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Ammonia borane at high pressures

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Chinese Science Bulletin 2014年第36期59卷 5227-5234页

作者： jiuhua chen Vadym Drozd Yongzhou Sun Shah Najiba Center for High Pressure Science and Technology Advanced Research Jilin University Center for the Study of Matter at Extreme Conditions Department of Mechanical and Materials Engineering Florida International University Miami FL 33199 USA

Ammonia borane has received tremendous research attention in the past decade because of its potential for chemical hydrogen storage. This paper reviews recent studies about the behavior of ammonia borane at high pressures. While much work is still needed to comprehensively understand the pressure influence on this molecular crystal, a phase diagram based on the available experimental and theoretical data is constructed. Raman spectroscopy studies indicate five transitions upon compression up to 65 GPa at ambient temperature. Diffraction experiments and theoretical studies demonstrate that three of these transitions are first-order phase transformations in the sequence of I4mm-Cmc21-P21-(different) P21, and two are iso-structural. A low-temperature phase(Pmn21) and a high-temperature high-pressure phase(Pmna) are also recognized.

关键词：高温高压硼烷氨衍射实验分子晶体理论数据拉曼光谱环境温度

Mineralogy of the deep lower mantle in the presence of H2O

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National Science Review 2021年第4期8卷 21-28页

作者： Qingyang Hu Jin Liu jiuhua chen Bingmin Yan Yue Meng Vitali B.Prakapenka Wendy L.Mao Ho-Kwang Mao Center for High Pressure Science and Technology Advanced Research(HPSTAR) Department of Geological Sciences Stanford University Center for Study of Matter under Extreme Conditions Department of Mechanical and Materials Engineering Florida International University High Pressure Collaborative Access Team(HPCAT) X-ray Science Division Argonne National Laboratory Center for Advanced Radiation Sources University of Chicago

Understanding the mineralogy of the Earth's interior is a prerequisite for unravelling the evolution and dynamics of our planet. Here, we conducted high pressure-temperature experiments mimicking the conditions of the deep lower mantle（DLM, 1800–2890 km in depth） and observed surprising mineralogical transformations in the presence of water. Ferropericlase,（Mg,Fe）O, which is the most abundant oxide mineral in Earth, reacts with H;2;O to form a previously unknown（Mg,Fe）O;2;H;x;（x ≤ 1）phase. The（Mg,Fe）O;2;H;x;has a pyrite structure and it coexists with the dominant silicate phases,bridgmanite and post-perovskite. Depending on Mg content and geotherm temperatures, the transformation may occur at 1800 km for(Mg;0.6;Fe;0.4;)O or beyond 2300 km for(Mg;0.7;Fe;0.3;)O. The（Mg,Fe）O;2;H;x;is an oxygen excess phase that stores an excessive amount of oxygen beyond the charge balance of maximum cation valences(Mg;2+;, Fe;3+;and H;+;). This important phase has a number of far-reaching implications including extreme redox inhomogeneity, deep-oxygen reservoirs in the DLM and an internal source for modulating oxygen in the atmosphere.

关键词： lower mantle water-mantle interaction ferropericlase high pressure mantle mineralogy

Evidence for oxygenation of Fe-Mg oxides at mid-mantle conditions and the rise of deep oxygen

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National Science Review 2021年第4期8卷 29-34页

作者： Jin Liu chenxu Wang Chaojia Lv Xiaowan Su Yijin Liu Ruilian Tang jiuhua chen Qingyang Hu Ho-Kwang Mao Wendy L.Mao Center for High Pressure Science and Technology Advanced Research (HPSTAR) Department of Geological Sciences Stanford University School of Earth and Space Sciences Peking University SLAC National Accelerator Laboratory Center for Study of Matter at Extreme Conditions Department of Mechanical and Materials Engineering Florida International University

As the reaction product of subducted water and the iron core, FeO2with more oxygen than hematite(Fe2O3) has been recently recognized as an important component in the D" layer just above the Earth’s core-mantle boundary. Here, we report a new oxygen-excess phase(Mg, Fe)2O3+δ(0 < δ < 1, denoted as‘OE-phase’). It forms at pressures greater than 40 gigapascal when(Mg, Fe)-bearing hydrous materials are heated over 1500 kelvin. The OE-phase is fully recoverable to ambient conditions for ex situ investigation using transmission electron microscopy, which indicates that the OE-phase contains ferric iron(Fe3+) as in Fe2O3but holds excess oxygen through interactions between oxygen atoms. The new OE-phase provides strong evidence that H2O has extraordinary oxidation power at high pressure. Unlike the formation of pyrite-type FeO2Hxwhich usually requires saturated water, the OE-phase can be formed with under-saturated water at mid-mantle conditions, and is expected to be more ubiquitous at depths greater than 1000 km in the Earth’s mantle. The emergence of oxygen-excess reservoirs out of primordial or subducted(Mg,Fe)-bearing hydrous materials may revise our view on the deep-mantle redox chemistry.

关键词： subducting slab hydrous phase lower mantle deep oxygen oxygen-excess oxides

An Investigation of Creep Resistance in Grade 91 Steel through Computational Thermodynamics

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Engineering 2020年第6期6卷 644-652页

作者： Andrew Smith Mohammad Asadikiya Mei Yang jiuhua chen Yu Zhong Department of Mechanical and Materials Engineering Florida International UniversityMiamiFL 33174USA Mechanical Engineering Department Worcester Polytechnic InstituteWorcesterMA 01609USA

This study was conducted to understand the relationship between various critical temperatures and the stability of the secondary phases inside the heat-affected-zone(HAZ)of welded Grade 91(Gr.91)steel *** IV cracking has been observed in the HAZ,and it is widely accepted that the stabilities of the secondary phases in Gr.91 steel are critical to the creep resistance,which is related to the crack failure of this *** this work,the stabilities of the secondary phases,including those of the M23C6,MX,and Z phases,were simulated by computational *** cooling and Scheil simulations were carried out in order to understand the phase stability in welded Gr.91 *** effect of four critical temperatures—that is,Acl(the threshold temperature at which austenite begins to form),Ac3(the threshold temperature at which ferrite is fully transformed into austenite),and the M23C6 and Z phase threshold temperatures—on the thickness of the HAZ and phase stability in the HAZ is ***,the simulations presented in this paper explain the mechanisms that can affect the creep resistance of Gr.91 steel,and can offer a possible solution to the problem of how to increase creep resistance at elevated temperatures by optimizing the steel composition,welding,and heat treatment process *** simulation results from this work provide guidance for future alloy development to improve creep resistance in order to prevent type IV cracking.

关键词： Grade 91 steel Creep resistance Ferritic-martensitic steels Welding microstructure Computational thermodynamics Secondary phase Alloy composition

Recent advances in high-pressure science and technology

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Matter and Radiation at Extremes 2016年第1期1卷 59-75页

作者： Ho-Kwang Mao Bin chen jiuhua chen Kuo Li Jung-Fu Lin Wenge Yang Haiyan Zheng Center for High Pressure Science and Technology Advanced Research Shanghai201203PR China

Recently we are witnessing the boom of high-pressure science and technology from a small niche field to becoming a major dimension in physical *** of the most important technological advances is the integration of synchrotron nanotechnology with the minute samples at ultrahigh *** of high pressure have greatly enhanced our understanding of the electronic,phonon,and doping effects on the newly emerged graphene and related 2D layered *** pressure has created exotic stoichiometry even in common Group 17,15,and 14 compounds and drastically altered the basic σ and π bonding of organic *** pressure measurements enable us to study the rheology and flow of mantle minerals in solid state,thus quantitatively constraining the *** also introduce a new approach to understand defect and plastic deformations of nano *** examples open new frontiers of high-pressure research.

关键词： High pressure science and technology Static high pressure Synchrotron X-ray probe Equation of state

Effect of Precipitation on the Hardness of Ternary Metallic Glass

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Advances in Materials Physics and Chemistry 2017年第6期7卷 255-262页

作者： Xue Liang jiuhua chen Maria Teresa Mora Jose Fernandez Urdaneta Qiaoshi Zeng MME/CeMSEC Florida International University EC Miami FL USA Center for High Pressure Science and Technology Advanced Research Changchun China

The present study reports effects of annealing treatment on the hardness of Ce75Al23Si2 rare earth-based metallic glasses (REMG). Then specimens were annealed at 100°C, 200°C, 250°C, 270°C, and 290°C five different temperatures for 30 minutes. After that, three different characteristic methods, including microindentation, X-ray Diffraction (XRD), and scanning electrical microscope (SEM) were conducted on the as received REMG sample and five annealed samples. XRD data demonstrate that the crystallization occurs in the sample at the annealing temperature as low as 200°C. The microindentation measurement shows that hardness of the REMG sample does not change at all before crystallization occurs in the sample and increases with the annealing temperature in the range of 200°C to 290°C. The average crystal size in the annealed samples was estimated using Debye-Scherrer equation to be 28-42 nm, in consistent with the SEM observation, indicating that nano-crystalline domains may give rise to the enhancement of hardness.

关键词： Ternary Rare Earth-Based Metallic Glasses (REMGs) Microindentation Annealing Treatment Hardness

Density measurements of molten minerals at high pressure using synchrotron x-ray radiography

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Density measurements of molten minerals at high pressure usi...

Influence of TiX (X=B_2 or N) Addition on the Interfacial Microstructure Features of CBN Grains and AgCuTi Composite Filler

18th International Conference on High Pressure Science and Technology

作者： jiuhua chen Donald J.Weidner Michael T.Vaughan Center for High Pressure Research and Department of Geosciences State University of New York at Stony BrookStony BrookNY 11794-2100 USA Center for High Pressure Research and Department of Geosciences State University of New York at Stony BrookStony BrookNY 11794-2100 USA Center for High Pressure Research and Department of Geosciences State University of New York at Stony BrookStony BrookNY 11794-2100 USA

＜正＞ Density of minerals is one of the key parametersfor earth modeling. While density measurements ofcrystalline mincrals at high pressure and temperaturecan be routinely carried out using in-situ diffractiontechniques, experiments to determine density of meltsat static high pressure are rare. Experimentaltechnique has hindered us from studying equation ofstate （EOS） of molten minerals, which is essential forunderstanding earth especially earth’s core. Effortshave been made to measure the density ofnon-crystalline materials under high pressure andtemperature by x-ray absorption [1, 2]. Howeverthis technique requires scanning across a spherical orcylindrical sample, and therefore the sample needs to

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Journal of Wuhan University of Technology(Materials Science) 2010年第4期25卷 579-582页

作者：丁文锋 College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and Astronautics

Joining experiments of CBN grains to AISI 1045 steel were conducted using Ag-Cu-Ti composite fillers containing TiX （X=B2 or N） particles at 920 ℃ for 5 min. The influences of TiB2 and TiN particles on the interfacial microstructure features between CBN and filler were investigated comparatively. The experimental results show that TiN particles are more effective than TiB2 ones to control the interfacial reaction and particularly the resultants. Thermodynamic analysis reveals that the varied interfacial reaction induced by the addition of TiB2 and TiN particles is mainly atttributed to the activity change of the B and Ti elements in the brazing reaction system.

关键词： CBN brazing interfacial microstructure chemical reaction TiX addition

基于城市职能的明清金州古城景观格局之发展演变研究

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沈阳建筑大学学报（社会科学版） 2024年第5期26卷 443-450页

作者：张健吕军辉陈九桦沈阳建筑大学建筑与规划学院辽宁沈阳110168

金州古城地处辽东边陲,其城市平面和功能布局既受到军事防御功能的影响,又体现出儒家礼制的特征。古城空间格局在明代已初具规模,又经清代的建设与发展,形成了较为成熟的城市功能和完善的道路体系。将历经时代变迁的金州古城三维城市肌... 详细信息

金州古城地处辽东边陲,其城市平面和功能布局既受到军事防御功能的影响,又体现出儒家礼制的特征。古城空间格局在明代已初具规模,又经清代的建设与发展,形成了较为成熟的城市功能和完善的道路体系。将历经时代变迁的金州古城三维城市肌理变化以二维方式来进行体现,通过对明清两代古城空间结构与营建特点的介绍,直观感受城市空间与职能的发展和演变,进而对金州古城空间形态、功能区域以及城市职能转变的推动力进行了解析,并阐释了城市发展的动因。

关键词：金州古城明清时期空间形态城市职能景观格局