金属－二氧化锡高选择CH_4气敏元件的研究

阐述了高选择ＣＨ４气敏元件的制造工艺，发现Ａｕ，Ｐｔ，Ｐｄ等金属超细粉的掺杂，可提高元件的抗干扰能力，对Ｃ２Ｈ５ＯＨ，Ｈ２，ＣＯ等干扰气体灵敏度＜２，而对ＣＨ４的灵敏度＞８．经２年多稳定性考核，＼Ｒ０≤±１０％，对金属超细粉在ＳｎＯ２晶粒表面状态进行了分析和探讨．     

SnO_2－SiO_2双层薄膜氢敏元件的特性研究

采用溶液－凝胶浸渍涂布工艺在Ａｌ＿２Ｏ＿３陶瓷管上制备了掺杂ＳｎＯ＿２气敏薄膜；利用高温热解法在ＳｎＯ＿２薄膜表面覆盖ＳｉＯ＿２气体分离膜后制得双层薄膜气敏元件。分别测试并比较单层和双层薄膜元件的气敏特性，结果表明：单层薄膜元件对可燃性气体无选择性、响应和恢复时间短；而双层薄膜元件对氢气表现出极高的灵敏度和优越的选择性，其响应和恢复时间都比单层薄膜元件有所延长，结合实验结果，从理论上阐述了双层薄膜元件对氢气的敏感机理。     

用PECVD制备的SnO_2薄膜气敏特性研究

ＳｎＯ２薄膜制备及其应用日益受到人们的重视。本文阐述了用低温等离子体化学气相沉积法制备ＳｎＯ２薄膜的工艺，并研究了所制得的纯净及掺杂Ａｇ，Ｐｄ的ＳｎＯ２薄膜的气敏特性。此法制得的元件对还原性气体，尤其是低浓度Ｈ２Ｓ，Ｃ２Ｈ５ＯＨ具有很高的灵敏度及快速的响应．     

贵金属催化剂对氧化镍气敏特性的影响

采用均匀沉淀法合成了氧化镍（ＮｉＯ）气敏微粉，利用浸渍法对氧化镍材料进行了掺杂，用Ｘ射线衍射、电子衍射和透射电镜对材料的陶瓷微结构进行了研究．实验结果表明：合成材料为颗粒状非晶体，颗粒尺寸＜１μｍ；该材料为Ｐ型半导体材料，对Ｃ２Ｈ５ＯＨ具有较高灵敏度，Ａｇ的掺杂能提高ＮｉＯ的气体灵敏度，Ｐｄ，Ｐｔ，Ａｕ，Ｒｕ，Ｒｈ的掺杂不能有效地提高其气体灵敏度，但可改善ＮｉＯ的气敏选择性．     

添加剂对氧化钛气敏材料敏感特性的影响

采用化学共沉淀法和浸渍法制备了不同金属或氧化物掺杂的ＴｉＯ２气敏材料，通过透射电镜、电子衍射和ｘ射线衍射对材料的结晶形态和物相进行了分析，用静态配气法测试了气敏材料的敏感特性．结果表明：这些材料的颗粒尺寸小于０．１μｍ，８００℃处理样品为金红石型ＴｉＯ２与锐钛矿型ＴｉＯ２的混合物．通过选择合适的添加剂和工作温度可分别获得选择性酒敏元件、ＣＯ气敏元件和可燃气体普敏元件     

WO3-SnO2薄膜的溶胶-凝胶制备及其气敏特性研究

以无机盐ＳnCl2.2H2O为主体原料、Ｈ２ＷＯ４为掺杂剂、无水乙醇为溶剂,采用溶胶－凝胶工艺制备了nw:nsn=1:1000的ＷＯ３－ＳnO2薄膜,并对共气敏性能进行了研究,实验表明,掺杂量为１％的ＷＯ３－ＳnO2薄膜在常温下对Ｈ２Ｓ,ＮＯx气体具有较好的气敏性能,对Ｈ２Ｓ气体的敏感温度为１００℃,对ＮＯx气体的最佳敏感温度为７０℃。     

复合膜高选择性CH_4元件研制

复合膜高选择性ＣＨ＿４元件研制吴家琨，韩晶波，孙良彦（吉林大学电子工程系长春１３００２３）关键词表面修饰；催化层；选择性中图分类号ＴＰ２１２．２文章应用了表面修饰技术．在敏感材料的外面加一层催化层，使干扰气体在表面层被阻隔、吸收或反应．明显地提高了Ｓ...     

掺杂镍酸镧材料的气敏特性研究

研究了ＴｉＯ＿２掺杂ＬａＮｉＯ＿３的气敏特性，实验表明，在中等掺杂时，材料的电导适中，气敏性能最好；ＸＲＤ证实，掺杂后ＬａＮｉＯ＿３仍属于ＡＢＯ＿３钙钛矿结构，且有新相生成。还对掺杂ＳｎＯ＿２，Ｓｂ＿２Ｏ＿３及Ｖ＿２Ｏ＿５进行了研究，指出ＳｎＯ＿２中等掺杂及Ｓｂ＿２Ｏ＿３，Ｖ＿２Ｏ＿５低掺杂时，同样能使ＬａＮｉＯ＿３的气敏性质有所改善。     

Au-SnO2高温CO气敏元件的研制

在 Ｓｎ Ｏ２ 基体材料中掺杂 Ｔｈ Ｏ２ 及 Ａｕ, Ｐｄ 等贵金属催化剂,获得了２７０ ℃高温区域对 Ｃ Ｏ 具有高灵敏度的气敏元件．通过活性碳过滤技术,改善了该元件的选择性．测试结果表明,该元件具有良好的稳定性,是一种实用化的 Ｃ Ｏ气敏元件．     

碱土金属掺杂SnO_2薄膜气体传感器

经过真空镀锡膜、氧化和化学浸渍，制作了碱土金属掺杂ＳｎＯ２薄膜气敏元件，并测试了元件的气敏特性．结果表明，元件对乙醇和丙酮气体灵敏度和选择性得到提高、而对苯、丁烷、液化石油气、氨气、氢气和煤气不敏感．     

一种抗干扰的H_2S传感器

在ＺｎＯ基体材料中添加稀土金属氧化物ＣｅＯ２制成了抗干扰的Ｈ２Ｓ气体传感器，研究了其对Ｈ２Ｓ气的响应特性，发现在１０ｐｐｍ的Ｈ２Ｓ气中，灵敏度可高达２０倍、且响应迅速，而对几种干扰气ＣＯ（１００ｐｐｍ），ＣＨ４（３０００ｐｐｍ），ｉ－Ｃ４Ｈ１０（１００ｐｐｍ）响应很小．     

CuO nanostructures as quartz crystal microbalance sensing layers for detection of trace hydrogen cyanide gas

In this work, quartz crystal microbalance (QCM) sensors for detection of trace hydrogen cyanide (HCN) gas were developed based on nanostructural (flower-like, boat-like, ellipsoid-like, plate-like) CuO. Responses of all the sensors to HCN were found to be in an opposite direction as compared with other common volatile substances, offering excellent selectivity for HCN detection. The sensitivity of these sensors is dependent on the morphology of CuO nanostructures, among which the plate-like CuO has the highest sensitivity (2.26 Hz/μg). Comparison of the specific surface areas of CuO nanostructures shows that CuO of higher surface area (9.3 m(2)/g) is more sensitive than that of lower surface area (1.5 m(2)/g), indicating that the specific surface area of these CuO nanostructures plays an important role in the sensitivity of related sensors. On the basis of experimental results, a sensing mechanism was proposed in which a surface redox reaction occurs between CuO and Cu(2)O on the CuO nanostructures reversibly upon contact with HCN and air, respectively. The CuO-functionalized QCM sensors are considered to be a promising candidate for trace HCN gas detection in practical applications.     

Experimental use of a gas sensor-based instrument for differentiation of Escherichia coli O157:H7 from non-O157:H7 Escherichia coli field isolates

The rapid and economical detection of human pathogens in animal and food production systems would enhance food safety efforts. An instrument based on gas sensors coupled with an artificial neural network (ANN) was developed for the detection of and differentiation between laboratory isolates of Escherichia coli O157:H7 and non-O157:H7 E. coli. The purpose of this study was to use field isolates of E. coli to further evaluate the sensor system. This gas sensor-based, computer-controlled detection system was used to monitor gas emissions from 12 isolates of E. coli O157:H7 and 8 non-O157:H7 E. coli isolates. A standard concentration of each isolate was grown in 10 ml of nutrient broth at 37 degrees C for 16 h, and gas sampling was carried out every 5 min. Readings were continuously plotted to generate gas signatures. A back-propagation ANN algorithm was used to interpret the gas patterns. By analysis of the response of the ANN, the sensitivity and specificity of the instrument were calculated. Detectable differences between the gas signatures of the E. coli O157:H7 isolates and the non-O157:H7 isolates were observed. The instruments degree of sensitivity was high for E. coli O157:H7 isolates, but a lower degree of accuracy was observed for non-O157:H7 isolates because of increased strain variation. The sensitivity of the detection system was improved by the normalization of the data generated from the gas sensors. Because of its ability to detect differences in gas patterns, this instrument has a broad range of potential food safety applications.     

Environmental monitoring of hydrocarbons: a chemical sensor perspective

Assessing the environmental impact of organic pollutants requires reliable analytical tools that can rapidly screen them with minimal sample handling. Chemical sensors are expected to play an increasing role in environmental monitoring, and recent technological advances are certain to facilitate the application of chemical sensing devices. The search for highly selective, sensitive, low cost, stable, and robust sensors for hydrocarbons is an area of interest that is reflected by many publications on this topic. This report surveys some of the work that has been undertaken using sensors to detect hydrocarbons in the gas and liquid phase. The analytical capabilities of various sensors are compared and discussed in terms of their selectivity, sensitivity, and detection limit. It was found that the sensitivity is highly dependent on the experimental conditions used in the preparation of the sensing surface. Many sensors display acceptable sensitivity under controlled laboratory conditions; however, very few are selective enough to distinguish among several hydrocarbons in complex mixtures. Selectivity is still a challenge that is hindering the widespread application of chemical sensors for environmental monitoring of hydrocarbons and a number of strategies have been proposed to help overcome some of these problems.     

常温乙炔敏感振荡元件研究

报道了一种新型乙炔气体敏感元件。这种元件以Ｓｎｏ２为基体材料，工作在室温条件，对低浓度Ｃ２Ｈ２气体非常敏惑，对１０００ｐｐｍＨ２几乎没有气敏响应；其输出特性与一般加热元件明显不同，呈现为规律性极强的振荡波形，并对这种元件的气敏振荡机理进行了讨论．     

Oxidation of H2S by iron oxides in unsaturated conditions

Previous studies have demonstrated that gas-phase H2S can immobilize certain redox-sensitive contaminants (e.g., Cr, U, Tc) in vadose zone environments. A key issue for effective and efficient delivery of H2S in these environments is the reactivity of the gas with indigenous iron oxides. To elucidate the factors that control the transport of H2S in the vadose zone, laboratory column experiments were conducted to identify reaction mechanisms and measure rates of H2S oxidation by iron oxide-coated sands using several carrier gas compositions (N2, air, and O2) and flow rates. Most experiments were conducted using ferrihydrite-coated sand. Additional studies were conducted with goethite- and hematite-coated sand and a natural sediment. Selective extractions were conducted at the end of each column experiment to determine the mass balance of the reaction products. XPS was used to confirm the presence of the reaction products. For column experiments in which ferrihydrite-coated sand was the substrate and N2 was the carrier gas, the major H2S oxidation products were FeS and elemental sulfur (mostly S8(0), represented as S(0) for simplicity) at ratios that were consistent with the stoichiometry of the postulated reactions. When air or O2 were used as the carrier gas, S(0) became the dominant reaction product along with FeS2 and smaller amounts of FeS, sulfate, and thiosulfate. A mathematical model of reactive transport was used to test the hypothesis that S(0) forming on the iron oxide surfaces reduces access of H2S to the reactive surface. Several conceptual models were assessed in the context of the postulated reactions with the final model based on a linear surface poisoning model and fitted reaction rates. These results indicate that carrier gas selection is a critical consideration with significant tradeoffs for remediation objectives.     

基于电子鼻检测香红梨腐烂程度

目的 为监测贮藏、运输过程中香红梨（Pyrus communis L. cv. Xianghong）的腐烂情况,确定腐烂果的特征传感器。方法 利用电子鼻技术对按腐烂点直径划分的3个等级香红梨的挥发性气体进行测定,同时比较了贮藏初期和后期果实挥发性气体的差异。采用主成分分析（PCA,principal components analysis）、线性判别分析（LDA,linear discriminant analysis）和载荷分析（LA,loading analysis）对电子鼻响应信号值进行分析。结果 电子鼻传感器W5S、W1S、W1W、W2S、W2W是检测香红梨挥发性气体的特征传感器。贮藏期间,氮氧化合物、甲烷、硫化物和萜烯类、醇类和部分芳香族化合物释放量逐渐增加。果实腐烂使硫化物和萜烯类（W1W）、甲烷（W1S）、氮氧化合物（W5S）挥发性物质进一步积累释放,传感器响应值比贮藏初期（P）分别提高了7.7、4.6、4.5 倍。通过监测W5S传感器响应值变化可判断果实的腐烂情况。LDA分析对不同贮藏时期和不同腐烂程度香红梨的区分能力更好。结论 电子鼻传感器W5S、W1S、W1W、W2S、W2W可灵敏反应香红梨的挥发性气体,其中W5S、W1S、W1W为果实腐烂特征性传感器,其响应值可区分果实腐烂程度。本结果为果实采后贮藏保鲜的无损检测技术及果实品质评价提供理论参考。     

Simultaneous absorption of CO2 and H2S into aqueous blends of N-methyldiethanolamine and diethanolamine

Removal of CO2 from gaseous streams by absorption with chemical reaction in the liquid phase is usually employed in industry as a method to retain atmospheric CO2 to combat the greenhouse effect. A broad spectrum of alkanolamines and, more recently, their mixtures are being employed for the removal of acid gases such as CO2, H2S, and COS from natural and industrial gas streams. In this research, simultaneous absorption of CO2 and H2S into aqueous blends of N-methyldiethanolamine and diethanolamine is studied theoretically and experimentally. The effect of contact time, temperature, and amine concentration on the rate of absorption and the selectivity were studied by absorption experiments in a wetted wall column at atmospheric pressure and constant feed gas ratio. The diffusion-reaction processes for CO2 and H2S mass transfer in blended amines are modeled according to Higbie's penetration theory with the assumption that all reactions are reversible. A rigorous parametric sensitivity test is done to quantify the effects of possible errors in the pertinent model parameters on the prediction accuracy of the absorption rates and enhancement factors. Model results based on the kinetics-equilibrium-mass transfer coupled model developed in this work are found to be in good agreement with the experimental results of rates of absorption of CO2 and H2S into (MDEA + DEA + H2O).     

Alkaline biofiltration of H2S odors

Hydrogen sulfide (H2S) is a very common odor nuisance which is best controlled by chemical or biological scrubbing. Under alkaline pH, the amount of H2S that can be solubilized in a scrubbing liquid increases significantly, and therefore, gas-liquid mass transfer limitations can be reduced. To date, biological scrubbing of H2S has been limited to neutral or acidic pH, despite the potential benefit of reduced mass transfer limitations at alkaline pH. In the present paper, an alkaliphilic sulfoxidizing bacterial consortium was deployed in a laboratory-scale biotrickling filter treating H2S at pH 10. The gas contact time ranged from 1 to 6 s, and H2S inlet concentrations, from 2.5 to 18 ppm(v). The results showed that under most conditions, H2S removal exceeded 98% and the degradation end-product was sulfate. At the highest H2S concentrations and shortest gas contacttimes, when the loading exceeded 30 g m(-3) h(-1), the H2S removal efficiency decreased significantly due to biological reaction limitation, and incompletely oxidized sulfides were measured in the trickling liquid. An analysis of the process demonstrated that operating the biotrickling filter at high pH results in an enhancement of the mass transfer by a factor of 1700-11 000. Overall, alkaline biotrickling filtration was shown to be very effective at low concentration of H2S and very short gas contact time. This is the first demonstration of a biotrickling filter for air pollution control operated at high pH.