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Synergetic deformation mechanism in hierarchical twinned high-entropy alloys

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Journal of Materials Science & Technology 2022年第7期102卷 80-88页

作者： Wenjun Lu Jianjun Li Department of Mechanical and Energy Engineering Southern University of Science and TechnologyShenzhen 518055China max-planck-institut für Eisenforschung Max-Planck-Straße 1Düsseldorf 40237Germany College of Mechanical and Electrical Engineering Central South UniversityChangsha 410083China

The mechanical properties of crystalline materials can be efficiently optimized using a hierarchical twinned *** deformation mechanisms for coherentΣ3 boundaries generally involve three basic models:cross-slip,partial dislocation step,and full dislocation *** this study,we report a novel deformation mechanism that allows the co-existence of twin-separation,phase transformations,grain rotation,and cracking,around a triple junction of twin boundaries in a hierarchical twinned highentropy *** deformation mechanisms in the reference high-entropy alloy(Fe-30 Mn-10 Co-10 Cr at.%)were investigated using *** triple junction of the hierarchical twinned structure gradually deformed during in-situ strain and showed mechanisms significantly different from that observed in the purely twinned *** new mechanisms are referred to as“novel synergetic deformation mechanisms of hierarchical twin boundaries”.Understanding the fundamental mechanisms of the hierarchical twin boundaries under deformation could assist the design of strong and ductile bulk materials with hierarchical twinned structure.

关键词： In-situ LAADF-STEM Hierarchical twin boundaries Twin-separation Phase transformations Grain rotation Cracking

BL Lacertae: Hard Optical Spectrum and GeV γ-ray Emission

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Chinese Journal of Astronomy and Astrophysics 2004年第3期4卷 231-246页

作者： Shan-JieQian Xi-ZhenZhang T.P.Krichbaum NationalAstronomicalObservatories ChineseAcademyofSciencesBeijing100012 max-planck-institutfürRadioastronomie AufdemHügel6953121BonnGermany

The spectral energy distribution (SED) of the γ-ray flare observed inJuly 1997 in BL Lacertae is re-considered. It is pointed out that the optical observa-tions made by Webb et al. showed the associated optical flare has a hard spectrum(the average spectral index αopt～ 0.48, F_v∝v^(-α)), and the ASCA observationsmade by Tanihata et al. showed very steep spectra in the soft X-ray band (0.7-1.5 keV) (α_x～3-4). We find that the flux densities and spectral indices in both theoptical and soft X-ray bands are closely consistent with a ‘canonical' synchrotronspectrum emitted by relativistic electrons of a power-law energy distribution witha high energy cutoff, and thus the peak of the SED of the synchrotron radiation (inrepresentation of vF_v) is located in the EUV -- soft X-ray bands. Therefore, theGeV γ-ray emission observed in the July 1997 outburst may be mainly due to thesynchrotron self-Compton (SSC) process, contrasting with the current explanationsin terms of external radiation Compton (ERC) process, in which the seed photonsare mostly taken to be the UV emission from the clouds of the broad emission lineregion. We argue that the hard optical spectra observed during the γ-ray outburstmay be an important signature for the acceleration of high energy electrons (γ_e～10~4)in the γ-ray emitting region.

关键词： galaxies:compact gamma rays:observations quasars:individual:BL Lacertae

碳纳米管的表征和重金属阴离子吸附性能(英文)

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新型炭材料 2011年第1期26卷 57-62页

作者：徐艺军 Rosa Arrigo 刘晰苏党生 Fritz Haber institute of the max planck Society

通过化学修饰使碳纳米管表面富含各种氧功能团,利用XPS和TPD方法表征了碳纳米管表面氧功能团的化学物理特性。研究发现:对比于未修饰的碳纳米管,化学修饰后的碳纳米管对高毒性的铬酸根阴离子有很强的吸附能力;其优异的吸附能力归结于金... 详细信息

通过化学修饰使碳纳米管表面富含各种氧功能团,利用XPS和TPD方法表征了碳纳米管表面氧功能团的化学物理特性。研究发现:对比于未修饰的碳纳米管,化学修饰后的碳纳米管对高毒性的铬酸根阴离子有很强的吸附能力;其优异的吸附能力归结于金属阴离子与纳米管表面氧功能团的相互作用。研究指出碳纳米管可以作为替代吸附材料用于处理废水中重金属阴离子。

关键词：碳纳米管铬酸根离子吸附化学修饰

Purified oxygenand nitrogen-modified multi-walled carbon nanotubes as metal-free catalysts for selective olefin hydrogenation

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Journal of Energy Chemistry 2013年第2期22卷 312-320页

作者： Peirong Chen Ly May Chew Aleksander Kostka Kunpeng Xie Martin Muhler Wei Xia Laboratory of Industrial Chemistry Ruhr-University Bochum Department of Microstructure Physics and Alloy Design Max-Planck-Institute for Iron Research

Oxygen and nitrogen-functionalized carbon nanotubes （OCNTs and NCNTs） were applied as metal-free catalysts in selective olefin hydro- genation. A series of NCNTs was synthesized by NH3 post-treatment of OCNTs. Temperature-programmed desorption, N2 physisorption, Raman spectroscopy, high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy were employed to characterize the surface properties of OCNTs and NCNTs, aiming at a detailed analysis of the type and amount of oxygen- and nitrogen-containing groups as well as surface defects. The gas-phase treatments applied for oxygen and nitrogen functionalization at elevated temperatures up to 600 ℃ led to the increase of surface defects, but did not cause structural damages in the bulk. NCNTs showed a clearly higher activity than the pristine CNTs and OCNTs in the hydrogenation of 1,5-cyclooctadiene, and also the selectivity to cyclooctene was higher. The favorable catalytic properties are ascribed to the nitrogen-containing surface functional groups as well as surface defects related to nitrogen species. In contrast, oxygen-containing surface groups and the surface defects caused by oxygen species did not show clear contribution to the hydrogenation catalysis.

关键词： multi-walled carbon nanotubes nitrogen-containing functional groups oxygen-containing functional groups metal-free catalyst selectiveolefin hydrogenation

Forging strength-ductility unity in a high entropy steel

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Journal of Materials Science & Technology 2022年第18期113卷 158-165页

作者： S.J.Tsianikas Y.Chen J.Jeong S.Zhang Z.Xie School of Mechanical Engineering The University of AdelaideSA 5005Australia Centre for Advanced Thin Film Materials and Devices Faculty of Materials and EnergySouthwest UniversityChongqing 400715China max-planck-institut für Eisenforschung Max-Planck-Straße 1Düsseldorf 40237Germany

Fe_(72.4)Co_(13.9)Cr_(10.4)Mn_(2.7)B_(0.34)high entropy steel was prepared by magnetron *** alloy exhibits a high yield strength of 2.92±0.36 GPa while achieving appreciable plasticity of 13.7±1.9%at the ultimate compressive strength(3.37±0.36 GPa).The distribution of iron and chromium shows an un-usual,characteristic spinodal-like pattern at the nanometer scale,where compositions of Fe and Cr show strong anticorrelation and vary by as much as 20 at.%.The high strength is largely attributable to the compositional modulations,combined with fine grains with body-centered cubic(BCC)crystal structure,as well as grain boundary segregation of interstitial *** impressive plasticity is accommodated by the formation and operation of multiplanar,multicharacter dislocation slips,mediated by coherent in-terfaces,and controlled by shear *** excellent strength-ductility combination is thus enabled by a range of distinctive strengthening mechanisms,rendering the new alloy a potential candidate for safety-critical,load-bearing structural applications.

关键词： Deformation mechanisms Micromechanical testing Compositional fluctuations Body-centered cubic High entropy steel

Interstellar Refractive Scintillation and Intraday Polarization Angle Swings

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Chinese Journal of Astronomy and Astrophysics 2005年第1期5卷 27-40页

作者： Shan-JieQian Xi-ZhenZhang A.Kraus NationalAstronomicalObservatories ChineseAcademyofSciencesBeijing100012 max-planck-institutfiirRadioastronomie aufdemHiigel6953121BonnGermany

Intraday polarization angle swings of ～180° observed in two sources (QSO0917+624 and QSO 1150+812) are discussed in the framework of refractive interstellar scintillationby a continuous interstellar medium. Model-fits to the I-, Q- and U- light curves were made for bothsources. It is shown that for the case of 0917+624 both the intraday intensity variations and thepolarization angle swing of ～180° could be explained consistently in terms of a four-componentmodel, which comprises one steady and two scintillating polarized components and one furthernon-polarized scintillating component. The polarization angle swing of ～180° observed in 1150+812,which occurred when the polarized flux density was almost constant, could not be explained in termsof refractive scintillation by a continuous medium and might be due to other mechanisms (e.g.,scintillation by interstellar clouds).

关键词： radio continuum galaxies polarization intraday variability scattering refractive scintillation quasars individual: QSO 0917+624 and 1150+812

The Galactic halo magnetic field revisited

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research in Astronomy and Astrophysics 2010年第12期10卷 1287-1297页

作者： Wolfgang Reich max-planck-institut für Radioastronomie Auf dem Hügel 69 53121 Bonn Germany

Recently, Sun et al. published new Galactic 3D-models of magnetic fields in the disk and halo of the Milky Way and the distribution of cosmic-ray electron density by taking into account the thermal electron density model NE2001 by Cordes ＆ Lazio. The models successfully reproduce observed continuum and polarization all-sky maps and the distribution of rotation measures of extragalactic sources across the sky. However, the model parameters obtained for the Galactic halo, although reproducing the observations, seem physically unreasonable： the magnetic field needs to be significantly stronger in the Galactic halo than in the plane and the cosmic-ray distribution must be truncated at about 1 kpc to avoid excessive synchrotron emission from the halo. The reason for these unrealistic parameters was the low scale-height of the warm thermal gas of about 1 kpc adopted in the NE2001 model. However, this scale- height seemed reasonable and was well studied by numerous investigations. Recently, the scale-height of the warm gas in the Galaxy was revised by Gaensler et al. to about 1.8 kpc, by showing that the 1 kpc scale-height results from a systematic bias in the analysis of pulsar data. This implies a higher thermal electron density in the Galactic halo, which in turn reduces the halo magnetic field strength to account for the observed rotation measures of extragalactic sources. We slightly modified the NE2001 model according to the new scale-height and revised the Sun et al. model parameters accordingly： the strength of the regular halo magnetic field is now 2 μG or lower, and the physically unrealistic cutoff in z for the cosmic-ray electron density is removed. The simulations based on the revised 3D-models reproduce all-sky observations as before.

关键词： ISM: magnetic fields -- ISM: structure -- radio continuum: ISM

The Chlamydomonas Chloroplast HLP Protein Is Required for Nucleoid Organization and Genome Maintenance

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Molecular Plant 2009年第6期2卷 1223-1232页

作者： Daniel Karcher Dietrich Koster Anne Schadach Anja Klevesath Ralph Bock max-planck-lnstitut fur Molekulare Pflanzenphysiologie Am Muhlenberg 1 D-14476 Potsdam-Golm Germany

The chloroplasts genome （plastome） occurs at high copy numbers per cell. Several chloroplast genome copies are densely packed into nucleoprotein particles called nucleoids. How genome packaging occurs and which proteins organize chloroplast nucleoids are largely unknown. Here, we have analyzed the Chlamydornonas reinhardtii homolog of the bacterial architectural DNA-binding protein HU, the histone-like protein HLP. We show that the Chlarnydornonas HLP protein is targeted to chloroplasts and associates with nucleoids. Knockdown of HLP gene expression by RNA interference （RNAi） alters the structure of chloroplast nucleoids and appears to reduce the level of compaction of chloroplast DNA. Unexpectedly, also chloroplast genome copy numbers are significantly decreased in the RNAi strains, suggesting that, in addition to its architectural role in nucleoid formation, the HIP protein is also involved in chloroplast genome maintenance.

关键词： Chloroplast nucleoid Chlamydomonas reinhardtii HLP DNA-binding protein genome maintenance

Importance of hydrogenotrophic, aceticlastic and methylotrophic methanogenesis for methane production in terrestrial, aquatic and other anoxic environments: A mini review

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Pedosphere 2020年第1期30卷 25-39页

作者： Ralf CONRAD max planck institute for Terrestrial Microbiology Karl-von-Frisch-Str.10Marburg 35043(Germany)

Microbial methanogenesis is a major source of the greenhouse gas methane(CH4).It is the final step in the anaerobic degradation of organic matter when inorganic electron acceptors such as nitrate,ferric iron,or sulfate have been *** of this degradation pathway is important for the creation of mechanistic models,prediction of future CH4 emission scenarios,and development of mitigation *** most anoxic environments,CH4 is produced from either acetate(aceticlastic methanogenesis)or hydrogen(H2)plus carbon dioxide(CO2)(hydrogenotrophic methanogenesis).Hydrogen can be replaced by other CO2-type methanogenesis,using formate,carbon monoxide(CO),or alcohols as *** ratio of these two pathways is tightly constrained by the stoichiometry of conversion *** the degradation of organic matter is complete(e.g.,degradation of straw in rice paddies),then fermentation eventually results in production of acetate and H2 at a ratio of>67%aceticlastic andres,***,temperature can strongly influence the methanogenic pathway,which may range from 100%aceticlastic methanogenesis at low temperatures to 100%hydrogenotrophic methanogenesis at high ***,if the degradation of organic matter is not complete(e.g.,degradation of soil organic matter),the stoichiometry of fermentation is not tightly constrained,resulting,for example,in the preferential production of H2,followed by hydrogenotrophic *** production of CH4 by either aceticlastic or hydrogenotrophic methanogenesis can also happen if one of the methanogenic substrates is not consumed by methanogens but is,instead,accumulated,volatilized,or utilized *** methano

关键词： electron acceptor fermentation methanogenic pathway organic matter degradation pH soil microbial community temperature Wood-Ljungdahl pathway