Structural Dynamics Behind the Formation of α'-Ni3Ga Alloy Nanoparticles from a Ni-Ga Phyllosilicate Dispersed on Silica Using X‑ray Probes

Our plain-English summary of Structural Dynamics Behind the Formation of α'-Ni3Ga Alloy Nanoparticles from a Ni-Ga Phyllosilicate Dispersed on Silica Using X‑ray Probes, by N.K. Zimmerli, D. Piankova, A. Kierzkowska, et al (Chemistry of Materials, 2025).

The study

• Authors: N.K. Zimmerli, D. Piankova, A. Kierzkowska, S. Checchia, F. Donat, C.R. Müller, P.M. Abdala
• Journal: Chemistry of Materials
• Published: 2025;37(14):5312-5324
• Read it: PubMed · Publisher · Free full text

Abstract

This study investigates the structural evolution during the formation of α'-Ni3Ga alloy nanoparticles from Ni-Ga phyllosilicate sheets upon heating in H2. The phyllosilicate sheets were produced through a deposition-precipitation process using Ni and Ga nitrates and colloidal SiO2. Advanced characterization techniques, including X-ray absorption spectroscopy, pair distribution function analysis, and electron microscopy, revealed the structure of the chrysotile-type phyllosilicates. Such phyllosilicates are composed of brucite-like layers with Ni2+ in octahedral coordination with oxygen (NiO6), intercalated by layers of silica tetrahedra (SiO4). Ga3+ ions partially replaced Ni2+ in octahedral positions within the brucite-like layers, but are also found in tetrahedral coordination, substituting Si4+ within the SiO4 layers of the phyllosilicate phase and/or dispersed on/in the surface of the amorphous SiO2 support. The structural transformation of the precursor material during thermal activation in H2 was monitored by d-PDF and XAS. It was observed that the decomposition of the Ni-Ga phyllosilicate starts in the temperature range 290-310 °C, resulting in the formation of small nickel-rich nanoparticles and gallium oxide (GaO x ) species. As the temperature is increased, Ga is reduced and is incorporated into the metallic nickel structure, ultimately forming intermetallic α'-Ni3Ga nanoparticles with an average size of about 5 nm. Our findings provide a detailed mechanistic understanding of the structural evolution of the phyllosilicate-based precursor, including alloy/intermetallic formation under thermal reduction conditions and highlight the potential of mixed-metal phyllosilicates as precursors for bimetallic catalysts.

© 2025 The Authors. Published by American Chemical Society.

In plain English

This was a laboratory chemistry study, not a study of people, animals or asbestos exposure. The authors made a catalyst precursor, NiGa/SiO2_DP, by a hydrothermal deposition-precipitation method using nickel and gallium nitrates and colloidal silica. Electron microscopy and X-ray measurements showed thin sheets whose atomic structure best matched a chrysotile-type model. Here the term describes the layered structure of a synthetic nickel silicate, not mined asbestos. Gallium sat in four-coordinated and six-coordinated positions, at a ratio of about 1.9 to 1. The material was then heated in hydrogen to 700 °C. Nickel reduction began at around 310 °C, half the nickel was metallic at about 450 °C, and nickel was fully reduced at 700 °C. The end product was an α′-Ni3Ga alloy. X-ray analysis gave an average coherence length of about 50 Å across the sample in the beam. Microscopy of roughly 30 particles showed diameters of about 6 to 8 nm. Some gallium oxide remained. The authors concluded that the findings should help guide the design of bimetallic catalysts.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Laboratory materials-chemistry experiment: synthesis and structural characterization of a catalyst precursor, including in situ X-ray measurements during heating in hydrogen. Not a health or exposure study.
• Who was studied: No human or animal subjects. The material studied was a synthetic nickel-gallium phyllosilicate on silica (NiGa/SiO2_DP). Nickel-only (Ni/SiO2_DP) and gallium-only (Ga/SiO2_DP) reference materials were made by a similar route.
• Exposure: No asbestos exposure was studied. The treatment examined was heating the synthetic material in hydrogen from 50 to 700 °C. 'Chrysotile-type' refers to the crystal-structure model of the synthetic nickel silicate.
• Main results:
  • Among the structural models tested, a chrysotile-type model (orthorhombic space group Cmc21) gave the best fit to the X-ray data for both NiGa/SiO2_DP and Ni/SiO2_DP.
  • In NiGa/SiO2_DP, fitting of gallium X-ray absorption data indicated a ratio of four-coordinated to six-coordinated gallium (GaO4 to GaO6) of approximately 1.9.
  • During heating of NiGa/SiO2_DP in hydrogen, reduction of nickel began at around 310 °C according to the X-ray absorption data.
  • About 50% of the nickel was metallic at about 450 °C, and nickel was fully reduced at 700 °C.
  • After hydrogen treatment, the final structure was an α′-Ni3Ga phase with a coherent particle size of about 50 Å by X-ray analysis. This is an average coherence length over the sample volume in the X-ray beam, not a direct measurement of particle diameter.
  • Electron microscopy of the hydrogen-treated material showed nickel-gallium nanoparticles about 6 to 8 nm in diameter on silica.
  • Some gallium oxide (GaOx) was not reduced and remained in the final activated catalyst.
• The authors' conclusion: The authors concluded that their findings are expected to help guide the design and synthesis of effective bimetallic catalysts.
• Limitations the authors state:
  • The pair distribution function analysis could not distinguish nickel from gallium.
  • The spectral decomposition method may have underestimated the amount of remaining gallium oxide.
  • The X-ray size is an average coherence length over the whole sampled volume. The microscopy size was based on a much smaller sample of about 30 particles.

Topics

Medical terms in this study, explained in our Lexicon: Phyllosilicates, Deposition, Chrysotile, Brucite, Octahedral Site.

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