Dislocation and Grain Boundary Diffusion in the Growth of α-Fe2O3Whiskers and Twinned Platelets peculiar to Gaseous Oxidation

Tallman, R.L.; Gulbransen, Earl A.

doi:10.1038/2181046a0

Cited by 36 publications

(15 citation statements)

References 4 publications

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“…6. Similar blades of Cr 2 O 3 , 12,13 Al 2 O 3 , 14 Fe 2 O 3 [15][16][17] and pyramids of CuO and NiO 18 have been also found. And their formation was enhanced by the existence of water vapour (H 2-O).…”

Section: External Oxidationsupporting

confidence: 66%

Thermal degradation of alloy CCA617 in pure steam at 750 and 850°C

Zheng

Yuan

et al. 2016

Corrosion Engineering, Science and Technology

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Oxidation and oxidation-induced microstructure evolution of CCA617 alloy was studied in pure steam at 750 and 850°C. Results showed that the alloy was oxidised approximately following a parabolic law. Temperature increase greatly promoted the external and internal oxidation. A single (Cr, Mn) 2 O 3 layer with distribution of minor TiO 2 and MnCr 2 O 4 formed at 750°C whereas a duplex oxide scale formed at 850°C consisting of a thin MnTiO 3 outer layer and a thicker (Cr, Mn) 2 O 3 inner layer. TiO 2 and Al 2 O 3 were formed internally especially along grain boundaries. Intragranular Mo-rich M 23 C 6 type carbides were also observed. The carbides dissolved into the matrix as oxidation progressed. Based on detailed compositional and microstructural characterisation of the oxidised alloy, the mechanisms of external and internal oxidation as well as dissolution of the intragranular carbides are presented.

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Section: External Oxidationsupporting

confidence: 66%

Thermal degradation of alloy CCA617 in pure steam at 750 and 850°C

Zheng

Yuan

et al. 2016

Corrosion Engineering, Science and Technology

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“…This, then, led Stringer (1972 to suggest that the dispersoid may only block short-circuit diffusion paths for chromium. These are not grain boundaries, which in ionic solids are short-circuit paths for anions and not cations (Laurent & Benard 1958), but dislocations, as possibly also occur in Fe20 3 (Tallman & Gulbransen 1968). The presence of the dispersoid in the alloy reduces the oxide grain size: if it is reduced below a level corresponding to the interdislocation distance in a pile-up, a single dislocation is not stable within the grain and will move to the grain boundary, where it ceases to be a cation diffusion path.…”

Section: P W Hittle and J Stringermentioning

confidence: 99%

Improvements in high temperature oxidation resistance by additions of reactive elements or oxide dispersions

Whittle

Stringer

1980

Phil. Trans. R. Soc. Lond. A

649

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The improvement in oxidation resistance of high temperature alloys as a result of additions of rare earth elements, other reactive metals, or dispersions of stable oxides, has been known for many years. Two effects seem the most important: first, the adhesion between scale and alloy is markedly improved and this increases the alloy’s resistance to thermal cycling exposure; secondly, in some but not all cases the actual growth rate of the oxide is also reduced. The various models proposed to explain these phenomena are discussed in the light of currently available experimental evidence. The most significant of these involve modification to the early, transient stages of oxidation, doping of the oxide which changes its transport properties, mechanical keying of the surface scale to the substrate by the formation of intrusions of oxide penetrating into the alloy and the elimination of void formation at the alloy-scale interface. The efficacies of the various beneficial additions are compared.

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“…With view to commercial applications, nanowire or nanostructure synthesis must also be realizable at low cost and with high reproducibility on a large scale. So far only few bottom-up techniques exist serving in principle this purpose (i) solution-based hydrothermal synthesis [18][19][20][21], (ii) electrodeposition [22], and (iii) thermal oxidation of iron [23][24][25][26][27]. That plain thermal oxidation of iron in air at elevated temperatures, as the method applied here, yields crystalline hematite nanowires and nanoflakes in a self-forming or catalystfree manner is known since the mid 50s [23] and was also observed for other metals such as copper [28].…”

Section: Introductionmentioning

confidence: 99%

Thermal oxidation synthesis of crystalline iron-oxide nanowires on low-cost steel substrates for solar water splitting

Dlugosch

Chnani

Muralidhar

et al. 2017

Semicond. Sci. Technol.

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Iron-oxide and in particular its crystallographic phase hematite (α-Fe 2 O 3 ) is a promising candidate for non-toxic, earth abundant and low cost photo-anodes in the field of photoelectrochemical water splitting. We report here on the synthesis of α-Fe 2 O 3 nanowires by thermal oxidation of low-cost steel substrates. Nanowires grown in this manner exhibit often a blade-like shape but can also possess a wire-like geometry partly decorated at their tip with an iron-rich ellipsoidal head consisting also of crystalline iron-oxide. We show furthermore that these ellipsoidal heads represent suitable growth sites leading in some cases to an additional growth of so-called antenna nanowires. Besides nanowires also nanoflakes were frequently observed at the surface. We discuss the influence of the oxidation temperature and other synthesis parameters as well as dispute the current growth models. Finally, we show that our α-Fe 2 O 3 nanostructures on steel are also photo-electrochemically active supporting in principle their use as photo-anode material.

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Dislocation and Grain Boundary Diffusion in the Growth of α-Fe2O3Whiskers and Twinned Platelets peculiar to Gaseous Oxidation

Cited by 36 publications

References 4 publications

Thermal degradation of alloy CCA617 in pure steam at 750 and 850°C

Thermal degradation of alloy CCA617 in pure steam at 750 and 850°C

Improvements in high temperature oxidation resistance by additions of reactive elements or oxide dispersions

Thermal oxidation synthesis of crystalline iron-oxide nanowires on low-cost steel substrates for solar water splitting

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