Site: National Research Institute for Metals (NRIM)
1-2-2 Sengen
Tsukuba 305, Japan
Fax: (81) 298-59 2008

Date Visited: 23 July 1997

WTEC: C. Koch (report author), E. Hu, D. Shaw, C. Uyehara

Hosts:

BACKGROUND

The WTEC panel's host at the National Research Institute for Metals (NRIM) was Dr. Masatoshi Okada, Director General of NRIM, and the panel had presentations/discussions with Drs. M. Kobayashi, I. Nakatani, N. Koguchi, M. Murayama, W. T. Reynolds, and M. Ohnuma.

NRIM is a national laboratory devoted to the development and improvement of new and advanced metallic (and other) materials. It is funded by the Science and Technology Agency (STA). There are about 330 researchers out of a total staff of 415 people and an annual budget of about $100 million.

We were greeted by Dr. Masatoshi Okada, who then described his organization. The laboratory can be divided into four major parts: (1) research in advanced physical field (high magnetic fields, high resolution beams, extreme high vacuum), (2) research for materials science, (3) research for materials development, and (4) social-needs-oriented research. Researchers in various areas related to nanostructured materials presented descriptions of their research.

RESEARCH AND DEVELOPMENT HIGHLIGHTS

Dr. M. Kobayashi described his work on particle assemblage. At present this work is focused on micron-scale particles (~ 5 Ám particles) and toward the preparation of "smart" materials. Particles are assembled by electrostatic force by several methods involving, for example, the atom probe or electrostatic patterning by electron beams with particles attracted to the patterned regions. Examples of materials include SiO2 particle assemblages for gas (e.g., CO) sensors and Ni-base magnetostrictive particles for actuators.

Dr. I. Nakatani has a program involved with research on quantum magnetic properties. Studies involve magnetic substances with sizes of around (a) 100 nm, (b) 10 nm, and (c) 1 nm in dimension.

  1. A novel reactive-ion etching method was developed and applied to producing ferromagnetic Fe-Ni thin wire arrays with 250 nm width and spacing.
  2. Magnetic relaxation phenomena of iron nitride or cobalt ferrofluids were studied. These are colloidal 10 nm diameter ferromagnetic particles. The relationship between the viscosities of the magnetic fluids and volume fractions of solid particles was determined. It was stated that these ferrofluids possess the highest performance achieved in the world.
  3. Giant magnetoresistance (GMR) was observed for 2 nm Fe particles embedded in SiO2 or MgF2. The GMR effect is due to spin-polarized electrons tunneling between the Fe particles.

Dr. N. Koguchi described his group's work on direct formation of GaAs/AlGaAs quantum dots by droplet epitaxy. The process consists of forming Ga droplets on the inert S-terminated AlGaAs substrate and reacting the droplets with As to produce GaAs microcrystals. First, a molecular beam of Ga is put on the substrate, followed by an As molecular beam. About 10 nm GaAs particles are formed. The photoluminescence of these structures is being studied.

Dr. M. Murayama and Dr. W.T. Reynolds (on sabbatical from VPI) described their studies of the microstructure of a variety of structural materials with nanoscale features. Included in their studies are fine atomic clusters in Al-base alloys in which clusters not resolvable with high resolution electron microscopy were revealed by special tomographic three-dimensional atom probes. NRIM has two of the three existing in the world. All materials they study with the atom probe are nanostructured, including

(from A. Inoue's group at Tohoku University)

The piano wire - Fe-0.8%C - with a pearlitic structure-after strains of 4.0 assume a nanocrystalline structure with 5 nm carbide particles, along with some amorphous regions.

Dr. M. Ohnumo described studies of GMR behavior in Co-Al-O granular thin films. This work is in collaboration with H. Fujimori from Tohoku University.

A new thrust of NRIM is enhanced cooperative programs with industry and universities, and with international programs. NRIM is designated as a Center of Excellence and is charged with development of state-of-the-art facilities for extreme high vacuum, high resolution beams, and high magnetic fields.


Published: September 1999; WTEC Hyper-Librarian