Formation of FeMo_2B_2 phase in boron containing 9Cr-1.5Mo ferritic steels

The segregation and diffusion of boron during heat treatments were studied. The influence of boron contents, aging time and applied stress on FeMo2B2 formation was also studied. Finally, the effects of boron contents and FeMo2B2 formation on the high temperature strength were studied. Boron atoms were segregated to prior austenite grain boundary during normalizing treatment. And these boron atoms were slowly diffused into the grain interior during tempering and aging at 700 ℃. The FeMo2B2 phase was only formed after 1,000 h aging at 700 ℃ in alloy containing 196 ppm boron. The formation of FeMo2B2 phase is accelerated by the applied stress. It was expected that the formation of FeMo2B2 is closely related to the redistribution of boron atoms. The tensile strengths at 700 ℃ are increased with the increase of boron contents. However, the formation of FeMo2B2 phase results in lower tensile strength.

Modeling the Impact of Cell Type and Substrate Stiffness on Cell Traction

We propose a mathematical model to suggest a unified explanation behind the observation that some cell types tend to spread more efficiently on stiff substrates and are able to adapt their internal stiffness to the external stiffness. Our model also offers an explanation regarding the dependence of cell spreading on cell type. We show that our model for stiffness adaptation is in good agreement with experimental data. We also apply our model to calculate the energy of traction on bulk substrates as well as thin coatings, thereby extracting estimates of critical coating thickness as a function of cell type and coating bulk modulus.

Synthesis of large-scale atomic-layer SnS2 through chemical vapor deposition

Two-dimensional layers of metal dichalcogenides have attracted much attention because of their ultrathin thickness and potential applications in electronics and optoelectronics. Monolayer SnS2, with a band gap of -2.6 eV, has an octahedral lattice made of two atomic layers of sulfur and one atomic layer of tin. Till date, there have been limited reports on the growth of large-scale and high quality SnS2 atomic layers and the investigation of their properties as a semiconductor. Here, we report the chemical vapor deposition （CVD） growth of atomic-layer SnS2 with a large crystal size and uniformity. In addition, the number of layers can be changed from a monolayer to few layers and to bulk by changing the growth time. Scanning transmission electron microscopy was used to analyze the atomic structure and demonstrate the 2H stacking poly-type of different layers. The resultant SnS2 crystals is used as a photodetector with external quantum efficiency as high as 150%, suggesting promise for optoelectronic applications.

Bench-top aqueous two-phase extraction of isolated individual single-walled carbon nanotubes

围单人赛的碳 nanotubes (SWCNT ) 的隔离和纯化是为他们在各种各样的应用的实现的前提。在这个工作，我们在场一快(5 min ) ，从在水的分散的捆和杂质的高质量的孤立的 SWCNT 的抽取的便宜、容易可伸缩的凳子顶途径。抽取过程，基于水二阶段(ATP ) 分离，对任何 SWCNT 来源广泛地适用(在直径在样品上测试了直到 1.7 nm ) 并且独立于缺点密度，纯净，直径，和长度。提取分散证明大总数，小捆，和杂质的移动由密度坡度 ultracentrifugation 比得上那，但是没有对高端乐器学的需要。拉曼和荧光刺激光谱学， single-nanotube 荧光成像，原子力量和传播电子显微镜学，和 thermogravimetric 分析都证实孤立的 SWCNT 的高纯净。由 predispersing 没有 sonication 的 SWCNT (仅仅轻轻激动人心) ，全身的、太古的 SWCNT 能被孤立(测试了多达 20 m ) 。因此，这个简单 ATP 方法将发现在为所有的 SWCNT 材料的产生的立即的申请 nanotube 研究和应用铺平，从基本研究到高效的设备。

Characterizing and modeling the precipitation of Mg-rich phases in Al 5xxx alloys aged at low temperatures

Al 5083 alloys(5.25 at.% Mg) of different tempers(H131 and H116) were aged at low temperatures(50and 70?C) for 41 months. Scanning transmission electron microscopy(STEM), energy-dispersive X-ray spectroscopy(EDS), and atom probe tomography(APT) were applied to characterize precipitates formed in the sensitized samples. Experimental results revealed that the size of Mg-rich precipitates increased with aging time at 70?C for both alloys. APT results showed that Mg-rich precipitates of different Mg concentrations and morphologies formed in Al matrix and on the interface of Al matrix/pre-existing particles. In addition, a model based on local equilibrium of chemical potential and multi-class precipitates number evolution was adopted to predict the multiphase precipitation process in the Al-Mg binary system. The overall trend of precipitate radius and number density predicted by the model matched well with the experimental results. Moreover, modeling results revealed that nucleation and coarsening occurred faster in Al 5083 H131 than in Al 5083 H116 when aged at same temperature. The high density of dislocations and the pipe diffusion mechanism of dislocations can be used to explain such behavior.

Synthesis of Ag/AgCl-mesoporous silica nanocomposites using a simple aqueous solution-based chemical method and a study of their antibacterial activity on E. coli

Simple aqueous solution-based chemical methods have been developed for the synthesis of Ag/AgCI nanoparticle-mesoporous silica nanocomposites. Ag loading in the mesoporous silica was accomplished using a wet-impregnation method. The AgCl-mesoporous silica nanocomposite material （AgCl-mSi） was synthesized by using a ＇one pot method. Synthesized materials were characterized using X-ray diffraction, N2 adsorption-desorption analysis and high-resolution transmission electron microscopy. Antibacterial activity of the synthesized materials was investigated against Escherichia coil （E. coil） using the conventional plate-count method. All the materials showed high antibacterial activity even when the percentage loading of Ag in the nanocomposite was as low as 10wt%.

An Experimentally Validated SOA Model for High-Bit Rate System Applications

A comprehensive model of the Semiconductor Optical Amplifier with experimental validation result is presented. This model accounts for various physical behavior of the device which is necessary for high bit-rate system application.

Molecular dynamics simulation of latent track formation in α-quartz

The latent ion track in α-quartz is studied by molecular dynamics simulations. The latent track is created by depositing electron energies into a cylindrical region with a radius of 3nm. In this study, the electron stopping power varies from 3.0keV/nm to 12.0keV/nm, and a continuous latent track is observed for all the simulated values of electron stopping power except 3.0keV/nm. The simulation results indicate that the threshold electron stopping power for a continous latent track lies between 3.0keV/nm and 3.7 keV/nm. In addition, the coordination defects produced in the latent track are analyzed for all the simulation conditions, and the results show that the latent track in α-quartz consists of an O-rich amorphous phase and Si-rich point defects. At the end of this paper, the influence of the energy deposition model on the latent track in α-quartz is investigated. The results indicate that different energy deposition models reveal similar latent track properties. However, the values of the threshold electron stopping power and the ion track radius are dependent on the choice of energy deposition model.

Microstructural characterization of polycrystalline materials by synchrotron X-rays

Third generation synchrotron X-rays provide an unprecedented opportu- nity for microstructural characterization of many engineering materials as well as natural materials. This article demonstrates the usage of three techniques for the study of structural materials： differential-aperture X-ray microscopy （DAXM）, three-dimensional X- ray diffraction （3DXRD）, and simultaneous wide angle/small angle X-ray scattering （WAXS/SAXS）. DAXM is able to measure the 3D grain structure in polycrystalline materials with high spatial and angular resolution. In a deformed material, streaked diffraction peaks can be used to analyze local dislocation content in individual grains. Compared to DAXM, 3DXRD is able to map grains in bulk materials more quickly at the expense of spatial resolution. It is very useful for studying evolving microstructures when the materials are under deformation. WAXS/SAXS is suitable for studying materials with inhomogeneous structure, such as precipitate strengthened alloys. Structural informa- tion revealed by WAXS and SAXS can be combined for a deeper insight into material behavior. Future development and applications of these three techniques will also be discussed.