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11.
《International Journal of Hydrogen Energy》2022,47(38):17056-17068
The study of steels which guarantee safety and reliability throughout their service life in hydrogen-rich environments has increased considerably in recent years. Their mechanical behavior in terms of hydrogen embrittlement is of utmost importance. This work aims to assess the effects of hydrogen on the tensile properties of quenched and tempered 42CrMo4 steels. Tensile tests were performed on smooth and notched specimens under different conditions: pre-charged in high pressure hydrogen gas, electrochemically pre-charged, and in-situ hydrogen charged in an acid aqueous medium. The influence of the charging methodology on the corresponding embrittlement indexes was assessed. The role of other test variables, such as the applied current density, the electrolyte composition, and the displacement rate was also studied. An important reduction of the strength was detected when notched specimens were subjected to in-situ charging. When the same tests were performed on smooth tensile specimens, the deformation results were reduced. This behavior is related to significant changes in the operative failure micromechanisms, from ductile (microvoids coalescence) in absence of hydrogen or under low hydrogen contents, to brittle (decohesion of martensite lath interfaces) under the most stringent conditions. 相似文献
12.
为研究既有线有砟轨道路基的翻浆冒泥机理,自主研发了一套能够模拟循环荷载–湿化耦合作用的模型试验系统。模型试样直径500 mm,由厚度分别为350 mm的路基土和200 mm的道砟组成,整个试样在高强度透明有机玻璃模型筒中制备完成。模型试验系统配备有监测荷载、位移、体积含水率和孔隙水压力的4种传感器,并通过高清相机对颗粒迁移过程进行图像捕捉。基于所研发的试验系统,针对辛泰铁路典型翻浆冒泥病害路段土样,开展翻浆冒泥模型试验。试验结果表明:动孔隙水压力是导致翻浆冒泥病害产生的关键因素。随着体积含水率的增加,动孔隙水压力引起的颗粒迁移量逐渐增加;在饱和状态下,会引起大量颗粒迁移,翻浆冒泥现象显著。试验结束时,道砟污染指数达到25%,在实际工程中已严重影响铁路的正常运营,有必要对污染道砟进行换填。 相似文献
13.
为探究泵站进水流速大小与泵站进水池水流流态、漩涡的产生与发展变化规律,结合泵站实际运行情况,建立引渠、前池、进水池和进水管的泵站物理模型和湍流数学模型,采用VOF模型和非定常的SST k-ω湍流模型对9种不同流速的泵站进水水流特性进行数值模拟,分析不同进水流速的泵站进水池水流流场分布、漩涡涡量的变化及分布规律。研究结果表明:当进水流速为0.322 2~0.564 2 m/s时,泵站表面漩涡的强度随进水流速的增大而增强:当进水流速为0.322 2~0.401 6 m/s时,进水池出现Ⅲ、Ⅳ型漩涡;当进水流速为0.483 5 m/s时,进水池出现Ⅴ型漩涡;当进水流速为0.520 8~0.564 2 m/s时,进水池出现Ⅵ型漩涡。将数值计算结果与模型试验结果进行对比,两者基本吻合。研究结果可为泵站工程设计提供参考。 相似文献
14.
《International Journal of Hydrogen Energy》2022,47(56):23583-23592
Carbon-based materials have been often employed as electrocatalytic substrates because of their large surface area/highly porous structure. Similar to carbon substrates, the non-carbon related materials such as transition metals also play an important role in improving catalytic performance. However, the simultaneous synthesis and metallic functionalization of carbon substrates is a highly challenging issue. Herein, a hydrothermal method has been used for the preparation of Ni-functionalized porous carbon balls. The significant role of Ni2+ ions in the synthesis of porous carbon balls has been confirmed. The results of transmission electron microscopy indicate that, the as-prepared porous carbon balls were suitable for the dispersion of Pt nanoparticles with small particle size (less than 4 nm). In addition to providing the OHads species, the Ni can also modify the surface electronic structure of Pt. Electrochemical measurements results reveal that, under the strong interactions between Ni and Pt, the as-prepared porous carbon balls supported Pt nanoparticles (Pt/Ni-CB) catalyst possesses excellent electrocatalytic activity, stability and CO anti-poisoning capability towards methanol electrooxidation reaction (MOR). This work opens a novel idea for the construction of the metal functionalization of carbon substrates and their subsequent applications in other electrocatalytic reactions. 相似文献
15.
16.
《International Journal of Hydrogen Energy》2022,47(39):17241-17251
Zinc cadmium sulfide (ZnxCd1?xS) is a good photocatalyst for hydrogen evolution reaction (HER), but an optimum x (xm) at which a maximum HER rate is reached varies from one report to another. In this work, we examine the effect of light wavelength, not only for the HER to H2 in the presence of Na2S and Na2SO3, but also for oxygen reduction reaction (ORR) without addition of any sacrifices. For the HER under a 365 and 420 nm LED lamp, the xm were 0.9 and 0.7, respectively. For the HER under a 330 and 395–515 nm cut-off xenon lamp, the xm were 0.7 and 0.5, respectively. For the ORR under a 420 nm cut-off halogen lamp, a maximum production of H2O2 was observed at x = 0.3. Furthermore, after 4% ZnCo2O4 loading, ZnxCd1?xS had an increased activity and stability, either for the HER or for the ORR. Through a (photo)electrochemical measurement, it is proposed that the photocatalytic activity of ZnxCd1?xS is determined by its light absorptivity and electron reactivity. The improved performance of n-type ZnxCd1?xS by p-type ZnCo2O4 is due to formation of a p-n junction, promoting the HER (ORR) on ZnxCd1?xS, and the sulfide (water) oxidation on ZnCo2O4. This work highlights that ZnxCd1-xS is a promising photocatalyst for H2 and H2O2 production, respectively. 相似文献
17.
《International Journal of Hydrogen Energy》2022,47(94):39864-39874
The reaction of H2 and O2 to water are studied over a Ag–Pd/TiO2 anatase catalyst, under dark and photo-irradiation conditions in the gas and liquid phases. The catalyst consisted of metal particles of mean size of ca.1 nm dispersed over 10–15 nm TiO2 particles. Kinetic parameters including order of reaction (n), rate constant (k), and activation energy (Ea), were evaluated. Ea for the thermal reaction was found to be 49-47 kJ mol?1. The oxidation reaction rate constant was found to be ca. 3 times higher in the presence of photons when compared to dark reaction at room temperature. The overall quantum yield of the reaction in the slurry phase was found to be 0.09. Considering the number of metal particles on TiO2, the photon yield per metal particle was found to be 0.16. A possible explanation of the changes in kinetics with respect to experimental conditions is given. 相似文献
18.
《International Journal of Hydrogen Energy》2022,47(60):25081-25089
Developing efficient, stable and ideal urea oxide (UOR) electrocatalyst is key to produce green hydrogen in an economical way. Herein, Ru doped three dimensional (3D) porous Ni3N spheres, with tannic acid (TA) and urea as the carbon and nitrogen resources, is synthesized via hydrothermal and low-temperature treated process (Ru–Ni3N@NC). The porous nanostructure of Ni3N and the nickel foam provide abundant active sites and channel during catalytic process. Moreover, Ru doping and rich defects favor to boost the reaction kinetics by optimizing the adsorption/desorption or dissociation of intermediates and reactants. The above advantages enable Ru–Ni3N@NC to have good bifunctional catalytic performance in alkaline media. Only 43 and 270 mV overpotentials are required for hydrogen evolution (HER) and oxygen evolution (OER) reactions to drive a current of 10 mA cm?2. Moreover, it also showed good electrocatalytic performance in neutral and alkaline seawater electrolytes for HER with 134 mV to drive 10 mA cm?2 and 83 mV to drive 100 mA cm?2, respectively. Remarkably, the as-designed Ru–Ni3N@NC also owns extraordinary catalytic activity and stability toward UOR. Moreover, using the synthesized Ru–Ni3N@NC nanomaterial as the anode and cathode of urea assisted water decomposition, a small potential of 1.41 V was required to reach 10 mA cm?2. It can also be powered by sustainable energy sources such as wind, solar and thermal energies. In order to make better use of the earth's abundant resources, this work provides a new way to develop multi-functional green electrocatalysts. 相似文献
19.
《International Journal of Hydrogen Energy》2022,47(63):27199-27222
In this present work, the effect of lanthanum oxides (La2O3) on the thermal cycle behavior of TBC coatings and mechanical properties such as adhesion strength and microhardness of 8% Yttria Stabilized Zirconia (8YSZ) TBCs were investigated. CoNiCrAlY and aluminium alloy (Al–13%Si) were used as bond coat and substrate materials. 8YSZ and different wt % of La2O3 (10, 20, and 30%) top coatings were applied using the atmospheric plasma spray (APS) method. The thermal cycling test for TBC coated samples were conducted at 800 °C in the electric furnace. The XRD pattern shows that the La2O3 doped 8YSZ material transformed to cubic pyrochloric structured La2Zr2O7 during thermal cycling. Further, the Taguchi-based grey relation analysis (GRA) method was applied to optimize the TBC coating parameters to achieve better mechanical properties such as adhesion strength and microhardness. And the optimized La2O3/8YSZ TBC coating was coated on CRDI engine combustion chamber components. The engine was tested with microalgae biodiesel and hydrogen, and the results were promising for the TBC-coated engine. The engine performance increased while using La2O3/8YSZ coated components, and the emissions from engine exhaust gas such as CO, HC, and smoke reduced considerably. It was found that there was no separation crack and spallation of the coating layer in the microstructure. Ultimately, the microstructural analysis of the optimized TBC coated piston sample after 50 h of running in the diesel engine confirmed that the developed coating had a superior thermal insulation effect and longer life. 相似文献
20.
Yinjuan Cao Shunzhong He Qunli Yu Ling Han Wei Zhang Xiaohong Zou 《International Journal of Food Science & Technology》2022,57(5):3001-3011
This study investigated the effect of 5 freeze–thaw cycles (freezing at −18°C for 12 h and then thawing at 4°C for approximately 12 h) on the meat quality, proximate composition, water distribution and microstructure of bovine rumen smooth muscle (BSM). As the number of freeze–thaw cycles increased, BSM pH, shear force, water content and protein content decreased by 3.06%, 35.50%, 14.49% and 21.11%, respectively, whereas BSM thawing loss, cooking loss, pressing loss, total aerobic count (TAC), ash content and fat content increased by 108.12%, 47.75%, 78.33%, 90.99%, 105% and 35.20%, respectively. The freeze–thaw cycles resulted in greater protein and lipid oxidation, as evidenced by a 36.46% reduction in the sulfhydryl content and a 209.06% and 338.46% increase in the carbonyl and malondialdehyde contents, respectively. Ice crystal formation disrupted the structural integrity of the muscle tissue. Low-field nuclear magnetic resonance results showed that the freeze–thaw cycles prolonged the relaxation times (T2b, T21 and T22), indicating that immobile water shifted to free water, and consequently, free water mobility increased. After 3 freeze–thaw cycles, the decline in shear force slowed, the increase in thawing loss became accelerated, and the TAC approached the domain value (6 log colony-forming units/g). Therefore, the number of freeze–thaw cycles of smooth muscle during transport, storage and distribution should be controlled to 3 or fewer. The current results provide a theoretical basis and data support for the further utilisation and culinary processing of smooth muscle. 相似文献