The effect of core-shell engineering on the energy product of magnetic nanometals.

Solution-based growth of magnetic FePt-FeCo (core-shell) nanoparticles with a controllable shell thickness has been demonstrated. The transition from spin canting to exchange coupling of FePt-FeCo core-shell nanostructures leads to a 28% increase in the coercivity (12.8 KOe) and a two-fold enhancement in the energy product (9.11 MGOe)

Precision Synthesis of Silicon Nanowires with Crystalline Core and Amorphous Shell

A synthetic route to crystalline silicon (Si) nanowires with an amorphous Si shell is reported. Trisilane (Si3H8) and Sn(HMDS)(2) are decomposed in supercritical toluene at 450 degrees C. Sn(HMDS)(2) creates Sn nanoparticles that seed Si nanowire growth by the supercritical fluid-liquid-solid (SFLS) mechanism. The Si : Sn ratio in the reaction determines the growth of amorphous Si shell. No amorphous shell forms at relatively low Si : Sn ratios of 20 : 1, whereas higher Si : Sn ratio of 40 : 1 leads to significant amorphous shell. We propose that hydrogen evolved from trisilane decomposition etches away the Sn seed particles as nanowires grow, which promotes the amorphous Si shell deposition when the higher Si : Sn ratios are used.Robert A. Welch Foundation F-1464U.S. Department of Energy Office of Science, Office of Basic Energy Sciences DE-SC0001091National Defense Science and Engineering Graduate FellowshipChemistr

Magic structures of helical multi-shell zirconium nanowires

The structures of free-standing zirconium nanowires with 0.6$-$2.8 nm in diameter are systematically studied by using genetic algorithm simulations with a tight-binding many body potential. Several multi-shell growth sequences with cylindrical structures are obtained. These multi-shell structures are composed of coaxial atomic shells with the three- and four-strands helical, centered pentagonal and hexagonal, and parallel double-chain-core curved surface epitaxy. Under the same growth sequence, the numbers of atomic strands in inner- and outer-shell show even-odd coupling and usually differ by five. The size and structure dependence of angular correlation functions and vibrational properties of zirconium nanowire are also discussed.Comment: 14 pages, 4 figure

All-inorganic core-shell silica-titania mesoporous colloidal nanoparticles showing orthogonal functionality

Colloidal mesoporous silica (CMS) nanoparticles with a thin titania-enriched outer shell showing a spatially resolved functionality were synthesized by a delayed co-condensation approach. The titaniashell can serve as a selective nucleation site for the growth of nanocrystalline anatase clusters. These fully inorganic pure silica-core titania-enriched shell mesoporous nanoparticles show orthogonal functionality, demonstrated through the selective adsorption of a carboxylate-containing ruthenium N3-dye. UV-Vis and fluorescence spectroscopy indicate the strong interaction of the N3-dye with the titania-phase at the outer shell of the CMS nanoparticles. In particular, this interaction and thus the selective functionalization are greatly enhanced when anatase nanocrystallites are nucleated at the titania-enriched shell surface

REMARKABLE AFFECT OF DIETS ON ABALONE (HAL/OTIS AS/NINA ) GROWTH AND SHELL PIGMENTATION

Absol u te growth and shell color of juvenile H asinina was moni tored over a period of 2-months in an experiment consisting of 8 treatments with 3 repl icates (n = !O individuals per replicate). The treatments were: fresh red seaweed ( Gracillaria verrucosa), and green algae ( Viva lactuca) and 6 formulated . feeds using different seaweed meals. This study is an attempt made on the effects of partially replacing fish meal with aigae (U lactuca) of the formulated feeds on the growth This preliminary study investigated the effect of seaweed and formulated feed on the growth, the shell color of this abalone and survival of abalone. The result s showed that the absolute growth of abalone fed by macroalgae G.verrucosa higher .than abalone fed with other feed and significantly different from the makroalgae U lactuca and others feeds fommlated. Results showed that abalones fed the seaweed G. 'verrucosa and formulated feed with G. verrucosa meal had dark - brown shells. However, abalones fod with makroalgae U !actuca and either of the formulated feeds (with spiru1ina) and formulated feeds (with U lactuca meal) remarkably had the s2me good growth performance and green shell appea;:ance. Investigations showed that seaweeds meal could be the better replacement for fish meal in pelleted feeds of H asinina. Keywords : abalone, growth, formulated feed, seaweed, seaweed mea

The fragmentation of expanding shells II: Thickness matters

We study analytically the development of gravitational instability in an expanding shell having finite thickness. We consider three models for the radial density profile of the shell: (i) an analytic uniform-density model, (ii) a semi-analytic model obtained by numerical solution of the hydrostatic equilibrium equation, and (iii) a 3D hydrodynamic simulation. We show that all three profiles are in close agreement, and this allows us to use the first model to describe fragments in the radial direction of the shell. We then use non-linear equations describing the time-evolution of a uniform oblate spheroid to derive the growth rates of shell fragments having different sizes. This yields a dispersion relation which depends on the shell thickness, and hence on the pressure confining the shell. We compare this dispersion relation with the dispersion relation obtained using the standard thin-shell analysis, and show that, if the confining pressure is low, only large fragments are unstable. On the other hand, if the confining pressure is high, fragments smaller than predicted by the thin-shell analysis become unstable. Finally, we compare the new dispersion relation with the results of 3D hydrodynamic simulations, and show that the two are in good agreement.Comment: 9 pages, 9 figures, accepted by MNRA

Energy transfers and magnetic energy growth in small-scale dynamo

In this letter we investigate the dynamics of magnetic energy growth in small-scale dynamo by studying energy transfers, mainly energy fluxes and shell-to-shell energy transfers. We perform dynamo simulations for magnetic Prandtl number $\mathrm{Pm}=20$ on $1024^3$ grid using pseudospectral method. We demonstrate that the magnetic energy growth is caused by nonlocal energy transfers from the large-scale or forcing-scale velocity field to small-scale magnetic field. The peak of these energy transfers move towards lower wavenumbers as dynamo evolves, which is the reason why the integral scale of the magnetic field increases with time. The energy transfers $U2U$ (velocity to velocity) and $B2B$ (magnetic to magnetic) are forward and local.Comment: 6 pages, 8 figure