Agglomeration of nano-MgAl₂O₄ spinel from microemulsion and CVD techniques

MgAl₂O₄ nanoparticles have been prepared using a microemulsion synthesis technique (ME) and a chemical vapour deposition (CVD) approach. In the wet-chemical route, the chain length of the surfactant molecules used to stabilise the microemulsion as well as the annealing conditions (temperature and time) after preparation were varied. For CVD samples, the influence of the target temperature and the consecutive annealing temperature were investigated. A pinhole small-angle X-ray scattering camera was employed to determine the size and size distribution of primary particles as well as agglomerates. ME material is primarily obtained in the form of amorphous non-agglomerated particles; CVD raw material is crystalline and agglomerated. Upon annealing, agglomerates of ME material form and then grow faster than the primary particles do; in CVD material the agglomerates do not grow. Agglomeration is suppressed if the CVD process is carried out at elevated target temperature.