Amorphous Ni0 Research Articles

Amorphous Ni-Fe-Mo Oxides Coupled with Crystalline Metallic Domains for Enhanced Electrocatalytic Oxygen Evolution by Promoted Lattice-Oxygen Participation.

The crystalline/amorphous heterophase nanostructures are promising functional materials for biomedicals, catalysis, energy conversion, and storage. Despite great progress is achieved, facile synthesis of crystalline metal/amorphous multinary metal oxides nanohybrids remains challenging, and their electrocatalytic oxygen evolution reaction (OER) performance along with the catalytic mechanism are not systematically investigated. Herein, two kinds of ultrafine crystalline metal domains coupled with amorphous Ni-Fe-Mo oxides heterophase nanohybrids, including Ni/Ni0.5-a Fe0.5 Mo1.5 Ox and Ni-FeNi3 /Ni0.5-b Fe0.5-y Mo1.5 Ox , are fabricated through controllable reduction of amorphous Ni0.5 Fe0.5 Mo1.5 Ox precursors by simply tuning the amount of used reductant. Due to the suited component in metal domains, the special structure with dense crystalline/amorphous interfaces, and strong electronic coupling of their components, the resultant Ni-FeNi3 /Ni0.5-b Fe0.5-y Mo1.5 Ox nanohybrids show greatly enhanced OER activity with a low overpotential (278mV) to reach 10mAcm-2 current density and ultrahigh turnover frequency (38160h-1 ), outperforming Ni/Ni0.5-a Fe0.5 Mo1.5 Ox , Ni0.5 Fe0.5 Mo1.5 Ox precursors, commercial IrO2 , and most of recently reported OER catalysts. Also, such Ni-FeNi3 /Ni0.5-b Fe0.5-y Mo1.5 Ox nanohybrids manifest good catalytic stability. As revealed by a series of spectroscopy and electrochemical analyses, their OER mechanism follows the lattice-oxygen-mediated (LOM) pathway. This work may shed light on the design of advanced heterophase nanohybrids, and promote their applications in water splitting, metal-air batteries, or other clean energy fields.

Intercalation Reaction in Amorphous Layer-Wrapped Ni0.2Mo0.8N/Ni3N Heterostructure Toward Efficient Lithium-Ion Storage.

Transition metal nitrides (TMNs) with high specific capacity and electric conductivity have drawn considerable attention as electrode materials of lithium-ion batteries (LIBs). However, the cycling stability of most TMNs is not satisfactory, which was caused by the large volume variation during cycles due to their intrinsic conversion reaction mechanism. Herein, by rational design, a much stable tremella-like Ni0.2Mo0.8N/Ni3N heterostructure with amorphous Ni0.2Mo0.8N wrapped layer has been fabricated. The Ni3N particles worked as pillars to support the Ni0.2Mo0.8N material as well as conductive medium to facilitate ionic and electronic transport. The amorphous layer can relieve the structural stress of Ni0.2Mo0.8N during cycles. Moreover, an exotic intercalation-type reaction mechanism in the ternary nitride Ni0.2Mo0.8N was revealed by a series ex situ and in situ characterization. Profiting from these advantages, the Ni0.2Mo0.8N/Ni3N heterostructure anode displays an outstanding electrochemical performance with a high initial reversible discharge capacity of 1001.6 mA h g-1 at 0.1 A g-1, excellent cycle stability of 695.5 mA h g-1 at 2 A g-1 after 600 cycles, and superior rate capability of 595.3 mA h g-1 at a high current density of 5 A g-1. This work provides a new insight for designing high efficiency LIBs based on intercalation reaction for practical applications.

Amorphous Ni-Fe double hydroxide hollow nanocubes enriched with oxygen vacancies as efficient electrocatalytic water oxidation catalysts.

In this study, we present an ingenious design of Fe-modulated nickel hydroxide hollow nanocubes with a systematically engineered structure. The Ni0.75Fe0.25(OH)x sample exhibits good O2 evolution activity, which should be attributed to electronic modulation and abundant oxygen vacancies. Based on Pourbaix slope analysis, a two proton-one electron transfer is discovered in the amorphous Ni0.75Fe0.25(OH)x catalyst. Ni0.75Fe0.25(OH)x exhibits an enhanced performance for the electrocatalytic OER with a low overpotential of 310 mV at a current density of 10 mA cm-2.

Insights into the Active Electrocatalytic Areas of Layered Double Hydroxide and Amorphous Nickel–Iron Oxide Oxygen Evolution Electrocatalysts

Layered double hydroxide (LDH) and amorphous nickel–iron (oxy)hydroxides (Ni1–xFexOOH) are emerging catalysts for the electrochemical oxygen evolution reaction (OER). It is still unresolved if the layered two-dimensional (2D) structure allows for active catalytic sites to exist below the traditional electrode/electrolyte interface. Herein, we utilized the surface interrogation mode of scanning electrochemical microscopy (SI-SECM) to directly measure active site densities in situ. We determined that Ni0.8Fe0.2OOH LDH showed a 10-fold increase in the active site density compared to rock salt Ni0.8:Fe0.2 oxide, giving direct evidence that water and hydroxide in the interlayer are able to create stable NiIV/FeIV active species at layers below the electrode/electrolyte interface. This result suggests that electrolyte permeability of the 2D LDH structure is a major contributor for its increased catalytic activity. Amorphous Ni0.8:Fe0.2 oxide also exhibits an anomalously high active site density and higher activ...

Amorphous Ni0.75Fe0.25(OH)2‐Decorated Layered Double Perovskite Pr0.5Ba0.5CoO3‐δ for Highly Efficient and Stable Water Oxidation

AbstractHighly active, durable, and cost‐effective electrocatalysts for water oxidation into oxygen gas hold a key role to realise a range of renewable energy solutions which include water‐splitting and rechargeable metal‐air batteries. Despite its very stable oxygen evolution reaction (OER) performance over large number of cycles, layered double perovskite PrBaCo2O5+δ (PBC) has a rather limited surface area. It is, thus, desirable to have the stability of PBC combined with the higher OER activity obtained by enlarging its surface area. Here, we used micro‐sized PBC particles as the substrate for the deposition of nano‐sized nickel‐iron hydroxide, Ni0.75Fe0.25(OH)2, which led to an order of magnitude improvement in the OER current density at 1.63 V versus the reversible hydrogen electrode for the amorphous Ni0.75Fe0.25(OH)2‐decorated PBC catalyst (A‐Ni0.75Fe0.25(OH)2+PBC), relative to the PBC catalyst. We showed that the crystal ordering of the decoration affects the OER activity, that is, the amorphous decoration provided a higher OER activity than the crystalline decoration by enabling a larger contact area between the catalyst and the aqueous electrolyte. The results we show here could potentially stimulate more innovative future works utilising simple chemical preparation route to realise high‐performance hybrid OER catalysts involving novel constituents.

Effect of tungsten alloying on short-to-medium-range-order evolution and crystallization behavior of near-eutectic amorphous Ni–P

The crystallization of near-eutectic amorphous Ni–P can be significantly retarded by alloying a small fraction of tungsten. To understand this phenomenon, amorphous Ni0.80 P0.20 and Ni0.76 W0.04 P0.20 with the same phorphous fraction were fabricated by electroless plating as 10 μm-thick continuous layers. Subsequently, the alloys were tempered to three different stages: (i) an “incubation stage” (still completely amorphous), (ii) a “partially crystalline” stage (amorphous and crystalline phases), and (iii) a “completely crystalline” stage (only crystalline phases). To understand the strong effect of tungsten alloying on the crystallization behavior, we investigate the atomistic structure of as-plated and tempered Ni0.76 W0.04 P0.20 and compare it with that of correspondingly treated amorphous Ni0.80 P0.20. The study focuses on SRO (short-range order) and MRO (medium-range order). SRO, characterized by typical nearest neighbors, was studied by XPS (X-ray photoelectron spectrometry). MRO, which includes neighbor atoms up to about 2 nm distance, was studied by FEM (fluctuation electron microscopy). In addition, the crystalline phases and microstructure of both alloys were studied by XRD (X-ray diffractometry) and TEM (transmission electron microscopy), respectively. Combining results of these complimentary techniques leads to models for the atomistic structure of amorphous Ni–P and Ni–W–P and models for the micromechanism of crystallization. Specifically, these models explain why tungsten reduces the driving force for crystallization and slows the crystallization kinetics. The principles we have recognized may be useful for identifying alloying elements that are potentially even more effective in retarding crystallization.

Amorphous mixed-metal hydroxide nanostructures for advanced water oxidation catalysts.

The design of highly efficient, durable, and earth-abundant catalysts for the oxygen evolution reaction (OER) is crucial in order to promote energy conversion and storage processes. Here, we synthesize amorphous mixed-metal (Ni-Fe) hydroxide nanostructures with a homogeneous distribution of Ni/Fe as well as a tunable Ni/Fe ratio by a simple, facile, green and low-cost electrochemical technique, and we demonstrate that the synthesized amorphous nanomaterials possess ultrahigh activity and super long-term cycle stability in the OER process. The amorphous Ni0.71Fe0.29(OH)x nanostructure affords a current density of 10 mA cm(-2) at an overpotential of a mere 0.296 V and a small Tafel slope of 58 mV dec(-1), while no deactivation is detected in the CV testing even up to 30 000 cycles, which suggests the promising application of these amorphous nanomaterials in electrochemical oxidation. Meanwhile, the distinct catalytic activities among these amorphous Ni-Fe hydroxide nanostructures prompts us to take notice of the composition of the alloy hydroxides/oxides when studying their catalytic properties, which opens an avenue for the rational design and controllable preparation of such amorphous nanomaterials as advanced OER electrocatalysts.

Facile synthesis of NiPt–CeO2 nanocomposite as an efficient catalyst for hydrogen generation from hydrazine borane

NiPt–CeO2 nanocomposites (NCs) have been easily prepared via a surfactant aided co-reduction route and characterized by ICP-AES, XRD, TEM, HRTEM, SAED, EDX and XPS techniques. The characterized results show that the NiPt–CeO2 NCs with an average particle size of 3 nm are in amorphous state and well-dispersed. The as-synthesized NiPt–CeO2 NCs are successfully applied as a highly efficient catalyst for rapid and high-extent dehydrogenation of hydrazine borane (Hy-B). The amorphous NiPt–CeO2 NCs obtained due to the addition of CeO2 display much better activity than that of Ni-, Pt–CeO2, and crystalline NiPt NCs. Especially, Ni0.9Pt0.1–CeO2 NCs with a low noble-metal content exhibit markedly high catalytic activity to release 5.74 equiv. (H2 + N2) per Hy-B in only 12.3 min with a high turnover frequency (TOF) value of 234 h−1 (molH2·molmetal−1·h−1). In the presence of this special amorphous state Ni0.9Pt0.1–CeO2 nanocatalyst, the hydrolysis of the group BH3 and the decomposition of the moiety N2H4 occur simultaneously and thus accelerate the rate of releasing hydrogen from Hy-B. This excellent catalytic performance is due to the synergistic effect between NiPt and CeO2 and the promotion effect of NaOH.

Temperature Dependence of the Elastic Modulus of (Ni0.6Nb0.4)1−xZrx Membranes: Effects of Thermal Treatments and Hydrogenation

Amorphous (Ni0.6Nb0.4)1−xZrx membranes were investigated by means of X-ray diffraction, thermogravimetry, differential thermal analysis and tensile modulus measurements. Crystallization occurs only above 673 K, and even after hydrogenation the membranes retain their mainly amorphous nature. However, after exposure to gaseous hydrogen, the temperature dependence of the tensile modulus, M, displays large variations. The modulus of the hydrogen reacted membrane is higher with respect to the pristine samples in the temperature range between 298 K and 423 K. Moreover, a sharp drop in M is observed upon heating to approximately 473 K, well below the glass transition temperature of these glasses. We propose that the changes in the moduli as a function of temperature on the hydrogenated samples are due to the formation of nanocrystalline phases of Zr hydrides in (Ni0.6Nb0.4)1−xZrx-H membanes.

Highly efficient hydrogen generation from hydrous hydrazine over amorphous Ni0.9Pt0.1/Ce2O3 nanocatalyst at room temperature

Amorphous Ni0.9Pt0.1/Ce2O3 nanoparticles with low noble-metal content have been facilely synthesized by a co-reduction route within 10 min at room temperature under ambient atmosphere. The resultant Ni0.9Pt0.1/Ce2O3 nanoparticles were successfully applied as a highly efficient catalyst for rapid and complete conversion of hydrous hydrazine. A high initial turnover frequency value of 28.1 h−1 for Ni0.9Pt0.1/Ce2O3 nanoparticles is achieved with 100% H2 selectivity at 298 K. Moreover, the amorphous Ni0.9Pt0.1/Ce2O3 catalyst obtained due to the addition of Ce2O3 demonstrates much better activity and much lower activation energy than that of the crystalline Ni0.9Pt0.1. The development of the improved performance and low-cost catalyst is a promising step towards the application of hydrous hydrazine as a hydrogen storage material.

Distorted icosahedral Ni5Nb3Zr5 clusters in the as-quenched and hydrogenated amorphous (Ni0.6Nb0.4)0.65Zr0.35 alloys

Local structures of the hydrogenated (Ni0.6Nb0.4)1-xZrx (x=0.3–0.4) amorphous alloys attract much attention for the sake of their epoch-making electronic transport behaviors. We investigated the local structures by XAFS for the as-quenched (Ni0.6Nb0.4)0.65Zr0.35 and hydrogenated [(Ni0.6Nb0.4)0.65Zr0.35]0.922H0.078 amorphous alloys, in which ballistic conductivity has been observed. XAFS results of the Ni K-edge are analyzed based on the structure model deduced by the first principle calculation. The analysis suggests that highly distorted icosahedral Ni5Nb3Zr5 cluster, which has a centered-Ni and a surrounding Nb triangle, is a main structural unit of (Ni0.6Nb0.4)0.65Zr0.35 and the [(Ni0.6Nb0.4)0.65Zr0.35]0.922H0.078 amorphous alloys. This distorted icosahedral Ni5Nb3Zr5 cluster can be associated with the occurrence of the singular electronic transport behaviors of the hydrogenated (Ni0.6Nb0.4)0.65Zr0.35 alloy.

Structural Characteristics and Ferroelectric Properties of Bismuth-Based Compound Thin Films Crystallized by Hot Isostatic Pressing

After depositing amorphous (Bi0.5La0.5)(Ni0.5Ti0.5)O3 (BLNT) films on BLNT seed layer/Pt(100)/ MgO(100) substrates by room-temperature sputtering, the crystallization of the perovskite-struc- tured films has been tried by hot isostatic pressing (HIP). The samples with a single-phase perovskite structure HIP-treated at 800°C for 1 h under gas pressures of 0.51.0 MPa showed good crystallinity of  = 0.960.98 without accompanying the precipitation of the secondary phase. It was confirmed that a large root mean square roughness value of 44.2 nm for the sample HIP-treated at 800°C for 1 h under gas pressure of 0.1 MPa is due to innumerable Bi4Ti3O12-like rod-shaped grains precipitated in the film surface, based on atomic force microscopy. It is shown that the BLNT sample HIP-treated at 800°C for 1 h under gas pressure of 1.0 MPa exhibits the best hysteresis loop shape with a remanent polarization of Pr = 5 C/cm2 and a coercive field of Ec = 150 kV/cm of the six.

Corrosion behaviour of amorphous Ni–Si thin films on AISI 304L stainless steel

Nanoscale Ni – Si thin films are widely used in commercial microelectronic devices because of their promising electrical properties as well as their chemical stability. However, their application in corrosive environment has not been frequently addressed in the literature. In this study, amorphous Ni0.66Si0.33, Ni0.40Si0.60, and Ni0.20Si0.80 thin films are prepared on AISI 304L stainless steel by means of ion-beam sputter (IBS) deposition and their corrosion behaviour is studied using potentiodynamic polarisation measurements. The electrochemical measurements were conducted in 0.05M HCl solution at room temperature. By means of optical interferometer, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), the surface morphology and chemical composition of the thin films were examined before and after the electrochemical measurement. The evaluated results showed that the Ni–Si thin films may exhibit improved corrosion resistance over the 304L substrate provided that Si content is high enough to facilitate the formation of a Si-rich passive film.

金属ガラスの最適製造プロセスの開発および得られた金属ガラスの性質

In this report, structures and mechanical properties were studies for rapidly solidified Ni-Nb-Zr alloys and glassy Fe-based alloys shots with high strength and long life time for shot peening. The results obtained are summarized as follows.Rapidly solidified Ni-Nb-Zr alloys were formed in a wide composition range of 20 to 75at%Ni, 0 to 60 at%Nb and 0 to 80 at%Zr for formation of amorphous phase, 50 to 70at%Ni, 5 to 35 at%Nb and 5 to 45 at%Zr for formation of glass phase, respectively. The largest value of the supercooled liquid region was 51 K for Ni60Nb20Zr20 alloy. The crystallization temperature (Tx), Vickers hardness (Hv) and fracture strength (σf) of the amorphous (Ni0.5Nb0.5)100-xZrx (x=10, 20, 30 40) alloys were in the rang from 770 to 870 K, 540 to 760 and 1530 to 2300 MPa, respectively. The σf and Hv of the glassy Ni60Nb20Zr20 alloy with the largest supercoold liquid region are 2160 MPa and 700, respectively. The hydrogen permeability of the amorphous (Ni0.6Nb0.4)70Zr30 alloy ribbon was 1.3×10-8 mol/m-1/s-1/Pa-1/2 at 673 K which is slightly larger than that of thin pure Pd metal. Wide ribbons of 50 mm in wide were prepared for the amorphous Ni42Nb28Zr30 and glassy Ni60Nb20Zr20 alloys.Amorphous/glassy phases with volume fraction exceeding 98% in (Fe, Co, Ni)75B14Si8Mo3 alloy powder with spherical form of about 500μm in diameter were formed with wide composition ranges of 45 to 100at%Fe, 0 to 50at%Co and 5 to 55at%Ni, respectively. Glass transition temperature (Tg), Tx and supercoold liquid region (ΔTx=Tx-Tg) of Fe46Co5Ni24B14Si8Mo3 alloy were 789 K, 833 K and 44 K, respectively. The endurance life time of the glassy Fe-based alloy shots was 4 to 10 times longer than those for the conventional cast steel and high speed steel shots in the same shot peening condition. The maximum value of compressive residual stress in the tool (SKD11) steel shotted were 1600 MPa for the glassy Fe-based alloy shot and 1470 MPa for high speed steel shot, respectively.

Mechanical Properties of Melt-Spun Amorphous Ni-Nb-Zr Alloys after Hydrogen Charging

The effect of pre-charged hydrogen on the mechanical behavior of melt-spun amorphous Ni-Nb-Zr alloys was investigated. A substantial increase in the tensile fracture strength is observed even in hydrogen content up to about 46 at%. The Vickers hardness gradually increases with an increase in hydrogen content up to about 27 at%, and keeps almost the same value in the higher content more than 46 at%. It might be said that the amorphous (Ni0:6Nb0:4)70Zr30 alloy is not embrittled distinctly even in the high hydrogen content at room temperature. The amorphous alloy ribbons always curled during hydrogenation and the outer side of the curled ribbon corresponds to the roll side due to preferential absorption of hydrogen. XPS study revealed that the zirconium content in the surface film of the roll side surface is lower than that of the top side surface. The difference in surface composition as well as higher surface roughness of the roll side surface seems responsible for the preferential hydrogen absorption. [doi:10.2320/matertrans.47.1523]

Thermodynamic Properties of the Ni0.333Zr0.667Alloy in Amorphous and Crystalline States

The heat capacity of the Ni0.667Zr0.333 alloy in amorphous and crystalline states is measured by adiabatic calorimetry from 12 to 325 K. The thermal behavior of the amorphous alloy is studied by differential scanning calorimetry between room temperature and 900 K. Amorphous Ni0.667Zr0.333 is found to crystallize in the range 817–874 K, with a heat evolution maximum at 841 K and an enthalpy increment Δcr H = 3.58 kJ/mol. The heat capacity data are used to evaluate the thermodynamic properties of the Ni0.667Zr0.333 alloy in amorphous and crystalline states in the temperature range 12–325 K.

Thermodynamic Properties of the Ni0.667Zr0.333Alloy in Amorphous and Crystalline States

The heat capacity of the Ni0.667Zr0.333 alloy in amorphous and crystalline states is measured by adiabatic calorimetry from 12 to 325 K. The thermal behavior of the amorphous alloy is studied by differential scanning calorimetry between room temperature and 900 K. Amorphous Ni0.667Zr0.333 is found to crystallize in the range 817–874 K, with a heat evolution maximum at 841 K and an enthalpy increment Δcr H = 3.58 kJ/mol. The heat capacity data are used to evaluate the thermodynamic properties of the Ni0.667Zr0.333 alloy in amorphous and crystalline states in the temperature range 12–325 K.

Electron and positron states in amorphous Ni0.4Pd0.4P0.2

We performed local density calculations of the electronic and positron statesfor a 300-atom model of bulk amorphous Ni0.4Pd0.4P0.2. The procedure for constructing the model and the resultingdistribution of bond angles and free volume are described. Comparisons aremade to experiment and to models of amorphous Ni0.8P0.2.

NMR Relaxation in the Amorphous Ni0.33Zr0.67H x System*

NMR Relaxation in the Amorphous Ni0.33Zr0.67H x System*

Optical properties of polycrystalline and amorphous Ni1?xPx layers by ellipsometry

The optical properties of polycrystalline and amorphous d.c.-electrodeposited Ni1−xPx alloys in the visible spectral range are reported. Spectroscopic ellipsometry measurements of the pseudo-optical constants were performed from 1.65 to 3.1 eV for specimens with atomic fraction of phosphorus of 0.06<x<0.28. It was found that the dielectric functions of asdeposited Ni1−xPx could be expressed in the modified Drude-like form, including separate contributions from the interband transitions. Estimated values of the plasmon energy in the range of 5.3–3.1 eV and scattering time of the order of 10−15 s seem to show quantitative validity. A decrease in plasma frequency by a factor of about 1.4 across the glass-forming range agrees well with the predicted decrease in the s-p density of states at the Fermi level. Transformation of the amorphous Ni0.725P0.275 to the crystalline Ni3P+Ni phase caused by heating results in changed optical functions which exhibit large deviation from the single nearly-free-carrier approach. This would suggest a two-carrier and/or frequency-dependent Drude parameters model as offering a more reasonable description of the optical conductivity of crystalline two-phase Ni-P systems.