【作者】 高瞻；

【导师】 董晟全；

【作者基本信息】 西安工业大学 ， 材料学， 2012， 硕士

【摘要】 随着纳米技术的快速发展,纳米气敏性材料的应用愈加广泛,继氧化锡、氧化锌之后,氧化铁系材料成为第三大系气敏材料,其良好的稳定性,广泛的选择性引起了人们的兴趣。本文分别采用两种方法合成了纯相α-Fe2O3纳米粉体,并进行了成份掺杂；对纳米粉体和所制元件进行了结构表征和性能测试,深入探讨α-Fe2O3基纳米粉体的制备工艺、微观结构和气敏性能之间的关系。得到的主要结论如下：以FeCl3.6H2O和NaOH为原料,分别采用化学沉淀法和超声化学法合成了纳米氧化铁粉末,并对其制备工艺进行了分析比较。实验结果表明：两种方法制备的纳米氧化铁粉末平均粒径均在20-40nm之间,且纯度较高。在化学沉淀法中选用不同烧结温度对粉体成形进行了考察：300℃和400℃烧结时有杂质相y-Fe203生成：在500℃,600℃烧结时α-Fe2O3粒径分别为32nm和37nm；采用400℃保温2h再升温至600℃焙烧0.5h后的试样无杂质相且粒径为28nm,且分散性较好,形貌呈现椭球形。在超声化学法中考察不同的震动功率对粉体的影响,随着震动功率的增大(45W-81W)粉体粒径不断减小,在81W时粒径为20nm,形貌呈现球形,分散性很好。在成功制备纯相α-Fe2O3纳米粉体的基础上进行掺杂试验：分别改变Sn4+、Mg2+、Ce4+与Zr4+的浓度,制备出掺杂成份的α-Fe2O3纳米粉体。借助于XRD、SEM与TEM分析测试,结果表明部分Sn4+、Mg2+、Ce4+可以代替α-Fe2O3晶格中的Fe3+,从而改变其晶格参数,减小了α-Fc2O3的晶粒大小。但Zr4+并没有进入α-Fe2O3的晶体,而是形成了两个独立的相：ZrO2和α-Fe2O3。采用超声化学法将ZrO2和Y2O3按不同浓度比也制备了掺杂成份的α-Fe2O3纳米粉体。结果表明Y3+进入了α-Fe2O3晶格内,Zr4+与α-Fe2O3形成共存,且纳米粉体的形貌主要呈现为棒状、纺锤形和球形。以掺杂成份的α-Fe2O3纳米粉体为基材,设计并制作了气敏元件,并测试了其对甲烷气体的敏感性。结果表明,含有Sn4+或Ce4+单相掺杂的α-Fe2O3纳米粉体气敏性优于含Zr4+或Mg2+的粉体。其中参7mol%Ce4+的试样在甲烷含量为1000ppm时的灵敏度为6.4；在响应-恢复时间上掺5mol%Sn4+的元件响应-恢复时间用时最短.分别为18s和21s。双相掺杂的纳米α-Fe2O3粉体对甲烷气体的灵敏度有所提高,掺杂5mol%Zr0210mol%Y2O3的试样在甲烷含量为1000ppm时的灵敏度为9.6；所有双相掺杂的元件响应—恢复时间都在20s左右。更多还原

【Abstract】 With the rapid development of nonatechnology, nonamaterials for gas sensing applications become more widespread. Nowadaysα-Fe2O3 has been used as the third kind gas-sensing materials and gained wide application after the development of ZnO and SnO2 nanomaterials, which has high stability and selectivity. In this dissertation, a-Fe2O3 nano-poeder were synthesised by two methods, and carried on the ingredient doping. On the basis of measurements and characterizations of a-Fe2O3-based nano-powders and gas sensitive sensors, the correlativity between the synthesis and structre of powders and the characters of sensors studied in detail and the sensitive mechanism was discussed. The main conclusions can be drawn as follows:a-Fe2O3 nano-powders were made by chemistry precipitation and ultrasonic chemistry with raw materials of FeCl3 6H2O and NaOH. The experiment results showed that the a-Fe2O3 nano-powders made by two methods are of high purity with its size of 20-40nm. During the process of chemistry precipitation various sintering temperatures were used. When they were sintered at 300℃and 400℃, few by-products of y-Fe2O3 can be detected. The average diameters ofα-Fe2O3 powder were 32nm and 37nm at 500℃and 600℃,respectively. When they were sintered at 400℃for 2h and then 600℃for 0.5h, ellipsoidal-shapedα-Fe2O3 nano-powders were uniform distributed with size of 28nm, and no other impurities were found. The influence of shock power in ultrasonic chemistry on nano-powders was studied. As the shock power increases, the size of nano-powders decreases, uniform dispersion and spherical liked nano-powders with size of 20nm were obtained as the shock power reaches 81W.Based on the preparation ofα-Fe2O3 nano-powders,doping experiments were performed. By changing the concentration Sn4+、Mg2+、Ce4+ and Zr4+. respectively the doped were successfull、Tabricated. With the help of XRD、SEM and TEM. the results showed that Fe3+ has partial replaced by Sn4+、Mg2+ and Ce4+. which changes the crystal structure. Additionly, the size of a-Fe2O3 nano-powders were decreased. However, Zr4+ did not enter in the crystal ofα-Fe2O3, thus resulting the formation of ZrO2 and a-Fe2O3. The dopedα-Fe2O3 nano-powders were made by changing the concentration of ZrO2 and Y2O3 using ultrasonic chemistry method. Results showed that Y3+ enter into the crysral of a-Fe2O3, and coexistence of Zr4+ and found. The nano-powders show three morphology:rod-like,spiudle-shaped and spherical-shape.The CH4 gas-sensor properties of a-Fe2O3 doped nano-powders were studied. Among all the investigated materials, can be achieved that gas sensing ofα-Fe2O3 doped nano-poeders containing Sn4+ or Ce4+ is superior to that ofα-Fe2O3 doped nano-powders containing Zr4+ and Mg2+. When the concentration of CH4 1000ppm reaches 6.4 for doping 7mol% Ce4+ doped nao-powders. The response and recovery time for 5mol% Sn4+ doped nao-powders are 18s and 21s, respectively under the condition of 1000ppm CH4. Two phase doping ofα-Fe2O3 nano-powder increased the sensitivity of the methane gas, which reaches 9.6 for 5mol% ZrO2 and 10mol% Y2O3 doped nano-powders at 1000ppm CH4. The response-recovery time of all was around reach 20s in the atomosphere of CH4.更多还原