PROCESS FOR PREPARING NANOCRYSTALLINE ZNO BY DISTILLATION AND OXIDATION IN MICROWAVE FIELD

摘要

The invention relates to a process and an installation for preparing nanocrystalline ZnO from metal wastes with Zn content, by distillation and oxidation in microwave field. According to the invention, the process comprises the following stages: feeding a crucible (3), which is placed for this particular purpose within a microwave oven (1), with metal wastes with Zn content in admixture with CuZnAl or NaOH, as a fusion agent, in a ratio of 10:1, followed by zinc distillation and oxidation at a temperature ranging between 920...1000°C, at &Dgr;= -1 ± 3 mm CA, for 1 h, resulting in the formation of nanostructured ZnO of a purity of 99.8...99.92% as columnar crystals with a cross section ranging between 2...3 nm and the length of up to 40...60 nm, which are then separated in a cyclone (8) provided with a bag filter (7), the material of the crucible (3) containing silicon carbide impurified with TiOand rare earths, while its shape exhibits a ratio between the surface of discharge of gas flow from the crucible (3) and the surface of evaporation which varies from 1:10 to 1:15, the effect of ZnO particles fragmentation in microwave field being achieved outside the oxidation chamber, by means of a microwave generator (4). The installation, as claimed by the invention, comprises an oven (1) whose crucible (3) has a thermal insulation (2) made of superaluminous ceramic fibres resisting to high temperatures of up to 1600°C, a microwave generator (4) mounted on the oven case (1), an oxidation chamber (5), a fan (6) and a cyclone (8) provided with a bag filter (7).