Nano-fried-eggs: structural, optical, and magnetic characterization of physically prepared iron-silver nanoparticles

FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORThe prospect of combining both magnetic and plasmonic properties in a single nanoparticle promises both valuable insights on the properties of such systems from a fundamental viewpoint and numerous possibilities for technological applications. However, the combination of two of the most prominent metallic candidatesiron and silverhas presented numerous experimental difficulties because their thermodynamic properties impede miscibility and even coalescence. Herein, we present the thorough characterization of physically prepared Fe50Ag50 nanoparticles embedded in carbon and silica matrices via electron microscopy, optical spectroscopy, magnetometry and synchrotron-based X-ray spectroscopy. Iron and silver segregate completely into structures resembling fried eggs, with a nearly spherical, crystallized silver part surrounded by an amorphous structure of iron carbide or oxide, depending on the environment of the particles. Consequently, the particles exhibit both plasmonic absorption corresponding to the silver nanospheres in an oxide environment and a reduced but measurable magnetic response. The suitability of such nanoparticles for technological applications is discussed from the viewpoint of their high chemical reactivity with their environment.111160746085FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIORFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOCNPQ - CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICOCAPES - COORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL E NÍVEL SUPERIOR2013/14262-716/12807-488881.030488/2013-01sem informaçã

Nano-fried-eggs: Structural, optical, and magnetic characterization of physically prepared iron-silver nanoparticles

International audienc

SOAR - Satellite for Orbital Aerodynamics Research

SOAR (Satellite for Orbital Aerodynamics Research) is a CubeSat mission designed to investigate the interaction between different materials and the atmospheric flow regime in Very Low Earth Orbits (VLEO) and to demonstrate aerodynamic attitude and orbit control manoeuvres. Improving knowledge of the gas-surface interactions is important for the design of future satellites operating in lower altitude orbits and will enable the identification of materials which can minimise drag or improve aerodynamic control, a key aim of the Horizon 2020 DISCOVERER project. In order to achieve these objectives, SOAR features two payloads: i) a set of steerable fins which provide the ability to expose different materials or surface finishes to the oncoming flow with varying angle of incidence whilst also providing variable geometry to investigate aerostability and aerodynamic control; and ii) an Ion and Neutral Mass Spectrometer with Time-of-Flight capability which enables accurate measurement of the in-situ flow composition, density, and thermospheric wind velocity. Using precise orbit and attitude determination information and the measured atmospheric flow characteristics the drag and side-force experienced by the satellite in orbit can studied and estimates of the aerodynamic coefficients calculated. This paper first presents the scientific design and operational concept of the SOAR mission, focusing on the stability and control strategy which enables the spacecraft to maintain the flow-pointing attitude required by the payloads. The methodology for recovery of the (relative) aerodynamic coefficients from the measured orbit and in-situ atmospheric data is then presented. Finally, the uncertainty of the resolved aerodynamic coefficients is estimated statistically using simulations