Journal of the American Ceramic Society最新文献

Lead zirconate titanate (PZT)-based piezoelectric ceramics are crucial components in high-power magnetoelectric (ME) antenna devices, contributing to the miniaturization of very low frequency (VLF) communication systems. The piezoelectric coefficient (d₃₃) and mechanical quality factor (Q_m) determine the quality of the radiation performance of the antenna device and, therefore, play a pivotal role in antenna preparation and selection. However, achieving high values for both d₃₃ and Q_m simultaneously proves challenging, as these properties often tend to compete with each other. Herein, we address this challenge by introducing MnCO₃-modified lead magnesium niobate (PMN)-PZT piezoelectric ceramics, leveraging elements doping to achieve a well-balanced performance, where the d₃₃ was optimized to 530 pC/N, while concurrently attaining a Q_m of 624, being attributed to the synergistic contributions from the defect dipole and lead vacancies. Notably, the PMN-PZT-based antenna device exhibits a significantly enhanced converse ME coefficient α_CME = 0.138 Oe·cm/V, which improves the antenna emission performance by about 25% compared to commercial PZT-4 samples. These findings offer a promising theoretical foundation and a feasible technical pathway for the development and design of ME antennas in the future.

This study investigates the grain boundary energy dependence on segregated dopants in nanocrystalline zinc aluminate ceramics. Atomistic simulations of Σ3 and Σ9 grain boundaries showed that trivalent ions of varying ionic radii [Sc³⁺ (74.5 pm), In³⁺ (80.0 pm), Y³⁺ (90.0 pm), and Nd³⁺ (98.3 pm)] have a tendency to segregate to both interfaces, with Y³⁺ presenting the highest segregation potentials. The connection between segregation and the reduction of interfacial energies was explored by measuring the grain boundary energy on nanoceramics fabricated via high-pressure spark plasma sintering (HP-SPS) using differential scanning calorimetry (DSC). The results revealed that Y³⁺ doping at 0.5 mol% reduces the grain boundary energy in zinc aluminate nanoceramics from 1.1–1.3 J/m² to 0.6–0.8 J/m²; the range correlates with the observed size dependence of the excess energy, with higher values observed for the smaller grain sizes (∼17 nm). The noted decrease in interfacial energies for doped samples suggests it is indeed possible to alter the stability of zinc aluminate grain boundaries via dopant segregation.

High energy density (W_rec) dielectrics with excellent efficiency (η) and thermal stability are crucial in high-power energy storage applications. In this work, we introduce Ba(Zr_0.2Ti_0.8)O₃ (BZT) into Bi_0.5Na_0.5TiO₃ (BNT) to delay saturation polarization and refine grain sizes for enhancing energy storage performance. BZT diffusing into BNT lattice not only increases electronegativity between A‒O/B‒O bond and the relaxor, but also is beneficial for refining grain sizes and suppressing the development of local electric branches. Therefore, high P_max with moderate P_r and improved breakdown strength is achieved in BNT‒xBZT ceramics with x = 0.6 mol. Additionally, BNT‒0.60BZT ceramics demonstrate enhanced recoverable energy storage density of 4.1 J cm⁻³ with high energy storage efficiency of 91%, along with favorable overdamped charge‒discharge properties including a maximum current, discharge energy density, and discharge time of 10 A, 2.4 J cm⁻³, and 150 ns, respectively.

The advancement of innovative energy storage electrode materials requires the immediate growth of redox-active and sensible design of multifunctional electrochemical active materials. Supercapacitors are increasingly favored for the storage of energy owing to their large specific power, rapid charge/discharge times, and long-term durability. The potential electrochemical energy storage using metal oxides motivated our research team to create DyMnO₃ and their hybrid with reduced graphene oxide (rGO), via hydrothermal process in rGO/DyMnO₃, as an electrocatalyst with comparatively high electrical conductivity and appropriate electrochemical active surface. This research was conducted utilizing a 2 M KOH as electrolyte within a possible window between −0.1 and 0.6 V. Impressively, our synthesized sample exhibited the remarkable specific capacitance of 1536.78 F g⁻¹ on current density of 1 A g⁻¹, attributed to quick charge storage and delayed discharging mechanism. The addition of rGO to porous spherical DyMnO₃ enhances electrochemical performance, providing a specific surface area of 250 m² g⁻¹ and an electroactive surface area of 2675 cm⁻². The created device displayed electrochemical activity with a high energy density of 149.40 Wh kg⁻¹ at a power density of 719.86 W kg⁻¹, respectively. Oxygen vacancy enhances results, indicating the rGO/DyMnO₃ nanocomposite's potential for SCs and other electrochemical applications.

In this work, the synthesized geopolymer was prepared using metakaolin and alkali activator, and during the geopolymerization process, g-C₃N₄ and different contents of GO were added to the geopolymer, and GO-g-C₃N₄-GP was finally obtained. These samples can remove methylene blue (MB) utilizing the synergistic effect of adsorption and photocatalysis. 10% GO-g-C₃N₄-GP had the best removal rate of 93.28% within 30 min, under visible light. The results confirmed that geopolymers can provide a reusable carrier for g-C₃N₄, and the presence of GO can hinder the recombination of charges and promote the migration of photogenerated electrons, further improving the photocatalytic performance. 10% GO-g-C₃N₄-GP was also used to 3D print a scaffold by using the direct ink writing technology. To improve the efficiency of MB removal, 3D printed samples were treated with acid, and the sample of the 3D printed 10% GO-g-C₃N₄-GP acid treatment was also effective in removing MB and facilitates the recovery of the active material. This work can provide a simple way for synthesizing green materials for removing organic dyes.

Quenching has been widely used as a strengthening strategy in metals and glass; however, it is rarely applied to ceramics due to the thermal shock effect. In this work, several types of ceramic rods including commercial corundum, Al₂O₃, ZrO₂, TiB₂, and B₄C were quenched in silicon oil for investigation. The flexural strength of all these ceramic rods showed an increase of 5.1%‒23.6% after quenched at 500°C. The strengthening mechanism was likely related to the transient stress at initial quenching stage. This work demonstrates that the quenching treatment is a potential method to strengthen ceramics.

To obtain high-performance magnetic sheet with high initial permeability and low magnetic loss for wireless charging system, Ni–Zn–Cu ferrite ceramics with a chemical formula of Ni_0.6 − xZn_0.4Cu_xFe₂O₄ (x = 0–0.30) were prepared by traditional solid reaction-sintering method. As expected, the doped Cu²⁺ ions could effectively reduce the sintering temperature and increase the density of the ferrites. With increasing doping amount of Cu²⁺, the coercivity, saturation magnetization, and Curie temperature of the resultant ferrites decreased. With x = 0.15, the sample presented the maximum initial magnetic permeability and highest Q-factor. On the basis of the measured magnetic parameters, the ferrites were examined as magnetic sheet in wireless charging system by digital simulation, while the structural parameters of the system were considered and the coefficients of hysteresis loss, eddy current loss, and excess loss were quantitatively separated under sinusoidal excitation. Specifically, because of its lower core loss, the optimal ferrite (x = 0.15) would perform better with much improved transmission efficiency than that without the doping of Cu²⁺, especially when the transmitting and receiving coils were settled more apart, which might be a good candidate for wireless charging system, and the proposed simple wireless charging system can be used as a general strategy for the evaluation of magnetic sheets.

The objective of this study is to investigate the interaction effects of anisotropic roughness interface (ARI) and component shape characteristics on the thermal fatigue life of thermal barrier coatings (TBCs). In this study, an ARI characterization method for 3D TBCs interfaces of circular tubes is established. Then, TBCs finite element model and TBCs thermal fatigue life prediction model based on particle swarm optimization are conducted. Finally, the effect of ARI on the interface stress state and thermal fatigue life of the TBCs is discussed. The results show that the maximum error in the fatigue life prediction model of TBCs is only 45.3%, and the fatigue life prediction error for TBCs under similar operating conditions is only 30.8%. When the axial interface wavelength is 0.060 mm and the circumferential wavelength interface is 0.057 mm, the maximum equivalent stress at the interface is the smallest, with a value of 241.4 MPa. The thermal fatigue life is maximum when the axial wavelength interface is 0.060 mm and the circumferential wavelength interface is 0.049 mm, with the value of 639 cycles, which is the 47.6% increase in fatigue life compared with the initial roughness TBCs model (The interface wavelengths are all 0.040 mm). The above findings demonstrate the effectiveness of ARI in enhancing the fatigue life of TBCs, which provides a new idea for the preparation of high fatigue life TBCs.

Er³⁺-doped fibers are widely used as 1.55 µm broadband optical amplifiers. Tellurite glasses are particularly suitable as a gain medium due to their lower phonon energy and better rare-earth solubility compared to silica glass. Various strategies, such as reducing the OH content and co-doping with silver nanoparticles (Ag NPs), are attempted to improve the spectroscopic properties. However, maintaining the glass drawability into fibers when developing glasses with improved spectroscopic properties remains a significant challenge. Indeed, it is confirmed that NH₄HF₂ can be added into the tellurite glass batch prior to the melting to reduce OH⁻ content. However, the presence of remaining F in the glass is demonstrated to have a detrimental impact on the glass thermal properties preventing the drawing of this glass into fiber. The successful drawing of a single-index optical fiber from a tellurite glass preform heavily doped with Er³⁺ ions is reported for the first time. The Ag NPs are grown in the fiber using a thermal treatment at the glass transition temperature. The presence of the NPs is confirmed using a TEM and from the spectroscopic properties. The interaction between Er³⁺ ions and the Ag species offers potential for modifying the luminescence properties of the fiber.

Super conductor Na₃SbS₄ has received substantial attention in electrolyte research because of its high ionic conductivity and low grain boundary resistance. A breakthrough in electrochemical stability with good ionic conductivity has yet to be captured. Calcium (Ca) appears as an ideal substitute for sodium (Na) due to its abundance in geological resources, nontoxic properties, and equivalent ionic radius. The proposed Na_3-2xCa_xSbS₄ glass–ceramic electrolytes were subsequently manufactured using ball milling and heat treatment. The results acquired the maximum ionic conductivity of 1.59 mS cm⁻¹ at room temperature, which reached the commercial use level when compared with the current popular lithium-ion battery. Moreover, calcium ions partially replaced sodium sites while creating massive Na vacancies to maintain charge neutrality, resulting in fast ion transport. Furthermore, a more stable ionic bond Ca–S was formed at the interface, which inhibited additional reactions at the electrolyte–metal interface and demonstrated exceptional cyclic stability, making it a viable electrolyte for solid-state sodium-ion batteries.