Potassium ion batteries (KIBs) are considered to be emerging and promising grid-scale energy storage devices owing to earth-abundant potassium resources. A pivotal limitation of KIBs is the sluggish diffusion kinetics and structural degradation resulting from huge mechanical stress during the repeated intercalation/deintercalation of K⁺ ions. Herein, we design open ZnSe/C nanocages composed of sub-10 nm nanoparticles with a multi-hierarchy stress-buffering effect for KIBs. The primary ultrafine nanoparticles, the secondary open structure and the tertiary hollow structure as stepwise stress-release hierarchies can effectively reduce diffusion-induced stresses and greatly enhance the structural integrity, which is further validated by detailed finite element simulation analysis. Meanwhile, the carbon layer can enhance the electronic conductivity and suppress the agglomeration of ZnSe nanoparticles, achieving high-rate performance. Owing to these merits, the open ZnSe/C nanocages deliver a high reversible capacity of 318 mA h g⁻¹ at 50 mA g⁻¹ as well as excellent cyclability of 189 mA h g⁻¹ up to 1000 cycles at 500 mA g⁻¹. This work provides new insight into excellent structural design with a multi-hierarchy stress-buffering effect for advanced potassium storage.

The fatigue property is significantly affected by the inner inclusions in steel. Due to the inhomogeneity of inclusion distribution in the micro-scale, it is not straightforward to quantify the effect of inclusions on fatigue behavior. Various investigations have been performed to correlate the inclusion characteristics, such as inclusion fraction, size, and composition, with fatigue life. However, these studies are generally based on vast types of steels and even for a similar steel grade, the alloy concept and microstructure information can still be of non-negligible difference. For a quantitative analysis of the fatigue life improvement with respect to the inclusion engineering, a systematic and carefully designed study is still needed to explore the engineering dimensions of inclusions. Therefore, in this study, three types of bearing steels with inclusions of the same types, but different sizes and amounts, were produced with 50 kg hot state experiments. The following forging and heat treatment procedures were kept consistent to ensure that the only controlled variable is inclusion. The fatigue properties were compared and the inclusions that triggered the fatigue cracks were analyzed to deduce the critical sizes of inclusions in terms of fatigue failure. The results show that the critical sizes of different inclusion types vary in bearing steels. The critical size of the spinel is 8.5 μm and the critical size of the calcium aluminate is 13.5 μm under the fatigue stress of 1200 MPa. In addition, with the increase of the cleanliness of bearing steels, the improvement of fatigue properties will reach saturation. Under this condition, further increasing of the cleanliness of the bearing steel will not contribute to the improvement of fatigue property for the investigated alloy and process design.

Two submerged entry nozzles (SENs) used for casting 1300 tons and 260 tons of Al-killed steel were dissected. Several parameters including block rate, nozzle clog angle, port width, and port height of the clogged nozzle were introduced to describe the geometry of clogs in the SENs based on the dissection; furthermore, a geometry model was established to describe the characteristics of the nozzle clogging of the SENs. A large-eddy simulation (LES) coupled with the volume of fraction (VOF) method was adopted to simulate the steel–slag interface’s interaction behavior. The vortex visualization and rotation magnitude were characterized by the Liutex method. Quantitatively, the influence of nozzle clogging resulted in block rates of 0% to 45.9% on the flow and vortex distribution in the mold, and the characteristics of the steel–slag interface fluctuation were well verified in the industrial experiment.