Dip-coating Research Articles

Corrosion Performance of Nano-Alumina Coatings over Anodized Aluminum Alloy by Dip Coating Method

Alumina coatings are widely used to enhance the wear, abrasion, and corrosion resistance of metal components. This investigation aims at studying the alumina sol-gel coating on the anodized aluminum alloy surface using a dip coating technique. A stable alumina coating was deposited over the anodized aluminum surface using oxime-modified aluminum(III) isopropoxide as sol-gel precursor. The scanning electron microscopy image of the coated anodized sample suggests deposition of a uniform and crack-free aluminum coating. The corrosion resistances of bare, anodized, and coated anodized aluminum alloy samples were investigated by electrochemical impedance spectroscopy and potentiodynamic polarization in 3.5 wt % aqueous NaCl solution. An appreciable shifting was observed in the equilibrium corrosion potential (Ecorr) and the corrosion current density (icorr) values of both anodized and coated anodized samples: i.e. Ecorr: from –1377.11 mV (anodized) to –711.54 mV (coated anodized) and icorr: from 80.37 μA/cm2 (anodized) to 0.090 μA/cm2 (coated anodized). The results clearly indicate the corrosion resistive behavior of nano-alumina coatings.

Immobilized Anatase/Rutile Mixed Phase Titanium Dioxide on Glass Beads Prepared via Dip Coating Technique.

In this work, anatase/rutile mixed phase titanium dioxide (TiO₂) particles prepared via sonochemical combined with calcination process was immobilized on borosilicate glass beads via sol-gel dip coating technique utilizing titanium tetraisopropoxide (TTIP). The optical properties of mixed phase TiO₂ was evaluated by diffuse reflectance UV-Vis spectrophotometer to confirm phase transformation of anatase to rutile phase at different calcination temperatures. Phase identification and structural properties of TiO₂ particles were analyzed using X-ray diffraction (XRD) and transmission electron microscopy (TEM). Surface morphology of mixed phase TiO₂ coated on glass beads with different coating precursor solution were monitored by scanning electron microscope. The chemical composition of coated beads was characterized by energy dispersive spectroscopy to affirm the presence of TiO₂ on glass bead substrate.

Influence of deposition techniques on quality and photodetection properties of tin disulfide (SnS2) thin films

Tin disulfide (SnS2) is one of the potential candidates for optoelectronics because of its chemical and environmental stability accompanied by favourable characteristics. Herein, the SnS2 thin films are deposited by different techniques; chemical bath deposition (CBD), dip coating (DC) and spin coating (SC). The energy dispersive analysis of x-ray confirms the stoichiometry of the films deposited by these techniques. The x-ray diffraction showed hexagonal lattice structure of thin films. The morphology is studied by transmission electron, scanning electron and optical microscopy. The selected area electron diffraction exhibited ring patterns, confirming the polycrystalline nature of the deposited thin films. The atomic force microscopy showed presence of globular grains, hills and valleys on surfaces of thin films. The absorption spectra analysis showed the thin film possess direct optical bandgap of 2.39 eV for CBD, 2.50 eV for DC and 2.75 eV for SC. Raman spectra of the as-deposited SnS2 thin films showed occurrence of A1g phonon mode at 314 cm−1. The electrical transport properties assessment depicts the n-type semiconducting nature of deposited thin films. The as-deposited thin films showed good pulsed photoresponse for white light illumination intensities of 80 mW/cm2 and 120 mW/cm2.

Morphological Optimization of Chemical-Conversion Sodium Titanate and Chitosan/Glass Nanocomposite Dip Coatings Deposited on a Titanium Alloy

In this paper, the effect of some parameters of a two-step surface-modification process, consisting of alkaline treatment followed by chitosan/bioactive glass nanocomposite coating, on the surface morphology of Ti–6Al–4V alloy is investigated. According to the results, the heat treatment of the alkaline-treated sample is critical to obtain a crack-free structure. It was also found that the deposition of three composite layers with the immersion time of 3 min for each layer is optimal to develop a desirable distribution of the composite nanoparticles on the surface. In other words, a coordinated optimization approach of composite-coating variables is required to control the morphology of the deposits.

Implant Coating Manufactured by Micro-Arc Oxidation and Dip Coating in Resorbable Polylactide for Antimicrobial Applications in Orthopedics

Prophylaxis and the treatment of implant-related infections has become a key focus area for research into improving the outcome of orthopedic implants. Functional resorbable coatings have been developed to provide an antimicrobial surface on the implant and reduce the risk of infection. However, resorbable coatings developed to date still suffer from low adhesive strength and an inadequate release rate of antibiotics. This study presents a novel double-coating of micro-arc oxidation and resorbable polylactide copolymer on a Ti-6Al-4V implant with the aim of reducing the risk of infection post-implantation. The adhesive strength, rate of coating degradation, and antibiotic release rate were investigated. A key finding was that the micro-arc oxidation coating with the addition of antibiotics increased the adhesive strength of the poly-l-lactide-co-ε-caprolactone (PLC) coatings. The adhesive strength was influenced by the concentration of the PLC solution, the surface structure of the titanium substrate, and the composition of the coatings. The antibiotics blended into the PLC coating had a release cycle of approximately 10 days, which would be long enough to reduce the risk of developing an infection after implantation. The double coatings presented in this study have an excellent potential for reducing the incidence and severity of implants-related early infections.

Dip Coating Passivation of Crystalline Silicon by Lewis Acids.

The reduction of carrier recombination processes by surface passivation is vital for highly efficient crystalline silicon (c-Si) solar cells and bulk wafer metrological characterization. Herein, we report a dip coating passivation of silicon surfaces in ambient air and temperature with Nafion, achieving a champion effective carrier lifetime of 12 ms on high resistivity n-type c-Si, which is comparable to state-of-the-art passivation methods. Nafion is a nonreactive polymer with strong Lewis acidity, thus leading to the formation of a large density of fixed charges at silicon surface, 1-2 orders of magnitude higher than what is achievable with conventional thin-film passivation layers. Notably, Nafion passivates the c-Si surface only by the fixed charges without chemical modification of dangling bonds, which is fundamentally different from the common practice of combining chemical with field-effect passivation. This dip coating process is simple and robust, without the need for complex equipment or parameter optimization as there is no chemical reaction involved.

Electrochemical impedance spectroscopy and corrosion point counting on metal sheet edges with different cathodic dip coat materials

Edge coverage with organic coatings is a very important but insufficiently investigated topic in the automotive industry. Several examinations in other scopes show an influence of different coating materials as well as the metal edge radii. For an improved understanding, the edge coating coverage of defined steel sheet edges is investigated regarding its corrosion protection potential in automotive use. Therefore, four different cathodic dip coat (CDC) materials are applied in different Mercedes‐Benz plants on well‐defined and topological analyzed edges. The coating thickness and edge coverage are determined in a non‐exposed state before a 7‐days exposure in a neutral salt spray (NSS) test. To quantify the behavior of the different materials edge coverage under corrosive load, electrochemical impedance spectroscopy and corrosion point counting are performed. The results demonstrate that the type of applied CDC‐material has a great influence on edge coating coverage as well as corrosion protection. A higher edge coverage causes a higher and more stable impedance and subsequently less counted corrosion points over the whole exposure time frame.

PREPARATION AND CHARACTERIZATION OF POLYVINYL ALCOHOL THIN FILMS FOR ORGANIC THIN FILM TRANSISTORS AND BIOMEDICAL APPLICATIONS

Thin films of poly vinyl alcohol (PVA) were prepared on pre-cleaned glass substrates by Dip Coating Method. FTIR spectrum was used to identify the functional groups present in the prepared films. The vibrational peaks observed at 1260 cm-1 and 851 cm-1 are assigned to C–C stretching and CH rocking of PVA.The characteristic band appearing at 1432 cm-1 is assigned to C–H bend of CH2 of PVA. The thickness of the prepared thin films were measured by using an electronic thickness measuring instrument (Tesatronic-TTD20) and cross checked by gravimetric method. XRD spectra indicated the amorphous nature of the films.Surface morphology of the coated films was studied by scanning electron microscope (SEM). The surface revealed no pits and pin holes on the surface. The observed surface morphology indicated that these films could be used as dielectric layer in organic thin film transistors and as drug delivery system for wound healing.

Study on the Effect of Varying Film Thickness on the Transparent Conductive Nature of Aluminum Doped Zinc Oxide Deposited by Dip Coating

Study on the Effect of Varying Film Thickness on the Transparent Conductive Nature of Aluminum Doped Zinc Oxide Deposited by Dip Coating

Processing and Characterization of ZrO<sub>2</sub>-TiO<sub>2</sub> Porous Films by Dip Coating for Application as Environmental Sensors

The main objective of this work is to study and characterize porous ZrO2-TiO2 films on alumina substrates that will be used for the production of porous ceramic sensors for the monitoring of air humidity in environments subject to the incidence of solar radiation. For the production of the films the dip coating technique was adopted. A viscosity study was performed to obtain stable suspensions of ZrO2-TiO2 in isopropyl alcohol with the para-aminobenzoic acid deflocculant (PABA), at concentrations of 10, 12.5 and 15% by weight of solids. X-ray diffraction (XRD) characterizations were performed for the identification of crystalline phases, morphological analyzes by scanning electron microscopy (SEM) and chemical analyzes by energy dispersive X-ray spectroscopy (EDS). The results allowed to determine the minimum value of viscosity and amount of deflocculant to stabilize the suspension. The sensor elements in the form of 1:1 (weight) ZrO2 - TiO2 porous films showed great potential to be used as sensors for the measurement of relative humidity the size and distribution of desirable pores in the porous film for application as moisture sensors was obtained with 12.5 and 15 % by weight ZrO2-TiO2

Biocompatibility of different graphene oxide coatings on polymers

Graphene Oxide has great potential to be used in tissue engineering applications. However, its stability in wet environment is questionable. Spin, dip and plasma cross-linked graphene oxide (GO) coatings of polymers (PEEK and PET) were used in a cell study to establish stability and biocompatibility. The different coatings procedure produced surfaces with different topography and functionality. All the coatings were stable in wet cell culture environment. Despite the fact that most of the coatings were highly oxidized, as measured by XPS, with high carboxyl groups relative concentration, they showed minimal toxic effect on the examined cell line (C2C12 myoblast). The effect of oxidative stress was not evident on this particular cell line as a typical fusiform shape and adherence on the surface were detected for all samples. With the exception of the GO dip coated PEEK sample, all other coatings showed high cell proliferation, comparable to the positive control. This reflects on the stability of GO dip coating process and suggests that coating stabilization is necessary for biomedical applications. We observed (using AFM) a higher rates of ripples and wrinkles in the spin and dip GO coated PEEK (but not PET) which led to observable myogenic differentiation, imaged by SEM.

Cu2ZnSnS4 Thin Films by Dip Coating from Metal-Thiourea Precursor Solution: Effect of Sulphurization Temperature on the Formation and Structural, Optical and Electrical Properties

A process for fabrication of kesterite-based Cu2ZnSnS4 (CZTS) thin films from metal-thiourea precursor solution by dip coating is described. As deposited CZTS films were sulphurized at different temperatures to study the effects of sulphurization temperature on structural, optical and electrical properties. Formation of tetragonal CZTS phase was confirmed by x-ray diffraction; phase purity of the films was further studied by Raman spectroscopy. The studies revealed phase pure crystal structure for the films sulphurized at 500°C and 550°C. Larger crystallite size was observed for films sulphurized at 550°C. Scanning electron microscopy studies showed uniform distribution of particles in the film sulphurized at 550°C, and the determined thickness of the films was ∼ 2 μm. Energy dispersive x-ray spectroscopy analysis revealed the effect of sulphurization temperature on elemental compositions of the films. Optical studies suggest that CZTS thin film sulphurized at 550°C has high absorption coefficient (105 cm−1) with an optical energy band gap of 1.43 eV. P-type nature of the films was confirmed from Hall Effect analysis. Carrier concentration, mobility and resistivity of the films sulphurized at 550°C were also calculated. The study optimized fabrication conditions for device quality CZTS thin films from metal-thiourea precursor solution by simple dip coating.

Flexible and Compressible PEDOT:PSS@Melamine Conductive Sponge Prepared via One-Step Dip Coating as Piezoresistive Pressure Sensor for Human Motion Detection.

Flexible and wearable pressure sensor may offer convenient, timely, and portable solutions to human motion detection, yet it is a challenge to develop cost-effective materials for pressure sensor with high compressibility and sensitivity. Herein, a cost-efficient and scalable approach is reported to prepare a highly flexible and compressible conductive sponge for piezoresistive pressure sensor. The conductive sponge, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)@melamine sponge (MS), is prepared by one-step dip coating the commercial melamine sponge (MS) in an aqueous dispersion of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). Due to the interconnected porous structure of MS, the conductive PEDOT:PSS@MS has a high compressibility and a stable piezoresistive response at the compressive strain up to 80%, as well as good reproducibility over 1000 cycles. Thereafter, versatile pressure sensors fabricated using the conductive PEDOT:PSS@MS sponges are attached to the different parts of human body; the capabilities of these devices to detect a variety of human motions including speaking, finger bending, elbow bending, and walking are evaluated. Furthermore, prototype tactile sensory array based on these pressure sensors is demonstrated.

Coating hydroxiapatite on stainless steel 316 L by using sago starch as binder with dip-coating method

Hydroxyapatite (HA) is a mineral form of naturally occurring apatite calcium with Ca10(PO4)6(OH)2 formula. One of the major innovations in the field of bone reconstruction is to apply HA as a surface coating on a mechanically strong implant metal and to improve the stability of bone implants thereby increasing the lifetime of the metal implants. Pure hydroxyapatite has poor mechanical properties so it is necessary to add sago starch as a binder to combine the strength and hardness of metal surfaces with bioactive properties of hydroxyapatite by Dip Coating method. Stainless steel 316L is the most commonly used alloy as an implant for bones and teeth due to its excellent corrosion and oxidation resistance and is easily formed. In this study, hydroxyapatite coatings used fixed variables as hydroxyapatite mass (10 grams), aquades mass (20 grams), dipping time (20 seconds), and calcination conditions (800°C, 1 hour). The variables are sago starch mass (1, 1.25, 1.5 gram) and stirring time (16, 20, 24 hours). The shear strength value is higher in the addition of 1.25, 10, 20, and again in the binder ratio of 1.5; 10; 20. The addition of stirring time causes a decrease in shear strength. The highest shear strength value obtained was 3.07 MPa. The layer attached to the substrate is a hydroxyapatite with a composition of 99.4% as evidenced by the results of XRD analysis.

Characterization of SnO2 Film with Al-Zn Doping Using Sol-Gel Dip Coating Techniques

Sn1-2x AlxZnxO2 film has been developed using sol-gel dip coating technique. The materials SnCl2.2H2O, AlCl3 and ZnCl2 dissolved in water and ethanol with 5:95 volume ratio. Variations dopant concentration x = 0.000, 0.005, 0.0025, and 0.050. The film was grown with sol concentration 0.4 M, the withdrawal speed of 12 cm/min and sintering at 600 °C for 30 minutes. The characteristics Sn1-2x AlxZnxO2 films with various doping concentration phase were characterized by XRD. The morphological characteristics and the composition of the constituent elements of the film were characterized by SEM-EDX. The characteristics of the shape, structure, and size of the particles were characterized by TEM. The XRD results show that all films have a tetragonal SnO2 rutile phase without any secondary phase with an average particle size in the range 5.14 – 2.09 nm. The SEM results show that the film grown has a smooth morphology with a striped texture (x = 0.00), and there is a crack (x = 0.050). The EDX results show that the composition and distribution of the constituent elements of the film are uniformly distributed. TEM results show that the particle films has tetragonal rutile structure, orthorhombic and amorphous with a spherical shape.

Preparation of sustained release capsules by electrostatic dry powder coating, using traditional dip coating as reference

Lately, a great deal of attention is being paid to capsule coating, since the coat protects active pharmaceutical ingredients (APIs) from damage, as is in the case of tablet and pellet. However, moisture and heat sensitivity of gelatin shells make it challenging to coat capsules using the conventional aqueous coating techniques. In an effort to overcome this challenge, the present study aims to coat capsules using two different coating techniques: electrostatic dry powder coating (EDPC) and dip coating (DC). Both capsule coatings and free films were prepared by these two coating techniques, and the effects of coating formulations and processing conditions on the film quality were investigated. The corresponding drug in vitro release and mechanisms were characterized and compared. The results of dissolution tests demonstrated that the drug release behavior of both EDPC and DC coated capsules could be optimized to a sustained release of 24 h, following the Fick’s diffusion law. The results of this study suggest that EDPC method is better than DC method for coating capsules, with respect to the higher production efficiency and better stability, indicating that this dry coating technology has promised in gelatin capsule coating applications.

Effects of the post-modification using bismuth chelate (BisBAL) on the anti-biofouling and performance properties of flat-sheet microfiltration membranes

Membrane biofouling defined as the attachment and growth of microorganisms on a membrane surface has been a major problem of membrane bioreactor (MBR) technology. The anti-biofouling properties like the inhibition of bacterial adhesion of a membrane are quite significant for a long-term MBR operation. Surface modification is thought to be one of the most common approaches to improve this property. In this study, polymeric microfiltration membranes were modified by adsorption BisBAL, which is a synthesized chelate using bismuth and have a high anti-bacterial effect on various microorganisms, on the membrane surface using dip coating (DC), spin coating (SC), and low pressure-treated coating (LPtC). The purpose was to increase the surface hydrophilicity, change the surface charge, and gain the surface an anti-bacterial characteristic. It was found that the higher adsorption time, lower feed flow rate and higher spinning velocity, and pressure application increased the efficiency of the process during DC, SC, and LPtC, respectively. Furthermore, improved strategies allow the adsorption of BisBAL on the membrane surface and modified membranes has strong resistance to biofouling. Since modification resulted in a decrease in pore fouling and irreversible fouling for all type of membranes, these membranes can be novel alternatives for energy-saving MBR operation.

New Simple Modification of Dip, Spray and Cathodic Electrodeposition Coating Methods for Wire Coating (3D Coating)

In the current paper three most applied coating methods modified to suit wire coating (three dimensional coating). Capillary-gravitational coating (CGM) with natural motions considered to compensate the lifting of substrates, which normally occurs in the dip coating method. Besides a new economic-environmental friendly spray coating (EESM) assisted by the motor rotating to coat different wires, and branched cathodic electrodeposition (BCE) used also for the same mission. Thoroughly, several tests and evaluations carried out for those applied techniques. Remarkably, easy application detected for all modified methods. Unusually perfect morphology output and functional layers were synthesized. Comparison of all mentioned methods carried out considering loses and the number of coating time. Evaluation analysis has been comprehensively considered to find out capability of using these methods later on in the future.

Co-Deposition of a Hydrogel/Calcium Phosphate Hybrid Layer on 3D Printed Poly(Lactic Acid) Scaffolds via Dip Coating: Towards Automated Biomaterials Fabrication.

The article describes the surface modification of 3D printed poly(lactic acid) (PLA) scaffolds with calcium phosphate (CP)/gelatin and CP/chitosan hybrid coating layers. The presence of gelatin or chitosan significantly enhances CP co-deposition and adhesion of the mineral layer on the PLA scaffolds. The hydrogel/CP coating layers are fairly thick and the mineral is a mixture of brushite, octacalcium phosphate, and hydroxyapatite. Mineral formation is uniform throughout the printed architectures and all steps (printing, hydrogel deposition, and mineralization) are in principle amenable to automatization. Overall, the process reported here therefore has a high application potential for the controlled synthesis of biomimetic coatings on polymeric biomaterials.

Sol–Gel Dip Coating Method Synthesis of Mn-Doped Titanium Dioxide Thin Films

Undoped and Mn-doped TiO2 thin films have been prepared by sol–gel dip-coating technique on glass and silicon substrates. X-ray diffraction studies showed that both TiO2 and Mn-doped TiO2 thin films are of anatase phase with (101) as preferential orientation. All films exhibit high transparency ([Formula: see text]80%) over the visible range. The optical bandgap decreases from 3.66[Formula: see text]eV to 3.52[Formula: see text]eV due to the extent of electronic states introduced by doping. Infrared transmission spectra showed Ti–O (625[Formula: see text]cm[Formula: see text]) and Ti–O–Ti (495–436[Formula: see text]cm[Formula: see text]) bands. Thermal analysis revealed endothermic reactions between 94∘C and 110∘C and exothermic reactions between 406∘C and 443∘C. The Nyquist plots depicted that equivalent circuit of the films is an [Formula: see text] parallel. The resistance [Formula: see text] decreases while the capacitance [Formula: see text] increases with Mn-doping.