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SURFACE MORPHOLOGY OF SELF-ASSEMBLED VERTICALLY STACKED InAs QUANTUM DOTS BY SIZE-CONTROLLED GROWTH

S.W.Li

金属学报(英文版)

Structural and optical properties of vertically aligned lnAs quantum dots (QDs) were embedded in Al0.5Ga0.5As spacer layers. The aligned QDs were grown at 520℃ in the Stranski-Krastanow (S-K) growth mode of molecular beam epitaxy. To improve QD characteristics, we employed a size- and density-controlled growth procedure in the upper layers. Measurements by reflection high-energy electron diffraction (RHEED) and atomic force microscopy (AFM) showed that both the size and density of the QDs. The temperature dependence of the wavelength-integrated photoluminescence (PL) intensity revealed the InAs QD emission.

关键词: quantum dot , null , null

Microstructure and preparation of nano S-W-S new solid lubrication system

Transactions of Nonferrous Metals Society of China

The method for preparing a new solid lubrication system of nano S-W-S was presented. The microstructure of the S-W-S nano cluster was investigated using TEM and XRD. The system is a mixture clusters of both monocrystal and polycrystal of layered hexagonal structure with one tungsten atom linking with two sulphur atoms, and the week Van der Waals' force bonding together the different layers. The changes of electronic structure were studied with XPS. The hybridization of different electronic shelf orbitals of the sulphur atom in the nano cluster is regarded as the quantum size effect. The clusters are found to be of a closed spherical,structure without any dangling bond.

关键词: solid lubrication system;nanometer cluster;quantum size effect;powders

Li_2S-GeS_2-LiI和Li_2S-GeS_2-LiBr-LiI系统玻璃的电导率

杨如玺

材料研究学报

实验得知0.5Li_2S-0.5GeS_2玻璃的电导率高于0.4Li_2S-0.6GeS_2玻璃的电导率。当在这两种组成的玻璃中分别掺杂LiI 后,则后者的电导率可高于前者。在0.4Li_2S-0.6GeS_2玻璃中同时掺杂LiBr 和LiI 后,其电导率约为掺杂一种同量盐玻璃电导率的两倍。本文用弱电解质理论解释了Li_2S-GeS_2玻璃经掺杂LiBr 和LiI 后电导率变化的原因。

关键词: 解离常数 , activity , ameliorator(modification) , organisator(formation) , transition temperature(transus temperature).

A flexible nanostructured sulphur-carbon nanotube cathode with high rate performance for Li-S batteries

Energy & Environmental Science

We report the template-directed synthesis of sulphur-carbon nanotubes and their use to form a membrane that is binder-free, highly conductive and flexible. This nanostructured membrane is used as a self-supporting cathode without metal current-collectors for Li-S batteries. The membrane cathode has a high electrical conductivity and renders a long life of sulphur of over 100 charge-discharge cycles. High discharge capacity of sulphur was attained at 712 mA h g(sulphur)(-1) (23 wt% S) and 520 mA h g(sulphur)(-1) (50 wt% S) at a high current density (6 A g(sulphur)(-1)). The overall capacity of the flexible cathode correspondingly reaches 163 mA h g(-1) (23 wt% S) and 260 mA h g(-1) (50 wt% S). These results demonstrate the great potential of this nanostructured flexible membrane as a cathode for Li-S batteries with fast charge-discharge performance and long life.

关键词: rechargeable lithium batteries;positive electrode materials;cell;temperature;composites;capacity;oxide

Ni-Fe-W-S刷镀层耐磨性机理研究

张远明 , 惠文华

材料保护 doi:10.3969/j.issn.1001-1560.2001.06.007

采用扫描电子显微镜、X射线光电子能谱(XPS)、俄歇电子能谱(AES)等手段研究了代铬镀层(Ni-Fe-W-S).在磨损前后的成分变化及价态变化,发现WS2具有固体润滑作用,并初步探讨了Ni-Fe-W-S合金层耐磨性的作用机理.研究表明,偏聚的WS形成立方晶系的WS2作为固体润滑剂可有效地降低摩擦系数,同时,W的偏聚使层错能降低,不易形成磨损裂纹.

关键词: 合金镀层 , 耐磨性 , 偏聚

S355J2W耐候钢的耐腐蚀性能

鲁二敬 , 卢峰华 , 许鸿吉 , 谢明 , 钮旭晶

机械工程材料

通过周期浸润腐蚀试验,对比研究了S355.12W耐候钢和Q345R低合金钢在NariSOs溶液中的耐腐蚀性能,并用扫描电镜对腐蚀产物进行了观察和分析。结果表明:在相同试验条件下,S355J2W耐候钢的腐蚀速率低于Q345R钢的;S355J2W耐候钢会在表面形成黑褐色锈层,而Q345R钢表面形成橘红色易剥落的疏松锈层;S355J2W耐候钢腐蚀产物微观形貌为沿放射性方向生长的针状晶体,Q345R钢为颗粒状聚合物堆积而成,形状无规则,颗粒之间有较大的空隙。

关键词: S355J2W耐候钢 , 周期浸润腐蚀试验 , 耐腐蚀性能

Unusual W-shaped Galvanic Cell Model of ISCC of α-brass in Neutral Mattsson's Solution

WU Shaobin , R. J. Arsenault , I. R. Kramer Metallurgical Materials Laboratory , University of Maryland , USA.

材料科学技术(英文)

Intergranular stress corrosion cracking (ISCC) of α-brass in neutral Mattsson's solution was found to be controlled by an unusual "W"-shaped galvanic cell whose cathode is the grain boundary oxide film (G.B.0. film) and surface film and the anode is fresh metal at the cracked tip on both sides of the G.B.0. film. Redox reactions involved in the cell have been proposed here. According to this mdel, initidtion of ISCC is caused by the rupturing of surface film along grain boundaries, thus forming a galvanic cell. Propagation of ISCC resulted from alternate advances of G.B.0. film and dissolution on both sides of G.B.0. film caused by the effect of electrochemical reaction. This work developed an effective approach to investigate the embrittlement process at the tip of the crack, by increasing the length of the embrittlement region through constant strain test and distinguishing the morphology and the nature of the corrosion products by optical microscopy and scanning electron microscopy (SEH).

关键词: α-brass , null , null , null

S355J2W+N钢激光-MAG复合焊与MAG焊对比

谷晓鹏 , 段珍珍 , 邓钢 , 谷晓燕

材料工程 doi:10.11868/j.issn.1001-4381.2015.02.004

利用激光-MAG复合焊和MAG焊进行了厚板S355J2W+N低碳钢的焊接实验,分析了两种焊接方法接头的微观组织和力学性能.结果表明:复合焊和MAG焊焊缝接头均由焊缝区、过热区、重结晶区和不完全重结晶区构成,复合焊接头截面呈“高脚杯”状特点,焊缝填充量和热影响区宽度较MAG焊明显减小.复合焊由于冷却速率快,过热区魏氏组织略有增多,硬度高于MAG焊,抗拉强度和弯曲性能与MAG焊相比,无显著差异,均能够满足生产标准的要求.

关键词: S355J2W+N , 激光 , MAG , 复合焊 , 接头组织 , 性能

金属表面功能性Mo(W)-S彩色簇合物膜的结构与性能

李道华 , 忻新泉

表面技术 doi:10.3969/j.issn.1001-3660.2004.04.015

采用加速腐蚀实验、LSV、CV、FT-IR、FT-Raman、XPSS和AES研究了Mo(W)S24-在金属表面的成键特征和波谱变化,探讨了生成的彩色簇合物膜的组成、结构、性能、化学状态和形成机理.结果表明,膜层中存在桥基Mo(W)-S-M键、端基Mo(W)=S和Mo(W)=O键.膜为多分子层组成的复杂体系,属于功能性修饰层,其颜色是各组分统计分布的结果.

关键词: 金属表面 , 配位化学反应 , Mo(W)-S , 彩色簇合物膜 , 结构与性能

A microporous-mesoporous carbon with graphitic structure for a high-rate stable sulfur cathode in carbonate solvent-based Li-S batteries

Physical Chemistry Chemical Physics

A microporous-mesoporous carbon with graphitic structure was developed as a matrix for the sulfur cathode of a Li-S cell using a mixed carbonate electrolyte. Sulfur was selectively introduced into the carbon micropores by a melt adsorption-solvent extraction strategy. The micropores act as solvent-restricted reactors for sulfur lithiation that promise long cycle stability. The mesopores remain unfilled and provide an ion migration pathway, while the graphitic structure contributes significantly to low-resistance electron transfer. The selective distribution of sulfur in micropores was characterized by X-ray photoelectron spectroscopy (XPS), nitrogen cryosorption analysis, transmission electron microscopy (TEM), X-ray powder diffraction and Raman spectroscopy. The high-rate stable lithiation-delithiation of the carbon-sulfur cathode was evaluated using galvanostatic charge-discharge tests, cyclic voltammetry and electrochemical impedance spectroscopy. The cathode is able to operate reversibly over 800 cycles with a 1.8 C discharge-recharge rate. This integration of a micropore reactor, a mesopore ion reservoir, and a graphitic electron conductor represents a generalized strategy to be adopted in research on advanced sulfur cathodes.

关键词: rechargeable lithium batteries;electrochemical properties;secondary;batteries;cell electrolyte;high-capacity;high-power;performance;discharge;composites;energy

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