Microstructure and compressive behavior of ice-templated copper foams with directional, lamellar pores

Park, Hyeji; Choi, Myounggeun; Choe, Heeman; Dunand, David C.

doi:10.1016/j.msea.2016.10.057

Cited by 40 publications

(39 citation statements)

References 54 publications

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“…Interdendritic fluid flow also explains observations of asymmetric, one-sided dendritic arms commonly reported in ice-templating studies for both particle suspensions [3,18,27,49,52,53,[71][72][73] and polymer solutions [74,75]: secondary arm growth is suppressed on the "downstream" side [68,76,77]. This is depicted in Fig.…”

Section: Interdendritic Fluid Flowsupporting

confidence: 58%

The effect of solidification direction with respect to gravity on ice-templated TiO2 microstructures

Scotti

Kearney

Burns

et al. 2019

Journal of the European Ceramic Society

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Unidirectional ice-templating produces materials with aligned, elongated pores via: (i) directional solidification of particle suspensions wherein suspended particles are rejected and incorporated between aligned dendrites, (ii) sublimation of the solidified fluid, and (iii) sintering of the particles into elongated walls which are templated by the ice dendrites. Most ice-templating studies utilize upward solidification techniques, where solid ice is located at the bottom of the solidification mold (closest to the cold source), the liquid suspension is on top of the ice, and the solidification front advances upward, against gravity. Liquid water reaches its maximum density at 4°C; thus, liquid nearest the cold source is less dense than warmer liquid above (up to 4°C, above which, a density inversion occurs, and liquid density decreases with increasing temperature). The lower density liquid nearest the cold source is expected to rise due to buoyancy, promoting convective fluid motion during solidification. Here, we investigate the effect of solidification direction with respect to the direction of gravity on ice-templated microstructures to study the role of buoyancy-driven fluid motion during solidification. We hypothesize that, for upward solidification, the convective fluid motion that results from a liquid density gradient occurs near the solidification front. For downward solidification, we expect that this fluid motion occurs farther away from the solidification front. Aqueous suspensions of TiO2 nanoparticles (10-30 nm in size, 10, 15, and 21 vol.%) are solidified upward (against gravity, with ice on bottom and water on top), downward (water on bottom, ice on top), and horizontally (perpendicular to gravity). Microstructural investigation of sintered samples shows evidence of buoyancy-driven, convective fluid flow during solidification for samples solidified upwards (against gravity), including (i) tilting of the wall (and pore) orientation with respect to the induced temperature gradient, (ii) ice lens defects (cracks oriented parallel to the freezing direction), and (iii) radial macrosegregation. These features are not observed for downward nor horizontal solidification configurations, consistent with the hypothesis that convective fluid motion does not interact directly with the solidification front for downward solidification.

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Section: Interdendritic Fluid Flowsupporting

confidence: 58%

The effect of solidification direction with respect to gravity on ice-templated TiO2 microstructures

Scotti

Kearney

Burns

et al. 2019

Journal of the European Ceramic Society

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“…When metal foam is subjected to external shock loads, the deformation is large and the flow stress level is low. The unique compressive deformation behaviour of metal foam makes it an ideal energy absorbing material . Metal foam has a low yield strength, which is beneficial for releasing the residual stress in the brazed joints .…”

Section: Introductionmentioning

confidence: 99%

Effects of Cu interlayers on the microstructure and mechanical properties of Al₂O₃/AgCuTi/Kovar brazed joints

Wang

Jin

Yang

et al. 2018

Int J Applied Ceramic Tech

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Al2O3 ceramic and Kovar alloy brazed joints were achieved using three types of Ag‐based interlayers: a AgCuTi foil, a AgCuTi/Cu foil/AgCuTi multi‐interlayer and a AgCuTi/Cu foam/AgCuTi multi‐interlayer. The effects of the addition of Cu interlayers on the interfacial microstructure and mechanical properties of Al2O3/AgCuTi/Kovar brazed joints were investigated. When Kovar alloy and Al2O3 ceramic were brazed with 50 μm Cu foil at 900°C for 10 minutes, the Cu foil was completely dissolved in the liquid filler. A nearly continuous Cu layer remained in the joint when the thickness of the Cu foil reached 100 μm under the same brazing conditions. With the increase in Cu foil thickness, the thickness of Ti–O compounds + Ti3Cu3O reaction layer formed nearby the Al2O3 ceramic first increased and then remained the same. The Al2O3/Kovar joints brazed with 100 μm Cu foil at 900°C for 10 minutes showed a maximum shear strength of 138 MPa. A low brazing temperature was beneficial to maintain the original structure of the Cu foam. Furthermore, when the joints were brazed at 880°C for 10 minutes, the average shear strength of the Al2O3/AgCuTi/Cu foam/AgCuTi/Kovar joints was 140 MPa, which was 30 MPa higher than that of a single AgCuTi interlayer.

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“…Here, it is noted that the directionality with respect to the loading axis is important for these directionally solidified metal foams. For example, metal foams with their pores normal to the loading axis yield at about 1/3 of the yield stress of the foams with the pores parallel to the loading axis due to bending being the major deformation mode of the walls as opposed to the plastic buckling of the latter . Strain‐hardening behavior is seen for all three alloy foams, in the plastic region of 10% strain for Cu 7 Ni 3 foam and up to 35% strain for Cu 5 Ni 5 and Cu 3 Ni 7 foams, where the stress then dramatically decreased.…”

Section: Resultsmentioning

confidence: 94%

“…Most of the developed metal foams have been pure and unalloyed, and their usage has significantly restricted their practical applications due to their inherent weak strength, low hardness, and poor corrosion resistance and reliability of pure, alloyed metal. For example, load‐bearing structural applications normally require carefully designed alloys and composites that have high strength and fracture toughness; however, a pure metal component has inherently weak strength and hardness, and is thus unsuitable for structural applications . Another example is the poor corrosion resistance of pure copper (Cu) or nickel (Ni) for potential applications in a corrosive fuel cell device .…”

Section: Introductionmentioning

confidence: 99%

Freeze Casting is a Facile Method to Create Solid Solution Alloy Foams: Cu–Ni Alloy Foams via Freeze Casting

et al. 2019

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Porous metals have attracted great attention for their functional and structural applications; however, they often possess limited applicability in their pure form for the areas requiring decent strength and corrosion resistance. In this study, pure copper (Cu), pure nickel (Ni), and Cu-Ni alloy foams with five different compositions are successfully fabricated using freeze casting, resulting in open-pore structures with varied porosity (from 55% to 75%). Their varied morphologies and crystal sizes are compared, and the lattice parameters and crystal sizes are calculated. The corrosion resistance of the synthesized Cu-Ni alloy foams is superior to those of the pure Cu and Ni foams. The weight loss rate of the Cu 7 Ni 3 alloy foam is six times and five times slower than those of the pure Ni and pure Cu foams in a sulfuric corrosive environment, respectively. The yield strength of Cu 7 Ni 3 alloy foam (53 AE 2% porosity) is 72 AE 2 MPa and its yield strength when normalized by the Gibson-Ashby model is the largest with a value of up to 852 AE 3 MPa. The elastic modulus and hardness values are varied in the range of 73.4-152.4 GPa and 1.6-4.7 GPa, respectively, depending on the composition of the alloy foam.

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Microstructure and compressive behavior of ice-templated copper foams with directional, lamellar pores

Cited by 40 publications

References 54 publications

The effect of solidification direction with respect to gravity on ice-templated TiO2 microstructures

The effect of solidification direction with respect to gravity on ice-templated TiO2 microstructures

Effects of Cu interlayers on the microstructure and mechanical properties of Al₂O₃/AgCuTi/Kovar brazed joints

Freeze Casting is a Facile Method to Create Solid Solution Alloy Foams: Cu–Ni Alloy Foams via Freeze Casting

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Microstructure and compressive behavior of ice-templated copper foams with directional, lamellar pores

Cited by 40 publications

References 54 publications

The effect of solidification direction with respect to gravity on ice-templated TiO2 microstructures

The effect of solidification direction with respect to gravity on ice-templated TiO2 microstructures

Effects of Cu interlayers on the microstructure and mechanical properties of Al2O3/AgCuTi/Kovar brazed joints

Freeze Casting is a Facile Method to Create Solid Solution Alloy Foams: Cu–Ni Alloy Foams via Freeze Casting

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Effects of Cu interlayers on the microstructure and mechanical properties of Al₂O₃/AgCuTi/Kovar brazed joints