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We developed two thermal concentrators, one with a 2D design of uniform thickness and another with a 3D design, using the coordinate transformation technique and metamaterials. By structuring the thermal conductor, we were able to achieve the desired local density-heat capacity product ρC and anisotropic thermal conductivities. Homogenized thermal conductivities were obtained from the boundary heat fluxes of the unit cells computed with finite element simulations and taking into account the cylindrical symmetry. We fabricated the 3D concentrator using 3D metal printing and used a thermal camera for characterization. By designing the unit cells to obtain the (ρ C) values given by the coordinate transformation, the time evolution characteristics of the metadevice are closer to those of an ideal concentrator when compared to devices that solely consider anisotropic conductivities. • Two thermal concentrators were designed using the coordinate transformation technique and metamaterials. • Not only the desired local anisotropic thermal conductivities K but also the local heat capacity ρC were achieved. • The 3D design was fabricated by metal 3D printing and characterized. • Taking into account ρC leads to the desired time evolution characteristics. [ABSTRACT FROM AUTHOR]

In this work, several copper alloy deposits were manufactured by cold spray with helium as accelerating and carrier gas. Electrical conductivity was measured to establish the potential of cold spray as a manufacturing process for high strength (>500 MPa) and high conductivity (>90% IACS) copper alloys. The deposits which are characterized by a low oxygen content (<200 ppm) and a low porosity level (<0.1%) present yield strength values up to about 700 MPa and electrical conductivity values up to 58.2 MS/m (100.3% IACS). Results show that, even if a compromise has to be made between the properties according to the objectives of the application, this additive manufacturing route appears suitable for the production of large copper alloys parts with high mechanical properties and high electrical and thermal conductivity. The role of alloy composition and post heat treatments on the strength and conductivity of the deposits was especially considered in this work. Cold spray deposits properties were finally compared with those obtained with other manufacturing routes. [ABSTRACT FROM AUTHOR]

This work was dedicated to the assessment of the mechanical properties of 304L stainless steel deposits obtained by cold spray using helium gas in order to increase particle velocity. The mechanical properties and the microstructure of the deposits were studied versus deposition parameters and post heat treatment. Deposition was also performed at two different nozzle pressures to evaluate the influence of particle velocity on the properties of the as-sprayed material. An ultimate tensile strength slightly above 400 MPa with about 10% elongation at rupture was obtained. The residual stress level was also investigated as a function of heat treating. [ABSTRACT FROM AUTHOR]

Abstract: This work focuses on the properties of a Cu-3wt.% Ag-0.5wt.% Zr alloy deposited by a Cold Spray process. Helium was used as the carrier gas and main gas to obtain a high deposition efficiency, low porosity and high mechanical properties. The effect of deposition parameters and heat treating on the microstructure and mechanical properties was explored. An ultimate tensile strength higher than 650MPa, a yield strength of about 600MPa and a Vickers micro hardness HV0.2 higher than 220 were obtained, values which compare quite favorably with those corresponding to a classically forged material. The deposits microstructure and more particularly the plastic deformation of particles upon impact were observed by optical and electronical microscopy. The residual stress level was also investigated as a function of heat treating. [Copyright &y& Elsevier]