Electronic Nose as an NDT Tool for Aerospace Industry

AbstractArtificial olfaction is an emerging technology aiming to develop tools for easy, rapid and mobile gas mixture analysis. So far, its application to several application fields is under investigation with some commercial solution already deployed. In this work we present the results of the development process for an electronic nose devised for NDT in aerospace industry focusing on its pattern recognition stage

Enhancement in the Selectivity and Sensitivity of Ni and Pd Functionalized MoS2 Toxic Gas Sensors

Atmospheric pollution is one of the major aspects of concern which led to the research of sensors for the detection of toxic gases. The supreme surface-to-volume ratio makes two-dimensional MoS2 a promising material to be used as an electronic sensor. Here, we demonstrate the fabrication of a high-performance gas sensor based on atomic-layered MoS2 nanoflakes synthesized by a facile hydrothermal process. Structural and morphological studies confirmed the formation of few-layered phase pure hexagonal MoS2 nanoflakes. The results demonstrate that the Pd-MoS2 layers exhibited a very high relative response to NO gas (700%) at 2 ppm concentration with a minimum NO detection limit of 0.1 ppm and Ni-MoS2 demonstrated a relative response of 80% towards H2S gas with a limit of detection of 0.3 ppm with good repeatability and selectivity, owing to the increased adsorption energy of NO on Pd-MoS2 and H2S on Ni-MoS2 through the formation of PdNOx and NiS2 complexes respectively. The improved sensing performance of this MoS2-based sensor also suggests the great potential and possibility of MoS2 related 2D materials and its combinations for the development of futuristic highly sensitive nanosized gas sensors suitable for anti-pollution automotive system and as volatile biomarkers

Combining Real Time Classifiers for Fast and Reliable Electronic Nose Response Analysis for Aerospace NDTs

AbstractFast response and reliability are a prerogative in non- destructive tests s p e c i f i c a l l y in aerospace industry for safety and efficiency reasons. Currently, composite panels bonding, in green aircraft concept, is lacking a validated NDT technique for the bond quality. E-noses equipped with PARC algorithms appear a promising choice to acquire speedily a complete pattern response maximizing reliability. In this paper, combining real time classifiers, we show how to obtain a rapid first- hand response with the possibility of increasing accuracy awaiting for the end of the e-nose measurement cycle. A reject option is casted on the base of classifier self-perceived reliability to nullify false negatives while keeping the false positive rate at minimum

Cooperative 3D Air Quality Assessment with Wireless Chemical Sensing Networks

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Extended Non-destructive Testing for Surface Quality Assessment

AbstractThis chapter introduces various extended non-destructive testing (ENDT) techniques for surface quality assessment, which are first characterized, then enhanced, and finally applied to assess the level of pre-bond contaminations intentionally applied to carbon fiber reinforced plastic (CFRP) adherends following the procedures described in the previous chapter. Based on two user cases comprising different scenarios that are characteristic of either aeronautical production or repair, the detailed tests conducted on two types of sample geometry, namely flat coupons and scarfed pilot samples with a more complex shape, form the basis for applying the advanced ENDT procedures for the monitoring of realistic and real aircraft parts, as will be described in Chap. 10.1007/978-3-319-92810-4_5. Specifically, the reported investigations were performed to assess the surface quality of first ground and then intentionally contaminated CFRP surfaces using the following ENDT tools: the aerosol wetting test (AWT), optically stimulated electron emission (OSEE), two differently implemented approaches based on electronic noses, laser-induced breakdown spectroscopy (LIBS), Fourier-transform infrared (FTIR) spectroscopy, laser-induced fluorescence (LIF), and laser vibrometry

Focused Ion Beam Nanopatterning for Carbon Nanotube Ropes Based Sensor

Focused Ion Beam (FIB) technology has been used to realize electrode patterns for contacting Single Walled Carbon Nanotubes (SWCNTs) ropes for chemical gas sensor applications. Two types of transducers, based on a single rope and on bundles, have been realized starting from silicon/Si3N4 substrate. Electrical behaviour, at room temperature, in toxic gas environments, has been investigated and compared to evaluate contribution of a single rope based sensor respect to bundles one. For all the devices, upon exposure to NO2 and NH3, the conductance has been found to increase or decrease respectively. Conductance signal is stronger for sensor based on bundles, but it also evident that response time in NO2 is faster for device based on a single rope. FIB technology offers, then, the possibility to contact easily a single sensitive nanowire, as carbon nanotube rope

Analysis of a calibration method for non-stationary CVD multi-layered graphene-based gas sensors

Limitations such as lack of detected stationary signal and slow signal recovery after detection currently affect graphene-based chemi-sensors operating at room temperature. In this work, we model the behavior of a sensor in a test chamber having limited volume and simulating the environmental conditions. From this model, we mathematically derive the calibration method for the sensor. The approach, focused on the time differential of the signal output, is tested on multi-layered graphene (MLG)-based sensors towards the chosen target gas (nitrogen dioxide) in the range from 0.12 to 1.32 ppm. MLG acting as sensing layer is synthesized by chemical vapor deposition. Our study paves the route for a wider applicability of the analysis to calibrate the class of devices affected by non-stationary and recovery issues