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 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.
Highlights
Solid-state transformer (SST), an intelligent device for voltage grade conversion and power transmission, has been extensively investigated due to its superiority in efficiently transmitting clean energy by distributed generation and microgrid [1,2]
The epoxy composites with high thermal conductivity and excellent insulating ability under high frequency bipolar square wave voltage become the crucial issues for improving the reliability of the devices [5,14,15,16]
Effects of Micro/Nano‐boron nitride (BN) Co‐Doping on Microstructure of Epoxy Composites wtthiemhipceoekr,xnedTyeEeascfisko.inismnTegthdpheoteahspseibettrerhEefseoPawrkMwmdiit2oath0hnwsmcatnenaicdnosrftdorEvienPfonigMllgtlaettNihgrms,e20eaUe‐nnb5ddiesatumwstrhaaeiecnnercnboee/rtxnewhaaaemaknstdopimcfolhiewlea,lernctrahrscoevtasoevsrrl‐oetiszalestegachdegtoi,ebowaynannpvSdpioEnlldMiteFaidgisgiemotuhenraneegtdhes2usae. rmTohafhnipgoctlhheesee vwolhtaitgeepealerctitcrloedse, manadrktehde tbimy eretchteanbgreualakrd,oawnnd hdaoptsp,emneadr.ked by circles, are the micro and nano‐BN fillers, respectively
Summary
Solid-state transformer (SST), an intelligent device for voltage grade conversion and power transmission, has been extensively investigated due to its superiority in efficiently transmitting clean energy by distributed generation and microgrid [1,2]. Despite the excellent breakdown strength of nanocomposites, their thermal conductivities are lower because of forming a large amount of interfacial area [23,24] This raises the issue of whether the thermal conductivity and breakdown performance could be simultaneously enhanced by co-doping micro and nanofillers into the epoxy matrix. Micro and nano-BN fillers modified by KH550 were loaded into an epoxy resin matrix to prepare epoxy composites with simultaneously improved thermal conductivity and breakdown performance. The effect of micro and nano-BN co-doping on thermal conductivity, breakdown strength at power frequency and voltage endurance capability under a bipolar square wave field with high frequency and high voltage of the epoxy composites were studied. Thheme ipseprhfoerremcaonpcpeeorfelveoclttraogdeesewndituhraandcieamweatserchoaf r2a0ctmermiz.eTdhbeyvovlotaltgaegbereenakdduorawnnce tetismt we,adsecfoinnedducatsedthwe iwthitahsbtoaonsdtirnagtetiomf e1 bkeVt/wse. eAn ttohtealtiomf e15thseamvopllteasgwe earpeptleisetdedonfotrheevheirgyh evxopletraigmeeenlteacltrcoodnediatniodnt.hTehteimbreetahkedborweanksdtroewnngthhaipspceanlceudla. ted according to the formula
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