TY - GEN A1 - Nguyen, Quyet Doan A1 - Wang, Jingwen A1 - Rychkov, Dmitry A1 - Gerhard, Reimund T1 - Depth Profile and Transport of Positive and Negative Charge in Surface (2-D) and Bulk (3-D) Nanocomposite Films T2 - 2nd International Conference on Electrical Materials and Power Equipment (ICEMPE 2019) N2 - In the present study, the charge distribution and the charge transport across the thickness of 2- and 3-dimensional polymer nanodielectrics was investigated. Chemically surface-treated polypropylene (PP) films and low-density polyethylene nanocomposite films with 3 wt % of magnesium oxide (LDPE/MgO) served as examples of 2-D and 3-D nanodielectrics, respectively. Surface charges were deposited onto the non-metallized surfaces of the one-side metallized polymer films and found to broaden and to thus enter the bulk of the films upon thermal stimulation at suitable elevated temperatures. The resulting space-charge profiles in the thickness direction were probed by means of Piezoelectrically-generated Pressure Steps (PPSs). It was observed that the chemical surface treatment of PP which led to the formation of nano-structures or the use of bulk nanoparticles from LDPE/MgO nanocomposites enhance charge trapping on or in the respective polymer films and also reduce charge transport inside the respective samples. KW - LDPE nanocomposites KW - MgO nanoparticles KW - Space charge KW - Charge transport KW - Charge stability KW - Acoustic probing of electric-field profiles KW - Piezoelectrically generated Pressure Steps (PPSs) Y1 - 2019 SN - 978-1-5386-8434-4 SN - 978-1-5386-8435-1 U6 - https://doi.org/10.1109/ICEMPE.2019.8727256 SP - 298 EP - 300 PB - IEEE CY - New York ER - TY - GEN A1 - Gerhard, Reimund T1 - Dielectric materials for electro-active (electret) and/or electro-passive (insulation) applications T2 - 2nd International Conference on Electrical Materials and Power Equipment (ICEMPE 2019) N2 - Dielectric materials for electret applications usually have to contain a quasi-permanent space charge or dipole polarization that is stable over large temperature ranges and time periods. For electrical-insulation applications, on the other hand, a quasi-permanent space charge or dipole polarization is usually considered detrimental. In recent years, however, with the advent of high-voltage direct-current (HVDC) transmission and high-voltage capacitors for energy storage, new possibilities are being explored in the area of high-voltage dielectrics. Stable charge trapping (as e.g. found in nano-dielectrics) or large dipole polarizations (as e.g. found in relaxor ferroelectrics and high-permittivity dielectrics) are no longer considered to be necessarily detrimental in electrical-insulation materials. On the other hand, recent developments in electro-electrets (dielectric elastomers), i.e. very soft dielectrics with large actuation strains and high breakdown fields, and in ferroelectrets, i.e. polymers with electrically charged cavities, have resulted in new electret materials that may also be useful for HVDC insulation systems. Furthermore, 2-dimensional (nano-particles on surfaces or interfaces) and 3-dimensional (nano-particles in the bulk) nano-dielectrics have been found to provide very good charge-trapping properties that may not only be used for more stable electrets and ferroelectrets, but also for better HVDC electrical-insulation materials with the possibility to optimize charge-transport and field-gradient behavior. In view of these and other recent developments, a first attempt will be made to review a small selection of electro-active (i.e. electret) and electro-passive (i.e. insulation) dielectrics in direct comparison. Such a comparative approach may lead to synergies in materials concepts and research methods that will benefit both areas. Furthermore, electrets may be very useful for sensing and monitoring applications in electrical-insulation systems, while high-voltage technology is essential for more efficient charging and poling of electret materials. KW - Dielectric materials KW - Electrets KW - Electrical insulation KW - Electro-active and electro-passive dielectrics KW - Nano-dielectrics KW - Charging or poling KW - Charge storage and transport Y1 - 2019 SN - 978-1-5386-8434-4 SN - 978-1-5386-8435-1 U6 - https://doi.org/10.1109/ICEMPE.2019.8727276 SP - 91 EP - 96 PB - IEEE CY - New York ER - TY - GEN A1 - Gerhard, Reimund T1 - Honoring Professor Gerhard M. Sessler on his 80th Birthday (15th of February 2011) T2 - IEEE transactions on dielectrics and electrical insulation Y1 - 2011 U6 - https://doi.org/10.1109/TDEI.2011.5704485 SN - 1070-9878 VL - 18 IS - 1 SP - 1 EP - 2 PB - Inst. of Electr. and Electronics Engineers CY - Piscataway ER - TY - GEN A1 - Gerhard, Reimund A1 - Kaltenbrunner, Martin T1 - In Memoriam Siegfried Bauer T2 - IEEE electrical insulation magazine N2 - Siegfried Bauer, an internationally renowned, very creative applied physicist, who also was a prolific materials scientist and engineer, died on December 30, 2018, in Linz, Austria, after a one-year battle with cancer. He was full professor of soft-matter physics at the Johannes Kepler University Linz, Austria, and a scientific leader and innovator across the fields but mainly in the areas of electro-active materials (including electrets) and stretchable and imperceptible electronics. Y1 - 2019 U6 - https://doi.org/10.1109/MEI.2019.8636175 SN - 0883-7554 SN - 1558-4402 VL - 35 IS - 2 SP - 76 EP - 78 PB - IEEE CY - Piscataway ER - TY - GEN A1 - Wang, Jingwen A1 - Rychkov, Dmitry A1 - Gerhard, Reimund T1 - Influence of Charge Density on Charge Decay in Chemically Modified Polypropylene Films T2 - 2018 IEEE 2nd International Conference on Dielectrics (ICD) N2 - Previous work has shown that surface modification with orthophosphoric acid can significantly enhance the charge stability on polypropylene (PP) surface by generating deeper traps. In the present study, thermally stimulated potential-decay measurements revealed that the chemical treatment may also significantly increase the number of available trapping sites on the surface. Thus, as a consequence, the so-called "cross-over" phenomenon, which is observed on as-received and thermally treated PP electrets, may be overcome in a certain range of initial charge densities. Furthermore, the discharge behavior of chemically modified samples indicates that charges can be injected from the treated surface into the bulk, and/or charges of opposite polarity can be pulled from the rear electrode into the bulk at elevated temperatures and at the high electric fields that are caused by the deposited charges. In the bulk, a lack of deep traps causes rapid charge decay already in the temperature range around 95 degrees C. KW - polypropylene KW - surface charge stability KW - thermally stimulated discharge KW - cross-over effect KW - chemical modification Y1 - 2018 SN - 978-1-5386-6389-9 U6 - https://doi.org/10.1109/ICD.2018.8514718 PB - IEEE CY - New York ER - TY - GEN A1 - Raman Venkatesan, Thulasinath A1 - Frübing, Peter A1 - Gerhard, Reimund T1 - Influence of Composition and Preparation on Crystalline Phases and Morphology in Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) Relaxor-Ferroelectric Terpolymer T2 - 2018 IEEE 2nd International Conference on Dielectrics (ICD) N2 - The influence of chemical composition and crystallisation conditions on the ferroelectric and paraelectric phases and the resulting morphology in Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)) terpolymer films with 55.4/37.2/7.3 mol% or with 62.2/29.4/8.4 mol% of VDF/TrFE/CFE was studied. Poly(vinylidene fluoride trifluoroethylene) (P(VDF-TrFE)) with 75/25 mol% VDF/TrFE was employed as reference material. Fourier-Transform Infrared Spectroscopy (FTIR) was used to determine the fractions of the relevant terpolymer phases, and X-Ray Diffraction (XRD) was employed to assess the crystalline morphology. The FTIR results show an increase of the fraction of paraelectric phases after annealing. On the other hand, XRD results indicate a more stable paraelectric phase in the terpolymer with higher CFE content. KW - P(VDF-TrFE-CFE) terpolymer KW - relaxor-ferroelectric polymer KW - ferroelectric and paraelectric phases KW - Curie transition Y1 - 2018 SN - 978-1-5386-6389-9 U6 - https://doi.org/10.1109/ICD.2018.8514758 PB - IEEE CY - New York ER - TY - GEN A1 - Loupos, Konstantinos A1 - Damigos, Yannis A1 - Tsertou, Athanasisa A1 - Amditis, Angelos A1 - Lenas, Sotiris-Angelos A1 - Chatziandreoglou, Chistos A1 - Malliou, Christina A1 - Tsaoussidis, Vassilis A1 - Gerhard, Reimund A1 - Rychkov, Dmitry A1 - Wirges, Werner A1 - Frankenstein, Bernd A1 - Camarinopoulos, Stephanos A1 - Kalidromitis, Vassilis A1 - Sanna, C. A1 - Maier, Stephanos A1 - Gordt, A. A1 - Panetsos, P. T1 - Innovative soft-material sensor, wireless network and assessment software for bridge life-cycle assessment T2 - Life-cycle analysis and assessmanet in civil engineering : towards an integrated vision N2 - Nowadays, structural health monitoring of critical infrastructures is considered as of primal importance especially for managing transport infrastructure however most current SHM methodologies are based on point-sensors that show various limitations relating to their spatial positioning capabilities, cost of development and measurement range. This publication describes the progress in the SENSKIN EC co-funded research project that is developing a dielectric-elastomer sensor, formed from a large highly extensible capacitance sensing membrane and is supported by an advanced micro-electronic circuitry, for monitoring transport infrastructure bridges. The sensor under development provides spatial measurements of strain in excess of 10%, while the sensing system is being designed to be easy to install, require low power in operation concepts, require simple signal processing, and have the ability to self-monitor and report. An appropriate wireless sensor network is also being designed and developed supported by local gateways for the required data collection and exploitation. SENSKIN also develops a Decision-Support-System (DSS) for proactive condition-based structural interventions under normal operating conditions and reactive emergency intervention following an extreme event. The latter is supported by a life-cycle-costing (LCC) and life-cycle-assessment (LCA) module responsible for the total internal and external costs for the identified bridge rehabilitation, analysis of options, yielding figures for the assessment of the economic implications of the bridge rehabilitation work and the environmental impacts of the bridge rehabilitation options and of the associated secondary effects respectively. The overall monitoring system will be evaluated and benchmarked on actual bridges of Egnatia Highway (Greece) and Bosporus Bridge (Turkey). Y1 - 2019 SN - 978-1-315-22891-4 SN - 978-1-138-62633-1 SP - 2085 EP - 2092 PB - CRC Press, Taylor & Francis Group CY - Boca Raton ER - TY - GEN A1 - Nguyen, Quyet Doan A1 - Gerhard, Reimund T1 - LDPE/MgO Nanocomposite Dielectrics for Electrical-Insulation and Ferroelectret-Transducer Applications T2 - 2018 IEEE 2nd International Conference on Dielectrics (ICD) N2 - Published results on LDPE/MgO nanocomposites (3wt%) show that they promise to be good electrical-insulation materials. In this work, the nanocomposites are examined as a potential (ferro-)electret material as well. Isothermal surface-potential decay measurements show that charged LDPE/MgO films still exhibit significant surface potentials after heating for 4 hours at 80 degrees C, which suggests good capabilities of LDPE/MgO nanocomposites to hold electric charges of both polarities. Open-tubular-channel ferroelectrets prepared from LDPE/MgO nanocomposite films show significant piezoelectricity with d(33) coefficients of about 20 pC/N after charging and are stable up to temperatures of at least 80 degrees C. Thus LDPE/MgO nanocomposites may become available as a new ferroelectret material. To increase their d(33) coefficients, it is desirable to optimize the charging conditions and the ferroelectret structure. KW - ferroelectrets KW - LDPE nanocomposites KW - electroacoustic probing KW - space-charge and polarization profiles KW - thermally stimulated discharge Y1 - 2018 SN - 978-1-5386-6389-9 SN - 978-1-5386-6388-2 SN - 978-1-5386-6390-5 PB - IEEE CY - New York ER - TY - GEN A1 - Cheilakou, E. A1 - Tsopelas, N. A1 - Anastasopoulos, A. A1 - Kourousis, D. A1 - Rychkov, Dmitry A1 - Gerhard, Reimund A1 - Frankenstein, B. A1 - Amditis, A. A1 - Damigos, Y. A1 - Bouklas, C. T1 - Strain monitoring system for steel and concrete structures T2 - Procedia Structural Integrity N2 - The present work is part of a collaborative H2020 European funded research project called SENSKIN, that aims to improve Structural Health Monitoring (SHM) for transport infrastructure through the development of an innovative monitoring and management system for bridges based on a novel, inexpensive, skin-like sensor. The integrated SENSKIN technology will be implemented in the case of steel and concrete bridges, and tested, field-evaluated and benchmarked on actual bridge environment against a conventional health monitoring solution developed by Mistras Group Hellas. The main objective of the present work is to implement the autonomous, fully functional strain monitoring system based on commercially available off-the-shelf components, that will be used to accomplish direct comparison between the performance of the innovative SENSKIN sensors and the conventional strain sensors commonly used for structural monitoring of bridges. For this purpose, the mini Structural Monitoring System (mini SMS) of Physical Acoustics Corporation, a comprehensive data acquisition unit designed specifically for long-term unattended operation in outdoor environments, was selected. For the completion of the conventional system, appropriate foil-type strain sensors were selected, driven by special conditioners manufactured by Mistras Group. A comprehensive description of the strain monitoring system and its peripheral components is provided in this paper. For the evaluation of the integrated system’s performance and the effect of various parameters on the long-term behavior of sensors, several test steel pieces instrumented with different strain sensors configurations were prepared and tested in both laboratory and field ambient conditions. Furthermore, loading tests were performed aiming to validate the response of the system in monitoring the strains developed in steel beam elements subject to bending regimes. Representative results obtained from the above experimental tests have been included in this paper as well. KW - Structural health monitoring KW - strain sensors KW - strain gauges KW - bridges KW - steel and concrete structures Y1 - 2018 U6 - https://doi.org/10.1016/j.prostr.2018.09.005 SN - 2452-3216 VL - 10 SP - 25 EP - 32 PB - Elsevier CY - Amsterdam ER - TY - GEN A1 - Loupos, Konstantinos A1 - Damigos, Yannis A1 - Amditis, Angelos A1 - Gerhard, Reimund A1 - Rychkov, Dmitry A1 - Wirges, Werner A1 - Schulze, Manuel A1 - Lenas, Sotiris-Angelos A1 - Chatziandreoglou, Christos A1 - Malliou, Christina A1 - Tsaoussidis, Vassilis A1 - Brady, Ken A1 - Frankenstein, Bernd T1 - Structural health monitoring system for bridges based on skin-like sensor T2 - IOP conference series : Materials science and engineering N2 - Structural health monitoring activities are of primal importance for managing transport infrastructure, however most SHM methodologies are based on point-based sensors that have limitations in terms of their spatial positioning requirements, cost of development and measurement range. This paper describes the progress on the SENSKIN EC project whose objective is to develop a dielectric-elastomer and micro-electronics-based sensor, formed from a large highly extensible capacitance sensing membrane supported by advanced microelectronic circuitry, for monitoring transport infrastructure bridges. Such a sensor could provide spatial measurements of strain in excess of 10%. The actual sensor along with the data acquisition module, the communication module and power electronics are all integrated into a compact unit, the SENSKIN device, which is energy-efficient, requires simple signal processing and it is easy to install over various surface types. In terms of communication, SENSKIN devices interact with each other to form the SENSKIN system; a fully distributed and autonomous wireless sensor network that is able to self-monitor. SENSKIN system utilizes Delay-/Disruption-Tolerant Networking technologies to ensure that the strain measurements will be received by the base station even under extreme conditions where normal communications are disrupted. This paper describes the architecture of the SENSKIN system and the development and testing of the first SENSKIN prototype sensor, the data acquisition system, and the communication system. Y1 - 2017 U6 - https://doi.org/10.1088/1757-899X/236/1/012100 SN - 1757-8981 VL - 236 PB - IOP Publ. Ltd. CY - Bristol ER -