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An ablation resistant coating with self-transpiration cooling effect was prepared on the surface of aluminum alloy by dilution effect of high speed laser cladding. The coatings mainly contain ablation resistant phases ZrB 2 and SiC, and low-melting phases Al and Al 3.21 Si 0.47. The ablation property of coatings was investigated at different heat fluxes (35.39, 70.77, 106.16, 141.54) MW⸱m−2. The mass ablation rate increased gradually, and the morphology of ablation region changed significantly with the increased heat flux. The self-transpiration cooling effect of coatings was studied by phase, morphology, and element distribution of ablation region. The self-transpiration cooling effect weakened the oxidation behavior of ZrB 2 and SiC at heat fluxes of 35.39 and 70.77 MW⸱m−2 and protected the coating from being exhausted when the heat fluxes were 106.16 and 141.54 MW⸱m−2. [ABSTRACT FROM AUTHOR]

This study utilizes modulation of ionic disorder and electronegativity differences for targeted component design of high-entropy ceramic compositions. A series of novel multicomponent ceramics with the general formula (LaGdYSm) x 2 Yb x 1 Zr 2 O 7 (x 1 +4x 2 = 2, x 1 = 0.6,0.4,0.2,0) were prepared by solid-state reaction. The evolution patterns of their microstructures were analyzed using XRD and TEM, and the anti-sintering ability and thermophysical properties were evaluated. The results confirm that the multicomponent ceramics gradually transform from the coexistence of pyrochlore/fluorite dual-phase structure to pyrochlore structure with the tuning of the size disorder degree. After 50h of exposure to air at 1500 °C, the ceramics retained excellent phase stability. Segregation of La and Yb elements with large differences in radius size occurs, forming a mixture of the La-rich pyrochlore and the Yb-rich fluorite phases. The specimen with the maximum size disorder exhibits the lowest grain growth rate and the greatest thermal insulation properties. Large lattice distortions and sluggish diffusion effects are responsible for the mutual inhibition of grain growth in the two-phase coexistence zone. The thermal insulation properties of the ceramics show well correlated with the degree of the size disorder, further validating the effectiveness of the component design. Meanwhile, the thermal expansion coefficients of prepared ceramic can reach 11.49 × ∼11.58 × 10−6 K−1 at 1000–1100 °C. The customization principles used in this work fill a gap in the compositional design methodology for multicomponent lanthanum zirconate-based high-entropy ceramics. It is essential for developing rare-earth zirconates with tunable thermophysical properties in the area of thermal barrier coatings. [ABSTRACT FROM AUTHOR]

Herein, the effects of Gd2O3 on the laser cladding NiCoCrAlYTa coatings in terms of microstructure, phase structures, high temperature oxidation behaviors were investigated. The results showed that the addition of Gd2O3 changed the composition of coating phases, promoted homogeneous phase distribution, reduced porosity and improved coating density. During oxidation at 1100 °C for 150 h, the increase in the content of added Gd2O3 (at mass fractions of 0, 0.5, 1, 2, 5 and 10%) exhibited an initial inhibitory and then increased effect on the weight-gain rate of the coatings. Overall, 1% Gd2O3 addition resulted in the greatest improvement in the oxidation resistance of the coatings, with 49.58% decreases in oxidation kinetic constants, respectively, compared with those of unmodified coatings. However, at a Gd2O3 content of 10%, the thermally grown oxide on the coating surface exhibited large flaking areas. The high-temperature oxidation kinetic parameters of the coatings exhibited an inverted parabolic form with increasing Gd2O3 content. The higher Gd2O3 content led to the formation of excessive oxygen diffusion channels along grain boundaries, which is the reason for the decrease in the anti-oxidant performance of the coating. [ABSTRACT FROM AUTHOR]

In this paper, by regulating the A-site doped rare earth elements to achieve the transformation of entropy, the composition of (La 1/3 Nd 1/3 Eu 1/3) 2 Zr 2 O 7 (LNEZ) and (La 1/4 Nd 1/4 Eu 1/4 Y 1/4) 2 Zr 2 O 7 (LNEYZ) medium entropy ceramic system and (La 1/5 Nd 1/5 Eu 1/5 Y 1/5 Gd 1/5) 2 Zr 2 O 7 (LNEYGZ) high entropy ceramic system were designed and prepared. The results show that the thermal and mechanical properties of the ceramics are enhanced as the entropy value increases, and from this it is demonstrated that the crystal structure of the high-entropy LNEYGZ ceramics is the most disordered. Severe lattice distortions have the effect of hindering and enhancing the behavior of elemental expansion, phonon scattering, etc., and have the effect of enhancing the resistance of ceramics to sintering and heat insulation. Moreover, the small grain size enables the ceramic to have an enhanced ability to deflect cracks, and the fracture toughness of the ceramic is thus enhanced. [ABSTRACT FROM AUTHOR]

In this work, rare-earth elements Eu and Y were added to La2Zr2O7 (LZ) as doping elements, and the ceramic coating of (La0.5Eu0.25Y0.25)2Zr2O7 (LEYZ) was prepared. The evolution of the sintering resistance, thermal shock resistance, and thermal insulation properties of the multi-element rare-earth co-doped modified coatings under long-term and high-temperature conditions was studied. The results showed that the sintering resistance of the doped coating was significantly improved, and the coating still does not fall off after 200 h at 1100 °C. The thermal shock life of the coating at 1000 °C is increased by 47% compared with that of the undoped modified LZ coating. The length of the vertical cracks in LEYZ ceramic layer is obviously shorter than that in LZ coating, which will be more beneficial to preventing the coating from peeling off. Compared with LZ coating, the insulation temperature of the LEYZ ceramic coating is increased by 24, 26 and 34% in the range of 900 ~ 1100 °C, respectively. The coating has the best thermal insulation effect, which is consistent with theoretical calculation results. The results demonstrate that the modified lanthanum zirconate coatings doped with Europium and Yttrium has great potential in high-temperature performance. [ABSTRACT FROM AUTHOR]

We study the vanishing shear viscosity limit and incompressible limit of two dimensional compressible dissipative elastodynamics systems near the equilibrium. The large value of the volume viscosity forces the limit system to be incompressible, and the vanishing shear viscosity indicates that the limit system is inviscid. Due to the weak dispersive estimate in dimensions two and the lack of the null structures in nonlinear terms, the generalised energy method (Klainerman and Sideris in Commun Pure Appl Math 49(3):615–666, 1996; Sideris in Ann Math 151(2):849–874, 2000; Sideris and Thomases in Commun Pure Appl Math 58(6):750–788, 2005), combined with the "ghost weight" method in (Alinhac in Invent Math 145(3):597–618, 2001), guarantees the global-in-time convergence from compressible dissipative elastodynamics to incompressible elastodynamics with the help of vector fields. [ABSTRACT FROM AUTHOR]

This work concerns the incompressible limit of compressible viscoelastic systems when the shear viscosity converges to zero. The incompressible limit is characterised by the large value of the volume viscosity. In the limit, the dispersive effect of pressure waves disappears and the global convergence to the limit system around an equilibrium is justified with the help of vector fields. [ABSTRACT FROM AUTHOR]

A novel Al 27 Cr 25 Ti 18 Nb 18 Zr 12 eutectic high entropy alloy (EHEA) coating with BCC/B2 and Laves phase has been developed by laser cladding on Ti–6Al–4V alloys. The average microhardness of EHEA coating was ∼697.6HV 0.3 , which significantly surpasses the values reported for most eutectic high-entropy alloy coatings. The strengthening effect and additional strain hardening sources generated by the intersecting nanometer-spaced stacking faults and Lomer-Cotrell locks which found in BCC/B2 phase are important reasons for the superior hardness. And the adhesive problem of Ti–6Al–4V alloy was ameliorated by the EHEA coating with lower friction coefficient (83.05 % of the Ti–6Al–4V alloy) and volumetric loss (27.75 % of the Ti–6Al–4V alloy). • A novel eutectic high entropy alloy (EHEA) coating consisting of BCC/B2 and Laves phases was firstly reported. • A large number of intersecting nanometer-spaced lattice imperfections were found inside the BCC/B2 phase. • Due to the rigid eutectic phases and lattice imperfections, microhardness in this work exceeds the majority of EHEAs. • The adhesive problem of Ti–6Al–4V alloy was ameliorated by this coating and the effect mechanism was investigated. [ABSTRACT FROM AUTHOR]

Wear is one of the primary challenges for high-temperature working components. In this paper, FeCoCrNi 2 MoSi eutectic high-entropy alloy coatings were successfully prepared by introducing MoNiSi ternary silicides with Laves structure into FeCoCrNi high-entropy alloys using laser cladding technology. The alloy achieves a balance of strength and toughness through the nanoscale eutectic structure with alternating FCC and Laves phases. Tribological experiments conducted over a wide temperature range from 25 °C to 800 °C show that the synergistic effect of the nano-lamellar structure and the alternating soft and hard structure makes the coating have excellent wear resistance at room temperature. The improvement of wear resistance at high temperatures (800 °C) is mainly due to the formation of the oxide film on the coatings. • Eutectic high-entropy alloys with nano-lamellar structure prepared by laser cladding technique. • The formation of a flake structure of the oxide film has a protective effect on the wear surface. • The synergistic effect of the lamellar structure and the nano-scale layer results in excellent wear resistance. [ABSTRACT FROM AUTHOR]

Two kinds of layered double hydroxides inhibition materials were synthesized on graphene oxide, and applied to strengthen the Ni-based coating on Mg-Li alloy. The composition and release properties of corrosion inhibition materials were studied. The formation of passivated film and the corrosion resistance mechanism of coating were summarized. The results show that two kinds of corrosion inhibition materials had good release properties. The addition of corrosion inhibition materials was helpful to form Ni-based composite coatings with fine and dense cell clusters, which strengthened the corrosion resistance of the coating, especially for a long time. • Two kinds of graphene-based corrosion inhibition materials were synthesized. • Corrosion resistance of Ni-based coatings in different soaking time was studied. • Inhibition materials enhanced the corrosion resistance of coatings on Mg-Li alloy. • Passivation film formation and corrosion resistance mechanism were studied. [ABSTRACT FROM AUTHOR]

Background: Intestinal immune dysfunction is involved in the onset of Crohn's disease (CD). Dendritic cells (DCs), antigen-presenting cells, play a key role in the maintenance of intestinal immune homeostasis. The aryl hydrocarbon receptor (AhR) is a ligand-dependent transcription factor widely expressed in various immune cells, including DCs. Although AhR plays an important role in immune tolerance, its role in the DCs is unclear. The purpose of this study was to investigate whether the activation of AhR can induce tolerogenic DCs (tolDCs) and the differentiation of regulatory T (Treg) cells, as well as ameliorate experimental colitis. Results: AhR activation in the DCs resulted in a lower expression of surface markers such as CD80, CD83, CD86, and pro-inflammatory cytokine production, and higher anti-inflammatory production (IL-1β, IL-23, and IL-12) compared to the control DCs. The surface dendrites in DCs were significantly reduced following AhR activation by 6-formylindolo [3,2-b]carbazole (FICZ). Such DCs with FICZ-mediated activation of AhR, namely tolDCs, promoted Treg cell differentiation. Adoptive transfer of tolDCs to a TNBS-induced colitis mouse model significantly alleviated the severity of inflammation by improving the colon length and decreasing the disease activity index (DAI) and histopathological score. Moreover, the transferred tolDCs decreased the frequency of Th17 cells and increased the frequency of Treg cells in the spleen and mesenteric lymph nodes (MLNs) in murine colitis models. Conclusions: Activation of AhR in the DCs could induce tolDCs, and the transplantation of tolDCs may help in relieving intestinal inflammation and maintaining the Th17/Treg differentiation balance. Thus, our data suggest that AhR may be a potential therapeutic target for CD. [ABSTRACT FROM AUTHOR]

In this study, a La 0.8 Ba 0.2 TiO 3− δ (LBT) upper layer was deposited on an yttria-stabilized zirconia (YSZ) thermal barrier coating (TBC) through atmospheric plasma spraying. The thermal cycling behaviors of the YSZ single-ceramic-layer and LBT–YSZ double-ceramic-layer coatings at 1000 °C were investigated through a water quenching method. Moreover, phases, microstructural evolution, and elemental distributions were studied through by X-ray diffraction and scanning electron microscopy–energy-dispersive X-ray spectroscopy. The results showed that the thermal cycling lifetime of the LBT–YSZ coating was 27% higher than that of conventional YSZ coating. The conventional YSZ coating failed after 251 cycles because of the joining of the continuous horizontal and vertical cracks caused by the formation of thermal growth oxides and the bending effect of the single-ceramic-layer structure. The thermal cycling behavior of the LBT–YSZ coating was different from that of the YSZ coating at the edge and center. Although the former was similar to the failure behavior of the YSZ coating, the cracks in the vertical direction were deflected as a result of the bending effect of the double-ceramic-layer structure during quenching. This deflection led to the formation of slope cracks with longer propagation paths and slope spallation zones. The latter showed small-debris spallation on top of the LBT upper layer due to the lower fracture toughness of the LBT, which protected the central coating from the structural damage of the ceramic coating. These two behaviors would either release the thermal stress or increase the crack-propagation energy requirement in the ceramic coating, consequently improving the thermal cycling lifetime of the LBT–YSZ coating. In summary, depositing an LBT upper layer could potentially improve the thermal cycling lifetimes of TBCs. [ABSTRACT FROM AUTHOR]

The (La0.5Eu0.25Y0.25)2Zr2O7 (LEYZ) ceramic powder for spraying was prepared and synthesised by combining spray granulation and solid phase reaction phase, and a double ceramic layer structure with (La0.5Eu0.25Y0.25)2Zr2O7 ceramic surface coating and YSZ intermediate coating was prepared by atmospheric plasma spraying. Experimental characterisation revealed that the moulding state of spray granulated powders was significantly influenced by the solid content. When the solid content is small, the viscosity of the slurry is insufficient, and the prepared powder has poor formability and small overall particle size. When the solid content is large, the slurry is too viscous, which easily leads to unfavourable conditions such as sticky walls. The best formability of the pelletised powder was obtained with a solid content of 55 wt-% and a binder content of 2.0 wt-%. Compared with La2Zr2O7 (LZ) ceramics, the fracture toughness of the rare-earth co-doped modified LEYZ ceramic coating was increased by 8.4% and the bond strength was increased by 49.9%, showing good toughness and crack resistance. Moreover, LEYZ coating has significantly better resistance to solid phase particle erosion than LZ coating, with 46.3% and 45.4% reduction in erosion rate at 45° and 90°, respectively. [ABSTRACT FROM AUTHOR]

In this work, a novel lightweight AlCrTiNbMo refractory high-entropy alloy (RHEA) coating has been developed to overcome the surface damage defects in Ti-6Al-4V alloys under wear and erosion conditions. A crack-free in-situ nitride (AlCrTiNbMo)N x RHEA coating were successfully prepared by the gas assisted laser nitriding. According to XRD, SEM and TEM analysis, AlCrTiNbMo coating was composed of single BCC phase, while (AlCrTiNbMo)N x coating was constituted by BCC and TiN phases. The average microhardness of AlCrTiNbMo and (AlCrTiNbMo)N x RHEA coatings were 591.2 HV 0.3 and 1070.1 HV 0.3 respectively. (AlCrTiNbMo)N x RHEA coating has lower friction coefficient and wear rate than AlCrTiNbMo RHEA coating and the substrate from room temperature to 600 °C. At 600 °C, (AlCrTiNbMo)N x RHEA coating showed a rare self-lubricating behavior, the friction coefficient decreased to 0.275 (61.9 % of the substrate), and the wear rate was 0.06 mm3/N m× 10−4 (1.24 % of the substrate). The erosion rates of (AlCrTiNbMo)N x RHEA coating at erosion angle of 30°, 60° and 90° were 11.0 %, 22.3 %, and 36.8 % of those of the substrate, respectively. The homogeneous and hard TiN array-BCC structure generated by in-situ self-reaction was the main factor for the excellent wear and erosion resistance of (AlCrTiNbMo)N x RHEA coating. Thus, (AlCrTiNbMo)N x RHEA coating and corresponding laser nitride technique were expected to be applied in the severe working environment of high temperature, wear, and erosion. • In-situ nitride (AlCrTiNbMo)N x refractory high-entropy alloy coating by gas assisted laser nitriding was first proposed. • The wear and erosion performance of Ti-6Al-4V alloy was improved significantly and the effect mechanism was investigated. • The homogeneous and hard TiN array-BCC structure generated was the main factor for the excellent performance. [ABSTRACT FROM AUTHOR]

This study proposes the utilization of rare earth combined with ultrasonic-assisted laser cladding technology to address the dilution problem encountered during the laser cladding coating of Ti alloy. The aim is to improve the performance of the coating. Using Ti alloy surface as a base, a novel Ti-Al-Si-Cr-SiC multi-principal element alloy coating is fabricated. To characterize the coating, various techniques such as transmission electron microscopy (TEM), electron backscatter diffraction (EBSD), and scanning electron microscopy (SEM) are employed to examine the microstructure and phase composition. The interface between the coating and the substrate is analyzed using focused ion beam and TEM. The coatings are also evaluated for corrosion and wear resistance through potentiodynamic polarization, electrochemical impedance spectroscopy, hardness, and friction tests. The results reveal that the rare earth combined with ultrasonic-assisted Ti-Al-Si-Cr-SiC coating consists of Ti 4 Cr phase, TiC phase, and eutectic phase (Ti 3 Al and Ti 5 Si 3). The combined effect of ultrasonic energy and rare earth reduces the dilution rate of the coating, resulting in a refined coating structure that improves the wear resistance and corrosion resistance. • A new preparation method of ultrasonic composite rare earth assisted laser cladding was proposed. • The dilution rate of the coating prepared by rare earth-ultrasonic assisted laser cladding is significantly reduced. • Microstructure refinement promotes the formation of stable passivation film and improves the corrosion resistance. • The coating prepared by rare earth combined with ultrasonic assisted laser cladding has good wear and corrosion resistance. [ABSTRACT FROM AUTHOR]

In this work, the fabrication of supersonic fine particle bombardment (SFPB)-doped rare-earth pretreatment modified vacuum carburized layers were applied. The SFPB-doped La 2 O 3 pretreated vacuum carburized reinforced layer was explored by common testing methods such as XRD, XPS, SEM, and TEM, focusing on the effects of La 2 O 3 -doped SFPB pretreatment on the decomposition, adsorption and diffusion of active carbon atoms and the diffusion mechanism. The composite carburizing behavior of La 2 O 3 -doped SFPB pretreatment modified layer under the action of thermal coupling is explored, and the influence law of rare earth modified carburizing and nano-modified carburizing on the thickness, residual stress, impact toughness, tribological properties of the carburized layer were clarified. The mechanism of mass transfer under the coupling role of pre-set surface defects and rare earth pinning was revealed. The case depth of the LSPC layer was increased by 14.3%, and the residual stress was significantly higher. The carbon diffusion coefficients of LSPC were 1.31 times superior to that of the vacuum carburizing layer, which is mainly attributed to the formation of a large number of nanocrystals with high-angle grain boundaries (HAGBs) by the rare-earth doped nanosized pretreatment, and the multiple synergistic strengthening effects of rare-earth oxides and nanocrystals. [Display omitted] • SFPB pretreatment introduces both La 2 O 3 and diffusion channels into the surface/subsurface layer. • Enhancement of carbon diffusion driving force by La 2 O 3. • High dislocation density and LAGBs provide fast diffusion channels for carbon diffusion. • The pretreatment increased the thickness of the carburized layer by 14.3%. [ABSTRACT FROM AUTHOR]

The excellent strength and hardness obtained from the customized phase compositions provide vast spaces for surface protection application of refractory high entropy alloy (RHEA) coatings in titanium alloys. However, the introduction of high-strength brittle phase in RHEA coatings commonly increases the cracking tendency and affects their service life. In this work, we propose a design strategy to enhance the mechanical properties of RHEA coatings by introducing an extremely stable high strength boride combined with a ductile phase. Experimentally, LaB 6 /NbNiTaTi RHEA coatings mainly consist of BCC phase, in-situ TaB phase and NiTi/IM eutectic phase. TaB phase with high-density (110) nanotwins inside presents needle-like morphology with the long side axis parallel to the [001] direction. Excessive needle-like TaB phase is fully fused and fractured due to its preferential growth along a specific direction. The fracture surface analysis shows that BCC phase bears the main deformation, NiTi phase can relieve stress concentration at the boundary while bearing a small amount of deformation. By contrast, the low-density dislocation distribution and the low energy extended dislocation structure in TaB phase exhibit the phase stability. In addition, the amorphous islands are formed near the high-deformation regions when the defect concentration reaches the critical value. [Display omitted] • TaB phase with high-density stacking faults was formed in situ. • The RHEA coatings exhibited superior compressive strength and ductility. • Different phases played different roles in the process of bearing deformation. • Grain boundary strengthening and dislocation strengthening were the main factors of strengthening mechanism. [ABSTRACT FROM AUTHOR]

The corrosion and wear requirements of Zr alloys for application as fuel cladding materials are becoming increasingly stringent. Accordingly, developing surface engineering techniques and high-performance coating materials is crucial for achieving improved surface properties of these alloys. Herein, we propose a strategy for preparing high-performance coatings on Zr alloys using the multilayer cladding technique to prevent the high dilution of Zr alloy substrates because of high-energy beams. A novel Al 0.2 NbTiV 0.1 W 0.5 Zr 0.3 high-entropy alloy (HEA) coating with a multilayer structure was prepared on a Zr alloy using multiple laser claddings. The top-layer and interlayer were composed of two body-centered cubic (BCC) phases and a Zr-rich phase. Owing to the multilayer cladding, the top-layer was almost unaffected by matrix dilution and substrate evaporation, leading to a significantly reduced precipitation of the Zr-rich phase in the top-layer. The high hardness and excellent wear resistance of the coating were attributed to the two BCC phases; moreover, both, the Zr-containing HEA and substrate, exhibited adhesive wear. The top-layer exhibited superior pitting corrosion properties, whereas the microstructural inhomogeneity in the interlayer led to intergranular corrosion, dominating the corrosion process. Thus, this study presents a coating material system suitable for Zr alloys with excellent wear and corrosion resistances. The findings can potentially contribute to expanding the application of the high-energy beam technology to Zr alloys. [Display omitted] • Al 0.2 NbTiV 0.1 W 0.5 Zr 0.3 HEA coating with multilayer structure was prepared on Zr alloy by multiple laser cladding. • The microstructure and properties of top-layer and interlayer on the multi-layer strategy were investigated. • The Zr-rich phase and two coexisting BCC phases are formed in the coating. • IGC dominates the corrosion process in the interlayer owing to microstructural inhomogeneity. • The corrosion and wear resistance of Zr alloy surface are significantly improved. [ABSTRACT FROM AUTHOR]

This work is aimed to explore ways to further improve corrosion properties of single-phase RHEA coating by introducing in-situ TiC phase. Results shown that C/Al 0.1 CrNbSi 0.1 TaTiV RHEA coatings exhibited better comprehensive resistance to pitting and general corrosion compared to most of reported HEAs and traditional alloys. The passive film was dominated by a muti-oxide crystalline structure with a thickness of ∼ 11.52 nm. The small-size and evenly distributed TiC phase with most thermodynamically stable could be obtained via doping C and retard the nearby pitting process, improving the pitting behavior and the dense of passive film in 1.0 wt% C coating. [Display omitted] • A small amount of in-situ TiC phase enhances the corrosion resistance of RHEA coatings. • The passive films show biphasic semiconductor behavior. • The passive film is a muti-oxide crystalline structure with a thickness of ∼ 11.52 nm. • Al, Si and Ta elements are the main component of passive films. [ABSTRACT FROM AUTHOR]

Background: The intestinal microbiota is thought to be involved in the occurrence of inflammatory bowel disease in remission with irritable bowel syndrome (IBS)-type symptoms, but the specific distinct profile of these bacteria remains unclear. This cross-sectional study aims to investigate the fecal microbiota profiling in patients with these diseases.Methods: Fecal samples from 97 subjects, including Crohn's disease patients in remission with IBS-type symptoms (CDR-IBS+) or without IBS-type symptoms (CDR-IBS-), ulcerative colitis patients in remission with IBS-type symptoms (UCR-IBS+) or without IBS-type symptoms (UCR-IBS-), IBS patients and healthy controls, were collected and applied 16S ribosomal DNA (rDNA) gene sequencing. The V4 hypervariable regions of 16S rDNA gene were amplified and sequenced by the Illumina MiSeq platform. The differences in the sample diversity index in groups were analyzed with R software.Results: The richness of the intestinal microbiota in the CDR-IBS group was markedly lower than those in the control and IBS groups based on the analysis of observed species and the Chao index (P < 0.05). The observed species index in the CDR-IBS+ group was higher than that in the CDR-IBS- group (median index: 254.8 vs 203, P = 0.036). No difference was found in alpha diversity between UCR patients with IBS-type symptoms and those without related symptoms. At the genus level, the number of Faecalibacterium in CDR patients with IBS-type symptoms increased significantly, while Fusobacterium decreased versus those without such symptoms (mean relative abundance of Faecalibacterium: 20.35% vs 5.18%, P < 0.05; Fusobacterium: 1.51% vs 5.2%, P < 0.05). However, compared with the UCR-IBS- group, the number of Faecalibacterium in the UCR-IBS+ group decreased, while the number of Streptococcus increased, but there was no significant difference in the genus structure. The abundance and composition of the microbiota of IBS patients were not distinct from those of healthy controls.Conclusions: The IBS-type symptoms in CD patients in remission may be related to an increase in Faecalibacterium and a decrease in Fusobacterium. The IBS-type symptoms in UC patients in remission cannot be explained by changes in the abundance and structure of the intestinal microbiota. [ABSTRACT FROM AUTHOR]

Immune disorders play an important role in the pathogenesis of Crohn's disease (CD). Notably, the increased immune response of Th1 cells and related cytokines is associated with the onset of CD. IL-27 is a newly discovered IL-12-related cytokine, but its expression and clinical significance in CD patients are still controversial. This study is aimed at evaluating the serum levels of IL-27 in CD patients and analyzing their clinical significance. The results indicated that serum levels of IL-27 in CD patients were significantly higher than those in control subjects (median (interquartile range (IQR)): 110.0 (95.0, 145.0) vs. 85.0 (80.0, 95.0) pg/ml, P < 0.001). Furthermore, the IL-27 levels significantly increased in CD patients at the active stage compared with CD patients in remission (CDR) (127.5 (100.0, 150.0) vs. 90 (80.0, 110.0) pg/ml, P < 0.001). However, there was no difference in IL-27 levels between CDR and control subjects. The levels of IL-27 were positively correlated with Crohn's disease activity index (CDAI), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), fecal calprotectin (FC), and Simple Endoscopic Score for Crohn's Disease (SES-CD) and negatively correlated with hemoglobin (Hb) and serum albumin (ALB). IL-27 combined with CRP favored the prediction of CD activity (area under the curve (AUC): 0.88). Additionally, the proportions of Th17 and Th1 cells in peripheral blood were higher in CD patients than in control subjects. Active CD patients exhibited significantly higher proportions of Th17 and Th1 cells than those in remission. Moreover, correlation analysis indicated that the serum levels of IL-27 were positively associated with the frequency of Th17 cells in CD patients (r = 0.519 , P = 0.013) but not associated with the frequency of Th1 cells in CD patients. IL-27 is positively associated with multiple inflammation indicators and may exert a proinflammatory profile by regulating Th17 cell differentiation in the development of Crohn's disease. In the future, IL-27 combined with CRP is expected to become an important biological marker of CD activity. [ABSTRACT FROM AUTHOR]

Multi-principal element alloy coatings (MPEACs) have great application potential for high-temperature diffusion barrier coatings. The sluggish diffusion and lattice distortion of this new coating material due to its own atomic size effect give the coating excellent resistance to high temperature oxidation and grain coarsening. In this study, the high-temperature oxidation properties, and microstructure evolution of quaternary, quinary, senary, and denary alloy coatings (whose lattice distortion magnitude is linearly increased) at 1100 °C were studied. The evolution of grain orientation, size, and grain boundaries of alloy coatings after high temperature exposure were analyzed by EBSD. The results showed that from quaternary to denary alloy coatings, with the rise in lattice distortion magnitude of the alloy system, the sluggish diffusion ability of the coating at high temperatures was more obvious. Specifically, the oxidative activation energy of quaternary to denary alloy coatings is 355.41, 480.96, 478.76, and 654.03 kJ/mol, respectively. A high distortion magnitude is beneficial to increase the activation energy of the alloy coating, as a result, grain growth of alloy coatings with high activation energy is significantly inhibited, and under the combined action of storage strain energy and solute dragging, the grain boundary migration rate of the coatings also declines. Finally, the denary alloy coating shows good resistance to high temperature softening. This study provides a positive reference for promoting the application of multi-principal alloys in diffusion barrier coatings. • High-temperature oxidation and microstructure evolution of quaternary, quinary, senary, and denary alloy coatings at 1100 °C were studied. • The oxidative activation energy increases linearly from quaternary to denary alloy coatings. • The grain growth of the coating gradually weakened from quaternary to denary alloy coatings. • Grain boundary migration rates are affected by the combined effects of storage strain energy and solute dragging. • The denary alloy coating shows good resistance to high-temperature softening. [ABSTRACT FROM AUTHOR]

It is challenging to obtain the underwater wet laser cladding layer with excellent properties while maintaining formability. In this paper, the method of using synchronous mechanical vibration assisted in the underwater wet laser cladding process of TiN/Fe-based cladding layer was introduced. The effect of mechanical vibration frequency on the dilution rate, microstructure, corrosion resistance, tribo-corrosion behavior of the cladding layer was studied. The result displayed that with increase of mechanical vibration frequency, the dilution effect of the substrate was obviously weakened and the phase changed from ferrite to ferrite and austenite, and TiN particles were evenly distributed. In addition, the grain size of the cladding layer showed a tendency to decrease first and then increase. When the mechanical vibration frequency was 400 Hz, the grain refinement phenomenon was the most obvious and the average grain size was 8.39 μm. Based on the effect of dispersion strengthening and fine grain strengthening, the microhardness and wear resistance of the cladding layer assisted at 400 Hz were improved, and the wear rate was 1.17 × 10−15m3N−1 m−1. While the cladding layer assisted at 400 Hz exhibited better corrosion resistance by forming a dense passivation film. In addition, the mechanism of mechanical vibration on microstructure evolution and performance enhancement of the cladding layer was also analyzed. This study provided the theoretical support for the formability of the underwater laser wet cladding assisted by mechanical vibration. • The TiN/Fe-based underwater wet cladding layer was successfully prepared assisted with mechanical vibration. • Action mechanism of mechanical vibration on TiN/Fe-based underwater wet cladding layer is explained. • The grain refinement mechanism of TiN/Fe-based underwater wet cladding layer is proposed. • Dispersion strengthening and grain refining strengthening are the main strengthening mechanisms. [ABSTRACT FROM AUTHOR]

The poor surface properties of Mg Li alloys and the excellent comprehensive performance of high-entropy alloy (HEA) coatings are highly complementary. This study uses laser cladding technology to deposit an AlTiVNiCu/Cu–Al gradient functional coating with favourable wear and corrosion properties on Mg Li alloy substrates. Through the design of the gradient coating structure, laser cladding is used to coat HEA layers on low-melting-point Mg Li alloys, which effectively reduces further dilution of Mg and Li in the substrate. Notably, the Mg content in the prepared AlTiVNiCu protective layer is only 2.34 %. Furthermore, the microstructure, phase structure, microhardness, tribological and corrosion properties of the gradient coating are systematically studied. The protective layer consists of V-rich BCC 1 , (Ni, Ti)-rich BCC 2 , Cu-rich FCC, Mg-rich BCC 3 and nanoscale β -Ti phases, with a predominance of body-centered cubic (BCC) structural phases. The average microhardness is 547.46 HV0.3. Under a load of 3 N, the average friction coefficient of the protective layer is 0.54, with a wear volume of only 2.87 % compared with that of the substrate, which is satisfactory wear resistance. In a 3.5 wt% NaCl solution, the protective layer exhibits the highest corrosion potential (−0.49 V SCE , where SEC denotes saturated calomel electrode), and the lowest corrosion current density (1.14 × 10−6 A·cm−2), representing a remarkable enhancement compared with those of the substrate (−1.57 V SCE and 5.41 × 10−4 A·cm−2). [Display omitted] • Laser-cladded AlTiVNiCu HEA coatings were designed and prepared on Mg Li alloy. • LC-Cu 6 Al layer helps to balance the thermal mismatch between the HEA coating and Mg Li. • HEA coatings consist of V-rich, (Ni, Ti)-rich, Cu-rich, Mg-rich and β-Ti phases. • HEA coatings show good wear resistance with a wear volume of 2.87 % of the substrate. • HEA coatings have higher E corr and lower i corr values for good corrosion resistance. [ABSTRACT FROM AUTHOR]

The sluggish diffusion effect of complex concentrated alloys (CCAs) affords them considerable application potential in the field of high temperatures. In this study, the role of refractory elements in the high temperature oxidation process of denary complex concentrated alloy coatings (CCACs, namely NiCoCrFeAl 0.8 Si 0.1 (MoNbTaW) x , where x is 0.025, 0.05, 0.1 and 0.15) prepared via laser cladding was investigated. Four groups of the CCACs with different refractory contents were subjected to 100 h of high-temperature oxidation experiments, and the oxidation products and microscopic characteristics of the samples were observed via XRD and SEM, respectively. Atomic-scale characterisation and analysis of the oxidised samples were performed using TEM and XPS technology to explore the diffusion behaviour of elements in the high-temperature process. Results indicate that the solid solution limit of the CCACs is obtained by regulating the topological instability of the lattice matrix via the addition of refractory elements. Consequently, when 0.1 > x > 0.025, the coating is a body-centred cubic (BCC) + face-centred cubic (FCC); when x = 0.1, the coating maintains a single-phase FCC structure; and when x > 0.1, the coating changes to an FCC + BCC duplex structure. The x 0.1 group exhibits the smallest relative strain among all coatings, which is conducive to maintaining the structural stability of the face-centred cubic at high temperatures and delaying atomic migration within the lattice. Furthermore, the oxidation kinetics curve of the CCACs with a single- phase FCC exhibits low K p values. In a single- FCC lattice, the atom diffusion rate through volume slows down and grain boundary diffusion decreases. Considering the Weibull modulus for the hardness statistical value after coating oxidation, the modulus of single-FCC phase CCACs is also higher than others. This study has the potential to contribute to the application of high-temperature thermal protection for CCACs. • The denary complex concentrated alloy coatings (CCACs) were prepared by laser cladding. • The solid solutioning limit of the CCACs can be adjusted by the topological instability of the lattice. • The diffusion rate of atoms in matrix is the combined action of the volume and the boundary diffusion. • The single-FCC CCACs with higher solid solubility have better oxidation resistance. [ABSTRACT FROM AUTHOR]

For the application of lightweight alloys, the corrosion and wear problems of magnesium-lithium (Mg-Li) alloys have always been important problems that cannot be ignored. The coupling protection of multiple technologies has gradually become a new trend. In this study, layered double hydroxides (LDH) nanosheet arrays were in-situ grown on Ni-P coating by the electroless plating technology combined with hydrothermal synthesis technology. The optimum deposition conditions (temperature-time-pH) were selected by orthogonal test. The surface morphology, structure, corrosion resistance and wear resistance of LDH/Ni composite coatings under different conditions were systematically studied by SEM, XRD, FT-IR, DSC, electrochemical and tribological tests. The growth mechanism of LDH suitable for Ni-P coating surface was proposed by analyzing the growth process of LDH nanosheet arrays. The results showed that the condition of 125 °C-12 h-13 was conducive to the growth of LDH nanosheet arrays. Compared with the Ni-P coating and the composite coating under other conditions, the LDH 125°C-12h-13 /Ni composite coating has the lowest self-etching current density (7.50 × 10−7 A·cm−2) and the average friction coefficient (0.35). The defect sealing effect and Cl− barrier property of LDH effectively improved the corrosion resistance of the coating. The frictional properties were improved by lubrication and heat absorption properties of LDH. In addition, it was found that the growth of LDH on the Ni-P coating surface followed the mechanism of "deposition nucleation-diffusion growth". • Nanosheet arrays in-situ coupled Ni-based coatings on Mg-Li alloy were prepared. • Optimum growth conditions of nanosheet arrays were selected by orthogonal test. • The composite coating had better corrosion and wear resistance for Mg-Li alloy. • Wear mechanism and growth mechanism of LDH nanosheet arrays were studied. [ABSTRACT FROM AUTHOR]

Underwater wet laser cladding technology has become one of the research hotspots in the marine engineering, but the existence of the water environment inevitably leads to process instability and defects. In this study, the nano-ZrO 2 protective layer was used to increase the viscosity of the molten pool surface to resist the impact force generated by the high-speed water jet, and the underwater wet laser Fe-based cladding layer with good forming quality and desirable performance was successfully prepared. The nano-ZrO 2 protective layer improved the formability of the cladding layer and guaranteed the depth of the melt pool, while reducing the depth of the heat affected zone. The addition of nano-ZrO 2 particles reduced the average grain size of the cladding layer from 4.90 μm to 3.66 μm. In addition,the corrosion resistance of the cladding layer was greatly improved with the application of the nano-ZrO 2 protective layer, with the evident passivation region of 0.74 V. The wear rate of the cladding layer with the nano-ZrO 2 protective layer (0.64×10-15m3N-1m-1) was significantly lower than that of the substrate (9.01×10-15m3N-1m-1), and the excellent wear resistance of the cladding layer with nano-ZrO 2 protective layer benefited from the good carrying capacities and high microhardness of the microstructure with ZrO 2 particles. This study reveals the strengthening mechanism of nano-ZrO 2 protective layer on the Fe-based cladding layer, which can provide theoretical guidance for the development of the underwater laser cladding. • The Fe-based cladding layer with good formability was successfully prepared underwater. • The protective mechanism of the nano-ZrO 2 protective layer is studied in detail. • The nano-ZrO 2 protective layer can refine grains and decline heat effect. • The corrosion and wear performances of Fe-based cladding layer were improved by nano-ZrO 2 protective layer. • The nano-ZrO 2 induced grain refinement enabled Fe-based cladding layer to be further wear resistant. [ABSTRACT FROM AUTHOR]

• A metallurgical AlCuTiVCr HEA coating was prepared on Mg-Li alloy. • Cu-Al layer can balance the thermal matching disparity among HEA layer and Mg-Li. • HEA coating consists of (V, Cr)-rich BCC 1 , Mg-rich BCC 2 , AlCu 2 Ti and β-Ti phases. • The corrosion resistance of Mg-Li alloy was significantly improved. AlCuTiVCr/Cu-Al lightweight high-entropy alloy gradient coating was successfully prepared by laser cladding to improve the corrosion resistance of Mg-Li alloy. The boundaries between AlCuTiVCr protective layer, Cu-Al transition layer and Mg-Li alloy substrate are distinct, forming an excellent metallurgical bonding. The gradient coating design has effectively balanced the thermal matching difference between HEA coating. The prepared AlCuTiVCr protective layer comprises (V, Cr)-rich BCC 1 , Mg-rich BCC 2 , AlCu 2 Ti and β-Ti phases. The Cu-Al transition layer is composed of β-Li, Cu 2 Mg and Al 2 Cu 3 phases. The corrosion potential of AlCuTiVCr protective layer (−0.46 V SEC) is 1.09 V SEC higher than that of Mg-Li alloy (−1.55 V SEC), while the corrosion current density of the protective layer (9.41 × 10−7 A cm−2) is about three orders of magnitude lower than that of the substrate (5.97 × 10−4 A cm−2). [ABSTRACT FROM AUTHOR]

High prevalence of vitamin D deficiency has been found among Crohn's disease (CD) patients. Vitamin D probably participates in the pathogenesis of CD, but this idea remains controversial. This study was to investigate the levels of vitamin D in CD patients and analyze the relationship between vitamin D and intestinal inflammation. Vitamin D levels were measured by chemiluminescence immunoassay in 198 CD patients (96 in active, 102 in remission) and 100 healthy controls. The correlation between vitamin D levels and clinical parameters was analysed. The expression of intestinal tight junction (TJ) proteins in CD patients was measured by immunofluorescence staining. Treg and Th17 percentages in the peripheral blood were determined by flow cytometry. CD patients exhibited significantly lower 25(OH)D levels than healthy controls, especially in active CD patients. Serum 25(OH)D levels in CD patients were negatively correlated with the CD activity index (CDAI), the simple endoscopic score for CD (SES-CD), and inflammatory markers, including erythrocyte sedimentation rate (ESR), platelet (PLT) count and faecal calprotectin (FC) levels. Moreover, in patients with vitamin D deficiency, the expression of TJ proteins (Occludin, claudin-1, ZO-1 and JAM-1) in the intestinal mucosa was reduced, and Treg cells in the peripheral blood were decreased, while Th17 cells were increased compared to those with vitamin D sufficiency and controls. Vitamin D deficiency in CD patients is common. Vitamin D is associated with disease activity and intestinal inflammation, which may affect the Treg/Th17 balance and the expression of gut TJ proteins. [ABSTRACT FROM AUTHOR]

Serotonin-selective reuptake transporter (SERT) regulates extracellular availability of serotonin (5-hydroxytryptamine; 5-HT) and participates in the pathogenesis of functional disorders. Colonic SERT expression is decreased in colonic sensitized rats, and the glucagon-like peptide-1 analogue, exendin-4, reduces visceral hypersensitivity by decreasing 5-HT levels and increasing SERT expression. The present in vitro study aimed to further investigate the effects of exendin-4 on SERT expression, and to examine the role of GLP-1 and its receptor in the regulation of 5-HT. SERT mRNA and protein expression levels were detected by reverse transcription-quantitative PCR and western blotting. A [3H]−5-HT reuptake experiment was performed in IEC-6 rat intestinal epithelial cells treated with exendin-4. Effects on the adenosine cyclophosphate (AC)/PKA pathway were examined by variously treating cells with the AC activator forskolin, the protein kinase A (PKA) inhibitor H89 and the AC inhibitor SQ22536. Exendin-4 treatment upregulated SERT expression and enhanced 5-HT reuptake in IEC-6 cells. Also, PKA activity in IEC-6 cells was increased by both exendin-4 and forskolin, whereas these effects were abolished by the pre-treatment of exendin-9, which is a GLP-1R inhibitor, SQ22536 and H89. In conclusion, exendin-4 may be associated with the upregulation of SERT expression via the AC/PKA signaling pathway. [ABSTRACT FROM AUTHOR]

In this paper, the oxidation behavior and high-temperature tribological properties of laser cladding Ti-Al-Si-SiCx system coatings at 800°C in the air were studied. The results demonstrated that these coatings had Ti 5 Si 3 /Ti 3 Al eutectic structure before oxidation. The results of oxidation resistance suggested that the oxidation weight gain conformed to the parabolic law. An appropriate increase in SiC content is beneficial to lower the oxidation rate. The Ti 5 Si 3 phase has excellent oxidation resistance. TiC phase forms CO 2 product during the oxidation process. In addition, the diffusion rates of Ti and Al elements in the oxide layer are different. The combined effect of the two eventually leads to the gradual formation of pores in the oxide layer. The TiC-reinforced phase improves the friction coefficient of high-temperature friction, but its introduction significantly improves the high-temperature wear resistance. Additionally, the adhesion of the oxide film in the high-temperature wear process exerted a great influence on the wear mechanism. Ti-Al-Si-SiC 3 exhibited the lowest wear rate of 6.73 × 10−7 mm3 N−1 m−1. The wear mechanism is primarily adhesive wear, abrasive wear, and oxidative wear. • Ti-Al-Si-SiC 3 coatings are mainly composed of Ti 3 Al, Ti 5 Si 3 , and TiC phases. • The improvement of oxidation resistance of Ti-Al-Si-SiCx coating is the result of the interaction of Al and Si. • An appropriate amount of Si can promote the formation of Al 2 O 3 oxidation products. • Compared with Ti-Al-Si,the Ti-Al-Si-SiC 3 coating has excellent oxidation resistance and wear resistance. [ABSTRACT FROM AUTHOR]

Ti-Al-Si-SiC-Cr x (X = 0, 5, 10, 15) coatings were prepared on TC4 alloy by laser cladding, and their microstructure and tribological properties were investigated. The results reveal that the coatings consist of Ti 3 Al, TiC, Ti 5 Si 3 , and Ti 4 Cr phases. In room temperature friction, with the addition of Cr, Ti 4 Cr soft phase was formed in the coating, which reduced the three-body wear of the coating. However, an excess of Ti 4 Cr soft phase induces a reduction in the wear resistance of the coating. Under high temperature friction conditions, due to the addition of Cr, a super-hard amorphous oxide protective layer is formed on the wear surface to improve the wear resistance of the coating. Therefore, Ti-Al-Si-SiC-Cr 10 coating has the best tribological properties. [ABSTRACT FROM AUTHOR]

In recent years, nickel–titanium (NiTi) coatings have shown excellent tribological performance due to their unique phase transition characteristics. However, in the laser cladding of NiTi coatings in a semi-open environment, there are still issues with nitrogen and oxygen impurities arising in the coatings due to their exposure to air. In this study, three rare earth (RE) compounds were used to modify NiTi coatings in a semi-open environment to obtain coatings without any impurities. The effect of different RE compounds (Y 2 O 3 , YF 3 and YCl 3) on phase composition, surface oxidation and mechanical properties were studied. NiTi, NiTi 2 and the impurity phase titanium nitride (TiN) were observed in the original and Y 2 O 3 modified coating. In addition, incompletely melted Y 2 O 3 exists in the Y 2 O 3 -modified coating. The coatings with YCl 3 and YF 3 were composed of NiTi and NiTi 2 phase and the TiN impurity phase was not observed in either coating. In addition, the oxidation phenomenon at the top of the coating gradually weakened in the original, Y 2 O 3 , YCl 3 and YF 3 -modified coatings. Furthermore, the R-phase was characterised in the YF 3 -modified coatings. The average microhardness values of the original, Y 2 O 3 , YCl 3 and YF 3 -modified coatings were 669.68 HV 0.3 , 755.1 HV 0.3 , 579.1 HV 0.3 and 390.47 HV 0.3 , respectively, of which the microhardness of the YF 3 -modified coating was the lowest. Although RE compounds did not significantly change the tribological properties, the Y 2 O 3 -modified coating exhibited the best tribological properties (∼0.886 mm, 2.6 mg). The results show that YF 3 can isolate pollutants from the air in the coating and protect the coating in a semi-open environment. • NiTi alloy coating was prepared by laser cladding in a semi-open environment. • The TiN impurity phase disappeared inside the coating after the addition of YF 3. • The coating with YF 3 addition has the lowest microhardness. • The YF 3 prevents the Ti element in coatings from being contaminated by N 2 in the air. [ABSTRACT FROM AUTHOR]

• The hypereutectic-eutectic-hypoeutectic gradient HEA coating is prepared. • The eutectic structure in the coating is nanoscale lamellar. • Hardness of the gradient HEA coating exhibits an outside-to-inside decrease trend. • Compared with FeCoCrNi HEA coating, the surface hardness is increased by 340%. • Compared with FeCoCrNi HEA coating, the wear rate is decreased by 94.1%. In this study, a hypereutectic-eutectic-hypoeutectic gradient high-entropy alloy (HEA) coating was successfully prepared by in-situ interfacial reaction between Nb and FeCoCrNi. Its microstructure is composed of Fe-rich FCC phase and Nb-rich Laves phase, and the eutectic structure is nano lamellar. The outside-to-inside hardness of the coating gradually decreases from 797.4 Hv 0.5 to 425.5 Hv 0.5. Compared with those of the FeCoCrNi HEA coating, the surface hardness, COF, and wear rate of the hypereutectic-eutectic-hypoeutectic gradient HEA coating are improved by 340%, 41.3%, and 94.1%, respectively. The design and preparation method applied in this study can provide new ideas for the development of new HEA coatings. [ABSTRACT FROM AUTHOR]

In this work, a new dual-phase high-entropy alloy (HEA) coating is successfully synthesized by laser cladding. XRD, SEM, TEM, EBSD, and TG-DSC are employed to investigate the microstructures and high-temperature stabilities. Simultaneously, under high-temperature friction and universal mechanical tester, the wear properties at 25 °C, 400 °C, and 800 °C and the mechanical properties at the compression speeds of 1 %, 2 %, and 3 % are explored. As indicated by the results, the FeCoNiAlCu HEA coating is composed of FCC phase with small angle grain boundaries and small size grains and BCC phase with HAGBs and large size grains. In terms of mechanical properties, FeCoNiAlCu HEA coating has good strength and toughness. When considering the fracture mechanism, it transfers gradually from a ductile fracture to a brittle fracture with increased compression speed. Besides, FeCoNiAlCu HEA coating maintains good stability at a high temperature of 764.2 °C. Meanwhile, the wear resistance and friction reduction of HEA coating are improved obviously at 800 °C. With the rise of temperature, the friction coefficient decreases gradually, the wear rate reduces, and the antifriction and wear resistance are enhanced. • The FeCoNiAlCu HEA is composed of FCC phase (LAGBs and small size grains) and BCC phase (HAGBs and large size grains). • The yield strengths of FeCoNiAlCu HEA are 1516.2 MPa, 1189.1 MPa and 929.8 MPa at the compression speeds of 1%, 2% and 3%. • With the increase of compression speed, the fracture gradually changes from ductile fracture to brittle fracture. • The FeCoNiAlCu HEA has good high temperature stability from 25°C to 764.2°C. • The frictional performance of HEA are improved obviously at 800°C. [ABSTRACT FROM AUTHOR]

Refractory high entropy alloys (RHEAs) with single-phase structure hold far great potential in the field of surface protection application under extreme environment such as high temperature, abrasion and corrosion. In this work, the effects of Cr, Zr and W on the microstructure evolution and properties of a single-phase body-centered-cubic (BCC) NbTaTiV RHEA coating have been investigated. Experimentally, in addition to a small amount of Laves phase introduced by Cr element, NbTaTiV-(Cr, Zr, W) RHEA coatings basically maintain the single BCC structure. The addition of different elements affects segregation degrees in dendrite microstructure, and Zr shows nanoscale chemical heterogeneity. Notably, grain refinement, elevated geometrically necessary dislocation density and high-density low angle grain boundaries lead to a dramatically increase of micro-hardness due to elements addition. The wear rate of NbTaTiVCr and NbTaTiVW RHEA coatings reduce by 74.98 % and 70.79 % compared with NbTaTiV coating. The wide passive passivation zones close to 1000 mV obtained by potentiodynamic polarization exhibit excellent corrosion resistance. In addition, the formation mechanism of oxide layers is studied by thermodynamic parameters and oxidation behavior of simple oxides. The current work provides theoretical support for the application of strengthening elements in a single-phase BCC RHEA coating. [Display omitted] • Lattice distortion of BCC phase after adding elements is affected to various degrees. • There exists nanoscale chemical heterogeneity in NbTaTiVZr RHEA coating. • The interaction between different types of grain boundaries and dislocations enhances hardness of RHEA coatings. • The wide passive passivation zones close to 1000 mV are exhibited in potentiodynamic polarization curves. • The thermodynamic parameters and oxidation behavior of simple oxides determine the formation of oxide layers. [ABSTRACT FROM AUTHOR]

Highlights • The interactions between laser, water and target are not only destructive but also helpful to repair damaged parts. • The as-repaired layers manufactured by underwater wet laser repairing process possesses good repairing quality. • Smaller heat affected zone, smaller coating thickness and more deformation are obtained. Abstract Today, many researchers focus on the destructive effects of the laser in underwater environment. In this paper, we present underwater wet laser repairing which is a kind of technique to avert the destructive effects of the interactions between laser, water and target. We introduce helpful materials to repair nickel aluminum bronze (NAB) plate and discuss the effect of interactions between the laser, water and target on the repairing quality during underwater wet laser repairing process. As a result, the useful materials, Zn and Ti, protect melting pool from damaging by the high-speed water jet and shock wave. The as-repaired layers possess good repairing quality. In addition, the as-repaired layer manufactured by underwater wet laser repairing process possesses smaller heat affected zone, smaller coating thickness and more deformation than the layer manufactured in the air. In summary, with the help of the useful materials, a good repairing quality can be obtained. [ABSTRACT FROM AUTHOR]

Abstract The requirement of repairing damaged surface of nickel aluminum bronze (NAB) parts from underwater environment is urgent in recent years. In this paper, a novel approach to underwater laser cladded NAB by adding Ti and applying Zn protective layer has been reported. The materials fabricated underwater from this approach possess desirable performance. Ti additives increases the surface tension in melting pool, and prevents the high-speed water jet from invading the melting pool. Therefore, pores are almost disappearing. Due to the fast heat loss during underwater laser cladding process, the microstructure of underwater laser cladded nickel aluminum with adding titanium is fine, homogeneous and stable, in addition, the heat affected zone is small. Electrochemical results shows that the corrosion resistance of underwater laser cladded nickel aluminum bronze with adding titanium is better than that of substrate. In this study, the underwater environment is favorable for manufacturing a good material by using laser processing technology. The results of this study will provide meaningful reference to repairing NAB parts in underwater environment. [ABSTRACT FROM AUTHOR]

Abstract In order to obtain metallurgical shape memory alloy with a better quality, electro-magnetic stirring (EMS) technology is selected as an aiding method during plasma arc deposition (PAD) process. In this work, Ti 51 Ni 49 alloys were successfully produced by EMS-assisted PAD technology. Influence of EMS on the microstructure, phase transformation behavior, micro-hardness and wear resistance of PAD TiNi alloy have been systematically investigated. The PAD TiNi alloy is composed of TiNi coarse columnar dendrites with a certain number of Ti 2 Ni phases distributed in the inter-dendritic regions. Under the action of EMS, TiNi coarse columnar dendrites transform into fine non-dendrites or spheroid grains and the homogeneity of microstructures improves significantly. The implementation of EMS during PAD do not change the path of phase transformation, but improve the degree of phase transformations and reduce the transformation temperatures of PAD TiNi alloy. The EMS-PAD TiNi alloy possesses better dry wear resistance than the PAD TiNi alloy, which can be attributed to the higher degree of pseudo-elasticity of TiNi phases and strengthening of Ti 2 Ni phases. Highlights • Ti 51 Ni 49 shape memory alloys were successfully produced by electromagnetic stirring (EMS) - assisted plasma arc deposition (PAD) technology. • Under the action of EMS, TiNi coarse columnar dendrites transform into fine non-dendrites and its homogeneity improves significantly. • The EMS-PAD TiNi alloy possesses better dry wear resistance than the PAD TiNi alloy due to the higher degree of pseudo-elasticity and strengthening of Ti 2 Ni phases. [ABSTRACT FROM AUTHOR]

Abstract Recently, additive manufacturing (AM) technology has drawn significant attention to fabricate shape memory alloys. In this study, plasma arc deposition (PAD), an AM technology, has been successfully applied to prepare the Ti 51 Ni 49 alloy directly and rapidly at the first time. The synthesized PAD Ti 51 Ni 49 alloy consisting of TiNi (B2), TiNi (B19′) and Ti 2 Ni phase, exhibited primary TiNi columnar dendrites structure with a certain number of Ti 2 Ni phases distributed in the interdendritic regions. The as-deposited Ti 51 Ni 49 alloy displayed a two-step phase transformation evidently (B2→ R → B19') during cooling process, and special linear superelasticity (up to 4.5%) with narrow hysteresis due to Ti 2 Ni phase embedded in TiNi matrix phase. This work suggests that the PAD is an effective technology to directly and rapidly synthesize shape memory alloy. Highlights • Plasma arc deposition has been successfully applied to fabricate the shape memory alloy for the first time. • The as-fabricated sample displays linear super-elasticity (up to 4.5%) with narrow hysteresis. • Ti 2 Ni phase intimated contact with the TiNi (B2) matrix phase is the origin of the unusual linear superelasticity. [ABSTRACT FROM AUTHOR]

Abstract Recently, additive manufacturing have gradually become an attractive processing technology for TiNi alloy. In this work, the Ti 5 0 Ni 50 alloy was successfully prepared by plasma arc deposition (PAD) technology. The microstructures, phase transformation characteristics and mechanical properties were investigated in detail. The PAD-TiNi alloy mainly comprised of TiNi (B2), TiNi (B19') and Ti 2 Ni phases. The TiNi cellular crystals, TiNi dendrite crystals and TiNi equiaxed crystals were presented at the bottom, middle and top area of PAD-TiNi alloys, respectively. Some irregular Ti 2 Ni phases were distributed in the inter-dendritic areas. The peritectic reaction of L (Ti) + TiNi →Ti 2 Ni led to the formation of irregular Ti 2 Ni phases. The coherence of Ti 2 Ni phases and TiNi matrix phases drove the two-step phase transformation (B2→ R → B19') during the cooling process. The as-deposited samples showed favorable hardness and high strength, especially possessing special quasi-linear superelasticity (up to 3.8%) with narrow hysteresis, which was derived from the quick appearance and disappearance of deformation microtwins under loading and unloading condition. The newly formed interface between Ti 2 Ni precipitates and TiNi matrix phase offered the nucleation sites for deformation microtwins and promoted the formation of microtwins. [ABSTRACT FROM AUTHOR]

The metastable materials have attracted the attention of researchers due to their promising physicochemical properties, but the thermal stability limits their practical application. In this paper, Ni-B/La 2 O 3 amorphous/nanocrystalline composite coatings were prepared on AISI 1045 steel substrate by electro-brush plating technique. The surface morphology, component and the phase structure of coatings were observed by Scanning Electron Microscope (SEM), Energy Dispersive X-Ray Spectroscopy (EDS) and X-Ray Diffraction (XRD), respectively. The coatings were further analyzed by Transmission Electron Microscope (TEM). Then the thermal stability of coatings with different content of La 2 O 3 was also analyzed under different annealing temperature. It was found that the coating had a unique microstructure consisting of amorphous and nanocrystalline structures. The addition of La 2 O 3 does improve the thermal stability of metastable Ni-B coatings when the annealing temperature is over 355 °C. In addition, the thermal stability of the amorphous/nanocrystalline coatings depends on the percentage of amorphous phase and grain sizes. [ABSTRACT FROM AUTHOR]

Fe/MWCNTs (multi walled carbon nanotubes) composite coatings with varying-content MWCNTs (0, 0.1, 0.2, 0.5 and 0.9 g/L) on the surface of AISI 1045 steel were produced by electro-brush plating technique. The effect of MWCNTs concentration in the plating solution on the microstructures and of the composite coatings was discussed in detail. The co-deposition of MWCNTs with Fe atom occurs in the Fe-based coating, which can decrease the number of through-wall cracks and increase the deposition velocity whereas the phase structure of the composite coatings cannot be affected. When the content of MWCNTs added in the plating solution is 0.2 g/L, the microhardness (612 HV 0.3 ) of coating is much higher than that of pure Fe coating (489 HV 0.3 ). The friction coefficient and weight loss of all Fe/MWCNTs composite coatings are significantly lower than that of pure Fe coating, which is attributed to the effect of reinforcement and lubrication of MWCNTs. [ABSTRACT FROM AUTHOR]

In the pursuit of high performance development of alloy materials, it is a long-standing problem to enhance strength and toughness simultaneously. In this study, by selecting heterogeneous high-entropy alloy (HEA) materials and conducting structural design and laser process optimization, an external-hard internal-tough HEA composite coating with an in-situ dual-phase interface layer was successfully prepared. For the microstructure, the phase structures at the top, middle, and bottom of the coating are single-phase body-centered cubic (BCC), dual-phase BCC/face-centered cubic (FCC), and single-phase FCC, respectively. Among them, the dual-phase interface layer gives priority to the FCC phase (79.4 %), supplemented by the BCC phase (16.7 %). In terms of mechanical properties, the hardness of the coating from the top to the bottom is 9.85 GPa, 5.53 GPa, and 4.86 GPa, respectively. As demonstrated by employing the three methods of K, H/E, and H3/E2, the HEA composite coating has favorable integrated characteristics of strength and toughness. Meanwhile, due to the in-situ generated dual-phase interface layer, the structural and performance differences between the high-hardness layer and the high-toughness layer are effectively alleviated, and the stress concentration is reduced, thus stabilizing the overall structure of the coating. Hence, the HEA composite coating designed and prepared in this study possesses better erosion resistance (mass erosion rate = 0.141 × 10−3 g.cm−2 s−1), tribological properties (wear rate = 0.30 × 10−6 mm3/(N · m)), and impact resistance (AKU = 103.5 ± 2.8 J). The study results can provide new methods and new theories for new HEA composite coatings with integrated strength and toughness, and can be used in guiding the development and design of similar HEA composite coating structures. [Display omitted] • The FCC/FCC + BCC/BCC HEA composite coating with gradient structure is successfully prepared. • The FeCoCrNiAl interface layer is formed in situ by FeCoCrNi and FeCoCrAl. • The interface layer alleviates the structural and performance differences between the surface and bottom layers. • The HEA composite coating possesses good strength and toughness. • The HEA composite coating has better erosion resistance, preferable tribological properties, and superior impact resistance. [ABSTRACT FROM AUTHOR]

As a lightweight material, the wide application of Mg-Li alloy is restricted by its corrosion resistance. Focusing on this, an innovative superhydrophobic composite coatings of nickel-based metal coupled with layered double hydroxides (LDHs) was prepared on Mg-Li alloy. The microstructure, hydrophobic property and corrosion resistance of coatings were investigated by SEM, TEM, XRD, FT-IR, AFM, contact angle tester and electrochemical test. The results indicated that the MgAl LDHs uniformly grown in situ on the NiP coating deposited on Mg-Li alloy through electroless plating and hydrothermal treatment. The MgAl LDHs with a complex honeycomb micro-nano structure improved the surface roughness of the composite coating to 126 nm. The two-step treatment achieved an excellent coupling between the metal-based coating and inorganic compounds. The low surface energy treatment of micro-nano structure on NiP coating surface with stearic acid (@SA) realized the superhydrophobic transition of the composite coating (WAC=154.27° ± 2.56°). Besides, MgAl LDHs showed better trapping properties for Cl-. Under the synergistic effect of anion capture and hydrophobic effect, the corrosion current density (1.35 ×10−7 A⋅cm−2) and impedance modulus of NiP/MgAl LDHs@SA coating were significantly better than those of NiP and NiP/MgAl LDHs coating. The superhydrophobic composite coating provided a better anticorrosion choice for Mg-Li alloy. [Display omitted] • A new superhydrophobic double-layer coatings were prepared on the Mg-Li alloy. • MgAl LDHs with uniform honeycomb structure were in situ grown on the NiP coating. • Modified by stearic acid, the double-layer coatings had good superhydrophobicity. • The superhydrophobic double-layer coatings showed excellent corrosion resistance. [ABSTRACT FROM AUTHOR]

Mg Li alloys have a wide application in the lightweight structure materials on account of their ultra-light-weight, good machinability and high specific strength. However, the low strength, insufficient wear and corrosion resistances of Mg Li alloys have become a critical problem that hinders their applications. In order to achieve excellent wear and corrosion properties, LC-Cu 3 Al, LC-Cu 6 Al and LC-Cu 9 Al coatings are designed and prepared on Mg Li alloy substrates in this study. The phase structure, microstructure, hardness, wear and corrosion properties of Cu Al alloy coatings are investigated in detail. The results show that a good metallurgical bond is achieved between the Cu Al alloy coatings and the substrates. LC-Cu 6 Al coating's hardness, wear and corrosion properties are the best. Compared with the Mg Li alloy substrate, the average hardness of LC-Cu 6 Al coating increases by 6.75 times, while the wear volume decreases by 88.32 % and the corrosion current density decreases by two orders of magnitude. The results suggest that using laser cladding Cu Al alloy coatings is an excellent strategy to enhance the surface properties of Mg Li alloy. [Display omitted] • Cu Al alloy coatings were prepared on Mg Li alloy by laser cladding. • LC-Cu 6 Al coating is mainly composed of Cu 9 Al 4 , Al 2 Cu 3 and Cu 2 Mg phase. • The peritectoid transition of γ 0 → Al 2 Cu 3 + Cu 9 Al 4 occurred during laser cladding. • The wear and corrosion resistance of Mg Li alloy are comprehensively improved. [ABSTRACT FROM AUTHOR]

Eutectic high-entropy alloys (EHEAs) possess in-situ composite structure, which provides a novel strategy for developing wear-resistant alloys or coatings. In this work, a new-type AlCoCrFeMn 0.5 Mo 0.1 Nb x (x = 0.4 hypoeutectic, 0.65 eutectic and 0.8 hypereutectic) EHEA coatings were designed and prepared by ultrasonic assisted laser cladding. The design strategy, microstructure and tribological behaviors of the EHEA coatings were studied in detail. The Nb 0.4 , Nb 0.65 and Nb 0.8 coatings were all composed of BCC solid solution and Laves phase. The Nb 0.65 coating showed typical nano-lamellar/nano-granular eutectic microstructure, while the Nb 0.4 and Nb 0.8 coatings had hypoeutectic and hypereutectic microstructures, respectively. The wear rates of the EHEA coatings (5.5 × 10−6 mm3/N·m for Nb 0.4 coating, 5.3 × 10−6 mm3/N·m for Nb 0.65 coating and 8 × 10−6 mm3/N·m for Nb 0.8 coating) were significantly lower than those of most metallic and metal-ceramic composite materials. The wear mechanisms of Nb 0.4 , Nb 0.65 and Nb 0.8 coatings were slight adhesive wear and oxidation wear. Numerous regular rolling structures formed on the wear scar of Nb 0.65 coating, which provides an anti-friction effect for the coating. The good carrying capacities and high hardness of the BCC, Laves and eutectic microstructures contributed to the excellent wear resistance of the EHEA coatings. [Display omitted] • A new type AlCoCrFeMn 0.5 Mo 0.1 Nb x eutectic HEA coating system were successfully designed and prepared. • Typical nano-lamellar and some nano-granular eutectic microstructures were obtained in the coatings. • The wear rates of the EHEA coatings were significantly lower than those of most metallic materials. • The high hardness, good elastic recovery and oxidation structure contribute to the excellent wear resistance. [ABSTRACT FROM AUTHOR]

• The ultrasonic assisted underwater NiTi 2 -based deposition layer was manufactured. • Ultrasonic promotes hypoeutectic transformation of the UWNT layer. • The stress-induced FCC-Ti was found in the UWNT layer. • The UWNT layer was wear-resistant, and the COF was less affected by the friction environment. An in situ TiC-enhanced NiTi 2 -based composite deposition layer was prepared by ultrasonic assisted underwater wet laser deposition. The evolution of the microstructure and interface state, and the friction properties in the air and brine solution environments of the deposition layer were analyzed and researched. The results demonstrated that the thermal and steady-state cavitation from ultrasound effects increase the total energy of the melt pool and promote mixing. The dilution rate of the ultrasonic assisted underwater laser deposition layer increases to 86.72 % compared with that of the underwater laser deposition layer (78.75 %). Ultrasonic reduced underwater laser deposition defects such as lack of fusion and weld slag, and enhanced the wettability between the deposition layer and substrate. The contact angle of the UWNT layer (24.40°, in average) is smaller than the WNT layer (29.80°, in average). Ultrasonic shortened the contact time between the deposition layer surface and the solution, which reduced the reaction of the Ni element with the brine solution. It also transformed the deposition layer from hypereutectoid microstructure to hypoeutectic microstructure and from planar interface to cellular interface. With the effect of the ultrasonic field, the elements in the deposition layer become more uniformly distributed and the secondary phases undergo spheroidization. In the ultrasonic assisted deposition layer, stress-induced FCC-Ti was discovered. Ultrasonic field also reduced the dispersion of the microhardness and increased the average microhardness to 863.3 ± 45.1 HV 0.3. Tribology properties show that ultrasonic field effectively improved the wear resistance and friction stability of the ultrasonic assisted deposition layer. The COF of the ultrasonic assisted deposition layer was less affected by the environment, with values of 0.25 and 0.24 observed in air and brine solution, respectively. Overall, the research results in this paper can provide a new insight to improve the surface properties of NiTi 2 -based alloy underwater laser deposition. [ABSTRACT FROM AUTHOR]

The phase instability of 6–8 wt% Y 2 O 3 partially stabilized ZrO 2 (YSZ) in high temperature and molten salt corrosion environment seriously limits its application above 1200 °C. In this study, the chemical co-precipitation method prepared Yb 2 O 3 and CeO 2 co-doping YSZ (YbCeYSZ) ceramic materials to improve the above issues. It was proposed to improve the defect of high-temperature phase instability of CeO 2 -doped YSZ materials by adding Yb 2 O 3. The phase stability, thermal insulation properties, and Na 2 SO 4 + V 2 O 5 molten salt corrosion behavior of YbCeYSZ ceramic materials were studied. The results showed that 2.5 mol% Yb 2 O 3 -4 mol% CeO 2 -YSZ material (2.5Yb4CeYSZ) had no monoclinic phase (m-ZrO 2) after holding at 1500 °C for 120 h due to forming more defect clusters in the system. Meanwhile, the 2.5Yb4CeYSZ had excellent thermal insulation performance and molten salt corrosion resistance, which was attributed to the strong phonon scattering in the 2.5Yb4CeYSZ material system and the low reactivity between the stabilizer and the corrosive salt. [ABSTRACT FROM AUTHOR]

The carburized 12Cr2Ni4A alloy steel was implanted by Ti + N double elements implantation. The microstructure, nano-hardness and corrosion properties were investigated by EPMA, TEM, XPS, nano-hardness and electrochemistry tests in detail. The results showed that the Ti + N co-implanted layer is composed of FCC TiN and TiC phases with BCC martensite. Compared with the un-implanted layer, the Ti + N implanted layer has higher nano-hardness and better corrosion resistance. In addition, the higher nano-hardness was presented below the surface of 1800 nm compared with un-implanted layer, which is far beyond the thickness of the implanted layer. The results also indicated that the generation of nanoscale ceramic phase and structures are not the only factor to impose the influence on the nano-hardness and corrosion resistance, but the radiation damage and lattice distortion will play an important role. [ABSTRACT FROM AUTHOR]