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Ultra-high temperature ceramics (UHTCs) are generally referred to the carbides, nitrides, and borides of the transition metals, with the Group IVB compounds (Zr & Hf) and TaC as the main focus. The UHTCs are endowed with ultra-high melting points, excellent mechanical properties, and ablation resistance at elevated temperatures. These unique combinations of properties make them promising materials for extremely environmental structural applications in rocket and hypersonic vehicles, particularly nozzles, leading edges, and engine components, etc. In addition to bulk UHTCs, UHTC coatings and fiber reinforced UHTC composites are extensively developed and applied to avoid the intrinsic brittleness and poor thermal shock resistance of bulk ceramics. Recently, highentropy UHTCs are developed rapidly and attract a lot of attention as an emerging direction for ultra-high temperature materials. This review presents the state of the art of processing approaches, microstructure design and properties of UHTCs from bulk materials to composites and coatings, as well as the future directions.

Based on the huge potential of graphene-based composites in electrical, thermal and mechanical applications, which have been widely used in electronics, energy storage and conversion, sensors and structural composites, the assembly and three-dimensional (3D) configuration of graphene nanosheets is an important routine to realize and even optimize its excellent properties. Considering the anisotropy of two-dimensional (2D) graphene and the accuracy of 3D architecture, 3D printing technology stands out in the preparation of periodic and diversified 3D graphene due to its efficient and controllable construction process. Moreover, the interconnected graphene conductive network and lightweight structural regulation can realize the integration of structure and function from low-dimensional to multidimensional. In these circumstances, the structural design and related functional applications of the printed graphene-based architecture are reviewed, and it is important to understand the inks properties, macro-microstructural regulation and corresponding application prospects. Besides, a summary and outlook is prepared in the last part, which points out the application difficulties and future development of 3D-printed graphene-based architecture.

Superconductor-ferromagnet interfaces in two-dimensional heterostructures present a unique opportunity to study the interplay between superconductivity and ferromagnetism. The realization of such nanoscale heterostructures in van der Waals (vdW) crystals remains largely unexplored due to the challenge of making atomically-sharp interfaces from their layered structures. Here, we build a vdW ferromagnetic Josephson junction (JJ) by inserting a few-layer ferromagnetic insulator Cr 2 Ge 2 Te 6 into two layers of superconductor NbSe 2 . The critical current and corresponding junction resistance exhibit a hysteretic and oscillatory behavior against in-plane magnetic fields, manifesting itself as a strong Josephson coupling state. Also, we observe a central minimum of critical current in some JJ devices as well as a nontrivial phase shift in SQUID structures, evidencing the coexistence of 0 and π phase in the junction region. Our study paves the way to exploring sensitive probes of weak magnetism and multifunctional building-blocks for phase-related superconducting circuits using vdW heterostructures. The superconductor-ferromagnet interface provides a unique opportunity to study the interplay between superconductivity and ferromagnetism. Here, the authors build a van der Waals ferromagnetic Josephson junction evidencing a strong 0 and π phase Josephson coupling.

Highlights A new strategy for elaborate regulation of microstructure was successfully introduced by the ice template‑assisted 3D printing and chemical vapor deposition strategy, including graphene nanoplate/silicon carbide nanowires hierarchical porous structure and graphene nanoplate/boron nitride composite heterogeneous interface. The composite exhibits excellent electromagnetic wave absorption performance with an RL min of -37.8 dB and an EAB max of 9.2 GHz (from 8.8 to 18.0 GHz) at 2.5 mm. And the high-temperature absorption stability makes it a promising absorber candidate under high temperature and oxidizing atmosphere. With vigorous developments in nanotechnology, the elaborate regulation of microstructure shows attractive potential in the design of electromagnetic wave absorbers. Herein, a hierarchical porous structure and composite heterogeneous interface are constructed successfully to optimize the electromagnetic loss capacity. The macro–micro-synergistic graphene aerogel formed by the ice template‑assisted 3D printing strategy is cut by silicon carbide nanowires (SiC nws ) grown in situ, while boron nitride (BN) interfacial structure is introduced on graphene nanoplates. The unique composite structure forces multiple scattering of incident EMWs, ensuring the combined effects of interfacial polarization, conduction networks, and magnetic-dielectric synergy. Therefore, the as-prepared composites present a minimum reflection loss value of − 37.8 dB and a wide effective absorption bandwidth (EAB) of 9.2 GHz (from 8.8 to 18.0 GHz) at 2.5 mm. Besides, relying on the intrinsic high-temperature resistance of SiC nws and BN, the EAB also remains above 5.0 GHz after annealing in air environment at 600 °C for 10 h.

In this work, three-dimensional (3D) C f /SiBCN composites were fabricated by polymer infiltration and pyrolysis (PIP) with poly(methylvinyl)borosilazane as SiBCN precursor. The 3D microstructure evolution process of the composites was investigated by an advanced X-ray computed tomography (XCT). The effect of dicumyl peroxide (DCP) initiator addition on the crosslinking process, microstructure evolution, and mechanical properties of the composites were uncovered. With the addition of a DCP initiator, the liquid precursor can cross-linking to solid-state at 120 °C. Moreover, DCP addition decreases the release of small molecule gas during pyrolysis, leading to an improved ceramic yield 4.67 times higher than that without DCP addition. After 7 PIP cycles, density and open porosity of the final C f /SiBCN composite with DCP addition are 1.73 g·cm −3 and ∼10%, respectively, which are 143.0% higher and 30.3% lower compared with the composites without DCP addition. As a result, the flexural strength and elastic modulus of C f /SiBCN composites with DCP addition (371 MPa and 31 GPa) are 1.74 and 1.60 times higher than that without DCP addition (213 MPa and 19.4 GPa), respectively.

Layer-structured interphase, existing between reinforcing fiber and ceramics matrix, is an indispensable constituent for fiber-reinforced ceramic composites due to its determinant role in the mechanical behavior of the composites. However, the interphase may suffer high residual stress because of the mismatch of thermal expansion coefficients in the constituents, and this can exert significant influence on the mechanical behavior of the composites. Here, the residual stress in the boron nitride (BN) interphase of continuous SiC fiber-reinforced SiC composites was measured using a micro-Raman spectrometer. The effects of the residual stress on the mechanical behavior of the composites were investigated by correlating the residual stress with the mechanical properties of the composites. The results indicate that the residual stress increases from 26.5 to 82.6 MPa in tension as the fabrication temperature of the composites rises from 1500 to 1650 °C. Moreover, the increasing tensile residual stress leads to significant variation of tensile strain, tensile strength, and fiber/matrix debonding mode of the composites. The sublayer slipping of the interphase caused by the residual stress should be responsible for the transformation of the mechanical behavior. This work can offer important guidance for residual stress adjustment in fiber-reinforced ceramic composites.

Fiber damage and uniform interphase preparation are the main challenges in conventional short fiber reinforced ceramic matrix composites. In this work, we develop a novel processing route in fabrication of short carbon fiber reinforced ZrB 2 -SiC composites (C sf /ZrB 2 -SiC) overcoming the above two issues. At first, C sf preforms with oriented designation and uniform PyC/SiC interphase are fabricated via direct ink writing (DIW) of short carbon fiber paste followed by chemical vapor infiltration. After that, ZrB 2 and SiC are introduced into the preforms by slurry impregnation and reactive melt infiltration, respectively. Microstructure evolution and optimization of the composites during fabrication are investigated in detail. The as-fabricated C sf /ZrB 2 -SiC composites have a bulk density of 2.47 g/cm 3 , with uniform weak interphase and without serious fiber damage. Consequently, non-brittle fracture occurs in the C sf /ZrB 2 -SiC composites with widespread toughening mechanisms such as crack deflection and bridging, interphase debonding, and fiber pull-out. This work provides a new opportunity to the material design and selection of short fiber reinforced composites.

The bulk photovoltaic effect (BPVE) in non-centrosymmetric materials has attracted significant attention in recent years due to its potential to surpass the Shockley-Queisser limit. Although these materials are strictly constrained by symmetry, progress has been made in artificially reducing symmetry to stimulate BPVE in wider systems. However, the complexity of these techniques has hindered their practical implementation. In this study, we demonstrate a large intrinsic photocurrent response in centrosymmetric topological insulator Ag 2 Te, attributed to the surface photogalvanic effect (SPGE), which is induced by symmetry reduction of the surface. Through diverse spatially-resolved measurements on specially designed devices, we directly observe that SPGE in Ag 2 Te arises from the difference between two opposite photocurrent flows generated from the top and bottom surfaces. Acting as an efficient SPGE material, Ag 2 Te demonstrates robust performance across a wide spectral range from visible to mid-infrared, making it promising for applications in solar cells and mid-infrared detectors. More importantly, SPGE generated on low-symmetric surfaces can potentially be found in various systems, thereby inspiring a broader range of choices for photovoltaic materials. The bulk photovoltaic effect holds promise for various optoelectronic applications, but it is usually restricted to non-centrosymmetric materials operating in the visible range. Here, the authors report a surface photogalvanic effect spanning from visible to midinfrared wavelengths in a centrosymmetric topological insulator, Ag 2 Te.

Ultrahigh temperature ceramic matrix composites (UHTCMCs) are critical for the development of high Mach reusable hypersonic vehicles. Although various materials are utilized as the thermal components of hypersonic vehicles, it is still challenging to meet the ultrahigh temperature ablation‐resistant and reusability. Herein, the Y2O3 reinforced Cf/ZrB2‐SiC composites are designed, which demonstrates near‐zero damage under long‐term ablation at temperatures up to 2500 °C for ten cycles. Notably, the linear ablation rate of the composites (0.33 µm s−1) is over 24 times better than that of the conventional Cf/C‐ZrC at 2500 °C (8.0 µm s−1). Moreover, the long‐term multi‐cycle ablation mechanisms of the composites are investigated with the assistance of DFT calculations. Especially, the size effect and the content of the Zr‐based crystals in the oxide layer fundamentally affect the stability of the oxide layer and the ablation properties. The ideal component and structure of the oxide layer for multi‐cycle ablation condition are put forward, which can be obtained by controlling the Y2O3/ZrB2 mole ratio and establishing Y‐Si‐O – t‐Zr0.9Y0.1O1.95 core‐shell nano structure. This work proposes a new strategy for improving the long‐term multi‐cycle ablation resistance of UHTCMCs. The Y2O3 reinforced Cf/ZrB2‐SiC composites are designed in this work to form the high stability oxide protective layer. The size effect of the formed Zr0.9Y0.1O1.95 nano‐crystals increases the viscosity of oxide layer and retarding the evaporation of SiO2 phase during ablation, which significantly improve the long‐term and cyclic ablation properties of the composites.

Residual stress originated from thermal expansion mismatch determines the mechanical properties of ceramic matrix composites (CMCs). Here, continuous SiC fiber reinforced SiC matrix (SiC f /SiC) composites were fabricated by nano-infiltration and transient eutectic-phase (NITE) method, and the residual stress of the composites was investigated using high-temperature Raman spectrometer. With temperature increasing from room temperature to 1400 °C, the residual stresses of the matrix and the fiber decrease from 1.29 to 0.62 GPa and from 0.84 to 0.55 GPa in compression respectively, while that of the interphase decreases from 0.16 to 0.10 GPa in tension. The variation of residual stress shows little effect on the tensile strength of the composites, while causes a slight decrease in the tensile strain. The suppression of fiber/matrix debonding and fiber pulling-out caused by the residual stress reduction in the interphase is responsible for the decreasing tensile strain. This work can open up new alternatives for residual stress analysis in CMCs.