Selective ion doping is a promising method to enhance the overall performance of perovskite dielectric ceramics. However, the confrontations among the dielectric constant ( epsilon r ), near-zero temperature coefficient of resonant frequency (TCF), and quality factor ( Q x f ) remain key challenges in high-performance dielectric ceramics. To leverage the trade-off conflicts, using dual-phase perovskite-based dielectric ceramic composites could be a potentially ideal solution. Unfortunately, the selected ions are hard to be doped into the perovskite phase due to the sintering temperature disparity of the two phases, thereby significantly impacting the modification effect. In this study, a "wedge" strategy was employed in a MgTiO3 -CaTiO3 dual-phase dielectric ceramic composite by using Ce as an auxiliary dopant to realize the main Hf doping in the CaTiO3 phase due to the lattice distortion. This strategy also harmonizes the confrontation of the sintering temperature disparity between the two components of CaTiO3 and MgTiO3 . The Hf4 + doping level of as high as 40 mol.% with a reduced sintering temperature of over 200 degrees C was successfully achieved by using this "wedge" strategy. Most importantly, the trade-off conflicts among the epsilon r , near-zero TCF, and Q x f have been considerably reduced and harmonized due to the successful introduction of a high dosage of Hf dopant in the CaTiO3 phase without sacrificing the intact structure of MgTiO3 . This strategy not only sheds light on manufacturing high-performance dual-phase dielectric ceramics with trade-off conflicts of properties but also provides an innovative pathway to address the challenge of mismatch of sintering temperature for selective ion doping in multiple-phase ceramic composites. (c) 2025 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science & Technology.

This study investigated the synthesis mechanism of tantalum boride (TaB2) powder via the boron/carbothermal reduction method, based on thermodynamic calculations and experimental results. The insufficient presence of the intermediate product B2O3 leads to the emergence of TaC and Ta3B4, while in the presence of a sufficient boron source in the reaction system, the primary products formed include TaB2, TaC, and B2O3, with TaC subsequently reacting with B(2)O(3 )and carbon to yield TaB2. TaB2 powder was successfully synthesized at 1500 degrees C with the addition of an excess of 20 wt% B4C. The particle size of the powder was approximately 298 nm, and the oxygen content and carbon content in the powder were 0.6 and 0.1 wt.%, respectively.

Three types of textured SiAlON ceramics (one-dimensional C-axis-oriented, two-dimensional randomly textured, and two-dimensional centripetally textured) were prepared using plastic deformation through extrusion, and then brazed to commercial cemented carbide substrates using vacuum brazing with a commercial Ag-Cu-Ti active brazing alloy to fabricate SiAlON brazed composite cutting tools for superalloy machining, simultaneously non-texture SiAlON cutting tools was prepared. The wear mechanisms of the cutting tools during superalloy machining include adhesive wear, oxidation wear, abrasive wear, and chipping. Among the four tools, the two-dimensional centripetally textured SiAlON composite tool, with rod-like grains oriented parallel to both the rake and flank faces, exhibited the best cutting performance. The reason is that the rod-like grains on its flank face are oriented toward the tool tip, providing enhanced fracture toughness and excellent resistance to chipping in the direction of the workpiece motion.

Previous research has shown that low-cost ZrSiO4 instead of ZrO2 resulted in coarse ZrB2 powders with generating SiC as secondary phase. In order to synthesize fine ZrB2 powders without SiC phase, 0-10 mol.% TaB2 were adopted to synthesize ZrB2 powders by boro/carbothermal reduction of ZrSiO4. A single solid solution of (Zr1- x Ta x )B 2 was formed, characterized by decreasing lattice parameters with increasing Ta doping, while maintaining the P6/mmm space group. With the addition of 10 mol.%TaB2, the particle size of ZrB2 decreased from 2.98 mu m to 0.67 mu m. After spark plasma sintering at 2000 degrees C, the relative density of (Zr0.9Ta0.1)B2 ceramics increased from 89.4 f 0.1 % to 98.7 f 0.1 %, the grain size decreased from 16.1 f 5.2 mu m to 4.0 f 1.5 mu m, and the hardness increased from 12.7 GPa to 16.6 GPa.

In the present investigation, the tribological properties of bulk high-entropy carbonitride (HECN) (W0.2Mo0.2Ta0.2Nb0.2Ti0.2)(C0.75N0.25) were studied under dry sliding conditions at room temperature, with applied loads of 5, 10, and 25 N. The dense (relative density of 97.52%) and fine-grained (average grain size of 2.83 μm) ceramics exhibited a Vickers hardness (HV1) of 23.45 GPa and an indentation fracture toughness of 2.73 MPa·m1/2. These tribological properties are strongly dependent on the applied load. The coefficient of friction (COF) ranged from a stable value of 0.28 at 5 N to 0.38 at 25 N, and the specific wear rate increased from an exceptionally low value of 3.23×10−9 mm3/(N·m) at 5 N to 5.56×10−8 mm3/(N·m) at 25 N. A detailed analysis revealed that the dominant wear mechanisms evolve with increasing load: At 5 N, wear is governed by the formation of a protective amorphous carbon (a-C) layer directly on the surface; at 10 N, a transitional regime with a composite a-C/oxide layer is observed; at 25 N, wear is controlled by the formation and continuous disruption of a hard, abrasive oxide “glaze” layer. The ability of this HECN material to form adaptive tribolayers, resulting in outstanding wear resistance, highlights its significant potential for demanding applications.

Radioactive iodine-129 (129I) presents a major challenge for nuclear waste management due to its long half-life and high environmental mobility. The design of iodine-bearing wasteforms is expected to balance the iodine loading with the chemical durability. Additionally, the volatile nature of iodine during high-temperature processing necessitates careful selection of wasteform type and accurate control of heat-treatment condition. This study introduces periodate-based Ba2NaIO6 double perovskites as the ceramic wasteform for immobilization of 129I. Ba2NaIO6 powder was initially synthesized by solid state reaction at 650 degrees C, followed by densification using spark plasma sintering (SPS) at 900-1000 degrees C under vacuum. It was found that optimal densification was achieved at 950 degrees C, with a relative density of 97.69 %. Phase-assemblage and microstructural analyses confirmed the thermal stability of Ba2NaIO6 phase, which maintained Fm-3 m double perovskites structure and minimal lattice distortion post-sintering. EDS mapping and composition analysis demonstrated the uniform distribution and effective incorporation of iodine in the matrix. XPS analysis revealed that iodine remained primarily in the +7 oxidation state, indicative of the chemical integrity during sintering. Leaching rate tests further displayed the excellent chemical stability, where the normalized iodine release rate of 1.65 +/- 0.16 x 10-4 g/(m2 center dot d) after 7 days was determined. The sintering condition, iodine incorporation capacity, and dissolution rate were systematically compared with previously reported iodine-containing wasteforms.

A novel powder medium-based ultrafast high-temperature sintering (P-UHS) configuration was applied to mass production of ceramics demonstrating time and energy efficient processing with heating rate as high as 500 degrees C/ min. The novel P-UHS technique enabled the fabrication of crack-free Al2O3 and SiC bulk specimens (30 cm3) which are 300 times larger than those produced using graphite felt based UHS methods reported in the open literature. Comparative runs, using direct firing based on a sample inserted in a high temperature furnace, resulted in cracking due to poor temperature homogenization during heating. Combined P-UHS experimental and simulation results confirmed the key role of even heat transfer from the heater toward the sintering body. Mechanical properties comparable to those obtained using conventional firing were observed.

In this study, the hydrothermal corrosion behavior of zirconium nitride (ZrN) ceramics used as a surrogate nuclear fuel of UN, which were added with different amounts of CrN/Cr2N (0, 10, 20, and 30 vol.%), was investigated with the objective of increasing the loss-of-coolant accident (LOCA) tolerance of pressurized water reactor fuel. The ZrN-based ceramic samples with a density exceeding 98% were fabricated by using a spark plasma sintering system at 1700 degrees C and applied stress of 30 MPa. Following 30 min of hydrothermal corrosion at 300 degrees C, the oxidation layer thickness of pure ZrN ceramics was 9.11 +/- 1.96 mu m, whereas that of 30 vol.% CrN/Cr2N-ZrN was only 1.23 +/- 0.3 mu m, which indicated that CrN/Cr2N offered an excellent protection effect for ZrN. This work can, thus, provide engineering design guidance for the UN with high uranium density to increase the LOCA tolerance of current nuclear power generation systems.

Excess B4C was incorporated into reactively sintered high-entropy boride ceramics to develop a (Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)B2-SiC-B4C ternary phase system. The results showed the addition of B4C effectively removed oxide impurities and enhanced densification during the sintering process. Despite the slight decrease in fracture toughness, (Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)B2-SiC-B4C exhibited significantly higher hardness, in comparison with (Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)B2-SiC. In addition, the ternary phase ceramics prepared in this study demonstrated superior hardness and fracture toughness compared to those typically reported of monolithic (Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)B2 ceramics.

This study investigates the cutting performance and wear mechanisms of high-entropy (Ti,W,Mo,Ta,Nb)(C,N) cermet tools, prepared by incorporating different volume fractions of Co (5 vol% and 10 vol%). The addition of Co enabled low-temperature densification sintering at 1450 degrees C. Among the tested tools, the (Ti,W,Mo,Ta,Nb)(C, N)-Co cermet tool with 5 vol% Co exhibited the highest toughness (7.07 +/- 0.29 MPa center dot m1/2) and relatively high hardness (22.71 +/- 0.55 GPa), resulting in superior cutting performance with a maximum cutting life of 1393 s, significantly surpassing the tool life of Ti(C,N)-based cermet tools from previous studies. The primary wear mechanisms identified were adhesive wear, abrasive wear, and oxidative wear. Overall, the results indicate that high-entropy (Ti,W,Mo,Ta,Nb)(C,N) cermet tools show great potential for turning nodular cast iron.

The oxidation behavior of (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )B 2 and (Hf 0.2 Zr 0.2 Ta 0.2 Cr 0.2 Ti 0.2 )B 2 high entropy boride ceramics at 1200 degrees C was investigated to provide insights into their microstructural evolution and oxidation mechanism. The results showed that the oxide layer thickness of (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )B 2 was about 112 mu m, much thicker than the counterpart of (Hf 0.2 Zr 0.2 Ta 0.2 Cr 0.2 Ti 0.2 )B 2 (-62 mu m). The differences in oxidation response and oxidation resistance between these two material systems were mainly pertained to the generation of different structures of oxide layer. For the (Hf 0.2 Zr 0.2 Ta 0.2 Nb 0.2 Ti 0.2 )B 2 sample, the oxide layer was composed of four-layer structure (porous-dense-porous-dense). In contrast, the oxide layers of (Hf 0.2 Zr 0.2 Ta 0.2 Cr 0.2 Ti 0.2 )B 2 sample exhibited a distinctly laminated structure.

Boron carbide (B4C) is difficult to be sintered, which limits its applications. To solve this problem, WB2-SiC-B4C composite powders with different B4C content were in-situ synthesized at 1400 degrees C using WSi2, B4C, and carbon black materials. The powders were then sintered by spark plasma sintering (SPS) at different temperatures. The effects of B4C content and SPS sintering temperature on phase composition, microstructure, relative density, and mechanical properties of the WB2-SiC-B4C composites were investigated. The WB2-SiC-B4C samples sintered at 1900 degrees C are almost fully dense, with the Vickers hardness of which is 31.5 +/- 1.1 GPa, and fracture toughness is 5.1 +/- 0.4 MPa center dot m1/2. These are the highest among all the samples prepared. The improved fractural toughness could be mainly attributed to the active toughening mechanisms of crack deflection and crack bridging. This study provides a feasible approach to prepare multiphase ceramics with excellent mechanical properties.

The microstructures and hoop tensile properties of duplex SiCf/SiC composite cladding tubes were investigated by using the C-ring specimen configuration after oxidation and water quenching at 600 degrees C, 1000 degrees C, and 1400 degrees C. Oxidation at 600 degrees C caused PyC interphase loss, reducing the maximum loading capacity (MLC), while fiber oxidation and embrittlement at 1000 degrees C further reduced the MLC. At 1400 degrees C, pore healing via SiO2 formation led to an MLC rebound. Water quenching at 600 degrees C had minimal impact on MLC, whereas quenching at 1000 degrees C caused cracks in the external CVD-SiC coating, slightly reducing MLC. Quenching at 1400 degrees C induced throughcracks in the CVD-SiC coating and SiCf/SiC composite, significantly degrading MLC. These results elucidate the mechanical behavior of SiCf/SiC composites under simulated accident conditions, highlighting the effects of oxidation and water quenching on their structural integrity.

In this study, a series of hierarchical porous Al2O3 with controlled morphology were synthesized using melamine foam (MF) as a sacrificial template. Comprehensive characterization through XRD, FTIR, Raman spectra, SEM, TEM, and N-2 adsorption-desorption confirmed the successful fabrication of graphite skeleton-guided hierarchical porousAl(2)O(3) by precise control of calcination temperature. The hierarchical porous Al2O3 materials calcined at 1000 degrees C,1400 degrees C, and 1500 degrees C demonstrated unique structural features and higher positive Zeta potential, exhibiting remarkably fast adsorption kinetics and exceptional Congo red (CR) adsorption capacities that significantly surpassed previously reported values in literature. The adsorption process followed pseudo-second-order kinetics, indicating chemisorption as the dominant mechanism. Furthermore, the adsorption isotherm was best described by the Langmuir model, suggesting monolayer adsorption behavior. These findings demonstrate that our cost-effectively fabricated hierarchical porous Al2O3 represents a highly promising adsorbent for efficient removal of organic dyes from wastewater.

α‐MoB 2 , which has been considered as one of the promising nonprecious transition metal borides catalysts for the hydrogen evolution reaction (HER), has recently been reported to be very efficient in the bulk form (self‐supported electrode). However, bulk α‐MoB 2 is normally synthesized under high‐temperature and high‐pressure conditions. In the present work, α‐MoB 2 porous self‐supported electrodes with relative density of ∼52%–55% were synthesized by a combination of mechano‐chemical process and low‐temperature (750°C, 800°C, 850°C, and 900°C) spark plasma sintering technique. The effects of the sintering temperature on HER activity of the self‐supported electrodes in acidic solution were investigated in this study. The results showed that an overpotential as low as 91.2 mV at a current density of 10 mA/cm 2 , and a Tafel slope of 61.8 mV/dec were obtained by the α‐MoB 2 electrode prepared at 850°C. This is the lowest overpotential value of the pure α‐MoB 2 at a current density of 10 mA/cm 2 ever reported in the open literature. Thus, the present study provides a new insight into the potentially innovative approach to manufacture α‐MoB 2 porous self‐supported electrodes with excellent HER performance.

This work investigated the formation mechanism and the effects of temperature on the microstructure and shear strength of vacuum-brazed SiAlON ceramic/WC-Co cemented carbide joints using an Ag-Cu-Ti active filler as the interlayer. The diffusion of Ti elements toward substrates and their subsequent reaction during the brazing process led to the formation of TiN, TiC, and Ti5Si3 phases, where the featured reaction layers were established. A continuous reaction layer of TiN in the SiAlON substrate side and TiC in the WC substrate side were formed. The ceramic phases (Ti5Si3 TiN, and TiC) were distributed in a brazed intermediate layer. The highest shear strength of the brazed joints obtained at 850 degrees C was 325.28 +/- 20.27 MPa, demonstrating the feasibility of the Ag-Cu-Ti active filler in producing robust joints.

The relative density of the tungsten diboride (WB2) ceramic prepared via the boron/carbon thermal method combined with spark plasma sintering(SPS) can reach as high as-96 % without addition of any sintering aids. In the present work, aiming to further increase the relative density of WB2, WB2 bulk samples with the addition of 0, 1, and 3 vol% of SiO2 as sintering aids were prepared. The effects of SiO2 content on phase composition, sintering behavior, relative density, microstructure, and mechanical properties of the WB2 ceramics were investigated. The results show that the WB2 powder is significantly refined with the addition of 1-3 vol% SiO2, while the finest powder is obtained with 1 vol% SiO2 addition. After being sintered by SPS at 1600 degrees C under the pressure of 30 MPa for 10 mins, the relative density of the WB2 ceramic sample with 1 vol% of SiO2 reaches to 98.4 %, and the Vickers hardness value is 24.9 +/- 0.5 GPa under an applied load of 9.8 N. The improved density and herein the Vickers hardness can be attributed to the reaction of SiO2 with the B2O3 covered on the surface of the WB2 powder, and the subsequent formation of B2O3-SiO2 glass phase, which promotes the sintering ability of the WB2 ceramic.

This study employed ZrC-Si as the joining material and utilized spark plasma sintering (SPS) technology to join SiC ceramics under an applied pressure of 30 MPa at 1600 degrees C in vacuum. The effects of varying molar ratios of ZrC-Si on microstructure, phase composition, and shear strength of the joints were investigated. The joint layers primarily consisted of ZrC, SiC, SiO2, Si5C3, t-ZrO2, Al2O3 and Al2(SiO4)O. As the Si content ratio in the joining material increased, the density of the joint layer increased, and the shear strength of the joint improved. The optimal shear strength of 137.1 f 18.9 MPa was achieved at the ZrC:Si ratio of 2:1. Compared to Si-C joining approach, the application of ZrC-Si joining material effectively reduces residual Si, and thus enhances the mechanical performance of the joint, making it suitable for applications as the SiC components designed for next generation nuclear reactors.