Ultrafine particles

Abstract

This presentation is a summarized review of the achievements of the ultrafine particle (UFP) project, which was a 5-yr research and development project inaugurated in 1981 by Research and Development Corporation of Japan, a government sponsored organization. Any creative work with regard to UFP’s having diameters in the range of 10 to 1000 Å, was encouraged for the purpose of obtaining new knowledge and basic technology for the future. Four groups, each composed of four or five research staffs, were budgeted at approximately 1.5 billion yen. A high-resolution (∼2 Å) very high vacuum (≲10−6 Pa) multifunctional transmission electron microscope, designed and manufactured for the project, revealed that an UFP (gold <50 Å) under the microscope changed its crystal structure so spontaneously that it should be considered to be in a quasisolid state. Another observation, which was obtained by tangential injection of an electron beam to a UFP, gave pictures of the first lattice layer, a technology which could be valuable for studying surface phenomena and other practical subjects, such as catalytic reactions. One of the possibly valuable techniques developed in the project is the transfer of UFP’s by flowing gas in a fine tube followed by jet formation to deposit the UFP’s on a solid plate. With sufficient jet speed (≳100 m/s), a tight deposit of Ag, Cu, Fe–Ag, TiN–Ni, Pb–Zn, etc., was obtained at a temperature of ≲600 K, exhibiting good homogeneous mixture under x-ray microanalysis. Several other results are presented.