Brass disk electrodes

An example of a PVC orientation depolarisation effect, measured with a combined TMA/TSD system is given in chapter 6. These orientation depolarisation effects were measured on small (i.e. 8 mm.) diameter, samples. Such samples proved to be too small, however, to detect the space charge depolarisation effects in non-polar SSBR rubbers. These non-vulcanised rubber samples were pressed, therefore, at 140°C between two (l mm thick) brass disks with a diameter of respectively 110 mm (high potential electrode) and 80 mm (low potential electrode) to a sample thickness of about 0.2 mm. A ring (inner/outer diameter 75/85 mm) of 50 micron thick Vespel foil avoided shortcircuiting between the two brass disks. 

Electrochemical Instrumentation. For the Ru complexes, a 1 cm diameter platinum disk brazed onto a brass holder was used as a working electrode. It was masked with ChemGrip (a teflon based epoxy) except for the upper face. Prior to use, it was polished with 1 micron diamond paste (Buehler) and rinsed with water, acetone and methanol. The working electrode for each Os complex was the uppermost platinum layer of a platinum/carbon layered synthetic microstructure (LSM) (Energy Conversion Devices). The LSM consisted of 200 layer pairs of carbon and platinum whose thicknesses were 24.4 and 17.0 A, respectively and where platinum was the outermost layer. The LSM was placed in 1.0 M H2SO4 and cleaned... 

FIGURE 8. (a) Electrochemical cell and ancillary components for quasi in situ conversion electron Mossbauer measurements/The counter and reference electrodes are not shown in this figure, (b) Schematic diagram of rotating system. A. Motor, B. aluminum support, C. reduction gear, D. phenolic shaft, E. brass contact, F. Teflon bushing, G. aluminum support, H. electrochemical cell, I. working electrode (disk), J. conversion electron counter, K. Mossbauer source, L. Mossbauer Doppler velocity transducer, M. carbon brush assembly. 

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