| Summary: | 碩士 === 國立清華大學 === 化學工程學系 === 89 === Nanoparticles of nickel can be synthesized from NiCl26H2O by hydrazine in alkaline solution in the presence of polymers (PVP and PAA) served as protective and stabilizing agents. In addition, palladium ion is added as a nucleator. By adjusting the nickel ion concentration from 0.01 M to 0.02 M, the colloidal size can be adjusted within the range of 14 nm to 21 nm. Other parameters such as reaction temperature and PVP amount showed only negligible effects on particle size. Results also indicated that by increasing temperature to above 80 C and/or reaction time, we can obtain high purity nickel precipitate, otherwise large amount of Ni(OH)2 still exists in the product. Adjusting the pH to below 3.8 can de-stabilize the stable colloidal solution and separate nickel from original solution. On the other hand, the precipitate can be re-dispersed by simply adding de-ionized water. As regards to thick films, our data showed that the film resistivity will decrease with sintering temperature. After sintering at 1000 C, the film made from nanoparticles of nickel exhibits a sheet resistivity of 373 mOhm/square. The SEM picture showed that film from nanoparticles was better sintered than that from micron sized nickel particles. Nevertheless, due to the formation of some oxide in the film, it had a higher resistivity. Further efforts are needed to improve on the process conditions. The Ni film fabricated by interpolymer complex method shows a well and completely sintered surface, but the film is still too thin to measure the electric properties on it. The rate constant of nanosized nickel powder oxidation is about 4E-16 cm2/s at 300 C and 1.3E-15 cm2/s at 350 C.
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