TiO2基陶湿敏元件的研究和发展

ＴｉＯ２基湿敏陶瓷是一类十分重要的湿敏陶瓷,应用十分广泛。本文综述了ＴｉＯ２基陶瓷湿敏元件的研究和发展,重要介绍了７种ＴｉＯ２基陶瓷湿敏元件的材料配方、制备工艺、湿敏性能及研究进展。     

陶瓷湿敏元件的长期稳定性问题及改进措施

陶瓷湿度传感器是湿度传感器的重要发展方向。改善陶瓷湿敏元件的长期稳定性是一项重要的研究课题。本文详细分析了湿敏陶瓷的微观结构和感温机理,评述了引起陶瓷湿敏元件性能漂移的因素和机理,以及改善陶瓷湿敏元件长期稳定性的有效措施。     

TiO2基气敏元件工作温度影响机理

对TiO2基气敏材料的能带结构及测试气体分子轨道能量进行理论计算,结合实验,对TiO2-SnO2复合材料气敏元件工作温度的影响机理进行理论研究.结果表明:掺杂使TiO2能带带隙中产生掺杂能带,导带产生负移,有利于电子热激发.对比未掺杂TiO2气敏元件,在工作温度为260℃时,掺杂使TiO2元件电阻值由44.5Mù下降到22.5Mù.气体分子LUMO能级降低,有利于降低气敏反应的活化能,从而降低气敏元件的工作温度及提高灵敏度.     

Mo6+掺杂TiO2纳米材料的表面性能及氧敏特性

以TiCl3为钛源, 采用溶胶-凝胶法制备Mo6+掺杂TiO2基纳米粉体,表明在400℃下低温烧结,即可得到金红石相为主晶相的TiO2基敏感材料.在低温工作条件(145℃)及1×10-4 O2下,Mo6+掺杂TiO2厚膜型气敏元件的氧敏特性比纯TiO2的好,并结合Zeta电位特性测量,其氧敏特性的增强在于表面电荷密度的提高.     

MgCr_2O_4湿敏陶瓷初步摸索

对MgCr_2O_4陶瓷湿敏元件进行了一些基本的配方与工艺研究,获得一些初步结果。为进一步研制稳定而价廉的湿敏器件和应用打下了一定基础。     

我国电子湿敏元件研制现状

湿度测量在国民经济的各个部门，在国防、科研及人民生活中有着非常广阔的应用领域，越来越显示其重要性。原来采用的毛发湿度计、干湿球湿度计，已经不能满足当前各行各业发展的需要，各类电子湿度计正在迅速发展，下面将对高分子电容湿敏元件及陶瓷湿敏元件作一简单介绍。1高分子电容湿敏元件高分子电容湿敏元件是当今国内外湿敏元件领域研究的热点之一，它的特点是测湿范围宽、响应快、温度系数小、工艺简单、价格便宜。对湿敏元件的要求不是要求元件有多高的精度，而是湿敏元件的稳定性和可靠性，尤其是技术指标不断与国外技术指标接近…     

一种新型陶瓷湿敏元件的阻容-湿度特性研究

陶瓷湿敏元件的感湿体一般都为多孔陶瓷。本工作发现了一类 Ca Ti 矿型铁电氧化物致密陶瓷具有好的湿敏特性,从而开展了这一研究。用氧化物和碳酸盐配料,按一般电子陶瓷工艺制成吸水率为0.1%左右的致密陶瓷     

Zn_2SnO_4-LiZnVO_4系厚膜湿敏元件的制备和性能研究

采用溶胶凝胶法制备 Zn2SnO4-LiZnVO4系陶瓷纳米粉体,用平面丝网印刷工艺在氧化铝基片上制备厚膜湿敏元件。与普通陶瓷粉体制备的元件相比,该元件低湿电阻小,长期稳定性较好。 测量不同工作频率时的湿敏特性表明,元件在 1kHz频率范围感湿线性最佳。复阻抗分析表明,采用溶胶凝胶法制备纳米粉体并控制烧结温度,可获得良好的微结构,是改善元件感湿特性的原因。     

稀土杂质对纳米BaTiO3湿敏性能的影响

分别研究了钠盐和稀土杂质对BaTiO3纳米晶材料湿敏元件电学性能的影响,结果表明钠盐和稀土金属氧化物都能降低湿敏元件的电阻和湿滞.掺钠盐的湿敏元件电阻较低,但长期稳定性不如掺稀土金属氧化物的湿敏元件.初步分析了掺杂影响湿敏材料特性的机理.     

Zn2SnO4—LiZnVO4系厚膜湿敏元件的制备和性能研究

采用溶胶凝胶法制备Zn2SnO4-LiZnVO4系陶瓷纳米粉体,用平面丝网印刷工艺在氧化铝基片上制备厚膜湿敏元件。与普通陶瓷粉体制备的元件相比,该元件低湿电阻小,长期稳定性较好。测量不同工作频率时的湿敏特性表明,元件在1kHz频率范围感湿线性最佳。复阻抗分析表明,采用溶胶凝胶法制备纳米粉体并控制烧结温度,可获得良好的微结构,是改善元件感湿特性的原因。     

The sol-gel template synthesis of porous TiO2 for a high performance humidity sensor

This research develops a simple template assisted sol-gel process for preparing porous TiO2 for a high performance humidity sensor. Tetraethyl orthosilicate (TEOS) as a template was directly introduced into TiO2 sol formed by the hydrolysis and condensation of titanium alkoxide; the following calcination led to the formation of TiO2-SiO2 composite, and the selective removal of SiO2 by dilute HF solution led to the formation of porous structure in TiO2. The resulting porous TiO2-based sensor exhibits high sensitivity and linear response in the wide relative humidity (RH) range of 11%-95%, with an impedance variation of four orders of magnitude to humidity change. Moreover, it exhibits a rapid and highly reversible response characterized by a very small hysteresis of <1% RH and a short response-recovery time (5 s for adsorption and 8 s for desorption), and a 30-day stability test also confirms its long-term stability. Compared with pure TiO2 prepared by the conventional sol-gel method, our product shows remarkably improved performance and good prospect for a high performance humidity sensor. The complex impedance spectra were used to elucidate its humidity sensing mechanism in detail.     

Nb5+掺杂与热处理对TiO2基材料气敏特性的影响

TiO2是响应三甲胺(TMA)气体最佳的金属氧化物半导体材料，为保持TiO2基TMA旁热式气敏器件具有较高灵敏度和较低空气阻值(Ra)，相应降低器件加热功率PH，本文通过N2气氛高温退火、高价Nb^5 掺杂和长时间烧结等方法，提高TiO2基敏感材料电导率获得成功．实验与理论证明：降低氧分压可增强TiO2自身半导化程度；掺入10％左右Nb2O5，Nb^5 替代Ti^4 形成固溶体，可使TiO2得到最佳半导化效果；采用长时间的烧结处理，促使Ti^3 转化为Ti^4 ，进一步提高材料电导率和器件稳定性，从而为制造低阻、高灵敏度、高选择性动物食品测鲜传感器开辟了一条新途径。     

TiO2-based nano-wells for fabricating nanocrystals

This paper reports a convenient bottom-up method to fabricate robust and inert TiO2-based nanowells for growing nanocrystals. These TiO2-based nanowells are fabricated in three steps: fabricating a thin film of self-organized TiO2 nanotubes by the convenient electrochemical anodization method (Step 1), striping the fabricated nanotube thin film to expose the ordered array of nanowells underneath (Step 2), and surface modifying the exposed nanowells to adjust their surface hydrophobicity and hydrophilicity (Step 3). These fabricated nanowells can then be used to template the growth of an ordered array of nanocrystals by trapping a tiny droplet of precursor solution inside each nanowell. The diameter and surface hydrophobicity and hydrophilicity of the TiO2-based nanowells can be easily tailored by controlling the anodization parameters used in Step 1 and surface modifying parameters used in Step 3, respectively, thus enabling these TiO2-based nanowells a promising template substrate for growing a wide range of nanocrystals with adjustable sizes from aqueous and organic solvent systems.     

Graft copolymer-templated mesoporous TiO(2) films micropatterned with poly(ethylene glycol) hydrogel: novel platform for highly sensitive protein microarrays

In this study, we describe the use of organized mesoporous titanium oxide (TiO(2)) films as three-dimensional templates for protein microarrays with enhanced protein loading capacity and detection sensitivity. Multilayered mesoporous TiO(2) films with high porosity and good connectivity were synthesized using a graft copolymer consisting of a poly(vinyl chloride) (PVC) backbone and poly(oxyethylene methacrylate) (POEM) side chains as a structure-directing template. The average pore size and thickness of the TiO(2) films were 50-70 nm and 1.5 μm, respectively. Proteins were covalently immobilized onto mesoporous TiO(2) film via 3-aminopropyltriethoxysilane (APTES), and protein loading onto TiO(2) films was about four times greater than on planar glass substrates, which consequently improved the protein activity. Micropatterned mesoporous TiO(2) substrates were prepared by fabricating poly(ethylene glycol) (PEG) hydrogel microstructures on TiO(2) films using photolithography. Because of non-adhesiveness of PEG hydrogel towards proteins, proteins were selectively immobilized onto surface-modified mesoporous TiO(2) region, creating protein microarray. Specific binding assay between streptavidin/biotin and between PSA/anti-PSA demonstrated that the mesoporous TiO(2)-based protein microarrays yielded higher fluorescence signals and were more sensitive with lower detection limits than microarrays based on planar glass slides.     

频率和温度对陶瓷湿敏元件感湿特性的影响

研究了工作频率和温度对TiO₂－K₂O－LiZnVO₄陶瓷薄膜湿敏元件感湿特性的影响．结果表明：在低湿区,元件的阻抗随频率增大、温度升高而减小,感湿灵敏度随频率增大、温度降低而显著减小,感湿特性曲线出现平台;在高湿区,频率和温度对元件感湿特性的影响可以忽略,感湿特性曲线线性良好．分析了陶瓷薄膜的极化现象,发现极化现象导致薄膜的微观电容在低温低湿时对湿度变化不敏感．据此解释了极化现象引起频率和温度对元件感湿特性影响的内在机理．     

二氧化钛基光催化抗菌材料的研究进展

以二氧化钛为代表的光催化抗菌材料是目前具有重要研究价值与广阔开发前景的无机抗菌剂.评述了其抗菌机理、有效利用太阳光与黑暗条件下有效抗菌的材料改性制备技术等方面的研究进展,重点评述了近年来为提高其材料特性、增强其抗菌性能、拓展其使用范围的材料制备与改性研究的最新进展,以及面临的主要问题.在此基础上,提出了今后值得关注与研究的方向.     

Fabrication of TiO2/Tin-doped indium oxide-based photoelectrode coated with overlayer materials and its photoelectrochemical behavior

The photoelectrochemical properties of TiO2-based photoelectrodes with metal oxide overlayers (e.g., ZnO, ZrO2, MgO, and Al2O3) were investigated. The metal oxides were deposited on TiO2/tin-doped indium oxide (ITO) films by spin-coating metal-alkoxide precursors. The formation of the overlayers was confirmed by energy dispersive X-ray spectroscopy (EDS) and high resolution transmission electron microscopy (HRTEM). Each overlayers were well-coated on the TiO2-based films and have approximately 2 nm thickness. The prepared films were used as photoanodes in a photoelectrochemical system with a Pt counter electrode to evaluate hydrogen production performance. Comparing with other overlayers, the ZnO-coated photoelectrode exhibits the highest rate of hydrogen evolution and which is better than the uncoated one. From the photoelectrochemical and spectroscopic study, the superior hydrogen production property of the ZnO-coated TiO2 photoelectrode was attributed to both the higher light absorbance of ZnO compared to TiO2 and the formation of hydroxyl groups at the ZnO surface.     

聚吡咯/二氧化钛复合薄膜的制备及气敏性研究

运用静电力自组装和原位化学氧化聚合相结合的方法制备了聚吡咯/纳米二氧化钛(PPy/TiO₂)复合薄膜, 并进行了紫外－可见光谱分析和原子力显微镜分析. 采用平面叉指电极制备了PPy/TiO₂复合薄膜气体传感器, 研究了其在常温下对有毒气体NH₃和CO的敏感性. 最后测试了该传感器的温度湿度特性. 结果表明, 该传感器对NH₃具有较高的灵敏度, 对CO几乎没有响应. 同时讨论了复合薄膜沉积时间对气敏特性的影响, 实验表明当沉积时间为20min时, 该传感器的NH₃敏感特性最好.     

Properties of TiO2 Thin Films Prepared by Magnetron Sputtering

With rapid progressive application of TiO2 thin films,magnetron sputtering becomes a very interesting method to prepare such multi-functional thin films.This paper focuses on influences of various deposition processes and deposition rate on the structures and properties of TiO2 thin films.Anatase,rtile or amorphous TiO2 films with various crystalline structures and different photocatalytic,optical and electrical properties can be produced by varying sputtering gases,substrate temperature,annealing process,deposition rate and the characteristics of magnetron sputtering.This may in turn affect the function of TiO2 films in many applications.Furthermore,TiO2-based composites films can overcome many limitations and improve the properties of TiO2 films.     

Doped-TiO_2 Photocatalysts and Synthesis Methods to Prepare TiO_2 Films

TiO2 is a promising photocatalyst. However, the low photocatalytic efficiency calls for the modification of TiO2. Metal- and nonmetal-doping of TiO2 have been proved to be effective ways to enhance photocatalytic properties. This review provides a deep insight into the understanding of the metal- and nonmetal-doped TiO2 photocatalysts. This article begins with the introduction of the crystal structures of TiO2 and applications of TiO2 materials. We then reviewed the doped-TiO2 system in two categories： （1） metal-doped TiO2 photocatalysts system, and （2） nonmetal-doped TiO2 photocatalysts system. Both experimental results and theoretical analyses are elaborated in this section. In the following part, for the advantages of TiO2 thin films over particles, various preparation methods to obtain TiO2 thin films are briefly discussed. Finally, this review ends with a concise conclusion and outlook of new trends in the development of TiO2-based photocatalysts.