Journal of Materials Science
Fatigue crack propagation behaviour of compact tension specimens of DSX40M alloy has been investigated in air at room temperature and at 850degreesC. The results indicate that the crystallographic cracking occurs on two or more planes simultaneously at room temperature. Slip bands are observed along the crack. Crack growth is affected by the temperature. The fatigue crack growth is higher at elevated temperature than room temperature. Microcracks start at the precipitates/eutectic and join the fatal crack. The number of planes intersecting each other determines the different microscopic features on the cleavage fracture surface. Dislocation structure in the plastic zone underneath the crack propagation at room temperature and at 850degreesC has been investigated by transmission electron microscopy. Dislocation pile up starts at lower DeltaK and dislocations are moving in a planar slip and few of the dislocations form network in the final broken area at room temperature. At 850degreesC the dislocations are piling up at lower DeltaK and dislocations are dispersing and forming network at higher DeltaK. The complete network formation was observed in the final broken area at 850degreesC. The dislocation density is very much higher at 850degreesC compared to that at room temperature. (C) 2002 Kluwer Academic Publishers.
关键词:
single-crystal
Journal of Applied Physics
A computer simulation program, based on a two sublattice model, is performed to analyze the magnetization process of ferromagnetic materials (like, for instance, RCo5 and R2Fe14B compounds). Without using the assumption of the existence of a small canting angle between the two sublattices, as has been used in the analysis of S. Rinaldi and L. Pareti [J. Appl. Phys. 50, 7719 (1979)], the magnetization curve as well as its derivatives curves are studied for the two sublattice system with high competing single-ion anisotropies. In the present work, a peak in the low field range of the second curve of magnetization is reported and the magnetic process is correspondingly discussed in terms of both the exchange energy and the anisotropy.
关键词:
single-crystal
Journal of Crystal Growth
Because of incongruent melting in YBa2Cu3O7-x, it is difficult to grow the textured 123 phase directly from the laser-heated molten zone in the laser floating zone (LFZ) method. To overcome this problem, the laser floating zone leveling (LFZL) method was utilized following a pseudo-binary diagram along the Y2BaCuO5-YBa2Cu3O7-x tie line and a crystal rod of textured 123 phases was directly grown from the molten zone. Experimental results indicate that the orientation of the textured tetragonal 123 phases is perpendicular to the c-axis and that the T(c) of the grown crystal rod is 91.2 K after annealing at 550-degrees-C for 40 h in flowing oxygen. Also, the solidified morphologies of some crystal rods grown at different growth rates were observed.
关键词:
single-crystal
Physica Status Solidi a-Applied Research
The magnetization process in a two-sublattice system is studied by a computer simulation program, without using the assumption of the existence of a small canting angle between magnetic moments of the two sublattices. Effects of the exchange and the anisotropy on the shape of the second-derivative curves of magnetization are discussed. In the present work, a peak in the low-field range of the second-derivative curve of magnetization is reported. This peak as well as a strong effective anisotropy are found to depend on the competition between the comparatively weak exchange and the opposite anisotropies.
关键词:
single-crystal
许元妹
,
方晓明
,
张正国
材料导报
采用强碱性水热处理法分别控制第一次水热反应为160℃和200℃,制备出一维纳米管和纳米棒2种形貌的产物,将其作为第二次水热反应的前驱体,考察了第二次水热体系中pH值和温度对TiO2纳米材料的晶相组成及其微观形貌的影响;采用XRD、TEM以及HRTEM对样品进行了分析.结果表明,当以纳米管为前驱体时,除在pH=0的体系中得到了以金红石相为主的单晶纳米棒外,在pH值为2、4和7的条件下均得到了单晶纯锐钛矿相TiO2纳米颗粒.当以纳米棒为前驱体时,在pH=0的体系中得到了金红石相与板钛矿相共存的纳米棒和纳米颗粒混合产物;在pH值为2、4和7的条件下均得到了纯锐钛矿相TiO2纳米棒;当二次水热温度低于180℃时,前驱体没有转化完全,所得产物为前驱体与锐钛矿相TiO2共存的纳米棒;当水热温度为180℃和210℃时,产物为纯锐钛矿相纳米棒.
关键词:
TiO2
,
纳米材料
,
水热法
,
单晶
董旭峰
,
关新春
,
欧进萍
,
齐民
复合材料学报
已有研究在Terfenol-D颗粒粒径及粒度分布对树脂基磁致伸缩复合材料性能的影响规律上存在分歧.本文中以Terfenol-D为磁致伸缩颗粒,以不饱和聚酯树脂为基体,采用5种窄分布颗粒(30～53μm、53～150 μm、150～300μm、300～450μm、450～500 μm)和1种宽分布颗粒(30～500 μm)制备颗粒体积分数为20%的磁致伸缩复合材料,并测试其动静态磁致伸缩系数、磁机械耦合系数、弹性模量及抗压强度等性能参数.在窄分布颗粒制备的试样中,以53～150μm制备的复合材料的磁致伸缩性能最佳;而采用宽分布颗粒制备的试样其性能优于窄分布颗粒制备的试样.该结果表明,增大颗粒粒径同时具有积极作用与消极作用,其对复合材料磁致伸缩性能的影响取决于哪一个居主导地位.
关键词:
树脂基磁致伸缩复合材料
,
Terfenol-D
,
粒径分布
,
磁致伸缩性能
,
单晶
