Sol Gel Alumina Coating on Fe–Cr–Al–Y Fibre Media for Catalytic Converters

Abstract Sol gel coating of γ-alumina was applied to Fe–Cr–Al–Y fine fibre media to examine the feasibility of using alloy fibres as a substrate for automobile catalytic converters. Two sol gel routes: aqueous based colloidal and alcohol based polymeric sol were used for coating. Prior to deposition, the fibre was oxidised in air to allow a dense α-alumina layer to form. The effect of several coating parameters such as withdrawal speed, sol concentration, soaking time and firing scheme on the coating quality and on the thickness were studied. The morphology of the coating was investigated with scanning electron microscopy (SEM) and the thickness of the coating was measured by the focused ion beam (FIB) technique. The crystal structures of the coating and the thermally grown oxide were studied with photo stimulated luminescence spectroscopy (PSLS). The coated fibre media exhibited different behaviour compared to the ordinary flat substrate. The performance of the alcohol based sol was better than that of the aqueous based sol with regard to the quality of the coating. PSLS was effective in differentiating the γ- and α-alumina.

[1]  S. Castillo.  Reduction of NO by CO under oxidizing conditions over Pt and Rh supported on Al2O3âZrO2 binary oxides , 2001 .

[2]  M. Fichtner,et al.  Preparation of microstructure compatible porous supports by sol–gel synthesis for catalyst coatings , 2001 .

[3]  M. Grimsditch,et al.  Pressure Dependence of Cr3+ Fluorescence in θ-Alumina , 2001 .

[4]  Luhua Xu,et al.  Structure and performance of γ-alumina washcoat deposited by plasma spraying , 2001 .

[5]  F. Stott,et al.  The Effects of Molybdenum on the High-Temperature Oxidation Resistance of Thin Foils of Fe–20Cr–5Al at Very High Temperatures , 2000 .

[6]  R. I. Zakharchenya,et al.  Luminescence of impurity 3d and 4f metal ions in different crystalline forms of Al2O3 , 2000 .

[7]  C. Lambert,et al.  Sol-gel preparation and thermal stability of Pd/γ-Al2O3 catalysts , 1999 .

[8]  A. Osaka,et al.  Properties and catalytic activity of NOx reduction of alumina-titania catalysts prepared by sol-gel method , 1999 .

[9]  D. Clarke,et al.  Determination of the growth stress and strain in α-Al2O3 scales during the oxidation of Fe–22Cr–4.8Al–0.3Y alloy , 1998 .

[10]  David R. Clarke,et al.  Nondestructive evaluation of the oxidation stresses through thermal barrier coatings using Cr3+ piezospectroscopy , 1996 .

[11]  J. Kašpar,et al.  Modification of the Redox Behaviour of CeO2Induced by Structural Doping with ZrO2 , 1996 .

[12]  L. Hobbs,et al.  The oxidation mechanism of θ-Al2O3 scales , 1995 .

[13]  F. Stott,et al.  The Relationship Between Oxide Grain Morphology and Growth Mechanisms for Fe‐Cr‐Al and Fe‐Cr‐Al‐Y Alloys , 1979 .

[14]  F. Stott,et al.  The influence of yttrium additions on the oxide-scale adhesion to an iron-chromium-aluminum alloy , 1976 .

[15]  Bulent E. Yoldas,et al.  Alumina gels that form porous transparent Al2O3 , 1975 .

[16]  C. Sigala,et al.  Sol-Gel Coatings on Non-Oxide Planar Substrates and Fibers: A Protection Barrier Against Oxidation and Corrosion , 2003 .

[17]  A. Jayaraman,et al.  Diamond anvil cell and high-pressure physical investigations , 1983 .

[18]  David L. Trimm,et al.  The combustion of methane on platinum—alumina fibre catalysts—I: Kinetics and mechanism , 1980 .