The precipitation and some properties of alumina coatings on rutile

Alumina was precipitated on to rutile in four different ways to provide a series of alumina‐coated rutiles. There were two main types of precipitate. Type A with alumina precipitated in an acid medium and type B with alumina precipitated at pH 8. The two types of coating differed in appearance, surface area and in the nature of alumina present. For the type A coatings, the precipitate was irregular with much interstitial material and consisted of amorphous alumina of surface area < 100 m2 g−1. The type B coatings were compact and almost invisible and had surface areas > 140 m2 g−1. Alumina gels were precipitated under similar conditions to the type A and type B coatings and compared with these coatings to see if the presence of rutile had modified the type of alumina that formed.