| With the rapid growth in aerospace,military,electronics,power,automotive and other fields,there is a growing need for flexible sensors with high temperature resistance and good thermal conductivity.These sensors need to be highly reliable and maintain resistance to heat,humidity and physical shock so that their end units can withstand extreme environments.In this context,conductive adhesives are of great interest due to their unparalleled potential for the development of high temperature flexible sensors and power electronics.In this work,we first comparatively investigated the structural morphology,mechanical properties,electrical and thermal conductivity of micron silver/epoxy resin systems(Ag-MFs)and nanosilver/micron silver/epoxy resin systems(Ag-NMs).It was concluded that the hybrid nano/micron silver system sintered in epoxy resin laps into a more continuous and compact network structure,exhibiting excellent pushing shear strength(28 MPa),lower volume resistivity(8×10-6?·cm),and higher thermal conductivity(29 W·m-1·K-1).Then,the effects of thermal aging(150°C)and hygrothermal aging(85°C/85%RH)on the structural morphology,mechanics and electrical properties of the two systems were analyzed.In the micron silver/epoxy resin system,the micron silver flakes are stacked in layers,and the wetting of resin on it is not completely fused and sintered,so the structure is not tight,and holes are easily formed after aging,but the resin is relatively continuous and strong bonding at the gluing interface.After thermal aging and hygrothermal aging for,the maxim um pushing shear strength decreased to 80%and 71%of the pre-aging,and the maxim um volume resistivity increased to 120%and 149%of the pre-aging.The silver nanoparticles in the nano-silver/micron silver/epoxy resin system melt after high temperature sintering so that the particles and particles,particles and sheets are intertwined with each other to form a tight mesh structure in the resin matrix,but at the same time,it causes the resin to have poor continuity at the gluing interface and cracks easily appear after aging.After thermal aging and hygrothermal aging,the maxim um pushing shear strength decreased to 76%and 67%of that before aging,and the maxim um volume resistivity increased to 118%and 129%of that before aging,respectively.Finally,combining the reliable bonding performance of the micron silver/epoxy resin system and the excellent performance of high conductivity and high thermal conductivity of the nanosilver/micron silver/epoxy resin system,we designed a high-temperature resistant flexible resistive strain sensor with a three-layer structure using 3D printing technology.This sensor exhibited high electrical conductivity(1.37×10-5?·cm),high thermal conductivity(39 W·m-1·K-1),high temperature resistance(capable of stable operation at 250°C),and high sensitivity(?R/R0values as high as 0.43 and 0.45 after bending to 100°at 25°C and 250°C,respectively;and?R/R0values as high as 0.31 and 0.18 after stretching at 2.5%at 25°C and 250°C,respectively.)and low fatigue after 1000 load-unload cycles.The flexible sensors operate effectively at temperatures up to 250°C for long periods of time,showing great promise for applications in aerospace,firefighting,resource exploration,automotive,and electronic packaging. |
PDF Full Text Request