13-Feb-2012 - National Institute for Materials Science (NIMS)

Materials That Shrink When Heated

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 electronic circuits, as well as the next-generation fuel cells and thermoelectric devices. 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 Crystalline Materials 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 hafnium tungstates - exhibiting negligible thermal expansion offer a promising route towards achieving this goal.

  • Koshi Takenaka et al. "Negative thermal expansion materials: Technological key for control of thermal expansion"; Science and Technology of Advanced Materials Vol. 13 (2012) 013001.
Facts, background information, dossiers
  • negative thermal ex…
  • National Institute…
  • thermal expansion
  • Nagoya University
More about National Institute for Materials Science
More about Nagoya University
  • News

    Industrial compound gets eco-friendly reaction

    Nagoya University scientists have developed a chemical reaction that produces high yields of a compound used in a wide variety of industries, without needing high temperatures or toxic catalysts. The approach was described in the journal ACS Catalysis and offers a practical and sustainable ... more

    Catalyzing a zero-carbon world by harvesting energy from living cells

    The imminent environmental crisis calls for an urgent transition to a green economy. A team of scientists at Nagoya University, Japan, led by Professor Susumu Saito, has recently found an interesting way to make this happen -- by leveraging an important metabolic pathway in living cells. Th ... more

    A new synthesis method for three-dimensional nanocarbons

    A team of scientists led by Kenichiro Itami, Professor and Director of the Institute of Transformative Bio-Molecules (WPI-ITbM), has developed a new method for the synthesis of three-dimensional nanocarbons with the potential to advance materials science. Three-dimensional nanocarbons, next ... more