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The method of making parts through additive manufacturing (AM) is becoming more and more widespread due to the possibility of the direct manufacturing of components with complex geometries. However, the technology's capacity is limited by the appearance of micro-cracks/discontinuities during the layer-by-layer thermal process. The ultrasonic (US) method is often applied to detect and estimate the location and size of discontinuities in the metallic parts obtained by AM as well as to identify local deterioration in structures. The Ti6Al4V (Ti64) alloy prepared by AM needed to acquire a high-quality densification if remarkable mechanical properties were to be pursued. Ultrasonic instruments employ a different type of scanning for the studied samples, resulting in extremely detailed images comparable to X-rays. Automated non-destructive testing with special algorithms is widely used in the industry today. In general, this means that there is a trend towards automation and data sharing in various technological and production sectors, including the use of intelligent systems at the initial stage of production that can exclude defective construction materials, prevent the spread of defective products, and identify the causes of certain instances of damage. Placing the non-destructive testing on a completely new basis will create the possibility for a broader analysis of the primary data and thus will contribute to the improvement of both inspection reliability and consistency of the results. The paper aims to present the C-scan method, using ultrasonic images in amplitude or time-of-flight to emphasize discontinuities of Ti64 samples realized by laser powder-bed fusion (L-PBF) technology. The analysis of US maps offers the possibility of information correlation, mainly as to flaws in certain areas, as well as distribution of a specific flaw in the volume of the sample (flaws and pores). Final users can import C-scan results as ASCII files for further processing and comparison with other methods of analysis (e.g., non-linear elastic wave spectroscopy (NEWS), multi-frequency eddy current, and computer tomography), leading to specific results. The precision of the flight time measurement ensures the possibility of estimating the types of discontinuities, including volumetric ones, offering immediate results of the inspection. In situ monitoring allows the detection, characterization, and prediction of defects, which is suitable for robotics. Detailing the level of discontinuities at a certain location is extremely valuable for making maintenance and management decisions. [ABSTRACT FROM AUTHOR]

The hypoeutectic aluminum alloy AlSi5Cu2Mg is used for the production of high-strength cylinder head castings. The alloy is unique for its specific low permitted Ti content (0.03 wt% max), which makes it impossible to refine the grain structure of this alloy using standard Al–Ti–B grain refiners. The specific chemical composition is specified by the supplier company. The aim of this paper is to find a suitable alloying element that would improve the selected properties (e.g., mechanical, and physical properties) that are crucial for cylinder head castings. The research focuses on the investigation of the effect of different Zr addition (0.05; 0.10; 0.15 and 0.20 wt% Zr in the form of AlZr20 master alloy) on the properties of AlSi5Cu2Mg in the as-cast state and after heat treatment T7. The obtained results showed that ultimate tensile strength, yield strength, hardness, and physical properties of as-cast samples do not change significantly with increasing Zr content. The experimental alloys showed a more significant increase in ultimate tensile strength, yield strength, hardness, and thermal conductivity after heat treatment T7. Zirconium-rich intermetallic phases were observed in the shape of separate thick needles or as a cluster of two crossed thinner needles. [ABSTRACT FROM AUTHOR]

In this paper, WE43-xCa (0, 1, 2 wt%) magnesium alloys were prepared by electromagnetic stirring (EMS) casting, and the solid solution-treated WE43-xCa (1, 2 wt%) alloys were subjected to aging treatment at 225 °C for different times. The results showed that the grain size of the alloy is refined after the addition of Ca. However, when the Ca content was high, the continuous reticular phase distributed along the grain boundaries and the generated Mg2Ca brittle phase led to the degradation of the mechanical properties. After the 225 °C × 10 h aging treatment, the 1Ca alloy had the best mechanical properties with a tensile strength of 284 MPa, yield strength of 227 MPa, and elongation of 9.0%. This material could meet the requirements of structural parts of high-speed railways. The combustion temperature test exhibited that the WE43-xCa alloy was able to be kept at 900 °C without ignition. The addition of Ca resulted in the formation of thin and continuous CaO oxide film on the outermost layer of the alloy, which helped prevent internal oxidation of the alloy, thereby increasing the ignition temperature. [ABSTRACT FROM AUTHOR]

This paper aims to study the effect of using modified nano‐TiO2 with fly ash (FA) on ultra‐high performance concrete's (UHPC) mechanical, transport, and microstructure properties (UHPC). A ball mill was used to disband the nano‐TiO2 and distribute it uniformly within the FA powder. In this research, 20% of the cement weight was replaced by FA, and nano‐TiO2 was added by 0.4%, 0.8%, 1.2%, 1.6%, and 2% of the FA weight. To investigate the effect of the ball mill period on the UHPC properties, periods of 10, 20, 30, and 40 min were applied to a binder of 20% FA and with 6% nano‐TiO2. In addition, a 30‐min ball mill period on a binder of 20% FA and 0.4%, 0.8%, 1.2%, 1.6%, and 2% nano‐TiO2 was also investigated. Tests of compressive strength after 1, 7, 28, and 91 days of curing in tap water, splitting tensile strength, flexural strength, and modulus of elasticity were performed after 28 days of curing in tap water. Tests of chloride permeability, sorptivity coefficient, water permeability, and microstructure were also performed after 28 days of curing in tap water. The results showed that the addition of higher percentages of nano‐TiO2 led to a decrease in workability. The addition of nano‐TiO2 improved the mechanical properties. The highest compressive strength of 208.9 MPa was achieved for the mixture of 20% FA with 1.2% nano‐TiO2 at the age of 28 days. The 30‐min period of application of the ball mill achieved the best performance compared with the other periods. The results of using a ball‐mill to re‐mix nano‐TiO2 between 1.2% and 2% by weight with FA showed impressive comparative results. [ABSTRACT FROM AUTHOR]

The Nyakong-Manyi Shear Zone (NMSZ) is a NE-SW elongated corridor found to the northwest of the Foumban-Bankim Shear Zone (FBSZ) along the Central Cameroon Shear Zone. Controversial chronology models has been proposed for the kinematic evolution of the sinistral and dextral shear phases in the Tikar Plain, thus in the FBSZ; early dextral and late sinistral shear phases for some authors and early sinistral and late dextral shear for others. Moreover, the NMSZ kinematic evolution implication on the mylonitization P-T-t path in the area seem to be problematic and the present paper aim is to clear enough those problems; since this shear zone is the main mylonitic corridor that registered the left and right lateral movement in this area. The NMSZ comprises amphibolites, protomylonites, strict sensus mylonites (garnet-kyanite-sillimanite mylonite and garnet-pyroxene mylonite), ultramylonites kyanite-sillimanite and garnet-kyanite-sillimanite gneiss. Field structures testify that the investigated area recorded three deformation phases: (i) the D1 deformation phase which is marked by NW-SE to N-S trending S1 metamorphic foliation with low to moderate dips (15°–45°) that was transposed during the D2 phase, is responsible for a regional metamorphism whose mineral paragenesis is garnet-kyanite-sillimanite; (ii) the early sinistral NNE-SSW to NE-SW shear phase D2 marked by S2 metamorphic and mylonitic foliations; responsible for, L2 stretching mineral lineation, F2 fold axes and B2 boudins structures; (iii) the late dextral NE-SW shear phase D3, characterized by F3 folds, B3 boudins and ductile dextral C3 shear planes. Mineral paragenesis garnet + kyanite + sillimanite and microstructures within gneiss testify that this rock underwent high grade regional metamorphism whose peak conditions are estimated at 11.5–13.5 kbar/850–900 °C. After the peak of metamorphism gneiss was overprinted by high grade pressure mylonitization during the early sinistral and late dextral shear deformations. Microstructural data here indicate a high-grade mylonitization whose P-T conditions are estimated at least at around 10 kbar/750 °C attained during the D2. Shear markers, indicates that the studied area underwent an intense mylonitization at deep crustal deformation level, probably at the ductile-brittle boundary structural level during a major dextral shear deformation. [ABSTRACT FROM AUTHOR]

The CubeSat microsatellites are structures that can be found in many applications of industry and educations, but not only. Based on this, a new concept Card‐Sat structure is used in the present study. For a better understanding of the functionality microstructure Card‐Sat, this paper aims to study the geometry of joints manufactured from plastic materials by using the FFF 3D printing method and assembling to identify the suitable joint for this type of structures. [ABSTRACT FROM AUTHOR]

In the paper we consider a problem for complex Ginzburg–Landau equations in a medium with locally periodic small obstacles. It is assumed that the obstacle surface can have different conductivity coefficients. We prove that the trajectory attractors of this system converge in a certain weak topology to the trajectory attractors of the homogenized Ginzburg–Landau equations with an additional potential (in the critical case), without an additional potential (in the subcritical case) in the medium without obstacles, or disappear (in the supercritical case). [ABSTRACT FROM AUTHOR]

With the existing pressure sensors, it is difficult to achieve the unification of wide pressure response range and high sensitivity. Furthermore, the preparation of pressure sensors with excellent performance for sleep health monitoring has become a research difficulty. In this paper, based on material and microstructure synergistic enhancement mechanism, a hybrid pressure sensor (HPS) integrating triboelectric pressure sensor (TPS) and piezoelectric pressure sensor (PPS) is proposed. For the TPS, a simple, low-cost, and structurally controllable microstructure preparation method is proposed in order to investigate the effect of carbon nano-onions (CNOs) and hierarchical composite microstructures on the electrical properties of CNOs@Ecoflex. The PPS is used to broaden the pressure response range and reduce the pressure detection limit of HPS. It has been experimentally demonstrated that the HPS has a high sensitivity of 2.46 V/104 Pa (50–600 kPa) and a wide response range of up to 1200 kPa. Moreover, the HPS has a low detection limit (10 kPa), a high stability (over 100,000 cycles), and a fast response time. The sleep monitoring system constructed based on HPS shows remarkable performance in breathing state recognition and sleeping posture supervisory control, which will exhibit enormous potential in areas such as sleep health monitoring and potential disease prediction. [ABSTRACT FROM AUTHOR]

This paper combines shape optimization and homogenization techniques in searching for the optimal design of microstructures in elastic scaffolds. The development of materials with specific properties is of practical interest, for example, for medical applications or for the development of lightweight structures in aeronautics. In particular, the optimal design of microstructures leads to fundamental questions for elastic porous media: how to calculate a microstructure leading to a target effective Hooke tensor. We propose a robust approach to find a design that is as insensitive as possible to domain variations. Our strategy is based on the shape derivative for the problem of achieving a prescribed effective tensor. We demonstrate the applicability and feasibility of our approach through numerical experiments. [ABSTRACT FROM AUTHOR]

In this paper, nickel-clad cubic boron nitride (Ni/c-BN)-reinforced Ni-based composite coating was prepared on the martensitic stainless steel substrate by laser melting technology. The microstructure, phases and properties of the cladding layer were investigated by x-ray diffractometry, scanning electron microscopy, energy-dispersive spectrometry, microhardness test, wear test and potentio-dynamic polarization. The experimental results show that surface quality of the cladding was excellent and free of obvious defects when the Ni/c-BN content was 5 wt.%, while reticulation cracks appeared when the content was higher than 5 wt.%. In addition, compared with the coating without Ni/c-BN, the addition of Ni/c-BN made the coating form a new phase Ni3B and a change in the eutectic tissue in the coating, which was made up of γ-Ni, Ni3B and Ni4B3. After added Ni/c-BN, the hardness, wear resistance, and corrosion resistance of the coating increased first and then decreased. Excess Ni/c-BN reduced the solid solution B element content in the matrix and accelerates the formation of the crack of the coating, thereby deteriorating the hardness, wear resistance and corrosion resistance. The coating had the best hardness, wear resistance and corrosion resistance when the Ni/c-BN content was 5 wt.%. [ABSTRACT FROM AUTHOR]

Alumina-magnesia dry materials are widely used in induction furnace linings, but they show different kinds of damage when melting different kinds of alloy steel. In this paper, the chemical composition, phase composition, and microstructure of the post-use dry materials for the working liners melting different kinds of steel were evaluated. Furthermore, the corrosion mechanism of the steel on the furnace lining materials was comprehensively analyzed. The findings reveal a significant ability of the Mn element in the molten steel to diffuse and penetrate into the refractories. Mn oxidizes to form MnO at the steel-refractory interface, and then forms a liquid phase with Al2O3. The Cr element is dissolved into corundum and spinel of the refractories, resulting in lattice defects and structural damage of the materials. TiO2 reacts with Al2O3 to form Al2TiO5, which plays a crucial role in preventing crack formation and propagation. Part of Ti4+ dissolves into magnesia-alumina (MA), densifying the materials. TiO2 also slows down the reaction between the Cr element and refractory components, further improving the corrosion resistance of the materials. [ABSTRACT FROM AUTHOR]

This paper introduces an approach for vacuum brazing of niobium-316L stainless steel transition joints for application in superconducting radiofrequency cavity helium jackets. The study takes advantage of good wettability of Ag-Cu-Pd brazing alloy to suppress brittle Fe-Nb intermetallic formation, hence improve the joints’ mechanical performance. The wettability of Ag-Cu-Pd filler metal on niobium, the interface microstructure and mechanical properties of the transition joints were investigated. Two kinds of Ag-Cu-Pd filler metals had been studied and wet well on the niobium, and the wettability of Ag-31.5Cu-10Pd filler metal on niobium was better than Ag-28Cu-20Pd filler metal. Microstructure characterization demonstrated the absence of brittle intermetallic layers in all of the joint interfaces. Mechanical properties of samples prepared with Ag-31.5Cu-10Pd filler metal were also better than their peers made with Ag-28Cu-20Pd filler metal both room temperature (300 K) and liquid nitrogen temperature (77 K). The transition joints displayed shear strengths of 356-375 MPa at 300 K and 440-457 MPa at 77 K, respectively. After undergoing ten thermal cycles between the room temperature and the liquid nitrogen temperature, the transition joints’ leak rates were all lower than 1.1×10–11 mbar·L/s. Therefore, Ag-Cu-Pd filler metal is applicable to high vacuum vessels used at cryogenic temperatures. [ABSTRACT FROM AUTHOR]

This paper conducts low temperature welding tests on Q460GJC thick plate (60 mm), and based on the basic theory of phase transformation structure evolution, a three-dimensional microstructure evolution analysis method for large welded joints is established, and the analysis of the evolution process of multi-layer and multi-pass weld structure under the low temperature environment of thick plates is completed. The comparison and analysis of test and numerical simulation results are in good agreement, which proves that the welding phase transformation model realizes the digitalization of metallurgical phase transformation in steel structure welding, and optimizes welding process parameters. It is of great significance to improve the quality of welding products and lay a foundation for predicting the performance of welded joints from the micro level. [ABSTRACT FROM AUTHOR]

The paper outlines the material and technological aspects of fine (whiteware) ceramics. Particular attention has been paid to the professional nomenclature of fine aluminosilicate ceramics as used in the past and today. Attention was drawn to this mostly overlooked and poorly studied problem. The reason for the durability problems of some semi-vitreous porcelain and faience materials has been explained. The microstructures of porcelain materials – historic as well as contemporary – have been presented in comparative terms, including the technical material, with a distinction and analysis of the basic phases that build up the shard. Generally similar parameters of microstructure and phase composition were found for all tested materials. [ABSTRACT FROM AUTHOR]

Carbon dioxide, or CO2, is responsible for most global greenhouse gas emissions. Sequestering CO2 in concrete can potentially reduce carbon emissions while simultaneously improving concrete's characteristics. This study's main objective is to use carbon dioxide in the Ready-Mix Concrete (RMC) during the mixing phase. This study also investigates the effects of carbon dioxide incorporation on the properties of concrete at different dosages (0% to 0.20% by weight of the binder) and binder types such as Ordinary Portland Cement (OPC) and Portland Pozzolana Cement (PPC). Through a detailed experimental study, the paper seeks to understand the changes in the various mixes' fresh, hardened, and microstructural properties. The results indicate that carbon dioxide had no adverse effect on fresh concrete properties, with minor changes leading to improved performance in concrete samples at precise dosages. The microstructural results reveal that the concrete tends to densify by utilizing the optimum dosage of carbon dioxide and thus achieve the best performance. Concrete mixtures treated with CO2 showed increased compressive strength; 0.10% CO2 in OPC-based mixes gave up to 30% benefit, and 0.05% in PPC-based mixes gave up to 25%. PPC-based had the highest compressive strengths at later ages, OPC-based at early ages. The time of set was reduced by 18% in OPC mixes and 28% in PPC mixes. Furthermore, the addition of CO2 during mixing had a positive impact on the concrete's durability. Therefore, it can be concluded that utilizing CO2 in concrete can help produce sustainable RMC with enhanced properties and reduced emissions. [ABSTRACT FROM AUTHOR]

Calcined attapulgite (CAG) is a fibrous calcined clay with strong pozzolanic activity, which is a good candidate for the development of cementitious materials to meet the requirements of CO2 emission reduction. In this paper, the effects of CAG on the early hydration, microstructure and mechanical properties of cementitious materials were evaluated, and the influence mechanism was further explained by XRD, TG-DTG, SEM–EDS, and hydration kinetics analysis. The results show that CAG accelerates the hydration rate and promotes the early hydration process of cement by introducing additional active sites. The secondary reaction of CAG in cement consumes Portlandite (CH) in cement hydration products and dissolves Mg2+ to promote the formation of hydrotalcite. The microfiber morphology and good compatibility of CAG in cementitious materials promote the establishment of the network structure of hydration products, inhibiting microcracks and making the structure more compact. CAG promotes the strength development, and the compressive strength reaches the optimal value of 82 MPa with 6% CAG. [ABSTRACT FROM AUTHOR]

Dredged sediments with high water content is difficult to be treated and beneficially reused because of their poor engineering characteristics. To treat those slurry, this paper introduces a novel mechanical-chemical combined method, i.e., vacuum-solidification (VS) combined method, and investigates its performance in dewatering and strength improvement. Corresponding model tests using vacuum-only preloading method and binder-only solidification method, respectively, were conducted. Ground granulated blast-furnace slag, an industrial by-product, activated by hydrated lime, magnesium oxide or carbide slag was used as the binder in the proposed method. The mass of discharged water due to vacuum consolidation was measured during the model test. Soil samples were taken after vacuum preloading for unconfined compression test, permeability test, X-ray diffraction, scanning electron microscopy and mercury intrusion porosimetry to analyze the strength development, hydraulic and microstructural properties of the treated soil. The results indicate that the VS combined method exhibits a remarkable enhancement in both volume reduction efficiency and the strength improvement effectiveness. The type and content of activators have an obvious influence on the performance of the combined method. This study preliminarily revealed the mechanism and effect of using the VS combined method with alkali-activated GGBS as binder to treat high water content dredged mud. [Display omitted] • Vacuum-solidification combined method outperforms single methods in stabilizing mud slurry. • Appropriate amount of binder improves dewatering and strength development efficiency. • Alkali-activated slag is a superior alternative to cement for proposed combined method. • Lime, MgO and carbide slag are sequentially preferred activators for proposed method. • Combined method with green binder is a promising technology to recycle dredged mud. [ABSTRACT FROM AUTHOR]

Inertia friction welding (IFW) is a solid-state welding process for joining engineering materials. In this paper, a 2.5D finite element (FE) model was developed to simulate IFW of MLX®19 maraging steel. The predicted results showed a non-uniform temperature distribution, with a decrease in temperature from the periphery to the center of the weld interface. Higher temperature and lower stress distributions were predicted in the weld zone (WZ) and the adjacent regions in the vicinity of the WZ. The von-Mises effective stress, effective strain, and strain-rate were investigated at different time-steps of the FE simulation. The effective stress was minimum at the weld interface, and the effective strain and strain-rate attained a quasi-steady-state status with the ongoing IFW after a threshold time (~6.5 s). The simulated results were validated by comparing the predicted flash morphology with an actual IFW weld, and temperature profiles measured at specific locations using embedded thermocouples. The difference between the experimental and the simulated results was ~4.7%, implying a good convergence of the model. Microstructural characterizations were performed across different regions, and the observed features were found to be in agreement with the expected microstructure based on the simulated thermal profiles, which included almost complete (~90%) and partial transformation of martensite to austenite in the WZ and thermomechanically affected zone (TMAZ), respectively. Analyses of crystallographic texture showed that the material (i.e., both transformed austenite and martensite) underwent pure shear deformation during IFW. [ABSTRACT FROM AUTHOR]

In this paper, a disk laser welding was developed to join 3-mm thin-Sect. 30Cr3 ultra-high-strength steel which was widely used in aerospace. The microstructure and mechanical properties of welded joint were investigated in detail. The results indicated that the recommended laser linear energy range were between 150 and 165 J/mm to guarantee that the melting width was up to 1 mm as well as less oxidation, spatter, and depression on the weld. Meanwhile, for the as-welded (AW) condition, the base metal (BM) consisted of ferrite matrix with distributing small spherical carbides, also known as spherical pearlite. While, the fine grained region, coarse grained region, and weld metal were all composed of martensite. However, the partially transformed region mainly consisted martensite with a little of spherical pearlite. Meanwhile, the average grain sizes of weld metal, HAZ, and base metal were 1.3 μm, 1.5 μm, and 1.8 μm, respectively. However, for the post-weld heat treatment (PWHT) condition, the whole welded joint was all composed of tempered martensite, and the average grain size of welded joint was about 1.7 μm. The tensile strength of the welded joint was higher than that of the base metal both in the AW and PWHT condition as all the fracture with shrinkage occurred in the BM of the specimens. Additionally, the average yield strength of the AW and PWHT are about 600 MPa and 1700 MPa, respectively. [ABSTRACT FROM AUTHOR]

The paper presents both the production method and its impact on selected properties of composite coatings reinforced with hard ZrC particles. The Fe/ZrC coatings were produced using diode laser by remelting the pre-coat in the form of paste consisting of ZrC powder and binder. Different values of laser beam power (500 W, 700 W, and 900 W) and different pre-coat thicknesses (100 µm, 150 µm, and 200 µm) were used to produce the composite coatings. During all processes, the scanning speed of laser beam was 3 m/min. Laser beam spot diameter was 1 mm. Microstructure study, microhardness tests, as well as EDS and XRD analysis were carried out. The obtained Fe/ZrC coatings were also tested for the effect of the corrosive medium in a 3.5% NaCl water solution. The effect of applied parameters on wear resistance of Fe/ZrC coatings was also studied. The tribological properties were assessed both by mass loss measurement and by scanning electron microscopy. Fe/ZrC coatings produced using the highest thickness of the pre-coat were characterised by cracks arising during production process. The very high concentration of carbides and hence high hardness of the coating produced in this way contributed to it. However, a positive effect of laser beam power increase on reduction of these cracks was observed. The coatings were characterised by very high hardness, reaching in some cases even more than 2000 HV. It was found that the most favourable properties regarding both tribology and corrosion resistance were obtained for Fe/ZrC coatings produced using 150 µm of pre-coat thickness. [ABSTRACT FROM AUTHOR]

Hot gas forming (HGF) is an advanced technique for fabricating complex-shaped hollow tubular parts. Practically, multi-step pre-forming involving pre-deformation is often necessary prior to HGF. This paper performs an experimental investigation to simulate the pre-forming operation evaluating the effect of pre-strain on the subsequent HGF. Firstly, the dislocation density was accumulated with uniaxial pre-stretching with different strains (5%, 10%, and 15%) at room temperature, simulating the pre-forming operations. Secondly, the sub-sized specimen from the pre-stretched sample was characterized at different temperatures (350, 400, and 450 °C) to evaluate the effect of pre-strain on successive hot deformation for simulating practical HGF. The experimental results proves the coupled influence of pre-strain and temperature on the flow stress and stress-strain variations. To thoroughly understand the micro-mechanisms, EBSD analysis of grains and grain boundary angles was carried out under different pre-deformation levels and temperatures, which shows the recrystallization phenomenon at 15% pre-strain and 450 °C temperature. Finally, a physical mechanism constitutive model is established based on the determined macro and micro results where the pre-strain effect shows the accurate modeling of stress flow behavior of the material. [ABSTRACT FROM AUTHOR]

In the present paper, the results of a research focused on microstructure investigation of steel welded joints by means of non destructive thermographic technique are presented. In particular, two rough joints obtained by means of irregular manual welding are analyzed. Active lock in thermography phase analysis is applied, basing on the evidence that thermal diffusivity is related to the thermal diffusion length, using the phase contrast trend as a function of the distance from the laser spot. Diffusivity is expected to be dependent on the local microstructure and vary through different directions. By the variation in diffusivity, it is possible to investigate the level of anisotropy.The results are compared with micrographic analysis. The proposed method provides an active lock-in infrared thermography analysis by means of a thermal camera and an exciting laser head to evaluate thermal diffusivity. [ABSTRACT FROM AUTHOR]

Nowadays, one of the most important challenges in the tribology field is to avoid the excessive consumption of soft metals such as Ag at elevated temperatures through the re-design of the self-lubricant films, to achieve the long-term lubricant under the temperature-cycling environments, for widely used in real industrial applications. This paper took up this challenge to develop a novel green film, by composing nano-particles Ag into the amorphous SiN x matrix using magnetron sputtering system, for achieving the long-term lubricant under the room temperature (RT)-500 °C temperature-cycling conditions. Results showed that the film exhibited a dual-phase of face-centered cubic (fcc) Ag and amorphous SiN x. An excellent RT-500 °C wear-resistance performance was observed for the films with the Ag content of 1.3–9.4 at.%, whilst the film at 15.8 at.% Ag exhibited the best anti-frictional performance (COF 0.3–0.5 for RT-500 °C conditions) at the cost of wear rate. The self-lubricant tribology behaviors under the RT-500 °C cycling conditions were mainly attributed by the synergism of: (1) mechanical properties, (2) excellent high-temperature chemical stability of SiN x matrix, and (3) the lubricant nature of Ag and its elevated temperature diffusion behaviors. [ABSTRACT FROM AUTHOR]

Antimonide semiconductor laser diodes with high brightness are ideal light sources for a variety of applications. However, the traditional structure of broad-area (BA) lasers with high-power output is normally accompanied by a multi-lobed far field profile and large lateral divergence. In this paper, we put up an on-chip microstructure for mode filtering. The excellent mode control capability is doubly confirmed by optical field simulations and complete device measurements. The optimized device shows an enhanced continuous-wave output power in exceeding of 1.3 W at room temperature, along with a reduced threshold current and increased peak power conversion efficiency. Moreover, it exhibits an ultra-stable lateral far field with a 45.6% reduction in divergence and a notable 75.5% improvement in current dependence compared with conventional BA diode lasers. The minimum divergence is as low as 5.64° for full width at half maximum definition. [ABSTRACT FROM AUTHOR]

The effect of Al and Ti additions on the microstructure and properties of CoNiFe alloys was studied in this paper. The investigations were conducted on four specially designed and produced arc furnace alloys (from 3 to 5 components, with medium to high entropy). Samples in various states were analyzed, i.e., as-cast, after homogenization, after solution heat treatment, and after solution heat treatment and aging. The obtained samples were characterized by: SEM observations, EDS, XRD, TEM analyses, and finally, hardness measurements. The solid solution strengthening coming from the addition of 5 at. pct. Al was negligible, while the effect from the 5 at. pct. of Ti addition was significant. The precipitation hardening effect related to the presence of the (CoNi)3Ti phase caused by the Ti addition is comparable with the total effect of the Al and Ti addition, which caused the precipitation of (NiCo)3AlTi. [ABSTRACT FROM AUTHOR]

In general, phosphate cements have a very rapid setting reaction at room temperature. The same holds for copper slag-based phosphate cements. This means that using them as a binder, for instance as mortar, is always possible on a small scale, but very difficult on a large scale. In this paper, the heat treatment of the copper slag was shown to be an effective way to increase the setting time and keep the mix workable for an adequate period. The main objective of this research was to examine the changes in the phase composition of quenched copper slag after exposure to 500 °C and to evaluate the impact of these changes on the reactivity of the material in an acidic environment, as well as on the mechanical properties, microstructure, and structure of the produced phosphate cement materials. Various experimental methods were utilized to characterize the raw materials and the obtained phosphate cementitious materials, including isothermal microcalorimetry (TAM Air), thermogravimetric analysis (TGA), infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), as well as the determination of the chemical composition using X-ray fluorescence (XRF) and the particle size distribution. Furthermore, compressive strength tests were conducted to gauge the mechanical resistance of the materials. The main findings of this work revealed that subjecting the copper slag to a thermal treatment of 500 °C induced a partial transformation in its structure. The high temperature caused the oxidation of some of the divalent iron oxide in the slag, leading to the formation of hematite. This treatment increased the setting time and reduced the reactivity of the copper slag with phosphoric acid, ultimately enabling the production of a dense phosphate-based cementitious material with outstanding mechanical properties. The compressive strength of the newly developed cement was recorded to be greater than 78.9 MPa after 7 days, and this strength continued to increase, reaching 82.5 MPa after 28 days. [ABSTRACT FROM AUTHOR]

Fasteners are widely used in automobile, electronic and other fields, and the demand for high performance fastener materials is increasingly urgent. 10B21 mild steel has the advantages of good plasticity, obvious heat treatment effect and so on. It is used to produce fasteners below grade 9.8. In this paper, the domestic 10B21 boron steel as the research object, through quenching, tempering and other heat treatment, change its structure from ferrite to tempered martensite, in order to improve the strength and hardness. [ABSTRACT FROM AUTHOR]

Additive manufacturing techniques are being used more and more to perform the precise fabrication of engineering components with complex geometries. The heterogeneity of additively manufactured microstructures deteriorates the mechanical integrity of products. In this paper, we printed AISI 316L stainless steel using the additive manufacturing technique of laser metal deposition. Both single-phase and dual-phase substructures were formed in the grain interiors. Electron backscatter diffraction and energy-dispersive X-ray spectroscopy indicate that Si, Mo, S, Cr were enriched, while Fe was depleted along the substructure boundaries. In situ micro-compression testing was performed at room temperature along the [001] orientation. The dual-phase substructures exhibited lower yield strength and higher Young's modulus compared with single-phase substructures. Our research provides a fundamental understanding of the relationship between the microstructure and mechanical properties of additively manufactured metallic materials. The results suggest that the uneven heat treatment in the printing process could have negative impacts on the mechanical properties due to elemental segregation. [ABSTRACT FROM AUTHOR]

The aim of this paper is to analyse the mechanical properties of butt joints between S355 steel and 6061-T6 aluminium alloy, as well as their relationship to changes in the structure of the material caused by welding. The effect of the tool offset was analysed in particular. For the analysis, tensile tests were carried out using macro- and mini-specimens taken from S355/AA6061-T6 joints and base materials. In addition, the macro- and microstructure of the joints was determined, the hardness profiles in the joints were analysed, and fractographic analysis of the fractures of the specimens was carried out. Based on the results of the macro- and microstructure examinations, typical friction stir welding (FSW) joint zones were characterised. The microstructure was observed in the interface line of the materials on the root side, the negative effect of which on the quality of the joint was confirmed by digital image correlation (DIC) strain analysis during the monotonic tensile test. The highest average value of su = 141 MPa for the entire joint was obtained for a 0.4 mm tool offset. The highest average value of su = 185 MPa for the selected joint layer was obtained for a 0.3 mm tool offset. Fracturing of the joint in the selected layer for the tool offset values of 0.3 mm and 0.4 mm occurred in the weld nugget zone (WNZ) where the lowest hardness was recorded. [ABSTRACT FROM AUTHOR]

In the present work, we report a thermoresponsive hydrogel formed by the self-assembly of compounds 1 and 2 Milli Q water. Both hydrogels showed thixotropic behavior. Atomic force microscopy (AFM) studies confirm the fiber-like microstructure of compounds 1 and 2, but denser fibers were observed in the case of compound 1. The hydrogel formed by compound 1 detected Cu2+, Fe3+, and Hg2+, whereas the hydrogel of 2 showed a change in the optical signal, specifically upon adding Cu2+ and Hg2+. Mechanistically, adding metal ions to the hydrogel resulted in the formation of a (1:1) complex with Fe3+ and Hg2+ and (2:1) with Cu2+. The detection of metal ions has also been achieved in real-life samples, such as in tap water. Low-cost portable gel-coated paper strips have also been developed for the onsite detection of these metal ions. [ABSTRACT FROM AUTHOR]

This paper presents protocols developed to quantitatively characterize the cellular microstructure of microcellular polyurethane foams, from scanning electron microscopy (2D) and X-ray micro-computed tomography (2D and 3D) data. The objectives are to provide, for both techniques: (i) a detailed description of the analysis steps based on open source Python algorithms; (ii) a method for automatic, robust and objective detection of the cells to limit user's biases; (iii) a statistical description of fraction, size, shape and spatial distribution of cells. The study considers 12 samples with densities ranging from about 400 to 600 kg m−3 and pore sizes from a few micrometers to several hundred micrometers. In addition, the database obtained is used to investigate the reliability of 2D measurements to describe the cellular microstructure statistics. [ABSTRACT FROM AUTHOR]

The paper gives the results of investigations on vacuum diffusion welding of МА2-1 magnesium alloy. Different technological measures were used in welding: unsupported welding, welding with application of forming matrices, welding without interlayers and with a zinc interlayer. It is found that it is not possible to produce the joint in unsupported welding without an interlayer at 400 °С temperature and process duration less than 60 min. Increase of welding temperature or time leads to considerable grain growth. Application of 250 ~m zinc interlayer and of the following welding mode: Т = 320 ºС, Р = 10 MPa, t = 30 min allows producing the joint. Analysis of chemical composition in different areas of the joint zone shows that development of diffusion processes in the butt during welding results in pore formation with magnesium content on the level of 17.8 – 20.12 wt. % in the zinc interlayer at 2 – 3 ~m distance from magnesium/zinc contact line. In the central part of the joint zone the metal chemical composition is close to pure zinc composition. Application of forming matrices and an interlayer of zinc in the solid-liquid state in welding in the following mode: Т = 340 ºС, Р = 10 MPa, t = 30 min. allows producing sound joints due to localisation of plastic deformation in the butt joint. Results of metallographic investigations showed formation in the butt joint of common grains and remains of the interlayer in the form of dispersed particles of 15…50 ~m size, with chemical composition of Mg–4.53Al–0.20Mn–63.49Zn, wt. %, having an irregular elongated shape. [ABSTRACT FROM AUTHOR]

Electric Field Assisted Sintering (EFAS, also referred to as spark plasma sintering) is a powerful technology for the consolidation of powder materials. The high heating rate during the sintering process is critical for minimizing energy consumption, but it can also cause microstructure heterogeneities in sintered parts, such as spatially varied porosity. The examination of localized porosity usually requires the use of a scanning electron microscope with a carefully prepared surface. In this paper, photothermal radiometry is used to measure local thermal diffusivity and extract localized porosity of EFAS-sintered parts by using a percolation-threshold model. Applying this approach, we identified the radial position-dependent porosity variation in EFAS parts, which is likely formed due to the large temperature gradient during the sintering process. This approach has a unique advantage because it can measure samples with minimal or no surface preparation, enabling the possibility of in situ characterization in EFAS with proper system modification. Necessary modifications on the measurement approach for EFAS deployment and in situ characterization are also discussed. [ABSTRACT FROM AUTHOR]

Numerical simulation of cone penetration testing using the Particle Finite Element Method In‐situ investigation methods, such as piezocone penetration testing, are increasingly used for site characterization due to their proven effectiveness, cost‐, and time‐efficiency. Further development of interpretation methods is subject of ongoing research activities, considering influencing factors such as partial drainage during test execution or microstructural bonding of the soil skeleton. In this paper, the two effects are investigated based on numerical simulations of piezocone penetration using the application G‐PFEM, which takes into account large deformations, soil‐structure interaction, and nonlinear constitutive behaviour. The results highlight the influence of partial drainage and microstructure on the measured tip resistance and pore water pressures, whereas different trends were observed. Furthermore, an in‐situ test conducted in postglacial, fine‐grained sediments was successfully recalculated, suggesting a possible approach to calibrate nonlinear constitutive models, which are commonly used for numerical analysis of geotechnical boundary value problems. [ABSTRACT FROM AUTHOR]

In recent years, nanofibers have excellent properties used in fuel cell materials, which has attracted widespread attention. Electrospinning technology is a low-cost, efficient, controllable, and easy-to-operate fiber preparation method. The micromorphology of the electrode material has a significant impact on cell performance. In this paper, the influencing factors of electrospinning technology are summarized into three categories: internal parameters, process parameters and environmental parameters. The influence of these parameters on the micromorphology of materials as discussed. Furthermore, the fiber structure formed by electrospinning as summarized, with a focus on the performance obtained on different microstructures. In addition, the latest research progress on electrospinning for solid oxide fuel cell materials as summarized. Finally, the development status of composite electrode materials and their microscopic formation mechanism are particularly emphasized' providing research ideas for relevant researchers. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of strain per pass over a cycle on, multi-axially forged cast AA5083 alloy at room temperature. To begin with, Multi-Axial Forging (MAF) with two different strains per pass was imposed on the alloy without changing the die geometry. Samples were deformed to cumulative strains of Σε = 2.46 (2 Cycles) and Σε = 2.79 (3 Cycles), with two different strains per pass ε = 0.41 and ε = 0.31 respectively. Microstructural analysis was carried out by using OM, XRD, and SEM with EDS. Structural changes were characterized, and it was revealed that grain fragmentation was caused by the frequent development of deformation and micro shear bands, which was followed by the evolution of new fine grains in the original grain structure. Mechanical properties were evaluated by tensile, and hardness tests. MAF of ε = 0.41 per pass results in high tensile strength and hardness, 428 MPa and 147 Hv; respectively at a cumulative strain of Σε =2.46. Processing with strain ε = 0.31 per pass produced strength of 380 MPa and hardness of 131 HV after cycle III with a cumulative strain of 2.79. MAF of strain ε = 0.41 per pass with cumulative strain of 2.46 resulted in a higher grain refinement structure with increased strength compared to a strain of 0.31 per pass with a cumulative strain of 2.79. Therefore, with the imposition of the high strain per pass produced more grain refinement and consequently higher strength. [ABSTRACT FROM AUTHOR]

With the increasing consumption of polyurethane (PU) products, more and more waste polyurethane (WPU) needs to be handled, resulting in the inefficient utilization of post-consumer PU becoming a key problem in the recycling of waste polymers. Therefore, this paper aims to explore the properties of WPU modified asphalt and assess the feasibility of using WPU materials for asphalt pavement applications. At the same time, the conventional properties, rheological properties, stability, and microscopic properties of the modified asphalt were analyzed. The results show that the rheological properties and permanent deformation resistance of the modified asphalt are improved when the WPU content is increased from 5% to 25%, while the storage stability of the WPU modified asphalt decreases with the WPU content. The optimal amount of WPU modified asphalt is accordingly recommended to be 20%. [ABSTRACT FROM AUTHOR]

In this paper, the i‐MAX phase (Mo2/3Y1/3)2AlC ceramic with high purity of 98.29 wt% (1.13 wt% Y2O3 and 0.58 wt% Mo2C) and high relative density of 98.59% was successfully synthesized by spark plasma sintering (SPS) at 1500°C with the molar ratio of n(Mo):n(Y):n(Al):n(C) = 4:2:3.3:2.7. The positions of C atoms in the crystal of (Mo2/3Y1/3)2AlC were determined. Microstructure and physical and mechanical properties of (Mo2/3Y1/3)2AlC ceramic were systematically investigated. It was found that the obtained (Mo2/3Y1/3)2AlC ceramic had an average grain size of 32.1 ± 3.1 μm in length and 14.2 ± 1.7 μm in width. In terms of physical properties, the measured thermal expansion coefficient (TEC) of (Mo2/3Y1/3)2AlC was 8.99 × 10−6 K−1, and the thermal capacity and thermal conductivity at room temperature were 0.43 J·g−1·K−1 and 13.75 W·m−1·K−1, respectively. The room temperature electrical conductivity of (Mo2/3Y1/3)2AlC ceramic was measured to be 1.25 × 106 Ω−1·m−1. In terms of mechanical properties, Vickers hardness under 10 N load was measured as 10.54 ± 0.29 GPa, while flexural strength, fracture toughness, and compressive strength were determined as 260.08 ± 14.18 MPa, 4.51 ± 0.70 MPa·m1/2, and 855 ± 62 MPa, respectively, indicating the promising structural applications. [ABSTRACT FROM AUTHOR]

This paper aims to act as a useful engineering tool for researchers who are studying the production of well-densified IN718 parts by uniaxial vacuum hot pressing. To the best of the authors' knowledge, there is no relevant information on literature about densification of IN718 parts by this technique. This work is focused on understanding the influence of uniaxial vacuum hot pressing sintering conditions (temperature and pressure) on Inconel 718 (IN718) powder densification, microstructural, fracture mode, and hardness properties. The optimization of temperature and pressure sintering conditions are presented as well as its influence on the densification, microstructural features, and hardness properties. The sintering conditions included temperatures of 1000, 1068, 1150, and 1200 °C; pressures of 50 and 60 MPa; and a dwell time of 60 min. The results showed an increase in the grain size (GS) of the compacts with the processing temperature and a change on the fracture mode from intergranular dominant fracture to fully dimple ductile fracture. Regarding the microstructural properties, the results showed that γ′(Ni3(Al, Ti)) intermetallic precipitate originated from IN718 powders was retained in the sintered specimens. The hardness results revealed that the sintering temperature of 1000 °C is not enough to promote accurate densification. The optimum hardness results were achieved at 1200 °C (327 HV) with high levels of densification and pure intragranular fracture mode. In future studies, shear and tensile strength test should be performed in order to properly evaluate the mechanical behavior of hot-pressed IN718 specimens. [ABSTRACT FROM AUTHOR]

In this paper, multi-stranded wires were used as the filling material for narrow gap oscillation laser wire filling welding of thick-walled titanium alloy. The effect of laser beam oscillation frequency and diameter on weld formation and welding defects was investigated. By using a high-speed camera, the melting process of the laser-melted multi-stranded wires was observed. The macrostructure and microstructure of the welded joint were analyzed using the optical microscope (OM), scanning electron microscope (SEM), electron back scattering diffraction (EBSD), and transmission electron microscope (TEM), and the mechanical property tests were also carried out. The results showed that the droplet was in the liquid bridge transition mode, while the oscillation diameter of the laser beam was 2 mm, and the frequency was 100 Hz. The obtained weld seam was continuous and stable, without pores and incomplete sidewall fusion. The base metal (BM) of the welded joint was composed of equiaxed α + β phase, the heat-affected zone (HAZ) was comprised of acicular α′ martensite and primary αp phase, and the welded metal (WM) consisted of coarse original β columnar grains and internal basketweave acicular α′ martensite. The microhardness of the WM was the highest. The average tensile strength of the welded joint reached 940 MPa. The tensile fracture occurred at BM. The fracture dimple was relatively deep, presenting the characteristics of ductile fracture. The average impact toughness of the welded joint was 12 J. The fracture dimple was shallow, appearing as a ductile fracture. [ABSTRACT FROM AUTHOR]

Laser polishing, as a post-processing or in situ precision-smoothing technology, is a surface modification method aimed at improving the rough surface and properties of additive manufactured components. In this paper, the effect of in situ laser polishing on the surface modification of Ti-6Al-4V alloy prepared by selective laser melting (SLM) has been investigated. The optimum process parameters were selected for experiments in the range of high power and low power, respectively. The results showed that the surface roughness was reduced by 81.8% (from 6.38 to 1.16 µm Sa) after laser polishing, which significantly improved the surface quality of SLM parts. The number of pores in the polished layer and heat-affected zone was greatly reduced, and the depth of remelted layer was more than 400 µm, which made the microhardness and wear resistance of the laser polished parts obviously increased compared with the as-printed ones. In addition, the reduction of microdefects (adhesive particles, partially melted powders, and pores) on polished surface and the grain refinement made the laser polished parts exhibit stronger corrosion resistance. Because of these enhancements, in situ laser polishing represents a suitable method to improve surface properties of SLM parts, and provides the feasibility and possibility for the integrated processing of 3D printing and laser polishing. [ABSTRACT FROM AUTHOR]

The influence of different dispersants on the dispersion of Y2O3 sintering aid in B4C powder and the microstructure and performance of the subsequently hot-pressed ceramics were studied in this paper. The results indicated that ammonium polycarboxylate (APC) could effectively enhance the distribution of Y2O3 in B4C powder, and further improve the distribution homogeneity of the formed second phase YB4 in the fabricated ceramics. Polyethyleneglycol (PEG) 600 was beneficial to breaking the Y2O3 agglomeration in B4C powder and improving the distribution of YB4. The remaining PEG 600 in the mixed powder would react with B4C and Y2O3 particles to form the dendritic-structure second phase in the sintering process, which comprised some whisker-like branches and a layer of film. The distribution of YB4 in the fabricated ceramics was slightly improved by adding sodium citrate (SC) dispersant. Y2O3 reacted with B4C to form the intergranular and intragranular YB4, and liquid phase was formed in the sintering process, facilitating the rearrangement of B4C grains and improving the densification. The dispersant APC could improve the homogeneity of YB4, promoting the densification and strength of the ceramics. [ABSTRACT FROM AUTHOR]

Design of mechanical metamaterials is typically realized by repeating microstructured building blocks or unit cells. Microstructures of these unit cells can be identical, whereas individual design of each cell and various combinations of unit cells definitely offer more freedoms and possibilities for combinatorial design of metamaterials. Unfortunately, this combinatorial design problem is prohibitively challenging, if not impossible, due mainly to its huge number of combinatorial cases. This paper poses and addresses the combinatorial optimization of a metabeam, aiming at maximizing its critical buckling load. The problem was conceptualized and solved by combination of ML accelerated surrogate modeling and optimization algorithm, and buckling and post-buckling performance of the optimal design was validated by high-fidelity simulations and experiments. The efforts provide efficient tools for combinatorial design of mechanical metamaterials. We publicly share all the data and codes for implementation. [ABSTRACT FROM AUTHOR]

Double-pulsed gas metal arc welding (DP-GMAW) is a high-performance welding method with low porosity and high frequency. Periodic shrinkage and expansion of the melt pool during DP-GMAW leads to unusual remelting, and the re-solidification behavior of the weld metal can significantly refine the weld structure. The advantages of DP-GMAW have been proven. In order to better apply DP-GMAW to aluminum alloy arc additive manufacturing, in this paper, the single-pass deposition layer parameters (double-pulse amplitude, double-pulse frequency and travel speed) of DP-GMAW will be optimized using the response surface method (RSM) with the width, height, and penetration of the deposition layer as the response values to find the superior process parameters applicable to the additive manufacturing of aluminum alloy DP-GMAW. The results show that the aluminum alloy components made by DP-GMAW additive are well formed. Due to the stirring of double-pulse arc and the abnormal remelting and solidification of metal, the microstructures in the middle and top areas show disordered growth. The average ultimate tensile strength of the transverse tensile specimen of the member can reach 175.2 MPa, and the elongation is 10.355%. [ABSTRACT FROM AUTHOR]

Aluminum alloy adhesive bonding joint widely appears in many industrial products. Improving the mechanical performances of aluminum alloy bonding joints has been attracting much effort. To acquire more excellent bonding strength, this paper focused on the effects of different surface treatments, including laser ablation and milling superposed by phosphoric acid anodizing (PAA). The treated surfaces were characterized by roughness and contact angle, and the effects of the geometric parameters of microstructures on wettability, failure mode, and shear strength were examined. The results indicate that those surfaces where the spacing is smaller than the diameter present a hydrophilic property and the corresponding specimens are mainly subject to cohesive failure, and vice versa. Additionally, laser ablation with a properly designed dimple pattern can greatly improve the bonding strength, and the maximum average shear strength of specimens with a thickness of 50 μm reaches 32.82 MPa, which is an increase of 28.15% compared with the original milling specimen. Moreover, fabricating groove or grid patterns on the surfaces and applying PAA treatment can also significantly enhance the bonding strength, reaching up to 36.28 MPa. [ABSTRACT FROM AUTHOR]

Recently, Mg-Zn/hydroxyapatite (HA) composites have attracted much attention as potential candidates for use in bone implants. In this paper, the MgZn/HA composites were prepared using powder metallurgy (PM) and the merging mechanism of MgZn and HA particles was investigated by adjusting the weight ratio of the HA powder. The evolution of the HA distribution in the matrix was examined using SEM and micro-CT images. Afterward, the mechanical properties and biocompatibility of the composites were discussed in detail. The results revealed that the mechanical properties and biocompatibility of the Mg-Zn/HA composites were significantly affected by the HA content. Composites with a low HA content showed increased porosity, improved mechanical strength, and enhanced corrosion resistance after ball milling and cold pressing. These results underscore the importance of optimizing the HA content in Mg-Zn/HA composites for bone implants. Based on our findings, PM Mg-Zn/HA composites with a moderate HA content demonstrate the most promising characteristics as bone implants. The insights gained from this work contribute to the advancement of bone implant materials and hold great potential for enhancing orthopedic surgery outcomes. [ABSTRACT FROM AUTHOR]

To solve the problem of the low coercivity of Nd-Fe-B-based nanowires impeding their application in magnetic storage media, highly ordered Nd-Fe-B/Fe-Co composite nanowires were fabricated in an anodic alumina template by means of the alternating electrochemical deposition method. In this paper, the effect of soft and hard magnetic phase compositing on the magnetic properties of Nd-Fe-B-based nanowires was investigated, and the coercivity improvement mechanism was demonstrated. The results show that after annealing at 600 °C for 2 h, Nd-Fe-B/Fe-Co nanowires crystallize into a multiphase structure containing a hard Nd2(Fe, Co)14B phase and soft NdB4, NdB6, Fe7Nd, and Fe7Co3 phases. It is characterized that the Nd2(Fe, Co)14B phase preferentially nucleates, followed by NdB4 + NdB6 + Fe7Nd, while Fe7Co3 has been formed in as-deposited nanowires. The existence of a Nd2(Fe, Co)14B phase with high anisotropy fields, the remanence enhancement effect produced by exchange coupling between hard–soft magnetic phases, and the pinning effect between different phases make the composite nanowires approximately exhibit single hard magnetic phase characteristics with coercivity and remanence ratio as high as 4203.25 Oe and 0.89. The results indicate that synthesizing Nd-Fe-B/Fe-Co exchange-coupled composite nanowires via alternating electrodeposition is an effective way to optimize the magnetic performance of Nd-Fe-B-based nanowires. [ABSTRACT FROM AUTHOR]

The wide distribution of alpine saline areas in China is faced with two major problems, which are salt intrusion and freeze–thaw. In total, 216 specimens were prepared with 6 kinds of concrete mix proportions in this paper. The effects of the single and compound incorporation of metakaolin (MK) and polypropylene fiber (PPF) of different amounts on the mechanical properties and microstructure properties of concrete were investigated under the dual action of multi-salt (NaCl, MgCl2, Na2SO4, and NaHCO3) soaking and freeze–thaw. Potable water and freeze–thaw concrete were adopted as the control group. Changes in the appearance morphology, mass loss, relative dynamic elastic modulus, and compressive strength of the concrete were tested, and the microstructure of the concrete was analyzed by scanning electron microscopy (SEM). The results showed that an admixture of both MK and PPF in the potable water and freeze–thaw cycle test can improve the mechanical properties and frost resistance of concrete. The admixture of PPF can effectively improve the mechanical properties and frost resistance of concrete. However, the admixture of MK failed to improve the mechanical properties and frost resistance of concrete during multi-salt soaking and freeze–thaw. The frost resistance of concrete under multi-salt soaking and freeze–thaw was optimally improved with 10% MK and 0.6 kg/m3 PPF. Its microstructure shows that PPF can effectively inhibit crack propagation and reduce the deterioration of concrete under multi-salt soaking and freeze–thaw. [ABSTRACT FROM AUTHOR]

This paper addresses the concept of adjusting the microstructure of the supports of solid oxide electrolyzers in order to boost performance. While several earlier studies focused on maximizing performance, reducing degradation, adjusting operating conditions and introducing new materials or designs of electrolysis stack, the current study addresses potential improvement of the cell by fine tuning the microstructure without any major redesign of existing cells. In the proposed approach, the study combined numerical simulations with definition of the model, which can aid in predicting the performance of a cell with adjusted porosity of the electrode support, and preparation of modified cells with alternative pore forming agents and two alternative sintering temperature levels. Supports of solid oxide cells were sintered at 1350 and 1400 °C with pore former content of 25–35%. This resulted in the porosity of supports being in the range of 47–54%. Cells with 10Sc1CeSZ and 8YSZ electrolytes were investigated in operando. The proposed approach makes it possible to quantitatively and qualitatively assess the potential gain when the reference cell is slightly modified, according to guidelines obtained from the model. It was found that the proposed method to fine tune the microstructure can result in improved performance, with a clear indication that adjusting the sintering temperature has a stronger effect on the microstructure of the support than increasing the pore forming agent. [Display omitted] [ABSTRACT FROM AUTHOR]

This paper develops a coupled chemo-mechanical model for stress-assisted diffusion in the framework of micropolar elasticity. The two-way interaction of mechanical and chemical driving forces as well as internal microstructure of the polar media is taken into account. The fundamental governing equations of chemo-mechanics with kinetics driven by diffusion and stress are developed, and mathematical expressions for stress and concentration fields are derived. Using Airy stress functions, a simplified formulation for two-dimensional chemo-elasticity problems under chemical equilibrium is presented. Using a perturbation approach to solve the presented system of equations, closed-form expressions for different field parameters can be obtained. As an illustrative case study, expressions for the stress and solute concentration in an infinite plate with circular hole embedded in a chemical medium have been written. The derived equation and proposed solution approach can be applied to various plane micropolar chemo-elasticity problems for studying the interaction between mechanical and chemical driving forces as well as material length-scale parameters. [ABSTRACT FROM AUTHOR]