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Developing efficient anode catalysts for direct ammonia solid oxide fuel cells (NH3-SOFCs) under intermediate-temperatures is of great importance, in support of hydrogen economy via ammonia utilization. In the present work, the pyrochlore-type La2Zr2−xNixO7+δ (LZNx, x = 0, 0.02, 0.05, 0.08, 0.10) oxides were synthesized as potential anode catalysts of NH3-SOFCs due to the abundant Frankel defect that contributes to the good conductivity and oxygen ion mobility capacity. The effects of different content of Ni2+ doping on the crystal structure, surface morphology, thermal matching with YSZ (Yttria-stabilized zirconia), conductivity, and electrochemical performance of pyrochlore oxides were examined using different characterization techniques. The findings indicate that the LZNx oxide behaves as an n-type semiconductor and exhibits an excellent high-temperature chemical compatibility and thermal matching with the YSZ electrolyte. Furthermore, LZN0.05 exhibits the smallest conductive band potential and bandgap, making it have a higher power density as anode material for NH3-SOFCs compared to other anodes. As a result, the maximum power density of the LZN0.05-40YSZ composite anode reaches 100.86 mW/cm2 at 800 °C, which is 1.8 times greater than that of NiO-based NH3-SOFCs (56.75 mW/cm2) under identical flow rate and temperature conditions. The extended durability indicates that the NH3-SOFCs utilizing the LZN0.05-40YSZ composite anode exhibits a negligible voltage degradation following uninterrupted operation at 800 °C for 100 h. [ABSTRACT FROM AUTHOR]

[Display omitted] • Polyaniline (PANi) and Ni particles modified composite electrode was prepared electrochemically on fluorine-doped tin oxide (FTO) • The FTO/PANi-Ni hybrid electrode exhibits high durability and low poisoning effect. • High performance, low cost and easy fabrication make this electrode a promising anode for DMFCs. A metal–organic composite thin film composed of polyaniline (PANI) and Ni was prepared and characterized for methanol electrooxidation reaction. First, PANI thin films were electrodeposited on a fluorine-doped tin oxide (FTO) coated glass support in an aqueous acidic solution. Subsequently, the polymer film was modified with Ni particles (FTO/PANI-Ni) by chronoamperometric (CA) technique. The composite film was characterized by structural, morphological and electrocatalytic analyses. X-ray diffraction (XRD) results confirmed the crystallization of Ni according to the cubic structure. Scanning electron microscopy (SEM) images showed that the Ni nanoparticles were uniformly dispersed on the PANI surface. The electrocatalytic performance of the FTO/PANI-Ni composite electrode for the methanol electrooxidation reaction was investigated in 0.5 M KOH solution containing methanol using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and chronoamperometry (CA) techniques. The effects of temperature and methanol concentration on the methanol electrooxidation performance were also studied. The modified composite catalyst exhibited an electrochemically active surface area of 0.5235 cm2. The presence of Ni nanoparticles on the polymer surface promoted the adsorption of methanol molecules and facilitated the oxidation process, leading to higher current densities and better overall performance. The maximum current density was 14 mA cm-2 and the electrode maintain 68 % of its initial activity even after 200 cycles, indicating that the FTO/PANI-Ni electrode exhibited good stability. The high methanol oxidation performance of the composite electrode was associated with large real surface area, a possible synergistic effect between the polymer moleucles and Ni particles as well as high intrinsic activity of Ni for this process. [ABSTRACT FROM AUTHOR]

Graphene has attained a considerable amount of popularity as an attractive ultra-thin reinforcement for nickel (Ni) matrix composites in recent years. However, its excellent reinforcement efficiency is suffered from the agglomeration of graphene nanosheets in manufacturing process and the poor bonding strength of graphene with Ni matrix. To overcome these two problems, one of the efficient strategies is to in-situ grow graphene reinforcements on Ni particles for powder metallurgy. This work aims to synthesize uniform graphene@Ni composite particles by using polymethyl methacrylate (PMMA) as the solid sources for chemical vapor deposition (CVD) process. The results demonstrate that few-layer or multilayer graphene with different morphologies can be grown on the particles by controlling the PMMA content and annealed temperature, respectively. The optimum condition for the formation of high-quality few-layer graphene is 1.0 mg·ml−1 PMMA and 900 °C. A competition mechanism rises from the growth kinetic, and the spatial confinement effect has led to the formation of graphene with different microstructures and morphologies. [ABSTRACT FROM AUTHOR]

Summary: Vitreous carbon (VC) and pyrolytic carbon (PC) were covered by nickel particles through sputter deposition, consisting in the Ni/VC and Ni/PC electrodes, respectively. These materials were tested as cathodes in an aqueous solution of tetrafluoroborate of the 3‐triethylammonium‐propane sulfonic acid ionic liquid (TEA‐PS.BF4) for hydrogen production and characterized by scanning electron microscopy (SEM), chronoamperometry (CA), linear and cyclic voltammetry (LV and CV), and electrochemical impedance spectroscopy (EIS). The mechanism of the hydrogen evolution reaction (HER) was that of Volmer‐Heyrovsky for all the cathodes tested, and the H2 desorption at the catalytic surface is the determining step. The results indicate that different carbon supports can affect the efficiency of the particulate electrocatalyst deposited on it. The low values of H+ adsorption and the H2 desorption resistances of the modified PC system (0.43 and 0.8 Ω cm2, respectively), in relation to the modified VC system (1.13 and 7.9 Ω cm2, respectively), attest that Ni particles presence on PC favored the adsorption of H+ and H2 nanobubble desorption. The Ni particles on PC increase exchange current density (80.5 μA cm2 for Ni/PC cathode about 38.3 Ω cm2 for Ni/VC cathode) and enhance catalytic activity. These results can be attributed to the faster liberation of the active sites due to the interaction between the Ni particles and the PC support. In addition, the TEA‐PS.BF4 solution can act as a stripper, avoiding the formation of passive oxides in the open circuit and preventing the deactivation of the electrocatalyst. [ABSTRACT FROM AUTHOR]

Abstract LaAl 1-x Ni x O 3 (with x = 0.05 and 0.2) perovskite oxides were successfully synthesized and its behavior under reduction atmosphere was studied. HRTEM and STEM studies, coupled to HAADF and EDX detection, allowed to evidence the Ni exsolution process to the surface of the solid and to build nano-catalytic centers. The size of these centers is independent of the reduction conditions in the range studied. The high specific surface of the raw material, its porosity and the structure defects could be responsible of the low temperature at which the exsolution process starts. The content of Ni dopants allows the control of Ni centers size on the surface and the synthesis method provides Ni-nanoparticles strongly anchored to the resultant support. Graphical abstract Ni-nanoparticle strongly anchored to the LaAlO 3 support. Image 1 Highlights • Perovskites behavior under reducing atmosphere were studied. • Ni exsolution process to surface build nano-catalytic centers. • The size of Ni particles is independent on the reduction conditions in the range studied. • The content of Ni dopants allows the control of Ni centers size at the surface. • The synthesis method provides Ni-nanoparticles strongly anchored to the resultant support. [ABSTRACT FROM AUTHOR]

Fabrication of transition-metal catalytic materials is regarded as a promising strategy for developing high-performance sodium-selenium (Na-Se) batteries. However, more systematic explorations are further demanded to find out how their bonding interactions and electronic structures can affect the Na storage process. This study finds that lattice-distorted nickel (Ni) structure can form different bonding structures with Na 2 Se 4 , providing high activity to catalyze the electrochemical reactions in Na-Se batteries. Using this Ni structure to prepare electrode (Se@NiSe 2 /Ni/CTs) can realize rapid charge transfer and high cycle stability of the battery. The electrode exhibits high storage performance of Na + ; i.e., 345 mAh g⁻ 1 at 1 C after 400 cycles, and 286.4 mAh g⁻ 1 at 10 C in rate performance test. Further results reveal the existence of a regulated electronic structure with upshifts of the d-band center in the distorted Ni structure. This regulation changes the interaction between Ni and Na 2 Se 4 to form a Ni 3 -Se tetrahedral bonding structure. This bonding structure can provide higher adsorption energy of Ni to Na 2 Se 4 to facilitate the redox reaction of Na 2 Se 4 during the electrochemical process. This study can inspire the design of bonding structure with high performance in conversion-reaction-based batteries., (© 2023 Wiley-VCH GmbH.)

Solvothermal synthesis offers an important approach to prepare nickel particles with high crystallinity and low agglomeration. In this study, submicron nickel particles are prepared by a solvothermal approach involving alcohol reduction with the assistance of different types of organic bases. The influences of the types of organic bases and solvents, and the amount of organic bases on the particle size and morphology of nickel are studied. It is found that an organic base with a stronger alkalinity is able to generate nickel particles with smaller size. Smaller nickel particles are also prone to be obtained from solvents with a stronger reducing ability. Moreover, the formation mechanism of nickel particles is investigated. It is found that the nickel precursor and OH− form nickel layered hydroxide salts at the initial stage, and then the nickel layered hydroxide salts gradually dissolve to form nickel particles. Magnetic measurement reveals the morphology-dependent magnetic properties. Although the sample which has the smallest size exhibits a relatively high coercivity, samples which have a rather large particle size but consist of smaller primary nanoparticles also show relatively high coercivity values. [Display omitted] • Nickel submicron particles are synthesized via a solvothermal approach in alcohols. • Organic bases with stronger alkalinity are found to generate smaller particles. • Nickel particles with a narrow size distribution (182 ± 18 nm) are obtained. • The formation mechanism of nickel particles in solvothermal conditions is revealed. • Morphology-dependent magnetic properties are observed. [ABSTRACT FROM AUTHOR]

5wt% of Ni supported on activated carbon, Al 2 O 3 and Carbon covered Al 2 O 3 (C-Al 2 O 3 ) prepared by impregnation technique have been subjected to nitrobenzene hydrogenation at atmospheric pressure in vapour phase conditions. The catalysts were characterized by XRD, BET surface area, TPR and H 2 -Pulse chemisorption. Among the catalysts, Ni/C-Al 2 O 3 catalyst exhibited excellent and steady activity in the nitrobenzene hydrogenation at 498 K which can be attributed to the presence of smaller Ni particles with proper metal support interaction. [ABSTRACT FROM AUTHOR]

The effect of the high order structure of an isotactic polypropylene (PP) composite on the resistivity of composites containing magnetically aligned Ni particles was studied. Only a small amount of particles needed to be added for the composite material to become conducting after heating while in a magnetic field. The Ni columns formed on applying the field were distorted by the formation of large PP spherulites. Changes to the crystallization process due to the addition of a nucleating agent gave rise to changes in the columnar structure, resulting in large changes in the resistivity of the composite material. Controlling the high order structure of the polymer matrix including its morphology is very important in order to be able to control the magnetically aligned Ni structure. [ABSTRACT FROM AUTHOR]

Abstract: Epidemiological studies show that exposure to nickel (Ni) compounds is associated with a variety of pulmonary adverse health effects, such as lung inflammation, fibrosis, emphysema and tumours. However, the mechanisms leading to pulmonary toxicity are not yet fully elucidated. In the current study we used Calu-3, a well differentiated human bronchial cell line, to investigate in vitro the effect of Ni in soluble form (NiCl2) and in the form of micro-sized Ni particles on the airway epithelium. For this purpose, we evaluated the effect of Ni compounds on the epithelial barrier integrity by monitoring the transepithelial electrical resistance (TEER) and on oxidative stress pathways by measuring reactive oxygen species (ROS) formation and induction of stress-inducible genes. Our results showed that exposure to NiCl2 and Ni particles resulted in a disruption of the epithelial barrier function observed by alterations in TEER, which occurred prior to the decrease in cell viability. Moreover, Ni compounds induced oxidative stress associated with ROS formation and up-regulation of the stress-inducible genes, Metallothionein 1X (MT1X), Heat shock protein 70 (HSP70), Heme oxygenase-1 (HMOX-1), and gamma-glutamylcysteine synthetase (γGCS). Furthermore, we have demonstrated that the induced effects by Ni compounds can be partially attributed to the increase in Ni ions (Ni2+) intracellular levels. [Copyright &y& Elsevier]

Abstract: This study forms composite solders by adding 0.5–3wt% of Ni particles in situ to Sn–3.5wt%Ag lead-free solder. Cu/solder/Cu specimens are prepared by dipping two Cu rods into a solder bath to produce a solder joint. Some of the joint specimens are retained in the as-soldered condition, while the others are aged at 150°C for 100, 200, 400, or 500h, respectively. The experimental results reveal that the addition of Ni to the molten Sn–Ag solder leads to the formation of in situ Ni3Sn4 dispersoids. The adhesive strength of the joint is found to increase with increasing Ni content in the as-soldered specimens. In general, the strength of the thermally processed specimens reduces as the thermal storage time increases. The Sn–Ag–0.5wt%Ni joints show a mixture of ductile and brittle fracture, whereas the joints containing more than 1wt% of Ni show mainly brittle fracture with solder residue at the exposed (Cu,Ni)6Sn5 IMC layer. [Copyright &y& Elsevier]

Results of molecular-dynamics simulations of the condensation of Ni atoms from a supersaturated gas phase and the subsequent formation and growth of particles in an Ar atmosphere are reported. The Ni concentration and the Ar partial pressure resemble the conditions found in recent shock-tube experiments. In order to achieve a realistic description of the microscopic processes leading to particle formation, the inert gas atoms were explicitly included in the simulations. Excess energy released during the nucleation processes is thereby transferred directly to the carrier gas via collision events. The influence of temperature on the speed of Ni atom condensation as well as particle growth is investigated. Rates of formation of Ni dimers are calculated and compared with values obtained from experiment. [ABSTRACT FROM AUTHOR]

Abstract: Polypyrrole films modified with Ni Particles were eletrodeposited using a constant potential on a Pt/quartz crystal electrode with the aim to investigate the changes in the voltammetric and mass profiles compared with pure polypyrrole. The electrochemical behavior of the polypyrrole with Ni showed a new cathodic peak at −0.73V associated to Ni2+ reduction. Besides, it was characterized that there is a redox-pair of the polymer and Ni and a model was proposed to explain the phenomenon considering the eletroneutrality principle. The transport of the ion into (or outside) the polymer is opposite to the expected direction. This occurs due to the redox-pair between the PPy chain and Ni species which can be explained by a loss of anions during Ni oxidation and the gain of anions during the Ni reduction. [Copyright &y& Elsevier]

In this study, various amounts of Ni particles were added in situ to Sn–3·5 wt-%Ag lead free solder to form new composite solders. Copper substrates were then dipped into these solders and aged at 150°C for 0, 25, 225, or 1000 h. The microstructure and microhardness of the as solidified solder and the aged solder/copper couples were investigated. Experimental results revealed that the addition of Ni particles increased the microhardness of the composite solder. Ni additions of less than 3 wt-% yielded a microstructure of β-Sn grains surrounded by a eutectic mixture of Ag3Sn and a Sn rich matrix. An intermetallic compound of Ni3Sn4 particles was dispersed throughout the eutectic. For 5 wt-%Ni addition, the Ni3Sn4 phase and the remaining Ni particles were agglomerated. In the case of copper substrate dipped with a thick layer of composite solder, water quenched and then aged at 150°C, the induced (Ni, Cu)3Sn4 particles coarsened and agglomerated. Additionally, the intermetallic (Cu, Ni)6Sn5 compound layer formed at the solder/Cu interface thickened with increasing Ni content. [ABSTRACT FROM AUTHOR]