Direct Current Electrophoretic Deposition Research Articles

Surface modification of surgical suture by chitosan-based biocompatible hybrid coatings: In-vitro anti-corrosion, antibacterial, and in-vivo wound healing studies

This work aims to develop chitosan-based biocompatible hybrid coatings on synthetic surgical sutured by direct current electrophoretic deposition (DC-EPD) method. The chitosan (CS), curcumin (CR), aloe-vera (AV), and 2-aminothiazolidin-4-one-5-ethanoic acid (AT) were used as suspensions of varying combinations and compositions (A–I). Each suspension has a further 05 samples (Aa–Ae–Ia–Ie) at selected DC-EPD set parameters (2–10 V, t; 240 s, D; 1 cm). Potentiodynamic polarization measurements (PDP) were carried out in the ringer solution. Among all samples, Ed (CS, 1.6 g/L; 8 V) and Hb (CS–CR–AT, 1.6 g/Leach; 4 V) have shown greatest corrosion inhibition efficiency (IEPDP: 99 %), least corrosion rates (CR; 0.001 mm/y and 0.017 mm/y, respectively), and least corrosion current density (Icorr.; 0.01 A cm−2). SEM and FTIR further confirmed these two best coatings stable and corrosion resistant before and after performing corrosion test, while the coating thickness by profilometry test was found to be greater (16.28 μm) for Hb. Mechanical stress and strain of bare and coated samples were found to have no significant difference. Antibacterial activity revealed greater resistance of Hb against S. aureus as compared to Ed. In-vivo incision wound model study further revealed better healing and less inflammation with coated sutures with comparatively enhanced wound healing effect of Hb coated suture.

Electrophoretically Deposited Protective Cu-Mn and Mn-Co Spinel Coatings for SOFC Interconnects

Stainless steel interconnects in solid oxide fuel cells can lead to chromium poisoning of the cathode, necessitating the use of protective coatings. Electrophoretic deposition is an efficient method to deposit coatings on substrates with complex microstructures. In this study, four spinel coatings; CuMn2O4, CuNi0.2Mn1.8O4, MnCo2O4, and MnFe0.34Co1.66O4, were deposited by direct-current electrophoretic deposition on flat SUS430 stainless steel substrates. The coatings were evaluated on multiple criteria, including microstructural stability, conductivity, Cr gettering ability, and the ability to act as a diffusion barrier at 700°C and 800°C. It was concluded that CuNi0.2Mn1.8O4 is an excellent candidate at temperatures at and below 700oC, while MnFe0.34Co1.66O4 coatings perform better at higher temperatures.

Alternating Current Electrophoretic Deposition of Gadolinium Doped Ceria onto Yttrium Stabilized Zirconia: A Study of the Mechanism.

Direct current electrophoretic deposition (DC-EPD) has been successfully adopted to deposit Gd-doped ceria (GDC) onto yttrium stabilized zirconia (YSZ) previously. However, bubble evolution associated with the proton reduction results in deterioration of the quality of the GDC layer. For the purpose of lowering the densification temperature of the GDC layer by improving its green density, alternating current electrophoretic deposition (AC-EPD) is used to eliminate the bubble evolution. A dense GDC layer with a thickness of 6 μm is successfully obtained after sintering at 1250 °C. The barrier layer effectively eliminates the reaction between LaxSr1-xCoyFe1-yO3-δ (LSCF) and YSZ. The voltage waveform consists of a negative voltage step and a positive voltage step of varying magnitude and step length. The optimum frequency of 500 Hz leads to the maximum deposition yield which is linear with regard to deposition time. Moreover, with the increase of the negative to positive voltage ratio and the length of the negative step relative to the length of the positive step, the deposition rate grows correspondingly. Because the AC step voltages result in negligible faradaic reactions, the deposition process is controlled by the transport process and the desorption process, wherein the latter process is irreversible.

Ultrasonically assisted electrophoretic deposition of oxidized graphite nanoparticle onto carbon fiber, amending interfacial property of CFRP

The performance of fiber-reinforced composites significantly relies on the microstructure and properties of the fiber–matrix interface. Escalating the aspect ratio of the fiber surface by coating with nanoparticles is a proven technique for improving the fiber/matrix adhesion. Subsequently, improved adhesion between epoxy and fiber, which is ascribed due to improved interfacial friction, chemical bonding, and resin toughening would enhance the interfacial strength of such laminated composites. Here, graphite nanoparticles were oxidized, and these charged particles were coated onto the carbon fibers (CFs) surface using ultrasonically assisted direct current electrophoretic deposition. Functionalization of the graphite nanoparticle upon oxidation was confirmed through dispersion analysis, Fourier transformed infrared spectroscope, thermogravimetric analysis, and field emission scanning electron microscope. The CFs fabrics were grafted with different sets of samples prepared by varying voltage and deposition time. The deposition of oxidized graphite nanoparticle over the CFs was authenticated through field emission scanning electron microscope. A transverse fiber bundle test was carried out to assess interfacial strength between CF and epoxy matrix. The transverse fiber bundle test strength is found 113% higher for CF coated with oxidized graphite nanoparticles at 50 V for 5 min compared to that of as-received sized CF composites. Field emission scanning electron microscopy analysis of transverse fiber bundle test fractures samples identified multiple crack propagation zone owing to the presence of graphite nanoparticle on CF.

Pulsed electrophoretic deposition of nanographitic flake-nanostructured Co3O4 layers for efficient lithium-ion-battery anode

In spite of the high capacity of Co3O4 nanomaterial to employ in lithium-ion battery anodes, the reduced conductivity and significant volume change of Co3O4 during long cycling of insertion and extraction of Li ions remain a challenge. Utilization of composite materials making use of graphene-based materials together with Co3O4 nanostructures can offer a suitable strategy to address these challenges. Here, a composite material consisting of nanographitic flake and CO3O4 nanoparticles is synthesized by solvothermal reactions. After successive oxidation treatments, two types of electrophoretic deposition processes, namely, direct current and square wave pulse current are used to fabricate binder-free anodes for lithium-ion batteries. Compared to the direct current electrophoretic deposition technique, the pulsed electrophoretic deposition technique with a square wave is found to enhance the efficiency of the fabricated anode. The pulsed electrophoretic deposition technique enables the formation of the anode from smaller agglomerated Co3O4 nanoparticles compared to the anode obtained with the direct current electrophoretic deposition. The selective deposition of less agglomerated Co3O4 nanoparticles results in an excellent rate capability and durability of the anode fabricated by the pulsed electrophoretic deposition (a charge capacity of 780 mAh/g after 50 cycles at 1 A/g with total retention of 89%).

Electrospun Ag/WO<sub>3</sub> Composite Nanofiber Photoanodes Prepared by DС Electrophoretic Deposition for Photoelectrochemical Water Splitting

In this work, tungsten oxide (WO3) nanofibers were synthesized using electrospinning technique. Direct current electrophoretic deposition (DC-EPD) was conducted to deposit the nanofibers onto fluorine-doped tin oxide (FTO) electrodes. The photoelectrochemical performance of WO3 nanostructured electrodes was investigated and compared between the samples containing pristine WO3 and Ag/WO3 composite nanofibers. An up-to-6-fold enhancement in photoconversion efficiency (PCE) was obtained from Ag/WO3 composite nanofiber photoanode.

Electrophoretic deposition of nanocrystalline TiO2 particles on porous TiO2-x ceramic scaffolds for biomedical applications

Nanocrystalline TiO2 coated scaffolds offers the possibility to be used in bone tissue regeneration providing not only space for new tissue formation, but also to enhance bioactivity of the implant. In the present study, direct current electrophoretic deposition (EPD) was chosen as simple and low cost technique to coat 3D porous structure of TiO2-x ceramic. Suspension for EPD was prepared suspending nanocrystalline TiO2 particles in isopropanol and adding triethanolamine as dispersant. TiO2 particles were electrophoretically deposited on the surface of TiO2-x scaffolds through varying EPD time and applied voltage. The scaffold pore structure was maintained after applying the coating by EPD. The deposition of nanocrystalline TiO2 coating can be a smart strategy to impart bioactive properties to the 3D scaffold, allowing formation of spherical hydroxyapatite particles on the coated scaffolds after immersion in simulated body fluid. In vitro cell studies does not show cytotoxic effect of nanocrystalline TiO2 coated scaffolds.

Formation of NiO nanoparticle-attached nanographitic flake layers deposited by pulsed electrophoretic deposition for ethanol electro-oxidation

Abstracts Our previous work demonstrated the fabrication of the NiO nanoparticle-nanographitic flake composite through a direct current (DC) electrophoretic deposition (EPD) process. The composite was used as a catalyst layer having a low onset voltage in ethanol electro-oxidation. This paper presents a new catalyst material fabricated through pulsed EPD, which permitted to acquire a higher efficiency of ethanol electro-oxidation when compared to the catalyst layer fabricated by the DC EPD. The reason behind the enhancement of the performances of the catalyst layers fabricated using the pulsed EPD is the selective deposition of low-weight NiO nanoparticles on nanographitic flakes causing a reduction in the deposition of agglomerated NiO nanoparticles and therefore an enhancement in the efficiency of the ethanol electro-oxidation.

Electrophoretic Deposition of Chitosan/45S5 Bioactive Glass Composite Coatings Doped with Zn and Sr.

In this research work, the original 45S5 bioactive glass was modified by introducing zinc and/or strontium oxide (6 mol%) in place of calcium oxide. Sr was added for its ability to stimulate bone formation and Zn for its role in bone metabolism, antibacterial properties, and anti-inflammatory effect. The glasses were produced by means of melting and quenching process. SEM and XRD analyses evidenced that Zr and Sr introduction did not modify the glass structure and morphology while compositional analysis (EDS) demonstrated the effective incorporation of these elements in the glass network. Bioactivity test in simulated body fluid (SBF) up to 1 month evidenced a reduced bioactivity kinetics for Zn-doped glasses. Doped glasses were combined with chitosan to produce organic/inorganic composite coatings on stainless steel AISI 316L by electrophoretic deposition (EPD). Two EPD processes were considered for coating development, namely direct current EPD (DC-EPD) and alternating current EPD (AC-EPD). The stability of the suspension was analyzed and the deposition parameters were optimized. Tape and bending tests demonstrated a good coating-substrate adhesion for coatings containing 45S5-Sr and 45S5-ZnSr glasses, whereas the adhesion to the substrate decreased by using 45S5-Zn glass. FTIR analyses demonstrated the composite nature of coatings and SEM observations indicated that glass particles were well integrated in the polymeric matrix, the coatings were fairly homogeneous and free of cracks; moreover, the AC-EPD technique provided better results than DC-EPD in terms of coating quality. SEM, XRD analyses, and Raman spectroscopy, performed after bioactivity test in SBF solution, confirmed the bioactive behavior of 45S5-Sr-containing coating while coatings containing Zn exhibited no hydroxyapatite formation.

Continuous Electrophoretic Deposition and Electrophoretic Mobility of Ligand-Free, Metal Nanoparticles in Liquid Flow

Direct current electrophoretic deposition (DC-EPD) of ligand-free metal nanoparticles in a flow-through reactor is studied by analyzing the educt colloid and the outflow of the flow through chamber while the concentration of the colloid and the strength of the electric field is varied. Metal nanoparticles synthesized by pulsed laser ablation in liquid (PLAL) are used to ensure that the colloidal nanoparticle surface is free of any ligands and that the colloid's stability and movement in an electric field is solely influenced by electrostatic forces. Electrophoretic mobility and deposition kinetics of these ligand-free nanoparticles on plain surfaces are examined for different electric field strengths. Additionally, a continuous liquid flow DC-EPD process is presented and optimized regarding deposition rate, colloid stability, and liquid flow rate. The reported parameter window for high deposition rates of nanoparticles without a negative impact on the colloid, allows to define an efficient stationary EPD process suitable for high throughput applications.

Effect of Sintering Profile and Composition of Ni/Al<sub>2</sub>O<sub>3</sub> Functional Gradient Materials Coating Layers via Pulsed DC Electrophoretic Deposition

Ni/Al2O3 functional gradient material (FGM) coating layers with its thickness of 20­25μm were fabricated by pulsed direct current (DC) electrophoretic deposition (EPD). The coarsening effect of Ni was studied to control sintering profile with an intermediate step of 1000°C for 3 h. Controlling the sintering conditions through an intermediate step and varying the number of layers played important roles in reducing cracks on the coating surface. The samples were characterized using X-ray diffraction (XRD), back scattered electron microscopy (BSE) and electron probe micro analyzer (EPMA). From these analyses, the effects of sintering step on microstructures of FGM coating layers were studied systematically to minimize crack problems within Ni-rich region by controlling its composition and form gradient through coarsening of Ni particles caused by intermediate step during sintering process. The high hardness was found for twoand three-layered samples by introducing intermediate step during sintering. Hence, pulsed DC EPD method was successfully employed to fabricate crack-free FGM with desirable microstructures. [doi:10.2320/matertrans.M2013347]

AC vs. DC electrophoretic deposition of hydroxyapatite on titanium

The bio-inertness of titanium and its alloys attracts their use as bone implants. However a bioactive coating is usually necessary for improving the bone bonding of such implants. In this study, electrophoretic deposition(EPD) of hydroxyapatite (HA) powder on titanium plate was performed using butanol as solvent under direct current (DC) and alternating current (AC) fields. The zeta potential of the suspensions was measured to understand their stability and the charge on the particles. Coating thickness was varied by adjusting the voltage and time of deposition. Surface morphology and cross section thickness were studied using scanning electron microscopy and image analysis software. Surface crack density was calculated from the micrographs. The results showed that the samples of similar thickness have higher grain density when coated using AC as compared to DC EPD. This facile but novel test proves the capability of AC-EPD to attain denser and uniform HA coatings from non-aqueous medium.

Comparison between metal ion and polyelectrolyte functionalization for electrophoretic deposition of graphene nanosheet films

Graphene nanosheets (GNSs) were modified either by metal magnesium (Mg) ions or a polyelectrolyte, polydiallyldimethylammonium chloride (PDDA), to produce positive charges on them. The two materials were used to produce GNS films with different surface morphologies. They were deposited on single-crystal silicon substrates using simple direct current electrophoretic deposition method. The Mg ion-modified GNS film has a relatively rough surface with some GNSs almost perpendicular to the surface, whereas the PDDA-modified GNS film has a relatively smooth surface with most GNSs parallel to the substrate. This difference is attributed to the different interactions of Mg ions and PDDA molecules with GNSs. Because of the favorable surface morphology, the Mg ion-modified GNS film displays better field emission compared with the PDDA-modified GNS film. Biocompatibility tests indicate that the rougher Mg ion-modified GNS film is more beneficial to cell adhesion and growth.

Fabrication of organic copper phthalocyanine nanowire arrays via a simple AAO template-based electrophoretic deposition

Copper phthalocyanine (CuPc) nanowire arrays were fabricated for the first time by the electrophoretic deposition (EPD) method using a porous anodic aluminum oxide (AAO) template. The barrier layer between the aluminum substrate and the AAO membrane was first removed by progressively reducing the applied anodizing voltage. The AAO template was then employed directly to fabricate CuPc nanowire arrays by direct current EPD. The morphology of the CuPc nanowires was characterized by transmission electronic microscopy and field emission scanning electronic microscopy. The nanowires exhibited smooth surfaces and uniform diameters of about 40 nm. The photoconductivity of the CuPc nanowire arrays was investigated as well.

Electrophoretic Deposition of Carbon Nanotubes into Device Structures: An Approach to Integrate Nanostructures into Micro devices

ABSTRACTCharged particles in suspension tend to move when an electric field is applied. This simple phenomenon of migration of charged particles in a liquid medium and their subsequent deposition onto an oppositely charged electrode is called electrophoretic deposition (EPD), and is used in assembly of nanoparticles into microfabricated devices. This work reports the application of the EPD process for deposition of commercially available purified single-walled carbon nanotubes (CNT) onto microfabricated device structures. A direct current EPD in aqueous medium was used to position CNTs into two different microfabricated device structures: gold electrodes of 100nm thickness and gold microcantilevers. Control of the mass of CNTs deposited using EPD process is addressed in this work.