Hollow FeCo-FeCoP@C nanocubes embedded in nitrogen-doped carbon nanocages for efficient overall water splitting

Designing readily available and highly active electrocatalysts for water splitting is essential for renewable energy technologies.Here we present the construction of FeCo-FeCoP@C hollow nanocubes encapsulated in nitrogen-doped carbon nanocages(FeCo-FeCoP@C@NCCs) through controlled carbonization and subsequent phosphorization of a Prussian blue analogue.With stronger electronic interaction and hollow structure,the as-obtained FeCo-FeCoP@C@NCCs material requires small overpotentials of 91 mV and280 mV to deliver 10 mA cm^(-2) in 1 M KOH toward hydrogen and oxygen evolution,respectively.More importantly,applying this material for overall water splitting,it only requires 1.64 V to afford10 mA cm^(-2) and exhibits impressively durability over 40 h without obvious performance decay.The present approach inspires potentials for the controllable synthesis of multi-component catalysts for practical applications.

Weak-focused acoustic vortex generated by a focused ring array of planar transducers and its application in large-scale rotational object manipulation

Contactless manipulation of multi-scale objects using the acoustic vortex(AV) tweezers offers tremendous perspectives in biomedical applications.However,it is still hindered by the weak acoustic radiation force(ARF) and torque(ART)around the vortex center.By introducing the elevation angle to the planar transducers of an N-element ring array,the weakfocused acoustic vortex(WFAV) composed of a main-AV and N paraxial-AVs is constructed to conduct a large-scale object manipulation.Different from the traditional focused AV(FAV) generated by a ring array of concave spherical transducers,a much larger focal region of the WFAV is generated by the main lobes of the planar transducers with the size inversely associated with the elevation angle.With the pressure simulation of the acoustic field,the capability of the rotational object driving in the focal plane for the WFAV is analyzed using the ARF and the ART exerted on an elastic ball based on acoustic scattering.With the experimental system built in water,the generation of the WFAV is verified by the scanning measurements of the acoustic field and the capability of object manipulation is also analyzed by the rotational trapping of floating particles in the focal plane.The favorable results demonstrate the feasibility of large-scale rotational manipulation of objects with a strengthened ART and a reduced acousto-thermal damage to biological tissues,showing a promising prospect for potential applications in clinical practice.

Beam alignments based on the spectrum decomposition of orbital angular momentums for acoustic-vortex communications

Given the enhanced channel capacity of wave chirality,acoustic communications based on the orbital angular momentum(OAM)of acoustic-vortex(AV)beams are of significant interest for underwater data transmissions.However,the stringent beam alignment is required for the coaxial arrangement of transceiver arrays to ensure the accuracy and reliability of OAM decoding.To avoid the required multiple measurements of the traditional orthogonality based algorithm,the beam alignment algorithm based on the OAM spectrum decomposition is proposed for AV communications by using simplified ring-arrays.Numerical studies of the single-OAM and OAM-multiplexed AV beams show that the error of the OAM spectrum increases with the translation distance and the deflection angle of the transceiver arrays.To achieve an ideal arrangement,two methods of the single-array translation alignment and the dual-array deflection alignment are developed based on the least standard deviation of the OAM spectrum(SD-OAM).By decreasing the SD-OAM towards zero using transceiver arrays of 16 transmitters and 16 receivers,accurate beam alignments are accomplished by multiple adjustments in three dimensions.The proposed method is also demonstrated by experimental measurements of the OAM dispersion and the SD-OAM for misaligned beams.The results demonstrate the feasibility of the rapid beam alignment based on the OAM spectrum decomposition by using simplified transceiver ring-arrays,and suggest more application potentials for acoustic communications.

Pulling force of acoustic-vortex beams on centered elastic spheres based on the annular transducer model

To solve the difficulty of generating an ideal Bessel beam,an simplified annular transducer model is proposed to study the axial acoustic radiation force(ARF)and the corresponding negative ARF(pulling force)exerted on centered elastic spheres for acoustic-vortex(AV)beams of arbitrary orders.Based on the theory of acoustic scattering,the axial distributions of the velocity potential and the ARF for AV beams of different orders generated by the annular transducers with different physical sizes are simulated.It is proved that the pulling force can be generated by AV beams of arbitrary orders with multiple axial regions.The pulling force is more likely to exert on the sphere with a smaller k0a(product of the wave number and the radius)for the AV beam with a bigger topological charge due to the strengthened off-axis acoustic scattering.The pulling force decreases with the increase of the axial distance for the sphere with a bigger k0a.More pulling force areas with wider axial regions can be formed by AV beams using a bigger-sized annular transducer.The theoretical results demonstrate the feasibility of generating the pulling force along the axes of AV beams using the experimentally applicable circular array of planar transducers,and suggest application potentials for multi-position stable object manipulations in biomedical engineering.

Second harmonic magnetoacoustic responses of magnetic nanoparticles in magnetoacoustic tomography with magnetic induction

Due to the unique magnetic, mechanical and thermal properties, magnetic nanoparticles(MNPs) have comprehensive applications as the contrast and therapeutic agents in biomedical imaging and magnetic hyperthermia. The linear and nonlinear magnetoacoustic responses determined by the magnetic properties of MNPs have attracted more and more attention in biomedical engineering. By considering the relaxation time of MNPs, we derive the formulae of second harmonic magnetoacoustic responses(2H-MARs) for a cylindrical MNP solution model based on the mechanical oscillations of MNPs in magnetoacoustic tomography with magnetic induction(MAT-MI). It is proved that only the second harmonic magnetoacoustic oscillations can be generated by MNPs under an alternating magnetic excitation. The acoustic pressure of the 2H-MAR is proportional to the square of the magnetic field intensity and exhibits a linear increase with the concentration of MNPs. Numerical simulations of the 2H-MAR are confirmed by the experimental measurements for various magnetic field intensities and solution concentrations using a laser vibrometer. The favorable results demonstrate the feasibility of the harmonic measurements without the fundamental interference of the electromagnetic excitation, and suggest a new harmonic imaging strategy of MAT-MI for MNPs with enhanced spatial resolution and improved signal-to-noise ratio in biomedical applications.

High-performance inverters based on ambipolar organic-inorganic heterojunction thin-film transistors

This work reports on the integration of organic and inorganic semiconductors as heterojunction active layers for high-performance ambipolar transistors and complementary metal-oxide-semiconductor(CMOS)-like inverters.Pentacene is employed as a p-type organic semiconductor for its stable electrical performance,while the solution-processed scandium(Sc)substituted indium oxide(ScInO)is employed as an n-type inorganic semiconductor.It is observed that by regulating the doping concentration of Sc,the electrical performance of the n-type semiconductor could be well controlled to obtain a balance with the electrical performance of the p-type semiconductor,which is vital for achieving high-performance inverters.When the doping concentration of Sc is 10 at.%,the CMOS-like logic inverters exhibit a voltage gain larger than 80 and a wide noise margin(53%of the theoretical value).The inverters also respond well to the input signal with frequency up to 500 Hz.

Phase-Dislocation-Mediated High-Dimensional Fractional Acoustic-Vortex Communication

With unlimited topological modes in mathematics,the fractional orbital angular momentum(FOAM)demonstrates the potential to infinitely increase the channel capacity in acoustic-vortex(AV)communications.However,the accuracy and stability of FOAM recognition are still limited by the nonorthogonality and poor anti-interference of fractional AV beams.The popular machine learning,widely used in optics based on large datasets of images,does not work in acoustics because of the huge engineering of the 2-dimensional point-by-point measurement.Here,we report a strategy of phase-dislocation-mediated high-dimensional fractional AV communication based on pair-FOAM multiplexing,circular sparse sampling,and machine learning.The unique phase dislocation corresponding to the topological charge provides important physical guidance to recognize FOAMs and reduce sampling points from theory to practice.A straightforward convolutional neural network considering turbulence and misalignment is further constructed to achieve the stable and accurate communication without involving experimental data.We experimentally present that the 32-point dual-ring sampling can realize the 10-bit information transmission in a limited topological charge scope from±0.6 to±2.4 with the FOAM resolution of 0.2,which greatly reduce the divergence in AV communications.The infinitely expanded channel capacity is further verified by the improved FOAM resolution of 0.025.Compared with other milestone works,our strategy reaches 3-fold OAM utilization,4-fold information level,and 5-fold OAM resolution.Because of the extra advantages of high dimension,high speed,and low divergence,this technology may shed light on the next-generation AV communication.

Oxidation behaviors of Co-Al-W-0.1B superalloys in a long-term isothermal exposure at 900~?C

Co-Al-W-0.1B superalloys have been isothermally oxidized at 900℃ for 1000,5000 and 10000 h in order to investigate their oxidation behaviors.The oxide layers and morphologies were characterized by X-ray diffraction and scanning electron microscopy combined with energy-dispersive spectroscopy.After1000 h exposure,a Co3W/γ zone,an Al2O3layer,a mixture of Co,Al,W oxides layer and a CoO layer are established on the substrate alloys.After extended oxidation,a discontinuous Al2O3layer in Co-9Al-8W-0.1B and Co-9Al-9W-0.1B alloys leads to an additional mixed oxide layer on the substrate instead of the Co3W/γ zone.The oxide layers that form on the Co-9Al-8W-0.1B and Co-9Al-9W-0.1B alloys are much thicker than those on the Co-9Al-11W-0.1B alloy,and continuously thicken during oxidation.The higher content of W is beneficial to improving the oxidation resistance as it facilitates a faster formation of Co3Was well as Al2O3.