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In the present work, novel Ni0.5Zn0.5Nd0.04Fe1.96O4 ferrite (NZNF)/polyaniline (PANI) nanocomposites were prepared by interfacial polymerization. The crystal structure, microstructure and electromagnetic parameters of the samples were investigated in detail, indicating that PANI grew uniformly on the surface of ferrite like coral. By testing the electromagnetic parameters, it was found that PANI significantly improved the real and imaginary parts of the dielectric constant of the samples, thus affecting the impedance matching and attenuation performance. The addition of PANI adversely affected the impedance matching, but had a good effect on attenuation capacity. When the amount of aniline was 25 wt% of the ferrite, the impedance matching and attenuation capacity of the as-prepared NZNF/PANI nanocomposite reached the optimal balance. The NZNF/PANI-25 nanocomposite exhibited a maximum reflection loss of −37.4 dB at 8.4 GHz, and the effective absorption bandwidth was 4.9 GHz at a thickness of 4.0 mm. This novel absorbing material is a promising absorbent with strong and wide band absorption characteristics.

Double-layer absorbers have recently been extensively studied because single-layer absorbers can hardly meet the requirements of advanced absorbing materials. However, determining how to couple the matching and absorption layers remains a challenge. In the present work, we applied the hydrothermal method to prepare an ultrasmall Fe3O4 nanoparticle and a hierarchical MXene/Fe3O4 composite and then studied the microwave attenuation capabilities of single- and double-layer absorbers containing these two materials with different thicknesses. Absorbers with well-coupled layers showed improved absorption performance on account of the excellent impedance matching behavior of the Fe3O4 layer and the high microwave attenuation capability of the MXene/Fe3O4 layer. When the thickness of the matching layer filled with Fe3O4 was 0.1 mm and that of the absorption layer filled with MXene/Fe3O4 was 1.9 mm, a maximum reflection loss of −48.7 dB was achieved at 9.9 GHz. More importantly, when the thicknesses of the matching and absorption layers were 0.9 and 1.1 mm, respectively, the effective bandwidth was nearly 3.9 GHz. The double-layer absorbers with enhanced absorption properties may be regarded as a new generation of materials for electromagnetic wave absorption.

Ideal electromagnetic (EM) wave absorption materials should exhibit strong absorption peaks and broad effective absorption bandwidths, which are important for EM protection and the stealth technology. Despite considerable advancements in this field in recent years, EM absorption materials have not reached their full potential to meet all the above-mentioned requirements, especially the broad absorption bandwidth at low frequencies. Herein, we synthesized a Co-doped NiZn ferrite (CNZFO)/polyaniline (PANI) on Ti3C2TX MXene composite with a hierarchical structure via three facile steps: exfoliation, hydrothermal process, and modified interfacial polymerization. The CNZFO particles and PANI chains as well as the small number of TiO2 particles uniformly grafted between the Ti3C2TX layers formed a unique sandwich-like structure. The multiple-layer composite showed excellent EM wave absorption with a maximum reflection loss (RL) of −37.1 dB at only 2.2 mm. It showed an effective bandwidth (RL

With the increased demand for high operating temperature of gas turbine engines, corrosion by molten calcium-magnesium-alumino-silicate (CMAS) exhibits a significant challenge to the development of durable environmental barrier coatings (EBCs). EBC candidates, γ-Y2Si2O7, β-Yb2Si2O7, and β-Lu2Si2O7 were explored on their corrosion resistance to CMAS melts at 1300 °C and 1500 °C for 50 h. Interaction and degradation mechanisms were investigated and the corrosion behaviors showed different trends at high temperatures. At 1300 °C, RE2Si2O7 dissolves into CMAS melts and apatite phases reprecipitate forming a thick recession layer. However, when the temperature increases to 1500 °C, CMAS melts vigorously penetrate through the grain boundary of RE2Si2O7 and ‘blister’ cracks form throughout the samples. The reduced grain boundary stability at 1500 °C promotes the penetration of CMAS melts in RE2Si2O7. Grain boundary engineering is critically demanded to optimize CMAS corrosion at high temperatures.

The thermal and environmental barrier coatings (T/EBC) are technologically important for advanced propulsion engine system. In this study, RE4Hf3O12 (RE=Ho, Er, Tm) with defect fluorite structure was investigated for potential use as top TBC layer. Dense pellets were fabricated via a hot pressing method and the mechanical and thermal properties were characterized. RE4Hf3O12 (RE=Ho, Er, Tm) possessed a high Vickers hardness of 11 GPa. The material retained high elastic modulus at elevated temperatures up to 1773 K, which made it attractive for high temperature application. The coefficient of thermal expansion (CTE) of RE4Hf3O12 (RE = Ho, Er, Tm) laid in the range between 7 × 10−6 K−1 to 10 × 10−6 K−1 from 473 K to 1673 K. In addition, the rare earth hafnates exhibited lower thermal conductivity which rendered it a good candidate material for thermal barrier applications.

Porous ultra-high temperature ceramics (UHTCs) are promising for ultrahigh-temperature thermal insulation applications. However, the main limitations for their applications are the high thermal conductivity and densification of porous structure at high temperatures. In order to overcome these obstacles, herein, porous high entropy (Zr0.2Hf0.2Ti0.2Nb0.2 Ta0.2)C was prepared by a simple method combing in-situ reaction and partial sintering. Porous high entropy (Zr0.2Hf0.2Ti0.2Nb0.2Ta0.2)C possesses homogeneous microstructure with grain size in the range of 100–500 nm and pore size in the range of 0.2–1 μm, which exhibits high porosity of 80.99%, high compressive strength of 3.45 MPa, low room temperature thermal conductivity of 0.39 W·m−1 K−1, low thermal diffusivity of 0.74 mm2·s−1 and good high temperature stability. The combination of these properties renders porous high entropy (Zr0.2Hf0.2Ti0.2Nb0.2Ta0.2)C promising as light-weight ultrahigh temperature thermal insulation materials.

Accident tolerant fuels are proposed for light water reactors to improve the safety margin in the event of severe accidents, especially under a LOCA scenario. In this work, Zr-Al-C coatings were synthesized by magnetron sputtering, with different aluminum concentrations incorporating binary carbide ZrC0.55. Based on the combined results of XRD, TEM, and XPS, 7.6 at.% Al coating resulted in a solid solution phase, while a further increase in the Al concentration to 17.7 at.% and 26.3 at.% led to the formation of nanocomposites. The average grain size of the Zr-Al-C coatings was in the range of 8–11 nm, and the hardness was on the order of 15–30 GPa. Meanwhile, the 7.6 at.% and 17.7 at.% Al coatings showed enhanced oxidation resistance against air up to 1000 °C due to formation of continuous oxide scale consisting of t-ZrO2 and Al2O3. Thus, in terms of the mechanical property and high-temperature oxidation resistance, the Zr-Al-C coatings had much better performance than the ZrC0.55 coatings.

Thermochemical reactions between rare earth (RE) monosilicates (RE2SiO5) and molten calcium-magnesium-aluminosilicate (CMAS) at 1300 °C were investigated. Some RE2SiO5 (RE = Tb, Dy, and Ho) dissolve readily into CMAS melts and thereby, crystalline Ca2RE8(SiO4)6O2 reprecipitate. Other RE2SiO5 (RE = Tm, Yb, and Lu) resist CMAS attack, and a continuous layer of Ca2RE8(SiO4)6O2 establishes at the interface. The recession of RE2SiO5 is related to RE ionic radius. RE2SiO5 with small RE ionic radius exhibits good CMAS corrosion resistance due to its low reactivity with CMAS. This result is consistent with the same trend of difference in the optical basicity of RE2SiO5/CMAS.

The rise of modern communication devices has seriously imperiled human health due to electromagnetic (EM) pollution. In this context, the aim of this work is to develop novel reduced graphene oxide/Co-doped ZnNi ferrite/polyaniline ternary composites that exhibit enhanced microwave absorption properties. It is observed that the ternary composite prepared by in-situ polymerization show best EM absorption. The maximum reflection loss (RL) reaches −24.2 dB and the efficient bandwidth (RL

High-temperature mechanical and thermal properties of h-BN based composite containing amorphous silica and Yb-riched silicate glass phases were systematically investigated in this work. Owing to anisotropic microstructure of h-BN matrix, the obtained composite demonstrates anisotropic mechanical and thermal properties. The composite possesses higher elastic modulus at 1673 K than that at room temperature and presents excellent high-temperature stiffness. Flexural strengths in parallel and perpendicular directions reach 496 ± 22 and 258 ± 21 MPa at 1073 K, respectively, and increases by 74 and 66% compared with the room-temperature strengths of 285 ± 4 and 155 ± 5 MPa. The composite containing dual glass phases shows lower coefficients of thermal expansion in the temperature range of 473–900 K, the values are −1.4 × 10−6 and 0.3 × 10−6 K−1 for the perpendicular and parallel directions, respectively. Thermal conductivities in the perpendicular and parallel directions at 373 K are 24.8 and 14.8 W m−1 K−1, respectively, and then decrease to 14.9 and 9.3 W m−1 K−1 at 1473 K.

In this work, a polyaniline (PANI) fibers/Co0.2Ni0.4Zn0.4Fe2O4 (CNZF) composite (mass ratio of PANI to CNZF is 1:1) with a novel urchin-like structure was successfully fabricated through interfacial polymerization. The CNZF was synthesized by the sol-gel method, and whereafter, the PANI fibers were grafted onto the CNZF surface through in-situ polymerization. Structural and morphological properties were systematically investigated by using field emission scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared spectra (FTIR). In the frequency range of 2–18 GHz, the microwave absorption properties of samples were investigated by using vector network analyzer (VNA). The results demonstrated that the microwave absorbing capability of the PANI/CNZF composite was superior to the pure CNZF or PANI. For the PANI/CNZF composite, its optimal absorption peak reached −41.9 dB at 10.48 GHz with a 2.8 mm thickness and the effective absorption bandwidth (RL

Electrical characteristics of SiC metal-oxide-semiconductor (MOS) capacitors with atomic-layer-deposited SiO2 (ALD-SiO2) gate dielectrics were investigated. Post-metallization annealing (PMA) with W gate electrodes at 950 °C showed a large recovery in the flatband voltage toward the ideal value and the hysteresis was reduced to 36 mV. Interface state density (Dit) of 3 × 1011 cm−2/eV was obtained after the PMA for 5 × 103 s. The concentration of the residual carbon atoms in the SiO2 gate dielectrics has been reduced after annealing, suggesting one of the possible origins of the improvements.

The effect of La-silicate interface layer (IL) on the electrical characteristics of 4H-SiC metal-oxide-semiconductor (MOS) capacitors with atomic-layer-deposited SiO2 (ALD-SiO2) gate dielectrics was investigated. In addition to a slight reduction in the interface state density (Dit), the surface potential fluctuation was greatly reduced due to the reduction in the fixed charges (Qfix) with La-silicate IL. Moreover, two orders of magnitude reduction in the oxide trap density in the ALD-SiO2 layer adjacent to the La-silicate IL was confirmed. Physical analysis revealed the reduction in carbon concentration and incorporation of La atoms adjacent to the La-silicate IL.

In this work, two novel flowerlike NiO hierarchical structures, rose-flower (S1) and silk-flower (S2), were synthesized by using a facial hydrothermal method, coupled with subsequent postannealing process. Structures, morphologies, and magnetic and electromagnetic properties of two NiO structures have been systematically investigated. SEM and TEM results suggested that S1 had a hierarchical rose-flower architecture with diameters in the range of 4–7 μm, whereas S2 exhibited a porous silk-flower architecture with diameters of 0.7–1.0 μm. Electromagnetic performances indicated that the NiO hierarchical structures played a crucial role in determining their dielectric behavior and impedance matching characteristic, which further influenced the microwave attenuation property of absorbers based on them. Due to its hierarchical and porous architectures, S2 had higher microwave absorption performances than S1. The maximum RL value for sample S2 can reach −65.1 dB at 13.9 GHz, while an efficient bandwidth of 3 GHz...

In this work, microwave absorption properties of single-layer and double-layer absorbers based on Co 0.2 Ni 0.4 Zn 0.4 Fe 2 O 4 (CNZF) ferrite and reduced graphene oxide (rGO) composites were investigated. The CNZF was prepared by using a sol-gel autoignition method and the rGO was prepared by using a thermal reduction process. Paraffin composites were synthesized by using a facile hot-press method. Their electromagnetic parameters were measured by using coaxial line method. The double-layer absorbers, consisting of 30 wt% CNZF composite as matching layer and 30 wt% rGO composite as absorption layer, with total thickness of 2.5 mm, exhibited a maximum reflection loss ( R L ) of −49.5 dB at 16.9 GHz, as well as an effective bandwidth below −10 dB of as wide as 6.0 GHz from 12.0 GHz to 18.0 GHz. The greater microwave absorption performance of the double-layer absorbers should be attributed to the better impedance matching characteristic of the CNZF layer and the greater dielectric loss ability of rGO layer. It is expected that our double-layer structures can be used as a reference to design new microwave absorbers with high absorption performances.

We herein report a porous nano-SiC foam fabricated by foam-gelcasting-freeze drying method with ultra-high porosity (96%). Porous nano-SiC sintered at 1300 °C and 1400 °C exhibit excellent balanced high compressive strength (1.44 MPa) and low thermal conductivity (0.064 W/(m·K)). The porous nano-SiC can be invoked as a candidate for high temperature thermal insulation. The low thermal conductivity mainly originates in the high porosity and the strong scattering of phonons by the nanostructure of the skeleton.

Delamination of the multiple layers in 2D MXenes is still a crucial challenge because this process generates single-layer nanosheets and extends specific surface area, which makes MXenes promising substrate to carry matters and endow them with enhanced dielectric loss. In present work, novel multilayered composites of Co0.2Ni0.4Zn0.4Fe2O4 nanoparticles (CNZF) attached to MXenes (Ti3C2Tx/CNZF) with various compositions were synthesized by hydrothermal process. Owing to the nano-sized ferrites that are helpful for the delamination of layered structure and improved anisotropic energy, the multiple scattering and dielectric loss of Ti3C2Tx/CNZF are greatly boosted. Hence, the Ti3C2Tx/CNZF composites showcased a prominent microwave attenuation property, with a minimum reflection loss value of −58.4 dB at 6.2 GHz. Simultaneously, the effective bandwidth is at lower frequency region of 3.8–6.0 GHz associated with an absorber thickness of 4.2 mm. The present work provides a strategy to construct novel 2D absorbing materials by allowing ultrasmall magnetic nanoparticles to decorate on the interlayers of hierarchical structure.

Self-assembly porous polyaniline (PANI) microspheres were synthesized via template-free interfacial method at the interface of gallic acid aqueous solution and carbon tetrachloride. The morphology of PANI can be controlled by changing the content of gallic acid. The obtained porous PANI microspheres showed good electromagnetic (EM) wave absorption performance. The maximum reflection loss value of which is −26.5 dB and the effective absorption bandwidth (reflection loss

This study presents the systematic potential effects of reaction parameters on the synthesis of Co-doped ZnNi ferrite/polyaniline composites prepared via novel interfacial polymerization. Through intensive experiments and analysis, optimum reaction conditions including the polymerization temperature and reaction time are proposed so that the performance of the material is significantly improved. The structure, functional groups and morphologies of composites are investigated by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM). In addition, the electromagnetic properties and microwave absorption properties of Co-doped ZnNi ferrite/polyaniline composites are examined by a vibrating sample magnetometer (VSM), Quantum Design (MPMS-VSM and MPMS-XL), the superconducting quantum interference device (SQUID) magnetometer and vector network analysis. Based on these analyses, it is found that by tuning the reaction conditions, i.e., polymerization temperature and reaction time, microwave absorption capabilities in terms of the maximum reflection loss (RL) value and absorber thickness can be readily optimized. The results show that the composite with an optimized polymerization condition of 20 °C for 12 h displays remarkable microwave absorption properties with maximum reflectivity of −54.3 dB, and the effective bandwidth (RL < −10 dB) is about 6.02 GHz at a thickness of 6.8 mm. Furthermore, the discussion shows that the promising microwave absorption may be due to the uniform urchin-like structure of the composites.