Tag Archives: insulation

Mimicking Polar Bear To Design An Heat Insulator

For polar bears, the insulation provided by their fat, skin, and fur is a matter of survival in the frigid Arctic. For engineers, polar bear hair is a dream template for synthetic materials that might lock in heat just as well as the natural version. Now, materials scientists in China have developed such an insulator, reproducing the structure of individual polar bear hairs while scaling toward a material composed of many hairs for real-world applications in the architecture and aerospace sectors.

Polar bear hair has been evolutionarily optimized to help prevent heat loss in cold and humid conditions, which makes it an excellent model for a synthetic heat insulator,” says co-senior author Shu-Hong Yu, a professor of chemistry at the University of Science and Technology of China (USTC). “By making tube aerogel out of carbon tubes, we can design an analogous elastic and lightweight material that traps heat without degrading noticeably over its lifetime.”

Unlike the hairs of humans or other mammals, polar bear hairs are hollow. Zoomed in under a microscope, each one has a long, cylindrical core punched straight through its center. The shapes and spacing of these cavities have long been known to be responsible for their distinctive white coats. But they also are the source of remarkable heat-holding capacity, water resistance, and stretchiness, all desirable properties to imitate in a thermal insulator.

The hollow centers limit the movement of heat and also make the individual hairs lightweight, which is one of the most outstanding advantages in materials science,” says Jian-Wei Liu, an associate professor at USTC. To emulate this structure and scale it to a practical size, the research team—additionally co-led by Yong Ni, a mechanical engineering professor at USTCmanufactured millions of hollowed-out carbon tubes, each equivalent to a single strand of hair, and wound them into a spaghetti-like aerogel block.

The findings appeared in the journal Chem.

Source: https://en.ustc.edu.cn/

How To Make Concrete Leaner, Greener, Stronger And More Elastic

Rice University scientists have developed micron-sized calcium silicate spheres that could lead to stronger and greener concrete, the world’s most-used synthetic material. To Rice materials scientist Rouzbeh Shahsavari and graduate student Sung Hoon Hwang, the spheres represent building blocks that can be made at low cost and promise to mitigate the energy-intensive techniques now used to make cement, the most common binder in concrete.

The researchers formed the spheres in a solution around nanoscale seeds of a common detergent-like surfactant. The spheres can be prompted to self-assemble into solids that are stronger, harder, more elastic and more durable than ubiquitous Portland cement.

Packed, micron-scale calcium silicate spheres developed at Rice University are a promising material that could lead to stronger and more environmentally friendly concrete

Cement doesn’t have the nicest structure,” said Shahsavari, an assistant professor of materials science and nanoengineering. “Cement particles are amorphous and disorganized, which makes it a bit vulnerable to cracks. But with this material, we know what our limits are and we can channel polymers or other materials in between the spheres to control the structure from bottom to top and predict more accurately how it could fracture.”

He said the spheres are suitable for bone-tissue engineering, insulation, ceramic and composite applications as well as cement.

Source: https://news.rice.edu/