COATING METAL-OXIDE PARTICLES VIA THE COMBUSTION OF DEPOSITED POLYMERPRECURSORS

Water-swellable chelated polymers were synthesized, starting either fr om (1) In(III) or In(III) and Sn(II) as central ions and N-trimethoxys ilylpropylethylenediamine or ethylenediamine each together with ethyle nediaminetetraacetic acid (EDTA) as coordination ligands, or from (2) Ag(I) as the central ion and ethylene glycol (EG) and EDTA as coordina tion ligands, as follows: The nitrate(s) of the above metal ions toget her with the corresponding ligands were dissolved in water, and the so lution was concentrated by heating to carry out the chelating polymeri zation. After cooling, the polymer was dried and ground to a fine powd er, which was then mixed with a metal oxide powder by grinding in the presence of a small amount of water. A paste was thus obtained, which, after drying, was calcined at 200 degrees C and subsequently at 750 d egrees C. The polymer became a sticky gel at 200 degrees C, which adhe red to the surface of the metal oxide particles; it was converted to a n inorganic coating, In2O3-SnO2-SiO2, In2O3-SnO2, SnO2, or Ag, during the subsequent calcination at 750 degrees C. Two metal oxide powders, namely, the electrically conductive In2O3 and the nonconductive SnO2, were used as substrates. Scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) indicated that the substrate particles were coated after calcination by a multicomponent oxide or silver laye r. Temperature-resistant electrically antistatic film could be prepare d by using the metal oxide coated In2O3 particles as pigments and poly propylsiloxane as the binder. The Ag-coated SnO2 powder had a conducti vity sigma = 1.0 x 10(-3) S cm(-1) at 8.6 vol % Ag, while the mechanic ally mixed powders of Ag and SnO2 exhibited a conductivity of 2.0 x 10 (-7) S cm(-1) at 16 vol %. (C) 1998 John Wiley & Sons, Inc.