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URN etd-0712105-175052 Statistics This thesis had been viewed 2262 times. Download 701 times. Author Chien-Chih Liu Author's Email Address email@example.com Department Materials Engineering Year 2004 Semester 2 Degree Master Type of Document Master's Thesis Language zh-TW.Big5 Chinese Page Count 88 Title Preparation of Cu-Co-Ni-Mn system NTC Ceramics
by the Chemical Coprecipitation
Keyword thermistor spinel NTC coprecipitation coprecipitation NTC spinel thermistor Abstract According to the electricity formula, when the material is the lower in resistance, its produced joule-heat is small too. So reduce the resistance of NTC in the match that the design of circuit , there is space chosen more, but the resistance of NTC stability it is also a quite important factor for consideration. In order to improve stability of low resistance NTC , coprecipitation is that suitable method to prepare powders. The raw materials of the coprecipitation are mixing under the solution state, powder of homogeneous is high , low mean grain size , high chemical activation , so reflects the reaction faster and complete than the traditional solid state . Therefore prepare of Cu-Ni-Mn , Co-Ni-Mn , Cu-Co-Ni-Mn system NTC ceramics by the chemical coprecipitation for study. The sintering condition is each 1000 , 1100 and 1200 ℃. Coprecipitation is to all prepare into the aqueous solution of 0.2M of nitrate and oxalic acid ammonium , and mix its heating form the salt precipitate of oxalic acid. According to the result of coprecipitation, there are several advantages. The precision of composition could reach 97%~99%. The formation of spinel structure was 300oC lower than that proceeding with solid-state reaction. The densification has enhanced as the content of cobalt or copper increased and the resistivity was also decreased. The resistivity of NTC with copper (774~844Ω-cm) was much lower than that with cobalt (13~27Ω-cm) measuring at room temperature. The resistivity and thermal stability has better performance than that proceeding with solid-state reaction. The lattice constant has decreased as the content of copper or cobalt dropped. The most important thing is that the wire should be calibrate since the resistivity of NTC at room temperature is less that 200Ω-cm. The higher content of copper could highly enhance the stability of NTC. Advisor Committee Hur-Lon Lin - advisor
Yi Hu - advisor
Chih-Wen Hsieh - co-chair
Files Date of Defense 2005-06-30 Date of Submission 2005-07-12