Micro-wires

Gun, I., Salaun, P. and van den Berg, C. M. G. (2006), Advantages of using a mercury coated, micro-wire, electrode in adsorptive cathodic stripping voltammetry. Anal. Chim. Acta, 571(1) 86-92. 

The first three investigators use tine type electrodes that are either the 100-pin array (devised by Dick Norman), and used by Donoghue and colleagues [2], or the Michigan probe used by Schwartz et al. [3j. Anderson and colleagues use their version of the array [ 1 ]. Nicholelis et al. use micro wires they have devised [4]. Let us take these characteristics point by point. Kennedy is the only one to use the NE so far [5,9,10]. 

D. Zhu, K. Wang, N.S. Qu, Micro wire electrochemical cutting by using in situ fabricated wire electrode, Annals of the CIRP 56 (1) (2007) 241-244. 

Y.-B. Zeng, Q. Yu, S.-H. Wang, Di Zhu, Enhancement of mass transport in micro wire electrochemical machining, CIRP Ann. - Manuf. Technol. 61 (2012) 195-198. 

CH-based dielectrics are commonly used for macro and micro Sinking-EDM as well as micro Wire-EDM processes, while water-based dielectrics are used in macro Wire-EDM operations. Nowadays there are also trends to use CH-based dielectrics in macro Wire-EDM to achieve a corrosion-free superior surface integrity. For Drilling-EDM both dielectrics are in use. 

Fracture of wires Fracture of metallic glasses Deformation texture Drawing defects Polycrystalline strengthening Fatigue of micro-wires Fatigue of metallic glasses Bonding wires... 

Fracture of massive brittle and ductile pieces are rather well understood. By taking proper account of the microstructure as well as the micro- and macro-defects, most catastrophic and fatigue failures find a satisfactory explanation within the scope of the linear elastic fracture mechanics or the elasto-plastic fracture mechanics. Metallic filaments are particular and in many respects deserve a treatment of their own. Particular fabrication methods, such as drawing, melt spinning or crystallization from the vapor phase for whiskers are needed to obtain their small lateral dimensions. These processes may give rise to particular textures, intrinsic and extrinsic defects. Thermal treatments may modify or eliminate such defects but in many cases fracture is initiated by defects that stem from the fabrication process. Moreover, the small lateral dimensions, especially in micro-wires, make metallic filaments prone to external influences. Corrosive attacks may rapidly affect an important fraction of their cross-section. Hydrogen, for instance, which usually results in a severe embrittlement, may diffuse up to the core in a rather short time. 

Similar observations on as-drawn micro-wires of Cu where made by Murr et al. (1997) and Murr and Flores (1998). In contrast to our results their samples appear to show even bigger microstructural differences between the core and the surface near regions. This may probably be attributed to different drawing conditions and techniques... 

Fig. 4. Typical fracture modes of Au micro-wires (a) diameter 50 M-m. as-drawn, and (b) the same wire strongly annealed (few grains per cross-section) (c) diameter 25 M-ni. as-drawn, and (d) the same wire annealed to bamboo structure. As-drawn wires show cylindrical necking fracture whereas oligocrystalline wires and wires with bamboo structure show wedge-shaped necking.

Table 4. Tensile strength of micro-wires produced by the Taylor process (Nixdorf, 1967)...

A number of comparable studies, which bear relevance for micro-wires, have been published on thin Cu foils. Judelewicz (1993) and Judelewicz et al. (1994) reported on... 

Contrary to macroscopic samples where the fracture surface of fatigue specimens is usually normal to the tensile stress direction, thin sheets are similar to micro-wires. They undergo a very large amount of plastic deformation and neck down to zero cross-section, ending in irregular knife edge rupture, very much like a high-temperature creep rupture. 

Fiti, Fiiligue curves ol small-gciiincU copper micro-wires and thin foils. 0, wire diamclcr d, foil thickness 1, longitudinal t, transverse to rolling direction. 

I.M. KolthofiF and C. Bamum, The anodic reaction and waves of cysteine at the dropping mercury electrode and at the platinum micro wire electrode, J. Am. Chem. Soc., 1940, 62, 3061-3065. 

Fig. 21 Micro wire arrangement for light-induced water splitting showing the basic structure of Si micro wires embedded in a membrane the upper part acts as photoanode, the lower as cathode electrocatalysts have not been included in the drawing...

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