Suchergebnisse

Traditional metal foams, which are incapable to meet the heat dissipation demands of today's electronics industry, were recently reformulated by the incorporation of thermal inclusions of graphite flakes that enhance their heat dissipation efficiency. In this work we manufacture, by means of a one-pot liquid metal infiltration synthesis, new layer-structured multicomponent materials that consist of aluminium foam components alternated with aluminium/diamond composite components. The thermal conductivity of aluminium/diamond components can substantially vary with processing conditions, which allow the nano-dimensional control of reaction products at the aluminium-diamond interface. The experimental and analytical results, plus finite element modelling, revealed that the low thermal resistance interface between components derived from the one-pot synthesis route, allowed multicomponent materials to significantly improve the thermal dissipation of traditional foams since aluminium/diamond components acted as effective thermal guides capable of transferring heat to the aluminium foam components where dissipation was achieved by forced convection. ; The authors acknowledge partial financial support from the Spanish Agencia Estatal de Investigación (AEI) and European Union (FEDER funds) through grant MAT2016-77742-C2-2-P.

Recent advances in cellular materials for active thermal management applications involve the integral design of their porous structure. In this work, open-cell aluminum foams with porosities in the range of 0.60–0.76 are developed, containing pores with spherical geometry and a bimodal pore size distribution. The fabrication strategy involves the use of the replication method by infiltration with liquid aluminum of porous preforms formed by packing NaCl spheres of two largely different sizes (7 mm and 1 mm average diameter), which are then removed by water dissolution. The paper describes cellular materials with different proportions of coarse and fine pores. Their detailed characterization by pore volume fraction, pressure drop, permeability, thermal conductivity and heat transfer coefficient is supported by analytical schemes. In addition, these materials were characterized under realistic operating conditions using computational fluid dynamics simulations. The material with 67 percent coarse pores and 33 percent fine pores, which has the highest porosity (and thus permeability), has the most appealing heat dissipation properties with the lowest pressure drops, making it an excellent candidate for emerging thermal management applications in electronic systems. ; The authors gratefully acknowledge partial financial support from the Spanish "Agencia Estatal de Investigación" (AEI) and European Union (FEDER funds) through grants MAT2016-77742-C2-2-P and PDC2021-121617-C21. The authors would also like to acknowledge the financial support received for the same purpose from the Conselleria d'Innovació, Universitats, Ciència, i Societat Digital of the Generalitat Valenciana through grant GVA-COVID19/2021/097. F.Ç. Durmus also acknowledges financial support from the Generalitat Valenciana through a "Santiago Grisolía" grant (GRISOLIA/2017/187). L.P. Maiorano also acknowledges the financial support from the University of Alicante through grant UAFPU2019-33 "Programa Propio para el fomento de la I+D+i del Vicerrectorado de Investigación y Transferencia de Conocimiento".

The preparation and use of Guefoams as heterogeneous catalyst is reported. The Guefoam catalyst consists of an open-pore Al-Si foam that accommodates a freely mobile guest phase (Ni/CeO2/Al2O3 particles) in its cavities, with neither a physical nor a chemical matrix-guest bond. A eutectic Al-12Si alloy was used as a low-melting matrix precursor to prevent thermal sintering of the active phase during liquid metal infiltration. CO2 methanation was chosen as the reaction test. The activity and CH4 selectivity (close to 100%) achieved with the Guefoam catalyst were similar to those obtained with a packed bed of the same active phase particles, but with the advantages of a structured reactor such as robustness and ease of handling. The thermal conductivity of the Guefoam catalyst is significantly improved with regard to the packed bed of active phase particles, which reduces the temperature gradients in the catalytic reactor, as demonstrated by computational fluid dynamic modelling. Since the permeability of the Guefoam catalyst is 2.7 times that of the packed bed, the pressure drop caused by the passage of a fluid through the novel material is reduced, resulting in a significantly higher catalytic performance index than the packed bed. ; Financial support from the Spanish Agencia Estatal de Investigación (AEI), the Spanish Ministry of Science and Innovation and the European Union (FEDER and NextGenerationEU funds) [projects MAT2016-77742-C2-2-P, PDC2021-121617-C21 and CTQ2015-67597-C2-2-R] and the Conselleria d'Innovació, Universitats, Ciència, i Societat Digital of the Generalitat Valenciana [projects GVA-COVID19/2021/097 and PROMETEO/2018/076, PhD grant of C.Y. Chaparro GRISOLIAP/2017/177 and contract of E. Bailón APOSTD/2019/030]. L.P. Maiorano also acknowledges the financial support from the University of Alicante through grant "Programa Propio para el fomento de la I+D+I del Vicerrectorado de Investigación y Transferencia de Conocimiento" (UAFPU2019-33).