Direct Measurements of Fundamental Sintering Parameters in Nanoparticles

University Of Texas At Austin, Austin TX

Investigators

Abstract

TECHNICAL SUMMARY: The intellectual merit of this proposal focuses on the fundamental mechanisms that influence the low temperature (<300&#730;C) sintering of metallic nanoparticles (NPs). Existing models cannot accurately predict the sintering response of NPs at low temperatures. A synergistic combination of state-of-the art processing and in-situ and ex-situ transmission electron microscopy will be employed to investigate sintering of NPs. Pairs of NPs that are free of dispersants will be produced to meet the stringent requirements necessary for this study. This is crucial as the presence of organic dispersants that are typically present on the surfaces of NPs interfere with the intrinsic sintering behavior of the NPs at low temperatures. Second, a state-of-the-art, aberration-corrected TEM/STEM equipped with a novel heating stage for in-situ sintering experiments will be utilized to perform real-time measurements on NPs of neck growth, interparticle distance and boundary mobility. Third, correlations will be made between the studies performed on pairs of NPs with studies using realistic, three-dimensional particle morphologies in thick films. These experiments will increase fundamental understanding of sintering in metallic nanoparticles by 1) Determining how particle size, temperature, and particle geometry influence sintering mechanisms in NPs, 2) Measuring the influence of particle size, temperature, and particle geometry on surface or grain boundary diffusivity and grain boundary mobility in NPs, 3) Identifying the role of defects, particularly twins on the sintering behavior of NPs, and 4) Determining the extent to which the electron beam, influences the measured mass transport rates during in situ TEM/STEM experiments. NON-TECHNICAL SUMMARY: Thick film materials are currently used in a large number of diverse applications including many electronic devices. The market for these devices is growing rapidly and improvements in technologies are critical for these advancements. For example, according to III-Vs Review (Vol. 17, no 2. March 2004, pg 7.), the market for thick films was estimated at $16.8 billion in 2008 with significant growth likely in the future due to the increases in portable telecommunication devices. Current technologies require processing temperatures of up to 800&#730;C, which severely restricts the materials that can be utilized and drives up costs significantly. In addition, there are a number of new technologies that would benefit from reduced processing temperatures for thick films including biosensors and thick film solar cells. The proposed research focuses on understanding the fundamental mechanisms that would allow the processing of thick films of metallic nanoparticles at temperatures less than 300&#730;C. The proposed activities encompass outreach activities offering deaf students, who are highly underrepresented in science and engineering, research opportunities related to the proposed work. A recently established partnership between UT Austin and the Texas School for the Deaf is in need of additional research projects in which students can be placed and the proposed activities will provide a critical mass of projects and students that will significantly benefit this program.