Due to their high electrical conductivity and layered structure,two dimensional MXene materials are re⁃garded as promising candidates for energy storage applications.However,the relatively low stability and specific c...Due to their high electrical conductivity and layered structure,two dimensional MXene materials are re⁃garded as promising candidates for energy storage applications.However,the relatively low stability and specific ca⁃pacity of MXene materials limit their further utilization.In this study,these issues are addressed using a heterostruc⁃ture strategy via a one-step selenization method to form Mo_(2)C@MoSe_(2).Synchrotron radiation X-ray spectroscopic and high-resolution transmission electron microscopy(HRTEM)characterizations revealed the heterostructure consisting of in-situ grown MoSe_(2)on Mo_(2)C MXene.Electrochemical tests proved the heterojunction electrode’s superior rate perfor⁃mance of 289.06 mAh·g^(-1)at a high current density of 5 A·g^(-1)and long cycling stability of 550 mAh·g^(-1)after 900 cycles at 1 A·g^(-1).This work highlights the useful X-ray spectroscopic analysis to directly elucidate the heterojunction structure,providing an effective reference method for probing heterostructures.展开更多
The (Y,Gd)BO 3∶Eu phosphor was synthesized by solid state reaction. The UV spectra showed that in a certain range of Gd 3+ concentration, more Gd 3+ absorbed energy and transferred it to Eu 3+ with its increasing con...The (Y,Gd)BO 3∶Eu phosphor was synthesized by solid state reaction. The UV spectra showed that in a certain range of Gd 3+ concentration, more Gd 3+ absorbed energy and transferred it to Eu 3+ with its increasing concentration. From the spectra in VUV region, it was observed that both the doping and the concentrations of Gd 3+ , Eu 3+ greatly affected the absorption of the host lattice. The absorbances at 147 nm and 170 nm increased when the Gd 3+ was doped which can be explained as that Gd 3+ transferred energy to BO 4. The optical properties of (Y,Gd)BO 3∶Eu were the best when the concentration of Eu 3+ was about 0.04.展开更多
Coconut-based activated carbons were modified with sodium dodecyl sulfate (SDS). The activated carbons, which were modified by different concentrations of SDS, were characterized by acid/base titrations, textural anal...Coconut-based activated carbons were modified with sodium dodecyl sulfate (SDS). The activated carbons, which were modified by different concentrations of SDS, were characterized by acid/base titrations, textural analysis (BET), atomic absorption spectrochemical analysis and Zeta potential measurements. The effects of SDS modification on Pb2+ absorption were studied further. The results indicate that after the modification of SDS, there are new functional groups on the surface of modified activated carbons and the number of functional group has changed remarkably, the total acidity decreases observably, but the total alkalinity increases dramatically. With the increase of surface load with SDS, the Pb2+ adsorption mass of activated carbons increases and the optimal pH for Pb2+ adsorption of the SDS modified activated carbons is 5. The experimental data are simulated better by Freundlich isotherm model for the modified activated carbons, and the experimental data are simulated better by Langmuir isotherm model for unmodified ones.展开更多
Microwave absorbing properties of high titanium slag were investigated by using microwave cavity perturbation technique. High titanium slag containing more than 90% TiO2 was prepared by carbothermal reduction of ilmen...Microwave absorbing properties of high titanium slag were investigated by using microwave cavity perturbation technique. High titanium slag containing more than 90% TiO2 was prepared by carbothermal reduction of ilmenite. The temperature rise curve of high titanium slag in microwave heating process was obtained. Crystalline compounds of high titanium slag before and after microwave irradiation were obtained and characterized by X-ray diffractometry （XRD）. Effects of particle size of high titanium slag anal mixtures of high titanium slag with different mass fractions of V2o5 on microwave absorbing properties were investigated systematically. The results show that high titanium slag has good microwave absorption property; untreated high titanium slag mainly consists of crystalline compounds of anatase and iron titanium oxide, while the microwave-irradiation treated one is mainly composed of crystalline compounds of rutile and irgn titanium oxide. Synthetic anatase is transformed completely into rutile at about 1 050 ℃ for 20 min under microwave irradiation. High frequency shift and low amplitude of voltage make high titanium slag an ideal microwave absorbent. 180 μm of particle size and 10% mass fraction of V2O5 are found to be the optimum conditions for microwave absorption.展开更多
The methods were studied to improve the cooling performance of the absorption refrigeration system(ARS) driven by low-grade solar energy with ultrasonic wave, while the mechanism of ultrasonic wave strengthening boili...The methods were studied to improve the cooling performance of the absorption refrigeration system(ARS) driven by low-grade solar energy with ultrasonic wave, while the mechanism of ultrasonic wave strengthening boiling mass transfer in LiB r solution was also analyzed with experiment. The experimental results indicate that, under the driving heat source of 60–100 oC and the ultrasonic power of 20–60 W, the mass flux of cryogen water in Li Br solution is higher after the application of ultrasonic wave than auxiliary heating with electric rod of the same power, so the ultrasonic application effectively enhances the heat utilization efficiency. The distance H from ultrasonic transducer to vapor/liquid interface significantly affects mass transfer enhancement, so an optimal Hopt corresponding to certain ultrasonic power is beneficial to reaching the best strengthening effect for ultrasonic mass transfer. When the ultrasonic power increases, the mass transfer obviously speeds up in the cryogen water; however, as the power increases to a certain extent, the flux reaches a plateau without obvious increment. Moreover, the ultrasound-enhanced mass transfer technology can reduce the minimum temperature of driving heat source required by ARS and promote the application of solar energy during absorption refrigeration.展开更多
基金National Key Research and Development Program of China(2020YFA0405800)National Natural Science Foundation of China(12322515,U23A20121,12225508)+2 种基金Youth Innovation Promotion Association of CAS(2022457)National Postdoctoral Program for Innovative Talents(BX20230346)China Postdoctoral Science Foundation(2023M743365)。
文摘Due to their high electrical conductivity and layered structure,two dimensional MXene materials are re⁃garded as promising candidates for energy storage applications.However,the relatively low stability and specific ca⁃pacity of MXene materials limit their further utilization.In this study,these issues are addressed using a heterostruc⁃ture strategy via a one-step selenization method to form Mo_(2)C@MoSe_(2).Synchrotron radiation X-ray spectroscopic and high-resolution transmission electron microscopy(HRTEM)characterizations revealed the heterostructure consisting of in-situ grown MoSe_(2)on Mo_(2)C MXene.Electrochemical tests proved the heterojunction electrode’s superior rate perfor⁃mance of 289.06 mAh·g^(-1)at a high current density of 5 A·g^(-1)and long cycling stability of 550 mAh·g^(-1)after 900 cycles at 1 A·g^(-1).This work highlights the useful X-ray spectroscopic analysis to directly elucidate the heterojunction structure,providing an effective reference method for probing heterostructures.
文摘The (Y,Gd)BO 3∶Eu phosphor was synthesized by solid state reaction. The UV spectra showed that in a certain range of Gd 3+ concentration, more Gd 3+ absorbed energy and transferred it to Eu 3+ with its increasing concentration. From the spectra in VUV region, it was observed that both the doping and the concentrations of Gd 3+ , Eu 3+ greatly affected the absorption of the host lattice. The absorbances at 147 nm and 170 nm increased when the Gd 3+ was doped which can be explained as that Gd 3+ transferred energy to BO 4. The optical properties of (Y,Gd)BO 3∶Eu were the best when the concentration of Eu 3+ was about 0.04.
基金Project(2007AA06Z121) supported by the National High Technology Research and Development Program of ChinaProject(50774095) supported by the National Natural Science Foundation of ChinaProject(CL12111) supported by the Undergraduate Innovation Experimentation Plan of Central South University,China
文摘Coconut-based activated carbons were modified with sodium dodecyl sulfate (SDS). The activated carbons, which were modified by different concentrations of SDS, were characterized by acid/base titrations, textural analysis (BET), atomic absorption spectrochemical analysis and Zeta potential measurements. The effects of SDS modification on Pb2+ absorption were studied further. The results indicate that after the modification of SDS, there are new functional groups on the surface of modified activated carbons and the number of functional group has changed remarkably, the total acidity decreases observably, but the total alkalinity increases dramatically. With the increase of surface load with SDS, the Pb2+ adsorption mass of activated carbons increases and the optimal pH for Pb2+ adsorption of the SDS modified activated carbons is 5. The experimental data are simulated better by Freundlich isotherm model for the modified activated carbons, and the experimental data are simulated better by Langmuir isotherm model for unmodified ones.
基金Project(2007CB613606) supported by the Major State Basic Research and Development Program of ChinaProject(50734007) supported by the National Natural Science Foundation of China
文摘Microwave absorbing properties of high titanium slag were investigated by using microwave cavity perturbation technique. High titanium slag containing more than 90% TiO2 was prepared by carbothermal reduction of ilmenite. The temperature rise curve of high titanium slag in microwave heating process was obtained. Crystalline compounds of high titanium slag before and after microwave irradiation were obtained and characterized by X-ray diffractometry （XRD）. Effects of particle size of high titanium slag anal mixtures of high titanium slag with different mass fractions of V2o5 on microwave absorbing properties were investigated systematically. The results show that high titanium slag has good microwave absorption property; untreated high titanium slag mainly consists of crystalline compounds of anatase and iron titanium oxide, while the microwave-irradiation treated one is mainly composed of crystalline compounds of rutile and irgn titanium oxide. Synthetic anatase is transformed completely into rutile at about 1 050 ℃ for 20 min under microwave irradiation. High frequency shift and low amplitude of voltage make high titanium slag an ideal microwave absorbent. 180 μm of particle size and 10% mass fraction of V2O5 are found to be the optimum conditions for microwave absorption.
基金Project(51275180)supported by the National Natural Science Foundation of ChinaProject(S201304416899)supported by the Natural Science Foundation of Guangdong Province,ChinaProject(sybzzxm201213)supported by Doctorate Dissertation Funds of Guangdong Province,China
文摘The methods were studied to improve the cooling performance of the absorption refrigeration system(ARS) driven by low-grade solar energy with ultrasonic wave, while the mechanism of ultrasonic wave strengthening boiling mass transfer in LiB r solution was also analyzed with experiment. The experimental results indicate that, under the driving heat source of 60–100 oC and the ultrasonic power of 20–60 W, the mass flux of cryogen water in Li Br solution is higher after the application of ultrasonic wave than auxiliary heating with electric rod of the same power, so the ultrasonic application effectively enhances the heat utilization efficiency. The distance H from ultrasonic transducer to vapor/liquid interface significantly affects mass transfer enhancement, so an optimal Hopt corresponding to certain ultrasonic power is beneficial to reaching the best strengthening effect for ultrasonic mass transfer. When the ultrasonic power increases, the mass transfer obviously speeds up in the cryogen water; however, as the power increases to a certain extent, the flux reaches a plateau without obvious increment. Moreover, the ultrasound-enhanced mass transfer technology can reduce the minimum temperature of driving heat source required by ARS and promote the application of solar energy during absorption refrigeration.
