NaNbO₃-based lead-free energy storage ceramics are essential candidates for next-generation pulsed power capacitors, especially under the background of energy saving and environmental protection. However, the room-temperature antiferroelectric P phase of pure NaNbO₃ ceramics limits its further development in energy storage owing to the irreversible antiferroelectric to ferroelectric phase transition under electric fields. In this work, CaZrO₃ was introduced to NaNbO₃ ceramics to destroy the long-range polarization ordering but keep large antiferrodistortion, causing the formation of superparaelectric state with macrodomains, which can be identified by the refinement results of high-energy synchrotron X-ray diffraction, neutron diffraction and TEM results. Combined with the fine grains, dense and homogeneous microstructure, ergodic relaxation behaviors, and delayed polarization saturation, a high recoverable energy storage density of ~5.4 J/cm³ and efficiency of ~82% can be realized in 0.85NaNbO₃-0.15CaZrO₃ ceramics at an ultrahigh breakdown electric field of ~68 kV/mm. The results found in this work suggest that the supersparaelectric with non-cubic phase would be a good candidate for generating excellent dielectric energy storage properties.

Van der Waals (vdW) ferroelectric CuInP₂S₆ (CIPS) has attracted intense research interest due to its unique ferroelectric properties that make it promising for potential applications in flexible electronic devices. A mechanical mean, or so-called strain gradient engineering, has been proven as an effective method to modulate its ferroelectric properties, but the key parameter elastic constants C_ij has not been accurately measured. Here, we utilized nanoindentation and contact resonance atomic force microscopy (CR-AFM) techniques to measure the elastic modulus on the (001) plane of nanoscale phase separated CuInP₂S₆-In_4/3P₂S₆ (CIPS-IPS). The Young’s modulus of the CIPS was slightly less than that of the IPS. Density Functional Theory was introduced to obtain the accurate full elastic constant C_ij of CIPS and IPS, and we deduced their respective Young’s moduli, all of which are in good agreement with our experimental values. We further discovered the asymmetrical domain switching and proposed an ion-mediated domain switching model. The results provide a reliable experimental reference for strain gradient engineering in the phase field simulation in CIPS-IPS.

Supercapacitors (SCs) have drawn growing attention due to their advantages in fast charge/discharge over batteries. Benefiting from their prominent electrical conductivity and metal-like characteristics, transition metal nitrides have emerged as promising electrode materials for SCs. Traditional ways to prepare metal nitrides through ammonolysis are inconvenient and induce severe environmental pollution. Herein, we report a facile synthetic method toward heterogenous Ni₃N-Co₂N_0.67/nitrogen-doped carbon (Ni₃N-Co₂N_0.67/NC) hollow nanoflower via pyrolyzing NiCo-TEOA (triethanolamine) complex precursor applying urea as nitrogen source. Electrochemical tests demonstrate that the Ni₃N-Co₂N_0.67/NC nanoflower delivers good specific capacitance (1582 F g^-1 at 1 A g^-1) and steady cycle performance (83.79% after 5000 cycles). Moreover, the as-assembled Ni₃N-Co₂N_0.67/NC//AC cell can reach a peak energy density of 32.4 W h kg^-1 at a power density of 851.3 W kg^-1. The excellent electrochemical performance confirms extensive application prospects of the Ni₃N-Co₂N_0.67/NC nanoflower.

The need for specialty powder composition limits the processing of a wide range of alloy products via the laser powder bed fusion (LPBF) technique. This work extends the adaptability of the LPBF technique by fabricating the first-ever Fe-30Mn-6Si (wt.%) product for potential use as a biodegradable shape memory alloy (SMA). Different LPBF processing parameters were assessed by varying the laser power, scan speed, and the laser re-scan strategy to achieve a fully dense part. The microstructure was found to respond to the processing conditions. For example, the microstructure of the parts produced by the high linear energy density (LED) had a columnar and strong crystallographic texture, while in the low LED, the parts were almost equiaxed and had a weak texture. To explain the evolved microstructure, the thermal history of the LPBF products was computed using the finite element analysis (FEA) of the melt pool gathered from a single-track laser scan experiment. The FEA results showed a varying temperature gradient, cooling and solidification rates, and temperature profile as a function of LED. Then, the relationship of hardness between grain size, phases present, and crystallographic misorientation of the LPBF-built alloy was analysed with reference to a control alloy of similar composition but prepared by arc melting. This study validates the LPBF processability of Fe-Mn-Si SMA and provides a new insight into the influence of processing parameters on the formed microstructure and hardness.

Potassium-ion batteries (PIBs) are considered as promising alternatives to lithium-ion batteries due to the abundant potassium resources in the Earth’s crust. Establishing high-performance anode materials for PIBs is essential to the development of PIBs. Recently, significant research effort has been devoted to developing novel anode materials for PIBs. Alloy-based anode materials that undergo alloying reactions and feature combined conversion and alloying reactions are attractive candidates due to their high theoretical capacities. In this review, the current understanding of the mechanisms of alloy-based anode materials for PIBs is presented. The modification strategies and recent research progress of alloy-based anodes and their composites for potassium storage are summarized and discussed. The corresponding challenges and future perspectives of these materials are also proposed.

Chromium (Cr) plays a critical role in the corrosion resistance of conventional alloys via the formation of a dense Cr oxide-based passive film. However, the exact role of Cr in the corrosion of high-entropy alloys (HEAs) remains unclear. The effect of Cr content on the corrosion behavior of the ultrafine-grained Cr_xMnFeCoNi (x = 0, 0.6, 1, and 1.5) HEAs in the sulfuric acid solution (0.5 M H₂SO₄) was investigated. These HEAs were fabricated using a combination of mechanical alloying and spark plasma sintering. The electrochemical tests show that the passive film was more compact and thicker at higher Cr concentration, but the corrosion rate first increased and then decreased, due to the presence of the nanocrystalline-amorphous phase boundaries in the passive film. Long-time immersion tests show that the corrosion rate increased exponentially with the Cr content, due to the gradual accumulation of the galvanic corrosion.

Microporous structures have attracted significant attention in recent years. In particular, metal-organic frameworks (MOFs) and covalent organic frameworks (COFs) have received considerable attention due to their tailorable structures that offer a wide range of choices in terms of molecular building blocks. Due to their high tunability, these materials are considered as ideal host matrices for templating and encapsulating guest materials, particularly quantum dots (QDs). QDs are investigated heavily for various applications such as light-emitting diodes (LED), biosensors, catalysts, and solar cells due to their unique properties from the quantum confinement effect. However, one of the drawbacks of QDs is their tendency to aggregate and exhibit low stability due to their small size and kinetic trapping in nanoparticle form. This perspective highlights promising approaches to enhance the performance and stability of QDs by using microporous materials as an encapsulation layer. Additionally, potential mitigating strategies are discussed to overcome current challenges and improve the practicality of QDs embedded in microporous nanocomposites.