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Metalenses with achromatic performance offer a new opportunity for high-quality imaging with an ultra-compact configuration; however, they suffer from complex fabrication processes and low focusing efficiency. In this study, we propose an efficient design method for achromatic microlenses on a wavelength scale using materials with low dispersion, an adequately designed convex surface, and a thickness profile distribution. By taking into account the absolute chromatic aberration, relative focal length shift (FLS), and numerical aperture (NA), microlens with a certain focal length can be realized through our realized map of geometric features. Accordingly, the designed achromatic microlenses with low-dispersion fused silica were fabricated using a focused ion beam, and precise surface profiles were obtained. The fabricated microlenses exhibited a high average focusing efficiency of 65% at visible wavelengths of 410–680 nm and excellent achromatic capability via white light imaging. Moreover, the design exhibited the advantages of being polarization-insensitive and near-diffraction-limited. These results demonstrate the effectiveness of our proposed achromatic microlens design approach, which expands the prospects of miniaturized optics such as virtual and augmented reality, ultracompact microscopes, and biological endoscopy.

Abstract Refractory high-entropy alloys (HEAs) have attracted considerable attention due to their stable phase structure and excellent high-temperature properties. In this work, we performed first-principles calculations, coupled with experiments, to explore HEAs with high corrosion resistance. The results revealed that TiNbTa-based HEAs exhibited a lower tendency for corrosion. However, the appearance of local chemical fluctuations (LCFs) increased the corrosion tendency of TiNbTa-based HEAs. Comprehensive SHapley Additive exPlanations analyses uncovered that in a sample with configurational LCFs, the atomic order near the surface was altered. Therefore, corrosion behavior was affected. Based on experiments, the annealed samples exhibited typical chemical segregation and declined corrosion resistance.

This work conducted tensile experiments from room temperature to 1100 °C on a new fourth-generation single crystal superalloys along [001]. The effect of temperature on the tensile properties and deformation mechanism of the alloy were investigated. Results showed that the yield strength of the alloy reached its peak value (1017 MPa) at 850 °C. From room temperature to 760 °C, the occurrence of stacking faults (SFs) was observed in the γ matrix channel. From the room temperature to 850 °C, the occurrence of stacking faults was observed in the γʹ phase. The interface dislocation networks appeared at 980 °C and above. At room temperature, stacking faults sheared γʹ phase, in which three types of stacking faults occurred, which controlled deformation process. The main deformation mechanism from 650 °C to 850 °C was the shearing of γʹ phase by stacking faults and super dislocations, and at 850 °C, stacking faults in different directions of propagation corresponded to the formation of Lomer-Cottrell locks (L-C locks), which greatly increased the yield strength. At 980 °C and 1100 °C, dislocation climbing and bypassing and anti-phase boundary (APB) coupled dislocation pair shear γʹ phase became the main deformation mechanism.

The electrochemical behavior and corrosion induced mechanical degradation of biodegradable Zn–2Cu–0.03Li alloy were in detail investigated. The results indicated that the corrosion product film presented an increasing corrosion resistance, while the localized corrosion induced by microgalvanic effect was intensified. Corrosion pits, as the typical defect, acted as the crack initiation sites and accelerated the fracture process of the Zn–2Cu–0.03Li alloy. Accordingly, the fracture mode transformed from ductile to brittle failure. Significant loss in ultimate tensile strength and elongation of the alloys occurred due to strong stress concentration at corrosion pit, threatening the mechanical reliability after implantation.

This work introduced a facile method for fabricating heterostructures in a medium Mn steel via a direct warm rolling process. The heavy warm rolling promoted the transformation of metastable austenite (∼12.2 vol%) into hard domain α’ martensite, which formed a heterogeneous microstructure with the untransformed γ (soft domain). After 600 °C re-annealing, the hard domain α’ re-reversed to α + γ, and the heterostructure disappeared. Compared to the homogeneous structure, the heterostructure exhibited the synergistic enhancement of strength-ductility (yield strength (YS): 782 → 1113 MPa; ultimate tensile strength (UTS): 1099 → 1304 MPa; total elongation (TEL): 20.8 % → 21.7 %). Quantitative analysis showed that the heterogeneous deformation induced (HDI) strengthening (∼261 MPa) was the primary contributor to the increased ΔYS (782 → 1113 MPa) value, rather than the traditional strengthening mechanisms. Transformation induced plasticity (TRIP) and twinning induced plasticity (TWIP) effect were the main deformation mechanisms of both homogeneous/heterogeneous structures. However, compared to the homogeneous microstructure, the heterogeneous structure possessed the more pronounced TRIP and HDI hardening effects as well as L-C locks, the cooperative effect of these three factors further improved the strain hardening ability to break through the strength-ductility trade-off dilemma.

Abstract The wide range of alloy composition controllability for multi-principal element alloys (MPEAs) may provide a great opportunity for discovering special forms of surface oxides to improve the corrosion and oxidation resistance in extreme environments. Changing the type and content of promoting passivation elements would not only change the microstructure of the alloy but also significantly affect the composition and structure of the surface passive film, resulting in a strong impact on the corrosion and oxidation resistance of the alloy. This article reviews recent research on the effects of alloying elements on the passivation properties, the contribution of each alloying element, and the synergistic effect between the elements on the passivation mechanisms and electrochemical dissolution characteristics of surface passive films that form on some MPEAs. In addition, the composition and structural characteristics of surface oxides relevant to the selective oxidation of elements are elaborated upon. Finally, several open questions and recommendations for research directions regarding the passivation and selective oxidation of MPEAs were provided to guide future exploration.

In material science and engineering, obtaining a spectrum from a measurement is often time-consuming and its accurate prediction using data mining can also be difficult. In this work, we propose a machine learning strategy based on a deep neural network model to accurately predict the dielectric temperature spectrum for a typical multi-component ferroelectric system, i.e., (Ba1−x−yCaxSry)(Ti1−u−v−wZruSnvHfw)O3. The deep neural network model uses physical features as inputs and directly outputs the full spectrum, in addition to yielding the octahedral factor, Matyonov–Batsanov electronegativity, ratio of valence electron to nuclear charge, and core electron distance (Schubert) as four key descriptors. Owing to the physically meaningful features, our model exhibits better performance and generalization ability in the broader composition space of BaTiO3-based solid solutions. And the prediction accuracy is superior to traditional machine learning models that predict dielectric permittivity values at each temperature. Furthermore, the transition temperature and the degree of dispersion of the ferroelectric phase transition are easily extracted from the predicted spectra to provide richer physical information. The prediction is also experimentally validated by typical samples of (Ba0.85Ca0.15)(Ti0.98–xZrxHf0.02)O3. This work provides insights for accelerating spectra predictions and extracting ferroelectric phase transition information.

Additive manufactured Ti6Al4V has shown high tensile anisotropy. The tribocorrosion properties involve the coupling of mechanical wear and surface corrosion, and its anisotropy is unclear. In this study, the corrosion resistance of the horizontal (XOY) plane and the vertical (V) plane was compared by electrochemical tests. The wear resistance and tribocorrosion resistance of different planes of laser powder bed fusion (L-PBF) Ti6Al4V were tested by using zirconia ball as friction pair. The results show that the corrosion resistance of the V plane was better than that of the XOY plane. However, the wear and tribocorrosion resistance recorded for the XOY plane was better than that of the V plane. The columnar crystals along the building direction led to the anisotropy of wear and tribocorrosion of L-PBF Ti6Al4V.

Sluggish diffusion effect of high entropy alloy limits its diffusion bonding with other components in practical applications. In this paper, the surface mechanical attrition treatment (SMAT) strategy for performing diffusion bonding joints of high entropy alloy (HEA) at a relative lower temperature is proposed. The EDS results demonstrate that the diffusion distance of Fe atoms increases significantly after SMAT since more gain boundaries are formed after SMAT. Furthermore, with this method the HEA/stainless steel joint can achieve a useable strength of 320 MPa at relative lower temperature of 850 °C (∼0.63 Tm, Temperature of melting). Molecular dynamics simulations show that the apparent diffusivity of Fe in the polycrystalline model is significantly higher than in the single-crystalline model because of fast diffusion at grain boundaries, i.e., the grain boundaries are fast diffusion channels. More detailed microstructure analysis indicates that although the density of dislocations increases after SMAT, its elemental diffusion ability is much weaker compared with grain boundaries. This study provides a feasible avenue for the application of diffusion bonding in HEAs, which could greatly broaden the applications fields of HEAs.

Ferroelectric (FE) phase transition with a large polarization change benefits to generate large electrocaloric (EC) effect for solid-sate and zero-carbon cooling application. However, most EC studies only focus on the single-physical factor associated phase transition. Herein, we initiated a comprehensive discussion on phase transition in Pb0.99Nb0.02[(Zr0.6Sn0.4)1−xTix]0.98O3 (PNZST100x) antiferroelectric (AFE) ceramic system under the joint action of multi-physical factors, including composition, temperature, and electric field. Due to low energy barrier and enhanced zero-field entropy, the multi-phase coexistence point (x = 0.12) in the composition–temperature phase diagram yields a large positive EC peak of maximum temperature change (ΔTmax) = 2.44 K (at 40 kV/cm). Moreover, the electric field–temperature phase diagrams for four representative ceramics provide a more explicit guidance for EC evolution behavior. Besides the positive EC peaks near various phase transition temperatures, giant positive EC effects are also brought out by the electric field-induced phase transition from tetragonal AFE (AFET) to low-temperature rhombohedral FE (FER), which is reflected by a positive-slope boundary in the electric field–temperature phase diagram, while significant negative EC responses are generated by the phase transition from AFET to high-temperature multi-cell cubic paraelectric (PEMCC) with a negative-slope phase boundary. This work emphasizes the importance of phase diagram covering multi-physical factors for high-performance EC material design.

For efficient solid-state refrigeration technologies based on electrocaloric effect (ECE), it is a great challenge of simultaneously obtaining a large adiabatic temperature change (ΔT) within a wide temperature span (Tspan) in lead-free ferroelectric ceramics. Here, we studied the electrocaloric effect (ECE) in (1-x)(Na0.5Bi0.5)TiO3-xCaTiO3 ((1-x)NBT-xCT) and explored the combining effect of morphotropic phase boundary (MPB) and relaxor feature. The addition of CT not only constructs a MPB region with the coexistence of rhombohedral and orthorhombic phases, but also enhances the relaxor feature. The ECE peak appears around the freezing temperature (Tf), and shifts toward to lower temperature with the increasing CT amount. The directly measured ECE result shows that the ceramic of x = 0.10, which is in the MPB region, has an optimal ECE property of ΔTmax = 1.28 K @ 60 °C under 60 kV/cm with a wide Tspan of 65 °C. The enhanced ECE originates from the electric-field-induced transition between more types of polar nanoregions and long-range ferroelectric macrodomains. For the composition with more relaxor feature in the MPB region, such as x = 0.12, the ECE is relatively weak under low electric fields but it exhibits a sharp increment under a sufficiently high electric field. This work provides a guideline to develop the solid–state cooling devices for electronic components.

Recently, there has been a new trend to design chemically heterogeneous austenite by adjusting the various thermal treatment processes in medium Mn steel. In this work, we found that the single or synergistic addition of ferrite stabilizers (e.g., Al) accelerated the heterogeneous distribution of Mn and the formation of a core-shell austenitic structure compared with the addition of an austenite stabilizer (e.g., Cu) under the conventional quenched-annealing process. In addition, the Mn-enriched austenite shell played a significant role in suppressing the martensitic transformation of the Mn-depleted austenite core upon cooling. The sharp Mn gradient distribution corresponded to the heterogeneous kinetics of the deformation-induced martensitic transformation, resulting in the gradual transformation-induced plasticity (TRIP) effect.

By trapping hydrogen, nanoprecipitates can mitigate the hydrogen embrittlement of high strength steels. Here, the authors report direct evidences on the structural and chemical features underlying distinct hydrogen-trapping behaviors at the incoherent interfaces of precipitates and steel matrix.

Stress corrosion cracking (SCC) is extremely detrimental to the long-term applications of high-strength low-alloy steels. In this work, the critical effects of the dimension and morphology of the non-metallic inclusions on the SCC susceptibility and pitting corrosion were investigated. With the trace-element regional supply method, the inclusions are transformed from the detrimental sharp-edged (Ti, V)N and enormous MnS into globular or elliptical Al2O3 and multicomponent inclusions with small dimensions (3.41 ± 2.36 μm) and high equivalent shape factor (0.93 ± 0.02) in the in-situ nanoparticles strengthened steel. As a result, the corrosion current, depth and diameter of pits, and roughness of the surface were reduced with suppression of pitting corrosion. The superior SCC resistance in the in-situ nanoparticles strengthened steel was obtained by inclusion refinement. The strategy of inclusion refinement by in-situ nanoparticles is beneficial for designing SCC resistant steels.

Abstract Introducing polarization field of piezoelectric materials is an effective strategy to improve photocatalytic performance. In this study, a new type of BaTiO3/CuO heterostructure catalyst was designed and synthesized to achieve high piezo-photocatalytic activity through the synergy of heterojunction and piezoelectric effect. The BaTiO3/CuO heterostructure shows a significantly enhanced piezo-photocatalytic degradation efficiency of organic pollutants compared with the individual BaTiO3 nanowires (NWs) and CuO nanoparticles (NPs). Under the co-excitation of ultrasonic vibration and ultraviolet radiation, the optimal degradation reaction rate constant k of polarized BaTiO3/CuO heterostructure on methyl orange (MO) dye can reach 0.05 min− 1, which is 6.1 times of photocatalytic rate and 7 times of piezocatalytic rate. The BaTiO3/CuO heterostructure with remarkable piezo-photocatalytic behavior provides a promising strategy for the development of high-efficiency catalysts for wastewater purification, and it also helps understand the coupling mechanism between piezoelectric effect and photocatalysis.

Abstract The outstanding abilities of metamaterials to manipulate physical fields are extensively studied in both wave‐based and diffusion‐based fields. However, mass diffusion metamaterials, with the ability to manipulate diffusion with practical applications associated with chemical and biochemical engineering, have not yet been experimentally demonstrated. In this work, ion cloaking, concentrating, and selection in liquid solvents are verified by both simulations and experiments, and the concept of a “plug and switch” metamaterial is proposed based on scattering cancellation (SC) to achieve switchable functions by plugging modularized functional units into a functional motherboard. Plugging in any module barely affects the environmental diffusion field, but the module choice impacts different diffusion behaviors in the central region. Cloaking strictly hinds ion diffusion, and concentrating increase diffusion flux, while cytomembrane‐like ion selection permits the entrance of some ions but blocks others. In addition, these functions are demonstrated in special applications like the catalytic enhancement by the concentrator and the protein protection by the ion selector. This work not only experimentally demonstrates the effective manipulation of mass diffusion by metamaterials, but also shows that the “plug and switch” design is extensible and reconfigurable. It facilitates novel applications including sustained drug release, catalytic enhancement, bioinspired cytomembranes, etc.

Covalent organic frameworks (COFs) present well-defined materials for constructing structure-property-activity relationships. Herein, authors explore isostructural porphyrinic two-dimensional COFs with tunable of photocatalytic H2 production rates arising from tailored charge-carrier dynamics.

Objective: Qili Qiangxin Capsule (QQC), a Chinese patent medicine, is clinically effective in treating dilated cardiomyopathy (DCM). However, the meta-analysis of QCC combined with conventional western medicine (CWM) on DCM remains unexplored. This study aimed to systematically evaluate the efficacy and safety of QCC in the treatment of DCM.Methods: Searched the studies of the combination of QQC and CWM in the treatment of DCM, from databases like PubMed, Cochrane Library, Web of Science, Wan Fang Databases, Chinese Biomedical Literature Database, China Science and Technology Journal Database, China National Knowledge Infrastructure, prior to 15 January 2022. Two reviewers respectively regulated research selection, data extraction, and risk of bias assessment. Review Manager Software 5.4 was used for meta-analysis. Furthermore, GRADE pro3.6.1 software was selected to grade the current evidence in our findings. This meta-analysis has been registered in PROSPERO (CRD42022297906).Results: There were 35 studies pertaining to 3,334 patients included. The meta-analysis showed compared with CWM alone, the combination therapy had significant advantages in improving the clinical efficiency rate (RR = 1.24, 95% CI: 1.19 to 1.29, p < 0.00001), 6 min walking distance (6MWD) (MD = 41.93, 95%CI: 39.82 to 44.04, p < 0.00001), superior in ameliorating the left ventricular ejection fraction (LVEF) (MD = 5.73, 95%CI: 4.70 to 6.77, p < 0.00001), left ventricular end-diastolic dimension (LVEDD) (MD = −4.09, 95%CI: −4.91 to −3.27), p < 0.00001), left ventricular end-systolic diameter (LVESD) (MD = −4.73, 95%CI: −5.63 to −3.84), p < 0.00001) and BNP (MD = −101.09, 95%CI: -132.99 to −69.18), p < 0.00001), and also superior in reducing hypersensitive-C-Reactive Protein (hs-CRP) (MD = −3.78, 95%CI: −4.35 to −3.21), p < 0.00001), Interleukin- 6 (IL-6) (MD = −25.92, 95%CI: −31.35 to -20.50), p < 0.00001), tumor necrosis factor-α (TNF-α) (MD = -5.04, 95%CI: −6.13 to −3.95), p < 0.00001), high mobility group protein B1 (HMGB1) (MD = −4.34, 95%CI: −5.22 to −3.46), p < 0.00001), and adverse reactions (ARs) (RR = 0.70, 95%CI: 0.51–0.97), p = 0.03). The GRADE evidence quality rating presented with moderate or low quality of evidence for the available data.Conclusion: Compared with the control group, QQC combined with CWM may be effective in treating DCM. However, the conclusion of this study must be interpreted carefully due to the inferior quality and ambiguity of bias in the included trials.Systematic Review Registration: https://www.crd.york.ac.uk/prospero, identifier [CRD42022297906].

Objective: Buyang Huanwu Decoction (BYHW), a famous herbal prescription in traditional Chinese medicine (TCM), has been used for 200 years for treating ischemic heart failure (IHF). This study aims to assess the efficacy and safety of BYHW combined with guideline-guided pharmacotherapy in patients with IHF and explore the biological mechanism by which BYHW exerts its efficacy.Methods: In the multicenter, double-blind, randomized controlled trial, a total of 80 patients with IHF were randomized to receive BYHW or placebo for 3 months. The primary efficacy endpoints were New York Heart Association (NYHA) classification, TCM syndrome scores, N-terminal pro-B-type natriuretic peptide (NT-ProBNP), whereas the mechanism exploration endpoints included energy metabolism parameters and coagulation function parameters. In addition, we performed the proteomic study of the serum of patients after treatment by label-free quantification technology to verify the candidate target proteins and pathways.Results: After 3 months of treatment, the NYHA classification, TCM syndrome scores, and the percentage of subjects with at least 30% reduction in NT-ProBNP were significantly improved in the BYHW group, compared with the control group (p < 0.05); BYHW treatment also significantly regulated blood glucose, blood lipid levels, ameliorated energy metabolism and improved coagulation function parameters. There were no significant differences in safety endpoints between the two groups. In addition, we obtained 56 differentially expressed proteins by proteomics, including 20 upregulated proteins and 36 downregulated proteins. Bioinformatic analysis revealed the mechanism of BYHW treatment was significantly related to complement and coagulation cascades, cholesterol metabolism, NF-kappa B signaling pathway, PI3K-Akt signaling pathway, and metabolic pathways. Among these differentially regulated proteins, fibrinogen gamma (FGG), fibrinogen beta (FGB), Carboxypeptidase B2 (CPB2), Coagulation factor XIII A (F13A1), Intercellular adhesion molecule1 (ICAM1), Apolipoprotein C-II(APOC2), Apolipoprotein C-I(APOC1), and CD44 were found to be signature proteins associated with the efficacy of BYHW against IHF.Conclusion: BYHW treatment can further improve cardiac dysfunction and clinical symptoms in IHF based on standard therapy without apparent adverse effects. Additionally, BYHW may play a therapeutic role in IHF by improving energy metabolism and regulating coagulation function through multiple targets and pathways.

Dielectric resonators on metallic surface can enhance far-field scattering and boost near-field response having promising applications in nonlinear optics and reflection-type devices. However, the dependence of gap size between dielectric resonator and metallic surface on Mie resonant frequency is complex and desires a comprehensive physical interpretation. Here, we systematically study the effect of metallic substrate on the magnetic dipole (MD) resonant frequency at X-band by placing a high permittivity CaTiO3 ceramic block on metallic substrate and regulating their gap size. The simulated and experimental results show that there are two physical mechanisms to codetermine the metallic substrate-induced MD frequency. The greatly enhanced electric field pair in the gap and the coupling of MD resonance with its mirror image are decisive for small and large gaps, respectively, making the MD resonant frequency present an exponential blue shift first and then a slight red shift with increasing gap size. Further, we use the two mechanisms to explain different frequency shifting properties of ceramic sphere near metallic substrate. Finally, taking advantage of the sharp frequency shifting to small gaps, the ceramic block is demonstrated to accurately estimate the thickness or permittivity of thin film on metallic substrate through a governing equation derived from the method of symbolic regression. We believe that our study will help to understand the resonant frequency shifting for dielectric particle near metallic substrate and give some prototypes of ultrasensitive detectors.

Zn–alloys are considered to be promising biodegradable materials due to suitable degradation rates. In this paper, novel Zn–Cu–Li alloys with layered CuZn4 structure were achieved. The corrosion properties of newly developed biodegradable Zn–Cu–Li alloys in simulated body fluid was studied. Results indicated that the cold-rolled alloys presented a relatively uniform corrosion mode, although early corrosion occurred preferentially at phase boundaries. Galvanic corrosion and corrosion product films jointly determined the later corrosion process. Cu improved the corrosion potential and film properties in its solid solution state, induced galvanic corrosion, and provided a physical barrier to corrosion by forming CuZn4 phase. Rolling accelerated the initial corrosion rate by enhancing the matrix electrochemical activity, while it contributed to uniform corrosion by improving the CuZn4 phase shape. Finally, cold-rolled Zn–4Cu–0.02Li possessed the best corrosion resistance and mechanical properties combination among the prepared alloys, with a yield strength of 256 MPa, an ultimate strength of 342 MPa, a fracture elongation of 39.8 %, and a corrosion rate of nearly 55 μm/year.

The purpose of this study is to investigate the correlation between intergranular stress corrosion cracking (IGSCC) and grain boundary characteristics in brass. The Volta potential and nature of the grain boundaries in H62 brass were studied by scanning Kelvin probe force microscopy and Electron Backscattered Diffraction, respectively. The α/β phase boundaries and random grain boundaries with low work functions can act as anodic areas to promote IGSCC propagation. Moreover, due to a combination of the inherent characteristics and high work function of Σ3 annealing twin boundaries (ATBs), IGSCC is successfully halted at a triple junction containing Σ3 ATB.

Fe-Ni-Cr austenitic alloys are widely used in hydrogen environments as structural materials. Their weld normally shows higher hydrogen-embrittlement sensitivity than the base metal, endangering large-scale applications. Herein, by using electron microscopy and numerical calculations, the influence of applied load on the fracture mode of hydrogen-embrittled JBK-75 alloy weldment is revealed and correlated with a competition between hydrogen-prompted intergranular decohesion (HPID) and hydrogen-enhanced localized plasticity (HELP). Therefore, independent of the load levels, the weld featuring a lower strength and smaller grain sizes is always more vulnerable to hydrogen embrittlement than the base metal.

The resistance of the Al0.5Cr0.9FeNi2.5V0.2 high-entropy alloy (HEA) to hydrogen embrittlement (HE) was investigated by a slow strain rate test (SSRT), and the fracture surface was examined through a scanning electron microscope. Compared with other high-strength steels, Al0.5Cr0.9FeNi2.5V0.2 showed insignificant strength loss after hydrogen charging. The fracture surface of the hydrogen-charged specimens mainly consisted of dimples, and no intergranular morphology was observed. The coupling effect of the dispersed nano-structured precipitates and high-density dislocations in Al0.5Cr0.9FeNi2.5V0.2 improves the resistance to hydrogen-induced strength loss.

Tribocorrosion behaviours of nickel (Ni) and niobium (Nb) in sodium sulfate (Na2SO4) solution under potentiodynamic and potentiostatic conditions were studied. Under the potentiodynamic condition, the passivation was early broken, accompanied by a sharp increase in frictional coefficient on Nb. The current was more fluctuant, and larger material loss appeared at the higher potential in the potentiostatic condition. However, these phenomena did not occur for Ni, and it even showed lower material loss at the higher potential in the potentiostatic tribocorrosion test. The differences in tribocorrosion behaviour had a close relationship to the passive film growth mechanism, which decided the passive film/metal interface structure. Nb with anionic diffusion dominated mechanism in passive growth would cause the accumulation of oxygen vacancies at the passive film/metal interface. This may weaken the adhesion between the metal and the passive film. However, with the cationic diffusion dominated passive film growth on Ni, cation vacancies concentrated at the passive film/tribo-film interface, and this did not affect the adhesion between metal and passive film. Ni or other passive elements with the cationic diffusion-dominated mechanism in passive film growth were recommended as the alloying element for improving the tribocorrosion resistance of alloys.

In pressurized water reactors, the existence of lead contamination can promote the corrosion of Alloy 690TT. During the manufacturing, transportation, and assembly processes, Alloy 690TT surface is easily scratched and it is easily ignored. The effect of added lead on the scratched surface is different from that on the unscratched surface. In the present study, Alloy 690TT was treated with mechanical polishing (MP) and electrochemical polishing (EP) to generate scratched and unscratched surfaces. With the addition of lead, the thickness of passive film on the MP sample increases by eight times, while that on the EP sample only slightly increases. These chemical composition changes of passive films induced by lead result in the drop of their electrical resistivity, and the electrical resistivity of passive film on the MP sample is reduced by two orders of magnitude, while that on the EP sample decreases only three times. Nevertheless, the thickness and electrical resistivity of passive film on the MP sample are always greater than those of the EP sample. The toxic effect of lead on the MP sample is more severe than that of the EP sample, which may be closely related to their subsurface microstructure. Therefore, Alloy 690TT should better avoid being scratched in the secondary circuit system of pressurized water reactors, as scratched behavior will result in a faster corrosion rate of Alloy 690TT with the presence of lead.

Relaxor ferroelectrics, with polar nanoregions (PNRs), are good candidates for electrocaloric (EC) refrigeration. This study investigates the EC performance of the Pb(1−1.5x)La(x)Zr(0.8)Ti(0.2)O(3) relaxor ferroelectric ceramics by the direct measurement using a modified differential scanning calorimeter. All the ceramics exhibit pure perovskite phase with a dense microstructure. The results indicate that the increasing La substitution strengthens the relaxor behaviour, promotes the transition from non-ergodic to ergodic state, and enhances the thermal stability of EC property (instability η

Tribocorrosion is a failure phenomenon which involves synergistic effect of electrochemical corrosion and mechanical wear. It usually results into early failure of mechanical components than simple wear and corrosion. Chloride (Cl ^− ) and sulfate ions $\left({{\rm{SO}}}_{4}^{{\rm{2}}-}\right)$ are often found together in corrosive media. In this study, the synergistic effect of Cl ^− and ${{\rm{SO}}}_{4}^{{\rm{2}}-}$ on tribocorrosion of 316L stainless steel was studied by changing the ratio of ${{\rm{SO}}}_{4}^{{\rm{2}}-}$ /Cl ^− in corrosive solution from 0.31 M : 0 to 0 : 0.62 M. The stainless steel was worn against with a ZrO _2 sphere. The coefficient of friction (COF), material loss volume, surface micro-topographies and surface chemical composition in different solutions were compared to explore the synergism between ${{\rm{SO}}}_{4}^{{\rm{2}}-}$ and Cl ^− . The results indicated that the mix of Cl ^− and ${{\rm{SO}}}_{4}^{{\rm{2}}-}$ reduced material loss volume by a quarter when compared with that in pure Na _2 SO _4 or NaCl solution. More than half of material loss was caused by the synergism between wear and corrosion in mixing solutions. The synergistic effect between ${{\rm{SO}}}_{4}^{{\rm{2}}-}$ and Cl ^− could promote the transmission of metal into oxides. This had two effects on tribocorrosion. First, the existence of oxides would cause abrasion which accelerated wear-affected corrosion and enhanced mechanical wear (corrosion-affected wear). On the other side, the transmission of metal into oxides benefited for the formation of tribo-film. The flexible stainless steel needed to coordinate deformation with the tribo-film which had relatively low deformability. This aggravated deformation of stainless steel and promoted surface work-hardening effect. It was helpful for stainless steel to resist wear, thus, the corrosion-affected wear was decreased.

Medium Mn steels have been considered as the next-generation materials for use in the automotive industry due to their excellent strength and ductility balance. To reduce the total weight and improve the safety of vehicles, medium Mn steels look forward to a highly promising future. However, hydrogen-induced delayed cracking is a concern for the use of high strength steels. This work is focused on the service characteristics of two kinds of medium Mn steels under different relative humidity conditions (40%, 60%, 80% and 100%). Under normal relative humidity (about 40%) at 25 °C, the hydrogen concentration in steel is 0.4 ppm. When exposed to higher relative humidity, the hydrogen concentration in steel increases slowly and reaches a stable value, about 0.8 ppm. In slow strain rate tensile tests under different relative humidity conditions, the tensile strength changed, the hydrogen concentration increased and the elongation decreased as well, thereby increasing the hydrogen embrittlement sensitivity. In other words, the smaller the tensile rate applied, the greater the hydrogen embrittlement sensitivity. In constant load tests under different relative humidity conditions, the threshold value of the delayed cracking of M7B (‘M’ referring to Mn, ‘7’ meaning the content of Mn, ‘B’ denoting batch annealing) steel maintains a steady value of 0.82 σb (tensile strength). The threshold value of the delayed cracking of M10B significantly changed along with relative humidity. When relative humidity increased from 60% to 80%, the threshold dropped sharply from 0.63 σb to 0.52 σb. We define 80% relative humidity as the ‘threshold humidity’ for M10B.

Trilayer Ni/PZT/Ni cylindrical magnetoelectric (ME) composites were prepared by electrodeposition, a process, which creates sub-millimeter raised edges due to current concentration near sharp points. The ME response in both axial and vertical modes was measured with the edges, with only outer edges removed, and with both outer and inner edges removed. The ME voltage coefficient improved at resonance by 40% and 147% without the edges in the vertical and axial modes, respectively. The observed improvements in three different samples were only present at the ME resonance and no changes were detected outside of the ME resonance. Mechanical quality factor at resonance also improved with no effect on the resonant frequency. Experimentally demonstrated minor geometry changes resulted in substantial ME improvement at resonant frequency. This study demonstrates device performance optimization. The observed effects have been attributed to improved vibrations in terms of decreased damping coefficient and enhanced vibration amplitude at resonance.

The prevention of hydrogen penetration into steels can effectively protect steels from hydrogen damage. In this study, we investigated the effect of a monolayer MoS2 coating on hydrogen prevention using first-principles calculations. We found that monolayer MoS2 can effectively inhibit the dissociative adsorption of hydrogen molecules on an Fe(111) surface by forming a S–H bond. MoS2 coating acts as an energy barrier, interrupting hydrogen penetration. Furthermore, compared with the H-adsorbed Fe(111) film, the work function of the MoS2-coated film significantly increases under both equilibrium and strained conditions, indicating that the strained Fe(111) film with the MoS2 coating also becomes more corrosion resistant. The results reveal that MoS2 film is an effective coating to prevent hydrogen damage in steels.

308L welding duplex stainless steel has been irradiated at 360 °C with 2 MeV protons, corresponding to a dose of 3 dpa at the maximum depth of 20 μm. Microhardness of the δ-ferrite and austenite phases was studied before and after proton irradiation using in situ nanomechanical test system (ISNTS). The locations of the phases for indentations placement were obtained by scanning probe microscopy from the ISNTS. The hardness of the δ-ferrite had a close relationship with the vacancy distribution obtained from the Stopping and Range of Ions in Matter (SRIM) Monte Carlo simulation code. However, the hardness of the austenite phase in the maximum damage region (17–20 μm depth) from the SRIM simulation was decreasing sharply, and a hardness transition region (>20 μm and 20 μm depth). However, the δ-ferrite hardness behavior was different. A hardness of the two phases increased on the irradiated surface and the interior due to different hardening mechanisms in the austenite and δ-ferrite phases after a long time high-temperature irradiation. A transition region (>20 μm and

Hydrostatic pressure effects on pitting initiation and propagation in X70 steel are investigated by evaluating metastable pitting probability using electrochemical methods and immersion corrosion tests in containing chlorine ion solution. Potentiodynamic tests indicated that hydrostatic pressure can decrease the breakdown potential and lead to a reduced transpassivity region. Metastable test results revealed that hydrostatic pressure can increase metastable pitting formation frequency and promote stabilization of metastable pitting growth. Electrochemical impedance spectroscopy (EIS) results indicate that Hydrostatic pressure decreases the charge transfer resistance and increases the dissolution rate within the cavities. Corrosion test results also indicated that pitting initiation and propagation are accelerated by hydrostatic pressure. Result validity was verified by evaluating metastable pitting to predict pitting corrosion resistance.

Inclusion-induced pitting initiation mechanisms in X70 steel were investigated by scanning electron microscopy, scanning Kelvin probe force microscopy (SKPFM), immersion and electrochemical polarization tests in chloride-containing ion solutions. There are three inclusion types in the X70 steel. Corrosion test results indicated that pitting corrosion resistance of type A inclusion < type C inclusion < type B inclusion, i.e., (Mn, Ca)S < matrix < (Al, Ca)O. SKPFM test results show that the type A inclusion exhibited both lower and higher potentials than the matrix, while the type B inclusion exhibited higher potential than the matrix. The corrosion test and the SKPFM potential test results are consistent. Potentiodynamic polarization results indicate that the type A and C are active inclusions, while the type B is an inactive inclusion. Three kinds of possible mechanisms of inclusion-induced pitting corrosion are established for the X70 steel.

We investigate the electronic structure and work function modulation of α-Fe2O3 films by strain based on the density functional method. We find that the band gap of clean α-Fe2O3 films is a function of the strain and is influenced significantly by the element termination on the surface. The px and py orbitals keep close to Fermi level and account for a pronounced narrowing band gap under compressive strain, while unoccupied dz2 orbitals from conduction band minimum draw nearer to Fermi level and are responsible for the pronounced narrowing band gap under tensile strain. The spin polarized surface state, arising from localized dangling-bond states, is insensitive to strain, while the bulk band, especially for pz orbital, arising from extended Bloch states, is very sensitive to strain, which plays an important role for work function decreasing (increasing) under compressive (tensile) strain in Fe termination films. In particular, the work function in O terminated films is insensitive to strain because pz orbitals are less sensitive to strain than that of Fe termination films. Our findings confirm that the strain is an effective means to manipulate electronic structures and corrosion potential.

This paper demonstrates the electrocaloric effect (ECE) around BaTiO3's orthorhombic-tetragonal first-order phase transition. By manipulating a field-induced transition of a metastable phase in the thermal hysteresis zone, a huge exothermic or endothermic peak appears after first applying or removing electric fields because of the energy change of lattice structure. A large ECE of ΔT/E = 1.4K·m/MV, equaling to latent heat, is achieved under 10kV/cm at 10°C. The entropy change for polarization ordering alone induces an ECE two orders of magnitude lower under the same condition. It confirms the dominant factor to ECE of the energy flow due to the structural phase transition.