Structure, Cation Distribution, and Properties of Nanocrystalline Titanomagnetites Obtained by Mechanosynthesis: Comparison with Soft Chemistry

Millot, Nadine; Perriat, Pascal; Caër, G. Le

doi:10.1006/jssc.1998.7808

Cited by 32 publications

(25 citation statements)

References 46 publications

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“…A room temperature aqueous precipitation method was developed to prepare Fe 3Àx Ti x O 4 titanomagnetite nanoparticles under ambient conditions in an anoxic glovebox (N 2 atmosphere from LN 2 boil-off; lower than 1 ppm residual O 2 ; hereafter referred to as the glovebox), using procedures similar to those described in [17][18][19][20]. A solution containing (1 + x) mol/L FeCl 2 : (2 À 2x) mol/L FeCl 3 , and x mol/L TiCl 4 was prepared by dissolving ferrous and ferric chloride in a 0.3 M HCl (pH < 1) solution, then adding titanium chloride drop-wise.…”

Section: Synthesismentioning

confidence: 99%

“…Because of the presence of a miscibility gap in the titanomagnetite series, synthesis of bulk materials requires growth at high temperature under a controlled atmosphere [14][15][16]. The nanoparticle format was desirable because high surface area materials are ideal for batch reactivity studies, allowing reaction rates to be measured on a laboratory timescale, and because early studies showed synthesis by aqueous precipitation at room temperature with controlled composition was possible [17][18][19][20]. To serve as a reference material and to act as standards for data analysis of the nanoparticles, microparticles were also synthesized using a high temperature protocol [3].…”

Section: Introductionmentioning

confidence: 99%

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Synthesis and properties of titanomagnetite (Fe3−xTixO4) nanoparticles: A tunable solid-state Fe(II/III) redox system

Pearce

Qafoku

Liu

et al. 2012

Journal of Colloid and Interface Science

121

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Titanomagnetite (Fe(3-x)Ti(x)O(4)) nanoparticles were synthesized by room temperature aqueous precipitation, in which Ti(IV) replaces Fe(III) and is charge compensated by conversion of Fe(III) to Fe(II) in the unit cell. A comprehensive suite of tools was used to probe composition, structure, and magnetic properties down to site-occupancy level, emphasizing distribution and accessibility of Fe(II) as a function of x. Synthesis of nanoparticles in the range 0≤x≤0.6 was attempted; Ti, total Fe and Fe(II) content were verified by chemical analysis. TEM indicated homogeneous spherical 9-12 nm particles. μ-XRD and Mössbauer spectroscopy on anoxic aqueous suspensions verified the inverse spinel structure and Ti(IV) incorporation in the unit cell up to x≤0.38, based on Fe(II)/Fe(III) ratio deduced from the unit cell edge and Mössbauer spectra. Nanoparticles with a higher value of x possessed a minor amorphous secondary Fe(II)/Ti(IV) phase. XANES/EXAFS indicated Ti(IV) incorporation in the octahedral sublattice (B-site) and proportional increases in Fe(II)/Fe(III) ratio. XA/XMCD indicated that increases arise from increasing B-site Fe(II), and that these charge-balancing equivalents segregate to those B-sites near particle surfaces. Dissolution studies showed that this segregation persists after release of Fe(II) into solution, in amounts systematically proportional to x and thus the Fe(II)/Fe(III) ratio. A mechanistic reaction model was developed entailing mobile B-site Fe(II) supplying a highly interactive surface phase that undergoes interfacial electron transfer with oxidants in solution, sustained by outward Fe(II) migration from particle interiors and concurrent inward migration of charge-balancing cationic vacancies in a ratio of 3:1.

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Section: Synthesismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Synthesis and properties of titanomagnetite (Fe3−xTixO4) nanoparticles: A tunable solid-state Fe(II/III) redox system

Pearce

Qafoku

Liu

et al. 2012

Journal of Colloid and Interface Science

121

View full text Add to dashboard Cite

show abstract

“…Among the numerous methods of nanometer-sized powder synthesis, soft chemistry precipitation has been chosen (17,18). Synthesis conditions were controlled to obtain powders homogeneous in size and oxygen stoichiometry (19).…”

Section: Nanoparticles Preparationmentioning

confidence: 99%

Influence of Grain Size, Oxygen Stoichiometry, and Synthesis Conditions on the γ-Fe2O3 Vacancies Ordering and Lattice Parameters

Belin

Millot

Caillot

et al. 2002

Journal of Solid State Chemistry

124

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“…Related strategies have been used elsewhere, including studies of methylene blue reduction by Fe 3Àx Ti x O 4 (0 6 x 6 0.78) in the presence of H 2 O 2 (Yang et al, 2009), and nitrobenzene reduction using partially oxidized magnetite (ratios 61:2) . Furthermore, titanomagnetite nanoparticles are relatively easy to produce with precisely controlled composition and structure by room temperature synthesis (Millot et al, 1998;Perriat et al, 1999;Guigue-Millot et al, 2001Pearce et al, 2012) and, because of their high specific surface area, experimental sensitivity to Tc(VII) reduction and accompanying changes to the solid surface is greatly improved. Finally, the selected system has unique advantages in terms of spectroscopic discrimination and tracking of concentration and oxidation state changes in various possible reactive pools of solid-associated Fe(II), including that structurally ordered within the bulk structure and that near the solid surface.…”

Section: Introductionmentioning

confidence: 99%

Tc(VII) reduction kinetics by titanomagnetite (Fe3−xTixO4) nanoparticles

Liu

Pearce

Qafoku

et al. 2012

Geochimica et Cosmochimica Acta

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Technetium contamination remains a major environmental problem at nuclear reprocessing sites, such as at the Hanford nuclear reservation, Washington, USA. Here we investigate the heterogeneous reduction of the highly soluble pertechnetate anion [Tc(VII)O 4 À ] to sparingly soluble Tc(IV)-bearing solids by a novel and well-characterized set of mixed-valent titaniumdoped magnetite nanoparticles, structurally and chemically analogous to titanomagnetites naturally present in Hanford sediments. Titanomagnetite (Fe 3Àx Ti x O 4 ) nanoparticles (10-12 nm) with varying Ti content (0 6 x 6 0.53) were synthesized in aqueous suspension. Reaction with 10 and 30 lM Tc(VII) solution yielded fast exponentially decaying reduction kinetics with rates that increased with increasing solid-state Fe(II)/Fe(III) ratio in the nanoparticles, a characteristic systematically controlled by the Ti-content. Nanoparticles before and after reduction experiments and surface-associated products of Tc(VII) reduction were characterized using transmission electron microscopy (TEM), X-ray absorption near-edge spectroscopy (XANES), extended X-ray absorption fine structure spectroscopy (EXAFS), micro X-ray diffraction (l-XRD), X-ray absorption (XA) and X-ray magnetic circular dichroism (XMCD). A mechanistic reaction model was developed involving reduction of Tc(VII) to form Tc(IV)/Fe(III) solids by structural Fe(II) enriched at the nanoparticle surface, a reactive Fe(II) pool that during reaction is resupplied and sustained by outward migration of Fe(II) from the particle interior with concurrent inward migration of charge-balancing cationic vacancies in a ratio of 3:1. The reaction process was quantitatively linked to mass and electron balanced changes in the Fe 3Àx Ti x O 4 nanoparticles, and the accessibility of structural Fe(II) from these phases was determined.

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Structure, Cation Distribution, and Properties of Nanocrystalline Titanomagnetites Obtained by Mechanosynthesis: Comparison with Soft Chemistry

Cited by 32 publications

References 46 publications

Synthesis and properties of titanomagnetite (Fe3−xTixO4) nanoparticles: A tunable solid-state Fe(II/III) redox system

Synthesis and properties of titanomagnetite (Fe3−xTixO4) nanoparticles: A tunable solid-state Fe(II/III) redox system

Influence of Grain Size, Oxygen Stoichiometry, and Synthesis Conditions on the γ-Fe2O3 Vacancies Ordering and Lattice Parameters

Tc(VII) reduction kinetics by titanomagnetite (Fe3−xTixO4) nanoparticles

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