|Place of Conferral||北京|
|Keyword||锰酸镧 厚膜 薄膜 热敏电阻 导电机制 复阻抗分析|
随着热敏电阻在各应用领域的不断扩展，对温度传感器精度也有着更为严格的要求，因此，开发出更高性能的温度敏感材料也成为了一项重要的任务；同时，随着信息技术的快速发展，电子元器件的微型化、集成化及多功能化成为其发展的主流，膜状化（厚膜和薄膜）成为了解决这些问题的一个关键技术。随着对宽温区热敏电阻的研究，钙钛矿结构的材料得到了愈发的关注。而锰酸镧基作为钙钛矿系中的一类，具有良好的负温度系数特性，因此我们在此基础上对其进行了系列研究。而对热敏电阻的导电机理，由于其内部结构的复杂性，也是目前其理论研究中的难点和重点。首先，我们通过丝网印刷技术，在Al2O3衬底上制备了厚膜样品。通过XRD和SEM观察，研究了材料组分与其结构及表面形貌的影响。而电性能的研究，发现其厚膜具有良好的线性NTC特性，并且其电阻率会因Al的掺杂带来很大的变化。在所有组分中，x=0.4掺杂含量的厚膜热敏电阻最佳，适合宽温区热敏电阻的应用，并且随后对x=0.4厚膜样品，采用复阻抗谱分析，进行了更深一步的研究。其次，通过溶胶凝胶法在(1 0 0)-LaNiO3上制备得到了（ 1 0 0 ） 高度取向的LaMn0.6Al0.4O3薄膜。通过材料的复阻抗谱测试，对比研究了自由取向与高度取向薄膜的电学特性。研究表明，高度取向的晶粒分布有助于降低材料的电阻率及激活能，而晶界特性不受其取向影响。在对阻抗与频率的曲线研究发现弛豫是与热激活相关。两种薄膜的内部晶粒、晶界激活能在0.2005-0.2373 eV范围内，且两者电导遵循阿累尼乌斯特性，而后也进一步的讨论了其相关其导电机制。对NTC膜状（厚膜和薄膜）材料制备工艺的研究及内部导电机理的分析，能够为厚膜和薄膜工业应用的提供有意义的指导。
The characteristic of diphenylethane is a kind of solvent with no color, no taste, non- poisonous and with high boiling point. Especially, one of its kind, 1-phenyl-xyxyl-ethane(PXE), it has the excellent performance in terms of compatibility, thermal resistance, lubricating and electrical property; it is widely used as plasticizer, high boiling solvent, heat medium, electrical insulated oil and lubricating oil. In the work reported here, four kinds of diphenylethane were synthesized using o-xylene, m-xylene, p-xylene, ethylbenzene and styrene as starting materials catalyzed by non-metallic mineral solid acid with special proportion of silicon and aluminum and the modified ZSM-5 molecular sieve in alkylation reaction. The author also did the analysis of refined products by IR and GC-MS spectra, the performance of crude product and purified product. Specific experiments as follows: ⒈ The key parameters such as raw material ratio, catalyst material, reaction time, reaction temperature and particle size of catalyst have been investigated and discussed in detail. The results showed that the optimal conditions were as follows：the weight percentage of the catalyst（with particle size 80-100mesh）is 3%, molar ratio of ethylbenzene to styrene is 7, reaction temperature is at 140℃, with addition time of styrene 2h and total reaction time 4h. The yield of phenyl ethylbenzene under such conditions could reach 90% when the raw materials were o-xylene, m-xylene and ethylbenzene, however, when using p-xylene , ethylbenzene and styrene as raw materials, medium yield of 70% was achieved. ⒉ O-xylene, m-xylene, p-xylene and styrene as raw materials in alkylation reaction, catalytic properties of different solid catalysts have been investigated and discussed in detail. The results showed that no-metallic mineral solid super acid catalyst has good catalytic effect, the yield of diphenylethylane was 90.8%,90.5%,78.8%,much higher than other solid acid catalyst effect. ⒊ The use of ammonium sulfate solution on the modified ZSM-5 zeolite synthesized HZSM-5 zeolite catalysts. Diphenylethylane was synthesized by O-xylene and styrene, under optimum conditions mentioned in 1, when the calcinations temperature was 500 ℃, alumina ratio was 40to 45 , the Diphenylethylane yield was 89.3%,,. ⒋ The analysis of refined products by IR and GC-MS spectra confirmed the structure of phenyl ethylbenzene ethane, and they may be mixture of several diphenylethylane isomers. Different substances analysis of refined product by Gas chromatography was analyzed quantitatively. The analysis of refined products by gas chromatography-mass spectrometry showed that o-xylene, m-xylene, ethylbenzene was raw materials, contained mainly C16H18 and C16H16. The content of C16H18 was more than 90%, the content of C16H16 was less 10%, and this indicated the higher rate of alkylation. Xylene as the starting material in the synthesis of refined product showed that the content of C16H18 was about 70%, the content of C16H16 was about 30%. This result showed that o-xylene, m-xylene was more suitable for the synthesis of diphenylethylane as feedstock. ⒌ The author also did rough preparation and purified preparation of diphenylethylane . The performance of both rude and purified product were evaluated .The performance testing included pour point, open flash point, the breakdown voltage, the viscosity and so on. The results showed that: purified product has better performance, in line with national standards GB/T2536-2011 (45 #), while crude processing performance is poor. ⒍ Experiment was also carried out to make exquisite product of diphenylethane and 15#industrial grade white oil. The results showed that the performance of purified diphenylethane was comparable to the national standard GB/T2536-20119（45#）. Furthermore, the exquisite product has many advantages and unique properties such as: the increasing breakdown voltage, reducing kinematic viscosity, reducing pour compared to the industrial grade while oil. In summary, in the work reported here, the diphenylethane synthesized and purified hold great promise for application as the transformer oil or its additives. when they were as transformer oil additives, the appropriate volume percentage was 10%～30%.
|熊信谦. 锰酸镧基膜状NTC热敏材料的制备与性能的研究[D]. 北京. 中国科学院大学,2014.|
|Files in This Item:|
|锰酸镧基膜状NTC热敏材料的制备与性能的（12851KB）||学位论文||开放获取||CC BY-NC-SA||View Application Full Text|
|Recommend this item|
|Export to Endnote|
|Similar articles in Google Scholar|
|Similar articles in Baidu academic|
|Similar articles in Bing Scholar|
Items in the repository are protected by copyright, with all rights reserved, unless otherwise indicated.