Influence of residual stresses on the evolution of micro-structure during the partial reduction of NiAl2O4

Üstündag, Ersan; Zhang, Zhimeng; Stöcker, Melanie; Rangaswamy, P.; Bourke, M.A.M.; Subramanian, Shanthi; Sickafus, Kurt E.; Roberts, J. A.; Sass, S.L.

doi:10.1016/s0921-5093(97)00433-4

Cited by 22 publications

(9 citation statements)

References 6 publications

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“…Partial reduction of mixed oxides has been exploited in other systems (Fe-Mn-O [37,38], Ni-Al-O [38][39][40], AlCr-O [41] ) to produce metal-ceramic composites. For example, large grain nickel aluminate spinel (NiAl 2 O 4 ) can be transformed into a microstructure consisting of fine metallic Ni particles dispersed in either a matrix of a-or halumina, depending on the reducing conditions [38,40]. The microstructure of the CuAlO 2 -derived Cu-alumina composite differs from that obtained from the aforementioned systems in several important aspects.…”

Section: Generalmentioning

confidence: 99%

Novel interpenetrating Cu–Al2O3 structures by controlled reduction of bulk CuAlO2

et al. 2014

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Bulk CuAlO 2 with the delafossite structure was processed using two different methods. In one case, stoichiometric CuAlO 2 powder was processed using the solution technique, and consolidation was carried out by pressureless sintering in air. In the second case, high purity starting powders of alumina and copper (I) oxide were consolidated by spark plasma sintering. The sintered body was then subjected to a high temperature anneal in air. Reduction of the bulk CuAlO 2 samples resulted in a novel composite microstructure with copper forming a continuous intergranular phase. The prior CuAlO 2 grains decomposed into an intimate two-phase mixture of metallic copper and h-alumina. The scale of the composite structures ranged from nanometers to microns. Previous work on the delafossite family has focused primarily on the electronic properties of thin films. The present study suggests that the reduction of this class of mixed oxides gives rise to metal-ceramic structures with unique interfacial and morphological properties.

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Section: Generalmentioning

confidence: 99%

Novel interpenetrating Cu–Al2O3 structures by controlled reduction of bulk CuAlO2

et al. 2014

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“…Many studies of the reduction in NiAl 2 O 4 are available in literature, but little information is available on the reduction of Ni x Mg 1− x Al 2 O 4 . Quenard investigated the reduction of Co x Mg 1− x Al 2 O 4 and Ni x Mg 1− x Al 2 O 4 , but the transition‐metal loadings were quite low, sufficient to give only 4 wt% metal at complete reduction.…”

Section: Reduction Processmentioning

confidence: 99%

Atomic Scale Mechanisms of the Reduction of Nickel–Magnesium Aluminate Spinels

Hill

Misture

2013

J. Am. Ceram. Soc.

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The dynamics of the reduction reaction of Ni x Mg 1−x Al 2 O 4 to form nickel metal and a remnant oxide was quantified to understand spinel behavior in catalysis applications. X-ray diffraction, thermogravimetry, and pycnometry were employed to track the evolution of high-Ni spinels to metastable nonstiochiometric spinels during reduction, but before the phase transformation to theta alumina. Rietveld refinements of X-ray diffraction data were used to quantify structural changes in the spinel and the phase fraction, crystallite size, and microstrain of all phases during H 2 reduction. During reduction, one O 2− is lost for each Ni 2+ reduced to Ni metal. Ni 0.25 Mg 0.75 Al 2 O 4 and Ni 0.5 Mg 0.5 Al 2 O 4 were shown to form Ni metal and a non-stoichiometric spinel of the same Mg-Al ratio as the starting composition. NiAl 2 O 4 and Ni 0.75 Mg 0.25 Al 2 O 4 were found to become unstable as full reduction was approached, and metastable spinel, Θ-Al 2 O 3 , and a-Al 2 O 3 formed sequentially given sufficient time at temperature. †

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“…Figure supports this, showing that small particles are developing on the sample surface and are believed to be Ni nanoparticles , , . Despite the decreased porosity, the scaled characteristic strength is found to be lower than for the 1 wt.% ALT doped samples; this can be explained by the fact that the reduction of NiAl 2 O 4 is accompanied by a theoretical volume shrinkage of ∼18% that can generate residual stresses detrimental to the system .…”

Section: Resultsmentioning

confidence: 99%

Effect of Aluminum Titanate (Al₂TiO₅) Doping on the Mechanical Performance of Solid Oxide Fuel Cell Ni‐YSZ Anode

McCleary

Amendola

2017

Fuel Cells

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The mechanical behavior of un‐doped and 1–10 wt.% aluminum titanate doped NiO‐YSZ anodes was evaluated in the oxidized and reduced state of the material. Sample bars 25 × 5 × 2 mm were fabricated and tested in a three‐point bending apparatus and statistical analyzes of the collected data were performed. A remarkable enhancement of the flexural strength was found both for the reduced and oxidized state of the material when compared to the un‐doped samples. In both cases, the development of a secondary phase was observed proportional to the doping amount of aluminum titanate. Morphological analysis along with preliminary phase identification and suspected mechanisms for strength enhancement are presented and discussed.

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Influence of residual stresses on the evolution of micro-structure during the partial reduction of NiAl2O4

Cited by 22 publications

References 6 publications

Novel interpenetrating Cu–Al2O3 structures by controlled reduction of bulk CuAlO2

Novel interpenetrating Cu–Al2O3 structures by controlled reduction of bulk CuAlO2

Atomic Scale Mechanisms of the Reduction of Nickel–Magnesium Aluminate Spinels

Effect of Aluminum Titanate (Al₂TiO₅) Doping on the Mechanical Performance of Solid Oxide Fuel Cell Ni‐YSZ Anode

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Influence of residual stresses on the evolution of micro-structure during the partial reduction of NiAl2O4

Cited by 22 publications

References 6 publications

Novel interpenetrating Cu–Al2O3 structures by controlled reduction of bulk CuAlO2

Novel interpenetrating Cu–Al2O3 structures by controlled reduction of bulk CuAlO2

Atomic Scale Mechanisms of the Reduction of Nickel–Magnesium Aluminate Spinels

Effect of Aluminum Titanate (Al2TiO5) Doping on the Mechanical Performance of Solid Oxide Fuel Cell Ni‐YSZ Anode

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Effect of Aluminum Titanate (Al₂TiO₅) Doping on the Mechanical Performance of Solid Oxide Fuel Cell Ni‐YSZ Anode