Co-deposition of arsenic and arsine on Pt,Cu, and Fe electrodes

An electrochemical investigation of arsenic in aqueous solutions was carried out in order to assess the possibility of removing it by reduction from As(III) to its elemental form. Arsine evolution was significant at potentials below −0.650 V_SCE on Cu, and below −0.728 V_SCE on Pt. As(V) could also be removed on Cu, with a larger evolution of arsine. When a potential equal to −0.560 V_SCE was applied to an iron electrode, arsenic deposition took place simultaneously with iron dissolution, and arsine evolution was negligible.     

Nanopatterning of Si(1 1 1) surfaces by atomic force microscope scratching of an organic monolayer

In this work, we demonstrate selective electroless deposition of Cu into nanoscratches produced on n-type Si(1 1 1) surfaces covered with an organic monolayer. The organic layer (undecylenic acid) was covalently attached to a hydrogen-terminated Si surface. The nanosize scratches were produced with an atomic force microscope (AFM) in contact mode using a diamond-coated tip. Copper was deposited in the scratched regions with an electroless (immersion plating) approach using a 0.05 M CuSO₄ + 1% HF electrolyte. The results show clearly that the organic layer can be used as a mask for the deposition of Cu. Optimization of the electrochemical parameters, leads to a very high selectivity and uniform and well-defined nanostructures. This process represents a novel approach for a direct patterning of Si surfaces using an immersion plating reaction.     

EDL structure and peculiarities of ferricyanide cyclic voltammetry for silver deposits on gold

The evolution of electrochemical characteristics of a gold electrode upon the deposition of one and more atomic silver layers was studied by means of cyclic voltammetry and the method of potential temperature jump induced by the laser irradiation. Characteristics of the electric double layer on Ag monolayer are determined to be close to those of a massive silver electrode. Meanwhile, the electron-transfer parameters for the model redox system Fe(CN)₆^{3 −/4 −} correspond to a gold electrode. The silver beyond the first atomic layer in multilayer deposits was shown to transform into Ag hexacyanoferrate (II) due to the spontaneous chemical reaction with K₃Fe(CN)₆ from the solution. For the Fe(CN)₆^{3 −/4 −} redox system, the difference between oxidation and reduction peak potentials on a cyclic voltammogram increases with the growth of the silver layers number. This effect results from the corresponding increase in the ohmic resistance of the silver hexacyanoferrate (II) film and is not attributed to the changes in the electron-transfer kinetics.     

Enhanced high-temperature cycle performance of LiFePO4/carbon batteries by an ion-sieving metal coating on negative electrode

LiFePO₄/mesocarbon microbead (MCMB) cells of which the carbon electrodes were, respectively, coated with different metal layers were characterized for their charge/discharge cycle performance at 55 °C. The examined metals included Au, Cu, Fe, Ni, Co, and Ti, and the superficial layers were 30–50 nm in thickness and deposited by vacuum sputtering. It was found that the presence of a either Au or Cu layer remarkably reduces capacity fading, while the rest metals only accelerate fading. There was observed a consistent trend between the capacity fading rate and the amount of the soild-electrolyte-interphase (SEI) deposition; the faster the capacity fading, the greater amount of SEI materials appearing on the surface of cycled carbon electrode. Microscopic and composition analyses indicates that the superficial Au and Cu layers act as a sieve to collect the Fe ions that result form erosion of LiFePO₄ before they diffuse into the interior of the carbon electrode, and that the so-deposited Fe particles do not show the tendency to catalyze the SEI formation, as in contrast to those directly deposited on the carbon surfaces.     

Fabrication of solid thin film electrolyte and LiCoO2 by aerosol flame pyrolysis deposition

Aerosol flame pyrolysis deposition method was applied to deposit the oxide glass electrolyte film and LiCoO₂ cathode for thin film type Li-ion secondary battery. The thicknesses of as-deposited porous LiCoO₂ and Li₂O–B₂O₃–P₂O₅ electrolyte film were about 6 μm and 15 μm, respectively. The deposited LiCoO₂ was sintered for 2 min at 700 °C to make partially densified cathode layer, and the deposited Li₂O–P₂O₅–B₂O₃ glass film completely densified by the sintering at 700 °C for 1 h. After solid state sintering process the thicknesses were reduced to approximately 4 μm and 6 μm, respectively. The cathode and electrolyte layers were deposited by continuous deposition process and integrated into a layer by co-sintering. It was demonstrated that Aerosol flame deposition is one of the good candidates for the fabrication of thin film battery.     

Synthesis of γ-MnOOH nanorods by successive ionic layer deposition method and their capacitive performance

It was first shown in the present study that layers of manganite γ-Mn OOH can be deposited on the surface of a substrate by its multiple successive treatment by the solutions of MnSO_4 and K_2S_2O_8 using the successive ionic layer deposition(SILD) technique. Their analysis was carried out by the XRD, XPS, FT-IR,SEM and EDX methods. It has shown that the synthesized layers are formed by aggregates of nanorods up to 80–100 nm in length and approximately 8–10 nm in diameter. A probable sequence of chemical reactions leading to the formation of a layer of the given morphology is suggested. Testing of performance of supercapacitors with nickel foam electrodes incorporating the γ-Mn OOH layers in the 0.1 M KOH electrolyte at 1 A/g indicated the specific capacitance equal to 1120 F/g. After 1000 work cycles the observed degradation of this value was less than 3%.     

The influence of chloride on the initial anodic dissolution of Cu3Au(1 1 1)

We report a detailed in situ X-ray diffraction study of the influence of chloride on the atomic structure evolution at the solid-electrolyte interface during the selective dissolution of Cu from a Cu₃Au(1 1 1) surface immersed in 0.1 M H₂SO₄. We disclose that the formation of the initial ultrathin Au-rich (1 1 1) with an inverted stacking sequence, as recently observed at Cu₃Au(1 1 1) in contact with pure 0.1 M H₂SO₄, is strongly influenced by adding 5 mM HCl. The main finding is a negative shift of about 150 mV of the critical potential at which the ultra-thin Au-rich layer transforms into thicker Au islands. The presented results support the view that it is not a thermodynamic driving force, but rather the rate of surface diffusion that dominates the formation of the structures of the metallic layer.     

A novel all-solid-state thin-film-type lithium-ion battery with in situ prepared positive and negative electrode materials

A novel all-solid-state thin-film-type rechargeable lithium-ion battery employing in situ prepared both positive and negative electrode materials is proposed. A lithium-ion conducting solid electrolyte sheet of Li₂O–Al₂O₃–TiO₂–P₂O₅-based glass–ceramic manufactured by OHARA Inc. (OHARA sheet) was used as the solid electrolyte, which was sandwiched by Cu and Mn metal films. The Cu/OHARA sheet/Mn layer became an all-solid-state lithium-ion battery after applying d.c. 16 V to the layer, and the resultant battery operated at 0.3–0.8 V with reversible capacity of 0.45 μAh cm^?2. High voltage battery was successfully prepared by applying the d.c. high voltage to a five-series of Cu/OHARA sheet/Mn layer, resulting in all-solid-state battery operating at 1.5–4.0 V. The proposed fabrication process will become a new technology to develop advanced all-solid-state rechargeable lithium-ion batteries.     

Synthesis of thick TiO2 nanotube arrays on transparent substrate by anodization technique

A vertically aligned transparent TiO₂ nanotube array (tTNA) of significantly enhanced tube-length 6.3 ± 0.3 µm was successfully synthesized on glass substrates by anodization technique with ammonium fluoride and ethylene glycol-based electrolyte. Prior to anodization, Ti metal was deposited on glass substrate by facing-target sputtering technique with various sputtering pressures at substrate temperature 420 °C to find out the relation between the structural properties of the Ti layer and the corresponding growth mechanism of the TiO₂ nanotube. The study revealed that structural properties of Ti metal layers and its adhesion to the glass substrate, which can be tuned by deposition parameters, play an important role in the process of tTNA formation.     

Formation of semi-permeable polyamide skin layers on the surface of supported liquid membranes

The instability of supported liquid membranes has been a major impediment to practical applications. To address this shortcoming, we have developed a method to form semi-permeable polyamide skin layers in situ on supported liquid membranes containing an anion-exchange extractant (trioctylamine) and a neutral extractant (tributyl phosphate). These skin layers encapsulate large extractant molecules within the membranes but allow the transport of small species across the membranes. A liquid–liquid interfacial polymerization reaction was employed to form the polyamide skin layers utilizing monomers that are compatible with the extractants. SEM examination of the membranes shows the polyamide skin layer to be about 1 micron thick with pore sizes below resolution. Membranes with polyamide skin layers showed a typical flux of 1 μmol/s m² of Cr(VI), about half that exhibited by similar membranes without skin layers.     

Electrochemical deposition of (Mn, Co)-codoped ZnO nanorod arrays without any template

(Mn, Co)-codoped ZnO nanorod arrays were successfully prepared on Cu substrates by electrochemical self-assembly in solution of 0.5 mol/l ZnCl₂–0.01 mol/l MnCl₂–0.01 mol/l CoCl₂–0.1 mol/l KCl–0.05 mol/l tartaric acid at a temperature of 90 °C, and these nanorods were found to be oriented in the c-axis direction with wurtzite structure. Energy dispersive X-ray spectroscopy and x-ray diffraction show that the dopants Mn and Co are incorporated into the wurtzite-structure of ZnO. The concentrations of the dopants, and the orientations and densities of nanorods can easily be well controlled by the current densities of deposition or salt concentrations. Magnetization measurement indicates that the prepared (Mn, Co)-codoped ZnO nanorods with a coercivity of about 91 Oe and a saturation magnetization (M_s) of about 0.23 emu/g. The anisotropic magnetism for the (Mn, Co)-codoped ZnO nanorod arrays prepared in solution of 0.5 mol/l ZnCl₂–0.01 mol/l MnCl₂–0.01 mol/l CoCl₂–0.1 mol/l KCl–0.05 mol/l tartaric acid with current density of 0.5 mA/cm² was also investigated, and the crossover where the magnetic easy axis switches from parallel to perpendicular occurs at a calculated time of about 112 min. The anisotropic magnetism, depending on the rod geometry and density, can be explained in terms of a competition between self-demagnetization and magnetostatic coupling among the nanorods.     

Synthesis,crystal structure,and magnetic properties of a copper(II) octacyanotungstate(V)-based magnet containing two types of organic ligands

Cu₃[W(CN)₈]₂(pyrimidine)₂(3-cyanopyridine)₂ · 4H₂O, a cyanide-bridged copper(II) octacyanotungstate(V) with two types of organic ligands (pyrimidine and 3-cyanopyridine), is prepared. In this compound, the coordination geometry of W is an 8-coordinated bicapped trigonal prism where five CN groups of [W(CN)₈] are bridged to five Cu ions, and the remaining three CN groups are free. The coordination geometries of the three types of Cu ions (Cu1, Cu2, and Cu3) are 6-coordinated pseudo-octahedron. The cyano-bridged-Cu2–W–Cu3-layer is linked by a Cu1 pillar unit, and a cavity along the a axis, which is occupied by 3-cyanopyridine molecules and zeolitic water molecules, exists. The present compound shows ferrimagnetism with a Currie temperature of 7 K, a saturation magnetization of 2.9 μ_B, and a coercive field of 7 Oe at 2 K.     

Line tension and its influence on droplets and particles at surfaces

In this review we examine the influence of the line tension τ on droplets and particles at surfaces. The line tension influences the nucleation behavior and contact angle of liquid droplets at both liquid and solid surfaces and alters the attachment energetics of solid particles to liquid surfaces. Many factors, occurring over a wide range of length scales, contribute to the line tension. On atomic scales, atomic rearrangements and reorientations of submolecular components give rise to an atomic line tension contribution τ_atom (～1 nN), which depends on the similarity/dissimilarity of the droplet/particle surface composition compared with the surface upon which it resides. At nanometer length scales, an integration over the van der Waals interfacial potential gives rise to a mesoscale contribution |τ_vdW| ～ 1–100 pN while, at millimeter length scales, the gravitational potential provides a gravitational contribution τ_grav ～ +1–10 μN. τ_grav is always positive, whereas, τ_vdW can have either sign. Near wetting, for very small contact angle droplets, a negative line tension may give rise to a contact line instability. We examine these and other issues in this review.     

Potentiodynamic electrochemical impedance spectroscopy of lead upd on polycrystalline gold and on selenium atomic underlayer

Pb upd on polycrystalline Au and on Au coated with Se atomic layer was investigated by potentiodynamic electrochemical impedance spectroscopy. Faradaic and double layer responses have disclosed two distinct stages in Pb upd on Au: a partly irreversible stage, attributed to formation and growth of Pb 2D islands, and a reversible phase transition in the final stage of a monolayer deposition. The completion of a continuous monolayer formation in the potential scan was signalised by a sharp minimum in double layer pseudocapacitance Q_dl. Pb²⁺ reduction, which was monitored concurrently by parameters of Faradaic response, continued shortly after the Q_dl minimum and showed sharp maxima of adsorption capacitance and inverse Warburg constant at 40 mV below Q_dl minimum. This was explained by surface free energy minimisation that forced continuous atomic layer formation with inclusion of some lead cations into Pb monolayer. The two-stage Pb upd transformed into a single-stage strongly irreversible upd as a result of Se atomic underlayer deposition on Au.     

Fabrication by Co-extrusion and electrochemical characterization of micro-tubular hollow fibre solid oxide fuel cells

A phase inversion process was used to co-extrude cerium–gadolinium oxide (Ce_0.9Gd_0.1O_1.95)/NiO–CGO dual-layer hollow fibres (HF), which were then sintered to form, respectively, the electrolyte and high porosity anode precursor of a solid oxide fuel cell (SOFC) with anode inner diameter of 0.8 mm. Graded CGO–lanthanum strontium cobalt ferrite (La_0.6Sr_0.4Fe_0.8Co_0.2O₃) cathode layers were then painted onto the CGO electrolyte to form a micro-tubular HF-SOFC. With a carefully designed anode current collector, this produced maximum power densities of 1186–5864 W m^? 2 at 450–570 °C. High magnification imaging analysis revealed large three-phase boundary regions within the anode, a dense electrolyte layer and clearly highlighted the multiple CGO–LSCF cermet and pure LSCF cathode layers. The performance of the HF-SOFC with a twenty millimetre active length showed no degradation after four thermal cycles between 300 °C and 570 °C.     

Tribological behaviour of nanostructured Ti-C:H coatings for biomedical applications

The development of a mechanically stable, functionally graded Ti-doped a-C:H interface layer in combination with a functional a-C:H coating requires a reduction of the brittle phases which induce generally problems in the transitions from Ti to TiC/a-C:H. The core objective of this study was to develop an optimum interlayer between the substrate and the functional top layer for biomedical applications, namely for tooth implants. Since the interlayer may be exposed to the sliding process, in the case of local failure of the top layer it has to fulfil the same criteria: biocompatibility, high wear resistance and low friction.The functional Ti-C:H layers with thickness in the range 2.5–3.5 μm were deposited by a magnetron sputtering/PECVD hybrid process by sputtering a Ti-target in a C₂H₂ + Ar atmosphere in dc discharge regime. The sets of coating samples were prepared by varying the C and H concentrations controlled by the C₂H₂ flow during the deposition process. The tribological properties were evaluated on a pin-on-disc tribometer at room temperature (RT) and at 100 °C using 440C balls with a diameter of 6 mm. The tests at 100 °C were performed to investigate the effect of the sterilization temperature on the tribological properties and the coating lifetime as well. The tribological performance was examined with respect to the friction coefficient, the wear rates of the coating and the counter-parts and the analysis of the wear debris. The Ti/C ratio decreased almost linearly from 4.5 to 0.1 with increasing C₂H₂ flow; the hydrogen content showed a minimum of 5 at.% at C₂H₂ flow of 30 sccm, while for lower flows it was about 10 at.%. The coatings could be divided into three groups based on the C₂H₂ flow: (i) 10–15 sccm, exhibiting severe abrasive damage during the sliding tests, (ii) 20–45 sccm, showing the highest hardness and friction values, and (iii) 52–60 sccm, with moderate hardness and minimal values of the friction coefficient and the wear rate.     

Synthesis of nanoporous activated iridium oxide films by anodized aluminum oxide templated atomic layer deposition

Iridium oxide (IrOx) has been widely studied due to its applications in electrochromic devices, pH sensing, and neural stimulation. Previous work has demonstrated that both Ir and IrOx films with porous morphologies prepared by sputtering exhibit significantly enhanced charge storage capacities. However, sputtering provides only limited control over film porosity. In this work, we demonstrate an alternative scheme for synthesizing nanoporous Ir and activated IrOx films (AIROFs). This scheme utilizes atomic layer deposition to deposit a thin conformal Ir film within a nanoporous anodized aluminum oxide template. The Ir film is then activated by potential cycling in 0.1 M H₂SO₄ to form a nanoporous AIROF. The morphologies and electrochemical properties of the films are characterized by scanning electron microscopy and cyclic voltammetry, respectively. The resulting nanoporous AIROFs exhibit a nanoporous morphology and enhanced cathodal charge storage capacities as large as 311 mC/cm².     

A completely spray-coated membrane electrode assembly

We present a proton exchange membrane fuel cell (PEMFC) manufacturing route, in which a thin layer of polymer electrolyte solution is spray-coated on top of gas diffusion electrodes (GDEs) to work as a proton exchange membrane. Without the need for a pre-made membrane foil, this allows inexpensive, fast, large-scale fabrication of membrane-electrode assemblies (MEAs), with a spray-coater comprising the sole manufacturing device. In this work, a catalyst layer and a membrane layer are consecutively sprayed onto a fibrous gas diffusion layer with applied microporous layer as substrate. A fuel cell is then assembled by stacking anode and cathode half-cells with the membrane layers facing each other. The resultant fuel cell with a low catalyst loading of 0.1 mg Pt/cm² on each anode and cathode side is tested with pure H₂ and O₂ supply at 80 °C cell temperature and 92% relative humidity at atmospheric pressure. The obtained peak power density is 1.29 W/cm² at a current density of 3.25 A/cm². By comparison, a lower peak power density of 0.93 W/cm² at 2.2 A/cm² is found for a Nafion NR211 catalyst coated membrane (CCM) reference, although equally thick membrane layers (approx. 25 μm), and identical catalyst layers and gas diffusion media were used. The superior performance of the fuel cell with spray-coated membrane can be explained by a decreased low frequency (mass transport) resistance, especially at high current densities, as determined by electrochemical impedance spectroscopy.     

Gold atomic contact: Electron conduction in the presence of interfacial charge transfer

This paper presents a work on hitherto unreported conductance alteration of gold atomic contact by electrochemical reduction of redox species at the contact. The interfacial charge transfer current due to reduction of Ru(NH₃)₆^3 + at Au atomic contacts can cause paradigm change of electron transport through the contacts: Conductance quantization is altered to random distribution with substantially reduced length of conductance plateau on the conductance traces. Transient oxidation of the Au atomic contact upon reduction of Ru(NH₃)₆^3 +, which relaxes atomic contact structures and hence the conductance, is proposed together with DFT calculation. The observations in the present work also disclose possible mechanistic information that might be generalized to electrochemical reduction at atomic scale.     

Electrochemical synthesis of orientation-ordered ZnO nanorod bundles

The high density and orientation-ordered ZnO nanorod bundles with wurtzite structures were prepared on Cu substrates by electrochemical deposition in solution of ZnCl₂ + tartaric acid at a temperature of 90 °C. This approach is a unique and size controlled synthetic method for the large-scale preparation of ZnO nanorod bundles. Cyclic voltammogram measured in solution of the mixture of ZnCl₂ and tartaric acid shows a restraining role of tartaric acid for the electro-reduction of Zn(II). The formation mechanism of ZnO on the surface of the cathode can be explained that the high temperature (⩾90 °C) promotes the corrosion of electrodeposited Zn via reacting with H₂O and O₂ to form the stable passive phase of ZnO. The compositions of the nanorod bundles can be entirely ZnO or Zn and ZnO composites determined by the temperature and deposition rate. The photoluminescence (PL) properties indicate that these ZnO deposits are highly crystallized and of excellent optical quality.