Huiqiu Deng (邓辉球)

Hydrogen embrittlement (HE) can lead to the unintentional fracture of large engineering materials, resulting in severe economic losses and safety hazards. It is critical to explore economical and scalable solutions to overcome the challenges of HE. In this work, the HE resistances of four face-centered cubic (FCC) concentrated solid solution alloys (CSAs), including NiFe20, NiCoCr, NiCoCrFe, NiCoCrFeMn, and pure Ni were comprehensively investigated and compared by using TDS, EBSD and TEM. It was found that Fe and Cr element can effectively inhibit the solubility of deuterium in the CSAs and alleviate the HE behaviors. In contrast, Mn element significantly increases the solubility of deuterium and caused brittle fractures. Tensile experiments were performed to compare the HE sensitivity of CSAs. The tensile strength of pure Ni and NiFe20 alloys decreased after deuterium charged, whereas the tensile …

Zirconium hydride (ZrH2) is an ideal neutron moderator material. However, radiation effects significantly alter its properties, subsequently impacting its behavior and the lifespan of the reactor. The threshold energy of displacement is an important quantity of the number of radiation defects produced, which helps us to predict the evolution of radiation defects in ZrH2. Molecular dynamics (MD) and ab initio molecular dynamics (AIMD) are two main methods for calculating the threshold energy of displacement. MD simulations with empirical potentials often fail to accurately depict the transitional states that lattice atoms must surpass to reach an interstitial state. Additionally, the AIMD method does not afford large-scale calculation, posing a computational challenge beyond the scope of density functional theory simulations. Machine learning potentials are renowned for their high accuracy and efficiency, making them an …

The short–range and mid–range structural features, as well as thermodynamic properties of a LiCl–AlCl3 mixed molten salt at 873 K, were investigated as a function of AlCl3 concentration using ab initio molecular dynamics methods. In all solutions, the short-range structure of Al3+ reveals a regular tetrahedral [AlCl4]– unit. These tetrahedral units exist in isolation within dilute AlCl3 solution and polymerize into dimers or trimers through Al–Cl–Al bridge bonds in concentrated solutions. The dynamic dissociation analysis of Al3+ and Li+ structures indicates that the Al–Cl bond considerably stronger than Li–Cl bond. The polymerization of the [AlCl4]– units leads to the dissociation of the Li+ coordination shells into freely isolated cations. Furthermore, we examined changes in density, self-diffusion coefficient, and ionic conductivity with varying AlCl3 concentration in terms of thermodynamic properties. The conductivity …

The search for catalysts with high activity in hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and oxygen reduction reaction (ORR) processes has been an eminent avenue for mankind to acquire clean and renewable energy. To this end, more than a dozen transition metal (TM)-doped AlN systems have been investigated based on first-principles calculations in this study. Our calculation results show that Co@ AlN-V Al can be operated as OER/ORR bifunctional catalysts with η OER/η ORR of 0.5/0.33 V. Meanwhile, Pd@ AlN-V Al exhibits the most excellent catalytic activity due to the very low HER overpotential (η H E R= 0.009 V). Furthermore, the origin of the high activity for Co@ AlN-V Al in the OER/ORR process is illustrated by stating the d-band center and descriptor (φ). The Bader charge, the crystal orbital Hamiltonian population (COHP), spin density, and density of states (DOS) are …

The electronic stopping power and charge state of protons and helium ions irradiating iron under both channeling and off-channeling geometries are studied by first-principles molecular dynamics. Using real-time time-dependent density functional theory, the inner-electron excitation of iron under ion irradiation is explored. The calculated electronic stopping powers, which take into account the effects of inner-electron excitation, were found to be in good agreement with experimental data. To further investigate the charges attracted by the projectiles moving in iron, we introduced a modified method to decompose the charges into the occupations of the respective projectile orbitals. When the projectile ion moves along off-channeling trajectories, the orbital distribution of the charges attracted by protons is found to be unstable, while that of helium ions remains relatively stable. However, it is worth noting that the orbital …

The microscopic mechanism of the effect of alloying element on the shock behavior for alloy materials is still limited. In this work, based on our developed Finnis–Sinclair (F–S) interatomic potential of Mg-Y alloy, using nonequilibrium molecular dynamics (NEMD) simulations, we gave new insights into the role of alloying element Y in dynamic deformation of Mg-xat.% Y (x= 1, 3, 6, 8 and 10) alloys, and further revealed the deformation mechanisms of these solid solution alloys, which is dependent on the compositions of Y and the crystallographic orientations. The results confirm that the lattice instability caused by Y atoms results in the reduced yield stress. Under shock along the [0001] direction, the improved plasticity is mainly attributed to the increasing amorphous activity and decreasing amorphous annihilation rate with Y additions, but the other mechanisms, eg, the dislocation nucleation and phase transition, are …

U-10Zr metallic fuel (alloys of U with 10 wt% Zr) is considered as a potential candidate for fast reactors due to its excellent performance. However, the fission gas swelling has a significant impact on its properties and prevents it from reaching higher burnup. To gain a deeper understanding of the fission gas swelling mechanism, molecular dynamics simulations based on interatomic potentials are underway to fill the key knowledge gaps. In this work, two modified embedded-atom method (MEAM) potentials are developed for the U-Zr system with Xe, one for α-U-Zr and δ-UZr2, and the other for γ-U-Zr. The parameters of the potentials are determined by fitting the material properties from experiments or density functional theory (DFT) calculations. It is verified that the potentials can reproduce well the lattice constants, elastic constants, point defects, surface energy, and the melting point of U. In addition, the lattice …

The most stable cluster of barium titanate (BaTiO3) is used to functionalize the surface and ends of (5,5) single wall boron nitride, silicon carbide, and zinc oxide nanotubes under water environment. The geometry optimization and the effect on the electronic and structural properties are investigated thorough density functional theory calculations. The BaTiO3 cluster is chemisorbed on the surface of the nanotubes enhancing the reactivity and polarity which favors the solubility and dispersion on aqueous solutions. The nanotubes are predicted to preserve their semiconductor character with narrower gap, with the consequent improvement on the conductivity. The work function for the functionalized nanotubes, respect to the pristine systems, is increased, appropriate features for field emission applications.