A high-performance adaptive radiative cooler comprising a multilayer-filter VO_(2)-based Fabry-Pérot(FP)cavity is proposed.The bottom FP cavity has four layers,VO_(2)/NaCl/PVC/Ag.Based on the phase transition of ...A high-performance adaptive radiative cooler comprising a multilayer-filter VO_(2)-based Fabry-Pérot(FP)cavity is proposed.The bottom FP cavity has four layers,VO_(2)/NaCl/PVC/Ag.Based on the phase transition of VO_(2),the average emissivity in the transparent window can be switched from 3.7%to 96.3%.Additionally,the average emissivity can also be adjusted with external strain to the PVC layer,providing another way to attain the desired cooling effect.An upper filter is included to block most of the solar radiation and provide a transmittance of 96.7% in the atmospheric window.At high temperature,the adaptive emitter automatically activates radiative cooling.The net cooling power is up to 156.4 W·m^(-2)at an ambient temperature of 303 K.Our adaptive emitter still exhibits stable selective emissivity at different incident angles and heat transfer coefficients.At low temperature,the radiative cooling automatically deactivates,and the average emissivity decreases to only 3.8%.Therefore,our work not only provides new insights into the design of high-performance adaptive radiative coolers but also advances the development of intelligent thermal management.展开更多
Germanium diselenide(GeSe_(2))is a promising candidate for electronic devices because of its unique crystal structure and optoelectronic properties.However,the evolution of lattice and electronic structure ofβ-GeSe_(...Germanium diselenide(GeSe_(2))is a promising candidate for electronic devices because of its unique crystal structure and optoelectronic properties.However,the evolution of lattice and electronic structure ofβ-GeSe_(2)at high pressure is still uncertain.Here we prepared high-qualityβ-GeSe_(2)single crystals by chemical vapor transfer(CVT)technique and performed systematic experimental studies on the evolution of lattice structure and bandgap ofβ-GeSe_(2)under pressure.High-precision high-pressure ultra low frequency(ULF)Raman scattering and synchrotron angle-dispersive x-ray diffraction(ADXRD)measurements support that no structural phase transition exists under high pressure up to 13.80 GPa,but the structure ofβ-GeSe_(2)turns into a disordered state near 6.91 GPa and gradually becomes amorphous forming an irreversibly amorphous crystal at 13.80 GPa.Two Raman modes keep softening abnormally upon pressure.The bandgap ofβ-GeSe_(2)reduced linearly from 2.59 eV to 1.65 eV under pressure with a detectable narrowing of 36.5%,and the sample under pressure performs the piezochromism phenomenon.The bandgap after decompression is smaller than that in the atmospheric pressure environment,which is caused by incomplete recrystallization.These results enrich the insight into the structural and optical properties ofβ-GeSe_(2)and demonstrate the potential of pressure in modulating the material properties of two-dimensional(2D)Ge-based binary material.展开更多
We report a new type of near-zero thermal expansion materialβ-CuZnV_(2)O_(7)in a large temperature range from 173 K to 673 K.It belongs to a monoclinic structure(C2/c space group)in the whole temperature range.No str...We report a new type of near-zero thermal expansion materialβ-CuZnV_(2)O_(7)in a large temperature range from 173 K to 673 K.It belongs to a monoclinic structure(C2/c space group)in the whole temperature range.No structural phase transition is observed at atmospheric pressure based on the x-ray diffraction and Raman experiment.The high-pressure Raman experiment demonstrates that two structural phase transitions exist at 0.94 GPa and 6.53 GPa,respectively.The mechanism of negative thermal expansion inβ-CuZnV_(2)O_(7)is interpreted by the variations of the angles between atoms intuitively and the phonon anharmonicity intrinsically resorting to the negative Grüneisen parameter.展开更多
基金supported by the Natural Science Foundation of Henan Province(Grant No.232102231023)。
文摘A high-performance adaptive radiative cooler comprising a multilayer-filter VO_(2)-based Fabry-Pérot(FP)cavity is proposed.The bottom FP cavity has four layers,VO_(2)/NaCl/PVC/Ag.Based on the phase transition of VO_(2),the average emissivity in the transparent window can be switched from 3.7%to 96.3%.Additionally,the average emissivity can also be adjusted with external strain to the PVC layer,providing another way to attain the desired cooling effect.An upper filter is included to block most of the solar radiation and provide a transmittance of 96.7% in the atmospheric window.At high temperature,the adaptive emitter automatically activates radiative cooling.The net cooling power is up to 156.4 W·m^(-2)at an ambient temperature of 303 K.Our adaptive emitter still exhibits stable selective emissivity at different incident angles and heat transfer coefficients.At low temperature,the radiative cooling automatically deactivates,and the average emissivity decreases to only 3.8%.Therefore,our work not only provides new insights into the design of high-performance adaptive radiative coolers but also advances the development of intelligent thermal management.
基金the National Natural Science Foundation of China(Grant Nos.12004339,11874328,11904322,61804047,22071221,and 21905252)China Postdoctoral Science Foundation(Grant Nos.2018M640679 and 2019T120629)the Zhongyuan Academician Foundation(Grant No.ZYQR201810163)。
文摘Germanium diselenide(GeSe_(2))is a promising candidate for electronic devices because of its unique crystal structure and optoelectronic properties.However,the evolution of lattice and electronic structure ofβ-GeSe_(2)at high pressure is still uncertain.Here we prepared high-qualityβ-GeSe_(2)single crystals by chemical vapor transfer(CVT)technique and performed systematic experimental studies on the evolution of lattice structure and bandgap ofβ-GeSe_(2)under pressure.High-precision high-pressure ultra low frequency(ULF)Raman scattering and synchrotron angle-dispersive x-ray diffraction(ADXRD)measurements support that no structural phase transition exists under high pressure up to 13.80 GPa,but the structure ofβ-GeSe_(2)turns into a disordered state near 6.91 GPa and gradually becomes amorphous forming an irreversibly amorphous crystal at 13.80 GPa.Two Raman modes keep softening abnormally upon pressure.The bandgap ofβ-GeSe_(2)reduced linearly from 2.59 eV to 1.65 eV under pressure with a detectable narrowing of 36.5%,and the sample under pressure performs the piezochromism phenomenon.The bandgap after decompression is smaller than that in the atmospheric pressure environment,which is caused by incomplete recrystallization.These results enrich the insight into the structural and optical properties ofβ-GeSe_(2)and demonstrate the potential of pressure in modulating the material properties of two-dimensional(2D)Ge-based binary material.
基金supported by the National Natural Science Foundation of China(Grant Nos.11874328,12004339,11574276,and 21905252)the China Postdoctoral Science Foundation(Grant Nos.2018M640679,2019T120629,and 2019M652558)the Zhongyuan Academician Foundation(Grant No.ZYQR201810163)。
文摘We report a new type of near-zero thermal expansion materialβ-CuZnV_(2)O_(7)in a large temperature range from 173 K to 673 K.It belongs to a monoclinic structure(C2/c space group)in the whole temperature range.No structural phase transition is observed at atmospheric pressure based on the x-ray diffraction and Raman experiment.The high-pressure Raman experiment demonstrates that two structural phase transitions exist at 0.94 GPa and 6.53 GPa,respectively.The mechanism of negative thermal expansion inβ-CuZnV_(2)O_(7)is interpreted by the variations of the angles between atoms intuitively and the phonon anharmonicity intrinsically resorting to the negative Grüneisen parameter.
