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Additive manufacturing (AM) techniques such as cold spray and fused filament fabrication allows for 3D build-up permitting fabrication of high complexity shapes and configurations. The fabrication of soft and hard magnetic materials using these techniques was investigated in the context of 3D electrical machines. The use of 3D finite element analysis (FEA) to develop new motor topologies based on the advantages offered by AM will be discussed. FEA was also used to orientate the material development by identifying the most critical properties. The hard magnetic properties (coercivity and remanence), soft magnetic properties (permeability and losses) of both types of materials fabricated by both AM processes will be presented., AMPM 2019: Additive Manufacturing with Powder Metallurgy Conference, 23-25 June 2019, Phoenix, USA

Manufacturing increasingly complex parts featuring advanced functionalities while reducing costs is a challenge for all industries. Automotive electric motor fabrication is no exception as high performance magnetic materials need to be shaped and installed into complex assemblies. Current fabrication procedures severely limit the design flexibility as magnetic materials are typically difficult to machine and manipulate. In this work, we will describe the use of cold spray additive manufacturing for the low-cost direct shaping of hard and soft magnetic materials on electric motor parts without the need for additional assembly steps. Combination of sprayed soft and hard magnetic materials opens up the possibilities for innovative designs leading to performance gain and cost savings. The role of the process parameters such as the gas temperature as well as the powder composition, size distribution and morphology on the magnetic properties is discussed. The use of robot toolpath programming necessary to spray on motor parts is illustrated by different examples of complex shape prototypes. Use of soft and hard magnetic materials for the realization of motor prototypes is shown, thus demonstrating the feasibility of using cold spray additive manufacturing as an effective technology to fabricate motor parts., International Thermal Spray Conference and Exposition, May 7-10, 2018, Orlando, FL, USA

International Forum on Magnetic Applications, Technologies and Materials (MAGNETICS 2017), January 18-19, 2018, Orlando, FL. USA

Hybrid and electric vehicles play an increasing role to alleviate the effects of our transportation needs on the environment. Permanent magnets are a key component of electric motors and represent a significant proportion of their total cost. We report on the fabrication of metal-NdFeB composite permanent magnets made using cold spray processes. In order to control the magnetic properties, coatings’ microstructure was varied using powders with various compositions, size distributions and morphologies. The obtained magnetic and mechanical properties results confirm the feasibility of using cold spray as an effective technology to deposit hard magnet coatings directly on the rotor surface., The 29th World Electric Vehicle Symposium and Exhibition (EVS29), June 19-22, 2016, Montréal, QC, Canada

Atmospheric plasma spray (APS) is an efficient technique for depositing high performance dielectric coatings at a low cost, with high deposition rate and on complex-shaped parts. Due to its availability, low price, ease to spray and good dielectric properties, alumina (Al2O3) is a very common choice of material for insulating applications. However, the coefficient of thermal expansion (CTE) of alumina does not represent the best match for the CTE of most metallic substrates hence alternative high CTE ceramic materials are of interest. We report on the microstructural and electrical properties of a dense high CTE forsterite (Mg2SiO4) coating deposited by APS. Annealed forsterite coatings' microstructure and dielectric properties are compared to that of annealed alumina coatings. The ceramics' electrical properties were evaluated by performing impedance measurements on as-sprayed coatings and coatings exposed to different annealing temperatures. We show that both materials exhibit important degradation after exposure to a threshold temperature. An equivalent electrical model is used to extract relevant coating properties such as resistivity and dielectric constant. The coating electrical degradation mechanisms are discussed., Thermal Spray 2014, May 21-23, 2014, Barcelona, Spain

International audience; The Cosmic Microwave Background (CMB) is one of the pillars on which the Big Bang theory relies. High-quality maps of this radiation strongly constrain the history of the Universe and its content. Such maps require accurate and sensitive measurements of tiny random features on a strong uniform background. Stray radiation must be rejected extremely efficiently and the response and noise of the instrument should be known to better than a percent, while full sky maps are needed for optimal data reduction. This is better achieved outside the atmosphere in the conditions of space. In a field where fundamental physics and astrophysics are closely related, the major advances came from the COBE and WMAP spacecraft, and further progress is now expected from the Planck mission and also from recently developed ground-based experiments with dedicated goals achievable on fractions of the sky.

Nanocomposite materials based on metal particles embedded in a dielectric matrix present, due to the nanometric size of the metal particles, unusual properties which cannot be found in bulk materials. Most notably, the conduction electron resonance in the presence of incident light excitation, so-called surface plasmon resonance (spr), gives rise to an absorption band in the visible which have a drastic impact on the optical properties of the nanocomposite. The position, the width and the amplitude of this absorption band are complex functions of the nanostructural characteristics of the nanocomposite such as: the kind and concentration of metal, the nanoparticles size and shape, the refractive index of the matrix, etc. Specifically, the presence of asymmetric particles, like nanoellipsoids for example, allows for the observation of multiple spr absorption bands resulting in a non-symmetric material with anisotropic properties. In this thesis, we will present the development and the analysis of advanced fabrication techniques allowing the precise control of the synthesis of nanocomposites formed of gold nanoparticles embedded in a silica matrix. We have developed a three-step technique allowing us to fabricate nanocomposite films with particles of controlled size and shape. These steps are the following: 1) hybrid deposition sputtering/ plasma-enhanced chemical vapor deposition, 2) thermal annealing, 3) high energy heavy ion irradiation. Subsequently, the optical performance of the fabricated materials was tested by different techniques to evaluate their linear and nonlinear properties. The former were studied using ellipsometry and spectrophotometry while the latter were evaluated by the P-Scan and Z-Scan techniques. More particularly, we devoted a lot of time to the metrology and control of the anisotropic properties of the nanocomposite system formed by ion irradiation. A new approach developed to measure anisotropic nonlinear optical properties will be presented. In this document, the lector will find an exhaustive theoretical description of the optical properties (linear and nonlinear) of metal/dielectric nanocomposites including detailed models for the description of the properties of each constituents of the nanocomposite: metal (Drude, Lorentz) and dielectric (Cauchy)., Les matériaux nanocomposites formés à partir de particules métalliques incluses dans une matrice diélectrique présentent des propriétés inusitées que l'on ne retrouve pas dans les matériaux massiques étant donné la taille nanométrique des particules métalliques. Notamment, la résonance des électrons de conduction du métal sous l'excitation d'une lumière incidente, appelée résonance plasmon de surface (spr), donne lieu à l'apparition d'une bande d'absorption dans le visible ayant une influence drastique sur les propriétés optiques du nanocomposite. La position, la largeur et l'amplitude de cette bande d'absorption sont des fonctions complexes des caractéristiques nano-structurales du nanocomposite, notamment : la nature et la concentration du métal, la taille des nanoparticules, leur forme, l'indice de réfraction de la matrice, etc. Spécifiquement, la présence de particules asymétriques, comme par exemple des particules de forme nano ellipsoïdale, permet l'observation de bandes d'absorption spr multiples résultant en un matériau non-symétrique possédant des propriétés anisotropes. Dans cette thèse, nous présenterons le développement et l'analyse de techniques avancées de fabrication permettant le contrôle précis de la synthèse d'un nanocomposite formé de nanoparticules d'or incluses dans une matrice de silice. Nous avons développé une technique en trois étapes permettant de fabriquer des couches nanocomposites comprenant des particules de tailles et de formes contrôlées. Ces étapes sont : 1) dépôt hybride pulvérisation/dépôt chimique en phase vapeur assisté par plasma, 2) recuits thermiques, 3) irradiation à l'aide d'un faisceau d'ions de haute énergie. Subséquemment, la performance optique des matériaux fabriqués a été testée par différentes techniques afin d'en évaluer les propriétés linéaires et non-linéaires. Les premières ont été étudiées par ellipsométrie et spectrophotométrie alors que les deuxièmes l'ont été par les techniques P-Scan et Z-Scan. Plus précisément, nous nous sommes intéressés à la métrologie et au contrôle de l'anisotropie des propriétés du système nanocomposite formé par faisceau d'ions. Une nouvelle approche de mesure des propriétés optiques non-linéaires anisotropes sera présentée. Dans ce document, le lecteur retrouvera une description théorique exhaustive des propriétés optiques (linéaires et non-linéaires) des matériaux nanocomposites métal/diélectrique incluant des modèles détaillés pour la description des propriétés de chacun des constituants du nanocomposite : métal (Drude, Lorentz) et diélectrique (Cauchy).