Heterointerface Engineering of β‑Chitin/Carbon Nano‑Onions/Ni-P Composites with Boosted Maxwell‑Wagner‑Sillars Effect for Highly Efficient Electromagnetic Wave Response and Thermal Management

The rational construction of microstructure and composition with enhanced Maxwell-Wagner-Sillars effect(MWSE)is still a challenging direction for reinforcing electromagnetic wave(EMW)absorption performance,and the related EMW attenuation mechanism has rarely been elucidated.Herein,MWSE boostedβ-chitin/carbon nano-onions/Ni–P composites is prepared according to the heterointerface engineering strategy via facile layer-by-layer electrostatic assembly and electroless plating techniques.The heterogeneous interface is reinforced from the aspect of porous skeleton,nanomaterials and multilayer construction.The composites exhibit competitive EMW response mechanism between the conductive loss and the polarization/magnetic loss,as describing like the story of“The Hare and the Tortoise”.As a result,the composites not only achieve a minimum reflection loss(RL_(min))of−50.83 dB and an effective bandwidth of 6.8 GHz,but also present remarkable EMW interference shielding effectiveness of 66.66 dB.In addition,diverse functions such as good thermal insulation,infrared shielding and photothermal performance were also achieved in the hybrid composites as a result of intrinsic morphology and chemicophysics properties.Therefore,we believe that the boosted MWSE open up a novel orientation toward developing multifunctional composites with high-efficient EMW response and thermal management.

Low-thermal-budget Au-free ohmic contact to an ultrathin barrier AlGaN/GaN heterostructure utilizing a micro-patterned ohmic recess

A pre-ohmic micro-patterned recess process,is utilized to fabricate Ti/Al/Ti/TiN ohmic contact to an ultrathin-barrier(UTB)AlGaN/GaN heterostructure,featuring a significantly reduced ohmic contact resistivity of 0.56Ω·mm at an alloy temperature of 550℃.The sheet resistances increase with the temperature following a power law with the index of +2.58,while the specific contact resistivity decreases with the temperature.The contact mechanism can be well described by thermionic field emission(TFE).The extracted Schottky barrier height and electron concentration are 0.31 eV and 5.52×10^(18) cm^(−3),which suggests an intimate contact between ohmic metal and the UTB-AlGaN as well as GaN buffer.A good correlation between ohmic transfer length and the micro-pattern size is revealed,though in-depth investigation is needed.A preliminary CMOS-process-compatible metal-insulator-semiconductor high-mobility transistor(MIS-HEMT)was fabricated with the proposed Au-free ohmic contact technique.

State of the art recent advances and perspectives in 2D MXenebased microwave absorbing materials:A review

Recently,great efforts have been made to explore high-performance microwave absorbing(MA)materials,which aim to reduce the booming electromagnetic wave(EMW)pollution caused by electronic devices.MXenes(i.e.,two-dimensional(2D)transition metal carbide/nitride),an emerging family of 2D nanomaterials,demonstrate superiority to conventional nanomaterials,such as tunable electrical conductivity,unique layer structure,abundant terminal groups,and great physico-chemical properties,becoming potential candidate materials for high-efficiency MA.By hybridizing MXenes with other lossy mediums and designing novel microstructures,MA properties can be further optimized and enhanced for practical applications.Furthermore,MXenebased materials,with smartly designed multi-functionality,become a research priority to develop new or advanced applications for the coming“intelligent era”.This review focuses on using MXenes to effectively absorb EMW energy.In the first part,the fabricating methods of MXenes are systematically introduced followed by a second part on the progress of MXene-based materials regarding the MA performances,as well as a summarization on their next-generation smart multifunctional materials.In the final part,opinions on the future perspectives and opportunities of MXene-based MA materials are presented.It is believed that this review will pave the way for further flourishing the development of MXene-based materials in MA field.

Chlorine substitution-dependent toxicities of polychlorinated biphenyls to the earthworm Eisenia fetida in soil

Polychlorinated biphenyls(PCBs)with different chlorine substitution patterns often coexist in e-waste-processing sites.However,the single and combined toxicity of PCBs to soil organisms and the influence of chlorine substitution patterns remain largely unknown.Herein,we evaluated the distinct in vivo toxicity of PCB28(a trichlorinated PCB),PCB52(a tetrachlorinated PCB),PCB101(a pentachlorinated PCB),and their mixture to earthworm Eisenia fetida in soil,and looked into the underlining mechanisms in an in vitro test using coelomocytes.After a 28-days exposure,all PCBs(up to 10 mg/kg)were not fatal to earthworms,but could induce intestinal histopathological changes and microbial community alterations in the drilosphere system,along with a significant weight loss.Notably,pentachlorinated PCBs with a low bioaccumulation ability showed greater inhibitory effects on the growth of earthworm than lowly chlorinated PCBs,suggesting that bioaccumulation was not the main determinant of chlorine substitution-dependent toxicity.Furthermore,in vitro assays showed that the highly chlorinated PCBs induced a high-percentage apoptosis of eleocytes in the coelomocytes and significantly activated antioxidant enzymes,indicating that the distinct cellular vulnerability to lowly/highly chlorinated PCBs was the main contributor to the PCBs toxicity.These findings emphasize the specific advantage of using earthworms in the control of lowly chlorinated PCBs in soil due to their high tolerance and accumulation ability.