New Technology: High Entropy Photothermal Film Assists Thermal Management Performance Of Fabric To Human Body

Maintaining a comfortable metabolic temperature is essential to maintain the basic physiological functions of the human body. Outdoor, stationary adults consume about 50% of the heat through infrared radiation, while traditional textile materials (such as cotton and polyester) have high infrared emissivity (~90%), resulting in a large amount of radiant heat loss. Therefore, processing the fabric surface and realizing human thermal management will remedy these defects.

At present, the reported absorption rate of thermal management fabric is not ideal, and it can not effectively heat the human body in cold weather. However, the existing selective absorption coating technology will lose spectral selectivity on the surface of ordinary cotton cloth due to high roughness. Therefore, it is of great significance to study zero energy consumption thermal management fabrics.

Recently, Gao Xianghu and Liu Gang, the researchers of the Clean Energy Chemistry and Materials Laboratory of Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, prepared multilayer films based on high entropy nitride (ZrNbMo-Al-N) on the surface of ordinary cotton cloth by magnetron sputtering, and realized human thermal management fabrics with high spectral selectivity. By establishing a steady-state heat transfer model, researchers found that both high absorption and low emissivity of fabrics contribute to the thermal insulation of human body in low temperature environment, especially the optimization of absorption, which can effectively increase the thermal insulation capacity in outdoor light environment (Figure 1).

Based on this, the researchers optimized the optical properties of multilayer films by theoretical calculation and experimental verification (Fig. 2). The optimized selective absorption coating achieves 92.8% high absorption rate and 39.2% low emissivity on the metal aluminum modified cotton cloth, and has excellent photothermal conversion efficiency (82.2%, 600 W m-2, 0 ℃), which has obvious advantages over the reported solar heated fabrics. The researchers tested the heating ability of the fabric. Due to the low emissivity of the fabric, the set temperature of the indoor air conditioner is reduced by 3.5 ℃, thus reducing energy consumption.

In winter morning, although the sunlight intensity is only 350W m-2 and the air temperature is 7.5 ℃, the use of the high entropy thermal insulation fabric studied by the team can increase the human body surface temperature by 12 ℃ (Figure 3). At the same time, the fabric also maintains the wearability of cotton cloth. Experimental tests show that it has good water vapor permeability, permeability and durability. After different washing cycles, the fabric still maintains excellent optical properties.

The high entropy fabric proposed by the team has the advantages of good photo thermal conversion efficiency, air permeability, water vapor permeability, mechanical strength, durability, washability, and easy preparation, and has an important contribution to the research and practical application of fabric thermal management. Relevant research achievements were published on Advanced Science under the title of Effective Warning Textile Enhanced by a High Enterprise Specially Selective Nanofilm with High Solar Absorption.

The relevant research work was supported by the Youth Innovation Promotion Association of the Chinese Academy of Sciences, the major science and technology projects of Gansu Province, and the major breakthrough projects of the "14th Five Year Plan" of Lanzhou Institute of Chemical Physics.

Figure 1 Heat preservation mechanism and theoretical verification of high entropy heat preservation fabric

Fig. 2 Preparation and optical properties of high entropy thermal insulation fabric

Figure 3 Outdoor verification of thermal insulation performance of high entropy thermal insulation fabric