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Advanced Insulating Materials and Technologies
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Advanced Insulating Materials and Technologies

A special issue of Materials (ISSN 1996-1944). This special issue belongs to the section "Energy Materials".

Deadline for manuscript submissions: closed (31 January 2022) | Viewed by 14658

Special Issue Editor

Prof. Dr. Jianying Li

E-Mail Website
Guest Editor
State Key Laboratory of Electrical Insulation and Power Equipment, Xi’an Jiaotong University, Xi’an, China
Interests: electric insulation; polymer insulating materials; ceramic dielectrics; power cable insulation; non-linear insulating materials

Special Issue Information

Dear Colleagues,

Insulating materials are widely applied in power equipment, electronic device and energy storage situations. It is clear that the future development of power energy transfer and storage depends on advanced insulating materials which can be solid, liquid or gas. Solid insulating materials can be polymeric materials, ceramics, biomaterials or composite materials. Although a large variety of materials is involved in the field of electric insulation, the main research interests have been the electrical performance of insulating materials such as polarization in electric field, dielectric loss, electric conductance and electric breakdown. Therefore，an exploration of the electrical performance and its dependence on the structure and components of varied materials is a key issue in the fields of both material science and electrical engineering.

This Special Issue aims to present the state-of-the-art in and perspectives on advanced insulating materials for future electrical and electronic applications. Therefore, the topics covered in this Special Issue include but are not limited to:

  • Advanced solid materials with high electric performance;
  • Advanced insulating liquids for high electric field applications;
  • Green gases for high-voltage insulation applications;
  • Environmentally friendly insulating materials;
  • Energy storage materials;
  • New dielectric phenomena in insulating materials;
  • Emerging simulation and calculation technologies for finding new insulating materials;
  • Nanomaterials as potential insulating materials

Prof. Dr. Jianying Li
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Materials is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • electrical insulation
  • electric breakdown
  • dielectric loss
  • energy storage
  • insulating liquid
  • green gas insulation
  • dielectric constant
  • space charge
  • electric conductance

Published Papers (7 papers)

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Research

11 pages, 4796 KiB  
Article
Evolution of Intrinsic and Extrinsic Electron Traps at Grain Boundary during Sintering ZnO Based Varistor Ceramics
by Pengkang Xie, Ziyue Wang and Kangning Wu
Materials 2022, 15(3), 1098; https://0-doi-org.brum.beds.ac.uk/10.3390/ma15031098 - 30 Jan 2022
Cited by 12 | Viewed by 1920
Abstract
In this paper, evolution of microstructures, electrical properties and defects of the double Schottky barrier during the sintering process were investigated by quenching ZnO varistor ceramics at different sintering stages. It was found that morphology of the samples changed little when the temperature [...] Read more.
In this paper, evolution of microstructures, electrical properties and defects of the double Schottky barrier during the sintering process were investigated by quenching ZnO varistor ceramics at different sintering stages. It was found that morphology of the samples changed little when the temperature was below 800 °C. Remarkable enhancement of the Schottky barrier height and electrical properties took place in the temperature range between 600 °C and 800 °C. The Bi-rich intergranular layer changed from β phase to α phase. The interfacial relaxation at depletion/intergranular layers became detectable in the samples. Meanwhile, a distinct relaxation loss peak from electron trapping of interface states was observed instead of two dispersed ones. It indicated that the differences among the Schottky barriers in ZnO varistor ceramics became smaller with the process of sintering, which was also supported by the admittance spectra. In addition, oxygen vacancy was found more sensitive to the sintering process than zinc interstitial. The results could provide guidance for fine manipulating the Schottky barrier and its underlying defect structures by optimizing sintering process. Full article
(This article belongs to the Special Issue Advanced Insulating Materials and Technologies)
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8 pages, 3561 KiB  
Article
Simultaneously Enhanced Potential Gradient and Nonlinearity of ZnO Varistor Ceramics by MnO Doping with Nano-Sized ZnO Powders
by Yao Wang, Zongke Hou, Jianying Li, Kangning Wu, Jiguang Song, Rui Chen, Kai Li, Liucheng Hao and Chenbo Xu
Materials 2021, 14(24), 7748; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14247748 - 15 Dec 2021
Cited by 3 | Viewed by 1884
Abstract
ZnO varistor ceramics with a high potential gradient, as well as a high nonlinear coefficient, were reported and analyzed in this paper. With the use of nano-sized ZnO powders, the average grain size was reduced to about 2.6 μm, which successfully raised the [...] Read more.
ZnO varistor ceramics with a high potential gradient, as well as a high nonlinear coefficient, were reported and analyzed in this paper. With the use of nano-sized ZnO powders, the average grain size was reduced to about 2.6 μm, which successfully raised the potential gradient to 1172 V/mm. Moreover, the nonlinear coefficient increased to 48, and the leakage current was decreased to 8.4 μA/cm2 by doping a moderate amount of MnO (0.9 mol%). This was proven to be caused by the high Schottky barrier height formed at the grain boundary, where the Mn element segregated and, consequently, led to the increased density of interface states. Therefore, this could be considered as a potential method to simultaneously enhance the potential gradient and the nonlinear coefficient of ZnO varistor ceramics. Full article
(This article belongs to the Special Issue Advanced Insulating Materials and Technologies)
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16 pages, 2658 KiB  
Article
Designing the Insulation System for Motors in Electrified Aircraft: Optimization, Partial Discharge Issues and Use of Advanced Materials
by Robin Ramin, Gian Carlo Montanari and Qichen Yang
Materials 2021, 14(24), 7555; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14247555 - 09 Dec 2021
Cited by 13 | Viewed by 1691
Abstract
Designing the insulation system for motors to be used in electrical aircraft requires efforts for maximizing specific power, but, in parallel, particular attention to achieve high reliability. As a major harm for organic insulation systems is partial discharges, design must be able to [...] Read more.
Designing the insulation system for motors to be used in electrical aircraft requires efforts for maximizing specific power, but, in parallel, particular attention to achieve high reliability. As a major harm for organic insulation systems is partial discharges, design must be able to infer their likelihood during any operation stage and handle their potential inception. This paper proposes a new approach to carry out optimized or conservative insulation system designs which can provide the specified life at the chosen failure probability as well as look at the option of possibly reducing the risk of partial discharges to zero, at any altitude. Examples of designing turn, phase to ground and phase-to-phase insulation systems are reported, with cases where the design can be optimized and other cases where the optimized design does not pass IEC testing standard. Therefore, the limits for design feasibility as a function of the required level of safety and reliability are discussed, showing that the presence of partial discharges cannot be always avoided even through conservative design criteria. Therefore, the use of advanced, corona-resistant materials must be considered, in order to reach a higher, sometimes redundant, level of reliability. Full article
(This article belongs to the Special Issue Advanced Insulating Materials and Technologies)
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12 pages, 3501 KiB  
Article
Electrochromism of Viologen/Polymer Composite: From Gel to Insulating Bulk for High-Voltage Applications
by Yongjie Nie, Meng Zhang, Yuanwei Zhu, Yu Jing, Wenli Shi, Guoping Li, Haopeng Chen, Yihang Jiang, Xianping Zhao, Tengfei Zhao, Guanghao Lu and Shengtao Li
Materials 2021, 14(19), 5901; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14195901 - 08 Oct 2021
Cited by 3 | Viewed by 1676
Abstract
Power equipment operates under high voltages, inducing space charge accumulation on the surface of key insulating structures, which increases the risk of discharge/breakdown and the possibility of maintenance workers experiencing electric shock accidents. Hence, a visualized non-equipment space charge detection method is of [...] Read more.
Power equipment operates under high voltages, inducing space charge accumulation on the surface of key insulating structures, which increases the risk of discharge/breakdown and the possibility of maintenance workers experiencing electric shock accidents. Hence, a visualized non-equipment space charge detection method is of great demand in the power industry. Typical electrochromic phenomenon is based on redox of the material, triggered by a voltage smaller than 5 V with a continuous current in μA~mA level, which is not applicable to high electric fields above 106 V/m with pA~nA operation current in power equipment. Until now, no naked-eye observation technique has been realized for space charge detection to ensure the operation of power systems as well as the safety of maintenance workers. In this work, a viologen/poly(vinylidene fluoride-co-hexafluoropropylene)(P(VDF–HFP)) composite is investigated from gel to insulating bulk configurations to achieve high-voltage electrical-insulating electrochromism. The results show that viologen/P(VDF–HFP) composite bulk can withstand high electric fields at the 107 V/m level, and its electrochromism is triggered by space charges. This electrochromism phenomenon can be visually extended by increasing viologen content towards 5 wt.% and shows a positive response to voltage amplitude and application duration. As viologen/P(VDF–HFP) composite bulk exhibits a typical electrical insulating performance, it could be attached to the surface of insulating structures or clamped between metal and insulating materials as a space charge accumulation indicator in high-voltage power equipment. Full article
(This article belongs to the Special Issue Advanced Insulating Materials and Technologies)
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10 pages, 2937 KiB  
Article
Synergistical Performance Modification of Epoxy Resin by Nanofillers and Carboxyl-Terminated Liquid Nitrile–Butadiene Rubber
by Yuanjin Liu, Lixiao Yao, Yue Bu and Qing Sun
Materials 2021, 14(16), 4601; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14164601 - 16 Aug 2021
Cited by 4 | Viewed by 1668
Abstract
Epoxy composite materials are widely used in power equipment. As the voltage level increases, the requirement of material properties, including electrical, thermal, and mechanical, has also increased. Introducing thermally conductive nanofiller to the epoxy/liquid rubber composites system is an effective approach to improve [...] Read more.
Epoxy composite materials are widely used in power equipment. As the voltage level increases, the requirement of material properties, including electrical, thermal, and mechanical, has also increased. Introducing thermally conductive nanofiller to the epoxy/liquid rubber composites system is an effective approach to improve heat performance, but the effects of thermally conductive nanofillers on relaxation characteristics remain unclarified. In this paper, nano-alumina (nano-Al2O3) and nano-boron nitride (nano-BN) have been employed to modify the epoxy/carboxyl-terminated liquid nitrile–butadiene rubber (epoxy/CTBN) composites system. The thermal conductivity and glass transition temperature of different formula systems have been measured. The effect of the nanofillers on the relaxation behaviors of the resin matrix has been investigated. Results show that the different kinds of nanofillers will introduce different relaxation processes into the matrix and increase the conductivity at the same time. This study can provide a theoretical basis for the synergistic improvement of multiple properties of epoxy resin composites. Full article
(This article belongs to the Special Issue Advanced Insulating Materials and Technologies)
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13 pages, 4897 KiB  
Article
Simultaneously Enhanced Thermal Conductivity and Breakdown Performance of Micro/Nano-BN Co-Doped Epoxy Composites
by Chuang Zhang, Jiao Xiang, Shihang Wang, Zhimin Yan, Zhuolin Cheng, Hang Fu and Jianying Li
Materials 2021, 14(13), 3521; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14133521 - 24 Jun 2021
Cited by 7 | Viewed by 1559
Abstract
Micro/nano- BN co-doped epoxy composites were prepared and their thermal conductivity, breakdown strength at power frequency and voltage endurance time under high frequency bipolar square wave voltage were investigated. The thermal conductivity and breakdown performance were enhanced simultaneously in the composite with a [...] Read more.
Micro/nano- BN co-doped epoxy composites were prepared and their thermal conductivity, breakdown strength at power frequency and voltage endurance time under high frequency bipolar square wave voltage were investigated. The thermal conductivity and breakdown performance were enhanced simultaneously in the composite with a loading concentration of 20 wt% BN at a micro/nano proportion of 95/5. The breakdown strength of 132 kV/mm at power frequency, the thermal conductivity of 0.81 W·m−1·K−1 and voltage endurance time of 166 s were obtained in the composites, which were approximately 28%, 286% and 349% higher than that of pristine epoxy resin. It is proposed that thermal conductive pathways are mainly constructed by micro-BN, leading to improved thermal conductivity and voltage endurance time. A model was introduced to illustrate the enhancement of the breakdown strength. The epoxy composites with high thermal conductivity and excellent breakdown performance could be feasible for insulating materials in high-frequency devices. Full article
(This article belongs to the Special Issue Advanced Insulating Materials and Technologies)
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11 pages, 2445 KiB  
Article
Charge Injection and Dielectric Characteristics of Polyethylene Terephthalate Based on Semiconductor Electrodes
by Guan-Yu Liu, Wei-Feng Sun and Qing-Quan Lei
Materials 2021, 14(6), 1344; https://0-doi-org.brum.beds.ac.uk/10.3390/ma14061344 - 10 Mar 2021
Cited by 5 | Viewed by 1715
Abstract
Employing a novel semiconductor electrode in comparison with the traditional semiconductor electrode made of polyethylene/ethylene-vinyl-acetate copolymer/carbon-black (PE/EVA/CB) composite, characteristic charge carriers are injected into polyethylene terephthalate (PET) as a polymer dielectric paradigm, which will be captured by specific deep traps of electrons and [...] Read more.
Employing a novel semiconductor electrode in comparison with the traditional semiconductor electrode made of polyethylene/ethylene-vinyl-acetate copolymer/carbon-black (PE/EVA/CB) composite, characteristic charge carriers are injected into polyethylene terephthalate (PET) as a polymer dielectric paradigm, which will be captured by specific deep traps of electrons and holes. Combined with thermal stimulation current (TSC) experiments and first-principles electronic-state calculations, the injected charges from the novel electrode are characterized, and the corresponding dielectric behavior is elucidated through DC conductance, electrical breakdown and dielectric spectrum tests. TSC experiments with novel and traditional semiconductor electrodes can distinguish the trapping characteristics between hole and electron traps in polymer dielectrics. The observable discrepancy in space charge-limited conductance and the stable dielectric breakdown strength demonstrate that the electron injection into PET film specimen is restricted by using the novel semiconductor electrode. Attributed to the favorable suppression on the inevitable electron injections from metal electrodes, adopting novel i-electrode can avoid the evident abatement of dipole orientation polarization caused by space charge clamp, but will engender the accessional high-frequency dielectric loss from dielectric relaxations of interface charges at i-electrodes. Full article
(This article belongs to the Special Issue Advanced Insulating Materials and Technologies)
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