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Functional grading of a ferritic steel (SA508 grade 3) and austenitic stainless steel (316L) powder via hot isostatic pressing (HIP) consolidation is investigated as an alternative to dissimilar welding. Fundamental aspects of this method such as the development of microstructure and diffusional processes during the HIP process of such mixed powder are studied in this work. A change of the post-HIP α to γ ratio with HIP temperature was observed in mixed powder specimens, combined with the formation of a ferritic lath zone which affects the properties of the specimens (throughout this work the term ferritic laths refers to a ferritic phase of unknown structure which is likely to consist of martensite, bainite or a mixture of both). These effects were attributed to extensive diffusion of alloying elements from 316L into SA508 grade 3. Simulation and experimental quantification of diffusion in diffusion couple experiments were applied to derive an empirical model for estimating α-Fe boundary migration and the formation of the ferritic lath zone and phase fractions for various temperatures and dwell times of the HIP process. KeywordsHot isostatic pressing, Functional grading, SA508, 316L

Al-12Si alloy processed through additive manufacturing exhibits a complex hierarchical structure. At the mesoscale, its melt pool boundaries constitute a network of weak interfaces that provides preferred pathways for crack kinking, leading to both marked anisotropy and apparent enhancement in the fracture energy. In this study, a multiscale cohesive zone-based computational model and a semi-analytical approach for kinked cracks are used to investigate the effect of melt pool configuration on fracture energy enhancement and anisotropy due to crack path tortuosity. We experimentally validate our methodology using fracture toughness testing of compact tension specimens, then systematically study the simultaneous effects of hatch spacing, layer thickness, and crack surface orientation on variations of the fracture energy. While the fracture energy increases with increasing hatch spacing and decreasing layer thickness, processing defects such as keyholing give practical limits to the melt pool geometry, limiting the fracture energy enhancement. We found that the fracture energy can be enhanced as high as a factor of two with an optimal crack surface orientation that is linearly proportional to the ratio of hatch spacing to layer thickness and varies between 60° and 100°. Agency for Science, Technology and Research (A*STAR) Published version This work was supported by the funding from A*STAR, Singapore via the Structural Metals and Alloys Programme (No. A18B1b0061). PP acknowledges the support from Thailand Science Research and Innovation (TSRI) under Fundamental Fund 2022 (Project: Advanced Materials and Manufacturing for Applications in new S-curve industries).

The process of diffusion bonding in air was successfully used to join 5A90 Al–Mg–Li alloy, which can greatly reduce the welding cycle and equipment requirements. Before diffusion bonding, the Cu nano-coating prepared on the surface of Al–Mg–Li alloy by ultrasonic electrodeposition was used as interlayer to hinder the formation of oxide film and increase the atomic diffusion. The effects of coating thickness, diffusion temperature and interlayer types on the microstructure and performance of joints were investigated. When the diffusion temperature was 530 °C and the coating thickness was 5.12 μm, the optimal shear strength of the joint with 1 μm-thick diffusing interface was 187.9 MPa, which was 90.6% of that in base metal. As the decomposition of unstable Al3(Mg, Cu)2, Cu atoms diffused into the Al matrix to precipitate Al6CuMg4, and enhanced nano-MgO phase was formed in situ. In addition, the element diffusion behavior and formation mechanisms of the joints were discussed in detail.

Generally, additively manufactured (AM) full martensitic titanium alloys (hexagonal-close-packed α’ phase) exhibits high yield strength (>1GPa) but poor elongation to failure (

The low electron/ion migration rate and the high deformability of conventional two-dimensional (2D) electrodes limit the growing demand for energy storage devices with high areal capacity and stable cycling performance. Designing three-dimensional (3D) electrodes is a promising strategy to improve this defect. Herein, we prepare metallic nickel aerogel via a facile hydrothermal reduction route, which was annealed to obtain a self-standing 3D porous NiO/Ni anode. The electrode material displays a networked porous structure and good electrical conductivity, which mitigates the volume effect during cycling and provides excellent electron transport pathways and conductive ion channels. The unique structure with many electrochemical active sites performs higher areal capacity. When used as the anode of lithium-ion batteries (LIBs), a high reversible areal capacity of 1.93 mAh cm−2 is delivered at a current density of 1 mA cm−2 with a capacity retention ratio of 98.4% after 100 cycles. Remarkably, a large reversible capacity of 1.30 mAh cm−2 is also achieved at a relatively high current density of 6 mA cm−2. The 3D porous NiO/Ni anode material provides a new strategy for enhancing the energy density and stable cycling for practical application in power-type LIBs.

Metal corrosion is a headache in marine industry. The existing technologies can hardly provide an effective long-term corrosion protection. Biomimetic slippery lubricant infused porous surface (SLIPS) has been developed as a potential alternative technique to resolve this problem. Herein, a stable triple-layered slippery surface which consist of compact-nickel-underlayer/porous-nickel-midlayer/PDMS/paraffin infused toplayer was designed and developed for corrosion protection. This composite surface exhibited a low sliding angle with good stability and thermal assitant self-healing property. Simultaneously, it demonstrated good anti-corrosion property with an extremly low corrosion current density and a large impedance of 2.301 × 107 Ω·cm−2, the as-prepared sample even can provide efficient corrosion protection for a long-term immersion in NaCl solution. Furthermore, the interface erosion mechanism was studied via the assistance of electrochemical and surface analysis techniques. The results revealed that no corrosion products were generated which further proved the good anti-corrosion performance. We believe that this triple-layered slippery surface can broaden the application of metals in the field of marine and other industries.

Additive manufacturing of structural metallic components is an emerging technology. The DED-arc (direct energy deposition) process combines efficiency with high degrees of freedom and predictable quality. Compared to powder-based processes, the surface is relatively coarse as a result of high heat input and larger molten zones. In industrial applications, the post-treatment of surfaces of DED-arc components cannot be guaranteed for economic reasons or due to geometric constraints. Hence, the surface topography must be evaluated and quality levels need to be defined. Unfortunately, established surface parameters and their determination cannot be directly transferred to DED-arc components and further research on this topic is needed. This article demonstrates surface topography features of representative DED-arc components. Furthermore, waviness profiles were established by applying an alternative cutoff wavelength to better represent the DED-arc surface characteristics. Based on these waviness profiles, 2-dimensional height parameters were calculated. The waviness parameters were determined for four DED-arc specimens made from high strength wire electrodes. The manufacturing parameters were varied in terms of different energy input and interpass temperature, resulting in varying deposition rates and surface qualities. The waviness parameters correlated with manufacturing parameters. A mixed deterministic and random nature of the surface topography was verified.

This study investigated the effects of laser scanning speed on the microstructure, phase transformation and properties of NiTi alloys fabricated by laser powder bed fusion (LPBF). In this study, the contributions of metallurgical factors under different scanning speeds, such as Ni evaporation, Ni4Ti3 precipitation, dislocations and internal stress, to the transformation temperature and transformation latent heat were clarified through specially designed experiments. Ni evaporation is found to have the most profound effect, followed by precipitation. Increasing scanning speed is found to reduce Ni loss, thus cause less increase in the transformation temperature and transformation heat of the LPBF-NiTi alloys. Increasing scanning speed also increases the microstructure non-uniformity and thus widens the transformation temperature interval. The orientations of residual stress exhibit strong crystallographic stiffness dependence. The LPBF-NiTi alloys with different scanning speeds all exhibited high strains (>13.4%) and excellent shape memory effect. A LPBF-NiTi honeycomb structure exhibited 96% shape recovery rate after a 60% pre-compressive deformation. Besides, there is an optimum scanning speed for minimum porosity and smallest average pore size. However, the pore structure is found to have weak influence on the tensile behaviour of the LPBF-NiTi alloys, possibly due to the high defect tolerance of the martensitic transformation.

Solid-state bonding is widely involved in metal forming and joining applications. The quality of the bonded interface is the key to the final integrity of the joint or formed structure; thus, its controllability and predictivity have been the focus over decades. The interface bond quality is jointly determined by the interface oxide behaviour and microstructure evolution. In this study, a new four-stage model, considering the cohesion of different contacting pairs (oxide-oxide, oxide-metal and metal–metal) and the reduced adverse effect of remaining oxides, is proposed to describe the bonding process under hot deforming conditions. This proposed model was validated through a range of hot compression bonding tests, using Gleeble under different strains (10%, 30% and 50%), strain rates (0.001 s−1, 0.01 s−1 and 0.1 s−1) at 1150 °C with references. Scanning electron microscope (SEM) and Electron Backscatter Diffraction (EBSD) were used to characterize the oxide behaviour and microstructure evolution. Tensile tests at room temperature were conducted on bonded samples and references to reveal the interface bond ratio. 100% bonding strength, equivalent to the base metal's strength and ductility, was achieved at the large strain of 50% for all three strain rates.

In this work, the effects of solidification and remelting under chessboard 67° rotation scanning strategy on the microstructure and properties of selective laser melted (SLMed) 316L stainless steel (316L SS) were studied, including dendrite microstructure, element distribution, grain orientation, dislocation structure, microhardness and corrosion resistance. We put forward a complete foundation relationship among texture, cellular structure and mechanical property influenced by anisotropy. Main results are summarized as follows: The 〈101〉 texture formation is the result of dendrite epitaxial growth. The cellular dislocation structure highly overlapped with dendrite significantly changed in remelting zone. Hence the high ratio of 〈101〉 texture signifies the anisotropy distribution of epitaxially growth dendrite which released the internal stress. The dislocation structure has a contribution to strength similar work hardening strengthening. Meanwhile, the 316L SS obtains Orowan strengthening via the nano oxide pinning effect in dislocation wall. Thus, the dislocation density and oxide distance obvious changed in different directions of cellular dislocation structure, resulting in the cellular dendrite regions performed higher microhardness than the columnar dendrite regions. The drastic change of dendrite increased the crack sensitivity of SLMed 316L SS, and the junction of different epitaxially growth direction dendrites formed high energy grain boundary.

In this work, a (6.4γ–Al2O3 + 18Al13Fe4)/Al (wt.%) composite (AFO) was in-situ synthesized through the chemical reaction between Al and oxide powders. After hot extrusion, the formed nanometric γ–Al2O3 particles exhibit networks, locating along matrix grain boundaries. The submicron Al13Fe4 particles have similar size with the α–Al grains and disperse uniformly among the matrix. It is supposed that the γ–Al2O3 particles are efficient for grain boundaries stabilization at elevated temperatures, while the Al13Fe4 particles generate further dispersion strengthening effect. As a result, the AFO composite exhibits attractive high-temperature intensity and heat stability. The yield strength of tensile test at 300 °C is 270 ± 6 MPa, while it can still remain to be 119 ± 10 MPa at 500 °C. It is regarded that this work may provide new insights for designing new Al based composites for elevated temperature applications.

In this research, a kind of 70-47-25% B4C/2024Al functionally graded materials (FGMs) were prepared by squeeze casting. The interfacial microstructure, precipitate characteristics and mechanical properties of B4C/2024Al FGMs were mainly studied. It was found that there was a small amount of interfacial reaction between B4C particles and Al. Mg and O elements segregated at the Al-B4C interface and MgO was formed. Under the same heat treatment conditions, the types and sizes of precipitates in different gradient layers were found to be different. Different amount of Mg segregation at the B4C-Al interface resulted in different proportion of Cu and Mg in 2024Al matrix and it makes the precipitation regions of 25 vol%, 47 vol% and 70 vol% B4C/2024Al locate in S, θ + S and θ respectively. The test results of basic properties indicated that the strength and plasticity of 70-47-25% B4C/2024Al FGMs show gradient changes. The bending stresses of 70%, 47% and 25% B4C/2024Al composites can reach 591.5 MPa, 953.4 MPa and 700.7 MPa respectively. And the elastic modulus are 240.3 GPa, 170.9 GPa and 130.7 GPa respectively. The results of this research will provide theoretical guidance for the interface structure design and heat treatment process of high strength B4C/Al composites.

Cu–Cr–Co combinatorial multilayer thin-films were prepared by a high-throughput ion beam sputtering system. Based on the thickness ratio among the individual nanoscale monolayers (Cu, Cr, Co), the resulting stoichiometry covered the entire phase diagram. The chemical composition and structure of Cu–Cr–Co combinatorial chip upon solid-state reaction were studied by lab-based micro-X-ray fluorescence (μ-XRF) and high-throughput synchrotron X-ray diffraction (XRD), respectively. A composition-structure map for Cu–Cr–Co combinatorial chip was developed through automated data analysis employing hierarchical clustering techniques. The structural evolution of Cu–Cr–Co combinatorial chip as a function of heat-treatment temperature, time, and modulation period were studied systematically. Furthermore, the effect of the elemental distribution in-depth direction was investigated to gain more insights regarding phase transformation. This work provides an efficient method and new perspectives for the design and optimization of the composition and structure of high-performance thin-films.

Due to its high hardness and brittleness, sapphire is difficult to obtain a low grinding roughness. In this paper, the cerium oxide liquid is used to assist the grinding of sapphire with a diamond wheel with relatively big-size grains to obtain a low roughness. The effects of grain size, the crystal orientation of the sapphire, and the pH values of the cerium oxide liquid on the assisted grinding process have been analyzed. It is shown that with the proposed method, the roughness of 45 nm and subsurface damage of 141 nm are obtained, respectively. Compared with the grinding surfaces obtained without the assistant, the roughnesses and the subsurface damage of the assisted grinding surfaces are reduced by 60.8% and 84.5% when #600 wheel is used, respectively. Moreover, in the grinding experiments, the crystal orientation of the sapphire and the pH values of the cerium oxide liquid have little effect on the roughness of the grinding surface, while the grain size has a great impact. It is concluded that the improvement of the surface roughness by using the proposed method benefits from the combined action of the grinding of grains and the polishing of the cerium oxide liquid.

Structural composites for electric vehicles should have lightweight, mechanically strong, efficient electromagnetic shielding. Although thermoplastic composite material plays a structural role and aluminum thin film (Al foil) plays the role of electromagnetic wave shielding, poor interfacial adhesion and tear-resistance of Al foil need to be overcome. In this work, we demonstrated a novel, high-performance EMI-shielding multilayer structure based on an aluminum thin film (Al), glass fabric (GF), carbon fiber-reinforced thermoplastic (CFT), and thermoplastic adhesive. In particular, the interfacial adhesion at the mechanically weak interface has been significantly improved by a factor of 1.15 via the application of an aramid nanofiber-embedded (ANF) thermoplastic interlayer. We found that the distribution and entanglement of aramid nanofibers in the ANF adhesive layer precisely determine the mechanical properties of the entire structural composite. Efficient EMI shielding performance (an average of 94 dB at 0.2–1.0 GHz) of structural EMI shielding composites was possible using a uniform aramid nanofiber layer.

The formation mechanism of sintering neck between magnesium oxide and magnetite under high temperature oxidation environment requires more investigation due to the limitations of high-temperature process monitoring techniques. Through a series of roasting experiments, this research quantitatively investigated the impact of MgO on the roasted microstructure and consolidation behavior of magnetite based on previous research. The results showed that with the increase of MgO content in pellets, the consolidation index of pellets decreased from 0.71 to 0.50, and the porosity increased from 7.24% to 13.57%. The existence of MgO could hinder the interface interaction, reduce the consolidation index and increase the porosity. Furthermore, molecular dynamics simulations were performed to investigate the crystal transformation and migration behavior from a molecular standpoint. The simulation findings revealed that the creation of the sintering neck was caused by atom migration and diffusion. Mg2SiO4 has minimal influence on the migration of the atoms, while MgO and MgFe2O4 have a large impact on pellet consolidation. This work gave new ideas for evaluating porous sintering materials, which may lead to additional research into the interface interaction between heterogeneous oxide during the sintering material formation process.

In the present study, the application and tailoring of the alloy composition of chromium martensitic hot-work steels using metal cored wires (MCW) for wire arc additive manufacturing (WAAM) in a modified short-circuit metal transfer process is demonstrated. The nickel content was varied and the alloys were fabricated as tubular-cored wires with various powder fillings. By recording the material transfer at high speed during processing, evidence was gathered indicating the suitability of the fabricated cored wires for WAAM. Optimized process parameters were identified by taking a Design of Experiment (DoE) approach and additive manufacturing (AM) structures were fabricated from the chromium martensitic hot-work tool steel alloys. The microstructure and mechanical properties of the parts were subsequently characterized. The phase fraction of the polygonally shaped delta ferrite could be reduced and microstructural refinement could be achieved by adding nickel to the investigated hot-work tool steel. In addition to molybdenum-enriched precipitates that covered the grain boundaries, randomly scattered non-metallic inclusions and oxides were observed. Modifying the microstructure by adding nickel also affects the mechanical properties of the product: an increase in hardness, impact toughness and yield strength as the nickel content increased in the AM structures fabricated by WAAM was observed.

The orientation-dependent corrosion rate and surface faceting of polycrystalline 90Cu-10Ni in acidic NaCl solution was investigated statistically. A good linear relationship was found between corrosion rate and the deviation angle from the 〈111〉 direction of the grain. For the three principle low-index planes, the corrosion rates followed the sequence of (001) < (101) < (111). More interestingly, there is a clear correlation between crystallographic orientation and surface faceting of grains in 90Cu-10Ni. Grains orientated near the three principle low-index planes and the (112) plane exhibit four different types of submicron-scale post-corrosion morphologies, respectively. However, each type of the faceted structure is bounded by {001} planes which have the lowest corrosion rate, independent of the substrate grain orientation. This is supported by the crystallographic models and AFM topographic measurements. Current study provides a simple way to identify grain orientation by etching, and also promising solutions to optimize corrosion properties through tailoring surface texture and design micro- or nano-scale surface structure by controlled etching.

Shell lattices are composed of smooth, non-intersecting and periodic thin shells. Their open-cell topology facilitates the manufacturing and multifunctional applications. This work proposes a shape optimization framework to obtain uniform thickness shell lattices with superior elastic moduli and isotropic elasticity. A B-spline parameterized Monge patch model is used to represent the mid-surface within the 1/48 unit cell, which maintains the cubic symmetry and simplifies the sensitivity evaluation. Two groups of elastically isotropic shell lattices are obtained, including Primitive (P) and I-graph-wrapped package (IWP). The highest achievable bulk, Young’s, shear moduli of P/IWP family lattices are nearly 70%/80%, 40%/60%, 40%/60% of the Hashin-Shtrikman upper bounds at 10% relative density. Besides, the Young’s/bulk modulus maximization is further introduced into the optimization to seek potential stiffness improvement, yielding similar optimized lattices with close stiffness for arbitrary initial designs. The highest achievable moduli are slightly improved by 3~5% than those without moduli maximization. In general, P-family lattices possess comparable Young’s, shear and higher bulk moduli to the stiffest truss lattices, while IWP-family lattices possess superior stiffness. This work proposes a systematic design approach to obtain elastically isotropic uniform thickness shell lattices, which can be applied to the other lattice families with Monge patch representations.

The presence of hydrogen in structural alloys reduces their ductility, a phenomenon called hydrogen embrittlement. Bake-out heat treatments are employed during processing to allow hydrogen trapped in microstructural features to effuse from the samples, but the optimal times and temperatures depend on the kinetics of hydrogen diffusion in the material. In this work, Gaussian process surrogate models are employed to emulate the outputs of microstructure-sensitive diffusion differential equations in steel. Training the models by sequentially increasing the number of dimensions results in better performances and shorter training times. Two main approaches are developed: single output models with experimental design for the prediction of optimal bake-out times, and multi-output principal component analysis models for the prediction of hydrogen concentration evolution. A novel approach is implemented to shorten the training times of multi-trap models by exploiting the symmetry of the equations with respect to different kinds of traps. The resulting models pave the way for the implementation of Gaussian processes on more computationally expensive diffusion simulations for the optimisation of heat treatments and other applications.

Short carbon fiber-reinforced Polyamide 12 composite materials were prepared and used as filaments for additive manufacturing (AM) of structures using the Fused Filament Fabrication (FFF) method. The effect of carbon fibers concentration and type, infill pattern and environmental temperatures on mechanical properties of the printed test samples were investigated. The measured tensile modulus of the printed composite ranged from 1.4 to 8.8 GPa, an increase of up to 6.3 times the value of the neat printed polymer. The tensile strength ranged from 40 to 90 MPa, for an increase of up to 2.15 times. Optimization of the environmental temperature for improved coalescence of filaments led to a fair increase in values of the tensile modulus and strength, with an improvement up to 1.5 and 2 times, respectively, for the printed samples with pattern orthogonal to the loading directions. Microstructure characterizations were performed for mechanical results interpretations, with the help of a specialized homogenization model. The combination of FFF and carbon fiber-reinforced composite shows high promises for applications in the transportation industry.

Eleven-layered AZ31/AA1050 composite plates were fabricated using a single-shot explosive welding process. The microstructural evolution of the interfacial layers were thoroughly investigated using scanning and transmission electron microscopy. The microstructural observations were correlated with microhardness measurements and bending tests to evaluate the mechanical properties of the clads. Under the applied detonation velocities, only the first interface was wavy, whereas the others were flat. Near all the interfaces, local melting and rapid solidification led to the formation of reaction regions composed of different phases with various chemical compositions and structures. In addition to the two equilibrium phases of γ-Mg17Al12 and β-Mg2Al3 identified in the reaction regions, a significant portion of the solidified melt was composed of non-equilibrium phases exhibiting an amorphous or ultra-fine-grained structure. During subsequent annealing, the high-hardness γ-Mg17Al12 and β-Mg2Al3 phases grew rapidly near all interfaces, whereas inside pre-existing reaction regions, the areas with various chemical compositions systematically transformed into the β-Mg2Al3 phase. It was found that the application of a pressure of 3 MPa plays an important role in avoiding clad delamination during heating; however, it does not prevent the formation of linear cracks in the β-Mg2Al3 phase, which significantly decreases the formability of the composite.

To simultaneously improve the strength and hydrophobicity of alginate-based fibers, a new wet spinning strategy for preparing alginate ester fibers (AE) based on esterification reaction with polyols as in-situ crosslinking agents through acid catalysis is proposed. The esterification was confirmed by FTIR and NMR. XRD analysis showed that the crystallinity of AE fiber increased by 235%. The test results of mechanical properties showed that the modulus has seen an increase of 41.18% and strength an increase of 78.4%. Interestingly, the contact angle was found to increase from 54.6° to 121.9°. Moreover, the influences of polyol types (Ethylene glycol, Glycerol, Pentaerythritol) on the properties of AE fiber are also investigated, the types of polyol have obvious influences on the mechanical properties, crystallinity, and hydrophobicity in AE fibers. These results indicate that this strategy provides a broad application space for alginate-based materials.

An investigation into the optimisation of a highly-concentrated (20 wt%) and stable platinum (Pt) organometallic ink, showing consistent jetting performance whilst minimising the negatives associated with particle-containing inks. The ink was synthesised and printing demonstrated onto glass by a piezoelectric drop-on-demand inkjet printer. Stable and rapid jetting (Z number: 1.83, 8 m/s) was achieved using cyclohexanol-based viscosity modifiers and optimisation of the print settings. Uniform nanofilms (10 – 30 nm) were obtained by the printing of successive layers which showed high conductivities (1.6 ± 0.13 × 106S/m, 17% of bulk Pt). The 20 wt% concentrated inks showed increased uniformity and electrical conductivity over previously reported 10 wt% equivalent inks, enabling for the first-time conductive features with a single print pass. High quality films were deposited by increasing the printed thickness due to significant uniformity improvements obtained across the centre of the printed films. A high film purity was demonstrated by X-ray diffraction, Scanning Electron Microscopy and Energy Dispersive X-rays. The suitability of the printed Pt films for production of Surface Enhanced Raman Scattering (SERS) detection platforms was also investigated. The presented work will pave the way for applications benefiting from selective deposition and low reactivity Pt nanofilms, as a proof of concept an LED circuit is demonstrated.

Metallic glass (MG)-particle-reinforced nanocrystalline CuCrZr alloys with ultrahigh strengths and good conductivities are designed and synthesized via mechanical milling and spark plasma sintering (SPS). The particle morphology and dispersion state of the CuZrAl MG reinforcement in the CuCrZr alloy matrix are optimized by regulating the milling time of the composite powders prior to SPS consolidation. Outstanding properties are achieved by 5 h and 10 h milling processes with ultimate compressive strengths of 1099 ± 33 and 1185 ± 29 MPa and high conductivities of 29.9 ± 0.8% IACS and 25.2 ± 0.6% IACS, respectively. According to the quantified results of strengthening and conductivity mechanisms, MG reinforcements and ultrafine grains are responsible for the balance of superior strength and conductivity of the composites.

The purpose of this study was to investigate the potential chiral recognition functions induced by two kinds of novel chiral microenvironment-responsive mesoporous silica nanoparticles (CMR-L-MSN and CMR-D-MSN) for the oral delivery of the poorly water-soluble achiral drug indomethacin (IMC). The as-synthesized CMR-L-MSN and CMR-D-MSN with molecular chirality and high specific surface area (SBET: 1141 and 1075 m2/g, respectively) were successfully prepared through grafting chiral molecular functional groups. The characterization results showed that CMR-L-MSN and CMR-D-MSN were spherical nanoparticles with opposite chiral features and clearly visible pore channels. Meanwhile, they exhibited good biosafety and degradability. In vitro drug release study indicated that both CMR-L-MSN and CMR-D-MSN significantly improved IMC dissolution compared with naked-MSN (N-MSN) (p

This paper studied the effects of iron powder types and contents on the friction and wear properties of copper matrix composites for breaking of high-speed trains. The mechanical properties, microstructure, interface, tribofilm, elements and microhardness of samples were analyzed by hardness tester, SEM, EDS and nanoindentation tests. The braking performances were measured by a tribometer mimicking the braking conditions. The results show that the wettability and combination between ferrophosphorus and matrix is poor and carbonyl iron is more suitable for strengthening matrix. The friction coefficient is most stable and the wear rate is also relatively low with 10% carbonyl iron. The increase of carbonyl iron content will promote oxidation and be conducive to the formation of friction film. The oxide degree of friction film increases in the direction from the matrix to the surface. However, too much iron powder produces excessive iron oxide which makes the friction film be easy to peel off especially under high speeds.

The purpose of this research is to obtain the method of measuring the residual deformation of plate with varying thickness (PWVT) based on nonlinear ultrasound (NLU) quantitatively. The arrangement of residual tensile deformation in PWVT was observed by optical microscope (OM) and simulation. The results showed that the residual strain increased linearly in the direction of deformation. Based on the arrangement of residual strain, the equation of stress wave in PWVT was established and the approximate solution which was verified by the finite difference method (FDM) was calculated. According to the calculation which presented the law of the ultrasound’s propagation, a quantitative method to measure the residual deformation of PWVT was proposed. Further, the feasibility of the method was verified in experiment. This study provides a reference for the application of NLU in the test of residual deformation in irregular structures.

Currently, the cold-spray process, or simply cold spray, is an extensively used technique in coating applications. The low temperature of the deposition process is the distinctive feature that makes it suitable for many additive manufacturing activities such as repair and restoration of damaged components. The reliability of the coatings is strongly dependent on the velocity of the powder during its impact on the target surface. Spraying conditions such as the pressure and temperature of the carrier gas and the geometry of the nozzle control the acceleration of the powder particles. Consequently, there is an increasing interest in the optimisation of nozzle geometry so as to maximise the acceleration of the particles through the nozzle path that they follow. In contrast with various extant approaches to achieve this aim (finite element modelling, experimental approach, and analytical methods), an alternative model based on the one-dimensional isentropic theory that accounts for the dynamics of the dilute two-phase flow was developed in this study. First, an analysis of the common hypotheses used to obtain the equation of motion of the particle was carried out. Subsequently, with the new insights revealed from the previous analysis, a new theoretical model for the optimisation of the divergent part of the nozzle was performed considering a geometric angle restriction. This model is based on the numerical integration of the equation of motion of the particle, ensuring the maximisation of the particle drag force by means of the Lagrange multiplier method. Once the analytical model is formulated, a set of curves describing the optimal geometric parameters for different conditions is obtained. Moreover, some optimal geometries are presented demonstrating the low influence of the angle restriction. Additionally, the inversely proportional relationship between stagnation pressure and temperature is revealed.

To explore relationship between the inter-laminar shear properties and the interfacial structure of carbon fiber (CF) reinforced epoxy resin (EP) composite materials (CFRPs), four CFRPs with different interfacial structures were prepared through introducing polar groups on the surface of the CF and then combining the modified CF with the EP, including CF/EP (where no polar group was introduced), CF-COOH-EP (where carboxyl group –COOH was chemically introduced), CF-COOH/MXene /EP (where –COOH was chemically introduced while MXene was physically introduced and the MXene was non-covalently bonded to CF and to EP), and CF-CONH-MXene-EP (where both of –COOH and MXene were chemically introduced and the MXene was covalently bonded to CF and to EP). Results of inter-laminar shear strength (ILSS) of the materials and morphology of transverse and longitudinal cross-sections of the damaged materials show that with enhancing the interfacial interaction between CF and EP, the ILSS increases and the interlayer shear failure gradually changes from a single interface debonding (for CF/EP) to a combination of interface debonding and matrix fragmentation. The interfacial structure of CF-COONH-MXene-EP with higher interfacial interaction could bear more interlayer shear forces, being beneficial for improving the service life of CFRPs.

One of the technological challenges aimed at improving the cyclotron-based radionuclides’(RNs) supply for Nuclear Medicine (NM), is the availability of proper heat sink systems able to remove the large amount of heat deposited during the irradiation stage onto isotope-enriched targets. In this regard, three different non-standard mockup configurations, made of pure copper by means of the Laser Powder Bed Fusion (LBPF) technique, have been tested with an in-house developed experimental apparatus. The experimental characterization has subsequently been compared with numerical results carried out by means of Computational Fluid Dynamics (CFD) simulations. Our numerical model, based on the Re-Normalization Group (RNG) k-epsilon formulation, has shown close agreement (within 1.06 % Mean Absolute Error) with the experimental results, despite the geometrical complexity of the heat sinks prototypes. The combined experimental and numerical approach, together with the flexibility of additive manufacturing production, was proved to be apt for further development of high-efficiency heat exchange applications in this field. ispartof: Materials & Design vol:214 status: Published online

This study mainly focuses on the structural design, acoustic performance prediction, and experimental validation of a novel composite sound absorber that is similar to the feather surface structure of barn owls. The composite sound absorber is composed of an ultra-light nanofibrous membrane backed with a substrate porous materials layer (NMSPM). A theoretical NMSPM model is proposed for predicting the sound absorption coefficient (SAC) of NMSPM. The experimental results demonstrate that the nanofibrous membrane can effectively improve the acoustic performance of substrate porous materials (SPM) based on specific material parameters conditions, which also compare well with the numerical results of the theoretical NMSPM model. The applicability of the theoretical NMSPM model for different sorts of SPMs is explained based on both the experimental and numerical results. A suitable thickness range of nanofibrous membrane for effectively improving the SAC of SPM is given through a series of numerical analyses. This study may provide new thinking for a novel composite sound absorber design without weight sacrifices.

Owing to their lightweight design, high energy absorption capacity, and excellent thermal and sound insulation properties, lattice structures have many potential applications in the fields of security, aerospace, biomedicine, and heat dissipation. In this study, a gyroid-type triply periodic minimal surface is used to design lattice structures. Gyroid uniform lattice structures and gyroid graded lattice structures are mathematically designed and fabricated using selective laser melting with a SS 316 L stainless steel powder. The mechanical properties of these structures are studied under a compression load, and the deformation differences between the graded and uniform structures are compared. The finite element method is used to simulate the compression process, and the experimental and simulation results are qualitatively compared. Results show that during plastic deformation, the stress change in the graded structure is larger than that in the uniform structure. By controlling the volume fraction, mechanical properties can be specifically tailored, which provides the design guidelines for the application of this structure.

This study discusses the effects of hot isostatic pressing (HIP) post-treatment on Laser Powder Bed Fusion of Ti6Al4V and Ti6Al4V reinforced with 1 wt% and 2.5 wt% of nano-yttria-stabilized zirconia (nYSZ). The bulk parts display a higher density after HIP post-treatment than the as-built counterparts. Besides, X-ray diffraction (XRD) analysis indicates a reduction of the β phase percentage after HIP. An increase in α grain thickness is noticed on both reinforced and unreinforced parts. Additionally, compared to their un-HIPed counterparts, the microhardness decreases after HIP post-treatment by 3%, 11%, 8% and 4% for the as-built Ti6Al4V, stress relieved Ti6Al4V, 1 wt% nYSZ reinforced and 2.5 wt% nYSZ reinforced parts, respectively. The same trend was observed for the yield stress, which decreases by 1%, 4% and 8%, for the as-built Ti6Al4V, stress relieved Ti6Al4V and 2.5 wt% nYSZ-reinforced parts respectively after HIP post-treatment, except for 1 wt% nYSZ-reinforced part, whose yield stress increase by about 7%, which could be attributed to the specific texture evolution within this material. The plastic strain was significantly enhanced after HIP in all materials.

SiO2/Cu equipment-friendly infrared interfering agent was built from tetraethoxysilane and flake copper powder through in-situ synthesis reaction. SEM images indicated the encapsulation structure of the samples. FT-IR, XPS and XRD spectra revealed the presence of SiO2 that was coated into the surface and edge of Cu. The shielding performance and the electrical property could be controlled by adjusting the content of SiO2. The infrared transmittance of SiO2/Cu was 23.29% at 1 ∼ 3 μm, 22.92% at 3 ∼ 5 μm and 21.70% at 8 ∼ 14 μm. The mass extinction coefficient was 1.47 m2·g−1 at 1 ∼ 3 μm, 1.48 m2·g−1 at 3 ∼ 5 μm and 1.54 m2·g−1 at 8 ∼ 14 μm, and the resistivity was 1.20 × 1010 Ω·cm at 10 MPa. There was no significant difference found between the shielding performance of Cu and SiO2/Cu. Deposition of SiO2 in this structure supplies high resistivity and excellent shielding performance, and provides highly efficient infrared interfering agent without damaging the basic structure of Cu. This work demonstrates that in-situ synthesis method is a facile and efficient strategy to obtaining optimal shielding performance of SiO2/Cu equipment-friendly infrared interfering agent and met the expectations and synthesis methods from our original material design.

Fused deposition molding (FDM) can complete most complex preparation of drug delivery implants to meet the personalized needs of patients. However, the drug activity has strict requirements on processing temperature and preparation method of filaments, the implant also has strict biocompatibility requirements for the materials. In this study, a drug delivery implant was prepared with good biocompatibility, controlled and efficient drug release using FDM printing for personalized administration. Drug-loaded filaments were developed for FDM process by hot-melt extrusion (HME). Polycaprolactone was used as a drug delivery carrier, and ibuprofen as the model drug. Notably, chitosan was dissolved to form controlled and efficient release channels. The printability, changes in physical and chemical properties during HME and FDM processes of the filament, and drug release behavior, mechanism and biocompatibility of the implants were investigated. The results showed that the filament tensile strength decreased with the increase of drug and chitosan content. No obvious degradation and chemical change occurred during the whole process. The drug release efficiency could reach>99% and lasted for 120 h mainly via the diffusion - erosion mechanism. The viability of cells cultured for 24 h in 72 h, 100% implant extract was 75.3%.

Compared with conventional sandwich structures with two identical face sheets, geometrically asymmetric porous sandwich structures (GAPSSs) can achieve better dynamic performances under certain load and boundary condition, since they provide more choices for geometric design. However, current studies regarding the GAPSSs are mainly analytical- and experimental-based methods with predefined face sheet thicknesses and core configurations, few works investigate the GAPSSs by optimization method. This paper presents a multiscale topology optimization method of the GAPSSs, which is capable of designing both thicknesses of two solid face sheets at macroscale and configurations of porous core at microscale for minimizing dynamic compliance. Specifically, at macroscale, a variable thickness sheet method is employed to optimize the thicknesses of two solid face sheets. Then, at microscale, a parametric level-set method integrated with a numerical homogenization approach is applied to topologically optimize the configuration of the periodic unit cell. The method of moving asymptotes is adopted to update the design variables at both scales. Several 2D and 3D numerical examples are illustrated to show the effectiveness and advantages of the proposed method for designing the GAPSSs. The results indicate that the dynamic compliance of the optimized GAPSSs show superior advantages over the conventional sandwich structures with identical face sheet thicknesses and predefined lattice core.

To fully utilize water, there is a great demand to develop eco-friendly materials with both ultra-high water absorbency and environmental response. In this study, the Al3+ coordinated chitosan (CIS-Al3+) hydrogels were prepared by formation of coordination bonds between Al3+ and the skeleton of CIS hydrogels. AlCl3 was used to provide coordination center, and the formaldehyde aqueous solution was chosen as crosslinker. The effect of Al3+ content and mass fraction of formaldehyde on gel formation, mechanical property and water storage capacity of CIS-Al3+ hydrogels was investigated deeply. The obtained CIS-Al3+ hydrogel can store more than 500% of its own weight of water without cracking, which demonstrates its super-absorbency. Besides, the CIS-Al3+ hydrogels can swell/shrink in response to the change of external stimuli such as temperature, pH and salinity. These outstanding properties, together with the low-cost raw materials, simple preparation method and biocompatible and biodegradable properties, enable CIS-Al3+ hydrogels to be applied as water storage materials in the agriculture field and pH-responsive materials in the future.

Austenitic oxide dispersion strengthened steels were developed to serve as a structural material in power plants. Mechanical alloying is used with the aim to homogeneously distribute rare earth elements like yttrium inside a steel matrix to form strengthening nano-scaled particles. Due to the ductile nature of a face centered cubic austenite matrix, mechanical alloying results in a large amount of cold-welding of powder and the milling equipment, which significantly reduces the production yield and the reproducibility of the process. Here, a novel 2-step mechanical alloying process using nitrogen as a process control agent was developed, resulting in a production yield close to 100 %. Vanadium was added to the steel prealloy to sequester the introduced nitrogen and to promote precipitation of nitride precipitates. Optimizations of process parameters were suggested after characterizing chemical compositions, particle sizes, dislocation densities, crystallite sizes, phase compositions and harnesses. A comparison of X-ray diffraction and scanning electron microscopy results revealed a new approach to define an optimized milling duration. After hot-rolling, a successful dual-precipitate formation of nano-scaled oxides and nitrides, with mean diameters of 3 and 37 nm, respectively, was proven using transmission electron microscopy methods.

The existed synthesis methods for producing high microhardness nanostructured metal materials (NMMs) are usually at the cost of reducing the tensile strength and introducing heterogeneous elements, thus making forming ultrahigh strength ultrapure NMMs significantly challengeable. We unprecedentedly produced ultrapure (99.9997%) nickel deposits simultaneously with an ultrahigh strength and mirror-like surfaces as well as an appreciably high ductility by using our proposed ultrafine anode scanning electrodeposition (UAS-ECD). Distinctively, the UAS-ECD is a speed-dependent localized scanning electrodeposition rather than a commonly-used current-dependent electrodeposition. Therefore, the UAS-ECD can create NMMs at extremely high local current densities and with no additives. This makes it achievable to generate ultrahigh strength ultrapure NMMs with microhardness of 656 HV and tensile strength of 664 MPa (fracture elongation, 8.5%), which are respectively 29% and 30% higher than those reported in the literature. Further surprisingly, the samples’ tensile strength has only an approximately 1% reduction after being annealed. This is attributed to minimum impurities introduction and evenly distributed ultrafine grains formed. In addition, UAS-ECD is able to produce grain-varying deposits just by adjusting the anode’s scanning speed, conveniently achieving 65 wt%-95 wt% nano-& micro-sized grains composite NMMs. This work provides a novel strategy for synthesizing ultrahigh strength ultrapure NMMs.

Wide bandgap semiconductors such as group III-nitrides and SiC are considered as key materials for the fabrication of smaller, more reliable and efficient power electronics. Fabrication of robust and durable power devices requires an optimized design based on the understanding of the interfacial adhesion properties of the constituent thin-film heterostructures. In this study, the adhesion properties of GaN/AlN layers grown on Si substrates were investigated. Particularly, the influence of the AlN buffer layers, necessary for GaN growth on Si, on the delamination response was determined. The interfacial adhesion strength was obtained using cross-sectional nanoindentation (CSN) and four-point bending (4PB) tests. Analytical models based on beam- and elastic plate theory which were applied respectively to calculate the interfacial fracture energy (Gic) for both methods are found to be in good agreement provided the loading conditions are similar. Detailed transmission and scanning electron microscopy investigations prior and subsequent to delamination reveal the microstructural details of the relevant interfaces and provide insights into the encountered mechanisms of interfacial failure. Finally, the probability of delamination along the weakest interface is discussed based on a fracture mechanics model.

The shear thickening fluid (STF) with unique rheology is generally combined with polyurethane (PU) skeleton to manufacture flexible sandwich composites which is widely applied in impact resistence field. In this work, experiments and numerical simulations were comparatively analyzed to investigate the non-Newtonian fluid–solid interaction (NFSI) between STF and PU skeleton during low-velocity impact. Optimization of materials selection is proposed to achieve a higher impact resistance performance. It has been found that the synchronous gradient thickening and flow of STF facilitate the load-bearing and stress diffusion performance. In contrast to Newtonian fluids, the internal STF displays both shear resistence of high-viscosity fluid and easy flow characteristic of low-viscosity fluid, creating areas of low stress in composites and improve the impact resistance performance. The fluid-optimized STF-2 sandwich composite exhibits an up to 154.7% lower peak load and 118.82% higher energy absorption. In terms of the skeleton, a lower modulus of PU foam is conductive to a stronger NFSI, which facilitates the energy exchange between STF and skeleton and further improve the impact resistance performance. As a result, the skeleton-optimized composite containing PU-1 exhibits a 20.10% lower peak load and 17.41% higher energy absorption. The NFSI mechanism and material selection optimization between non-Newtonian fluid and large deformation materials proposed in this work provide an analysis idea and design method for flexible buffering composites.

This study describes the application of a new technological parameter in the alternating-current (AC) electrospinning process for enhancing the electrospinnability and productivity of polycaprolactone (PCL) electrospun nanofibers (ENF). High-voltage AC is influenced via changes in both the waveform and the frequency; however, the overall contribution to PCL electrospinnability remains unclear. This study hypothesizes that the electrospinnability, morphology, diameter and productivity of PCL ENF are dependent on both the waveform and the frequency of the AC high-voltage signal. Thus, the paper demonstrates that both the waveform and the frequency significantly affect the formation of a stable fibrous plume and the PCL ENF morphology. Consequently, trimodal- (beads, spindles and helical), bimodal- (beads and spindles) and unimodal-structured ENF morphologies were attained for square, sine and triangle waveforms, respectively. Moreover, the frequency of the waveform directly influences the number of beads and/or spindles per unitary length. The square waveform reflects higher productivity (23.6 ± 0.4 g/h) than the sine (16.5 ± 0.3 g/h) and triangle waveforms (6.9 ± 0.2 g/h). This study presents a simple approach to the industrial-scale fabrication of PCL ENF via the tuning of the AC high-voltage signal shape and/or frequency with the added advantage of the potential for obtaining a range of PCL ENF morphologies.

We introduce a novel computational framework designed to allow an experimentalist to extract the local toughness associated with crack growth along an individual grain boundary from fracture experiments on standard specimens. The proposed framework relies on the ability of a graph neural network to perform high accuracy predictions of the micro-scale material toughness, utilizing a limited size dataset that can be obtained from standard fracture experiments. We analyze the functionality of the different components of the framework, focusing on the minimum size of the dataset required for the network training following an initial training cycle on a synthetic dataset. We demonstrate the high efficiency of the algorithm in accurately predicting the local (>68%) and global (>95%) crack growth toughness in scenarios where the toughness dependence on the microstructural parameters is substantially different than the one used for the synthetic dataset. The merit of the proposed framework arises from its flexibility: it is not limited to a specific mathematical description of the toughness at the micro-scale and simplicity: the required experiments are rather standard. As such, the proposed framework enables the study of a wide range of material microstructure properties and the investigation of their influence on the material toughness.

Mass reduction is a main issue in mechanical design. Over millions of years, Nature had to face this issue. Nature came up with an efficient solution using a stress-driven structure to reduce the mass of bones while saving their mechanical performances. This optimized structure is used in several species and persists throughout Evolution. Thus, it may be considered as optimal for this issue. In this article, a method bio-inspired from both bone medullar cavity and trabecular structure is proposed to reduce the mass of parts subjected to mechanical stresses. The objective of this method is to provide high mass reduction, just like bone does. First, the method removes iteratively unloaded areas of material from the mechanical part to mimic the medullar cavity structure. Second, a final mass reduction is done integrating small holes bio-inspired from trabecular structure in the remaining material. An experimental validation was carried out on a torsion disc and provided a 60% mass reduction. Using this mass reduction rate, the topology optimization method was used to define a standard geometry to evaluate the mechanical performances of the proposed method. Experimental results highlight that regarding torsional stiffness, the bio-inspired part is 27% stiffer than the standard one. (c) 2021 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Post-build rolling can mitigate residual stress (RS) and distortion in large-scale components built by wire arc additive manufacturing (WAAM). In this study, based on numerical simulations that considered both WAAM deposition and vertical rolling, the mechanisms of rolling-enabled mitigation of RS and distortion in a WAAM-built steel wall are elucidated. The influences of process configuration and condition, such as roller design (flat, profiled and slotted rollers), rolling load (25–75 kN) and roller-to-wall friction coefficient (0–0.8) on the distributions of plastic strain (PS) and RS were investigated. It is found that the slotted roller is most effective to introduce tensile PS for counteracting the compressive PS generated by the WAAM deposition, thereby reducing the tensile RS in the clamped condition and the final distortion after removal of clamps. Higher rolling load increases the rolling-induced tensile PS, which leads to more extensive mitigation of the WAAM-generated tensile RS. The simulations also demonstrate that the friction coefficient significantly affects the PS and RS when the slotted roller is employed. However, the efficacy of the flat/profiled roller is insensitive to friction coefficient. This study could underpin the development of an optimal post-build rolling process for efficient mitigation of RS and distortion in WAAM components.

Owing to the relatively lower dimensional accuracy and poorer surface finish compared to other additive manufacturing (AM) technologies, directed energy deposition (DED) yields parts that often require extensive post-processing. Thus, it is well suited to be combined with subtractive or deformation processes into hybrid manufacturing strategies, which may enable microstructure engineering of near-net-shape parts directly upon production. In this work, we use a custom-made machine that combines DED and single point incremental forming (SPIF) processes to produce samples of stainless steel 316L which are amenable to undergo recrystallization upon heat treatment. After recrystallization, the microstructure exhibits a high density of twin boundaries, which are known to enhance the physical and mechanical properties of alloys. We investigate how different SPIF parameters affect the extent of recrystallization and find that our strategy may be used to produce both gradient and “sandwich” microstructures, which integrate dissimilar grain boundary character distributions and grain structures. We assess the corrosion resistance and mechanical properties of such samples and discuss the resulting performance enhancement. Our results showcase new opportunities for microstructure engineering of DED components and lay the groundwork for the design of AM processes that enable grain boundary engineering of metal alloys. National Research Foundation (NRF) Published version This work was supported by the National Research Foundation (NRF) Singapore, under the NRF Fellowship programme (NRF-NRFF2018-05).

Structural health monitoring of composite structures from manufacturing to operation is receiving significant attention to ensure their performance and safety. In this paper, capacitive sensor arrays were designed and embedded between adhesively bonded composite laminates for curing quality monitoring during manufacturing and loading detection in operation. A loading inversion method was proposed to quantitatively determine the loading location and value on composite structure. The results showed that the whole curing process of adhesive bonding was successfully monitored. Based on capacitance monitoring, the embedded sensors can capture poor curing quality of adhesively bonded composite laminates due to abnormal curing conditions. The embedded sensors between composite laminates after curing showed perception of external loading. With the evenly distributed sensing capacitors, loading applications on composite laminates were detected. Based on the proposed loading inversion method, loading distribution mapping on the composite laminates was constructed, and the quantitative calculation of the coordinate location and value of loading was achieved. The calculated results agreed well with the actual loading in experiments, affirming the feasibility of the capacitive sensor array and the loading inversion method.

With the rapid development of the marine industry, biofouling and surface corrosion of underwater equipment have become a major issue. Traditional antifouling or anticorrosion coatings with a single function cannot meet the current requirements. Recent developments in materials science and synthesis techniques have brought new opportunities and challenges in the field of integrated antifouling and anticorrosion coatings (IAACs). In this review, the mechanisms of biofouling and corrosion are introduced to help readers understand how their negative impact can be mitigated. Most of the IAACs are designed by combining antifouling and anticorrosion units into one coating, while several IAACs disobey the mentioned design principle since they have inherent antifouling and anticorrosion functions. This review highlights the recently developed IAACs, including polyaniline-based coatings, copper/amorphous carbon coatings, polydopamine/polymer brushes, amphiphilic polymers, endospore-loaded sol–gel coatings, hydrophobic/corrosion inhibitor coatings, nanocomposites, and bioinspired coatings. These emerging IAACs have been introduced in the last decade and may not yet be mature in practical applications and commercialization; therefore, their advantages and disadvantages are discussed. Finally, the future development of IAACs is discussed. We expect that this review will not only help readers understand the design principle of IAACs but also contribute to their development.

Iron oxide (maghemite and magnetite) nanoparticles are the most commonly used magnetic materials in nanomedicine because of their high biocompatibility. However, their low saturation magnetization (60���90 emu/g) limits their applicability. Here, we report a new core���shell (Fe@Fe$_x$O$_y$) nanoring system, which combines the high magnetic saturation of a metallic iron core (220 emu/g) and the biocompatibility of an iron oxide shell. To produce these nanostructures, hematite (��-Fe$_2$O$_3$) nanorings were annealed in a H$_2$ gas atmosphere for different periods to optimize the amount of metallic iron percentage (��) in the system. Thus, nanostructures with different magnetic saturation (97 to 178 emu/g) could be obtained; based on their metallic iron content, these particles are labeled as Vortex Iron oxide Particle �� (VIP��). Micromagnetic simulations confirmed that the VIP�� nanorings exhibit a vortex configuration, guaranteeing low remanence and coercitivity. Moreover, the system shows good biocompatibility in various assays as determined through cell viability measurements performed using two different human cell lines, which were exposed to VIP78% for 24 h. Therefore, VIP�� nanorings combine a magnetic vortex state and biocompatibility with their high magnetic saturation and can thus serve as a platform that can be tuned during the synthesis based on desired biomedical application.