But achieving both high mechanical strength and thermal insulation in porous ceramics is challenging. That is because when more pores are introduced to the material to increase thermal insulation, it typically results in significantly reduced mechanical strength.

There can also be shrinkage and degradation of strength when conventional porous materials are put under high temperatures, meaning they would be no good for aerospace applications.

But the new ceramic, developed by a team at the Guangzhou university’s School of Materials Science and Engineering, has a multiscale structural design they say overcomes these limitations. They reported their study in peer-reviewed journal Advanced Materials on January 2.

“The ceramic, named 9PHEB, shows exceptional dimension and strength retention up to 2,000 degrees Celsius [3,600 Fahrenheit], making it suitable for use in extreme conditions,” Chu, who led the study, wrote in the paper.

It is based on the high-entropy concept, which involves mixing five or more elements. In the case of 9PHEB – or 9-cation porous high-entropy diboride – there are nine components.

All of them are cationic, meaning they are positively charged ions.

In the paper, Chu noted the significant research interest in high-entropy design since it was first applied to ceramic materials in 2015, because of the potential for developing a unique microstructure and tunable properties.

He said 9PHEB had about 50 per cent porosity, yet its compressive strength was ultra-high at about 337 million pascals (MPa) at room temperature – significantly stronger than previously reported porous ceramics.

The ceramic also performed well on insulation and thermal stability tests, retaining 98.5 per cent of room temperature strength even at 1,500 degrees, according to the paper.

And unlike some traditional ceramics that tend to brittle fracture at high temperatures, 9HPEB exhibited plastic deformation when compressed at 2,000 degrees.

When the material was deformed at high temperature it was subjected to a strain of 49 per cent. That took its strength to 690 MPa – more than twice where it started.

Importantly, the high heat did not have any significant impact on the material’s volume or dimensions – it had shrunk by about 2.4 per cent after being annealed at 2,000 degrees.

Chu attributed the mechanical and thermal properties to the ceramic’s “multiscale” design.

“[The design features] ultrafine pores at the microscale, high-quality interfaces at the nanoscale, and severe lattice distortion at the atomic scale,” he said.

The microstructures of the ceramic’s pores, in terms of both size and their distribution, are significant to the design. About 92 per cent of the pores are ultrafine – measuring just 0.8 to 1.2 micrometres – which the scientists say makes them unmatched for their thermal insulation properties.

At the nanoscale, the ceramic has strong, defect-free connections that boost mechanical strength.

And at the atomic scale, the lattice distortion from its high-entropy design improves stiffness and reduces thermal conductivity.

Together, these characteristics increase the material’s mechanical strength and thermal insulation, making it suitable for use in extreme conditions, the researchers concluded.

Zhuang Lei, an associate professor at the materials science and engineering school and a co-corresponding author, told China Science Daily that the material could have broad applications in industries such as aerospace, energy and chemical engineering.