A layered multifunctional framework based on polyacrylonitrile and MOF derivatives for stable lithium metal anode

Composite Li metal anodes based on three-dimensional(3D) porous frameworks have been considered as an effective material for achieving stable Li metal batteries with high energy density.However,uneven Li deposition behavior still occurs at the top of 3D frameworks owing to the local accumulation of Li ions.To promote uniform Li deposition without top dendrite growth,herein,a layered multifunctional framework based on oxidation-treated polyacrylonitrile(OPAN) and metal-organic framework(MOF) derivatives was proposed for rationally regulating the distribution of Li ions flux,nucleation sites,and electrical conductivity.Profiting from these merits,the OPAN/carbon nano fiber-MOF(CMOF) composite framework demonstrated a reversible Li plating/stripping behavior for 500 cycles with a stable Coulombic efficiency of around 99.0% at the current density of 2 mA/cm~2.Besides,such a Li composite anode exhibited a superior cycle lifespan of over 1300 h under a low polarized voltage of 18 mV in symmetrical cells.When the Li composite anode was paired with LiFePO_(4)(LFP) cathode,the obtained full cell exhibited a stable cycling over 500 cycles.Moreover,the COMSOL Multiphysics simulation was conducted to reveal the effects on homogeneous Li ions distribution derived from the above-mentioned OPAN/CMOF framework and electrical insulation/conduction design.These electrochemical and simulated results shed light on the difficulties of designing stable and safe Li metal anode via optimizing the 3D frameworks.

EFFECTS OF STATIC ELECTRIC FIELD ON THE FRACTURE BEHAVIOR OF PIEZOELECTRIC CERAMICS

The paper gives an overview on experimental observations of the failure behavior of electrically insulating and conducting cracks in piezoelectric ce- ramics.The experiments include the indentation fracture test,the bending test on smooth samples,and the fracture test on pre-notched(or pre-cracked)compact ten- sion samples.For electrically insulating cracks,the experimental results show a com- plicated fracture behavior under electrical and mechanical loading.Fracture data are much scattered when a static electric field is applied.A statistically based frac- ture criterion is required.For electrically conducting cracks,the experimental results demonstrate that static electric fields can fracture poled and depoled lead zirconate titanate ceramics and that the concepts of fracture mechanics can be used to mea- sure the electrical fracture toughness.Furthermore,the electrical fracture toughness is much higher than the mechanical fracture toughness.The highly electrical fracture toughness arises from the greater energy dissipation around the conductive crack tip under purely electric loading,which is impossible under mechanical loading in the brittle ceramics.

Threshold resistance switching in silicon-rich SiO_x thin films

Si-rich SiOx and amorphous Si clusters embedded in SiOx films were prepared by the radio-frequency magnetron cosputtering method and high-temperature annealing treatment.The threshold resistance switching behavior was achieved from the memory mode by continuous bias sweeping in all films,which was caused by the formation of clusters due to the local overheating under a large electric field.Besides,the Ⅰ-Ⅴ characteristics of the threshold switching showed a dependence on the annealing temperature and the SiOx thickness.In particular,formation and rupture of conduction paths is considered to be the switching mechanism for the 39 nm-SiOx film,while for the 78 nm-SiOx film,adjusting of the Schottky barrier height between insulator and semiconductor is more reasonable.This study demonstrates the importance of investigation of both switching modes in resistance random access memory.

Preparation and Performance of Graphene Oxide Modified Polyurethane Thermal Conductive Insulating Adhesive

A novel graphene oxide (GO) modified polyurethane thermal conductive insulating adhesive with small addition and excellent insulation properties was prepared by in-situ polymerization using GO as thermal conductive filler.The effects of GO content on the mechanical performance,thermal conductivity,thermal stability and insulation properties of the modified polyurethane adhesive were studied.The results showed that the tensile strength and elongation at break of polyurethane adhesive increased at first and then decreased with the increase of GO content.The thermal conductivity and thermal decomposition temperature of GO/PU composite adhesive can be effectively improved by adding appropriate amount of GO.The tensile strength,thermal conductivity and thermal decomposition temperature of polyurethane adhesive reached the maximum when GO content was 1.5 wt%.The novel GO-modified polyurethane adhesive exhibited good insulation property.The development of GO/PU thermal conductive adhesive will provide a facile method for effectively solving the “trade-off” problem between low filling and high thermal conductivity.

Parasitic effects of air-gap through-silicon vias in high-speed three-dimensional integrated circuits

In this paper,ground-signal-ground type through-silicon vias（TSVs） exploiting air gaps as insulation layers are designed,analyzed and simulated for applications in millimeter wave.The compact wideband equivalent-circuit model and passive elements（RLGC） parameters based on the physical parameters are presented with the frequency up to 100 GHz.The parasitic capacitance of TSVs can be approximated as the dielectric capacitance of air gaps when the thickness of air gaps is greater than 0.75 μm.Therefore,the applied voltage of TSVs only needs to achieve the flatband voltage,and there is no need to indicate the threshold voltage.This is due to the small permittivity of air gaps.The proposed model shows good agreement with the simulation results of ADS and Ansoft＇s HFSS over a wide frequency range.

Transforming a Two-Dimensional Layered Insulator into a Semiconductor or a Highly Conductive Metal through Transition Metal Ion Intercalation

Atomically thin two-dimensional(2D) materials are the building bricks for next-generation electronics and optoelectronics, which demand plentiful functional properties in mechanics, transport, magnetism and photoresponse.For electronic devices, not only metals and high-performance semiconductors but also insulators and dielectric materials are highly desirable. Layered structures composed of 2D materials of different properties can be delicately designed as various useful heterojunction or homojunction devices, in which the designs on the same material(namely homojunction) are of special interest because preparation techniques can be greatly simplified and atomically seamless interfaces can be achieved. We demonstrate that the insulating pristine ZnPS_3, a ternary transition-metal phosphorus trichalcogenide, can be transformed into a highly conductive metal and an n-type semiconductor by intercalating Co and Cu atoms, respectively. The field-effect-transistor(FET) devices are prepared via an ultraviolet exposure lithography technique. The Co-ZnPS_3 device exhibits an electrical conductivity of 8 × 10^(4) S/m, which is comparable to the conductivity of graphene. The Cu-ZnPS_3 FET reveals a current ON/OFF ratio of 1-05 and a mobility of 3 × 10^(-2 )cm^(2)·V^(-1)·s^(-1). The realization of an insulator, a typical semiconductor and a metallic state in the same 2D material provides an opportunity to fabricate n-metal homojunctions and other in-plane electronic functional devices.

A novel double trench reverse conducting IGBT with robust freewheeling switch

The phenomenon that the wide P-emitter region in the conventional reverse conducting insulated gate bipolar transistor （RC-IGBT） results in the non-uniform current distribution in the integrated freewheeling diode （FWD）, and then causes a parasitic thyristor to latch-up during its reverse-recovery process, which induces a hot spot in the local region of the device is revealed for the first time. Furthermore, a novel RC-IGBT based on double trench IGBT is proposed. It not only solves the snapback problem but also has uniform current distribution and high ruggedness during the reverse-recovery process.