The development of co-precipitation method for preparing metal-oxide nanoparticles
Powder is very practical material for further processing, to be used as a bulk, slab, pellet, even film as well as solution or colloid. Price of commercial powder is generally dependent on its purity and fineness of the grain/crystallite size. These factors are associated with the complexity of preparation, thus determining the resale value. Besides metal, powder is widely available in the form of ceramic compounds, which are generally the oxides, carbonates, sulfates, carbides and so on.
The metal-oxide ceramic powders can be prepared by simple coprecipitation. This method not only can produce high purity powder, but also that with a crystal size in the order of nanometer (nm), or so-called nano-ceramic precipitates. To cite some examples, a number of powder types have been successfully synthesized with potential application as follows: Fe3O4 and BaFe6O19 (magnetic materials, microwave absorbent, magnetic fluid and gel), TiO2 (optical applications and anti-corrosion layers), MgO and Al2O3 (fillers to enhance mechanical strength), CaCO3 (food additives, cosmetics and drugs). In addition, some metalic cations can be produced from natural sources such as iron ore (Fe, Ti), limestone (Ca, Mg), mud volcano (Si, Al) and so on.
The Fe3O4 particles resulted by coprecipitation process of iron sand (left), of iron sand with PEG template – 1000 (middle); and Fe3O4 commercial products of Aldrich (right).
The TiO2 particles (anatase) produced by coprecipitation with stirring for 25 hours (left); TiO2 (rutile) produced by employing catalyst of NaCl 3M (middle); and TiO2 (rutile) prepared with stirring for 85 hours (right).
Particles resulted from coprecipitation method followed by heating process :
MgO (left); Al2O3 (middle); and BaFe6O19 (right).
Particles with different morphologies as a result of the varying rate of CO2 during the coprecipitation process, which produces CaCO3 with phases: calcite (left), vaterite (middle) and aragonite (right). The image size is 5 μm x 5 μm.