Tailoring Size of α-Al2O3 Nanopowders via Polymeric Gel-net Method

Acrylamide (as monomer), N,N -methylene-bis-acrylamide (as cross-linker),ammonium persulphate (as initiator), N,N,N ,N -tetramethylethyldiamine (asaccelerator), and aluminium nitrate salt were used to produce a low temperaturepolymeric gel-net, in order to tailor the particle size of alumina powder. Themonomers/salt ratio, metal ion/monomers interaction, furnace atmosphere, thermalstability and pore size of polymeric gel-net are the key factors to control the aluminaparticle size. Mercury porosimetry data and transmission electron microscopy (TEM)micrographs indicated that increasing the monomers/salt ratio from 1/1 to 3/1 resultedin polymeric gel-net with smaller pore size, and hence, nanopowders with narrowerparticle size distribution. The X-ray diffraction (XRD) patterns for nanopowdersexhibited the amorphous phases below 1100°C and a single phase α-Al2O3 above1100°C. Thermal analysis showed that for pre-oxidized samples below 200°C polymericgel-net possesses better thermal stability at higher temperature in the presenceof inert gas. Trapping of metal ions, with specific coordination numbers, into polymericgel-net pores prevents their migration and reduces the nanopowder particlesagglomeration. These observations were also confirmed by Fourier transform infrared(FTIR) and UV-vis spectrometry measurments. Polymeric gel-net inhibits the aggregationof Al2O3 nanopowder, improves its homogeneity, and provides a powder withnarrower particle size distribution.