jianfeng su

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Study of Morphology and Corrosion Behavior of Aluminum Coatings on Steel Substrates under Simulated Acid Rain Conditions

Metals

In this paper, aluminum coatings were prepared on a steel substrate by thermal spraying, and the ... more In this paper, aluminum coatings were prepared on a steel substrate by thermal spraying, and the corrosion morphology and corrosion resistance of the coating were investigated by salt spray and immersion tests. The results showed that after three months of salt spray tests, the coating still exhibited a surface morphology without significant damage and had good damage tolerance. Further effective protection of the substrate can be achieved by spraying the coating surface with paint. After three months of immersion test, the corrosion rate of samples with thicker coatings was located between 0.002 mm/y and 0.005 mm/y, and only a small amount of corrosion products was observed on the coating surface. The coated samples after salt spray and immersion tests maintained sufficient adhesion (17.07 MPa and 19.25 MPa), and the surface aluminum coating was highly reliable for protection of the steel substrate. In general, the reliability of the coating can be further improved by painting the ...

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Characteristics of Fair-weather Atmospheric Electric Field in Tibetan Ngari Prefecture

Chinese Journal of Space Science, 2022

Friction Properties of Black Phosphorus: A First-principles Study

Based on the first-principle, the friction anisotropy, structural super-lubricity and oxidation i... more Based on the first-principle, the friction anisotropy, structural super-lubricity and oxidation induced ultra-low friction of black phosphorus at atomic scale under different loads have been studied. The results show that the interface friction of black phosphorus shows anisotropy, that is, the friction along the armchair direction is greater than that along the zigzag direction. Moreover, the friction between the black phosphorus interfaces shows a structural superlubricity property, and the incommensurate interface friction is about one thousandth of the commensurate interface friction. In addition, the oxidation of black phosphorus is beneficial to the lubrication between interfaces.

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Synthesis and Visible Light Catalytic Performance of BiOI/Carbon Nanofibers Heterojunction

Catalysts

Semiconductor materials as photocatalysts hold great prospects for renewable energy substitutes a... more Semiconductor materials as photocatalysts hold great prospects for renewable energy substitutes and environmental protection. Nanostructured BiOX (X=Cl, Br, I) with favorable features of a unique layered crystal structure and suitable band gaps has been demonstrated to be a promising photocatalytic material. In this paper, a two-step synthesis route combining an electrospinning technique and SILAR reaction has been accepted as a straightforward protocol for the exploitation of BiOI/carbon nanofibers’ (CNFs) hierarchical heterostructures. As expected, the BiOI/CNFs presented a much higher degradation rate of methyl orange than that of the pure BiOI under visible light. The degradation rate of methyl orange reaches 85% within 210 min. The enhanced photocatalytic activity could be attributed to the fact that conductive CNFs as substrate could effectively improve the separation and transformation of photogenerated charges. Moreover, the fabricated BiOI/CNFs after five cycles could be ea...

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PID Control of Iodine Molecules Containing Gas Generator Based on Differential Evolution Algorithm

2020 Chinese Control And Decision Conference (CCDC)

In this paper, a simple design method of iodine molecules containing gas generator is proposed. T... more In this paper, a simple design method of iodine molecules containing gas generator is proposed. Then the mathematical model of the system is derived and the transfer function of the system is obtained by step response modeling. Meanwhile, a method of optimizing PID controller parameters in real time using a differential evolution algorithm is proposed, which solves the problem that the existing PID controller parameter tuning methods are complicated and take a lot of time. Finally, the different control schemes are compared in simulation, and the results show that the control algorithm proposed in this paper has better performance even if there is external interference.

Measurement of atmospheric conductivity on the Qinghai-Tibet Plateau in China

Meteorology and Atmospheric Physics, 2022

Two feasible methods (the current–voltage method and the voltage decay method) for measuring atmo... more Two feasible methods (the current–voltage method and the voltage decay method) for measuring atmospheric conductivity were introduced in this paper, both variants within the Gerdien tube method. To explore the characteristics of atmospheric conductivity, we performed two balloon flight experiments on the Qinghai-Tibet Plateau on 27 August 2019 and 14 September 2020, and these two approaches were used. Detailed experiments and methods and a series of experimental results are presented in this paper. The current–voltage method was used during the first experiment, and we further demonstrated that atmospheric conductivity changed with changing altitude, primarily under the action of atmospheric gas and ionic composition. The balloon passed through the clouds by chance, and we found that clouds caused abnormal variation in atmospheric conductivity; the measured conductivity of the atmosphere changed suddenly by 7.5 × 10–13 − 1.5 × 10–12 Ω−1 m−1, which may have been caused by water vapor or charges in the clouds. For the second experiment, the voltage decay method was used to explore further characteristics of atmospheric conductivity at the same location on the plateau. Unfortunately, the balloon did not fly because of the device, and positive conductivity and negative conductivity were measured on the ground at an altitude of 3.2 km. The feasibility of the two methods was proven by the two experiments. At the end of the paper, we have discussed the experimental error and details of the two measuring methods, which can be used as a reference for researchers concerned with atmospheric electricity.

High-magnetic-field solidification on magnetostrictive effect of Ni-doped MnCoSi alloy

Materials Letters, 2021

Abstract Ni-doped MnCoSi alloy was prepared by high-magnetic-field solidification with a slow coo... more Abstract Ni-doped MnCoSi alloy was prepared by high-magnetic-field solidification with a slow cooling rate. At a 3 at% Ni substitution for Mn, the room-temperature critical field was decreased to 0.4 T and the tricritical temperature between first-order and second-order antiferromagnetic-ferromagnetic metamagnetic phase transformation was tuned to 280 K. As a result, we obtained oriented and dense Mn0.97Ni0.03CoSi alloy and observed anisotropic reversible magnetostrictive effects under the magnetic field of 3.1 T near room temperature.

Optimizing LADRC Bubble Tower Control System Based on Differential Evolution Algorithm

2020 Chinese Control And Decision Conference (CCDC), 2020

The linear active disturbance rejection controller (LADRC) does not rely on models and has strong... more The linear active disturbance rejection controller (LADRC) does not rely on models and has strong robustness, which makes it widely used in engineering fields. In the chemical process, the internal mechanism of the bubble column reactor is complicated. It is difficult to model, has many interferences and is impossible to measure, so the control effect of LADRC has huge application potential. In order to solve the problem that the parameters of LADRC are not conducive to tune, this paper proposes a method for tuning LADRC parameters based on differential evolution algorithm. The simulation results show that the control system has good robustness, can effectively suppress the effects of model uncertainty and external uncertain disturbances, and has good control effect in the removal of iodine process in acid environment in the bubble column.

H omogeneous b uffer layer techn ique for the growth of Al doped ZnO fi lms on flexible substrate

Optoelectronics and Advanced Materials-rapid Communications, 2017

Al doped ZnO films were grown on PI flexible substrate by Sol-Gel method. To improve the optical ... more Al doped ZnO films were grown on PI flexible substrate by Sol-Gel method. To improve the optical and electrical properties, homogeneous buffer layers were introduced before the grown of ZnO films using magnetron sputtering techno logy. A systematical and detailed study of the effect of buffer layer sputtering time on structural, optical and electrical properties were discussed using XRD, SEM and PL. For samples with homogeneous buffer layer, excellent crystallization quality and op tical properties were obtained. Moreover, as increasing the sputtering time of buffer layer, the properties of ZnO films were improved further. All Al doped samples demonstrate more than 85% of the optical tra…

The controlling factors of high suspended sediment concentration in the intertidal flat off the Huanghe River Estuary

Acta Oceanologica Sinica, 2020

The Huanghe River (Yellow River) is known by its high suspended sediment concentration (SSC) in i... more The Huanghe River (Yellow River) is known by its high suspended sediment concentration (SSC) in its river mouth tidal flat. However, the factors controlling the high SSC over there are not well understood. Therefore, we conducted 7-d hydrodynamic observations (water depth, wave height, and current velocity) and SSC measurements on the tidal flat off the Huanghe River Mouth. The data shows that in most of time, under the calm sea condition, the SSC ranges 0.1-3.5 g/L, and sediment discharge from the river is the main source. However, when hydrodynamics are enhanced in a tidal cycle and large-scale erosion occurs on the seafloor, resuspended sediment becomes the main source, and the SSC in the water column reaches 17.3 g/L. We find the suspended sediment flux is mainly controlled by the tidal current and Stokes drift, while the wave-induced shear stress could also affect the variation of suspended sediment flux. During the observation period, when sea under calm-rippled conditions, the current-induced resuspended sediment concentration (RSC) was greater than the wave-induced RSC. In contrast, in smooth-wavelet sea conditions, the wave-induced RSC was greater than the current-induced RSC, for instance, a single wave event was found to cause 11.8 cm seabed erosion within 6 h. This study reveals different controlling factors for the high SSC near a river-influenced tidal flat, and helps us get a better understanding of a delta's depositional and erosional mechanisms.

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Facile fabrication of inorganic polymer microspheres as adsorbents for removing heavy metal ions

Materials Research Bulletin, 2019

This work reports a simple preparation process of slag-based inorganic polymer microspheres (IPMs... more This work reports a simple preparation process of slag-based inorganic polymer microspheres (IPMs) using the suspension dispersion solidification (SDS) method. The SEM results showed that the microspheres exhibit good spherical shape with controllable diameter range within 40-1000 μm. The size of the microspheres is closely related to the temperature and dispersion rate of the suspension. Based on the results obtained by varying the temperature and dispersion rate of the suspension, it was found that the best spherical shape and the highest yield are obtained at 80°C and 800 r/min. The H 2 O/Na 2 O molar ratio of the geopolymer paste affected the BET surface area of the microspheres. The microspheres exhibited outstanding adsorption capacity towards the removal of Pb 2+ (310.84 mg/g), Cu 2+ (47.71 mg/g) and Cd 2+ (36.26 mg/g), with their high adsorption rate attributed to their large surface area. Selectivity adsorption experiments show that the IPMs have high selectivity for Pb 2+ .

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Low-frequency gravitational wave detection via double optical clocks in space

Classical and Quantum Gravity, 2018

We propose a Doppler tracking system for gravitational wave detection via Double Optical Clocks i... more We propose a Doppler tracking system for gravitational wave detection via Double Optical Clocks in Space (DOCS). In this configuration two spacecrafts (each containing an optical clock) are launched to space for Doppler shift observations. Compared to the similar attempt of gravitational wave detection in the Cassini mission, the radio signal of DOCS that contains the relative frequency changes avoids completely noise effects due for instance to troposphere, ionosphere, ground-based antenna and transponder. Given the high stabilities of the two optical clocks (Allan deviation ∼ 4.1 × 10 -17 @ 1000 s), an overall estimated sensitivity of 5 × 10 -19 could be achieved with an observation time of 2 years, and would allow to detect gravitational waves in the frequency range from ∼ 10 -4 Hz to ∼ 10 -2 Hz.

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Contributions of vector leptoquark to Ξb→Ξcτν¯τ decay

Nuclear Physics B, 2019

Abstract Motivated by the R D ( ⁎ ) anomalies in semileptonic B meson decay which can be explaine... more Abstract Motivated by the R D ( ⁎ ) anomalies in semileptonic B meson decay which can be explained by adding a single vector leptoquark U 3 ( 3 , 3 , 2 3 ) to the Standard Model, we further analyse the New Physics effects of vector leptoquark to the heavy baryon Ξ b → Ξ c τ − ν ¯ τ decay. Using the best-fit solutions for Wilson coefficients of operators resulted from experimental measurement R D ( ⁎ ) anomalies and the form factors resulted from relativistic quark model, we study the contributions of the leptoquark to several observables, such as differential branching ratio, ratio of differential branching ratio, lepton-side forward-backward asymmetry, longitudinal polarization fraction of Ξ c baryon and τ lepton as well as the convexity parameter of this decay with the helicity amplitude formalism. We find that the contributions of vector leptoquark to differential branching ratio, ratio of differential branching ratio and convexity parameter are significant which show deviations at high level from the corresponding Standard Model predictions. Nevertheless, the observables lepton-side forward-backward asymmetry, longitudinal polarization fraction of Ξ c baryon and τ lepton have the same behaviours in vector leptoquark as that in the Standard Model which displays the three observables are not sensitive to the New Physics effects of vector leptoquark.

Carrier transport mechanisms of p-SiC/n-Si hetero-junctions

Solid State Sciences, 2011

Hetero-junctions have been fabricated on Al-doped silicon carbide thin films onto n-type silicon ... more Hetero-junctions have been fabricated on Al-doped silicon carbide thin films onto n-type silicon single crystals using low-pressure chemical vapor deposition method. Temperature-dependent currentevoltage measurements and Hall-effect measurements have been performed to determine the electrical properties of the structures. The temperature-dependent IeV characteristics demonstrated that the forward conduction at lower voltages was dominated by thermionic emission process, while, the forward conduction at higher voltages was determined by multi-step tunneling current. The activation energy of saturation current was about 0.32 eV. Hall-effect measurements proved the p-type properties of obtained SiC films. Deduced from the results of Hall measurements, the junction built-in potential was 1.32 V at room temperature. Moreover, using deep level transient spectroscopy measurements, Al Si acceptor ionization energy was estimated.

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A single point defect diffusion near a Cu (100) surface

Solid State Sciences, 2011

ABSTRACT As part of our investigations on the disordering of metal surfaces, we report the result... more ABSTRACT As part of our investigations on the disordering of metal surfaces, we report the results of our calculations of the energetics of formation and migration of a single point defect (vacancy and interstitial) in the Cu (100) surface using molecular dynamics method. We used the embedded-atom method to describe inter-atomic interactions. Defect formation and migration energies have been calculated at the surface as well as in the near-surface region. Vacancy and interstitial formation and migration energies converge to bulk values already at a few layers below the surface. We find that the surface vacancy and interstitial formation and migration energies are all lower than their bulk values. For the inter-layer migration, a point defect in each of the first six layers is favorable to migrate into the corresponding upper layer, especially for the first three layers.

Effects of sic buffer layer on the optical properties of ZnO films grown on Si (111) substrates

Journal of Luminescence, 2007

ABSTRACT ZnO films have been grown by a sol–gel process on Si (1 1 1) substrates with and without... more ABSTRACT ZnO films have been grown by a sol–gel process on Si (1 1 1) substrates with and without SiC buffer layers. The influence of SiC buffer layer on the optical properties of ZnO films grown on Si (1 1 1) substrates was investigated. The intensity of the E2 (high) phonon peak in the micro-Raman spectrum of ZnO film with the SiC buffer layer is stronger than that of the sample without the SiC buffer layer, and the breadth of E2 (high) phonon peak of ZnO film with the SiC buffer layer is narrower than that of the sample without the SiC buffer layer. These results indicated that the crystalline quality of the sample with the SiC buffer layer is better than that of the sample without the SiC buffer layer. In photoluminescence spectra, the intensity of free exciton emission from ZnO films with the SiC buffer was much stronger than that from ZnO film without the SiC buffer layer, while the intensity of deep level emission from sample with the SiC buffer layer was about half of that of sample without the SiC buffer layer. The results indicate the SiC buffer layer improves optical qualities of ZnO films on Si (1 1 1) substrates.

Facile synthesis of Bi 2 S 3 nanoflowers arrays

Journal of Experimental Nanoscience, 2013

Bi 2 S 3 nanoflowers arrays have been synthesised by a facile hydrothermal method. The nanoflower... more Bi 2 S 3 nanoflowers arrays have been synthesised by a facile hydrothermal method. The nanoflowers are composed of nanobelts. The Bi 2 S 3 nanobelts are along [1 3 0] direction with a width of about 100 nm and a length of about 2 mm. It is found that the substrate, the height of the substrate in the autoclave and the reaction time play key roles for the formation of the nanoflowers arrays. The growth of the nanoflowers is attributed to the lowest interfacial tension and the growth of the nanobelts can be ascribed to the anisotropic growth of the Bi 2 S 3 nanocrystals. The room temperature photoluminescence (PL) spectrum shows that there is a strong and broad PL band in the wavelength range from 650 to 800 nm. It is expected that the Bi 2 S 3 nanoflowers arrays grown on the substrate could have potential application in optics and catalysts.

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Transport and thermoelectric properties of Sr3(Ti0.95R0.05)2O7 (R = Ta, Nb, W) oxides

Journal of Applied Physics, 2012

The Sr3(Ti0.95R0.05)2O7 (R = Ta, Nb, W) polycrystalline compounds were fabricated, and their tran... more The Sr3(Ti0.95R0.05)2O7 (R = Ta, Nb, W) polycrystalline compounds were fabricated, and their transport and thermoelectric properties were investigated. The results indicate that at T > 300 K electrical resistivity ρ for all the doped compounds increases monotonically with temperature, and basically can be described by a relation ρ ∝ TM at T > ∼650 K, with M = 1.39, 1.66, and 1.77 for R = Ta, Nb, and W, respectively, implying that at the high temperatures the acoustic phonon scattering dominates the scattering process. Although the resistivity ρ of Sr3(Ti0.95Ta0.05)2O7 exhibits a metallic-like behavior at the temperature as low as 5 K, a transition from metallic state (dρ/dT > 0) to semiconductor-like state (dρ/dT < 0) was observed at a critical low temperature ∼41 K and ∼79 K for R = Nb and W, respectively. At T < ∼22 K, ∼57 K, and ∼80 K, a relation of σ ∝ T1/2 (here conductivity σ = 1/ρ) holds for the doped compounds with R = Nb, Ta, and W, respectively, suggesting t...

Influence of annealing on the structural and optical properties of ZnO films grown by MOCVD

Journal of Alloys and Compounds, 2011

The properties of ZnO films grown on Si (1 1 1) substrates by Metal-Organic Chemical Vapor Deposi... more The properties of ZnO films grown on Si (1 1 1) substrates by Metal-Organic Chemical Vapor Deposition technique using diethylzinc and H 2 O as reactant gases are reported. The primary focus is on understanding the origin of deep-level luminescence. As increasing the annealing temperature, a visible emission is observed both in samples annealing in oxygen atmosphere and nitrogen atmosphere. In addition, this broad defect emission becomes obviously asymmetric when the annealing temperature was increased to 1000 • C in oxygen atmosphere. Theoretical investigations have reported that the formation enthalpy of defects is varied under different conditions. With these results, it is suggested that the visible emission in ZnO films annealed in oxygen atmosphere is related to zinc vacancy and oxygen interstitial defects. While, the green emission in ZnO films which were annealed in nitrogen atmosphere is attributed to oxygen vacancy defects.

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Luminescence and recombine centre in ZnO/Si films

Frontiers of Electrical and Electronic Engineering in China, 2008

The D 0 h luminescence of ZnO films deposited on p-type Si substrates is produced by metal-organi... more The D 0 h luminescence of ZnO films deposited on p-type Si substrates is produced by metal-organic chemical vapor deposition (MOCVD). After annealing in the air at 700°C for an hour, the photoluminescence (PL) spectra, the I-V characteristics and the deep level transient spectroscopy (DLTS) of the samples are measured. All the samples have a rectification characteristic. DLTS signals show two deep levels of E 1 and E 2 . The Gaussian fit curves of the PL spectra at room temperature show three luminescence lines b, c and d, of which b is attributed to the exciton emission. The donor level E 1 measured by DLTS and the location state donor ionization energy E d of the closely neighboring emission lines c and d are correlated. E 1 is judged as neutral donor bound to hole emission (D 0 h). Moreover, the intensity of the PL spectra decreases while the relative density of E 2 increases, showing that E 2 has the property of a nonradiative center.

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