Hydrogel-based flexible micro-reference electrodes for use in alkaline and neutral pH solutions

Two types of nonbreakable, flexible micro-reference electrodes filled with gel-electrolytes were prepared for use in solutions with alkaline and neutral pH. The electrodes are intended for electrochemical measurements, in which chloride-free conditions are important. Due to the flexible, bendable construction of the electrodes, electrochemical experiments at locations difficult to access with common reference electrodes are enabled. Hg|HgO-type electrodes were prepared from amalgamated Au wires, followed by oxidation of the amalgam, which is mounted in a PTFE tube filled with 0.1M NaOH solution immobilized in a PAA-g-PEO gel. The potential of this type of electrode was found to be 0.1620.002 V (SHE) at room temperature. Cu|CuSO4 electrodes, consisting of a Cu wire immersed in a saturated CuSO4 solution jellied with gelatin, showed a stable open-circuit potential of 0.3120.001 V (SHE). Further characterization of the electrodes was performed in terms of electrochemical impedance spectroscopy and micro-polarization measurements. As an alternative to the flexible electrodes, rigid electrodes in glass enclosure were fabricated in analogy to the flexible-type electrodes.(VLID)342007

Downstream analytics quantification of ion release during high voltage anodisation of niobium

In operando quantification of field-assisted ion release during high-voltage anodisation (up to 100 V SHE) of Nb in 0.1 M sulphuric acid was performed. Electrochemical high-field oxide formation under both potential and current control was studied separately. The quantification of in situ ion release via ICP-MS revealed an increase of the oxide dissolution factor (from 337 to 422 fm V1) when decreasing the potential scan rate from 200 to 100 mV s1. Dissolution rates measured during galvanostatic oxide formation allowed measuring oxide dissolution factors of 719 and 837 fm V1 for current densities of 1.0 and 0.5 mA cm2, respectively. As compared to the potentiodynamic case, higher dissolution rates and oxide dissolution factors were measured for galvanostatic anodisation. The overall fraction of the charge used for generation of soluble Nb species was below 0.4% for all oxide growth regimes. Cross-sectional SEM imaging proofs an oxide formation factor of 2.1 nm V1. The surface of anodised films was extremely smooth and featureless without any cracks or voids. Based on X-ray diffraction, the films were found to be amorphous, indicating that no field crystallisation is occurring under the applied oxide growth conditions even at higher voltages.(VLID)340177

Basic properties mapping of anodic oxides in the hafniumniobiumtantalum ternary system

A thin film combinatorial library deposited by co-sputtering of Hf, Nb and Ta was employed to characterise fundamental properties of the Hf-Nb-Ta system. Compositional mappings of microstructure and crystallography revealed similarities in alloy evolution. Distinct lattice distortion was observed upon addition of hexagonal Hf, leading to amorphisation of alloys containing more than 32 at.% Hf and less than 27 and 41 at.% Nb and Ta, respectively. Volta potential and open circuit potential mappings indicated minimal values for the highest Hf concentration. Localised anodisation of the library by scanning droplet cell microscopy revealed valve metal behaviour. Oxide formation factors above 2 nm V1 were identified in compositional zones with high amounts of Nb and Ta. Fitting of electrochemical impedance spectroscopy data allowed electrical permittivity and resistivity of mixed oxides to be mapped. Their compositional behaviours were attributed to characteristics of the parent metal alloys and particularities of the pure oxides. MottSchottky analysis suggested n-type semiconductor properties for all HfNbTa oxides studied. Donor density and flat-band potential were mapped compositionally, and their variations were found to be related mainly to the Nb amount. Synergetic effects were identified in mappings of Hf-Nb-Ta parent metals and their anodic oxides.(VLID)341510

Corrosion and Structural Properties of ErbiumZinc Thin Films at LowtoMedium Erbium Concentrations

A combinatorial erbiumzinc thin film material library is deposited by thermal coevaporation. The library is screened for its structural and compositional properties by energydispersive Xray (EDX), Xray diffraction (XRD), and scanning electron microscopy (SEM), and shows a compositional range from 3.1 to 31.2at% Er. XRD proofs an amorphous region around 20at% Er. This is rarely encountered in binary systems, and supports an improved corrosion resistance for this composition. SEM shows the formation of a compact film at the same compositional range. The alloys' electrochemical characteristics are assessed with opencircuit potential (OCP), electrochemical impedance spectroscopy (EIS), cyclic voltammetry, and potentiodynamic polarization measurements in a scanning droplet cell microscopy (SDCM) setup coupled with an inductively coupled plasma optical emission spectrometer (ICPOES). This allows capturing the relation between current, potential, and metal ion dissolution in the system. The experiments are performed in aqueous 0.01m Na2SO4 solution under constant flow (0.0136mLs1). Increased corrosion resistance is found for alloys containing 1922at% in all four used methods, showing the superior properties at this compositional range.(VLID)4918838Version of recor

Basic properties mapping of anodic oxides in the hafnium–niobium–tantalum ternary system

<p>A thin film combinatorial library deposited by co-sputtering of Hf, Nb and Ta was employed to characterise fundamental properties of the Hf-Nb-Ta system. Compositional mappings of microstructure and crystallography revealed similarities in alloy evolution. Distinct lattice distortion was observed upon addition of hexagonal Hf, leading to amorphisation of alloys containing more than 32 at.% Hf and less than 27 and 41 at.% Nb and Ta, respectively. Volta potential and open circuit potential mappings indicated minimal values for the highest Hf concentration. Localised anodisation of the library by scanning droplet cell microscopy revealed valve metal behaviour. Oxide formation factors above 2 nm V⁻¹ were identified in compositional zones with high amounts of Nb and Ta. Fitting of electrochemical impedance spectroscopy data allowed electrical permittivity and resistivity of mixed oxides to be mapped. Their compositional behaviours were attributed to characteristics of the parent metal alloys and particularities of the pure oxides. Mott–Schottky analysis suggested n-type semiconductor properties for all Hf–Nb–Ta oxides studied. Donor density and flat-band potential were mapped compositionally, and their variations were found to be related mainly to the Nb amount. Synergetic effects were identified in mappings of Hf-Nb-Ta parent metals and their anodic oxides.</p