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291.
The geothermal steam turbines are exposed to mechanisms of corrosion/erosion that weakens its components and reduces their useful life. Due to this problem work has been done in application and characterization of coating in solid state by means of the technique of high-velocity Oxygen Fuel (HVOF), evaluating the corrosion rate (Vcorr) at high temperature of MCrAlY and Diamalloy 4006 coatings deposited on stainless steel SS304. Test was performance in an Autoclave at 170 0C using a modified geothermal fluid as electrolyte. Open circuit potential was monitoring during 24 hours until the system reached the equilibrium. After that, Polarization and Impedance Spectroscopy techniques were used to evaluate the specimens. For microstructure characterization; X–ray Diffraction (XRD), electron sweep microscope (SEM) and Optical microscope were applied. Results show that both coatings (Diamalloy 4006 and MCrAlY), have low current density compare with the substrate, which is an indicative of a lower corrosion rate due to the passive behavior of the species deposited on the Surface of the coating. 相似文献
292.
二氧化碳浓度持续升高导致的温室效应已在全球范围内引发极端天气、冰川融化等一系列生态环境问题。为降低二氧化碳含量,改善气候变暖带来的恶劣影响,研发高效、绿色、安全的二氧化碳处理技术,促进碳资源循环可持续发展刻不容缓。熔盐离子液体作为一种良好的电化学转化介质,为二氧化碳还原提供了一条极具应用前景的技术路线。综述了国内外近几年高温熔盐中二氧化碳的捕获与电化学还原的研究,简述了熔盐电沉积碳的电化学机理和热力学机制,对不同形貌高附加值碳材料:无定形碳、碳球和碳纳米管的制备进行了总结,最后对未来发展方向做出展望。 相似文献
293.
An analytical method for the simultaneous determination of 12 additives in beverages was developed using evaporation-assisted dispersive liquid-liquid microextraction based on the solidification of floating organic droplets EVA-DLLME-SFOcombined with high performance liquid chromatography HPLC. The samples were extracted twice with 70%V/Vmethanol aqueous solution and extracted by EVA-DLLME-SFO method after the combination of the extractsand finally determined by HPLC. Extraction parameterssuch as types and amounts of extractantevaporant and heating agentthe concentration of saltand the extraction time were optimized. Under the optimized conditionsthere were good relationships in the ange of 0.25-50 μµg/mL with the limits of detection of 1.5 to 13.6 mg/kg and limits of quantification of 5.2 to 45.3 mg/kg. The recoveries at three spiked levels1025 and 50 mg/kgwere 76.8% to 101.2% with the relative standard deviations of 0.11% to 4.7%. The method can be used for rapid detection of 12 additives in beverages. © 2022, Youke Publishing Co.,Ltd. All rights reserved. 相似文献
294.
Lithium ion batteries (LIBs) have broad applications in a wide variety of a fields pertaining to energy storage devices. In line with the increasing demand in emerging areas such as long-range electric vehicles and smart grids, there is a continuous effort to achieve high energy by maximizing the reversible capacity of electrode materials, particularly cathode materials. However, in recent years, with the continuous enhancement of battery energy density, safety issues have increasingly attracted the attention of researchers, becoming a non-negligible factor in determining whether the electric vehicle industry has a foothold. The key issue in the development of battery systems with high specific energies is the intrinsic instability of the cathode, with the accompanying question of safety. The failure mechanism and stability of high-specific-capacity cathode materials for the next generation of LIBs, including nickel-rich cathodes, high-voltage spinel cathodes, and lithium-rich layered cathodes, have attracted extensive research attention. Systematic studies related to the intrinsic physical and chemical properties of different cathodes are crucial to elucidate the instability mechanisms of positive active materials. Factors that these studies must address include the stability under extended electrochemical cycles with respect to dissolution of metal ions in LiPF6-based electrolytes due to HF corrosion of the electrode; cation mixing due to the similarity in radius between Li+ and Ni2+; oxygen evolution when the cathode is charged to a high voltage; the origin of cracks generated during repeated charge/discharge processes arising from the anisotropy of the cell parameters; and electrolyte decomposition when traces of water are present. Regulating the surface nanostructure and bulk crystal lattice of electrode materials is an effective way to meet the demand for cathode materials with high energy density and outstanding stability. Surface modification treatment of positive active materials can slow side reactions and the loss of active material, thereby extending the life of the cathode material and improving the safety of the battery. This review is targeted at the failure mechanisms related to the electrochemical cycle, and a synthetic strategy to ameliorate the properties of cathode surface locations, with the electrochemical performance optimized by accurate surface control. From the perspective of the main stability and safety issues of high-energy cathode materials during the electrochemical cycle, a detailed discussion is presented on the current understanding of the mechanism of performance failure. It is crucial to seek out favorable strategies in response to the failures. Considering the surface structure of the cathode in relation to the stability issue, a newly developed protocol, known as surface-localized doping, which can exist in different states to modify the surface properties of high-energy cathodes, is discussed as a means of ensuring significantly improved stability and safety. Finally, we envision the future challenges and possible research directions related to the stability control of next-generation high-energy cathode materials. 相似文献
295.
5-羟甲基糠醛(HMF)的电催化氧化被认为是合成2,5-呋喃二甲酸(FDCA)最环保、经济和有效的方法之一,它可作为聚呋喃二甲酸乙二醇酯(PEF)的生物基前体。在这项工作中,我们通过低温溶剂热法合成了PtRuAgCoNi高熵合金纳米颗粒,并在不改变颗粒结构和组成的情况下进行了简易的处理以去除表面活性剂。负载在碳载体上的合金纳米催化剂无论是否含有表面活性剂在HMF电催化氧化为FDCA的过程中都表现出比商业Pt/C更好的催化性能。且表面活性剂的去除可以进一步提高其电催化性能,表明高熵合金纳米粒子在电催化和绿色化学中具有广阔的应用前景。 相似文献
296.
Polymer electrolytes have attracted great interest for next-generation lithium-based batteries on account of safety and high energy density. In this review, we assess recent progress on the design of poly(ethylene oxide)(PEO)-based solid polymer electrolytes in high voltage lithium batteries and identify possible side reactions between PEO-based electrolytes and existing cathodes. We provide an overview of the ways to enhance high voltage resistance of PEO-based electrolytes. Those include components blend, molecular design and interface modification. With these efforts, we want to present new insights into rational design of PEO-based electrolytes to develop solid-state lithium batteries for advanced performance. 相似文献
297.
LUO Zha LIU Hao SHEN Wei SHI Kun CHEN Ankang SHENG Libo SUI Yongming ZOU Bo 《高等学校化学研究》2022,38(3):843-846
We used a diamond anvil cell(DAC) to control the deformation of synthesized copper nanorods and silver nanoparticles. And we measured the surface plasmon resonance of copper nanorods and silver nanoparticles, which exhibit redshifts or blueshifts. The surface plasmon resonance shows an abnormal blue shift for both copper nanorods and silver nanoparticles. The solvents of copper nanorods and silver nanoparticles are n-hexane and water, where the pressure loads include quasi-hydrostatic and non-hydrostatic. 相似文献
298.
High-entropy transition metal chalcogenides (HE-TMCs) are advantageous in electrocatalytic applications compared to other entropy-stabilized systems owing to the greater orbital extension and energetic match of p-orbitals in chalcogenides with d-orbitals of the transition metals providing additional space to tailor their electronic structure. The high-configurational entropy of HE-TMCs leads to stabilization of cubic rock salt, wurtzite-type and hexagonally packed 2D structures. Due to the multi-element nature of HE-TMCs, the synergy among different elements results in tunable d- and p-band positions. As a consequence, the adsorption energies of electrocatalytic reaction intermediates can be tailored to enhance catalytic performance in water splitting and CO2 reduction. Furthermore, the entropy-stabilized disordered microstructural state of the material endows HE-TMCs with improved corrosion resistance. Despite recent advances in HE-TMC electrocatalysis, challenges such as identification and synthesis of efficient HE-TMCs as well as the identification of catalytically active sites and reaction mechanisms on HE-TMCs remain to be investigated. 相似文献
299.
P.L. Ríos I. Araya-Durán S. Bonardd J.L. Arroyo P. Povea M.B. Camarada 《Materials Today Chemistry》2022
Ferrocene (Fc)-based systems are frequently used as burning rate catalysts in the decomposition of ammonium perchlorate (AP)-based propellants. However, small Fc derivatives migrate to the surface of the propellant resulting in undesirable changes in the designed burning parameters and unstable combustion. To retard the migration and to increase the combustion rate of AP, fourth-generation polyamidoamine (PAMAM) dendrimers modified with Fc (PAMAM generation 4 [G4]-Fc) were synthetized and used as support for the obtention of copper nanoparticles (CuNPs). PAMAM G4 produced smaller nanoparticles (1–2 nm) with lower aggregation than PAMAM G4-Fc (12–14 nm). X-ray photoelectron spectroscopy (XPS) characterization confirmed the superior stabilizing and protecting effect against oxidation of CuNPs by PAMAM G4 in comparison to PAMAM G4-Fc, whereas molecular dynamics simulations have shown less flexibility and lower presence of stabilizing sites for nanoparticles in PAMAM G4-Fc. Antimigration tests confirmed the negligible migration of PAMAM G4-Fc compared with Fc, whereas PAMAM G4-Fc|CuNP affected the high-temperature decomposition of AP positively, decreasing the decomposition temperature in 87 °C owing to a synergistic effect between CuNPs and Fc. PAMAM G4-Fc can act both as an effective antimigration system of Fc and as a stabilizing framework of metal nanoparticles with application as catalysts of AP. 相似文献
300.
Phosphors with outstanding luminescence thermal stability are desirable for high-power phosphor-converted light-emitting diode (pc-LED) lightings. High structural rigidity and large bandgap of phosphor hosts are helpful to suppress nonradiative relaxation of optical centers and realize excellent thermal stability. Unfortunately, few host materials simultaneously possess aforementioned structural features. Herein, we confirm that Sr3(PO4)2 (SPO) phosphate possesses high structural rigidity (Debye temperature, ΘD = 559 K) and large bandgap (Eg = 8.313 eV) by density functional theory calculations. As expected, Eu2+-doped SPO purple-blue phosphors show extraordinary thermal stability. At 150/300 °C, SPO:5%Eu2+ presents emission loss of only 4%/8% and a predicated ultrahigh thermal quenching temperature of 973 °C. The most strikingly discoveries here are that thermal-induced emission compensation appears within two distinct Eu2+ sites of SPO host. The outstanding thermal stability, on one hand, is attributed to rigid structure and large bandgap of host that inhibits nonradiative relaxation of Eu2+ and on the other hand, the emission self-compensation of Eu2+. Benefiting from synergistic effect of emission compensation and nonradiative transition restriction of Eu2+, as-prepared SPO:5%Eu2+ purple-blue phosphor not only presents superior thermal stability but also high internal quantum efficiency of 95.1% and excellent hydrolysis resistant. Some advanced applications are explored including white LED lighting and wide-color-gamut display. Our work provides in-deep insights into structure-property relationships of thermally stable phosphors. 相似文献