1992 Fiscal Year Final Research Report Summary
Ultra-high pressure isostatic pressing of ultra-line powders for preparation of nanoctystalline
| Project/Area Number |
02403022
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| Research Category |
Grant-in-Aid for General Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Research Field |
化学工学
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| Research Institution | Nagoya University |
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Principal Investigator |
GIMBO Genji Engineering, Professor, 工学部, 教授 (80022995)
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| Co-Investigator(Kenkyū-buntansha) |
KAMIYA H Nagoya Univ. Eng. Assi. Prof., 工学部, 助手 (20183783)
SUZUKI H Toyota Tech.Inst. Asso.Prof., 助教授 (70154573)
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| Project Period (FY) |
1990 – 1992
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| Keywords | Ultra-fine / Sol-gel / Grinding / Aggregation / Isostatic press / Sintering / Simulation / DLA model |
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| Research Abstract |
Smaller particles, especially below 100nm in diameter, are very difficult to compact into a close-packed structure, because of strong, open aggregation. We believe that a closely-packed green compact structure is essential to use very active ultra-fine powders effectively. In this report, firstly ultra-fine powders were produced by a grinding process. And secondly, amorphous and ultra-fine particles with high chemical activity were prepared, and finely dispersed these hard aggregation in suspensions, Furthermore, to obtain highly dense green compacts of ultra-fine, the green compacts of these powders were consolidated by ultra-high pressure isostatic pressing up to 1GPa. As the uniform and high dense green compacts were sintered at relatively low temperature, nanocrystalline were prepared.
The analysis for the aggregating, packing and sintering mechanism of these ultra-fine powders used a computer simulation. The aggregating process of ultra-fine powders was simulated by the extending diffusion limited aggregation model. The effect of the interaction between particles and initial concentration of particles on the microstructure of aggregates were quantitatively analyzed by fractal dimension. The packing simulation of these aggregates obtained by the extending DLA model were carried out, and the high porous structure of ultra-fine powder beds with a porosity ratio exceeding 90% could be reproduced. The consolidating process due to the deformation and collapse of particles and aggregates during high pressure isostatic pressing were analyzed. Furthermore, we apply a similar concept in the case of the producing process for Si3N4 ceramics used fine powders of about less than 1 mum in diameter. The uniform structure of green bodies and the high reliability of ceramics were obtained by the control of strength of spray-dried granules. The control of powder aggregation was the most important process for production of ceramics.
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