Effect of milling conditions on structure and magnetic properties of nanocrystalline cobalt

Fenineche, N.; Guessasma, Sofiane; Abdelbaki, Noureddine

doi:10.1016/j.mseb.2005.01.011

Cited by 6 publications

(2 citation statements)

References 15 publications

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“…The two modifications are interchangeable by a reversible martensite phase change at 422 • C [34,35]. The increased ductility of fcc cobalt has strongly motivated investigations on the possible preparation of pure fcc cobalt which is favoured at very small grain sizes [36][37][38][39][40]. Early studies by Konstanty et al [41] have shown that the hardness of conventionally processed cobalt powder (HV ∼ 140-160 N mm −2 [34]) could be strongly improved by the use of ultrafine fcc-cobalt powder (HV = 433 N mm −2 , relative density >98%).…”

Section: Introductionmentioning

confidence: 99%

Grain growth resistance and increased hardness of bulk nanocrystalline fcc cobalt prepared by a bottom-up approach

et al. 2007

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Bulk nanocrystalline cobalt was prepared from reducing flame-spray-derived cobalt nanopowders exclusively in the face-centred cubic (fcc) modification. Compacts of approximately 60% density were obtained from uniaxial compression at room temperature and showed a strong resistance towards grain growth upon subsequent sintering to 90% relative density. The nanocrystalline structure remained stable well above 1000 degrees C and resulted in a pore-rich metal with about 10(15) nanovoids cm(-3). These sintered compacts displayed an up to three times higher bulk hardness if compared to conventional cobalt and local ductility as evidenced from scanning electron microscopy and nanoindentation. The strong grain-growth resistance and consequent increase in material hardness are discussed in respect of the presence of nanovoids, twin boundaries and material contamination.

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Section: Introductionmentioning

confidence: 99%

Grain growth resistance and increased hardness of bulk nanocrystalline fcc cobalt prepared by a bottom-up approach

et al. 2007

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“…The hcp-fcc transition point is T t = 422 • C. However, fcc-Co has been frequently reported at room temperature in powders processed by ball milling [9][10][11]. Usually, nano-size Co and Co-based materials are processed by ball milling [12,13]. Sort et al have reported the correlation between microstructure, allotropic phase transformations and magnetic properties of cobalt subjected to ball milling in detail [12].…”

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confidence: 99%

Preparation of the HCP Nano-Sheet Cobalt via a Green-Solvothermal Route

Yuan¹

2007

ECS Trans.

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The nano-sheet cobalt has been prepared via a green-solvothermal route. The spectra of X-ray powder diffraction (XRD) prove that as-prepared cobalt is hexagonal close-packed cobalt (hcp) phase in this research. The saturated magnetization intensity (M s ), coercive force (Hc) and remanence (Br) of the hcp cobalt sheets with 59.2 nm thickness are 318 emu g -1 , 199 Oe and 25 emu g -1 at 293K, respectively. The nano-size hcp cobalt with higher M s and lower Hc is soft magnetic materials.Advance materials prepared via solvothermal synthesis techniques attract broad research interests [1][2][3]. In relative high temperature and pressure, the size and structure of materials are controlled through the synthesis condition. Qian and co-workers have revealed that the solvothermal and nonequilibrium process may be used to synthesis some novel nanomaterials [3]. Magnetic materials have widely been fabricated via the solvothermal synthesis [2][3][4][5][6][7][8]. Cobalt is an element with excellent ferromagnetic properties. Besides, it is relatively stable against corrosion and easy to handle, which makes it even more useful for technical applications. According to the metallic Co phase diagram, Co exists in two crystal structures: a low temperature hexagonal close-packed (hcp) and a high temperature face-centered cubic (fcc). The hcp-fcc transition point is T t = 422 • C. However, fcc-Co has been frequently reported at room temperature in powders processed by ball milling [9][10][11]. Usually, nano-size Co and Co-based materials are processed by ball milling [12,13]. Sort et al. have reported the correlation between microstructure, allotropic phase transformations and magnetic properties of cobalt subjected to ball milling in detail [12]. However, no reports have been searched about the relationship of the size, morphology and properties of Co prepared via the solvothermal route.In this study, the nano-size hcp Co have been synthesized via the green-solvothermal route. The magnetic properties of Co have been investigated. ExperimetalAll chemical reagents in this work were of analytical grade purity. CoCl 2 ·6H 2 O was dehydrated at 160 • C under vacuum for 10 h as precursor. CoCl 2 (1.00 g) and NaBH 4 (0.38 g) added in absolute ethanol (40 mL) were reacted in a stainless autoclave with 80 mL capacity. The autoclave was maintained at 250, 350, 400 and 450 • C for 8 h, respectively, and then allowed to cool to room temperature naturally. The gray precipitate was collected and washed with dilute acetic acid, absolute ethanol, distilled water and absolute ethanol. The obtained sample was dried in vacuum at 60 • C for 4 h.

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Preparation of nano-crystalline Co powder from CoCO3

Liu

Xu²

2009

International Journal of Refractory Metals and Hard Materials

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Effect of milling conditions on structure and magnetic properties of nanocrystalline cobalt

Cited by 6 publications

References 15 publications

Grain growth resistance and increased hardness of bulk nanocrystalline fcc cobalt prepared by a bottom-up approach

Grain growth resistance and increased hardness of bulk nanocrystalline fcc cobalt prepared by a bottom-up approach

Preparation of the HCP Nano-Sheet Cobalt via a Green-Solvothermal Route

Preparation of nano-crystalline Co powder from CoCO3

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