To overcome the reliance on external pressure—a longstanding limitation in conventional ceramic joining—this study proposes a non-external-pressure joining strategy based on mechanically constrained expansion-induced stress (MCES) of SiC substrates at high temperature. This approach enables the in-situ synthesis of a highly dense and homogeneous Ti3SiC2 interlayer. The constraint-induced compressive stress serves as the primary driving force for high-integrity joining, significantly enhancing atomic diffusion by regulating the interfacial microstructure and reducing diffusion energy barriers, as revealed by molecular dynamics simulations. Experimental results demonstrate that SiC joints fabricated using this method exhibit a flexural strength of 266 ± 23 MPa, which is attributed to the uniform distribution of the Ti3SiC2 phase and the crack-deflection toughening effect associated with its lamellar structure. By eliminating the need for complex pressure-assisted equipment, this technique simplifies processing procedures and reduces manufacturing costs, offering a practical route for producing complex SiC components for extreme-environment applications and promoting the engineering deployment of SiC in advanced fields such as aerospace thermal protection systems and nuclear energy technologies.

Zirconium carbide (ZrC) is a leading candidate for advanced nuclear reactor components due to its ultra-high melting point, thermomechanical stability, and low neutron absorption. However, its irradiation damage behavior and mechanism remains underexplored. In this work, dense pressureless-sintered ZrC ceramics with low-neutron-absorption MoSi2 additives were irradiated with 500 keV He2+ ions at room temperature to peak damage levels of 0.30, 1.49, and 2.97 dpa. The changes in their microstructure, bonding states, and property were analyzed via TEM, GIXRD, Raman spectroscopy, nanoindentation, and TDTR. ZrC retained crystallinity regardless of high-density black-spot defects, while MoSi2 exhibited severe amorphization and swelling. Lattice expansion and partial Zr-C bond breakage with C-C bond formation were confirmed, with maximum hardening at 1.49 dpa and significant elastic modulus reduction at 2.97 dpa. Thermal conductivity decreased modestly and showed minimal dose dependence, indicating a saturation effect. These results elucidate defect evolution in pressureless-sintered ZrC-MoSi2 ceramics and support its application in high-irradiation nuclear environments.

Silicon carbide (SiC) ceramics have found extensive application in strategic fields, such as semiconductor technology, nuclear energy, aerospace engineering, and marine engineering, due to their remarkable properties, which encompass excellent mechanical properties, resistance to high-temperature creep, acid and alkali corrosion, and high thermal conductivity. However, the fracture strength of these brittle ceramic materials typically exhibits significant discreteness, which adversely affects reliability and limits their wider application as engineering structural materials. In this work, reliability of fracture strength in solid-state sintered silicon carbide (SSiC) ceramics was enhanced through regulation of grain size. The influence of grain size on mechanical properties, Weibull distribution of fracture strength, and crack extension resistance curve (R-curve) characteristics of SSiC ceramics was systematically evaluated. Reliability regulatory mechanism for fracture strength of SSiC ceramics was analyzed. The results indicated that, with an increase in sintering temperature from 2100 degrees C to 2200 degrees C, average grain size of SSiC ceramics increased from 3.01 & micro;m to 8.45 & micro;m, while coefficient of grain size distribution uniformity dropped from 0.70 to 0.62. As the average grain size was reduced from 8.45 & micro;m to 3.01 & micro;m, Weibull modulus of fracture strength for SSiC ceramics increased gradually from 8.5 to 12.2, representing a 44% increment. This clearly indicates the positive impact of grain refinement on reliability of fracture strength. Enhancement in Weibull modulus of fracture strength as a result of grain refinement can primarily be attributed to high-density grain boundary network, which effectively mitigates stress concentration via crack bifurcation and bridging mechanisms. Additionally, uniformity of grain distribution and reduced defect size contribute to an elevated energy threshold for crack propagation, leading to an ascending R-curve behavior. This work achieves a significant improvement in the fracture strength reliability of SiC ceramics through regulating grain size, which is expected to promote the wider engineering application of SiC ceramic materials.

High-purity SiC ceramic is an excellent material for semiconductor components due to its outstanding physical and chemical properties. However, fabricating high-purity and high-strength SiC ceramics using conventional sintering processes remains challenging. In this study, a high-purity (99.9999 %) and high-strength (520.8 MPa) SiC ceramic is fabricated through a chemical vapor deposition (CVD) SiC compressive stress layer deposited on a solid-state sintered SiC (S-SiC) ceramic surface. Firstly, the influence of deposition pressure on the microstructural evolution of SiC coatings deposited on S-SiC ceramic substrates was investigated. The role of the gas diffusion mean free path in governing the defect density and grain orientation of the coatings was elucidated, thus enabling the fabrication of high-purity SiC coatings with grain uniform. Subsequently, the effect of coating thickness variation on the mechanical performance of pre-stressed SiC ceramics was discussed, and the relationship between coating thickness and residual stress magnitude was analyzed in detail. Thinner coatings were found to generate higher residual compressive stresses, which are more effective in enhancing the mechanical performance of SiC ceramics. The Weibull modulus of pre-stressed ceramics increases 46.7 % (from 7.5 to 11) and the R-curve exhibits an upward trend, indicating improved damage tolerance, and the underlying mechanism responsible for the mechanical enhancement is investigated. These results confirm that the introduction of a compressive stress layer via the CVD process can significantly improve the purity and reliability of SiC ceramics, this work presents a promising approach for the fabrication of high-purity, high-strength SiC ceramics.

Ceramic-based electromagnetic wave (EMW) absorbing materials with lightweight characteristics and strong absorption properties can effectively reduce EMW pollution and interference. A simple technique for introducing wave-absorbing phases with multi-component and multi-microstructure in wave-transmitting ceramic matrices is essential for practical applications. Herein, porous SiCNnw/C/Si3N4 ceramics comprising a two-component absorbing phase with a heterogeneous interface and nanowire structure have been prepared via simple vacuum impregnation and heat treatment. Porous Si3N4 ceramics with low permittivity are used as the impedance matching matrix, while carbon layer and SiCN nanowires are used as wave loss phases. The heterogeneous interface between the carbon layer and Si3N4 and the nanowire structure of SiCN can enhance the polarization relaxation behavior and electron transport capacity in the material. The conversion of carbon into SiCN nanowires can be promoted by elevating the heat treatment temperature, which can effectively regulate the ratio of the two wave-absorbing phases, thus optimizing the impedance matching and realizing efficient EMW absorption. The prepared C1400/20 sample has a minimum reflection loss of -61.24 dB at a thickness of 2.77 mm and an effective absorption bandwidth (EAB) of 6.30 GHz at a thickness of 2.63 mm. The C1400/25 realizes an EAB of 5.61 GHz at a smaller thickness of 2.09 mm. Overall, this study provides new ideas for designing ceramic-based materials with excellent EMW absorption performance.

In this work, the metal salts were introduced into the resin-solvent gel system to leverage their ortho-substitution effect, thereby accelerating the polymerization-induced phase separation process. Subsequent in-situ carbonization resulted in the preparation of porous carbon materials with three-dimensional interconnected pores. By precisely tuning the parameters of the resin-solvent-metal ion system, control over the pore structure of the porous carbon was achieved, with a porosity range of 16.5% to 66.5% and a pore diameter range of 8 to 248 nm. The addition of metallic salts can simply and effectively increase the pore structure after carbonization, making the infiltration of molten silicon easier. This is beneficial to the joining process of silicon carbide ceramics. Based on these findings, a high-reliability joining technique for large-sized (135 mm × 205 mm) silicon carbide ceramics was developed. The resulting interlayer was dense and defect-free, exhibiting a joining strength of 309 ± 33 MPa and a Weibull modulus of 10.67. These results highlight the critical role of structured porous media in advancing the field of large-sized ceramic joining.

In this work, the internal stress induced by the self-thermal expansion of the ceramic matrix was utilized, instead of external pressure, to drive the densification of the ceramic joint. The theoretical results indicate that a large axial compressive stress (on the GPa order) is generated at the joint interface under constrained expansion. The microstructure and joining performance of the homogeneous interlayer under constrained expansion-induced stress were investigated via experiments, and the joining mechanism driven by this stress was explored. Under constrained conditions, the induced compressive stress facilitates the diffusion of Si-C and mass transfer processes, which results in the formation of a fully dense interlayer. The joining process comprises two stages: internal stress-driven interlayer densification and epitaxial grain growth at the joining interface. The joint strength reaches 359 +/- 39 MPa, with a Weibull modulus of 10.9. The proposed technique was successfully adopted for joining Al2O3 ceramics, indicating its broad applicability.

High-performance SiCp/Al composites were fabricated via a vacuum hot-pressing powder metallurgy process. The effects of SiC particle size on the composite microstructures and their thermal and mechanical properties were systematically investigated. The vacuum hot-pressed SiCp/Al composites exhibited a well-bonded interface between the SiC particles and Al matrix, while not exhibiting any Al4C3 brittle phase. Particle gradation effectively enhanced the densification of SiCp/Al composites, resulting in dense bulks with a relative density of 99.7%. When the SiC particle size increased from 5 to 50 μm, the fracture morphologies gradually transitioned from intergranular to transgranular, while the relative density, bending strength, and thermal conductivity increased. Overall, SiCp/Al composites with excellent thermal conductivity (201.42 W/(m·K)) and bending strength (523 ± 29.45 MPa) were obtained. To address the scarcity of research on SiCp/Al composites' thermal properties, this study establishes SiC size/gradation-property relationships, innovatively filling the gap in thermal performance regulation.

The mullite-whisker-modified SiC porous ceramics were prepared by the oxide bonding method, using two additives (MoO3 as a mineralizer and AlF3 as a crystallization catalyst) to promote the growth of mullite whiskers. The microstructure and comprehensive properties of the sintered bodies were adjusted by controlling the sintering temperature and the additive content. The mullite whiskers obtained by controlling the sintering temperature and additives exhibit excellent microstructural characteristics (diameter: 0.1-0.5 mu m, length: 3-6 mu m, length-to-diameter ratio: 15-25). These formed mullite whiskers effectively intercepted particulate matter, and their interlocking structure provided higher strength to the sintered body. The resultant mullite-whiskermodified SiC porous ceramics demonstrated remarkable mechanical strength (43.8 f 0.1 MPa) while maintaining high porosity (41.27 %) and excellent gas permeability (1.96 x 10-14 m2). After undergoing five thermal shock cycles at 850 degrees C, the material retained 92.69 % of its original strength and exhibited superior filtration efficiency of 99.6 % for PM2.5 particles.

As for high-power laser diode (LD) driven lighting, Y3Al5O12:Ce3+ phosphor ceramics (YAG:Ce-CPs) are regarded as ideal converters to produce white light. Due to the lack of the red component, it is still one of the biggest challenges to obtain high-quality light for YAG:Ce-CPs in LD lighting. In this work, CaAlSiN3:Eu2+ phosphor-in-glass-films (CASN:Eu-PiGFs) are introduced to offset the emitting spectrum of YAG:Ce and suitable glass powders are employed as the inorganic binder to fabricate CASN:Eu-PiGFs. After coating CASN:Eu-PiGFs, a broad emitting spectrum (from 500 to 750 nm) is achieved. The luminous performances and thermal stability are optimized by modifying the CASN:Eu content in PiGF. In LD lighting, high luminous flux (858 lm) and luminous efficiency (165 lm W-1) can be obtained. Meanwhile, owing to the remedy of the emitting spectrum, a high color render index (CRI, 82) is acquired for YAG:Ce-CPs in LD lighting. The strategy makes big progress in designing phosphor converters and will inspire more researchers to pursue high-quality white light in LD-driven lighting. By combining YAG:Ce-CPs with CASN:Eu-PiGFs, emission spectra are extended and the bandwidth reaches to 154 nm. White light with a CRI of 82 is achieved driven by blue lasers, which is beneficial to improve the high-quality in LD lighting.

Due to excellent performances and easy adjustability, more and more researchers pay attention to high-entropy ceramics, which can be applied in many fields. In this work, a high-entropy transition metal carbide ceramic, (Hf0.2Ta0.2Zr0.2Nb0.2W0.2)C, was fabricated by pressureless sintering method. To obtain highly dense ceramic, dual sintering aids (Cr3C2 and C), are employed in the sintering process. Owing to suitable microstructure (grain size and defect density), the ceramics exhibit excellent electric conductivity(0.7040MS/m) and flexural strength (378±11.4 MPa). Meanwhile, the relationship between electromagnetic shielding effectiveness and different aid content in the X-band is also investigated. The P3 ceramic with a thickness of 1 mm can achieve an EMI shielding efficiency of 92dB in the X-band as a result of the stronger interface polarization and relaxation effects. High-entropy ceramic obtained in this work would give a different way to fabricate shielding material and can promote the use of high-entropy ceramics as effective EMI shielding materials.

The effects of Ti doping on the microstructure and properties of SiCp/Al composites fabricated by pressureless infiltration were comprehensively investigated using first-principles calculations and experimental analyses. First-principles calculations revealed that the interface wetting and bonding strength in an Al/SiC system could be significantly enhanced by Ti doping. Subsequently, the Ti element was incorporated into SiC preforms in the form of TiO2 and TiC to verify the influence of Ti doping on the pressureless infiltration performance of SiCp/Al composites. The experimental results demonstrated that the pressureless infiltration of molten Al into SiC preforms was promoted by adding TiC or TiO2 due to the improved wettability. However, incorporating TiO2 leads to the growth of AlN whiskers under a N2 atmosphere, thereby hindering the complete densification of the composites. On the other hand, TiC doping can improve wettability and interface strength without deleterious reactions. As a consequence, the TiC-doped SiCp/Al composites exhibited excellent properties, including a high relative density of 99.4%, a bending strength of 287 ± 18 MPa, and a thermal conductivity of 142 W·m−1·K−1.

Zirconium carbide (ZrC) ceramics have a high melting point, low neutron absorption cross section, and excellent resistance to the impact of fission products and are considered to be one of the best candidate materials for fourth-generation nuclear energy systems. ZrC ceramics with a high relative density of 99.1% were successfully prepared via pressureless sintering using a small amount of MoSi2 as an additive. The influence of the MoSi2 content on the densification behavior, microstructure, mechanical properties, and thermal properties of ZrC ceramics was systematically investigated. The results show that the densification of ZrC was significantly enhanced by the introduction of MoSi2 due to the formation of a liquid phase during sintering. In addition, the ZrC grains were refined due to the pinning effect of the generated silicon carbide. The flexural strength and Vickers hardness of ZrC ceramics with 2.5 vol% MoSi2 sintered at 1850 °C were 408 ± 12 MPa and 17.1 GPa, respectively, which were approximately 30% and 10% higher compared to the samples without the addition of MoSi2. The improved mechanical properties were mainly attributed to the high relative density (99.1%) and refined microstructure.

SiCp/Al composites are widely used in space vehicles, electronic packaging, automobiles, rail vehicles and other fields due to their excellent mechanical and thermal properties. Complex-shaped SiCp/Al parts are usually manufactured by mechanical processing, which is expensive and time-consuming due to the high hardness of SiC phase. As a highly effective 3D molding method, Fused Deposition Modelling (FDM) of the complex-structure SiCp/Al composites was reported for the first time in this paper. SiCp/Al composites was densified by pressureless infiltration after FDM, and as-acquired bulk possessed high densification of 92.67 % and the SiC volume fraction of 43.2 %. Moreover, excellent performances were also presented, including flexural strength of 211 MPa, thermal conductivity of 112(W/m & sdot;K), and the thermal expansion coefficient of 8.67 x 10-6K-1.

Bismuth telluride is the only commercially available thermoelectric material, but the poor n-type thermoelectric performance restricts its further development. Herein, we report the n-type Bi2Te2.7Se0.3 + x wt% PbI2 poly-crystalline with both high texture degree and various microstructures by the temperature gradient method. Based on the superior carrier mobility maintained by high grain orientation, dilute PbI2 doping not only tunes the carrier concentration to an optimal level but also induces multiscale phonon scattering centers to realize a very low lattice thermal conductivity. As a result, a peak ZT of 1.26 at 350 K, a high ZTavg of 1.22 (300-400 K), and an improved Vickers hardness of 0.48 GPa are realized in Bi2Te2.7Se0.3 + 0.22 wt% PbI2 sample. This work suggests that the dilute PbI2 doping by temperature gradient method is an effective solution for preparation of n-type bismuth telluride materials with both high thermoelectric and moderate mechanical properties.

Far-red (FR) photosensitive pigment (PFR) is important for plant photomorphogenesis. Phosphor-converted (pc) LED is the next-generation FR light device. How to obtain FR-emitting phosphors with a good external quantum efficiency (EQE), suitable photoluminescence and high thermal stability is still a challenge. Herein, by optimizing the sintering technology and chemical design, we develop an excellent FR phosphor, Gd3Al4GaO12:Cr3+. The phosphor has an emission peak at 734 nm and a band width of 70 nm, matched well with the PFR absorption band. By adjusting the flux of H3BO3 and Cr3+ concentration, the EQE reaches 47.2%, and the thermal stability maintains 96.8% at 423 K. Because of its excellent optical properties, the power-conversion efficiency of the FR pc-LED reaches 24.0% driven at 100 mA, demonstrating the high performance and promising applications in the next-generation FR light source.

Developing high-performance broadband near-infrared (NIR) phosphors for NIR phosphor-converted light-emitting diodes (pc-LEDs) is still a challenge. Co-doping is an effective strategy to enhance performances of the NIR phosphors. Herein, we explore a novel NIR phosphor by co-doping Yb3+ into LiGaP2O7:Cr3+ (LGAP:Cr3+) and systematically analyse its microtopography. Under 450 nm excitation, LGAP:Cr3+,Yb3+ emits a broad NIR band from 700 to 1100 nm. Due to the energy transfer from Cr3+ to Yb3+, the Yb3+ emission is strengthened more than 8 times and the external quantum efficiency reaches 25.5%. The addition of Yb3+ suppresses the thermal quenching compared with the Cr3+ single-doped specimen. The LGAP:Cr3+,Yb3+ phosphors and commercial blue chips are used to fabricate the NIR pc-LED. At 100 mA, the NIR pc-LED manifests an output NIR power of 24.86 mW and a photoelectric conversion efficiency of 8.30%, demonstrating possible applications in night version and bioimaging. (c) 2023 Elsevier B.V. All rights reserved.

The NIR phosphor-converted light-emitting diode (NIR pc-LED) is a new near-infrared light source that has been widely studied. Among various NIR phosphors, Cr3+ doped gadolinium aluminum gallium garnet (GAGG:Cr3+) ceramic phosphor has shown great potential due to its ultra-high efficiency and thermal stability. Despite its capabilities, its detection range may be limited due to a relatively narrow emission bandwidth. To make the GAGG:Cr3+ ceramic phosphors achieve both high efficiency and broadband emission, a series of Gd3Al2-x-yScxGa3O12:yCr3+ (GASGG:Cr3+) ceramic phosphors were prepared. Thanks to the decrease of crystal field strength with the doping of Sc3+, the full width at half maximum (FWHM) of GASGG:Cr3+ ceramic phosphors were extended from 84 nm to 117 nm, and the emission peak exhibited a red-shift of 46 nm. Meanwhile, it still retained extremely high external quantum efficiency (EQE = 47%) and excellent thermal stability (90.7% @150 degrees C). Then, a NIR pc-LED prototype device was fabricated by combining GASGG:Cr3+ ceramic phosphor with a blue LED chip. The NIR light output power and the photoelectric conversion efficiency of this device achieved 646 mW and 19.2%, respectively. Finally, the application effect in night vision and venography of this prototype device was demonstrated.

In the high-power white light LEDs/LDs area, obtaining phosphor-converted materials with high thermal stability and high luminous emittance with proper blue/yellow light ratio has been the main challenge in recent years. In this study, a group of (CexY1-x)3(ScyAl1-y)5O12 transparent ceramics with high optical quality were proposed to rise to that challenge. Their spectra were regulated by incorporating Sc3+, showing blue shifted emission bands (peak position from 554 nm-538 nm), blue shifted excitation bands (462-445 nm) and narrowed full width at half maxima (120-112 nm). Significantly, the prepared Ce:YScAG transparent ceramics (TC) exhibited decent thermal quenching performance with the photoluminescence intensity at 150 degrees C maintaining 88.7% of its original value at room temperature. The Sc incorporation impacted the atoms' occupation and distance, crystal field splitting and energy band structure. Under remote LD excitation mode, the luminous efficiency of the prepared Ce:YScAG TC can achieve 164.8 lm/W. And even if the Ce3+ doping reaches 2.0 at%, the LE can still maintain 117.8 lm/W, exhibiting decent concentration quenching characteristic. Consequently, Ce:YScAG TCs have great potential as promising phosphor-converted materials in future high-power LED and LD white lighting.