MOFs‑Derived Strategy and Ternary Alloys Regulation in Flower‑Like Magnetic‑Carbon Microspheres with Broadband Electromagnetic Wave Absorption

Broadband electromagnetic(EM)wave absorption materials play an important role in military stealth and health protection.Herein,metal–organic frameworks(MOFs)-derived magnetic-carbon CoNiM@C(M=Cu,Zn,Fe,Mn)microspheres are fabricated,which exhibit flower-like nano–microstructure with tunable EM response capacity.Based on the MOFs-derived CoNi@C microsphere,the adjacent third element is introduced into magnetic CoNi alloy to enhance EM wave absorption performance.In term of broadband absorption,the order of efficient absorption bandwidth(EAB)value is Mn>Fe=Zn>Cu in the CoNiM@C microspheres.Therefore,MOFs-derived flower-like CoNiMn@C microspheres hold outstanding broadband absorption and the EAB can reach up to 5.8 GHz(covering 12.2–18 GHz at 2.0 mm thickness).Besides,off-axis electron holography and computational simulations are applied to elucidate the inherent dielectric dissipation and magnetic loss.Rich heterointerfaces in CoNiMn@C promote the aggregation of the negative/positive charges at the contacting region,forming interfacial polarization.The graphitized carbon layer catalyzed by the magnetic CoNiMn core offered the electron mobility path,boosting the conductive loss.Equally importantly,magnetic coupling is observed in the CoNiMn@C to strengthen the magnetic responding behaviors.This study provides a new guide to build broadband EM absorption by regulating the ternary magnetic alloy.

Recent Advances in Design Strategies and Multifunctionality of Flexible Electromagnetic Interference Shielding Materials

With rapid development of 5G communication technologies,electromagnetic interference(EMI)shielding for electronic devices has become an urgent demand in recent years,where the development of corresponding EMI shielding materials against detrimental electromagnetic radiation plays an essential role.Meanwhile,the EMI shielding materials with high flexibility and functional integrity are highly demanded for emerging shielding applications.Hitherto,a variety of flexible EMI shielding materials with lightweight and multifunctionalities have been developed.In this review,we not only introduce the recent development of flexible EMI shielding materials,but also elaborate the EMI shielding mechanisms and the index for"green EMI shielding"performance.In addition,the construction strategies for sophisticated multifunctionalities of flexible shielding materials are summarized.Finally,we propose several possible research directions for flexible EMI shielding materials in near future,which could be inspirational to the fast-growing next-generation flexible electronic devices with reliable and multipurpose protections as offered by EMI shielding materials.

岳西黑猪与北京黑猪和巴克夏猪的杂交效果分析

岳西黑猪为安徽省岳西县独有的地方猪品种。文章通过繁殖、胴体、肉质性能的测定和比较分析,综合评价北京黑猪和巴克夏猪与岳西黑猪的杂交效果,筛选可推广的杂交组合模式,为岳西黑猪的杂交利用奠定基础,旨在更好地促进岳西黑猪产业化开发。

Realizing optimized interfacial polarization and impedance matching with CNT-confined Co nanoparticles in hollow carbon microspheres for enhanced microwave absorption

The hollow porous structure with exceptional interfacial effect and customizable internal environment shows significant potential for application as electromagnetic shielding and absorption materials.However,designing hollow porous electromagnetic absorbers with both desirable impedance matching and high loss capability remains a challenge.Herein,3D hollow porous electromagnetic microspheres were constructed by assembling 0D Co magnetic nanoparticles,1D carbon nanotubes,and 2D carbon nanosheets.Due to the sufficient sites for Co^(2+)riveting,the high loading of magnetic carbon nanotubes(CoNC)and porous carbon spheres formed high-density interfaces,enhancing the interfacial polarization.Furthermore,high-density CoNC were grown in situ on the hollow porous carbon(HPC)microsphere,forming a highly dispersed 3D magnetic network that inhibited the aggregation of magnetic nanoparticles and enhanced magnetic coupling.Therefore,the asprepared CoNC/HPC microspheres exhibited excellent microwave absorption(MA)performance,with a minimum reflection loss of-33.2 dB and an effective bandwidth of 5.5 GHz at a thickness of only 1.8 mm.The interfacial polarization mechanism for enhanced MA performance was demonstrated by electron holography and density functional theory calculations.Magnetic holography and micromagnetic simulations also revealed magnetic confinement and coupling mechanism.This work provides a new approach for designing electromagnetic absorbers with optimized impedance matching and loss capability.

Building the conformal protection of VB-group VS_(2)laminated heterostructure based on biomass-derived carbon for excellent broadband electromagnetic waves absorption

Although VB-Group transition metal disulfides(TMDs)VS_(2)nanomaterials with specific electronic properties and multiphase microstructures have shown fascinating potential in the field of electro-magnetic wave(EMW)absorption,the efficient utilization of VS_(2)is limited by the technical bottleneck of its narrow effective absorption bandwidth(EAB)which is attributed to environmental instability and a deficient electromagnetic(EM)loss mechanism.In order to fully exploit the maximal utilization values of VS_(2)nanomaterials for EMW absorption through mitigating the chemical instability and optimizing the EM parameters,biomass-based glucose derived carbon(GDC)like sugar-coating has been decorated on the surface of stacked VS_(2)nanosheets via a facile hydrothermal method,followed by high-temperature carbonization.As a result,the modulation of doping amount of glucose injection solution(Glucose)could effectively manipulate the encapsulation degree of GDC coating on VS_(2)nanosheets,further imple-menting the EM response mechanisms of the VS_(2)/GDC hybrids(coupling effect of conductive loss,interfacial polarization,relaxation,dipole polarization,defect engineering and multiple reflections and absorptions)through regulating the conductivity and constructing multi-interface heterostructures,as reflected by the enhanced EMW absorption performance to a great extent.The minimum reflection loss(Rmin)of VS_(2)/GDC hybrids could reach52.8 dB with a thickness of 2.7 mm at 12.2 GHz.Surprisingly,compared with pristine VS_(2),the EAB of the VS_(2)/GDC hybrids increased from 2.0 to 5.7 GHz,while their environmental stability was effectively enhanced by virtue of GDC doping.Obviously,this work provides a promising candidate to realize frequency band tunability of EMW absorbers with exceptional perfor-mance and environmental stability.

High-performance microwave absorption enabled by Co_(3)O_(4) modified VB-group laminated VS_(2) with frequency modulation from S-band to Ku-band

High performance microwave absorption(MA)materials especially those with tunable frequency are highly desirable for telecommunication industries and military camouflage in the information era.Herein,we constructed hierarchical heterostructures based on VB-group laminated vanadium disulfide(VS_(2))nanosheets embedded with cobalt tetroxide(Co_(3)O_(4))nanoparticles.The highly dispersed Co_(3)O_(4)nanoparticles generate strong electromagnetic coupling networks that could enhance the loss properties of MA materials.Moreover,the interconnected VS_(2)layered network results in dipolar/interfacial polarization,multiple reflection and scattering favorable for the enhanced MA performance.Impressively,the maximum reflection loss of the VS_(2)/Co_(3)O_(4)hybrids containing 10%Co_(3)O_(4)can reach 57.96 dB at a thin thickness of 1.57 mm,and the bandwidth with an RL value less than-10 dB is as large as 3.5 GHz.The effective MA band could be adjusted in a range of 15.1 GHz(2.9-18 GHz)from S to Ku bands by the increase in thickness from 1.2 mm to 5.5 mm.The results show that the synergistic effect of multiple loss mechanisms and good impedance matching could be the reasons for strong MA capability in nearly all frequency bands,and thus,the high-performance and lightweight MA materials could be developed by the VS_(2)/Co_(3)O_(4)hybrids.

Construction of multiple interfaces and dielectric/magnetic heterostructures in electromagnetic wave absorbers with enhanced absorption performance:A review

The construction of structures with multiple interfaces and dielectric/magnetic heterostructures enables the design of materials with unique physical and chemical properties,which has aroused intensive interest in scientific and technological fields.Especially,for electromagnetic(EM)wave absorption,enhanced interface polarization and improved impedence match with high Snoek's limitation could be achieved by multiple interfaces and dielectric/magnetic heterostructures,respectively,which are benificial to high-efficiency electromagnetic wave absorption(EWA).However,by far,the principles in the design or construction of structures with multiple interfaces and dielectric/magnetic heterostructures,and the relationships between those structures or heterostructures and their EWA performance have not been fully summarized and reviewed.This article aims to provide a timely review on the research progresses of high-efficency EM wave absorbers with multiple interfaces and dielectric/magnetic heterostructures,focusing on various promising EWA materials.Particularly,EM attenuation mechanisms in those structures with multiple interfaces and dielectric/magnetic heterostructures are discussed and generalized.Furthermore,the changllenges and future developments of EM wave absorbers based on those structures are proposed.

Engineering flexible and green electromagnetic interference shielding materials with high performance through modulating WS_(2) nanosheets on carbon fibers

Flexible and wearable electromagnetic interference(EMI)shielding material is one of the current research focuses in the field of EMI shielding.In this work,for the first time,WS_(2)-carbon fiber(WS_(2)-CF)composites are synthesized by implanting WS_(2),which has a multiphase structure and a large number of defects,onto the surface of carbon fiber(CF)by using a simple one-step hydrothermal method,and are applied to protect electronic devices from EMI.It is found that the EMI shielding performance of WS_(2)-CF is significantly improved,especially for those at Se and C-bands.At 2 GHz,the EMI shielding efficiency could reach 36.0 dB at a typical thickness of 3.00 mm of the composite,which is much better than that of pure CF(25.5 dB).Besides paving a novel avenue to optimize the electromagnetic shielding performance of flexible and wearable CF-based EMI shielding materials,which have great potential in the practical application for EMI shielding,this work provides a new paradigm for the design and synthesis of EMI shielding materials which have a broad application prospect.

Dual-surfactant templated hydrothermal synthesis of CoSe_(2) hierarchical microclews for dielectric microwave absorption

Cobalt diselenide(CoSe_(2))hierarchical clew-like structure is synthesized via a dual-surfactant templated hydrothermal process,and for the first time,its microwave absorption capability has been established.Specifically,the as-synthesized hierarchical interconnected structure is assembled by numerous dense nanobelts.Meticulous tuning of the synthetic conditions which could influence the hierarchical architecture indicates that,in this system,cetyltrimethylammonium bromide(CTAB)plays a dominate role of“balling”while protonated diethylenetriamine(DETA)plays the role of“stringing”.As a novel absorbent,the microwave absorption performance of CoSe_(2)microstructure is evaluated in 2–18 GHz band.Particularly,3D hierarchical CoSe_(2)microclews exhibit superior minimum reflection loss of−26.93 dB at 7.28 GHz and effective absorption bandwidth of 3.72 GHz,which are∼120%and∼104%higher than those of simple CoSe_(2)nanosheets,respectively.Such drastic enhancement could be attributed to the large specific surface area,and more dissipation channels and scattering sites enabled by the unique clew-like microstructure.The versatile dual-surfactant templated assembly of hierarchical CoSe_(2)microstructure,along with its appreciable dielectric microwave absorption performance,provides new inspirations in developing novel microwave absorbents for mitigation of electromagnetic pollution.

Brief report on the status of Kozlov’s pika,Ochotona koslowi(Büchner),in the east Kunlun mountains of China

Koslov’s pika,Ochotona koslowi(Büchner),was surveyed in western China.This endangered species is poorly known.We determined that it is a burrowing pika,and lives in social family groups at high densities.It primarily occupies high-elevation cold grassland vegetation.It appears to have a high reproductive rate.More emphasis should be placed on research into this unique species in China.

Genetic analysis of the br gene in halophilic archaea isolated from Xinjiang region, China

Some novel members of extremely halophilic archaea,strains AJ11,AJ12 and AJ13,were isolated from the Aularz Lake located in the Altun Mountain National Nature Reserve of Xinjiang,Uygur Autonomous Region in China.Partial DNA fragments encoding a bacteriorhodopsin(BR),as well as for 16S rRNA of isolated strains,were amplified by PCR and their DNA sequences were determined subsequently.On the basis of homology and phylogenetic analysis of the 16S rDNA,we thought that the isolated strains forming a microbiological population are the members of the genus Natrinema.The results of genetic analysis,such as GC content,transition/transversion(Ti/Tv)rate ratios and synonymous substitution rates(Ks)indicate that the br fragments,with a high level of genetic divergence,are faced with both purifying selection and bias mutation pressure.The study provides the basis for use of species and BR proteins resources.