In this study, we prepared 40, 45, 50, 55, 60, 65, and 70 wt% content composites filled in epoxy matrix for two micro silica and three micro alumina types for use as a GIS heavy electric machine. As a filler type of epoxy composite, micro silica composites showed excellent AC breakdown strength properties compared to micro alumina composites in the case of electrical properties of micro silica and alumina. The electrical breakdown properties of micro silica composites increased with increasing filler content, whereas those of micro alumina decreased with increasing filler content. In the case of mechanical properties, the micro silica composite showed improved tensile strength and flexural strength compared with the micro alumina composite. In addition, mechanical properties such as tensile strength and flexural strength of micro silica and alumina composites decreased with increasing filler content. This is probably because O-H groups are present on the surface of silica in the case of micro silica but are not present on the surface of alumina in the case of micro alumina.

The epoxy/micro-and nano-mixed silica composites (EMNC) systems were prepared and the AC insulation breakdown strength was evaluated. Glass transition temperature (Tg) and crosslink density were also measured by dynamic mechanical analyzer (DMA) in order to correlate them with the electrical and mechanical properties, and the effect of silane coupling agent on the electrical properties was also studied. Electrical properties and crosslink density of epoxy/micro-silica composite were noticeably improved by addition of nano-silica and silane coupling agent, and the highest breakdown strength was obtained by addition of 0.5～5phr of nano-silica and 2.5phr of silane coupling agent, and the highest tensile and flexural strength were obtained by addition of 2.5phr of nano-silica.

Citations

• Constructing a Double Crosslinking Structure on Spherical Silica Powder for Enhancement in the Interfacial Adhesion of Epoxy Composite
  Daobei Wang, Yining Wang, Changmei Liao, Zhiqiang Yao, Ning Xie, Dongzhi Wang
  Polymer Composites.2026;[Epub]     CrossRef

Lead-free piezoelectric ceramic/epoxy composites with ``0-3`` connectivity were prepared by cold-pressing with a temperature controlled curing method. A ceramic powder with a composition of (Na0.51K0.47Li0.02)(Nb0.8Ta0.2)O3 was synthesized by a conventional solid state reaction route. The dielectric and piezoelectric properties of ceramic/epoxy composites were characterized as a function of the volume fraction (φ) of piezoelectric ceramics, which was varied from 70 to 95vol%. The results indicated that the piezoelectric properties of composites were significantly affected by the volume fraction of ceramics. In terms of the piezoelectric properties, specimens showed the best performance at φ= 85vol%, resulting in the piezoelectric constant d33 of 39pC/N and the figure of merit as a piezoelectric energy harvester (d33·g33) of 1.24 pm2/N.