An Effect of Addition of NiO Powder on Pore Formation in Lotus-Type Porous Nickel

Onishi, Hiromitsu; Ueno, Shunkichi; Nakajima, Hideo

doi:10.2320/matertrans.mra2008150

Cited by 9 publications

(4 citation statements)

References 9 publications

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“…At present, the nucleation sites of the oxide for formation of pores cannot be observed, because the amount of the oxides is rather small. However, our further research [15] supported the finding that the oxides may serve as the nucleation sites for pore formation. The effect of addition of NiO powder on pore formation in lotus nickel was investigated.…”

Section: Resultssupporting

confidence: 75%

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Fabrication of Lotus-Type Porous Cobalt and Silicon through Decomposition of Moisture

Onishi

Ueno

Hyun

et al. 2008

Metall Mater Trans A

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Porous cobalt and silicon with cylindrical pores were fabricated by unidirectional solidification in a mold, including moisture in argon atmosphere. The pores are evolved by hydrogen decomposed from the moisture during solidification. Hydrogen atoms dissolve into molten cobalt and silicon according to the reaction xM + yH 2 O = M x O y + yH 2 at the given temperature. Insoluble hydrogen evolves long pores oriented in one direction during the unidirectional solidification. However, no pores are observed in solidified copper. It is suggested that the formation of pores strongly depends on the magnitude of the dissociation constant of water at the casting temperatures for materials. The oxide clusters formed by metallic elements and oxygen may serve as nucleation sites for the pore evolution to yield fine pore distribution. Thus, the moisture decomposition method is superior to the conventional fabrication method, which requires high-pressure hydrogen gas.

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Section: Resultssupporting

confidence: 75%

“…Then, the mold was kept in a closed chamber with constant humidity (90 pct), which was measured by a hydrometer attached to the chamber for a given time, and 0. 15 work can be found in a previous article. [12] The solidification occurs from the bottom of the mold to the top.…”

Section: Introductionmentioning

confidence: 94%

Fabrication of Lotus-Type Porous Cobalt and Silicon through Decomposition of Moisture

Onishi

Ueno

Hyun

et al. 2008

Metall Mater Trans A

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“…There is another factor to contribute the pore size in lotus metals. Recently Onishi et al 11) revealed that intentional addition of fine ceramics powders affects the pore size and the number density of pores in lotus nickel fabricated in hydrogen; the pore size becomes smaller and the number density of pores increases by addition of NiO. NiO may serve as nucleation sites for pore evolution.…”

Section: Resultsmentioning

confidence: 99%

Fabrication of Porous High-Purity Iron with Directional Pores by Continuous Zone Melting Technique

et al. 2010

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Lotus-type porous iron rods were fabricated by continuous zone melting technique under the pressure of 2.5 MPa of hydrogen, using iron with three different purities: 99.5%, 99.9% and 99.999%. It was found that the pore size in lotus iron with high purity (99.999% pure) is much larger than that in lotus iron with lower purity (99.5% and 99.9% pure), while the porosity in lotus iron with high purity is lower than that in lotus iron with lower purity. The transfer velocity does not affect the porosity in all lotus iron, but may affect the pore size; the pore diameter decreases with increasing transfer velocity. Thus, it is apparent that the purity of iron significantly affects the pore morphology and the impurities in iron serve as the nucleation sites of pores to increase the pore number density and also suppress the growth of pores due to slower diffusion of hydrogen.

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“…Therefore, it is important to find out a method to reduce the pore size without increasing pressure. Recently, Onishi et al [10] reported that addition of NiO powder in molten Ni promoted pore nucleation and led to reduction of pore diameter in lotus Ni fabricated by mold casting technique. This paper concluded that addition of pore nucleation sites in the melt is an effective method to reduce pore diameter.…”

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Effect of Addition of NiO Powder on Pore Formation in Lotus-Type Porous Carbon Steel Fabricated by Continuous Casting

Kashihara¹,

Yonetani²,

Suzuki

et al. 2010

MSF

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Lotus-type porous carbon steel (lotus carbon steel) plates were fabricated by continuous casting technique in a pressurized nitrogen atmosphere. The experiments were done both with adding 0.3wt% of NiO powder in molten carbon steel in a ceramic crucible and without NiO powder. The lotus carbon steel fabricated without NiO powder under nitrogen pressures of 0.1 and 0.5 MPa had single pores which grew independently. On the other hand, the lotus carbon steel fabricated with adding NiO powder had pores which coalesced each other and became in irregular shapes. Under nitrogen pressure of 2.5 MPa, the pores formed with adding NiO powder were smaller than that formed without NiO powder. The porosity increased by adding NiO powder in every pressurized nitrogen atmosphere. From these results, NiO powder in molten carbon steel is considered to act as nucleation sites for pores at the solid-liquid interface and to increase of the pore number.

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An Effect of Addition of NiO Powder on Pore Formation in Lotus-Type Porous Nickel

Cited by 9 publications

References 9 publications

Fabrication of Lotus-Type Porous Cobalt and Silicon through Decomposition of Moisture

Fabrication of Lotus-Type Porous Cobalt and Silicon through Decomposition of Moisture

Fabrication of Porous High-Purity Iron with Directional Pores by Continuous Zone Melting Technique

Effect of Addition of NiO Powder on Pore Formation in Lotus-Type Porous Carbon Steel Fabricated by Continuous Casting

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