Interstitial Alloys Research Articles

2D Amorphous Mo‐Doped CoB for Bidirectional Sulfur Catalysis in Lithium Sulfur Batteries

AbstractThe amorphous metal boride materials are attractive catalyst for advanced lithium sulfur batteries, but their catalytic mechanism remains unclear. Herein, 2D amorphous Mo‐doped cobalt boride (Co7Mo3B) is designed for the first time as bidirectional sulfur catalysis by rapid chemical reduction. The atom cluster structure of Co7Mo3B is revealed by theoretical calculation. Electron paramagnetic resonance test further confirms that Co7Mo3B has interstitial compound structure characteristics. Experimental results show that the porous 2D nanosheets structure and the interaction of Mo, B, Co atoms contribute to enhanced conductivity, high long‐chain lithium polysulfides affinity, and reversible Li2S nucleation and dissociation, thus accelerating LiPSs reduction and Li2S oxidation kinetics. In addition, the interstitial Co7Mo3B enables intercalation of Li and B during charging–discharging while keeping the structure stable. As a result, the S cathode with Co7Mo3B catalyst delivers good life (1000 cycles at 5 C), superior rate performance (10 C). Even at high sulfur areal loading of 6.79 mg cm–2 and electrolyte/sulfur ratio of 5 μL mg–1, the Co7Mo3B/S composite cathode still exhibits good areal capacity and capacity retention rate.

The determining role of carbon addition on mechanical performance of a non-equiatomic high-entropy alloy

• The role of C on the microstructure and mechanical properties are discussed. • The microstructure of the tensile specimen interrupted at different tensile strains are examined by EBSD and TEM. The deformation mechanism of a C-doped iHEA with excellent mechanical properties is discussed. • The contributions of different strengthening mechanism to yield strength are calculated and the comprehensive strengthening mechanism is discussed. The mechanical properties and deformation mechanism of a C-doped interstitial high-entropy alloy (iHEA) with a nominal composition of Fe 49.5 Mn 29.7 Co 9.9 Cr 9.9 C 1 (at.%) were investigated. An excellent combination of strength and ductility was obtained by cold rolling and annealing. The structure of the alloy is consisted of FCC matrix and randomly distributed Cr 23 C 6 . For gaining a better understanding of deformation mechanism, EBSD and TEM were conducted to characterize the microstructure of tensile specimens interrupted at different strains. At low strain (2%), deformation is dominated by dislocations and their partial slip. With the strain increase to 20%, deformation-driven athermal phase transformation and dislocations slip are the main deformation mechanism. While at high strain of 35% before necking, deformation twins have been observed besides the HCP phase. The simultaneous effect of phase transformation (TRIP effect) and mechanical twins (TWIP effect) delay the shrinkage, and improve the tensile strength and plasticity. What's more, compared with the HEA without C addition, the yield strength of the C-doped iHEA has been improved, which can be attributed to the grain refinement strengthening and precipitation hardening. Together with the lattice friction and solid solution strengthening, the theoretical calculated values of yield strength match well with the experimental results.

SỰ KHUẾCH TÁN TRONG CÁC KIM LOẠI Au, Cu VÀ CÁC HỢP KIM XEN KẼ AuSi, CuSi

The paper performs numerically the vacancy activation volume, the activation energy, the pre-exponential factor, and the diffusion coefficient for metals Au, Cu, and alloys AuSi, CuSi in the interval of the concentration of interstitial atoms from zero to 4%, in the interval of temperature from 700 to 1873 K, in the interval of pressure from zero to 180 GPa and the interval of strain from zero to 5%. The paper determines the dependence of the diffusion coefficient on pressure and stress for above mentioned metals and alloys. SMM numerical results show that the Arrhenius law is satisfied for metals and interstitial alloys at different pressures and concentrations of interstitial atoms. SMM numerical results for Au at T = 1000 K and T = 1250 K and at zero pressure are in good agreement with experiments for the activation energy (errors are below 10%) and agree in terms of magnitude for the pre-exponential factor and the diffusion coefficient. SMM numerical results of the diffusion coefficient for Au in the interval of temperature from 977 to 1321 K and for Cu in the interval of temperature from 933.95 to 1336.15 K are compared with experiments and other calculations and there are rather good agreement in terms of magnitude. SMM numerical results of the activation volume of Au and Cu agree well with other calculations. SMM numerical results for diffusion quantities of interstitial alloys AuSi, CuSi in different temperatures, pressures, stresses, and concentrations of interstitial atoms anticipate and orient experiments in the future.

BIẾN DẠNG ĐÀN HỒI VÀ VẬN TỐC SÓNG ĐÀN HỒI CỦA CÁC HỢP KIM TAM NGUYÊN FeCrSi VÀ AuCuSi

The paper uses the model of cubic ternary substitutional and interstitial alloy and conditions in which the interstitial atom concentration is very small compared to the substitutional atom concentration, the substitutional atom concentration is very small compared to the main metal atom concentration. On that basis together with the elastic wave and the elastic deformation theory of this alloy obtained by the statistical moment method, we perform numerical calculations for temperature, pressure, the concentration of substitutional atoms, and concentration of interstitial atoms dependences of the elastic moduli E, K, G, the elastic constants C11, C12, C44, the longitudinal wave velocity Vd and the transverse wave velocity Vn of alloys FeCrSi and AuCuSi. Numerical results for FeCrSi and AuCuSi are compared with that of Fe, FeCr, FeSi, Au, AuCu, AuSi, and other calculations, and experiments. Numerical results for ternary alloys predict experimental results in the future.

Massive interstitial solid solution alloys achieve near-theoretical strength

Interstitials, e.g., C, N, and O, are attractive alloying elements as small atoms on interstitial sites create strong lattice distortions and hence substantially strengthen metals. However, brittle ceramics such as oxides and carbides usually form, instead of solid solutions, when the interstitial content exceeds a critical yet low value (e.g., 2 at.%). Here we introduce a class of massive interstitial solid solution (MISS) alloys by using a highly distorted substitutional host lattice, which enables solution of massive amounts of interstitials as an additional principal element class, without forming ceramic phases. For a TiNbZr-O-C-N MISS model system, the content of interstitial O reaches 12 at.%, with no oxides formed. The alloy reveals an ultrahigh compressive yield strength of 4.2 GPa, approaching the theoretical limit, and large deformability (65% strain) at ambient temperature, without localized shear deformation. The MISS concept thus offers a new avenue in the development of metallic materials with excellent mechanical properties.

Characterization of deformation substructure evolution in metastable Fe49Mn30Co10Cr10B1 interstitial high entropy alloy

Interstitial alloying has been utilized to overcome the strength-ductility trade-off in high entropy alloys (HEAs). In this work, boron-doping in a typical metastable FeMnCoCr HEA is chosen to investigate deformation substructure evolution by using electron backscatter diffraction and high-angle annular dark field scanning transmission electron microscopy, to understand how interstitial atoms tune the deformation modes. Boron-doping facilitates the formation of Cr2B particles, which can effectively decrease the grain size and retard the thermal-induced ε phase. Under the initial deformation (10% rolling reduction), the coexistence of dislocations slip in γ phase and of {10 1‾ 2} twins in ε phase is the dominant deformation modes. With the increasing strain (20% rolling reduction), the interaction of ε lamellas is significantly strengthened, which is favor of the formation of intersecting ε products. The occurring of intrinsic stacking faults in γ phase act as the nucleation sites for ε phase. Moreover, two types of dislocations (1/2<a+c> and <a>) are revealed in ε phase. At the ultimate deformation stage (40% rolling reduction), due to the saturation of γ → ε transformation, the coexistence of dislocations slip and twins ({10 1‾ 1} and {101‾ 3}) in ε phase can further accommodate strain, and the saturated ε phase is dominated by one persisting ε variant. Accordingly, the differences in deformation substructures of metastable FeMnCoCr HEA with or without B-doping are intrinsically arising from boron interstitial alloying effect.

Microstructure and wear behavior of laser clad interstitial CoCrFeNi high entropy alloy coating reinforced by carbon nanotubes

In this study, the effect and characteristics of the laser clad interstitial CoCrFeNi high entropy alloy coating reinforced with carbon nanotubes (CNTs) was investigated. 1.0 wt% of CNTs were added as the reinforcement. To prepare composite powders before cladding, the CNTs and pre-alloyed CoCrFeNi powders were mechanically mixed without ball milling treatment. As a result, the microstructure of the CNTs on powder surface was well protected from serious damage. The effects of the CNTs upon the microstructure and wear behavior of the produced interstitial CoCrFeNi-CNTs coating were evaluated. The results showed that the intergranular (Fe, Cr)7C3/α eutectics were found to fully precipitate in the clad CoCrFeNi-CNTs coating. The hardness of the CoCrFeNi-CNTs coating was enhanced by 42.2% compared with that of the CoCrFeNi coating. The wear property was positively correlated with the hardness. The wear rate of the CoCrFeNi-CNTs coating (2.18 × 10−5 mm3·N−1·m−1) was significantly lower than that of the CoCrFeNi coating (10.54 × 10−5 mm3·N−1·m−1). The enhancements of the wear property originated from the solution strengthening of carbon on grains and the precipitation strengthening of (Fe, Cr)7C3 carbides on grain boundaries. In wear process, the lamellar (Fe, Cr)7C3/α eutectics deposited on worn surface and eventually formed a carbide hardening layer structure and prevent severe wear on the CoCrFeNi-CNTs coating.

Effects of thermal aging on mechanical properties and microstructures of an interstitial high entropy alloy with ultrasonic surface mechanical attrition treatment

In this work, indentation tests have been carried out on the surface of an interstitial high-entropy alloy, which is treated with ultrasonic surface mechanical attrition treatment and thermal aging treatment at 400 °C. We present and discuss these two treatments on the mechanical behavior of the material by using flat indentation method. Meanwhile, changes in its microscopic morphology, grain size, phase structure, etc. are investigated using X-ray diffraction, electron backscatter diffraction, etc. and its microstructure evolution mechanism under the long-term high temperature condition is revealed. Flat indentation tests and microstructural investigations reveal that the mechanical behavior of interstitial high entropy alloy is significantly affected by surface mechanical attrition treatment and thermal aging time. The gradient refined and strengthened surface layers are demonstrated to appreciably upgrade the mechanical performance of interstitial high entropy alloy, while thermal aging treatment will lead to a reduction of mechanical performance and a phase transformation.

Study on thermodynamic and elastic properties of B2-FeSi by statistical moment method

The thermodynamic and elastic theory of B2 substitutional alloy AB and B2 interstitial alloy AB under temperature and pressure are derived by the statistical moment method. In the case of zero concentration of substitutional atoms B and interstitial atoms B, we obtain the thermodynamic and elastic theory of main metal A with simple cubic structure. Our numerical calculations according to the model of interstitial alloy for B2-Fe99Si1 and the model of substitutional alloy for B2-Fe50Si50 in the temperature interval from zero to 1500 K and the pressure interval from zero to 160 GPa are in relatively good with experiments and other calculations.

Neutron diffraction study of the Ti1-xMoxC alloy

In this work, the crystal structure and (RMSD) root-mean-square displacement of atoms in new cubic refractory interstitial alloys Ti0.74Mo0.26C and Ti0.70Mo0.30C were determined by neutron diffraction. These alloys are obtained by powder metallurgy by sintering fine powders of cubic titanium carbides TiC and molybdenum MoC. The values of the RMSD of atoms in these alloys, obtained by the methods of least squares and full-profile analysis from the neutron diffraction data, turned out to be identical. They turned out to be much larger than in the stoichiometric TiC alloy, which has a similar cubic structure and close geometric parameters of atoms with the Ti0.74Mo0.26C and Ti0.70Mo0.30C alloys. These alloys were explained by the occurrence of large static distortions in the lattice of the Ti0.70Mo0.30C alloy due to the differences in the masses and atomic radii of the titanium and molybdenum elements.

Nitridation of Cr–urea complex into nanocrystalline CrN and its antiferromagnetic magnetostructural transition study

An antiferromagnetic nanocrystalline CrN interstitial compound was prepared using Cr(NO3)3·9H2O and urea as starting materials.

Strengthening by customizing microstructural complexity in nitrogen interstitial CoCrFeMnNi high-entropy alloys

Interstitial alloying has been proved to be a promising option to improve the mechanical properties in various commercial alloys. Herein, we systematically investigate the microstructure evolution and mechanical property change of CoCrFeMnNi high-entropy alloys (HEAs) with varied nitrogen contents as an interstitial alloying element. To equilibrate the thermal history, all the alloys are heat-treated as follows: homogenization (1100 ℃ for 20 h), cold-rolling (reduction ratio of 60%), and subsequent annealing (900 ℃ for 3 min). In N1 alloy (CoCrFeMnNi HEA with 1 at% of nitrogen doping), we could observe fully recrystallized grains with a small amount of Cr2N precipitates. As the nitrogen contents increased to 3 at% (N3 alloy), the recrystallization was significantly retarded by the formation of 3 different types of Cr2N precipitates, leading to having ~60% of non-recrystallized grains. Furthermore, the various precipitates let the alloy have a heterogeneous complex microstructure. With increasing nitrogen contents, the yield strength and ultimate tensile strength can be improved without significant reduction of ductility, which exceeds those of Cantor HEA by nearly a factor of two. The effect of each strengthening mechanism on the improved strength in heterogeneous complex microstructure is systematically discussed. These results are expected to provide a novel guideline on how to effectively control key properties of HEAs by interstitial alloying through tailoring of heterogeneous microstructure as well as the inherent complexity of HEAs.

Temperature effect on tensile behavior of an interstitial high entropy alloy: Crystal plasticity modeling

Previous tensile tests showed that the typical coarse-grained (CG) interstitial high entropy alloy (iHEA) with the nominal composition Fe49.5Mn30Co10Cr10C0.5 (at.%) has higher yield stress and better strain hardening at cryogenic conditions compared to that at room temperature. However, the yield stress of the fine-grained (FG) iHEA is little influenced by decreasing temperature, while the strain hardening is significantly enhanced. The fundamental reasons for these observations need to be further investigated. Thus, a micromechanism-based crystal plasticity model is developed to investigate the temperature effect on the tensile behavior of the iHEA. A thermodynamic model is established to calculate the stacking fault energy of the iHEA at different temperatures. The developed constitutive model is verified by comparing the simulated the stress-strain curves and martensite volume fraction of the CG and FG iHEAs at different temperatures with the corresponding experimental results. Moreover, the contributions of different strengthening mechanisms, such as dislocations, grain boundaries, nano-precipitation, and lattice friction, are quantified to reveal the effect of temperature on the iHEA's yield stress. Furthermore, the grain size effects on deformation twinning and martensite phase transformation are considered. The developed constitutive model is further applied to predict the stress-strain curves of the iHEA with various grain sizes at different temperatures. The present study thus provides a useful modeling tool for understanding the underlying mechanisms of the strength and plasticity in the iHEA, paving a way for optimizing the mechanical properties of advanced alloys at various temperatures.

In Situ Grown Co-Based Interstitial Compounds: Non-3d Metal and Non-Metal Dual Modulation Boosts Alkaline and Acidic Hydrogen Electrocatalysis.

Interfacial engineering and elemental doping are the two parameters to enhance the catalytic behavior of cobalt nitrides for the alkaline hydrogen evolution reaction (HER). However, simultaneously combining these two parameters to improve the HER catalytic properties of cobalt nitrides in alkaline media is rarely reported and also remains challenging in acidic media. Herein, it is demonstrated that high-valence non-3d metal and non-metal integration can simultaneously achieve Co-based nitride/oxide interstitial compound phase boundaries on stainless steel mesh (denoted Mo-Co5.47 N/N-CoO) for efficient HER in alkaline and acidic media. Density functional theory (DFT) calculations show that the unique structure does not only realize multi-active sites, enhanced water dissociation kinetics, and low hydrogen adsorption free energy in alkaline media, but also enhances the positive charge density of hydrogen ions (H+ ) to effectively allow H+ to receive electrons from the catalysts surface toward promoting the HER in acidic media. As a result, the as-prepared Mo-Co5.47 N/N-CoO demands HER overpotential of -28mV@10mAcm-2 in an alkaline medium, and superior to the commercial Pt/C at a current density >44mAcm-2 in acidic medium. This work paves a useful strategy to design efficient cobalt-based electrocatalysts for HER and beyond.

Correction to: Extreme Expansion and Reversible Hydrogen Solubility in h.c.p. Titanium Stabilized by Colossal Interstitial Alloying

Correction to: Extreme Expansion and Reversible Hydrogen Solubility in h.c.p. Titanium Stabilized by Colossal Interstitial Alloying

In-situ interstitial alloying during laser powder bed fusion of AISI 316 for superior corrosion resistance

• L-PBF of a 316L admixed with 2.5 wt% Cr 2 N enhanced the Cr and N contents as compared to 316L. • A nitrogen content of 0.31 wt% in solid solution was obtained. • The parts were fully austenitic, exhibiting the favorable cellular substructure. • The enhanced nitrogen content improved corrosion resistance and hardness as compared to 316L. • The results show an alternative to manufacturing of high nitrogen steels. The present work explores for the first time additive manufacturing of powder mixtures consisting of Chromium Nitride (Cr 2 N) and AISI 316L with laser powder bed fusion (L-PBF). The addition of 2.5 wt% Cr 2 N to an AISI 316L powder resulted in the successful dissolution of both chromium and nitrogen into a fully austenitic stainless steel microstructure. The nitrogen content was augmented from 0.09 wt% in the as-delivered AISI 316L powder to 0.31 wt% in the L-PBF built part, causing a slight expansion of the austenite lattice. Elongated austenite grains with an internal cellular substructure were obtained in both the Cr 2 N modified 316L and the 316L specimens manufactured by L-PBF. The addition of nitrogen (and chromium) from Cr 2 N resulted in a Vickers hardness increase of about 40 HV 0.1 , mainly by interstitial solid solution strengthening. The modification of 316L by the addition of Cr 2 N significantly improved the corrosion resistance. The improved hardness and corrosion resistance while retaining the manufacturability and cellular microstructure illustrate the potential for modifying the composition and properties of L-PBF 316L with targeted dosing with Cr 2 N powders.

Enhancements in the Bonding Properties of a Friction Stir Lap-Welded Interstitial Free Steel and Al Alloy by Introducing a Ni Interlayer

A pure Ni interlayer with a thickness of 0.1 mm was introduced between high-strength interstitial free steel and Al–Mg–Si alloy, which were friction stir lap welded, producing an excellent welded joint. The interface layer consisted of a γ-Ni solid solution, and the mixed stirring zone contained alternate lamellae of γ-Ni and α-Fe solid solutions. The addition of a Ni interlayer strongly suppressed the reaction between Al and Fe because of the atomic arrangement of Ni. Furthermore, the insertion depth of the stirring pin has a significant influence on the Al/steel interfacial reaction. Under shallow insertion depth, the intermetallic compounds of both FeAl and Fe2Al5 were observed at the interface layer. A maximum tensile-shear fracture load of 4.3 kN was achieved, with fractures being present in the steel substrate far away from the Al/steel weld.

Custom-Made Titanium Mesh Tray for Mandibular Reconstruction Using an Electron Beam Melting System.

Mandibular reconstruction using a titanium mesh tray and autologous bone is a common procedure in oral and maxillofacial surgery. However, there can be material problems—such as broken titanium mesh trays—which may undermine long-term functionality. This study was designed to investigate the optimal conditions for a titanium mesh tray with an ideal mandibular shape and sufficient strength, using computer-aided design, computer-aided manufacturing technology, and electron beam additive manufacturing. Specimens were prepared using Ti-6Al-4V extra low interstitial titanium alloy powder and an electron beam melting (EBM) system. The mechanical strength of the plate-shaped specimens was examined for differences in the stretch direction with respect to the stacking direction and the presence or absence of surface treatment. While evaluating the mechanical strength of the tray-shaped specimens, the topology was optimized and specimens with a honeycomb structure were also verified. Excellent mechanical strength was observed under the condition that the specimen was stretched vertically in the stacking direction and the surface was treated. The results of the tray-shaped specimens indicated that the thickness was 1.2 mm, the weight reduction rate was 20%, and the addition of a honeycomb structure could withstand an assumed bite force of 2000 N. This study suggests that the EBM system could be a useful technique for preparing custom-made titanium mesh trays of sufficient strength for mandibular reconstruction by arranging various manufacturing conditions.

Mechanical Behavior Assessment of Ti-6Al-4V ELI Alloy Produced by Laser Powder Bed Fusion

The present work correlates the quasi-static, tensile mechanical properties of additively manufactured Ti-6Al-4V extra low interstitial (ELI, Grade 23) alloy to the phase constituents, microstructure, and fracture surface characteristics that changed with post-heat treatment of stress relief (670 °C for 5 h) and hot isostatic pressing (HIP with 100 MPa at 920 °C for 2 h under an Ar atmosphere). Ti-6Al-4V ELI alloy tensile specimens in both the horizontal (i.e., X and Y) and vertical (Z) directions were produced by the laser powder bed fusion (LPBF) technique. Higher yield strength (1141 MPa), higher tensile strength (1190 MPa), but lower elongation at fracture (6.9%), along with mechanical anisotropy were observed for as-stress-relieved (ASR) samples. However, after HIP, consistent and isotropic mechanical behaviors were observed with a slight reduction in yield strength (928 MPa) and tensile strength (1003 MPa), but with a significant improvement in elongation at fracture (16.1%). Phase constituents of acicular α′ phase in ASR and lamellar α + β phases in HIP samples were observed and quantified to corroborate the reduction in strength and increase in ductility. The anisotropic variation in elongation at fracture observed for the ASR samples, particularly built in the build (Z) direction, was related to the presence of “keyhole” porosity.

Synergistically enhanced thermoelectric properties of Bi2S3 bulk materials via Cu interstitial doping and BiCl3 alloying

Synergistically enhanced thermoelectric properties of Bi2S3 bulk materials via Cu interstitial doping and BiCl3 alloying