材料期刊网

Stress Distribution and Cleavage Analysis in a 16MnNiMo5 Bainitic Steel X-ray Diffraction and Multiscale Polycrystalline Modelling

Raphaë , l Pesci , Karim Inal , Renaud Masson

材料科学技术（英文）

Many tensile tests have been realized on the 16MnNiMo5 bainitic pressure vessel steel at low temperatures [-196℃,-60℃. The damaging processes (ductile/fragile) are observed with a scanning electron microscope (SEM), while X-ray diffraction (XRD) is used to determine the internal/residual stresses within the ferritic phase during loading (in-situ) and after unloading: stress states are lower in ferrite than in the bulk material due to cementite particles, the difference never exceeding 150 MPa. A polycrystalline modelling with a two-level homogenisation is also developed concurrently with the experimental characterization. It correctly reproduces the stress distribution in each phase, the intergranular strain heterogeneity as well as the macroscopic fracture stress and strain in relation to temperature, considering a constant number of grains (7%) reaching an experimentally identified crystallographic criterion of cleavage.

关键词: Internal stresses , null , null , null

氧化物系的多维键参数分析

刘征先 , 郑龙如 , 陈念贻 , 阎立诚

金属学报

运用化学键参数模式识别方法,总结氧化物系热力学性质的半经验规律,提出经验函数L作为氧化物酸碱性的标度。L和复合氧化物生成热、氧化物熔体的混合热、活度系数以及Masson熔渣模型聚合平衡常数K_(1,n)等均有对应关系。举例说明了L函数的应用。

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Synthesis of single-walled carbon nanotubes, their ropes and books

Comptes Rendus Physique

The carbon nanotube (CNT) is a model system of one-dimensional nanomaterials, which shows numerous unique properties and vast potential applications. The synthesis and assembly of high-quality CNTs are the basis for studies of their properties and applications. In this contribution, we briefly review our works on the controlled synthesis of single-walled CNTs (SWCNTs) and double-walled CNTs via floating catalyst chemical vapor deposition and arc-discharge methods. The in situ assembly of such CNTs into ordered macrostructures with various dimensions including ropes, films, and buckybooks are also presented. Finally, we introduced our recent findings on metal-catalyst-free growth of SWCNTs. (C) 2010 Academie des sciences. Published by Elsevier Masson SAS. All rights reserved.

关键词: Carbon nanotubes;Floating catalyst chemical vapor deposition;Arc-discharge;Macrostructures;Metal-catalyst-free;floating catalyst method;hydrogen-arc-discharge;diameter distribution;raman-scattering;free growth;large-scale;long ropes;in-situ;decomposition;hydrocarbons

Facile hydrothermal synthesis of 3D hierarchical Bi(2)SiO(5) nanoflowers and their luminescent properties

Solid State Sciences

Facile hydrothermal synthesis of novel hierarchical flowerlike Bi(2)SiO(5) nanostructures consisting of single-crystal nanosheets is reported using polyvinylpyrrolidone (PVP, K30) as capping reagent in the presence of NaOH. The obtained products are systematically characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy and Fourier transform infrared spectroscopy. Control experiments are carried out to investigate various factors that affect the morphology and size of the products. The results indicate that the nucleation and growth of the flowerlike nanostructures are dominated by a nucleation-dissolution-recrystallization growth mechanism. It is demonstrated that the concentrations of PVP and NaOH play important roles in the formation of the hierarchical nanoflowers. Moreover, the room-temperature photoluminescence properties of the Bi(2)SiO(5) nanoflowers are also investigated. (C) 2010 Elsevier Masson SAS. All rights reserved.

关键词: Hydrothermal synthesis;Self-assembly;Luminescent property;Bismuth;silicate;growth-mechanism;hollow spheres;route;nanostructures;nanoparticles;architectures;particles;oxides

一个新的聚合模型在CaO-SiO_2熔体中的应用

王之昌 , 周继程 , 程兆年

金属学报

用严格正规阴离子亚晶格代替Whiteway-Smith-Masson(WSM)模型中理想阴离子亚晶格的假定,推导了二元硅酸盐熔体的四参数分支链聚合模型。对于大多数熔渣,该模型中三个交换能参数W_(01),W_(12)和C(C=W_(02)-W_(01))可假定都等于零;于是简化得一参数模型,即WSM分支链聚合模型,对于CaO-SiO_2熔渣,上述三个交换能参数可假定为相等但不为零,于是得两参数模型,取交换能参数W_(12)/RT=-0.023,热力学平衡常数Ko~(11)~0=0.0044,所得两参数模型能较好地解释1600℃时0.412≤N_(SiO_2)≤0.450范围内CaO-SiO_2熔渣的活度数据。

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冶金熔体热力学的若干研究

邹元燨 , 周继程 , 徐元森 , 赵彭年 , 张子青

金属学报

为了从二元系中两组元活度的测定值之比求得该两组元的活度值,导出了一个变通的 Gibbs-Duhem 方程式,并在 PbCl_2-SnCl_2,PbCl_2-CdCl_2,AgCl-CuCl,Cu_2S-FeS,PbO-BiO_(1.5),PbO-SbO_(1.5),CaO-CaF_2及 CaO-SiO_2-CaF_2等冶金熔体中得到应用.多年前所发展的从 Ag 和 Pb 二元相图求得两组元活度的方法已扩大到含有单个 AB 化合物的二元系.用这一方法已求得 In-Sb 和 Sn-Te 系中各组元的活度.在研究某些黑色冶金渣与金属间的平衡时,用一适当选择的非铁金属代替 Fe作为熔剂金属有助于克服某些实验上的困难.采用 Sn 或 Cu 与熔渣平衡研究了 CaO-SiO_2,CaO-Al_2O_3和 CaO-SiO_2-Al_2O_3体系.对 CaO-SiO_2二元系获得的数据可以认为具有足够的准确度来验证 Masson 模型的合理性.

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