Subcategory: STEM Research
Rami Bommareddi - Alabama A&M University
Co-Author(s): Matthew Edwards, Ashok Batra, Satilmis Budak, Vernessa Edwards, Kristopher Liggins, Bir Bohara, Samuel Uba, Eshirdanya McGhee, Ashley Owens and Mersaydes Goodson, Alabama A&M University
Accomplishments: Two PhD students completed their dissertation work and secured jobs. Two Masters students completed their thesis work. Two more students will complete their Master’s thesis by the end of Spring 2020 semester. Technical details: Oxide glasses embedded with rare-earth ions and silver were made by the melt quenching technique. Dy, Tb and Sm doped glasses emitted white light under diode laser excitation. Color co-ordinates were measured as a function of glass composition to evaluate the samples. Color coordinates for some of the materials are close to that of sunlight. Upon heat treatment of the glasses silver ions formed into metallic nanoparticles. Heat treated glasses exhibited enhanced emission under blue diode laser excitation revealing the plasmonic effect. Multilayered heterostructured thermoelectric thin films were deposited using sputtering and electron beam systems. They were annealed at different temperatures to cause the forming of quantum structures in the multilayers to increase the efficiency. After the completion of thermoelectric properties of Ni/Bi2Te3/Sb2Te3/Ni, Si/Si+Sb, Si/Si+Ge, two new systems of Sb/Sb+SnO2 and Sn/Sn+SnO2 multilayer thin films have been characterized. Si/Si+Sb, Si/Si+Ge, Ni/Bi2Te3/Sb2Te3/Ni multilayer devices reached their highest figure of merit (efficiency) values of 2.6, 0.37, and 4×10-3, respectively at some annealed temperatures. The figure of merit, ZT of Sb/Sb+SnO2 multilayer thin films reached 1.54, the figure of merit of Sn/Sn+ SnO2 multilayer thin films reached 3.40. A comprehensive characterization study based on the electrical transport, sensing and energy harvesting capabilities of nanocomposites has been evaluated. Pyroelectric coefficient and figure of merit enhanced with PLZT and PMN-PT content and temperature. The output voltage and power generated from PLZT/paint and PMN-PT/paint piezoelectric energy harvester is relatively small (51.7 mV and ~0.38 micro-Watt and 65 mV and ~1.0 n-Watt). The output voltage and power of PMN-PT/paint nanocomposite films-based cantilever harvester increased with a temperature gradient (of about 3 ?C) and mechanical vibrations (61 Hz.) resulting in a maximum output voltage ranging from 53.6 mV to 61.6 mV at a load resistance of 4 M?. To determine the minimum energy and other thin film properties in relation to energy harvesting, under density functional theory, we have studied the weak perturbation nonlinear Klein-Gordon (KG) equation.
Funder Acknowledgement(s): NSF HBCU RISE Grant Number 1546965
Faculty Advisor: None Listed,
NSF Affiliation: CREST