Analysis of Mg content of Zn_(1-x)Mg_xO film grown on sapphire substrates by plasma-assisted molecular beam epitaxy

Semiconductor materials with wide band gap have been extensively used to fabri-cate the blue laser light emitting diodes and ultraviolet photodetectors, which are impor-tant elements of semiconductor instruments, such as displays, optical data storages, ul-traviolet sensors, electroluminescent devices and solar-blind detectors. This kind of ma-terials is now becoming a hot research object in semiconductor physics. GaN was the first suitable ultraviolet laser material people found in this real…     

比利时UGINE ＆ ALZ新建不锈钢厂投产一年的运行情况

2000年11月奥钢联从比利时ALZ获得将其不锈钢产能提高1倍、达到120万t／a的合同。介绍了相关设备及投产一年以来的运行结果。     

过共析钢的亚动态和静态再结晶

利用热压试验确定了碳含量为1％的过共析钢的亚动态和静态再结晶情况。双击压力试验在900～1050℃之间进行，变形率为0.01-1／s，再结晶时间为0．1～500s。静态与亚动态再结晶的特征明显不同。试验结果显示，亚动态运动比静态运动快一倍。这些数据用于建立方程式以预测静态和亚动态再结晶动力学以及再结晶后的晶粒度。     

23 ^122Cs与^136La高自旋态研究

由于质子与中子不同的形状驱动效应影响，A=130缺中子核区的核在高自旋态下可呈现丰富多彩的核结构特性，如形状共存、扁椭形变、旋称反转、手征二重带结构等。对双奇核^122Cs与^136La进行了高自旋态研究，目的是在^122Cs中寻找手征二重带，在^136La中研究旋称反转与扁椭形变特性。     

钛和304L型不锈钢异种连接的腐蚀和微观组织

为了将装载高放射性和强腐蚀性硝酸溶液的Ti基加Zr基合金(Ti，Zr-2，Ti-5％，Ta，Ti-5％Ta-1．8Nb)的溶解器和核燃料后处理厂由304L型不锈钢制成的其它部件连在一起，就需要它们之间的异种连接有良好的完整性和抗腐蚀性：熔化焊方法会产生叮溶解于硝酸的二次沉淀，因此建议采用固态焊接方法。在本工作中，多种用于关键场合使Ti-304L SS连接有足够的强度、延性和抗腐蚀性的异种金属连接方法受到关注，Kalpakkam的1GCAR(印度甘地原子能研究中心)对开发工作做了规划，与三相（液相、汽相，冷凝相)腐蚀试验的结果一起，对可能的方法以及微观组织和冶金特性做了讨论。在这些结果基础上，后处理厂采用了爆炸焊方法得到的异种连接技术。     

TEM image analysis and modelling: application to boehmite nanoparticles

Boehmite occurs in the form of nanoparticles. Upon drying, it can form the alumina that is common in catalyst support used in refining and petrochemicals. The topotactic transformation of boehmite alumina led to an interest in the precise shape and size of these nanoparticles which is highly linked to the catalyst activity. Boehmite nanoparticles can be observed by transmission electron microscopy. Although they are highly aggregated, the analysis of transmission electron microscopy images with a specific random model approach, here a dilution model, can give an accurate estimate of their size. To use this approach, electronic noise and diffraction artefacts on the edges of the nanoparticles have to be removed. Covariance measurements on micrographs can be performed. They can be used to fit a model. The fitting uses a novel numerical method to estimate the covariogram of grains. The model can take into account the specific orientations of the nanoparticles. The influence of noise, image filters used to remove noise and diffraction artefacts, as well as all the parameters of the model are all studied in this paper. We propose nanoparticle size estimations procedures based on both single and mixture-of-two particle models.     

Note: high-pressure generation using nano-polycrystalline diamonds as anvil materials

Nano-polycrystalline diamonds (NPDs) consist of nanosized diamond grains oriented in random directions. They have high toughness and isotropic mechanical properties. A NPD has neither the cleavage feature nor the anisotropy of hardness peculiar to single-crystal diamonds. Therefore, it is thought to be useful as a diamond anvil. We previously reported the usefulness of a NPD as an anvil for high-pressure development. In this study, some additional high-pressure generating tests using diamond anvils of various shapes prepared from NPDs were conducted to investigate the advantage of using NPDs for anvil applications. The results revealed that the achievable pressure value of a NPD anvil with a culet size of more than 300 μm is about 1.5 to 2 times higher than that of single-crystal diamond anvils, indicating that NPD anvils have considerable potential for large-volume diamond anvils with large culet sizes.     

Imaging biofilm in porous media using X-ray computed microtomography

In this study, a new technique for three-dimensional imaging of biofilm within porous media using X-ray computed microtomography is presented. Due to the similarity in X-ray absorption coefficients for the porous media (plastic), biofilm and aqueous phase, an X-ray contrast agent is required to image biofilm within the experimental matrix using X-ray computed tomography. The presented technique utilizes a medical suspension of barium sulphate to differentiate between the aqueous phase and the biofilm. Potassium iodide is added to the suspension to aid in delineation between the biofilm and the experimental porous medium. The iodide readily diffuses into the biofilm while the barium sulphate suspension remains in the aqueous phase. This allows for effective differentiation of the three phases within the experimental systems utilized in this study. The behaviour of the two contrast agents, in particular of the barium sulphate, is addressed by comparing two-dimensional images of biofilm within a pore network obtained by (1) optical visualization and (2) X-ray absorption radiography. We show that the contrast mixture provides contrast between the biofilm, the aqueous-phase and the solid-phase (beads). The imaging method is then applied to two three-dimensional packed-bead columns within which biofilm was grown. Examples of reconstructed images are provided to illustrate the effectiveness of the method. Limitations and applications of the technique are discussed. A key benefit, associated with the presented method, is that it captures a substantial amount of information regarding the topology of the pore-scale transport processes. For example, the quantification of changes in porous media effective parameters, such as dispersion or permeability, induced by biofilm growth, is possible using specific upscaling techniques and numerical analysis. We emphasize that the results presented here serve as a first test of this novel approach; issues with accurate segmentation of the images, optimal concentrations of contrast agents and the potential need for use of synchrotron radiation sources need to be addressed before the method can be used for precise quantitative analysis of biofilm geometry in porous media.