A new attempt on reduction of ultrafine oxide particles

A method to coat the surface of ultrafine particles by an amorphous carbon layer was developed and a characteristic reduction of the ultrafine particles has been observed for WO₃ ultrafine particles. The carbon layer formation and the reduction process have been observed in situ in a transmission electron microscope. The growth of the carbon layer predominately occurred upon heating at 200°C by using a heating stage. The characteristic graphitization of the carbon layer took place at about 400°C. The characteristic gap formation at the interface of the carbon layer and WO₃ particles started at about 400°C. The reduction indicates that a reaction between O and C atoms occurred and CO or CO₂ gas evaporated into vacuum during the observation. The WO₃ particles with the gap between carbon layers were also reduced.