掺杂Al2O3纳米粉对ZnO厚膜气敏传感器性能的影响

以ZnO纳米粉(平均粒径30 nm)和Al2O3纳米粉(平均粒径5 nm)为原料,利用传统的厚膜气敏传感器制备工艺制备了纯ZnO厚膜气敏传感器和掺杂Al2O3(掺杂量为2wt%和5wt%)的ZnO厚膜气敏传感器.对这三种厚膜传感器的本征电阻及对乙醇蒸汽的敏感特性进行了测试.结果表明:掺杂少量Al2O3纳米粉可明显降低ZnO气敏传感器的本征电阻,改善传感器的烧结性能,同时还可降低其最佳工作温度,提高器件对乙醇的灵敏度.结合厚膜气敏传感器的显微结构分析结果,对出现上述差异的原因进行了讨论.     

ZnO多孔纳米固体厚膜气敏传感器的制备和性质表征

以ZnO纳米粉(平均粒径30nm)为原料,利用水热热压方法制备了多孔的ZnO体块纳米固体,测试了以多孔纳米固体为原料制成的厚膜气敏传感器对挥发性有机化合物(VOCs)乙醇、丙酮、苯、甲苯和二甲苯蒸气的气敏特性,并与用ZnO纳米粉制备的厚膜传感器进行了比较.结果发现,与ZnO纳米粉相比,用ZnO多孔纳米固体制备的厚膜传感器在空气中的电阻大大减小,最佳敏感温度降低、响应时间和恢复时间大大缩短.通过综合分析ZnO纳米粉和ZnO多孔纳米固体的XRD、TEM及厚膜传感器的SEM测试结果研究了厚膜传感器气敏特性的差异.     

利用纳米ZnO粉制备厚膜气敏传感器的研究

以ZnO纳米粉(平均粒径30nm)为原料,利用水热热压方法制备了ZnO多孔纳米固体,同时用通常的水热法对ZnO纳米粉进行了预处理(预处理ZnO纳米粉)。然后,分别以ZnO多孔纳米固体和预处理ZnO纳米粉为原料,制备了厚膜气敏传感器。本征电阻的测试结果表明,这两种厚膜气敏传感器的本征电阻比用未经处理的ZnO纳米粉(以下简称“原料ZnO纳米粉”)制备的厚膜气敏传感器大大降低并很快达到稳定状态。有效地改善了器件工作的稳定性。结合对三种传感器的显微结构分析,对出现上述差异的原因进行了讨论。     

基于正交试验的La_2O_3掺杂SnO_2气敏传感器的研究

以SnO2纳米粉和La2O3纳米粉为原料,采用高能球磨技术,结合正交试验设计,制备了经过高能球磨的纯SnO2纳米粉体和掺杂适量La2O3的SnO2纳米粉体。利用传统的厚膜气敏传感器制备工艺,制备了纯SnO2厚膜气敏传感器及掺杂一定量La2O3的SnO2厚膜气敏传感器。并对其本征电阻及其对乙醇、汽油、丙酮、氢气和CO等气体的敏感特性进行了测试。结果表明各因素对综合气敏性能影响的显著性水平由大到小依次为La2O3掺杂浓度〉烧结时间〉老化时间〉烧结温度。同时,通过分析还得到了最佳组合工艺。La2O3掺量为5%（质量分数）,烧结时间为2h,老化时间为7d,烧结温度为650℃条件下制备的气敏元件的综合气敏性能最好,其中对1.0×10-3乙醇蒸气的灵敏度达107.2,对相同浓度的干扰气体的选择性分别为S乙醇/S汽油=11.3,S乙醇/S丙酮=9.1。     

水热处理对SnO2厚膜气敏传感器性能的影响

研完了水热处理对于SnO2厚膜气敏传感器性能的影响。为了便于作对比,首先把SnO2纳米粉（平均粒径约200nm）平均分为两份：一份不经处理,直接用传统的厚膜传感器制备工艺制成气敏传感器（称为“原粉传感器”）;另一份经过200℃水热处理后,用同样的工艺制备成厚膜气敏传感器（称为“预处理粉传感器”）。利用乙醇、丙酮、CH4、H2和CO气体对这两种气敏传感器的性能进行了测试,结果表明预处理粉传感器的灵敏度和选择性明显优于原粉传感器。为了分析出现这种差异的原因,我们对这两种传感器的显微结构进行了分析,并在此基础上对实验现象进行了讨论。     

Sb掺杂对ZnO厚膜的电导和气敏性能的影响

用共沉淀的方法,制备了纤锌矿结构的ZnO及其掺Sb的ZnO纳米粉.X射线衍射(XRD)分析表明,当锑掺量小于5wt%时没有新相生成.纯ZnO和掺Sb的ZnO器件的气敏和电阻测试结果发现:不同的厚膜烧结工艺对气体的敏感性影响较大,并且掺Sb后ZnO的气敏性能有所提高,电导峰消失.从缺陷角度、XPS分析的结果进行了讨论,初步解释了锑的掺入导致电导变化和气敏性能提高的原因.     

ZnO-Bi2O3混合氧化物厚膜的结构和气敏性能

采用金属蒸气氧化的方法制备了针状ZnO和椭球形Bi2O3纳米颗粒作为气敏厚膜的原材料，其中得到的Bi2O3为δ相和β相的混合物．通过XRD和SEM分析了ZnO、Bi2O3以及ZnO-Bi2O3混合物厚膜的物相和表面形貌，并测试了厚膜的电导和气敏性能．结果发现纯Bi2O3对乙醇和丙酮蒸气有一定的气敏性能，表现为P型导电；与纯ZnO相比，ZnO-Bi2O3混合物厚膜对苯、甲苯和二甲苯的敏感度降低，这与厚膜晶粒尺寸增大、其晶界势垒高度增大有关，然而Bi2O3可能作为一种弱的催化剂提高了厚膜对乙醇和丙酮的敏感性能．     

溶剂热法制备铝掺杂纳米ZnO及其气敏性能

采用溶剂热法合成了铝掺杂的纳米ZnO气敏材料,运用XRD和BET等手段对产物进行了表征并进行了相应的气敏性能测试.结果表明,掺杂1.5%Al后的ZnO比表面最大,粒径最小;材料对乙醛、90#汽油、90#乙醇汽油、硫化氢、二氧化氮响应较高.掺杂量为1.5%Al的元件对90#汽油在浓度为50ppm时灵敏度接近120.     

利用Sb掺杂提高SnO_2基热线型气体传感器响应值

以SnCl_4·5H_2O和SbCl_3为前驱体,采用共沉淀法制备了Sb掺杂SnO_2纳米复合材料(ATO),并用X射线和扫描电镜对粉末进行了表征。考察了Sb掺杂对SnO_2基热线型气体传感器的气敏性能影响,并分析了气敏机理。结果显示:6%Sb掺杂的ATO材料粒径减小至3.5nm,Sb的掺杂抑制了SnO_2材料晶粒的生长;Sb掺杂能有效提高SnO_2基热线型气体传感器响应值,6%Sb掺杂使SnO_2基传感器对0.1%H_2的最佳响应值从115mV提高到了435mV;工作电压为3.5V时,响应和恢复时间分别小于10和30s。机理分析表明:Sb掺杂降低了SnO_2气敏材料的电阻,从而提高了SnO_2基传感器的响应值。     

sol-gel法制备的SnO_2-TiO_2厚膜及其气敏特性研究

采用sol-gel法,以钛酸丁酯、四氯化锡为前驱体制备了不同掺杂量的Sn O2-Ti O2纳米粉末,样品经300,500,700和900℃退火后,利用浸渍提拉法,在Al2O3陶瓷管表面制备了Sn O2-Ti O2厚膜。通过XRD和SEM对制备的纳米粉末的物相、形貌进行表征,静态配气法对其气敏性能进行测试,并结合分子轨道理论探讨了气敏机理。实验结果表明,经700℃退火的4%(原子分数)掺杂的Sn O2-Ti O2气敏元件,对乙醇气体具有很好的选择性,在工作温度为63℃时,对乙醇气体的灵敏度可达1 903,响应-恢复时间分别为1和3 s,所制备的气敏元件有望用于乙醇气体的实用化检测。     

Preparation and characterization of TiO2 bulk porous nanosolids

A novel TiO₂ bulk porous nanosolid (also called a “TiO₂ nanosponge”) was prepared by a solvothermal hot-press (SHP) technique, using TiO₂ nanoparticles (average particle size of 15 nm) and various solvents as the starting materials. The pore diameters of the nanosolids were rather uniform, and the maximum value of pore volume and specific surface area were 0.249 cm³/g and 59.455 m²/g, respectively. The pore volume and diameter of TiO₂ bulk porous nanosolid could be controlled by changing either the type or the amount of the solvent used in the experiment. No residual solvents could be detected by FTIR analysis, which means that the solvents had entirely escaped from the samples during the process of preparing TiO₂ bulk porous nanosolids.     

Preparation of ZnO bulk porous nanosolids of different pore diameters by a novel solvothermal hot press (STHP) method

ZnO bulk porous nanosolids were prepared by a novel solvothermal hot press (STHP) method with different pore-forming agents using ZnO nanoparticles. The samples were characterized with SEM, XRD, FTIR, a mercury intrusion porosimeter and N₂ adsorption–desorption method. Experimental results showed that pore size of the nanosolids was between 20–32 and 20–100 nm when de-ionized water and CTAB solution were used as pore-forming agents, respectively. There was no obvious morphological change in the samples when all pore-forming agents were removed from the autoclave.     

Preparation and characterization of ZrO2 porous nanosolid and its composite fluorescent materials

ZrO₂ porous nanosolid has been successfully prepared by a novel hydrothermal hot-press (HHP) method, using ZrO₂ nanoparticles as the starting material. Furthermore, a kind of O, O-donating chelating regent, morin was assembled into the pores of ZrO₂ porous nanosolids, and a morin/ZrO₂ porous nanocomposite was obtained. Because of the interaction between morin molecules and the surface of ZrO₂ porous nanosolid, a blue-shift of the photoluminescence (PL) peak was observed in ZrO₂/morin nanocomposite by comparing with that of morin.     

固相反应法制备MgAl2O4纳米粉体及其烧结行为研究

在800℃下煅烧Al(OH)3和MgSO4混合粉末,冷却后经过水洗得到了结晶良好的MgAl2O4纳米粉体.采用DSC/TG、XRD、TEM和SEM等分析手段研究了混合粉末中Mg/Al原子比对颗粒尺寸及团聚状况的影响,以及MgAl2O4纳米粉体的烧结性能.所制备的MgAl2O4纳米粉体平均颗粒尺寸为12 nm,尺寸分布窄,团聚少.MgAl2O4的生成归因于γ-Al2O3和MgSO4的固相反应.MgAl2O4纳米粉体显示了良好的烧结活性,在1450℃烧结1 h即能获得相对密度为95%的MgAl2O4陶瓷.     

Rapid synthesis of pure and narrowly distributed Eu doped ZnO nanoparticles by solution combustion method

Pure ZnO:Eu³⁺ nanoparticles (~ 50 nm) were prepared by a solution combustion method. ZnO and Eu₂O₃ were used as starting materials and dissolved in nitric acid. Citric acid was used as a fuel. The reaction mixture was heated at 350 °C resulting into a rapid exothermic reaction yielding pure nanopowders. The atomic weight concentration of Eu³⁺ doped in ZnO was 20%. Transmission electron microscopy (TEM) was used to study the particle size and morphology. The nanopowders were characterized for phase composition using X-ray diffractrometry (XRD). Particle size distribution (PSD) analysis of ZnO: Eu³⁺ showed particle sizes ranging from 30 to 80 nm.The photoluminescence emission spectra of ZnO:Eu³⁺ nanostructures showed a strong band emission around 618 nm when excited with 515 nm wavelength.     

液氨沉淀法制备ZnO超微粉

以Zn(NO3 ) 2 为原料 ,NH3 ·H2 O为沉淀剂 ,采用直接沉淀法制备Zn(OH) 2 白色沉淀 ,经洗涤、干燥、煅烧后生成ZnO超微粉末。通过TEM观察到ZnO为球形晶体 ,平均粒径 15 0nm。探讨了溶液pH值、沉淀剂浓度、反应时间、反应温度对前躯体Zn(OH) 2 粒度的影响以及煅烧过程中煅烧温度与煅烧时间对ZnO粒度的影响 ,得出了最佳工艺条件。     

Microstructural and electrical properties of varistors prepared from coated ZnO nanopowders

This paper describes a solution-based technique for fabrication of varistor grade composite nanopowders. The method consists of coating major varistor dopants on the surface of the ZnO nanoparticles. As a result, a homogenous mixture of dopants and ZnO nanoparticles will be achieved. TEM results indicated that a composite layer of dopants with the average particle size of 9 nm on the surface of ZnO nanoparticles has been successfully prepared. Sintering of the coated powders was performed in temperatures as low as 850 °C and final specimens with average particle size of 900 nm and density of 98.5% were achieved. In comparison to conventional mixing, varistors prepared from coated nanopowders exhibited superior electrical properties and microstructure homogeneity. The improvement of electrical properties can be attributed to small grain size, homogenous distribution of dopants and elimination of large Bi-Pockets. In addition, the processing route of schottky barrier formation is quite different from what is generally considered as the method of barrier formation in ZnO grain boundaries.     

氧化铝-氧化钛纳米粉末的形貌、微结构和晶型转变

用溶胶-凝胶法合成了含氧化钛质量分数为10wt.%、30wt.%和50wt.%的氧化铝-氧化钛纳米复合粉末和单纯氧化铝纳米粉末,用溶胶-凝胶法合成的氢氧化物前驱体在700-1200℃锻烧2h转变为相应的氧化物,用XRD和TEM对氧化铝-氧化钛纳米复合粉末的形貌、微结构和晶相进行表征,结果表明,二氧化钛质量含量每增加约20wt.%,复合氧化物中氧化铝的α相转变温度就降低100℃,随着氧化钛加入量的增加,复合氧化物的晶粒迅速减小。第二相的加入有效地抑制了氧化铝基体晶粒的快速长大。添加质量分数为30wt.%氧化钛且在1000℃下煅烧的样品拥有25-32nm的最小晶粒。