查看更多>>摘要：In this work,microbiologically influenced corrosion(MIC)of 316L stainless steel(SS)caused by oral mi-crobiota was investigated with HOMINGS 16S rRNA gene sequencing technology,and electrochemical and surface analysis techniques.The results showed that oral microbiota from different subjects developed multi-species biofilms with significant differences in structure and composition of bacteria strains on the 316L SS coupons.In the presence of oral microbiota,more severe pitting corrosion and faster dissolu-tion of metallic ions including Ni and Cr were observed.The biofilm considerably decreased the pitting potential of 316L SS from 1268.0±29.1 mV vs.SCE(abiotic control)to less than 500 mV vs.SCE.The corrosion current density in the presence of oral microbiota from subject 1(115.3±83.3 nA cm-2)and subject 2(184.4±162.0 nA cm-2)was at least 4 times more than that in the abiotic medium(28.0±2.3 nA cm-2).The electroactive microorganisms with the potential to facilitate corrosion via extracellular electron transfer found in oral microbiota may be mainly responsible for the accelerated corrosion.
查看更多>>摘要：Friction and wear performance is critical for dental materials which are inevitably subject to reciprocat-ing friction against opposing teeth in applications.Here in-vitro friction and wear behavior of bioinspired ceramic-polymer composites,which possess nacre-like lamellar and brick-and-mortar architectures and resemble human teeth in their stiffness and hardness,against human tooth enamel were quantitatively investigated to imitate actual service conditions in line with standardized testing configuration.The com-posites were revealed to exhibit different wear mechanisms and lead to differing extents of wear to the opposing tooth enamel depending on their specific architectural types and orientations.In particular,the brick-and-mortar architecture displayed much less wear than the lamellar one,without obviously rough-ening the contact surfaces with enamel owing to its high ceramic content,and as such did not accelerate the wear of enamel as compared to smooth ceramics.Such characteristics,combined with its unique stiffness and hardness matching those of human enamel as well as the good fracture toughness and machinability,endow the composite with a promising potential for dental applications.This work may provide an experimental basis to this end and may also give insights towards designing new bioinspired wear-resistant materials for reducing friction and wear.
查看更多>>摘要：Resistive switching devices with a high self-rectifying ratio are important for achieving the crossbar mem-ristor array that overcomes the sneak current issue.Herein,we demonstrate a single amorphous lithium lanthanum titanium oxide(LLTO)layer based Pt/LLTO/Pt device possessing a self-rectifying ratio higher than 1×104 that is comparable to the reported devices with complicated multi-layer stacking structures.Moreover,the device shows forming-free and highly uniform bipolar resistive switching(BRS)character-istic that facilitates the potential applications.The trap-controlled and trap-free space charge limited con-ductions are demonstrated to dominate the high and low resistance states of the device,respectively.The fast migration of lithium ions under external voltage accelerates the electron injection across the Pt/LLTO interface and also the space charge accumulation in the LLTO layer,and as a result,the high performance of the Pt/LLTO/Pt device was achieved.As demonstrated Pt/LLTO/Pt device sheds a light on the potential applications of the lithium ionic conductors in self-rectifying resistive switching devices.
查看更多>>摘要：In this study,a new lightweight one-dimensional absorber Co@NC@MoS2 was designed and prepared.Firstly,polydopamine(PDA)was coated by oxidative self-polymerization with cobalt-nitrilotriacetic acid chelate nanowires(Co-NTAC)as template.Then core-shell structured magnetic hierarchical nanotubes(Co@PDA@MoS2)were prepared by one-step hydrothermal method.After thermal annealing,PDA layer was transformed into nitrogen doped carbon layer(NC)to obtain the efficient microwave absorber Co@NC@MoS2.The removal of template and growth of MoS2 were completed simultaneously,the prepa-ration process was simplified.Because of its good magnetic loss and dielectric loss,Co@NC@MoS2 shows excellent microwave absorption performance.Under filler content of 15 wt.％,the minimum reflection loss(RLmin)can reach-61.97 dB@9.2 GHz,and the effective absorption bandwidth(EAB)is 5.6 GHz.The elec-tromagnetic parameters of Co@NC@MoS2 can be further adjusted by changing the load of MoS2.Mean-while,the structure and composition of Co@NC@MoS2 were systematically analyzed.The influence of the microstructure on the microwave absorbing properties was investigated,and the microwave attenuation mechanism is revealed.As an efficient and lightweight absorber,Co@NC@MoS2 has potential application value in the construction of new stealth coatings.
查看更多>>摘要：The Cu65Ni35,Cu60Ni40 and Cu55Ni45 alloys were undercooled by fluxing method,and the rapid so-lidification structure with different undercoolings were also obtained.At the same time,the interface migration process during rapid solidification was photographed by high-speed photography,and the rela-tionship between the morphological characteristics of solidification front and undercooling was analyzed.The microstructures of the three alloys were observed by metallographic microscope,and the microstruc-ture characteristics and evolution law were systematically studied.It was found that two grain refinement events occurred in the low undercooling range and high undercooling range,respectively.The EBSD test of grain refined microstructures showed that the microstructure in the low undercooling range has a high proportion of low-angle grain boundaries and high strength textures.However,there were a large propor-tion of high-angle grain boundaries and a high proportion of twin grain boundaries and more randomly oriented grains in the microstructure in the high undercooling range.The TEM test of the Cu55Ni45 al-loy with the maximum undercooling of 284 K showed that there were high-density dislocation networks and stacking faults in the grains.Finally,the evolution relationship between microstructure hardness and undercooling was systematically studied.It was found that the microhardness of the three alloys de-creased sharply near the critical undercooling.Combined with EBSD,TEM and microhardness analysis,it was confirmed that the grain refinement under low undercooling was caused by dendrite remelting,while the grain refinement under high undercooling was caused by stress-induced recrystallization.
查看更多>>摘要：Allvac 718Plus alloy is a compromising Ni-based superalloy at elevated-temperature of 704℃,due to its combination of good mechanical properties and excellent structure stability.The precipitation behaviors during heat treatment in Allvac 718Plus alloy processed by rapid solidification technique were systemat-ically investigated in this work.The evolution of secondary phases in rapidly solidified(RS)718Plus alloy during annealing at 960℃is:η+MC in 1 h,η+MC+Laves(C14)in 6 h,and MC+Laves(C14)in longer duration.The growth and dissolution behaviors of η phase are evidenced in RS samples and differ-ent types of dislocations at the η/γ interface are characterized.Based on these experimental observations,we examine the transformation mechanisms of γ→η and η→γ,which are related to the formation of stacking faults(SFs)with a 1/6[211]γ Shockley partial dislocation and the climbing of 1/4[00001]η edge dis-locations at the η/γ interface,respectively.Both MC and Laves(C14)phases are enriched in Nb and Mo,with a higher level of Ti in MC carbides and Cr in the Laves(C14)phase.The precipitation of MC carbides is driven by the high concentration of C atoms in γ-matrix,while the Cr segregation promotes the later nucleation of Laves(C14)phase in γ-matrix around MC carbides,which is due to the Cr atoms rejection from MC carbides into the matrix.
查看更多>>摘要：In this work,the mechanical properties and strengthening mechanisms induced by microstructural evolu-tion in a rheo-extruded 5087 alloy processed via accumulative continuous extrusion forming(ACEF)were investigated.Electron back-scattered diffraction(EBSD)and transmission electron microscopy(TEM)were utilized to characterize the microstructure of the alloy subjected to ACEF with various passes.The grain refinement caused by continuous dynamic recrystallization(CDRX)was discussed.The results demon-strated that after 3 passes of ACEF,there was a significant grain refinement effect on the alloy,and the average grain size decreased from 45.6 μm to 2.5 μm;the ultimate tensile strength(UTS)and yield strength(YS)of the alloy increased to 362.8 MPa and 234.6 MPa,respectively.Dislocation cells/walls gen-erated during deformation promoted the formation of low angle grain boundaries(LAGBs).The accumu-lative strain accelerated the transformation of LAGBs to high angle grain boundaries(HAGBs).Dislocation pile-up enhanced the driving force of CDRX,and nano-sized Al6(Mn,Fe)phases at the grain boundaries inhibited the growth of grains due to the pinning effect.Based on the quantitative estimation,dislocation strengthening and grain boundary strengthening dominated the enhancement in YS of the ACEFed alloy.
查看更多>>摘要：Prolonging the lifespan of oxygen catalysts in Zn-air batteries was urgently required for the potential commercialization.Herein,two interactional active species were integrated into porous N-doped carbon microspheres(Co-Fe-Ru/PNCS)to act as bifunctional oxygen electrocatalysts.Due to the electron transfer from Ru to Co/Fe element,the high value state of Ru could promote OER performance and reduce the charge voltage of the battery.An extended cycle stability of 200 h was achieved in Co-Fe-Ru/PNCS-based battery.Moreover,the quasi in-situ potentiodynamic sweep of air-electrode in battery cell confirmed it was the incorporation of Ru that avoided the passivation of Co/Fe-based nanoparticles.Accordingly,this novel electrocatalyst may provide a new strategy of designing durable bifunctional oxygen electrocatalyst for Zn-air batteries.
查看更多>>摘要：The ternary chalcopyrite CuGaTe2 has emerged as a promising p-type thermoelectric material with its advantages of low cost,good stability,and non-toxic elements.However,its thermoelectric performance is limited by the intrinsic low electrical conductivity and high lattice thermal conductivity.In this work,A deficiency of Cu in Cu1-xGaTe2 semiconductors can be used to optimize the electrical properties by im-proving the carrier concentration and to reduce thermal conductivity through multi-scale phonon scat-tering,which is predicted and guided by the First-principles density functional theory calculations.The carrier concentration is increased to 1020,which compensates for the low electrical performance caused by the intrinsic low nH of CuGaTe2.The average power factor of Cu0.96GaTe2 reaches 106.3％higher than that of the original CuGaTe2.In addition,the lattice thermal conductivity of the defective samples is greatly reduced at high temperatures,which is mainly due to the reduction of sound speed and phonon scattering.All the above factors contribute to the highest dimensionless figure of merit(ZT)value of 1.23 at 823 K in Cu0.96GaTe2,which is 114％higher than the pristine CuGaTe2,and the average ZT is 171.4％higher.
查看更多>>摘要：The fast development of both biomaterials and regulatory science calls for a convergence,which is ad-dressed in this article via their link through medical products of biomaterials and related safety and efficacy evaluation.The updated definition of biomaterials,and concepts of biomaterials-related medi-cal products and so-called medical-grade and implantable materials are firstly introduced.Then a brief overview of the concept and history of regulatory science and its assessment of safety and efficacy of medical products,as well as the currently ongoing biomaterials-related regulatory science programs are presented.Finally,the opportunities provided by regulatory science for biomaterials as well as challenges on how to develop a biomaterials-based regulatory science system are discussed.As the first article in the field to elucidate the relationship between biomaterials and regulatory science,key take-home messages include(1)biomaterials alone are not medical products;(2)regulatory authorities approve/clear final medical products,not biomaterials;(3)there is no definition/regulation on the so-called medical-grade or implantable materials;and(4)safety and efficacy refer to final medical products,not biomaterials alone.
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