Defense of Thesis Proposal: Xiaobai Yu

Thursday, November 21, 2013, 10:00am-12:00pm

Jackson Conference Room

“High-Performance Anti-Oxidation Solution-Processed Ni Nanochain-SiOx Selective Solar Thermal Absorbers”

Thesis Committee:
Jifeng Liu, Ph.D. (Chair)
Ian Baker, Ph.D.
Christopher G. Levey, Ph.D.
Juejun Hu, Ph.D.

Abstract: Cermet selective solar thermal absorber coatings, which incorporate metal nanoparticles into a ceramic matrix, have been explored and developed in recent years. However, metal oxidation at high temperatures has long been an issue in cermet solar thermal absorbers, which impedes the development of high-temperature high-performance products. In this project, we focus on solution-processed Ni nanochain-SiOx (x<=2) selective solar thermal absorbers that exhibit a high efficiency on solar energy conversion with minimal thermal radiation losses. The thermal stability is far superior to more conventional Ni nanoparticle-Al2O3 selective solar thermal absorbers, which readily oxidize at 450C. The SiOx and SiO2 matrices are derived from Hydrogen Silsesquioxane (HSQ) and tetraethyl orthosilicate (TEOS) precursors, respectively, which comprise Si-O cage-like structures and Si-O networks. Fourier transform infrared spectroscopy (FTIR) shows that the dissociation of Si-O structures may have enabled the formation of new bonds to passivate the surface of Ni nanoparticles and prevent oxidation. Si excess in matrices helps to protect Ni nanoparticles from being oxidized, which results in the fact that Ni-SiOx (x<2) systems perform better than Ni-SiO2 systems. The aim of this project includes:

  1. Measuring and comparing the anti-oxidation property performance of Ni-based cermet coatings in different matrices on Si or stainless steel substrates. Characterizing the microstructures of as-coated thin films by using a combination of different characterization methods which involve FEI XL-30 field emission gun (FEG) scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS);  X-ray diffraction (XRD) using a rotating anode X-ray set; Fourier transform infrared spectroscopy (FTIR); UV-VIS-NIR spectrometer with an integrating sphere.
  2. Determining and understanding the mechanism of different anti-oxidation performances. FTIR can be used to do bonding analysis.
  3. Dispersing Ni nanoparticles in matrices more uniformly and improving the quality of the coated thin films.
  4. Simulating the optical response from a rough Ni-SiOx surface with or without anti-reflectance layers; adjusting the nanoparticle size based on mathematical calculations so that better optical properties can be achieved.

For more information, contact Daryl Laware at daryl.a.laware@dartmouth.edu.