Selenium particle size distribution

Figure 5. Particle-size distribution of selenium aerosols ( ) 400°C, (O) 375°C...

The cadmium red pigment intermediate is obtained as a precipitate which is filtered off, washed, and calcined at approx. 600 °C. As with cadmium yellow, calcination yields the red pigment and determines the particle size, particle size distribution, and color shade. Analogously to the cadmium yellow process, cadmium red can be produced by direct reaction of cadmium oxide or cadmium carbonate with sulfur and the required amount of selenium at approx. 600 °C. 

Depending on the amount and the distribution of selenium, up to 5% hydrogen peroxide formation has been observed in the oxygen reduction reaction. As hydrogen peroxide leads to a rapid degradation of the membrane and the gas diffusion media and enhances the corrosion of the carbon catalyst support and finally to a loss of performance due to this side reaction, the formation of hydrogen peroxide has to be minimized. Further details on the effect of particle size, particle distribution and the effect of the carbon support on the hydrogen peroxide production has been mentioned above. 

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