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Enzyme immobilization method in packaged freestanding microfluidic channel is developed for biomolecule assembly of biosensor in this research. A new micro fluidic fabrication method is proposed to fabricate freestanding fluidic structure by MEMS technology. The SU-8 polymer channel is treated by plasma treatment to change hydrophobic surface to hydrophilic property which can automatically drive the liquid into the channel by capillary force. The electro click chemistry method is carried out in hydrophilic SU-8 micro channel by capillary effect. The results show that enzyme immobilization can be immobilized by electro click chemistry in completely packaged freestanding channel. The proposed enzyme immobilization method in micro channel is capable of minimizing biosensor device for healthcare application.

The microstructures and strength of pure Ni ball after high speed collision process were investigated. The elongated and equiaxed nanocrystallines with high angle grain boundaries and random grain orientation were formed near the interface position due to high strain and strain rate. Sufficient intragranular recrystallization occurred due to shock induced storage energy. Sufficient recrystallization in the grain interior facilitated to activate dislocation in the process of subsequent deformation and resulted in ameliorated hardness. Moreover, the high angle grain boundaries could effectively impede the dislocation movement, which also significantly enhanced the strength of Ni ball near the interface.

The ratio of the twin decreased after thermomechanical process for the CoCrNi medium-entropy alloy. The grain refinement decreased the passive current and increased the breakdown potential of the CoCrNi medium-entropy alloy in sodium chloride solution. The electrochemical impedance spectroscopy analysis showed that the grain refinement of the CoCrNi medium-entropy alloy facilitated to form thicker passive films and larger passive film resistance, which thus resulted into better corrosion resistance in sodium chloride solution. More nucleation sites after the grain refinement could enhance diffusion rate of alloying element and promote to form thicker and more stable passive films on refined grain CoCrNi medium-entropy alloy. Moreover, sufficient recrystallization level within refined grains for the CoCrNi MEA also improved its corrosion resistance.

The ultrafine grained pure Ni and Ni-W alloy were obtained by electrodeposition technique and subsequent annealing treatment. The effects of annealing on the microstructures, the mechanical properties and the corrosion resistance of pure nickel and Ni-W alloy were investigated. The EBSD analyses showed that annealed pure Ni displayed preferred grain orientation, while annealed Ni-W alloy showed relatively more random grain orientation. Moreover, abnormal grain growth was observed in annealed pure Ni, while annealed Ni-W alloy displayed a more uniform grain size distribution. It could be predicted that solid solution of tungsten significantly suppressed grain growth and induced uniform grain size distribution during low temperature annealing process. Moreover, comparing with annealed pure Ni, the tungsten in annealed Ni-W alloy changed the semiconducting characteristic of surface passive films. Annealed Ni-W alloy showed higher corrosion resistance than annealed pure Ni in 3.5 wt% NaCl solution and in borate buffer solution.

The effects of the ball milling on microstructures of the graphene/Ni composites and subsequent hydrogen evolution reaction in acidic solution were investigated. Ni nanoparticles with average grain size of 4 nm were uniformly dispersed on the graphene surface after short time ball milling. While amorphous characteristic was observed due to long time ball milling. The graphene/Ni composites with amorphous structure exhibited higher electrocatalytic performance than the graphene/Ni composites with nanocrystalline structure. The Volmer-Heyrovsky mechanism was found for the graphene/Ni composites with nanocrystalline structure, while the graphene/Ni composites with amorphous structure showed evident Heyrovsky mechanism. The excellent hydrogen evolution reaction and stability of the graphene/Ni composites could be attributed to superior interfacial contact, amorphous Ni, and synergistic effect between amorphous Ni and high conductive graphene.

NiMoO4 nanoparticles and quantum dots were uniformly distributed on the surface of reduced nanohole graphene oxide (rNHGO). NiMoO4@rNHGO exhibited a higher specific capacitance and better cycling stability than NiMoO4@reduced graphene oxide (rGO), which were attributed to the large surface area and high electrical conductivity. NiMoO4 nanoparticles and quantum dots (QDs) had high surface to volume ratio, which would not result in change in volume during the electro–chemical operation and induced better supercapacitor performance. Moreover, synergistic effect between NiMoO4 and the rNHGO also improved undoubtedly high specific capacitance and cycle stability.

3D MoS 2 hollow spheres were successfully fabricated by hydrothermal process. Commercial bulk MoS 2 had quite large grain size and preferential (002) grain orientation, while as-prepared MoS 2 hollow spheres had refined grain and random grain orientation. Meanwhile, the hydrogen evolution reaction of the commercial bulk MoS 2 and as-prepared MoS 2 hollow spheres was systematically investigated in acidic solution. The as-prepared MoS 2 hollow spheres catalyst exhibited a lower onset overpotential for hydrogen evolution reaction than bulk MoS 2 . The superior hydrogen evolution reaction activity could be attributed to the unique 3D MoS 2 hollow spheres which provided more active edge sites. In addition, 3D MoS 2 hollow spheres also exhibited excellent high chemical stability after 1000 potential cycles.

Cotton-like NiO is formed on the surface of bare Ni foam after hydrothermal process and calcination process, while ultrathin NiO nanoflakes occur on Ni foam coated with graphene. The high specific capacitance of 1782 F g− 1 at 1 A g− 1 and 90.2% capacity retention at 1 A g− 1 after 5000 cycles charge-discharge test are found. The graphene induces the high electrical conductivity and excellent interfacial contact, in addition, the graphene facilitates the forming of ultrathin NiO nanoflakes which result in huge pseudocapacitance due to large surface area and abundant mesoporous. The unique microstructure characteristic promotes interfacial electron transport in the electrode material and improves ion diffusion during the electrochemical reaction process.

A large number of pitting pits were formed on the surface of Ni foam by immersion corrosion in NaCl solution. The graphene was deposited on Ni foam templates, then 3D graphene foams were obtained by removing Ni foam in the mixed solution of ferric chloride and hydrochloric acid. It was found that pitting pits on Ni foam facilitated to form fewer-layers graphene, however, pitting pits on Ni foam induced more defects on 3D graphene foam. The graphene with fewer-layers exhibited better electrical and mechanical properties for strain sensor devices. Moreover, fewer-layers graphene effectively inhibited degradation of resistance during cycling stability tests.

The effects of urea concentration on microstructures of ZnCo 2 O 4 during hydrothermal process and their supercapacitors performance were investigated. The sphere ZnCo 2 O 4 oxide with nanostructure arrays was formed after hydrothermal process containing low urea concentration. The slim and curved ZnCo 2 O 4 nanowires were formed on Ni foam due to medium urea concentration, while sharp and separated ZnCo 2 O 4 nanostructure arrays were formed on Ni foam due to high urea concentration. The sharp and separated ZnCo 2 O 4 nanostructure arrays on Ni foam showed the best electrochemical performance. ZnCo 2 O 4 nanostructure arrays obtained were composed of interconnected ZnCo 2 O 4 nanoparticles. The gaps between ZnCo 2 O 4 nanoparticles promoted penetration of the electrolyte, which induced the high supercapacitive performance. The sharp and separated ZnCo 2 O 4 nanostructure arrays on Ni foam had the lowest charge transfer resistance, which improved supercapacitive performance. In addition, the strong and separated ZnCo 2 O 4 nanowires improved significantly cycle life during the charge-discharge process due to good strain accommodation of the unique structure.

Pure CoMoO4 nanoplate arrays grew on nickel foam by one-step hydrothermal process, while flower-like nanoflake CoMoO4@RGO nanocomposites grew on nickel foam. Flower-like nanoflake CoMoO4@RGO nanocomposites electrode exhibited higher capacitance than pure CoMoO4 nanoplate arrays electrode. Maximum specific capacitance of 856.2 F g−1 was obtained at current density of 1 A g−1 for CoMoO4@RGO nanocomposites electrode. In addition, after 2000 cycles of continuous galvanostatic charge–discharge cycles, only 5.5% degradation of specific capacitance was found for CoMoO4@RGO nanocomposites. CoMoO4@RGO nanocomposites exhibited lower electrochemical resistance than pure-CoMoO4. This was because that the former had larger specific surface area and average pore diameter than the latter. The flower-like nanoflake CoMoO4 facilitated electrolyte movement during charge or discharge process and provided more active sites for the electrochemical reactions. In addition, the synergetic effect between RGO and CoMoO4 also improved the supercapacitor performance.

The effect of strain and low temperature sensitization on corrosion resistance of AISI 321 stainless steel in elevated borate buffer solution was investigated. The study found that the AISI 321 stainless steel with 20% strain showed the lowest degree of sensitization due to the fact that sample with 20% strain had high dislocation density which promoted chromium diffusion and a small amount of α'-martensites. The results from electrochemical impedance spectroscopy indicated that sensitized sample with 20% strain showed the best corrosion resistance after immersion test at 290 °C. A good agreement was found between the electrochemical impedance spectroscopy and the degree of sensitization. The oxide film was composed of three layers according to the results of the XPS and Raman spectra. In addition, the outer part compositions of the oxide film were mainly γ-Fe2O3 and Fe-Cr spinel and iron hydroxide, while the inner and intermediate layers were mainly Fe-Cr spinel and the mixtures of the oxides of Fe, Cr, Ni. The ratio of hydroxide in oxide film increased due to large strain, especially for chromium hydroxide. Mott-Schottky analysis showed that more hydroxides induced more donor and acceptor concentrations in oxide film. More hydroxides reduced corrosion resistance of oxide film.

The thermal reduced graphene oxide deposition on nickel foam was successfully synthesized by ultrasonic and subsequent thermal reduction process. Ultrathin mesoporous Ni3S2 was formed on the bare nickel foam after hydrothermal process, while Ni3S2 nanotube arrays were formed on the surface of nickel foam with the thermal reduced graphene oxide due to catalysis action of thermal reduced graphene oxide. The resulting Ni3S2 nanotube arrays exhibited higher catalytic activity than ultrathin mesoporous Ni3S2 for hydrogen evolution reaction. In addition, and excellent stability was also obtained in Ni3S2 nanotube arrays.

The undulate bulk Ni 3 S 2 with porous surface was obtained on bare Ni foam after hydrothermal process, while plume-like Ni 3 S 2 was formed on the surface of Ni foam with the thermal reduced graphene oxide (rGO) due to catalysis action of thermal rGO. The Ni 3 S 2 on Ni foam with rGO showed better electrochemical performance than Ni 3 S 2 on Ni foam. In addition, Ni 3 S 2 on Ni foam with rGO also improved long-cycle stability. This made it become a good current collector in energy storage applications. The reason for the improvement of the supercapacitor performance of Ni 3 S 2 on Ni foam with rGO was discussed.

The effects of urea on microstructures of SnO2 during hydrothermal process and its supercapacitor performance were investigated. The sphere SnO2 was formed on Ti plate in hydrothermal solution without urea, while the SnO2 micro-flowers were assembled by numerous few-layered nanopetals due to adding to urea during hydrothermal process. The separated SnO2 nanopetals arrays showed better electrochemical performance than sphere SnO2. The gap between SnO2 nanopetals promoted penetration of the electrolyte and induced high supercapacitive performance.

3D Co 3 O 4 @CoMoO 4 core–shell architectures directly grown on nickel foam for supercapacitor electrode were obtained by two-step hydrothermal process. The Co 3 O 4 @CoMoO 4 nanocomposites electrode exhibited higher capacitance than Co 3 O 4 nanowire electrode. Maximum specific capacitance of 2530 F g − 1 was obtained at current density of 1 A g − 1 for Co 3 O 4 @CoMoO 4 core–shell architectures. In addition, after 3000 cycles of continuous galvanostatic charge–discharge cycles, only about 3.7% degradation in specific capacitance could be noticed. The CoMoO 4 nanorods stack on Co 3 O 4 nanowires arrays allowed facile electrolyte movement during charge or discharge process and provided more active sites for the electrochemical reactions. The unique architecture had a large interfacial area and numerous channels for rapid diffusion of electrolyte ions and fast electron transport. In addition, the synergetic effect between Co 3 O 4 nanowire and CoMoO 4 nanorods also improved the supercapacitor performance.

The effects of urea concentration on microstructures of Ni3S2formed on nickel foam and its hydrogen evolution reaction were investigated. The Ni3S2 nanosheets with porous structure were formed on nickel foam during hydrothermal process due to low urea concentration. While high urea concentration facilitated the forming of Ni3S2 nanotube arrays. The resulting Ni3S2 nanotube arrays exhibited higher catalytic activity than Ni3S2nanosheets for hydrogen evolution reaction. This was mainly attributed to a fact that Ni3S2 nanotube arrays facilitated diffusion of electrolyte for hydrogen evolution reaction.

The microscopic structures of different burnished layers in 2024 aluminum alloy were characterized by Transmission Electron Microscopy. The corrosion resistance of the burnished 2024 aluminum alloy was improved by grain refinement. The decreasing of electron work function improved corrosion resistance of the burnished 2024 aluminum alloy, moreover, less donor and acceptor concentrations in passive film also improved corrosion resistance of the burnished 2024 aluminum alloy. However, the substructures with high density dislocations deteriorated significantly the corrosion resistance of burnished 2024 aluminum alloy. More aluminum oxides improved the corrosion resistance of nanocrystalline 2024 aluminum alloy based on result of XPS.

The corrosion resistance of coarse grained and nanocrystalline Ni Fe alloys in chloride solutions and proton exchange membrane fuel cell environment was investigated. The nanocrystalline Ni Fe alloys were obtained by electrodeposition, while coarse grained Ni Fe alloys were obtained by annealing. The results from electrochemical tests showed that coarse grained Ni Fe alloys had higher corrosion resistance than nanocrystalline samples in NaCl solution due to more compact passive films formed on the surface of coarse grained Ni Fe alloys. In addition, Raman spectra test showed that many nanocrystalline boundaries in electrodeposited Ni Fe alloys promoted the diffusion of nickel, which resulted in the formation of more nickel oxides and nickel hydroxides. However, the electrochemical study showed that coarse grained sample had lower corrosion resistance than nanocrystalline one in a typical proton exchange membrane fuel cell environment. The present study showed that nanocrystalline Ni Fe alloys were more suitable for the bipolar plates in proton exchange membrane fuel cell environment.

The nanocrystalline pure nickels with different grain orientations were fabricated by direct current electrodeposition process. The grain size slightly decreased with the increasing of electrodeposition solution temperature. However, grain orientation was affected significantly. Comparing with samples obtained at 50 °C and 80 °C, sample obtained at 20 °C had the strongest (111) orientation plane which increased electrochemical corrosion resistance of this sample. At the same time, the lowest (111) orientation plane deteriorated electrochemical corrosion resistance of sample obtained at 50 °C.

Surface enriched molybdenum 316L stainless steel was obtained by ball milling technique. The electrochemical tests showed surface enriched molybdenum improved the corrosion resistance of the 316L stainless steel. This was attributed to a fact that more molybdenum oxides improved the corrosion resistance of the 316L stainless steel in borate buffer solution. In addition, more chromium oxides in the passive film after ball milling also improved corrosion resistance of the 316L stainless steel.

The effect of grain refinement on the corrosion resistance of the passive film formed on 2099 Al–Li alloy was investigated. The microscopic structures of cold rolled 2099 Al–Li aluminum alloy were characterized by Transmittance Electron Microscopy and surface activity was analysed by electron work function. The corrosion resistance of the passive film was studied by electrochemical techniques and Raman spectra. It was found that nano/ultrafine grained 2099 Al–Li alloy with refined precipitation phases was obtained by several plastic deformation process. The corrosion resistance of the 2099 Al–Li aluminum alloy was improved by grain refinement and refined precipitation phases. The improved corrosion resistance of 2099 Al–Li alloy after grain refinement was attributed to decreased electron work function. The grain refinement promoted the forming of thicker passive film and decreased acceptor concentration in passive film.

The nickel, nickel-molybdenum alloy, nickel-graphite and nickel-reduced graphene oxide composite coatings were obtained by the electrodeposition technique from a nickel sulfate bath. Nanocrystalline molybdenum, graphite and reduced graphene oxide in nickel coatings promoted hydrogen evolution reaction in 0.5 M H2SO4 solution at room temperature. However, the nickel-reduced graphene oxide composite coating exhibited the highest electrocatalytic activity for the hydrogen evolution reaction in 0.5 M H2SO4 solution at room temperature. A large number of gaps between ‘cauliflower’ like grains could decrease effective area for hydrogen evolution reaction in slight amorphous nickel-molybdenum alloy. The synergistic effect between nickel and reduced graphene oxide promoted hydrogen evolution, moreover, refined grain in nickel-reduced graphene oxide composite coating and large specific surface of reduced graphene oxide also facilitated hydrogen evolution reaction.

The passivation properties of deformed 304 stainless steels after immersion in borate buffer solution containing 0.2821 mol/L Cl− at 288 °C were investigated. The spinel and magnetite oxides were formed on all the samples. However, the hematite oxides reduced significantly with the increasing of strain. The sample with maximum strain possessed the poorest corrosion resistance. The hematite oxide could offer high corrosion resistance, while magnetite evidently deteriorated corrosion resistance. Moreover, the influence of the donors in outer layer of oxide film on corrosion resistance was more important than that of the acceptors in inner layer.

The passive film formed on the surface of the alloy 690 in borate buffer solution was studied by potentiodynamic curves and electrochemical impedance spectroscopy. With the increasing of the passivation potential, the corrosion resistance of the alloy 690 reduced. Moreover, the corrosion resistance of the passive film was the lowest in the vicinity of 0.6 V SCE . These results were supported by XPS and Mott–Schottky analyses. The corrosion resistance of the alloy 690 increased with the increasing of passivated potential in borate buffer solution with chloride ion. The chloride ion decreased corrosion resistance of the alloy 690 according to point defect model.

The stain-induced nanocrystalline α'-martensite was obtained by cryogenic cold rolling at liquid-nitrogen temperature for 316L stainless steel. The electrochemical results showed nanocrystalline 316L stainless steel deteriorated its corrosion resistance in a typical proton exchange membrane fuel cell environment compared with coarse grained one. However, comparing with electrochemically nitrided coarse grained stainless steel, electrochemically nitrided nanocrystalline stainless steel improved significantly corrosion resistance in the same environment, which was supported further by Mott–Shottky analysis. X-ray photoelectron spectroscopy analysis revealed that the nanocrystalline promoted the enrichment of nitrogen and chromium and inhibited form of NH 3 on the surface, which could significantly improve the corrosion resistance of the 316L stainless steel. The present study showed that the electrochemically nitrided 316L stainless steel was more suitable for the bipolar plates in proton exchange membrane fuel cell environment than the untreated one, especially for nanocrystalline stainless steel.

The effects of electrochemical nitridation on the corrosion resistance of the 2205 duplex stainless steel were investigated. It was found that increased nitrogen content in the 2205 duplex stainless steel affected donor and acceptor concentration distribution in the passive films on the surface of the 2205 duplex stainless steel. Moreover, the total donor and acceptor concentration in passive films decreased with the increasing of nitrogen content. The electrochemically nitridation facilitated to induce compact passive film and thus improved significantly the corrosion resistance of the 2205 duplex stainless steel in borate buffer solution.

The effect of the strain of 316L stainless steel on its corrosion resistance in PEMFC environment was investigated. Higher tensile strain facilitated the formation of more dislocations. The 316L stainless steel with 20% strain showed the best corrosion resistance in PEMFC environment containing a few fluoride ions, however, the corrosion resistance of the stainless steel decreased with the increasing of engineering strain in PEMFC environment with a considerable amount of fluoride ions. The morphology and density of the dislocations in strained 316L stainless steel could both affect significantly its corrosion resistance in PEMFC environment. This conclusion was supported by Mott–Schottky measurement and XPS analysis.

The effects of cold rolling temperature on grain size and grain orientation of pure iron were investigated. Comparing with sample rolled at room temperature, the grain refinement was facilitated in sample obtained by cryogenic cold rolling at liquid-nitrogen temperature. However, the grain orientation changed little for two samples. It was shown that cathodic hydrogen evolution reaction could govern the corrosion reaction for pure iron in sulfuric acid solution. The grain refinement obtained by rolling improved the corrosion resistance of iron in sulfuric acid solution, borate buffer solution and borate buffer solution with chloride ion. However, comparing with iron rolled at room temperature, the corrosion resistance of iron obtained by cryogenic temperature rolling was lower. Comparing with iron rolled at room temperature, higher dislocation density in iron rolled at cryogenic temperature reduced its corrosion resistance.

The passive film of iron showed n-type semiconductor characteristic in borate buffer solution, and its donor concentration increased slightly after tensile strain in the present study. However, comparing with solution-annealed sample, the anodic passive film formed on tensile-strained one was highly protective. The more dislocations on tensile-strained sample promoted the diffusion of iron and oxygen vacancy. Moreover, more donor density (mainly oxygen vacancies) promoted the diffusion of oxygen. They all facilitated tensile-strained sample to form Fe2O3 and thicker passive film on the surface. More Fe2O3 and thicker passive film on the surface of tensile-strained iron could improve corrosion resistance. Copyright © 2014 John Wiley & Sons, Ltd.

{011} planes which were medium close-packed planes were the dominating orientation in A sample (without burnishing) and B sample (a burnished sample) surfaces. There was not a common close-packed plane dominating orientation parallel to C sample (the other burnished sample) surface, and texture in this sample was abnormal. The corrosion property by electrochemical impedance spectroscopy was improved by burnishing process. Considering similar dislocation density obtained by XRD and grain boundary characteristic of two burnished samples, although the surface energy quantity for Al was (111)

The nano/ultrafine grain (NUG) with an average grain size of 230 nm was obtained by cold rolling down to 94% reduction in thickness and reversion annealing at 800 °C for 200 s. The NUG sample exhibited a lower corrosion resistance than coarse grain (CG) sample in 0.1 M NaCl solution at room temperature, indicating that the passive film formed on the surface of the NUG austenite did not improve corrosion resistance in the solution. However, the corrosion resistance of the former was higher than that of the latter in 0.5 M H 2 SO 4 solution at room temperature, which was proved by electrochemical impedance spectroscopy and Mott–Schottky plots in conjunction with the point defect model. Comparing slightly difference of acceptor density (i.e. cation vacancies) between CG and NUG samples, higher corrosion resistance of NUG sample was probably attributed to significant decreased donor density (i.e. oxygen vacancies and cation interstitials) in 0.5 M H 2 SO 4 solution. Moreover, the corrosion resistance of the passive films formed on CG and NUG samples in borate buffer solution at room temperature showed little difference.

The effect of burnish process on 2024 aluminum alloy was studied by electron work function and electron backscattered diffraction (EBSD). Moreover, the corrosion resistance of thin passive films formed on 2024 aluminum alloy in borate buffer solutions was studied by the electrochemical impedance spectroscopy (EIS), the Mott–Schottky plots and the galvanostatic techniques. The composition of passive films was analyzed by Raman spectra. The results obtained indicated that the impedance increased due to burnish and this was attributed to decreased electron work function and higher current efficiency in the burnished aluminum alloy which led to thicker passive films. It was further supported by Raman spectra experiment. Moreover, the donor and acceptor concentration of passive films and their the semiconductor type have changed due to burnish.

The martensitic phase transformation and reverse transformation of AISI 304 austenitic stainless steel by tensile pre-strain and sensitization at 948 K were investigated by X-ray diffraction. Martensite reversion was found to occur by an athermal shear mechanism at this temperature. A small quantity of “supposed secondary α′-martensite” was generated in a specimen suffering 40% engineering strain after being sensitized for a long time and water quenched. This could be due to the redistribution of carbon and chromium in the reverted austenitic phase and dislocations, which promoted the nucleation of the martensitic transformation.