Common strategies for catalytic graphitization of biochar into graphitic porous carbon(GPC)still face great challenges,such as the realization of simple procedures,energy conservation,and green processes.Controlling o...Common strategies for catalytic graphitization of biochar into graphitic porous carbon(GPC)still face great challenges,such as the realization of simple procedures,energy conservation,and green processes.Controlling over the graphitization degree and pore structure of biochar is the key to its structural diversification.Herein,a clean and energy-efficient method is developed to synthesize adjustable graphitic degree and structure porosity GPC from rice husk-based carbon(RHC)at a relatively low temperature of 800–1000°C with environment-benign organometallic catalyst ethylenediaminetetraacetic acid ferric sodium salt(EDTA-iron)and the recovery ratio of catalyst is as high as 97%.The formed by the organic ligands of EDTA-iron facilitates the etching of RHC surface and pore by iron,resulting in highly graphitized and developed porous GPCs.The pore structure and graphitization degree of GPCs can be adjusted by altering the catalyst loading,temperature,and holding time.The catalyst EDTA-iron with a lower concentration mainly plays the role of etching,which promotes the formation of porous carbon with larger surface area(SBET=1187.2 m^(2)·g^(-1)).The catalyst with higher concentration mainly plays the role of catalyzing graphitization and promotes the obtaining of graphitic carbon with high graphitization degree(ID/IG=0.19).The mechanism of EDTA-iron catalyzed graphitization of RHC is explored by the comprehensive analysis of BET,XRD,Raman,TEM and TGA.This research not only provides an efficient method for the preparation of high-quality biomass-based graphite carbon,but also provides a feasible method for the preparation of biomass-based porous carbon.展开更多
Surface morphological features and nanostructures generated during SiC graphitization process can significantly affect fabrication of high-quality epitaxial graphene on semiconductor substrates.In this work,we investi...Surface morphological features and nanostructures generated during SiC graphitization process can significantly affect fabrication of high-quality epitaxial graphene on semiconductor substrates.In this work,we investigate the surface morphologies and atomic structures during graphitization process of 4H-SiC(0001) using scanning tunneling microscopy.Our high-magnified scanning-tunneling-microscope images exhibit the appearance and gradual developments of SiC(1 × 1)nanostructures after 1100℃ cleaning treatments,irregularly distributed among carbon nanocaps and(√3×√3) reconstruction domains.A model for the formation and growth progression of SiC(1 × 1) nanostructures has been proposed.When post-annealing temperature reaches 1300 ℃,the nanoholes and nanoislands can be observed on the surface,and multilayer graphene is often detected lying on the top surface of those nanoislands.These results provide profound insights into the complex evolution process of surface morphology during SiC thermal decomposition and will shed light on fabrication of SiC nanostructures and graphene nanoflakes.展开更多
The lack of methods to modulate intrinsic textures of carbon cathode has seriously hindered the revelation of in-depth relationship between inherent natures and capacitive behaviors,limiting the advancement of lithium...The lack of methods to modulate intrinsic textures of carbon cathode has seriously hindered the revelation of in-depth relationship between inherent natures and capacitive behaviors,limiting the advancement of lithium ion capacitors(LICs).Here,an orientateddesigned pore size distribution(range from 0.5 to 200 nm)and graphitization engineering strategy of carbon materials through regulating molar ratios of Zn/Co ions has been proposed,which provides an effective platform to deeply evaluate the capacitive behaviors of carbon cathode.Significantly,after the systematical analysis cooperating with experimental result and density functional theory calculation,it is uncovered that the size of solvated PF6-ion is about 1.5 nm.Moreover,the capacitive behaviors of carbon cathode could be enhanced attributed to the controlled pore size of 1.5-3 nm.Triggered with synergistic effect of graphitization and appropriate pore size distribution,optimized carbon cathode(Zn90Co10-APC)displays excellent capacitive performances with a reversible specific capacity of^50 mAh g-1at a current density of 5 A g-1.Furthermore,the assembly pre-lithiated graphite(PLG)//Zn90Co10-APC LIC could deliver a large energy density of 108 Wh kg-1 and a high power density of 150,000 W kg-1 as well as excellent long-term ability with 10,000 cycles.This elaborate work might shed light on the intensive understanding of the improved capacitive behavior in LiPF<sub>6 electrolyte and provide a feasible principle for elaborate fabrication of carbon cathodes for LIC systems.展开更多
Pore structure is an important factor influencing coke strength,while the property of coke is essential to maintaining gas and liquid permeability in a blast furnace.Therefore,an in-depth understanding of the pore str...Pore structure is an important factor influencing coke strength,while the property of coke is essential to maintaining gas and liquid permeability in a blast furnace.Therefore,an in-depth understanding of the pore structure evolution during the graphitization process can reveal the coke size degradation behavior during its descent in a blast furnace.Coke graphitization was simulated at different heating temperatures from 1100 to 1600℃ at intervals of 100℃.The quantitative evaluation of the coke pore structure with different graphitization degree was determined by vacuum drainage method and nitrogen adsorption method.Results show that the adsorption and desorption curves of graphitized coke have intersection points,and the two curves did not coincide,instead forming a“hysteresis loop.”Based on the hysteresis loop analysis,the porous structure of the graphitized coke mostly appeared in the shape of a“hair follicle.”Furthermore,with an increase in heating temperature,the apparent porosity,specific surface area,total pore volume,and amount of micropores showed good correlation and can divided into three stages:1100-1200,1200-1400,and 1400-1600℃.When the temperature was less than 1400℃,ash migration from the inner part mainly led to changes in the coke pore structure.When the temperature was greater than 1400℃,the pore structure evolution was mainly affected by the coke graphitization degree.The results of scanning electron microscopy,energy dispersive spectrometry,and ash content analyses also confirmed that the migration of the internal ash to the surface of the matrix during the graphitization process up to 1400℃ contributed to these changes.展开更多
We introduced a new catalyst,rare earth element praseodymium,for the catalytic graphitization of furan resin carbon.The extent of graphitization of the furan resin carbon was examined by X-ray diffraction and Raman sp...We introduced a new catalyst,rare earth element praseodymium,for the catalytic graphitization of furan resin carbon.The extent of graphitization of the furan resin carbon was examined by X-ray diffraction and Raman spectroscopy.The morphology of furan resin carbon was characterized by scanning electron microscopy.The effects of the praseodymium content and the heat-treatment temperature on the catalytic graphitization of furan resin carbon were also investigated.The results indicated that the praseodymium content and the heat-treatment temperature were two important factors on the catalytic graphitization of furan resin carbon and the significant catalytic graphitization was achieved at 2400 ?C and 15 wt.% praseodymium.展开更多
Materialization of coal is one of effective and clean pathways for its utilization. The microstructures of coal-based carbon materials have an important influence on their functional applications. Herein, the microstr...Materialization of coal is one of effective and clean pathways for its utilization. The microstructures of coal-based carbon materials have an important influence on their functional applications. Herein, the microstructural evolution of anthracite in the temperature range of 1000–2800 ℃ was systematically investigated to provide a guidance for the microstructural regulation of coal-based carbon materials.The results indicate that the microstructure of anthracite undergoes an important change during carbonization-graphitization process. As the temperature increases, aromatic layers in anthracite gradually transform into disordered graphite microcrystals and further grow into ordered graphite microcrystals, and then ordered graphite microcrystals are laterally linked to form pseudo-graphite phase and eventually transformed into highly ordered graphite-like sheets. In particular, 2000–2200 ℃ is a critical temperature region for the qualitative change of ordered graphite crystallites to pseudo-graphite phase,in which the relevant structural parameters including stacking height, crystallite lateral size and graphitization degree show a rapid increase. Moreover, both aromaticity and graphitization degree have a linear positive correlation with carbonization-graphitization temperature in a specific temperature range.Besides, after initial carbonization, some defect structures in anthracite such as aliphatic carbon and oxygen-containing functional groups are released in the form of gaseous low-molecular volatiles along with an increased pore structure, and the intermediates derived from minerals could facilitate the conversion of sp^(3) amorphous carbon to sp^(2) graphitic carbon. This work provides a valuable reference for the rational design of microstructure of coal-based carbon materials.展开更多
The structure of white iron treated with Si-Bi-AI complex inoculant has been observed bySEM and TEM. The results show that, in comparison with the samples treated with ordinaryinoculants, disorder, overlapping and inf...The structure of white iron treated with Si-Bi-AI complex inoculant has been observed bySEM and TEM. The results show that, in comparison with the samples treated with ordinaryinoculants, disorder, overlapping and inflexion of the pearlitic lamella appear, besides, the dis-location density increases apparently. The graphitization can be quickly realized at the tem-perature lower than that of austenitic transition (720℃).展开更多
Hard carbon material is one of the most promising anode materials for potassium ion batteries(PIBs)due to its distinct disordered and non-expandable framework.However,the intrinsically disordered microarchitecture of ...Hard carbon material is one of the most promising anode materials for potassium ion batteries(PIBs)due to its distinct disordered and non-expandable framework.However,the intrinsically disordered microarchitecture of hard carbon results in low electric conductivity and poor rate capability.Herein,nitrogendoped and partially graphitized hard carbons(NGHCs)derived from commercial coordination compound precursor-ethylenediaminetetraacetic acid(EDTA)disodium cobalt salt hydrate are designed and prepared as high-performance PIBs anode materials.By means of a facile annealing method,nitrogen elements and graphitic domains can be controllably introduced to NGHCs.The resulting NGHCs show structural merits of mesoporous construction,nitrogen doping and homogeneous graphitic domains,which ensures fast kinetics and electron transportation.Applying in anode for PIBs,NGHCs exhibit robust rate capability with high reversible capacity of 298.8 m Ah g^-1 at 50 m A g^-1,and stable cycle stability of 137.6 mAh g^-1 at 500 m A g^-1 after 1000 cycles.Moreover,the ex situ Raman spectra reveal a mixture"adsorption-intercalation mechanism"for potassium storage of NGHCs.More importantly,full PIBs by pairing with perylenetetracarboxylic dianhydride(PTCDA)cathode demonstrate the promising potential of practical application.In terms of commercial precursor,facile synthesis and long cycle lifespan,NGHCs represent a brilliant prospect for practical large-scale applications.展开更多
The shrinkage and chilling tendency of spheroidal graphite (abbreviated SG) cast iron is much greater than that of the flake graphite cast iron in spite of its higher amount of C and Si contents. Why? The main reason ...The shrinkage and chilling tendency of spheroidal graphite (abbreviated SG) cast iron is much greater than that of the flake graphite cast iron in spite of its higher amount of C and Si contents. Why? The main reason should be the difference in their graphitization during the eutectic solidification. In this paper, we discuss the difference in the solidification mechanism of both cast irons for solving these problems using unidirectional solidification and the cooling curves of the spheroidal graphite cast iron. The eutectic solidification rate of the SG cast iron is controlled by the diffusion of carbon through the austenite shell, and the final thickness is 1.4 times the radius of the SG, therefore, the reduction of the SG size, namely, the increase in the number, is the main solution of these problems.展开更多
The aim of this project is studying the effect of thermal operation parameters on the graphitization of self-diffused ethane-based catalytic coke.The novelty of this study refers to self-diffused metals that had given...The aim of this project is studying the effect of thermal operation parameters on the graphitization of self-diffused ethane-based catalytic coke.The novelty of this study refers to self-diffused metals that had given unique properties to the catalytic coke and had improved the graphitization degree at low temperatures.The main feature of this research is presenting a remarkable energy saving approach that uses low-cost installations for production of graphitized carbon.The experiments were performed in two steps including preparation of self-diffused ethane-based catalytic coke and then low-temperature graphitization of coke samples below 1500 ℃.Characteristic tests were performed by determination of electrical resistivity and XRD pattern of graphitized samples including graphitization degree,aromaticity,coke rank,number of carbon rings,graphene thickness and length.The results revealed that the blanket atmosphere,final temperature and exposure time had the greatest impact on the aforementioned criteria,while the role of thermal ramp and sulfur content of catalytic coke was negligible.The electrical resistivity tests on the graphitized sample showed how the electrical resistivity of graphitized samples is a function of graphitization degree.展开更多
From the points of both molten cast iron structure and the appearing ratio of electrons in outer-layer of different atoms, analysis on enhancement mechanism of graphitization ability after processing of the iron by pu...From the points of both molten cast iron structure and the appearing ratio of electrons in outer-layer of different atoms, analysis on enhancement mechanism of graphitization ability after processing of the iron by pulse electric discharge has been made, and the theory has been proofed by corresponding experiments. The results show that when the molten cast iron is being processed by pulse electric discharge, both the size of crystal embryos that composed by Fe and C atoms as well as the number of clusters can be reduced, even be separated by such discharging; consequently results in the segre- gation of C atoms in the molten cast iron near the cathode of discharging. The nucleation of graphite in these areas of the iron has been promoted at the discharging temperature; even though such degree has not been reached, the most favorable nucleation conditions of graphite can be at least created. Under the preconditions of not breaking up the graphite crystal embryos, with proper adjustment of discharging frequency, the stronger of the electric field and the longer of the pulsation treatment time are, the more graphitization ability of the molten cast iron is. The theoretical analysis on the above rules consists well with experimental results.展开更多
The process of electrodepositing Fe-Cr2O3 composite coating on polyacrylonitrile(PAN)-based carbon fibers and its catalytic graphitization were studied.Carbon fibers with and without electrodeposited Fe-Cr2O3 composit...The process of electrodepositing Fe-Cr2O3 composite coating on polyacrylonitrile(PAN)-based carbon fibers and its catalytic graphitization were studied.Carbon fibers with and without electrodeposited Fe-Cr2O3 composite coating were heat treated at different temperatures and the structural changes were characterized by XRD,Raman spectroscopy and SEM.The results indicate that Fe-Cr2O3 composite coating exhibits a significant catalytic effect on graphitization of carbon fibers at low temperatures.When the Fe-Cr2O3-coated carbon fibers were heat treated at 1 300°C,the interlayer spacing(d002) and ratio of relative peak area(AD/AG) reach 3.364-and 0.34,respectively.Whereas,the extent of graphitization of pristine carbon fibers is comparatively low even after heat treatment at 2 800°C and the values of d002 and AD/AG are 3.414 and 0.68,respectively.The extent of graphitization of carbon fibers increases not only with the increase of the catalyst gross but also the Cr2O3 content in Fe-Cr2O3 coating.The catalytic effect of Fe-Cr2O3 composite coating accords with the dissolution precipitation mechanism.展开更多
Cu-Fe based diamond composites used for saw-blade segments are directly fabricated by vacuum and pressure- assisted sintering. The carbide forming elements Cr and Ti are added to improve interfacial bonding between di...Cu-Fe based diamond composites used for saw-blade segments are directly fabricated by vacuum and pressure- assisted sintering. The carbide forming elements Cr and Ti are added to improve interfacial bonding between diamond and the Cu-Fe matrix. The interfacial reactions between diamond/graphite and Cr or Ti, and diamond graphitization are investigated by thermodynamics/kinetics analyses and experimental methods. The results show that interfacial reactions and graphitization of diamond can automatically proceed thermodynamically. The Cr3C2 , Cr7C3 , Cr23C6 , and TiC are formed at the interfaces of composites by reactions between diamond and Cr or Ti; diamond graphitization does not occur because of the kinetic difficulty at 1093 K under the pressure of 13 MPa.展开更多
The microstructures of vapor-grown carbon nanofibers(CNFs) before and after graphitization process were analyzed by high resolution transmission electron microscopy(HRTEM),Raman spectroscopy,X-ray diffractometry(XRD),...The microstructures of vapor-grown carbon nanofibers(CNFs) before and after graphitization process were analyzed by high resolution transmission electron microscopy(HRTEM),Raman spectroscopy,X-ray diffractometry(XRD),near-edge-X-ray absorption fine structure spectroscopy(NEXAFS) and thermogravimetric analysis(TGA).The results indicate that although non-graphitized CNFs have the characteristics of higher disorder,a transformation is found in the inner layer of tube wall where graphite sheets become stiff,which demonstrates the characteristics of higher graphitization of graphitized CNFs.The defects in outer tube wall disappear because the amorphous carbon changes to perfect crystalline carbon after annealing treatment at about 2 800 ℃.TGA analysis in air indicates that graphitized CNFs have excellent oxidation resistance up to 857 ℃.And the graphitization mechanism including four stages was also proposed.展开更多
The graphitization behavior of ultrahigh carbon steels containing Si in hot rolling processes was investigated. The graphite stringers went mostly through the small pores and generally paralleled to the rolling direct...The graphitization behavior of ultrahigh carbon steels containing Si in hot rolling processes was investigated. The graphite stringers went mostly through the small pores and generally paralleled to the rolling direction. The influence of alloy elements on graphitization was estimated based on thermodynamics, which showed that Si content was important for graphitization. Graphite stringers nucleated at small pores and grew with carbon diffusion during hot rolling. Alloy contents, pores and hot deformation at γ+Fe3C phase range were the key factors for the formation of graphite. The probable effect of deformation on graphite formation during hot rolling was discussed in this paper.展开更多
One-step pretreatment,anodization,is used to activate the polyacrylonitrile (PAN)-based carbon fibers instead of the routine two-step pretreatment,sensitization with SnCl2 and activation with PdCl2.The effect of the a...One-step pretreatment,anodization,is used to activate the polyacrylonitrile (PAN)-based carbon fibers instead of the routine two-step pretreatment,sensitization with SnCl2 and activation with PdCl2.The effect of the anodization pretreatment on the graphitization of PAN-based carbon fibers is investigated as a function of Ni-P catalyst.The PAN-based carbon fibers are anodized in H3PO4 electrolyte resulting in the formation of active sites,which thereby facilitates the following electroless Ni-P coating.Carbon fibers in the presence and absence of Ni-P coatings are heat treated and the structural changes are characterized by X-ray diffraction and Raman spectroscopy,both of which indicate that the graphitization of PAN-based carbon fibers are accelerated by both the anodization treatment and the catalysts Ni-P.Using the anodized carbon fibers,the routine two-step pretreatment,sensitization and activation,is not needed.展开更多
A novel carbon fiber pretreatment was proposed.Polyacrylonitrile(PAN)-based carbon fibers were first anodized in H3PO4 electrolyte to achieve an active surface,and then coated with Mo-B catalysts by immersed the carbo...A novel carbon fiber pretreatment was proposed.Polyacrylonitrile(PAN)-based carbon fibers were first anodized in H3PO4 electrolyte to achieve an active surface,and then coated with Mo-B catalysts by immersed the carbon fibers in a uniformly dispersed Mo-B sol.The as-treated carbon fibers were then graphitized at 2 400 ℃ for 2 h.The structural changes were characterized by X-ray diffractometry(XRD),Raman spectroscopy,scanning electron microscopy(SEM) and high-resolution transmission electronic microscopy(HRTEM).The results show that much better graphitization can be achieved in the presence of Mo-B,with an interlayer spacing(d002) of 0.335 8 nm and a crystalline size(Lc) of 28 nm.展开更多
The etching technique using Ce is a convenient and fast method for polishing and shaping diamond films. In this study, the influence of polishing parameters such as polishing temperature and time on the surface crysta...The etching technique using Ce is a convenient and fast method for polishing and shaping diamond films. In this study, the influence of polishing parameters such as polishing temperature and time on the surface crystallinity and phase composition of diamond films was thoroughly investigated via the analysis of Raman spectra such as FWHM and ID/IG. Moreover, the issue on the graphitization of diamond after polishing with Ce was further researched through the detailed study of the depth distribution of Raman data including FWHM and ID/IG, and a result completely different from the hot-iron metal polished ones was obtained. The results showed that polished diamond films had considerably higher diamond content than those before polishing, and not a bit of graphitization was found in the polished ones, owing to a higher solubility of carbon in rare earth metal Ce than that in transition metals, and the original crystallinity of the films polished with Ce did not deteriorate.展开更多
The purpose of this study was to determine the inffuence of heat treatment cycle on graphite phase formation on CK 45 steel. The presence of well distributed graphite in the matrix is responsible for the good mechanic...The purpose of this study was to determine the inffuence of heat treatment cycle on graphite phase formation on CK 45 steel. The presence of well distributed graphite in the matrix is responsible for the good mechanical and thermal properties of this kind of alloy. Such properties include excellent wear resistance, higher resistance to thermal shock, and higher resistance to oxidation at high temperature. A number of specimens were made up of appropriate design to provide the experimental materials. The transformation phase to a free carbon microstructure during graphitization under different conditions was then examined for the most successful experimental steels. Austenitising temperature of 920°C and the following isothermal heat treatment of 750°C at different holding times were used. Microstructures were examined by OM (optical microscopy) and SEM (scanning electron microscopy). Furthermore, it was found that isothermal transformation at 750°C for different soaking times produced a typical microstructure. Also, the amount of graphite increased with increasing isothermal heat treatment time. Heat treatment leading to supersaturation of iron with carbon was described and some of the consequences of the supersaturation were presented. Finally, the formation of the thermodynamically stable state of the graphite taken from the supersaturated solid solution was discussed.展开更多
基金the Science and Technology Research Project of Education Department of Jilin Province(JJKH20220683KJ)Natural Science Foundation of Jilin Province(20220101093JC).
文摘Common strategies for catalytic graphitization of biochar into graphitic porous carbon(GPC)still face great challenges,such as the realization of simple procedures,energy conservation,and green processes.Controlling over the graphitization degree and pore structure of biochar is the key to its structural diversification.Herein,a clean and energy-efficient method is developed to synthesize adjustable graphitic degree and structure porosity GPC from rice husk-based carbon(RHC)at a relatively low temperature of 800–1000°C with environment-benign organometallic catalyst ethylenediaminetetraacetic acid ferric sodium salt(EDTA-iron)and the recovery ratio of catalyst is as high as 97%.The formed by the organic ligands of EDTA-iron facilitates the etching of RHC surface and pore by iron,resulting in highly graphitized and developed porous GPCs.The pore structure and graphitization degree of GPCs can be adjusted by altering the catalyst loading,temperature,and holding time.The catalyst EDTA-iron with a lower concentration mainly plays the role of etching,which promotes the formation of porous carbon with larger surface area(SBET=1187.2 m^(2)·g^(-1)).The catalyst with higher concentration mainly plays the role of catalyzing graphitization and promotes the obtaining of graphitic carbon with high graphitization degree(ID/IG=0.19).The mechanism of EDTA-iron catalyzed graphitization of RHC is explored by the comprehensive analysis of BET,XRD,Raman,TEM and TGA.This research not only provides an efficient method for the preparation of high-quality biomass-based graphite carbon,but also provides a feasible method for the preparation of biomass-based porous carbon.
基金Project supported by the Natural Science Foundation of Shanghai Science and Technology Committee (Grant No. 18ZR1403300)。
文摘Surface morphological features and nanostructures generated during SiC graphitization process can significantly affect fabrication of high-quality epitaxial graphene on semiconductor substrates.In this work,we investigate the surface morphologies and atomic structures during graphitization process of 4H-SiC(0001) using scanning tunneling microscopy.Our high-magnified scanning-tunneling-microscope images exhibit the appearance and gradual developments of SiC(1 × 1)nanostructures after 1100℃ cleaning treatments,irregularly distributed among carbon nanocaps and(√3×√3) reconstruction domains.A model for the formation and growth progression of SiC(1 × 1) nanostructures has been proposed.When post-annealing temperature reaches 1300 ℃,the nanoholes and nanoislands can be observed on the surface,and multilayer graphene is often detected lying on the top surface of those nanoislands.These results provide profound insights into the complex evolution process of surface morphology during SiC thermal decomposition and will shed light on fabrication of SiC nanostructures and graphene nanoflakes.
基金financially supported by National Key Research and Development Program of China(2018YFC1901605)the National Postdoctoral Program for Innovative Talents(BX201600192)+1 种基金Hunan Provincial Science and Technology Plan(2017TP1001)Innovation Mover Program of Central South University(GCX20190893Y)。
文摘The lack of methods to modulate intrinsic textures of carbon cathode has seriously hindered the revelation of in-depth relationship between inherent natures and capacitive behaviors,limiting the advancement of lithium ion capacitors(LICs).Here,an orientateddesigned pore size distribution(range from 0.5 to 200 nm)and graphitization engineering strategy of carbon materials through regulating molar ratios of Zn/Co ions has been proposed,which provides an effective platform to deeply evaluate the capacitive behaviors of carbon cathode.Significantly,after the systematical analysis cooperating with experimental result and density functional theory calculation,it is uncovered that the size of solvated PF6-ion is about 1.5 nm.Moreover,the capacitive behaviors of carbon cathode could be enhanced attributed to the controlled pore size of 1.5-3 nm.Triggered with synergistic effect of graphitization and appropriate pore size distribution,optimized carbon cathode(Zn90Co10-APC)displays excellent capacitive performances with a reversible specific capacity of^50 mAh g-1at a current density of 5 A g-1.Furthermore,the assembly pre-lithiated graphite(PLG)//Zn90Co10-APC LIC could deliver a large energy density of 108 Wh kg-1 and a high power density of 150,000 W kg-1 as well as excellent long-term ability with 10,000 cycles.This elaborate work might shed light on the intensive understanding of the improved capacitive behavior in LiPF<sub>6 electrolyte and provide a feasible principle for elaborate fabrication of carbon cathodes for LIC systems.
基金This work was financially supported by the National Natural Science Foundation of China(Nos.51604148,51874171,and 51974154)the Science Foundation for the Talents by University of Science and Technology Liaoning(USTL),China(2019RC11).
文摘Pore structure is an important factor influencing coke strength,while the property of coke is essential to maintaining gas and liquid permeability in a blast furnace.Therefore,an in-depth understanding of the pore structure evolution during the graphitization process can reveal the coke size degradation behavior during its descent in a blast furnace.Coke graphitization was simulated at different heating temperatures from 1100 to 1600℃ at intervals of 100℃.The quantitative evaluation of the coke pore structure with different graphitization degree was determined by vacuum drainage method and nitrogen adsorption method.Results show that the adsorption and desorption curves of graphitized coke have intersection points,and the two curves did not coincide,instead forming a“hysteresis loop.”Based on the hysteresis loop analysis,the porous structure of the graphitized coke mostly appeared in the shape of a“hair follicle.”Furthermore,with an increase in heating temperature,the apparent porosity,specific surface area,total pore volume,and amount of micropores showed good correlation and can divided into three stages:1100-1200,1200-1400,and 1400-1600℃.When the temperature was less than 1400℃,ash migration from the inner part mainly led to changes in the coke pore structure.When the temperature was greater than 1400℃,the pore structure evolution was mainly affected by the coke graphitization degree.The results of scanning electron microscopy,energy dispersive spectrometry,and ash content analyses also confirmed that the migration of the internal ash to the surface of the matrix during the graphitization process up to 1400℃ contributed to these changes.
基金supported by the National Basic Research Program of China (2006CB600903)
文摘We introduced a new catalyst,rare earth element praseodymium,for the catalytic graphitization of furan resin carbon.The extent of graphitization of the furan resin carbon was examined by X-ray diffraction and Raman spectroscopy.The morphology of furan resin carbon was characterized by scanning electron microscopy.The effects of the praseodymium content and the heat-treatment temperature on the catalytic graphitization of furan resin carbon were also investigated.The results indicated that the praseodymium content and the heat-treatment temperature were two important factors on the catalytic graphitization of furan resin carbon and the significant catalytic graphitization was achieved at 2400 ?C and 15 wt.% praseodymium.
基金supported by the National Natural Science Foundation of China(Nos.51974110,52074109 and 52274261)the Key Scientific and Technological Project of Henan Province(No.202102210183)the Coal Green Conversion Outstanding Foreign Scientists Foundation of Henan Province(No.GZS2020012).
文摘Materialization of coal is one of effective and clean pathways for its utilization. The microstructures of coal-based carbon materials have an important influence on their functional applications. Herein, the microstructural evolution of anthracite in the temperature range of 1000–2800 ℃ was systematically investigated to provide a guidance for the microstructural regulation of coal-based carbon materials.The results indicate that the microstructure of anthracite undergoes an important change during carbonization-graphitization process. As the temperature increases, aromatic layers in anthracite gradually transform into disordered graphite microcrystals and further grow into ordered graphite microcrystals, and then ordered graphite microcrystals are laterally linked to form pseudo-graphite phase and eventually transformed into highly ordered graphite-like sheets. In particular, 2000–2200 ℃ is a critical temperature region for the qualitative change of ordered graphite crystallites to pseudo-graphite phase,in which the relevant structural parameters including stacking height, crystallite lateral size and graphitization degree show a rapid increase. Moreover, both aromaticity and graphitization degree have a linear positive correlation with carbonization-graphitization temperature in a specific temperature range.Besides, after initial carbonization, some defect structures in anthracite such as aliphatic carbon and oxygen-containing functional groups are released in the form of gaseous low-molecular volatiles along with an increased pore structure, and the intermediates derived from minerals could facilitate the conversion of sp^(3) amorphous carbon to sp^(2) graphitic carbon. This work provides a valuable reference for the rational design of microstructure of coal-based carbon materials.
文摘The structure of white iron treated with Si-Bi-AI complex inoculant has been observed bySEM and TEM. The results show that, in comparison with the samples treated with ordinaryinoculants, disorder, overlapping and inflexion of the pearlitic lamella appear, besides, the dis-location density increases apparently. The graphitization can be quickly realized at the tem-perature lower than that of austenitic transition (720℃).
基金support of the Innovation Program of Central South University(No.2018zzts139)。
文摘Hard carbon material is one of the most promising anode materials for potassium ion batteries(PIBs)due to its distinct disordered and non-expandable framework.However,the intrinsically disordered microarchitecture of hard carbon results in low electric conductivity and poor rate capability.Herein,nitrogendoped and partially graphitized hard carbons(NGHCs)derived from commercial coordination compound precursor-ethylenediaminetetraacetic acid(EDTA)disodium cobalt salt hydrate are designed and prepared as high-performance PIBs anode materials.By means of a facile annealing method,nitrogen elements and graphitic domains can be controllably introduced to NGHCs.The resulting NGHCs show structural merits of mesoporous construction,nitrogen doping and homogeneous graphitic domains,which ensures fast kinetics and electron transportation.Applying in anode for PIBs,NGHCs exhibit robust rate capability with high reversible capacity of 298.8 m Ah g^-1 at 50 m A g^-1,and stable cycle stability of 137.6 mAh g^-1 at 500 m A g^-1 after 1000 cycles.Moreover,the ex situ Raman spectra reveal a mixture"adsorption-intercalation mechanism"for potassium storage of NGHCs.More importantly,full PIBs by pairing with perylenetetracarboxylic dianhydride(PTCDA)cathode demonstrate the promising potential of practical application.In terms of commercial precursor,facile synthesis and long cycle lifespan,NGHCs represent a brilliant prospect for practical large-scale applications.
文摘The shrinkage and chilling tendency of spheroidal graphite (abbreviated SG) cast iron is much greater than that of the flake graphite cast iron in spite of its higher amount of C and Si contents. Why? The main reason should be the difference in their graphitization during the eutectic solidification. In this paper, we discuss the difference in the solidification mechanism of both cast irons for solving these problems using unidirectional solidification and the cooling curves of the spheroidal graphite cast iron. The eutectic solidification rate of the SG cast iron is controlled by the diffusion of carbon through the austenite shell, and the final thickness is 1.4 times the radius of the SG, therefore, the reduction of the SG size, namely, the increase in the number, is the main solution of these problems.
文摘The aim of this project is studying the effect of thermal operation parameters on the graphitization of self-diffused ethane-based catalytic coke.The novelty of this study refers to self-diffused metals that had given unique properties to the catalytic coke and had improved the graphitization degree at low temperatures.The main feature of this research is presenting a remarkable energy saving approach that uses low-cost installations for production of graphitized carbon.The experiments were performed in two steps including preparation of self-diffused ethane-based catalytic coke and then low-temperature graphitization of coke samples below 1500 ℃.Characteristic tests were performed by determination of electrical resistivity and XRD pattern of graphitized samples including graphitization degree,aromaticity,coke rank,number of carbon rings,graphene thickness and length.The results revealed that the blanket atmosphere,final temperature and exposure time had the greatest impact on the aforementioned criteria,while the role of thermal ramp and sulfur content of catalytic coke was negligible.The electrical resistivity tests on the graphitized sample showed how the electrical resistivity of graphitized samples is a function of graphitization degree.
文摘From the points of both molten cast iron structure and the appearing ratio of electrons in outer-layer of different atoms, analysis on enhancement mechanism of graphitization ability after processing of the iron by pulse electric discharge has been made, and the theory has been proofed by corresponding experiments. The results show that when the molten cast iron is being processed by pulse electric discharge, both the size of crystal embryos that composed by Fe and C atoms as well as the number of clusters can be reduced, even be separated by such discharging; consequently results in the segre- gation of C atoms in the molten cast iron near the cathode of discharging. The nucleation of graphite in these areas of the iron has been promoted at the discharging temperature; even though such degree has not been reached, the most favorable nucleation conditions of graphite can be at least created. Under the preconditions of not breaking up the graphite crystal embryos, with proper adjustment of discharging frequency, the stronger of the electric field and the longer of the pulsation treatment time are, the more graphitization ability of the molten cast iron is. The theoretical analysis on the above rules consists well with experimental results.
基金Project(2006CB600903) supported by the National Basic Research Program of China
文摘The process of electrodepositing Fe-Cr2O3 composite coating on polyacrylonitrile(PAN)-based carbon fibers and its catalytic graphitization were studied.Carbon fibers with and without electrodeposited Fe-Cr2O3 composite coating were heat treated at different temperatures and the structural changes were characterized by XRD,Raman spectroscopy and SEM.The results indicate that Fe-Cr2O3 composite coating exhibits a significant catalytic effect on graphitization of carbon fibers at low temperatures.When the Fe-Cr2O3-coated carbon fibers were heat treated at 1 300°C,the interlayer spacing(d002) and ratio of relative peak area(AD/AG) reach 3.364-and 0.34,respectively.Whereas,the extent of graphitization of pristine carbon fibers is comparatively low even after heat treatment at 2 800°C and the values of d002 and AD/AG are 3.414 and 0.68,respectively.The extent of graphitization of carbon fibers increases not only with the increase of the catalyst gross but also the Cr2O3 content in Fe-Cr2O3 coating.The catalytic effect of Fe-Cr2O3 composite coating accords with the dissolution precipitation mechanism.
基金Project supported by the National Natural Science Foundation of China (Grant No. 51165021)the Science Fund for Distinguished Young Scholars of Gansu Province, China (Grant No. 111RJDA0103)
文摘Cu-Fe based diamond composites used for saw-blade segments are directly fabricated by vacuum and pressure- assisted sintering. The carbide forming elements Cr and Ti are added to improve interfacial bonding between diamond and the Cu-Fe matrix. The interfacial reactions between diamond/graphite and Cr or Ti, and diamond graphitization are investigated by thermodynamics/kinetics analyses and experimental methods. The results show that interfacial reactions and graphitization of diamond can automatically proceed thermodynamically. The Cr3C2 , Cr7C3 , Cr23C6 , and TiC are formed at the interfaces of composites by reactions between diamond and Cr or Ti; diamond graphitization does not occur because of the kinetic difficulty at 1093 K under the pressure of 13 MPa.
文摘The microstructures of vapor-grown carbon nanofibers(CNFs) before and after graphitization process were analyzed by high resolution transmission electron microscopy(HRTEM),Raman spectroscopy,X-ray diffractometry(XRD),near-edge-X-ray absorption fine structure spectroscopy(NEXAFS) and thermogravimetric analysis(TGA).The results indicate that although non-graphitized CNFs have the characteristics of higher disorder,a transformation is found in the inner layer of tube wall where graphite sheets become stiff,which demonstrates the characteristics of higher graphitization of graphitized CNFs.The defects in outer tube wall disappear because the amorphous carbon changes to perfect crystalline carbon after annealing treatment at about 2 800 ℃.TGA analysis in air indicates that graphitized CNFs have excellent oxidation resistance up to 857 ℃.And the graphitization mechanism including four stages was also proposed.
文摘The graphitization behavior of ultrahigh carbon steels containing Si in hot rolling processes was investigated. The graphite stringers went mostly through the small pores and generally paralleled to the rolling direction. The influence of alloy elements on graphitization was estimated based on thermodynamics, which showed that Si content was important for graphitization. Graphite stringers nucleated at small pores and grew with carbon diffusion during hot rolling. Alloy contents, pores and hot deformation at γ+Fe3C phase range were the key factors for the formation of graphite. The probable effect of deformation on graphite formation during hot rolling was discussed in this paper.
基金Funded by the National Basic Research Program of China (No.2006CB600903)
文摘One-step pretreatment,anodization,is used to activate the polyacrylonitrile (PAN)-based carbon fibers instead of the routine two-step pretreatment,sensitization with SnCl2 and activation with PdCl2.The effect of the anodization pretreatment on the graphitization of PAN-based carbon fibers is investigated as a function of Ni-P catalyst.The PAN-based carbon fibers are anodized in H3PO4 electrolyte resulting in the formation of active sites,which thereby facilitates the following electroless Ni-P coating.Carbon fibers in the presence and absence of Ni-P coatings are heat treated and the structural changes are characterized by X-ray diffraction and Raman spectroscopy,both of which indicate that the graphitization of PAN-based carbon fibers are accelerated by both the anodization treatment and the catalysts Ni-P.Using the anodized carbon fibers,the routine two-step pretreatment,sensitization and activation,is not needed.
基金Project(2006CB600903) supported by the National Basic Research Program of China
文摘A novel carbon fiber pretreatment was proposed.Polyacrylonitrile(PAN)-based carbon fibers were first anodized in H3PO4 electrolyte to achieve an active surface,and then coated with Mo-B catalysts by immersed the carbon fibers in a uniformly dispersed Mo-B sol.The as-treated carbon fibers were then graphitized at 2 400 ℃ for 2 h.The structural changes were characterized by X-ray diffractometry(XRD),Raman spectroscopy,scanning electron microscopy(SEM) and high-resolution transmission electronic microscopy(HRTEM).The results show that much better graphitization can be achieved in the presence of Mo-B,with an interlayer spacing(d002) of 0.335 8 nm and a crystalline size(Lc) of 28 nm.
文摘The etching technique using Ce is a convenient and fast method for polishing and shaping diamond films. In this study, the influence of polishing parameters such as polishing temperature and time on the surface crystallinity and phase composition of diamond films was thoroughly investigated via the analysis of Raman spectra such as FWHM and ID/IG. Moreover, the issue on the graphitization of diamond after polishing with Ce was further researched through the detailed study of the depth distribution of Raman data including FWHM and ID/IG, and a result completely different from the hot-iron metal polished ones was obtained. The results showed that polished diamond films had considerably higher diamond content than those before polishing, and not a bit of graphitization was found in the polished ones, owing to a higher solubility of carbon in rare earth metal Ce than that in transition metals, and the original crystallinity of the films polished with Ce did not deteriorate.
基金funded by the research scholarship ofthe Ferdowsi University of Mashhad, Iran. This support isgratefully appreciated.
文摘The purpose of this study was to determine the inffuence of heat treatment cycle on graphite phase formation on CK 45 steel. The presence of well distributed graphite in the matrix is responsible for the good mechanical and thermal properties of this kind of alloy. Such properties include excellent wear resistance, higher resistance to thermal shock, and higher resistance to oxidation at high temperature. A number of specimens were made up of appropriate design to provide the experimental materials. The transformation phase to a free carbon microstructure during graphitization under different conditions was then examined for the most successful experimental steels. Austenitising temperature of 920°C and the following isothermal heat treatment of 750°C at different holding times were used. Microstructures were examined by OM (optical microscopy) and SEM (scanning electron microscopy). Furthermore, it was found that isothermal transformation at 750°C for different soaking times produced a typical microstructure. Also, the amount of graphite increased with increasing isothermal heat treatment time. Heat treatment leading to supersaturation of iron with carbon was described and some of the consequences of the supersaturation were presented. Finally, the formation of the thermodynamically stable state of the graphite taken from the supersaturated solid solution was discussed.
