The Effects of Annealing on the Surface Properties of Titania Films Prepared on Titanium by Micro-Arc Oxidation

Titanium and its alloys are widely used in the aerospace, marine, and biomedical industry due to their unique bulk properties such as high strength-to-weight ratio and melting temperature, good corrosion resistance, and favorable biocom- patibility. However, in some applications, com- ponents made of titanium or titanium alloys exhibit poor wear resistance under stationary or dynamic loading as well as contact corrosion manifested by the relatively negative standard electrode potential （-1.63 V ） . In order to improve the surface properties of titanium and its alloys, several techniques such as PVD （ physical vapor deposition ） /CVD （chemical vapor deposition ） coatings,

Microstructure and mechanical properties of ceramic coatings formed on 6063 aluminium alloy by micro-arc oxidation

The microstructure and mechanical properties of ceramic coatings formed on 6063 aluminium alloy obtained in silicate-,borate- and aluminate-based electrolyte without and with nanoadditive Al2O3 and TiO2 by micro-arc oxidation（MAO） were studied by scanning electron microscopy（SEM）,energy-dispersive X-ray spectroscopy（EDS）,X-ray diffraction（XRD）,microhardness and friction-abrasion tests,respectively.SEM results show that coatings with nanoadditive have less porosities than those without nanoadditive.XRD results reveal that nanoadditive-containing coatings contain more oxides compared with nanoadditive-free coatings in all cases,which are consistent with the EDS analysis.Mechanical properties tests show that nanoadditive Al2O3-containing coatings have higher microhardness values compared with the other coatings obtained in silicate-,borate- and aluminate-based electrolyte.On the other hand,nanoadditive has a positive effect on improving the wearing-resistance of MAO coatings in all cases.Furthermore,the borate-MAO coatings present an inferior anti-wearing property compared with the silicate- and aluminate-MAO coatings for both the nanoadditive-free and nanoadditive-containing coatings.

Corrosion and wear properties of micro-arc oxidation treated Ti6Al4V alloy prepared by selective electron beam melting

In order to analyze the effect of voltage during micro-arc oxidation(MAO)on corrosion and wear properties of Ti6Al4V(TC4),the MAO technology was employed to treat TC4 samples fabricated by selective electron beam melting(SEBM)at the voltages of 400,420 and 450 V.The results show that the metastable anatase phase gradually transforms to rutile phase with oxidation time and temperature increasing.The surface morphology of coating contains numerous micropores with uniform size distribution.Cracks and pores over 10μm are found on MAO-TC4 sample with applied voltage of 450 V.The thickness of MAO coating is positively correlated with the voltage.The corrosion resistance and wear resistance are related to phase composition,micropore size distribution on the surface and film thickness.When the voltage is 420 V,the coating shows the smallest corrosion current density(0.960×10^-7 A/cm^2)and the largest resistance(7.17×10^5Ω·cm^2).Under the same load condition,the coating exhibits larger friction coefficient and wear loss than the TC4 substrate.With the increase of voltage,the wear mechanism of the coating changes from abrasive wear to adhesive wear,and the adhesive wear is intensified at applied voltage of 450 V,with a maximum friction coefficient of 0.821.

Preparation and properties of a cerium-containing hydroxyapatite coating on commercially pure titanium by micro-arc oxidation

A porous cerium-containing hydroxyapatite coating on commercially pure titanium was prepared by micro-arc oxidation （MAO） in an electrolytic solution containing calcium acetate, p-glycerol phosphate disodium salt pentahydrate （β-GP）, and cerium nitrate. The thickness, phase, composition morphology, and biocompatibility of the oxide coating were characterized by X-ray diffraction （XRD）, electron probe microanalysis （EPMA）, scanning electron microscopy （SEM） with energy dispersive X-ray spectrometer （EDS）, and cell culture. The thickness of the MAO film is about 15-25 ~tm, and the coating is porous and uneven, without any apparent interface to the titanium substrates. The results of XRD and EDS show that the porous coating is made up of hydroxyapatite （HA） film containing Ce. The favorable osteoblast cell affinity makes the Ce-HA film have a good biocompatibility. The Ce-HA film is expected to have significant medical applications as dental implants and artificial bone joints.

Quick Surface Treatment of AZ31B by AC Micro-arc Oxidation

In order to explore an effective way to shorten treatment time and enhance the quality of treatment coating, AC micro-arc oxidation was conducted to treat the surface of AZ31 B deformation magnesium alloy in KF＋KOH treatment solution. The infl uences of micro-arc oxidation parameters such as concentration of KF, concentration of KOH, output voltage of booster, temperature of treatment solution, and treatment time on treatment coating thickness were raveled out under different conditions. The structure and composition of treatment coating were determined, the growth mechanism of treatment coating was discussed, and the quick surface treatment technology for compact treatment coating with maximum thickness was developed. The experimental results show that： A maximum 33 μm-thick compact treatment coating, consisting of MgF2 and MgO mainly, can be formed on AZ31 B in 112 s under the conditions of 1 132 g/L KF, 382 g/L KOH, 66 V for output voltage of booster and 34 ℃ of treatment solution which were optimized by a genetic algorithm from the model established by artifi cial neural networks. There are no ＂crater-shaped＂ pores in this treatment coating as the heat shock resulting from the smooth variation of AC sinusoidal voltage is far smaller than that of the rigidly varied DC or pulse current. The treatment time is only one sixth of that adopted in the other surface treatment technology at best, principally for the reason that the coating can always grow irrespective of the electric potential of AZ31 B. This investigation lays a fi rm foundation for the extensive application of magnesium alloy.

Tailoring the surface structures of iron oxide nanorods to support Au nanoparticles for CO oxidation

Iron oxide supported Au nanomaterials are one of the most studied catalysts for low-temperature CO oxidation.Catalytic performance not only critically depends on the size of the supported Au nanoparticles(NPs)but also strongly on the chemical nature of the iron oxide.In this study,Au NPs supported on iron oxide nanorods with different surface properties throughβ-FeOOH annealing,at varying temperatures,were synthesized,and applied in the CO oxidation.Detailed characterizations of the interactions between Au NPs and iron oxides were obtained by X-ray diffraction,transmission electron microscopy(TEM),and X-ray photoelectron spectroscopy.The results indicate that the surface hydroxyl group on the Au/FeOOH catalyst,before calcination(Au/FeOOH-fresh),could facilitate the oxygen adsorption and dissociation on positively charged Au,thereby contributing to the low-temperature CO oxidation reactivity.After calcination at 200℃,under air exposure,the chemical state of the supported Au NP on varied iron oxides partly changed from metal cation to Au0,along with the disappearance of the surface OH species.Au/FeOOH with the highest Au0 content exhibits the highest activity in CO oxidation,among the as-synthesized catalysts.Furthermore,good durability in CO oxidation was achieved over the Au/FeOOH catalyst for 12 h without observable deactivation.In addition,the advanced identical-location TEM method was applied to the gas phase reaction to probe the structure evolution of the Au/iron oxide series of the catalysts and support structure.A Au NP size-dependent Ostwald ripening process mediated by the transport of Au(CO)x mobile species under certain reaction conditions is proposed,which offers a new insight into the validity of the structure-performance relationship.

A Novel Dinuclear Copper(Ⅱ)Complex:Synthesis,Crystal Structure,Properties and Hirshfeld Surface Analysis

A novel copper complex [Cu2（L）（DMF）2]（1, H4L =（1 Z,N？Z）-3,5-dibromo-N？-（（3,5-dibromo-2-hydroxyphenyl）（hydroxy）methylene）-2-hydroxybenzohydrazonic acid which was synthesized by in-situ oxidation reaction derived from H2hdb（H2hdb = 6,6′-（（1 E,1？E）-hydrazine-1,2-diylidenebis（methanylylidene）） bis（2,4-dibromophenol）） has been synthesized and characterized by IR, elemental analysis（CHN）, TG and single-crystal X-ray diffraction. The single crystal belongs to monoclinic system, space group P21/c with a = 13.538（1）, b = 3.912（1）, c = 23.778（1）A°, β = 105.232（5）o, Mr = 857.08, V = 1214.9（1） A°^3, Z = 2, Dc = 2.343 g/cm^3, F（000） = 824, μ = 8.375 mm^–1, R = 0.0566, and w R = 0.1610. Compound 1 displays weak anti-ferromagnetic interactions through a η^1：η^1：η^1：η^1：η^1：η^1：μ2-L^4- bridging mode. Hirshfeld surface analysis revealed that complex 1 was supported mainly by Br···H and H···H intermolecular interactions.

Preparation and osteoinduction of active micro-arc oxidation films on Ti-3Zr-2Sn-3Mo-25Nb alloy

A layer of porous film containing Ca and P was prepared by the micro-arc oxidation method on the surface of a novel near β biomedical Ti-3Zr-2Sn-3Mo-25Nb alloy, and then NH2- active group was introduced to the films by activation treatment. The phase composition, surface micro-topography and elemental characteristics of the micro-arc oxidation films were investigated with XRD, SEM, EDS and XPS, and the osteoinduction of the micro-arc oxidation films was tested using the simulated body fluid immersion, the in-vitro osteoblast cultivation test and animal experiment. The results show that the oxide layer is a kind of porous ceramic intermixture and contains Ca and P. The films in the simulated body fluid can induce apatite formation, resulting in excellent bioactivity. The cell test discovers that osteoblasts can grow well on the surface of micro-arc oxidation films. And the Ti-3Zr-2Sn-3Mo-25Nb biomedical alloy coated with active porous calcium-phosphate films shows better osteoinduction in vivo.

Optimizing the micro-arc oxidation (MAO) parameters to attain coatings with minimum porosity and maximum hardness on the friction stir welded AA6061 aluminium alloy welds

Micro-arc oxidation(MAO) technique is capable of producing dense oxide films on the aluminium alloy surface. This oxide film protects the aluminium alloy from the corrosion attack for longer duration.Empirical relationships were derived to evaluate the MAO coating properties(porosity and hardness) by incorporating very important MAO parameters(current density, inter-electrode distance and oxidation time). MAO parameters were also optimized to achieve coatings with minimum porosity and maximum hardness. Further, the effect of MAO parameters on coating characteristics was analysed. From the results, it is found that the current density has greater influence on the responses than the other two parameters.

Preparation and characterization of the micro-arc oxidation composite coatings on magnesium alloys

The magnesium alloys attract the light-weight manufacture due to its high strength to weight ratio,however the poor corrosion resistance limits the application in automobile industry.The Micro-arc Composite Ceramic(MCC)coatings on AZ91D magnesium alloys were prepared by Micro-arc Oxidation(MAO)and electrophoresis technologies.The microstructure,corrosion resistance,abrasion resistance,stone impact resistance and adhesion of MCC coatings were studied respectively.The cross section morphologies showed that the outer organic coating was filled into the hole on surface of MAO coating,and it acted as a shelter against corrosive products.The copper-accelerated acetic acid salt spray Test,abrasion resistance test,stone impact resistance test,thermal shock resistance test and adhesion test were used to evaluate the protective characterization by the third testing organization which approved by GM.The test results showed the composite coatings meet all the requirements.The MCC coating on Mg presents excellent properties,and it is a promising surface treatment technology on magnesium alloys for production vehicles.

CHARACTERIZATION OF AMPHIPHILIC AND MICROPHASE SEPARATED GRAFT COPOLYMERS Ⅱ SURFACE CHARACTERIZATION AND IN VITRO BLOOD-COMPATIBILITY ASSESSMENT OF POLYSTYRENE-GRAFT-ω-STEARYLPOLY (ETHYLENE OXIDE)

This paper reported the research results concerning the surface characterization ofpolystyrene-graft-w-stearyl poly(ethylene oxide) (PS-g-SPEO) by means of XPS,contactangle measurement and TEM, and its in vitro blood compatibility assessment by measuringthe plasma recalcification time (RT) and partial thromboplastin time (PTT). The XPSresults demonstrated that the surface and bulk composition of the PS-g-SPEO graftcopolymers differ remarkably from each other,and that SPEO component was constantlyenriched at the copolymer/air interface. Contact angle studies indicated that the surfacewater wettability can be adjusted effectively by changing the composition of the copolymer.PS-g-SPEO graft copolymers can undergo microphase separation as clearly illustrated byTEM photographs. The relationship between the surface properties of PS-g-SPEO graftcopolymer and its blood compatibility was also discussed.

Investigation of Microwave Surface-Wave Plasma Deposited SiO_x Coatings on Polymeric Substrates

In this paper, we reported nano-scale SiOx coatings deposited on polyethylene terephthalate （PET） webs by microwave surface-wave assisted plasma enhanced chemical vapor deposition for the purpose of improving their barrier properties. Oxygen （O2） and hexamethyl- disiloxane （HMDSO） were employed as oxidant gas and Si monomer during SiOx deposition, re- spectively. Analysis by Fourier transform infrared spectroscope （FTIR） for chemical structure and observation by atomic force microscopy （AFM） for surface morphology of SiO~ coatings demon- strated that both chemical compounds and surface feature of coatings have a remarkable influence on the coating barrier properties. It is noted that the processing parameters play a critical role in the barrier properties of coatings. After optimization of the SiOx coatings deposition conditions, i.e. the discharge power of 1500 W, 2 ： 1 of O2 ： HMDSO ratio and working pressure of 20 Pa, a better barrier property was achieved in this work.

Anodic Oxidation on Structural Evolution and Tensile Properties of Polyacrylonitrile Based Carbon Fibers with Different Surface Morphology

Polyacrylonitrile （PAN） based carbon fibers with different surface morphology were electrochemically treated in 3 wt% NH4HCO3 aqueous solution with current density up to 3.47 A/m 2 at room temperature, and surface structures, surface morphology and residual mechanical properties were characterized. The crystallite size （La） of carbon fibers would be interrupted due to excessive electrochemical etching, while the crystallite spacing （d（002）） increased as increasing current density. The disordered structures on the surface of carbon fiber with rough surface increased at the initial oxidation stage and then removed by further electrochemical etching, which resulting in continuous increase of the extent of graphitization on the fiber surface. However, the electrochemical etching was beneficial to getting ordered morphology on the surface for carbon fiber with smooth surface, especially when the current density was lower than 1.77 A/m 2 . The tensile strength and tensile modulus could be improved by 17.27% and 5.75%, respectively, and was dependent of surface morphology. The decreasing density of carbon fibers probably resulted from the volume expansion of carbon fibers caused by the abundant oxygen functional groups intercalated between the adjacent graphite layers.

Formation characterization and rheological properties of zirconia and ceria-stabilized zirconia

Zirconia and ceria-stabilized zirconia (12Ce-TZP) were synthesized by the dicarboxylate coprecipitation technique such as fumarate, succinate, tartarate and adipate. The formation of these dicarboxylate precursors was studied by elemental analysis, thermal analysis and infrared spectroscopy. The precursors were further decomposed at 650oC for 2 hours to form respective zirconia and ceria-stabilized zirconia. The composition of these oxides was checked by Atomic absorption spectrometer and Energy dispersive X-ray analysis. The structural and morphological characterization of these oxides was done by using X-ray diffraction analysis, surface area, scanning electron micrographs and particle size distribution analysis. These properties were found depending to great extent on the nature of the precursors. The zirconia and ceria-stabilized zirconia obtained from adipate precursor were found to be good for slip- casting. The slips (i.e., suspensions) of these oxides with different solid contents were prepared at different pH with distilled water and ethanol as dispersing agents, with and without deflocculant. The suspension rheological flow (i.e., variation of shear stress and viscosity with shear rate) was determined. The minimum viscosities were observed at pH = 10.16 for ZrO2- water and pH = 10.26 for 12Ce–TZP-water system. The slip, green and sedimentation bulk density were measured.

Influence of processing parameters on coating surface roughness of aluminum alloy

The influence of processing parameters on the coating surface roughness of LD10 aluminum alloy treated by the power source with positive and negative pulse in the alkaline electrolyte was discussed.Lots of experiments were done with different processing parameters including the positive final voltage,the negative final voltage,the frequency,the duty ratio,the processing time and electrolyte temperature.And the surface roughness tester TR200 was used to measure the coating surface roughness.The influence of the processing time on the surface roughness is the smallest,less than 0.2μm.The surface roughness decreases gradually with the duty ratio decreasing or the frequency increasing;it decreases gradually with each of the other parameters increasing,and then increases gradually after achieving the minimum value.Appropriately by selecting processing parameters,the coating with Ra 0.6 can be obtained.

Corrosion and antimicrobial property of TiO_(2)/Cu_(2)O and TiO_(2)/Cu_(2)O@CeO_(2)micro-arc oxidation coatings on Ti-6Al-4V alloys in natural seawater

Microarc oxidation is an effective surface treatment for improving certain properties of metals and their alloys.In this paper,TiO_(2)/Cu_(2)O and TiO_(2)/Cu_(2)O@CeO_(2)coatings were prepared on Ti-6Al-4V by microarc oxidation.Thecoatings exhibited good corrosion resistance and antimicrobial properties.X-ray diffraction(XRD),scanning electronmicroscopy(SEM),and 3D laser confocal were used to characterize the coatings.The properties of TiO_(2)/Cu_(2)O and TiO_(2)/Cu_(2)O@CeO_(2)coatings were analyzed,including microstructure,surface roughness,corrosion resistance,andantimicrobial properties.The electrochemical results showed that the coatings prepared by microarc oxidation hadenhanced corrosion resistance compared to the substrate.The antibacterial properties of TiO_(2)/Cu_(2)O and TiO_(2)/Cu_(2)O@CeO_(2)coating against Pseudomonas aeruginosa were evaluated by fluorescence microscopy and plate counting.The antibacterial rate of TiO_(2)/Cu_(2)O@CeO_(2)coating was up to 99.70%.In summary,the TiO_(2)/Cu_(2)O and TiO_(2)/Cu_(2)O@CeO_(2)coatings prepared by microarc oxidation have a potential application background in the field of marine corrosionprotection and biofouling.

Effects of surface modifications on the physicochemical properties of iron oxide nanoparticles and their performance as anticancer drug carriers

The feature of the surface coating can affect important properties of iron oxide nanoparticles(IONPs), it is therefore critical for further understanding how these materials react to physiological conditions, which is still needed to fully exploit the potential of IONPs for their theranostic applications. In this work, we prepared IONPs which surface were modified with citric acid(CA), chitosan(CS) and folic acid conjugated chitosan(FA-g-CS). respectively. Their physicochemical properties were investigated using FT-IR, TEM,powder XRD, VSM, TGA, DLS and zeta potential. We found that CA-IONP dispersion was composed of monocrystalline particles while CS-IONP and FA-g-CS-IONP were composed of polycrystalline aggregates. All IONPs retained the crystalline structure of magnetite and exhibited the superparamagnetic behavior. Their saturation magnetization decreased with the increase in the amount of their organic coatings. Their drug loading capacities, drug release patterns and in vitro anticancer efficiencies were studied by using doxorubicin(DOX) as a model drug. DOX@CS-IONP and DOX@FA-g-CSIONP exhibited lower drug loading while showing higher water dispersity when compared with DOX@CA-IONP. All IONPs were surface charged and they tended to agglomerate in medium with high pH value and ionic strength. In the presence of chitosan or FA-g-CS coatings, their DOX release rate was slowed down compared with that of DOX@CA-IONP. Unloaded IONPs exhibited nearly no cytotoxicity on both cancer cells and normal cells in the presence of chitosan and FA-g-CS when compared with CA-IONP which presented high cytotoxicity. However, DOX@FA-g-CS-IONP showed significantly cytotoxicity on folate receptors(FRs) positive breast cancer cells while exhibiting nearly no cytotoxicity on FRs negative normal cells. Results presented in this study were valuable to the design and fabrication of IONPs-based system for better theranostic applications.

Perovskite Oxides La0.8Sr0.2Co1-xFexO3 for CO Oxidation and CO＋NO Reduction： Effect of Redox Property and Surface Morphology

This work aims to study the effect of redox property and surface morphology of perovskite oxides on the catalytic activity of CO oxidation and CO＋NO reduction, with the redox property being tuned by doping Fe at the Co site of La0.8Sr0.2Co1-xFexO3 and the surface morphology being modified by supporting La0.8Sr0.2CoO3 on various mesoporous silicas（i.e., SBA-16, SBA-15, MCF）. Characteristic results show that the Fe doping improves the match of redox potentials, and SBA-16 is the best support of La0.8Sr0.2CoO3 when referring to the oxidation ability（e.g., the Co^3＋/Co^2＋ molar ratio）. A mechanism for oxygen desorption from perovskite oxides is proposed based on O2-TPD experiments, showing the evolution process of oxygen released from oxygen vacancy and lattice framework. Catalytic tests indicate that La0.8Sr0.2CoO3 is the best for CO oxidation, and La0.8Sr0.2FeO3 is the best for CO＋NO reduction. The mechanism of CO＋NO reduction changes as the reaction temperature increases, with XNO/XCO value decreases from 2.4 at 250℃ to 1.0 at 400℃. As for the surface morphology, La0. Sr0.2CoO3 supported on SBA-16 possesses the highest surface Co^3＋/Co^2＋ molar ratio as compared to the other two, and shows the best activity for CO oxidation.

The exclusive surface and electronic effects of Ni on promoting the activity of Pt towards alkaline hydrogen oxidation

Ni modification is considered as an efficient strategy for boosting the performance of Pt towards alkaline hydrogen oxidation reaction(HOR),yet its specific role is largely undecoded.Here,ultrathin Pt nanowires(NWs)are selected as models for revealing the significance of Ni modification on HOR by precisely positioning Ni on distinct positions of Pt NWs.Ni solely influences the electronic properties of Pt and thus weakens*H adsorption when it is located in the core of PtNi alloyed NWs,leading to a moderate improvement of alkaline HOR activity.When Ni is distributed in both core and surface of PtNi alloyed NWs,Ni strongly weakens*H adsorption but strengthens*OH adsorption.On the other hand,the electronic properties of Pt are hardly influenced when Ni is deposited on the surface of Pt NWs,on which the strong*H and*OH adsorptions lead to the improved HOR activity.This work reveals the significance of Ni modification on HOR,but also promotes the fundamental researches on catalyst design for fuel cell reactions and beyond.

Nd–Mg–Ni alloy electrodes modified by reduced graphene oxide with improved electrochemical kinetics

To improve the electrochemical kinetics of Nd–Mg–Ni alloy electrodes, the alloy surface was modified with highly conductive reduced graphene oxide(rGO) via a chemical reduction process. Results indicated that rGO sheets uniformly coated on the alloy surface, yielding a threedimensional network layer. The coated surfaces contained numerous hydrophilic functional groups, leading to better wettability of the alloy in aqueous alkaline media. This, in turn, increased the concentration of electro-active species at the interface between the electrode and the electrolyte, improving the electrochemical kinetics and the rate discharge of the electrodes. The high rate dischargeability at 1500 mA·g^(–1) increased from 53.2% to 83.9% after modification. In addition, the modification layer remained stable and introduced a dense metal oxide layer to the alloy surface after a long cycling process. Therefore, the protective layer prevented the discharge capacity from quickly decreasing and improved cycling stability.