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13th December 2018, Osaka

Progress with metal-ceramic composites

Researchers at Osaka University have developed a method for manufacturing composites of alumina ceramics and titanium.

Various types of metal-ceramic composite have been researched and developed, the researchers say, but their combination and fine structures have been limited. In particular, the combination of ceramics such as alumina used as matrices and titanium – a biocompatible metal – has proved problematic, in that the structure of the composites achieved has not been uniform. This is due to the high reactivity of titanium – oxidation happens and chemical compounds are produced – and the large particle size of commercially-available titanium powders, of several tens of micrometres.

Upper left: This is a structure of Ti-dispersed AI2O3 composites. Lower left: Ti content dependency of fracture roughness and electrical resistivity. Middle: Nanostructure of the surface of AI2O3 composites produced via chemical and heat treatments. Right: Discolouration by the photocatalytic activity of AI2O3 composites after chemical and heat treatments. © University of Osaka

In order to fully exploit the advantages of both ceramics and metal in composites, the Osaka team has designed a percolation structure for forming a continuous conduction pathway by dispersing fine-sized titanium particles into an alumina matrix, optimising the particle size of the metallic titanium powder and sintering processes. The result is said to be improved fracture toughness and electrical conductivity, while simultaneously providing the composites with photocatalytic ability through chemical and/or thermal treatment.

The researchers have also demonstrated that, while ceramics are not electrically conductive, the composites can be machined by electrical discharge machining like metals.

They could also be used for industrial products and biomaterials as new multi-functional composites that have an active surface layer with antibacterial properties and a photocatalytic ability to break down pollutants.

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