Site: Osaka University
Research Center for Intermaterials
Institute of Scientific and Industrial Research
8-1 Mihogaoka, Ibaragi-shi
Osaka-fu 567, Japan
Tel: (81) 6-879 8440; Fax: (81) 6-879 8444

Date Visited: 24 July 1997

WTEC: J. Mendel (report author), D.M. Cox, C. Koch, H. Morishita, R.W. Siegel

Host:

BACKGROUND

The Institute of Scientific and Industrial Research was founded in 1939 as part of Osaka University. Its whole purpose is to study scientific principles necessary for industry to make progress in the fields of electronics, computer science, and metallic and inorganic materials, as well as other disciplines in biochemistry and radiation science. In 1995 the Institute was restructured into 6 divisions and 24 departments. The six divisions are (1) Quantum Engineering; (2) Advanced Materials Science and Technology; (3) Organic Molecular Science; (4) Intelligent Systems Science; (5) Biological Science; and (6) Quantum Beam Science and Technology.

The Institute's budget in 1996 was $25 million. For the area of Intermaterials, the budget amounted to $4 million plus grants from companies. For the Department of Structure Ceramic Materials, there are a total of 25 individuals supporting this technology. Professor Niihara, who heads this department, had been at the institute for eight years. Eighty per cent of the students work on ceramics, both functional and structural, and 20% are involved with metals and polymers.

RESEARCH AND DEVELOPMENT HIGHLIGHTS

The main focus for programs within Structure Ceramic Materials is ceramic-based nanocomposites prepared by sintering methods. There is special emphasis placed on understanding the relationships between the nanostructure of materials and their mechanical properties. Ceramic nanocomposites can be divided into intragranular, intergranular, and nano/nano composites. Intragranular and intergranular nanocomposites, even at elevated temperatures, result in remarkably improved mechanical properties, including (1) fracture toughness, (2) abrasive and cutting performance, (3) fracture mode, (4) fracture strength, (5) maximum operating temperature, and (6) creep resistance. As an example, toughness may increase 1.5 to 4 times in the Al2O3/SiC system. Hybridization of micro- and nanocomposites using fiber-reinforced components results in toughness improvements at higher temperatures.

SPECIFIC CLASSIFICATIONS

Multifunctional ceramics, then, can have some specific classifications:

  1. micro-nano composites with enhanced toughness (Al2O3/SiC)
  2. hard matrix/soft dispersion nanocomposites (Si3/Nu/BN)
  3. soft matrix/hard dispersion nanocomposites
  4. structural ceramics
  5. nanopore composites as future targets

PREPARATION

The process for preparing these ceramic materials involves a sintering reaction where the challenge is to keep different size particles uniformly dispersed to prevent nonuniform distribution.

Wet ball milling is also used, where materials like Si3Nu are mixed with Al2O3, Y2O3, H3BO3, and urea. After ball milling, the material is dried and subjected to hydrogen reduction. Such processes have yielded properties like high strength, excellent thermal shock resistance, good chemical inertness, and easy machinability similar to metals. Addition of chrome oxide has also yielded improvements in Young's modulus and fracture strength.

Although the institute has no formal process for patents, the work has resulted in the granting of 35 patents from this ceramic technology. Collaboration with the Massachusetts Institute of Technology and laboratories in Germany is ongoing.

EQUIPMENT

A tour of laboratory facilities showed a wide range of processing and characterization equipment. Included are (1) ceramic ovens, (2) Instron with filament-winding equipment (3) X-ray diffractometer with temperature range to 2000oC, (4) laser Raman, (5) hot isostatic press, (6) SEM, (7) AFM, (8) nano-indentor, and (9) spark plasma sintering systems.


Published: September 1999; WTEC Hyper-Librarian