Electrophoretic Deposition of Chitosan/h-BN and Chitosan/h-BN/TiO₂ Composite Coatings on Stainless Steel (316L) Substrates

2D materials for Tribo-corrosion and -oxidation protection: A review

The recent rise of 2D materials has extended the opportunities of tuning a variety of properties. Tribo-corrosion, the complex synergy between mechanical wear and chemical corrosion, poses significant challenges across numerous industries where materials are subjected to both tribological stressing and corrosive environments. This intricate interplay often leads to accelerated material degradation and failure. This review critically assesses the current state of utilizing 2D nanomaterials to enhance tribo-corrosion and -oxidation behavior. The paper summarizes the fundamental knowledge about tribo-corrosion and -oxidation mechanisms before assessing the key contributions of 2D materials, including graphene, transition metal chalcogenides, hexagonal boron nitride, MXenes, and black phosphorous, regarding the resulting friction and wear behavior. The protective roles of these nanomaterials against corrosion and oxidation are investigated, highlighting their potential in mitigating material degradation. Furthermore, we delve into the nuanced interplay between mechanical and corrosive factors in the specific application of 2D materials for tribo-corrosion and -oxidation protection. The synthesis of key findings underscores the advancements achieved through integrating 2D nanomaterials. An outlook for future research directions is provided, identifying unexplored avenues, and proposing strategies to propel the field forward. This analysis aims at guiding future investigations and developments at the dynamic intersection of 2D nanomaterials, tribo-corrosion, and -oxidation protection.

Transparent chitosan/hexagonal boron nitride nanosheets composite films with enhanced UV shielding and gas barrier properties

It is of great significance to develop natural renewable polymer materials for different applications. Herein, the nano-sized hexagonal boron nitride nanosheets (hBNNSs) were facilely exfoliated through liquid-nitrogen, microwave, and ultrasonication treatments, and novel chitosan/hBNNSs (CS/hBNNSs) films were fabricated via solution casting. The obtained transparent CS/hBNNSs films demonstrated outstanding UV shielding ability with 98.51 % UV-A and 96.40 % UV-B lights being resisted. Compared to those properties of CS film, the oxygen permeability (OP) and carbon dioxide permeability (CO2P) of CS/hBNNSs films are significantly lowered by 96.35 % and 94.06 %, respectively, which are much better than CS/graphene oxide or other CS nanocomposite films. Moreover, the addition of hBNNSs in CS films also obviously improves their water vapor barrier ability, thermostability, mechanical properties, and antibacterial activity. The CS/hBNNSs films and the strategy developed in this work prove their great prospect in producing high-performance packaging films with desirable excellent UV shielding and oxygen barrier qualities.

Boron-incorporated biocomposite coatings on 316L and NiTi alloys: Enhanced structural, antibacterial activity, and cell viability performances

Boron doped (5 %, 10%, and 15 wt.%) Hydroxyapatite (B-HA) biocomposites were syntesized and coated on 316L SS and NiTi (Ni-45Ti) metallic substrates by using the electrophoretic deposition process (EPD). The morphological and structural characterization of the coatings was executed using scanning electron microscopy (SEM) and X-ray diffraction devices (XRD). Antibacterial tests were conducted using Escherichia coli ( E. coli, JM103) and Staphylococcus aureus ( S. aureus, ATCC29293) microorganisms. The mitochondrial activity assay (MTT)-[3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] was used to examine cell viability and cytotoxicity in Saos-2 osteoblast cells. HA and boron peaks, as well as B-TCP and metallic components, were detected in XRD examinations. Porous morphologies were generated on the surface with boron doped B-HA coatings, as revealed by SEM views. Antibacterial activity studies revealed that both metallic coating groups, notably with boron doping, demonstrated antibacterial activity against gram-negative E. coli and gram-positive S. aureus. The antibacterial activity of the 316L group was shown to be better than that of the NiTi group in comparisonal testing. The syntesized boron-doped biocomposite coatings did not have any detrimental effects on living cells, according to cell viability studies. The cell viability rate was found to be greater in NiTi coatings than in 316 SS coatings, and the impact was amplified by the addition of boron.

Bioactive Chitosan-Based Organometallic Scaffolds for Tissue Engineering and Regeneration

Captivating achievements in developing advanced hybrid biostructures through integrating natural biopolymers with inorganic materials (e.g., metals and metalloids) have paved the way towards the application of bioactive organometallic scaffolds (OMSs) in tissue engineering and regenerative medicine (TERM). Of various biopolymers, chitosan (CS) has been used widely for the development of bioactive OMSs, in large part due to its unique characteristics (e.g., biocompatibility, biodegradability, surface chemistry, and functionalization potential). In integration with inorganic elements, CS has been used to engineer advanced biomimetic matrices to accommodate both embedded cells and drug molecules and serve as scaffolds in TERM. The use of the CS-based OMSs is envisioned to provide a new pragmatic potential in TERM and even in precision medicine. In this review, we aim to elaborate on recent achievements in a variety of CS/metal, CS/metalloid hybrid scaffolds, and discuss their applications in TERM. We also provide comprehensive insights into the formulation, surface modification, characterization, biocompatibility, and cytotoxicity of different types of CS-based OMSs.

Novel Strategy for Gallium-Substituted Hydroxyapatite/Pergularia daemia Fiber Extract/Poly(N-vinylcarbazole) Biocomposite Coating on Titanium for Biomedical Applications

The current work mainly focuses on the innovative nature of nano-gallium-substituted hydroxyapatite (nGa-HAp)/Pergularia daemia fiber extract (PDFE)/poly(N-vinylcarbazole) (PVK) biocomposite coating on titanium (Ti) metal in an eco-friendly and low-cost way through electrophoretic deposition for metallic implant applications. Detailed analysis of this nGa-HAp/PDFE/PVK biocomposite coating revealed many encouraging functional properties like structure and uniformity of the coating. Furthermore, gallium and fruit extract of PDFE-incorporated biocomposite enhance the in vitro antimicrobial, cell viability, and bioactivity studies. In addition, the mechanical and anticorrosion tests of the biocomposite material proved improved adhesion, hardness, and corrosion resistance properties, which were found to be attributed to the presence of PDFE and PVK. Also, the swelling and degradation behaviors of the as-developed material were evaluated in simulated body fluids (SBF) solution. The results revealed that the as-developed composite exhibited superior swelling and lower degradation properties, which evidences the stability of composite in the SBF solution. Overall, the results of the present study indicate that these nGa-HAp/PDFE/PVK biocomposite materials with improved mechanical, corrosion resistance, antibacterial, cell viability, and bioactivity properties appear as promising materials for biomedical applications.

Electrophoretic deposition of collagen/chitosan films with copper-doped phosphate glasses for orthopaedic implants

Coatings with bioactive properties play a key role in the success of orthopaedic implants. Recent studies focused on composite coatings incorporating biocompatible elements that can increase the nucleation of hydroxyapatite (HA), the mineral component of bone, and have promising bioactive and biodegradable properties. Here we report a method of fabricating composite collagen, chitosan and copper-doped phosphate glass (PG) coatings for biomedical applications using electrophoretic deposition (EPD). The use of collagen and chitosan (CTS) allows for the co-deposition of PG particles at standard ambient temperature and pressure (1 kPa, 25 °C), and the addition of collagen led to the steric stabilization of PG in solution. The coating composition was varied by altering the collagen/CTS concentrations in the solutions, as well as depositing PG with 0, 5 and 10 mol% CuO dopant. A monolayer of collagen/CTS containing PG was obtained on stainless steel cathodes, showing that deposition of PG in conjunction with a polymer is feasible. The mass of the monolayer varied depending on the polymer (collagen, CTS and collagen/CTS) and combination of polymer + PG (collagen-PG, CTS-PG and collagen/CTS-PG), while the presence of copper led to agglomerates during deposition at higher concentrations. The deposition yield was studied at different time points and showed a profile typical of constant voltage deposition. Increasing the concentration of collagen in the PG solution allows for a higher deposition yield, while pure collagen solutions resulted in hydrogen gas evolution at the cathode. The ability to deposit polymer-PG coatings that can mimic native bone tissue allows for the potential to fabricate orthopaedic implants with tailored biological properties with lower risk of rejection from the host and exhibit increased bioactivity.

Mechanical Behavior of Bi-Layer and Dispersion Coatings Composed of Several Nanostructures on Ti13Nb13Zr Alloy

Titanium implants are commonly used because of several advantages, but their surface modification is necessary to enhance bioactivity. Recently, their surface coatings were developed to induce local antibacterial properties. The aim of this research was to investigate and compare mechanical properties of three coatings: multi-wall carbon nanotubes (MWCNTs), bi-layer composed of an inner MWCNTs layer and an outer TiO₂ layer, and dispersion coatings comprised of simultaneously deposited MWCNTs and nanoCu, each electrophoretically deposited on the Ti13Nb13Zr alloy. Optical microscopy, scanning electron microscopy, X-ray electron diffraction spectroscopy, and nanoindentation technique were applied to study topography, chemical composition, hardness, plastic and elastic properties. The results demonstrate that the addition of nanocopper or titanium dioxide to MWCNTs coating increases hardness, lowers Young’s modulus, improves plastic and elastic properties, wear resistance under deflection, and plastic deformation resistance. The results can be attributed to different properties, structure and geometry of applied particles, various deposition techniques, and the possible appearance of porous structures. These innovative coatings of simultaneously high strength and elasticity are promising to apply for deposition on long-term titanium implants.

Double-side microcantilevers as a key to understand the adsorption mechanisms and kinetics of chemical warfare agents on vertically-aligned TiO2 nanotubes

Microgravimetric sensor platforms with physico- or chemo-selective interfaces offer promising sensing properties. They are widely used to detect chemical warfare agents (CWAs). However, a comprehensive insight into adsorption mechanisms and interactions between low concentrations of these adsorbates and low-mass adsorbents is still lacking. In this study, we report a complete and detailed analytical method to model the adsorption processes of low traces of vapor-phase DiMethyl MethylPhosphonate (DMMP), a conventional simulant of CWAs, on a double-side nanostructured microcantilever coated with vertically-aligned titanium dioxide nanotubes (TiO₂-NTs). We find that the geometrical configuration of NTs plays an important role in the diffusion regimes of molecules during the adsorption. This study shines light on the adsorption and kinetic mechanisms of low-traces DMMP offering opportunities to have a better insight of the adsorption of CWAs on complex nanostructures and to improve microcantilever sensors.

Electrophoretic deposition and characterization of chitosan-molybdenum composite coatings

In this paper, the effect of the electric field on the properties of a new chitosan-molybdenum (Chit-Mo) composite coating obtained by electrophoretic deposition (EPD) was investigated. The composite coatings obtained showed different morphologies depending on the conditions used during the deposition process. Chemical composition results and microstructure analysis showed homogeneous distribution of molybdenum in a chitosan matrix. Corrosion test results showed that the Chit-Mo composite coatings can increase corrosion resistance of 1020 steel in NaCl medium (3.5 %). The coatings obtained at 5 V, pH 5.5, and using a low concentration of reagents (suspension 1: chitosan 0.5 g/L and 1 mM sodium molybdate) reached an inhibition efficiency of up to 76.7 %. Therefore, the results obtained in this work prove the achievement of a new class of chitosan-based composite materials with potential application in the protection of metal structures against corrosion.

Alternating Current Electrophoretic Deposition of Chitosan-Gelatin-Bioactive Glass on Mg-Si-Sr Alloy for Corrosion Protection

Magnesium alloys have gained significant attention as degradable implant materials, but the fast and localized corrosion behavior leading to hydrogen gas evolution and alkaline poisoning limits their clinical application. In this research, the possibility of controlling the fast degradation rate of an experimental Mg-Si-Sr alloy by applying hybrid biopolymer chitosan (CS)-gelatin (G)-bioactive glass (BG) coatings was investigated. Electrophoretic deposition using alternating current fields (AC-EPD) was employed for surface coating and the influence of suspension parameters (biopolymer type and concentration, BG particle size), and key AC-EPD parameters (voltage amplitude, frequency, and time) on the coating quality were investigated. Stable suspensions of positively charged biopolymer/BG particles deposited on the Mg alloy coupled as a cathode during the high-amplitude peak. Furthermore, coating homogeneity improved with increasing peak-to-peak-voltage and the hybrid nature of the coatings was confirmed by scanning electron microscopy and Fourier transform infrared spectroscopy. Corrosion studies revealed a significantly decreased corrosion rate down to 0.08 mm/year for the Mg-Si-Sr alloy incorporating CS-G-BG b AC-EPD coating.

Double side nanostructuring of microcantilever sensors with TiO2-NTs as a route to enhance their sensitivity

We reported a new strategy to enhance the sensing performances of a commercial microcantilever with optical readout in dynamic mode for the vapor detection of organophosphorus compounds (OPs). In order to increase significantly the surface area accessible to the molecules in the vapor phase, we nanostructured both sides of the microcantilever with ordered, open and vertically oriented amorphous titanium dioxide nanotubes (TiO2-NTs) in one step by an anodization method. However, due to the aggressive conditions of anodization synthesis it remains a real challenge to nanostructure both sides of the microcantilever. Consequently, we developed and optimized a protocol of synthesis to overcome these harsh conditions which can lead to the total destruction of the silicon microcantilever. Moreover, this protocol was also elaborated in order to maintain a good reflection of the laser beam on one side of the microcantilever towards the position sensitive photodiode and limit the light diffusion by the NTs film. The results related to the detection of dimethyl methylphosphonate (DMMP) showed that TiO2 and the nanostructuring on both sides of the microcantilever with NTs indeed improved the response of the sensor to vapors compared to a microcantilever nanostructured on only one side. The dimensions and morphology of NTs guaranteed the access of molecules to the surface of NTs. This approach showed promising prospects to enhance the sensing performances of microcantilevers.

Development of Stable Boron Nitride Nanotube and Hexagonal Boron Nitride Dispersions for Electrophoretic Deposition

Boron nitride nanotubes (BNNTs) represent a relatively new class of materials that provides alternative electrical and thermal properties to the carbon analogue. The high chemical and thermal stability and large band gap combined with high electrical resistance make BNNTs desirable in several thin-film applications. In this study, stable BNNT and hexagonal boron nitride (hBN) particle dispersions have been developed using environmentally friendly advanced oxidation processing (AOP) that can be further modified for electrophoretic deposition (EPD) to produce thin films. The characterization of the dispersions has revealed how the hydroxyl radicals produced in AOP react with BNNT/hBN and contaminant boron nanoparticles (BNPs). While the radicals remove the carbon contaminant present on BNNT/hBN and increase dispersion stability, they also oxidize the BNPs and the boron oxide produced, which, conversely, reduces the dispersion stability. The use of high- or low-powered ultrasonication in combination with the AOP affects the rate of the competing reactions, with low-powered sonication and AOP providing the best combination for producing stable dispersions with high concentrations. BNNT/hBN dispersions were functionalized with polyethyleneimine to facilitate EPD, where films of several micrometer thickness were readily deposited onto stainless steel and glass-fiber fabrics. BNNT/hBN films produced on glass fabrics by EPD exhibited a consistent through-thickness macroporosity that was facilitated by platelet and nanotube stacking. The film macroporosity present on the coated fabrics was suitable for use as separator layers in supercapacitors and provided improved device robustness with a minimal impact on electrochemical performance.

Curcumin-Containing Orthopedic Implant Coatings Deposited on Poly-Ether-Ether-Ketone/Bioactive Glass/Hexagonal Boron Nitride Layers by Electrophoretic Deposition

Electrophoretic deposition (EPD) was used to produce a multilayer coatings system based on chitosan/curcumin coatings on poly-ether-ether-ketone (PEEK)/bioactive glass (BG)/hexagonal boron nitride (h-BN) layers (previously deposited by EPD on 316L stainless steel) to yield bioactive and antibacterial coatings intended for orthopedic implants. Initially, PEEK/BG/h-BN coatings developed on 316L stainless steel (SS) substrates were analyzed for wear studies. Then, the EPD of chitosan/curcumin was optimized on 316L SS for suspension stability, thickness, and homogeneity of the coatings. Subsequently, the optimized EPD parameters were applied to produce chitosan/curcumin coatings on the PEEK/BG/h-BN layers. The multilayered coatings produced by EPD were characterized in terms of composition, microstructure, drug release kinetics, antibacterial activity, and in vitro bioactivity. Scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) confirmed the deposition of chitosan/curcumin on the multilayer coating system. The release of curcumin upon immersion of multilayer coatings in phosphate-buffered saline (PBS) was confirmed by ultraviolet/visible (UV/VIS) spectroscopic analysis. The antibacterial effect of chitosan/curcumin as the top coating was determined by turbidity tests (optical density measurements). Moreover, the multilayer coating system formed an apatite-like layer upon immersion in simulated body fluid (SBF), which is similar in composition to the hydroxyapatite component of bone, confirming the possibility of achieving close bonding between bone and the coating surface.

Ångstrom-Scale, Atomically Thin 2D Materials for Corrosion Mitigation and Passivation

Metal deterioration via corrosion is a ubiquitous and persistent problem. Ångstrom-scale, atomically thin 2D materials are promising candidates for effective, robust, and economical corrosion passivation coatings due to their ultimate thinness and excellent mechanical and electrical properties. This review focuses on elucidating the mechanism of 2D materials in corrosion mitigation and passivation related to their physicochemical properties and variations, such as defects, out-of-plane deformations, interfacial states, temporal and thickness variations, etc. In addition, this review discusses recent progress and developments of 2D material coatings for corrosion mitigation and passivation as well as the significant challenges to overcome in the future.

Enhancement of the Electrical Conductivity and Interlaminar Shear Strength of CNT/GFRP Hierarchical Composite Using an Electrophoretic Deposition Technique

In this work, an electrophoretic deposition (EPD) technique has been used for deposition of carbon nanotubes (CNTs) on the surface of glass fiber textures (GTs) to increase the volume conductivity and the interlaminar shear strength (ILSS) of CNT/glass fiber-reinforced polymers (GFRPs) composites. Comprehensive experimental studies have been conducted to establish the influence of electric field strength, CNT concentration in EPD suspension, surface quality of GTs, and process duration on the quality of deposited CNT layers. CNT deposition increased remarkably when the surface of glass fibers was treated with coupling agents. Deposition of CNTs was optimized by measuring CNT’s deposition mass and process current density diagrams. The effect of optimum field strength on CNT deposition mass is around 8.5 times, and the effect of optimum suspension concentration on deposition rate is around 5.5 times. In the optimum experimental setting, the current density values of EPD were bounded between 0.5 and 1 mA/cm². Based on the cumulative deposition diagram, it was found that the first three minutes of EPD is the effective deposition time. Applying optimized EPD in composite fabrication of treated GTs caused a drastic improvement on the order of 10⁸ times in the volume conductivity of the nanocomposite laminate in comparison with simple GTs specimens. Optimized CNT deposition also enhanced the ILSS of hierarchical nanocomposites by 42%.

Review of Electrochemically Triggered Macromolecular Film Buildup Processes and Their Biomedical Applications

Macromolecular coatings play an important role in many technological areas, ranging from the car industry to biosensors. Among the different coating technologies, electrochemically triggered processes are extremely powerful because they allow in particular spatial confinement of the film buildup up to the micrometer scale on microelectrodes. Here, we review the latest advances in the field of electrochemically triggered macromolecular film buildup processes performed in aqueous solutions. All these processes will be discussed and related to their several applications such as corrosion prevention, biosensors, antimicrobial coatings, drug-release, barrier properties and cell encapsulation. Special emphasis will be put on applications in the rapidly growing field of biosensors. Using polymers or proteins, the electrochemical buildup of the films can result from a local change of macromolecules solubility, self-assembly of polyelectrolytes through electrostatic/ionic interactions or covalent cross-linking between different macromolecules. The assembly process can be in one step or performed step-by-step based on an electrical trigger affecting directly the interacting macromolecules or generating ionic species.

Effect of Alternating Current on the Cathodic Protection and Interface Structure of X80 Steel

This study employs potential-monitoring techniques, cyclic voltammetry tests, alternating current (AC) voltammetry methods, and surface characterization to investigate the AC corrosion of cathodically protected X80 pipeline steel. In a non-passive neutral solution at pH 7.2, a sufficiently negative potential completely protects steel at an AC current density of 100 A/m². In an alkaline solution at pH 9.6, more serious AC corrosion occurs at more negative cathodic protection (CP) potential, whereas without CP the steel suffers negligible corrosion. In addition, the interface capacitance increases with AC amplitude. Based on these results, the AC corrosion mechanisms that function under various conditions are analyzed and described.

Study of the Electrophoretic Deposition of Chitosan/Halloysite Nanotubes/Titanium Dioxide Composite Coatings Using Taguchi Experimental Design Approach

This study presents experimental results on the electrophoretic deposition (EPD) of chitosan/halloysite nanotube/titanium dioxide composite coatings based on the Taguchi design of experiments (DOE) approach. Taguchi array of L18type with mixed levels of the control factor was used to study the influence of EPD parameters, including halloysite nanotubes concentration, electric voltage and deposition time, on deposition yield. For identifying the significant factors that affected the deposition yield, multivariate analysis of variance (MANOVA) and regression analysis based on partial least-square method were used. The coatings were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy analyses, respectively. It was found that the deposition time has significantly influenced the deposition rate but the halloysite nanotube concentration and the applied voltage have the smallest effect on the deposition. The optimum condition for high yield of deposition with low standard deviation is achieved when the concentration of halloysite nanotubes is 0.3 g/L and the applied voltage is 40 volt with 300 sec. as a deposition time. The predicted EPD conditions were verified by experiments and qualitative agreement was obtained.

Polypropylene Biocomposites with Boron Nitride and Nanohydroxyapatite Reinforcements

In this study, we develop binary polypropylene (PP) composites with hexagonal boron nitride (hBN) nanoplatelets and ternary hybrids reinforced with hBN and nanohydroxyapatite (nHA). Filler hybridization is a sound approach to make novel nanocomposites with useful biological and mechanical properties. Tensile test, osteoblastic cell culture and dimethyl thiazolyl diphenyl tetrazolium (MTT) assay were employed to investigate the mechanical performance, bioactivity and biocompatibility of binary PP/hBN and ternary PP/hBN-nHA composites. The purpose is to prepare biocomposite nanomaterials with good mechanical properties and biocompatibility for replacing conventional polymer composites reinforced with large hydroxyapatite microparticles at a high loading of 40 vol%. Tensile test reveals that the elastic modulus of PP composites increases, while tensile elongation decreases with increasing hBN content. Hybridization of hBN with nHA further enhances elastic modulus of PP. The cell culture and MTT assay show that osteoblastic cells attach and proliferate on binary PP/hBN and ternary PP/hBN-20%nHA nanocomposites.