1 Gas phase method (1) Chemical vapor deposition technology The high purity ultrafine alumina particles are synthesized by gas phase pyrolysis or chemical reaction, mainly using metal elemental, halide, hydride or organic compound as raw material. Among them, chemical vapor deposition technology is widely used. For example, Italian researchers used alkyl aluminum and N2O with high vapor pressure at room temperature as reactants, added ethylene as a reaction accelerator, and successfully synthesized spherical α-Al2O3 particles with a particle size of 15-20nm by CO2 laser heating.