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Flexible and miniaturized photodetectors, offering a fast response across the ultraviolet (UV) to millimeter (MM) wave spectrum, are crucial for applications like healthcare monitoring and wearable optoelectronics. Despite their potential, developing such photodetectors faces challenges due to the lack of suitable materials and operational mechanisms. Here, the study proposes a flexible photodetector composed of a monolayer graphene connected by two distinct metal electrodes. Through the photothermoelectric effect, these asymmetric electrodes induce electron flow within the graphene channel upon electromagnetic wave illumination, resulting in a compact device with ultra‐broadband and rapid photoresponse. The devices, with footprints ranging from 3 × 20 µm2 to 50 × 20 µm2, operate across a spectrum from 325 nm (UV) to 1.19 mm (MM) wave. They demonstrate a responsivity (RV) of up to 396.4 ± 5.1 mV W−1, a noise‐equivalent power (NEP) of 8.6 ± 0.1 nW Hz−0.5, and a response time as small as 0.8 ± 0.1 ms. This device facilitates direct imaging of shielded objects and material differentiation under simulated human body‐wearing conditions. The straightforward device architecture, aligned with its ultra‐broadband operational frequency range, is anticipated to hold significant implications for the development of miniaturized, wearable, and portable photodetectors. [ABSTRACT FROM AUTHOR]

The trial-and-error method used in ceramics research has certain limitations such as the high blindness of material component design. Moreover, calculations of the toughness of ceramics using the extended finite element method, which is the most broadly applied technique, are complicated. To overcome these issues, in this study, multilayer graphene (MLG)/Si 3 N 4 whisker (Si 3 N 4w)-reinforced Si 3 N 4 ceramics (MWSCs) were used as the model material, and the modeling of MWSCs was conducted using Voronoi tessellation. Additionally, a more concise novel approach was applied for the prediction of the fracture toughness of MWSCs. Furthermore, the optimal MLG and Si 3 N 4w contents were predicted, and then they were verified by fabricating MWSCs using spark plasma sintering (SPS). Simulation results indicated that the optimum MLG and Si 3 N 4w contents to enable the toughness and hardness to reach the maximum values (9.87 MPa·m1/2 and 23.19 GPa) were 1 wt% and 3 wt%, which were consistent with the experimental results. Consequently, the effectiveness of the proposed method was verified. Moreover, the experimental values of the maximum fracture toughness and hardness were 11.04 MPa·m1/2 and 20.29 GPa, which were 47.20% and 12.10% higher than those of Si 3 N 4 ceramics reinforced with 1 wt% MLG, respectively. The synergistic toughening effects of MLG and Si 3 N 4w were significantly reflected. The load-bearing effect, bridging, and crack deflection induced by MLG and Si 3 N 4w were the key reasons for the improvement in the mechanical properties of MWSCs. [ABSTRACT FROM AUTHOR]

The poor thermal properties of ceramics limited its wide application. Recently, upgrading via reinforcing ceramics with graphene has been recognized as a feasible approach to enhance the thermal performance of ceramics, and then advance the applications due to the exceptional thermal properties of graphene. Thus, this review summarized the latest advances in manufacturing process, microstructure as well as the thermal properties of graphene reinforced ceramics (GRC), highlighting the impacts of sintering techniques, sintering parameters and graphene/ceramic matrix parameters on the thermal performance of GRC. Furthermore, microstructure model simulation was proposed as a supplement to the traditional trial and error method, so as to facilitate the research associated with GRC. Besides, the challenges coupled with outlook for GRC with the superior thermal properties were also envisioned to providing readers with deep understanding of future development of GRC. [ABSTRACT FROM AUTHOR]

This work aimed at investigating the superiorities of multilayer graphene (MLG) and β-Si 3 N 4 whisker (β-Si 3 N 4w) in synergistically enhancing the toughness of Si 3 N 4 ceramic composites. First, Si 3 N 4 ceramic composites with hybrid 1 wt% MLG and 0 – 5 wt% β-Si 3 N 4w were sintered by spark plasma sintering. Phase constitutions and microstructures of Si 3 N 4 -based ceramic composites were characterized by X-rays diffraction, Raman spectra, and scanning electron microscope. Then, the optimal β-Si 3 N 4w content and sintering process of MLG/β-Si 3 N 4w -toughened Si 3 N 4 ceramic composites were comprehensively optimized by orthogonal experiments. Results indicated that in the case of maintaining the hardness of 15.87 – 18.84 GPa, the fracture toughness of Si 3 N 4 ceramic composites incorporated with 1 wt% MLG and 3 wt% β-Si 3 N 4w was advanced to 11.04 MPa·m1/2, which was 11.29% and 87.12% higher than that of 1 wt% MLG- and 3 wt% β-Si 3 N 4w -reinforced Si 3 N 4 ceramic composites, respectively. Orthogonal experiments demonstrated that 1 wt% MLG/3 wt% β-Si 3 N 4w -toughened Si 3 N 4 ceramic composites sintered at 1600 ℃, 40 MPa, and holding time for 6 min had optimum comprehensive mechanical properties. MLG wrapping and the synergistic effects of pull out, crack deflection, crack branching, and bridging resulted by MLG and β-Si 3 N 4w were the main responsible for the enhancement of toughness. [Display omitted] • MLG/β-Si 3 N 4w synergistic toughened Si 3 N 4 ceramics were sintered by SPS. • Fracture toughness of Si 3 N 4 -based ceramics was enhanced to 11.04 MPa·m1/2. • Optimal contents of MLG and β-Si 3 N 4w were 1 wt% and 3 wt%. • Optimum sintering process were 1600 ℃, 40 MPa, and holding time for 6 min. [ABSTRACT FROM AUTHOR]

Combining the advantages of spark plasma sintering (SPS) and incomplete sintering (IS) in preparation of Si 3 N 4 ceramics, the spark plasma incomplete sintering (SPIS) was presented to fabricate porous Si 3 N 4 ceramics. Considering balancing the contradictory relationship between the porosity and toughness, 1 wt% multilayer graphene (MLG) was incorporated into porous Si 3 N 4 ceramics. Meanwhile, for the sake of compensating for the decrease in the hardness of porous Si 3 N 4 ceramics induced by MLG, 0–8 wt% β-Si 3 N 4 whisker (β-Si 3 N 4w) were synergistically added. The element distribution, phase constitutions and microstructures of MLG/β-Si 3 N 4w -reinforced porous Si 3 N 4 ceramics were characterized by energy dispersive spectroscopy (EDS), x-rays diffraction (XRD) and scanning electron microscope (SEM). The effects of β-Si 3 N 4w content on porosity, hardness and fracture toughness of porous Si 3 N 4 -based ceramics were analyzed. Results indicated that the porosity of porous Si 3 N 4 -based ceramics reached 21%, and then decreased significantly after the β-Si 3 N 4w content exceeded 4 wt%. The hardness of porous Si 3 N 4 -based ceramics obtained the maximum value 2.81 GPa when β - Si 3 N 4w was added 8 wt%, which was 31.92% higher than monolithic porous Si 3 N 4 ceramic. The mass transfer, diffusion and fusion induced by β-Si 3 N 4w were considered to be the main responsible for the increase of hardness. The fracture toughness of specimen with 1 wt% MLG and 4 wt% β-Si 3 N 4w was advanced to 3.14 MPa m1/2, which was 15.44% higher than monolithic porous Si 3 N 4 ceramic. The markedly enhanced of the fracture toughness was attributed to the synergistic effects of crack deflection, pull-out and bridging resulted by MLG/β-Si 3 N 4w. • Spark plasma incomplete sintering was proposed to fabricate porous Si 3 N 4 ceramics. • MLG/β-Si 3 N 4w were doped into porous Si 3 N 4 ceramics to advance its strength. • MLG/β-Si 3 N 4w -enhanced Si 3 N 4 ceramics with a porosity of 21% were prepared at 1500 °C. • Hardness of MLG/β-Si 3 N 4w -reinforced porous Si 3 N 4 ceramics reached 2.81 GPa. • Fracture toughness of porous Si 3 N 4 -based ceramics was improved to 3.14 MPa m1/2. [ABSTRACT FROM AUTHOR]