High-energy Peak Research Articles

Porous W/N/C nanoframework: A trifunctionally effective cathodic electrocatalyst for rechargeable Zn-Air/iodide hybrid battery

Different from the conventional Zinc-Air batteries which only involves oxygen reduction and evolution (ORR/OER) in the cathode, the cathode of rechargeable zinc–air/iodide hybrid batteries (ZAIHBs), with the addition of I− species, involves I− electrooxidation (IOR) during charging and oxygen/iodate reduction (ORR and IDR) during discharging. This work reports the synthesis of a hierarchically porous tungsten-based nitrogen-doped carbon framework (W/N/C) with abundant WNx active sites and numerous ultrafine WN nanoclusters and explores their application as a trifunctional IOR/ORR/IDR electrocatalyst for ZAIHBs. The formation mechanism of ZIF-8-derived W/N/C framework as well as its structural and compositional features were investigated. The catalyst demonstrates high trifunctional catalytic activity and robust durability towards IOR/ORR/IDR in alkaline condition, owing to the uniform copresence of the numerous sub-nanometer-sized WN nanoclusters and the abundant single atom WNx sites in the hierarchically structured carbon framework. When applied in homemade ZAIHBs, it revealed a high peak energy density (141.9 mW cm−2) and remarkable cycling stability (65 h), outperforming the commercial Pt/C catalysts. This work demonstrates the multi-functional electrocatalytic activity of tungsten-based non-noble metal electrocatalyst for high-performance ZAIHBs.

Dissecting the broad-band emission from γ-ray blazar PKS 0735+178 in search of neutrinos

ABSTRACT The origin of the diffuse flux of TeV–PeV astrophysical neutrinos is still unknown. The γ-ray blazar PKS 0735+178, located outside the 90 percent localization region at 2.2° from the best-fitting IC-211208A event, was found to be flaring across all wavebands. In addition to leptonic synchrotron (SYN) and SYN self-Compton (SSC) emission, we invoke photohadronic (pγ) interactions inside the jet to model the spectral energy distribution (SED) and neutrino emission. We analyse the 100 d γ-ray and X-ray data and 10 d around the neutrino event is chosen to generate the broad-band SED. The temporal light curve indicates that the source was in a high state in optical, UV, γ-ray, and X-ray frequencies during the neutrino detection epoch. In the one-zone lepto-hadronic model, the SSC photons do not provide enough seed photons for pγ interactions to explain the neutrino event. However, including an external photon field yields a neutrino event rate of 0.12 in 100 d, for the IceCube detector, using physically motivated values of the magnetic field, an external photon field peaking at optical wavelength, and other jet parameters. The radiation from secondary electrons at X-ray energies severely constrains the neutrino flux to a lower value than found in previous studies. Moreover, the flux of high-energy γ-rays at GeV energies from the decay of neutral pions is sub-dominant at the high-energy peak of the SED, suggesting a higher correlation of neutrinos flux with X-ray flux is plausible.

Monolithic tapered Yb-doped fiber chirped pulse amplifier delivering 126 μJ and 207 MW femtosecond laser with near diffraction-limited beam quality

In this work, a high-energy and high peak power chirped pulse amplification system with near diffraction-limited beam quality based on tapered confined-doped fiber (TCF) is experimentally demonstrated. The TCF has a core numerical aperture of 0.07 with core/cladding diameter of 35/250 µm at the thin end and 56/400 μm at the thick end. With a backward-pumping configuration, a maximum single pulse energy of 177.9 μJ at a repetition rate of 504 kHz is realized, corresponding to an average power of 89.7 W. Through partially compensating for the accumulated nonlinear phase during the amplification process via adjusting the high order dispersion of the stretching chirped fiber Bragg grating, the duration of the amplified pulse is compressed to 401 fs with a pulse energy of 126.3 μJ and a peak power of 207 MW, which to the best of our knowledge represents the highest peak power ever reported from a monolithic ultrafast fiber laser. At the highest energy, the polarization extinction ratio and the M2 factor were respectively measured to be ~ 19 dB and 1.20. In addition, the corresponding intensity noise properties as well as the short- and long-term stability were also examined, verifying a stable operation of the system. It is believed that the demonstrated laser source could find important applications in, for example, advanced manufacturing and photomedicine.Graphical

57Fe Mössbauer Spectroscopy and X-ray Diffraction of Annealed Highly Metamict Perrierite: Activation Energy and Recrystallization Processes

This paper presents the results of 57Fe Mössbauer spectroscopy and X-ray diffraction analysis of highly metamict perrierite (REE,Ca,Th)4(Fe2+,Mg)2(Ti,Fe3+)3Si4O22 after annealing in argon from 673 to 1273 K for one hour. Radioactive elements in metamict minerals damage crystal structure on geologic time scales primarily due to recoil nuclei from α-decay of 238U, 232Th, 235U, and their daughter products. Metamict minerals are widely used in geochronology and can serve as natural analogs for the study of radiation effects in high-level nuclear waste. Analyses were performed on fragments of a perrierite sample collected from granitoids near Amherst, Virginia (USA). Electron microprobe and gamma-ray spectrometry recorded Fe concentrations of 4.7 wt.% and Th and U concentrations of 0.64 and 0.06 wt.%, respectively. The calculated total absorbed α-dose was 7.8 × 1015 α-decay mg−1. The Mössbauer spectrum of the untreated sample can be fitted to two Fe2+ and two Fe3+ doublets in octahedral coordination with a relative ΣFe2+/ΣFe of 0.63. For samples annealed at 1173 K and 1273 K, spectra show a decrease in the total contribution of Fe2+ to 0.58 due to dehydroxylation associated with the simultaneous oxidation of post-metamict Fe2+ to Fe3+. In the examined perrierite, Fe2+ occurs in structural positions B and C(1). The broad, predominant Fe3+ doublet observed in the spectrum of the unannealed sample splits into two components at 973 K interpreted to represented positions C(1) and C(2) in the perrierite structure. The Mössbauer spectra show a prominent decrease in the width of the high-energy absorption peak representing Fe2+ components with increasing temperature. The variation in the width of this peak versus the annealing temperature seems to be an indicator of thermally induced recrystallization. Based on the exponential dependence of the derivative function of the parameter with the inverse temperature and using an Arrhenius plot, an activation energy (EA) of 0.73 eV was determined for thermally-induced recrystallization. Corresponding XRD data show progressive recrystallization with increasing annealing temperature. The XRD pattern of the fragment annealed at 1273 K indicates that highly metamict perrierite recrystallized to the pre-metamict state that can be indexed to the C2/m space group.

INVESTIGATION ON CHARACTERISTICS OF TURBOCHARGER VIBRATION USING DIGITAL SIGNAL PROCESSING TECHNIQUE

High-speed rotating machinery such as a turbocharger is always subject to imperfection that causes strong vibrations. The problem is that there is no way of knowing the root causes of these vibrations by just using our five senses. This problem is significant since unattended heavy vibrations on a turbocharger may lead to permanent damage and a high cost to fix them. The purpose of this study is to investigate the vibration characteristics of a running turbocharger using the Digital Signal Processing (DSP) method, hence identifying the sources of such vibration profiles. In this context, DSP is the process of taking vibration signals that have been digitized and then mathematically manipulating them. Usually, it involves converting time domain data into frequency domain using Fast Fourier Transform (FFT). To identify the causes of turbocharger vibrations, a literature review was done by studying past research of the same methodology. An experiment was conducted by running the machine at different speeds and operating conditions across the choke, regular, and surge conditions. Vibrational data was obtained by mounting a piezoelectric accelerometer onto the compressor housing. The data was then later post-processed using MATLAB to execute FFT. The result shows high energy peaks at various frequencies associated with an unbalanced rotor, oil whirl, looseness, misalignment, and surging noise. On this basis, it is concluded that the vibrational data of a turbocharger can be identified using DSP.

Superior bifunctional oxygen electrocatalysts based on Co2MnO4 with mixed site occupancy, Mn-rich surfaces and twin defects

Co/Mn-based spinel oxides are promising electrocatalysts for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), however, it is challenging to achieve high activities for ORR and OER simultaneously in one composition. Here, we report Co2MnO4 (C2M) with Mn-rich surfaces and abundant twin defects synthesized by a simple coprecipitation and annealing route, which exhibits excellent ORR activity (half-wave potential E1/2 = 0.830 V), long ORR durability (91% current retained after 12 h-chronoamperometry test at 0.45 V vs. RHE) and a low ΔE = 0.767 V between E1/2 and E10 mA/cm2 in alkaline electrolyte, which enables its excellent performances in rechargeable Zn-air batteries showing a high peak energy density of 136 mW/cm2 and a large specific capacity of 809.4 mAh/gZn. Combining comprehensive experimental investigations and DFT simulations, we reveal that the Mn-rich surfaces benefit bridge adsorption of O2 to promote the 4-electron reaction pathway in ORR, and the mixed site occupancy in the crystal structure induces Mn/Co-O orbital hybridizations to form an impurity energy level in the band gap to facilitate charge transfer. Furthermore, the bifunctional performance and the ORR durability can be further enhanced by acid treatment to show a lower ΔE = 0.750 V and to retain 98.5% ORR current in 12 h. This work provides not only a promising bifunctional electrocatalyst but also a new perspective of exploring simple synthesis method suitable for mass-producible electrocatalysts with highly active surfaces.

Anisotropy-Driven Crystallization of Dimensionally Resolved Quasi-1D Van der Waals Nanostructures.

Unusual behavior in solids emerges from the complex interplay between crystalline order, composition, and dimensionality. In crystals comprising weakly bound one-dimensional (1D) or quasi-1D (q-1D) chains, properties such as charge density waves, topologically protected states, and indirect-to-direct band gap crossovers have been predicted to arise. However, the experimental demonstration of many of these nascent physics in 1D or q-1D van der Waals (vdW) crystals is obscured by the highly anisotropic bonding between the chains, stochasticity of top-down exfoliation, and the lack of synthetic strategies to control bottom-up growth. Herein, we report the directed crystallization of a model q-1D vdW phase, Sb2S3, into dimensionally resolved nanostructures. We demonstrate the uncatalyzed growth of highly crystalline Sb2S3 nanowires, nanoribbons, and quasi-2D nanosheets with thicknesses in the range of 10 to 100 nm from the bottom-up crystallization of [Sb4S6]n chains. We found that dimensionally resolved nanostructures emerge from two distinct chemical vapor growth pathways defined by diverse covalent intrachain and anisotropic vdW interchain interactions and controlled precursor ratios in the vapor phase. At sub-100 nm nanostructure thicknesses, we observe the hardening of phonon modes, blue-shifting of optical band gaps, and the emergence of a new high-energy photoluminescence peak. The directional growth of weakly bound 1D ribbons or chains into well-resolved nanocrystalline morphologies provides opportunities to develop ordered nanostructures and hierarchical assemblies that are suitable for a wide range of optoelectronic and quantum devices.

DFT + U Simulation of the X-ray Absorption Near-Edge Structure of Bulk UO2 and PuO2.

Hubbard U-corrected density functional theory within the periodic boundary condition model in the WIEN2k code is used to simulate the actinide LIII and O K edge X-ray absorption near-edge structure (XANES) for UO2 and PuO2. Spin-orbit coupling effects are included, as are possible excitonic effects using supercells with a core hole on one of the atoms. Our calculations yield spectra in excellent agreement with previous experiments and superior to previous simulations. Density of states analysis reveals the mechanism behind the XANES peaks: the main contribution to the U/Pu LIII edges comes from the U/Pu d states hybridized with O p states, while as expected, the O p states primarily determine the O K edges of both UO2 and PuO2. The O K edges also feature O p hybridizing with U/Pu d and f states in the low-energy region and with U/Pu s and p states for the higher-energy peaks.

Origins of the high-energy electroluminescence peaks in long-wavelength (∼495–685 nm) InGaN light-emitting diodes

We investigate the unexpected high-energy electroluminescence (EL) peaks observed in long-wavelength InGaN light-emitting diodes (LEDs) with ground state emission peaks between ∼495 and 685 nm by studying the EL spectra of LEDs with varying quantum well (QW) thicknesses and indium compositions. In addition to the ground state emission, two high-energy emission peaks were observed in the LEDs with thick QWs and high indium compositions. The less energetic high-energy emission peak (2.4–2.6 eV) is attributed to the optical transitions involving excited states. Factors influencing the excited state transitions, such as the QW thickness and indium compositions, were also examined by simulations to better understand the occurrence of these transitions. The more energetic high-energy emission peak (2.8–3.1 eV) originates from V-defect sidewalls and was verified through micro-photoluminescence measurements. Identification of the high-energy emission peaks is essential as it enables targeted epitaxial or growth optimizations to minimize or eliminate these undesirable emission peaks. This work demonstrates the importance of using thin QWs to suppress the unwanted high-energy emissions due to excited state transitions and V-defect sidewalls for long-wavelength InGaN LEDs.

On the prospect of identifying visible emissions from optical measurements of self-assembled QDs

The work presented here focuses on the optical properties of molecular beam epitaxy-grown self-organized InAs quantum dots (QDs). Under low excitation power densities, the photoluminescence (PL) spectrum of the structure under study exhibits a double-peak profile, which has been related to the optical emission from the dots. To properly argue for or against explaining a high energy peak as being the result of different-sized QDs or excited state emissions, a comparative study of the optical properties of a set of two grown QD samples was employed. The laser power dependence of the linearity of the PL intensities of the QD transitions was shown to be very useful in determining the possible origins of the PL sub-bands detectable in a double-peak emission from an ensemble of self-organized QDs. Indeed, the change in the linearity of the dot-luminescence intensity with the increase of the excitation density could give helpful information about the active confinement states from which the dots are emitting. On the other hand, despite the use of very low excitation power densities, the optical measurements of the studied structure have revealed an appearance of a PL signal relating to the radiative emission from the first excited state of the dots. A random pathway of carrier capture by the intrinsic levels of the QDs is thought to be the most likely cause of this aspect.

Energy Distribution of Sputtered Atoms Explored by SRIM Simulations

The energy of the sputtered atoms is important to control the microstructure and physical properties of thin films. In this work, we used the SRIM program to simulate the energy of sputtered atoms. We analyzed the energy distribution functions (EDFs) and the average energies of the atoms in different spatial directions for a range of target materials and Ar ion energies. The results were compared to the analytical equations for EDFs derived by Sigmund and Thompson and with experimental data from the literature. The SRIM simulations give realistic EDFs for transition metals, but not for elements lighter than Si. All EDFs show a low-energy peak positioned close to one-half of the surface binding energy and a high-energy tail decreasing as approximately E−2. We analyzed the characteristics of EDFs, specifically, the position of low- and high-energy peaks, FWHM, and the energy tail, with respect to the ion energy and position of the element in the periodic table. The low-energy peak increases with atomic number for elements within each group in the periodic table. Similar changes were observed for FWHM. For the period 5 and 6 elements, additional broad high-energy peaks were observed at emission angles above 45° when sputtered by Ar ions with 300 eV and also in some heavier elements when bombarded by 600 eV and 1200 eV ions. The transition metals in groups 4, 5, and 6 in periods 5 and 6 have the highest average energies, while the lowest average energies have elements in group 11. The results of simulations show that the average energies of sputtered atoms were inversely proportional to the sputtering yield, i.e., the higher the sputtering yield, the lower the average energy of sputtered atoms. We established an empirical equation for transition metals to estimate the average energy of sputtered atoms from the sputtering yield. The angular distribution of the average atom energy depends on the atomic number. Transition metals with 22 < Z < 72 have an anisotropic energy distribution, with the highest average energies in the 40°–70° range. For the elements in group 11, the angular distribution of the average energies is more isotropic.

Automatic Recognition of Vertical-Line Pulse Train from China Seismo-Electromagnetic Satellite Based on Unsupervised Clustering

Pulse signals refer to electromagnetic waveforms with short duration and high peak energy in the time domain. Spatial electromagnetic pulse interference signals can be caused by various factors such as lightning, arc discharge, solar disturbances, and electromagnetic disturbances in space. Pulse disturbance signals appear as instantaneous, high-energy vertical-line pulse trains (VLPTs) on the spectrogram. This paper uses computer vision techniques and unsupervised clustering algorithms to process and analyze VLPT on very-low-frequency (VLF) waveform spectrograms collected by the China Seismo-Electromagnetic Satellite (CSES) electric field detector. First, the waveform data are transformed into time–frequency spectrograms with a duration of 8 s using the short-time Fourier transform. Then, the spectrograms are subjected to grayscale transformation, vertical line feature extraction, and binarization preprocessing. In the third step, the preprocessed data are dimensionally reduced and fed into an unsupervised K-means++ clustering model to achieve automatic recognition and labeling of VLPTs. By recognizing and studying VLPT, not only can interference be recognized, but the temporal and spatial locations of these interferences can also be determined. This lays the foundation for identifying VLPT sources and gaining deeper insights into the generation, propagation, and characteristics of electromagnetic radiation.

Time Evolution of Plasmonic Features in Pentagonal Ag Clusters.

In the present work, we apply recently developed real-time descriptors to study the time evolution of plasmonic features of pentagonal Ag clusters. The method is based on the propagation of the time-dependent Schrödinger equation within a singly excited TDDFT ansatz. We use transition contribution maps (TCMs) and induced density to characterize the optical longitudinal and transverse response of such clusters, when interacting with pulses resonant with the low-energy (around 2-3 eV, A1) size-dependent or the high-energy (around 4 eV, E1) size-independent peak. TCMs plots on the analyzed clusters, Ag25+ and Ag43+ show off-diagonal peaks consistent with a plasmonic response when a longitudinal pulse resonant at A1 frequency is applied, and dominant diagonal spots, typical of a molecular transition, when a transverse E1 pulse is employed. Induced densities confirm this behavior, with a dipole-like charge distribution in the first case. The optical features show a time delay with respect to the evolution of the external pulse, consistent with those found in the literature for real-time TDDFT calculations on metal clusters.

High peak power and energy scaling in the mid-IR chirped-pulse oscillator-amplifier laser systems.

The paper introduces a new route towards the ultrafast high laser peak power and energy scaling in a hybrid mid-IR chirped pulse oscillator-amplifier (CPO-CPA) system, without sacrificing neither the pulse duration nor energy. The method is based on using a CPO as a seed source allowing the beneficial implementation of a dissipative soliton (DS) energy scaling approach, coupled with a universal CPA technique. The key is avoiding a destructive nonlinearity in the final stages of an amplifier and compressor elements by using a chirped high-fidelity pulse from CPO. Our main intention is to realize this approach in a Cr2+:ZnS-based CPO as a source of energy-scalable DSs with well-controllable phase characteristics for a single-pass Cr2+:ZnS amplifier. A qualitative comparison of experimental and theoretical results provides a road map for the development and energy scaling of the hybrid CPO-CPA laser systems, without compromising pulse duration. The suggested technique opens up a route towards extremely intense ultra-short pulses and frequency combs from the multi-pass CPO-CPA laser systems that are particularly interesting for real-life applications in the mid-IR spectral range from 1 to 20 μm.

Raman spectroscopy of bimagnon and trimagnon excitations and rotonlike points in a distorted triangular lattice antiferromagnet

We investigate the experimental signatures of Raman spectroscopy of bi- and tri-magnon excitations in the distorted triangular lattice antiferromagnets alpha-LCr2O4 (L=Sr, Ca). We utilize spin wave theory to analyze the nearly 120 degree spin-3/2 spiral ordered antiferromagnetic ground state to compute the single-magnon density of states, single-magnon dispersion, and bimagnon and trimagnon Raman spectra (polarized and unpolarized). It is found that Raman scattering is capable of capturing the effect of the rotonlike M and M' points on the bimagnon Raman spectrum. Our calculation confirms the connection between single-magnon rotonlike excitation energy and bimagnon Raman excitation spectrum observed experimentally. The roton energy minimum in momentum space is half of the energy of a bimagnon excitation signal. The experimental magnetic Raman scattering result displays two peaks which have a Raman shift of 15 meV and 40 meV, respectively. Theoretical modeling and analysis of the experimental spectrum of alpha-SrCr2O4 within our distorted Heisenberg Hamiltonian lattice suggests that the low-energy peak at 15 meV is associated with the bimagnon excitation, whereas the high-energy peak around 40 meV is primarily a trimagnon excitation. Based on our fitting procedure we propose a new set of magnetic interaction parameters for alpha-SrCr2O4. These parameters reproduce not only the experimental Raman spectrum, but also the inelastic neutron scattering response (including capturing high energy magnon branches). We also compute the unpolarized bimagnon and trimagnon Raman spectra for alpha-CaCr2O4. Furhtermore, we found that the polarization sensitivity of Raman spectrum can be utilized to distinguish the bi- and tri-magnon excitation channels.

The Effect of the Laser Light Polarization on the Generation of Proton Ignitor Beam

In this study, the effect of laser light polarization (linear polarization (LP) and circular polarization (CP)) on the shape of the proton energy spectrum and its energy cut-off is explored. The obtained results from 1D3V PIC simulation showed that two different acceleration mechanisms including target normal sheath acceleration (TNSA) and radiation pressure acceleration (RPA) are dominant. It is found that for the amplitude of a = 27 and pulse duration 333 fs when the laser polarization is changed from LP to CP, the electron heating is reduced which caused the generation of the multi-peak quasi-monoenergetic proton beam. Then by applying the 1D3T hydrodynamic code, the potential of the aforementioned proton beam with a high peak energy 510 MeV to irradiation on pre-compressed DT capsule was examined. Finally, the proton ignition energy threshold at a distance of 0.78 cm between the proton source and pre-compressed DT fuel capsule was investigated. (The threshold proton ignition energy is 15.52 kJ)

Storm-driven variations in depositional environments modify pyrite sulfur isotope records

The sulfur isotopic composition of marine pyrite (δ34Spyr) is one of the major geochemical tools to reconstruct global changes in Earth's surface environment. Storm-driven variations in depositional environments, however, can play key roles in modifying the δ34Spyr signal. Here we present δ34Spyr values in a complete Holocene muddy storm deposit on the East China coastal plain, which is identified by comprehensive analyses of sediment components, organic matter composition, bulk organic carbon isotopic ratios, carbon and oxygen isotopic ratios of carbonates and trace element concentrations. We find that positive (+5.8‰ to +15.8‰) and negative (−9.0‰ to −19.7‰) δ34Spyr values were preserved in two successive intervals of the muddy storm deposit (ca. 62 cm long), corresponding to the high-energy storm peak phase (HESPP) and the waning-energy late storm phase (WELSP), respectively. We propose that the 34S enrichment in pyrite from the HESPP is most likely due to a combination of storm reworking of sediments and high sedimentation rates, which involves various physical and chemical processes leading to the accumulation of 34S-enriched pyrite, such as oxidation of near-surface sulfides, reduced exchange of sulfate between sediment pore fluids and the overlying water column, and/or input of excess reactive iron minerals. In contrast, lower sedimentation rates and limited sedimentary remobilization during the WELSP allow the isotopic signal of early-formed 32S-enriched pyrite to be preserved. The striking shift in δ34Spyr values, therefore, reflects a dramatic change in the local depositional environment between the HESPP and WELSP, suggesting that non-steady-state deposition induced by storm activity facilitates the formation of isotopically “heavy” pyrite. This sharp shift can be further generalized as a characteristic feature of δ34Spyr values in storm deposits. Our work highlights the critical impact of weather- and climate-event-driven depositional variations on δ34Spyr values, adding to the growing evidence emphasizing the local environmental and diagenetic controls on these records.

Multiwavelength monitoring of the nucleus in PBC J2333.9−2343: the giant radio galaxy with a blazar-like core

ABSTRACT PBC J2333.9−2343 is a giant radio galaxy at z = 0.047 with a bright central core associated to a blazar nucleus. If the nuclear blazar jet is a new phase of the jet activity, then the small orientation angle suggests a dramatic change of the jet direction. We present observations obtained between 2018 September and 2019 January (cadence larger than three days) with Effeslberg, SMARTS-1.3m, ZTF, ATLAS, Swift, and Fermi-LAT, and between 2019 April and 2019 July (daily cadence) with SMARTS-1.3 m and ATLAS. Large (>2 ×) flux increases are observed on time-scales shorter than a month, which are interpreted as flaring events. The cross correlation between the SMARTS-1.3 m monitoring in the NIR and optical shows that these data do not show significant time lag within the measured errors. A comparison of the optical variability properties between non-blazars and blazars AGN shows that PBC J2333.9−2343 has properties more comparable to the latter. The SED of the nucleus shows two peaks, that were fitted with a one-zone leptonic model. Our data and modelling show that the high energy peak is dominated by External Compton from the dusty torus with mild contribution from Inverse Compton from the jet. The derived jet angle of 3 deg is also typical of a blazar. Therefore, we confirm the presence of a blazar-like core in the centre of this giant radio galaxy, likely a Flat Spectrum Radio Quasar with peculiar properties.

Polyaniline–Cobalt Hexacyanoferrate Composites as High‐Performance Cathodes for Zn‐Ion Hybrid Supercapacitor

Zn‐based hybrid supercapacitors (ZHSCs) have received increasing attention in recent research, due to their high electrochemical performance and low cost. Herein, a composite cathode is developed based on polyaniline (PANI) and cobalt hexacyanoferrate (CoHCF), exhibiting excellent electrochemical performance. The results showed that PANI is coated on CoHCF, thereby enhancing the electrical conductivity and Zn2+ transport kinetics. As a result, the as‐prepared materials demonstrate remarkable specific capacitance (741.7 F g−1 at 5 mV s−1), good cycling durability (86.15% capacitance retention over 5000 cycles at 10 A g−1), high peak energy density (312 Wh kg−1 at 500 W kg−1), and superior power density (75 294 W kg−1 at 25 Wh kg−1). The excellent electrochemical performance confirms that PANI–CoHCF composites are promising cathode candidates for ZHSCs in practical applications.

Non-isothermal crystallization behavioral analysis of detonation sprayed Fe-based amorphous coating

The non-isothermal crystallization behaviors of a detonation sprayed Fe-based amorphous coating (AMC) was systematically investigated through differential scanning calorimetry, X-ray diffraction and transmission electron microscopy. The crystallization mechanism of the Fe-based AMC is analyzed and discussed in detail using a combination of the Kissinger-Akahira-Sunose and Ozawa-Flynn-Wall approaches, as well as the local Avrami exponent. The results indicate that the crystallization process of the Fe-based AMC is affected by the non-isothermal heating rate with a significantly higher initial crystallization activation energy (917.7 kJ mol−1) and first peak activation energy (479.6 kJ mol−1), indicating excellent thermal stability. After four stages of amorphous crystallization and phase transformation, the crystallization products of the equilibrium state were primarily composed of 78.5%, 11.3%, and 5.8% (Cr, Fe)23(C, B)6, α-Fe phases, and FeMo2B2 phases, respectively.