Best Literature Review Winners!

February 23, 2007 on 3:31 pm | In News & Events |

Congratulations to Jonathan H. Tao and Stephanie L. Svetlik, who won the S&E Library’s “Best Literature Review” Awards at yesterday’s Jacobs School of Engineering Research Expo. Each one received a $125 bookstore giftcard, and their posters will soon be on display at S&E.

Jonathan H. Tao
Graduate Program in Materials Science (Jan Talbot, Faculty Advisor)
SYNTHESIS AND LIGHT EMISSION CHARACTERISTICS FOR RARE-EARTH DOPED NITRIDE MATERIALS FOR USE IN PHOSPHORLESS SOLID STATE LIGHTING

Stephanie L. Svetlik
Structural Engineering (Vistasp Karbhari, Faculty Advisor)
EXTENDING PREDICTIVE DEGRADATION MODELS TO HOT, HUMID ENVIRONMENTS

Jonathan H. Tao. SYNTHESIS AND LIGHT EMISSION CHARACTERISTICS FOR RARE-EARTH DOPED NITRIDE MATERIALS FOR USE IN PHOSPHORLESS SOLID STATE LIGHTING

“The recent discovery of fluorescence from rare earth ions in nitride hosts opens up the possibility of creating a white light solid state source via the combination of different rare earth ions. By controlling the type of dopant and its concentration, the color of the emitted light upon e-h recombination in the active layer of a double heterostructure design of a GaN-based LED light source may be tuned. Using combustion synthesis as part of a two-step process, and a three-step wet-chemical synthesis process, we were able to synthesize nitride hosts doped with various rare-earth ions. Pure GaN powders have been synthesized with oxide precursors made by combustion synthesis, and AlN powders doped with Eu3+, Tm3+, and Tb3+ have been synthesized from fluoride precursors. X-ray diffraction (XRD) and energy dispersive spectrometry (EDS) have been used to characterize the phase and composition of the powders, respectively. Photoluminescence (PL) was measured on doped AlN powders and cathodoluminescence (CL) was measrued on pure GaN powders to characterize the emission of each sample at room temperature. Among the successful nitride samples, Eu3+, Tm3+, and Tb3+ doped AlN samples demonstrated strong dopant-related emission and reduced defect emission compared to the pure nitride host. The 3-step process has been extended to synthesize high purity GaN powders as well as GaAlN alloys, with as low as ~4 at% oxygen and an 8% oxygen- to-nitrogen ratio.”

---

Stephanie L. Svetlik. EXTENDING PREDICTIVE DEGRADATION MODELS TO HOT, HUMID ENVIRONMENTS

“Moisture sorption of polymer composites immersed in deionized water at different temperatures has been investigated at length as a means for performing accelerated degradation. The relation of this sorption behavior to actual behavior in various hygrothermal environments still remains to be seen. This test program will model the behavior of a pultruded E-glass/vinyl ester composite in thirteen environments involving three temperatures and three relative humidities. Low humidity exposures result in a post-cure effect at high temperatures, enabling the isolation of moisture sorption effects at higher humidities from purely thermal effects. Additionally, the sorption behavior of the glass composite due to immersion in deionized water at four temperatures (20, 40, 60, 80 degrees Celsius) is investigated in order to link behavior in non-saturated environments to immersion environments. A main goal of this work is to create a model which will relate the change in tensile properties, short beam shear strength, and glass transition temperature with moisture sorption. Substitution of moisture content for time in standard time dependent predictive models will remove the necessity to investigate the temporal nature of the sorption trend and degradation of mechanistic properties. Investigation of common known mechanisms of degradation such as pitting of glass fiber and interfacial facial degradation will be extended by consider moisture gain or loss in conjunction with microscopy.”