In many high-precision technologies, even tiny temperature changes can cause serious problems.
Optical instruments, cryogenic systems, and sensitive sensors all rely on materials that do not expand or shrink when heated or cooled.
These so-called zero-thermal-expansion (ZTE) materials help devices stay accurate and stable. However, designing materials that combine zero expansion with good heat transfer and strong mechanical performance has proven extremely difficult.
Traditionally, most ZTE materials conduct heat poorly, making it hard to remove excess heat from sensitive equipment.
Some metal-based ZTE composites improve heat flow but rely on large amounts of brittle particles that cancel thermal expansion.
While effective at controlling size changes, these particles weaken the material, making it prone to cracking and failure under stress. Engineers have long faced a trade-off between thermal stability, heat conduction, and toughness.
Now, a research team from the Hefei Institutes of Physical Science at the Chinese Academy of Sciences has developed a new copper-based composite that breaks this compromise.
Inspired by natural structures such as abalone shells and bamboo, the team created a layered metal material that combines zero thermal expansion, excellent heat transfer, and high mechanical toughness.
Their findings were published in the journal Acta Materialia.
The researchers took inspiration from nacre, also known as mother-of-pearl, which lines abalone shells.
Nacre has a “brick-and-mortar” layered structure that gives it remarkable strength and resistance to cracking.
They also drew ideas from bamboo, whose thin internal membranes efficiently transport water and nutrients while maintaining structural stability.
Using these natural designs as a guide, the team built a laminated composite made of alternating layers of pure copper foil and copper reinforced with special particles that shrink slightly when heated. These particles, known as negative thermal expansion materials, balance copper’s natural tendency to expand as temperatures rise.
In this layered design, each component has a clear role. The pure copper layers act as continuous pathways for heat, allowing thermal energy to move quickly through the material. At the same time, the particle-reinforced layers control expansion and contraction, keeping the overall structure dimensionally stable. By separating these functions into different layers, the researchers avoided the performance trade-offs seen in conventional ZTE materials.
Tests showed that the composite achieved thermal conductivity about three times higher than typical ZTE metal composites, placing it among the best heat-conducting ZTE materials reported so far.
The layered structure also greatly improved mechanical performance. Instead of failing suddenly when stressed, cracks spread and deflect across layers, allowing the material to absorb much more energy before breaking. As a result, the composite’s resistance to fracture was four times higher than that of comparable single-layer materials.
The design also ensures zero thermal expansion in all directions, thanks to stress interactions between layers that cancel out expansion and contraction. According to the researchers, this bio-inspired approach opens the door to tougher, more reliable ZTE materials, especially for applications exposed to repeated heating, cooling, and mechanical impacts.
Source: KSR.
