Autonomic thermal switch based on phase transition alloys

Eutectic;Eutectoid

Li, Xuejiao ; Braun ; Paul V.

关键词: Eutectic;    Eutectoid;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/99530/LI-THESIS-2017.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Thermal management opens the new era of next generation electronic and thermal devices. Research on nano-scaled autonomic thermal switching is lacking because the suitable material is hard to synthesis. Our approach is utilizing the phase change property of eutectic/eutectoid materials. Triggered by heat, this type of material is possible to be directionally solidified into anisotropic structure, such as ordered lamellae and rods. We have surveyed the whole family of binary eutectic and eutectoid alloys and come up with a few good candidates for thermal switching applications. Two of the materials we studied in this thesis are Cu-P-Ag alloy and Cu-P eutectic alloy. The experimental methods we use are directional solidification and Time-domain Thermo-reflectance (TDTR) measurement. We have achieved large area of ordered lamellar structure up to hundreds of micron meters using Cu-P eutectic alloy. We include a few modern techniques to study the composition of both materials, which could be applied to other candidates for this type of application. The thermal conductivities of both materials are measured using TDTR. The Cu-P-Ag alloy and Cu-P eutectic alloy have thermal conductivity of 13.34 W/mK and 8.23 W/mK respectively. The theoretical estimation of thermal conductivity of Cu-P-Ag is around 40 W/mK, and the theoretical estimation for Cu-P eutectic alloy is around 200 W/mK. Both of our measured values are a little off from our estimated thermal conductivity of composite alloys, but the directional solidified alloys of these types were not measured before. It may due to the fact of surface reaction of our alloys with the environment and caused oxidation and contamination, and TDTR is a surface sensitive technique for thermal conductivity measurement. Other possible thermal measurements like Scanning Thermal Microscopy (SThM) and 3-omega thermal measurement should be included as a comparison in future.