1,720,989 research outputs found
Flexibele oledverlichting klaar voor de markt
No full textOnderzoekers van Holst Centre en Fraunhofer FEB produceerden eind 2018 een oled-rol van 15 meter; ‘s werelds langste verlichtingsdevice uit 1 stuk. Pim Groen, professor aan de TU Delft en projectleider Large Area Printing bij Holst Centremarkeert deze prestatie als een absolute gamechanger. ‘We hebben nu aangetoond dat opschaling naar continu-productie mogelijk is. Daarmee is de weg vrijgemaakt voor de definitieve doorbraak van een revolutionaire lichtbron.’Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Novel Aerospace Material
Highly Flexible lead-free piezoelectric composites- For vibration damping and noise cancellation application
No full textVibrations are inherent part in an aircraft system and supressing them has always been a technological challenge. Over the recent years, damping of mechanical vibrations is becoming increasing important to improve the reliability and performance of the aircraft systems and also increase the safety of passengers. As a response to these issues, much effort has been expended in the development and exploitation of damping materials. Among the various damping materials, piezoelectric particulate polymer composite have shown great potential towards damping due to the specialised damping mechanism based on the unique energy transferring effect between the viscoelastic polymer matrix and piezoelectric ceramic filler. As a results, the main objective of the master thesis is to develop a highly flexible and highly voltage sensitive vibration damper with piezoelectric particular composite. Lead free system with sodium potassium niobate (KNN) ceramics doped with lithium is identified has the suitable ceramic filler system applicable for this purpose. Hence, the effect of lithium dopant on dielectric and piezoelectric properties on the structured and random KNN/Epoxy composites is explored in order to identify the optimal ceramic filler composition with the highest dielectric and piezoelectric properties. To increase the passive damping potential of the composite, a flexible PDMS polymer matrix with excellent damping capabilities is selected and mixed with the optimal ceramic filler composition to investigate further on the piezoelectric voltage sensing properties in combination with the passive damping capabilities of the composite to be usable as vibration damper is presented. Finally, moving towards real-time application, feasibility study on processing relatively large area flexible piezoelectric sensor with high voltage sensitivity and capability of dampening vibrations is investigated.Novel Aerospace MaterialsAerospace Design, Integration & OperationsAerospace Engineerin
Piezoelectric and dielectric properties of polymer-ceramic composites for sensors
No full textThe main objective of this PhD thesis is to develop new routes and concepts for manufacturing piezoelectric ceramic-polymer composites with adequate piezoelectric properties while retaining ease of manufacturing and mechanical flexibility and explore new possibilities to maximize especially the voltage sensitivity while taking into account environmentally relevant issues such as avoiding the use of the chemical element Lead in the piezoelectric ceramics. The starting status of the field and the targets are described in Chapter 1. The production of structured Lead Zirconium Titanate (PZT)–epoxy composites, fabricated using dielectrophoresis, is described in Chapter 2. The resulting thread-like arrangement of the PZT particles in the composites was found to enhance the piezoelectric and dielectric constants of the structured composites. The piezoelectric and dielectric properties of the composites as a function of PZT volume fraction were investigated and compared with the corresponding properties of unstructured composites. The experimentally observed piezoelectric and dielectric constants of the structured and unstructured composites could be described by existing theoretical models. It was found that an attractive combination of decent flexibility and good piezoelectric voltage sensitivity could be obtained for structured composites at around 10 vol.% PZT particles loading. In Chapter 3, a Zn based ionomer was used as the new polymer matrix because of its high flexibility, decent electrical conductivity, excellent adhesion to the ceramic phase and most importantly its self-healing potential. The effective poling conditions for PZT-Zn ionomer composites were investigated and the results were compared with those for the reference PZT-EMAA (ethylene methacrylic acid copolymer) composites and monolithic PZT ceramic. The experimentally observed dielectric and piezoelectric coefficient were compared with Yamada’s model. The tensile properties and high cycle fatigue of the composites for large strain levels were also studied. It was demonstrated that the partial loss of sensorial functionality of the composites after high cyclic tensile fatigue could be recovered by thermal healing, due to the self-healing character of the polymer matrix. The goal of Chapter 4 was to develop an approach to quantify the state of poling of the PZT granules inside the Zn-ionomer matrix by using high energy synchrotron X-ray diffraction. For this study, we used a 30 vol.% Zn-ionomer PZT composite which was optimally poled as described in Chapter 3. The poling efficiency, crystallographic texture and lattice strain of the PZT particles inside the polymer matrix were determined and compared with the values for corresponding bulk ceramics reported in literature. It was shown that for an applied macroscopic field of 15 kVmm-1 the PZT particles are effectively poled, leading to a maximum ?(002) domain reorientation volume fraction, of around 0.70. It is also found that a significant tensile lattice strain, ?{111}, of 0.6% occurs in the direction of the applied electric field, indicating the occurrence of residual stresses within the 2-4 µm size diameter particles. The PZT particles within the polymeric matrix were found to experience significant elastic constraints. In Chapter 5 the processing window of PZT based piezoelectric composites was unveiled over the entire phase diagram composition range and a material selection criterion for high g33 composites was formulated. The piezoelectric and dielectric properties for the complete set of PZT ceramics were reported and correlated to their microstructure, polarisation and strain hysteresis loops. The effect of the dielectric and piezoelectric properties of the filler particles on the effective properties of their composites was studied using theoretical models. It was demonstrated that the combination of low dielectric constant and moderately high d33 of the ceramic filler can lead to lead-free piezoelectric composites having sensorial properties not having been reported ever before for composite materials. Finally, in Chapter 6 we describe the preparation of regular single phase cubic Lead- free (K, Na)xLi1-xNbO3 (KNN) piezoceramic particles using a new solid state double calcination processing route. These particles were subsequently used to create random and structured KNN-epoxy composites. Using dielectrophoresis, these cubical KNN particles were structured into one dimensional chains in an epoxy matrix. Composites produced with these powders showed piezoelectric properties about a factor of 2 higher than those of composites processed with conventionally calcined powder. The dielectrophoretically structured KNN-epoxy composites with optimized particle size and morphology showed excellent piezoelectric properties which can replace lead -containing piezoelectric composite for sensor applications in future. In Figure S.1, we present an overview of the properties of the new composites created in the course of this graduation project and note with pleasure that in many cases the properties fall outside the domains of systems known at the start of the thesis project to yield attractive properties.Aerospace Structures and Materials (ASM)Aerospace Engineerin
Exploration of Non-MPB PZT Compositions for High Piezoelectric Voltage Sensitive 0-3 Composites
No full textPiezoelectric composites provide an opportunity to make robust piezoelectric sensors. These materials are based on piezoelectric ceramic powders or particles, which are dispersed in a polymer matrix. In most cases, piezoelectric composites use the same ceramic compositions as the ones used in piezoelectric ceramics. These compositions consist of lead zirconium titanate (PZT) with a composition close to the morphotropic phase boundary (MPB). This research work focuses on exploring the performance of non-MPB compositions of PZT ceramic particles in order to obtain high voltage sensitive 0-3 PZT-Epoxy composites. The PZT ceramic compositions (PbNb0.01[ZrxTi(1-x)]O3), ranging from pure tetragonal lead titanate (x=0) to rhombohedral (x=0.80) were prepared using the mixed oxide method. These ceramic particles were characterized using XRD, SEM and particle size analyser and were used to prepare both sintered ceramics and 0-3 PZT-epoxy composites. The effect of the ceramic filler composition on the dielectric and piezoelectric properties of the PZT-Epoxy composites was investigated. Unlike PZT ceramics, the best piezoelectric properties were not observed in the MPB-based composites but in the pure tetragonal phase. It was observed that the dielectric constant of the ceramic particles had minimal influence on the effective dielectric constant (?r) and the piezoelectric charge constant (d33) of the piezoelectric composite due to the depolarization effect of the high dielectric filler materials. The experimentally determined values of the dielectric and piezoelectric properties of the piezoelectric composites were validated using analytical models. The influence of electric fatigue on the polarization of the PbTiO3 (PT) and morphotropic phase boundary (MPB) based composites were also examined. Finally, a material selection criterion was proposed in order to develop piezoelectric composites with high voltage sensitivity. This general material selection criterion is not limited to PZT based ceramics but is also applicable to lead-free ceramic filler materials. Thus, the current research work paves the way for the development of environmental friendly lead-free piezoelectric composites devices with enhanced sensory properties.Novel Aerospace Materials (NovAM)Mechanics, Aerospace Structures & MaterialsAerospace Engineerin
Cold Sintering of Ceramics
No full textAerospace Engineering | Novel Aerospace MaterialsAerospace Engineerin
Roll-to-Roll Fabrication of Solution Processed Electronics
No full textThe production of electronic devices using solution based (“wet”) deposition technologies has some decisive technical and commercial advantages compared to competing approaches like vacuum based (“dry”) manufacturing. Particularly, the potential to scale up production processes to large areas and high volumes by introducing continuous roll-to-roll (R2R) methods on flexible substrates has been the topic of intense studies from both applied research institutes and industry already for some years. Decisive steps forward have been achieved during that time, resulting in the dawn of commercial applications for a number of processes, while additional development work is still needed in some other fields. This review summarizes the work published during the last few years on the R2R printing and wet coating of electronic devices. An overview is presented of the basic operational principles for the most commonly used R2R printing and coating methods and techniques for proper web handling in R2R lines. Then, the most commonly used types of flexible substrate materials are introduced, followed by a review of the work published in the application areas of transparent conductor materials, printed electric connections, light emitting devices, photovoltaic energy generation, printed logic, and sensing.Green Open Access added to TU Delft Institutional Repository ‘You share, we take care!’ – Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Novel Aerospace Material
Flexible piezoelectric composites: Bridging the gap between materials and applications
No full textThe main objective of this thesis was to develop new piezoelectric ceramic polymercomposites that maintain the ease of manufacturing of random composites andcould function as a human touch sensor, while simultaneously exploring their potential as energy harvesters
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
- …
