XPS study of silicon spheres as a density standard

As density is one of the basic physical properties of materials, an accurate density standard is absolutely essential. To determine density with high accuracy and precision, two 1-kg single-crystal silicon spheres (NMIJ-S4 and NMIJ-S5) are used as the primary standard at the National Metrology Institute of Japan. For the accurate measurement of the mass and volume of the silicon spheres, the effects of the surface layer must be carefully considered. In this work, a surface layer model of NMIJ-S4 and NMIJ-S5 was proposed and the thicknesses of each surface layer were determined using X-ray photoelectron spectroscopy. A detailed uncertainty budget is presented to aid use of the density standard.     

Effect of the shear layer on the etching behavior of 6060 aluminum extrusion alloys

The occurrence of preferential grain etching (PGE) during alkaline etching of aluminum extrusion alloys from the 6XXX series is often linked to the presence of certain impurity elements such as zinc, causing an undesired etching appearance. In the presented work, an additional culprit in this context is identified, which has not been investigated yet. A clear relation between PGE and the presence of a subsurface shear layer is identified for extruded Al 6060 alloys containing 0.02 and 0.06 wt% Zn. This shear layer can be distinguished from the bulk of the metal by its difference in crystallographic texture as visualized by electron backscatter diffraction (EBSD). For the Zn enriched alloy, the <111>//ND grains are etched away faster than grains with other orientations, resulting in the grainy appearance typical for PGE. Independent of the Zn content in the alloy, once the shear layer is removed and <111>//ND grains are practically absent on the new surface, the depths variations caused by preferential etching disappear. Instead, the surface of the alloy is attacked uniformly by the caustic etch bath.     

Modelling of streaky structures and turbulent-spot generation process in wing boundary layer at high free-stream turbulence

Results of an experimental study of turbulent breakdown in gradient boundary layer at high freestream turbulence are reported. For the first time it is shown that, like the flat-plate boundary layer, the wing boundary layer at high freestream turbulence is modulated with streaky structures. One of possible mechanisms underlying the generation of turbulence spots in wing boundary layer is modelled assuming the interaction of streaky structures with high-frequency waves. Qualitative and quantitative data concerning the evolution of streaky structures in swqpt-wing boundary layer and in swept-wing boundary layer are presented. Certain differences between the evolution of streaky structures in wing boundary layer and in flat-plate boundary layer are revealed. This work was supported by the President of the Russian Federation (Grants NSh-454.2008.1, MK- 101.2007.1), by the Russian Foundation for Basic Research (Grant No. 05-01-00034), by the Ministry of Education and Science of the Russian Federation (Grant No. RNP 2.1.2.3370), and by the Russian Government (State Contract No. 02.513.12.0043).     

Optimized FIB silicon samples suitable for lattice parameters measurements by convergent beam electron diffraction

The aim of this paper is to check the effect of artefacts introduced by focused ion beam (FIB) milling on the strain measurement by convergent beam electron diffraction (CBED). We show that on optimized silicon FIB samples, the strain measurement can be performed with a sensitivity of about 2.5 × 10⁻⁴ which is very close to the theoretical one and we conclude that FIB preparation can be suitable for such measurements in microelectronic devices.

To achieve this, we first used CBED and electron energy loss spectroscopy (EELS) which provide a procedure permitting an exact knowledge of the sample geometry, i.e. the thickness of both amorphous and crystalline layers. This procedure was used in order to measure the FIB-amorphized sidewall layer. It was found that if the FIB preparation is optimized one can reduce this amorphous layer down to around 7 nm on each side. Secondly different preparation techniques (cleavage, Tripod™ and FIB) permit to check if the surface damaged layer introduced by FIB influences the strain state of the sample. Finally, it was found that the damaged layer does not introduce measurable strain in pure silicon but reduces appreciably the quality of the CBED patterns.     

Study on Interaction Between Two Parallel Plates with Iteration Method in Functional Theory

利用泛函分析理论中的迭代法,分别计算了平行平板双电层在高、中、低电位下的相互作用能,并以数值法所得结果为参照,在各电位下分别与Debye-Hückel线性近似法、Langmuir近似法所得的结果进行比较．结果表明,DH线性近似法和Langmuir近似法均只能分别局限于极低或极高电位,而泛函迭代法不但有简单的解析表达式,而且在各种电位下都能得到较满意的结果.     

地面铺设缆线的高空电磁脉冲响应研究

 利用时域多分辨分析方法,对地面铺设缆线屏蔽层感生电流的规律进行了研究。给出了屏蔽层感生电流与缆线距离地面的高度、缆线的长度、电磁脉冲的入射方向等的关系。结果表明：屏蔽层电流幅度随着缆线距离地面高度增高而增加;屏蔽层电流幅度、前沿、半高宽随着缆线长度增加而增加,直到分别达到各自的最大值;电磁脉冲正入射时,屏蔽层电流幅度沿缆线分布呈现中间大、两边小的规律;电磁脉冲斜入射时,屏蔽层电流相对电磁脉冲正入射时,幅度更高、前沿更快、半高宽更窄,幅度沿缆线的分布情况为从一端到另一端逐渐增大。     

亚单分子层三聚氰胺的便携式拉曼检测

通过改进Lee和Meisel法,制备了两种银胶。以三聚氰胺分子为探针分子,银胶为SERS基底,使用便携式拉曼光谱仪进行拉曼测试。拉曼光谱表明银纳米粒子和三聚氰胺发生的吸附作用明显,三聚氰胺的四个较强振动峰有4～9cm-1的频移和强度比变化较大。由于SERS基底的表面增强作用,三聚氰胺的便携式拉曼光谱仪最小检测量达到了6×10-12g,实现了三聚氰胺的亚单分子层检测水平。该检测方法快捷、简便,如果结合奶粉或食品中三聚氰胺的固相萃取技术,将可以应用于三聚氰胺的现场、快速、半定量检测。     

Kaolin as support for porous layer open tubular columns

Summary PLOT columns have been prepared with kaolin as the liquid phase support. These columns show good efficiency with different stationary phases and good thermal stability with polar phases. The performance of columns is shown by the separation of various mixtures such as fatty acids, phenols and anilines which are of analytical importance.     

厚度模压电超声换能器无源声学材料研究进展*

厚度模压电超声换能器作为超声波发射、接收以及电信号间转换的载体,是超声成像与检测系统的核心器件,一般由压电层、匹配层和背衬层3部分组成。超声换能器的性能一定程度上决定着整体超声设备的性能,影响了其在工业、医学、军事等领域的应用。该换能器的关键性能指标(带宽、灵敏度)除了受到压电层的影响,还与匹配层、背衬层等无源声学材料的设计密切相关。该文综述了近年来厚度模压电超声换能器无源声学材料(匹配层、背衬层和声透镜)的研究进展,提出了当前该类材料面临的难题和解决途径,并对其未来发展方向进行了展望。