With new, advanced equipment, scientists at Risø DTU have shown that materials to produce micro-and nanocomponents react very differently depending on whether crystals are large or small. This research creates important knowledge that can be used to develop technologies aimed at the nanoproduction of micro-electro-mechanical systems such as digital microphones in mobile phones, miniature pressure sensors in water pumps and acceleration sensors in airbags.
The nanotechnology toolbox is expanding continuously and the material for nanocomponents is a chapter by itself, because materials at nanoscale often react quite differently than materials at large scale. Therefore it is necessary to know what happens when you squeeze, flatten and stamp out metals for nanocomponents. Otherwise, the finished component may not be functioning as it should.
Using transmission electron microscopy (TEM) and cooperating with research institutions in China and the USA, Risø DTU has looked into what happens when you deform crystals of nanosize from the metal titanium. At this scale the size of the titanium crystals determines the behaviour of the metal during mechanical treatment. Titanium crystals of a certain size are deformed in a way that each atom is systematically displaced in proportion to the neighbouring atoms, which results in a macroscopic deformation. This process is called 'deformation twinning'. When the titanium crystals become smaller, they are much more difficult to deform. However, this only applies to a certain lower limit.
When titanium crystals become smaller than 1 micrometer (0.001 mm), they are deformed in the same way as very large crystals. This kind of deformation is called 'dislocation plasticity'. The discovery has great significance for how to produce nanocomponents of metal and ceramics in order to obtain the desired properties in a final component.
With support from the Danish Council for Independent Research | the Danish Research Council for Nature and Universe (FNU), Risø National Laboratory for Sustainable Energy, DTU has acquired new, advanced equipment to study nanocrystals of metal while they are being deformed in an electron microscope. This equipment has recently been developed by the company Hysitron Incorporated in the USA. The new equipment allows scientists to study in very fine detail structural changes in the TEM while they, with great precision, can deform the metal crystals, and thereby obtain a detailed knowledge of the surprising new nano phenomena.
The results will provide the technologies for nano production with important new knowledge.
- Yu et al. Strong crystal size effect on deformation twinning. Nature, 2010; 463 (7279): 335 DOI: 10.1038/nature08692
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