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The influence of micro-sized Cr 2 O 3 particles on the corrosion, mechanical and thermal control performance of plasma electrolytic oxidation coated Mg was studied. More contents of Cr 2 O 3 particles were embedded into phosphate containing PEO coatings compared with coatings produced from silicate based electrolytes, resulting in green coatings with enhanced thermal control and mechanical property. The existence of particles has slightly improved the corrosion resistance and hardness of the coating. It was found that the absorptance of the coating was increased if higher concentration of Cr 2 O 3 particles is incorporated into the layer, which is probably ascribed to low band gap of Cr 2 O 3. [ABSTRACT FROM AUTHOR]

Abstract Self-healing coatings inspired by biological systems possess the ability to repair physical damage or recover functional performance with minimal or no intervention. This article provides a comprehensive and updated review on the advantages and limitations associated with common autonomous and non-autonomous self-healing mechanisms in protective organic coatings used for anti-corrosion purposes. The autonomous healing mechanisms are often enabled by embedding polymerizable healing agents or corrosion inhibitors in the coating matrices. For non-autonomous mechanisms, the healing effects are induced by external heat or light stimuli, which trigger the chemical reactions or physical transitions necessary for bond formation or molecular chain movement. [ABSTRACT FROM AUTHOR]

Abstract: A thin layer of Pd deposition on the surface significantly improves the corrosion resistance of 316L stainless steel in 0.5molL−1 H2SO4 +2ppm F− solution at 80°C. Compared with the air-formed passive film, the passive film formed in the stainless steel/Pd couple contains more Cr, Cr(OH)3 and Fe3O4 and less point defects, which provides better protection to the stainless steel substrate. The interfacial contact resistance of the stainless steel surface is also decreased. The Pd plated stainless steel is a potential material for bipolar plates in proton exchange membrane (PEM) fuel cells. [Copyright &y& Elsevier]

This paper investigates applicability of polysiloxane/MoS 2 lubricating coatings in low-earth orbit (LEO). Results show that wear resistance of the polysiloxane lubricating coatings is related to R/Si value and epoxy group of the epoxy-functionalized polysiloxanes resin. The prepared polysiloxane lubricating coatings exhibited better wear resistance than existing organic coating due to the synergistic effect of low surface energy polysiloxane and MoS 2. Furthermore, the polysiloxane coating achieved excellent AO resistance ascribe to the generation of SiO 2 protective layer. The thickness of SiO 2 layer was only 60 nm, which has no effect on vacuum tribological properties of the polysiloxanes lubricating coating. After AO irradiation, the polysiloxane lubricating coating maintained a low friction coefficient and excellent wear resistance under the vacuum condition. [Display omitted] [ABSTRACT FROM AUTHOR]

• An lubricating coating based on the solid-liquid dual lubrication was achieved, just as a liquid water serves as the lubricant when you skating. • The S8-POSS melted and covered the worn surface, resulting in a liquid film between the coating and counterpart. • The friction coefficient and wear rate of the composite coating with 20 wt.% S8-POSS decreased under high temperature. In order to improve the high-temperature tribological properties, the composite lubricating coating with unique structure and properties was designed based on the solid-liquid composite lubrication just as liquid water serves as the lubricant when you skating on ice. In this work, the synthetic sulfur-polyhedral oligomeric silsesquioxane (S8-POSS) were introduced into the polyamide-imide/polytetrafluoroethylene (PAI/PTFE) lubricating coating and their wear resistance at different temperatures were investigated. As a result, the friction coefficient decreased obviously as the temperature rises, but the wear rates trend to rise. Importantly, compared with PAI/PTFE coating, the friction coefficients and wear rates at high temperatures significantly reduced with the increase of the amount of S8-POSS. It can be concluded that high temperature result in S8 melting and gathering in the wear tracks during the friction process, forming solid-liquid composite lubrication, which significantly reduces the friction coefficient. Moreover, the presence of POSS improves the load-bearing capacity of the coating, which finally imparts the composite coatings with outstanding tribological properties under high temperature. [ABSTRACT FROM AUTHOR]

• The thickness and mass loss of OMPOSS reinforced coating decreased much lower than the PAI/PTFE coating after AO exposure. • The surface of OMPOSS-containing coating after AO attack shows a SiO 2 protective layer that result from the oxidation of POSS. • The lifetime of OMPOSS modified coatings increased significantly after AO exposure compared with that of PAI/PTFE coatings. The atomic oxygen (AO) in the low Earth orbit (LEO) severely damages the traditional polymer materials used for surface protective coatings in spacecraft. To solve this problem, organic-inorganic composite coatings with excellent AO resistance were prepared by covalently grafting octa- and mono-amino polyhedral oligomeric silsesquioxane (OMPOSS) onto the polyamide-imide (PAI) matrix in this paper. The pristine PAI/PTFE and OMPOSS/PAI/PTFE composite coatings before and after AO exposure were detail investigated by Fourier transform infrared spectrometry, X-ray diffraction, and X-ray photoelectron spectroscopy. Compared with the pristine PAI/PTFE coating, the mass loss of OMPOSS/PAI/PTFE coating reduced by about 80% significantly. The findings indicate that AO attack can lead to the oxidation of the OMPOSS on the surface of the composite coatings, furthermore generate a SiO 2 passivating layer. The formation of the passivating layer can effectively prevent further erosion and degradation of the underlying composites. In addition, the wear tests prove that the octa- and mono-amino POSS impart the PAI/PTFE coating with outstanding tribological properties under AO irradiation. Therefore, such OMPOSS-containing PAI/PTFE composite coatings have great potential for the application in the space environment. [ABSTRACT FROM AUTHOR]

Bonded lubricating coatings for spacecraft are subject to the combined effect of the low-earth orbit environment, ground environment and mechanical wear, making it difficult to meet long-life and high-reliability requirements. In this study, Polydimethylsiloxane (PDMS)-modified polyamide-imide (PAI) /molybdenum disulfide (MoS 2) coatings were prepared using a self-stratifying strategy. The structural and tribological performance changes of coatings after atomic oxygen (AO) irradiation were investigated. The results showed that the PDMS segments improved the AO erosion resistance due to the inorganic layer produced on the surface of coating. The structural integrity of the binder and lubricant decreased the effect of AO erosion on the tribological performance of lubricating coatings. The PDMS-PAI/MoS 2 coating have application prospects in the field of lubricating coating for spacecraft. [ABSTRACT FROM AUTHOR]

We compared the tribological behaviors and the tribo-chemical mechanisms of AlMgB 14 -TiB 2 coatings and B 4 C coatings under lubrication with molybdenum dialkyl-dithiocarbamate (MoDTC). In unidirectional sliding contact, the boride coatings exhibited an unstable tribological performance, while the friction coefficients of these coatings maintained a very steady low level in reciprocating sliding contact. No severe wear occurred to the boride coatings. However, significant abrasive wear was observed on the steel balls rubbing against the boride coatings under unidirectional sliding contact. Analysis indicated incomplete dissociation of MoDTC at coating wear tracks and no formation of MoS 2 tribofilms on steel counterfaces in the case of unidirectional sliding contact, whereas well-developed MoS 2 tribofilms were formed on AlMgB 14 -TiB 2 coatings under reciprocating sliding condition. • The tribological behaviors and the tribo-chemical mechanisms of AlMgB 14 -TiB 2 coatings and B 4 C coatings under lubrication with molybdenum dialkyl-dithiocarbamate were compared. • In unidirectional sliding contact, the boride coatings exhibited an unstable tribological performance. the friction coefficients of these coatings maintained a steady low level in reciprocating sliding contact. • No severe wear occurred to the boride coatings. • The tribo-chemical processes for the boride coatings were found to be closely related to the sliding contact configurations and the surface chemical states of the boride coatings. [ABSTRACT FROM AUTHOR]

Highlights • Sodium dodecyl sulphate (SDS) is found to be an efficient Mg corrosion inhibitor. • Inhibitors are adsorbed on AlMn intermetallics to suppress micro-galvanic corrosion. • Large amounts of inhibitors are physically adsorbed on corroded α-Mg region. • A passive hydrophobic corrosion layer is formed to kinetically inhibit corrosion. • Adsorption of SDS on Mg surface follows Langmuir adsorption isotherm. Abstract The inhibition mechanism of a high-efficiency corrosion inhibitor (sodium dodecyl sulfate, SDS) is unveiled and the strategy to design effective inhibitors for Mg alloys is suggested. It was found that SDS is chemically absorbed on the cathodic intermetallics to inhibit micro-galvanic corrosion. Anodic Mg dissolution is also kinetically suppressed by physisorption of SDS since the long hydrophobic tail of the surfactant contributes to building up a protective corrosion layer. Utilization and synthesis of such green inhibitors can pave the way for a wider range of applications for Mg alloy and provide active corrosion protection for coated Mg surfaces. [ABSTRACT FROM AUTHOR]

The corrosion behavior of 40Cr steel under the synergistic effect of plastic tensile strain and UV was investigated. The results show that the corrosion current density increases under the synergistic effect of strain and illumination. Before the formation of the complete rust layer, it is mainly attributed to the variation of the electric double layer, and the strain can enhance the effect of illumination on the electric double layer. After the formation of the complete rust layer, the increase in corrosion current density was mainly related to the change in the inner rust layer composition. The data that has been used is confidential. • Corrosion of 40Cr steel with strain and UV synergism was investigated. • UV reduces the electrical double layer thickness and strain enhances this effect. • The strain-enhanced photo response depends on the γ-FeOOH/γ-Fe 2 O 3 ratio. [ABSTRACT FROM AUTHOR]

Abstract: Nano-TiO2 modified rare earth composite coatings are prepared on 2024 aluminum alloy by brush plating. The composite coating is composed of mainly Ce(OH)3, Ce(OH)4, CeO2 and TiO2, with less cracks and lower porosity. The addition of nano-TiO2 enhances the adhesive strength of the rare earth coating to Al substrate, results in refined coating grains and increases the micro-hardness of the coating. The nano-TiO2 modification obviously improves the corrosion resistance of the rare earth coating. For the composite coating containing 2% TiO2, both the corrosion current density and the impedance are reduced by more than one order of magnitude in contrast to the values for the pure rare earth coating. The higher barrier ability and increased Ce3+ content in the Ce oxides may explain the increase of the corrosion resistance. [Copyright &y& Elsevier]

High entropy ceramics (HECs) films (TiCrZrVAl)N were deposited on Inconel 718 alloys by multi-arc ion plating (MAIP) equipment at different nitrogen flow ratios Rn N 2 /(N 2 + Ar). The effects of Rn (0%, 20%, 50%, 80%, 90%) on the evolution of microstructure, mechanical properties, and tribological properties of films were systematically studied. The films deposited at low Rn exhibited an amorphous structure and smooth cross-section, whereas the films at Rn of 50% and higher showed a face-centered-cubic (FCC) NaCl-type structure with loose columnar cross-section. With the increase of Rn , the content of the N element increased, the Cr element decreased, and other elements (Ti, Zr, V, Al) nearly remained stable. The films' hardness and elastic modulus increased gradually and reached the maximum value of 31.08 ± 1.81 GPa and 387.66 ± 12.49 GPa, respectively, when Rn was 80%. The films deposited at Rn of 20% invalided easily in tribology tests, whereas the films prepared under Rn exceeded 20% presented outstanding wear resistance and obtained the minimum wear rate of 7.4×10-16 m3/(N·m) when Rn is 80%. [ABSTRACT FROM AUTHOR]

The corrosion behavior of 316 stainless steel under the cooperation of plastic tensile stress and UV was investigated. The results showed that the pitting corrosion resistance of the film deteriorates under the combined effect of both factors. Among them, UV illumination could increase the Cr 2 O 3 ratio and reduce the electric field strength, thus improving the pitting corrosion resistance of the film. The plastic tensile stress not only increases the corrosion rate by increasing the defect density but also enhances the photo-induced electric field strength and photocurrent density by decreasing the band gap value and increasing the flat band potential. • The corrosion mechanism under the cooperative effect of stress and UV was studied. • UV illumination modifies the composition and electronic properties of the films. • UV illumination inhibits the dissolution of the passive film and the matrix. • Mechanism of plastic stress enhancing photoelectrochemical properties was proposed. [ABSTRACT FROM AUTHOR]

In this paper, we report an approach for synthesizing "plate-anchor" shaped polyhedral oligomeric silsesquioxane (POSS)-functionalized graphene oxide nanosheets with self-fixing effect via the amide formation. The resultant POSS-GO hybrid has excellent dispersibility in various organic solvents, such as N, N′-dimethylacetamide, pyridine, tetrahydrofuran and carbon tetrachloride. The molecular dynamics simulation (MD) indicates that the POSS-GO nanocomposites can not only react with PI resin by amidation, but also can be self-fixed in the resin through the "plate-anchor" structure, in which the GO nanosheet acts as "plate", the POSS is considered as the "anchor", thus being highly attractive for reinforcing polymer matrix. As expected, only 0.3 wt % addition of POSS-GO into polyimide (PI) can significantly increase the mechanical strength, thermal stability and friction and wear properties of polymer matrix. It is envisioned that the "plate-anchor" shaped composite exhibits outstanding advantages in the field of advanced materials. [ABSTRACT FROM AUTHOR]

The protection mechanism and corrosion behavior of the Pd film-plated stainless steel in a boiling H 2 SO 4 solution were investigated in this paper. Potentiodynamic measurements, galvanic corrosion tests, electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy were conducted to study the electrochemical modification effect of the Pd film on the passivation of stainless steel substrate. The results showed that the Pd film mainly influenced the cathodic process of corrosion. The corrosion potential of the Pd-plated stainless steel was determined by the cathode/anode area ratio. The degradation process of Pd film-plated stainless steel included three stages: stable passivation, slow corrosion and accelerated corrosion. [ABSTRACT FROM AUTHOR]

The friction behavior and the mechanism of DLC films in CO 2 atmosphere are rarely explored, which is a significant obstacle for the potential practical application of DLC films in primarily CO 2 environment. Here, the experiment s and first-principles calculations are performed to simultaneously investigate this theme. We find that DLC films in CO 2 atmosphere exhibit astoundingly low friction coefficient compared with in ambient air and vacuum atmospheres. The XPS and Raman spectrums demonstrate the possibly activation of CO 2 molecule in the shearing interfaces, which may be critical for the low friction of DLC films in CO 2 atmosphere. The calculated results reveal that the lactone groups can easily form during the horizontally chemisorption of CO 2 molecule on the DLC surface, which is energetic and is a favorable process under the interfacial stress. Because of the presence of the lone-pairs of the lactone group, the lactone-terminated surfaces appear to be responsible for the low friction of DLC films in CO 2 atmosphere. The studies may open up the possibility for DLC films usage in Mars applications. [ABSTRACT FROM AUTHOR]

Coagulation is a feasible process to reclaim municipal wastewater, however, the role of coagulation in removing effluent organic matter (EfOM) from underutilized wastewater treatment plants (WWTPs) has not been fully explored. We identified the characteristics of the EfOM from a typical underutilized WWTP (i.e., the ratio of actual capacity to design capacity is 50%–70%), and investigated the performance of coagulation on suspended solids (SS) and dissolved organic matter (DOM) removal. The effluent could even satisfy the highest national standard of China (Class 1 A) for WWTP effluent, as evaluated by the traditional parameters such as SS and chemical oxygen demand (COD). However, the DOM in the EfOM we studied contained considerable biomass-associated products (BAPs), which were dominated by proteins with a molecular weight of approximately 150 kDa. In addition, protein also dominated the DOM after coagulation. Fulvic acid and humic-like acid organics were poorly removed by either AlCl 3 or polyaluminum chloride (PAC) coagulation, even with a dosage as high as 24 mg Al L −1 . Biodegradability was very poor, as the ratio of biological oxygen demand (BOD 5 ) to COD was less than 0.17. After coagulation the typical BAPs, protein and polysaccharide, remained as high as 1.6 mg L −1 and 1.2 mg L −1 respectively. In this study we found coagulation was ineffective for removal of recalcitrant BAPs. [ABSTRACT FROM AUTHOR]

In order to reduce the effects of solar energy on the instruments and the apparatus in the outer space, two different kinds of ceramic coatings were prepared on Ti6Al4V alloys by plasma electrolytic oxidation (PEO) in zirconate electrolytes. The phase composition, microstructure, thickness, and roughness of coatings were examined by XRD, SEM, EDS, thickness measurement gauge, and roughness measuring instrument, respectively. The infrared emissivity and solar absorbance of the ceramic coatings were studied with the UV–vis–NIR spectrophotometer and infrared reflectometer. The results show that ZrO 2 coatings are dense and deep gray–green, and mainly composed of m -ZrO 2 , t -ZrO 2 . In addition, a small amount of TiO 2 , ZrTiO 4, and the amorphous compound containing P exists in the coating. The intrinsic solar absorbance and emissivity of ZrO 2 coatings are 0.92 and 0.76, respectively. The KZr 2 (PO 4 ) 3 coating is rough, thick, and white with the main crystalline of KZr 2 (PO 4 ) 3 . The intrinsic solar absorbance and emissivity of the KZr 2 (PO 4 ) 3 coating are 0.62 and 0.91, respectively. For both coatings, the absorbance decreases while the emissivity increases due to an increase in the real surface area of the coatings by increasing thickness and roughness of the coatings as the PEO time progresses. The porous structure of the KZr 2 (PO 4 ) 3 is proved to be ideal for high emissivity and low absorbance materials with the lowest solar absorbance (0.239), the highest infrared emissivity (0.99), and a corresponding balance temperature of the coating of 276 K. [ABSTRACT FROM AUTHOR]

A Pd-Ni-Mo film was prepared on stainless steel substrate as a novel electrode material for hydrogen evolution reaction catalysis. The surface micro-morphology, chemical composition and microstructure of the Pd-Ni-Mo film were characterizated with SEM, EDS, XPS and TEM. The obtained film is a multiple phase ternary alloy containing crystallines and amorphous phases. The electrochemical measurements showed that the Pd-Ni-Mo film has excellent catalytic activity for hydrogen evolution reaction with good corrosion resistance in 1 M NaOH solution. The proton discharge electrosorption is the rate determining step of hydrogen evolution reaction on Pd-Ni-Mo film surface. The better electrocatalysis performance of the Pd-Ni-Mo film is attributed to its larger real surface as well as the enhanced electrochemical activity of the film surface due to the alloying effect. [ABSTRACT FROM AUTHOR]

Ceramic coatings with high emission and low absorptance were prepared on Ti6Al4V alloy by plasma electrolytic oxidation (PEO) in zirconate electrolyte. The effects of current density and working frequency on the structure and thermal control properties of the coatings were investigated. The phase composition, microstructure, thickness and roughness of coatings were examined by XRD, SEM, EDS, thickness measurement gauge and roughness measuring instrument, respectively. Thermal control properties of the coatings were studied with a UV–VIS–NIR spectrophotometer and an infrared reflectometer. The results show that the coatings are porous and composed of a large amount of KZr 2 (PO 4 ) 3 , and a little monoclinic ZrO 2 , tetragonal ZrO 2 and ZrP 2 O 7 as well. The thickness of the coatings increases with the increase of the current density or the decrease of the working frequency while the roughness of the coatings increases with the increase of the current density and the working frequency. The increase of current density reduces the absorptance, but improves the emissivity; the increase of working frequency improves the absorptance, but does not change emissivity apparently. The coating prepared at 10 A/dm 2 , 50 Hz and 50 min, has the lowest solar absorptance (0.34) and the highest infrared emissivity (0.9). [ABSTRACT FROM AUTHOR]

Abstract: It is of great significance for the research of thermal control coatings on Ti alloys due to their wide applications in aerospace and satellites and many other fields. In this work, black thermal control coatings were prepared on Ti–6Al–4V alloy by plasma electrolytic oxidation (PEO) technique. The coatings were characterized by SEM, EDS and XRD, respectively. The thermal control properties (solar absorbance, α S and emissivity, ε) were investigated by ultraviolet–visible-near infrared spectrophotometer instrument and solar absorption reflectometer. Meantime, the thermal shock properties of the coated samples were investigated as well. The results show that the ceramic coatings are black and porous and the elements such as Fe, Co and Ni and W from the electrolyte incorporate into the coating and exist in the form of an amorphous state. The coatings are of high emissivity and high absorbance character, which are influenced by the doping of Na2WO4 and the PEO time. Increasing the concentration of Na2WO4, α S increases firstly and then remains constant while ε increases gradually. Extending PEO time, both α S and ε increase. The annealing treatment reduces the solar absorbance greatly, but does not influence the emissivity apparently, which may be due to the improvement of the crystallization of the coating. When the dosage of Na2WO4 is 7.5g/L and the reaction time is 25min, the best coating is obtained with α S and ε of 0.93 and 0.88, respectively. This work not only provides an effective method to prepare thermal control coating for Ti alloys as the engineering materials, but also expands the application range of PEO technique in the fields of functional coatings. [Copyright &y& Elsevier]

Abstract: Chromium–palladium alloy films with good adhesive strength and higher micro-hardness have been deposited on 316L stainless steel by pulse electroplating. The films are composed mainly of chromium and palladium crystallites in the metallic state, with grain sizes less than 100nm. On the film surface Cr(OH)3 and Cr2O3 are present. The co-deposited Cr and Pd in the films show a synergetic effect on passivation. In boiling 20wt.% H2SO4 solution, boiling acetic–formic acid mixture, and simulated PEM fuel cells environment, the Cr–Pd-plated 316L steel shows excellent corrosion resistance. [Copyright &y& Elsevier]