Qi Yuan,Yutong Meng,Sen Wang,Gaobin Liu,Qiyao Wang,Kuoming Song,He Zhao,Shuai Yan,Xin Li
The effects of different contents of B 2 O 3 -Bi 2 O 3 on the sintering temperature and dielectric properties of MgO-12%TiO 2 (w) ceramics were investigated. B 2 O 3 -Bi 2 O 3 addition effectively reduced the sintering temperature and improved the dielectric properties of ceramic samples; however, an excessive amount of B 2 O 3 -Bi 2 O 3 led to the deterioration of dielectric properties. This is because Bi 2 O 3 participated in the chemical reaction between MgO and TiO 2 and generated a high-dielectric-loss Bi 2 Ti 2 O 7 phase, resulting in an increased dielectric loss in the ceramic samples. In contrast, B 2 O 3 formed a liquid phase to fill the grain gaps and pores during sintering, improving the densities of the ceramic samples. An appropriate amount of B 2 O 3 -Bi 2 O 3 accelerated the reaction between MgO and TiO 2 and formed ultralow-dielectric-loss phases—MgTiO 3 and Mg 2 TiO 4 , and the dielectric losses of the ceramic samples decreased to an order of 10 −5 .
Ziqin Lin,Tianxia Xie,Zhuolin Xie,Anqi Dai,Yang Yuan,Peng Sun,Yanqi Song,Zhenggang Fang,Chunhua Lu
Solar absorbers are vital for concentrated solar power (CSP) systems, yet spectral selectivity solar absorbers (SSAs) struggle with high-temperature stability in air. This study introduced Mn ions into MgTiO 3 (MTO) via a high temperature solid-phase synthesis technique to optimize the spectral selectivity. Unlike conventional doping that increased both absorptance and emittance, MgTi 0.4 Mn 0.6 O 3 (MTMO-0.6) boosted solar absorptance (α = 0.85) while maintaining low emittance (ε = 0.39, 1073.15 K) in the 2.5–15 μm wavelength range. Besides, the material retained high spectral selectivity (α/ε = 0.84/0.41) after heat treatment at 800 °C in air atmosphere for 90 h in total (9 h cycles −1 , 10 cycles), showing excellent thermal stability. Moreover, under concentrated solar irradiation of 10.83 W·cm −2 , MTMO-0.6 sample reached an equilibrium temperature of 848 ℃, surpassing that of MTO and SiC. The proposed Mn-doped MgTiO 3 has the potential as a solar absorber for high temperature solar thermal conversion.
Extreme solidification processes in advanced manufacturing (e.g., laser additive manufacturing and in space fabrication) amplify challenges in predicting phase selection under severe thermodynamic non-equilibrium. Using aerodynamic levitation containerless processing, we investigate the solidification behavior of pseudo-binary MgTiO 3 -TiO 2 system. Our experiments reveal an anomalous trans-phase-regime selection phenomenon in which the thermodynamically stable MgTi 2 O 5 phase is kinetically suppressed from precipitation. This selection arises from nucleation kinetic barriers of MgTi 2 O 5 , where coupled undercooling and compositional fluctuations destabilize critical nuclei formation. By integrating composition- and temperature-dependent interfacial energy dynamics into classical nucleation theory , we develop a predictive framework that quantitatively maps anomalous phase selection regions. This approach establishes the first non-equilibrium kinetic phase diagram of this system with experimental validation, resolving long-standing discrepancies between equilibrium predictions and non-equilibrium experimental outcomes. The proposed methodology establishes a generalized paradigm for phase selection prediction, offering transformative insights into microstructure and phase control under extreme non-equilibrium solidification conditions.
Fei Liu,Zhixiang Wei,Yujie Zhao,Shaojun Liu,Hao Li
The rapid densification of ceramics printed by digital light processing (DLP) has been a technical and scientific challenge in the field of additive manufacturing. This work explores the rapid microwave hybrid sintering (MS) process for DLP-printed 0.95MgTiO 3 -0.05CaTiO 3 (MT-CT) microwave ceramics, aiming at reducing the densification time. The sintering trajectories of DLP-printed MT-CT ceramics at 1300°С show that highly dense ceramics without significant grain growth can be achieved by only 75 min and a fast heating rate (30°С/min). The MS process can enable DLP-printed MT-CT ceramics to reach the initial, intermediate, and final stages of sintering at a temperature 100 °C lower than that required for the CS process by integrating uniform volumetric heating with thermal radiation. DLP-printed MT-CT ceramics sintered by MS exhibit excellent dielectric properties: ε r = 20.4, Q × f = 75,300 GHz, τ f = −2.5 ppm/°C, representing a 13.4 % enhancement in Q × f values compared to ceramics by CS for 240 min. DLP-printed MT-CT dielectric resonator antenna sintered by MS at 1300°С for 75 min exhibits a radiation efficiency exceeding 90 % at 5.9 GHz ( S 11 = −42.43 dB), showing their promising potential for high-frequency communication applications.
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