Study of Nd-Fe-B Alloys with Nonstoichiometric Nd Content in Optimal Magnetic State

Characterization of two rapid-quenched Nd-Fe-B alloys with nonstoichiometric Nd content in the optimized magnetic state was carried out using the X-ray diffractometry (XRD), (57)Fe Mossbauer spectroscopic phase analysis (MS), electron microscopy (TEM), high resolution TEM (HREM) and Superconducting Quantum Interference Device (SQUID) magnetometer. The experimental results demonstrate the fundamental difference in the structure and magnetic properties of the two investigated alloys in the optimized magnetic state. The Nd-Fe-B alloy with the reduced Nd content (Nd(4.5)Fe(77)B(18.5)) was found to have the nanocomposite structure of Fe(3)B/Nd(2)Fe(14)B and partly alpha-Fe/Nd(2)Fe(14)B, with mean grain size below 30 nm. On the other side, the overstoichiometric Nd(14)Fe(79)B(7) alloy has almost a monophase structure with the dominant content of the hard magnetic phase Nd(2)Fe(14)B (up to 95 wt. %) and a mean crystallite size about 60 nm, as determined by XRD and TEM analysis. The results of magnetic measurements on SQUID magnetometer also suggest the nanocomposite structure of the Nd-low alloy and nanocrystalline decoupled structure of the Nd-rich alloy after the optimal heat treatment.open

The effects of microalloying with silicon and germanium on microstructure and hardness of a commercial aluminum alloy

The effect of small additions of Si and Ge on the microstructure and hardness was investigated during aging of a commercial 2219 aluminum alloy It was found that for the same level of microalloying in alloy 2219SG (containing St and Ge), a maximum hardness was achieved 3 times faster than in alloy 2219S (without Ge). The accelerated precipitation kinetics is a consequence of the presence of fine Si-Ge particles. serving as heterogeneous precipitation sites for theta strengthening particles

Resonance properties and microstructure of ultracompliant metallic nanoelectromechanical systems resonators synthesized from Al-32 at. % Mo amorphous-nanocrystalline metallic composites

This study details the resonance properties of 20 nm thick nanoelectromechanical system scale cantilevers fabricated from a metallic Al-32 at. %Mo nanocomposite. The advantage of the Al-32 at. %Mo alloy is that its strength and near-atomic surface smoothness enable fabrication of single-anchored metallic cantilevers with extreme length-to-thickness ratios, as high as 400:1. This yields uniquely compliant structures with exquisite force sensitivity. For example, an 8 ??m long, 20 nm thick Al-32 at. %Mo device has a spring constant of K280 ??Nm. We show through transmission electron microscope analysis and continuum modeling that the relevant damping mechanisms are related to the device microstructure.open3

Pt-Sn/C as a possible methanol-tolerant cathode catalyst for DMFC

An effective method was developed for preparing highly dispersed nano-sized Pt–Sn/C electrocatalyst synthesised by a modified polyol reduction method. From XRD patterns, the Pt–Sn/C peaks shifted slightly to lower 2θ angles when compared with commercial Pt/C catalyst, suggesting that Sn formed alloy with Pt. Based on HR-TEM images, the Pt–Sn/C nanoparticles showed small particle sizes and well dispersed onto the carbon support with a narrow particle distribution. The methanol oxidation reaction on the as-prepared Pt–Sn/C catalyst appeared at lower currents (+7.08 mA at +480 mV vs. Ag/AgCl) compared to the commercial Pt/C (+8.25 mA at +480 mV vs. Ag/AgCl) suggesting that the Pt–Sn/C catalyst has ‘methanol tolerance capabilities’. Pt–Sn/C HA Slurry pH3 catalysts showed better activity towards the oxygen-reduction reaction (ORR) than commercial Pt/C which could be attributed to smaller particle sizes. In our study, the Pt–Sn/C catalyst appears to be a promising methanol-tolerant catalyst with activity towards the ORR in the DMFC.Web of Scienc

Metal-induced assembly of a semiconductor-island lattice: Getruncated pyramids on Au-patterned Si

We report the two-dimensional alignment of semiconductor islands using rudimentary metal patterning to control nucleation and growth. In the Ge on Si system, a square array of sub-micron Au dots on the Si (001) surface induces the assembly of deposited Ge adatoms into an extensive island lattice. Remarkably, these highly ordered Ge islands form between the patterned Au dots and are characterized by a unique truncated pyramidal shape. A model based on patterned diffusion barriers explains the observed ordering and establishes general criteria for the broader applicability of such a directed assembly process to quantum dot ordering

Systematic documentation and analysis of human genetic variation in hemoglobinopathies using the microattribution approach

We developed a series of interrelated locus-specific databases to store all published and unpublished genetic variation related to hemoglobinopathies and thalassemia and implemented microattribution to encourage submission of unpublished observations of genetic variation to these public repositories. A total of 1,941 unique genetic variants in 37 genes, encoding globins and other erythroid proteins, are currently documented in these databases, with reciprocal attribution of microcitations to data contributors. Our project provides the first example of implementing microattribution to incentivise submission of all known genetic variation in a defined system. It has demonstrably increased the reporting of human variants, leading to a comprehensive online resource for systematically describing human genetic variation in the globin genes and other genes contributing to hemoglobinopathies and thalassemias. The principles established here will serve as a model for other systems and for the analysis of other common and/or complex human genetic diseases