The corrosion behavior of air-plasma-sprayed Yb2SiO5 environmental barrier coatings is investigated under exposure to natural volcanic ash (VA) and synthetic calcium-magnesium-aluminosilicate (CMAS) at high temperatures. Yb2SiO5 demonstrates superior resistance to VA at 1300 degrees C/1400 degrees C. From one perspective, Ca-lean VA possesses higher viscosity, leading to slower intrinsic infiltration rate. Furthermore, a more modest chemical degradation is exhibited by Yb2SiO5 coating when being attacked by VA versus CMAS. Against CMAS, Yb2SiO5 dissolution is followed by apatite reprecipitation, forming a dense layer that could slow but not stop further infiltration and thermochemical interaction. In contrast, the interaction with Ca-lean VA melt results in the conversion of coating surface into a thin, dense Yb2Si2O7 layer via dissolution-precipitation. This process would drive the melt system to be in thermodynamic equilibrium with the remaining coating, after which Yb2SiO5 stabilizes and no longer reacts with the modified VA melt, except for residual Yb2O3 impurities present in plasma-sprayed coating. With thermodynamic equilibrium mechanism being dominant in VA corrosion, both crystal structure and microstructural integrity of Yb2SiO5 coating are preserved even under longer VA exposures.

Molybdenum (Mo) is characterized by its high melting point, high strength, exceptional thermal stability, and outstanding corrosion resistance. The preparation of Mo nanopowders with ultrafine particle sizes is critical for achieving superior properties. This paper introduces various methods for preparing Mo nanopowders, including mechanical ball milling, hydrogen (H2) reduction of Mo oxides and MoCl6, pretreatment-assisted H2 reduction, metallothermic reduction (isothermal heat treatment and self-propagating synthesis), RBH4 (where R = Na or K) reduction, electrolytic reduction, pyrolysis of Mo(CO)6 and electrical explosion. Various pretreatment methods were utilized in the pretreatment-assisted H2 reduction methods, including mechanical ball milling activation, metal salt addition, plasma treatment, carbon (C) reduction, sol-gel processes, and solution combustion. This paper presents and reviews the reaction mechanisms, influencing factors, and the advantages and disadvantages associated with each method.

To enhance the properties of ZrB2-SiC based ceramics, molybdenum (Mo) was deposited onto SiC powders and introduced into the ceramics. Using a two-step method involving sequential reduction by carbon and hydrogen, and a C/Mo molar ratio of 1.1, Mo-modified SiC powders were successfully obtained and throughly mixed with ZrB2. The ZrB2-SiC based ceramics were then fabricated through hot-press sintering. The incorporation of Mo improved the densification of the ceramic, achieving a relative density of 99.59% and reducing the average grain size of ZrB2 to 2.38 mu m. The ceramic exhibited improved mechanical properties, including an elastic modulus of 260.12 GPa, hardness of 20.86 GPa, a fracture strength of 739.07 MPa, toughness of 6.80 MPa m1/2, and a fracture work of 162.94 J/m2. Its critical thermal shock resistance was 320 degrees C, which increased to 524 degrees C after pre-oxidation, likely due to crack healing by a glass layer formed on the surface. The linear and mass ablation rates after oxygen-acetylene ablation at 1855 degrees C for 101 s were -0.46 mu m/s and -0.13 mg/s, respectively.

Molybdenum modified SiC powders were synthesized via a C-H-2 reduction and uniformly mixed with ZrB2 to ensure an even distribution of Mo. ZrB2-SiC based ceramics were prepared through hot-press sintering, and the effects of Mo on composition, microstructure, and properties were investigated. As the Mo content increased, the MoB phase gradually increased, while the structural continuity of ZrB2 was disrupted. Toughness and fracture work, exhibited an initial improvement followed by a decline with increasing Mo content. The introduction of 10 vol% Mo resulted in the ceramic with a uniform phase distribution, a fine-grained microstructure (2.12 mu m), improved toughness (7.42 MPa m(1/2)), and enhanced fracture work (200.05 J/m(2)). Its critical thermal shock temperature difference was 416 degrees C, which increased to 536 degrees C after pre-oxidation. After ablation for 100 s, it showed linear and mass ablation rates of -0.27 mu m/s and -0.05 mg/s, respectively, with a maximum surface temperature reaching 2398 degrees C.

To address the problem of inferior thermal shock resistance in ZrB2-based ceramics, a yield in-situ ZrB2-SiCPyrolytic Carbon (ZSPyC) ceramic was developed to improve the thermal ablation resistance of ZrB2-SiC ceramics. Analysis on the mechanical, thermal and ablative properties ceramics reveals that the ZSPyC ceramic possesses flexural strength of 420 f 35 MPa and fracture toughness of 5.4 f 0.4 MPa m1/2. ZSPyC possesses a thermal expansion coefficient of 5.58 f 0.04 & times; 10-6 K- 1, slightly lower than those of ZSG. Thermal conductivities of the ZSPyC at room temperature and 1000 degrees C are 122.43 W/m center dot K and 91.37 W/m center dot K, respectively, which are higher than those of the ZSG counterpart. Compared with ZSG, ZSPyC presents high stability in shapes when exposured in oxyacetylene flame at 3000 degrees C for 300 s. Such enhanced ablative resistance was attributed to the polyethersulfone derived PyC, which enhanced thermal conductivity and fracture toughness while reduced thermal expansion of ZrB2-SiC ceramics.

To address the need for high-performance conductive composites in flexible electronics, this study developed a novel silicone rubber composite reinforced with copper-plated carbon nanotubes. A uniform and dense metallic copper coating was successfully constructed on the nanotubes through a combined process of acid oxidation and palladium-catalyzed chemical plating. This coating not only serves as an effective thermal barrier, enhancing the composite's thermal stability but also enables synergistic performance enhancement through optimized interfacial design. Electrically, the copper-plated nanotubes form an efficient three-dimensional conductive network within the silicone rubber matrix, allowing the composite's conductivity to be precisely tuned across three orders of magnitude, from 8 x 10-3 S/m at low loading to 5 x 101 S/m at high loading. Mechanically, the rigid metallic coating transforms the nanotubes into an effective reinforcing phase, providing strong interfacial bonding and resulting in a maximum tensile strength of 4.3 MPa at optimal loading, along with significantly improved Young's modulus and hardness. This work demonstrates that surface metallization is an effective interfacial strategy for developing multifunctional elastomers, showing particular promise for applications requiring both reliable conductivity and mechanical durability.

Uranium oxides, with excellent thermal and chemical stability, are widely used as nuclear fuels. They also offer unique advantages in catalysis, due to their complex electronic structures, tunable valence states, and abundant oxygen vacancies. This article reviews the state of the art in the synthesis of uranium oxide nanomaterials using various methods, including hydrothermal synthesis, template methods, surfactant-assisted techniques, ionizing irradiation, laser ablation, sol–gel processes, and others. The reaction mechanisms and influencing factors of each method are discussed in detail, along with a comprehensive evaluation of their advantages and disadvantages. Furthermore, the catalytic performance of uranium oxides in applications such as volatile organic compound degradation, alcohol oxidation, desulfurization, nitrogen oxide conversion, and enzyme-like catalysis is examined, highlighting their potential in environmental catalysis and energy conversion.

In order to overcome the inherent brittleness of ZrB2-based ceramics, ZrB2-SiC composites toughened by BN fiber and C fiber were prepared by hot pressing. The mechanical properties, residual strength after oxidation and ablation performance of BNf/ZrB2-SiC (ZSB) and Cf/ZrB2-SiC (ZSC) ceramics were investigated. The flexural strength and fracture toughness of ZSB at room temperature were 610 f 21 MPa and 5.5 f 0.3 MPa m1/2, respectively. After plasma flame ablation for 60 s, the mass and linear ablation rates of ZSB were -0.14 mg/s and -0.33 mu m/s, respectively. ZSB ceramics exhibited non-ablative characteristics. And the sample remained intact after ablation, while ZSC was catastrophically destroyed. The superior ablation resistance of ZSB was attributed to the introduction of BNf, which gave ZSB higher toughness, lower thermal expansion coefficient and modulus. The thermal shock resistance of ZSB was improved. In addition, the oxidation of BNf was slowed down by the formation of liquid phase. Cf directly generated gas. Gas volatilization provided a preferential path for oxidation to accelerate oxidation.

Rare-earth hafnates RE4Hf3O12 exhibit tremendous potential as candidates for exterior thermal barrier coatings (TBCs) in the manufacture of multilayer thermal/environmental barrier coating (T/EBC) architectures, providing enhanced protection for SiCf/SiC ceramic matrix composites (CMCs). Three RE4Hf3O12 (RE = Y, Er and Yb) ceramics were fabricated, and their phase structures were characterized by x-ray diffractometry and Raman spectroscopy. It has been revealed that the crystal structure of RE4Hf3O12 shows great dependence on the ionic radius ratio r(RE)/r(Hf). The three RE4Hf3O12 compounds not only demonstrate excellent phase stability up to 1500 degrees C, but also exhibit exceptional chemical inertness to Yb-based monosilicate, a leading EBC material. Furthermore, the intermediate linear thermal expansion coefficient (8-9 x 10(-6) K-1), low thermal conductivity (1.30-1.86 W/mK, 1000 degrees C), high hardness (similar to 10.0 GPa) and fracture toughness (1.93-2.02 MPa m(1/2)) jointly highlight the potential T/EBC application of RE4Hf3O12 compounds, especially Yb4Hf3O12.

Uranium dioxide (UO2) aerogels were prepared through a sol-gel approach combined with supercritical CO2 drying, followed by thermal treatment. Two technical schemes were used to synthesize the UO2 aerogel. The first scheme involved the synthesis of U3O8 aerogel, which was subsequently converted to UO2. In the second scheme, UO2 aerogel was synthesized via the reduction of the precursor aerogel at elevated temperatures. The influence of the reduction temperature was systematically examined on the density, porosity, phase composition, and microstructure of the obtained aerogel. As the temperature increased, the density of the UO2 aerogel rose, while its porosity decreased. The composition and phase transition from the precursor gel to UO2 aerogel were elucidated, revealing the synthesis mechanism of UO2. The UO2 aerogel exhibited superior catalytic activity and stability in the degradation of 3,3 ',5,5 '-tetramethylbenzidine (TMB) and tetracycline hydrochloride (TCH).

Tantalum carbide (TaC) ceramics are promising candidates for various aerospace and hypersonic vehicles because of their high melting temperature. Here, we proposed a reactive sintering approach by spark plasma sintering and in situ synthesis of Ti3SiC2 at 1500 degrees C to lower the sintering temperature and then enhance the mechanical properties of TaC ceramics via composite engineering. It is found that the relative density of the TaC/ Ti3SiC2 ceramics increased with the increase of Ti3SiC2 phase while the growth of TaC grains was inhibited because of the pinning effect of Ti3SiC2 grains. The Ti3SiC2 phase gave rise to some toughening mechanisms ascribed to its layer structure, thus the flexural strength of the TaC/Ti3SiC2 ceramics increased from 423 f 12.4 MPa to 472 f 7.8 MPa and the fracture toughness increased from 4.2 f 0.24 MPa m1/2 to 5.2 f 0.25 MPa m1/2. This work provides insight into optimizing the composition design and mechanical properties of TaC ceramics.

In this study, fibrous monolithic precursors with uniform cell boundary were prepared by wet-spinning and co-extrusion, then the fibrous monolithic SiCw/ZrB2-SiC (FZS) and BN/ZrB2-SiC (FZN) ceramics with SiCw and BN as interface materials were compacted by hot pressing. The room temperature mechanical properties of FZS and FZN were investigated and compared. The flexural strength and fracture toughness of FZS ceramic at room temperature are 115 MPa and 3.4 MPam1/2, respectively, superior to FZN ceramic. The oxidation behavior and residual strength after oxidation of FZS and FZN ceramics were also compared. After 0.5 h oxidation, the strength and toughness of FZS ceramic could reach a highest value of 199 MPa and 4.06 MPam1/2, respectively. Meanwhile, the fracture work of FZS is 153 J/m2. It is worth noting that after 5 h of oxidation, FZS ceramic demonstrates excellent strength retention. The high strength retention of FZS after oxidation is mainly attributed to the fact that SiCw, as an interface layer, generates high viscosity SiO2 glass phase during 1500 degrees C oxidation. The large amount of glass phase fills the surface cracks in FZS, and forms a dense protective diffusion barrier on the surface, hindering the further oxidation.

To enhance the mechanical properties of ZrB2-based ceramics, especially the toughness, molybdenum (Mo) was introduced into the ceramic matrix by in-situ synthesis on ceramic powders. With Mo(CO)6 as the precursor, Mo was uniformly deposited on ZrB2 and ZrB2-SiC powders by solvothermal method. Compared with ZB and ZS, the introduction of Mo increased the relative densities of ZM and ZSM from 96.39 % and 98.01 % to 98.41 % and 99.26 %, respectively. The Mo additive also enhanced the elastic modulus and hardness of ZB and ZS significantly, and refined the ZrB2 grain size of ZB and ZS. Compared with ZS, the flexural strength and fracture toughness of ZM were enhanced by 30.49 % and 13.37 %, respectively. The flexural strength and fracture toughness of ZSM were improved by 41.37 % and 19.57 % over those of ZS, respectively. Uniformly distributed Mo on ceramic powders was superior to SiC in the densification and grain refinement, which improved the properties of both ZrB2 and ZrB2-SiC ceramics.

In this paper, polysilazane photocurable slurry with low viscosity and excellent rheological properties was prepared with (3-Si3N4 filler. Digital light processing (DLP) technique was utilised to form green bodies through optimized printing parameters. It was found that the introduction of (3-Si3N4 filler reduced the shrinkage and improved the mechanical properties of the polysilazane derived SiCN ceramics. The flexural strength of the resulted ceramics reached a maximum of 253.0 f 15.1 MPa while 20 wt% of (3-Si3N4 powder was added, and the fracture toughness increased to 3.1 f 0.3 MPa m1/2 at 30 wt% of the (3-Si3N4 powder addition. The shape of the introduced (3-Si3N4 particles were believed to be faveriable for uniform dispersion in the printing slurry without agglomeration. In the following pyrolysis treament the (3-Si3N4 powders promoted the release of gaseous products so that maintained the structure integrety of the printed parts and the rod-like (3-Si3N4 particles enhanced the energy dissipation during ceramic fracture. In this study, silicon-based composite of (3-Si3N4/SiCN ceramics with excellent mechanical properties were prepared by DLP additive manufacturing technology, which confirmed the feasibility and the great potential of photo-curing additive manufacturing technology in the manufacturing of SiCN ceramic matrix composites with complex structures.

The protection for carbon fibers is crucial for carbon fiber-reinforced materials. Carbon coatings were prepared on carbon fibers through gelation, hydrothermal caramelization and pyrolysis, with glucose as precursor of carbon. The glucose-to-carbon conversion mechanism was explored, as well as the effect of high pressure in hydrothermal reactor and the catalytic role of KCl. The high pressure suppressed gas escape and was beneficial to the formation of dense carbon coating. The KCl promoted the generation of 5-HMF, thereby accelerated the glucose-to-caramel conversion. Cf/ZrB2-SiC composites were prepared by introducing ZrB2-SiC slurry into the carbon fiber preform and hot press sintering. The carbon coating protected the carbon fibers from damage during sintering at high temperature. The carbon coating significantly improved the flexural strength, fracture toughness, and fracture work of Cf/ZrB2-SiC composites from 122 MPa, 3.24 MPam1/2, and 231.6 J/m2 to 321 MPa, 5.87 MPam1/2, and 567.1 J/m2, respectively.

The synergistic improvement of interlaminar toughness, thermal conductivity, and electromagnetic wave absorption of carbon fiber/epoxy (CF/EP) composites is a far-reaching and challenging research work. In this study, CF/EP composites with SiC nanowires (SiCnw) loaded polypropylene nonwoven fabrics (PPNWF) interleaves were prepared by mold pressing process. The effect of SiCnw-loaded PPNWF on the mechanical properties, thermal properties, DMA, and reflection loss of CF/EP composites was investigated. The results showed that the G(IIC) and thermal conductivity of SiCnw/PPNWF/CF/EP composites with PPNWF surface density of 10 g/cm(2) were 1285.4 J/m(2) and 0.75 Wm(-1)K-1, respectively, which were 65.6% and 92.3% higher than those of CF/EP composite, respectively. The impact strength of PPNWF/CF/EP composites reached 253.4 kJ/m(2) with a PPNWF face density of 20 g/cm(2), which was 29.9% higher than that of CF/EP composites. The reflection loss of SiCnw/CF/EP composite reached -17.57 dB at 1.96 GHz with a thickness of 7.5 mm, which was 258% lower than that of CF/EP composite. DMA tests showed that the T-g of SiCnw-loaded PPNWF modified CF/EP composites was higher than that of CF/EP composites. This work was of great significance to broaden the high-end applications of composite materials.

Lightweight materials with wide absorption capabilities, particularly in the C-band, have remained a challenge thus far. Recent research has indicated that effective absorption networks built by microfiber polarization loss can be a significant factor in increasing the effective absorption bandwidth (EAB). In this study, leaf vein-like carbon (LVC) was synthesized using an in situ blowing strategy. Taking inspiration from photosynthesis energy conversion mechanisms, a leaf veins-like hierarchical structure was created to establish an effective impedance-matching network and generate a high-density polarization region through leaf vein microfibers. This enhanced polarization relaxation effectively broadens the EAB of the LVC. At a low filling ratio of 6.3 wt