Interface engineering in ferromagnetic high-thermal conductivity iron-diamond/metal composites for electric conversion applications

Abstract

The objective of this work is to investigate whether any combination of metal and magnetic particles may fit the specifications of electric conversion applications, which require, among other properties, sufficiently high magnetic permeability and thermal conductance and a low (adjustable) thermal expansion coefficient. After having explored a wide variety of combinations, guided by both chemical and physical considerations, it was decided to investigate composites fabricated by gas pressure infiltration of Ag or Ag3wt%Si alloys into compacts of bimodal mixtures of diamond (high thermal conductivity) and iron particles (high magnetic permeability). Three average particle sizes of each component were used to fabricate the composites, namely, diamond particles of 230, 285 and 295 µm and iron particles of 30, 42 and 398 µm. In addition the volume fraction varied in the ranges 0.1-0.59 (diamond) and 0.12-0.43 (iron). In order to avoid alloying with the infiltrating metal and iron-diamond reaction, iron particles were coated with amorphous carbon. The results indicate that only composites containing a volume fraction of carbon-coated iron particles higher than 0.4 showed properties (a thermal conductance higher than 200 W/mK and a relative magnetic permeability above 0.3) within the range valid for electric conversion applications. Composites containing non-coated iron particles reached in almost all cases very low values of both properties. Highlights Fe-diamond/Ag and Fe-diamond/AgSi composites are fabricated by metal infiltration Fe and diamond particles undergo detrimental solid-solid reactions during processing Interface engineering by carbon coating of Fe particles (Fe C) is followed Carbon coating sharply decreases the Ag-Fe and AgSi-Fe interface thermal conductance Fe C (>40%)-diamond/Ag-Si composites are adequate for electric conversion applications

Application of New Materials in Aerospace Thermal Management

“…J. M. Molina et al [15], in order to solve the problem of poor thermal conductivity of materials encountered in the field of electrical conversion, prepared a diamond iron composite by adding Ag and Ag-3wt% Si using the air pressure infiltration method. The material has a thermal conductivity of more than 200W/m•K, while its relative permeability is more than 0.3.…”

Evaluation of Interfacial Thermal Resistance of Al-Si Alloy by Using Image-Based Simulation

“…In addition, the thermal resistance at the interface within the alloys affects the thermal conductivity of the material, so it is important for the thermal design of the material. In the two-phase materials, reflection and scattering occur at the interface of two different substances, and interfacial thermal resistance greatly affects TC of material [1][2][3][4][5]. However, it is difficult to measure interfacial thermal resistance in materials, and few data have been reported.…”

Evaluation of Interfacial Thermal Resistance of Al-AlN Composites by Using Image-Based Calculation

“…On the other hand, the heat in ceramics is transmitted by the only lattice vibrations. In the MMCs, reflection and scattering occur at the interface of two different substances, and interfacial thermal resistance greatly affects TC of composite materials [1][2][3][4]. Actual measurement of interfacial thermal resistance is difficult and only a few data of MMCs are reported.…”