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| Lux L., Heželová M., Gálová M., Markušová K. |
| PARAFFIN IMPREGNATED GRAPHITE ELECTRODEFOR THE INVESTIGATION OF THE SURFACE STATE OF POWDER MATERIALS |
Abstract
Electrochemical investigation of the state of powder surface can favourably be made using the method of abrasive voltammetry with paraffine impregnated graphite electrode as sensor. According to our knowledge, this method was not used for that purpose so far. The electrochemical process investigated was the anodic dissolution of Fe powder particles. The normal pulse voltammetry peak potential, current and total charge were the parameters measured. The size of the particles substantially influences the values of both peak potential and shape : with increasing particle size the peak potential shifts to more positive values and the peak becomes broader and less defined.
The aim of this work was however to find suitable electrochemical parameter reflecting the reactivity of the powder surface which is important from the point of view of its further chemical or electrochemical reactions. Various ways of pretreatment of the powder in order to enhance its reactivity were used : mechanical - grinding, thermal -annealing, and chemical - etching in a reductive solution as well as the combinations of these pretreatment ways.
It was found that the ratio of peak current to total charge value, ip/Qt, named here as steepness of the peak provides a parameter which could reflect the electrochemical dissolution rate of the powder from the electrode, therefore it could reflect the surface reactivity of the powder investigated. The best results as to the reactivity of Fe powder can be obtained by chemical way of pretreatment which was shown by highest values of the peak steepness and afterwards proved by best results of the electrochemical plating of Ni layer on such surfaces.
Other ways of activation than the chemical one lead to less active powder surfaces, the value of ip/Qt does not reach the values measured for chemically pretreated powders. The dissolution process is the slowest in the case of thermally or mechanicallly and thermally treated powders.
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| No 1 (1999), p. 16-23 |
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