Scratch and wear resistance of hydrophobic CeO2-x coatings synthesized by reactive magnetron sputtering

CeO_2-x coatings were deposited under variable oxygen flow ratios (%f_O2) onto Si substrates by reactive magnetron sputtering. Nanoindentation testing revealed an increase in the hardness, elastic modulus, H/E and H³/E² ratio with increasing oxygen flow ratio, which in turn increased the adhesion and tribological performance of the coatings. Scratch testing yielded the highest critical load (L_C2 = 28.8 N) and CPR_S = 103 for the coating deposited with the highest oxygen flow ratio (57 %f_O2). Cracking events during scratch testing were initiated by tensile forces behind the scratch stylus, which led to the formation of semi-circular ring cracks. As the normal load increased, transverse cracks emerged extending outwards from the scratch track towards the edge causing the exposure of substrate. Beyond L_C2, severe spallation of the CeO_2-x coatings led to coating failure. Furthermore, the specific wear rates of the CeO_2-x coatings were determined to be within the ~10⁻¹⁵ m³/Nm range influenced by three-body abrasive wear. In-depth analyses from scratch and wear data indicates that these coatings possess good adhesion and durability.     

Morphological investigation of synthetic poly(amic acid)/cerium oxide nanostructures

A new kind of intermediate hybrid nanocomposites (NCs) composed of poly(amic acid) (PAA) and surface modified ceria nanoparticles (NP)s had been prepared by sonochemical assisted synthesis. The PAA containing pendent benzamide units had been synthesized by the reaction of 3,5‐diamino‐N‐(4‐hydroxyphenyl) benzamide and benzene‐1,2,4,5‐tetracarboxylic dianhydride through polycondensation reaction. The structure of the prepared PAA was studied by spectroscopic techniques. The surface modifications of ceria NPs were achieved by using hexadecyltrimethoxysilane. Results of FTIR analysis demonstrated that the aliphatic chains have been covalently bonded to the surface of the CeO₂ NPs. PAA/CeO₂ NCs with different contents including 4, 8, and 12 wt% of CeO₂ NPs was prepared by using sonochemical method. Characterization with FTIR, powder X‐ray diffraction, field emission scanning electron microscopy (FE‐SEM), transmission electron microscopy (TEM), and atomic force microscopy (AFM) confirmed the success in synthesis of NCs with well dispersion properties. XRD analysis results showed that the obtained NCs displayed the crystalline nature of ceria NPs and the amorphous character of PAA matrix. The particles size of ceria NPs in NCs are about 50–70 nm as characterized by FE‐SEM, TEM, and AFM analyses. This work demonstrates the application of intermediates as new matrices for preparation of hybrid nanostructures. POLYM. ENG. SCI., 55:2339–2348, 2015. © 2015 Society of Plastics Engineers     

Role of Sn on the adhesion in Cu–Sn alloy-coated steel–rubber interface

Cu–Sn coatings with varying Sn content were deposited on steel substrate by immersion route and the effect of variation of Sn content and the substrate roughness on the interfacial adhesion strength of Cu–Sn-coated steel substrates vulcanized with styrene butadiene rubber were investigated. The surface roughness of the coatings did not vary compared to pristine steel substrate with change in Sn weight% in the coatings. The coated surfaces exhibited bare spots or deep trough as micro-discontinuities in the coatings, where formation of Fe₂O₃ was evident from SEM-EDS, AES, and XPS analysis. Microstructural study of the coating cross-section and coating-substrate interface by transmission electron microscopy of cross-sectioned samples revealed inadequate penetration of coating inside these troughs. Peel test carried out on the Cu–Sn-coated steel–rubber joints showed mixed mode i.e. adhesive and cohesive mode of interfacial fracture irrespective of the coating composition. The peel test further indicated higher interfacial adhesion strength for Cu–Sn-coated samples than pure Cu-coated samples, with an optimum adhesion strength for the coatings containing 3–4?wt.% Sn.     

Protein corona: implications for nanoparticle interactions with pulmonary cells

Background

We previously showed that cerium oxide (CeO₂), barium sulfate (BaSO₄) and zinc oxide (ZnO) nanoparticles (NPs) exhibited different lung toxicity and pulmonary clearance in rats. We hypothesize that these NPs acquire coronas with different protein compositions that may influence their clearance from the lungs.

Methods

CeO₂, silica-coated CeO₂, BaSO₄, and ZnO NPs were incubated in rat lung lining fluid in vitro. Then, gel electrophoresis followed by quantitative mass spectrometry was used to characterize the adsorbed proteins stripped from these NPs. We also measured uptake of instilled NPs by alveolar macrophages (AMs) in rat lungs using electron microscopy. Finally, we tested whether coating of gold NPs with albumin would alter their lung clearance in rats.

Results

We found that the amounts of nine proteins in the coronas formed on the four NPs varied significantly. The amounts of albumin, transferrin and α-1 antitrypsin were greater in the coronas of BaSO₄ and ZnO than that of the two CeO₂ NPs. The uptake of BaSO₄ in AMs was less than CeO₂ and silica-coated CeO₂ NPs. No identifiable ZnO NPs were observed in AMs. Gold NPs coated with albumin or citrate instilled into the lungs of rats acquired the similar protein coronas and were cleared from the lungs to the same extent.

Conclusions

We show that different NPs variably adsorb proteins from the lung lining fluid. The amount of albumin in the NP corona varies as does NP uptake by AMs. However, albumin coating does not affect the translocation of gold NPs across the air-blood barrier. A more extensive database of corona composition of a diverse NP library will develop a platform to help predict the effects and biokinetics of inhaled NPs.

     

Mechanistic investigation of aluminide coating formation by low-pressure chemical vapor deposition method on NiCoCrAlY coating in presence of nickel-ceria composite layer

In this study, a hybrid coating comprised of NiCoCrAlY fabricated by HVOF method, Ni–CeO₂ composite coated by electrodeposition, and aluminide coating applied by low pressure chemical vapor deposition (LPCVD) method are investigated. To elucidate the formation process of aluminide coating, the microstructure and properties of the applied coatings were examined by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD), and EDS analyses. It was concluded that the desired β-NiAl phases are uniformly created within a single step on the surface. Furthermore, with the extending of the coating duration from 2 to 4 h, the thickness of the aluminide coating was increased from 14 to 25 μm. The thickness values were increased even further in the presence of Ni–CeO₂ coating, where the growth mechanism was also changed. Within 4 h, a coating with a thickness of roughly 50 μm was obtained. Moreover, in the presence of Ni–CeO₂ coating, it was observed that the inward diffusion of aluminum was predominant at the beginning of the process, whereas with longer processing durations, the outward diffusion of the nickel becomes dominant instead.     

Adhesion of extrusion‐coated polymer sealing layers to a fiber‐based packaging material with an atomic layer deposited aluminum oxide surface coating

Adhesion of extrusion‐coated polymer sealing layers on an atomic layer deposited (ALD) aluminum oxide (Al₂O₃) surface coating was investigated with a view to gain information on the applicability of ALD deposited barrier layers in fiber‐based packaging materials. The polymers used for the sealing layer were low density polyethylene (LDPE), polyethylene terephthalate (PET), and polylactide (PLA). They were extrusion‐coated onto the ceramic side of paper/PET/Al₂O₃ substrates, where the Al₂O₃ layer was a few tens of nanometers thick. According to the results, good adhesion was obtained for LDPE coating, whereas the other coatings showed a considerable lack of adhesion. Presumably, the oxidation faced by LDPE in the air gap of the extrusion‐coating process was able to create an extensive number of reactive sites that strongly bonded with the hydroxyl groups on the oxide surface of the substrate. With the PET and PLA coatings, such oxidation did not occur and the adhesion obtained remained at a relatively poor level. With all of the coatings, the adhesion levels were improved using corona discharge equipment as a pretreatment prior to the extrusion‐coating process. POLYM. ENG. SCI., 52:1985–1990, 2012. © 2012 Society of Plastics Engineers     

Characterization and property of bifunctional Zn-incorporated TiO2 micro-arc oxidation coatings: The influence of different Zn sources

In the present work, Zn-incorporated TiO₂ coatings are prepared through a one-step micro-arc oxidation (MAO) method on a grade 4 pure titanium with the addition of either Na₂Zn-EDTA solution or ZnO nanoparticles (NPs) as Zn sources. The microstructural features of both Zn-incorporated TiO₂ coatings were systematically examined. It is revealed that different Zn sources result in significant difference of phase component, chemical state, composition and morphology between the resultant Zn-incorporated MAO coatings. Zn species could be present as ZnO and Zn(OH)₂ in the coating when Na₂Zn-EDTA was used as Zn source whereas the presence of ZnO nano-clusters is obvious on the coating surface with ZnO NPs as Zn source. The addition of ZnO NPs during the MAO process also leads to a lower Zn content of the resultant coating, which is more defective with increased thickness in comparison to that of Na₂Zn-EDTA. Further, antibacterial property and osteogenic activity of both Zn-incorporated coatings were examined. Both Zn-incorporated coatings exhibit favourable bacterial inhibition ability and bone formability, suggesting the successful synthesis of bifunctional coatings through the facile one-step micro-arc oxidation method.     

Heat‐resistant hydrophobic–oleophobic coatings

Thermally and chemically durable hydrophobic oleophobic coatings, containing different ceramic particles such as SiO₂, SiC, Al₂O₃, which can be alternative instead of Teflon, have been developed and applied on the aluminum substrates by spin‐coating method. Polyimides, which are high‐thermal resistant heteroaromatic polymers, were synthesized, and fluor oligomers were added to these polymers to obtain hydrophobic–oleophobic properties. After coating, Al surface was subjected to Taber‐abrasion, adhesion, corrosion, and thermal tests. The effects of the particle size of ceramic powders, organic matrix, and heat on the coating material were investigated. Coating material was characterized by FTIR spectrophotometer. Surface properties and thermal resistance of the coating materials were investigated by SEM and TGA analyses. After thermal curing, contact angles of these coatings with H₂O and n‐hexadecane were measured. It was observed that coatings like ceramic particles are more resistant against scratch and abrasion than the other coatings. Also, they are harder than coatings, which do not include ceramic particles. It was seen that coatings, containing Fluorolink D10H, have high‐contact angles with water and n‐hexadecane. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2386–2392, 2006     

Analysis of corrosion protection behavior of Al2O3-TiO2 oxide ceramic coating on carbon steel pipes for petroleum industry

Corrosion is the deterioration of materials by chemical interaction with their environment. In the oil and gas industry, corrosion of the pipelines and other equipment is one of the leading causes of failure and the corrosion-related costs are very high. Hence, corrosion protection is an essential requirement. In this study, the objective is to analysis of the corrosion protection behavior of spray Alumina-Titania (Al₂O₃-TiO₂) oxide ceramic coating on carbon steel pipes C45 using two different thermal spray coatings processes. These two different thermal spraying coating, High velocity oxy-fuel (HVOF) and plasma thermal spraying techniques can be used instead of extensive treatment by expensive chemical formation of coatings on pipelines and equipment to improve or restore a component's surface properties or dimensions and to protect them from corrosion. Molten or semi-molten ceramic composite powders are sprayed on the surface in order to produce a dense coating layer. FESEM of coated samples showed that a high temperature of plasma coating method end in melting the ceramic powders and creation of completely melted regions on the coated samples’ surface compared to HVOF coating techniques. Corrosion testing of coated samples in seawater (3.5% NaCl) was conducted within 30 days. Electrochemical impedance spectroscopy (EIS) as well as potentiodynamic polarization outcomes represented that the corrosion resistivity of plasma coating technique for this type of ceramic composite is better than HVOF coating technique. However, both types of coating techniques are protecting the substrate against seawater.     

Hard machining performance of PVD AlCrN coated Al2O3/TiCN ceramic inserts as a function of thin film thickness

In the present work, AlCrN coating was deposited on Al₂O₃/TiCN ceramic inserts with varying thin film thickness using physical vapor deposition (PVD) technique. The thickness, surface morphology, chemical composition, hardness and adhesion strength of the coating to the substrate were characterized by field-emission scanning electron microscopy (FESEM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), micro-indentations and scratch tests respectively. The machining performance of uncoated and coated tools was investigated in hard turning of AISI 52100 steel (62 HRC) under dry environment. The cutting behavior was analyzed in terms of machining forces, tool temperature, wear, friction and chip morphology. Further, a 3D finite element model with hybrid friction criterion has been adopted to support the experimental findings. The results revealed that coating/substrate adhesion and edge radius were the deciding criteria for the machining performance of coated tools with 3 µm coating thickness tool exhibiting best turning performance on Al₂O₃/TiCN mixed ceramic insert.     

Transparent and durable SiO2‐containing superhydrophobic coatings on glass

We fabricated novel superhydrophobic coatings based on SiO₂ nanoparticles combined with NH₂‐terminated silicone (SN₂) or SN₂‐modified polyurethane (SN₂‐prePU) by alternately spin‐coating them onto glass slides. The final fabricated surface contained SN₂/SiO₂ or SN₂‐prePU/SiO₂ bilayers. The conditions of spin‐coating method were also explored. SN₂‐prePU with different SN₂/prePU molar ratios were synthesized to study the influence of SN₂ ratio on the water contact angles of ultimate spin‐coated surfaces. The surface was found to be tunable from hydrophobic to superhydrophobic by choosing SN₂‐prePU with different SN₂/prePU molar ratios or SN₂ content. Water droplets easily rolled off on these superhydrophobic surfaces. Surfaces coated with SN₂/SiO₂ bilayers showed better transparency, whereas surfaces coated with SN₂‐prePU(2 : 1)/SiO₂ bilayers exhibited better durability. Droplets of varied pH were prepared to test the anti‐wettability of the coatings. Results showed that the as‐coated surfaces had stable superhydrophobicity to droplets with pH values ranging from 1 to 14. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41500.     

Fabrication and properties of dense α-cordierite glass-ceramic coating on porous BN/Si2N2O ceramic

α-Cordierite glass-ceramic coating was fabricated on the porous BN/Si₂N₂O ceramic by glass-ceramic method. The effect of the heating temperature on the phase composition, microstructure, mechanical properties, water resistance and dielectric properties of the coatings was investigated. A large amount of α-cordierite precipitated from the glass phase when the heating temperature was 1050?°C and the content of α-cordierite in the coating increased with increasing the heating temperature. The resulting α-cordierite glass-ceramic coatings had a good wettability and adhesion with the porous ceramic substrate. The coating/substrate interface was continuous without defects. When the heating temperature was 1050–1200?°C, the resulting coatings possessed positive mechanical properties and good water resistance due to the high densification. And the dielectric constant and loss tangent of the coated samples prepared at 1050–1200?°C were 4.1–4.3 and 0.005–0.01 respectively in the frequency of 21–36?GHz.     

Ion beam assisted electron beam vacuum deposition of antireflective SiO2 coating on MgAl2O4 spinel

In this paper, the electron beam vacuum coating method was used to coat a SiO₂ film on an MgAl₂O₄ spinel substrate. The thickness of the coating was aimed to be 925 nm based on the physics of the antireflection coatings. Atomic force microscope images revealed that the coated silica was 880 nm thick, which is close to the aimed theoretical thickness and had 2.11 nm roughness. It could enhance the transparency of the spinel substrate by being coated on it. The infrared transmittance of the sample coated with SiO₂ film in the range of 3700 nm-4800 nm was measured by a Fourier transform infrared spectrometer and reached 92.5% to 78.5%, which was about 2%–4% higher than that of MgAl₂O₄ spinel. In addition, it was discovered that the bonding force between the coating and the substrate is determined to be about 200 MPa. The results of this study can be used for further precise design and production of antireflection coatings on the transparent materials that need more transparency.     

Effect of ceria and zirconia nanoparticles on corrosion protection and viscoelastic behavior of hybrid coatings

Organic–inorganic hybrid nanocomposite coatings contain inorganic particles that are dispersed in organic phase in nanometric dimensions. Ceria and zirconia colloidal dispersions are uniformly distributed in the epoxy silica-based hybrid nanocomposite by sol–gel method and coated on 1050 aluminum alloy substrate with spin-coating technique. The hybrid sol is prepared by organic–inorganic precursors formed by hydrolysis and condensation of 3-glycidoxypropyltrimethoxysilane and tetraethylorthosilicate (TEOS) in acidic solution using bisphenol A as networking agent and 1-methylimidazole as initiator in the presence of various ratios of ZrO₂ and CeO₂ colloidal nanoparticles. Particle size distribution, surface morphology and inorganic components distribution were determined by scanning electron microscopy (SEM) and EDXA techniques. SEM and Si, Zr, Ce mapping micrographs proved the uniform distribution of nanoparticles in the coatings. Transmission electron microscopy indicated that the nanoparticles dimension stay at the nanoscale level. The glass transition temperature (T _g) and loss properties (damping) of coatings were evaluated by dynamic mechanical thermal analysis. The corrosion protection of the coatings on the 1050 AA substrate was studied by potentiodynamic measurements. The results indicated that by introducing ceria nanoparticles in 1:1 molar ratio to TEOS in coating composition, corrosion protection was improved. However, the simultaneous presence of two nanoparticles (i.e., ceria and zirconia in 1:1 molar ratio) in the coating compositions increased the corrosion protection efficiency up to 99.8 %. The multiple glass transitions and shifting to higher and wide range of temperatures by adding ceria and zirconia nanoparticles indicated a better network interaction between inorganic nanoparticles and organic molecular chains which also led to better corrosion protection of the coating in this composition.     

Production of Re doped La2Zr2O7 based TBCs and numerical analysis of their use on IC engine piston surface

In this study, first of all, a metallic bond layer was coated on the metal substrate using the HVOF method. Then, Gd and Yb doped La₂Zr₂O7 powders, which were specially produced to obtain a low thermal conductivity value, were coated on the metallic bond layer by atmospheric plasma spraying method. The coatings were produced in single-layer and double-layer designs using YSZ as the buffer layer. In the microstructure analysis, it was observed that the coatings exhibited the characteristic microstructure properties of the materials produced by atmospheric plasma spraying method. In the phase analysis, it was found that the Gd and Yb doped La₂Zr₂O₇ was in the form of defect fluorite type structure after plasma spraying. The thermal conductivity of the YSZ coating ranged from 0.88 to 1.00 W/mK, while the thermal conductivity of the doped La₂Zr₂O₇ coatings was measured between 0.38 and 0.68 W/mK. Especially, the lowest thermal conductivity values were obtained in the double-layer Gd doped coating. As a result of modeling these coatings on the piston surface of a diesel engine using the finite element method, it was found that the maximum and minimum surface temperatures of the pistons increased by 69% and 60%, respectively. There was also a reduction of up to 6.5% in the temperature of the piston substrate surface.     

Effect of MoS2/PTFE coatings on performance of Si3N4/TiC ceramics in dry sliding against WC/Co

To enhance the tribological performance of Si₃N₄/TiC ceramics, MoS₂/PTFE composite coatings were deposited on the ceramic substrate through spraying method. The micrographs and basic properties of the MoS₂/PTFE coated samples were investigated. Dry sliding friction experiments against WC/Co ball were performed with the coated ceramics and traditional ones. These results showed that the composite coatings could significantly reduce the friction coefficient of ceramics, and protect the substrate from adhesion wear. The primary tribological mechanisms of the coated ceramics were abrasive wear, coating spalling and delamination, and the tribological property was transited from slight wear to serious wear with the increase of load because of the lower surface hardness and shear strength. The possible mechanisms for the effects of MoS₂/PTFE composite coatings on the friction performance of ceramics were discussed.     

Plasma-sprayed TiO2 coatings: Hydrophobicity enhanced by ZnO additions

Titanium dioxide (TiO₂) powder mixed individually with 10 and 30 weight percentage (wt%) ZnO was thermally sprayed onto a grade B API 5 L carbon steel substrate by atmospheric plasma spraying. The effect of the addition of ZnO (10 wt% and 30 wt%) on the microstructures and wettability properties of the TiO₂/ZnO coatings was investigated. The characterization of the coatings was carried out using scanning electron microscopy, X-ray diffraction (XRD), laser confocal microscope, and sessile droplet system. The XRD analysis of the coating revealed that the anatase phase of TiO₂ in the powder state transformed into rutile phases for the produced TiO₂/ZnO coatings. Surface microstructure analysis revealed that the coatings had typical micro-roughened surfaces of plasma spraying products. The coating with 30 wt% ZnO produced a coating with remarkable pores and microcracks compared with the TiO₂ coating and coating with 10 wt% ZnO. Additionally, the increase in the wt% of ZnO increased the surface roughness value of the produced coatings and substantially changed the wettability properties of the TiO₂ coating from hydrophilic to hydrophobic.     

Mussel-inspired catechol-based chemistry for direct construction of super-hydrophilic and waterproof coatings on intrinsic hydrophobic surfaces

Super-hydrophilic coatings are useful in many applications such as agricultural greenhouses. However, the direct modification of super-hydrophilic coatings on intrinsic hydrophobic surfaces is still a challenge, particularly without any pretreatment. Here, highly transparent super-hydrophilic and waterproof coatings on intrinsic hydrophobic surfaces were prepared via layer-by-layer (LbL) assembly catechol-grafted polymer-branched poly(ethylenimine) (bPEI)-3-(3,4-dihydroxyphenyl)propionic acid (denoted as C) and poly(acrylic acid) (PAA)-dopamine (denoted as D) inspired by the mussel. The catechol-functionalized polymer facilitates a mechanically robust coating that is tightly attached to the surface of the intrinsic hydrophobic polymers. This gives the coating excellent antifogging ability with a lowest contact angle of 0°. These coatings also demonstrated excellent stability after cross-linking with Fe³⁺ or alkali species. The super-hydrophilic and waterproof coatings on intrinsic hydrophobic surfaces can also be prepared by the spray method. The super hydrophilic coating exhibits favorable antifogging ability, making it potentially useful in numerous applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48013.     

Corrosion Resistance of MgZn Alloy Covered by Chitosan-Based Coatings

Chitosan coatings are deposited on the surface of Mg20Zn magnesium alloy by means of the spin coating technique. Their structure was investigated using Fourier Transform Infrared Spectroscopy (FTIR) an X-ray photoelectron spectroscopy (XPS). The surface morphology of the magnesium alloy substrate and chitosan coatings was determined using Scanning Electron Microscope (FE-SEM) analysis. Corrosion tests (linear sweep voltamperometry and chronoamperometry) were performed on uncoated and coated magnesium alloy in the Hank’s solution. In both cases, the hydrogen evolution method was used to calculate the corrosion rate after 7-days immersion in the Hank’s solution at 37 °C. It was found that the corrosion rate is 3.2 mm/year and 1.2 mm/year for uncoated and coated substrates, respectively. High corrosion resistance of Mg20Zn alloy covered by multilayer coating (CaP coating + chitosan water glass) is caused by formation of CaSiO₃ and Ca₃(PO₄)₂ compounds on its surface.     

The influence of multilayer structure on mechanical behavior of TiN/TiAlSiN multilayer coating

Nitride coatings have been generally applied on light alloys like titanium and aluminium to promote their multiple performances, including hardness, thermal stability and wear resistance. In this work, TiAlSiN/TiN multilayered (ML) coating and TiAlSiN single-layer (SL) coating were deposited on TC18 (Ti5Al5Mo5V1CrFe) alloy by Multi-arc ion plating technique. The microstructure and chemical composition of the coatings were evaluated by SEM, XRD and XPS. Additionally, hardness, adhesion and wear resistance were measured through nanoindentation, scratch spectrometer and ball-on-disk tribometer. The results present that both ML and SL coating contain three main phases of TiN, Al₂O₃ and Si₃N₄. Nevertheless, the adhesion of ML coating is 62.4 N, compared to that of the SL coating is 51.8 N. The parameter H³/E² as an indication of plastic deformation to evaluate wear resistance shows that the ML coating has high hardness and high toughness concurrently. The tribological study indicated that the wear rate of the ML coated specimen was 1/7 of the SL coated counterpart.