Effect of temperature and time on properties of Spark Plasma Sintered NiCuZn: Co ferrite

3 pagesInternational audienceSpark Plasma Sintering is a powerfal method to produce fine grain dense ferrite at low temperature. However, the process, usually conducted in neutral atmosphere in a carbon die, yields carbon surface deposition and reduction of Fe3+ into Fe2+. It's shown that subsequent annealing in air can remove carbon and, under some conditions, produce complete oxidation of Fe2+ ions. Regular values of the resistivity and permittivity (resp. 1 M­m, 13 "0) are recovered for most samples annealed not higher than 750±C. Relatively high value of the permeability (up to 240) and high merit factor (μs × fr > 5 GHz) have been achieved

Highly integrated power electronic converters using active devices embedded in printed-circuit board

International audienceIn this paper, we present a short overview of the power dies interconnects based on PCB technology, then we focus on embedding of power dies in the PCB material. In the second part of the article, we present in details the technology we developed to embed dies in PCB. Results show that the electrical performance of the die remains satisfying after embedding, but that dies with a copper topside metal layer are required for this process

Nuclear Thermal Propulsion

This chapter will cover the fundamentals of nuclear thermal propulsion systems, covering basic principles of operation and why nuclear is a superior option to chemical rockets for interplanetary travel. It will begin with a historical overview from early efforts in the early 1950s up to current interests, with respect to fuel types, core materials, and ongoing testing efforts. An overview will be provided of reactor types and design elements for reactor concepts or testing systems for nuclear thermal propulsion, followed by a discussion of nuclear thermal design concepts. A section on system design and modeling will be presented to discuss modeling and simulation of driving phenomena: neutronics, materials performance, heat transfer, and structural mechanics, solved in a tightly coupled multiphysics system. Finally, it will show the results of a coupled physics model for a conceptual design with simulation of rapid startup transients needed to maximize hydrogen efficiency

Preservation of kinetics parameters generated by Monte Carlo calculations in two-step deterministic calculations

The generation of accurate kinetic parameters such as mean generation time Λ and effective delayed neutron fraction βeff via Monte Carlo codes is established. Employing these in downstream deterministic codes warrants another step to ensure no additional error is introduced by the low-order transport operator when computing forward and adjoint fluxes for bilinear weighting of these parameters. Another complexity stems from applying superhomogenization (SPH) equivalence in non-fundamental mode approximations, where reference and low-order calculations rely on a 3D full core model. In these cases, SPH factors can optionally be computed for only part of the geometry while preserving reaction rates and K-effective, but the impact of such approximations on kinetics parameters has not been thoroughly studied. This paper aims at studying the preservation of bilinearly-weighted quantities in the Serpent–Griffin calculation procedure. Diffusion and transport evaluations of IPEN/MB-01, Godiva, and Flattop were carried out with the Griffin reactor physics code, testing available modeling options using Serpent-generated multigroup cross sections and equivalence data. Verifying Griffin against Serpent indicates sensitivities to multigroup energy grid selection and regional application of SPH equivalence, introducing significant errors; these were demonstrated to be reduced through the use of a transport method together with a finer energy grid

Effet de la température et du temps de frittage sur les propriétés du ferrite NiCuZn :Co fritté avec le procédé Spark Plasma Sintering ( SPS ) et réalisation d'une inductance intégrès.

National audienceLe frittage du ferrite spinelle NiCuZn par le procédé Spark Plasma Sintering a été étudié pour une poudre nanométrique qui a été synthétisée préalablement par voie solide. Les propriétés structurales, diélectrique et magnétique pour ce ferrite ont été étudiées pour différentes valeurs de la température et du temps de frittage. Le matériau est bien densifié pour les différentes températures et temps de frittage. La résistivité du ferrite est assez élevée de l'ordre de 107 Ωm pour une température de frittage de 750 °C pendant 5 mn, la permittivité est proche de la littérature pour des températures inférieures à 750 °C et la perméabilité initiale est comprise entre 20 et 250. L'étude du cofrittage du ferrite avec le cuivre a montré que la diffusion à l'interface est très limitée, ce qui a permis de réaliser un composant intégré qui présente une inductance de 0,62 µH mais un facteur de qualité moyen dû au fait que le cuivre est directement noyé dans le ferrite

EDT for Power Devices

International audienceThis presentation gives an overview of the packaging requirements for power electronics, especially in terms of thermal aspects. Then, it briefly describes the state-of-the-art in the topic of advanced Printed-Circuit-Board (PCB) use in power electronics. Finally, the embedding technology developed in the 3DPHI platform is presente

Effet de la température et du temps de frittage sur les propriétés structurales, diélectrique et magnétique du ferrite spinelle Ni0.195Cu0.2Zn0.599Co0.006Fe2O4 fritté avec le procédé Spark Plasma Sintering ( SPS )

LGEP 2010 ID = 710National audienc

Effet de la température et du temps de frittage sur les propriétés structurales, diélectrique et magnétique du ferrite spinelle Ni0.195Cu0.2Zn0.599Co0.006Fe2O4 fritté avec le procédé Spark Plasma Sintering ( SPS )

LGEP 2010 ID = 710National audienc