Nanodielectrics: Opportunities and challenges

Abstract

Nanodielectrics, a nowadays popular term in the dielectrics community, has been the subject of intensive research over the past 10 years. In fact, the term "nanodielectrics" stems out of the field of polymer nanocomposites-an emerging field of nanotechnology. Whereas polymer nanocomposites concern polymers within which nanometer-sized fillers are homogeneously dispersed at just a few weight percentage (wt%), the term "nanometric dielectrics," [1] or "nanodielectrics" [2], [3], refers to nanocomposites of specific interest in connection with their dielectric characteristics. Nevertheless, for the scope of HV electrical insulation research, the terms "nanocomposites" and "nanodielectrics" are used interchangeably to refer to polymer/ nanoparticle mixtures of dielectric interest. The year 2015 marked the 21st anniversary of nanodielectrics from their first conceptual introduction in the 1990s [1]. Over this period, progress in nanodielectric research can be divided into two main phases [4], [5], i.e., the one before 2002 and the one thereafter. Initially, experimental studies on nanodielectrics were scarce and countable [6], [7]. Researchers only began to shift their attention to these materials when promising applications of nanodielectrics in electrical insulation were experimentally demonstrated by Nelson and his coworkers in 2002 [8]. Whereas conventional microfilled materials come with reduced dielectric strength due to bulk charge accumulation, Nelson et al. [8] discovered mitigated space charge accumulation and enhanced charge decay in nanofilled materials as compared with their microfilled counterparts, which could lead to improved dielectric strength of nanofilled materials over microfilled materials. Since then, research interest in nanodielectrics has increased tremendously, and various electrical insulation properties such as partial discharge resistance, treeing progression, space charge formation, and dielectric breakdown strength of nanodielectrics have been compared with their unfilled and microfilled counterparts. Promising improvements in these properties have been reported with nanofiller addition [9]-[17].