Rare-earth phosphates (REPO₄) are regarded as one of the promising thermal/environmental barrier coating (T/EBC) materials for SiC_f/SiC ceramic matrix composites (SiC-CMCs) owing to their excellent resistance to water vapor and CaO–MgO–Al₂O₃–SiO₂ (CMAS). Nevertheless, a relatively high thermal conductivity (κ) of the REPO₄ becomes the bottleneck for their practical applications. In this work, novel xenotime-type high-entropy (Dy_1/7Ho_1/7Er_1/7Tm_1/7Yb_1/7Lu_1/7Y_1/7)PO₄ (HE (7RE_1/7)PO₄) has been designed and synthesized for the first time to solve this issue. HE (7RE_1/7)PO₄ with a homogeneous rare-earth element distribution exhibits high thermal stability up to 1750 ℃ and good chemical compatibility with SiO₂ up to 1400 ℃. In addition, the thermal expansion coefficient (TEC) of HE (7RE_1/7)PO₄ (5.96×10⁻⁶ ℃⁻¹ from room temperature (RT) to 900 ℃) is close to that of the SiC-CMCs. What is more, the thermal conductivities of HE (7RE_1/7)PO₄ (from 4.38 W·m⁻¹·K⁻¹ at 100 ℃ to 2.25 W·m⁻¹·K⁻¹ at 1300 ℃) are significantly decreased compared to those of single-component REPO₄ with the minimum value ranging from 9.90 to 4.76 W·m⁻¹·K⁻¹. These results suggest that HE (7RE_1/7)PO₄ has the potential to be applied as the T/EBC materials for the SiC-CMCs in the future.

Mechanical properties consisting of the bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, etc., are key factors in determining the practical applications of MAX phases. These mechanical properties are mainly dependent on the strength of M-X and M-A bonds. In this study, a novel strategy based on the crystal graph convolution neural network (CGCNN) model has been successfully employed to tune these mechanical properties of Ti₃AlC₂-based MAX phases via the A-site substitution (Ti₃(Al_1-xA_x)C₂). The structure-property correlation between the A-site substitution and mechanical properties of Ti₃(Al_1-xA_x)C₂ is established. The results show that the thermodynamic stability of Ti₃(Al_1-xA_x)C₂ is enhanced with substitutions A = Ga, Si, Sn, Ge, Te, As, or Sb. The stiffness of Ti₃AlC₂ increases with the substitution concentration of Si or As increasing, and the higher thermal shock resistance is closely associated with the substitution of Sn or Te. In addition, the plasticity of Ti₃AlC₂ can be greatly improved when As, Sn, or Ge is used as a substitution. The findings and understandings demonstrated herein can provide universal guidance for the individual synthesis of high-performance MAX phases for various applications.

In this work, gold nanoparticles (AuNPs) decorated Ti₃C₂T_x nanosheets (MXene/AuNPs composite) are fabricated through a self-reduction reaction of Ti₃C₂T_x nanosheets with HAuCl₄ aqueous solution. The obtained composite is characterized as AuNPs with the diameter of about 23 nm uniformly dispersing on Ti₃C₂T_x nanosheets without aggregation. The composite (MXene decorated on 4.8 wt% AuNPs) is further employed to construct supercapacitor for the first time with a higher specific capacitance of 278 F·g^-1 at 5 mV·s^-1 than that of pure Ti₃C₂T_x and 95% of cyclic stability after 10,000 cycles. Furthermore, MXene/AuNPs composite symmetric supercapacitor with filter paper as separator and H₂SO₄ as electrolyte, is assembled. The supercapacitor exhibits a high volumetric energy density of 8.82 Wh·L^-1 at a power density of 264.6 W·L^-1 and ultrafast-charging/ discharging performance. It exhibits as a promising candidate applied in integrated and flexible supercapacitors.

In the present work, we report the growth of all-inorganic perovskite nanorings with dual compositional phases of CsPbBr₃ and CsPb₂Br₅ via a facile hot injection process. The self-coiling of CsPbBr₃-CsPb₂Br₅ nanorings is driven by the axial stress generated on the outside surface of the as-synthesized nanobelts, which results from the lattice mismatch during the transformation of CsPbBr₃ to CsPb₂Br₅. The tailored growth of nanorings could be achieved by adjusting the key experimental parameters such as reaction temperature, reaction time and stirring speed during the cooling process. The photoluminescence intensity and quantum yield of nanorings are higher than those of CsPbBr₃ nanobelts, accompanied by a narrower full width at half maximum (FWHM), suggesting their high potential for constructing self-assembled optoelectronic nanodevices.

The new ternary CM₂A₈ (CaMg₂Al₁₆O₂₇) and C₂M₂A₁₄ (Ca₂Mg₂Al₂₈O₄₆) pure and dense ceramics were first prepared by a hot-press sintering technique, and their physical and mechanical properties were investigated. The purity of obtained CM₂A₈ and C₂M₂A₁₄ ceramics reaches 98.1 wt% and 97.5 wt%, respectively. Their microstructure is dense with few observable pores, and their grain size is about a few dozen microns. For their physical properties, the average apparent porosity of CM₂A₈ and C₂M₂A₁₄ ceramics is 0.18% and 0.13%, and their average bulk density is 3.66 g/cm³ and 3.71 g/cm³, respectively. The relative density of CM₂A₈ ceramic is 98.12% and that of C₂M₂A₁₄ ceramic is 98.67%. The thermal expansivity (50–1400 ℃) of CM₂A₈ and C₂M₂A₁₄ ceramics is 9.24×10^–6 K^–1 and 8.92×10^–6 K^–1, respectively. The thermal conductivity of CM₂A₈ and C₂M₂A₁₄ ceramic is 21.32 W/(m·K) and 23.25 W/(m·K) at 25 ℃ and 18.76 W/(m·K) and 19.42 W/(m·K) as temperature rises to 350 ℃, respectively. In addition, the mechanical properties are also achieved. For CM₂A₈ ceramic, the flexural strength is 248 MPa, the fracture toughness is 2.17 MPa·m^1/2, and the Vickers hardness is 12.26 GPa. For C₂M₂A₁₄ ceramic, the flexural strength is 262 MPa, the fracture toughness is 2.23 MPa·m^1/2, and the Vickers hardness is 12.95 GPa.

Highly pure Al₄SiC₄ powders were prepared by carbothermic reduction at 2173 K using Al₂O₃, SiO₂, and graphite as raw materials. The obtained Al₄SiC₄ powders owned hexagonal plate-like grains with a diameter of about 200-300 μm and a thickness of about 2-6 μm. Based on the experimental results, the reaction of Al₄SiC₄ formation and grain evolution mechanisms were determined from thermodynamic and first-principles calculations. The results indicated that the synthesis of Al₄SiC₄ by the carbothermic reduction consisted of two parts, i.e., solid-solid reactions initially followed by complex gas-solid and gas-gas reactions. The grain growth mechanism of Al₄SiC₄ featured a two-dimensional nucleation and growth mechanism. The gas phases formed during the sintering process favored the preferential grain growth of (0010) and $(1\overline{1}0)$ planes resulting in formation of hexagonal plate-like Al₄SiC₄ grains.