Refrigeration is essential for modern society. United Nations statistics show that 25% -30% of the world ’s electricity is used for refrigeration every year. Researchers from the Institute of Metal Research, Chinese Academy of Sciences and other units have found that plastic crystals (a type of disordered solid crystals that are easily deformed) have the Ponzo pressure effect, that is, the cooling effect of pressure-induced phase transformation, which can be used to develop high-end refrigeration technology. New materials may reduce cooling energy consumption. This provides new ideas for the development of next-generation solid-state refrigeration technology. Related research results were published in the journal Nature on March 28.

Most current refrigeration systems use gas compression refrigeration technology, but the materials used in this technology will have an adverse impact on the environment. As a most promising alternative technology, refrigeration technology based on the solid-state phase change heat effect has received extensive attention in recent decades. The solid phase-change refrigeration material used in this technology will produce a temperature change when exposed to external stimuli. "However, the existing solid phase change refrigeration materials have shortcomings: the change in entropy is small, only a few tens of joules per kilogram (J kg-1K-1), and the cooling capacity is poor, which limits its application." The first part of the paper Corresponding author Li Bing, a researcher at the Institute of Metal Research, Chinese Academy of Sciences, said.

The researchers found that a variety of plastic crystals can achieve huge entropy changes under the drive of extremely small pressures. One of the materials is neopentyl glycol, which produces an entropy change of up to 389 joules per kilogram. Phase change refrigeration materials are greatly improved. This excellent property is due to the unique molecular structure of plastic crystals: plastic crystals are highly disordered, that is, the molecular orientation is irregular. This disordered structure is easily compressed, and relatively small pressures can induce regular alignment of these disordered molecules, resulting in a large entropy change.

Li Bing pointed out that the plastic crystal reported in this study has the advantages of abundant raw materials, environmental friendliness and low energy consumption, and has broad application prospects in the field of refrigeration. (Reporter Lu Chengkuan Hao Xiaoming)

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