixed silicate and phosphate electrolytes with pectin as an additive

AZ31B magnesium alloy as a medical implant material is hampered in its application due to its excessive corrosion rate in the human environment. This work used pectin as an electrolyte additive to prepare micro-arc oxidation (MAO) coatings on the surface of magnesium alloys. The surface and cross-section morphology, chemical composition of the coatings were examined using scanning electron microscopy, energy dispersive spectroscopy and X-ray diffractometry. The effect of pectin concentrations on the corrosion resistance of the coatings under simulated body fluid media was evaluated by electrochemical tests. The results showed that the addition of pectin could fill the pores (resulting in a reduction in porosity by 2.3 %) and micro-cracks within the coatings, increasing the corrosion resistance with the increase in pectin concentration. Notably, the MAO-0.75 coating exhibited densest coating structure and then best corrosion resistance with the corrosion current density as low as 1.259 × 10−6 A/cm2, which was four order of magnitudes lower compared to the substrate. The experimental results showed that the use of pectin as an additive prolongs the service life of magnesium alloy MAO coatings in simulated body fluids, thus giving them great potential as medical implant materials.

Study of wear and corrosion resistance of ATO nanoparticle–doped micro‐arc oxide film layers

AbstractIn order to enhance the corrosion and wear resistance of aluminum alloys in complex and variable environments, an Al2O3 ceramic film was prepared on the surface of 7A04 aluminum alloy in a silicate electrolyte system using a micro‐arc oxidation technique. Subsequently, antimony tin oxide (ATO) nanoparticles were used to dope the micro‐arc oxidation film to enhance the protective properties of the 7A04 aluminum alloy. The structural characteristics of the film were investigated by examining the surface and cross‐sectional morphology and the composition of the physical phases. The results show that ATO nanoparticles can promote the micro‐arc oxidation reaction, improve the surface morphology of the film layer, increase the thickness of the film layer and the denseness after sintering, and enter the film layer in the form of melt wrapping, which plays a role in refining the grain. In the study of the wear resistance and corrosion resistance of ATO‐doped ceramic film layers, it was found that the introduction of ATO nanoparticles did not significantly improve the wear resistance of the micro‐arc oxide ceramic film layers but significantly improved the corrosion resistance of the film layers.