Ce基金属玻璃的力学弛豫

采用动态热机械分析技(DMA),对Ce70Al10Cu20块体金学弛豫行为进行了研究.在?70°C-70°C温度间内,测了等温条件下频率依赖动态学弛豫谱.结果发现在Tg(Tg=68°C)附近及Tg温度以下,材料内耗值与频率之间在不同频率范围存在相反变化.在低频部分,内耗随着频率增加而降低,在高频部分,随着频率增加内耗值增加.初步分析认为这由于非晶合金材料存在着两种不同弛豫机制造成,且这两种机制和金中存在软硬不同结构单元有关系.

Deep Learning Hybrid Model for Lithium-Ion Battery Aging Estimation and Prediction

The degradation process of lithium-ion batteries is intricately linked to their entire lifecycle as power sources and energy storage devices,encompassing aspects such as performance delivery and cycling utilization.Consequently,the accurate and expedient estimation or prediction of the aging state of lithium-ion batteries has garnered extensive attention.Nonetheless,prevailing research predominantly concentrates on either aging estimation or prediction,neglecting the dynamic fusion of both facets.This paper proposes a hybrid model for capacity aging estimation and prediction based on deep learning,wherein salient features highly pertinent to aging are extracted from charge and discharge relaxation processes.By amalgamating historical capacity decay data,the model dynamically furnishes estimations of the present capacity and forecasts of future capacity for lithium-ion batteries.Our approach is validated against a novel dataset involving charge and discharge cycles at varying rates.Specifically,under a charging condition of 0.25 C,a mean absolute percentage error(MAPE)of 0.29%is achieved.This outcome underscores the model's adeptness in harnessing relaxation processes commonly encountered in the real world and synergizing with historical capacity records within battery management systems(BMS),thereby affording estimations and prognostications of capacity decline with heightened precision.

中国散裂中子源缪子谱仪及其应用展望

中国散裂中子源二期升级工程包含建设缪子实验终端和一条表面缪子束线,并规划未来建设负缪子束线和衰变缪子束线.表面缪子束线预计2029年建成出束,有望成为我国首个人造缪子源实验平台.缪子自旋弛豫/旋转/共振谱学和负缪子X射线分析谱学是缪子源平台最重要的应用技术,分别在材料磁性分析和元素成分无损测量方面具有独特优势,在磁性、超导、新能源、科技考古等多学科领域取得了大量瞩目成果.本文围绕中国散裂中子源缪子实验终端及其谱仪建设,分别介绍了缪子自旋弛豫/旋转/共振谱学和负缪子X射线分析谱学的基本原理、特色优势,以及基于缪子实验终端的谱仪物理设计和应用展望;最后展望了该缪子实验终端未来的缪子束线规划和更多样化的应用场景.

Molecular dynamics simulation of relationship between local structure and dynamics during glass transition of Mg_7Zn_3 alloy

The rapid solidification process of Mg7Zn3 alloy was simulated by the molecular dynamics method. The relationship between the local structure and the dynamics during the liquid-glass transition was deeply investigated. It was found that the Mg-centered FK polyhedron and the Zn-centered icosahedron play a critical role in the formation of Mg7Zn3 metallic glass. The self-diffusion coefficients of Mg and Zn atoms deviate from the Arrhenius law near the melting temperature and then satisfy the power law. According to the time correlation functions of mean-square displacement, incoherent intermediate scattering function and non-Gaussian parameter, it was found that the β-relaxation in Mg7Zn3 supercooled liquid becomes more and more evident with decreasing temperature, and the α-relaxation time rapidly increases in the VFT law. Moreover, the smaller Zn atom has a faster relaxation behavior than the Mg atom. Some local atomic structures with short-range order have lower mobility, and they play a critical role in the appearance of cage effect in theβ-relaxation regime. The dynamics deviates from the Arrhenius law just at the temperature as the number of local atomic structures begins to rapidly increase. The dynamic glass transition temperature （Tc） is close to the glass transition point in structure （TgStr）.

Investigation on Exciton Relaxation Kinetics of ZnCulnS/ZnSe/ZnS Quantum Dots by Time-Resolved Spectroscopy Techniques

The exciton relaxation kinetics of ZnCuInS/ZnSe/ZnS quantum dots （QDs） is investigated by time-resolved spectroscopy techniques in detail. Based on the rate distribution model, the wavelength-dependent emission dynamics shows that the intrinsic exciton, the exciton in the interface defect state and that in donor-acceptor pair state （DAPS） together participate in the photoluminescence process of QDs, and the whole emission process is mainly dependent on the DAPS emission. Transient absorption data show that the intrinsic exciton and the interface defect species maybe together appear after excitation and the intensity-dependent Auger recombination process also exists in QDs at high excitation intensity.

Evolution of distribution and content of water in cement paste by low field nuclear magnetic resonance

The low field nuclear magnetic resonance (NMR), as a nondestructive and noninvasive technique, was employed to investigate the water distribution and content in cement paste with different water-to-cement ratio (w/c ratio) during early and later hydration stages. From the water distribution spectrum deduced from relaxation time distribution in paste, it is suggested that the water fills in the capillary pores at initial period, and then diffuses to the mesopores and gel pores in hydration products with the hydration proceeding. The decrease of peak area in water distribution spectrum reflects the transformation from physically bound water to chemically bound water. In addition, based on the connection between relaxation time and pore size, the relative content changes of water in various states and constrained in different types of pores were also measured. The results demonstrate that it is influenced by the formation of pore system and the original water-to-cement ratio in the paste. Consequently, the relative content of capillary water is dropped to less than 2% in the paste with low w/c ratio of 0.3 when being hydrated for 1 d, while the contents are still 16% and 36% in the pastes with w/c ratios of 0.4 and 0.5, respectively.

Hydrogen-bonded Intramolecular Charge Transfer Excited State of Dimethylaminobenzophenone using Time Dependent Density Functional Theory

Density functional theory and time-dependent density-functional theory have been used to investigate the photophysical properties and relaxation dynamics of dimethylaminobenzophe- none （DMABP） and its hydrogen-bonded DMABP-MeOH dimer. It is found that, in non- polar aprotic solvent, the transitions from So to S1 and S2 states of DMABP have both n→π and π→π＊ characters, with the locally excited feature mainly located on the C=O group and the partial CT one characterized by electron transfer mainly from the dimethylaminophenyl group to the C=O group. But when the intermolecular hydrogen bond C=O…H-O is formed, the highly polar intramolecular charge transfer character switches over to the first excited state of DMABP-MeOH dimer and the energy difference between the two low- lying electronically excited states increases. To gain insight into the relaxation dynamics of DMABP and DMABP-MeOH dimer in the excited state, the potential energy curves for con- formational relaxation are calculated. The formation of twisted intramolecular charge trans- fer state via diffusive twisting motion of the dimethylamino/dimethylaminophenyl groups is found to be the major relaxation process. In addition, the decay of the Si state of DMABP-MeOH dimer to the ground state, through nonradiative intermolecular hydrogen bond stretching vibrations, is facilitated by the formation of the hydrogen bond between DMABP and alcohols.

Ultrafast quasiparticle dynamics in spin-density-wave LaOFeAs single crystal

Ultrafast quasiparticle dynamics of single crystalline LaOFeAs were investigated by pump-probe measurement.The compound experiences structural and spin-density-wave(SDW)phase transitions at 150 K(TS1)and 130 K(TS2),respectively.The relaxation time of quasiparticles was somewhat temperature independent at high temperature but exhibited a sharp upturn at TS1and reached the maximum at approximately TS2.The remarkable slowing down of quasiparticle relaxation time is caused by the formation of energy gap.By employing the Rothwarf-Taylor model analysis,we found that there should be already energy gaps opening just below the structural transition.The magnitude of SDW gap was identified to be 72 meV.

Ultrafast exciton relaxation dynamics of PbS and core/shell PbS/CdS quantum dots

Optical properties and ultrafast exciton relaxation dynamics in PbS and core/shell PbS/CdS quantum dots(QDs) have been studied using UV-vis absorption and fluorescence spectroscopy as well as femtosecond(fs) transient absorption spectroscopy.The electronic absorption spectrum of the PbS QDs features broad absorption in the entire near IR-vis-UV region with a monotonic increase in intensity towards shorter wavelength.Relative to PbS,the absorption of the core/shell PbS/CdS QDs shows a slight blue shift in the 600?800 nm region,due to the decrease of the PbS crystal size caused by the synthetic process of the core/shell structure,and increased absorption near 400 nm due to the CdS shell.The PL of the PbS/CdS QDs was ~2.6 times more intense than that of the PbS QDs,due to surface passivation of PbS by CdS,and blue-shifted,attributable to smaller PbS size and thereby stronger quantum confinement in the core/shell QDs.Fs transient absorption measurements of both systems showed a strong transient absorption feature from 600 to 750 nm following excitation at 750 nm.The transient absorption decays can be fit to a biexponential with time constants of 8 and 100 ps for PbS and 6 and 80 ps for PbS/CdS.The amplitude and lifetime of the fast component were excitation intensity dependent,with the amplitude increasing more than linearly with increasing excitation intensity and the lifetime decreasing with increasing intensity.The fast decay is attributed to exciton-exciton annihilation and it occurs more readily for the PbS/CdS than the PbS QDs,which is attributed to a lower density of trap states in the core/shell QDs,as supported by their stronger PL.

High Efficiency Four-Wave Mixing with Relaxation Coupling of Longitude-Optical Phonons in Semiconductor Quantum Wells

The time-dependent analysis of four-wave mixing(FWM) has been performed in four-level double semiconductor quantum wells(SQWs) considering the cross-coupling of the longitude-optical phonons(LOP) relaxation. It is shown that both the amplitude and the conversion efficiency of the FWM field enhance greatly with the increasing strength of cross-coupling of LOP relaxation. Interestingly, a double peak value of the conversion efficiency is obtained under a relatively weak single-photon detuning considering the LOP coupling. When the detuning becomes stronger,the double peaks turn into one peak appearing at the line respect to the about equality two control fields. The results can be interpreted by the effect of electromagnetically induced transparency and the indirect transition. Such controlled high efficiency FWM based on the cross-coupling LOP may have potential applications in quantum control and communications.

Glassy magnetic ground state in layered compound MnSb_(2)Te_(4)

As a sister compound of MnBi_(2)Te_(4),the highquality MnSb_(2)Te_(4) single crystals are grown via solid-state reaction where prolonged annealing and narrow temperature window play critical roles on account of its thermal metastability.Single-crystal X-ray diffraction(SCXRD)analysis on MnSb_(2)Te_(4) illustrates a crystal model that is isostructural to MnBi_(2)Te_(4),consisting of Te-Sb-Te-Mn-Te-Sb-Te septuple layers(SLs)stacking in an ABC sequence.However,MnSb_(2)Te_(4) reveals a more pronounced cation intermixing in comparison with MnBi_(2)Te_(4),comprising 28.9(7)%Sb antisite defects on the Mn(3a)site and 19.3(6)%Mn antisite defects on the Sb(6c)site,which may give rise to novel magnetic properties in emerging layered MnBi_(2)Te_(4)-family materials.Unlike the antiferromagnetic(AFM)nature in MnBi_(2)Te_(4),MnSb_(2)Te_(4) exhibits a glassy magnetic ground state below 24 K and can be easily tuned to a ferromagnetic state under a weak applied magnetic field.Its magnetic hysteresis,anisotropy,and relaxation process are investigated in detail via static and dynamic magnetization measurements.Moreover,anomalous Hall effect as a p-type conductor is demonstrated with transport measurements.This work grants MnSb_(2)Te_(4) a possible access to the future exploration of exotic quantum physics by removing the odd/even layer number restraint in realizing quantum transport phenomena in intrinsic AFM MnBi_(2)Te_(4)-family materials,as a result of the crossover between its magnetism and potential topology arising from the Sb-Te layer.