材料期刊网

Catalytic Activity of Iridium Dioxide With Different Morphologies for Oxygen Reduction Reaction

WANG Guangjin , HUANG Fei , XU Tian , YU Yi , CHENG Feng , ZHANG Yue , PAN Mu

武汉理工大学学报-材料科学版(英文版) doi:10.1007/s11595-015-1244-0

关键词:

Effect of stress on mu phase formation in single crystal superalloys

Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing

Precipitation behavior of the mu phase under applied stress was systematically investigated in two single crystal superalloys CMSX-4 and R0. The investigation has shown that both the sign and magnitude of the applied stress can affect the precipitation behavior of the mu phase with a certain degree of regularity. At first, the precipitation of the mu phase varied significantly when a small amount of stress was applied, regardless of whether the specimen is under tension or under compression. Under most conditions however, precipitation of the mu phase was restrained by this low application of stress. After increasing the applied stress, precipitation of the mu phase increased relative to the amount of tension or decreased under compression. (C) 2010 Elsevier B.V. All rights reserved.

关键词: Single crystal superalloy;Topologically close-packed (TCP) phase;Thermal exposure;Rhenium (Re);kinetics;cmsx-4

A mu-Phase behavior in a cast Ni-base superalloy

Journal of Materials Science

The response of mu phase to applied stress and long-term thermal exposure has been investigated in the cast Ni-base superalloy K446. It is found that during stress rupture, the applied stress accelerates the precipitation and growth of mu phase. However, during thermal exposure the mu phase precipitating in the form of needles and granules experiences a complicated evolution. The needles, fiber- or sheet-shaped in three-dimension, align very regularly during exposure, either lying in three directions with an acute angle to one another or in two directions perpendicular to each other, the mechanisms of which are characterized in detail. In addition, it is concluded that an excessive precipitation of mu phase severely degrades the mechanical properties of the alloy, whereas its evolution behavior during thermal exposure is determined to have an insignificant influence on the properties.

关键词: single-crystal superalloy;thermal exposure;precipitation;stability;rupture;stress

Precipitation behavior of mu phase and creep rupture in single crystal superalloy CMSX-4

Journal of Alloys and Compounds

Precipitation behavior of a topologically close packed (TCP) mu phase as well as its role during the creep deformation in single crystal superalloy CMSX-4 have been investigated. The mu particles nucleated and grew based on low index planes of both the mu phase ({11 (2) over bar 0} and {1 0 (1) over bar0}) and the matrix ({110}, {001} or {111} and {112}) by epitaxial growth toward < 0001 >(mu) or < 110 >gamma directions, which predominantly resulted in a rod-like morphology. Interestingly, composition of these rod-like mu particles varied with the ratio of Ni/(W + Re) due to the different diffusion rates of these elements in the matrix during thermal exposure. Moreover, the gamma' evolution played an important role in the precipitation behavior and the fracture behavior of the mu phase. The rod-like mu particles were not fractured by stress concentration, as they were surrounded by the gamma' envelope. (C) 2011 Elsevier B.V. All rights reserved.

关键词: Nickel-base single crystal superalloy;Topologically close packed phase;Thermal exposure;Creep;nickel-base superalloys;ni;deformation;microstructure;mechanisms;diffusion;exposure;fatigue;design;damage

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

Intergrowth of P phase with mu phase in a Ru-containing single-crystal Ni-based superalloy

Philosophical Magazine Letters

The precipitation of topologically close-packed (TCP) phases in a Ru-containing single-crystal Ni-based superalloy has been investigated. The high-angle annular dark field, selected area electron diffraction, and high-resolution transmission electron microscopy were used to analyze the TCP precipitates in this study. The intergrowth of P phase with m phase was found. This finding indicates that P phase may nucleate at stacking faults and subsequently grow at the expense of mu phase. The orientation relationship between P and mu phases was (1 0 0)(P)//(1 (1) over bar 1 2)(mu) and [0 1 (1) over bar](P)/[4 2 (1) over bar](mu).

关键词: superalloys;topologically close-packed phases;intergrowth;scanning;transmission electron microscopy;electron-microscopy;packed phases;precipitation;behavior;microstructure;deformation;co7w6

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

On the role of mu phase during high temperature creep of a second generation directionally solidified superalloy

Materials Science and Engineering a-Structural Materials Properties Microstructure and Processing

The role of mu phase in a second generation directionally solidified Ni-base superalloy during high temperature creep has been characterized in the present work. A large amount of blocky mu phase enveloped by thick gamma'-film is found at the grain boundaries and in the vicinity of primary MC carbides after heat treatment. However, the creep-rupture properties of the alloy are not affected by the presence of the blocky p, phase at 760-1070 degrees C under a stress of 120-850 MPa. By the investigation of creep microstructure at 975 degrees C/255 MPa, it is found that the thick gamma'-film plays a pivotal role in toughening the grain boundaries and the interfaces between the mu phase (or carbides) particles and the matrix, and preventing the formation of cracks. Meanwhile, during high temperature creep, M(23)C(6) carbides are continuously coarsening with the dissolution of the p. phase particles and MC carbides, especially at the grain boundaries. The poor interface cohesion strength between such large M(23)C(6) carbides and the gamma matrix at the vertical segments of the directionally solidified grain boundaries leads to the final creep failure of the present alloy. (C) 2010 Elsevier B.V. All rights reserved.

关键词: mu phase;Directionally solidified Ni-base superalloy;Creep;Carbide;Grain boundaries;precipitation