| 摘要 |
PURPOSE: A method of manufacturing a magnetic fluid for seal dust-proof of a hard disk drive motor is provided to prepare magnetic fluid having low viscosity and vapor pressure of 10¬(-7) torr and having grain size of 8nm or below, thereby enhancing the sealing dust-proof properties of high rotation parts. CONSTITUTION: Ammonia is added to mixture solution of ferric chloride and ferrous chloride to have pH of 10-11 and then amorphous magnetite is synthesized by agitating the mixture for 5min. Then, the amorphous magnetite is exposed for 10min to be crystallized. The synthesized magnetite is cleaned by pure water at least three times and then is dried by filtering and dewatering processes. Next, surface active agent of 10-30 wt% is added to the dried magnetite, and the mixture is heated for 2hr under the temperature of 80°C together with heat resistant synthetic oil to be distributed. Then, magnetic fluid obtained by the distribution is purified at 7000G using a centrifugal machine.
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