Alumina–silica coatings were prepared on polyimide substrate by sol–gel method using aluminium isopropoxide and tetraethyl orthosilicate as the precursors. The molar ratios of Si/Al were designed as 1∶3, 1∶1 and 3∶1. The surface morphology and structure of as-deposited coatings were investigated by various complementary analysis techniques. The results indicate that all silica–alumina coatings show a smooth and dense surface and have a thickness of ∼400 nm. After treatment at 230°C, the alumina–silica coatings are a diphase structure of AlOOH and amorphous silica, the same as the corresponding gel powders. Moreover, after calcination at 550°C, the alumina–silica gel powders still remain a diphase structure, but AlOOH transforms into γ-Al2O3. The Si content has no obvious effect on the phase structure. However, increasing the Si/Al ratio in the as deposited coatings causes the binding energies of Si 2p, Al 2p and O 1s peaks to shift to higher energy.
TiwariS. K., MishraT., GunjanM. K., BhattacharyyaA. S., SinghT. B. and SinghR.:‘Development and characterization of sol–gel silica–alumina composite coatings on AISI 316L for implant applications’, Surf. Coat. Technol., 2007, 201, 7582–7588.
2.
LandryC. C. and BarronA. R.:‘MOCVD of alumina-silica oxidation resistant coatings on carbon fibers’, Carbon, 1995, 33, 4, 381–387.
3.
KaiserN., UhligH., SchallenbergU. B., AntonB., KaiserU., MannK. and EvaE.:‘Very high-damage threshold Al2O3/SiO2 dielectric coatings for excimer lasers’, Proc. SPIE Int. Soc. Opt. Eng., 1993, 2114, 325–334.
4.
BodemannA., ReichlingM., KaiserN., WelschE.:‘Photothermal microscopy of defects and laser damage morphology in Al2O3/SiO2 dielectric mirror coatings for 248 nm’, Proc. SPIE Int. Soc. Opt. Eng., 1993, 2114, 405–414.
5.
ChenZ. F., LinM. and ShiY. K.:‘Alumina–silica composite coatings on graphite by CVD at 550°C’, JCT Res., 2006, 3, (3), 231–235.
6.
CrepeauG., MontouilloutV., VimontA., MarieyL., CseriT. and MaugeF.:‘Nature, structure and strength of the acidic sites of amorphous silica alumina: an IR and NMR study’, J. Phys. Chem. B, 2006, 110B, 15172–15185.
7.
OmegnaA., van BokhovenJ. A. and PrinsR.:‘Flexible aluminum coordination in alumino-silicates structure of zeolite H-USY and amorphous silica-alumina’, J. Phys. Chem. B, 2003, 107B, 8854–8860.
8.
GilA., VicenteM. A. and KoriliS. A.:‘Effect of the Si/Al ratio on the structure and surface properties of silica–alumina-pillared clays’, J. Catal., 2005, 229, 119–126.
9.
HerrerosB., HeH., BarrT. L. and KlinowskiJ.:‘ESCA studies of framework silicates with the sodalite structure comparison of purely siliceous sodalite and aluminosilicate sodalite’, J. Phys. Chem., 1994, 98, 1302–1305.
10.
BarrT. L. and LishkaM. A.:‘ESCA studies of the surface chemistry of zeolites’, J. Am. Chem. Soc., 1986, 108, 3178–3186.
11.
PadmajaP., WarrierK. G. K., PadmanabhanM., WunderlichW., BerryF. J., MortimerM. and CreamerN. J.:‘Structural aspects and porosity features of nano-size high surface area alumina–silica mixed oxide catalyst generated through hybrid sol–gel route’, Mater. Chem. Phys., 2006, 95, 56–61.
12.
La ParolaV., DeganelloG., ScireS. and VeneziaA. M.:‘Effect of the Al/Si atomic ratio on surface and structural properties of sol–gel prepared aluminosilicates’, J. Solid State Chem., 2003, 174, 482–488.
13.
OreficeR. L. and VasconcelosW. L.:‘Sol–gel transition and structural evolution on multicomponent gels derived from the alumina–silica system’, J. Sol– Gel Sci. Technol., 1997, 9, 239–249.
14.
HenchL. L. and WestJ. K.:‘The sol–gel process’, Chem. Rev., 1990, 90, (1), 33–72.
15.
DingX. Z., HeY. Z. and DongY. D.:‘Applications of sol–gel technique in material science’, Mater. Sci. Eng., 1994, 12, (2), 1–8.
16.
TadanagaK., KitamuroK., MatsudaA. and MinamiT.:‘Formation of superhydrophobic alumina coating films with high transparency on polymer substrates by the sol–gel method’, J. Sol– Gel Sci. Technol., 2003, 26, 705–708.
17.
UrreagaJ. M., MatıasM. C., LorenzoV. and de la OrdenM. U.:‘Abrasion resistance in the Tumble test of sol–gel hybrid coatings for ophthalmic plastic lenses’, Mater. Lett., 2000, 45, 293–297.
18.
ChouT. P. and CaoG. Z.:‘Adhesion of sol–gel-derived organic–inorganic hybrid coatings on polyester’, J. Sol– Gel Sci. Technol., 2003, 27, 31–41.
19.
ZhangX., WuY. Y. and HeS. Y.:‘FTIR study on chemical modification of polyimide surface’, Hebei Ind. Sci. Technol., 2010, 27, 149–152.
20.
LinC., RitterJ. A. and AmiridisM. D.:‘Effect of thermal treatment on the nanostructure of SiO2-A12O3 xerogels’, J. Non-Cryst. Solids, 1997, 215, 146–154.
21.
KurokawaY., SugaT. and NakataS.:‘Transparent alumina films derived from two sources of AlCl3·6H2O and aluminium isopro-poxide by sol–gel method’, J. Mater. Sci. Lett., 1998, 17, 275–278.
22.
UrretavizcayaG., CavalieriA. L., Porto LopezJ. M., SobradosI. and SanzJ.:‘Thermal evolution of alumina prepared by the sol–gel technique’, J. Mater. Synth. Process., 1998, 6, (1), 1–7.
23.
ZhangX., WuY. Y., LiuG., HeS. Y. and YangD. Z.:‘Investigation on sol–gel boehmite-AlOOH films on Kapton and their erosion resistance to atomic oxygen’, Thin Solid Films, 2008, 516, 5020–5026.
24.
ZhangX., WuY. Y., HeS. Y. and YangD. Z.:‘Structure and properties of organic/inorganic hybrid silica coatings’, Aerosp. Mater. Technol., 2007, 37, (4), 19–23.
25.
ZhangX., WuY. Y., HeS. Y. and YangD. Z.:‘Structure characterization of sol–gel composites using TEOS/MEMO as precursors’, Surf. Coat. Technol., 2007, 201, 6051–6058.
26.
LucovskyG., WongC. K. and PollardW. B.:‘Vibrational properties of glasses: intermediate range order’, J. Non-Cryst. Solids, 1983, 59/60, (2), 839–846.
27.
SocratesG.:‘Infrared characteristic group frequencies’, 2nd edn, 188–194; 1994, Chichester, Wiley.
28.
LabyL., KleinL. C.. TurnianskyA. and AvnirD.:‘Synthesis of alumina and silica-containing alumina xerogel hosts’, J. Sol– Gel Sci. Technol., 1997, 10, 177–184.
29.
TakahashiR., SatoS., SodesawaT., ShizukuishiM., MorofujiK. and OguraK.:‘Change in local coordination structure of aluminum cations in silica–alumina solution during coprecipitation’, J. Non-Cryst. Solids, 2005, 351, 826–832.
30.
AravindP. R., MukundanP., Krishna PillaiP. and WarrierK. G. K.:‘Mesoporous silica–alumina aerogels with high thermal pore stability through hybrid sol–gel route followed by subcritical drying’, Microporous Mesoporous Mater., 2006, 94, 14–28.
31.
ShenS. C., ChenQ., ChowP. S., TanG. H., ZengX. T., WangZ. and TanR. B. H.:‘Steam-assisted solid wet-gel synthesis of high-quality nanorods of boehmite and alumina’, J. Phys. Chem. C, 2007, 111C, 700–707.
32.
PopaA. F., RossignolS. and KappensteinC.:‘Influence of drying technique on silicon insertion into γ-alumina and consequences for the homogeneity and thermal stability of silica–alumina aquagels’, J. Mater. Chem., 2002, 12, 2866–2868.
