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Lightweight, High-Strength Nanocomposite Magnesium for Radiators

New material offers an exceptional balance of properties and cost.
Marshall Space Flight Center, Alabama

The next generation of radiators will be designed using a composite with the combination of the lowest density, highest thermal conductivity, and highest strength. A scalable, low-cost process was developed to advance state-of-the-art metal matrix thermal conductors to reach a theoretical goal of 578 W/mK (270W/mK achieved), a density less than aluminum ( achieved), and a yield strength over 30 ksi (≈207 MPa, 42 ksi achieved). The incorporation of nanofibers into metals has been heavily researched to improve mechanical and thermal properties of materials, with limited technical and commercial success. The problem of incorporating high-aspect-ratio, high-surface-area particles (including fiber and flake) with controlled and repeatable concentration and distribution into molten metals is a large undertaking, and must factor in the molten metal temperature, composition, and surface tension. Direct feeding of the particles does not work, as particles burn, react with the molten metal, or do not stay in the metal. Other feeding mechanisms such as auger feeding into the metal, in-situ formation, and stir casting are cost-prohibitive and not always scalable.

To solve these problems, a method was developed to incorporate high-aspect-ratio nanoparticles into a pre-dispersed mastercomposite that enables safe and reliable feeding into molten magnesium to create a high-strength, high-thermal-conductivity magnesium nanocomposite. The process is based on ultrasonication technologies with chemistry control to disperse nanoparticles into a metal-compatible binder that can be rolled, spread, or molded into various shapes that can be directly inserted into a pool of molten metal. Without fabrication of these master-composites, the nanoparticles agglomerate at the surface of the molten metal, being burned or removed from the casting with slag, instead of being incorporated into a nanocomposite. The method has resulted in both strength increase (>50%) and improvement in thermal conductivity (>150%) in magnesium using multiwalled carbon nanotubes and high-strength castable magnesium alloys. Low-cost methods of achieving high-strength, high-conductivity magnesium using casting techniques have now been demonstrated, leading to an exceptional balance of properties and cost not achievable in currently available alloys or materials.

Other applications for this technology include consumer electronics, aerospace, combustion engine components, automobile components such as brake systems, corrosion-resistant coatings, and drill bits, tool holders, and mining equipment.

his work was done by Nicholas Farkas of Terves, Inc. for Marshall Space Flight Center. For more information, contact Ronald C. Darty, Licensing Executive in the MSFC Technology Transfer Office, at Refer to MFS-33253-1.

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