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neutron Diffraction of Large-Volume Samples at High Pressure Using Compact Opposed-Anvil Cells

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Chinese physics Letters 2018年第4期35卷 12-15页

作者：倪小林房雷鸣李欣陈喜平谢雷贺端威寇自力 institute of Atomic and Molecular physics Sichuan University Key Laboratory of Neutron Physics and Institute of Nuclear Physics and Chemistry China Academy of Engineering Physics

neutron diffraction techniques of large-volume samples at high pressure using compact opposed-anvil cells are developed at a reactor neutron source, China＇s Mianyang research reactor. We achieve a high-pressure condition of in situ neutron diffraction by means of a newly designed large-volume opposed-anvil cell. This pressure calibration is based on resistance measurements of bismuth and the neutron diffraction of iron. Pressure calibration experiments are performed at room temperature for a new cell using the tungsten carbide anvils with a tapered angle of 30°, Φ4.5 mm culet diameter and the metal-nonmetal composite gasket with a thickness of 2 mm. Transitions in Bi（Ⅰ–Ⅱ 2.55 GPa, Ⅱ–V 7.7 GPa） are observed at 100 and 300 kN, respectively, by resistance measurements.The pressure measurement results of neutron diffraction are consistent with resistance measurements of bismuth.As a result, pressures up to about 7.7 GPa can routinely and stably be achieved using this apparatus, with the sample volume of 9 mm^3.

关键词： neutron Diffraction of Large-Volume Samples at High Pressure Using Compact Opposed-Anvil Cells

Compressive Behavior of TATB Grains inside TATB-Based PBX Revealed by In-Situ neutron Diffraction

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Chinese physics Letters 2017年第6期34卷 75-78页

作者：田懿王虹张昌盛田强张伟斌李洪佳李建刘本德孙光爱彭太平徐尧龚建 key laboratory for neutron physics of Chinese Academy of Engineering physics Institute of Nuclear Physics and Chemistry Mianyang 621900 institute of Chemical Materials Mianyang 621900

We investigate the （002） lattice strain evolution of triaminotrinitrobenzene （TATB） grains inside one TATB-based plastic bonded explosive （PBX） through the in-situ neutron diffraction. By comparing the untreated specimen with the thermal-treated one, it is found that the volume-average response of measured TATB grains remains nearly elastic during quasi-static uniaxial compression. The observed changes in TATB （002） lattice strains correlate tightly with the evolution of damage. A damage parameter defined by the macroscopically determined residual strain is further used to describe the damage degree of PBX, which suggests that the compressive behavior of TATB-based PBX is significantly influenced bv the damage evolution.

关键词： neutron diffraction QUASISTATIC processes THERMODYNAMIC equilibrium LATTICE theory WAVE diffraction

Influence of thermal and resonance neutron on fast neutron flux measurement by ^(239)Pu fission chamber

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Chinese physics C 2015年第1期39卷 50-53页

作者：曾丽娜王强宋凌莉郑春 institute of nuclear physics and chemistry China Academy of Engineering Physics key laboratory of neutron physics China Academy of Engineering Physics

The ^239Pu fission chambers are widely used to measure fission spectrum neutron flux due to a fiat response to fast neutrons. However, in the meantime the resonance and thermal neutrons can cause a significant influence on the measurement if they are moderated, which could be eliminated by using ^10B and Cd covers. At a column enriched uranium fast neutron critical assembly, the fission reaction rates of ^239gpu are measured as 1.791 × 10^-16 2.350 × 10^-16 and 1.385×10^-15 per second for 15 mm thick ^10B cover, 0.5 mm thick Cd cover, and no cover respectively, while the fission reaction rate of 239pu is rapidly increased to 2.569×10^-14 for a 20 mm thick polythene covering fission chamber. The average 239pu fission cross-section of thermal and resonance neutrons is calculated to be 500 b and 24.95 b with the assumption of 1/v and 1/E spectra respectively, then thermal, resonance and fast neutron flux are achieved to be 2.30×10^6, 2.24×10^6 and 1.04×10^8 cm^-2·s^-1.

关键词： fission chamber neutron flux thermal and resonance neutrons fast neutrons

Recent progress of in-situ characterization of LiNi_(1−x−y)Co_(x)Mn_(y)O_(2) cathodes for lithium metal batteries: A mini review

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Nano Research 2024年第3期17卷 1384-1401页

作者： Huanzhu Lv Xiaoqi Zhu Jun Mei Yuanhua Xia Bin Wang institute of Fundamental and Frontier Science University of Electronic Science and Technology of ChinaChengdu 611731China Chengdu Development Center of Science and Technology China Academy of Engineering PhysicsChengdu 610200China Key Laboratory of Neutron Physics and Institute of Nuclear Physics and Chemistry China Academy of Engineering Physics(CAEP)Mianyang 621999China

In the context of the gradual popularity of electric vehicles(EVs),the development of lithium battery systems with high energy density and power density is regarded as the foremost way to improve the range of EVs.LiNi_(1-x-y)Co_(x)Mn_(y)O_(2)(NCM)cathodes have been the focus of researchers due to their high energy density,excellent power performance,and low-temperature resistance.However,the elaboration of the decay mechanism of NCM cathode based on lithium metal batteries(LMBs)is still being restricted to the primary level.In the past decades,the development and application of advanced in-situ characterization tools have facilitated researchers'understanding of the internal operation mechanism of batteries during charging and discharging.In this minireview,the latest progress of in-situ observation of the NCM cathode by X-ray diffraction(XRD),fourier transform infrared(FT-IR)spectroscopy,Raman spectroscopy,atomic force microscopy(AFM),transmission electron microscope(TEM),optical microscope,and other characterization tools is summarized.The mechanisms of structural degradation,cathode-electrolyte interfaces(CEIs)composition,and dynamic changes of NCM,electrolyte breakdown,and gas production are elaborated.Finally,based on the existing research progress,the opportunities and challenges for future in-situ characterization technology in the study of the mechanism of LMBs are discussed in depth.Therefore,the purpose of this minireview is to summarize recent work that focuses on the outstanding application of in-situ characterization techniques in the mechanistic study of LMBs,and pointing the way to the future development of high energy density and power density LMBs systems.

关键词： lithium metal batteries(LMBs) In-situ characterization LiNi_(1-x-y)Co_(x)Mn_(y)O_(2)(NCM)

Enhancement of neutron irradiation uniformity for the CFBR-Ⅱ fast burst reactor with a biaxial rotational technique

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nuclear Science and Techniques 2015年第2期26卷 27-31页

作者：梁文峰邱东项伟灵孙文清 CAEP key laboratory of neutron physics institute of nuclear physics and chemistry China Academy of Engineering Physics

A biaxial rotational technique is proposed to improve the neutron irradiation uniformity for a large sample,and the theoretical method is established to predict and design the main parameters. The technique used a device to rotate the target sample around two perpendicular axes simultaneously. Numerical calculations found that the lowest common multiple of the two angular speeds should be large enough to improve the uniformity,and the minimal experimental time should be no less than 600 s. For a three-dimensional sample with a size of 20 cm × 12 cm × 14 cm, the maximal non-uniform neutron irradiation factor of the sample is mainly determined by the distance between the center of the sample and of the point neutron source. It was computed to be less than 10% when the distance was no less than 34 cm. Experiments were carried out on the CFBR-II reactor and the experimental results were in good accordance with the theoretical analysis. As a result, the theoretical conclusions given above are reasonable and of reference value for the design of future irradiation experiments.

关键词：照射均匀性脉冲反应堆中子辐照旋转技术双轴实验时间数值计算最小公倍数

Small-angle X-ray analysis of the effect of grain size on the thermal damage of octahydro-1, 3, 5, 7-tetranitro-1, 3, 5, 7 tetrazocine-based plastic-bounded expolsives

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Chinese physics B 2014年第7期23卷 560-564页

作者：闫冠云田强刘佳辉陈波孙光爱黄明李秀宏 key laboratory for neutron physics and institute of nuclear physics and chemistry China Academy of Engineering Physics institute of Chemical Materials China Academy of Engineering Physics institute of Shanghai Apply physics Chinese Academy of Sciences

The microstmcture evolution of plastic-bonded explosives （PBXs） after thermal stimulus plays a key role in PBX performance. In this paper, the nanoscale pores of thermal-treated octahydro-1,3,5,7-tetranitro-1,3,5,7 tetrazocine （HMX）- based PBXs with different HMX particle sizes [approximately 40 （FLIP） and 100 μm （LHP）] were measured using small- angle X-ray scattering （SAXS）. No obvious pore variations were found in the LHP samples heated at 160 ℃ for 6 h, whereas the amount of pores of FHP decreased when subjected to 160 ℃ for 6 h. At 180 ℃, the average pore radii of FHP and LHP decreased from approximately 45 nm to 25 nm, and the total pore volume increased distinctively because of phase transformation. The LHP sample reached a high level of pore content after being held at 180 ℃ for 1 h, whereas FHP required 3 h. Both FHP and LHP had relatively high pore volumes when subjected to 200 ℃ for 1 and 3 h.

关键词： HMX-based plastic-bonded explosives small-angle X-ray scattering pores thermal-treated

Diffusion behavior of helium in titanium and the effect of grain boundaries revealed by molecular dynamics simulation

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Chinese physics B 2016年第7期25卷 349-355页

作者：程贵钧付宝勤侯氢周晓松汪俊 institute of nuclear physics and chemistry China Academy of Engineering Physics key laboratory for Radiation physics and Technology Institute of Nuclear Science and Technology Sichuan University

The microstructures of titanium（Ti）, an attractive tritium（T） storage material, will affect the evolution process of the retained helium（He）. Understanding the diffusion behavior of He at the atomic scale is crucial for the mechanism of material degradation. The novel diffusion behavior of He has been reported by molecular dynamics（MD） simulation for the bulk hcp-Ti system and the system with grain boundary（GB）. It is observed that the diffusion of He in the bulk hcp-Ti is significantly anisotropic（the diffusion coefficient of the [0001] direction is higher than that of the basal plane）,as represented by the different migration energies. Different from convention, the GB accelerates the diffusion of He in one direction but not in the other. It is observed that a twin boundary（TB） can serve as an effective trapped region for He.The TB accelerates diffusion of He in the direction perpendicular to the twinning direction（TD）, while it decelerates the diffusion in the TD. This finding is attributable to the change of diffusion path caused by the distortion of the local favorable site for He and the change of its number in the TB region.

关键词： diffusion grain boundary helium and titanium molecular dynamics

Epoxy-POSS/silicone rubber nanocomposites with excellent thermal stability and radiation resistance

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Chinese Chemical Letters 2022年第7期33卷 3534-3538页

作者： Mengni Shi Yinyong Ao Lei Yu Lang Sheng Shuangxiao Li Jing Peng Hongbing Chen Wei Huang Jiuqiang Li Maolin Zhai Beijing National laboratory for Molecular Sciences Radio Chemistry and Radiation Chemistry Key Laboratory of Fundamental ScienceThe Key Laboratory of Polymer Chemistry and Physics of the Ministry of EducationCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing 100871China institute of nuclear physics and chemistry China Academy of Engineering PhysicsMianyang 621900China

Due to the rigid Si-O-Si backbone,silicone rubber(SR)have a widespread application in extreme environment such as high temperature and high-level radiation.However,the radiation stability of SR still does not meet the practical needs in special radiation environments.Herein we prepared epoxy POSS(e POSS)/SR nanocomposites with excellent thermal stability and radiation resistance.As a physical crosslinking point in the SR,addition of small amount of ePOSS not only enhanced the mechanical properties of the matrix,but also improved its thermal stability greatly due to their good compatibility.e POSS/SR had higher radiation stability in air than SR owing to the inhibition of radiation oxidation by ePOSS,and the yield of main gaseous radiolysis products(CH_(4),H_(2),CO and CO_(2))of SR and ePOSS/SR nanocomposites was determined.By analyzing the changes of chemical structure,thermal properties and mechanical properties of the ePOSS/SR nanocomposite,combined with the characteristics of gas products afterγ-irradiation,the radiation induced crosslinking and degradation mechanism of the nanocomposites was proposed comprehensively.

关键词： POSS Silicone rubber Thermal stability Radiation resistance Radiation crosslinking and degradation mechanism

Development of a displacement-reactivity feedback model for dynamic behavior simulation in fast burst reactor

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nuclear Science and Techniques 2019年第5期30卷 82-91页

作者： Jiang-Meng Wang Hui Gao Qi-Lin Xie Xiao-Qiang Fan Da-Zhi Qian key laboratory of neutron physics China Academy of Engineering Physics institute of nuclear physics and chemistry China Academy of Engineering Physics

In this study, a displacement-reactivity feedback model, which can directly represent the inherent ‘‘thermal expansion extinction effect'' of fast burst reactors(FBRs),was developed with the aid of the static neutron transport component of the FBR-MPC code. Dynamic behaviors of bursts in the Godiva I reactor were simulated by coupling the simplified multiphysics models consisting of the point kinetic equations for neutronics, adiabatic equation for temperature, and thermoelastic equations for displacement/stress with the developed model. The results were compared with the corresponding experimental data and those obtained using the traditional fission yield(temperature rise)-reactivity feedback models. It was found that the developed model can provide good results for the bursts with no or a small inertia effect. For the bursts with a prominent inertia effect, the smaller burst width and asymmetric distribution of the fission rate curve, noticed in the experiments but not evident using the traditional models, can be reproduced. In addition, the realistic oscillations in reactivity and fission rate caused by the core vibration, as well as the deeper sub-prompt criticality in the plateau following the burst, can be observed. Therefore, the developed displacement-reactivity feedback model can be expected to be an effective tool for calculating the dynamic behaviors of bursts.

关键词： Displacement-reactivity feedback model Prompt supercritical Coupled calculation Fast burst reactor