In this paper, different preparation routes and designs for pH sensing metal/metal oxide electrodes are evaluated. Crystallographic changes in the oxide film are responsible for the pH‐sensing capability of tungsten oxide. As the present oxide structure is directly limiting the measuring range, as‐received tungsten oxide powders were heat treated to produce polymorphs of WO3, in an attempt to extend the measuring range. Furthermore, electrochemical oxide covered electrodes ranging from micro‐ down to nano‐dimensions have been implemented. Optional coating with Nafion, serving as a membrane material, allows shifting the measuring range even to strongly alkaline conditions.

Three different AlFeNb alloys of various compositions were prepared by arc melting. X-ray diffraction (XRD) investigation of the melted samples proved the presence of two phases identified as a bcc a(Fe,Al) solid solution and a hexagonal C14 (Fe,Al) 2 Nb Laves phase. Subsequent electrochemical treatment allowed for a selective dealloying of the a(Fe,Al) or respective FeAl phase and resulted in releasing differently microstructured surfaces. These structures ranged from regular lamellar structures towards branched, fibrous structures. Scanning electron microscope (SEM) characterisation along with a local energy dispersive X-ray spectroscopic (EDX) analysis of the samples and atomic absorption spectrometry (AAS) analysis of the electrolyte revealed a preferential Fe dissolution and the passive nature of the Nb. The results demonstrate that the phases present in the alloys strongly depend on the production and heat treatment history of the sample. SEM micrograph of (A) Fe-15Al-10Nb and (B) Fe-26Al-4Nb after anodisation in 0.4 M borate buffer.

No abstract

No abstract

Directional solidification of eutectic NiAl–W alloys offers an intuitive method to produce tungsten nanowires. Through the use of two different methods, the well‐established Bridgman method and a newer type floating zone method, the direct influence of process parameters, like the withdrawal rate and the temperature gradient, onto the sample microstructure were studied. The sharp temperature gradient, built up using a four mirror system focusing the light emitted by halogen lamps inside the optical floating zone furnace allows producing nanowires with a diameter as small as 75 nm. Differences in the solid/liquid interface morphology depending on the solidification method used are discussed.