Hard tungsten carbide (WC) with brittle behavior is frequently applied for mechanical purposes. Here, ultralarge elastic bending deformation is reported in defect-rare WC [0001] nanowires; the tested bending strain reaches a maximum of 20% ± 3.33%, which challenges the traditional understanding of this material. The lattice analysis indicates that the dislocations are confined to the inner part of the WC nanowires. First, the high Peierls-Nabarro barrier hinders the movement of the locally formed dislocations, which causes rapid dislocation aggregation and hinders long-range glide, resulting in a dense distribution of the dislocation network. In this case, the loading is dispersed along multiple points, which is then balanced by the complex internal mechanical field. In the compressive part, the possible dislocations predominantly emerge in the (0001) plane and mainly slip along the axial direction. The disordered shell first forms at the tensile side and prevents the generation of nanocracks at the surface. The novel lattice kinetics make WC nanowires capable of substantial bending strain resistance. Analytical results of the force-displacement (F-d) curves based on the double-clamped beam model exhibit an obvious nonlinear elastic characteristic, which originates fundamentally from the lattice anharmonicity under moderate stress.

Vapor-solid-solid (VSS) process has recently received continued attention as an alternative to grow Si nanowire. In comparison with common vapor-liquid-solid (VLS) growth with liquid catalyst, VSS growth can prevent the catalyst species from incorporating into nanowires with deep-level impurity, and achieve the compositionally abrupt interfaces by restraining the so-called "reservoir effect". However, despite the huge advances in experimental observations with in situ electron microscopy, VSS growth still remains much less understood in theory. Here, we developed a general mass-transport-limited kinetic model to describe the VSS growth process of Si nanowires by considering three surface diffusion processes and a slow interface diffusion process, where the former determines the atoms supplies way, while the latter dominates the growth of nanowires. The present model is not only well consistent with the available experimental data of Si nanowire, but also gives a clear physical image for the successive side-to-side ledge flow VSS growth.

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An analytical approximate technique for nonlinear problems, namely the homotopy analysis method, is employed to propose an approach for the aeroelastic system of a two-dimensional airfoil with a cubic nonlinearity. The frequency and amplitude of the limit cycle oscillation are expanded as power series of an embedding parameter. A series of algebraic equations governing the coefficients of the series are then derived. All the equations are linear except the first one. This provides us with a simple iteration scheme to seek high-order approximations. The frequency and amplitude of the limit cycle oscillation are obtained with a high degree of accuracy. It turns out that the frequency is independent of the coefficient of the cubic nonlinearity, and that the amplitude is in inverse proportion to the square root of this coefficient.