Engineering ceramics with high strength, toughness and electromagnetic interference (EMI) shielding effectiveness (SE) are highly desirable as electromagnetic protecting material in harsh environment. Herein, we show that both excellent mechanical and EMI shielding performance can be realized in alumina composites embedded with highly aligned reduced graphene oxide (RGO), which are readily prepared via sintering of core-shell structured RGO@Al₂O₃ nanoplates with pressure. Compared to monolithic Al₂O₃, the highly aligned RGO/Al₂O₃ composites show simultaneously improved strength and toughness up to ~26.1% and ~60.2%, respectively. The steeply rising R-curve behavior proves the better crack tolerance in the highly aligned structure with respect to randomly oriented one. Moreover, the RGO/Al₂O₃ composites also exhibit a high specific EMI SE reaching ~34 dB/mm in K band, due to the reflection and highly enhanced absorption after percolation in the out-of-plane direction. These findings provide a novel strategy of designing mechanically reliable engineering ceramic for EMI shielding.

Glass with high visible-light transparency is widely considered as the most important optical material, which typically requires a processing temperature higher than 1000 ℃. Here, we report a translucent aluminosilicate glass that can be prepared by cold sintering process (CSP) at merely 300 ℃. After eliminating structural pores in hexagonal faujasite (EMT)-type zeolite by heat treatment, the obtained highly active nanoparticles are consolidated to have nearly full density by adding NaOH solution as liquid aids. However, direct densification of EMT powder cannot remove the structural pores of zeolite completely, leading to an opaque compact after the CSP. It is proved that the chemical reaction between the NaOH- and zeolite-derived powders is highly beneficial to dissolution–precipitation process during sintering, leading to the ultra-low activation energy of 27.13 kJ/mol. Although the addition of 5 M NaOH solution greatly promotes the densification via the reaction with aluminosilicate powder, lower or higher concentration of solvent can deteriorate the transmittance of glass. Additionally, the CSP-prepared glass exhibits a Vickers hardness of 4.3 GPa, reaching 60% of the reported value for spark plasma sintering (SPS)-prepared sample.

As a semiconducting material with relatively low thermal conductivity, MoS₂ nanoflake has the potential to serve as a modulator for optimizing the performance of thermoelectric (TE) materials. However, the low yield of MoS₂ nanoflakes prepared by conventional methods has constrained the development of MoS₂ optimized TE materials. We propose a mechanical exfoliation method for mass production of MoS₂ nanoflakes using attrition mill. After mixed with La and Nb co-doped SrTiO₃ (SLNT) powder, the MoS₂/SLNT composites are fabricated by spark plasma sintering. It is found that the heterojunctions formed at MoS₂/SLNT interfaces with proper band offset can effectively scatter the low-energy electrons, resulting in enhanced Seebeck coefficient without significantly undermining the electrical conductivity. The power factor of composites is improved when the MoS₂ content is lower than 1.5 vol%. Meanwhile, the thermal conductivity of composites is significantly decreased due to the phonon scattering induced large thermal resistance at MoS₂/SLNT interfaces, which is much higher than that in graphene embedded SrTiO₃ composites. Consequently, a maximum ZT = 0.24 is obtained at 800 K in 1.5 vol% MoS₂/SLNT composite, which is ~26 % higher compared with pristine matrix. This work paves the way for application of TE materials modulated by transition metal dichalcogenides.

Correlated phase and microstructural evolution are systematically investigated by electron microscopies in Sr-deficient Sr(Ti, Nb)O₃ (STNO) thermoelectric ceramics incorporated with different fraction of reduced graphene oxide (RGO). It is found that while no impurity except for very few Ti₃O₅ precipitates are observed in monolithic STNO, the Nb-enriched rutile TiO₂ appears in RGO/STNO composites. With increasing RGO content, the amount of precipitates increase at first and then decrease when RGO content becomes high, which can be ascribed to the formation of local Magnéli phase. In addition, the energy-dispersive X-ray spectra combined with cathodoluminescence characterization indicates that the variation of Sr deficiency experiences the opposite trend with respect to the precipitates content. These findings clearly reveal the unique reducing effect of RGO on the microstructure of doped SrTiO₃ with Sr deficiency, which can greatly facilitate the design of perovskite based thermoelectric materials of hierarchical structure.