石化项目地下水保护措施有效性分析

石化产品在储运过程中若发生污染事故,污染物会通过包气带渗入到地下水中,对地下水质量产生影响。通过预测,制定科学的地下水防治措施,是防止项目对地下水环境造成影响的有效手段。以广东某石化建设项目为例,在查明水文地质条件的基础上,预测和评价项目运营期对地下水环境可能造成的影响,并针对这种影响提出相应的防渗技术措施且预测了防渗措施的有效性。预测结果表明:采取防渗措施后,污染源强对地下水的影响范围明显缩小,说明防渗措施能有效的防止污染物进入地下水,保护地下水资源。     

智能制造关键使能技术发展及应用

信息通信技术对传统制造企业产生深远影响,催生智能制造生态系统范式。企业向智能制造范式转型,可从生命周期及价值链、制造层次结构和物理系统功能等三维度部署和实施。智能制造关键使能技术一般涵盖工业物联网、云计算、大数据、计算机仿真、增强现实、增材制造、水平和垂直系统集成、自主机器人和网络安全等九大技术。文章对上述关键使能技术进行梳理与综述,并分析其在智能制造领域应用的最新进展。     

Perovskite ceramic oxide as an efficient electrocatalyst for nitrogen fixation

The electrochemical conversion of N₂ to NH₃ is an interesting research topic as it provided an alternative and energy-saving method compared with the traditional way of NH₃ production. Although different materials have been proposed for N₂ reduction, the use of defects in oxides was only reported recently and the relevant working mechanism was not fully revealed. In this study, Sr was used as the dopant for LaFeO₃ to create oxygen vacancies, forming the Sr-doped LFO (La_0.5Sr_0.5FeO_3-δ) perovskite oxide. The La_0.5Sr_0.5FeO_3-δ ceramic oxide used as a catalyst achieves an NH₃ yield of 11.51 μgh^?1 mg^?1 and the desirable faradic efficiency (F.E.) of 0.54% at ?0.6 V vs reversible hydrogen electrode (RHE), which surpassed that of LaFeO₃ nanoparticles. The ¹⁵N isotope labeling method was employed to prove the La_0.5Sr_0.5FeO_3-δ catalyst had the function of converting N₂ into NH₃ under the electrolysis condition. The first principle calculations were used to investigate the mechanism at the atomistic level, revealing that the free energy barriers changed significantly with the introduction of oxygen vacancies that accelerated the overall nitrogen reduction reaction (NRR) procedure.     

Nanocrystalline transition metal oxides and their composites with reduced graphene oxide and carbon nanotubes for photocatalytic applications

Transition metal oxide nanoparticles (CuO, ZnO & Fe₂O₃) and mixed metal oxides CuO. ZnO.Fe₂O₃ were fabricated by facile co-precipitation approach for photocatalytic treatment of organic dyes. The structural features, phase purity, crystallite size and morphology of individual and mixed metal oxides were analysed by X-rays diffraction patterns (XRD) and scanning electron microscopic (SEM) analysis. Electrical behaviour of CuO, ZnO, Fe₂O₃ and mixed metal oxides CuO. ZnO.Fe₂O₃ was explored by current-voltage (I-V) measurements. Functional groups present in the synthesized metal oxides were investigated by Fourier transform infrared spectroscopy (FTIR) which ensures the existence of M-O functional groups in the samples. The optical bandgap analysis was carried out by UV–visible spectroscopic technique which revealed that the blend of three different transition metal oxides reduced the bandgap energy of mixed metal oxides. The reason behind this reduced bandgap energy is formation of new electronic state which arises due to the metal-oxygen interactions. Moreover, the nanocomposites of CuO.ZnO.Fe₂O₃ with reduced graphene oxide (rGO) and carbon nanotubes (CNTs) were prepared to study the effect of the carbonaceous materials on the rate of photodegradation. These carbonaceous nanomaterials have plethora properties which can bring advancement in sector of photocatalytic treatment of wastewater. The photocatalytic experiments were performed using methylene blue (MB) as standard dye for comparative study of metal oxides and their composites with rGO and CNTs. The percentage degradation of methylene blue (MB) by nanocomposite CuO.ZnO.Fe₂O₃/rGO is 87% which is prominent among all samples. This result ascribed the photocatalytic aspects of reduced graphene oxide along with mixed metal oxides.     

Mn3O4 nanosheets coated on carbon nanotubes as efficient electrocatalysts for oxygen reduction reaction

MnO-MnC_x coated carbon nanotubes (MnO/MnC_x/CNTs) nanocomposites were prepared by a one-pot deposition method. The coating consisted of MnO, Mn₅C₂, Mn₁₅C₄ and Mn₂₃C₆ was formed on the surface of CNTs by heating a mixture of Mn particles and CNTs at 600 °C for 40 min under vacuum. Then after heated MnO/MnC_x/CNTs in air at 350 °C for 2 h, MnO nanoparticles were partially converted to Mn₃O₄ nanosheets. Then Mn₃O₄-MnC_x coated carbon nanotubes (Mn₃O₄/MnC_x/CNTs) composed of interconnected nanosheets structure were successfully synthesized by a two-step method of one-pot deposition and heat post-treatment. The Mn₃O₄/MnC_x/CNTs showed better oxygen reduction reaction performance in alkaline condition than MnO/MnC_x/CNTs and pristine CNTs. Besides, the formed MnC_x (Mn₅C₂ and Mn₂₃C₆) by one-pot deposition method provided a strong interface bonding between Mn₃O₄ and CNTs, leading to improved stability of Mn₃O₄/MnC_x/CNTs as an electrode material.     

Effect of microbial hydrogen consumption on the hydrogen permeation behaviour of AISI 4135 steel under cathodic protection

The feasibility of microbial hydrogen consumption to mitigate the hydrogen embrittlement (HE) under different cathodic potentials was evaluated using the Devanathan-Stachurski electrochemical test and the hydrogen permeation efficiency η. The hydrogen permeation efficiency η in the presence of strain GA-1 was lower than that in sterile medium. The cathodic potential inhibited the adherence of strain GA-1 to AISI 4135 steel surface, thereby reducing the hydrogen consumption of strain GA-1. The adherent GA-1 cells were capable of consuming ‘cathodic hydrogen’ and reducing the proportions of absorbed hydrogen, indicating that it is theoretically possible to control HE by hydrogen-consuming microbes.     

Some molecular aspects of hydrogen production by marine Chlorella pyrenoidosa under nitrogen deprivation condition in natural seawater

In this study, marine microalgae Chlorella pyrenoidosa produced 186 ml H₂/l under nitrogen deprivation in natural seawater, and adding 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) to medium reduced the total volume of hydrogen production by 85%. This suggested water was the main electron donor for hydrogenase. An active starch accumulation was observed during the first two days in nitrogen deprivation. But the starch content in cell decreased only by 7% at the end of the hydrogen evolution stage. This was shown the absence of a large contribution of starch to the hydrogen production by C. pyrenoidosa in nitrogen deprivation. Different from the hydrogen production by Chlamydomonas reinhardtii under sulfur deprivation condition, the concentration of acetate in the medium decreased not only at the stage of oxygen consumption but also during the stage of hydrogen evolution by C. pyrenoidosa. Thus, acetate is involved not only in the establishment of anaerobiosis but also plays an important role in the production of hydrogen by C. pyrenoidosa as an exogenous electron donor.     

First demonstration of photoelectrochemical water splitting by commercial W–Cu powder metallurgy parts converted to highly porous 3D WO3/W skeletons

Hydrogen evolution through photoelectrochemical (PEC) water splitting by tungsten oxide-based photoanodes, as a stable and environmental-friendly material with moderate band gap, has attracted significant interest in recent years. The performance of WO₃ photoanode could be hindered by its poor oxygen evolution reaction kinetics and high charge carrier recombination rate. Additionally, scalable and cost-effective commercial procedure to prepare nanostructured electrodes is still challenging. We present, for the first time, a novel and scalable method to fabricate highly efficient self-supported WO₃/W nanostructured photoanodes from commercial W–Cu powder metallurgy (P/M) parts for water splitting. The electrodes were prepared by electrochemical etching of Cu networks followed by hydrothermal growth of WO₃ nanoflakes. Interconnected channels of W skeleton provided high active surface area for the growth of WO₃ nanoflakes with a thickness of ~40 nm and lateral dimension of ~250 nm. The optimized photoelectrode having 35% interconnected porosity exhibited an impressive current density of 4.36 mA cm⁻² comprising a remarkable photocurrent of 1.71 mA cm⁻² at 1.23 V vs. RHE under 100 mW cm⁻² simulated sunlight. This achievement is amongst the highest reported photocurrents for WO₃ photoelectrodes with tungsten substrate reported so far. Impedance and Mott-Schottky analyses evidenced fast charge transfer, low recombination rate, and accelerated O₂ detachment provided by optimum 3D porous WO₃/W electrode. Due to the nature of the commercial P/M parts and low-temperature hydrothermal processing, the procedure is cost-effective and scalable which can pave a new route for the fabrication of highly porous and efficient water splitting electrodes.     

Phase-transition induced optimization of electrostrain,electrocaloric refrigeration and energy storage of LiNbO3 doped BNT-BT ceramics

((Bi_0.5Na_0.5TiO₃)_0.88-(BaTiO₃)_0.12)_(1-x)-(LiNbO₃)_x (x = 0.0, 0.01, 0.02, 0.03, 0.04, 0.05, 0.06, and 0.07; abbreviated as LiNbO₃-doped BNT-BT) ceramics possessing many excellent performances (large electrostrain, negative electrocaloric effect and energy storage density with high efficiency) was fabricated by the conventional solid-state reaction method. A large electrostrain (maximum ~ 0.34% at 100 kV/cm and room temperature) with high thermal stability over a broad temperature range (~80 K) is obtained at x = 0.03. A large energy storage density (maximum W_energy ~ 0.665 J/cm³ at 100 kV/cm and room temperature) with a high efficiency (η ~ 49.3%) is achieved at x = 0.06. Moreover, a large negative electrocaloric (EC) effect (maximum ΔT ~ 1.71 K with ΔS ~ - 0.22 J/(K kg) at 70 kV/cm)) is also obtained at x = 0.04. Phase transition (from ferroelectric to antiferroelectric and then to relaxor) induced by increasing the doping amount of LiNbO₃ plays a very key role on the optimization of these performances. These findings and breakthroughs make the LiNbO₃-doped BNT-BT ceramics very promising candidates as multifunctional materials.     

液压约束活塞发动机的流量脉动仿真分析

为研究间隙误差对液压约束活塞发动机流量脉动的影响,在ADAMS中建立其含有间隙误差的主运动系统动力学模型,将ADAMS中得到的模型数据导入AMESim中,建立液压系统模型。通过对比不同间隙误差模型的参数输出,分析间隙误差对系统流量脉动的影响。研究结果表明,在一定范围内,间隙误差对流量脉动有明显的影响,并随着间隙误差的增大而增加;而且,连杆大头和曲轴曲柄之间转动副径向间隙误差对系统流量脉动的影响最大。