XJIPC OpenIR  > 材料物理与化学研究室
Thesis Advisor常爱民 ; 刘力
Degree Grantor中国科学院研究生院
Place of Conferral北京
Degree Discipline材料物理与化学
KeywordNtc热敏电阻 Al2o3 微波水热 纳米粉体
Abstract大多数负温度系数(Negative Temperature Coefficient, NTC)热敏电阻是由过渡金属(Co、Mn、Ni、Fe、Cu等)元素组成的具有尖晶石结构、钙钛矿结构或其他结构的复合氧化物。本论文选择三元系MnNiCoO和四元系MnNiCuFeO NTC热敏电阻为研究对象,分别采用氧化物法和微波水热法制备NTC热敏电阻材料,利用多种检测手段对产物进行分析和表征,并对其电学性能进行了测试。其主要研究内容如下: 1. 选择三元系MnNiCoO NTC热敏电阻为研究对象,采用传统的氧化物法工艺制备NTC热敏电阻材料,研究了Al2O3掺杂对MnNiCo系NTC热敏电阻的显微结构和电学性能的影响。由实验结果可知:Al2O3掺杂并不改变材料晶体结构(尖晶石固溶体),掺杂后材料的阻温变化关系与负温度系数热敏电阻的阻温特性一致;材料的晶粒随Al2O3含量的增加而减小,其室温电阻率和B值由339.07 Ω•cm、3489.07 K分别增加到3723.89 Ω•cm、4018.99 K,老化稳定性由1.65 %提高至0.17 %。该材料系列电阻率和B值调整范围较大,是一种具有实际应用价值的NTC热敏电阻。 2. 以Mn(NO3)2,Ni(NO3)2•6H2O,Cu(NO3)2•3H2O,Fe(NO3)2•9H2O和NaOH的共沉淀物为前驱体,采用微波水热法制备MnNiCuFeO系NTC热敏电阻材料。研究了反应温度、反应时间、pH值、填充率、表面活性剂等对粉体形成的影响。采用XRD、SEM、TG-DSC和激光粒度分析等检测手段,对粉体进行了研究。结果表明,温度在微波水热反应中对产物结晶度和晶粒形成机理影响比较大,表面活性剂的加入对粉体的团聚控制方面没有太大的改善。同时,填充度对产物的结晶度有一定的影响,在填充度为50 %时,能够形成较完整的尖晶石相和氧化铜相的固溶体。在pH=13,填充度为50 %的碱性介质中用微波水热法在200 °C,30 min内制备了晶粒大小为100 nm左右的NTC热敏电阻纳米粉体。在1000°C下烧结,可得到相对致密度为98.16 %的陶瓷体,测其室温电阻率ρ25°C为98 Ω•cm,材料常数B25/50为2100 K。
Other AbstractMost of NTC (Negative Temperature Coefficient, NTC) thermistors were composed of of transition-metal oxides composite (Mn, Ni, Co, Fe, Cu) with spinel structure and perovskite structure or other structure. In this thesis the ternary system MnCoNiO and quarternary system MnNiCuFeO NTC thermistors was selected to serve as the research object and Oxides method and Microwave-hydrothermal method was employed to prepare the NTC thermistor materials. The synthesized powders were characterized by several kinds of analysis equipments. Meanwhile the electrical properties were measured. The main research contents were described as follows: 1.Ternary MnCoNiO NTC thermistor was selected as the research object, which were prepared via traditional solid-state reaction method. Effects of Al2O3 doped amount on microstructures and electrical properties were investigated. The experimental results show that the doped Al2O3 did not affect the crystalline structure (spinel solid solutions). Doped material change in resistance-temperature relationship was the same as negative temperature coefficient thermistor resistance-temperature characteristics. The crystal particle size of materials decreased as the Al2O3 content increased. Electrical resistivity and thermal constant B were increased from 339.07 Ω•cm and 3489.07 K to 3723.89 Ω•cm and 4018.99 K, respectively. The aging stability was improved from 1.65 % to 0.17 %. This means that electrical resistivity and B value of such system could be adjusted to the desired values and then considered this ternary system as advanced materials for NTC thermistor applications. 2.With the Mn(NO3)2,Ni(NO3)2•6H2O,Cu(NO3)2•3H2O,Fe(NO3)2•9H2O and NaOH co-precipitated being precursors, the MnNiCuFeO NTC thermistors materials were prepared by the Microwave-hydrothermal method . It was studied that influence of reaction temperature, reaction time, pH, degree of filling, surface active agent on the crystalline size and morphology of NTC nano-powders. The resultant precipitates were characterized by X-ray Diffraction (XRD), Scan Electron Microscope (SEM), TG-DSC, and Laser Particle Sizer (LPS) techniques. The results showed that the temperature of the Microwave-hydrothermal had remarkably influenced on the crystallization and mechanism. The adding surfactant had little influence on agglomeration. At the same time, the filling degrees influenced the crystallization. solid solutions of spinel phase and copper oxide phase were well formed at degree of filling 50 %. Under 200 °C and within 30 min, NTC thermistor nanocrystals with crystalline size about 100 nm were produced with microwave-hydrothermal reaction at pH=13 and degree of filling 50 %. The nano-powders of the NTC thermistors were sintered at 1000 °C. The electrical properties: ρ25°C is about 98 Ω•cm and B25/50 is about 2100 K.
Document Type学位论文
Recommended Citation
GB/T 7714
黄霞. Mn-Ni-O基NTC热敏电阻材料微波水热合成及Al掺杂特性研究[D]. 北京. 中国科学院研究生院,2011.
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