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Chord length sampling correction analysis for dispersion fuel in Monte Carlo simulation

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Nuclear Science and Techniques 2024年第4期35卷 57-64页

作者： Zhao-Yu Liang Ding She Yu-Tong Wen Lei Shi Institute of Nuclear and New Energy Technology(INET) Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of EducationTsinghua UniversityBeijing 100084China

Dispersion fuels,knowned for their excellent safety performance,are widely used in advanced reactors,such as hightemperature gas-cooled *** with deterministic methods,the Monte Carlo method has more advantages in the geometric modeling of stochastic *** explicit modeling method has high computational accuracy and high computational *** chord length sampling(CLS)method can improve computational efficiency by sampling the chord length during neutron transport using the matrix chord length?s probability density *** study shows that the excluded-volume effect in realistic stochastic media can introduce certain deviations into the CLS.A chord length correction approach is proposed to obtain the chord length correction factor by developing the Particle code based on equivalent transmission *** numerical analysis against reference solutions from explicit modeling in the RMC code,it was demonstrated that CLS with the proposed correction method provides good accuracy for addressing the excludedvolume effect in realistic infinite stochastic media.

关键词： Stochastic media Monte Carlo Chord length sampling Excluded-volume effect Chord length correction

Progress and prospect of Pt-based catalysts for electrocatalytic hydrogen oxidation reactions

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Nano Research 2024年第3期17卷 960-981页

作者： Xu Zhang Ying Xie Lei Wang key laboratory of Functional Inorganic Material Chemistry Ministry of Education of the People’s Republic of ChinaHeilongjiang UniversityHarbin 150080China

To achieve the goals of the peak carbon dioxide emissions and carbon neutral,the development and utilization of sustainable clean energy are extremely *** fuel cells are an important system for converting hydrogen energy into electrical ***,the slow hydrogen oxidation reaction(HOR)kinetics under alkaline conditions has limited its ***,elucidating the catalytic mechanism of HOR in acidic and alkaline media is of great significance for the construction of highly active and stable *** terms of practicality,Pt is still the primary choice for commercialization of fuel *** the above basis,we first introduced the hydrogen binding energy theory and bifunctional theory used to describe the HOR activity,as well as the pH *** that,the rational design strategies of Pt-based HOR catalysts were systematically classified and summarized from the perspective of activity *** addition,we further emphasized the importance of theoretical simulations and in situ characterization in revealing the HOR mechanism,which is crucial for the rational design of ***,the practical application of Pt-based HOR catalysts in fuel cells was also *** closing,the current challenges and future development directions of HOR catalysts were *** review will provide a deep understanding for exploring the mechanism of highly efficient HOR catalysts and the development of fuel cells.

关键词： Pt-based catalysts hydrogen oxidation reaction(HOR) electrocatalytic mechanism hydrogen binding energy theory bifunctional theory

Solvent transport dynamics and its effect on evolution of mechanical properties of nitrocellulose(NC)-based propellants under hot-air drying process

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Defence Technology（防务技术） 2024年第2期32卷 262-270页

作者： Enfa Fu Mingjun Yi Qianling Liu Zhenggang Xiao key laboratory of Special Energy Materials Ministry of EducationSchool of Chemistry and Chemical EngineeringNanjing University of Science and TechnologyNanjing 210094People's Republic of China

Appropriate drying process with optimized controlling of drying parameters plays a vital role in the improvement of the quality and performance of propellant ***,few research on solvent transport dynamics within NC-based propellants was reported,and its effect on the evolution of mechanical properties was not interpreted *** study is conducted to gain a comprehensive understanding of hot-air drying for NC-based propellants and clarify the effect of temperature on solvent transport behavior and further the change of mechanical properties during *** drying kinetic curves show the drying time required is decreased but the steady solvent content is increased and the drying rate is obviously increased with the increase of hot-air temperatures,indicating hot-air temperatures have a significant effect on drying kinetics.A modified drying model was established,and results show it is more appropriate to describe solvent transport behavior within NC-based ***,two linear equations were established to exhibit the relationship between solvent content and its effect on the change of tensile properties,and the decrease of residual solvent content causes an obvious increase of tensile strength and tensile modulus of propellant products,indicating its mechanical properties can be partly improved by adjustment of residual solvent *** outcomes can be used to clarify solvent transport mechanisms and optimize drying process parameters of double-based gun propellants.

关键词： Nitrocellulose-based propellants Solvent transport dynamics Mechanical properties Drying kinetics Effective solvent diffusion coefficient

Engineering oxygen vacancies on Tb-doped ceria supported Pt catalyst for hydrogen production through steam reforming of long-chain hydrocarbon fuels

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Chinese Journal of Chemical Engineering 2024年第4期68卷 181-192页

作者： Zhourong Xiao Changxuan Zhang Peng Li Desong Wang Xiangwen Zhang Li Wang Jijun Zou Guozhu Li State key laboratory of Metastable Materials Science and Technology(MMST) Hebei Key Laboratory of Applied ChemistryCollege of Environmental and Chemical EngineeringYanshan UniversityQinhuangdao 066004China key laboratory for Green Chemical Technology of ministry of education School of Chemical Engineering and TechnologyTianjin UniversityTianjin 300072China

Steam reforming of long-chain hydrocarbon fuels for hydrogen production has received great attention for thermal management of the hypersonic vehicle and fuel-cell *** this work,Pt catalysts supported on CeO_(2)and Tb-doped CeO_(2)were prepared by a precipitation *** physical structure and chemical properties of the as-prepared catalysts were characterized by powder X-ray diffraction,scanning electron microscopy,transmission electron microscopy,Raman spectroscopy,H_(2)temperature programmed reduction,and X-ray photoelectron *** results show that Tb-doped CeO_(2)supported Pt possesses abundant surface oxygen vacancies,good inhibition of ceria sintering,and strong metal-support interaction compared with CeO_(2)supported *** catalytic performance of hydrogen production via steam reforming of long-chain hydrocarbon fuels(n-dodecane)was *** with 2Pt/CeO_(2),2Pt/Ce_(0.9)Tb_(0.1)O_(2),and 2Pt/Ce_(0.5)Tb_(0.5)O_(2),the 2Pt/Ce_(0.7)Tb_(0.3)O_(2)has higher activity and stability for hydrogen production,on which the conversion of n-dodecane was maintained at about 53.2%after 600 min reaction under 700℃at liquid space velocity of 9 ml·g^(-1)·h^(-1).2Pt/CeO_(2)rapidly deactivated,the conversion of n-dodecane was reduced to only 41.6%after 600 min.

关键词： Steam reforming n-Dodecane Hydrogen production Pt-based catalyst Oxygen vacancy CeO_(2)

Effect of carbon material and surfactant on ink property and resulting surface cracks of fuel-cell microporous layers

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Chinese Journal of Chemical Engineering 2024年第5期69卷 1-12页

作者： Zhekun Chen Weitong Pan Longfei Tang Xueli Chen Fuchen Wang Engineering Research Center of Resource Utilization of Carbon-containing Waste with Carbon Neutrality Ministry of EducationEast China University of Science and TechnologyShanghai 200237China key laboratory of Pressure Systems and Safety Ministry of EducationEast China University of Science and TechnologyShanghai 200237China

Ensuring the consistency of electrode structure in proton-exchange-membrane fuel cells is highly desired yet challenging because of wide-existing and unguided cracks in the microporous layer(MPL). The first thing is to evaluate the homogeneity of MPL with cracks quantitatively. This paper proposes the homogeneity index of a full-scale MPL with an area of 50 cm~2, which is yet to be reported in the literature to our knowledge. Besides, the effects of the carbon material and surfactant on the ink and resulting MPL structure have been studied. The ink with a high network development degree produces an MPL with low crack density, but the ink with high PDI produces an MPL with low crack homogeneity. The polarity of the surfactant and the non-polarity of polytetrafluoroethylene(PTFE) are not mutually soluble,resulting in the heterogeneous PTFE distribution. The findings of this study provide guidelines for MPL fabrication.

关键词： Proton-exchange-membrane fuel cell Microporous layer Crack density Crack homogeneity Polytetrafluoroethylene distribution Surfactant

Introducing sulfur to nickel-iron selenide for high-efficiency alkaline seawater electrolysis

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Science China Chemistry 2024年第8期67卷 2747-2754页

作者： Xuanwa Chen Yanhui Yu Xingqi Han Huan Wang Yingjie Hua Daoxiong Wu Peilin Deng Juanxiu Xiao Xinlong Tian Jing Li School of Marine Science and Engineering Hainan Provincial Key Lab of Fine ChemistrySchool of Chemistry and Chemical EngineeringHainan UniversityHaikou 570228China key laboratory of advanced Energy Materials Chemistry(ministry of education) College of ChemistryNankai UniversityTianjin 300071China key laboratory of Electrochemical Energy Storage and Energy Conversion of Hainan Province School of Chemistry and Chemical EngineeringHainan Normal UniversityHaikou 571158China

Seawater electrolysis is an effective way to obtain hydrogen(H_(2))in a sustainable ***,the lack of electrocatalysts with high activity,stability,and selectivity for oxygen evolution reaction(OER)severely hinders the development of seawater electrolysis ***,sulfur-doped nickel-iron selenide nanosheets(S-NiFeSe_(2))were prepared by an ion-exchange strategy and served as highly active OER electrocatalyst for alkaline seawater *** overpotential is 367 m V,and it can run stably for over 50 h at 100 m A cm^(-2).Excitingly,the S-NiFeSe_(2)||Pt/C pair exhibits cell voltage of 1.54 V at 10 m A cm^(-2)under alkaline seawater conditions,which can run smoothly for 100 h without decay,and the efficiency of electricity-tohydrogen(ETH)energy conversion reaches more than 80%.Such electrode,with abundant accessible reactive sites and good corrosion resistance,is a good candidate for seawater ***,density functional theory calculations reveal that the surface sulfur atoms can activate the adjacent Ni sites and decrease the free energy changes of the associated intermediates at the adjacent Ni sites for OER,and the step of~*OH→~*O is the potential rate-limiting *** this work,the true reactive site in nickel-iron selenides is the Ni sites,but not the Fe sites as commonly believed.

关键词： S-doping nickel-iron selenide electrocatalysts oxygen evolution reaction alkaline seawater electrolysis

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Deciphering dynamic surface of PtRu alloy nanocatalysts to revisit their synergistic effects during the electrooxidation

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Science China Chemistry 2024年第7期67卷 2224-2233页

作者： Xiao-Chong Li Bo Wang Zhou Yu Qiang Wan Ju-Fang Zheng Emmanuel Maisonhaute Xiao-Shun Zhou Ya-Hao Wang key laboratory of the ministry of education for advanced Catalysis Materials Institute of Physical ChemistryZhejiang Normal UniversityJinhua 321004China Laboratoire Interface et Systèmes Electrochimiques CNRS UMR 8235Sorbonne UniversitéF-75252 Paris cedex 5France

Correlating dynamic structural transformation of catalysts with the surface intermediate species under operating conditions is critical for updating the understanding of structure–performance ***,we probe the electrochemical potentialdependent surface structures and adsorbed intermediates on PtRu binary alloy nanocatalysts to revisit its synergistic mechanisms for CO electrooxidation enhanced ***-situ spectral characteristics by using modified shell-isolated nanoparticle-enhanced Raman spectroscopy,show that in acidic solution,when the potential is positively scanned from 0.1 V to 1.5 V relative to reversible hydrogen electrode(RHE),the surface of the alloy catalyst evolves from metallic PtRu to adsorbed oxygen gradually covering and accumulating on Ru sites(denoted as PtRuO_(x),x≤2),forming segregated RuO_(2),and finally forming a threedimensional oxide layer(denoted as 3D PtRuO_(4)).Moreover,molecular evidence associated with periodic density functional theory calculations reveals that electronic effects promote ruthenium to become more oxidizable and *** particular,we found here that ^(*)O and ^(*)OH at surface RuO_(x) sites are highly efficient CO oxidation active species in comparison to the same entities adsorbed on metallic Ru *** work sheds light on the complex surface dynamic process of practical Pt-based binary nanocatalysts and improves the understanding of synergistic mechanism for the development of fuel cell devices.

关键词： in-situ Raman spectroscopy surface evolution bifunctional mechanism PtRu electrooxidation

Review on heat-to-power conversion technologies for hypersonic vehicles

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Chinese Journal of Aeronautics 2024年第5期37卷 148-179页

作者： Yinke QI Xiaofeng MA Peixue JIANG Yinhai ZHU key laboratory for Thermal Science and Power Engineering of ministry of education Department of Energy and Power EngineeringTsinghua UniversityBeijing 100084China Beijing key laboratory of CO_(2)Utilization and Reduction Technology Department of Energy and Power EngineeringTsinghua UniversityBeijing 100084China

Hypersonic vehicles have enormous military and economic value,while their power and thermal protection demands will increase substantially with the rise in Mach number and *** the tremendous high-quality heat on the vehicle surface and engine wall into electrical energy through heat-to-power technologies will not only play a role in thermal protection,but also supply power for the *** paper provides a comprehensive review of heat-to-power conversion technologies on hypersonic vehicles,including the indirect conversion of Brayton and Rankine cycles,direct conversion of thermoelectric materials,and combined *** the open Brayton cycle with hydrocarbon fuel as the working fluid,the Power-to-Weight Ratio(PWR)can achieve the highest,at around 1.8,due to the high PWR of the hydrocarbon fuel turbine and the few components of the ***,its work capacity is limited by the flow rate of the supplied *** closed Brayton cycle can maintain a relatively high PWR,ranging from 0.2 to 0.8,while achieving relatively high output power and conversion *** Rankine cycle has a higher PWR,its range is close to that of the closed Brayton cycle,peaking at about *** thermoelectric materials technology has a small power generation level,making it more suitable for scenarios with low power *** review provides a basis for selecting and developing heat-to-power conversion technologies on hypersonic vehicles.

关键词： Hypersonic vehicles Heat-to-power conversion Brayton cycle Rankine cycle Thermoelectric materials

A brand new green coating technology for realizing the regulation of spherical propellant energy release process

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Defence Technology（防务技术） 2024年第6期36卷 78-94页

作者： Wenhao Fan Yajun Ding Zhongliang Xiao School of Chemistry and Chemical Engineering Nanjing University of Science and TechnologyNanjing210094China key laboratory of Special Energy Materials Nanjing University of Science and TechnologyMinistry of EducationNanjing 210094China

To achieve the controllable release of energy of nitrocellulose-based propellants,this paper combines the cellulose-based nanocomposites aqueous coating(Surelease?-NC)with fluidized bed coating equipment to successfully prepare the coated spherical propellant for the first *** effects of fluidized bed coating temperature,air velocity,flow speed and atomization pressure on the adhesion rate,coating integrity and coating uniformity of the coated spherical propellant were investigated,and the preparation of coated spherical propellant with homogeneous size and structural integrity was achieved for the first *** microscopic morphology,chemical structure,water vapor adsorption behavior,combustion performance,and ageing resistance property of the coated spherical propellant were systematically investigated by,Fourier transforms infrared spectroscopy(FTIR),Micro confocal raman spectrometer,field scanning electron microscopy(SEM),dynamic vapor adsorption techniques,and closed bomb test,confirming the surface core-shell structure and the tightly bonded interfacial structure of coated spherical ***,the coated spherical propellant has good hygroscopic,excellent progressive burning and long storage stability.

关键词： Nanocomposites aqueous coating Fluidized bed coating equipment Coated spherical propellant Controllable release of energy Long storage stability