Glass-like carbons （GCs） were prepared by carbonization of acetone-furfural resin in nitrogen atmosphere at 850℃, followed by heat treatment over a range of 1 200-2 500℃in inert atmosphere. The effect of heat trea...Glass-like carbons （GCs） were prepared by carbonization of acetone-furfural resin in nitrogen atmosphere at 850℃, followed by heat treatment over a range of 1 200-2 500℃in inert atmosphere. The effect of heat treatment temperature （HTT） on the oxidation behavior was investigated by dynamic and isothermal thermogravimetric analyses. The structure of GC was examined by X-ray diffractometry （XRD） and the morphologies of GC before and after oxidation were examined by scanning electron microscopy （SEM）. It is shown that the GC samples present peculiar oxidation behavior. The anti-oxidation behavior increases with increasing the HTT to 1 600 ℃, whereas decreases gradually thereafter. GC sample heat treated at 1 600℃ obtains relatively optimal anti-oxidation properties under this condition. During the oxidation, this material produces grid network matrix surface and numerous nodular residues on the surface, resulting in excellent resistance to the attack of oxygen atoms.展开更多
Thermoelectric properties of orthorhombic or rhombohedral GeSe have attracted great attention recently,with the rise of its structural analog Sn Se.However,the p-type cubic GeSe with higher symmetry and higher valence...Thermoelectric properties of orthorhombic or rhombohedral GeSe have attracted great attention recently,with the rise of its structural analog Sn Se.However,the p-type cubic GeSe with higher symmetry and higher valence band degeneracy,which might exhibit higher thermoelectric performance,has never been synthesized.Here we report on the successful synthesis of p-type crystalline cubic GeSe by alloying with Sb2Te3 and the spontaneously formed Ge-vacancies.An unexpected glass-like temperature independent lattice thermal conductivity is observed in crystalline cubic GeSe,which results from strong phonon scattering by vacancy-induced disorders.Combining the multiple scattering theory and chemical bond analysis,we further reveal the existence of Anderson localization induced by Ge-vacancies.The Anderson localization results in a nearly constant Seebeck coefficient with increasing the carrier concentration.These results provide a general insight towards understanding and improving the thermoelectric properties of thermoelectric materials with vacancies and atomic-scale disorders.展开更多
We systematically investigate the effect of pressure on the magnetic properties of GdCo2B2 on the basis of alternating current（AC） susceptibility,AC heat capacity and electrical resistivity measurements under pressu...We systematically investigate the effect of pressure on the magnetic properties of GdCo2B2 on the basis of alternating current（AC） susceptibility,AC heat capacity and electrical resistivity measurements under pressures up to 2.2 GPa.A detailed magnetic phase diagram under pressure is determined.GdCo2B2 exhibits three anomalies that apparently reflect magnetic phase transitions,respectively,at temperatures TC= 20.5 K,T1= 18.0 K and TN= 11.5 K under ambient pressure.Under pressures up to 2.2 GPa,these anomalies are observed to slightly increase at TCand T1,and they coincide with each other above 1.6 GPa.Conversely,they decrease at TN and disappear under pressures higher than 1.4 GPa.The results indicate that the low-temperature magnetic phases can be easily suppressed by pressure.Moreover,the spin-glass-like behavior of GdCo2B2 is examined in terms of magnetization,aging effect and frequency dependence of AC susceptibility.A separation between the zero-field-cooled（ZFC） and field-cooled（FC） magnetization curves becomes evident at a low magnetic field of 0.001 T.A long-time relaxation behavior is observed at 4 K.The freezing temperature Tfincreases with frequency increasing.展开更多
Rechargeable batteries based on solid-state electrolytes are of great interest and importance for the next-generation energy storage due to their high energy output and improved safety.For building the solid-state bat...Rechargeable batteries based on solid-state electrolytes are of great interest and importance for the next-generation energy storage due to their high energy output and improved safety.For building the solid-state batteries,Na_(3)Zr_(2)Si_(2)PO_(12)(NZSP)represents a promising candidate as it features high chemical stability against air exposure and a high Na^(+)conductivity.NZSP pellets were usually calcined at a high temperature,and the high volatility of Na and P elements easily led to the formation of impurity phase.In this work,the effects of calcination temperature and stoichiometry on the phase purity and ionic conductivity of the NZSP electrolyte were studied.At an elevated sintering temperature,the NZSP electrolyte showed a high ionic conductivity owing to decreased porosity,and the highest ionic conductivity at 30℃was observed to be 2.75×10^(-5)S·cm^(-1)with an activation energy of 0.41 eV.For the stoichiometry,the introduction of 5 mol%excessive P results in formation of more Na_(3)PO_(4) and glass-like phase at the grain boundary,which caused the blurred grain boundary and reduced grain barrier,and effectively suppressed Na dendrite growth,then accounted for improved cycling performance of a Na‖Na symmetric cell.Our work provided insights on reasonable design and preparation of NZSP electrolyte towards practical realization of solid-state Na-metal batteries.展开更多
基金Project (2006CB600902) supported by the National Basic Research Program of China
文摘Glass-like carbons （GCs） were prepared by carbonization of acetone-furfural resin in nitrogen atmosphere at 850℃, followed by heat treatment over a range of 1 200-2 500℃in inert atmosphere. The effect of heat treatment temperature （HTT） on the oxidation behavior was investigated by dynamic and isothermal thermogravimetric analyses. The structure of GC was examined by X-ray diffractometry （XRD） and the morphologies of GC before and after oxidation were examined by scanning electron microscopy （SEM）. It is shown that the GC samples present peculiar oxidation behavior. The anti-oxidation behavior increases with increasing the HTT to 1 600 ℃, whereas decreases gradually thereafter. GC sample heat treated at 1 600℃ obtains relatively optimal anti-oxidation properties under this condition. During the oxidation, this material produces grid network matrix surface and numerous nodular residues on the surface, resulting in excellent resistance to the attack of oxygen atoms.
基金financial support from Dalian Institute of Chemical Physics(Grant:DICP ZZBS201608)。
文摘Thermoelectric properties of orthorhombic or rhombohedral GeSe have attracted great attention recently,with the rise of its structural analog Sn Se.However,the p-type cubic GeSe with higher symmetry and higher valence band degeneracy,which might exhibit higher thermoelectric performance,has never been synthesized.Here we report on the successful synthesis of p-type crystalline cubic GeSe by alloying with Sb2Te3 and the spontaneously formed Ge-vacancies.An unexpected glass-like temperature independent lattice thermal conductivity is observed in crystalline cubic GeSe,which results from strong phonon scattering by vacancy-induced disorders.Combining the multiple scattering theory and chemical bond analysis,we further reveal the existence of Anderson localization induced by Ge-vacancies.The Anderson localization results in a nearly constant Seebeck coefficient with increasing the carrier concentration.These results provide a general insight towards understanding and improving the thermoelectric properties of thermoelectric materials with vacancies and atomic-scale disorders.
基金Project supported by JSPS KAKENHI(Grant No.24540366,Grant-in-Aid for Scientific Research(C))
文摘We systematically investigate the effect of pressure on the magnetic properties of GdCo2B2 on the basis of alternating current（AC） susceptibility,AC heat capacity and electrical resistivity measurements under pressures up to 2.2 GPa.A detailed magnetic phase diagram under pressure is determined.GdCo2B2 exhibits three anomalies that apparently reflect magnetic phase transitions,respectively,at temperatures TC= 20.5 K,T1= 18.0 K and TN= 11.5 K under ambient pressure.Under pressures up to 2.2 GPa,these anomalies are observed to slightly increase at TCand T1,and they coincide with each other above 1.6 GPa.Conversely,they decrease at TN and disappear under pressures higher than 1.4 GPa.The results indicate that the low-temperature magnetic phases can be easily suppressed by pressure.Moreover,the spin-glass-like behavior of GdCo2B2 is examined in terms of magnetization,aging effect and frequency dependence of AC susceptibility.A separation between the zero-field-cooled（ZFC） and field-cooled（FC） magnetization curves becomes evident at a low magnetic field of 0.001 T.A long-time relaxation behavior is observed at 4 K.The freezing temperature Tfincreases with frequency increasing.
基金financially supported by the National Natural Science Foundation of China(Nos.51902238 and 52172234)the Fundamental Research Funds for the Central Universities(Nos.2020IVA069,2020IVB043 and 2021IVA020B)
文摘Rechargeable batteries based on solid-state electrolytes are of great interest and importance for the next-generation energy storage due to their high energy output and improved safety.For building the solid-state batteries,Na_(3)Zr_(2)Si_(2)PO_(12)(NZSP)represents a promising candidate as it features high chemical stability against air exposure and a high Na^(+)conductivity.NZSP pellets were usually calcined at a high temperature,and the high volatility of Na and P elements easily led to the formation of impurity phase.In this work,the effects of calcination temperature and stoichiometry on the phase purity and ionic conductivity of the NZSP electrolyte were studied.At an elevated sintering temperature,the NZSP electrolyte showed a high ionic conductivity owing to decreased porosity,and the highest ionic conductivity at 30℃was observed to be 2.75×10^(-5)S·cm^(-1)with an activation energy of 0.41 eV.For the stoichiometry,the introduction of 5 mol%excessive P results in formation of more Na_(3)PO_(4) and glass-like phase at the grain boundary,which caused the blurred grain boundary and reduced grain barrier,and effectively suppressed Na dendrite growth,then accounted for improved cycling performance of a Na‖Na symmetric cell.Our work provided insights on reasonable design and preparation of NZSP electrolyte towards practical realization of solid-state Na-metal batteries.
