We have performed low temperature resistivity p（T） and specific heat C（T） measurements on a superconducting polycrystalline Nb0.75Mg0.25B2 sample. The results indicate that the superconducting transition temperatu...We have performed low temperature resistivity p（T） and specific heat C（T） measurements on a superconducting polycrystalline Nb0.75Mg0.25B2 sample. The results indicate that the superconducting transition temperature is -4.6 K. The zero temperature upper critical field determined from the resistivity and specific heat is 3123 Oe. The electronic coefficient of specific heat γn=4.51 mJmol^-1K^2 and the Debye temperature θD=419 K are obtained by fitting the zero-field specific heat data in the normal state. At low temperatures, the electronic specific heat in the superconducting state follows Ces/γnTc = 2.84 exp（-1.21Tc/T）. This indicates that the superconducting pairing in Nb0.75Mg0.25B2 has s-wave symmetry.展开更多
Is it possible to improve CO_(2)solubility in potassium carbonate(K_(2)CO_(3))-based transition temperature mixtures(TTMs)?To assess this possibility,a ternary transition-temperature mixture(TTTM)was prepared by using...Is it possible to improve CO_(2)solubility in potassium carbonate(K_(2)CO_(3))-based transition temperature mixtures(TTMs)?To assess this possibility,a ternary transition-temperature mixture(TTTM)was prepared by using a hindered amine,2-amino-2-methyl-1,3-propanediol(AMPD).Fourier transform infrared spectroscopy(FT-IR)was employed to detect the functional groups including hydroxyl,amine,carbonate ion,and aliphatic functional groups in the prepared solvents.From thermogravimetric analysis(TGA),it was found that the addition of AMPD to the binary mixture can increase the thermal stability of TTTM.The viscosity findings showed that TTTM has a higher viscosity than TTM while their difference was decreased by increasing temperature.In addition,Eyring’s absolute rate theory was used to compute the activation parameters(∆G^(*),∆H^(*),and ∆S^(*)).The CO_(2)solubility in liquids was measured at a temperature of 303.15 K and pressures up to 1.8 MPa.The results disclosed that the CO_(2)solubility of TTTM was improved by the addition of AMPD.At the pressure of about 1.8 MPa,the CO_(2)mole fractions of TTM and TTTM were 0.1697 and 0.2022,respectively.To confirm the experimental data,density functional theory(DFT)was employed.From the DFT analysis,it was found that the TTTM+CO_(2)system has higher interaction energy(|∆E|)than the TTM+CO_(2)system indicating the higher CO_(2)affinity of the former system.This study might help scientists to better understand and to improve CO_(2)solubility in these types of solvents by choosing a suitable amine as HBD and finding the best combination of HBA and HBD.展开更多
基金Supported by the National Natural Science Foundation of China, the Knowledge Innovation Project of Chinese Academy of Sciences, and National Basic Research Programme of China under Grant Nos 2003CCC01000, 2005CB32170X and 2006CB921301.
文摘We have performed low temperature resistivity p（T） and specific heat C（T） measurements on a superconducting polycrystalline Nb0.75Mg0.25B2 sample. The results indicate that the superconducting transition temperature is -4.6 K. The zero temperature upper critical field determined from the resistivity and specific heat is 3123 Oe. The electronic coefficient of specific heat γn=4.51 mJmol^-1K^2 and the Debye temperature θD=419 K are obtained by fitting the zero-field specific heat data in the normal state. At low temperatures, the electronic specific heat in the superconducting state follows Ces/γnTc = 2.84 exp（-1.21Tc/T）. This indicates that the superconducting pairing in Nb0.75Mg0.25B2 has s-wave symmetry.
基金support of National Key Research and Development Program of China(Grant No.2019YFC1904602)the Key SCI-Tech Innovation 2025 Program of Ningbo,China(Grant No.2018B10025).
文摘Is it possible to improve CO_(2)solubility in potassium carbonate(K_(2)CO_(3))-based transition temperature mixtures(TTMs)?To assess this possibility,a ternary transition-temperature mixture(TTTM)was prepared by using a hindered amine,2-amino-2-methyl-1,3-propanediol(AMPD).Fourier transform infrared spectroscopy(FT-IR)was employed to detect the functional groups including hydroxyl,amine,carbonate ion,and aliphatic functional groups in the prepared solvents.From thermogravimetric analysis(TGA),it was found that the addition of AMPD to the binary mixture can increase the thermal stability of TTTM.The viscosity findings showed that TTTM has a higher viscosity than TTM while their difference was decreased by increasing temperature.In addition,Eyring’s absolute rate theory was used to compute the activation parameters(∆G^(*),∆H^(*),and ∆S^(*)).The CO_(2)solubility in liquids was measured at a temperature of 303.15 K and pressures up to 1.8 MPa.The results disclosed that the CO_(2)solubility of TTTM was improved by the addition of AMPD.At the pressure of about 1.8 MPa,the CO_(2)mole fractions of TTM and TTTM were 0.1697 and 0.2022,respectively.To confirm the experimental data,density functional theory(DFT)was employed.From the DFT analysis,it was found that the TTTM+CO_(2)system has higher interaction energy(|∆E|)than the TTM+CO_(2)system indicating the higher CO_(2)affinity of the former system.This study might help scientists to better understand and to improve CO_(2)solubility in these types of solvents by choosing a suitable amine as HBD and finding the best combination of HBA and HBD.
