The Sol-gel coating to stengthen an alumina substrate has been studied
. Increase the strength for two times the strength of uncoated substra
te has been achieved. The strengthening depends on coating microstruct
ure and the degree of bonding to the substrate. The coating microstruc
ture has been changed by changing the processing parameters of silica
sol preparation. The coating microstructure has been related to the pH
value and water content of silica sol. (C) 1997 Elsevier Science S.A.