| Home | Log-in | Admin | Sitemap |
Home | Program | Detailed Program
Detailed Program
Paper Number : ST-I04
Time Frame : 15:00~15:30
Presentation Date : Friday, 28, November
Session Name : Structual Ceramics & Refractory materials
Session Chair 1# : Do-Kyung Kim
Session Chair 2# : MAsaki Narisawa
Evaluation of internal defects and their coarsening during sintering in alumina ceramics system
Satoshi TANAKA
Nagaoka Univeristy of Technology
Keywords: Structure, Powder Process, Sintering

The large cracks or coarse defects are present in ceramics if it was prepared by well-controlled processing. By the optical microscopy, coarse defects were observed and their influence was revealed on their characteristics. The size and the number density of coarse defects govern the mechanical properties of ceramics. [1,2] In this study, we examined the development of coarser defects in alumina ceramics by micro-focus x-ray computer tomography (レ-CT) etc.
The origin of coarser defects in ceramics was examined by evaluation of the powder compact. First, we observed the internal structures by the liquid immersion method with the optical microscope. Then we observed the powder compact with レ-CT. There were low packing regions originated from the interstices of granules in the pressed compact. The internal coarse defects in the ceramics were successfully observed. A large number of coarse defects were observed as 3-dimensional image.
The coarser defects formation during sintering was also examined in alumina ceramics by the レ-CT. Using one sample, we repeated the experiment of sintering and observation with レ-CT. The relative density gradually increased with 60% to 96%. With sintering, coarse defects generally grow, and the number of coarse defects with > 5 レm increased. Particularly, a coarser defect with 20 レm in size also grew by incorporating a neighbor coarse defect with ~ 5 レm at the middle stage of sintering. This results shows that the sintering among granules cause the rearrangement of coarse defects. We must focus on inhomogeneous sintering.

References:
[1] K. Uematsu et al., J.Ceram.Soc.Japan, 101, 1400 (1993)
[2] S. Nakamura, S.Tanaka et al., J.Am.Ceram.Soc., 92, 688 (2009)
Acknowledgements : This research was in-part supported by Grant-in-Aid for Scientific Researches (C) (25420706) from Japan Society for the Promotion of Science.