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Kyungwho Choi [1] and Woongchul Choi [2] and Choongho Yu [2; 3] and Yong Tae Park [4]

Academic Editor: Magnus Willander

1, New Transportation Systems Research Center, Korea Railroad Research Institute, Uiwang-si, Gyeonggi-do 16105, Republic of Korea, krri.re.kr

2, Department of Materials Science and Engineering, Texas A & M University, College Station, TX 77843, USA, tamu.edu

3, Department of Mechanical Engineering, Texas A & M University, College Station, TX 77843, USA, tamu.edu

4, Department of Mechanical Engineering, Myongji University, Yongin-si, Gyeonggi-do 17058, Republic of Korea, mju.ac.kr

Received Apr 10, 2017; Revised Aug 14, 2017; Accepted Sep 12, 2017

This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

1. Introduction

Lead zirconate titanate (PZT), which is a typical piezoelectric material, is widely used in the aviation [1, 2], automobile [3, 4], and precision machinery [5] industries due to its excellent performance capabilities. However, while there have been various studies of lead-free piezoelectric materials, lead-based materials have adverse effects on the environment and on human health [6]. Moreover, piezoelectric ceramics are vulnerable to external vibration or shocks given their brittleness. In order to overcome this, a polymeric material such as polyvinylidene fluoride (PVDF), which is flexible and environmentally friendly, was introduced [7, 8]. However, ceramic fillers must be incorporated because piezoelectric polymers are not applicable alone due to their low dielectric constant [9]. To obtain higher piezoelectric performance, lead nickel niobate-lead zirconate titanate (PNN-PZT) [10], BaTiO3 [11], lead magnesium niobate-lead titanate (PMN-PT) [12], and ZnO [13–18] can be used as fillers. Among them, ZnO nanowires have been found to be mechanically strong, biocompatible, and environmentally friendly, making them suitable candidates for wearable electronics or biosensors [19].

In this article, a ZnO nanowire/PVDF composite with a high dielectric constant was synthesized and piezoelectric behavior was observed while varying the concentration of the ZnO nanowires, the nanowire alignment process, and the poling condition. The dielectric constant was increased with an increase in the ZnO nanowire concentration. Specifically, the alignment process of the nanowires enhanced the poling effect due to the directionality of the network structures. The resulting dielectric constant shows an improvement of nearly 400% when compared...

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