Materials that shrink when heated

February 9, 2012
Invar, also known as FeNi36, is an iron-nickel alloy notable for its lack of expansion or contraction with temperature changes.

One common reason that people with fillings experience toothache is that their fillings expand at a different rate to the original tooth when, for example, drinking a hot drink. Contrary to intuition, however, not all materials expand when heated - some actually contract. Recent research on these so-called negative thermal expansion (NTE) materials has led to the discovery of alloys exhibiting unexpectedly large thermal contraction.

Controlling the thermal expansion of composites is important for producing nanometer-scale , as well as the next-generation fuel cells and . An ability to combine NTE materials with 'normal' materials which expand upon heating ensures a reduction in thermal expansion in a composite material - something that people with tooth fillings would appreciate. An example of such a composite is Invar, an iron-nickel alloy with a uniquely low coefficient of thermal expansion. As a result it is used where high dimensional stability is required, such as precision instruments, clocks or seismic creep gauges.

Koshi Takenaka at the Department of Science, Nagoya University in Japan works on NTE materials for practical applications. In the latest issue of Science and Technology of Advanced Materials he summarizes the physical mechanisms governing NTE with emphasis on recent developments.

Takenaka notes that, "NTE materials will expand our capability of thermal-expansion control, opening a new paradigm of materials science and technology thermal-expansion-adjustable composites". One challenge facing the scientist is that the addition of NTE materials to composites leads to undesirable instabilities at interfaces. New methods for producing stable interfaces between the host composite and NTE compensators are of critical importance. Nevertheless, the so-called 'one-component' materials - such as manganese antiperovskites, zirconium vanadates, and tungstates - exhibiting negligible thermal expansion offer a promising route towards achieving this goal.

Explore further: Understanding heat flow at the nanoscale is the goal of new project

More information: 'Negative thermal expansion materials: Technological key for control of thermal expansion' by Koshi Takenaka, Science and Technology of Advanced Materials Vol. 13 (2012) 013001.

Related Stories

Researchers measure nanometer scale temperature

December 19, 2011

Illinois researchers have developed a new kind of electro-thermal nanoprobe that can independently control voltage and temperature at a nanometer-scale point contact. It can also measure the temperature-dependent voltage ...

Magnetic actuation enables nanoscale thermal analysis

January 12, 2012

Polymer nano-films and nano-composites are used in a wide variety of applications from food packaging to sports equipment to automotive and aerospace applications. Thermal analysis is routinely used to analyze materials for ...

Recommended for you

New polymer creates safer fuels

October 1, 2015

Before embarking on a transcontinental journey, jet airplanes fill up with tens of thousands of gallons of fuel. In the event of a crash, such large quantities of fuel increase the severity of an explosion upon impact. Researchers ...

Researchers print inside gels to create unique shapes

September 30, 2015

(—A team of researchers at the University of Florida has taken the technique of printing objects inside of a gel a step further by using a highly shear-rate sensitive gel. In their paper published in the journal ...

How a molecular motor untangles protein

October 1, 2015

A marvelous molecular motor that untangles protein in bacteria may sound interesting, yet perhaps not so important. Until you consider the hallmarks of several neurodegenerative diseases—Huntington's disease has tangled ...

Anti-aging treatment for smart windows

October 1, 2015

Electrochromic windows, so-called 'smart windows', share a well-known problem with rechargeable batteries – their limited lifespan. Researchers at Uppsala University have now worked out an entirely new way to rejuvenate ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

not rated yet Feb 09, 2012
I always thought it was because the filling conducts heat or cold better. I didn't even think about the difference in expansion and contraction. Interesting.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.