A new theoretical model of gray cast iron taking into account a locally interconnected structure of flake graphite was designed,and the corresponding effective thermal conductivity was calculated using the thermal res...A new theoretical model of gray cast iron taking into account a locally interconnected structure of flake graphite was designed,and the corresponding effective thermal conductivity was calculated using the thermal resistance network method.The calculated results are obviously higher than that of the effective medium approximation assuming that graphite is distributed in isolation.It is suggested that the interconnected structure significantly enhances the overall thermal conductivity.Moreover,it is shown that high anisotropy of graphite thermal conductivity,high volume fraction of graphite,and small aspect ratio of flake graphite will cause the connectivity effects of graphite to more obviously improve the overall thermal conductivity.Higher graphite volume fraction,lower aspect ratio and higher matrix thermal conductivity are beneficial to obtain a high thermal conductivity gray cast iron.This work can provide guidance and reference for the development of high thermal conductivity gray cast iron and the design of high thermal conductivity composites with similar locally interconnected structures.展开更多
The thermal radiation properties of pyrolytic carbon(PyC)protective coatings for monocrystalline silicon furnace prepared by different processes were tested.The changes of normal emissivity of carbon materials caused ...The thermal radiation properties of pyrolytic carbon(PyC)protective coatings for monocrystalline silicon furnace prepared by different processes were tested.The changes of normal emissivity of carbon materials caused by PyC protective coatings were discussed,and the influence of phase structure and surface appearance on the thermal radiation properties was investigated.The results show that the thermal radiation properties of PyC protective coatings with the wave band of 5-25μm are better than C/C substrate,further,normal spectral emissivity of CVD PyC coating remains basically at 0.85-0.90,and the normal total emissivity can reach0.89,which shows high thermal radiation performance.For resin PyC coating and CVD PyC coating,the degree of graphitization are 44.53%and 16.28%respectively,and the R value of Raman spectrum are 0.964and 1.384 respectively.Relatively disorder graphite structure of the latter causes various vibration modes,and the spectral emissivity is better,so the thermal radiation property of CVD PyC coating is excellent.A lot of spherical particles exists on the surface of the CVD PyC coating,and the more interface and spacing of particles reduce the number of particles per unit volume.Therefore,the scattering of thermal radiation is strongly strengthened,and the spectral emissivity is higher.展开更多
Sodium metal batteries(SMBs)have attracted increasing attention over time due to their abundance of sodium resources and low cost.However,the widespread application of SMBs as a viable technology remains a great chall...Sodium metal batteries(SMBs)have attracted increasing attention over time due to their abundance of sodium resources and low cost.However,the widespread application of SMBs as a viable technology remains a great challenge,such as uneven metallic deposition and dendrite formation during cycling.Carbon skeletons as sodiophilic hosts can alleviate the dendrite formation during the plating/stripping.For the carbon skeleton,how to rationalize the design sodiophilic interfaces between the sodium metal and carbon species remains key to developing desirable Na anodes.Herein,we fabricated four kinds of structural features for carbon skeletons using conventional calcination and flash Joule heating.The roles of conductivity,defects,oxygen content,and the distribution of graphite for the deposition of metallic sodium were discussed in detail.Based on interface engineering,the J1600 electrode,which has abundant Na-C species on its surface,showed the highest sodiophilic.There are uniform and rich F-Na species distributed in the inner solid electrolyte interface layer.This study investigated the different Na-deposition behavior in carbon hosts with distinct graphitic arrangements to pave the way for designing and optimizing advanced electrode materials.展开更多
The capacitive performance of carbon materials as supercapacitor electrode is synergistically influenced by the surface porous structure,graphitization structure,and surface atomic doping.However,simple realization of...The capacitive performance of carbon materials as supercapacitor electrode is synergistically influenced by the surface porous structure,graphitization structure,and surface atomic doping.However,simple realization of their synergistic regulation still faces significant challenges.Based on the biological porous structure,heteroatom-rich content and low cost of chestnut,this work adopt chestnut as precursor to prepare carbon electrode,of which the pores,graphitization,and surface atomic doping are synergistically regulated by simply changing the activation temperature.The optimized carbon electrode possesses a hierarchical porous structure with partial graphitization and O and N co doping.Benefited from these merits,the chestnut-derived porous carbon as a supercapacitor electrode,can achieve a high specific capacitance of 328.6 F/g at 1 A/g,which still retains 80.8%when the current density enlarging to 20 A/g.By packaging the symmetric electric double-layer capacitor,the device exhibits a specific capacitance of 63.6 F/g at 1 A/g,delivering an energy density of 12.7 W·h/kg at a power density of 600 W/kg.The stability of the device is tested at a current density of 20 A/g,which shows a capacitance retention rate of up to 90%after 10000 charge-discharge cycles.展开更多
基金the National Natural Science Foundation of China(Grant No.51371104)。
文摘A new theoretical model of gray cast iron taking into account a locally interconnected structure of flake graphite was designed,and the corresponding effective thermal conductivity was calculated using the thermal resistance network method.The calculated results are obviously higher than that of the effective medium approximation assuming that graphite is distributed in isolation.It is suggested that the interconnected structure significantly enhances the overall thermal conductivity.Moreover,it is shown that high anisotropy of graphite thermal conductivity,high volume fraction of graphite,and small aspect ratio of flake graphite will cause the connectivity effects of graphite to more obviously improve the overall thermal conductivity.Higher graphite volume fraction,lower aspect ratio and higher matrix thermal conductivity are beneficial to obtain a high thermal conductivity gray cast iron.This work can provide guidance and reference for the development of high thermal conductivity gray cast iron and the design of high thermal conductivity composites with similar locally interconnected structures.
基金Sponsored by the National High Technology Research and Development Program of China(863 Program)(Grant No.2009AA035301)the ChinaPostdoctoral Science Foundation(Grant No.2012M511544)
文摘The thermal radiation properties of pyrolytic carbon(PyC)protective coatings for monocrystalline silicon furnace prepared by different processes were tested.The changes of normal emissivity of carbon materials caused by PyC protective coatings were discussed,and the influence of phase structure and surface appearance on the thermal radiation properties was investigated.The results show that the thermal radiation properties of PyC protective coatings with the wave band of 5-25μm are better than C/C substrate,further,normal spectral emissivity of CVD PyC coating remains basically at 0.85-0.90,and the normal total emissivity can reach0.89,which shows high thermal radiation performance.For resin PyC coating and CVD PyC coating,the degree of graphitization are 44.53%and 16.28%respectively,and the R value of Raman spectrum are 0.964and 1.384 respectively.Relatively disorder graphite structure of the latter causes various vibration modes,and the spectral emissivity is better,so the thermal radiation property of CVD PyC coating is excellent.A lot of spherical particles exists on the surface of the CVD PyC coating,and the more interface and spacing of particles reduce the number of particles per unit volume.Therefore,the scattering of thermal radiation is strongly strengthened,and the spectral emissivity is higher.
基金supported by the National Natural Science Foundation of China(32271799,31870570)the Science and Technology Plan of Fujian Provincial,China(3502ZCQXT2022001,2020H4026,2022G02020 and 2022H6002)the Scientific Research Start–up Funding for Special Professor of Minjiang Scholars。
文摘Sodium metal batteries(SMBs)have attracted increasing attention over time due to their abundance of sodium resources and low cost.However,the widespread application of SMBs as a viable technology remains a great challenge,such as uneven metallic deposition and dendrite formation during cycling.Carbon skeletons as sodiophilic hosts can alleviate the dendrite formation during the plating/stripping.For the carbon skeleton,how to rationalize the design sodiophilic interfaces between the sodium metal and carbon species remains key to developing desirable Na anodes.Herein,we fabricated four kinds of structural features for carbon skeletons using conventional calcination and flash Joule heating.The roles of conductivity,defects,oxygen content,and the distribution of graphite for the deposition of metallic sodium were discussed in detail.Based on interface engineering,the J1600 electrode,which has abundant Na-C species on its surface,showed the highest sodiophilic.There are uniform and rich F-Na species distributed in the inner solid electrolyte interface layer.This study investigated the different Na-deposition behavior in carbon hosts with distinct graphitic arrangements to pave the way for designing and optimizing advanced electrode materials.
基金Project(2023JJ40040)supported by the Natural Science Foundation of Hunan Province,ChinaProject(502221904)supported by the Project of Innovation-Driven Plan in Central South University,ChinaProject(24C0140)supported by the Scientific Research Fund of Hunan Provincial Education Department,China。
文摘The capacitive performance of carbon materials as supercapacitor electrode is synergistically influenced by the surface porous structure,graphitization structure,and surface atomic doping.However,simple realization of their synergistic regulation still faces significant challenges.Based on the biological porous structure,heteroatom-rich content and low cost of chestnut,this work adopt chestnut as precursor to prepare carbon electrode,of which the pores,graphitization,and surface atomic doping are synergistically regulated by simply changing the activation temperature.The optimized carbon electrode possesses a hierarchical porous structure with partial graphitization and O and N co doping.Benefited from these merits,the chestnut-derived porous carbon as a supercapacitor electrode,can achieve a high specific capacitance of 328.6 F/g at 1 A/g,which still retains 80.8%when the current density enlarging to 20 A/g.By packaging the symmetric electric double-layer capacitor,the device exhibits a specific capacitance of 63.6 F/g at 1 A/g,delivering an energy density of 12.7 W·h/kg at a power density of 600 W/kg.The stability of the device is tested at a current density of 20 A/g,which shows a capacitance retention rate of up to 90%after 10000 charge-discharge cycles.
