On the magnetic and crystallization behaviour of iron based amorphous alloys determined by nuclei quenched in

The tendency of boron-containing, iron-based glasses to show non monotonic changes of Curie Temperature (T _c ) and room temperature saturation magnetization (SM) was examined by magnetic measurements and Mossbauer spectroscopy. Depending on B/Fe ratio theT _c and SM first increased up to a maximum value and then steadily decreased, probably because of a shortrange ordering, due to the strong chemical interaction between iron and boron atoms, leading iron atoms in vicinity with Fe-atoms rather than another TM-atom. Finally, the phenomenon becomes analogous to the order-disorder phenomenon in crystalline alloys. An observed unusual crystallization behaviour, consisting of heterogeneous nucleation, was also ascribed to this ordering, which leads to the formation of associations, acting as the first nuclei of crystallization.     

Patterned uniformly orientated silicon nanocrystallite films and efficient field emission characteristics

Patterned uniformly (100)-orientated silicon nanocrystallite (SiNC) films were fabricated based on hydrogen ion implantation technique and typical electrochemical anodic etching method. The surface morphology and microstructure characteristics of the films were characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, and atomic force microscopy. The efficient field emission with low turn-on field of about 3.2 V/μm at current density of 0.1 μA/cm² was obtained. The emission current density from the SiNC films reached 1 mA/cm² under a bias field of about 11 V/μm. The experimental results demonstrate that the SiNC films have great potential applications for flat panel displays.     

The effect of Fe and Ru substitution on the superconductivity in MgCNi3

We report the effects of partial substitutions of the VIIIa elements: Fe (3d) and Ru (4d) in the intermetallic perovskite superconductor MgCNi₃. In both the MgCNi_3−xRu_x and MgCNi_3−xFe_x systems, the superconducting critical temperature (T_C) decreases monotonically as x is increased. T_C decreases more slowly in the case of Ru, suggesting that the 3d electrons in Fe are magnetically pair breaking. This is supported by the normal state magnetic susceptibility measurements (χ), which shows that χ increases with Fe and decreases with Ru doping. No ferromagnetism is observed in either system.     

Control of calcium carbonate crystallization utilizing amphiphilic block copolypeptides

Control over the morphology of calcium carbonate (CaCO₃) crystals has been achieved through the use of anionic, amphiphilic block copolypeptides during crystallization. Microspheres of CaCO₃ can be synthesized by the introduction of preformed organic, amphiphilic block copolypeptide templates, poly(l-aspartate sodium salt)₁₀₀-block-[poly(l-phenylalanine)₂₅-random-(l-leucine)₂₅] (1) and poly(l-glutamate sodium salt)₁₀₀-block-[poly(l-phenylalanine)₂₅-random-(l-leucine)₂₅] (2). When cationic amphiphiles are used in lieu of the anionic amphiphiles, only CaCO₃ rhombohedra are produced. The self-assembling amphiphile controls the precipitation of the microspheres by acting as a template to form giant CaCO₃ microspheres. These microspheres are composed of nanocrystals ranging in size from 10 to 60 nm using 1 and 20 to 100 nm using 2.     

Use of new composite materials for the determination of Cu, Cd, Mo, As, and Sb in biological samples by radiochemical neutron activation analysis

Summary  Vezetéknév     

Quasiparticle and Cooper pair tenneling in small capacitance Josephson junctions

The tunneling of single electrons in small capacitance tunnel junctions is influenced by charging effects and by the fluctuations of the elecromagnetic environment. We study the effect of an external circuit with arbitrary impedance on the tunneling of quasiparticles and Cooper pairs in voltage driven Josephson junctions. We present results at finite temperatures and also consider an acdriven system.     

Surface enhanced Raman scattering from mildly roughened surfaces: variation of signal with metal grain size

The intensity of surface enhanced Raman scattering from benzoic acid derivatives on mildly roughened, thermally evaporated Ag films shows a remarkably strong dependence on metal grain size. Large grained (slowly deposited) films give a superior response, by up to a factor of 10, to small grained (quickly deposited) films, with films of intermediate grain size yielding intermediate results. The optical field amplification underlying the enhancement mechanism is due to the excitation of surface plasmon polaritons (SPPs). Since surface roughness characteristics, as determined by STM, remain relatively constant as a function of deposition rate, it is argued that the contrast in Raman scattering is due to differences in elastic grain boundary scattering of SPPs (leading to different degrees of internal SPP damping), rather than differences in the interaction of SPPs with surface inhomogeneities.     

Self-assembly of nanoparticles on the surface of ionic crystals: Structural properties

With a suitable combination of ligand-stabilised nanoparticle suspension and ionic salt solutions, it is possible to produce microcrystals that are coated with nanoparticles. The self-assembly process of coating microcrystals by gold nanoparticles (NP) is mediated by the crystal lattice. This is the so-called CLAMS process - a generic process for self-organisation of nanoparticles on the surface of crystals [M. Murugeshan, D. Cunningham, J.-L. Martnez-Albertos, R. Vrcelj, B.D. Moore, Chem. Commun. (2005) 2677]. We are exploring here the structural properties of these self-assembled structures by using different imaging techniques.     

Preparation and characterization of hcp Co-coated Fe nanoparticles

A relatively simple method was described for coating and modifying iron nanoparticles with a hexagonal close-packed (hcp) cobalt layer. It was realized by depositing cobalt onto the poly(N-vinyl-2-pyrrolidone) (PVP) modified iron particles in ethanol solution. XRD, XPS and HRTEM were used to characterize the product. The Co layers, grown as the exclusive hcp phase, were ascribed to the inducement of the body-centered cubic (bcc) iron cores. Thus-prepared hcp Co-coated Fe particles displayed a much enhanced coercivity and decreased saturation magnetization (M_S) compared with that of the uncoated sample.     

Analysis of iron storage proteins in chicken liver and spleen tissues in comparison with human liver ferritin by Mössbauer spectroscopy

Summary Characterization of iron storage proteins in liver and spleen from normal chicken and chicken with lymphoid leukemia in comparison with human liver ferritin were considered by M?ssbauer spectroscopy (preliminary results). Small differences in M?ssbauer hyperfine parameters for both normal and lymphoid leukemia chicken liver and spleen were observed. The value of quadrupole splitting for human liver ferritin was higher than those for chicken tissues. A decrease of iron content in lymphoid leukemia chicken tissues was also found, however, the reason of this fact (pathology or feeding) was not clear yet.