Gas atomization of Al–Ni powders: Solidification modeling and neutron diffraction analysis

Tourret, Damien; Reinhart, Gunther; Gandin, Charles‐André; Iles, Gail N.; Dahlborg, U.; Calvo-Dahlborg, M.; Bao, C.M.

doi:10.1016/j.actamat.2011.07.023

Cited by 51 publications

(22 citation statements)

References 23 publications

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“…Neutron and X-ray diffraction studies [13,21] have shown that for Ni concentrations of  25 at.% the fraction of NiAl 3 decreases with increasing cooling rates (which for gas atomization corresponds to decreasing particle diameter) while the fraction of A further complexity when considering gas atomized powders is that the stochastic nature of the nucleation process within a population of rapidly cooling droplets leads to considerable variability within a sample of notionally similar droplets. To a good first approximation, droplets of the same size will be subjected to the same cooling rate.…”

Section: Introductionmentioning

confidence: 99%

“…A number of studies have shown that melt spun ribbons [11,12] could lead to a catalyst with higher activity and could allow the possibility of higher Al concentrations, something that proves difficult via the castcrush route due to the extreme friability of the resulting catalyst [10]. In recent years there has been an upsurge in interest in gas atomized Raney type Ni precursors [13][14][15], with Al concentrations in the range 68.5-82.5 at.% being investigated. Gas atomization would be expected to give cooling rates of the order 10 2 -10 5 K s -1 [16][17][18] (depending upon particle size and, to a lesser extent, gas type) with catalytic activities in the subsequently activated catalyst [14] more than twice that of conventional Raney type Ni being reported.…”

Section: Introductionmentioning

confidence: 99%

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A microstructural investigation of gas atomized Raney type Al-27.5 at.% Ni catalyst precursor alloys

Mullis

Bigg

Adkins

2015

Journal of Alloys and Compounds

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Quantitative image analysis has been used to investigate the phase composition of gas atomized powders of a Raney type Ni catalyst precursor alloys of composition Al-27.5 at.% Ni in the powder size range 150-212 m. We find that there are considerable variations in phase composition both between powders from the same batch and as a function distance from the particle surface within individual particles. Such variations may have significant implications for the future production and uptake of such catalysts, including the necessity for post-production crushing of gas atomized powders. Models are proposed to account for both variations.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A microstructural investigation of gas atomized Raney type Al-27.5 at.% Ni catalyst precursor alloys

Mullis

Bigg

Adkins

2015

Journal of Alloys and Compounds

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“…A number of studies have shown that melt spun ribbons [9,10] could lead to a catalyst with higher activity and could allow the possibility of utilising higher Al concentrations, something that proves difficult via the cast-crush route due to the extreme friability of the resulting catalyst [8]. In recent years there has been an upsurge in interest in gas atomized Raney-type Ni precursors [11][12][13][14], with Al concentrations in the range 68.5-82.5 at.% being investigated. Gas atomization would be expected to give cooling rates of the order 10 3 -10 5 K s -1 (see e.g.…”

Section: Introductionmentioning

confidence: 99%

Structure and phase-composition of Ti-doped gas atomized Raney-type Ni catalyst precursor alloys

2015

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Raney-type Ni precursor alloys containing 75 at.% Al and doped with 0, 0.75, 1.5 and 3.0 at.% Ti have been produced by a gas atomization process. The resulting powders have been classified by size fraction with subsequent investigation by powder XRD, SEM and EDX analysis. The undoped powders contain, as expected, the phases Ni 2 Al 3 , NiAl 3 and an Al-eutectic. The Ti-doped powders contain an additional phase with the TiAl 3 DO 22 crystal structure. However, quantitative analysis of the XRD results indicate a far greater fraction of the TiAl 3 phase is present than could be accounted for by a simple mass balance on Ti. This appears to be a (Ti x Ni 1-x )Al 3 phase in which higher cooling rates favour small x (low Ti-site occupancy by Ti atoms). SEM and EDX analysis reveal that virtually all the available Ti is contained within the TiAl 3 phase, with negligible Ti dissolved in either the Ni 2 Al 3 or NiAl 3 phases.

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“…Tourret et al 1 stated that the catalytic activity depends on the amount of phases in the atomized powders. The desired microstructural arrangement is mainly affected by alloy composition and powder size.…”

Section: Introductionmentioning

confidence: 99%

Rapid solidification of an Al-5Ni alloy processed by spray forming

et al. 2012

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Recently, intermetallic compounds have attracted much attention due to their potential technological applications as high-temperature materials. In particular the intermetallic compounds, associated with the Al-Ni binary system stand out as promising candidates for high-temperature materials for the use in harsh environments. It is expected that a bulk Al-Ni alloy may exceed the strength of many commercial materials. The great challenge in developing these alloys is to manipulate the solidification thermal parameters in order to obtain the desired microstructural features. One of the indicated routes to obtain very refined intermetallic phases dispersed in the microstructure is the spray forming process. The dendritic and eutectic growth dependences on cooling rate are already known for directionally solidified (DS) hypoeutectic Al-Ni alloys. In the case of rapidly solidified (RS) samples, extrapolations of such experimental laws are needed, which can be very helpful to estimate realistic values of high cooling rates imposed during the spray forming process. The present study aims to compare directionally solidified and spray-formed Al-5 wt. (%)Ni alloy samples with a view to providing a basis for understanding how to control solidification parameters and the as-cast microstructure. The Al-5.0 wt. (%)Ni alloy was shown to have a cellular morphology for the overspray powder size range examined (up to 500 µm). The mean cell spacing decreased from 5.0 to 1.1 µm with the decrease in the powder average diameter. It was found that the experimental cooling rates imposed during the atomization step of the overspray powder solidification varied from 10 3 to 2.10 4 K/s. The DSC trace depicted a crystallization peak of an amorphous structure fraction in the smallest Al-5.0 wt. (%)Ni alloy powder size range (<32 µm) estimating a 15 µm critical diameter of amorphous powder in the binary Al 97.5 Ni 2.5 (at%) alloy.

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Gas atomization of Al–Ni powders: Solidification modeling and neutron diffraction analysis

Cited by 51 publications

References 23 publications

A microstructural investigation of gas atomized Raney type Al-27.5 at.% Ni catalyst precursor alloys

A microstructural investigation of gas atomized Raney type Al-27.5 at.% Ni catalyst precursor alloys

Structure and phase-composition of Ti-doped gas atomized Raney-type Ni catalyst precursor alloys

Rapid solidification of an Al-5Ni alloy processed by spray forming

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