Precursors for coating metals and ceramics.(COATINGS)

US researchers have devised low vapour pressure precursors for the manufacture of protective coatings on metallic and ceramic substrates.

The precursors are phosphate esters or aryl phosphate esters in solution, with additives that include iron, chromium, and/or other transition metals. Magnesium compounds can also be added to facilitate growth of films on substrates that do not contain magnesium, the researchers say.

According to the researchers--from US National Aeronautics and Space Administration's (NASA's) John H. Glenn Research Center, Cleveland, Ohio, and Cleveland State University--the precursors were formulated by mixing the ingredients into a high vapour pressure solvent, to form a homogeneous solution.

Next, the solvent is extracted by evaporation--aided, if necessary, by a vacuum aspirator, the researchers say. The solvent is judged to be fully extracted when the viscosity of the remaining solution closely resembles that of the phosphate ester or aryl phosphate ester.

In addition, satisfactory removal of the solvent can be verified by means of differential scanning calorimetry: the absence of endothermic processes for temperatures below 150[degrees]C indicates that the residual solvent has been eliminated from the solution beyond a detectable dilution level.

For further information, contact: Steve Fedor, Mail Stop 4-8, NASA Glenn Research Center, Commercial Technology Office, 21000 Brookpark Road, Cleveland, OH 44135, USA; tel: +1-216-433-2144; fax: +1-216-433-5544; E-mail: steven.l.fedor@lerc.nasa.gov; Internet: www.lerc.nasa.gov