An interdigitated microelectrode array (IDA) was applied to the determination of formaldehyde released from textiles produced in industry. The proposed method is based on formaldehyde reaction with hypobromite which is formed in weakly basic media by control current electrooxidation of bromide on the generator segment of the IDA array. The unreacted hypobromite diffuses through the gap between individually polarisable IDA segments and it is amperometrically detected on the collector segment of the IDA. The efficiency of this nonconvective transfer process in the absence of formaldehyde was substantially higher (78%) in comparison with that when using the rotating ring disc electrode. The influence of the added formaldehyde on the transfer process can be utilised to develop a simple and sensitive analytical procedure for formaldehyde detection with a detection limit of 4 x 10(-6) mol dm(-3).
This paper deals with the study of the crystallization and phase transformation of Ni-P coatings deposited on AZ91 magnesium alloy. Prepared samples were characterized in terms of surface morphology and elemental composition by means of scanning electron microscopy with energy-dispersive spectroscopy analysis. The results of X-ray diffraction analysis and differential scanning calorimetry suggested that increasing the phosphorus content caused Ni-P coatings to develop an amorphous character. The crystallization of Ni was observed at 150, 250, and 300 °C for low-, medium- and high-phosphorus coatings, respectively. The Ni crystallite size increased with increasing temperature and decreasing P content. Conversely, the presence of the Ni3P phase was observed at a maximum peak of 320 °C for the high-phosphorus coating, whereas the crystallization of the Ni3P phase shifted to higher temperatures with decreasing P content. The Ni3P crystallite size increased with increasing temperature and increasing P content. An increase in microhardness due to the arrangement of Ni atoms and Ni3P precipitation was observed. The deposition of as-deposited Ni-P coatings led to an improvement in the corrosion resistance of AZ91. However, the heat treatment of coatings resulted in a deterioration in corrosion properties due to the formation of microcracks.
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