Gas Sensing Materials

Nanocrystalline gamma iron oxide (y-Fe203) recently been studied as a gas sensing material, has been synthesised at 70°C using sonication-assisted precipitation technique [21]. The synthesised material was then used for fabricating the... 

Semiconductor photocatalysis has been successfully applied in degradation of pollutants e.g. S02 and phenolic waste [69], It is mainly Ti02, which have been used and studied for this purpose, but there are reports where hematite has been used for photodegradation [52-54, 56, 57, 110, 111]. Hematite has also been studied as a gas sensing material [40]. 

Siemons, M. Koplin, T. J. Simon, U., Advances in high throughput screening of gas sensing materials, Appl. Surf. Sci. 2007, Appl. Surf. Sci. 2007, 254, 669-676... 

Simon, U. Sanders, D. Jockel, J. Brinz, T., Setup for high-throughput impedance screening of gas-sensing materials, J. Comb. Chem. 2005, 7, 682-687... 

Design of Selective Gas Sensing Materials by Combinatorial Solution Deposition... 

Figure 12.10 summarizes applications of combinatorial solution deposition to development of gas sensing materials. First, uniform sol solutions are needed to guarantee precise and uniform chemical composition throughout the sensing films. 

Tan, O.K. eL al., Nanostrnctnred oxides by high-energy ball milling techniqne Application as gas sensing materials. Solid State Ionics 172 (2004) 309-316. 

Gas sensing materials are doped in the cladding of an optical fiber. Refractive indices of core and cladding are adjusted as to satisfy the condition for perfect reflection. In this system, the objective gases are detected from the change of evanescent waves caused by the interaction between a gas and a sensing material. The sensor can be sensitized by repeating perfect reflections many times. 

Optical gas sensors generally have some characteristics such as a high insulating capacity, independence of electrical noises and operation in safety. Moreover it is possible for them to detect a variety of gases by choosing a gas sensing material. For environmental use of optical sensors, applications for NO , SOj, CO2 and CO are expected. 

Hie experimental results show a good match to the theory. In addition, it was becoming clear that the use of p-type materials as chemoresistive gas sensing materials is not optimal. The same surface chemistry (same band bending) results in a much lower sensor signal for the p-type material compared with n-type materials, where the conduction is described by a... 

Thaditionally, solid-state gas sensors have a two-electrode configuration, where the gas sensing material is located between two metal electrodes, and a third metal electrode, which is usually platinum, is used for the heating of the sensor device. There are numerous methods by which such sensors can be realized. Figure 3.5 shows traditional gas sensor-electrode geometries.To make measurements on a semiconductor gas sensing material it is possible to use a compressed sintered or unsintered pellet with metal contacts on each face. 

CVD techniques can give control over important aspects of gas-sensing materials porosity, grain size and film thickness can all be well-controlled (Guo et al, 2006). The rapid speed of film growth is an advantage of the technique, with a rate of up to 1 micrometer per minute for processes that occur at atmospheric pressure. 

Resistance controlled oscillator circuit for gas sensing material interface (adapted from Grassi et a ., 2007). Q and Q are two complementary signals at the output of the flip flop. 

Logarithmic compression circuit for gas-sensing material interface (adapted from Barrettino eta ., 2002). (Voon,roi is a voltage applied from outside which will fix the voltage across the sensing material and thus fix the current at the reference arm of th are two output terminals of the circuit.)... 

Consequently, there is a significant market pull for sensor arrays containing selective gas-sensing materials (multi-gas devices) and partially-selec-tive gas-sensing materials (electronic noses). The two main challenges in sensor array-based technology is cost and power consumption. First, the... 

In this electronic age, it is mandatory to use solid polymer electrolytes for different applications in science and technology. Polymer electrolytes can be shaped in the form of thin film, thereby reducing the internal resistance leading to application as gas sensing material. Few reports appeared on proton-conducting polymer films and their application to gas sensors [65]. 

Epifani M, Comini E, Arbiol J, Sicdiano P, SbervegUeri G, Joan RM. Oxide nanopowders from the low-temperature processing of metal oxide sols and their application as gas-sensing materials. Sens Actuators B 2006 118(l/2) 105-9. 

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