99.99% yellow tungsten oxide may be produced by microemulsion method. This method adopts ammonium tungstate solution as raw material. The processes are shown as follows:
1. Add the ammonium tungstate solution into emulsion with surfactant.
2. After super-emulsifying, add in strong acid such as hydrochloric acid (HCL) and sulfate (H2SO4) to react and precipitate.
3. After centrifugal precipitants, clean the precipitants with solvent.
4. Dry to get yellow tungsten oxide.
In microemulsion method, surfactant and co-surfactant is composed of a single molecular layer interface surrounded by the formation of micro-emulsion particles. The grain size of yellow tungsten oxide prepared by microemulsion method can be controlled in a few to several tens of nanometers.
While the cost of surfactant is expensive and the reacting process is complicated, so it is widely used in research institute and lab instead of industrial production.
Microemulsion method is the formation of two kinds of immiscible solvent in the role of surfactant emulsion, in the micro-bubble by nucleation, coalescence, agglomeration, heat treatment to obtain nano-particles, which is characterized by good monodisperse particles and interface so that Ⅱ~Ⅵ semiconducting nanoparticles are prepared by this method.
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