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USING THE SKEW-SYMMETRIC ITERATIVE METHODS FOR SOlUTION OF AN INDEFINITE NONSYMMETRIC lINEAR SYSTEMS

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Journal of Computational Mathematics 2014年第3期32卷 266-271页

作者： b.l. Krukier l.A. Krukier Southern Federal University Computer Center Rostov-on-Don Russia

The concept of the field of value to localize the spectrum of the iteration matrices of the skew-symmetric iterative methods is further exploited. Obtained formulas are derived to relate the fields of values of the original matrix and the iteration matrix. This allows us to determine theoretically that indefinite nonsymmetric linear systems can be solved by this class of iterative methods.

关键词： Skew-symmetric iterative methods Indefinite nonsymmetric linear systems.

Surface Characterization and Cell Response of binary Ti-Ag Alloys with CP Ti as Material Control

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Journal of Materials Science & Technology 2012年第9期28卷 779-784页

作者： b.b. Zhang K.J. Qiu b.l. Wang l. li Y.F. Zheng Center for biomedical Materials and Engineering Harbin Engineering University Harbin 150001 China Department of Materials Science and Engineering College of Engineering Peking University Beijing 100871 China

In this study, the surface passive films, dissolution behavior and biocompatib.l.ty of Ti-Ag alloys （with 5%, 10% and 20% Ag） were evaluated by X-ray diffraction （XRD） tests, electrochemical corrosion tests, X-ray photoelectron spectroscopy （XPS） tests, dissolution tests and in-vitro cytotoxicity tests. The surface films on the Ti-20Ag alloy are rich in Ti and much deficient in Ag with respect to alloy composition, as identified by XPS. Compared to CP Ti, Ti-SAg and Ti-20Ag alloys show larger impedances and lower capacitances, which can be associated with an increase of the passive layer thickness. Moreover, all Ti-Ag alloys exhibit negligible or low metal release in the test solutions. The in-vitro cytotoxicity results show Ti-Ag alloys seem to be as cytocompatible as CP Ti. From the viewpoint of surface passive film and cytotoxicity, Ti-SAg and Ti-20Ag are considered to be more suitable for dental applications.

关键词： Ti-Ag alloy Surfaces Electrochemical corrosion Cytotoxicity

EFFECTS OF TREATMENT TEMPERATURE ON THE MICROSTRUCTURE AND MAGNETIC PROPERTIES OF Fe-N THIN FIlMS

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Acta Metallurgica Sinica(English letters) 2007年第4期20卷 293-300页

作者： b.l. li H.M. du X.F. Wang E.Y. Jiang Z.Q.li P. Wu Department of Applied Physics Institute of Advanced Materials Physics School of Science Tianjin University Tianjin 300072 China Tianjin Key laboratory of low Dimensional Materials Physics and Preparing Technology Tianjin University Tianjin 300072 China

Fe-N thin films were fabricated on both 100Si and NaCl substrates by RF magnetron sputtering under low nitrogen partial pressure. The microstructure and magnetic properties of Fe-N thin films were investigated with the increase of the substrate temperature （Ts） and the annealing temperature （Ta）. It is more difficult for nitrogen atoms to enter the Fe lattice under higher Ts above 150℃. The phase evolution is visible at higher Ta above 200℃. The phase transformation of α＇＇-Fe16N2 occurred at 400℃. The change of crystal size with Ta was clearly visible from bright and dark field images. The clear high-resolution electron microscope （HREM） images of 110α, 111γ＇, 112α＇＇, and 200α＇＇ phases were observed. The interplanar distances from TEM （transmission electron microscope） and HREM match the calculated values very well. From the results of the vibrating sample magnetometer （VSM）, the good magnetic properties of Fe-N films were obtained at 150℃ of Ts and 200℃ of Ta, respectively.

关键词： Fe-N thin film magnetic property HREM α''-Fe16N2

INVESTIGATION ON THE FORMATION MECHANISM OF TITANIUM CARbIDE PREPARED bY IN SITU REACTION IN MOlTEN AlUMINUM

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Acta Metallurgica Sinica(English letters) 1997年第6期10卷 485-488页

作者： Yang, b. Wang, Y.Q Zhang, J. Zhou, b.l. Inst of Metal Research Chinese Acad of Sciences Shenyang China

A novel technique in which TiC particulate are prepared by an in situ reaction in molten aluminum was introduced for producing TiC/Al composite. In order to reveal the characteristics of the technique, the formation mechanism of TiC particulate prepared by this method was studied. both theoretical and experimental results show that the TiC particulate is formed by a diffusion mechanism when the molar fraction of aluminum in the preforms is higher than 20.02%. On the contrary, the TiC particulate is formed by a solution-precipitation mechanism when the fraction of aluminum in the preforms is lower than 20.02%.

关键词： Aluminum metallurgy In situ processing Metallic matrix composites Titanium carbide

Constitutive equation and model validation for a 31 vol.% b_4Cp/6061Al composite during hot compression

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Journal of Materials Science & Technology 2018年第10期34卷 1730-1738页

作者： l. Zhou C. Cui Q.Z. Wang C. li b.l. Xiao Z.Y. Ma Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China School of Electromechanical and Vehicle Engineering Yantai University Yantai 264005 China School of Mechanical Engineering Shenyang Ligong University Shenyang 110159 China Nuclear and Radiation Safety Center Ministry of Environmental Protection Beijing 100082 China

An accurate constitutive equation is essential to understanding the flow behavior of b4C/A1 compos-ites during the hot deformation. However, the constitutive equations developed previously in literature are generally for low strain rate deformation. In the present work, we modified the general consti-tutive equation and take the high strain rate correction into account. The constitutive equation for a 31 vol.% b4Cp/6061AI composite was constructed based on the flow stresses measured during isothermal hot compression at temperatures ranging from 375 to 525 ℃ and strain rates from 0.01 to 10 s^-1. The experimental flow stresses were corrected by considering temperature-dependent Arrhenius factor. The modified equation was then verified by using DEFORM-3D finite element analysis to simulate the exper-imental hot compression process. The results show that the modified equation successfully predicts flow stress, load-displacement, and the temperature rise. This helps to optimize the hot deformation process, and to obtain desirable properties, such as reduced porosity and homogenous particle distribution in b4C/AI composites.

关键词： Composites b4C/AI Constitutive equation Hot compression Finite element simulation

INFlUENCE OF FIbER COATING ON TENSIlE bEHAVIOR OF UNIDIRECTIONAl C/Mg COMPOSITES

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Acta Metallurgica Sinica(English letters) 1997年第5期10卷 398-402页

作者： Zhang, K. Wang, Y.Q. Zhou, b.l. Zhou, Y.H. li, H.l. Inst of Metal Research Chinese Acad of Sciences Shenyang China

The mechanical properties and deformation mechanisms of unidirectional carbon fiber reinforced magnesium composites under tensile loading are studied. Two different materials are used as fiber coatings: a single silica and a gradient C/SiC/SiO[sb 2]. The results show that, under the same preparation conditions, composite with the former coating is broken in a non-cumulative mode and its failure stress is rather low. Conversely, the latter coating demonstrates much better efficiency and the corresponding composite is broken in a cumulative mode.

关键词： Metallic matrix composites Carbon fibers Tensile strength Elastic moduli Coatings Silica Deformation Crack propagation Crack initiation Fracture Stresses Strain

Microstructural evolution of aluminum alloy during friction stir welding under different tool rotation rates and cooling conditions

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Journal of Materials Science & Technology 2019年第6期35卷 972-981页

作者： X.H. Zeng P. Xue l.H. Wu D.R. Ni b.l. Xiao K.S. Wang Z.Y. Ma Shenyang National laboratory for Materials Science Institute of Metal Research Chinese Academy of Sciences Shenyang 110016 China University of Chinese Academy of Sciences Beijing 100049 China School of Metallurgical Engineering Xi'an University of Architecture and Technology Xi'an 710055 China

The microstructural evolution during friction stir welding(FSW) has long been studied only using one single welding parameter. Conclusions were usually made based on the final microstructure observation and hence were one-sided. In this study, we used the "take-action" technique to freeze the microstructure of an Al-Mg-Si alloy during FSW, and then systematically investigated the microstructures along the material flow path under different tool rotation rates and cooling conditions. A universal characteristic of the microstructural evolution including four stages was identified, i.e. dynamic recovery(DRV), dislocation multiplication, new grain formation and grain growth. However, the dynamic recrystallization(DRX)mechanisms in FSW depended on the welding condition. For the air cooling condition, the DRX mechanisms were related to continuous DRX associated with subgrain rotation and geometric DRX at high and low rotation rates, respectively. Under the water cooling condition, we found a new DRX mechanism associated with the progressive lattice rotation resulting from the pinning of the second-phase *** on the analyses of the influencing factors of grain refinement, it was clearly demonstrated that the delay of DRV and DRX was the efficient method to refine the grains during FSW. besides, ultra-high strain rate and a short duration at high temperatures were the key factors to produce an ultrafine-grained material.

关键词： Aluminum alloys Grain refinement Dynamic recrystallization Severe plastic deformation Friction stir welding

Predicting glass structure by physics-informed machine learning

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npj Computational Materials 2022年第1期8卷 1839-1847页

作者： Mikkel l.bødker Mathieu bauchy Tao du John C.Mauro Morten M.Smedskjaer Department of Chemistry and bioscience Aalborg University9220AalborgDenmark Physics of AmoRphous and Inorganic Solids laboratory(PARISlab) Department of Civil and Environmental EngineeringUniversity of CaliforniaLos AngelesCA90095USA Department of Materials Science and Engineering The Pennsylvania State UniversityUniversity ParkPA16802USA

Machine learning(Ml)is emerging as a powerful tool to predict the properties of materials,including *** Ml models with knowledge of how glass composition affects short-range atomic structure has the potential to enhance the ab.l.ty of composition-property models to extrapolate accurately outside of their training ***,we introduce an approach wherein statistical mechanics informs a Ml model that can predict the non-linear composition-structure relations in oxide *** combined model offers an improved prediction compared to models relying solely on statistical physics or machine learning ***,we show that the combined model accurately both interpolates and extrapolates the structure of Na_(2)O–SiO_(2)***,the model is able to extrapolate predictions outside its training set,which is evidenced by the fact that it is able to predict the structure of a glass series that was kept fully hidden from the model during its training.

关键词： glasses structure glass

Upcycling the spent graphite/liCoO_(2) batteries for high-voltage graphite/liCoPO_(4)-co-workable dual-ion batteries

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International Journal of Minerals,Metallurgy and Materials 2024年第7期31卷 1745-1751页

作者： Miao du Hongyan lü Kaidi du Shuohang Zheng Xiaotong Wang Xiaotong Deng Ronghua Zeng Xinglong Wu Key laboratory for UV light-Emitting Materials and Technology of Ministry of Education Northeast Normal UniversityChangchun 130024China Faculty of Chemistry Northeast Normal UniversityChangchun 130024China School of Chemistry South China Normal UniversityGuangzhou 510006China

The worldwide proliferation of portable electronics has resulted in a dramatic increase in the number of spent lithium-ion batteries(lIbs).However,traditional recycling methods still have limitations because of such huge amounts of spent ***,we proposed an ecofriendly and sustainable double recycling strategy to concurrently reuse the cathode(liCoO_(2))and anode(graphite)materials of spent lIbs and recycled liCoPO_(4)/graphite(RlCPG)in li^(+)/PF^(-)_(6) co-de/intercalation dual-ion *** recycle-derived dualion batteries of li/RlCPG show impressive electrochemical performance,with an appropriate discharge capacity of 86.2 mAh·g^(-1) at25 mA·g^(-1) and 69%capacity retention after 400 *** recycling of the cathode and anode from spent lIbs avoids wastage of resources and yields cathode materials with excellent performance,thereby offering an ecofriendly and sustainable way to design novel secondary batteries.

关键词： recycle lithium cob.l. oxide lithium cob.l. phosphate graphite dual-ion batteries spent lithium-ion batteries