To investigate the bonding behavior of SiC-free composite ceramics via spark plasma sintering, this study demonstrates the successful joining of B₄C–40 vol% TiB₂ ceramics using a Ti foil interlayer within the temperature range of 1000–1400 ^oC. The bonding mechanisms across temperatures were systematically elucidated through integrated approaches, including phase composition analysis, microstructural observation, thermodynamic and diffusion kinetic calculations. Results reveal that the competitive reactions between active Ti and ceramic phases drive a sequential compositional evolution at the joint interface: starting from pure Ti, the interface transitions to a mixture of TiB₂, TiC, TiB, and residual Ti, ultimately forming a stable TiB₂–TiC–TiB ceramic assemblage as temperature increases. Kinetic analysis shows that between 1000–1300 °C, reaction layer thickness follows a diffusion-controlled growth model, directly correlated with temperature via Arrhenius-type kinetics. At the highest temperature of 1400 °C, complete consumption of Ti yields a full-ceramic joint. Mechanical characterization indicates that these temperature-dependent microstructural changes significantly affect joint performance: the maximum shear strength of 72 MPa is achieved at 1300 °C, accompanied by crack penetration through the ceramic, reaction layer, and residual Ti layer.

La₂Ce₂O₇ exhibits intense absorption ability in the ultraviolet (UV) region with excellent photostability, and can replace TiO₂ and ZnO as an UV absorber in sunscreen formulations. Traditionally, La₂Ce₂O₇ powder is synthesized by the solid-state method, which has problems such as high synthesis temperature, small specific surface area of the powder, and poor light absorption ability. In this study, La₂Ce₂O₇ powder was successfully synthesized by a sol-gel method with metal nitrates, citric acid and ethylene glycol as raw materials, chelating agent and stabilizer, respectively. The conversion process of the precursor, phase change of the product, morphology of the powder, and the valence state of the elements were analyzed by TG-DSC, XRD, SEM and XPS. The UV absorption performance of the product was tested using a UV-visible spectrophotometer. The photostability of the product was evaluated by photocatalytic degradation of Rhodamine B dye. The results show that pure phase La₂Ce₂O₇ powder can be synthesized by the sol-gel method at 250 ℃, which is more than 1000 ℃ lower than that of the traditional solid-state method. The maximum specific surface area of the La₂Ce₂O₇ powder synthesized by the sol-gel method is 10.04 m²/g, while that of the powder synthesized by the solid-phase method is only 0.19 m²/g.The La₂Ce₂O₇ powder synthesized at 300 ℃ shows the best UV absorption performance, 25% higher than that synthesized by the solid-state method. Compared with TiO₂, La₂Ce₂O₇ exhibits better UV absorption performance and almost no photocatalytic activity.

B₄C–TiB₂ is an advanced electrically conductive ceramic with excellent mechanical and electrical discharge machinable properties. It is challenging and rewarding to achieve highly conductive and hard B₄C–TiB₂ composites at a minimum content of conductive TiB₂ that has inferior hardness but double specific gravity of the B₄C matrix. A novel strategy was used to construct conductive networks in B₄C‒15 vol% TiB₂ composite ceramics with B₄C, TiC, and amorphous B as raw materials by a two-step spark plasma sintering method. The influences of particle size matching between B₄C and TiC on the conducting of the strategy and the microstructure were discussed based on the selective matrix grain growth mechanism. The mechanical and electrical properties were also systematically investigated. The B₄C–15 vol% TiB₂ composite ceramic prepared from 10.29 µm B₄C and 0.05 µm TiC powders exhibited a perfect three-dimensional interconnected conductive network with a maximum electrical conductivity of 4.25×10⁴ S/m, together with excellent mechanical properties including flexural strength, Vickers hardness, and fracture toughness of 691±58 MPa, 30.30±0.61 GPa, and 5.75±0.32 MPa·m^1/2, respectively, while the composite obtained from 3.12 µm B₄C and 0.8 µm TiC powders had the best mechanical properties including flexural strength, Vickers hardness, and fracture toughness of 827±35 MPa, 32.01±0.51 GPa, and 6.45±0.22 MPa·m^1/2, together with a decent electrical conductivity of 0.65×10⁴ S/m.

To achieve lightweight B₄C-based composite ceramics with high electrical conductivities and hardness, B₄C–TiB₂ ceramics were fabricated by reactive spark plasma sintering (SPS) using B₄C, TiC, and amorphous B as raw materials. During the sintering process, fine B₄C–TiB₂ composite particles are firstly in situ synthesized by the reaction between TiC and B. Then, large raw B₄C particles tend to grow at the cost of small B₄C particles. Finally, small TiB₂ grains surround large B₄C grains to create a three-dimensional interconnected intergranular TiB₂ network, which is beneficial for an electro-conductive network and greatly improves the conductivity of the ceramics. The effect of the B₄C particle size on the mechanical and electrical properties of the ceramics was investigated. When the particle size of initial B₄C powders is 10.29 µm, the obtained B₄C–15 vol% TiB₂ composite ceramics exhibit an electrical conductivity as high as 2.79×10⁴ S/m and a density as low as 2.782 g/cm³, together with excellent mechanical properties including flexural strength, Vickers hardness (HV), and fracture toughness (K_IC) of 676 MPa, 28.89 GPa, and 5.28 MPa·m^1/2, respectively.

Porous ceramics were prepared by a high-temperature melting foaming method with red mud and high-aluminum fly ash as main raw materials. The effects of raw material composition and foaming process on the cellular structure and properties were investigated. The results show that the cellular structure of porous ceramic obtained after melt foaming at 1200 ℃ for 1 h changes from closed to open, eventually forming a composite cellular structure. Also, the average pore size and porosity increase, while the bulk density and thermal conductivity decrease with increasing the mass ratio of SiO₂/Al₂O₃ from 1.2 to 1.9 in the raw material composition. At the blowing agent of 5% (in mass fraction) SiC and the melting agent of albite and microcline of 35%, a composite cellular structure porous ceramic with the bulk density of 0.63 g/cm³, average pore size of 0.98 mm and bulk porosity of 70% is obtained, and its flexural strength and thermal conductivity are 7.17 MPa and 0.34 W/(m·K), respectively.