Al的添加对Cu-B合金及Cu-ZrB2复合材料显微组织的影响

采用扫描电子显微镜、X射线衍射以及第一性原理计算方法研究Al的添加对Cu-B合金及Cu-ZrB2复合材料显微组织的影响。结果表明,在Al的变质作用下,Cu-B合金中的共晶B相由粗大针状转变为细小纤维状,同时可以在亚共晶Cu-B合金中析出初生B相。对于Cu-ZrB2复合材料,Al能够细化合成的ZrB2颗粒,改变其形貌,同时改善其分布,这归因于Al在ZrB2晶面上的选择性吸附。第一性原理计算表明,Al会优先吸附在ZrB2■面上,其次是ZrB2■面,最后是ZrB2 (0001)面,进而使复合材料中形成多面体状、乃至近球状细小ZrB2颗粒。Al的加入使Cu-ZrB2复合材料硬度显著提高,但其电导率严重降低。

颗粒增强金属基复合材料近邻颗粒间的应力及应变分布（英文）

采用内聚力模型研究颗粒增强金属基复合材料近邻颗粒间的应力及应变分布。结果表明,复合材料的应变主要集中于基体上,在加载路径上存在一个应变较高的区域,从而促进了颗粒极点附近空洞的形成。基体的应力和应变都随着基体与增强颗粒距离的增大而减小。模拟结果表明,增强颗粒之间的相互影响有一个临界距离,而且这个临界距离会随粒径的增大而增大。此外,加载方向和颗粒的中心线夹角对应力和应变的分布也有一定的影响,当加载方向和颗粒的中心线夹角为0°时,颗粒之间的相互影响最大,其夹角为45°时颗粒之间的相互影响最小。

Microstructure evolution of Ti5Si3 in Cu-Ti-Si alloys

The Cu-Ti-Si alloys containing in-situ formed Ti5Si3 are prepared. In order to clarify the Ti5Si3 formation processes and its microstructure characteristics, the as-cast and deeply etched Cu-Ti-Si alloys with different compositions and cooling rates were investigated using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). It is found that the eutectic Ti5Si3 phases in Cu-Ti-Si alloys are rod-like with hexagonal cross section which tend to intertwine with each other to form a firm skeleton like a bird nest structure which can make the alloys keep their original shape even after etching off the Cu matrix. In addition, there is Cu in the center of many Ti5Si3 rods, resulting in a core-shell structure. With the increase of the cooling rate, Ti5Si3 distributes more uniformly, and the diameter of Ti5Si3 significantly decreases, with a minimum size of less than 100 nm, while the aspect ratio of Ti5Si3 increases.

Shielding of the geomagnetic field reduces hydrogen peroxide production in human neuroblastoma cell and inhibits the activity of CuZn superoxide dismutase

Accumulative evidence has shown the adverse effects of a geomagnetic field shielded condition, so called a hypomagnetic field （HMF）, on the metabolic processes and oxidative stress in animals and cells. However, the underlying mechanism remains unclear. In this study, we evaluate the role of HMF on the regulation of cellular reactive oxygen species （ROS） in human neuroblastoma SH-SY5Y cells. We found that HMF exposure led to ROS decrease, and that restoring the decrease by additional H2O2 rescued the HMF-enhanced cell proliferation. The measurements on ROS related indexes, including total anti-oxidant capacity, H2O2 and superoxide anion levels, and superoxide dismutase （SOD） activity and expres- sion, indicated that the HMF reduced H2O2 production and inhibited the activity of CuZn-SOD. Moreover, the HMF accelerated the denaturation of CuZn-SOD as well as enhanced aggregation of CuZn-SOD protein, in vitro. Our findings indicate that CuZn-SOD is able to response to the HMF stress and suggest it a mediator of the HMF effect.

Adsorption of boron and its relationship with morphologies of TiC

First-principle calculations were performed to study the adsorption of boron and its relationship with the morphologies of Ti C.It is found that although the adsorption of boron on all the low-index Ti C crystal planes is thermally favorable,it will be adsorbed more easily by C-terminated {111} and {011} planes,while less possible to be adsorbed by {001}.The study of the formation of B–B clusters indicates that the distribution of boron adatoms on C-terminated（111） and {011} planes will be more uniform,and the diffusion of the adatom further confirms the above results.According to the geometry relationship and growth rate of different crystal planes,it is deduced that the adsorption of boron on Ti C will seriously impede the growth of {111} and {011} planes,which can make Ti C grow into hexagonal platelets.