Platinum Metals Review - Volume 45, Issue 3, 2001

Research into supported palladium complexes is described. The complexes are immobilised on porous silica supports using both grafting and templated sol-gel techniques. The resultant complexes are efficient catalysts for various C-C bond forming reactions, including Heck, Suzuki and allylic substitution. The catalysts are stable and can be easily recovered and reused, making them suitable for cleaner processing.

The first part of this paper describes a combination of physical metallurgical techniques and hydrogen (H2) solubilities employed to help in the characterisation of defects in palladium and its alloys. Cold working or hydride formation and decomposition introduce large dislocation densities into palladium and palladium alloys. These can be examined by transmission electron microscopy and correlated with hydrogen (H) segregation to the stress fields of the dislocations determined from H2 solubilities. H atoms are strongly trapped by vacancies in the palladium lattice and evidence for vacancy trapping in cold-worked palladium is shown by deviations in H2 solubility, different to that expected if H segregated only to the dislocation stress fields. The second part of this paper, to be published in the October 2001 issue, will be concerned with hydrogen segregation to defects introduced by the internal oxidation of palladium alloys or by treatment at moderately high temperatures and hydrogen pressures.

Titanium alloys are used in the manufacture of gas turbine aircraft engine compressor section components, which in use are exposed to high temperatures and corrosive environments. The platinum aluminide coatings described here have been developed to protect titanium alloys from oxidation and alpha case formation and can thus significantly improve the life of the alloys. The coatings showed a very low weight gain and alpha case formation did not occur during the entire period of exposure. The superior performance of the coating is due to the formation of a protective, adherent and continuous alumina scale on its surface. The results clearly suggest that this platinum aluminide coating is a prospective coating material to protect the titanium alloy components both from oxidation and alpha case formation.