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Sodium-ion batteries (SIBs) are promising power sources due to the low cost and abundance of battery-grade sodium resources, while practical SIBs suffer from intrinsically sluggish diffusion kinetics and severe volume changes of electrode materials. Metal-organic framework (MOFs) derived carbonaceous metal compound offer promising applications in electrode materials due to their tailorable composition, nanostructure, chemical and physical properties. Here, we fabricated hierarchical MOF-derived carbonaceous nickel selenides with bi-phase composition for enhanced sodium storage capability. As MOF formation time increases, the pyrolyzed and selenized products gradually transform from a single-phase Ni 3 Se 4 into bi-phase NiSe x then single-phase NiSe 2 , with concomitant morphological evolution from solid spheres into hierarchical urchin-like yolk-shell structures. As SIBs anodes, bi-phase NiSe x @C/CNT-10h (10 h of hydrothermal synthesis time) exhibits a high specific capacity of 387.1 mAh/g at 0.1 A/g, long cycling stability of 306.3 mAh/g at a moderately high current density of 1 A/g after 2,000 cycles. Computational simulation further proves the lattice mismatch at the phase boundary facilitates more interstitial space for sodium storage. Our understanding of the phase boundary engineering of transformed MOFs and their morphological evolution is conducive to fabricate novel composites/hybrids for applications in batteries, catalysis, sensors, and environmental remediation.

Biphasic and multiphasic compounds have been well clarified to achieve extraordinary electrochemical properties as advanced energy storage materials. Yet the role of phase boundaries in improving the performance is remained to be illustrated. Herein, we reported the biphasic vanadate, that is, Na1.2V3O8/K2V6O16·1.5H2O (designated as Na0.5K0.5VO), and detected the novel interfacial adsorption–insertion mechanism induced by phase boundaries. First‐principles calculations indicated that large amount of Zn2+ and H+ ions would be absorbed by the phase boundaries and most of them would insert into the host structure, which not only promote the specific capacity, but also effectively reduce diffusion energy barrier toward faster reaction kinetics. Driven by this advanced interfacial adsorption–insertion mechanism, the aqueous Zn/Na0.5K0.5VO is able to perform excellent rate capability as well as long‐term cycling performance. A stable capacity of 267 mA h g−1 after 800 cycles at 5 A g−1 can be achieved. The discovery of this mechanism is beneficial to understand the performance enhancement mechanism of biphasic and multiphasic compounds as well as pave pathway for the strategic design of high‐performance energy storage materials. A novel interfacial adsorption–insertion mechanism is observed in biphasic Na1.2V3O8/K2V6O16·1.5H2O cathode for aqueous Zn‐ion battery. The numerous phase boundaries in biphasic material could absorb H+ and Zn2+ ions and facilitate the subsequent ions insertion process. This advanced mechanism could bring about enhanced capacity as well as faster reaction kinetics, thus leading to brilliant capacity and remarkable long‐term cycling stability.

The proton exchange membrane water electrolysis (PEMWE) is a promising technology for green hydrogen production. However, the wide‐spread application of PEMWE is hindered by the insufficient lifetime due to the degradation of anode material and structure, thus it is crucial first to understand the degradation mechanisms of PEMWE in actual applications. Generally, the degradation in anode side can be classified as chemical degradation and physical degradation. The considerable research focus from academia to enhance performance and durability is mainly by chemical methods. However, based on the experience from industry, many of the performance and lifetime limitations originated from physical factors. Herein, the impact of the physical characteristic of anode catalyst layer (ACL) on performance and durability of PEMWE is investigated, including cracking and deformation of ACL, swelling and creeping of ionomers, and detachment of catalyst particles. Finally, an outlook of future research focus is provided, based on the demand of developing efficient and durable industrial PEMWE devices. This article reviews the degradation mechanisms of PEMWE devices, focusing on the physical degradation of the anode catalyst layer. Specifically, it emphasizes issues including crack formation, ionomer swelling and creeping, and catalyst particle detachment. Highlighting the gap between academic research and industrial applications, it offers new insights for the development of efficient and durable PEMWE systems.

Currently, in the modification methods of K 0.5 Na 0.5 NbO 3 (KNN) ceramics to enhance their piezoelectric performance, key parameters such as Curie temperature are usually sacrificed. However, this trade-off limits the practical application of piezoelectric materials. Thus, addressing the trade-off between different performance parameters of piezoelectric ceramics becomes a major challenge.The present research employs the conventional solid phase sintering process and utilizes controlled doping of (Bi 0.5 Li 0.5 ) 0.9 Sr 0.1 ZrO 3 to regulate the ceramic system, K 0.44 Na 0.55 Ag 0.01 Nb 0.95 Ta 0.05 O 3 , at its polycrystalline phase boundary, thereby achieving a trade-off between performance. The ceramic samples of the system formed a compact solid solution with a single-phase perovskite structure and formed orthorhombic-tetragonal and rhombohedral-tetragonal polycrystalline phase boundaries at 0.02 ≤  x  ≤ 0.03 and 0.035 ≤  x  ≤ 0.06, respectively, according to XRD, SEM, and EDS analysis. The electrical properties test results show that in the multiphase coexisting region of x  = 0.035, the ceramics of the system show excellent electrical properties, respectively d 33  = 312 pC/N, k p  = 46.5%, ε r  = 1019, tanδ = 3.78%, P r  = 20.08 μC/cm 2 , E c  = 12.97 kV/cm, and T C  = 342 ℃. These results show that the properties of the system ceramics have reached a relatively high level, which provides an effective strategy for the practical application of piezoelectric ceramics.

Due to issues with Pb toxicity, there is an urgent need for high performance Pb-free alternatives to Pb-based piezoelectric ceramics. Although pure BaTiO3 material exhibits fairly low piezoelectric coefficients, further designing of such a material system greatly enhances the piezoelectric response by means of domain engineering, defects engineering, as well as phase boundary engineering. Especially after the discovery of a Ba(Zr0.2Ti0.8)O3–x(Ba0.7Ca0.3)TiO3 system with extraordinarily high piezoelectric properties (d33 > 600 pC/N), BaTiO3-based piezoelectric ceramics are considered as one of the promising Pb-free substitutes. In the present contribution, we summarize the idea of designing high property BaTiO3 piezoceramic through domain engineering, defect-doping, as well as morphotropic phase boundary (MPB). In spite of its drawback of low Curie temperature, BaTiO3-based piezoelectric materials can be considered as an excellent model system for exploring the physics of highly piezoelectric materials. The relevant material design strategy in BaTiO3-based materials can provide guidelines for the next generation of Pb-free materials with even better piezoelectric properties that can be anticipated in the near future.

In this paper, the S32101 duplex stainless steel welded joints were produced by a K-TIG welding system. The weld geometry parameters under different welding speeds were analyzed by combining the morphological characteristics of the keyhole. The microstructure and impact toughness of the base metal and weld metal zone under different welding speeds were studied. The experiment results show that the welding speed has quite an effect on the geometry profile of the weld. In addition, the characteristic parameters of the keyhole can effectively predict the geometry profile of the weld. The test results prove that the microstructure, Σ3 coincidence site lattice grain boundary, and phase boundary of ferrite and austenite have an effect on the impact property of the weld metal zone. When the proportion of the austenite, Σ3 coincidence site lattice grain boundary and random phase boundary increased, the impact property of the weld metal zone also increased.

Ternary of PZN- x PZT relaxation ferroelectric ceramics were successfully prepared by conventional solid-phase reaction. With the increase of Pb(Zr, Ti)O 3 (PZT) content, XRD analysis shows a gradual decrease of the inclusion crystal phase and a decrease in the formation of secondary phases such as Zn(NbO 3 ) 2 , leading to a more homogeneous phase structure, which is conducive to the improvement of piezoelectric properties. SEM images and densitometric measurements show a decrease in grain size and an increase in the degree of densification of the ceramics, which contributes to the enhancement of the ability of reorientation of electrical domains and thus the improvement of piezoelectric response. The 0.4PZN-0.6PZT ceramic samples demonstrate favorable grain sizes and exhibit the following optimal properties: T c = 272 ℃, d 33  = 570 pC/N, k p = 0.67, ε r  = 2175, and tan δ = 1.6%. However, the ceramic sample of 0.45PZN-0.55PZT has better comprehensive properties ( T c = 261 ℃, d 33  = 443 pC/N, k p = 0.59, ε r  = 1908, tan δ = 1.7%, P r = 37.3 µC/cm 2 , P s = 30.2 µC/cm 2 , E c = 1.08 kV/mm). PZN- x PZT ceramics are well known for their excellent dielectric, Curie temperature, phase boundary modulation, piezoelectric and ferroelectric properties and are widely used in sensors and transducers.

In order to explore the ceramic composition in the morphotropic phase boundary suitable for the high temperature electronic components, Pb(Sc 1/2 Nb 1/2 )O 3 -Pb(In 1/2 Nb 1/2 )O 3 -PbTiO 3 (PSN-PIN-PT) ceramics were designed and prepared by using the solid-state reaction method. Effect of the ceramic composition on the phase structure and electric properties of the PSN-PIN-PT ceramics were investigated. For 0.40PSN-(0.60- x )PIN- x PT( x  = 0.360, 0.375, 0.390, 0.405), the increase in the PT could improve gradually Curie temperature T c (262–292°C), but will reduce the phase transition T R-T (94–181 °C). Maximum of piezoelectric coefficient d 33 (578 pC/N) could be obtained in the 0.40PSN-0.21PIN-0.39PT ceramics, together with large residual polarization P r (~36.7 µC/cm 2 ) and high coercive field E c (~9.3 kV/cm). These performances make the PSN-PIN-PT ceramics have great potential applications in the high temperature device. Graphical Abstract Highlights It shows the degree of influence of different contents of PSN endmembers and PIN endmembers on the ternary phase of ceramics. The ceramic with high phase transition temperature and high Curie temperature is designed, and the gap between the two is narrowed. While taking good temperature performance into account, the ceramic obtains good piezoelectric performance near the quasi-homogeneous phase boundary.

In the present hyper-scaling era, memory technology is advancing owing to the demand for high-performance computing and storage devices. As a result, continuous work on conventional semiconductor-process-compatible ferroelectric memory devices such as ferroelectric field-effect transistors, ferroelectric random-access memory, and dynamic random-access memory (DRAM) cell capacitors is ongoing. To operate high-performance computing devices, high-density, high-speed, and reliable memory devices such as DRAMs are required. Consequently, considerable attention has been devoted to the enhanced high dielectric constant and reduced equivalent oxide thickness (EOT) of DRAM cell capacitors. The advancement of ferroelectric hafnia has enabled the development of various devices, such as ferroelectric memories, piezoelectric sensors, and energy harvesters. Therefore, in this review, we focus the morphotropic phase boundary (MPB) between ferroelectric orthorhombic and tetragonal phases, where we can achieve a high dielectric constant and thereby reduce the EOT. We also present the role of the MPB in perovskite and fluorite structures as well as the history of the MPB phase. We also address the different approaches for achieving the MPB phase in a hafnia material system. Subsequently, we review the critical issues in DRAM technology using hafnia materials. Finally, we present various applications of the hafnia material system near the MPB, such as memory, sensors, and energy harvesters.

Controlling the properties of piezoelectric thin films is a key aspect for designing highly efficient flexible electromechanical devices. In this stud）~ the crystallographic phenomena of PbZr1-xTixO3 （PZT） thin films caused by distinguished interfacial effects are deeply investigated by overlooking views, including not only an experimental demonstration but also ab initio modeling. The polymorphic phase balance and crystallinity, as well as the crystal orientation of PZT thin films at the morphotropic phase boundary （MPB）, can be stably modulated using interfacial crystal structures. Here, interactions with MgO stabilize the PZT crystallographic system well and induce the texturing influences, while the PZT film remains quasi-stable on a conventional A1203 wafer. On the basis of this fundamental understanding, a high-output flexible energy harvester is developed using the controlled-PZT system, which shows significantly higher performance than the unmodified PZT generator. The voltage, current, and power densities are improved by 556%, 503%, and 822%, respectively, in comparison with the previous flexional single-crystalline piezoelectric device. Finally, the improved flexible generator is applied to harvest tiny vibrational energy from a real traffic system, and it is used to operate a commercial electronic unit. These results clearly indicate that atomic-scale designs can produce significant impacts on macroscopic applications.