抄録
The effect of ball milling on the surface condition of CdS powders was investigated. The sample powders were precipitated from aqueous solution of cadmium sulfate. The mean particle sizes of the precipitates were about 10 and 2μm. The sample powders were ground in an alumina ball mill for different periods from 30min to 240hr. In the early stage of the grinding process, the particle size of the specimen having the initial particle size of 10μm decreased rapidly to about 2μm and it did not decrease any more even if grinding time was prolonged. On the other hand, the particle size of the specimen having the initial particle size of 2μm did not decrease any more. However, the degree of structural imperfections increased with increasing grinding time for both specimens.
Using an interdigital electrode, the decrease in photocurrent associated with an adsorption of oxygen has been measured. The magnitude of the decrease in the photocurrent of ground CdS powders became larger with increasing grinding time. This suggests that the structural imperfections, generated by ball milling, act as adsorption sites for oxygen molecules.
Corona-charging potentials of ground CdS powders have been measured as a function of relative humidity. The initial surface potentials decreased with increasing grinding time over a whole range of relative humidity for all specimens. This is attributable to a decrease in apparent resistivity of the powder layer, which is associated with an increase in adsorbed moisture. The adsorption of ambient moisture is enhanced by the ball milling.
