A layered ruthenate Ca2RuO4-y ceramic body contracts on heating, or exhibits negative thermal expansion (NTE). The sintered-body structure shows colossal NTE when extremely anisotropic thermal expansion of the crystal grains produces deformation, consuming open spaces (voids) on heating. The total volume change related to NTE reaches 6.7 percent at most, the largest reported so far. Credit: Koshi Takenaka
Machines and devices in modern industry are required to withstand harsh conditions. When environmental temperature changes, the volume of the materials used to make these devices usually changes slightly, typically by <0.01%. Although this may seem trivial, over time this thermal expansion can seriously degrade the performance of industrial systems and equipment.
Materials that contract o...
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