Longer-lived, more efficient electronics and telecommunications systems are on the horizon according to Sydney University’s Dr Karena Chapman, who outlined new research today revealing how certain solids shrink when warmed (known as Negative Thermal Expansion – NTE) while normal materials expand.
“A common reason for failure in electronic components is thermal stress. As the electronics heat up they expand and can break,” she said. “Our new materials have the potential to compensate for this type of expansion and may allow us to fix this problem.
“By bouncing neutrons or X-rays off our samples we can deduce what is happening within the materials at an
atomic level as they are warmed, allowing us to see exactly what causes the contraction.
“The results are extremely important as understanding the structural basis for NTE behaviour will help us tailor the thermal expansion of new materials to suit particular applications and ultimately to design better materials or the electronics industry,” said Dr Chapman.
“The atomic structure of these materials – the way the atoms are holding hands – is responsible for their contraction with heating,” explained Dr Chapman. “Metal atoms are connected by what is essentially a molecular skipping rope.
As the temperature is increased, atoms within the material start to vibrate, that is, to move around more. Ultimately, as the molecular skipping rope circles wider, the connected metal atoms have no option but to be drawn closer together.
“On the macro-scale, this decrease in the individual atomic separations is seen as a contraction of the material.
“In a nutshell, these NTE materials have the potential to remove the influence of thermal shock and stress on electronic components as they repeatedly expand and contract in response to being heated when switched on, and cooled when switched off.
“In the telecommunications area, the efficiency of certain components degrades rapidly when their dimensions change in response to temperature fluctuations,” said Dr Chapman.
“By including NTE materials to compensate for expansion, such components could maintain peak efficiency regardless of temperature.”
Dr Chapman and her co-workers have used neutron beams from the HIFAR reactor at ANSTO for their research in addition to experimental facilities around the world.
Published: 28/11/2005