Thermal interface materials(TIMs)with high through-plane thermal conductivity are urgently desired to avoid overheating of high-power density electronics.Introducing and aligning fillers in polymer matrixes via magnet...Thermal interface materials(TIMs)with high through-plane thermal conductivity are urgently desired to avoid overheating of high-power density electronics.Introducing and aligning fillers in polymer matrixes via magnetic field is a promising method to improve the thermal conductivity of the polymer.However,either the fillers need to be modified with magnetic particles or a strong magnetic field is needed for good alignment in high filler content.This prevents further improvement of the through-plane thermal conductivity.Herein,mesophase pitch-based carbon fibers(MPCFs)with a content as high as 76 wt.%are aligned vertically in water-soluble polyvinyl alcohol(PVA)under a low magnetic field(~0.4 T),forming a vertically aligned MPCF(VAMPCF)/PVA composite with an extraordinary through-plane thermal conductivity of 86 W/(m·K),which is higher than that of many alloys.In addition,both theoretical and experimental results demonstrate that the critical intensity of the magnetic field needed for good alignment of the fillers depends on their size and magnetic susceptibility.Furthermore,the water solubility of PVA makes it easy to recycle MPCFs.This study offers an inspired venue to develop excellent and eco-friendly TIMs to meet ever increasing demand in heat dissipation for electronics.展开更多
The quantum confinement effect is important in nanoelectronics and optoelectronics applications; however, there is a discrepancy between the theory of quantum confinement, which indicates that band-gap widening occurs...The quantum confinement effect is important in nanoelectronics and optoelectronics applications; however, there is a discrepancy between the theory of quantum confinement, which indicates that band-gap widening occurs only at small sizes, and experimental observations of band-gap widening in large-diameter nanowires （NWs）. This paper reports an obvious blue shift of the absorption edge in the UV-visible absorption spectra of SiC NWs with diameters of 50-300 nm. On the basis of quantum confinement theory and high-resolution transmission electron microscopy images of SiC NWs, band-gap widening in SiC NWs with diameters of up to hundreds of nanometers is fully explained; the results could help to explain similar band-gap widening in other NWs with large diameters.展开更多
基金the National Natural Science Foundation of China(Nos.11874423 and 12174321)the Fundamental Research Funds for the Central Universities(No.20720190050).
文摘Thermal interface materials(TIMs)with high through-plane thermal conductivity are urgently desired to avoid overheating of high-power density electronics.Introducing and aligning fillers in polymer matrixes via magnetic field is a promising method to improve the thermal conductivity of the polymer.However,either the fillers need to be modified with magnetic particles or a strong magnetic field is needed for good alignment in high filler content.This prevents further improvement of the through-plane thermal conductivity.Herein,mesophase pitch-based carbon fibers(MPCFs)with a content as high as 76 wt.%are aligned vertically in water-soluble polyvinyl alcohol(PVA)under a low magnetic field(~0.4 T),forming a vertically aligned MPCF(VAMPCF)/PVA composite with an extraordinary through-plane thermal conductivity of 86 W/(m·K),which is higher than that of many alloys.In addition,both theoretical and experimental results demonstrate that the critical intensity of the magnetic field needed for good alignment of the fillers depends on their size and magnetic susceptibility.Furthermore,the water solubility of PVA makes it easy to recycle MPCFs.This study offers an inspired venue to develop excellent and eco-friendly TIMs to meet ever increasing demand in heat dissipation for electronics.
基金This work was supported by the NationalNatural Science Foundation of China （Grant No. 61675234） and the Advanced Research Foundation of the National University of Defense Technology （Grant No. zk16-03-40）.
文摘The quantum confinement effect is important in nanoelectronics and optoelectronics applications; however, there is a discrepancy between the theory of quantum confinement, which indicates that band-gap widening occurs only at small sizes, and experimental observations of band-gap widening in large-diameter nanowires （NWs）. This paper reports an obvious blue shift of the absorption edge in the UV-visible absorption spectra of SiC NWs with diameters of 50-300 nm. On the basis of quantum confinement theory and high-resolution transmission electron microscopy images of SiC NWs, band-gap widening in SiC NWs with diameters of up to hundreds of nanometers is fully explained; the results could help to explain similar band-gap widening in other NWs with large diameters.
