Manganese oxide electrode with excellent electrochemical performance for sodium ion batteries by pre-intercalation of K and Na ions

Materials with a layered structure have attracted tremendous attention because of their unique properties. The ultrathin nanosheet structure can result in extremely rapid intercalation/de-intercalation of Na ions in the charge-discharge progress. Herein, we report a manganese oxide with pre-intercalated K and Na ions and having flower-like ultrathin layered structure, which was synthesized by a facile but efficient hydrothermal method under mild condition. The pre-intercalation of Na and K ions facilitates the access of electrolyte ions and shortens the ion diffusion pathways. The layered manganese oxide shows ultrahigh specific capacity when it is used as cathode material for sodium-ion batteries. It also exhibits excellent stability and reversibility. It was found that the amount of intercalated Na ions is approximately 71% of the total charge. The prominent electrochemical performance of the manganese oxide demonstrates the importance of design and synthesis of pre-intercalated ultrathin layered materials

Extraction of Electron Self-Energy and Gap Function in the Superconducting State of Bi_2Sr_2CaCu_2O_8 Superconductor via Laser-Based Angle-Resolved Photoemission

Super-high resolution laser-based angle-resolved photoemission measurements have been performed on a high temperature superconductor Bi_2Sr_2CaCu_2O_8. The band back-bending characteristic of the Bogoliubov-like quasiparticle dispersion is clearly revealed at low temperature in the superconducting state. This makes it possible for the first time to experimentally extract the complex electron self-energy and the complex gap function in the superconducting state. The resultant electron self-energy and gap function exhibit features at ~54 meV and ~40 meV, in addition to the superconducting gap-induced structure at lower binding energy and a broad featureless structure at higher binding energy. These information will provide key insight and constraints on the origin of electron pairing in high temperature superconductors.Comment: 4 pages, 4 figure

Characteristics of focal mechanisms in Chile subduction

We use the Centroid Moment Tensor (CMT) solution of the earthquakes occurred in Chile subduction to analyze the characteristics of focal mechanisms. We define the angle between P, B, and T axes of focal mechanisms and three stress axes of tectonic stress field as the consistency parameter, to research the dynamic changes of focal mechanism pattern in earthquake preparation area before the 2010 Maule, Chile earthquake. The result shows that the consistency parameter decreases before the earthquake, and the area of the lower consistent parameter visually coincides with the distribution of aftershocks. This phenomenon is similar to the Load-Unload Response Ratio (LURR) decreases prior to the occurrence of macro-fracture happened in the acoustic emission experiments involving large rock specimens under tri-axial stress

Mineral Reaction Kinetics during Aciding of the Gaoyuzhuang Carbonate Geothermal Reservoir in the Xiong’an New Area, Northern China

There are abundant geothermal resources in the Xiong’an New Area, China. Drilling has revealed a greater potential in the deep Gaoyuzhuang geothermal reservoir. However, the reservoir required acidification to increase its water production. In this study, three types of core samples with different mineral compositions from different depths in the target boreholes were selected for acid rock reaction experiments at the temperature of 40 °C, 60 °C, 80 °C and 100 °C, and pressure of 30 MPa. The kinetics of the acid rock reaction of the major minerals were modeled based on the transitional state theory. The kinetic parameters were obtained by comparing the modelling and experimental results. The results show that the lithology of the Gaoyuzhuang reservoir is primarily dolomite. The dissolution ratio for 15 wt.% HCl reached 84.1% on average for the rock fragments. Temperature has a significant effect on the dissolution rate of the minerals. In the presence of HCl (acidic mechanism), the reaction rate constants of the dolomite, calcite and illite reached 2.4 × 10−4 mol/m2/s, 5.3 × 10−1 mol/m2/s and 9.5 × 10−2 mol/m2/s, respectively. The results of this study provide the basic parameters for the design and evaluation of field acidizing

Retention properties and mechanism of agricultural waste maize whisker on atmospheric mercury

Abstract Mercury (Hg) is a global pollutant transmitted mainly through the atmosphere, posing a serious threat to biological survival and human health. Porous materials, with high specific surface area, high porosity, and high adsorption, are particularly suitable for the purification of atmospheric Hg mixtures. However, plant porous materials are rarely directly used for atmospheric Hg purification. In this study, the properties and mechanism of maize whisker in removing atmospheric Hg were analyzed. The results show that the Hg content in the whiskers increases significantly as the initial Hg concentration increases, and 79.38% Hg can be removed by 0.2 g maize whiskers after 1 h exposure when the initial Hg concentration is 0.1 μg m−3, indicating that maize whiskers can accumulate atmospheric Hg rapidly and effectively. The hole diameter of the maize whisker is between 0.83 and 3.06 μm, which is suitable for the adsorption of small substances. Correlation analysis shows that maize whiskers have a significant correlation between atmospheric Hg retention and its specific surface area, pore size, medium pore ratio, and micropore ratio, suggesting that the maize whisker hole feature has a significant influence on its ability to retain atmospheric Hg. Compared with the energy profiles before and after Hg treatment, the peak of Mg decreased after Hg adsorption. Fourier infrared spectrometer analysis suggests that functional groups such as -OH, -COOH, and -O- are involved in the adsorption process. The change in pH value shows an obvious effect on the overall change in zeta potential in the adsorption process. Therefore, a variety of mechanisms, including physical adsorption, electrostatic adsorption, complexation, chelation, and ion exchange, are involved in Hg retention with the maize whisker. This study reveals the important potential value of agricultural waste maize whiskers in the purification of atmospheric heavy metal Hg. Graphical Abstrac

Characterization of Ground Thermal Conditions for Shallow Geothermal Exploitation in the Central North China Plain (NCP) Area

The central North China Plain (NCP) is one of the rapidly developing regions in China which has a great potential for ground source heat pump (GSHP) system applications. However, the ground thermal property, which is a prerequisite for GSHP system design, has been insufficiently investigated. In this paper, the ground thermal conditions including ground temperature and thermal conductivity are characterized in three representative hydrogeological regions in the NCP area: the piedmont alluvial plain, the central alluvial plain, and the coastal plain. Results show that the geothermal gradient below 40 m in depth in this area ranges from 0.018 °C/m to 0.029 °C/m. Although the thermal conductivity measured by soil samples differs slightly among the three regions, parameters in the piedmont plain have a larger variability than in the central and coastal plain due to the significant heterogeneity of the lithology. Thermal conductivity measured by the thermal response test (TRT) ranges between 2.37 and 2.68 W/(m·K) in the piedmont plain and varies between 1.35 and 1.94 W/(m·K) in the central and coastal plain, indicating that the piedmont plain has a higher potential for shallow geothermal exploitation than other two sub-areas. Comparing the TRT with laboratory measurements, the thermal conductivity obtained by the TRT is greater than that of the lab measurements in the piedmont plain due to the TRT outputs including the effects of groundwater flow. Therefore, the TRT is highly recommended to estimate the effective thermal conductivity of the ground in the piedmont plain, while laboratory and field tests are both suitable methods for the determination of thermal conductivity in the central and coastal plains

Mineral Reaction Kinetics during Aciding of the Gaoyuzhuang Carbonate Geothermal Reservoir in the Xiong’an New Area, Northern China

There are abundant geothermal resources in the Xiong’an New Area, China. Drilling has revealed a greater potential in the deep Gaoyuzhuang geothermal reservoir. However, the reservoir required acidification to increase its water production. In this study, three types of core samples with different mineral compositions from different depths in the target boreholes were selected for acid rock reaction experiments at the temperature of 40 °C, 60 °C, 80 °C and 100 °C, and pressure of 30 MPa. The kinetics of the acid rock reaction of the major minerals were modeled based on the transitional state theory. The kinetic parameters were obtained by comparing the modelling and experimental results. The results show that the lithology of the Gaoyuzhuang reservoir is primarily dolomite. The dissolution ratio for 15 wt.% HCl reached 84.1% on average for the rock fragments. Temperature has a significant effect on the dissolution rate of the minerals. In the presence of HCl (acidic mechanism), the reaction rate constants of the dolomite, calcite and illite reached 2.4 × 10−4 mol/m2/s, 5.3 × 10−1 mol/m2/s and 9.5 × 10−2 mol/m2/s, respectively. The results of this study provide the basic parameters for the design and evaluation of field acidizing