Thermal treatment at temperatures up to 1000 °C improves the pigment properties of the ZnO and is mainly applied to oxide produced by the direct method. Controlled atmospheric calcination also improves the photoconducting properties of the high — purity oxide used in photocopying.
The ZnO surface is made more organophilic by coating it with oil and propionic acid. The ZnO is often deaerated and increasingly pelletized or granulated to improve handling properties.
2.3.4