Conventional boron nitride (BN)-based composites are often limited by high porosity and long processing cycles, which severely restrict their mechanical performance and engineering applications. To overcome these limitations, a novel organic–inorganic hybrid matrix combined with a hot-compression orientation strategy is proposed. Liquid-phase polyborazylene (PBZ) was employed to promote the rearrangement and alignment of h-BN lamellae during pressing, and subsequent pyrolysis yielded a dense and continuous BN matrix with in situ precipitated nanocrystals serving as load-transfer nodes. This process significantly enhanced densification, reduced porosity, and enabled the construction of an ordered lamellar structure. Unlike conventional PIP processes that typically require ~10 repeated infiltration–pyrolysis cycles, this method achieves dense composites in a single pyrolysis step, effectively avoiding fiber damage and greatly shortening the fabrication cycle. The synergistic effects of aligned lamellae inducing extended crack propagation paths and in situ nanocrystals providing additional load-transfer mechanisms effectively improved the mechanical performance of the composites. The proposed PBZ-assisted hybrid matrix and lamellar-orientation design strategy offers a new and efficient route for developing high-performance BN-based composites with excellent wave-transmitting and thermal protection capabilities.

A new sintering densification method without the aid of a liquid phase is proposed for preparing [001]_c-textured BaTiO₃ ceramics with high ferroelectric performance. With the help of phase-field modeling, the size and concentration of the templates are optimized to control the densification process. Compared with randomly oriented BaTiO₃ ceramics, the prepared textured BaTiO₃ ceramics with designed templates demonstrate an improvement in the crystallographic preferred orientation and densification due to the orientation fluctuation of nucleation and growth, which overcomes the limitation of symmetric-constrain strains. This new densification mechanism is comprehensively revealed by the active energies of the sintering curves and electron backscattered diffraction analysis, where the obvious anisotropic shrinkage that increases the densification manifests a different driving force from that of the normal liquid-phase sintering method. The resulting highly textured BaTiO₃ ceramics exhibit abnormal comprehensive ferroelectric properties, achieving a high piezoelectric constant (d₃₃) of 490±11 pC·N⁻¹, which exceeds that of BaTiO₃ single crystals while having small remanent polarization (8.5 μC·cm⁻² at 15 kV·cm⁻¹). Thus, the current method is expected to provide a new strategy for preparing textured ferroelectric ceramics with high performance.

SiBCN based metastable ceramics and their composites possess unique microstructure and excellent high-temperature performance, and exhibit significant application potential under harsh conditions such as high-temperature oxidation, severe thermal shock, and gas flow ablation. This review focused on the SiBCN based metastable ceramics and their composites by mechanical alloying, summarized the research progress on the microstructure characteristics and evolution, mechanical properties, oxidation resistance, thermal shock resistance, and ablation resistance of SiBCN based amorphous ceramic powders and bulk ceramics based on mechanical alloying technology in recent years, also in comparison with the polymer derived counterparts. The future research focus and development trend of SiBCN based metastable ceramics with higher performance were finally pointed out.

To improve the oxidation resistance of short carbon fiber (C_sf)-reinforced mechanically alloyed SiBCN (MA-SiBCN) (C_sf/MA-SiBCN) composites, dense amorphous C_sf/SiBCN composites containing both MA-SiBCN and polymer-derived ceramics SiBCN (PDCs-SiBCN) were prepared by repeated polymer infiltration and pyrolysis (PIP) of layered C_sf/MA-SiBCN composites at 1100 °C, and the oxidation behavior and damage mechanism of the as-prepared C_sf/SiBCN at 1300–1600 °C were compared and discussed with those of C_sf/MA-SiBCN. The C_sf/MA-SiBCN composites resist oxidation attack up to 1400 °C but fail at 1500 °C due to the collapse of the porous framework, while the PIP-densified C_sf/SiBCN composites are resistant to static air up to 1600 °C. During oxidation, oxygen diffuses through preexisting pores and the pores left by oxidation of carbon fibers and pyrolytic carbon (PyC) to the interior of the matrix. Owing to the oxidative coupling effect of the MA-SiBCN and PDCs-SiBCN matrices, a relatively continuous and dense oxide layer is formed on the sample surface, and the interfacial region between the oxide layer and the matrix of the as-prepared composite contains an amorphous glassy structure mainly consisting of Si and O and an incompletely oxidized but partially crystallized matrix, which is primarily responsible for improving the oxidation resistance.

The atomic structural features and the mechanical properties of amorphous silicoboron carbonitride ceramics with 13 different compositions in the Si–BN–C phase diagram are investigated employing ab-initio calculations. Both chemical bonds and local structures within the amorphous network relate to the elemental composition. The distribution of nine types of chemical bonds is composition-dependent, where the B–C, Si–N, Si–C, and B–N bonds hold a large proportion for all compositions. Si prefers to be tetrahedrally coordinated, while B and N prefer sp²-like trigonal coordination. In the case of C, the tetrahedral coordination is predominant at relatively low C contents, while the trigonal coordination is found to be the main feature with the increasing C content. Such local structural characteristics greatly influence the mechanical properties of SiBCN ceramics. Among the studied amorphous ceramics, SiB₂C₃N₂ and SiB₃C₂N₃ with low Si contents and moderate C and/or BN contents have high elastic moduli, high tensile/shear strengths, and good debonding capability. The increment of Si, C, and BN contents on this basis results in the decrease of mechanical properties. The increasing Si content leads to the increment of Si-contained bonds that reduce the bond strength of SiBCN ceramics, while the latter two cases are attributed to the raise of sp²-like trigonal configuration of C and BN. These discoveries are expected to guide the composition-tailored optimization of SiBCN ceramics.

Geopolymers have attracted recent attention due to their wide source of raw materials, environmental protection, low-carbon technology and unique properties. However, the geopolymerization behavior of geopolymers is susceptible to the reaction reactivity of raw materials, leading to large fluctuations in the properties such as mechanical properties and durability. The issues mentioned above are directly related to the geopolymerization mechanism of geopolymers, geopolymerization kinetics, and influencing factors and regulation approach of the properties of geopolymers. Therefore, this review represented recent work and gave some future research aspects in this field to promote the utilization of low-quality aluminosilicate minerals or aluminosilicate industrial waste for the possible purpose of ‘peak carbon dioxide emissions’ and ‘carbon neutrality’.

Textured hexagonal boron nitride (h-BN) matrix composite ceramics were prepared by hot- pressing using different contents of 3Y₂O₃-5Al₂O₃ (molar ratio of 3:5) as the sintering additive. During hot-pressing, the liquid Y₃Al₅O₁₂ (YAG) phase showing good wettability to h-BN grains was in situ formed through the reaction between Y₂O₃ and Al₂O₃, and a coherent relationship between h-BN and YAG was observed with [010]_h-BN// $[\overline{1}11]$_YAG and (002)_h-BN//(321)_YAG. In the YAG liquid phase environment formed during hot-pressing, plate-like h-BN grains were rotated under the uniaxial sintering pressure and preferentially oriented with their basal surfaces perpendicular to the sintering pressure direction, forming textured microstructures with the c-axis of h-BN grains oriented parallel to the sintering pressure direction, which give these composite ceramics anisotropy in their mechanical and thermal properties. The highest texture degree was found in the specimen with 30 wt% YAG, which also possesses the highest anisotropy degree in thermal conductivity. The aggregation of YAG phase was observed in the specimen with 40 wt% YAG, which resulted in the buckling of h-BN plates and significantly reduced the texture degree.