|Place of Conferral||北京|
|Keyword||一步水热法 微乳-水热法 低热固相球磨法 低热固相球磨-水热法 Ntc热敏电阻 纳米粉体|
尖晶石型过渡金属（Mn、Co、Ni）氧化物材料制备而成的负温度系数（NegativeTemperature Coefficient，NTC）热敏电阻，在温度测量和控制、温度补偿、抑制浪涌电流等方面均有较为广泛的应用。作为热敏电阻的起始材料，粉体材料的化学组成、物相结构、颗粒尺寸等均会直接影响最终产物陶瓷材料的电学性能。目前粉体材料的制备仍然主要沿用传统固相法，其具有工艺简单、条件宽松等优点，也有组分扩散不均匀、高温煅烧结晶过程易混入杂质等缺点。Mn1.56Co0.96Ni0.48O4 材料是一种优秀的热敏材料，作为热敏性红外探测器，具有性能稳定，灵敏度高，长波响应等优点，在军事和民用领域具有广泛应用。故而本论文以Mn1.56Co0.96Ni0.48O4 材料为研究对象，采用一步水热法、低热固相球磨法、低热固相球磨-水热法、微乳-水热法等合成方法，结合粒度测试、X 射线衍射（XRD）、热重分析（TG-DSC）、扫描电子显微镜（SEM）、能量色散谱（EDS）和阻温测试等表征方法，探索了新的粉体制备工艺中各参数变化对粉体性能及最终产物陶瓷材料性能的影响。工作内容和所得结论如下：（1）采用一步水热法制备Mn1.56Co0.96Ni0.48O4 粉体材料，以丙三醇为分散剂，分别以NaOH、KOH、氨水为沉淀剂与矿化剂，其中以NaOH 为矿化剂效果最佳。随着矿化剂浓度的升高产物粉体的形貌由不规则多面体过渡为规则的立方八面体，产物同时具有四方尖晶石相和立方尖晶石相。（2）采用微乳-水热法制备Mn1.56Co0.96Ni0.48O4 粉体材料，以去离子水为水相、以环己烷为油相、以曲拉通100 为乳化剂、以正己醇为助乳化剂。在反应时间为8 h、反应温度为220℃条件下可制得粒径较小约60 nm 左右、形貌较一致且分散性能良好的单一立方尖晶石相产物粉体。（3）采用低热固相球磨法制备Mn1.56Co0.96Ni0.48O4 粉体材料，在预烧温度为600℃、预烧时间为2 h 条件下可制得粒径较小约为130 nm 左右的立方尖晶石相纳米粉体。（4）采用低热固相球磨-水热法制备Mn1.56Co0.96Ni0.48O4 粉体材料，在水热时间为10 h、水热温度为220℃条件下可制得粒径较小约为80 nm 左右、纯度较高且分散性能良好的单一四方尖晶石相产物粉体。（5）将低热固相球磨-水热法制备所得产物粉体高温烧结成陶瓷后，测得陶瓷体积密度处于4.94-5.56 g·cm-3之间。室温电阻率、材料常数B25/80值、活化能分别处于226-1085 Ω·cm、2451-3731 K、0.21-0.32 eV之间。
Transition-metal (Mn, Co, Ni) spinel oxide ceramics are widely used as negative temperature coefficient (NTC) themistors for temperature measurement, control and compensation as well as suppression of inrush current. As starting material for the NTC thermistors, the chemical components, phase structures, sizes, distribution and agglomeration of the powders will directly affect the electrical properties of the final products. As a traditional method for preparation of NTC thermistor powders, the solid phase method has many disadvantages such as component uneven distribution and impurities produced during high temperature calcinations, although its process is simple. In this thesis, Mn1.56Co0.96Ni0.48O4 materials that has excellent optical, electrical and magnetic properties for infrared radiation detector were selected as the research object, and one step hydrothermal method, microemulsion hydrothermal method, low heating solid ball-milling method and solid-phase ball milling-hydrothermal method were employed to systhesis Mn1.56Co0.96Ni0.48O4 powders. The structure, microstructure and electrical properties of the samples were characterized by X-ray diffraction(XRD), scanning electron microscope(SEM), laser particle size analysis, energy dispersive spectrometer(EDS), thermo gravimetric analysis, differential scanning calorimetry(TG-DSC) and DC resistance tester, respectively. The effect of new production process parameters on properties of powders and ceramic materials were discussed. The main results are described below: (1) The Mn1.56Co0.96Ni0.48O4 powder materials were prepared by one step hydrothermal method. Glycerol was used as the dispersant. NaOH, KOH and ammonia were used as the precipitating agent and mineralizing agent, respectively. The experimental results showed that NaOH was the best mineralized agent. Powders’ morphology had changed from irregular polyhedron to a cube octahedron due to the increase of NaOH concentration. Powders had composite spinel structure, the cubic spinel structure and the tetragonal spinel structure. (2) The Mn1.56Co0.96Ni0.48O4 powder materials were prepared by microemulsion hydrothermal method. Deionized water, cyclohexane, triton 100 and hexanol were used as the aqueous phase, oil phase, emulsifier, co-emulsifier, respectively. The experimental results showed that the nanopowders of cubic spinel structure with a small size (60 nm) and high dispersity could be obtained at a low crystallization temperature. The optimal hydrothermal temperature was 220℃, and the best hydrothermal time was 8 h. (3) The Mn1.56Co0.96Ni0.48O4 powder materials were prepared by low heating solid ball-milling method. The experimental results showed that nanopowders with small grain size (130 nm) and cubic spinel structure could be prepared by this method when the calcining temperature was 600℃. (4) The Mn1.56Co0.96Ni0.48O4 powder materials were prepared by solid-phase ball milling-hydrothermal method. The experimental results showed that the nanopowders of tetragonal spinel structure with a small size (80 nm) and high dispersity could be obtained at a low crystallization temperature. The optimal hydrothermal temperature and time was 220 ℃ and 10 h. (5) The ceramic materials were obtained from the samples which were prepared by solid-phase ball milling-hydrothermal method. The ceramic bulk density was in the range of 4.94-5.56 g?cm-3. The ceramic materials had a significant characteristic of negative temperature coefficient. The obtained B value, room temperature resistivity, activation energy were in the range of 3396-3625 K, 226-1085 Ω?cm, 0.21-0.32 eV, respectively. Keywords: one step hydrothermal method; low heating solid ball-milling method; solid-phase ball milling-hydrothermal method; microemulsion hydrothermal method; NTC thermistor; nanopowder.
|马仁君. Mn1.56Co0.96Ni0.48O4负温度系数热敏电阻材料合成方法及性能研究[D]. 北京. 中国科学院大学,2014.|
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