Increasing Ni Content Research Articles

Reversible Configurations of 3-Coordinate and 4-Coordinate Boron Stabilize Ultrahigh-Ni Cathodes with Superior Cycling Stability for Practical Li-Ion Batteries.

Ultrahigh-Ni layered oxide cathodes are the leading candidate for next-generation high-energy Li-ion batteries owing to their cost-effectiveness and ultrahigh capacity. However, the increased Ni content causes larger volume variations and worse lattice oxygen stability during cycling, resulting in capacity attenuation and kinetics hysteresis. Herein, a Li2SiO3-coated Li(Ni0.95Co0.04Mn0.01)0.99B0.01O2 ultrahigh-Ni cathode that well-addresses all the above issues, which is also the first time to realize the real doping of B ions is demonstrated. The as-obtained cathode delivers a reversible capacity of up to 237.4 mAh g-1 (924 Wh kg-1 cathode) and a superior capacity retention of 84.2% after 500 cycles at 1C in pouch-type full-cells. Advanced characterizations and calculations verify that the boron-doping is existed in terms of 3-coordinate and 4-coordinate configurations and their high electrochemical reversibility during de-/lithiation, which greatly stabilizes oxygen anions and impedes Ni-ion migration to Li layer. Furthermore, the B-doping engineers the primary particle microstructure for better relaxing the lattice strain and accelerating Li-ion diffusion. This work advances the energy density of cathode materials into the domain of above 900 Wh kg-1, and the concept will inspire more intensive study on ultrahigh-Ni cathodes.

Effects of nickel substitution on structural, magnetic and optical properties of Sillenite bismuth ferrite nanoparticles

The Ni-doped Bi25FeO40 nanoparticles [Bi25 NixFe(1-x)O40, x = 0.1, 0.3, and 0.5] were synthesized by the hydrothermal method at a temperature of 180 °C. The effects of the Ni substitute on the structural, optical, magnetic, and photocatalytic performance have been investigated. The successful synthesis of the materials was confirmed by Rietveld's refined powder X-ray diffraction and Fourier transform infrared spectroscopy. Scanning electron microscopy together with energy dispersive X-ray spectroscopy (EDS) revealed the morphology of the synthesized nanomaterials as well as its chemical composition. The studied materials exhibited anomalous magnetic properties as evident from the vibrating sample magnetometry (VSM) analysis. These features display a weak ferromagnetic nature and demonstrate increased magnetization when doping elements are incorporated. Furthermore, Optical analysis revealed that bandgaps of Bi25NixFe(1-x)O40 were found to be increased from 2.06 eV to 2.31 eV with increasing Ni content. Additionally, the expansion of sillenite bismuth nickel ferrite's optical bandgap was further confirmed by the photocatalytic degradation of methylene blue as a model dye under the low-power white LED illumination. Lower bandgap undoped nanoparticles showed the highest photocatalytic efficiency, with a degradation rate of ∼43.11 % compared to higher bandgap doped nanoparticles, without adjustment of any reaction conditions such as pH or catalyst amount. The kinetic reaction rate of undoped Bi25FeO40 was roughly twice as fast as that of the material doped with 50 % Ni.

Effect of charge-discharge with higher capacitance performance of Ni-substituted CoFe2O4 magnetic nanoparticles for energy storage

In this work, we synthesized NixCo1-xFe2O4 (0 ≤ x ≤ 0.8) magnetic nanoparticles (MNPs) by using ultrasonication-assisted reverse chemical co-precipitation method. The X-ray diffraction (XRD) patterns confirm the single-phase with mixed spinel structure of the NixCo1-xFe2O4 (0 ≤ x ≤ 0.8) MNPs with the crystallite size range between 12 nm - 17 nm. The molecular dynamics and oleic acid coated Ni-substituted CoFe2O4 magnetic nanoparticles were confirmed by FTIR measurements. The surface composition of NixCo1-xFe2O4 (0 ≤ x ≤ 0.8) MNPs (Ni, Co, Fe and O) and their oxidation states were estimated using X-ray photoelectron spectroscopy. The NixCo1-xFe2O4 (0 ≤ x ≤ 0.8) MNPs are spherical in shape and polycrystalline in nature, confirmed by FESEM and HRTEM measurements. The Ni-substituted CoFe2O4 MNPs with higher zeta potential (ζ) from −24 mV to -41 mV with an increase in Ni concentration, signifies the stable colloidal stability due to the electrostatic repulsion between MNPs. The DC magnetization (M-vs-H) measurements reveal the ferrimagnetic behavior of NixCo1-xFe2O4 (0 ≤ x ≤ 0.8) MNPs, which suppress the saturation magnetization (MS) from 48.6 emu/g to 5.3 emu/g with the enhanced coercivity (HC) from 335 Oe to 1700 Oe with the substitution of Ni2+ ions is in corroboration with electron paramagnetic resonance (EPR) measurements. The enhanced EPR resonance field (Hres = 2335 Oe - 3261 Oe) with the substitution of Ni2+ ions is attributed to the generation of oxygen vacancies and defects, which are predominant in Ni0.8Co0.2Fe2O4, resulting in significantly enhanced electrochemical performance. Therefore, the three-electrode system was utilized to investigate the electrochemical properties of NixCo1-xFe2O4 (0 ≤ x ≤ 0.8) MNPs. The Ni-substituted CoFe2O4 MNPs have demonstrated significantly enhanced capacity retention of 77 % even after 5000 cycles in 1 M H2SO4 electrolyte solution. NixCo1-xFe2O4 (0 ≤ x ≤ 0.8) MNPs exhibit an excellent specific capacity (Cs) of 794.5 F/g at a current density of 1 A/g, signifies the rate of redox reaction at surface electrolyte interface (SEI) is greatly influenced by the surface to volume ratio. Thus, with the enhancement of Ni2+ ions, redox reaction kinetics might become more efficient resulting in the enhanced charge storage capacity.

Corrosion Susceptibility and Microhardness of Al-Ni Alloys with Different Grain Structures

The development of Al-Ni alloys with a controlled microstructure has had a great impact on the field of study of aluminum-based alloys. In the present research, the influence of thermal parameters on the grain structures resulting from the directional solidification process of Al-Ni alloys with different alloy content has been studied. It has also been evaluated how different structures and the distribution of second phases influence the corrosion behavior and microhardness of alloys. The columnar-to-equiaxed transition (CET) was observed to occur when the temperature gradient in the melt decreased to values between 1.3 and 2.9 °C/cm. In addition, a small increase in the microhardness values was observed as a function of the Ni content. When the Ni content increases, the resistance to polarization decreases for samples with equiaxed grain structure throughout the range of compositions studied. Furthermore, the equiaxed grain structure presents higher resistance to polarization values than the columnar grain zone for alloys with a composition equal to or lower than the eutectic composition.

Dilution induced magnetic localization in Rb(Co[formula omitted]Ni[formula omitted])2Se2 single crystals

We report experimental studies on a series of Rb(Co1−xNix)2Se2 (0.02 ≤x≤ 0.9) powder and single crystal samples using x-ray diffraction, neutron diffraction, magnetic susceptibility, and electronic transport measurements. All compositions are metallic and adopt the body-centered tetragonal structure with I4/mmm space group. Anisotropic magnetic susceptibilities measured on single crystal samples suggest that Rb(Co1−xNix)2Se2 undergo an evolution from ferromagnetism to antiferromagnetism, and finally to paramagnetism with increasing Ni concentration. Neutron diffraction measurements on the samples with x = 0.1, 0.4, and 0.6 reveal an A-type antiferromagnetic order with moments lying in the ab plane. The moment size changes from 0.69 (x=0.1) to 2.80μB (x=0.6) per Co ions. Our results demonstrate that dilution of the magnetic Co ions by substitution of nonmagnetic Ni ions induces magnetic localization and evolution from itinerant to localized magnetism in Rb(Co1−xNix)2Se2.

Effects of Ni cation ratio and sintering temperature on microstructure and electrical properties of NiMnCoO4-based ceramics

Negative temperature coefficient (NTC) thermistors as temperature sensors play an important role in various electrical/electronic devices and are widely applied in the fields such as, automotive sensor modules, home appliances and control applications. The electrical properties of NTC thermistors can be effectively controlled by regulating the content of their chemical components or changing the microstructures. Therefore, this study investigated the effects of Ni cation ratio and sintering temperature on microstructures, crystal structures, and electrical properties of NiMnCoO4-based ceramics. With increasing Ni content, it was found that sinterability of NiMnCoO4-based ceramics was decreased with forming rock-salt phase of NiO, resulting in degrading resistivity. Furthermore, the spinel structures were detected by X-ray diffraction analysis regardless of sintering temperatures. Notably, values of average grain size for sintered samples were increased with increasing sintering temperature. Besides, it was clarified that electrical properties were significantly influenced by average grain size. The room temperature resistivity was increased from approximately 300 kΩ⋅cm for the sintered sample at 1100°C to about 600 kΩ⋅cm for for the sintered sample at 1300oC. On the other hand, the B(25/85) constant was not significantly influenced by the sintering temperature. Accordingly, it is expected that the results of this study are useful for controlling electrical properties of MnCoNiO4-based ceramics.

Spray pyrolysis grown Cu and Ni co-doped ZnO thin films: a study of their structural, optical, wettability, and photocatalytic performance

This study explores the impact of Cu and Ni doping on the structural, wettability, optical, and photocatalytic properties of ZnO thin films. The co-doped thin films, with varying Ni concentrations, were deposited using a spray pyrolysis method onto pre-heated soda lime glass substrates. X-ray diffraction analysis confirmed the hexagonal wurtzite structure with preferred orientation primarily along the (002) plane, while crystallinity decreased with higher Ni concentrations. Scanning electron microscopy reveals a compact, adherent structure in all films, with Ni incorporation altering the surface morphology. Fourier transform infrared spectroscopy identified characteristic absorption bands for metal-oxygen bonds. Optical analysis indicated that all thin films exhibited over 88% average transmittance in the visible region, accompanied by a red shift in the optical bandgap. Photoluminescence spectra exhibited a broad emission band in the visible region, indicating intrinsic and extrinsic defects induced by doping. Co-doping transforms the wettability character of ZnO thin films from hydrophilic to hydrophobic. Finally, the photodegradation efficiency of the thin films against methylene blue under sunlight significantly increases from 72% to 92% with an increase in Ni concentration.

Comparison of the corrosion behavior of four Fe-Cr-Ni austenitic alloys in supercritical water

The corrosion behavior of four Fe-Cr-Ni austenitic alloys were investigated after exposure to deaerated supercritical water (SCW) at 650°C. Results show that the corrosion resistance follows the trend:Fe-29Cr-61Ni > Fe-16Cr-75Ni > Fe-25Cr-20Ni > Fe-21Cr-31Ni. The increase in Cr and Ni contents promote a transition from low-protective multilayer oxide scales to protective Cr2O3 scales. After surface grinding, the weight gains of all specimens dropped by one order of magnitude. Surface grinding induces the formation of ultrafine grains and a high density of dislocations, which enhances the corrosion resistance among all studied austenitic alloys. However, the beneficial effects of grinding diminish with increased Cr and Ni contents due to the pre-existing portion of Cr2O3 scales. The lower critical Cr content required to form Cr2O3 scales in high Ni austenitic alloys is primarily attributed to their lower solubility of O and the slower diffusion rates of Ni, which inhibit corrosion behavior.

New insights from crystallography into the effect of Ni content on ductile-brittle transition temperature of 1000 MPa grade high-strength low-alloy steel

The significant effect of Ni content (0.92, 1.94 and 2.94 wt%) on ductile-brittle transition temperature (DBTT) and microstructure in a 1000 MPa grade high-strength low-alloy (HSLA) steel was studied. Using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), transmission electron microscopy (TEM), Charpy impact test and low-temperature tensile test to study the fundamental reasons for the effect of Ni content on toughness. The results indicated that increasing the Ni content can reduce the DBTT of HSLA steel and improve the impact toughness at low temperatures. EBSD data post-processing analysis revealed that the key reason for the increase in low-temperature toughness is the refinement of the microstructural crystallographic structure, specifically the significant increase in the boundary density of the block and packet. With the increase of Ni content, the density of grain boundary with an orientation difference greater than 5° between two adjacent {110} crystal planes was higher, which can form a higher density of dislocation pile-up group, thus better reducing local stress concentration. Meanwhile, the stacking fault energy (SFE) increases with the increase of Ni content, which made the screw dislocation more prone to cross slip at low temperature, resulting in an increase in plasticity at low temperatures. These observed phenomena and reasons provided a theoretical explanation for the role of Ni content in reducing DBTT and enhancing the toughness of the core in heavy gauge plates.

The role of phase transformation (tetragonal – spinel) on the structural and mechanical properties of Ni doped CuFe2O4

Nano-ferrites of Cu1–xNixFe2O4 (x = 0 to 1 with step 0.2) system was synthesized utilizing the flash auto combustion process annealed at 600oC for 3 h. The structural characterization for synthesized samples was carried out using x-ray Diffraction (XRD), Fourier transition infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). The hardness of the prepared material was measured using micro-indentation creep technology. XRD pattern verified the creation of a single-phase cubic spinel structure. The undesired CuO phase forms around \\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\:2\ heta\\:={50}^{^\\circ\\:}\\:$$\\end{document}for pure Copper ferrite and decreases with increasing Ni content. The average crystalline size decreases from 27.92 nm to 13.28 nm by doping process from x = 0.2 to x = 1 which retards the growth of crystalline size. FTIR spectra are distinguished by the presence of two prominent absorption bands, ν2 for the octahedral site and ν1 for the tetrahedral site, in the range of approximately 593 and 471 cm− 1, respectively. FTIR analysis verified the formation of the ferrite system’s spinel structure. The TEM images show a nanocrystalline nature with some agglomeration and the crystallites are spherical in shape which their sizes are agrees well with that obtained from XRD measurements. The hardness decreases as the dwell time increases. The hardness and yield strength (Y) values were significantly improved due to the decrease in the crystallite size after Ni doping. The stress exponent (n) value increases by increasing Ni content which means that the mechanical properties improved due to increment of resistance.

Performance enhancement of SAW based hydrogen sensor employing Pd/Ni alloy thin film

Abstract This study focuses on determining the optimized design parameters of palladium/nickel (Pd/Ni) thin film coated surface acoustic wave (SAW) hydrogen (H2) sensors with high sensitivity and fast response by modulating the ratio and thickness of Pd/Ni thin film. The Pd/Ni thin films deposited on the wave propagation path of delay-line patterned SAW sensors had Ni content ranging from 0 to 30 at% and thickness ranging from 20 to 400 nm. A phase discrimination circuit was used to collect the signal of SAW H2 sensor. The experimental results indicated that the response sensitivity of the sensor decreased with the increase of Ni content, while the response time gradually accelerated. Besides, the stability of the sensor deteriorated with increasing thickness, and there existed a non-linear relationship between sensitivity and thickness, and the response time slowed down as the thickness increased. To analyze the SAW sensing mechanism, a theoretical simulation model of the Pd/Ni thin film coated SAW H2 sensor was established using perturbation theory, which was well-validated by experimental results. Considering the requirements of fast response, high sensitivity, and stability of the H2 sensor, the optimal thin film structure parameters were determined as Pd9Ni1 thin film with the thickness of 40 nm.

Physicochemical, Morphological and Anticorrosive Properties of Electrodeposited ZnNi Alloy Coating

Corrosion in its many forms is a major problem for many types of materials, extending from machining to manufacturing and daily use. In fact, it affects practically all engineering projects, from the biggest to the smallest: energy production, construction, transport, medical sector, electronics, etc. Consequently, corrosion generates both economic and environmental problems. To prevent corrosion and preserve materials' durability, several protection methods can be applied. These included protection by applying a coating on the metal surface. In this context, Zinc based alloy coatings have attracted much interesting scientific community because of their excellent mechanical and anti-corrosive properties. In the present work, ZnNi coatings were electrodeposited on steel substrates using a chloride bath containing ammonium salts. The effect of some experimental parameters, namely, potential and metal ion concentration ratio on the deposition kinetics of ZnNi system as well as on its physicochemical, morphological and anticorrosive properties has been investigated. For this purpose, an appropriate experimental work was performed by using both electrochemical (cyclic voltammetry, chronoamperometry, open circuit potential, potentiodynamic polarization) and nonelectrochemical (SEM-EDX) analysis methods. Based on the obtained results, it has been revealed that simultaneous codeposition of both elements Zn and Ni is possible in our experimental conditions. However, deposition kinetics exhibited a strong dependence on explored parameters. Also, morphological aspect and chemical composition of deposits are strongly influenced by metal ion concentration ratio. Investigation of corrosion behaviour confirms the protective effect of coatings acted as a sacrificial anode. Furthermore, increasing Ni content in the deposits induces a significant enhancement in corrosion resistance. Thus, Zn-Ni alloy coatings prepared from the Ni(II)-rich bath exhibited better corrosion resistance.

Influence of Ni substitution on Structural, Optical, magnetic and transport properties of Mn0.5-xNixZn0.4Cu0.1Fe1.95Al0.05O4

A series of spinel ferrites Mn0.5-xNixZn0.4Cu0.1Fe1.95Al0.05O4 have been prepared by auto-combustion technique. X-ray diffraction (XRD) and Field Emission Scanning Electron Microscopy (FESEM) have been used for structural and morphological investigations. The XRD patterns confirm the formation of cubic spinel structure of ferrites. The lattice constants decrease with the increase of Ni contents due to the smaller ionic radii of Ni2+ compared to Mn2+ as well as particle size decreases. Density is increased and porosity is decreased with the increase of Ni contents in the samples due to the higher atomic weight of Ni2+ compared to Mn2+. The FESEM analysis reveal that the average size of the irregularly shaped grains increased with Ni contents. The mixed spinel structure is further confirmed by the FTIR spectra, which show a doublet band at about 600 cm−1. The observed optical band gap and the particle size variations are comparable, and the quantum size effect supports this conclusion. The real part of initial permeability and relative quality factor increase with the increase of Ni contents due to increase of density and grain size as well as decrease of porosity. Also, it is found that magnetic loss decreased with the increase of Ni contents. All the samples exhibit ferrimagnetic behavior and the number of Bohr magneton has been calculated for all compositions. The dielectric constant shows large value in the lower frequencies and decreases with frequency shows dispersion due to Maxwell-Wagner space charge polarization. The investigation of electric modulus has demonstrated the existence of the hopping conduction mechanism. The AC conductivity is very low at lower frequency region and very large at higher frequency region which can be explain according to the polaron hopping model of Austin and Mott. The AC conductivity enhances nearly linearly with frequency, suggesting that the mechanism of conduction is due to small polaron hopping, which can be described according to Jonscher’s power law. Also, the effect of grain and grain boundary resistance on transport properties has been investigated using complex impedance analysis and it has been observed that both exhibit an increase trend as the Ni content increases.

Effect of Ni on the mechanical and corrosion properties of TiC-reinforced steel matrix composites

Particle-reinforced steel matrix composites typically lead to a decrease in corrosion resistance while enhancing mechanical properties. However, steel matrix composites for marine applications require superior mechanical properties and corrosion resistance. In this study, 8 vol% TiC/Fe–C composites were prepared using the master alloy method. The effects of Ni contents (0, 1.2 wt%, 1.6 wt%, 2.0 wt%, and 2.4 wt%) on the mechanical and corrosion properties of the composites were evaluated. Results indicated that the tensile strength, elongation, and corrosion resistance of the composites initially increased and then decreased with increasing Ni content. The σUTS and εf of Ni2.0 composites increased from 536 MPa and 4.1 % for Ni0 to 1100 MPa and 9.0 %, respectively. The icorr and corrosion rate of the Ni2.0 composite were 0.440 μA/cm2 and 0.0057 mm/year, respectively. The mechanical properties and corrosion resistance of TiC particle-reinforced steel matrix composites were simultaneously enhanced by the addition of 2.0 wt% Ni. The increase in strength is mainly attributed to changes in thermal mismatch resulting from Ni addition, solid solution strengthening of the Fe–Ni solid solution, and improved interface compatibility between the TiC particles and the matrix, thus enhancing load transfer efficiency. The increase in plasticity can be attributed to the significant improvement in interface deformation compatibility with Ni addition. The increase in corrosion resistance primarily results from the steel matrix alloying, uniform distribution of TiC particles, and strong interface bonding between the particles and the matrix.

Occurrence and enrichment of cobalt and nickel in the Yindongshan ultramafic–mafic intrusion-hosted iron deposit, western Hubei Province, China

The Yindongshan iron deposit in western Hubei Province of China is hosted within Ordovician ultramafic–mafic intrusions. Recent field geological surveys have detected cobalt (Co) and nickel (Ni) enrichment within the Yindongshan clinopyroxenite, suggesting good potential for subeconomic Co-Ni mineralization. This study investigated the occurrence modes and enrichment processes of Co and Ni in the Yindongshan deposit through field geology and in situ analysis of the rock texture, geochronology, and geochemistry of sulfides, Fe-Ti oxides, and silicate minerals. The Yindongshan clinopyroxenites were emplaced at 440.2 ± 7.2 Ma via titanite LA-ICP-MS U-Pb dating, and underwent extensive post-magmatic metamorphism at 401.2 ± 8.6 Ma via apatite U-Pb dating. This metamorphism led to the widespread formation of amphibole via the replacement of clinopyroxene. Subsequently, hydrothermal epidote-albite veins, calcite-pyrite veins, and later actinolite veins developed. Pyrites from both clinopyroxenites and calcite veins show limited δ34S variations from −5.4 ‰ to −1.2 ‰, suggesting a magmatic sulfur source. Late-vein actinolites display geochemical characteristics distinct from those of amphiboles, indicating possible involvement of external fluids. LA–ICP–MS trace element results reveal a general increase in Co and Ni contents from silicate minerals and Fe-Ti oxides to pyrite and from earlier-crystallized coarse-grained clinopyroxenite to later medium- to fine-grained clinopyroxenite. The highest Co and Ni contents observed in pyrite from coarse-grained clinopyroxenite suggest their preferential incorporation into early sulfide minerals and then progressively depleted through magmatic evolution such as fractional crystallization. The positive correlation between Co and Ni with Fe in pyrite, along with the consistent parallel time-resolved LA–ICP–MS depth profiles among different mineral phases, indicates that isomorphic substitution occurred in pyrite. In silicate minerals, the Co and Ni contents increase from pyroxene, amphibole, to actinolite, with almost no Co or Ni present in epidote. The elevated Co and Ni contents in metamorphic amphiboles are attributed to their remobilization from magmatic pyrite to newly formed amphiboles. During the late hydrothermal phase, external fluids might transport additional Co and Ni, contributing to higher concentrations in late actinolite veins. In general, Co and Ni in the Yindongshan iron deposit are primarily hosted in sulfide minerals and can be remobilized during regional metamorphism and metasomatism. Thus, magmatic iron or iron–titanium oxide deposits hosted by mafic–ultramafic intrusions with sulfide mineralization may serve as promising targets for further Co-Ni exploration.

Effect of Ni and Nb concentration on microstructural evolution in a 20Cr ferritic alloy strengthened by Ni16Nb6Si7-G phase

The effects of Nb and Ni contents on the precipitation of the Ni16Nb6Si7-G phase and the resulting hardening behavior in Fe–20Cr ferritic alloys were systematically investigated using micro-hardness, electron microscopy, and atom probe techniques. The results demonstrate that an optimal Nb content of ∼0.75 wt. % promotes the precipitation of the Ni16Nb6Si7-G phase, leading to a maximum micro-hardness of approximately 430 H V when aged at 560 °C for 24 h. Excess Nb content (>0.75 wt. %) introduces the Fe2Nb-Laves phase at grain boundaries and within the grains, which competes with the G-phase for precipitation. Conversely, an increase in Ni content effectively raises the dissolution temperature of the Ni16Nb6Si7-G phase to approximately 850 °C. The austenite phase begins to form when the Ni content exceeds 4 wt. %. Finally, the strengthening effect of the Ni16Nb6Si7-G phase and its underlying competition precipitation with the Fe2Nb-Laves phase as well as the possible benefit of inducing austenite phase was discussed in the context of developing 20Cr ferritic alloys with high strength and good ductility. These findings provide valuable insights into the influence of Nb and Ni contents on the microstructural evolution and mechanical properties of the newly developed 20Cr alloy, which may be helpful in guiding the design of high performance ferritic alloys by optimizing composition and heat treatment processes.

In-situ synthesis of NiTi shape memory alloys with tunable chemical composition and thermomechanical response by dual-wire-feed electron beam directed energy deposition

In this study, we demonstrate the direct in-situ synthesis of NiTi alloys with tunable chemical composition (Ni/Ti atomic ratio) and corresponding thermomechanical response. This synthesis is achieved by regulating the feeding speed ratio of pure Ni and Ti wires during the additive manufacturing process based on dual-wire-feed electron beam directed energy deposition (EB-DED) technology. Under appropriate process conditions, the resulting NiTi alloys exhibit a controllable evolution around the near-equiatomic composition and display a typical columnar grain morphology characteristic of additively manufactured NiTi alloys. With an increase in Ni content (shifting from Ti-rich to Ni-rich), the second phase particles present in the samples change from Ti-rich phase (Ti2Ni) to Ni-rich phases (such as Ni4Ti3 and Ni3Ti2). The phase transformation temperatures gradually decrease with increasing Ni content, and the predominant matrix phase transitions from martensite to austenite. The as-built NiTi alloy exhibits a typical tensile curve with a good tensile elongation of 11 %, fabricated under suitable composition and microstructure conditions. This result surpasses values reported in current in-situ synthesized NiTi alloys through additive manufacturing methods. Moreover, it almost reaches the levels achieved by additively manufactured NiTi alloys using pre-alloyed raw materials. Furthermore, this study reports, for the first time in the field of in-situ synthesized NiTi alloys, a good tensile shape memory effect, achieving an impressive recovery rate of up to 70 % under a tensile strain of 6 %. This investigation provides a meaningful theoretical perspective and technical strategy for the integrated customization of NiTi alloy components in structure, composition, and function. This low-cost and high-efficiency approach is particularly attractive for the preparation of functional graded, large-scale and disposable NiTi components.

Understanding of magnetic behavior of the pseudo-binary Co2-xNixZn11: in the light of crystal and electronic structures.

A high-temperature synthetic approach is used to prepare a series of pseudo-binary phases-Co2-xNixZn11. In the structures of Co2-xNixZn11, the statistical distribution between Co and Ni that is suggested by compositional analysis is confirmed by combined refinements of X-ray and neutron powder diffraction (NPD) experimental data. The aforementioned phases adopt a body-centered cubic lattice with a noncentrosymmetric space group I4̄3m (217). Their crystal structures comprise two 26-atom γ-brass clusters. Each γ-cluster is made of four sequential polyhedral shells: inner tetrahedron (IT), outer tetrahedron (OT), octahedron (OH), and distorted cuboctahedron (CO). Diffraction experiments and the computations endorse that the OT site is statistically distributed by Co and Ni atoms, while the other three sites (IT, OH, and CO) are occupied by Zn atoms. The density of states (DOS) curve for Co1.5Ni0.5Zn11 displays a similar feature as binary Co2Zn11, whereas the wide pseudo-gap is formed near EF as Ni-concentration increases in Co2-xNixZn11. Bonding analysis shows that this specific atomic distribution nearly optimizes heteroatomic Co/Ni-Zn contacts in the Co1.0Ni1.0Zn11 and Co0.5Ni1.5Zn11. The Co1.7Ni0.3Zn11 exhibit paramagnetic behavior, whereas Co0.5Ni1.5Zn11 shows distinct diamagnetic behavior. With the increase in Ni concentration in the structure of Co2-xNixZn11, Ni atoms gradually substitute the Co atoms at OT sites; hence, magnetic characteristics change from para- to diamagnetism.

Preparation of high quality carbon nanotubes by catalytic pyrolysis of waste plastics using FeNi-based catalyst

Plastic waste pollution is the serious environmental problem, and catalytic pyrolysis of waste plastics is an effective way to solve this problem. Carbon nanotubes (CNTs) are prepared by catalytic pyrolysis of low-density polyethylene (LDPE) waste plastics by one-stage method using iron nitrate and nickel nitrate as catalyst. The growth mechanism of CNTs is analyzed in detail. TPO, XRD, SEM and Raman analyses show that increasing Ni content contributes to the production of CNTs with good morphology and high graphitization degree. While the increasing Fe content contributes to improving the yield of CNTs. The outer and inner diameters of the FeNi12-CNTs-800 are about 21 nm and 8 nm with the length of 18.9 μm, respectively. LDPE pyrolysis gases are analyzed to determine that the primary carbon source required for CNTs growth is C2H4. The C2H4 adsorption and decomposition processes on FeNi alloys are performed to reveal the growth mechanism of CNTs, based on density functional theory calculation. Three kinds of the growth models are proposed to explain the difference of the CNTs tubular shape. FeNi12-CNTs-800 are used to remove microplastics from wastewater due to existence of magnetic. PVC can be quickly removed from wastewater with removal of 100 % at 20 min. This study provides an effective way for recycling and treatment of waste plastic.

Understanding Ni-Rich Layered Cathode Materials for Fast-Charging Li-Ion Batteries

The market for electric vehicles (EVs) has experienced significant growth, and this trend is expected to continue in the coming years. While the lithium-ion battery (LIB) technologies for EVs have made significant progress so far, they still face several disadvantages compared to the internal combustion engines. A predominate challenge is reducing battery charging time. [1] Traditional LIBs typically use Li[Ni1-x-yCox(Mn and/or Al)y]O2 as cathode materials. To improve the driving range of EVs, energy density has been the focus of research and development in the past decade, which led to the wide adoption of Ni-rich (Ni content > 80%) layered oxide cathodes in LIBs.[2] With increasing Ni content, however, the structural changes that the cathode material undergoes during electrochemical reactions also become more severe, which negatively impact their fast-charging performances.[3-5] It is evident that addressing the fast charging limitations requires a deep understanding of the active materials. In this presentation, we show our recent effort in improving fast charging performances of Ni-rich layered cathodes. As the reactivity of Li[Ni1-x-yCox(Mn and/or Al)y]O2 cathodes vary with the states of dis/charges, their fast charging performances are directly linked to the charging/discharging protocol. In addition, we report how various physical properties of the cathode materials, such as microstructures and facets, can affect kinetics and charging rates. Our perspectives on future development strategies for fast charging Ni-rich layered cathode materials will also be discussed.[1] X. Wang, Y.-L. Ding, Y.-P. Deng, Z. Chen, Adv. Energy Mater. 2020, 10, 1903864.[2] S.-T. Myung; F. Maglia; K.-J. Park; C. S. Yoon; P. Lamp; S.-J. Kim; Y.-K. Sun, ACS Energy Lett. 2017, 2, 196.[3] F. Schipper; E. M. Erickson; C. Erk; J.-Y. Shin; F. F. Chesneau; D. Aurbach, J. Electrochem. Soc. 2017, 164, A6220.[4] H.-H. Ryu, K.-J. Park, C. S. Yoon, Y.-K. Sun, Chem. Mater. 2018, 30, 1155.[5] J. Park, H. Zhao, S. D. Kang, K. Lim, C.-C. Chen, Y.-S. Yu, R. D. Braatz, D. A. Shapiro, J. Hong, M. F. Toney, M. Z. Bazant, W. C. Chueh, Nat. Mater. 2021, 20, 991.