The development of oxygen reduction reaction (ORR) electrocatalysts based on earth‐abundant nonprecious materials is critically important for sustainable large‐scale applications of fuel cells and ...metal–air batteries. Herein, a hetero‐single‐atom (h‐SA) ORR electrocatalyst is presented, which has atomically dispersed Fe and Ni coanchored to a microsized nitrogen‐doped graphitic carbon support with unique trimodal‐porous structure configured by highly ordered macropores interconnected through mesopores. Extended X‐ray absorption fine structure spectra confirm that Fe‐ and Ni‐SAs are affixed to the carbon support via FeN4 and NiN4 coordination bonds. The resultant Fe/Ni h‐SA electrocatalyst exhibits an outstanding ORR activity, outperforming SA electrocatalysts with only Fe‐ or Ni‐SAs, and the benchmark Pt/C. The obtained experimental results indicate that the achieved outstanding ORR performance results from the synergetic enhancement induced by the coexisting FeN4 and NiN4 sites, and the superior mass‐transfer capability promoted by the trimodal‐porous‐structured carbon support.
A hetero‐single‐atom oxygen reduction reaction (ORR) electrocatalyst is presented, which has atomically dispersed Fe and Ni coanchored to a microsized nitrogen‐doped carbon support with unique trimodal‐porous structure configured by ordered macropores interconnected through mesopores. The achieved outstanding ORR performance results from the synergetic enhancement induced by the coexisting FeN4 and NiN4 sites, and the superior mass‐transfer capability.
Electrical communication between a biological system and outside equipment allows one to monitor and influence the state of the tissue and nervous networks. As the bridge, bioelectrodes should ...possess both electrical conductivity and adaptive mechanical properties matching the target soft biosystem, but this is still a big challenge. A family of liquid‐metal‐based magnetoactive slurries (LMMSs) formed by dispersing magnetic iron particles in a Ga‐based liquid metal (LM) matrix is reported here. The mechanical properties, viscosity, and stiffness of such materials rapidly respond to the stimulus of an applied magnetic field. By varying the intensity of the magnetic field, regulation within a factor of 1000 of the Young's modulus from ≈kPa to ≈MPa, and the ability to reach GPa with more dense iron particles inside the LMMS are demonstrated. With the advantage of high conductivity of the LM matrix, the functions of the LMMS are not only limited to the soft implanted electrodes or penetrating electrodes in biosystems: the electrical response based on the LMMS electrodes can also be precisely tuned by simply regulating the applied magnetic field.
A family of liquid‐metal‐based magnetoactive slurries (LMMSs) has been developed as mechanically adaptive bioelectrodes responsive to magnetic stimuli. Taking advantage of the high conductivity and mechanically stimulus‐responsive properties, LMMSs can be used as smart implanted electrodes in biosystems, whose electrical response and stiffness can be tuned by magnetic field.
Upon flowing hot steam over hexagonal boron nitride (h‐BN) bulk powder, efficient exfoliation and hydroxylation of BN occur simultaneously. Through effective hydrogen bonding with water and ...N‐isopropylacrylamide, edge‐hydroxylated BN nanosheets dramatically improve the dimensional change and dye release of this temperature‐sensitive hydrogel and thereby enhance its efficacy in bionic, soft robotic, and drug‐delivery applications.
A metastable β Ti–10V–3Fe–3Al–0.27O (wt.%) alloy was subjected to thermo-mechanical processing to induce α and ω phase formation, so that the alloy can exhibit the features responsible for both ...transformation induced plasticity (TRIP) and twinning induced plasticity (TWIP) behaviour during deformation. The alloy thereafter was deformed at different strain rates (10−3, 10−1, 101, 102 s−1) at ambient temperature. At slow strain rate (≤10−3 s−1), in addition to slip the alloy displayed a dominant deformation mechanism with α′′ martensite formation, where mechanical {332}〈113〉β twinning and deformation-induced ω phase were also activated. At an intermediate strain rate, 10−1 s−1, there was a competition between stress-induced phase transformations and stress-induced twinning deformation mechanisms. With increasing strain rate to 101 s−1 or higher; it was found that the dominant deformation mode was twinning. These results have been correlated with the β phase stability of the samples.
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The prospective utilization of nanoscale superconductors as micro/nanocoils or circuits with superior current density and no electrical resistance loss in next‐generation electronics or ...electromagnetic equipment represents a fascinating opportunity for new microsystem technologies. Here, a family of superconducting liquid metals (Ga–In–Sn alloys) and their nanodroplets toward printable and stretchable superconducting micro/nanoelectronics is developed. By tuning the composition of liquid metals the highest superconducting critical temperature (Tc) in this family can be modulated and achieved as high as 6.6 K. The liquid metal nanodroplets retain their bulk superconducting properties and can be easily dispersed in different solvents as inks. The printable and stretchable superconducting micro/nano coils, circuits and electrodes have been fabricated by inkjet printer or laser etching by using superconducting nanodroplets inks. This novel superconducting system greatly promotes the commercial utilization of superconductors into advanced flexible micro/nanoelectronic devices and offers a new platform for developing more application with superconductors.
Superconducting eutectic gallium–indium–tin (EGaInSn) alloys and their nanosized droplets with different weight ratios are developed for realizing printable and stretchable superconducting circuits. The highest superconducting critical temperature of EGaInSn is 6.6 K. The corresponding EGaInSn nanodroplets retain the bulk superconducting properties. Their dispersion in various solvents shows excellent wettability, which can be easily applied to print stretchable superconductive micro/nanoelectronics.
Graphene and single-walled carbon nanotubes are carbon materials that exhibit excellent electrical conductivities and large specific surface areas. Theoretical work suggested that a covalently bonded ...graphene/single-walled carbon nanotube hybrid material would extend those properties to three dimensions, and be useful in energy storage and nanoelectronic technologies. Here we disclose a method to bond graphene and single-walled carbon nanotubes seamlessly during the growth stage. The hybrid material exhibits a surface area >2,000 m(2) g(-1) with ohmic contact from the vertically aligned single-walled carbon nanotubes to the graphene. Using aberration-corrected scanning transmission electron microscopy, we observed the covalent transformation of sp(2) carbon between the planar graphene and the single-walled carbon nanotubes at the atomic resolution level. These findings provide a new benchmark for understanding the three-dimensional graphene/single-walled carbon nanotube-conjoined materials.
Dynamic and metadynamic recrystallisation behaviour of Ni-30Fe-Nb-C model alloys during plane strain compression was investigated by optical and electron microscopy. The dynamically recrystallised ...grains were primarily located at the pre-existing grain boundaries with few additional new recrystallised grains in the prior grain interior. A limited nucleation of recrystallised grains at >400nm size NbC particles was also evident. On the other hand, smaller semi-coherent particles (~10–150nm) severely inhibit the dislocations rearrangement and subgrain boundary mobility, thus leading to sluggish or even suppressed dynamic and metadynamic recrystallisation. These smaller NbC particles maintained cube-on-cube orientation relationship with austenite matrix (001)NbC||(001)γ, 001NbC||001γ. The shape of the NbC particles changes from nearly ellipsoidal to octahedral followed by hexagonal and tetra-kai-decahedral by truncation of {111} facets by {001} ones.
Lattice mismatch in a bimetallic core–shell nanoparticle will cause strain in the epitaxial shell layer, and if it reaches the critical layer thickness misfit dislocations will appear in order to ...release the increasing strain. These defects are relevant since they will directly impact the atomic and electronic structures thereby changing the physical and chemical properties of the nanoparticles. Here we report the direct observation and evolution through aberration-corrected scanning transmission electron microscopy of dislocations in AuPd core–shell nanoparticles. Our results show that first Shockley partial dislocations (SPD) combined with stacking faults (SF) appear at the last Pd layer; then, as the shell grows the SPDs and SFs appear at the interface and combine with misfit dislocations, which finally diffuse to the free surfaces due to the alloying of Au into the Pd shell. The critical layer thickness was found to be at least 50% greater than in thin films, confirming that shell growth on nanoparticles can sustain more strain due to the tridimensional nature of the nanoparticles.
► Atomic resolution imaging of the interfaces of AuPd nanoparticles. ► Systematic study of the growth of Pd shells over Au nanoparticles. ► Shockley partial dislocations, edge dislocations and Au migration into the shell release the interfacial strain.
Hexagonal boron nitride nanosheets (h-BNNS) have been proposed as an ideal substrate for graphene-based electronic devices, but the synthesis of large and homogeneous h-BNNS is still challenging. In ...this contribution, we report a facile synthesis of few-layer h-BNNS on melted copper via an atmospheric pressure chemical vapor deposition process. Comparative studies confirm the advantage of using melted copper over solid copper as a catalyst substrate. The former leads to the formation of single crystalline h-BNNS that is several microns in size and mostly in mono- and bi-layer forms, in contrast to the polycrystalline and mixed multiple layers (1-10) yielded by the latter. This difference is likely to be due to the significantly reduced and uniformly distributed nucleation sites on the smooth melted surface, in contrast to the large amounts of unevenly distributed nucleation sites that are associated with grain boundaries and other defects on the solid surface. This synthesis is expected to contribute to the development of large-scale manufacturing of h-BNNS/graphene-based electronics.
Nanoindentation measurements of polygonal ferrite (PF), bainitic ferrite (BF) lath, ferrite in granular bainite (GB) and retained austenite (RA) in a low-alloyed multi-phase transformation-induced ...plasticity steel were carried out in conjunction with electron backscattering diffraction and scanning transmission electron microscopy (STEM). PF returned the lowest hardness followed by ferrite in GB, BF lath and RA. Dislocation glide and austenite-to-martensite transformation can be correlated with the first and second pop-in observed in the load–displacement curve, respectively. The martensite transformation induced by nanoindentation was demonstrated via correlative STEM. Film RA generally shows a higher stability than blocky RA, associated with a larger average onset load for martensite transformation in the former. It is noted that some ferrite in GB had similar hardness to BF lath and some blocky RA grains in GB showed a similar stability to that of film RA between BF lath, which can be attributed to a higher carbon content in GB due to chemical inhomogeneity.
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