Secondary ion mass spectrometry and multireflection infrared analyses of conversion coatings on Fe–Cr–Al stainless steels for catalysis: study of thermal stability

Abstract

The thermal stability of three stainless steel conversion coatings for high temperature applications (e.g. photothermal conversion catalysis) are investigated. The thermal oxidation in air up to 1000°C of Fe–17Cr, Fe–18Cr–1·3Al, and Fe–22Cr–5Al coatings (all wt-%) are compared. This study has revealed a critical temperature below which the coating thickness is preserved; the critical temperature increases and the thermal oxidation of the conversion coating decreases with higher chromium and aluminium content. This is attributed to the difference in the substitution ratio of γ lacunar phase (additionally oxidised substituted magnetite), which is the main component of the conversion coatings. The thermal stability of this phase is higher when it is richer in chromium or aluminium. Higher contents of these elements raise the temperature of formation of chromite (FeCr₂O₄) and alumina, the occurrence of which causes thickening of the coating during thermal treatment.

MST/1891     

Quantification of silver ion release,in vitro cytotoxicity and antibacterial properties of nanostuctured Ag doped TiO2 coatings on stainless steel deposited by RF magnetron sputtering

Surface treatments on biomaterials using several methods have greatly reduced the in vivo bacterial attachment, surface colonization and formation of biofilm. In this study, the effect of silver (Ag) ion release against in vitro antibacterial activity and cytotoxicity of 1–4wt% Ag doped titania (TiO₂) thin film coatings were evaluated. These coatings were deposited for 1–6 h onto stainless steel substrate (SS) using (radio frequency) RF magnetron sputtering technique. The coatings predominantly in the crystalline anatase phase were configured using X-ray Diffraction (XRD). Scanning electron microscopy (SEM) observation showed the presence of Ag–TiO₂ nanoparticles of less than 100 nm in all the coated surfaces confirming the formation of nanostructured coatings. An initial rapid release, followed by a sustained lower release of Ag ion concentration was measured between 0.45 and 122 ppb when all the coated substrates immersed in Phosphate Buffered Saline (PBS) for 1–10 days. The obtained concentration was less than the maximum toxic concentration for human cells; yet achieved antibacterial concentration, sufficient to kill or inhibit the growth of bacteria. In vitro cytotoxicity results have indicated that 1–4 wt% of Ag doped TiO₂ coatings had no adverse effect on mouse fibroblast proliferation, confirming its cytocompatibility. The antibacterial assessment was performed on 1 and 2 wt% Ag–TiO₂ coatings using Staphylococcus aureus (S. aureus) whereby significant antibacterial activity was observed in 2 wt% Ag–TiO₂ coatings.     

Synthesis and characterization of antibacterial polyurethane coatings from quaternary ammonium salts functionalized soybean oil based polyols

In this study, a simple and versatile synthetic approach was developed to prepare bactericidal polyurethane coatings. For this purpose, introduction of both quaternary ammonium salts (QASs), with well-known antibacterial activity, and reactive hydroxyl groups on to the backbone of soybean oil was considered. Epoxidized soybean oil was reacted with diethylamine and the intermediate tertiary amine containing polyol was reacted with two different alkylating agents, methyl iodide and benzyl chloride, to produce MQAP and BQAP, respectively. These functional polyols were reacted with different diisocyanate monomers to prepare polyurethane coatings. Depending on the structure of monomers used for the preparation of polyurethane coatings, initial modulus, tensile strength and elongation at break of samples were in the ranges of 122–339 MPa, 4.6–12.4 MPa and 8.4–46%, respectively. Polyurethane coatings based on isophorone diisocyanate showed proper mechanical properties and adhesion strength (0.41 MPa) for coating application. Study of fibroblast cells interaction with prepared polyurethanes showed promising cells viability in the range of 78-108%. Meanwhile, MQAP based samples with higher concentration of QASs showed better adhesion strength, surface hydrophilicity and antibacterial activity (about 95% bacterial reduction). Therefore, these materials can find applications as bactericidal coating for biomedical devices and implants.     

Osteoblastic cells culture on electrospun poly(ε-caprolacton) scaffolds incorporating amphiphilic PEG–POSS telechelic

In this work, novel poly(ε-caprolactone) (PCL) fibrous membranes incorporating amphiphilic polyhedral oligosilsesquioxane (POSS) telechelic (PEG–POSS telechelic) were prepared via electrospinning. The unique microstructure, morphology, thermal stability of the resulting PCL/PEG–POSS telechelic electrospun nanowebs were investigated by X-ray diffraction, scanning electron microscopy, and thermogravimetric analysis, respectively. The addition of amphiphilic PEG–POSS telechelic strongly influenced the fiber diameters, microstructures of the resultant PCL/PEG–POSS telechelic nanofibers, compared to pure PCL nanofibers. The potential biomedical applications of such PEG–POSS telechelic nanowebs as a scaffolding material were also evaluated in vitro using mouse osteoblast-like MC3T3-E1 cells. The cell adhesion, spreading, and interaction behavior of pure PCL and PCL/PEG–POSS telechelic fibrous membranes were explored. It was found that electrospun PCL fibrous membranes incorporating amphiphilic PEG–POSS telechelic showed higher initial cell attachment than pure PCL due to the higher surface free energy of POSS siloxanes. Moreover, the obtained PCL/PEG–POSS telechelic fibrous scaffolds were found to be nontoxic and to maintain the good adhesion ratio between cells and surface (about ~93 %) after cell culturing for 24 h.     

Preparation of modified nano ZnO/polyester/TGIC powder coating nanocomposite and evaluation of its antibacterial activity

Powder coating nanocomposite with antibacterial properties is the aim of this study. For this purpose, nano zinc oxide was modified by vinyltrimethoxysilane (VTMS) and Triethoxy(methyl)silane (TEMS). Then various percentages of modified and non-modified nano ZnO (1, 3 and 5%), polyester resin and triglycidyl isocyanurate as a hardener were blended by twin screw extruder. Prepared polymer–matrix composite (PMC) was atomized and coated by electrostatic method on aluminum plates. Finally, samples were cured for 10 min at 200 °C. For investigating the thermal stabilities of modified nano particles, thermogravimetric analyses (TGA) were used. Antibacterial properties of coatings were investigated by gram negative bacteria Escherichia coli and gram positive Staphylococcus aureus. The results showed that the coatings demonstrate significant antibacterial activity by increasing amounts of ZnO nanoparticles (5%) when were modified by VTMS.     

Synthesis, characterization, and biological activities of organosoluble and thermally stable xanthone-based polyamides

A series of polyamides, poly (xanthone-amide)s (PXAs) were prepared by direct polycondensation of 2,7-diaminoxanthone with various available aliphatic and aromatic dicarboxylic acids. The monomer and all the PXAs were characterized by FT-IR, ¹H NMR and ¹³C NMR. The prepared polyamides showed inherent viscosities in the range of 0.41–0.68 dL g^?1 in NMP at 25 °C. The PXAs with low crystallinity were soluble in aprotic polar solvents such as DMF, NMP, DMSO, and DMAc at room temperature. These PXAs showed low glass transition temperatures (T _g) (200–310 °C) and high thermal stability, the 10 % weight loss temperature was up to 432 °C under nitrogen. These polymers exhibited strong UV–Vis absorption maxima at 301–316 nm in NMP solutions. Their photoluminescence showed fluorescence emission maxima around 433–444 and 503–521 nm for aliphatic and aromatic polyamides, respectively. The resulting polymers were analyzed for their antioxidant activities using DPPH assay and the antibacterial activities against some bacterial strains (S. aureus, B. subtilis, E. coli and P. aeruginosa). The results revealed that the antioxidant and antibacterial activities of PXAs were more than xanthone nucleus and used standard, respectively. It showed that these polymers can be used in pharmaceutical and food industries (food packaging).     

Evaluation of the physical and antimicrobial properties of silver doped hydroxyapatite depending on the preparation method

In the present study, the effect of the preparation method on the physical and antibacterial properties of silver doped hydroxyapatite (HAp/Ag) samples was investigated. HAp/Ag with 0.1–5 % of silver was prepared using two different modified wet chemical precipitation methods. A comparison of thermal stability and thermodynamical properties indicated that the thermal stability and sintering temperature of HAp/Ag were higher than those of pure hydroxyapatite if Ca(NO₃)₂·4H₂O, AgNO₃, NH₄OH and (NH₄)₂HPO₄ were used as raw materials. Phase composition and silver release were determined by XRD and ICP-MS. The study showed that, after 50 h in simulated body fluid 0.8–1.8 % of silver of the total silver amount was released from compact HAp/Ag scaffolds, and release kinetics strongly depended on the HAp/Ag preparation method. In vitro antibacterial activity of samples from each method against the bacterial strains Staphylococcus epidermidis and Pseudomonas aeruginosa was approved. Results showed that, in the case of using Ca(OH)₂, H₃PO₄ and AgNO₃ as raw materials for HAp/Ag synthesis, higher antibacterial activity towards both bacterial strains could be obtained.     

Photo-induced birefringence and all-optical switching effect in azobenzene-grafted polyurethanes

In this study, azobenzene-containing chromophore 4-N,N′-bis-(2-hydroxyethyl)amino-4′-nitro-azobenzene were synthesized by using 4-nitroaniline and m-tolyldiethanoamine. Then they were polymerized with toluene 2,4-di-isocyanate (TDI) and polyethylene glycol (PEG) in N,N′-dimethylformamide (DMF) to obtain novel polyurethanes which exhibit photo-induced birefringence properties. Polyols such as 1,4-dibutanol or tri-hydroxyl propane were introduced into the polyurethane structure to adjust the flexibility of the polymer chain segments. An experimental setup, in which the He–Ne lasers produced signal beams and Ar⁺ lasers the pump beams, was employed to investigate the photo-induced birefringence and optic–optic switching properties of these polyurethane materials. It is found that, with increasing pump beam power, the extent of both birefringence and optic switching response first slightly increased due to reorientation mechanism, and then decreased due to thermal effects. And the flexibility for the chain segment also has remarkable effects on birefringence extents and optic switching modulations.     

Green synthesized silver nanoparticle from Allium ampeloprasum aqueous extract: Characterization,antioxidant activities,antibacterial and cytotoxicity effects

In the current study for the first time, silver nanoparticles (AgNPs) were biosynthesized by reducing agents from hot water extract of Allium ampeloprasum, an antibacterial and anti-inflammatory edible plant. UV–vis. spectroscopy, Fourier transform infrared spectroscopy, dynamic light scattering, X-ray diffractometric, and transmission electron microscopy (TEM) analyses have been applied to confirm the formation of biosynthesized AgNPs. Total phenol content and antioxidant activities of AgNPs and extract together with their antibacterial and cytotoxic properties, were evaluated. According to TEM, AgNPs were spherical with a diameter of 8–50 nm. Total phenolic compounds were 15.58 μg/mL, and 10.94 μg/mL at a concentration of 150 μg/mL for the A. ampeloprasum extract and the biosynthesized AgNPs, respectively. Biosynthesized AgNPs showed significant antioxidant activity (81%) as compared to A. ampeloprasum extract (32%) and were active on multi-drug resistant P. aeruginosa. Besides, the cytotoxic activity response was also demonstrated that AgNPs were more potent than the A. ampeloprasum extract and showed high activity against Hela cell line with an IC₅₀ value of less than 25 µg/mL. In conclusion, AgNPs synthesized by A. ampeloprasum extract with excellent antioxidant and antibacterial effects and acceptable cytotoxicity on cervical cancer cells have the potential to be used in biological applications.     

Antibacterial activity of electroless Ni–B coating

Abstract

A surface deposition treatment like electroless Ni–B deposition, which is a new candidate to use in a wide range of engineering applications owing to many advantages, including low cost and good wear resistance, may improve the antibacterial activity and physical properties of stainless steel biomedical devices. In the present study, the structural and antibacterial properties of electroless Ni–B coatings deposited on AISI 304 stainless steels under different deposition conditions were investigated. Escherichia coli, the most important causative organism for infection, were used as the testing bacteria for in vitro test, including incubation at 37°C and 24 h. X-ray diffraction for crystallographic examination and scanning electron microscopy for morphological analysis were also used. The characterisation results showed that the antibacterial activity of the steel substrates deposited with coatings having especially high NaBH₄ concentrations (1·2 g L^?1), thus being amorphous, was strongly improved. Furthermore, the bactericidal performance difference of the coatings exhibiting cauliflower-like surface morphology was more obvious than that of the others. Electroless Ni–B surface treatment may be utilised for increasing the lifetime of stainless biomedical devices.     

Hafnium nitride coatings prepared by very high rate reactive sputtering

Hafnium nitride (HfN_x) coatings were prepared via very high rate reactive sputtering in an ArN₂ atmosphere over a wide range of nitrogen concentrations. The color of the coatings varied from a pale yellow at low nitrogen levels to a rich golden yellow color at the higher nitrogen levels. This color is different from the greenish yellow color for chemically vapor-deposited HfN coatings. As the nitrogen content of the films was increased, the cell size also increased, which is contrary to what has been reported for bulk HfN_x. The reactively sputtered HfN_x coatings have a (111) preferred orientation, and the cell size is 4.56 Å for the rich golden-colored films compared with 4.52 Å for the bulk material. In addition, the reactively sputtered HfN_x coatings have an unexpectedly high Vickers hardness of 2570 kgf mm^-2 (for a 1000 gf load). The bulk HfN hardness is reported to be 1600 kgf mm^-2. The HfN coatings have very high compressive residual stresses, and the adhesion of these coatings to M2 tool steel, as measured by the Laboratoire Suisse de Recherches Horlogères scratch tester, is excellent.     

Antibacterial burst-release from minimal Ag-containing plasma polymer coatings

Biomaterials releasing silver (Ag) are of interest because of their ability to inhibit pathogenic bacteria including antibiotic-resistant strains. In order to investigate the potential of nanometre-thick Ag polymer (Ag/amino-hydrocarbon) nanocomposite plasma coatings, we studied a comprehensive range of factors such as the plasma deposition process and Ag cation release as well as the antibacterial and cytocompatible properties. The nanocomposite coatings released most bound Ag within the first day of immersion in water yielding an antibacterial burst. The release kinetics correlated with the inhibitory effects on the pathogens Pseudomonas aeruginosa or Staphylococcus aureus and on animal cells that were in contact with these coatings. We identified a unique range of Ag content that provided an effective antibacterial peak release, followed by cytocompatible conditions soon thereafter. The control of the in situ growth conditions for Ag nanoparticles in the polymer matrix offers the possibility to produce customized coatings that initially release sufficient quantities of Ag ions to produce a strong adjacent antibacterial effect, and at the same time exhibit a rapidly decaying Ag content to provide surface cytocompatibility within hours/days. This approach seems to be favourable with respect to implant surfaces and possible Ag-resistance/tolerance built-up.     

Anti-microbial and anti-corrosive poly (ester amide urethane) siloxane modified ZnO hybrid coatings from Thevetia peruviana seed oil

The utilization of renewable resources for the development of organic coatings is a viable means of creating alternatives to petroleum-based chemicals which are not eco-friendly. This paper reports the synthesis of polyesteramide–urethane–silica–zinc oxide hybrid coatings from Thevetia peruviana seed oil (TPSO). The periphery of ZnO nano-particles is modified with 3-aminopropyltrimethoxysilane to prepare silica grafted ZnO composite particles. The TPSO based polyesteramide was reacted with 4,4′-diisocyanatodicyclohexylmethane in presence of siloxane modified ZnO to obtain –NCO terminated polyesteramide–urethane–silica ZnO prepolymer. These hybrid pre-polymers were casted on tin foil and cured under atmospheric moisture to obtain eco-friendly, moisture cured polyesteramide–urethanes–silica–zinc oxide hybrid coating films. The synthesized polyester and polyurethane formation was confirmed by using FT-IR and NMR spectroscopic techniques. The resultant hybrid coating films were characterized by using FT-IR, TGA, DSC, SEM, corrosion resistance and microbial resistance. Results confirm that with increase of siloxane modified ZnO content in the polyurethane matrix thermal stability, glass transition temperature and corrosion resistance improved. The antibacterial activity shows that the hybrid films exhibit excellent resistance towards Escherichia coli and Staphylococcus aureus. The salt spray test on coated panel samples show good corrosion resistance properties.     

Differential Thermal Analysis of Polyethylene Glycol and Glycerol Monostearate Suppository Bases Containing Theophylline

Abstract

Water soluble polyethylene glycol 4000 (PEG4) suppositories were prepared containing 4% (w/w) theophylline. Various concentrations of polyethylene glycol 1000 (PEG1) and glycerol monostearate (GMS) were also added. Differential thermal analysis (DTA) of the PEG4 and PEG1 combination suppositories showed no melting endotherm for theophylline. But when theophylline concentration in the base was 12% (w/w) and above, sharp endothermic peak of theophylline was obtained. In contrast, when GMS was added as a base material above 50% (w/w) with PEG4, the melting endotherm of theophylline (4%, w/w) appeared at 273-274°C. The melting endotherm of the suppository bases increased up to 2 to 4°C due to storage at 4°C for six months.     

Physicochemical characterization of spray-dried PLGA/PEG microspheres,and preliminary assessment of biological response

Context: The use of spray-drying to prepare blended PLGA:PEG microspheres with lower immune detection.

Objective: To study physical properties, polymer miscibility and alveolar macrophage response for blended PLGA:PEG microspheres prepared by a laboratory-scale spray-drying process.

Methods: Microspheres were prepared by spray-drying 0–20% w/w ratios of PLGA 65:35 and PEG 3350 in dichloromethane. Particle size and morphology was studied using scanning electron microscopy. Polymer miscibility and residual solvent levels evaluated by thermal analysis (differential scanning calorimetry – DSC and thermogravimetric analysis – TGA). Immunogenicity was assessed in vitro by response of rat alveolar macrophages (NR8383) by the MTT-based cell viability assay and reactive oxygen species (ROS) detection.

Results: The spray dried particles were spherical, with a size range of about 2–3?µm and a yield of 16–60%. Highest yield was obtained at 1% PEG concentration. Thermal analysis showed a melting peak at 59?°C (enthalpy: 170.61 J/g) and a degradation-onset of 180?°C for PEG 3350. PLGA 65:35 was amorphous, with a T_g of 43?°C. Blended PLGA:PEG microspheres showed a delayed degradation-onset of 280?°C, and PEG enthalpy-loss corresponding to 15% miscibility of PEG in PLGA. NR8383 viability studies and ROS detection upon exposure to these cells suggested that blended PLGA:PEG microspheres containing 1 and 5% PEG are optimal in controling cell proliferation and activation.

Conclusion: This research establishes the feasibility of using a spray-drying process to prepare spherical particles (2–3?µm) of molecularly-blended PLGA 65:35 and PEG 3350. A PEG concentration of 1–5% was optimal to maximize process yield, with minimal potential for immune detection.     

Effect of bias voltage on microstructure and mechanical properties of arc evaporated (Ti, Al)N hard coatings

In the present study, authors report on the effect that substrate bias voltage has on the microstructure and mechanical properties of (Ti, Al)N hard coatings deposited with cathodic arc evaporation (CAE) technique. The coatings were deposited from a Ti _{0· 5}Al _{0· 5} powder metallurgical target in a reactive nitrogen atmosphere at three different bias voltages: U _B ?=??? 25, ?50 and ?100 V. The coatings were characterized in terms of compositional, microstructural and mechanical properties. Microstructure of the coatings was investigated with the aid of X-ray diffraction in glancing angle mode, which revealed information on phase composition, crystallite size, stress-free lattice parameter and residual stress. Mechanical properties were deduced from nano-indentation measurements. The residual stress in all the coatings was compressive and increased with increasing bias voltage in a manner similar to that reported in literature for Ti–Al–N coatings deposited with CAE. The bias voltage was also found to significantly influence the phase composition and crystallite size. At ?25 V bias voltage the coating was found in single phase fcc-(Ti, Al)N and with relatively large crystallites of ~ 9 nm. At higher bias voltages (?50 and ?100 V), the coatings were found in dual phase fcc-(Ti, Al)N and fcc-AlN and the size of crystallites reduced to approximately 5 nm. The reduction of crystallite size and the increase of compressive residual stress with increasing bias voltage both contributed to an increase in hardness of the coatings.     

Catalyst-free synthesis of high elongation degradable polyurethanes containing varying ratios of isosorbide and polycaprolactone: physical properties and biocompatibility

Biocompatible and biodegradable polyurethanes were prepared with fixed aliphatic diisocyanate level and varying ratios of isosorbide, and PCL diol via a simple one-shot polymerization without a catalyst. The successful synthesis of the polyurethanes was confirmed by gel permeation chromatography, ¹H-nuclear magnetic resonance and Fourier transform-infrared spectroscopies and the thermal properties were determined by differential scanning calorimetry and showed glass transition temperatures of around 30–35 °C. The degradation tests were performed at 37 °C in phosphate buffer solution (approx. pH 7.3) and showed a mass loss of around 5 % after 12 weeks, except for the polymer with the highest isosorbide content which showed an initial rapid mass loss. The in vitro cytocompatibility test results following culture of osteoblasts on the polymer surface showed that relative cell number on all of the polyurethane films after 5 days of cultured on polymer films was lower compared to the proliferation rate on the optimized tissue culture plastic. These polymers offer significant promise due to the simplicity of the synthesis and the controlled degradation.     

Antibacterial and tribological properties of TaN–Cu,TaN–Ag,and TaN–(Ag,Cu) nanocomposite thin films

In this study, attempts were made to prepare and characterize TaN–(Cu,Ag) nanocomposite films by using a hybrid approach combining reactive co-sputtering and rapid thermal annealing at various temperatures to induce the formation of soft metal particles in the matrix or on the surface. The films’ properties and their antiwear and antibacteria behaviors were compared with those previously studied TaN–Cu and TaN–Ag films. All three types of TaN–(soft metal) films showed good tribological properties due to the lubricious Ag and/or Cu layers. It was also found that the antibacteria efficiency of TaN–(Ag,Cu) film against either Escherichia coli or Staphylococcus aureus could be much improved, comparing with that of TaN–Ag or TaN–Cu film. The synergistic effect due to the coexistence of Ag and Cu is obvious. The annealing temperature used to develop TaN–(Cu,Ag) films with good antibacterial and antiwear behaviors could be as low as 250 °C. The lowering of the annealing temperature made these films applicable onto low-melting-point materials, such as polymers.     

Quantification of silver ion release, in vitro cytotoxicity and antibacterial properties of nanostuctured Ag doped TiO2 coatings on stainless steel deposited by RF magnetron sputtering

Surface treatments on biomaterials using several methods have greatly reduced the in vivo bacterial attachment, surface colonization and formation of biofilm. In this study, the effect of silver (Ag) ion release against in vitro antibacterial activity and cytotoxicity of 1-4wt% Ag doped titania (TiO₂) thin film coatings were evaluated. These coatings were deposited for 1-6 h onto stainless steel substrate (SS) using (radio frequency) RF magnetron sputtering technique. The coatings predominantly in the crystalline anatase phase were configured using X-ray Diffraction (XRD). Scanning electron microscopy (SEM) observation showed the presence of Ag-TiO₂ nanoparticles of less than 100 nm in all the coated surfaces confirming the formation of nanostructured coatings. An initial rapid release, followed by a sustained lower release of Ag ion concentration was measured between 0.45 and 122 ppb when all the coated substrates immersed in Phosphate Buffered Saline (PBS) for 1-10 days. The obtained concentration was less than the maximum toxic concentration for human cells; yet achieved antibacterial concentration, sufficient to kill or inhibit the growth of bacteria. In vitro cytotoxicity results have indicated that 1-4 wt% of Ag doped TiO₂ coatings had no adverse effect on mouse fibroblast proliferation, confirming its cytocompatibility. The antibacterial assessment was performed on 1 and 2 wt% Ag-TiO₂ coatings using Staphylococcus aureus (S. aureus) whereby significant antibacterial activity was observed in 2 wt% Ag-TiO₂ coatings.     

In situ formation of Al2O3–ZrO2–Y2O3 composite ceramic coating by plasma electrolytic oxidation on ZAlSi12Cu3Ni2 alloy

In situ formation of Al₂O₃–ZrO₂–Y₂O₃ composite ceramic coating on ZAlSi12Cu3Ni2 aluminum alloy was successfully prepared by plasma electrolytic oxidation (PEO) technology in a zirconate electrolytic solution. The morphologies, phase components, the thermal diffusion coefficient and thermal conductivity of the composite coatings were investigated by scanning electron microscope, energy dispersive spectroscopy, X-ray diffraction and laser pulse tester. The results indicate that the composite coatings are relatively dense and uniform in thickness, and predominantly composed of Al₂O₃, c-Y0.15Zr0·85O1·93Vo0·07(Vo-oxygen vacancies), monoclinic ZrO₂ (m-ZrO₂) and littleY₂O₃. The composite coatings exhibit a gradient distribution in phase component from the surface to the inner part. With the increase of the applied voltage, the micropores, the discharges products, thickness and the ZrO₂ content of the composite coatings increase. With the oxidation time increasing, the surface of coating generates oxide ceramic particles around the holes and accumulates repeatedly. The content of zirconium is the higher on the surface and interface. The content of Al is less and it shows that the ceramic coating contains mainly the zirconium oxide. This is attributed to the presence of micropores and microcracks, plus the extremely fine grain size and the presence of an amorphous phase. When considered in conjunction with the possible thickness range, it’s clear that this PEO coatings offer considerable promise as thermal barriers.