All-organic modification coating prepared with large-scale atmospheric-pressure plasma for mitigating surface charge accumulation

The surface charge accumulation on polymers often leads to surface flashover.Current solutions are mainly based on the introduction of inorganic fillers.The high-cost process and low compatibility remain formidable challenges.Moreover,existing researches on all-organic insulation focus on capturing electrons,contrary to alleviating charge accumulation.Here,an all-organic modification coating was prepared on polystyrene(PS)with the large-scale atmospheric-pressure plasma,which exhibits outperformed function in mitigating surface charge accumulation.The surface charge dissipation rate and surface conductivity are promoted by about 1.37 and 9.45 times,respectively.Simulation and experimental results show that this all-organic modification coating has a smaller electron affinity potential compared with PS.The decrease of electron affinity potential may result in accelerated surface charge decay of PS,which has never been involved in previous works.Moreover,this coating also has good reliability in a repeated surface flashover.This facile and large-scale approach brings up a novel idea for surface charge regulation and the manufacture of advanced dielectric polymers.

Large-scale plasma grafts voltage stabilizer on hexagonal boron nitride for improving electrical insulation and thermal conductivity of epoxy composite

Better electrical insulation and thermal management are both urgently required in integrated power semiconductors.Electrical insulation epoxy encapsulation suffers from poor heat conduction,which has increasingly become a bottleneck of power semiconductors integration.Although incorporating high thermal conductivity ceramics,such as hexagonal boron nitride(hBN),aluminium nitride etc.into epoxy promotes the thermal conductivity,the eco-friendly scalable fabrication of these composites with sufficient electrical breakdown strength remains a formidable challenge.Suitable voltage stabilizers are known to provide additional benefits to breakdown strength.Herein,a highthroughput approach combining plasma with roll-to-roll was developed.The voltage stabilizer(acetophenone)was grafted on interfaces between hBN and epoxy matrix through plasma.The high-energy electrons are consumed by the grafted interface,which leads to the significant suppression of partial discharge in Epoxy/hBN.Meanwhile,interfacial phonon scattering is repaired by grafting.Therefore,the epoxy composite concurrently exhibits improved breakdown strength(by 27.4%)and thermal conductivity(by 142.9%)at about 11.9 wt.%filler content,outperforming the pure epoxy.Consequently,a promising modification strategy for mass production is provided for the encapsulation materials in various high-power-density semiconductor devices.

A novel high-voltage solid-state switch based on the SiC MOSFET series and its overcurrent protection

All-solid-state switches are one of the core components of pulsed power supply systems.However,the voltage level of a single switch is limited.By optimizing the chip structure,the voltage level of a single switch can be improved.Due to the immaturity of the production process and the positive correlation between the blocking voltage and the onresistance of the switch,it is difficult to improve the blocking voltage and the continuous forward current of a single switch simultaneously.The series-connected switch is a way to increase the switch's blocking voltage without reducing the switch's continuous forward current.Magnetically coupled isolated drive and resistor-capacitor forced voltage equalization techniques are investigated to increase the blocking voltage of the switches using multiple SiC metal-oxide-semiconductor field-effect transistors(MOSFETs)in series connections.Meanwhile,a special overcurrent protection scheme is designed to improve the reliability of the series-connected switch.Finally,a high-voltage solid-state switch is developed based on the SiC MOSFET series connections,whose output pulse width is adjustable from 20 to 300μs,frequency is adjustable from 1 Hz to 3 kHz,the maximum output voltage can reach 57 kV(1 Hz),and the overcurrent protection time is about 1μs.

A supersaturated Cu-Ag nanoalloy joint with ultrahigh shear strength and ultrafine nanoprecipitates for power electronic packaging

Ag-Cu bimetallic nanoalloy,integrating the advantages of reducing migration and cost of nano-Ag and alleviating oxidation of nano-Cu,is a prospective bonding material for power electronic packaging.The Ag-coated Cu nanoparticles(Cu@Ag NPs)paste can execute bonding with high quality at 250℃,and the achieved supersaturated Ag-Cu nanoalloy joint with ultrahigh shear strength(152 MPa)dramatically exceeds most nano-paste joints.The interstitial solid solutions with atomic-level metallurgical bonds at the interface dominantly promoted the shear strength.Besides,the numerous ultrafine nanograin,high proportion of low angle grain boundaries(7.44%)without deformation,and the Cu nanoprecipitates in the joint would improve subordinately.Furthermore,the high content(16.8%)of∑3 twin boundaries would contribute to the electrical and thermal conductivity.Thus,the multiple strengthening mechanisms with the solid solution,the second precipitated phase,and ultrafine nanograin can dramatically enhance shear strength and electro-thermal conductivity of joints for high-temperature device packaging.

A Rubik’s microfluidic cube

A Rubik’s cube as a reconfigurable microfluidic system is presented in this work.Composed of physically interlocking microfluidic blocks,the microfluidic cube enables the on-site design and configuration of custom microfluidics by twisting the faces of the cube.The reconfiguration of the microfluidics could be done by solving an ordinary Rubik’s cube with the help of Rubik’s cube algorithms and computer programs.An O-ring-aided strategy is used to enable self-sealing and the automatic alignment of the microfluidic cube blocks.Owing to the interlocking mechanics of cube blocks,the proposed microfluidic cube exhibits good reconfigurability and robustness in versatile applications and proves to be a promising candidate for the rapid deployment of microfluidic systems in resource-limited settings.