Valence band offset of InN/BaTiO3 heterojunction measured by X-ray photoelectron spectroscopy

X-ray photoelectron spectroscopy has been used to measure the valence band offset of the InN/BaTiO(3 )heterojunction. It is found that a type-I band alignment forms at the interface. The valence band offset (VBO) and conduction band offset (CBO) are determined to be 2.25 ± 0.09 and 0.15 ± 0.09 eV, respectively. The experimental VBO data is well consistent with the value that comes from transitivity rule. The accurate determination of VBO and CBO is important for use of semiconductor/ferrroelectric heterojunction multifunctional devices

One-pot melamine derived nitrogen doped magnetic carbon nanoadsorbents with enhanced chromium removal

Novel nitrogen doped magnetic carbons (NMC), in-situ synthesized through facile pyrolysis-carbonization processes using Fe(NO3)3 and melamine as precursors, were demonstrated as excellent nanoadsorbents to remove Cr(VI) effectively. The achieved removal capacity in both neutral and acidic solution was 29.4 and 2001.4 mg g−1 respectively, much higher than the reported adsorbents so far. The unprecedented high adsorption performance can be attributed to the incorporation of the nitrogen dopant, which increased the negative charge density on the surface of adsorbent and thereby enhanced the interaction between the adsorbents and Cr(VI) ions. The density functional theory (DFT) calculation demonstrated that the nitrogen dopants can decrease the adsorption energy between the Cr(VI) ions and NMC (−3.456 kJ mol−1), lower than the undoped sample (−3.344 kJ mol−1), which boosted the adsorption behavior. Chemical rather than physical adsorption was followed for these magnetic nanoadsorbents as revealed from the pseudo-second-order kinetic study. Furthermore, the NMC showed high stability with recycling tests for the Cr(VI) removal

Poly(vinylidene fluoride) derived fluorine-doped magnetic carbon nanoadsorbents for enhanced chromium removal

Newly designed fluorine-doped magnetic carbon (F-MC) was synthesized in situ though a facile one-step pyrolysis-carbonization method. Poly(vinylidene fluoride) (PVDF) served as the precursor for both carbon and fluorine. 2.5% F content with core-shell structure was obtained over F-MC, which was used as a adsorbent for the Cr(VI) removal. To our best knowledge, this is the first time to report that the fluorine doped material was applied for the Cr(VI) removal, demonstrating very high removal capacity (1423.4 mg g−1), higher than most reported adsorbents. The unexpected performance of F-MC can be attributed to the configuration of F dopants on the surface. The observed pseudo-second-order kinetic study indicated the dominance of chemical adsorption for this process. High stability of F-MC after 5 recycling test for the Cr(VI) removal was also observed, indicating that F-MC could be used as an excellent adsorbent for the toxic heavy metal removal from the wastewater

Gas kick during carbonate reservoirs drilling and its risk assessment

The gas kick characteristics during carbonate reservoir drilling were analyzed taking carbonate reservoirs in Shunnan area of Tazhong as an example, a quantitative evaluation method for gas kick risk was established, and then a case was simulated. Looking into reservoir space characteristics and gas invasion mechanisms of carbonate reservoirs in Shunnan area based on drilling geologic data, it is found that the reservoirs are rich in fractures, pores and caves, and the gas invades into wellbore through gas-liquid replacement and differential pressure. By fully considering the gas invasion mechanism, gas migration law and wellbore temperature-pressure field, and introducing the gas volume fraction density function, a quantitative evaluation method for gas kick risk and a method for ranking well control risk were established. The case study shows that the wellhead back pressure method can be used to tell the mode of gas invasion; pore-fracture-cave and acid gas characteristics in carbonate reservoirs have stronger effect on the gas volume fraction in wellbore, and may cause hidden and severe gas kick; the effects of well depth, well diameter, drilling fluid density, drilling fluid displacement, drilling fluid viscosity and drilling rate on gas kick risks weaken in that order. Key words: carbonate reservoir, well drilling, gas kick, gas-liquid replacement, well control, risk assessmen

Ultimate Bearing Capacity of Bottom Sealing Concrete in Underwater Deep Foundation Pit: Theoretical Calculation and Numerical Analysis

The cofferdam method is generally applied in the construction of underwater pier foundation in bridge engineering, and the pouring of bottom sealing concrete is one of the important links in the construction of the cofferdam. The bottom sealing concrete can prevent water seepage and balance the main body of the cofferdam, and its structural size and construction quality have a great influence on the above functions. Under the condition of large water level difference, it is difficult to determine the reasonable thickness of the bottom sealing concrete. There are few related studies in this field, and there is a lack of systematic summary of calculation theory. This work theoretically deduces the approximate solution of ultimate bending moment and ultimate stress of the bottom sealing concrete, introduces two different calculation methods, systematically summarizes the calculation methods of three kinds of ultimate stress, analyzes the calculation methods of ultimate bonding force, and uses ANSYS finite element software to simulate a specific bottom sealing concrete model, and compares it with the theoretical calculation results. The maximum stress obtained by the approximate solution is closer to the actual monitoring data than the traditional method, and the calculation method of the bonding force can be used to make a rough estimate

Valence band offset of InN/BaTiO₃heterojunction measured by X-ray photoelectron spectroscopy

Abstract X-ray photoelectron spectroscopy has been used to measure the valence band offset of the InN/BaTiO3 heterojunction. It is found that a type-I band alignment forms at the interface. The valence band offset (VBO) and conduction band offset (CBO) are determined to be 2.25 &#177; 0.09 and 0.15 &#177; 0.09 eV, respectively. The experimental VBO data is well consistent with the value that comes from transitivity rule. The accurate determination of VBO and CBO is important for use of semiconductor/ferrroelectric heterojunction multifunctional devices.</p

Realization of Multi‐Level State and Artificial Synapses Function in Stacked (Ta/CoFeB/MgO)N Structures

Abstract Spintronic devices can realize multi‐state storage and be used to simulate artificial synapses or artificial neurons, which makes them have promising application prospect in the field of artificial neural networks (ANN). This work investigates the current‐induced magnetization reversal in stacked (Ta/CoFeB/MgO)N structures and their application in ANN. It is demonstrated that the complete current‐induced magnetization reversal with large intermediate transition region can be achieved in the sample with N = 2. The magneto‐optical Kerr microscope imaging shows that the large transition region for the sample is ascribed to the “layer‐by‐layer” reversal, owing to the difference of the coercivity of two CoFeB layers. In addition, the simulation of artificial synapses and artificial neurons function based on current‐induced magnetization reversal in the sample is also demonstrated. These results substantiate the stacked (Ta/CoFeB/MgO)N structures as a promising platform for realizing the multi‐level state and artificial synapses function, and its potential application in the field of ANN

Magnetic epoxy nanocomposites with superparamagnetic MnFe2O4 nanoparticles

Manganese iron oxide (MnFe2O4) nanoparticles successfully served as nanofillers for obtaining magnetic epoxy nanocomposites. The viscosities of MnFe2O4/epoxy resin liquid suspensions increased with increasing the nanoparticles loading except the suspension with 5.0 and 1.0 wt% loading, whose viscosities were lower than that of pure epoxy. The introduction of MnFe2O4 nanoparticles showed a lower onset decomposition temperature and glass transition temperature (Tg), which decreased with increasing the nanoparticles loading. The storage modulus and tensile strength of 1.0 wt% MnFe2O4/epoxy were a little higher than that of pure epoxy. The coercivity of MnFe2O4/epoxy nanocomposites with 5.0 wt% (44.7 Oe) and 10.0 wt% (43.9 Oe) displayed much higher than that of pure MnFe2O4 nanoparticles (14.94 Oe). The magnetic moment (m) of nanocomposites (1.354 μB for 10 wt% MnFe2O4/epoxy) are higher than that of pure MnFe2O4 nanoparticles (1.244 μB). The increased real permittivity observed in the nanocomposites was attributed to the interfacial polarization. The intrinsic permittivity of the MnFe2O4 nanoparticles was also calculated