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The evolution and morphological stability of a spherical crystal

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science China(Technological sciences) 2008年第3期51卷 225-243页

作者： CHEN MingWen1,2, WANG ZiDong2 & XU JianJun3.4 1 School of Applied sciences, university of science and {3. Beijing, Beijing 100083. China 2 School of materials science and engineering, university of science and {3. Beijing, Beijing 100083. China 3.School of Mathematical sciences, Nankai university, Tianjin 3.0071, China 4 department of Mathematics and Statistics, McGill university, Montreal H3. 2K6, Canada 1. School of Applied sciences University of Science and Technology Beijing Beijing 100083 China 2. School of materials science and engineering University of Science and Technology Beijing Beijing 100083 China 3. School of Mathematical sciences Nankai University Tianjin 300071 China 4. department of Mathematics and Statistics McGill University Montreal H3A 2K6 Canada

The growth model of a spherical crystal in the undercooled melt including the surface energy, interfacial kinetics and convective flow is established. The effect of the convective flow induced by a small far field flow on the evolution and morphological stability of the interface of the spherical crystal is studied. The interface shape of the spherical crystal, which is affected by the far field flow, and the dispersion relation of the growth rate of amplitude of the perturbed interface are derived. It is shown that the convection induced by the far field flow makes the interface of the growing spherical crystal further grow in the upstream direction of the far field flow and inhibit growth in the downstream direction; the interface of the decaying spherical crystal further decays in the upstream direction and inhibits decay in the downstream direction. The theoretical result suggests that both the growth of the sphere in the upstream direction and the decay of the sphere in the downstream direction make the spherical crystal tend to evolve into an oval; the morphological stability of the interface depends on a certain radius R c such that the spherical crystal is unstable when its radius is greater than R c and stable when its radius is less than R c . The surface energy and interfacial kinetics have strong stabilizing effects on the growth of the spherical crystal. In the meantime interfacial kinetics is a table factor of the interface when the interface of the sphere is growing; it is an unstable factor of the interface when the interface is decaying.

关键词： solid-liquid interface spherical crystal convective flow crystal growth morphological stability

Thermodynamic Behavior of Manganese and Phosphorus between Liquid Iron and CaO-MgO-SiO_2-Al_2O_3.Fe_tO-MnO-P_2O_5 Slags

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Journal of university of science and technology Beijing 2001年第3期8卷 171-176页

作者： Bo Song, Seon-Hyo Kim, Jinghong Mao, Qing Lin Metallurgy School, university of science and technology Beijing, Beijing 100083. China {3. of materials science & engineering, Pohang university of science & technology, Pohang 790-784, Korea Material S Univ Sci & Technol Beijing Met Sch Beijing 100083 Peoples R China Pohang Univ Sci & Technol Dept Mat Sci & Engn Pohang 790784 South Korea Univ Sci & Technol Beijing Sch Mat Sci & Engn Beijing 100083 Peoples R China

The thermodynamic behavior of manganese and phosphorus between liquid iron and CaO-MgO-SiO2-Al2O3.FetO-MnO-P2O5 ladle slag system was addressed by investigating the thermodynamic equilibria between liquid iron containing Mn and P and the ladle slag at 1873.K. The Mn distribution ratio L-Mn increases with increasing FetO content and decreasing the basicity ((%CaO + %MgO)/(%SiO2 + %Al2O3.+ %P2O5)) in slag, while the P distribution ratio Lp seems to be increased as FetO content and the basicity increases. The values of L-Mn and L-p decrease by the addition of Al2O3.into slag. The expression of the dependence of L-Mn and L-p on the basicity and FetO content in slag was obtained.

关键词： manganese phosphorus liquid iron ladle slag thermodynamic behavior

Mathematic Expression of Kinetic Compensation Effect and Relationship between the Exothermic Decomposition Temperature and Critical Temperature of Thermal Explosion of Eighty-six Energetic materials

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含能材料 2001年第1期9卷 8-9页

作者： HU Rong zu 1, YANG De suo 2, ZHANG Jiao qiang 3. (1. department of Chemistry,Northwest university, Xi′an 710065, China 2. department of Chemistry and Chemical {3., Baoji College of Arts and science, Baoji 721007, China 3. department of 西北大学陕西西安 710065 宝鸡文理学院陕西 721007 西北工业大学陕西西安 710072

Two relationships are established using the least squares method,between the kinetic parameters (the apparent activation energy and pre exponential constant),and the exothermic decomposition temperature and ther... 详细信息

关键词： critical temperature of thermal explosion decomposition temperature DSC energetic materials.

Effects of Na/K ratio on the phase structure and electrical properties of Na_xK_(1-x)NbO_3.lead-free piezoelectric ceramics

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Rare Metals 2010年第2期29卷 220-225页

作者： ZHANG Qian, ZHANG Boping, Li Haitao, and SHANG Pengpeng School of materials science and engineering, {3. of science and technology Beijing, Beijing 100083. China School of materials science and engineering University of Science and Technology Beijing

Lead-free piezoelectric NaxK1-xNbO3.x = 0.3.0.8）（NKN） ceramics were fabricated by normal sintering at 1060°C for 2 *** and electrical properties of the ceramics were investigated with a special emphasis on the influence of Na *** grain size of the produced dense ceramic was decreased by increasing Na content.A discontinuous change in the space distance was found at the composition close to Na0.7K0.3.bO3.ceramic, which indicates the presence of a transitional composition between two different orthorhombic phases, which is similar to the behavior of morphotropic phase boundary（MPB） in NaxK1-xNbO3.*** MPB-like behavior contributes to the enhanced piezoelectric coefficient d3. of 122 pC/N, planar-mode electromechanical coupling coefficient kP of 28.6%, and dielectric constant εr of 703. respectively for the Na0.7K0.3.bO3.*** temperature TC and the transitional temperature TO-T from orthorhombic to tetragonal phase are observed at around 420°C and 200°C, respectively.

关键词： lead-free piezoelectric ceramics NKN sintering morphotropic phase boundary(MPB)

Microstructures of laser cladding of intermetallic-ceramic composite coatings

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International Journal of Minerals,Metallurgy and materials 1997年第3期11卷 8-10页

作者： ZHOU Xianglin CHEN Chuanzhong CHANG Chun YU Jiahong HU Hanqi ( department of materials, Shandong university of {3., Jinan 250061, China) (materials science and engineering School, university of science and {3. Beijing, Beijing 100083. Shandong Univ of technology Jinan China

The microstructures of laser cladding of (Ni-24.5%(atom fraction)Al)+5O%(mass haction)WC coatingsbefore and after aging was comparetively studied by using SEM and TEM. It is shown that dissolving of WC and reprecipitating in the forms of WC and W,Coccurred during laser cladding, and intermetallic γ' (Ni3.l) orderly precipitatefrom metastable supersaturant Ni-matrix solid solution after heat treatment. The structures are favorable for coating'sproperties.

关键词： intermetallic ceramic laser cladding metastable Phase aging

An improved approach to the efficient construction of and search operations in motion graphs

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science China(Information sciences) 2012年第5期55卷 1042-1051页

作者： GAO Yan 1,CHEN ZhiHua 2,CHEN MinGang 3.& SHEN Yang 3.1 Software engineering Institute,East China Normal university,Shanghai 200062,China 2.department of Computer {3. and engineering,East China university of {3. and technology,Shanghai 20023.,China 3.department of Computer {3. and engineering,Shanghai Jiao Tong university,Shanghai 200240,China 1. Software engineering Institute East China Normal University Shanghai 200062 China2. Department of Computer Science and Engineering East China University of Science and Technology Shanghai 200237 China3. Department of Computer Science and Engineering Shanghai Jiao Tong University Shanghai 200240 China

Motion graphs have been widely used as an effective technique in the synthesis of human *** synthesize well-formed motions,motion graphs require smooth transitions and good ***,the time and costs grow quadratically as the graph size *** this paper,we present a method to set up a hierarchical structure,called a structure *** coarse level of this graph models different motion categories and their transitions,and the fine level mainly captures different motion *** interpolation space method is used to improve the graph connectivity at the fine *** structure guides the establishment of a faster and more realistic graphical *** the building process,this structure also helps with searching the motion graph,by performing a traverse search and placing the findings into a direct look-up table or local search ***,when there is no direct link between the different motions,a navigation map is introduced to conduct an appropriate search path via a series of transition motion *** experimental results indicate that our approach could lower the computation time in construction and searching,while simultaneously providing a richer variety of motion styles.

关键词： motion graph structure table registration curve motion interpolation

Transformation Behaviour of Austenite in Steel under Condition of Stress-strain and Its Application

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Journal of materials science & technology 1995年第6期11卷 440-442页

作者： Xu WANG Sigen WANG and Lixian HUA (Dept. of materials science and engineering, {3. of science and technology Beijing, Beijing, 100083. China) Beijing Univ of science and Technology Beijing China

Austenite can be retained at ambient temperature in steels by alloying and processing control. The transformation from austenite to martensite occurs under a certain conditions : thermal or deformation. Stress-strain induced martensitic transformation is important to improve the plasticity of steels which is called transformation induced plasticity (TRIP). Strength-ductility balance of the steels is greatly superior to that of other high strength steels due to the TRIP effect. A new type of steels-TRIP steel is developed

关键词： TRIP Transformation Behaviour of Austenite in Steel under Condition of Stress-strain and Its Application

Effect of surface nanocrystallization on the corrosion behavior of Zircaloy-4

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science China(Technological sciences) 2009年第8期52卷 2227-2231页

作者： ZHU YuTao1,2 & ZHANG XiYan1,2,3.1 College of materials science and engineering, Chongqing {3., Chongqing 400045, China 2 National engineering Research Center for Magnesium Alloys, Chongqing {3., Chongqing 400044, China 3.School of Physical science and engineering technology, Guangxi {3., Nanning 53.004, China 1. College of materials science and engineering Chongqing University Chongqing 400045 China 2. National engineering Research Center for Magnesium Alloys Chongqing University Chongqing 400044 China 3. School of Physical science and engineering technology Guangxi University Nanning 530004 China

The contrastive corrosion experiments between surface nanocrystallined Zircaloy-4 and coarse-grained Zircaloy-4 under the condition of 673.K/10.3.MPa in pure water are carried out, and the microstructure of oxide films has been studied. The results indicate that the growth rate of oxide films formed on the nanocrystalline Zircaloy-4 is lower than that of oxide films formed on the coarse-grained Zircaloy-4. Simultaneously, the oxide/metal interface of the former is more regular and glossy than that of the latter. For nanocrystalline Zircaloy-4, the low oxygen diffusion rate through the oxide/metal interface can hinder the reaction of oxygen ion with metal ion. Furthermore, more tetragonal ZrO2 are observed in the oxide films, which can delay the martensite phase transition from tetragonal to monoclinic phase in oxide films.

关键词： nanocrystalline Zircaloy oxide film microstructure

Aging Behaviors of W-Ni-Fe Ternary Alloys with High Ni-to-Fe Ratios

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Journal of materials science & technology 2003年第6期19卷 631-633页

作者： Ronghua LI, Jihua HUANG, Sheng YIN and Jun ZHAOSchool of materials science & engineering, {3. of science & technology Beijing, Beijing 100083. China Sch. of Mat. Sci. and Eng. Univ. of Sci. and Technol. Beijing Beijing 100083 China

The hardness variation of two kinds of alloys with 3. wt pct W content and 7/3. 9/1 Ni-to-Fe ratios during strain aging at 800℃ was studied. The microstructures of the aged alloys were analyzed by X-ray diffraction and TEM. The results show that the strain aging hardness of W-Ni-Fe ternary alloy with 7/3.Ni-to-Fe ratio decreases monotonically with the increase of aging time. Under the same conditions, the hardness of 9/1 Ni-to-Fe ratio alloy decreases in the initial aging stage, but then increases as aging process goes on. X ray diffraction and TEM analysis show that there is not any precipitation depositing from the alloy with 7/3.Ni-to-Fe ratio during aging. The monotonic decrease in hardness of this alloy during aging process results from the recovery, recrystallization and solid solubility declining. In the alloy of 9/1 Ni-to-Fe ratio, the fine β phase precipitates dispersively during aging which hardens the alloy. The two different kinds of mechanisms (the softening one and the hardening one) decide the hardness variation of the alloy with 9/1 Ni-to-Fe ratio mentioned above.

关键词： W-Ni-Fe Tungsten heavy alloys Ni-to-Fe ratio Strain aging β phase