1989 Fiscal Year Final Research Report Summary
Study on the Correlation Effect and the Percolation Phenomenon in Two-Phase Composites
| Project/Area Number |
63550537
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
金属材料(含表面処理・腐食防食)
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
YOSHIDA Katsukuni KYOTO UNIVERSITY, INSTITUTE OF ATOMIC ENERGY, ASSOCIATE PROFESSOR, 原子エネルギー研究所, 助教授 (70027142)
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| Co-Investigator(Kenkyū-buntansha) |
UEDA Sizumasa KYOTO UNIVERSITY, INSTITUTE OF ATOMIC ENERGY, TECHNICIAN, 原子エネルギー研究所, 教務職員 (00093196)
TOMII Yoich KYOTO UNIVERSITY, FACULTY OF ENGINEERING, LECTURER, 工学部, 講師 (90026245)
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| Project Period (FY) |
1988 – 1989
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| Keywords | Percolation / Cluster / Two-Phase Sintered Mixture / Effective Conductivity / Critical Behavior / Niobium-Alumina Cermet / Image Processor / Effective Medium Theory |
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| Research Abstract |
In order to reveal the mechanism by which the physical properties of multiphase materials are related with such structural features, we investigated the behavior of the cluster-structure in particular reference to the percolation process taking place in two phase cermet of niobium (Nb) and alumina (Al_2O_3). Through this process, the finite clusters grow rapidly, interlinking with one another, to unite into an infinite cluster. The material investigated was fabricated by a hot-press method. Sixteen specimens were prepared with volume fraction (f) of Nb ranging from 0 to 0.92. Main results are as follows. (1) When f passes a critical point f_c <similar or equal> 0.16 the electrical conduction suddenly takes place, rising up in a manner characteristic of the critical phenomena with an exponent of about 2. (2) In the non-conducting region 0<less than or equal>f<less than or equal>0.15, the dielectric constant ( or capacitance ) increases toward infinity when f approaches to f_c, implying a rapid growth of the conducting clusters (Nb), which eventually unite into a percolation cluster with infinite size. (3) Two-value images of the clusters were produced by using an image processor, and on those images the distribution of clusters was measured. After undergoing the percolation transition the distribution becomes broad and discrete, indicating an interlinking process among clusters. (4) The behavior of the conductivity and the dielectric constant can be explained by our effective medium model, where the structure of the mixture is reconstructed by aggregating complex cells consisting of two phases. (5) The anisotropic conduction observed can be explained by extending the link-node model. (6) Crossover between the 3 dimensional and the 2 dimensional percolation - transitions occurs around f <similar or equal> 0.41 in agreement with the prediction given by an existing theory.
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