102,473 research outputs found
MOX-NW Electronic Nose for detection of food microbial contamination
No full textas chemical sensors were identified in the past few years as valuable candidate
for food safety controls, eg early diagnosis of microbial contamination. Microbial
management is a crucial task in food processing industry all along the entire food production
chain; residual contamination may lead to loss of quality and, if the microorganisms are
pathogens, can bring about severe risks for consumers' health. For this reason an accurate
and fast control of production using, possibly, at-line sensor systems is highly demanded
SN1-XFEXOY - A NEW MATERIAL WITH HIGH-CARBON MONOXIDE SENSITIVITY
No full textThe preparation method and the sensing properties (sensitivity and selectivity to interfering gases) towards carbon monoxide of the new ternary compound Sn1-xFexOy, deposited in the form of thin films, are presented in this paper. The metal of the VIIIB group is introduced with concentrations in the range 0<x<25 at. %. Thin films are sputtered using the RGTO (rheotaxial growth and thermal oxidation) technique. This technique consists of metal deposition onto a substrate maintained at a temperature higher than the metal melting point and metal oxidation by means of an annealing cycle in pure oxygen. Particular emphasis is given to the relations between some preparation parameters of the material, namely the atomic percentage of iron or the annealing cycle, and to the sensor sensitivity towards CO and other interfering gases like C2H5OH, H-2 and NOx diluted in dry air. A sensitivity S=(C-gas-G(air))/G(air)=3.5 towards 10 ppm of CO has been measured: the kinetic characteristics of the sensors are also presented, together with the working mechanism
Investigation on the O-3 sensitivity properties of WO3 thin films prepared by sol-gel, thermal evaporation and r.f. sputtering techniques
No full textWO3 thin films have been deposited on alumina substrates provided with platinum interdigital electrodes by sol-gel (SG), r.f. sputtering (RFS), and vacuum thermal evaporation (VTE) techniques and annealed at temperatures between 500 degrees C and 600 degrees C for 1 to 30 h in static air. The morphology, crystalline phase and chemical composition of the films have been characterised using SEM, glancing XRD and XPS techniques. The electrical response has been measured exposing the films to O-3 (10-180 ppb), NO2 (0.2-1 ppm), NOx (27 ppm NO and 1 ppm NO,) at different operating temperatures ranging between 200 and 400 degrees C and humid air at 50% R.R. SG prepared films have shown bigger responses (S = I-Air/I-gas) with respect to VTE and RFS for all the investigated gases and operating temperatures. RFS prepared has resulted to be less sensitive, but faster in the response and more stable in terms of signal reproducibility. The response to O-3 has been found to be at maximum at 400 degrees C. At this temperature the response to 80 ppb of ozone has been: S = 35 (SG), S = 18 (VTE) and S = 5 (RFS). The NO2 and NOx response reached the maximum at 200 degrees C and becomes negligible at 400 degrees C. Improvements on the O-3 gas sensitivity and selectivity can be achieved by fixing the operating temperature of the films at 400 degrees C. (C) 2000 Elsevier Science S.A. All rights reserved. RI Faglia, Guido/E-6991-2010; Sberveglieri, Giorgio/A-5030-2010; li , yongxiang/C-5059-2009; Comini, Elisabetta/C-6721-200
Radio-Frequency Magnetron Sputtering Growth And Characterization Of Indium Tin Oxide (Ito) Thin-Films For No2 Gas Sensors
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Carbon monoxide response of molybdenum oxide thin films deposited by different techniques
No full textMoO3 thin films have been deposited on alumina substrates by radio frequency (RF) sputtering from a metallic molybdenum target in a reactive atmosphere and by the sol-gel (SG) technique using molybdenum ethoxide solutions. The as-deposited RF films have been annealed at 500 degrees C for 1 h, while the SG films have been annealed at temperature range between 400 degrees C and 700 degrees C for 1 h. The formation of a well-developed nanoparticle structure for the RF films with respect to the SG ones was suggested by scanning electron microscopy (SEM) characterisation, X-ray diffraction (XRD) has confirmed the formation of crystalline orthorhombic MoO3 structures (JCPDS 5-508) for both the RF and SG films after annealing. The gas sensing properties towards CO have been examined. MoO3-based gas sensors developed are capable of CO down to few ppm with a very fast response. (C) 2000 Elsevier Science S.A. All rights reserved. RI Faglia, Guido/E-6991-2010; Sberveglieri, Giorgio/A-5030-2010; li , yongxiang/C-5059-2009; Comini, Elisabetta/C-6721-200
Microstructural Characterisation of RF Magnetron Sputtered ZnO Thin Films on SiC
No full textThe microstructural characterization of r.f. magnetron sputtered ZnO thin films deposited on 6H-SiC is presented with a comprehensive investigation of their properties as a function of annealing temperature and film thickness. These structures, with some modifications, are utilised as Schottky diode hydrogen gas sensors and Surface Acoustic Wave (SAW) devices. RI Ippolito, Samuel/B-8539-2008; Sberveglieri, Giorgio/A-5030-2010; kalantar-zadeh, Kourosh/C-2439-200
MICROSTRUCTURAL CHARACTERIZATION OF FE-AL THIN-FILMS
No full textThe structural properties of thermally evaporated Al-Fe layers were studied as a function of the aluminium layer thickness delta-Al (taking values of 1, 2 and 4 nm), with an iron layer of constant thickness, delta-Fe = 30 nm. The quality and orientation of the material were examined by X-ray diffraction and transmission electron microscopy. Crystallites of alpha-Fe oriented in the (110) direction were around 7-8 nm in size for any value of delta-Al except near delta-Al = 1 nm where a mostly amorphous iron layer was obtained. It was also verified that a bilayer of composition delta-Al = 2 nm and delta-Fe = 30 nm, twice repeated, led to a two-phase metal system consisting of an amorphous component and crystalline alpha-Fe type material texturized along the (110) direction. The Fe3Al phase was also detected in the bilayer structure with delta-Al = 4 nm
Microstructural characterization of a titanium-tungsten oxide gas sensor
No full textThin films of Ti-W-O were prepared from a W-Ti alloy target by rf magnetron sputtering in reactive atmosphere. Analysis devoted to investigate the microstructural properties of this material was carried out in order to explain the origin for the high sensing performance of a W-Ti-oxide gas sensor. Scanning and transmission electron microscopy techniques showed that after annealing the film consists of a polycrystalline layer, isostructural to tetragonal WO3, over which crystallites of pure WO3 are dispersed. The WO3 crystallites are insulated from each other and do not enter into the process of conduction of the layer. It was shown that Ti is soluted in the tetragonal WO3 lattice of the underlying layer. This layer exhibits fine granularity, which is an optimal feature for materials suited to gas sensing
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