查看更多>>摘要：Ferrite/carbon composited materials,especially the bio-derived composited materials possessing both environmental friendliness and outstanding microwave absorption performance,attract numerous attentions for solving the"electromagnetic problem"in the Gigahertz frequency range.In this work,we demonstrate a bio-derived ferrite/carbon material by compositing functional carbonized cotton fibers(CCFs)and Fe3O4 nanoparticles with optimized microwave-absorption properties.By adjusting the carbonization conditions systematically,the Fe3O4 loading contents and the microwave absorption properties can be varied simultaneously-and,indeed,optimized and tuned.The CCFs-Fe3O4 composites exhibited a minimum reflection-loss capacity RL(dB)of-56.8 dB at 10.9 GHz with a thickness of 1.67 mm,and its effective absorption bandwidth(RL(dB)＜-20 dB)was found to broaden to 7.1 GHz.Electromagnetic characterizations,coupled with microstructure analyses,revealed that the enhancement in microwave absorption was triggered by the different microstructures of CCFs-Fe3O4 composites-attributable to the different carbonization processes.These different conditions result in different amounts of Fe3O4 attachment sites and lead to the enhancement of dielectric polarization at localized microstructures.The present work of bio-derived ferrite/carbon materials has important implications in understanding structure-performance relationships in dielectric-magnetic materials,and,meanwhile,could well be extended to a microwave-absorber design approach.
查看更多>>摘要：Chemo-resistance has pushed cancer treatment to the boundary of failure.This challenge has encouraged scientists to look for nanotechnological solutions.In this study,we have taken this goal one step further without depending on chemotherapy.Specifically,hybrid metal,polymer,and lipid nanoparticles that formed an IR780-a photosensitizer and Zinc copper oxide incorporated nanoparticle(ZCNP)nanoparti-cles were utilized in a combined photothermal and photodynamic therapy.Through the mediation of triphenylphosphonium(TPP)as a mitochondria-targeting moiety,TPP-conjugated polymer-lipid hybrid nanoparticles containing ZCNP/IR-780 significantly enhanced cellular uptake by cancer cells and selec-tively targeted the mitochondria,which improved the induction of apoptosis.In tumor-bearing mice,the nanoparticles were detected predominantly in tumors rather than in the other principle organs,which did not show notable signs of toxicity.Both in vitro and in vivo results demonstrated a great improvement in photothermal and photodynamic efficacy in combination when compared to either one individually,and a significant inhibition of tumor growth was observed with the combined therapies.In summary,this study describes an effective mitochondria-targeting nanocarrier for the treatment of cancer using combined photothermal and photodynamic therapies.
查看更多>>摘要：Metal phthalocyanine is considered one of the most promising candidates for the design and fabrication of flexible resistive random access memory(RRAM)devices due to its intrinsic flexibility and excel-lent functionality.However,performance degradation and the lack of multi-level capability,which can directly expand the storage capacity in one memory cell without sacrificing additional layout area,are the primary obstacles to the use of metal phthalocyanine RRAMs in information storage.Here,a flex-ible RRAM with pristine nickel phthalocyanine(NiPc)as the resistive layer is reported for multi-level data storage.Due to its high trap-concentration,the charge transport behavior of the device agrees well with classical space charge limited conduction controlled by traps,leading to an excellent performance,including a high on-off current ratio of 107,a long-term retention of 106 s,a reproducible endurance over 6000 cycles,long-term flexibility at a bending strain of 0.6％,a write speed of 50 ns under sequential bias pulses and the capability of multi-level data storage with reliable retention and uniformity.
查看更多>>摘要：High-entropy alloys(HEAs)have attracted great research interest owing to their good combination of high strength and ductility at both room and cryogenic temperatures.However,expensive raw mate-rials are always added to overcome the strength-ductility trade-off at low temperatures,leading to an increased production cost for the cryogenically used alloys.In this work,a series of nitrogen-doped FeMnCoCr HEAs have been processed by homogenization annealing,cold rolling and recrystallization annealing followed by water quenching.The microstructural evolution and mechanical properties of the alloys are studied systematically.The Fe49Mn30Co10Cr10N1 alloy shows excellent mechanical properties at both 293 K and 77 K.Particularly,the yield and ultimate tensile strength of 1078 and 1630 MPa are achieved at the cryogenic temperature,respectively,while a satisfactory uniform elongation of 33.5％is maintained.The ultrahigh yield strength results from the microstructure refinement caused by the acti-vation of athermal martensitic transformation and mechanical twinning that occur in the elastic regime together with the increased lattice friction due to the cryogenic environment.In the plastic regime,the dynamic Hall-Petch effect caused by twinning,martensitic transformation,and reverse transformation together with the high barrier to dislocation motion jointly contribute to the ultrahigh tensile strength.Simultaneously,the transformation induced plasticity(TRIP)and the twinning induced plasticity(TWIP)effects jointly contribute to the ductility.The design strategy for attaining superior mechanical properties at low temperatures,i.e.by adjusting stacking fault energy in the interstitial metastable HEAs,guides the development of high-performance and low-cost alloys for cryogenic applications.
查看更多>>摘要：The risk of leakage and low thermal conductivity severely hinder the wide application of phase change materials(PCMs).In this work,the high-density polyethylene/carbon nanotubes(HDPE/CNTs)porous scaffolds were successfully fabricated via a sacrificial template method followed by the general melt blending and water solvent etching.Subsequently,a series of paraffin wax HDPE/CNTs/PW composite PCMs were obtained combined with the simple vacuum impregnation method.The obtained HDPE/CNTs porous scaffolds can effectively avoid the leakage of PW,meanwhile,the thermal conductivity and electri-cal conductivity of HDPE/CNTs/PW-3:7 are increased by 2.94 times and 13 orders of magnitude compared with the HDPE/PW-3:7 respectively,also,it exhibits high phase change enthalpy(153.95 J/g for melting enthalpy and 152.82 J/g for crystallization enthalpy).From the above perspectives,the HDPE/CNTs/PW-3:7 has promising potential value in the application of light-to-thermal conversion,electro-to-thermal conversion and thermal energy storage.
查看更多>>摘要：Grain growth and shrinkage are essential to the thermal and mechanical stability of nanocrystalline metals,which are assumed to be governed by the coordinated deformation between neighboring grain boundaries(GBs)in the nanosized grains.However,the dynamics of such coordination has rarely been reported,especially in experiments.In this work,we systematically investigate the atomistic mechanism of coordinated GB deformation during grain shrinkage in an Au nanocrystal film through combined state-of-the-art in situ shear testing and atomistic simulations.We demonstrate that an embedded nanograin experiences shrinkage and eventually annihilation during a typical shear loading cycle.The continu-ous grain shrinkage is accommodated by the coordinated evolution of the surrounding GB network via dislocation-mediated migration,while the final grain annihilation proceeds through the sequen-tial dislocation-annihilation-induced grain rotation and merging of opposite GBs.Both experiments and simulations show that stress distribution and GB structure play important roles in the coordinated defor-mation of different GBs and control the grain shrinkage/annihilation under shear loading.Our findings establish a mechanistic relation between coordinated GB deformation and grain shrinkage,which reveals a general deformation phenomenon in nanocrystalline metals and enriches our understanding on the atomistic origin of structural stability in nanocrystalline metals under mechanical loading.
查看更多>>摘要：The underlying mechanism of discontinuous yielding behavior in an ultrafine-grained(UFG)Fe-31Mn-3Al-3Si(wt.％)austenitic TWIP steel was investigated by the use of advanced TEM technique with taking the plastic deformation mechanisms and their correlation with grains size near the macroscopic yield point into account.Typical yield drop mechanisms such as the dislocation locking by the Cottrell atmo-sphere due to the presence of interstitial impurities cannot explain the origin of this phenomenon in the UFG high-Mn austenitic TWIP steel.Here,we experimentally revealed that the plastic deformation mechanisms in the early stage of deformation,around the macroscopic yield point,show an obvious association with grain size.More specifically,the main mechanism shifts from the conventional slip in grain interior to twinning nucleated from grain boundaries with decreasing the grain size down to less than 1 μm.Our observation indicates that the grain size dependent deformation mechanisms transition is also deeply associated with the discontinuous yielding behavior as it could govern the changes in the grain interior dislocation density of mobile dislocations around the macroscopic yield point.
查看更多>>摘要：As an eco-friendly thermoelectric material,SnTe has attracted extensive attention.In this study,we use a stepwise strategy to enhance the thermoelectric performance of SnTe.Firstly,AgCl is doped into SnTe to realize band convergence and enlarge the band gap of AgCl-doped SnTe.AgCl-doping also induces dense point defects,strengthens the phonon scattering,and reduces the lattice thermal conductivity.Secondly,Sb is alloyed into AgCl-doped SnTe to further optimize the carrier concentration and simultaneously reduce the lattice thermal conductivity,leading to improved thermoelectric dimensionless figure of merit,ZT.Finally,(Sn0.81Sb0.19Te)0.93(AgCl)0.07 has approached the ZT value as high as～0.87 at 773 K,which is 272％higher than that of pristine SnTe.This study indicates that stepwise AgCl-doping and Sb-alloying can significantly improve thermoelectric performance of SnTe due to synergistic band engineering,carrier concentration optimization and defect engineering.
查看更多>>摘要：Topological morphology that dominates the surface electronic properties of nanostructures plays a key role in producing desired materials for versatile functions and applications in many fields,but its modula-tion for specific functions remains a big challenge.Herein,we report an acid-induced method to prepare S-doped graphitic carbon nitride/graphitic carbon nitride(S-CN/CN)homojunction by simply pyrolyzing a supramolecular precursor synthesized from melamine and H2SO4.The topological morphology and electronic structure of CN homojunction can be easily adjusted only by changing the ratio of raw materi-als.Moreover,the topological morphology of S-CN/CN homojunction can be further adjusted from hollow cocoon to 2D nanosheets by changing the annealing conditions.The optimized S-CN/CN homojunction shows highly efficient in charge transfer and separation and exhibits superior OER activity and high abil-ity to degrade organic pollutants.Impressively,S-CN/CN nanosheets only demand low overpotential of 301 mV to drive a current density of 10 mAcm-2 in 1 M KOH media,and the corresponding Tafel slope is only 57.71 mV/dec,which is superior to the most advanced precious metal IrO2 catalyst.Moreover,under visible light irradiation,its photodegradation kinetic rate of RhB is 2.38,which is 47.6 times higher than that of bulk CN.This work provides useful guidance for designing and developing efficient multifunctional metal-free catalysts.
查看更多>>摘要：Bearings are one of the most important components in modern industry.Rolling contact fatigue(RCF)initiating from surface and subsurface is the major failure mode.In this paper,a typical high speed thrust angular contact ball bearing was selected,and the machined surface quality and near-surface microstruc-ture of the race-way and rolling ball were systematically characterized by using of a probe surface profiler,white light interferometer,optical microscopy(OM),scanning electron microscopy(SEM),elec-tron backscatter diffraction(EBSD)and transmission electron microscopy(TEM)combined with focused ion beam(FIB).Two kinds of precursor,probably resulting in pitting or spalling during the following rolling contact,were detected.One is the defects on the surface of either the race-way or the rolling ball,such as heavy machining marks,scratches and slag-hole.The other is nano-crystalline layer due to machining,in the outermost layer around the surface of race-way.The results may well lay foundation for our further research on RCF with the real part of such typical rolling bearings.
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