Designing g-C_(3)N_(4)/N-Rich Carbon Fiber Composites for High-Performance Potassium-Ion Hybrid Capacitors

Potassium-based energy storage devices(PEDS)are considered as hopeful candidates for energy storage applications because of the abundant potassium resources in nature and high mobility in the electrolyte.although carbon materials show great potential for potassium-ion storage,poor rate performance,and unsatisfactory cycle lifespan in existing carbon-based PIBs anode,it also cannot match the dynamics and stability of the capacitor cathode.Nitrogen doping has been proven to be a effective modification strategy to improve the electrochemical performance of carbon materials.Hence,we prepare carbon nanofibers and g-C_(3)N_(4)composites with high nitrogen contents(19.78 at%);moreover,the sum of pyrrolic N and pyridinic N is up to 59.51%.It achieves high discharge capacity(391 m Ah g^(-1)at0.05 A g^(-1)),rate capacity(141 m Ah g^(-1)at 2 A g^(-1)),and long cycling performance(201 m Ah g^(-1)at 1 A g^(-1)over 3000 cycles)when as an anode for PIBs.Furthermore,it can deliver promising discharge capacity of132 m Ah g^(-1)at 0℃.Moreover,as battery anode for potassium-ion hybrid capacitors(PIHC)device with an active carbon cathode,it delivers energy/power density(62 and 2102 W kg^(-1))as well as high reversible capacity(106 m Ah g^(-1)at 1 A g^(-1)).

Defect engineering on the electronic and transport properties of one-dimensional armchair phosphorene nanoribbons

We investigate the electronic and transport properties of one-dimensional armchair phosphorene nanoribbons(APNRs) containing atomic vacancies with different distributions and concentrations using ab initio density functional calculations. It is found that the atomic vacancies are easier to form and detain at the edge region rather than a random distribution through analyzing formation energy and diffusion barrier. The highly local defect states are generated at the vicinity of the Fermi level, and emerge a deep-to-shallow transformation as the width increases after introducing vacancies in APNRs.Moreover, the electrical transport of APNRs with vacancies is enhanced compared to that of the perfect counterparts. Our results provide a theoretical guidance for the further research and applications of PNRs through defect engineering.

Thickness-dependent structural stability and transition in molybdenum disulfide under hydrostatic pressure

Understanding the physical mechanism of structural stability and transition in various polytypes of layered transition metal dichalcogenides under the external stimulus is of crucial importance for their new applications.Here,we investigate the thickness-dependent structural properties of MoS2 under the condition of hydrostatic pressure in terms of bond relaxation and thermodynamics considerations.For both types of MoS2 structures,we find that the transition and metallization are significantly modulated by hydrostatic pressure and the number of layers.We establish a pressure-size phase diagram to address the transition mechanism.Our study not only provides insights into the thickness-dependent structural properties of MoS2,but also shows a theoretical guidance for the design and fabrication of MoS2-based devices.

Decay constants of B_(c)(nS) and B_(c)^(*)(nS)^(*)

The decay constants of the low lying S-wave B_(c)mesons,i.e.B_(c)(nS) and B_(c)^(*)(nS) with n ≤3,are calculated in the nonrelativistic quark model.The running coupling of the strong interaction is taken into account,and the uncertainties due to varying parameters and losing Lorentz covariance are considered carefully.As a byproduct,the decay constants of the low lying S-wave charmonium and bottomium states are given in the appendixes.

The ■ tetraquark states and the structure of X(2239) observed by the BESⅢ collaboration

We investigate the mass spectrum of the■tetraquark states in the relativized quark model.By solving the Schrodinger-like equation with the relativized potential,the masses of S-and P-wave■tetraquarks are obtained.The screening effects are also taken into account.It is found that the resonant structureX(2239)observed in thee+e-→K+K-process by the BESIII collaboration can be assigned as a P-wave 1--■tetraquark state.Furthermore,the radiative transition and the strong decay behavior of this structure are also estimated,which can provide helpful information for future experimental searches.

Mass spectrum and strong decays of strangeonium in a constituent quark model

In this work we calculate the mass spectrum of strangeonium up to the 3D multiplet within a nonrelativistic linear potential quark model.Furthermore,using the obtained wave functions,we also evaluate the strong decays of the strangeonium states with the ^3P_0 model.Based on our successful explanations of the well established states φ(1020) , φ(1680) , h_1(1415) , f'_2(1525) ,and φ_3(1850) ,we further discuss the possible assignments of strangeonium-like states from experiments by combining our theoretical results with observations.It is found that some resonances,such as f_2(2010) and f_2(2150) ,listed by the Particle Data Group,and X(2062) and X(2500) ,newly observed by BESIII,may be interpreted as strangeonium states.The possibility of φ(2170) as a candidate for φ(3S) or φ(2D) cannot be excluded.We expect our results to provide useful references for looking for the missing s\bar{s} states in future experiments.

Further study ofΩ^(*)|1P_(3/2^(-))within a chiral quark model

In our previous studies,we analyzed the two-body strong decays of the low-lyingΩbaryon states within a chiral quark model.The results showed that the mass,total width,and two body decayΩ(2012)→■could be well reproduced with the spin-parity J^(P)=3/2^(-)stateΩ^(*)|1P_(3/2^(-))>classified in the quark model.Stimulated by the new observations of the three-body decay processΩ(2012)^(-)→■at Belle,in the present study,we further investigate the three-body strong decayΩ^(*)|1P_(3/2^(-))>→■within the chiral quark model.It is found that theΩ^(*)|1P_(3/2^(-))>has a sizeable decay rate into the three-body final states■.When consideringΩ^(*)|1P_(3/2^(-))>as theΩ(2012)resonance,the predicted ratio■is close to the upper limit 11%measured by the Belle Collaboration in 2019;however,it is too small to be comparable to the recent measurement 0.97±0.24±0.07.In addition,the coupled-channel effects on the bare three-quark stateΩ^(*)|1P_(3/2^(-))>from nearby channels■are studied.Our theoretical results show that the coupled-channel effects onΩ^(*)|1P_(3/2^(-))>are not very large,and the molecular component is no more than 30%.To clarify the nature ofΩ(2012)resonance,precise measurements on the ratio■are needed,and further investigation on the effects of coupled channels is recommended.

Production of d_(NΩ)dibaryon in kaon induced reactions

In this paper,we propose to investigate the d_(NΩ)dibaryon production in the K-p-→d_(NΩ)≡0 process by utilizing a kaon beam with a typical momentum of approximately 10 GeV,which may be available at COMPASS,OKA@U-70,and SPS@CERN.The cross sections for K-p-→d_(NΩ)=O are estimated,and in particular,the magnitude of the cross sections is evaluated to be several hundred nanobarns at Pk=20 GeV.Considering that the d_(NΩ)dibaryon dominantly decays into≡Λand≡∑,we also estimate the cross sections for K-p→≡0Λ≡0 and K~p→≡-∑+≡0,where the d_(NΩ)dibaryon can be observed in the invariant mass distributions of≡0Λand≡-∑+,respectively.

碳纤维中可控修饰FeV_(2)S_(4)及其高容量长寿命储钠研究

拥有高比容量的金属硫化物作为负极材料在钠离子电池(SIBs)领域备受关注.FeV_(2)S_(4)作为一种典型的金属硫化物,由于体积变化大,存在容量衰减快、稳定性差的问题.本文利用氧化石墨烯(GO)实现了对FeV_(2)S_(4)纳米粒子尺寸和分布的调控,使其更好地包裹在碳纳米纤维(CNFs)中,从而制备了FeV_(2)S_(4)@GO@CNF.FeV_(2)S_(4)@GO@CNF负极与表面拥有更多粒子的FeV_(2)S_(4)@CNF负极相比具有更优异的Na+存储性能.FeV_(2)S_(4)@GO@CNF用于钠离子电池负极时,200次循环(0.1 A g^(−1))后容量仍然可保持在411 mA h g^(−1),500次循环(1 A g^(−1))后可保持在227 mA h g^(−1).此外,在0℃下,经过150次循环(0.1 A g^(−1))后,仍可以输出170.2 mA h g−1的容量.以FeV_(2)S_(4)@GO@CNF作为负极,Na_(3)V_(2)(PO4)3/C作为正极的全电池在0.5 A g^(−1)下循环100次后,其容量达到164 mA h g^(−1).FeV_(2)S_(4)@GO@CNF表现出高比容量和稳定性,这是由于GO控制了FeV_(2)S_(4)的颗粒大小及其在CNFs中的分布,从而提高了FeV_(2)S_(4)@GO@CNF的稳定性.本研究为纳米CNF复合材料的制备提供了新思路.

使用NiS2作为硫源和前驱体合成Ni3S2@S纳米管用于高性能钠离子半/全电池（英文）

由于结构的多样性和丰富的自然储量,硫化镍是钠离子电池极具潜力的负极材料.然而,大体积膨胀和差的循环性能阻碍了它们的应用.引入中空结构和杂原子掺杂碳层是解决这些问题的有效方法.本文通过新颖的模板法制备了氮、硫共掺杂碳层包覆的Ni3S2纳米管(Ni3S2@NSCs).在退火过程中, NiS2既作为形成Ni3S2的前体又作为S掺杂的硫源.在S掺杂过程中没有使用额外的硫源,这表明合成过程具有原子经济性.作为钠离子半电池的阳极, Ni3S2@NSCs在0.1 A g^-1的电流密度下循环100次后表现出481 mA h g^-1的高放电容量,具有98.6%的优异容量保持率.此外,即使在5 A g^-1的高电流密度下,它们仍保持318 m A h g^-1的优异倍率性能.由Ni3S2@NSC阳极和Na3V2(PO4)3(NVP@C)阴极组装的钠离子全电池也具有优异的容量和循环稳定性.这些特征可归因于N, S共掺杂碳涂覆的中空结构.此结构可使电极和电解质之间充分接触,增强表面离子存储性能(电容效应),并改善电极材料的结构稳定性.

Effective shape-controlled synthesis of gallium selenide nanosheets by vapor phase deposition

The controlled synthesis of large and uniform gallium selenide(GaSe)crystals is crucial for its various applications based on the attractive properties of this emerging material.In this work,vapor phase growth of high-quality monolayer GaSe nanosheets with multiple shape and size is achieved by tuning the Ga/GaSe ratio in the precursor.A theoretical model based on density functional theory calculations and kinetic Wulff construction theory describe the observed shape evolution of the GaSe nanosheets.Results show that the Ga/Se ratio plays a critical role in the evolution of the domain shape and size.Moreover,the as-grown GaSe nanosheets show improved performance with photoresponse time less than 0.7 ms and responsibility up to 3,000 AW.This study presents a previously unexplored strategy for the controlled growth of two-dimensional(2D)GaSe nanosheets for promising applications in next-generation optoelectronics.

The Buchdahl stability bound in Eddington-inspired Born-Infeld gravity

We give the Buchdahl stability bound in Eddington-inspired Born-Infeld (EiBI) gravity. We show that this bound depends on an energy condition controlled by the model parameter κ. From this bound, we can constrain κ≤10^8m^2 if a neutron star with a mass around 3M⊙ is observed in the future. In addition, to avoid the potential pathologies in EiBI, a Hagedorn-like equation of state associated with κ at the center of a compact star is inevitable, which is similar to the Hagedorn temperature in string theory.

A possible explanation of the threshold enhancement in the process e^+e^-→∧■

Inspired by the recent measurement of the process e^+e^-→ΛΛ^-,we calculate the mass spectrum of the Φ meson with the GI model.For the excited vector strangeonium states Φ(3S,4S,5S,6S)and Φ(2D,3D,4D,5D),we investigate the electronic decay width with the Van Royen-Weisskopf formula,and the partial widths of theΛΛ^-,■^-(*)■^-+,and Σ+(*)Σ^- -(*)decay modes with the extended quark-pair creation model.We find that the electronic decay width of the D-wave vector strangeonium is about 3~8 times larger than of the S-wave vector strangeonium.Around 2232 MeV,the partial decay width of theΛΛ^-mode can be up to several MeV for Φ(33S1),while the partialΛΛ^-decay width of Φ(23D1)is O(10^-3)keV.If the threshold enhancement reported by the BESIII collaboration arises from the strangeonium meson,this state is very likely the?(33S1)state.We also note that theΛΛ^- and Σ+Σ^--partial decay widths of the states Φ(33D1)and Φ(43S1)are several MeV,which is sufficient to be observed in future experiments.

Toward discovering low-lying P-wave excited∑_(c)baryon states

In this study,by combining the equal spacing rule with recent observations of Ω_(C)(X)and Ξ_(C)(X)baryons,we predict the spectrum of the low-lying λ-mode 1P-wave excited ∑_(c) states.Furthermore,their strong decay properties are predicted using the chiral quark model and the nature of∑_(c)(2800)is investigated by analyzing the invariant mass spectrum.The ∑_(c)(2800)structure observed in the Λ_(c)πmass spectrum was found to potentially arise from two overlapping P-wave resonances,∑_(c)(2813)3/2^(-)and ∑_(c)(2840)5/2^(-).These resonances have similar decay widths of Г〜40 MeV and predominantly decay into the Λ_(c)π channel.The ∑_(c)(2755)1/2^(-)state is likely to be a very narrow state with a width of Г〜15 MeV,with its decays almost saturated by the Λ_(c)π channel.Additionally,evidence of the Lc(2755)1/2^(-)resonance as a very narrow peak may be seen in the Λ_(c)π invariant mass spectrum.The other two P-wave states,∑_(c)(2746)1/2^(-)and ∑_(c)(2796)3/2^(-),are relatively narrow states with similar widths of「〜30 MeV and predominantly decay into ∑_(c)π and ∑^(*)_(c)π,respectively.This study can provide useful references for discovering these low-lying P-wave states in forthcoming experiments.

Strong decays of the low-lying bottom strange baryons

In this work,the strong decay behaviors of theλ-mode low-lyingΞ_(b) andΞ^(’)_(b) baryons are investigated within the 3 P0 model.Our results suggest that all of the low-lying 3F statesΞ_(b)(2 S),Ξ_(b)(1 P),andΞ_(b)(1 D)have small decay widths of less than 20 MeV,and these states have good potentials to be observed in theΞ^(’)_(b)πandΞ^(’)_(b)^(*)πinvariant masses.Further,most of the 6F multiplets are relatively narrow and may decay into theΞ_(b)π,Ξ^(’)_(b)π,Ξ^(’)_(b)^(^(*))π,andΔbK final states.Considering the masses and strong decay behaviors,we can assign the newly observedΞ_(b)(6100)resonance as theΞ_(b)(1 P)state with J^(P)=3/2-and interpret theΞ_(b)(6227)structure as the J^(P)=3/2-Ξ^(’)_(b)(1 P)state with a proper mixing angle.We expect that our predictions for these excited bottom strange baryons will provide helpful information for future experimental research.