Direct Measurements of Fundamental Sintering Parameters in Nanoparticles

Desiderio Kovar, University of Texas at Austin, DMR 1006894

Metal nanoparticles are vital for a number of applications including catalysts, textiles, healthcare, electronics, and energy. To utilize the particles effectively, it is important that the rate at which individual particles sinter into a network of particles be understood. We have found that sintering of nanoparticles occurs at temperatures several hundred degrees lower than for conventional micron-scale Ag particles. This process could enable patterned conducting lines to be deposited onto lower cost polymer substrates rather than glass or ceramic substrates that are currently used. We have used a transmission electron microscope to directly image nanoparticles while heating them. By capturing and analyzing these images, fundamental sintering parameters can be determined.

Transmission electron micrographs showing sintering of Ag Nanoparticles

Scanning electron micrographs showing sintering of NPs

Log Diffusivity versus the reciprocal of temperature for Ag (right) and Pt (left)

Direct Measurements of Fundamental Sintering Parameters in Nanoparticles

Desiderio Kovar, University of Texas at Austin, DMR 1006894

We have contributed to a UT Austin summer program (Alice in Wonderland) that brings female high school students to UT Austin. The goal is to attract women to physics by getting high-school students involved in research over the summer before they make decisions about colleges. Participants work in research labs in the STEM fields. In addition, a short course is given by UT graduate students, covers subjects from computer modeling and quantum mechanics to scanning tunneling microscopy and thin film growth.

Graduate students supported by this project have presented the results of our research at regional, national and international conferences and have published their work including:1.“Nanostructured Ag Bonds Produced at Low Process Temperatures,” G. Noiseau, J. Keto, M. Becker, D. Kovar, Materials

Science and Technology Conference, Symposium on Pb-free Solders and Advanced Interconnecting Materials; Montreal, Canada, October 27-31, 20132. “An Aberration –Corrected STEM HAADF Study on the Atomic Structure and Degradation Mechanism of Pt 3Co Nanocatalysts in

PEM Fuel Cells,” S. Rasouli, D. Groom, B. Patrick, M. Asoro, H. Ham, Y. Shao-Horn, L. Allard, D. Kovar, G. Hwang, M. Gummalla, S. C. Ball, D. Myers, and P.J. Ferreira, 4th International Workshop on Remote Electron Microscopy and In Situ Studies, May 22-24, 2013, Lisbon, Portugal.3. M. Asoro, D. Kovar. , P.J. and Ferreira, “In-situ TEM Observations of Sublimation in Silver Nanoparticles,” ACS Nano, Vol. 7, No.

9, pp. 7844-7892, 2013.4. M. Asoro, D. Kovar. D., and P.J. Ferreira, “Effects of Surface Carbon Coating on Sintering of Silver Nanoparticles: In-situ TEM

Observations,” Chemical Communications, Vol. 50, No. 37, pp. 4835 – 4838, 2014.5. M. Nahar, M.F. Becker, J.W. Keto, and D. Kovar, “Low Temperature Sintering of Nanoparticulate Ag,” Journal of Electronic

Materials, In Review, 2014.6. M. Asoro, P.J. Ferreira, and D. Kovar “In-situ TEM Observations of Sintering in Nanoparticles,”Acta Materialia, In Review 2014.