Preface

Chapter 9 **Ultrasound-Assisted Melt Extrusion of Polymer**

Mata-Padilla and Víctor J. Cruz-Delgado

Heidi Conrad and Teresa D. Golden

Chapter 10 **Electrodeposited Zinc-Nickel Nanocomposite Coatings 187**

Carlos A. Ávila-Orta, Pablo González-Morones, Diana Agüero-Valdez, Alain González-Sánchez, Juan G. Martínez-Colunga, José M.

**Nanocomposites 163**

**VI** Contents

Recently, material structures at the nanometric scale have had an influence on functional abilities in all fields of interest, especially in medical, aircraft, spacecraft, and structural properties fields. The adoption of nanocomposite materials by the research community in real-time applications is increasing rapidly in the world. Because of this, this book focuses on a number of recent contributions by several authors, which address the latest develop‐ ments in nanocomposite material development, various synthesis routes, methods of charac‐ terization, several properties correlations, and applications. This book will help all academicians, research scholars, and those working in industries towards the designing of new nanomaterials, by investigating their output, exploring their utilizations, emphasizing their behavior, and making decisions for real-time applications.

> **Dr. Subbarayan Sivasankaran** College of Engineering Qassim University, Saudi Arabia

**Chapter 1**

Provisional chapter

**Nanocomposite for Space Charge Suppression in HVDC**

DOI: 10.5772/intechopen.80217

HVDC cable accessories made of ethylene-vinyl acetate copolymer (EVA) by incorporation of specific fillers have to face the problem of space charge accumulation. The effects of doping contents on the space charge behaviors of EVA/ZnO composite are not completely clear. EVA composites are prepared with the fraction of 0, 1, 5 and 10 wt%, respectively, with which 5 wt% nano-sized plus 5 wt% micro-sized ZnO-doped samples are chosen for comparison. Obtained results show that the particles in EVA composite are in homodisperse. The permittivity is increased by ZnO doping and the dissipation factor of EVA composites with 1 and 5 wt% nanoparticles is lower at the lower frequencies. The homocharge injection occurs in cathode instead of anode when ZnO nanoparticles are introduced and 5 wt% nanoparticle doping performs well in suppressing space charge injection. The electric field in the 5 wt% nanoparticle-doped EVA distributes more uniformly under the high electric stress than that of others. During the depolarization procedure, the total remnant charges of 10 wt% doped samples are the least in the final. The above results are well explained by the DC conduction, apparent mobility and trap

Keywords: HVDC, cable accessory, space charge, ZnO nanoparticle, trap distribution,

The features of the transmission capability and the material are combined by the polymer insulated HVDC cables for high-power, long-distance underwater or underground transmission,

> © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

Nanocomposite for Space Charge Suppression in HVDC

**Cable Accessory**

Cable Accessory

Abstract

Boxue Du, Jin Li and Zhuoran Yang

Boxue Du, Jin Li and Zhuoran Yang

http://dx.doi.org/10.5772/intechopen.80217

distribution characteristics.

carrier mobility

1. Introduction

Additional information is available at the end of the chapter

Additional information is available at the end of the chapter

#### **Nanocomposite for Space Charge Suppression in HVDC Cable Accessory** Nanocomposite for Space Charge Suppression in HVDC Cable Accessory

DOI: 10.5772/intechopen.80217

Boxue Du, Jin Li and Zhuoran Yang Boxue Du, Jin Li and Zhuoran Yang

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.80217

#### Abstract

HVDC cable accessories made of ethylene-vinyl acetate copolymer (EVA) by incorporation of specific fillers have to face the problem of space charge accumulation. The effects of doping contents on the space charge behaviors of EVA/ZnO composite are not completely clear. EVA composites are prepared with the fraction of 0, 1, 5 and 10 wt%, respectively, with which 5 wt% nano-sized plus 5 wt% micro-sized ZnO-doped samples are chosen for comparison. Obtained results show that the particles in EVA composite are in homodisperse. The permittivity is increased by ZnO doping and the dissipation factor of EVA composites with 1 and 5 wt% nanoparticles is lower at the lower frequencies. The homocharge injection occurs in cathode instead of anode when ZnO nanoparticles are introduced and 5 wt% nanoparticle doping performs well in suppressing space charge injection. The electric field in the 5 wt% nanoparticle-doped EVA distributes more uniformly under the high electric stress than that of others. During the depolarization procedure, the total remnant charges of 10 wt% doped samples are the least in the final. The above results are well explained by the DC conduction, apparent mobility and trap distribution characteristics.

Keywords: HVDC, cable accessory, space charge, ZnO nanoparticle, trap distribution, carrier mobility

#### 1. Introduction

The features of the transmission capability and the material are combined by the polymer insulated HVDC cables for high-power, long-distance underwater or underground transmission,

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

so they have many advantages [1–4]. Space charge can be accumulated under DC electric stress within the insulation matrix through charge injection from impurities' electrodissociation and electrodes [5]. The electrical field in cable insulation may be changed seriously because of the accumulation of space charge, particularly after polarity reversal which causes probably premature failure and material degradation [6, 7].

2. Experiments

ties as well as the mechanism for dielectric.

Figure 1. Distribution of ZnO particles in EVA composite.

There is a density of 0.93 g/cm3 and 14% vinyl acetate content in the EVA 1045. ZnO particles' grain sizes are 2 μm and 40 nm. The ZnO had been dried for over 24 h within a desiccator prior to dispersion in the EVA. The mixing was performed at 90C for 15 min by a two-roll mill set at 30 rpm rotor speed and 2 mm nip gap. All the compounds had been cured for about 5 min at 120C in a press that was heated electrically under the pressure of 10 MPa and chilled down in a natural way to the room temperature. Specimens that had 500 μm thickness had been prepared through the incorporation of ZnO nanoparticles to EVA matrix with 10, 5, 1 and 0 wt% fraction respectively, where 5 wt% micro-sized and 5 wt% nano-sized ZnO filled EVA specimen had been set as contrast. ZnO's dispersion in the EVA matrix had been explored through scanning energy dispersive spectrum analysis (EDS) and electron microscopy (SEM) with Hitachi S4800. The mixed doping composites as well as 5 wt% nano ZnO doped EVA's SEM photograph can be seen in Figure 1. The white spots are the nano fillers in Figure 1a. No important aggregation can be seen in the specimens and the nano fillers are dispersed in a uniform way. The bigger particle stands for the micro-sized ZnO in Figure 1b. Figure 2 is EDS's from Figure 1 and the zinc factor's higher contents are introduced because of more ZnO doping. The fillers' uniform dispersion may be helpful for analyzing the space charge proper-

Nanocomposite for Space Charge Suppression in HVDC Cable Accessory

http://dx.doi.org/10.5772/intechopen.80217

3

2.1. Specimens

Especially being a vital part of the HVDC networks, the performance of cable accessories is critical to the system's reliability considering the mechanical, thermal and electrical characteristics of the models which are combined with great dangers with install faults and environmental pollution [8–10]. Given the complicated geometry, particular fillers' doping and the inferfaces' existence between the accessories insulation and the cable insulation, the accumulation of the space charge as well as its influence has become much harder to make predictions [11].

People use EVA composites very often within the cable accessories because of the manufacture of cable accessory insulation, semi-conductive insulation jackets as well as heat shrinkable insulation and it is able to sustain higher filling contents with no yielding to the mechanical strength loss nor embrittlement and can be cross-linked in an easy way [12, 13]. The use of nonlinear resistive fillers as well as particular conductive additives and so on can create cable accessories which are from EVA composites, for the uniform electric field [14]. At the same time, the cable accessories which are created by EVA also needed to deal with the issue of the accumulation of space charge.

It has been proved that nano-sized particles are a useful strategy of suppressing the accumulation of space charges in dielectrics. A lot of reports have shown that the space charges are suppressed by the interfaces between the polymer matrix and the additives. Fabiani et al. argued that the use of larger TiO2 nanoparticles to detect conductive processes in EVA nanocomposites has less accumulation of space charges, lower activation energy and lower conductivity [15]. Delpino et al. put forward the outcomes of conduction current measurements and space charges of 5 wt% EVA/montmorillonite nanoplayer composite and discovered big conduction current magnitude and space charge [16]. Montanari et al. did some researches on the electrical properties of layered micron and nano-sized silicate-filled EVA copolymers, and improved the space charge accumulation behavior by changing the nanofillers [17]. However, few studies have helped to know EVA's space charge dynamic actions full of ZnO under the DC electrical stress.

The paper aims at revealing ZnO doping's influence on the actions of space charges, electric field distribution as well as dielectric properties within EVA composites. According to the outcomes, an important influence on the dielectric properties and DC conduction exists in ZnO introduction. Homocharges accumulate near the negative electrode after introducing ZnO nanoparticles and 5 wt% concentration shows better suppression of space charge injection. The distribution of the electric field is more uniform in the 5 wt% doped EVA. The chains can be damaged by the extra micro-sized particles and brand-new disadvantages may be created as well, which may act as carriers.
