Synthesis, characterization and thermal behaviour of Fe0.65Co0.35-MgAl2O4 and Fe0.65Ni0.35-MgAl2O4 nanocomposite powders

Quénard, Olivier; Grave, E. De; Billon, Laurent; Rousset, A.

doi:10.1039/a703773b

Cited by 19 publications

(26 citation statements)

References 20 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Other catalysts (Co, Ni, and Fe/Co/Ni binary alloys) have been studied using the appropriate MgAl 2 O 4 -based solid solutions, with cobalt and equimolar Fe/Co alloys giving the best results. [12][13][14][15] Mg 1-x Co x O powders were also studied as precursors and are notably interesting because a simple soaking in HCl allows one to separate the CNTs from the CNT-Co-MgO powders formed upon reduction in H 2 /CH 4 . 2,3 The so-obtained CNTs, 90% of which are SWNTs and double-walled CNTs (DWNTs) with a diameter between 0.7 and 3 nm, are dispersed individually rather than in bundles and have a very high specific surface area (ca.…”

Section: Introductionmentioning

confidence: 99%

Carbon Nanotubes by a CVD Method. Part II: Formation of Nanotubes from (Mg, Fe)O Catalysts

et al. 2002

Self Cite

View full text Add to dashboard Cite

OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible. This is an author-deposited version published in : http://oatao.univ-toulouse.fr/ Eprints ID : 10385 The aim of this paper is to study the formation of carbon nanotubes (CNTs) from different Fe/MgO oxide powders that were prepared by combustion synthesis and characterized in detail in a companion paper. Depending on the synthesis conditions, several iron species are present in the starting oxides including Fe 2+ ions, octahedral Fe 3+ ions, Fe 3+ clusters, and MgFe 2 O 4 -like nanoparticles. Upon reduction during heating at 5°C/min up to 1000°C in H 2 /CH 4 of the oxide powders, the octahedral Fe 3+ ions tend to form Fe 2+ ions, which are not likely to be reduced to metallic iron whereas the MgFe 2 O 4 -like particles are directly reduced to metallic iron. The reduced phases are R-Fe, Fe 3 C, and γ-Fe-C. Fe 3 C appears as the postreaction phase involved in the formation of carbon filaments (CNTs and thick carbon nanofibers). Thick carbon nanofibers are formed from catalyst particles originating from poorly dispersed species (Fe 3+ clusters and MgFe 2 O 4 -like particles). The nanofiber outer diameter is determined by the particle size. The reduction of the iron ions and clusters that are well dispersed in the MgO lattice leads to small catalytic particles (<5 nm), which tend to form SWNTS and DWNTs with an inner diameter close to 2 nm. Well-dispersed MgFe 2 O 4 -like particles can also be reduced to small metal particles with a narrow size distribution, producing SWNTs and DWNTs. The present results will help in tailoring oxide precursors for the controlled formation of CNTs.

show abstract

Section: Introductionmentioning

confidence: 99%

Carbon Nanotubes by a CVD Method. Part II: Formation of Nanotubes from (Mg, Fe)O Catalysts

et al. 2002

Self Cite

View full text Add to dashboard Cite

show abstract

“…By contrast, much smaller (<5 nm) surface particles, in rather large quantities, are formed at higher temperature (1000 • C, maybe also at lower temperatures, notably 900 and 950 • C but with too small a size to be detected by FEG-SEM) and seem to correspond to the metallic Fe produced by each zirconia crystallite located at the surface. They could be attributed to ␥-Fe [24,25] solid solutions have revealed that the reduction of the more easily reducible transition metal cation promotes the reduction of the less reducible one(s), resulting in the formation of Fe/Cr, Co/Fe/Ni and Co/Fe alloy nanoparticles, respectively. However, this promoting effect is not thought to be probable if the two M/M x O y systems are too far apart in the Ellingham diagram that plots the variation of the free energy G of the oxidation reaction versus temperature, as is the case for Fe/Fe 2 O 3 and Zr/ZrO 2 , where ZrO 2 is considered to be unreducible.…”

Section: Resultsmentioning

confidence: 98%

“…In earlier works, we have shown that oxide solid solutions prepared by decomposition and calcination of oxalate mixtures or by nitrate/urea combustion are also potentially high-performance precursors because the as-such produced materials feature a very homogeneous distribution of the desired metallic ions in their structures. Using the appropriate temperature and duration in the reduction process of these precursors, one is able to precisely control the micro/nanostructure of Fe/Cr-Al 2 O 3 [15][16][17][18][19], Fe/CrCr 2 O 3 [20], Fe/Co/Ni-MgO [21,22] and Fe/Co/Ni-MgAl 2 O 4 [23][24][25] nanocomposite powders. Although Ni-Y 2 O 3 -ZrO 2 composites are claimed to be materials of greater importance for solid-oxide fuel cells [26], Fe-ZrO 2 ceramic-matrix micro-or nanocomposites have been seldom studied.…”

Section: Introductionmentioning

confidence: 99%

Synthesis of Fe-ZrO2 nanocomposite powders by reduction in H2 of a nanocrystalline (Zr, Fe)O2 solid solution

Resende

García

Peigney

et al. 2009

Journal of Alloys and Compounds

View full text Add to dashboard Cite

a b s t r a c tThe formation of Fe-ZrO 2 nanocomposite powders by reduction in hydrogen of a nanocrystalline totally stabilized Zr 0.9 Fe 0.1 O 1.95 solid solution was investigated by X-ray diffraction (XRD), field-emission-gun scanning electron microscopy (FEG-SEM) and Mössbauer spectroscopy. The reduction of the stabilized Zr 0.9 Fe 0.1 O 1.95 solid solution and the formation of metallic particles precedes the transformation of zirconia into the monoclinic phase, which becomes the major zirconia phase upon reduction at 950 • C. ␣-Fe particles with a size distribution slightly increasing from 10-50 to 20-70 nm upon the increase in reduction temperature are observed and a second population of smaller (<5 nm) ␥-Fe nanoparticles is also noticed when the reduction is performed at 1000 • C. Another metallic phase with a hyperfine field of ∼200 kOe at RT (∼250 kOe at 80 K) is detected, which could account for an Fe/Zr phase. It could be formed by the reduction on an Fe 2+ -rich transient phase incorporating a small fraction of the Zr 4+ ions, formed by a phase partitioning process superimposed to the reduciton processes.

show abstract

“…Examples of results obtained on these materials are given in recent publications. [1][2][3][4][5][6][7][8][9][10][11][12] To create nano-micro or nano-nano ceramic-based composites with excellent performance, a process for achieving a homogeneous dispersion of secondary particles in the matrix is required. The present study focused on developing a route using porous alumina preforms to obtain Ni-Al 2 O 3 nanocomposite powders with a uniform distribution of nano-sized metal particles in the ceramic matrix.…”

Section: Introductionmentioning

confidence: 99%

Nickel–alumina nanocomposite powders prepared by novel in situchemical reduction

Huang

Jiang

Michel³

et al. 2002

J. Mater. Res.

View full text Add to dashboard Cite

Nanocomposite powders of Ni-Al 2 O 3 (5 and 10 vol% Ni) were prepared from porous alumina preforms with high specific area (100 m 2 и g −1 ) impregnated with nickel nitrate. Samples were obtained by reduction under a controlled oxygen partial pressure either directly or through an intermediate step, giving nickel aluminum spinel. In both cases, homogeneous dispersions of nickel particles in the alumina matrix were achieved. The Ni particle size ranged from 10 to 100 nm, depending on the preparation conditions and temperature.

show abstract

Synthesis, characterization and thermal behaviour of Fe0.65Co0.35-MgAl2O4 and Fe0.65Ni0.35-MgAl2O4 nanocomposite powders

Abstract: OATAO is an open access repository that collects the work of Toulouse researchers and makes it freely available over the web where possible.

Cited by 19 publications

References 20 publications

Carbon Nanotubes by a CVD Method. Part II: Formation of Nanotubes from (Mg, Fe)O Catalysts

Carbon Nanotubes by a CVD Method. Part II: Formation of Nanotubes from (Mg, Fe)O Catalysts

Synthesis of Fe-ZrO2 nanocomposite powders by reduction in H2 of a nanocrystalline (Zr, Fe)O2 solid solution

Nickel–alumina nanocomposite powders prepared by novel in situchemical reduction

Contact Info

Product

Resources

About