Ceramics toughen up

Clay Technology magazine
,
16 Apr 2010
The material absorbing crack energy

A building material that could lead to less brittle, crack resistant, ceramics has been developed by researchers at The University of Manchester.

The polymer-based material, is formed from polystyrene and a single crystal of calcium carbonate.

The reinforced material, which could be used to strengthen ceramic tiles was developed after scientists observed the properties and behaviour of nacre, which comprises of calcium carbonate and proteins.

Dr Stephen Eichorn, Lead Researcher at the University, explains, ‘When a shell fractures you can see small fibrils of the protein bridging the crack zone. The ductile polymer mimics the protein fraction to assist the material to behave like a shell. When cracks open and wish to grow, they can only do so if the polymer is extended.

Absorbing crack energy and toughening the material so that it requires more energy for cracks to grow than in pure calcium carbonate, results in stronger crack resistance.’
Although fibres have been put in plaster to reinforce and toughen material for many years, typically building materials do not contain polymer, this meant the team had to manipulate the polystyrene.

‘We had to make the polystyrene beads hairy by placing smaller polymer chains on them. These were then charged and it is this interaction between the ions that form the calcium carbonate and incorporates them during crystallisation. The calcium carbonate gives high bulk mechanical properties and the polymer gives the toughness,’ Eichorn adds.

At this time, Eichorn suggests the material would be better applied as a reinforcement material for generating tougher building applications, rather than for use on its own.

Tests will continue to assess at what stages the materials can be merged and how it can be incorporated into ceramic processing. This may be problematic, as the polymer attempts to survive and maintain durability under high temperature processing and the team is currently looking at other inclusions to help withstand the heat.