Plasma electrolytic oxidation (PEO) processing for light metals is known for decades and has been established as a well-known industrial surface treatment offering a reasonable wear and corrosion protection. However, long-term protection is compromised by the intrinsic porosity and limited range of composition in the PEO layer. A novel approach is to introduce particles to the electrolyte, aiming at their in-situ incorporation into PEO coatings during growth. The idea is that with the help of particles the defects can be sealed, and the composition range and the functionalities of produced coatings can be enhanced. So far, multifunctional coatings with anticorrosion, self-lubrication, anti-wear, bioactive and photocatalytic properties were produced with the aid of particle addition. The properties of particle itself, together with electrical and electrolyte parameters during PEO processing determine the way and efficiency of particle uptake and incorporation into the coatings. Normally incorporation of the particles into the coating can range from fully inert to fully reactive. This paper reviews recent progress on particle-containing PEO coatings formed on Mg, Al and Ti alloy substrates. The main focus is given to the uptake mechanism of particle into PEO layers and the introduced microstructural and functional changes.

Plasma electrolytic oxidation coatings with particle additions – A review

Review of the biocompatibility of micro-arc oxidation coated titanium alloys

Surface characterization and corrosion behavior of calcium phosphate-base composite layer on titanium and its alloys via plasma electrolytic oxidation: A review paper.

Plasma electrolytic oxidation (PEO) of AZ31 magnesium alloy under pulsed bipolar constant current regimes has been carried out in a silicate–hexametaphosphate electrolyte without and with the suspension of SiC nanoparticles. The coatings were characterized by eddy current method, X-ray diffraction (XRD), scanning electron microscopy (SEM), dry sliding wear and electrochemical tests. Higher growth rates were found for the coatings formed with the presence of nanoparticles. The incorporation of SiC nanoparticles into the coatings has been verified by XRD and SEM, and the incorporated particles were found to distribute relatively uniformly along the coating depth. “Weak sites” existed in the SiC free coatings, which significantly lowered the wear performance of the coatings. In contrast, “weak sites” are not found in the coatings with the incorporation of SiC nanoparticles, resulting in an excellent wear performance of the coatings. The applied current densities of the PEO processes also affect the performance of the coatings, with higher wear rates for the coating prepared under higher current densities. All the coatings show improved corrosion resistances.

An improvement of the wear and corrosion resistances of AZ31 magnesium alloy by plasma electrolytic oxidation in a silicate–hexametaphosphate electrolyte with the suspension of SiC nanoparticles

The plasma electrolytic oxidation is an innovative method for the surface treatment of titanium and its alloys. This review provides an overview of the historical development of the process and summarizes the current state of the art. The chemical as well as the electro- and plasma-chemical basics of the layer forming mechanisms, which comprises the substrate/electrolyte interface before discharge initiation and the different types and stages of plasma electrolytic discharge phenomena are explained within the context of titanium-based materials. How these phenomena can be influenced by the use of suitable electrolytes and controlled by the electrical regime is described. Subsequently, the microstructures and composition of the layers are described in detail, and the properties for specific applications are then discussed. The resistance of a PEO coating to corrosive environments, tribological factors, and alternating mechanical stress is viewed critically, and the extensive functional properties such as physiological compatibility, photocatalytic activity, and decorative properties are revealed. Finally, examples of various practical applications in the medical engineering, aviation, automotive, and environmental technology fields, as well as other branches of industry, are presented.

Review of plasma electrolytic oxidation of titanium substrates: Mechanism, properties, applications and limitations

Study plasma electrolytic oxidation process and characterization of coatings formed in an alumina nanoparticle suspension

Effects of alumina nanoparticles concentration on microstructure and corrosion behavior of coatings formed on titanium substrate via PEO process

Kinetic analysis on nickel laterite ore calcination using model-free and model-fitting methods

This study introduces a novel, non-toxic, scalable, two-step method for the fabrication of highly nanoporous nickel and nickel oxide (Ni–NiO) foam/Electrochemically reduced graphene oxide (ERGO) electrodes with exceptional capacitance suitable for supercapacitor application. This procedure includes drop cast and graphene oxide (GO) reduction by galvanostatic process. To create the electrodes, electrodeposition process and selective electrochemical dealloying accompanied by a hydrogen evolution reaction (HER) were performed on a copper substrate. Afterwards, drop cast and galvanostatic processes were accomplished to coat GO nanosheets on Ni–NiO foam. The structure of achieved nanocomposites was investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS). High-specific capacitance of 1995 F g−1 at a current density of 1 A g−1 (galvanostatic charge–discharge) (GCD) was achieved for the Ni–NiO foam/electrochemically reduced graphene oxide (ERGO) electrode with excellent cycling stability. A constant, high-specific capacitance (95.1% of the initial value) was achieved after 6000 cycles at 20 A g−1.

Sahand Sarbishei

Papers

Study plasma electrolytic oxidation process and characterization of coatings formed in an alumina nanoparticle suspension

Effects of alumina nanoparticles concentration on microstructure and corrosion behavior of coatings formed on titanium substrate via PEO process

Kinetic analysis on nickel laterite ore calcination using model-free and model-fitting methods

Facile synthesis of nano dendrite-structured Ni–NiO foam/ERGO by constant current method for supercapacitor applications

The effect of sulfur content of rotary kiln fuel on the composition of nickel laterite calcine