TiC原位增强块状Cu_(47)Ti_(34)Zr_(11)Ni_8非晶合金复合材料

在电弧炉中利用吸铸法制备了直径1-4 mm的原位生成TiC和β-Ti枝晶联合增强的块状Cu47Ti34Zr11Ni8非晶合金复合材料.DSC热分析结果表明,原位生成TiC颗粒的引入,没有影响基体合金的非晶形成能力.用OM,XRD,SEM,EDS等方法研究了复合材料的相组成、微观组织以及成分分布,结果表明,TiC颗粒作为异质形核中心促进了β-Ti枝晶的形成,形成了TiC颗粒和β-Ti枝晶联合增强的块状Cu47Ti34Zr11Ni8非晶合金复合材料,而且β-Ti枝晶的尺寸和数量与TiC颗粒的多少以及试样的尺寸有关.室温压缩试验表明,同单相非晶合金相比,块状Cu47Ti34Zr11Ni8非晶合金复合材料提高了抗压强度及塑性.

Room temperature (34 degrees C) operation of strain-compensated quantum cascade lasers

A short wavelength (lambda similar or equal to 3.5 mu m) strain-compensated InxGa(1-x)As/InyAl(1-y)As quantum cascade laser is reported. Quasi-continuous wave operation of this device at 34 degrees C with an output power of 11.4mW persisted for more than 30 minutes without obvious degradation. A very low threshold current density of 1.2KA/cm(2) at this temperature was observed.

Neutron spectroscopic factors of Ar-34 and Ar-46 from (p,d) transfer reactions

Single-neutron-transfer measurements using (p,d) reactions have been performed at 33 MeV per nucleon with proton-rich Ar-34 and neutron-rich Ar-46 beams in inverse kinematics. The extracted spectroscopic factors are compared to the large-basis shell-model calculations. Relatively weak quenching of the spectroscopic factors is observed between Ar-34 and Ar-46. The experimental results suggest that neutron correlations have a weak dependence on the asymmetry of the nucleus over this isotopic region. The present results are consistent with the systematics established from extensive studies of spectroscopic factors and dispersive optical-model analyses of Ca40-49 isotopes. They are, however, inconsistent with the trends obtained in knockout-reaction measurements.

Crystallization and Si incorporation mechanisms of SAPO-34

In this study of the synthesis of SAPO-34 molecular sieves, XRD, SEM, XRF, IR and NMR techniques were applied to monitor the crystalloid, structure and composition changes of the samples in the whole crystallization process in order to get evidence for the crystallization as well as Si incorporation mechanism of SATO-34. XRD results revealed that the crystallization contained two stages. In the first 2.5 h (the earlier stage), high up to similar to80% of relative crystallinity could be achieved and the crystal size of SAPO-34 was almost the same as that of any longer time, indicating a fast crystallization feature of the synthesis. In this stage, IR revealed that the formation of SAPO-34 framework structure was accompanied by the diminution of hydroxyls, suggesting that crystal nuclei of SAPO-34 may arise from the structure rearrangement of the initial gel and the condensation of the hydroxyls. NMR results reveal that the template and the ageing period are crucial for the later crystallization of SAPO-34. Preliminary structure units similar to the framework of SAPO-34 have already formed before the crystallization began (0 h and low temperature). Evidence from IR, NMR, and XRF shows that the formation of the SAPO-34 may be a type of gel conversion mechanism, the solution support and the appropriate solution circumstance are two important parameters of the crystallization of SAPO-34. Meanwhile, NMR measurements demonstrated that about 80% of total Si atoms directly take part in the formation of the crystal nuclei as well as in the growth of the crystal grains in the earlier stage (<2.5 h). Evidence tends to support that Si incorporation is by direct participation mechanism rather than by the Si substitution mechanism for P in this stage (<2.5 h). In the later stage (>2.5 h), the relative content of Si increased slightly with a little decrease of Al and P. The increase of Si(4Al) and the appearance of the Si(3Al), Si(2Al), Si(1Al) and Si(OAl) in this stage suggest that substitution of the Si atoms for the phosphorus and for the phosphorus and aluminum pair takes place in the crystallization. The relationship among structure, acidity and crystallization process is established, which suggests a possibility to improve the acidity and catalytic properties by choosing a optimum crystallization time, thus controlling the number and distribution of Si in the framework of SAPO-34. (C) 2002 Elsevier Science Inc. All rights reserved.

Ti_(0.17)Zr_(0.08)V_(0.34)Nb_(0.01)Cr_(0.1)Ni_(0.3)氢化物电极合金微观结构及电化学性能研究

采用XRD、FESEM-EDS、ICP及EIS等方法研究了Ti0.17Zr0.08V0.34Nb0.01Cr0.1Ni0.3氢化物电极合金微观结构和电化学性能。X射线衍射分析表明:该合金由体心立方结构(bcc)的V基固溶体主相和少量六方结构的C14型Laves相组成;FESEM及EDS分析表明:V基固溶体主相形成树枝晶,C14型Laves相呈网格状围绕着树枝晶的晶界,元素在两相中的分布呈现镜像关系。电化学性能测试结果表明:该合金的氢化物电极在303￣343K较宽的温度区间内,表现出较高的电化学容量,在303K和343K时,电化学容量分别为337.0mAh·g-1和327.9mAh·g-1。在303K循环100周后,容量为282.7mAh·g-1。ICP分析结果表明,氢化物电极在充放电循环过程中,V及Zr元素向KOH电解质中的溶出较为严重。EIS研究表明,金属氢化物电极表面电化学反应的电荷转移电阻(RT)随循环次数的增加而增加,相应的交换电流密度则随循环次数的增加而降低。氢化物电极循环过程中RT的增大以及V和Zr元素的溶解,可能是导致电极容量衰减的主要原因。

热带西太平洋次表层水和中层水分布特征及其年代变化

热带西太平洋是一个流系和水团分布十分复杂的海域。热带西太平洋是一个在别处形成的几种水团的交汇区。许多起源于中、高纬度海域的次表层和中层水团，由不同流系带入和带出这个海域。热带西太平洋水团分布及其变化，与各种时间尺度的大尺度海洋环流和全球水循环变化密切联系，所在位势密度层次越深，所关联的气候变化时间尺度越长。因此，研究该海域次表层水和中层水的分布、扩散及其变化特征，对大洋环流动力学和气候变化研究有重要意义。本文利用中国ARGO资料中心提供的ARGO延时处理资料和美国NODC提供的WOD01中的高分辨率CTD资料，运用盐度极值法确定水团的核心，通过水团核心位置的分布及变化反映热带西太平洋次表层水和中层水的分布及其起源和归宿问题，试图获得较以往更加准确的NPIW和AAIW以及NPTW和SPTW的向南及向北扩散的特征，以及ITF在不同层次上的水源。对新发现的西太平洋热带水（WPTW）和西太平洋热带中层水（WPTIW）的水团性质、分布特征，成因和起源进行了比较系统的分析。在此基础上，分析上述次表层水和中层水20世纪八九十年代以来的年代变化特征。主要结果如下：（1）SPTW在137°E以西跨越赤道后，仍在很大程度上保持原有盐度，向西北和东北方向发展。SPTW在131°E以东几乎没有越过5°N，但在131°E以西可局部影响到6°N，棉兰老冷涡和哈马黑拉暖涡的涡混合输运在这一局部过程中可能起主要作用。NPTW主要位于10°N－20°N之间，在NEC输送下从东向西一直延伸到菲律宾沿岸，分成向北和向南两个分支，南分支在130°E以西沿棉兰老沿岸向南扩散大约到2°N，部分向西进入苏拉威西海，部分与SPTW相遇后有向东扩散的趋势。（2）AAIW几乎齐头并进地向北扩散到12°N－13°N，在125°E附近向北可以到达13°N左右。NPIW的主体分布在10°N以北、122°E以东，呈东北向西南的扩散趋势，在132°E以西至棉兰老沿岸之间可以到达4°N附近。（3）在已知的NPTW与SPTW之间，发现一个以往从未被报道过的次表层水，称之为WPTW。WPTW存在于3°N－12°N之间，核心盐度低于34.8psu，位势密度约在23.7 －24.7 之间。WPTW源于东太平洋20-25°N附近，由NEC南翼携带向西到达西边界后，部分经MC向南，经NECC向东折回，被局限在NEC与NECC之间的狭长水域。（4）2°N－10°N之间、从170°W到西边界分布着一片盐度比较均匀、呈现垂向盐度极小值特征的中层水。该水体位势密度约为26.0 －26.6 、位于AAIW之上、NPIW以南，核心盐度与AAIW相仿、但高于NPIW，在以往研究中未给予重视。从流场配置来看，这个被本文称为WPTIW的水体恰好处在NEC-NECC-SEC之间的强剪切区，在其北侧的是NPIW与同样起源于东北太平洋的浅的盐度极小值（SSM）之间的混合水，在其南侧相应层次上则是AAIW与SPTW之间的过渡水，两者之间被剪切流充分混合，形成盐度相对均匀的WPTIW。因此，WPTIW是热带西太平洋局地混合和再循环的产物。（5）在20世纪八九十年代和2000年以后这两个时期，本文所关注的次表层水和中层水在热带西太平洋扩散和在西边界附近交织在一起的总体态势基本一致。两个时期相比较，SPTW向西扩散程度变化不大，向北扩散程度有所加大，由前一时期的5°N，进一步扩散到6°N－7°N。NPTW在西边界附近的向南扩散程度有所削弱，在2002－2005年间只向南扩散到4°N，并且被SPTW阻挡于128°E以西，而前一个时期则可向南扩散到2°N，并且在2°N－4°N之间转向东跨过130°E。AAIW在西边界附近向北扩散程度有所加大，在2002－2005年到13°N附近，而前一个时期只到达11°N。NPIW在西边界附近的向南扩散程度有所削弱。（6）ITF的次表层水源基本上可以确定主要来自北太平洋，中层水源既有北太平洋，也有南太平洋。其中北太平洋次表层水和中层水经苏拉威西海、望加锡海峡到达弗罗勒斯海，层次越深趋势越明显。南太平洋次表层水没有进入印度尼西亚海域，AAIW则明显是经哈马黑拉海峡和马鲁古海峡到班达海。在各层次上，南海次表层水和中层水通过苏禄海进入ITF的可能性不大。