United Kingdom Atomic Energy Authority

Robert L Nelson

James A Cairns

James L Woodhead

Richard Stuart Nelson

Jim W Isaacs

Peter W Sutcliffe

Colin E Lyon

Michael Joseph Holdoway

Brian Stringer

Carbonaceous deposition on the surface of steel cracker tubes in chemical plant for the thermal cracking of hydrocarbons is a serious problem. It is met, in the invention, by providing the surface with a refractory oxide coating by contacting the surface with a sol comprising an aqueous dispersion of substantially unaggregated primary particles, the sol being capable of conversion to a gel the bulk density of which being at least 40% of the theoretical density of the refractory oxide when measured at ambient temperature and the gel being convertible to the refractory material, converting the sol to the gel, and firing.

Method of coating steel substrates to reduce carbonaceous deposition

The invention is concerned with providing substrates with coatings obtainable from sols, for example to protect the substrate (such as in nuclear reactors or hydrocarbon cracking plant) or to provide a carrier for catalytically active material. Hitherto, coatings obtained from sols have had a high porosity and high surface area so that they have not been entirely satisfactory for the above applications. In the invention, dense, low-porosity coatings are provided by contacting the substrate with a sol of refractory material (e.g. CeO.sub.2 or SiO.sub.2) convertible to a gel of density at least 40% of the theoretical density of the refractory material, and converting the sol to the gel. Optionally, the gel may be converted to a ceramic coating by firing.

Method of producing dense refractory oxide coatings on metallic

There is disclosed a method for the preparation of a shaped body which includes the step of cold pressing a material to give the shaped body, wherein the material has been prepared by means of a gelation process and not substantially comminuted prior to cold pressing. The shaped body can be heated subsequently to pressing to produce a sintered shaped body. Preferably the material for pressing, prepared by a gelation process and not substantially comminuted, is a selected physical configuration.

Preparation of shaped bodies

A catalyst suitable, for example, for treatment of cat exhaust emissions is prepared by providing a substrate with a continuous adherent, surface layer of a carrier material for catalytic material by providing on the substrate a layer of carrier material, at least part of which comprises a gel, and firing; and sputtering catalytic material onto the surface layer by bombarding a source of the catalytic material in the neighbourhood of the surface layer with energetic ions, the conditions of atmosphere and selectivity of ions permitted to bombard the catalytic material being such that co-deposition upon the surface layer of unwanted material is avoided.

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Kingston Bagpuize, United Kingdom

Robert L Nelson