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The chemical compositions of Sanicro 25 stainless steel added with different concentrations of niobium (Nb) (0, 0.29, 0.58, and 0.86 wt-%) were investigated. X-ray diffraction analysis showed that ...

The corrosion behaviour of 2101 duplex stainless steel (DSS) in NaCl solution was studied and compared with that of 2205 DSS. The effects of chloride concentration and solution temperature on pitti...

The oxidation behavior of 22Cr25NiWCoCu stainless steel with 0&ndash, 0.86 wt.% Nb addition was investigated at 900 &deg, C in air. With an increase in Nb addition, the volume fraction and average particle size of Nb (C, N) increased, but the grain size decreased. The results of grazing incidence X-ray diffraction indicated that the steels with Nb additions promoted Cr2O3 formation. After 10&ndash, 100 h of oxidation, Cr depletion occurred at the region with Nb (C, N) precipitates because of its high Cr consumption rate, leading to Fe oxide generation. Finally, after 100 h of oxidation, the outer layer of Fe2O3 and the inner layer of (Cr, Fe, Mn)3O4 were formed.

The feasibility of filling a high aspect-ratio micro-hole with electrodeposited Ni P alloy by employing an emulsified supercritical CO 2 (sc-CO 2 ) bath was studied. The effects of current density and deposition time on the efficiency of micro-hole filling were also explored. The experimental results showed that void-free Ni P alloy could be successfully filled into a micro-hole with a diameter of 50 μm and a depth of 400 μm under proper electrodeposition conditions, with the advantage of low surface tension characteristics of sc-CO 2 in wetting the micro-hole over that of the conventional aqueous bath. The experimental results also showed that the deposition efficiency and the deposit morphology were significantly affected by the deposition time and current density applied. Material characterization indicated that the super-filled Ni P exhibited a uniform chemical composition, and an average microhardness value of 730 Hv.

The electrochemical behaviors of various metals with and without diamond-like-carbon (DLC) coating in 3.5 wt% NaCl solution were investigated. The effect of hydrodynamic conditions was focused by employing a rotating disc electrode (RDE). The experimental results showed that each bare metal had a more positive corrosion potential and a higher corrosion rate due to enhanced oxygen transport at the higher rotating speed of the RDE. DLC coating caused a substantial increase in the corrosion resistance of all metals studied. However, localized corrosion was still found in the DLC-coated metal at sites where deposition defects existed. Surface morphology examination was performed after the electrochemical test to confirm the roles of hydrodynamic conditions and DLC coating.

A complex catalyst consisting of metal particles and multi walled carbon nano tubes (MWCNTs) was developed in an attempt to reduce the dehydrogenation temperature of LiAlH4. By chemical reduction method, Ni and Co particles can be decorated on MWCNTs. The dehydrogenation behavior of LiAlH4 admixed with various amount of Ni, Co-decorated MWCNTs was investigated by using thermal gravimetric analysis (TGA) and in-situ synchrotron X-ray diffraction (XRD) technique. The TGA and in-situ XRD results shows that both Ni and Co-decorated MWCNTs can reduce the dehydrogenation temperature of LiAlH4. The results also reveal that Ni-decorated MWCNTs is more effective in catalyzing the dehydrogenation reaction of LiAlH4, even can lead to room temperature hydrogen desorption.

A novel catalyst was developed to modify the dehydrogenation behavior of LiAlH4 (lithium alanate). Using a chemical reduction method, Pd and Pt nano-particles were decorated on multi-walled carbon nanotubes (MWCNTs). The homogeneity and surface morphology of Pd and Pt decorated MWCNTs were examined by using transmission electron microscopy and scanning electron microscopy. The dehydrogenation behavior of LiAlH4 admixed with Pd and Pt decorated MWCNTs was investigated by thermal gravimetric analysis (TGA) and the in-situ synchrotron X-ray diffraction (XRD) technique. The TGA results revealed that the addition of Pd or Pt decorated MWCNTs would have either catalytic or inhibitive effects on the dehydrogenation of LiAlH4, which were concentration dependent. The in-situ XRD analysis confirmed the catalytic power of Pd or Pt decorated MWCNTs and the corresponding dehydrogenation reaction pathway of LiAlH4. The TGA results showed that both Pd and Pt decorated MWCNTs acted not only as a catalyst for LiAlH4, but also a hydrogen absorber.

Display Omitted SnO2 is observed in the Sn film plated by conventional method (CONV).Sn film plated with supercritical CO2 emulsion (EP-SCE) is consisted of pure Sn.Grain size of the Sn film by CONV is smaller than that of the EP-SCE film.Grain size of the EP-SCE film can be as large as 60µm.Yield strength of the CONV pillar is higher than that of the EP-SCE pillar. This paper reports mechanical properties of Sn films electrodeposited by the conventional method (CONV) and supercritical CO2 emulsions (EP-SCE). Sn is often used in electric devices as solders and load bearing components. Defects formed in the Sn structures could be fatal and can cause malfunction or shorten life time of the devices. Therefore, it is necessary to investigate the mechanical properties to understand the reliability and life time. The Sn films were prepared in an electrolyte of the acid Sn solution. Sn pillars for mechanical properties measurement were fabricated by focused ion beam and evaluated by a micro-compression test. Yield strength of the CONV pillar was higher than that of the EP-SCE pillar. Grain size of the EP-SCE film was about 60µm, which was much larger than the CONV film. Moreover, presence of SnO2 in the CONV film by was confirmed by X-ray photoelectron spectroscopy. Therefore, the high purity of Sn and the large crystal size are believed to be the main causes for the lower strength of the EP-SCE pillar when compared to the CONV pillar.

Modern wind turbine technology has been a great improvement over the past couple decades, leading to large scale wind power penetration. The increasing penetration of wind power resulted in emphasizing the importance of reliable and secure operation of power systems, especially in a weak power system. In this paper, the main wind turbine control schemes, the wind penetration levels and wind farm dynamic behavior for grid code compliance were investigated in the Penghu wind power system, a weak isolated power system.

Electrochemical carburization (ECC) of pure iron in a 1 M Na2SO4 bath containing supercritical CO2 (sc-CO2) fluids was investigated. The experimental results showed that the carbon-bearing films electrodeposited on iron substrate could be successfully produced under either galvanostatic or potentiostatic modes. The formation of carbon film on metal substrate and the subsequent carburization of iron substrate were analyzed by X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES) and scanning transmission electron microscopy (STEM) coupled with energy dispersive X-ray spectroscopy (EDS), with the aid of a focused ion beam (FIB). Keywords: Electrochemical carburization, Supercritical CO2, Aqueous carburization, Carbidic carbon

The use of an emulsified supercritical CO2 (sc-CO2) bath for electrodeposition of Ni–P alloys was attempted. The material characteristics of the deposits with various P contents, formed by varying the electrolyte composition and deposition current density, were investigated by means of scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) for surface morphology and chemical composition and crystal structure analyses. The experimental results showed that the presence of sc-CO2 in the electrodeposition bath could substantially improve the microhardness and the corrosion performance of the as-deposited Ni–P coatings. The roles of phosphorus and carbon in modifying the material properties of the deposits are discussed in detail.

Rehydrogenation behavior of the discharged MgH 2 -LiAlH 4 composites was investigated by using thermal gravimetric analysis (TGA) and in situ synchrotron X-ray diffraction (XRD) technique. For 4MgH 2 -LiAlH 4 composite, the experimental results showed that at least 3 wt% of hydrogen could be recharged at 170 psi H 2 /400°C to form MgH 2 after its first dehydrogenation reaction. The XRD results indicated that not only Mg but also Mg 17 Al 12 could be rehydrogenated in the hydrogen atmosphere investigated although LiAlH 4 was found irreversible.

Dehydrogenation behavior of LiAlH 4 –MgH 2 composites was investigated by using thermal gravimetric analysis (TGA) and in situ synchrotron X-ray diffraction (XRD) technique. The experimental results showed that MgH 2 could play a catalytic role in lowing the initial dehydrogenation temperature of LiAlH 4 . Besides, MgH 2 could be destabilized by the dehydrogenation reaction products of LiAlH 4 . The initial dehydrogenation temperature of LiAlH 4 –MgH 2 composites was as low as 145 °C and MgH 2 could decompose below 300 °C. The compounds such as LiMgAlH 6 , Al 3 Mg 2 , Al 12 Mg 17 and Li 0.92 Mg 4.08 formed during dehydrogenation process suggested some mutual reactions proceeded between LiAlH 4 and MgH 2 .

The co-deposition of Ni and Al2O3 by electrodeposition in supercritical CO2 (sc-CO2) baths with and without emulsification was studied. The material characteristics of the Ni-Al2O3 composite coatings, including its crystal structure, surface morphology, chemical composition, micro-hardness, wear resistance, and corrosion resistance, were all examined and compared with those of pure deposited Ni. Although a reduction in electrodeposition rate and a lower solid Al2O3 particle content in the composite coatings were obtained incorporating sc-CO2 bath, substantial increases in the micro-hardness and wear resistance of the coatings were observed comparing with those formed in conventional bath. The advantages of sc-CO2 electrodeposition, with and without surfactant addition, over the conventional electrodeposition of composite coatings, are addressed.

Carbon films on SiC have many applications, ranging from tribology to electrical energy storage. Formation of epitaxial or heteroepitaxial layers of carbon on SiC by “soft solution process,” such as electro- or photochemical ones, is attractive for various fields of application, decreasing the energy consumption and making the process compatible with electronic device fabrication. We have demonstrated formation of a carbon layer on SiC ceramics by electrochemical etching in a nonaqueous electrolyte. The selective etching of Si from SiC in a single step reaction with hydrofluoric acid (HF) in different organic solvents has been carried out and the role of polarity, surface tension, density, and viscosity of the organic solvents in the formation of the carbon layer has been investigated. The solution of 1:4.6 ratio HF and ethanol at low current densities (10 and 20 mA/cm2) allows the best control over selective etching of Si forming amorphous and ordered carbon on the SiC surface. The presence of an intense G band of graphitic carbon in Raman spectra and high resolution transmission electron microscopy analysis indicate formation of ordered carbon on the surface of SiC. X-ray diffraction shows that the etching rate of α-SiC is much higher when compared to β-SiC.

Dehydrogenation behavior of LiAlH4 (lithium alanate) admixed with multi-walled carbon nanotubes (MWCNTs) was investigated by using high-pressure thermal gravimetric analysis (HPTGA) and in-situ synchrotron X-ray diffraction (XRD) technique. HPTGA results indicated that MWCNTs play a catalytic role in the dehydrogenation of LiAlH4, subsequently decreasing the dehydrogenation temperature and improving the desorption kinetics. With the proper amount of MWCNT, the initial dehydrogenation temperature of LiAlH4 decreased by approximately 60 °C. Furthermore, in-situ synchrotron XRD analysis confirmed the dehydrogenation reaction products and paths of LiAlH4, with and without MWCNT addition.

The corrosion behaviours of two high entropy alloys (HEAs, namely Fe–Al–Ni–Cr–Co and Fe–Al–Ni–Cr–Co–Mn) in molten Al, each with and without pre-oxidation treatment, were investigated. Both bare alloys lost their thickness owing to dissolution, and various intermetallic compounds formed on their substrate surfaces during immersion in molten Al. Pre-oxidation treatment gave rise to the formation of an effective oxide barrier on each alloy surface against molten Al attack. The characteristics of pre-formed oxides in resisting molten Al attack were examined using electron backscatter diffraction (EBSD) analysis.

The dehydrogenation performance and mechanism of the synthesized NaAlH 4 –Mg(AlH 4 ) 2 powders were investigated by performing thermogravimetric analysis and in situ synchrotron X-ray diffraction analysis. NaAlH 4 not only facilitates the first step dehydrogenation of Mg(AlH 4 ) 2 in lowering its initial dehydrogenation temperature but also increases the total amount of H 2 released. Besides, MgH 2 and/or Al phases, the products of the first step dehydrogenation reaction, play a catalytic role in lowering the initial dehydrogenation temperature of NaAlH 4 . The synthesized NaAlH 4 –Mg(AlH 4 ) 2 mixture has an initial dehydrogenation temperature as low as 120 °C, and is able to release 5.35 wt% H 2 below 350 °C. The self-catalytic dehydrogenation behavior of the NaAlH 4 –Mg(AlH 4 ) 2 mixture was elaborated in this work with the aid of in situ synchrotron XRD.

The susceptibility of Ti–6Al–4 V alloy to stress corrosion cracking (SCC) in a Lewis neutral AlCl 3 –EMIC ionic liquid (IL) was investigated employing U-bend tests. The results indicated that cracking initiated at the α/β phase boundary, propagated intergranularly, followed by transgranular cracking and failed in dimple mode under overloaded stress.

The electrochemical behavior of anodically deposited Mn oxide in N-butyl-N-methylpyrrolidinium–dicyanamide (BMP–DCA) ionic liquid (IL) at various temperatures (30–80 °C) is investigated. Cyclic voltammetry (CV) is used to evaluate the electrochemical performance of the Mn oxide. Surface morphology of the deposited oxide after charging/discharging is examined by scanning electron microscopy (SEM). The experimental data show that the Mn oxide electrode exhibits good pseudo-capacitance performance even at 80 °C. In the ionic liquid studied, the specific capacitance increases with increasing BMP–DCA IL temperature. A specific capacitance of 93 F g −1 in a potential window of 3 V is obtained at 80 °C, which is about 50% higher than that obtained at 30 °C. The experimental results also show that the capacitance-retained ratio of the oxide electrode increases with increasing temperature at a high potential sweep rate. Furthermore, the capacitance decline about 40% after 500 repeated charging/discharging cycles in BMP–DCA IL at 80 °C is observed, which is better than that measured in an aqueous electrolyte.

Polyaniline (PANI) is doped with poly(styrenesulfonic acid) (PSS) using doping time of 10, 60, 300, 900, and 1800 s to obtain PANI–10PSS, PANI–60PSS, PANI–300PSS, PANI–900PSS, and PANI–1800PSS films, respectively. Fourier transform infrared spectroscopy (FT-IR) results confirm that PANI is doped with PSS. X-ray photoelectron spectroscopy (XPS) results indicate that a saturated doping state is achieved when PANI dope with PSS up to 300 s. Scanning electron microscopy (SEM) images reveal that PANI doped with PSS films are composed of highly porous nanowires. Platinum (Pt) can be incorporated into PANI–10PSS, PANI–60PSS, PANI–300PSS, PANI–900PSS, and PANI–1800PSS via electrochemical deposition to obtain PANI–10PSS–Pt, PANI–60PSS–Pt, PANI–300PSS–Pt, PANI–900PSS–Pt, and PANI–1800PSS–Pt composite electrodes, respectively. Scanning electron microscopy (SEM) and Transmission electron microscopy (TEM) results indicate that Pt particles disperse more uniformly into the spatial regions of PANI–300PSS than those of other films, and the PANI–300PSS–Pt electrode provides the most active surface area of Pt in these electrodes. Cyclic voltammetry results and chronoamperometric response measurements show that the activity and stability toward methanol oxidation of the PANI–300PSS–Pt electrode are the best in these electrodes, respectively.

The electrodeposition behavior and material properties of the Ni–P alloy coatings produced in emulsified supercritical CO2 (sc-CO2) bath with different surfactants (dodecyl octaethylene glycol ether (C12EO8) and a commercial fluorosurfactant) were investigated. The formation of holes or voids which is normally found in conventional aqueous coating could be avoided if the electrodeposition was conducted in the emulsified sc-CO2 bath with proper addition of surfactant, but with the sacrifice of current efficiency. At a lower concentration of surfactant addition, the experimental results showed that fluorosurfactant was more effective than C12EO8 in reducing the surface roughness and void formation in the coating. A significant increase in micro-hardness of the Ni–P coating was observed if it was electrodeposited in the emulsified sc-CO2 bath as compared with that formed at conventional aqueous bath. The wear rate of the Ni–P coating formed in the emulsified sc-CO2 bath was relatively lower with fluorosurfactant as the surfactant than that with C12EO8.

Diamond-like carbon (DLC) coatings have been deposited onto stainless steel, carbon steel and brass by plasma-enhanced chemical vapor deposition, respectively. Atomic arrangement, chemical structure, surface morphology and cross-section microstructure of the DLC coatings were examined by X-ray diffraction, Raman scattering spectroscopy and scanning electron microscopy. The electrochemical behaviors of the DLC coatings in 3.5 wt.% NaCl solution were investigated by performing an open circuit potential (OCP) measurement and a potentiodynamic polarization test. The experimental results showed that properly deposited DLC coatings could cause an increase of OCP by hundreds of millivolts and a reduction of anodic current density by several orders of magnitude as compared to that of the substrate. The results also demonstrated that electrochemical techniques could be used as tools to detect the soundness of the DLC coating by examining OCP and polarization curve, which varied with the form of defect and depended on the type of substrate.

The effect of multi-walled carbon nanotubes (MWCNTs) addition on the dehydrogenation behavior of NaAlH4 (sodium alanate) is investigated using high-pressure thermal gravimetric analysis (HPTGA) and in-situ synchrotron X-ray diffraction (in-situ synchrotron XRD) technique. The HPTGA results show that the addition of MWCNTs facilitates dehydrogenation of NaAlH4 by lowering the first-step dehydrogenation temperature to 80 °C. In-situ synchrotron XRD analysis demonstrates that the dehydrogenation pathway can be modified by the addition of MWCNTs which resulting in an enhanced hydrogen desorption rate and reduced desorption temperature.

A mechano-chemical activation synthesis (MCAS) is employed to fabricate Mg(AlH4)2 via milling the precursors, specifically NaAlH4 and MgCl2. The corresponding dehydrogenation behavior of the synthesized powders is investigated. The experimental results showed that incomplete synthesis or premature dehydrogenation may occur if the milling process was not properly controlled. The hydrogen content of each synthesized powder is determined by using a thermal gravimetric analyzer (TGA). The dehydrogenation reactions of the synthesized powders are investigated by employing ex situ X-ray diffraction (XRD), in situ synchrotron XRD and differential thermal analysis (DTA). The results showed that the incompletely synthesized powder consisted of residual NaAlH4 in the synthesized Mg(AlH4)2, which demonstrated an initial dehydrogenation temperature as low as 100 °C and accompanied with a maximum amount (3.1 wt%) of H2 released below 350 °C. The mutual catalytic effect of both NaAlH4 and Mg(AlH4)2 on lowering their initial dehydrogenation temperature is confirmed.

Acidic etching and Pt particle decoration were applied to modify the hydrogen absorption behavior of carbon nanotubes (CNTs). Two different acidic solutions, namely H 2 SO 4 /HNO 3 and FeSO 4 /H 2 SO 4 /H 2 O 2 , were used for etching treatment. A novel electroless deposition process, incorporating supercritical CO 2 (sc-CO 2 ) fluid, was used to decorate finely-dispersed nano-sized Pt particles on CNTs. The hydrogen storage capacities of various modified CNTs were measured by using a high pressure thermal gravimetric microbalance (HPTGA). The experimental results showed that acidic etching could increase the surface defect density and lead to open-up of the caps of CNTs, resulting in an increase in the active adsorption site for physical sorption of H 2. The electroless deposition of nano-Pt particles on CNTs, using conventional electrolyte, could promote chemical sorption of hydrogen via spillover mechanism. By employing sc-CO 2 bath, the Pt particle size became much finer and more uniformly distributed on the surfaces of CNTs, giving rise to a high hydrogen storage capacity. When a hybrid process including sc-CO 2 Pt decoration following acidic etching was applied to modify CNTs, a substantial enhancement of hydrogen storage capacity (about 2.7 wt%) was observed.

Hydrogen storage properties of carbon nanotubes (CNTs) modified by oxidative etching and decoration of Pd spillover catalysts are investigated. A mixed H 2 SO 4 /H 2 O 2 solution containing ferrous ions (Fe 2+ ) is useful to open the caps, to shorten the length, and to generate defects on CNTs. The Pd catalysts are deposited on the CNTs with the aid of supercritical carbon dioxide (scCO 2 ); as a result, a highly dispersed Pd nanoparticles and an intimate connection between Pd and carbon surface can be obtained. Combination of the two approaches can optimize a hydrogen spillover reaction on CNTs, resulting in a superior hydrogen storage capacity of 1.54 wt% (at 25 °C and 6.89 MPa), which corresponds to an enhancement factor of ∼4.5 as compared to that of pristine CNTs.

The electrodeposition of Ni–P alloy in an emulsified supercritical carbon dioxide (sc-CO 2 ) bath was investigated to explore the effect of H 3 PO 3 concentration (ranging from 0 to 1.6 M) on the material characteristics of the deposits. The experimental results showed that the P content in the deposit increased with increasing H 3 PO 3 concentration in the emulsified sc-CO 2 bath, while the weight gain of the Ni–P film decreased. At the same concentration of H 3 PO 3 , the significant decreases in weight gain and P content of the Ni–P films deposited in the emulsified sc-CO 2 bath were found, as compared with that plated in the conventional aqueous electrolyte at ambient pressure. X-ray photoelectron analyses revealed that the carbon-containing Ni–P deposit could be obtained in the bath with the presence of sc-CO 2 fluid. Transmission electron microscopy was employed for microstructure analysis. The average grain size of the Ni–P films deposited in the conventional aqueous electrolyte at ambient pressure or in the emulsified sc-CO 2 bath varied, depending on the H 3 PO 3 concentration and P content. The Ni–P films deposited from the emulsified sc-CO 2 bath had a higher hardness as compared with that formed in conventional electrolyte. The hardness of Ni–P alloy deposited in the emulsified sc-CO 2 bath was enhanced by the additional solid solution strengthening mechanism.

The pseudocapacitance and morphology of an electrodeposited cobalt hydroxide (Co(OH) 2 ) significantly depends on the architecture of the electrode substrate. The nano-porous Ni framework, derived from the selective dissolution of Cu from a Ni–Cu alloy, effectively promotes the electrochemical utilization of deposited Co(OH) 2 even at a high loading amount condition. The great electronic and ionic conduction within the nano-structured electrode improves the energy storage performance of Co(OH) 2 as compared to that for a conventional flat Ni substrate. In this work, the Co(OH) 2 mass specific capacitance, evaluated using cyclic voltammetry (CV), only slightly decreases from 2650 to 2470 F g −1 when the potential sweep rate is substantially increased from 5 to 200 mV s −1 . The developed Ni(OH) 2 /NiOOH (from the nano-porous framework) incorporates with the deposited Co(OH) 2 upon CV cycling; the mixed hydroxide shows a noticeably synergistic capacitance. Furthermore, the dissolution of Co(OH) 2 in KOH electrolyte is greatly suppressed due to the incorporation of Ni(OH) 2 /NiOOH, consequently prolonging the electrode cycle life.

Ni decoration on carbon nanotubes (CNTs) performed by electroless nickel (EN) deposition is investigated. The effect of Ni particle distribution on hydrogen uptake of CNTs is also studied. The chemical composition, crystal structure and microstructure of the CNTs with or without Ni loading are characterized using an inductively coupled plasma spectrometer (ICP), X-ray diffraction meter (XRD) and transmission electron microscope (TEM) coupled with an energy dispersive spectroscope (EDS). The hydrogen uptake in CNTs with or without Ni loading is measured using a high-pressure microbalance at room temperature under a hydrogen pressure of 6.89 MPa. The experimental results show that fine and well-dispersed metallic Ni nanoparticles can be obtained by EN. The density and particle distribution depend on deposition temperature and time. An enhanced hydrogen storage capacity of CNTs can be obtained by Ni decoration, which provided a spillover reaction. The hydrogen storage capacity of the as-received CNTs was 0.39 wt.%. As much as 1.27 wt.% of hydrogen can be stored when uniformly distributed nano-sized Ni particles are formed on the surface of the CNTs. However, the beneficial effect is lost when the active sites for either physical or chemical adsorption are blocked by excessive Ni loading.

The vanadium borohydride was synthesized by a mechano-chemical milling method and its hydrogen desorption performance was evaluated. The effect of cooling during milling process on the hydrogen desorption behavior was also investigated. Nearly pure hydrogen was detected using a mass spectrometer coupled with a simultaneous thermal analyzer. Thermogravimetric method was conducted to determine the initial desorption temperature and the amount of hydrogen released from the hydride. The initial desorption temperature of vanadium borohydride was found below 100 °C, with an enthalpy change of 25.4 kJ/mol V(BH 4 ) 3 . The amount of hydrogen released from the hydride prepared by milling but without cooling was 0.25 wt%, while that prepared with controlled cooling at 20 °C was 1 wt%. A beneficial effect of enhanced hydrogen release to 2.2 wt% from borohydride was found if multi-walled carbon nanotubes (MWCNTs) were added as an additive.

Electrochemical atomic force microscope (ECAFM) was employed for in situ observation of corrosion of solution annealed and furnace cooled Ti–6Al–4V titanium alloy in 0.5 mol l −1 H 2 SO 4 + 1 mol l −1 HCl mixed solution. A scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS) was also used for microstructure examination and chemical composition analysis. For solution annealed followed by furnace-cooled Ti–6Al–4V titanium alloy, selective corrosion of α phase and galvanic effect at α/β interface could be clearly observed at open circuit potential under ECAFM. A higher dissolution rate was also found in α phase than β phase on the bare Ti–6Al–4V titanium alloy. The effect of potential on the corrosion behavior was also explored. Negligible corrosion was found after potentiostatic etching at −0.5 and −0.85 V Pt for 120 min. However, selective dissolution of α phase with respect to β phase occurred when the potential was controlled at −0.9 V Pt . The polarity inversion during potentiostatic etching at −0.9 V Pt was also found and discussed in this study.

Ni–P alloy coatings with different phosphorus contents were prepared by electroplating in a nickel sulfate bath containing phosphorous acid (H3PO3). Hardening mechanism, such as dispersion hardening of Ni nano crystals in amorphous matrix of the as-deposited Ni–P coating and coarsening weakening of Ni3P for the high P coating after 1 h of heat treatment at 400 °C were concluded from the experimental data. Hardening mechanism of Ni–P alloys were further discussed based on the microstructure evolution with increasing deposit P content and during the heat treatment by using high resolution TEM (HR-TEM). A maximum hardness was observed for the as-deposited and heat-treated Ni–P alloys with 4 wt.% and 6 wt.% P, respectively. These composition ranges corresponding to the microstructure with high hardness proposed are believed to be useful for the industrial applications and further study.

Electrodeposition of Ni in a Watt's bath at different applied pressure, and in the presence of CO 2 fluid was investigated. The reduction of carbon and its alloying into the Ni deposit was focused. The current efficiency of electrodeposition and the carbon content in the Ni deposit were found to vary with the applied pressure. The crystal structure of the resulting Ni–C film was characterized by performing X-ray diffraction. The composition of the deposit was analyzed using X-ray photoelectron spectroscopy. Transmission electron microscopy was employed for microstructure analysis. The results showed that nanocrystalline Ni–C deposit could be obtained. The grain size of the Ni–C film varied from 14 to 43 nm, depending on the deposition pressure and carbon content. A significant increase in microhardness from 450 to 720 Hv could be obtained for the Ni film electrodeposited from a bath of 15 MPa supercritical CO 2 fluid. In 1 M HCl solution, a higher open circuit potential and a lower anodic current density were found when the carbon content in the Ni deposit was increased.

The electroless deposition of boron-containing Ni (EN-B) film from a supercritical carbon dioxide (sc-CO 2 ) bath was introduced. The deposition rate in sc-CO 2 bath was one order of magnitude lower than that at ambient pressure without the presence of sc-C0 2 . A more uniform chemical composition of the EN-B film could be obtained if it was deposited in the sc-CO 2 bath. X-ray diffraction analyses revealed that the as-deposited film was amorphous in nature, despite of the deposition condition. Deposition defects such as cracks and voids could be avoided if the deposition was conducted in the sc-CO 2 bath. Crystallization and boride precipitation were found after heat treatment at 400 °C for 1 h. The EN-B film deposited from the sc-CO 2 bath had a higher hardness as compared with that of the normal EN-B coating. A substantial increase in hardness was obtained due to boride precipitation.

An Al coating film, electrodeposited on a Mg alloy from aluminum chloride–1-ethyl-3-methylimidazolium chloride (AlCl 3 –EMIC) ionic liquid, effectively prevents the substrate from rapid corrosion in a hostile environment. The thickness of the Al film can be easily determined by controlling the total cathodic charge applied, because the current efficiency of the electrodeposition reaction is close to 100%. Heat treatment at 450 °C under an argon atmosphere for 10 min causes an inter-diffusion at the Al/Mg interface, optimizing the protective performance of the coating film. Prolonging heating leads to a Mg 17 Al 12 intermetallic phase and a Mg solid solution phase to be formed at the expense of the deposited Al film. This phase transformation gives rise to a degradation in the corrosion resistance of the Al-coated sample.

The corrosion properties of carbon steel (CS), 304 stainless steel (304 SS), and pure titanium (Ti) are first studied in aluminum chloride–1-ethyl-3-methylimidazolium chloride ionic liquid (IL). An active-to-passive transition behavior was clearly observed for CS. The 304 SS exhibited the best stability among the materials; no considerable corrosion was recognized even in this high-chloride environment. In contrast, although Ti resists corrosion in ambient environments, it was not passivated in the IL and became severely corroded under an anodic applied potential. The material corrosion behaviors and mechanisms in the non-aqueous, low-oxygen, and high-halogen-containing IL are completely different from those in traditional aqueous solutions. Keywords: Ionic liquid, Corrosion behavior, Titanium, Stainless steel, Carbon steel

A facile and low-cost electroless deposition technique is utilized to decorate multi-walled carbon nanotubes (CNTs) with Ni. The obtained composites are attempted to use as hydrogen storage materials, whose performance is evaluated with a high-pressure microbalance. Effects of the concentration of plating solution, deposition time, and reaction temperature on the loading amount, particle size, morphology, and distribution density of Ni are studied using a transmission electron microscope. With proper deposition parameters, highly dispersed Ni nanoparticles with a uniform diameter can be fabricated on CNTs, causing a notable hydrogen spillover reaction on the composite. The optimum hydrogen storage capacity of the prepared Ni-decorated CNTs with a average diameter of 5 nm, measured at 6.89 MPa and 25 °C, is 1.02 wt%, which is almost three times higher than that (0.35 wt%) of pristine CNTs.

A hybrid synthesis protocol that combines electroless plating and the supercritical CO2 (scCO2) technique is developed for the first time to decorate multi-walled carbon nanotubes (CNTs) with Ni nanoparticles. The scCO2 fluid, which is immiscible with aqueous plating solution, renders a heterogeneous Ni deposition reaction and suppresses the lateral growth of Ni, which leads to the formation of nanoparticles. A uniform dispersion of tightly anchored particles, a few nanometers in diameter, on CNTs can be achieved. Since the electroless deposition process can be easily manipulated, large-scale production should be realizable. The constructed CNT/Ni nano-composite exhibits a synergistic property in hydrogen storage performance, which is evaluated using a high-pressure microbalance. The deposited nanoparticles enhance the hydrogen spillover reaction on CNTs, tripling the hydrogen storage amount at room temperature as compared to pristine CNTs.

Manganese oxide film for supercapacitor applications was prepared by potentiodynamic electrodeposition in a manganese acetate plating solution. The effects of the potential sweep rate on the oxide microstructure, crystallinity, and chemical states were examined using a scanning electron microscope, an X-ray diffractometer, and an X-ray photoelectron spectrometer, respectively. Electrochemical performance of the film electrodes was evaluated using a cyclic voltammetric measurement. The experimental results indicate that the deposition potential sweep rate significantly affected the material properties of the prepared oxide films. The oxide-specific capacitance increased from 262 to 337 F/g when the sweep rate was increased from 100 to 400 mV/s. The key material factors that govern the specific capacitance and cyclic stability of the oxide electrodes were discussed.

The co-deposition of Al and Zn on AZ91D magnesium alloy from a Lewis acidic aluminum chloride–1-ethyl-3-methylimidazolium chloride (AlCl3–EMIC, with a molar ratio of 60:40) ionic liquid containing 1 wt% ZnCl2 at room temperature was studied. The effect of potential on the deposition rate, the microstructure and the chemical composition of the deposit was explored. The experimental results show that the simultaneous deposition of Al and Zn on Mg alloy can be achieved under properly controlled potential conditions. The deposition rate increased while the amount of Zn existing in the coating decreased with increasing negative deposition potential. In the ionic liquid studied, a uniform chemical composition of the coating was obtained when the deposition was performed at −0.2 V (vs. Al).

Charge storage mechanisms of electrodeposited MnO2 in various aprotic ionic liquids (ILs) are studied using in situ X-ray absorption spectroscopy (XAS). The analytical results show that a unique thiocyanate (SCN−) anion can reversibly insert/desert into/from the tunnels between the [MnO6] octahedral subunits depending on the applied potential. This process charge compensates the Mn3+/Mn4+ redox transition upon charging–discharging and thus contributes to an ideal pseudocapacitive behavior of the MnO2 electrode. The present work would open up a route for developing a novel oxide-based supercapacitor, with high cell-voltage, high thermal stability, and high safety, incorporating IL electrolytes.

Nano-sized nickel particles were dispersed on multi-walled carbon nanotubes (MWCNTs) via an improved electroless deposition route using a supercritical CO2 fluid. The microstructure, chemical composition and crystallinity of the Ni-decorated CNTs were examined using a transmission electron microscope (TEM), an X-ray energy dispersive spectrometer (EDS), and an X-ray diffractometer (XRD), respectively. The analytical results indicate that, with assistance of the supercritical fluid, Ni nanoparticles with a diameter of approximately 10 nm can be uniformly dispersed on the surface of CNTs. The hydrogen storage capacity of the Ni-decorated CNTs was evaluated with a high-pressure microbalance at room temperature and under a hydrogen pressure of 6.89 MPa. The measured hydrogen adsorption amount of the Ni/CNTs nanocomposite was 1.06 wt%, which was much higher than 0.33 wt% found for the plain CNTs.