[Che-student-staff-list] Haiyu Fang Dissertation Defense, Thursday, November 13th, at 1:30p.m. in FRNY 3062B

[Maus, Amy M]

This e-mail is to announce that Haiyu Fang will be defending his dissertation, Synthesis and Characterization of Nanostructured Materials for Thermoelectric Energy Conversion, on Thursday, November 13th  at 1:30PM in FRNY 3062B. The dissertation is being co-directed by Dr. Morgan, and the abstract is below. All are welcome to attend.


Abstract:
The rapid development of thermoelectric materials in the past decade has raised new hopes for the possibility of directly converting waste thermal energy back to electricity. However, the large scale deployment of thermoelectric devices is still limited by the mediocre conversion efficiency. Nanostructured materials have been proved to be able to significantly improve conversion efficiency. My research is devoted to developing efficient solution phase reactions to synthesize nanostructured thermoelectric materials in an economical and scalable way. Meanwhile, we also aim at exploring the unique applications of solution synthesized nanostructured materials, e.g. developing nanocrystal ink to coat on flexible substrates for applications in wearable thermoelectric devices.

In this study, we developed a general method to synthesize a variety of telluride nanowires and binary phase heterostructures with solution phase reaction. To demonstrate the scalability of our solution phase synthesis, a 1 liter reactor is used to synthesize over 17 gram of Bi2Te3 nanowires at a yield of 94% with low reaction temperature of 120 °C and short reaction time of 70 minutes. Furthermore, we have taken advantage of the flexibility of our method and successfully synthesized different heterostructures with two tellurides in a single nanowire, e.g. Te-Bi2Te3, PbTe-Bi2Te3 and Ag2Te-Bi2Te3, which provide great platforms to study the electron and phonon transport through interfaces. Meanwhile, to investigate the applications of nanoparticles in flexible thermoelectrics, we also developed a method to synthesize extremely stable nanocrystal ink for coating on various substrates.

In order to demonstrate the benefits of solution synthesized nanoparticles for thermoelectric applications, we applied hot press to consolidate the nanowires and heterostructures into nanocomposites which possess extremely low thermal conductivity, leading to enhanced ZT. Especially, the binary phase nanocomposites made from heterostructures show much lower thermal conductivity than single phase bulk and even nanocomposite. To further improve the thermoelectric performance, we also applied doping to tune the carrier concentration of our materials to gain more thermoelectric performance enhancement. For example, Se was used to dope Bi2Te3 nanocomposites, which leads to 60% of power factor enhancement. In addition to hot press, we also coated solution synthesized nanoparticles on different substrates, even flexible ones, to fabricate thin films. Particularly, the effects of size and iodine doping concentration on the thermoelectric properties on the PbTe nanocrystal thin films are investigated to enhance the understanding of using nanocrystal thin film for flexible thermoelectric applications.

Kind Regards,

Amy Maus
Graduate Program Secretary
School of Chemical Engineering
Purdue University
480 Stadium Mall Drive
West Lafayette, Indiana 47907-2100
Phone: 765-494-7343
Email: amaus at purdue.edu<mailto:amaus at purdue.edu>



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