World’s first visualization of nanoparticle sintering in four dimensions

The research outcome of Mr. Yoshinaga (currently working at Toppan Printing), Assistant Professor Ihara, Associate Professor Saito, and Professor Murayama has been published in Nanoscale. This paper is the outcome of joint research with Prof. Hata and Mr. Wada of Interdisciplinary Graduate School of Science and Engineering, Kyushu University, and Mel-build Co.

Metal nanoparticles have a large surface area relative to their volume, thereby sintering at lower temperatures than normal-sized particles. The nanoparticles are attracting attention, for example, as a new wiring material for electronic circuits. Since the nanoparticles are prone to aggregate, it is difficult to capture their sintering behavior under actual use conditions with ordinary two-dimensional observation, and therefore, three-dimensional observation has been desired. However, many nanoparticles are highly reactive, i.e., exposing to air or electron beams alters their surface properties, resulting in making it difficult to capture the actual sintering process. Since 3D observation requires electron beams to irradiate from multiple directions, to capture the time evolution of the process would require an enormous amount of electron beams. In addition, when transporting specimens into a transmission electron microscope (TEM), exposure to the atmosphere is inevitable with conventional techniques.

In this study, in collaboration with Mel-build Co., we overcame contamination caused by air exposure by developing an in-situ heating TEM holder which can maintain the airtightness during sample transport. The electron dose during the observation was reduced to the level of observing biological samples, and the sintering process of nanoparticles was visualized in three dimensions by using an advanced noise filter. Such techniques are expected to clarify the heat treatment process of various nanoparticles, which will be useful for material development.

This outcome was announced in a press release from the Public Relations Office of Kyushu University.