Techniques for In Situ Monitoring the Performance of Organic Coatings and Their Applicability to the Pre-Finished Steel Industry: A Review

A review is carried out in this paper into techniques that currently exist for, of have the potential to be used for, monitoring the performance of organic coating. Specific attention is paid to the applicability of each method to pre-finished steel used in the construction industry as these are rarely monitored in situ and their expected performance is often only estimated from lab-based accelerated corrosion testing. Monitoring could allow more accurate estimates of building cladding lifespan and required maintenance schedules; provide customers with active performance data; additionally, with a better understanding of performance, more appropriate coatings or coating weights could be selected for a construction project, offering economic benefits as part of smart building developments. An introduction to coatings, their use for corrosion protection, failure mechanisms, and relevant monitoring techniques is given before current assessment techniques are described in terms of their working principles. Examples of recent work are presented for the techniques that have been investigated for monitoring or directly relatable purposes. The review concludes that there are several good reasons why an optimum corrosion monitoring technology does not currently exist, however, promising research is emerging in the field of wireless and embedded sensor design which is providing optimistic results

Dadansoddiad o berfformiad lampau electroymoleuol printiedig ar is-haen ddi-draidd

Er mwyn archwilio marchnadoedd newydd ar gyfer deunyddiau electronig printiedig, cynhaliwyd astudiaeth ymchwil i geisio deall perfformiad lampau electroymoleuol (EL) a gynhyrchwyd ar is-haen ddi-draidd. Daw’r posibilrwydd o greu’r lampau o ddeunydd inc PEDOT:PSS sy’n ffurfio uwchben electrod yn y lamp ac sy’n cael ei amnewid am yr ITO a ddefnyddir mewn lampau confensiynol. Gan ddefnyddio proses printio sgrin syml, cynhyrchwyd lampau ar bedair is-haen ddi-draidd (un blastig a thair bapur) a chymharwyd eu perfformiad drwy fesur lefel eu disgleirdeb. Yn gyffredinol, gwelwyd lleihad o tua 50% yn nisgleirdeb y lampau o’i gymharu â disgleirdeb lampau a gynhyrchwyd gan ddefnyddio ITO. Roedd papur ysgafnach a mwy garw yn lleihau’r disgleirdeb ymhellach. Nid oedd modd cynyddu disgleirdeb y lampau drwy ychwanegu haen ychwanegol o PEDOT:PSS gan fod hynny’n lleihau'r nodweddion tryloyw. Wrth gynyddu maint y lamp, mae effaith gwrthiant y PEDOT:PSS o’i gymharu â’r ITO yn achosi dirywiad sylweddol ym mherfformiad y lamp ac yn cyrraedd lefel o 25% yn unig o ddisgleirdeb lamp ITO o 5000 mm2. Nid y lleihad yn nargludedd a thryloywder y PEDOT:PSS o’i gymharu ag ITO yn unig sy’n gyfrifol am berfformiad cymharol wael y lampau di-draidd, ond hefyd natur dopolegol y gronynnau ffosffor, sy’n golygu bod rhai o’r gronynnau y tu hwnt i effaith y maes trydanol a grëwyd rhwng y ddau electrod.Understanding performance deficiencies in printed thick film EL lamps on paperIn order to examine new potential markets for printed electronics, a research study was undertaken to understand the performance of opaque substrate electroluminescent (EL) lamps. Opaque EL lamps are made possible by a PEDOT:PSS top electrode which replaces the ITO used in the conventional lamps. Screen-printed lamps were manufactured on four substrates (one plastic and three paper) and their performance was measured through brightness measurement. Generally, opaque substrate lamps were 50% less bright than a comparable ITO lamp. Further reductions in brightness were observed with the lighter and rougher papers. Additional layers of PEDOT:PSS increased sheet conductivity but reduced lamp brightness due to a reduction in layer transparency. As lamp size increased, the resistive nature of the PEDOT:PSS caused a significant reduction in lamp output, with a brightness of 25% of a comparable ITO lamp with an illuminated area of 5000 mm2. The relatively poor performance of the opaque lamps is derived not only from the reduced conductivity and transparency of the PEDOT:PSS compared to ITO, but is also caused by the topological nature of the phosphor particles which result in some phosphor material lying outside the electric field created between the two electrodes

Design of a Chipless RFID Tag to Monitor the Performance of Organic Coatings on Architectural Cladding

Coating degradation is a critical issue when steel surfaces are subject to weathering. This paper presents a chipless, passive antenna tag, which can be applied onto organically coated steel. Simulations indicated that changes associated with organic coating degradation, such as the formation of defects and electrolyte uptake, produced changes in the backscattered radar cross section tag response. This may be used to determine the condition of the organic coating. Simulating multiple aging effects simultaneously produced a linear reduction in tag resonant frequency, suggesting coating monitoring and lifetime estimation may be possible via this method. For coatings thinner than calculations would suggest to be optimum, it was found that the simulated response could be improved by the use of a thin substrate between the coated sample and the antenna without vastly affecting results. Experimental results showed that changes to the dielectric properties of the coating through both the uptake of water and chemical degradation were detected through changes in the resonant frequency

Food packaging simulant failure mechanisms in next generation steel packaging

Legislative pressures have led to the mature dominant chromium‐coated steel (ECCS) substrate and epoxy phenolic lacquer replacement in Europe. An investigation was carried out to examine the interaction between a steel surface engineered with a novel, developmental substrate coated using Cr (III)‐based electrolytes and the food stuff being canned. Samples of lacquered material were subjected to a typical retort process (121°C for 90 minutes) and examined using a variety of laboratory analytical techniques. The foodstuff being packaged has a significant impact on the substrate/lacquer adhesion with clear differences in failure mechanisms between foodstuffs. There is clear evidence of chemical species transfer through the next generation lacquer, and this can instigate corrosion at the surface where incomplete chromium coverage leads to exposed iron. In general, the novel developmental material exhibits lower adhesive properties and shows a greater sensitivity to the foodstuff, although this is largely attributed to the homogeneity of the coverage. The novel substrate proves to be a promising alternative to ECCS due to REACH legislation, but improvement is required to achieve equivalent performance

Improved Manufacturing Performance of Screen Printed Carbon Electrodes through Material Formulation

Printed carbon graphite materials are the primary common component in the majorityof screen printed sensors. Screen printing allows a scalable manufacturing solution, acceleratingthe means by which novel sensing materials can make the transition from laboratory material tocommercial product. A common bottleneck in any thick film printing process is the controlled dryingof the carbon paste material. A study has been undertaken which examines the interaction betweenmaterial solvent, printed film conductivity and process consistency. The study illustrates that itis possible to reduce the solvent boiling point to significantly increase process productivity whilemaintaining process consistency. The lower boiling point solvent also has a beneficial effect on theconductivity of the film, reducing the sheet resistance. It is proposed that this is a result of greaterfilm stressing increasing charge percolation through greater inter particle contact. Simulations ofmaterial performance and drying illustrate that a multi layered printing provides a more time efficientmanufacturing method. The findings have implications for the volume manufacturing of the carbonsensor electrodes but also have implications for other applications where conductive carbon is used,such as electrical circuits and photovoltaic devices

The application of orthogonal array analysis to the screen printing process

This paper outlines the development and results of a comprehensive experimental programme to investigate the effect of the primary screen printing parameters on the print quality. The selection of the parameters to be included in the experiments was based on both experience and discussions with industry. Three key areas were identified which were thought to have a substantial effect on the print quality; these were mesh characteristics, squeegee characteristics and ink rheology. Since the investigations found a number of parameters which may have an effect on the quality of the screen process a full factorial experiment was deemed impractical and thus it was decided to use orthogonal array analysis. By engineering design and astute choice of variables, an L18 orthogonal array for the print machine parameters consisting of mesh tension, mesh structure, mesh ruling, a squeegee pressure and edge hardness parameter, squeegee angle and ink characteristics was developed. A test form was designed which facilitated the measuring of image distortion and tonal reproduction Five copies were analyzed from each experiment using spectrophotometry. Control conditions were specified which ensured minimum variation between successive experiments by controlling the ink temperature, room temperature and screen ink film thickness. It was found that 7 of the 8 parameters chosen effect the quality of the printed image and that the experiment had been a success. Recommendations for further investigations are made

A Multi-Criteria decision making (MCDM) methodology for high temperature thermochemical storage material selection using graph theory and matrix approach

Industrial waste heat is currently underutilized due to the techno-economic challenges, inherent variability and intermittency of this source. To overcome the existing barriers, reduce the emission of greenhouse gases and protect the global environmental conditions, energy recovery is one of the most effective strategies. In the design of heat storage systems, the material selection procedure plays an important role and requires complex interrelationships between the various factors and parameters to be elucidated toachieve the best candidate material for a given application. This paper presents a Multi-Criteria Decision Making (MCDM) methodology based on Graph Theory and Matrix approach for high temperature thermochemical storage (TCS) material selection. Furthermore, the presented approach has been used to select the suitable candidate material for recovering the high temperature waste heat (over 500 °C) in Port Talbot Steelworks

Deposition of High Conductivity Low Silver Content Materials by Screen Printing

A comprehensive experimental investigation has been carried out into the role of film thickness variation and silver material formulation on printing capability in the screen printing process. A full factorial experiment was carried out where two formulations of silver materials were printed through a range of screens to a polyester substrate under a set of standard conditions. The materials represented a novel low silver content (45%–49%) polymer material and traditional high silver content (65%–69%) paste. The resultant prints were characterised topologically and electrically. The study shows that more cost effective use of the silver in the ink was obtained with the low silver polymer materials, but that the electrical performance was more strongly affected by the mesh being used (and hence film thickness). Thus, while optimum silver use could be obtained using materials with a lower silver content, this came with the consequence of reduced process robustness

Solution processing of TiO2 compact layers for 3rd generation photovoltaics

In this study, we introduce a new method for the deposition of TiO2 compact layers which involves the deposition of a wet film of an inorganic titanium (IV) precursor followed by fast hydrolytic conversion to crystalline TiO2 under near infrared radiative (NIR) treatment. With this, we aim to provide a scalable alternative to methods conventionally employed in laboratories for the fabrication of 3rd generation photovoltaic devices, such as high temperature pyrolysis or spin coating of organic titanium (IV) precursors. Optimization of our solution process is presented in detail. Structural features and crystalline properties of solution processed compact layers are characterized by FEG-SEM imaging and x-ray diffraction analyses and compared to compact layers produced by conventional laboratory techniques. Minimization of electron recombination is evaluated in standard liquid I-/I3- dye-sensitized solar cells (DSC). The results show that a compact, homogenous, high coverage yield crystalline TiO2 anatase layer can be produced by sequential deposition of 2–3 solution processed titanium oxide layers, each in under 30 s. In standard liquid I-/I3- DSC the solution processed compact layers strongly increased the electron lifetime, τn, when compared to cells prepared on a bare FTO substrate

Thermal sintering of printable copper for enhanced conductivity of FTO coated glass substrates

Copper inks potentially provide a cost effective replacement to silver for printed electronic circuits. In glass based applications such as PV or smart glass, it can provide a means of conductivity enhancement or additional functionality. Three inks consisting of a mixture of nano and micro copper particles were systematically studied to examine the relationship between sintering temperature, sintering time and gaseous environment on the electrical qualities of the sintered printed films deposited on FTO coated glass. There is a definite interaction between the particulate nature of the ink, the sintering conditions and the conductive properties of the film. Films containing only nano-particles provide the most conductive films with optimum sintering conditions of temperatures of 225 °C for 60 min. The inclusion of micro particles increased the ideal sintering temperature but lowered the sintering time. An ink containing an equal mixture of nano and micro particles exhibited the lowest performance and this could be attributed to partial oxidation of the nano-particles along the conductive path, which occurs as a result of the presence of the micro particles