In this work, amorphous FeCrAlTiSi high entropy alloy coatings (HEACs) were designed and fabricated via magnetron sputtering technique under different sputtering powers. Their microstructure, mechanical properties and LBE corrosion behavior were investigated through SEM, EDX, TEM, XRD and XPS. Results demonstrate that with the sputtering power increasing from 200 W to 500 W, the hardness and Young's modulus increased at first and then decreased, reaching the maximum of 27 GPa and 356 GPa, respectively, at 300 W. Furthermore, this coating demonstrated excellent corrosion resistance to liquid lead-bismuth eutectic (LBE), with a lamellar oxide layer formed on its surface upon 500 h of exposure to LBE at 550 degrees C, which consisted of, from outside to inside, discrete Fe3O4 layer, FeCr2O4 layer, Al-rich oxide layer and inner mixed (Al, Cr, Ti, Si)-O layer, subsequently, without the occurrence of lead-bismuth penetration into the substrate. Correspondingly, a novel corrosion mechanism was established. These results indicate that the FeCrAlTiSi HEA coatings are promising protective coatings used in Gen-IV lead-cooled fast reactor.

In the present work, FeCrAl based alloys with low Cr contents (10, 11, 12, and 13 wt.%) were successfully prepared by vacuum induction melting. The mechanical properties, microstructure, and high-temperature oxidation resistance of lean-Cr FeCrAl based alloys were investigated. The results indicate that the lattice constant gradually increases with the increasing Cr contents while the matrix remains α-Fe across all compositions. After annealing, 10Cr alloy is in the recovery state with a lowest degree of recrystallization, which has the highest strength at room temperatures, 400 °C and 800 °C. This is attributed to the much stronger pinning effects of the uniformly distributed (Fe, Cr, Si)₂(Nb, Mo) Laves phase particles with a smallest size and a maximum number density. By contrast, Cr content has a relatively minor impact on the mechanical properties of 11–13Cr alloys. And comparing with 10Cr alloy, 11–13Cr alloys are in the partial recrystallization state with a lower tensile strength. The coarsening, aggregation and nonuniformly distribution of (Fe, Cr, Si)2(Nb, Mo) Laves phase in 11–13Cr alloys results a weak pinning effect. However, the elongations of 11–13Cr alloys are larger than that of 10Cr alloy, which is due to the heterogeneous structure in 11–13Cr alloys, where recrystallized grains and sub-grains coexist. Reducing Cr content does weaken oxidation resistance, but the performance of 10Cr alloy is still sufficient for use as a cladding material.

In this work, FeCrAlTiSi high-entropy alloy coatings (HEACs) were prepared using magnetron sputtering (MS) under various substrate biases with a Ti interlayer pre-deposited through multiarc ion plating (M-AIP) to enhance the coating/substrate adhesion strength. The morphology, microstructure, elemental and phase composition, nanohardness, Young's modulus, adhesion strength and corrosion resistance were characterized using SEM, XRD, TEM, XPS, nanoindenter, scratch tester and electrochemical workstation. Results indicated that all FeCrAlTiSi coatings were in an amorphous state. Nanohardness and Young's modulus had a strong substrate bias dependence, reaching the maximum of 16.04 GPa and 241.3 GPa, respectively, at-100 V bias. Meanwhile, FeCrAlSiTi coatings at-100 V exhibited superior corrosion resistance to that of 316L in 3.5 wt% NaCl aqueous solution, about 60 times improvement in terms of corrosion current density owing to the combined effect of homogeneous composition distribution, amorphous structure, and chemically stable oxide film predominantly composed of Al2O3, TiO2 and SiO2.

The application of W alloys is greatly hindered by the low-temperature brittleness and recrystallization embrittlement. In this work, hot-rolled W alloys with enhanced mechanical properties and thermal stability were fabricated by the dispersion of nanoscale potassium (K) bubbles and ZrC particles. The K bubbles and ZrC particles strengthened W (WZCK) alloy is ductile with a tensile strength of 960 MPa at 150 degrees C, while the K-doped W (WK) alloy is brittle. WZCK exhibits both higher strength and lower ductile-brittle transition temperature (DBTT) than the WK, and the recrystallization temperature is similar to 1600 degrees C. After annealing at 1600 degrees C for 1 h, the tensile strength of WZCK at 500 degrees C is 460 MPa, which is over 40 % higher than that of WK, and the total elongation is 26 %. Nanosized ZrC particles and K bubbles dispersed in W significantly improve the strength and high temperature stability of the alloys, while ZrC particles can also react with impurity oxygen to form Zr-C-O or ZrO2 particles and suppress low-temperature brittleness.

The selective dissolution corrosion behavior of silicon carbide (SiC) exposed to lead-bismuth eutectic (LBE) was investigated through experimental and theoretical approaches. Sintered SiC undergoes rapid and severe corrosion, particularly at grain boundaries (GBs), when exposed to oxygen-saturated LBE at 600 degrees C for 700 h. The concentration of lead (Pb) near the GBs is significantly higher than that of bismuth (Bi), accompanied by grain spalling. To elucidate the experimental observations, first-principles calculations were employed to model the interactions between LBE and SiC at typical GBs. It is found that Pb atoms tend to segregate at GBs, especially those with high grain boundary energy compared to Bi. The segregated Pb atoms could promote the formation of vacancies at neighboring C sites, facilitating rapid diffusion of Pb along the GBs. This process leads to the formation of an amorphous phase in the affected regions and the development of a carbon-rich zone as observed in experiment. Additionally, the accumulation of Pb at GBs distorts the local atomic structure and significantly weakens GB cohesion and even lead to the spalling of the grain. The findings provide critical insights into the corrosion mechanisms of SiC in LBE, with implications for material performance in high-temperature applications.

To investigate the properties of Mo2N/MoSi2 multi-layer films, pure Mo2N films, pure MoSi2 films, and Mo2N/MoSi2 multi-layer films with 4, 8, 12, 16, and 20 layers were prepared using magnetron sputtering. Before and after oxidation, the phase structure, morphology, and elemental composition of the films were analyzed using X-ray diffraction, field-emission scanning electron microscopy, atomic force microscopy, and energy-dispersive spectroscopy. The mechanical properties of the films were characterized by nanoindentation. The results indicate that the Mo2N/MoSi2 multi-layer films consist of cubic Mo2N and hexagonal MoSi2. As the number of layers increases, the thickness of the Mo2N and MoSi2 individual layers gradually decreases, significant changes occur in the surface and cross-sectional morphology of the Mo2N/MoSi2 multi-layer films, and the average grain size decreases with an increase in the number of layers. The Mo2N/MoSi2 multi-layer films exhibit superior oxidation resistance compared to the pure Mo2N films. However, as the thickness of an individual layer increases, the oxidation resistance of the multi-layer films decreases. The hardness of Mo2N/MoSi2 multi-layer films increases from 21.65 ± 1.08 GPa for the 4-layer film to 32.14 ± 1.38 GPa for the 20-layer film.

Achieving simultaneous enhancement of both mechanical and self-lubricating properties by incorporating soft lubricants into nitride films has been a longstanding challenge in the development of solid lubricant materials. This paper introduced a novel approach to overcome this challenge by developing coherent-structured Mo2N/Ag-SiNx multilayered films using radio frequency (RF) magnetron sputtering. The multilayer films were designed with a fixed modulation period of 30 nm, while the modulation ratio (gamma) was varied from 1:9 to 1:1. The Mo2N layers exhibited a single fcc-Mo2N phase, while the Ag-SiNx layers formed a dual-phase structure comprising fcc-Ag nanoparticles embedded in an amorphous SiNx matrix. At a modulation ratio of 1:9, the Ag-SiNx layer epitaxially grew on the Mo2N template, resulting in a coherent structure. This coherent structure significantly enhanced both the hardness and elastic modulus, reaching approximately 36 GPa and 230 GPa, respectively. The improved wear resistance at room temperature can be attributed to the coherent strengthening effect, which not only elevated the film's hardness but also eliminated sharp interfaces between modulation layers, thereby reducing crack initiation sites. In temperature-cycling tribo-testing from room temperature to 600 degrees C, the film with a gamma of 1:9 maintained a stable coefficient of friction around 0.2, except during the initial room temperature, where it was 0.4. The wear rate could not be accurately calculated due to the adhered tribolayer on the top of the wear track following the initial tribo-test at 600 degrees C. The excellent tribological properties across temperature cycles were attributed to the synergistic lubricant characteristics of both layers and the formation of selflubricating tribo-phases. The optimized Mo2N/Ag-SiNx multilayered films provide an effective balance of lubrication and mechanical stability under extreme conditions, making them highly promising for highperformance engineering applications.

In order to compare the microstructures and tribological properties of films, pure Mo2N, pure MoS2, 3-layer and 13-layer MoS2/Mo2N gradient films were deposited by reactive magnetron sputtering. The crystalline structure, surface and cross-section morphologies, 3D surface topography, binding energy, hardness and tribological properties of films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), atom force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), nanoindenter, and wear tester, respectively. The results indicate that the preferred orientation of MoS2 in gradient films has changed. The surface and cross-section structures of gradient films become denser with increasing the number of gradient layers. Average surface roughness (Ra) of pure MoS2 film is the highest, and Ra of 13-layer film is the lowest. The binding energy of MoS2 in the composite layer of gradient film has changed. The hardness of gradient film is higher than that of MoS2 and lower than that of Mo2N. The wear resistance of gradient films is much better than that of pure MoS2, and this phenomenon is more obvious under high load conditions. The improvement in the wear resistance of gradient films is attributed to the increase of dense, hardness, H/E and H3/E2. In the initial stage of friction, the 3-layer gradient film can maintain low friction coefficient (≤0.15), which is attributed to the thick MoS2 surface layer. The wear resistance of 13-layer is much better than that of 3-layer gradient film, because it has higher hardness, higher H/E and H3/E2 than 3-layer gradient film.

In order to compare the microstructures and tribological properties of films, pure Mo2N, 2 N, pure MoS2, 2 , 3-layer and 13-layer MoS2/Mo2N 2 /Mo 2 N gradient films were deposited by reactive magnetron sputtering. The crystalline structure, surface and cross-section morphologies, 3D surface topography, binding energy, hardness and tribological properties of films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), atom force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), nanoindenter, and wear tester, respectively. The results indicate that the preferred orientation of MoS2 2 in gradient films has changed. The surface and cross-section structures of gradient films become denser with increasing the number of gradient layers. Average surface roughness (Ra) of pure MoS2 2 film is the highest, and Ra of 13-layer film is the lowest. The binding energy of MoS2 2 in the composite layer of gradient film has changed. The hardness of gradient film is higher than that of MoS2 2 and lower than that of Mo2N. 2 N. The wear resistance of gradient films is much better than that of pure MoS2, 2 , and this phenomenon is more obvious under high load conditions. The improvement in the wear resistance of gradient films is attributed to the increase of dense, hardness, H/E and H3/E2. 3 /E 2 . In the initial stage of friction, the 3-layer gradient film can maintain low friction coefficient (<= 0.15), <= 0.15), which is attributed to the thick MoS2 2 surface layer. The wear resistance of 13-layer is much better than that of 3-layer gradient film, because it has higher hardness, higher H/E and H3/E2 3 /E 2 than 3-layer gradient film.

In order to investigate the properties of MoNx/AlN multilayer gradient films, MoNx/AlN gradient films with 4, 8, 12, 16 and 20 gradient layers were prepared by double-target co-sputtering. The phase structure, morphology, and element composition of films before and after oxidation were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), and energy dispersive spectrometer (EDS). The mechanical properties of films were characterized by nanoindenter. The results indicate that the MoNx/AlN multilayer gradient films are composed of face-centered cubic Mo2N and hexagonal AlN. With increasing the number of gradient layers, and the columnar structure of films gradually becomes uniform and dense. The average grain size of MoNx in gradient films decreases first, then increases slightly and finally decreases. The oxidation resistance of gradient films is better than that of pure MoNx film. And with increasing the number of gradient layers, the oxidation resistance of MoNx/AlN gradient films is gradually enhanced. The hardness of MoNx/AlN gradient films first decreases from 23.68 +/- 1.18 GPa of 4-layer film to 16.68 +/- 0.83 GPa of 12-layer film and then increases to 21.12 +/- 1.06 GPa of 20-layer film.

The intrinsic room-temperature ferromagnetism, stability in air, and easy tunability make chromium telluride Cr3Te4 a material with great promise for application in spintronics. This study investigates the magnetic entropy change (ΔSM) associated with critical exponents of Cr3Te4 single crystal. Temperature-dependent ΔSM suggests a drastic entropy change caused by the transition, the parameters of which show field-dependent power-law behaviors. Fitting the ΔSM(T,H) parameters yields critical exponents α=0.056(9), β=0.365(4), γ=1.212(3), δ=4.318(1), and Δ=1.562(5) for H//ab, while α=−0.077(3), β=0.369(6), γ=1.338(1), δ=4.620(6), and Δ=1.689(2) for H//c. The universality principle allows the ΔSM(T,H) to be scaled onto a single universal curve independent of external field. The direction-dependent differing critical exponents imply anisotropic magnetic couplings in Cr3Te4, which reveal a magnetic interaction of the 3D-Ising type for H//ab while a 3D-XY one for H//c. This work is beneficial for understanding the intrinsic and anisotropic room-temperature ferromagnetism in CrxTey family.

The growing concern about thermal conductivity and electromagnetic shielding m electronic equipment has promoted the development of interfacial film materials. In this work, polyvinylidene fluoride (PVDF)/graphene composite films with different graphene contents were fabricated by high-energy ball milling, cold isostatic pressing, scraping and coating, successively. High-energy ball milling is beneficial to the dispersion of graphene powder, while cold isostatic pressing can greatly enhance thermal conductivity and mechanical strength by reducing the voids in the film and increasing the contact area of graphene sheets. The thermal conductivity, tensile strength and electromagnetic shielding properties of the films were carefully investigated and compared. It was demonstrated that the thermal conductivity increased from 0.19 Wm(-1)K-1 for pure PVDF to 103.9 Wm(-1)K-1 for the composite film with PVDF:graphene=l:3. Meanwhile the electromagnetic shielding efficiency can reach 36.55 dB. The prepared PVDF/ graphene composite films exhibit outstanding overall performance and have the potential for practical applications.

Chromium telluride Cr3Te4 with intrinsic room-temperature ferromagnetism has substantially practical appli-cation in spintronics. In this work, the microwave response of Cr3Te4 single crystal is investigated by the elec-tronic spin resonance (ESR) with the magnetic field applied along various directions. Two resonance lines are observed for both H//ab and H//c, which are suggested to result from ferromagnetic (FM) and antiferromagnetic (AFM) fluctuations respectively. The angle-dependent ESR spectra show considerable anisotropy, with a strong microwave response for H//ab and a weak microwave response for H//c. The analysis of the ESR spectra reveals the coexistence of FM and AFM fluctuations in this system. Moreover, this anisotropic microwave response in single crystal Cr3Te4 could benefit the microwave-based spintronic device.

In a fusion reactor, plasma-facing tungsten (W) materials inevitably suffer severe thermal shock, and the performance of W materials under repetitive high heat loads is one of the key concerns for long-term stable operation of the reactor. In this work, the microstructural evolution and thermal fatigue resistance of two representative W-0.5 wt.% ZrC (WZC) and W-1.0 wt.% Y2O3 (WYO) composites were investigated under cyclic heat loads. Due to the intrinsic properties of ZrC and Y2O3 particles such as coefficients of thermal expansion, particle size and distributions in W grains, the WZC composite exhibited a better thermal shock resistance than WYO. After thermal loads with the absorbed power density (APD) ≥ 22 MW/m2, WYO showed obvious grain growth, Y2O3 particles shedding and degradation of mechanical properties. While, in the case of WZC, these damage behaviors only occurred when APD ≥ 25 MW/m2. Furthermore, an interesting crack mechanism in W composites was revealed due to interface debonding and progressive shedding of second-phase particles from the W matrix. The microstructures and tensile properties of the thermally loaded WZC and WYO specimens were also investigated and the correlations between the microstructure evolution and performance degradation are demonstrated. The results are useful for evaluating the thermal fatigue resistance of oxide/carbide dispersion strengthened W composites and their application in future fusion reactors.

Oxygen control technology is considered to be one of the most effective means to resist the dissolution corrosion of liquid metals. The mechanism for resisting the dissolution corrosion by oxygen is investigated by the inter-action between oxygen and liquid metals using First-principles calculations. The energetics results indicate that O atom prevents the adsorption of Pb and Bi atoms and the escape of Fe atoms. The electronics characters of the surfaces indicate there is a trend in bonding O and Pb atoms in a certain distance, and the binding of surrounding Fe atoms is strengthened by the adsorbed O atom. These are predicted to be the initial stages of the formation of protective oxide layers. Besides, the increase in the coverage of liquid metals weakens the bond between Fe and O atoms. In addition, Pb and Bi atoms tend to migrate from the position far away from O atom to the Fe matrix by replacing Fe atoms. The O atoms that cover the surfaces uniformly are beneficial to the corrosion resistance of liquid metals. The results of energetics, electronics and dynamic calculations provide indispensable data to understand the corrosion resistance of the O atom in the environment of liquid metals.

Two ferrite/martensitic (F/M) steels with different Si concentrations (0 and 0.4 wt.%) were irradiated by 250 keV He2+ ions with different fluences of 2 × 1016 ions/cm2 and 1 × 1017 ions/cm2. Transmission electron microscopy and a nanoindenter were employed to investigate their microstructure evolution and irradiation hardening effects induced by high-energy He2+ ions. A large number of He bubbles formed in the Si-free and Si-containing F/M steels, which preferentially nucleated and grew at the lath and phase boundaries. Owing to the inhibiting effect of Si addition on He bubble growth, the He bubbles in the Si-containing sample exhibited smaller size and higher density at the same He2+ fluence. Nanoindenter measurement revealed that typical irradiation hardening was observed in the F/M steel, and 1/2<111> and <100> type dislocation loops formed by He2+ irradiation was recognized as the dominant mechanism. The addition of Si induced an increase in the number density of dislocation loops, leading to the exacerbation of the irradiation hardening, and the results are basically in agreement with the theoretical analysis based on the dispersion barrier hardening (DBH) and Friedel–Kroupa–Hirsch (FKH) models.

Titanium nitride and silver (TiN/Ag) composite films exhibited the excellent self-lubricating properties in a wide temperature range due to the formation of the Ag rich tribolayer in the contact. However, Ag addition usually reduces the hardness and oxidation resistance properties of the films. In this paper, TiN/Ag/Si3N4 composite films were deposited using RF magnetron co-sputtering system to improve the mechanical and oxidation resis-tance properties of the TiN/Ag film. XRD and TEM analysis revealed that three-phases could be identified on the TiN/Ag/Si3N4 films: face-centered cubic (fcc) TiN, fcc-Ag and amorphous Si3N4 phases. The hardness of the TiN/ Ag film increased from-16 GPa to-24 GPa for TiN/Ag/Si3N4 with 15.3 at.% of Si due to the formation of the nanocomposite structure. The addition of Si allowed a significant improvement on the oxidation resistance temperature, and effectively avoiding of Ag diffusion, and thereby contributing the stability of the hardness of the film after annealing treatment.

The cermet fuels have been considered as a potential key component for the nuclear thermal propulsion, and the homogeneity of the fuel particles in the metal matrix plays a crucial role in stabilizing the structure at extremely high temperatures. In this work, liquid paraffin was used as additive to improve the distribution of yttria-stabilized zirconia (YSZ, an appropriate surrogate for UO2 fuel) microspheres in the tungsten (W) matrix, and the W-YSZ cermet wafers (volume ratio 1:1) with a relative density of 97.6