By Howard Lee
The second half of my day was spent hearing more interesting talks and ended on a high note with the reminder that we are all “sitting on the shoulders of giants.” Here is a summary of this afternoon’s great experience:
Titanium Nitride (TiN), new material for thermophotovotaics
To enhance the efficiency of thermo-photovoltaics, the loss of the unusable photons (low energy photon which lower than the bandgap of the photovoltaics) need to be minimized and the operational temperatures need to keep high (~1500°C) for enhancing the power output, thus the emitter needed to convert the input thermal energy into the emission above the band-gap of photovoltaic cells. In the talks of Dr. Urcan Guler and Jingjing Liu (FM4C.5, FM4C.8)(both from the groups of Alexandra Boltasseva and Vladimir Shalaev at Purdue university), they presented the use of TiN material to make a ultra-thin plasmonic thermal emitter. The selective emitter they demonstrated shows high emittance around 2.5 μm and shorter wavelengths, and suppresses emittance at longer wavelengths (while working at high temperature of 830K)(figure below). As discussed by Guler, such high melting temperature TiN (melting temperature of 2950 degree celsius)(together with metallic properties and high absorption) would be potentially be used for the field of thermo-photonvotaics applications and heat-assisted magnetic recording (HAMR) where high temperature environment are required.
Fig. 1. (a) Absorption of TiN metamaterial absorber and radiance of TiN selective emitter giv en along with solar irradiance and emission from a blackbody at 1500 oC. Dashed orange lines show the bandgap energies of several thermophotovoltaic semiconductors. (b) Metamaterial broadband absorber design (top) given with SEM images of TiN (left) and Au (right) samples after thermal testing at 800 oC for 1 hour. [FM4C.5, FM4C.8]
The last event I attended is the “Special Symposium in Memory of James P. Gordon”. It is a really amazing event with three Nobel Prize winners (Steven Chu, Arno Penzias and Charles To
wnes) and five invited speakers to speak about the personal life, scientific achievement and scientific attitude of James Gordon. The symposium started with the introductions of James Gordon by his wife (Susanna Gordon) and daughter, followed by his colleges and friends. As mention by the speakers, James Gordon was one of their smartest colleague/friends, but he is also one of the most humble person. The most amazing I found is that he did so many significant achievements in various fields of science, starting from the development of MASER (“Microwave Amplification by Stimulated Emission of Radiation”), followed by the investigation of optical trapping and optical fiber solitons. I was grateful to able to attend this symposium hearing all of these talks about such an admired scientist.
Posted: 10 June 2014 by
Howard Lee
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