Rational design of carbon skeleton interfaces for highly reversible sodium metal battery anodes

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.

Calculating the effective thermal conductivity of gray cast iron by using an interconnected graphite model

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.

Study of Thermal Radiation Properties of Pyrolytic Carbon Protective Coatings for Monocrystalline Silicon Furnace

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.