Towards self-diagnosis composites: Detection of moisture diffusion through epoxy by embedded evanescent wave optical fibre sensors

Abstract This paper reports on an epoxy matrix for glass fibre reinforced polymers equipped with low cost optical fibre sensors for the early detection of water diffusion, with devised applications in the oil and gas industry. Novel evanescent wave optical fibre sensors were designed, fabricated and embedded in epoxy resin samples. The tips of the optical fibre sensors were coated with a silver layer to work in reflection, so that they could be used as probes. Accelerated diffusion tests were performed: the samples were exposed to simulated sea water at 80 °C for up to 148 h. The water diffusion resulted in a remarkable change of the reflected signal from the sensors, a result that was then confirmed through gravimetric measurements and a theoretical prediction, according to Fick's diffusion law. The results corroborate the feasibility of "sensitive" fibre reinforced polymers in harsh environments and that chemicals diffusion in these materials can be remotely and continuously monitored by means of the presented sensing system

Advanced glasses, Composites And Ceramics for High growth Industries

CoACH (Advanced glasses, Composites and Ceramics for High Growth Industries, www.coach-etn.eu) is a 4 year project coordinated by Politecnico di Torino and supported by the European Commission through the Marie Sklodowska-Curie Action. It provides an innovative and inter-sectorial doctoral training for young researchers in prestigious academic institutions as well as private companies. CoACH, which includes five academic partners and ten private companies from seven different European countries, promotes international excellence in glass, ceramic and composite science and technology, modelling, design, characterization and commercialization of advanced glass, ceramic and composite based products. In the CoACH project, 15 recruited PhD researchers are currently trained in creative, independent problem solving under time and resource constraints. This is typical of a scientific and technical working environment in continuous contact with the industrial world, through inter-sectorial and interdisciplinary secondment and mobility activities between academia and industry. CoACH provides training-through-research in: • Glasses and composites for HEALTH care industries. • Glasses, ceramics and composites for the ENERGY production and ICT industries. • ENVIRONMENTALLY-friendly, low cost glass, ceramic and composite materials. Its scientific goals, based on specific needs expressed by industries, have strong potential for excellent research and technological development and for disseminating and converting the results into social and economic benefits

Up-cycling of vitrified bottom ash from MSWI into glass-ceramic foams by means of ‘inorganic gel casting’ and sinter-crystallization

The transformation of vitrified waste, such as bottom ash from municipal waste incineration, into cellular glass-ceramics is convenient, if the additional processing is simple and inexpensive. The present paper aims at presenting a possible route to achieve this goal, based on the recently proposed mechanical foaming of alkali-activated suspensions of waste glass powders, followed by sinter-crystallization at moderate temperatures (from 800 to 900 °C). Compared to previously studied glasses, in this experiment bottom ash-derived glass suspensions underwent progressive hardening at low alkali molarity and in limited times. The firing did not alter the open-celled structure that had developed upon low temperature foaming, owing to a significant crystallization. With an overall porosity of 80%, the optimized foams exhibited a remarkable compressive strength (>6 MPa). Finally, the process had no negative impact on the leaching of toxic elements, which remained well below the thresholds for inert materials

Towards self-diagnosis composites: Detection of moisture diffusion through epoxy by embedded evanescent wave optical fibre sensors

This paper reports on an epoxy matrix for glass fibre reinforced polymers equipped with low cost optical fibre sensors for the early detection of water diffusion, with devised applications in the oil and gas industry. Novel evanescent wave optical fibre sensors were designed, fabricated and embedded in epoxy resin samples. The tips of the optical fibre sensors were coated with a silver layer to work in reflection, so that they could be used as probes. Accelerated diffusion tests were performed: the samples were exposed to simulated sea water at 80 °C for up to 148 hours. The water diffusion resulted in a remarkable change of the reflected signal from the sensors, a result that was then confirmed through gravimetric measurements and a theoretical prediction, according to Fick’s diffusion law. The results corroborate the feasibility of “sensitive” fibre reinforced polymers in harsh environments and that chemicals diffusion in these materials can be remotely and continuously monitored by means of the presented sensing system

An Epoxy Adhesive Crosslinked through Radical‐Induced Cationic Frontal Polymerization

AbstractUV‐initiated cationic frontal polymerization is exploited as a solvent‐free, extremely fast, and low‐temperature technique to obtain epoxy‐based adhesives. Epoxy formulations are prepared by blending commercial resins at different weight ratios and adding photo and thermal initiators at different percentages. In addition, the influence of other critical parameters, including the joint thickness, the nature of the adherends, and the temperature, is studied. As the reaction front is thermally sustained, the boundary conditions play a key role during the curing process and heat dissipation through the adherends in particular. The thermal properties of the epoxy formulation are studied through differential scanning calorimetry analysis, and the joint strengths are investigated by carrying out single lap off‐set shear tests under compression. The results demonstrate the feasibility of obtaining joints by means of the radical induced cationic frontal polymerization of the epoxy adhesives, which exhibit comparable epoxy group conversion and mechanical performances to the ones cured by traditional energy‐intensive techniques

Interface stability between bare, Mn-Co spinel coated AISI 441 stainless steel and a diopside-based glass-ceramic sealant

This document is the Accepted Manuscript version of the following article: A. G. Sabato, A. Crysanthou, M. Salvo, G. Tempura, and F. Smeacetto, ‘Interface stability between bare, Mn-Co spinel coated AISA 441 stainless steel and a diopside-based glass-ceramic sealant’, International Journal of Hydrogen Energy, Vol. 43 (13): 1824-1834, January 2018, made available under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives License CC BY NC-ND 4.0 ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ), which permits non-commercial re-use, distribution, and reproduction in any medium, provided the original work is properly cited, and is not altered, transformed, or built upon in any way. Under embargo until 16 December 2018. The final, definitive version of this paper is available online at doi: https://doi.org/10.1016/j.ijhydene.2017.11.150.This study is focused on a diopside-based glass-ceramic sealant for solid oxide fuel cells and its compatibility with AISI 441 stainless steel interconnect. The morphological and chemical stability with both bare and Mn–Co spinel coated AISI 441 steel, after 3500 h exposure at 800 °C in air, is reviewed and discussed. Post-mortem samples are morphologically and chemically analysed by SEM-EDS. Reaction products at the glass-ceramic/bare AISI 441 interface, resulting from the reaction of Mg from the sealant and Cr and Mn from the steel, are detected, without affecting negatively the integrity of the joints. In the case of Mn–Co spinel coated AISI 441, interactions between the glass-ceramic and the outer part of the Mn–Co spinel coating, along with crystallization of oxides rich in Si and Mg, are detected, but still no corrosion phenomena are present. The glass-ceramic is found to be compatible with both bare and coated AISI 441.Peer reviewe

Oxidation protective glass coating for magnesium silicide based thermoelectrics

A Mg2Si-Mg2Sn based thermoelectric material (TE), with composition of Mg2Si0.487Sn0.5Sb0.013, produced by ball-milling combined with spark plasma sintering, is successfully coated with a new silica-based glass, which is specifically designed, characterised and tested as an oxidation protective coating for mid-temperature range (up to 500 °C) applications. Despite the relatively high coefficient of thermal expansion (CTE) of Mg2(Si,Sn) based materials, very good thermo-mechanical compatibility between the substrate and the coating material is obtained. Oxidation tests, performed at 500 °C for 120 hrs in air, demonstrate the effectiveness of the glass coating for the protection of Sb doped Mg2(Si,Sn) thermoelectric materials

Atmospheric pressure plasma jet for surface texturing of C/SiC

C/SiC composites are materials to be used in harsh environments overcoming the limits imposed by the intrinsic brittleness of their ceramic constituents while providing both high mechanical performances at high-temperature temperatures and low weight. In order to manufacture the final component, joining C/SiC, to itself or to other materials, is often necessary, and it is critical to maximize the strength of the joints (similar or dissimilar) in order to meet reliability criteria. In the present work, a pre-joining treatment based on an atmospheric pressure plasma jet (APPJ) was proposed to introduce a brush-like texture on the surface via the selective removal of carbon fibers. The investigation of treated surfaces via electron microscopy and confocal 3D-profilometry confirmed that the treatment was effective in introducing a brush-like texture and in increasing the available contact area. Wettability test and inspection of cross-section of CB4 wetted samples were then carried out. The latter confirmed the formation of anchoring points given by the brush-like texture. Finally, the effectiveness of the treatment in improving the joint strength was assessed by comparing the apparent shear strength of CB4 brazed composites, with and without the APPJ pre-treatment. The joints with plasma pre-treated C/SiC showed a shear strength of about 66 MPa, 44% more than the strength of joints produced with untreated C/SiC

Effect of pulsed laser irradiation on the SiC surface

The effect of a pulsed laser irradiation (Nd:YVO4, 1064 nm) in air on the Surface morphology and chemical composition of silicon carbide and on the adhesion with an epoxy adhesive was investigated. Scanning and transmission electron microscopies, atomic force microscopy, and X-ray photoelectron spectroscopy revealed that the laser treatment reduced the contamination level of the Surface and induced the formation of a silica-based nanostructured colum nar layer on the SiC surface. The mechanism for the formation of five different microstructural regions is described in this paper. In addition, the formation of a 5-10-nm-thick graphite layer between the oxide layer and SiC was observed. The joining test with Hysol EA9321 showed that the nanostructured columnar silica layer was completely infiltrated by the adhesive, thus leading to a significant increase in the joined specific area and a mecha nical interlocking at the adhesive/substrate interface. Nevertheless, the apparent shear strength of the joined SiC samples slightly decreased after the laser processing of the surfaces from about 42 MPa for lapped SiC to about 35 MPa for laser-nanostructured SiC. The formation of the graphite layer was found to be responsible of the poor adhesion properties of the SiC surfaces modified by the laser radiation