1,236 research outputs found
Sensing Properties of E-Beam Evaporated Nanostructured Pure and Iron-Doped Tungsten Oxide Thin Films
No full textGas sensing properties of nanostructured pure and iron-doped WO(3) thin films are discussed. Electron beam evaporation technique has been used to obtain nanostructured thin films of WO(3) and WO(3):Fe with small grain size and porosity. Atomic force microscopy has been employed to study the microstructure. High sensitivity of both films towards NO(2) is observed. Doping of the tungsten oxide film with Fe decreased the material resistance by a factor of about 30 when exposed to 5 ppm NO(2). The high sensitivity is attributed to an improved microstructure of the films obtained through e-beam evaporation technique, and subsequent annealing at 300 degrees C for 1 hour
Simile, M.M., Pagnan, G., De Miglio, M.R., Muroni, M.R., Asara, G., Frau, M., Seddaiu M.A., Feo, F., Ponzoni, M., and Pascale, R.M
No full text
SiC Foams Decorated with SnO2 Nanostructures for Room Temperature Gas Sensing
No full textSberveglieri, Giorgio/0000-0003-0080-8117; Ponzoni, Andrea/0000-0001-9955-5118; Comini, Elisabetta/0000-0003-2559-5197; Vakifahmetoglu, Cekdar/0000-0003-1222-4362Cell walls of the commercial silicon carbide (SiC)-based foams were decorated by one-dimensional tin dioxide (SnO2) nanostructures. Thermal evaporation of SnO2 powder with the assistance of a Au catalyst in inert atmosphere caused the formation of SnO2 nanobelts on the pore surfaces. The room temperature (RT) ammonia (NH3) and nitrogen dioxide (NO2) gas sensing behaviors were investigated systematically in both dry and humid air atmosphere with/without UV activation. The results were compared to those for bare SnO2 and SiC. It was shown that SiC/SnO2 composite was efficient to detect low concentration of NH3 (10-50 ppm) and NO2 (1-5 ppm) under humid air and UV activation at RT.TUBITAK (The Scientific and Technological Research Council of Turkey)Turkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [CAYDAG-113Y533]The author wishes to express sincere appreciation to Prof. Gian Domenico Soraru and his team in University of Trento for the N2 adsorption and desorption data. C. V. gratefully acknowledge the support of TUBITAK (The Scientific and Technological Research Council of Turkey) under the project Grant No. CAYDAG-113Y533
Deformational response of a marine silty-clay with varying organic content in the triaxial compression space
No full textThis study characterises the effects of naturally varying organic content on the compression and shear behaviour of a marine silty-clay from the Netherlands. Index properties and mechanical properties are determined through laboratory tests, including oedometer and multistage loading-unloading triaxial stress paths. The results indicate a significant impact of the organic content on the compression response, with both the loading and reloading indexes increasing as the loss on ignition increases from 3% to 7%. Additionally, the study suggests a directional response of the compression behaviour, with the loading index increasing with the stress ratio. The influence of the organic content on shear strength appears to be less significant. No brittle response is observed during shearing and a similar ultimate stress ratio is attained by all samples. However, a unique critical state line can only be identified for samples with similar organic content, as its intercept and slope are found to increase with increasing organic content. The experimental results from stress paths at constant stress ratio reveal an anisotropic pre-failure plastic deformation mode, which depends on the previous stress history and loading direction. This suggests that the stress-dilatancy relationship cannot be formulated as a unique function of the stress ratio. The high-quality experimental data presented in the paper enlarge the database on soft organic soils in view of the development of advanced constitutive models.Accepted Author ManuscriptGeo-engineerin
Identification and quantification of transitional modes of behaviour in sediments of Venice lagoon
No full textAn analysis was made of an extensive series of oedometer and triaxial tests on intact samples of silts and silty clays from the lagoon of Venice, as well as a more limited series of carefully controlled oedometer tests on reconstituted specimens. The soils appear to have transitional modes of behavior with compression curves that converge only slowly in the v–log s'v plane and critical state lines defined for triaxial compression that are non-unique in the v–lnp' plane. Two means of quantifying the degree of transitional behaviour are introduced, one factor, m, being based on the oedometer data
and the second, P, on the critical state data. The values of m were in general lower than those of P, because of the higher stress level considered. The values of m were also found to depend on unloading, which must be accounted for when comparing data from intact and reconstituted specimens
Determination of water retention properties of silty sands by means of combined commercial techniques
No full textA recent increase in frequency and severity of exceptional climatic events is of concern for the stability of natural and artificial slopes. These undergo continuous evaporation and infiltration cycles, which change the suction distribution and trigger shrinkage, swelling, cracking, and surfi-cial erosion, overall decreasing the soil strength. To assess the impact of these climatic stresses, the determination of water retention properties is a priority. Although advanced techniques have been proposed in the last few decades to this end, simpler commercially available techniques allow col-lecting data for a larger number of samples in a shorter time, thus enabling a basic description of the water retention properties for a larger database of soils. Data on two silty sands, coming from very different climatic environments in Europe, were collected with a combination of two simple commercial devices, and the results were modelled with a van Genuchten’s law. The fitted pa-rameters were found to correlate well with the amount of fines, irrespective of the different origin and composition of the two soils. Eventually, the limitation of the approach is discussed based on the results of cyclic drying–wetting tests.</p
Preliminary analysis on cellulose-based gas sensor by means of aerosol jet printing and photonic sintering
No full textIn this paper, we present a preliminary analysis on the possibility to realize low-cost and eco-friendly cellulose-based gas sensors by means of Aerosol Jet Printing (AJP) and flash lamp annealing (FLA). To the authors knowledge, it is the first time that these two techniques are combined in the realization of such a device. The intrinsic hygroscopic properties are the key element of this device: cellulose contains substantial amount of moisture, adsorbed from the environment, enabling the use of wet chemical methods for sensing without manually adding water to the substrate. The sensors were tested in terms of electrical resistance. The penetration of the carbon ink in the cellulose network was stated thanks to cross-sections captured at the microscope. Once placed in a damp environment, all the sensors showed a comparable behavior settling at an asymptotic value of 3.68 MΩ (relative standard deviation of 8%). In presence of different concentration of NH4OH, the sensors showed a resistance proportional to the amount of analyte present in the working volume, showing 25.6% increase compared to the 0.5 M concentration, while 34.1% compared to the 1M
- …
