材料期刊网

Effect of Li and Ti Additions on L■α(Al)+Mg_2Si Pseudobinary Eutectic Reaction

Shengxu ZHAO , Shunpu LI , Deqian ZHAO , Mingxiang PAN and Xichen CHEN(Institute of Physics , Chinese Academy of Sciences , Beijing 100080 , China)

材料科学技术（英文）

Effect of Li and Ti additions on Lα(AI)+Mg2Si pseudobinary eutectic reaction in ternary Al-Mg-Si system has been investigated by thermoanalysis, directional solidification and metallographic techniques in this study. It has been found that Li addition causes decreasing of the volume fraction of Mg2Si, while a little amount of Ti causes to increasing, which is of a great importance to the adjustment of phase constitution and alloy properties. Doping components have little influence on the eutectic temperature.

关键词:

Discovery and Research of High Tc Superconductor in the Institute of Physics, Academia Sinica

CHEN Liquan A special member of CCAST (World Laboratory) , Post Address: Institute of Physics , Academia Sinica , P.O. Box. 603. Beijing , China.

材料科学技术（英文）

关键词:

Chen系统的状态变量周期性反馈控制

李开明 , 李亚洲 , 冯维贵 , 林长

量子电子学报 doi:10.3969/j.issn.1007-5461.2007.05.014

采用非线性反馈控制,用附加了带参数的正弦项对Chen系统进行了有效的控制.随着参数k的逐渐增大,系统的动力学行为呈现出一系列的变化.数值研究结果表明:随控制参数的增大,驱动信号的强度渐大,混沌系统由混沌运动到周期轨道,最终到一相点.

关键词: 混沌 , Chen系统 , 不动点 , Lyapunov指数 , 反馈控制

Kunming Institute of Precious Metals

WANG Yonglu NING Yuantao Kunming Institute of Precious Metals , Kunming , China.

材料科学技术（英文）

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PAN基炭纤维经济规模分析

夏春霞 , 闫亚明 , 邓蜀平 , 白光君 , 蒋云峰 , 宋惠森 , 王钰

新型炭材料 doi:10.3969/j.issn.1007-8827.2001.04.013

聚丙烯腈(Polyacrylonitrile缩写为PAN)基炭纤维市场需求旺盛,但由于我国PAN基炭纤维生产企业规模小、产品性能低,产品占领不了市场,企业效益欠佳.通过经济规模方法的分析,就国内现有技术状况和两个样本生产线,用工程技术法对PAN基炭纤维的经济规模进行分析,为我国炭纤维产业化发展提供参考.分析表明,国内PAN基炭纤维经济规模的起点为200t/a～275t/a.

关键词: PAN基炭纤维 , 经济规模 , 工程技术法

PAN/PI复合纤维的结构

李常清 , 袁姗 , 罗荣 , 郭雅明 , 徐樑华

高分子材料科学与工程

将聚酰亚胺(PI)加入丙烯腈-衣康酸-二甲基亚砜体系进行聚丙烯腈(PAN)溶液聚合,湿法纺丝制备了PAN/PI复合纤维.利用流变仪、红外光谱、X射线衍射仪、扫描电镜、差示扫描量热仪等研究了PAN/PI溶液的性质和复合纤维的结构特点.研究发现,加入PI后,聚合物溶液的稳态黏度降低,弹性和粘性模量在低剪切速率区降低;PI作为成核剂,引起初生纤维结晶度增大、晶粒尺寸减小;PI与PAN的溶解性差异导致凝固加快,初生纤维形成皮芯结构;引起原丝体密度减小.PAN/PI纤维在N2下放热量较少,在空气中由于结构疏松放热量较大.

关键词: 聚丙烯腈纤维 , 聚酰亚胺 , 原液改性 , 晶态结构

PAN初生纤维拉伸性能试验研究

谢奔 , 朱波 , 王政 , 井敏 , 王进军 , 张春雷 , 吴益民

功能材料

为了提高聚丙烯腈（PAN）初生纤维的可拉伸性能,将溶液纺丝得到的初生纤维进行不同时间的恒温干燥处理,研究其拉伸性能随干燥时间的变化规律。结果表明,干燥处理可以大幅度提升PAN初生纤维的力学性能,其拉伸强力可达10.3cN,断裂伸长可达263.5%;随着干燥时间的延长,纤维的可拉伸性能增强,经过10h干燥后的初生纤维具有最佳可牵伸性能;而拉伸速率的提高可以有效促进未干燥初生纤维的拉伸变形,而对干燥处理后纤维的拉伸性能的影响不大。用SEM观察纤维断裂形貌发现,PAN纤维的致密性随牵伸比的增加而提高。

关键词: 聚丙烯腈 , 初生纤维 , 干燥 , 拉伸性能 , 断裂形貌

Effect of carbonization atmosphere on the structure changes of PAN carbon membranes

Journal of Porous Materials

PAN carbon membranes were prepared by carbonizing the initial PAN membranes in vacuum and Ar at different temperatures. FTIR, Raman and XRD were applied to study the influence of carbonization atmosphere on the structure changes of PAN carbon membranes. The variations in adsorption peaks of FTIR, the intensity, position and FWHM of the Raman peaks, and microcrystallite parameters from XRD (e.g., d(002), Lc and La) are correlated with the structure change of PAN carbon membranes. Analyses results reveal that vacuum atmosphere can produce PAN carbon membranes with higher order degree than those in Ar atmosphere, although the structures of PAN carbon membranes prepared in the two atmospheres are both amorphous. In addition, vacuum atmosphere can significantly accelerate the degradation reaction of PAN membranes and favors the preparation of carbon membranes with smaller pore size.

关键词: Carbonization;Atmosphere;Carbon membranes;PAN;Structure;molecular-sieve membranes;gas separation membranes;phenolic resin;pyrolysis conditions;thermal-degradation;polyimide;polyacrylonitrile;deposition;graphite;kapton

New Evaluation on the Preoxidation Extent of Different PAN Precursors

Wangxi ZHANG , Jie LIU , Jieying LIANG , null , null , null

材料科学技术（英文）

Structural changes in carbon fibers at each stage of, especially, preoxidation process are well known to play a great role in achieving the ultimate product quality. Differential scanning calorimetry (DSC), scanning electron microscope (SEM), density method and optical microscope were used to characterize the preoxidation extent. A conventional approach, e:g., density aim, to evaluate the extent of preoxidation is not very exact. A DSC curve of a PAN precursor only can provide general information, major in the temperature regime of preoxidation reaction. However, the evaluation of a preoxidation extent, especially from conventional preoxidation temperature with a great span regime of 200~400℃, is put forward in this paper, in which the evolution of core/shell morphological structure is a kind of straightforward evidence.

关键词: Preoxidation , null , null

CURRENT STATUS OF HIGH-RESOLUTION ELECTRON-MICROSCOPY AND ITS APPLICATIONS TO MATERIALS SCIENCE AND CONDENSED MATTER PHYSICS

材料科学技术（英文）

The present paper summarizes the current status of high resolution elect;on microscopy ( HREM) and the applications of HREM to materials science and condensed matter physics. This review recounts the latest development of high resolution electron microscope, progress of HREM and the applications of HREM, including the crystal structure determination of microcrystalline materials and characterization of the local structure of the defects and nanostructured materials as well as qualitative and quantitative analysis of the grain boundaries, interfaces and interfacial reactions in the advanced materials by means of HREM in combination with electron diffraction, subnanometer level analysis, image simulation and image processing.

关键词: juxtaposed pentagonal antiprisms;two-dimensional quasicrystal;domain;boundary structures;close-packed phases;nanocrystalline materials;crystal-structure;copper oxidation;initial-stage;translational;symmetry;rotational symmetry