| Budget Amount *help |
¥4,800,000 (Direct Cost: ¥4,800,000)
Fiscal Year 1994: ¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1993: ¥2,900,000 (Direct Cost: ¥2,900,000)
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| Research Abstract |
We report a processing for preparation of metal/ceramic composites by electrical deposition of metal ions into pores of ceramic material at room temperature. The feature of the new processing is to be summarized as follows ; (1) The final microstructure of metal/ceramic composite depends upon a starting pore structure of ceramic material, (2) The metal ions dissolved in an aqueous or a nonaqueous solution are electrochemically precipitated in the pores of ceramic material at a low temprature, leading to possibilities of no control of processing atmosphere and no restriction of a melting point of metal, (3) No or little reaction at the interfaces of metal/ceramics, (4) the fraction of metal in the composite is controlled by the electric charge passed during the processing, (5) Once the electrochemical reaction starts, the deposited metal itself acts as a following electrode, indicating continuous electrochemical deposition of metal in the open spaces of ceramic material. Based on the ab
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ove concept, a basic experiment was performed with porous alumina compacts and a nickel solution.
Nickel was infiltrated into porous alumina compacts of 37-62% of theoretical density by electrochemical reaction of Ni^<2+> ions with direct, pulsed and conical current of 110-300mA in an aqueous solution of nickel nitrate/urea/ethylene glycol/ammonium sulfate. The weight of Ni deposited was in proportion to t^<0.22-0.64> (t : deposition time). The deposition rate of Ni was higher for direct current than for pulsed or conical current, and for a higher-porosity alumina compact. Use of pulsed or conical current seemed to suppress the dendritic growth of Ni which was observed in a porous alumina with direct current. The Vickers hardness of composites with 93-94% of theoretical density increased from 17.5GPa in the nickel/alumina region (outside of sample) to 21.5GPa in the inside alumina matrix, indicating formation of a functionally gradient composite. The composite showed a non- linear relation between displacement and stress, indicating the improvement of mechanical properties associated with brittle ceramics. The electrical properties of composite is under investigation. Less
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