ABSTRACT Zirconia‐toughened alumina (ZTA) ceramics reinforced with Ti 3 AlC 2 MAX phase are successfully fabricated through pressureless sintering to investigate the influence of Ti 3 AlC 2 addition on the microstructural, physico‐mechanical properties and scratch resistance behavior of the composites. Ti 3 AlC 2 content varies from 0 to 5 wt.%, and the green compacts are prepared by uniaxial pressing at 200 MPa followed by sintering at 1350°C under an argon atmosphere. XRD analysis confirms the successful retention of Ti 3 AlC 2 within the ZTA matrix without the formation of secondary phases. The monolithic ZTA exhibits a density and relative density of 4.12 g/cm 3 and 96.17%, respectively, which increases to a maximum of 4.14 g/cm 3 and 96.68% at 2 wt.% Ti 3 AlC 2 addition. FESEM analysis reveals significant grain refinement at lower reinforcement contents. The microhardness increases from 1736 HV for monolithic ZTA to 1938 HV at 2 wt.% Ti 3 AlC 2 , while fracture toughness improves from 4.45 to 5.54 MPa.m 0.5 due to crack deflection, crack bridging and crack branching mechanisms induced by the layered Ti 3 AlC 2 structure. Furthermore, the 2 wt.% Ti 3 AlC 2 composite exhibits superior scratch resistance with the minimum scratch depth among all compositions.
ABSTRACT Magnesium aluminate spinel (MgAl 2 O 4 ) is a critical ceramic material for applications in transparent armors, infrared windows, and radiation environments due to its exceptional opto‐mechanical properties and resistance to harsh conditions. However, a comprehensive understanding of the point defect formation and migration process is still lacking. In this study, we revisited the formation and migration energies of point defects in MgAl 2 O 4 using state‐of‐the‐art first‐principles calculations. We systematically evaluated the formation energies of intrinsic defects following the Schottky, cation/anion Frenkel, and anti‐site defect reactions. Ab initio molecular dynamics (AIMD) simulations at 1200 K revealed that isolated interstitial defects of Mg, Al, and O ions undergo spontaneous reconfiguration into defect clusters, reducing the system energy and thus the defect formation energy by 0.56–1.08 eV. Migration energies of Mg, Al, and O ions via vacancy mechanisms were studied by climbing‐image nudged elastic band (CI‐NEB) calculations. The migration barrier of the Mg ion is 0.44 eV, which is the lowest among the three. The migration barrier of Al ions is 1.54 eV due to stronger lattice constraints and electrostatic interactions. The migration barriers of O ions have multiple values of 1.0 eV, 1.8 eV, and 2.7 eV, among which the lowest one allows a percolative path for long‐range diffusion. Our results show the critical role of defect clusters in point defect formation, and Al ions have the highest migration barrier due to high cation valence. Further implications for mass transport, sintering, and microstructure evolution of MgAl 2 O 4 ceramics shall be discussed.
ABSTRACT The C/C‐ZrC‐TiC‐SiC composites were successfully prepared by a joint process of ultrasonication‐assisted multicomponent ceramic slurry impregnation and reactive melt infiltration. The microstructure, phase composition, and ablation resistance of the composite were characterized and investigated. Results indicated that the ceramic matrix, comprising Zr 0.754 Ti 0.246 C, SiC, and TiC, was uniformly distributed within the chopped fiber web layers and among the fiber bundles, resulting in a final composite with a density of 2.86 g/cm 3 and an open porosity of 10.10%. After being subjected to 120 s of ablation by a plasma flame with a heat flux of 5.23 MW/m 2 , the composite exhibited a linear ablation rate of 2.26 µm/s and a mass ablation rate of 2.40 mg/s, respectively.
A new family of rare-earth fluoroborates, Ba5Ln3(BO3)6F (Ln = Pr, Nd, Sm, Eu, Gd, and Dy), has been synthesised via a conventional solid-state route and systematically investigated as potential luminescent host materials. Structural analyses reveal that the compounds adopt a monoclinic framework structure of isolated BO3 units, with lattice contraction observed across the lanthanide series. The fluoroborates exhibit wide optical band gaps (3.84-5.62 eV) and excellent thermal stability, making them suitable hosts for rare-earth activation. Among the investigated compositions, Eu3+-activated Ba5Gd3- xEux(BO3)6F displays intense red emission under both near-ultraviolet (near-UV) (394 nm) and blue (465 nm) excitation. The dominant 5D0 -> 7F2 transition and resolved Stark splitting indicate that Eu3+ occupies a low-symmetry, non-centrosymmetric environment within the fluoroborate lattice. The emission intensity reaches a maximum at x = 0.7, beyond which concentration quenching occurs through multipolar interactions as the quenching pathway. Furthermore, the phosphor exhibits deep-red chromaticity coordinates and a high color purity of approximately 93%. The combination of structural robustness, strong excitation in the near-UV/blue spectral region, and high-quality red emission highlights Ba5Gd3- xEux(BO3)6F as a promising fluoroborate phosphor for solid-state lighting applications.
Severe saggar corrosion by cathode materials hinders the sustainable production of lithium-ion batteries. Herein, high-performance refractory saggars were fabricated via high-temperature reconstruction using waste high-voltage porcelain insulators as the main raw material, combined with other solid wastes and mineral additives to form a dense mullite-corundum matrix. A physical-chemical synergistic strategy was adopted by optimizing calcium hexa-aluminate (CA6) particle-size gradation and Si powder addition. At an optimal coarse-to-fine CA6 ratio of 5:15, a stable interlocking skeleton was formed, reducing open pores and enhancing matrix packing density. Meanwhile, 2 wt% Si enabled in situ modification through oxidation-derived liquid SiO2 filling and mullitization-induced micro-expansion, effectively sealing residual micro- and nanoscale pores. Consequently, the apparent porosity decreased below 1% while maintaining high mechanical strength and thermal shock resistance. During service, the refined matrix forms a liquid-solid double interfacial barrier: high-viscosity lithium silicate glass immobilizes Li+, while a compact beta-eucryptite layer blocks Li2O inward diffusion. This work offers a low-cost route for long-life refractory saggars and high-value solid-waste utilization.
