An international team of researchers led by Drexel University has discovered that a thin layer of MXene — a type of two-dimensional nanomaterial that has been discovered and studied at Drexel for more than a decade — can enhance the material’s ability to trap or shed heat. This discovery, related to MXene’s ability to regulate the passage of ambient infrared radiation, could lead to advances in thermal clothing, heating elements, and new materials for radiant heating and cooling.
The group, including materials scientists and optoelectronics researchers from Drexel and computational scientists from the University of Pennsylvania, recently presented their discovery about the radiative heating and cooling potential associated with MXene in a paper entitled “The Versatility of Infrared Properties of MXene” in material today.
“This research reveals another aspect of the versatility of MXene materials,” said Yuri Gogotsi, Ph.D., Distinguished University Professor and Bach Chair Professor in the Drexel School of Engineering, who was the lead on the research.
“MXene coatings that possess exceptional capabilities to contain or emit infrared radiation, while remaining extremely thin – 200-300 times thinner than a human hair – are lightweight and flexible, and can find applications in both local thermal management and large-scale radiant heating and cooling systems. There are Significant advantages of passive infrared heating and cooling over traditional active ones, which require electrical energy to operate.”
MXenes are a family of two-dimensional nanomaterials originally discovered by Drexel researchers in 2011, which — due to their two-dimensional composition and structure — have progressively proven exceptional in conducting electricity, storing electrical energy, filtering chemical compounds, and blocking electromagnetic radiation, among other capabilities. Over the years, materials scientists have produced and extensively researched MXenes with different chemical compositions, which has led to the discovery of many applications.
In their latest paper, the team measured the ability of 10 different formulations of MXene to help or hinder the passage of infrared radiation—a measure called “emissivity”—which relates to their ability to passively capture or dissipate ambient heat.
“We knew from previous research that MXenes are more than capable of reflecting or absorbing radio waves and microwave radiation, so looking at their interaction with infrared radiation, which has a much shorter wavelength, was the next step,” said Danzhen Zhang, one of the participants. – PhD researcher at Gogotsu Lab and co-author of the research.
“The advantage of being able to control the passage of infrared radiation is that we can use this type of radiation for passive heating — if we can contain it — or passive cooling — if we can dissipate it. The MXenes we tested showed they could do both, depending on their configuration The racial and number of atomic layers.”
Compared to passive cooling materials available on the market today, which allow thermal infrared radiation from the body — body heat — to escape through the fabric’s lightweight, breathable construction, mexene-coated textiles can perform better, according to Tetiana Hryhorchuk, PhD researcher in the Gogotsi lab. , and co-author of the paper, because these coated textiles have the additional ability to reflect external infrared radiation, to avoid heating from sunlight, while also allowing infrared radiation, emitted by the body, to pass through.
The researchers found that the niobium carbide MXenes could effectively dissipate heat while the titanium carbide showed exceptional heat shield, rising to just 43 degrees Celsius after being heated for five minutes on a 110-degree hot plate.
“High emissivity such as niobium carbide is also possible in dielectric materials,” Gogotsi said. “However, MXenes combine this ability with electrical conductivity, which means that MXenes can also be used as active electric heating elements with an external power supply.”
MXene titanium carbide coating has been found to harden the material against infrared penetration and emission. In testing, MXene-coated materials, even with a thin film, performed better at shielding infrared radiation than brushed metals, which are currently the best-performing commercial materials. This means that MXenes can be incorporated into lightweight clothing that keeps the wearer warm in harsh environments.
To test it, the team doused a cotton shirt with a moxene solution of titanium carbide and used an infrared thermal camera to monitor the temperature of the person wearing it. The results showed that a maxi-coated shirt kept the wearer about 10-15°C cooler – about room temperature – than a person wearing a regular T-shirt.
These results indicate that MXene-coated garments are effective in maintaining body temperature, while also offering the advantage of being applied via a relatively more extensive dip-coating process than most thermal garments require.
“Commercial thermal clothing uses very thin polymer fibers with low thermal conductivity — wool, for example,” said Lingyi Bi, a doctoral researcher in Gogotsi’s lab, with expertise in textiles. “It keeps us warm by reducing heat transfer through the fabric, to do this effectively it has to be very thick. But MXene mainly keeps us warm by blocking the escape of body heat such as infrared radiation. Therefore, a coating of MXene that is thinner than silk can Provides efficient heating. This is the same principle used in the thermal mylar blankets runners get after a cold-weather race.”
Gogotsi suggests that the infrared blocking capability could also be used to camouflage people and equipment from thermal detectors, or to secretly transmit information via radio frequency identification codes visible only to infrared readers.
The team plans to further study the mechanisms behind MXene’s infrared mass and emission behavior, as well as test MXenes with different chemical compositions to improve their potential as radiative heating and cooling materials.
The versatility of the infrared properties of the MXenes, material today (2023). DOI: 10.1016/j.mattod.2023.02.024
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