Tioxide Group Services Limited

Croda International, Inc.

Tioxide Group, Plc

Imperial Chemical Industries Limited

Graham P Dransfield

Terence A Egerton

Susan Cutter

Kevin A Fothergill

Frank L Riley

Anthony P Bromley

Phillip Lawrence Lyth

Paul McColgan

Phillip Laurence Lyth

Denis J King

Philip Laurence Lyth

A particulate metal oxide having the mean length of the primary particles in the range from 50 to 90 nm, the mean width of the primary particles in the range from 5 to 20 nm, and the median volume particle diameter of the secondary particles is less than 45 nm. The metal oxide can be used in a sunscreen product that exhibits both effective UV protection and improved transparency.

Particulate metal oxide

A particulate metal oxide having a mean length of the primary particles in the range from 50 to 90 nm, the mean width of the primary particles in the range from 5 to 20 nm, and the median volume particle diameter of the secondary particles is less than 45 nm. The metal oxide can be used in a sunscreen product that exhibits both effective UV protection and improved transparency.

An article is provided which has a surface which is contactable in use with water at a temperature of at least 100.degree. C. The surface of the article is protected from attack by the water, because it is formed of a shaped fired ceramic material which is formed from particulate zirconia having a coating on the particles thereof of a hydrous oxide of yttrium and optionally also a hydrous oxide of zirconium, titanium or aluminum. Preferably the particles have a diameter of not more than 0.5 micron and the amount of hydrous oxide of yttrium falls within the range 0.5 to 10 mole percent as Y.sub.2 O.sub.3 on moles of zirconia. Typical articles are internal combustion engines and parts thereof, mills and impact plates therefor, and pump surfaces. Fuel cells are also described.

Method for protecting shaped articles from attack by water

A process for coating particulate zirconia for use in ceramics is claimed. The particulate zirconia is coated with a hydrous oxide of a stabilizing metal such as yttrium, an alkaline earth metal or a rare earth metal by hydrolysis of a salt of the metal. An initial dispersion of the zirconia is prepared at a pH above 7.5 and, preferably, in the presence of an organic dispersing agent. The coated zirconia produced according to the process has been shown to form ceramic bodies with a higher strength than those prepared from particulate zirconia coated by prior known processes.

Metallic oxides

A composition suitable for use in the manufacture of ceramics comprises particulate zirconia the particles of which are coated with a hydrous oxide of yttrium and a hydrous oxide of manganese, iron, cobalt, nickel, copper or zinc. Preferably the particles also have an inner coating of titania, zirconia, hafnia or alumina. Ceramics prepared from the particulate zirconia of the invention are resistant to degradation by water at temperatures above 100.degree. C.

Stabilized metal oxides

Green bodies suitable for use in manufacturing ceramic articles are provided. The bodies comprise a coherent mass of particles of aluminium oxide free of organic binder and having a fracture stress measured by a biaxial disc flexure test of at least 10 MPa. The particles of aluminium oxide are coated with at least one inorganic oxide or hydrous oxide. The green body can be shaped by drilling, sawing etc. to a desired shape approximating to that of the ceramic article which it is used to produce. Generally such shaping is considerably easier than shaping the finished ceramic article.

Ceramic green bodies

Green bodies suitable for use in manufacturing ceramic articles are provided. The bodies comprise a coherent mass of particles of titanium dioxide free of organic binder and having a fracture stress measured by a biaxial disc flexure test of at least 5 MPa. The particles of titanium dioxide are coated with at least one inorganic oxide or hydrous oxide. The green body can be shaped by drilling, sawing etc. to a desired shape approximating to that of the ceramic article which it is used to produce. Generally such shaping is considerably easier than shaping the finished ceramic article.

The invention provides a form of particulate zirconia suitable for forming zirconia ceramics in which the zirconia is stabilized in the cubic and/or tetragonal phase. The particles of zirconia are coated with a hydrous oxide of cerium and at least one hydrous oxide of lanthanum, neodymium or praseodymium. In a preferred embodiment a mixture of hydrous oxides of lanthanum and neodymium is used. Preferably the particles are also provided with an inner coating comprising hydrous titania, zirconia or alumina. The products of the invention can be converted into ceramics having a greater strength than ceramics produced from zirconia coated with a similar amount of ceria alone or those produced by physically mixing similar quantities of stabilizing oxides with the particulate zirconia.

The stabilization of zirconia when used as a ceramic by various stabilizers has been known but a new and improved stabilized particulate zirconia has now been developed showing the important advantages. The particulate zirconia now developed is coated with a hydrous oxide of titanium and/or of aluminium and with at least one hydrous oxide of yttrium, calcium, magnesium, strontium or cerium.

Growing community of inventors

Stockton on Tees, United Kingdom

Graham P Dransfield