Search

Nowadays, the issue of electromagnetic pollution has become increasingly prominent, underscoring the critical importance of developing high-performance microwave absorbers. This study put forwards the synthesis process of two-dimensional (2D) FeCo/Co8FeS8/C carbon nanosheets, wherein CoSO4 and FeCl3 serve as inorganic salt templates, and dopamine functions as the carbon source. FeCo alloy nanoparticles and Co8FeS8 nanoparticles are loaded on the surface of the carbon layer. 2D structure forms the conductive network, which proves advantages in establishing efficient electronic channels and minimizing conduction losses. The carbon component increases the dielectric constant of the composite and improves its impedance matching, and the FeCo alloy provides a certain ML. The synergistic effect between these components significantly contributes to the exceptional microwave absorption performance of the composites. Accordingly, the minimum reflection loss (RLmin) of FeCo/Co8FeS8/C composite reaches −47.4 dB, its effective absorption bandwidth (EAB) reaches 5.3 GHz. In particular, CST confirms that radar cross-section reduction value of FeCo/Co8FeS8/C composite can reach 20.2 dB m2 in the range of −90°

The rafting of the microstructure of Ni-based superalloys significantly deteriorates the mechanical properties. According to the plastic rafting model based on the dislocation mechanism, the directional atomic diffusion induced by the interaction between the alloying atom and the interfacial dislocation is critical to the evolution of the rafting microstructure. In the present work, the interactions between the alloying atom and dislocation core in both matrix γ phase and the precipitate γ′ phase are investigated by using a first principles method in combination with the semi-discrete variational Peierls-Nabarro dislocation model. We show that the alloying atoms Al, Cr, Co, Mo, Ru, Ta, W, Re lower the (edge for Cr and Co) dislocation core energy in the γ phase, indicating that the alloying atoms are attractive to the dislocation core. For the γ′ phase, Cr, Mo, Ta, W, Re raise whereas Co and Ru lower the dislocation core energy, i.e., Cr, Mo, Ta, W, Re are repulsive but Co and Ru are attractive to the dislocation core. With the calculated interaction between the alloying atoms and the dislocation core, the influence of these alloying elements on the rafting of the superalloy is discussed.

By employing high-throughput first-principles calculations, the segregation capacity of fifteen widely used metallic alloying elements (viz., Be, Mn, Co, Cr, Ni, Al, Mo, W, Mg, Ta, Nb, Sb, Sn, Zr, and Bi) at ∑3 grain boundary in low alloy ferritic steel, as well as their impact on grain boundary stability, interfacial separation work, and other properties, were systematically investigated. The findings reveal that, for alloying atoms Sb, Sn, Bi, Nb, and Zr, whose size is notably larger than that of the matrix Fe atoms, the effect of strain energy minimization in segregation is comparable to that of chemical energy minimization. Furthermore, the impact of strain energy minimization is closely related to the volume of the alloying atoms both at the solid solution sites in the crystal and at the segregation sites at the grain boundary. Thus, the segregation of large alloy atoms on the grain boundaries can be predicted by atomic volume of each segregation site, which can provide valuable insights for the development of new alloys and for grain boundary engineering.

Peierls stress (τp) of face-centered-cubic (FCC) structures from the Peierls-Nabarro (PN) model calculation is extremely sensitive to the input parameters including the shear modulus (μ), Poisson's ratio (ν) and generalized stacking fault energy (GSFE), which makes the model not a very reliable tool for the prediction of τp because uncertainties occur inevitably in the theoretical calculation or experimental measurements of these input parameters. In the present work, we scrutinized systematically the sensitivity of τps of the FCC metals to the input parameters within the framework of semi-discrete variational PN (SVPN) model. We showed that τp oscillates drastically with varying input parameters. The period of the oscillation is associated with the dependence of the distance between the two partials of the extended dislocation (D) on μ, ν and GSFE while the amplitude of the oscillation is modulated by the dependence of the half-width of the partial dislocation (ζ) on these input parameters. Based on the explored origin of the oscillation, a modified SVPN model is proposed to relieve the sensitivity of τp on the input parameters. The Peierls stresses evaluated with the modified SVPN model are in general agreement with the available experimental values for all the FCC metals.

Determining the competition between the {110}⟨111⟩, {112}⟨111⟩ and {123}⟨111⟩ slip systems in body-centered cubic (BCC) metals is important to understand their mechanical properties. In this paper, the unstable stacking fault energy (γus) and Peierls stress (σp) of the three slip systems of a series of BCC metals are calculated in order to evaluate the competition among them. We find that γus of BCC metals is proportional to (B+G)/a2/3, where B, G and a are the bulk modulus, shear modulus and lattice constant, respectively. The calculations of γuss predict that the {110}⟨111⟩ dislocation slip is prior to the {112}⟨111⟩ and {123}⟨111⟩ slips, however, γus may not be used to identify the priorities of the latter two slips because γuss of these two slip systems are too close to each other. According to σps, the mobility of dislocations decreases in the sequence of {110}⟨111⟩, {112}⟨111⟩, {123}⟨111⟩ for all the metals considered except for K. Noticeably, it is shown that γus and σp are not monotonically related to each other.