Mg-2.7Nd-0.2Zn-0.4Zr （mass fraction, %） alloy was designed for degradable biomedical material. The ingots of the alloy were solution treated and then hot extruded. The extruded rods were heat treated with aging trea...Mg-2.7Nd-0.2Zn-0.4Zr （mass fraction, %） alloy was designed for degradable biomedical material. The ingots of the alloy were solution treated and then hot extruded. The extruded rods were heat treated with aging treatment, solution treatment and solution＋aging treatment, respectively. Microstructures of the alloy were observed by optical microscopy （OM） and scanning electron microscopy （SEM）. Mechanical properties at room temperature were tested. In vitro degradation behavior of the alloy immersed in simulated body fluid was measured by hydrogen evolution and mass loss tests. The degradation morphologies of the alloy with and without degradation products were observed by SEM. The results show that the grains grow apparently after solution treatment. Solution treatment improves the elongation of as-extruded alloy significantly and decreases the strength, while aging treatment improves the strength and reduces the elongation of the alloy. The yield ratio is reduced by heat treatment. The in vitro degradation results of the alloy show that solution treatment on the as-extruded alloy results in a little higher degradation rate and aging treatment on the alloy can reduce degradation rate slightly.展开更多
Organic Light Emitting Devices (OLED) have attracted much attention recently, for their applications in futureFlat Panel Displays and lighting products. However, their fast degradation remained a major obstacle to the...Organic Light Emitting Devices (OLED) have attracted much attention recently, for their applications in futureFlat Panel Displays and lighting products. However, their fast degradation remained a major obstacle to theircommercialization. Here we present a brief summary of our studies on both extrinsic and intrinsic causes for the fastdegradation of OLEDs. In particular, we focus on the origin of the dark spots by 'rebuilding' cathodes, which confirms thatthe growth of dark spots occurs primarily due to cathode delamination. In the meantime, we recapture the findings from thesearch for suitable OLED packaging materials, in particular polymer composites, which provide both heat dissipation andmoisture resistance, in addition to electrical insulation.展开更多
The chemical stability of cefixime was determined by high-performance liquid chromatography （HPLC） under different conditions, including factors such as pH, solvents, initial concentration, temperature and additives...The chemical stability of cefixime was determined by high-performance liquid chromatography （HPLC） under different conditions, including factors such as pH, solvents, initial concentration, temperature and additives. The degradation process follows the first-order kinetics. A pH-rate profile exhibits the U-shape and shows the maximum stability of cefixime at pH = 6. The stability in different pure solvents is ranked as acetone 〉 ethanol 〉 methanol 〉 water, while the degradation rate of cefixime exists a maximum at the ratio of 0.6 in water ＋ methanol mixtures. In addition, the degradation rate increases with the temperature increasing and the activation energy of degradation was found to be 27.078 kJ. mol- 1 in acetone ＋ water mixed solvents. The addition of different additives was proven to either inhibit or accelerate the degradation. The degradation products were analyzed using HPLC, LC-MS and infrared spectroscopy, and the possible degradation pathways in acid as well as alkaline environment were proposed to help us understand the degradation behavior of cefixime.展开更多
Defect engineering has been regarded as a versatile strategy to maneuver the photocatalytic activity.However,there are a few studies concerning how to maintain the stability of defects,which is important to ensure sus...Defect engineering has been regarded as a versatile strategy to maneuver the photocatalytic activity.However,there are a few studies concerning how to maintain the stability of defects,which is important to ensure sustainable photocatalytic performance.Here,a novel strategy to modulate the structural properties of BiSbO_(4)using light-induced dynamic oxygen vacancies is reported by us for efficient and stable photocatalytic oxidation of formaldehyde.Interestingly,the continuous consumption and replenishment of vacancies(namely dynamic vacancies)ensure the dynamic stability of oxygen vacancies,thus guaranteeing the excellent photocatalytic stability.The oxygen vacancies could also accelerate the electron migration,inhibit the photogenerated electron/hole recombination,widen the light absorption spectra,and thus improve the photocatalytic formaldehyde removal performance.Combined with the results of in situ DRIFTS,the reaction mechanism for each step of formaldehyde oxidation is revealed.As supported by DFT calculation of Gibbs free energy,the introduction of oxygen vacancies into BiSbO_(4)can promote spontaneous process of formaldehyde oxidation.Our work highlights a promising approach for stabilizing the defects and proposes the photocatalytic reaction mechanism in combination with the thermodynamic functions.展开更多
The reaction of chitosan with cinnamic acid gave the corresponding N-cinnamoyl chitosan (NCC) polymer. The chem-ical structure of the modified polymer was characterized by IR, 1H-NMR and elemental analysis. Thermograv...The reaction of chitosan with cinnamic acid gave the corresponding N-cinnamoyl chitosan (NCC) polymer. The chem-ical structure of the modified polymer was characterized by IR, 1H-NMR and elemental analysis. Thermogravim- etric analysis reveals that the thermal stability of chitosan polymer is greater than NCC polymer. The activation energies of thermal degradation of chitosan and NCC polymers were determined using Arrhenius relationship. Thermal degradation of NCC polymer was studied and the products of degradation were identified by GC-MS technique. It seems that the mechanism of degradation of NCC polymer is characterized by elimination of low-molecular weight radicals. Combination of these radicals and random scission mechanism along the backbone chain are the main source of the degradation products.展开更多
The stability of slope rock masses is influenced by freeze-thaw cycles in cold region,and the mechanism of stability deterioration is not clear.In order to understand the damage and progressive failure characteristics...The stability of slope rock masses is influenced by freeze-thaw cycles in cold region,and the mechanism of stability deterioration is not clear.In order to understand the damage and progressive failure characteristics of rock masses under the action of freezing and thawing,a model test was conducted on slope with steep joint in this study.The temperature,frost heaving pressure and deformation of slope rock mass were monitored in real-time during the test and the progressive failure mode was studied.The experimental results show that the temperature variations of cracking and the rock mass of a slope are different.There are obvious latent heat stages in the temperature-change plot in the crack,but not in the slope rock masses.The frost heaving effect in the fracture is closely related to the constraint conditions,which change with the deformation of the fracture.The frost heaving pressure fluctuates periodically during freezing and continues to decrease during thawing.The surface deformation of the rock mass increases during freezing,and the deformation is restored when it thaws.Freeze-thaw cycling results in residual deformation of the rock mass which cannot be fully restored.Analysis shows that the rock mass at the free side of the steep-dip joint rotates slightly under the frost heaving effect,causing fracture propagation.The fracture propagation pattern is a circular arc at the beginning,then extends to the possible sliding direction of the rock mass.Frost heaving force and fracture water pressure are the key factors for the failure of the slope,which can cause the crack to penetrate the rock mass,and a landslide ensues when the overall anti-sliding resistance of the rock mass is overcome.展开更多
The preparation of perovskite solar cells(PsCs)in the air environment has attracted the attention of numerous experimenters due to its low preparation cost and the possibility of commercialization.Although the power c...The preparation of perovskite solar cells(PsCs)in the air environment has attracted the attention of numerous experimenters due to its low preparation cost and the possibility of commercialization.Although the power conversion efficiency(PCE)of PSCs has increased rapidly and exceeded 25%,which is comparable to commercial polysilicon solar cells,most certified or reported high-efficiency perovskite solar cells are still confined to glove boxes or relatively small active areas in the air environment due to moisture,oxygen,high temperature,and ultraviolet(UV)factors.In this review.展开更多
Five new heat treatment processes were designed,which were divided into three groups by their characteristics. The microstructures and mechanical properties of the alloy after the five heat treatments and thermal expo...Five new heat treatment processes were designed,which were divided into three groups by their characteristics. The microstructures and mechanical properties of the alloy after the five heat treatments and thermal exposure at 500,550 ℃ for 100 h were tested. The results indicate that a little differences exist in the performance of mechanical properties at room-temperature after the five heat treatments,and the thermal stability is the key factor for determining heat treatment process. Among the three groups of heat treatment processes,the best thermal stability is achieved after the first group of heat treatment. After annealing treatment at intermediate temperature,some defects and uneven grain boundaries are remained,which leads to the reduction fractions of precipitations on unit grain boundary and the harmful effect of precipitations on grain boundary is weakened. The process of annealing at 650 ℃ for 4 h is recommended the best heat treatment process for Ti40 alloy.展开更多
基金supported by the Introducing Talents Funds of Nanjing Institute of Technology,ChinaProject(20100470030) supported by the China Postdoctoral Science Foundation
文摘Mg-2.7Nd-0.2Zn-0.4Zr （mass fraction, %） alloy was designed for degradable biomedical material. The ingots of the alloy were solution treated and then hot extruded. The extruded rods were heat treated with aging treatment, solution treatment and solution＋aging treatment, respectively. Microstructures of the alloy were observed by optical microscopy （OM） and scanning electron microscopy （SEM）. Mechanical properties at room temperature were tested. In vitro degradation behavior of the alloy immersed in simulated body fluid was measured by hydrogen evolution and mass loss tests. The degradation morphologies of the alloy with and without degradation products were observed by SEM. The results show that the grains grow apparently after solution treatment. Solution treatment improves the elongation of as-extruded alloy significantly and decreases the strength, while aging treatment improves the strength and reduces the elongation of the alloy. The yield ratio is reduced by heat treatment. The in vitro degradation results of the alloy show that solution treatment on the as-extruded alloy results in a little higher degradation rate and aging treatment on the alloy can reduce degradation rate slightly.
文摘Organic Light Emitting Devices (OLED) have attracted much attention recently, for their applications in futureFlat Panel Displays and lighting products. However, their fast degradation remained a major obstacle to theircommercialization. Here we present a brief summary of our studies on both extrinsic and intrinsic causes for the fastdegradation of OLEDs. In particular, we focus on the origin of the dark spots by 'rebuilding' cathodes, which confirms thatthe growth of dark spots occurs primarily due to cathode delamination. In the meantime, we recapture the findings from thesearch for suitable OLED packaging materials, in particular polymer composites, which provide both heat dissipation andmoisture resistance, in addition to electrical insulation.
基金Supported by the National Natural Science Foundation of China(81361140344 and21376164)National High Technology Reseach and Development Program of China(863Program,2015AA021002)Major National Scientific Instrument Development Project(21527812)
文摘The chemical stability of cefixime was determined by high-performance liquid chromatography （HPLC） under different conditions, including factors such as pH, solvents, initial concentration, temperature and additives. The degradation process follows the first-order kinetics. A pH-rate profile exhibits the U-shape and shows the maximum stability of cefixime at pH = 6. The stability in different pure solvents is ranked as acetone 〉 ethanol 〉 methanol 〉 water, while the degradation rate of cefixime exists a maximum at the ratio of 0.6 in water ＋ methanol mixtures. In addition, the degradation rate increases with the temperature increasing and the activation energy of degradation was found to be 27.078 kJ. mol- 1 in acetone ＋ water mixed solvents. The addition of different additives was proven to either inhibit or accelerate the degradation. The degradation products were analyzed using HPLC, LC-MS and infrared spectroscopy, and the possible degradation pathways in acid as well as alkaline environment were proposed to help us understand the degradation behavior of cefixime.
基金supported by the National Natural Science Foundation of China (21822601, 21777011, and 21501016)the Innovative Research Team of Chongqing (CXQT19023)
文摘Defect engineering has been regarded as a versatile strategy to maneuver the photocatalytic activity.However,there are a few studies concerning how to maintain the stability of defects,which is important to ensure sustainable photocatalytic performance.Here,a novel strategy to modulate the structural properties of BiSbO_(4)using light-induced dynamic oxygen vacancies is reported by us for efficient and stable photocatalytic oxidation of formaldehyde.Interestingly,the continuous consumption and replenishment of vacancies(namely dynamic vacancies)ensure the dynamic stability of oxygen vacancies,thus guaranteeing the excellent photocatalytic stability.The oxygen vacancies could also accelerate the electron migration,inhibit the photogenerated electron/hole recombination,widen the light absorption spectra,and thus improve the photocatalytic formaldehyde removal performance.Combined with the results of in situ DRIFTS,the reaction mechanism for each step of formaldehyde oxidation is revealed.As supported by DFT calculation of Gibbs free energy,the introduction of oxygen vacancies into BiSbO_(4)can promote spontaneous process of formaldehyde oxidation.Our work highlights a promising approach for stabilizing the defects and proposes the photocatalytic reaction mechanism in combination with the thermodynamic functions.
文摘The reaction of chitosan with cinnamic acid gave the corresponding N-cinnamoyl chitosan (NCC) polymer. The chem-ical structure of the modified polymer was characterized by IR, 1H-NMR and elemental analysis. Thermogravim- etric analysis reveals that the thermal stability of chitosan polymer is greater than NCC polymer. The activation energies of thermal degradation of chitosan and NCC polymers were determined using Arrhenius relationship. Thermal degradation of NCC polymer was studied and the products of degradation were identified by GC-MS technique. It seems that the mechanism of degradation of NCC polymer is characterized by elimination of low-molecular weight radicals. Combination of these radicals and random scission mechanism along the backbone chain are the main source of the degradation products.
基金supported by the National Natural Science Foundation of China(Project No.52179110,41877280 and 51309025)the Fundamental Research Funds for Central Public Welfare Research Institutes(CKSF 2019180/YT)the Research Funding of Wuhan Polytechnic University(NO.2021RZ028)。
文摘The stability of slope rock masses is influenced by freeze-thaw cycles in cold region,and the mechanism of stability deterioration is not clear.In order to understand the damage and progressive failure characteristics of rock masses under the action of freezing and thawing,a model test was conducted on slope with steep joint in this study.The temperature,frost heaving pressure and deformation of slope rock mass were monitored in real-time during the test and the progressive failure mode was studied.The experimental results show that the temperature variations of cracking and the rock mass of a slope are different.There are obvious latent heat stages in the temperature-change plot in the crack,but not in the slope rock masses.The frost heaving effect in the fracture is closely related to the constraint conditions,which change with the deformation of the fracture.The frost heaving pressure fluctuates periodically during freezing and continues to decrease during thawing.The surface deformation of the rock mass increases during freezing,and the deformation is restored when it thaws.Freeze-thaw cycling results in residual deformation of the rock mass which cannot be fully restored.Analysis shows that the rock mass at the free side of the steep-dip joint rotates slightly under the frost heaving effect,causing fracture propagation.The fracture propagation pattern is a circular arc at the beginning,then extends to the possible sliding direction of the rock mass.Frost heaving force and fracture water pressure are the key factors for the failure of the slope,which can cause the crack to penetrate the rock mass,and a landslide ensues when the overall anti-sliding resistance of the rock mass is overcome.
基金This research was funded by the National Natural Science Foundation of China(NSFC)(51833004,22005131,52173169 and U20A20128)the Natural Science Foundation of Jiangxi Province(20212BAB214055).
文摘The preparation of perovskite solar cells(PsCs)in the air environment has attracted the attention of numerous experimenters due to its low preparation cost and the possibility of commercialization.Although the power conversion efficiency(PCE)of PSCs has increased rapidly and exceeded 25%,which is comparable to commercial polysilicon solar cells,most certified or reported high-efficiency perovskite solar cells are still confined to glove boxes or relatively small active areas in the air environment due to moisture,oxygen,high temperature,and ultraviolet(UV)factors.In this review.
基金Project(MKPT-01-101ZD) supported by the National Key Project of ChinaProject(2007CB613807) supported by the National Basic Research Program of China
文摘Five new heat treatment processes were designed,which were divided into three groups by their characteristics. The microstructures and mechanical properties of the alloy after the five heat treatments and thermal exposure at 500,550 ℃ for 100 h were tested. The results indicate that a little differences exist in the performance of mechanical properties at room-temperature after the five heat treatments,and the thermal stability is the key factor for determining heat treatment process. Among the three groups of heat treatment processes,the best thermal stability is achieved after the first group of heat treatment. After annealing treatment at intermediate temperature,some defects and uneven grain boundaries are remained,which leads to the reduction fractions of precipitations on unit grain boundary and the harmful effect of precipitations on grain boundary is weakened. The process of annealing at 650 ℃ for 4 h is recommended the best heat treatment process for Ti40 alloy.
