Influences of NiCO3 content on the microstructure and magnetic properties of Ni0.5Zn0.5Fe2O4 powders prepared by SHS

Wang, Keqiang; He, Xiaodong; Xiao, Li; Jiang, Jing; Sun, Yue

doi:10.1007/s12598-009-0097-0

Cited by 5 publications

(2 citation statements)

References 13 publications

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“…These all match well with observations of turbostratic α-Ni(OH) 2 . ,− The Fe catalyst showed reflections at similar positions, 14°, 20°, 36°, and 60° 2θ, however with lower intensity, which have been reported for highly distorted FeOOH structures. − The d -spacings were found between ∼6–8 Å obtained from the (0 0 3) reflection, with small variations as a function of Fe-content. Changes in turbostratic oxyhydroxide structures are difficult to accurately interpret due to c -axis stacking faults. ,,,,− The relative peak intensities of the (1 0 1) and (1 1 0) reflections continued to decrease at increased Fe content, which is consistent with formation of more distorted phase, in line with earlier observations of the effect of Fe intrusion in Ni lattices. , …”

Section: Results and Discussionsupporting

confidence: 78%

Oxygen Evolution Reaction Dynamics, Faradaic Charge Efficiency, and the Active Metal Redox States of Ni–Fe Oxide Water Splitting Electrocatalysts

et al. 2016

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Mixed Ni-Fe oxides are attractive anode catalysts for efficient water splitting in solar fuels reactors. Because of conflicting past reports, the catalytically active metal redox state of the catalyst has remained under debate. Here, we report an in operando quantitative deconvolution of the charge injected into the nanostructured Ni-Fe oxyhydroxide OER catalysts or into reaction product molecules. To achieve this, we explore the oxygen evolution reaction dynamics and the individual faradaic charge efficiencies using operando differential electrochemical mass spectrometry (DEMS). We further use X-ray absorption spectroscopy (XAS) under OER conditions at the Ni and Fe K-edges of the electrocatalysts to evaluate oxidation states and local atomic structure motifs. DEMS and XAS data consistently reveal that up to 75% of the Ni centers increase their oxidation state from +2 to +3, while up to 25% arrive in the +4 state for the NiOOH catalyst under OER catalysis. The Fe centers consistently remain in the +3 state, regardless of potential and composition. For mixed Ni100-xFex catalysts, where x exceeds 9 atomic %, the faradaic efficiency of O2 sharply increases from ∼30% to 90%, suggesting that Ni atoms largely remain in the oxidation state +2 under catalytic conditions. To reconcile the apparent low level of oxidized Ni in mixed Ni-Fe catalysts, we hypothesize that a kinetic competition between the (i) metal oxidation process and the (ii) metal reduction step during O2 release may account for an insignificant accumulation of detectable high-valent metal states if the reaction rate of process (ii) outweighs that of (i). We conclude that a discussion of the superior catalytic OER activity of Ni-FeOOH electrocatalysts in terms of surface catalysis and redox-inactive metal sites likely represents an oversimplification that fails to capture essential aspects of the synergisms at highly active Ni-Fe sites.

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Section: Results and Discussionsupporting

confidence: 78%

Oxygen Evolution Reaction Dynamics, Faradaic Charge Efficiency, and the Active Metal Redox States of Ni–Fe Oxide Water Splitting Electrocatalysts

et al. 2016

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“…The Ni-Cu-Zn ferrite powder prepared by SHS has many advantages such as high purity magnetic powder, well sintering activity, low processing cost and energy efficiency; therefore, it has great extension value [1][2][3][4]. In the process of SHS preparation, the iron powder particle-size is larger(≥75 μm), so after ball grinding mixture the uniformity of the hybrid materials is low.…”

Section: Introductionmentioning

confidence: 99%

Self-Propagating High-Temperature Synthesis of Ni-Cu-Zn Ferrites with Alternative Fuel of Carbon Powder

Wang

Jiang

Tan

et al. 2014

AMR

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Ni-Cu-Zn ferrite powders were prepared by self-propagating high-temperature synthesis (SHS) using carbon powder with different mass fractions as fuel. The effects of carbon content in the raw materials on the phase composition, microstructure, density and magnetic property of the Ni-Cu-Zn powders were investigated by X-ray diffractometry(XRD), scanning electron microscope(SEM) and vibrating sample magnetometer(VSM), respectively. The results show that the use of carbon as a fuel brings no other impurities and improved the permeability. The single spinel phase powder was obtained when the precursor materials with a carbon powder of 5% in mass were used.

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Combustion synthesis of oxide powders

Liu,

Chen,

2025

Combustion Synthesis

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Influences of NiCO3 content on the microstructure and magnetic properties of Ni0.5Zn0.5Fe2O4 powders prepared by SHS

Cited by 5 publications

References 13 publications

Oxygen Evolution Reaction Dynamics, Faradaic Charge Efficiency, and the Active Metal Redox States of Ni–Fe Oxide Water Splitting Electrocatalysts

Oxygen Evolution Reaction Dynamics, Faradaic Charge Efficiency, and the Active Metal Redox States of Ni–Fe Oxide Water Splitting Electrocatalysts

Self-Propagating High-Temperature Synthesis of Ni-Cu-Zn Ferrites with Alternative Fuel of Carbon Powder

Combustion synthesis of oxide powders

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