Preparation of ‘‘amorphous’’ Ni60Nb40 by mechanical alloying

Koch, Carl C.; Cavin, O.B.; McKamey, C.G.; Scarbrough, J. O.

doi:10.1063/1.94213

Cited by 1,093 publications

(201 citation statements)

References 5 publications

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“…10 The microstructural refinement and the defect storage processes increase the chemical reactivity to such a level that unusual behaviors arise with the formation of metastable structures. [11][12][13] In a sense, the mechanical energy transferred by the grinding balls to the powders in the course of the processing plays a role similar to other forms of energy more commonly employed to induce physical and chemical transformations. However, the difficulty in quantifying and controlling the dynamical variables greatly hindered a better understanding of the complex phenomenology observed in a milling process.…”

Section: Introductionmentioning

confidence: 99%

Onset of chaotic dynamics in a ball mill: Attractors merging and crisis induced intermittency

Manai¹,

Delogu²,

Rustici³

2002

Chaos: An Interdisciplinary Journal of Nonlinear Science

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In mechanical treatment carried out by ball milling, powder particles are subjected to repeated high-energy mechanical loads which induce heavy plastic deformations together with fracturing and cold-welding events. Owing to the continuous defect accumulation and interface renewal, both structural and chemical transformations occur. The nature and the rate of such transformations have been shown to depend on variables, such as impact velocity and collision frequency that depend, in turn, on the whole dynamics of the system. The characterization of the ball dynamics under different impact conditions is then to be considered a necessary step in order to gain a satisfactory control of the experimental set up. In this paper we investigate the motion of a ball in a milling device. Since the ball motion is governed by impulsive forces acting during each collision, no analytical expression for the complete ball trajectory can be obtained. In addition, mechanical systems exhibiting impacts are strongly nonlinear due to sudden changes of velocities at the instant of impact. Many different types of periodic and chaotic impact motions exist indeed even for simple systems with external periodic excitation forces. We present results of the analysis on the ball trajectory, obtained from a suitable numerical model, under growing degree of impact elasticity. A route to high dimensional chaos is obtained. Crisis and attractors merging are also found. Among the others, the scarce knowledge of the dynamics of ball milling devices, where milling bodies undergo a huge number of collisions during the processing. Under such conditions, indeed, any experimental measurement of the exact number of impacts and of the energy transferred to powders at collisions is greatly hindered. It becomes therefore impossible to relate the degree of structural evolution to the mechanical energy dissipated, maybe the most important macroscopic parameter used to characterize the yield of a mechanochemical reaction. Any information on the dynamics of milling bodies is then extremely valuable in order to quantitatively describe and rationalize the kinetic features of mechanically induced transformations. Preliminary investigations have already shown the possible occurrence of chaotic regimes during milling treatments. 6,7 On the other hand, modeling results and experimental evidences demonstrate the occurrence of regular dynamical regimes allowing for the direct measurement of both the average collision frequency and impact energy. 8 It becomes therefore important to study the transition from periodic to chaotic regimes in order to understand when and why transition takes place, so as to avoid it. Experimentalists are indeed mainly interested in periodic and regular regimes, which permit the full control of experimental parameters.

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Section: Introductionmentioning

confidence: 99%

Onset of chaotic dynamics in a ball mill: Attractors merging and crisis induced intermittency

Manai¹,

Delogu²,

Rustici³

2002

Chaos: An Interdisciplinary Journal of Nonlinear Science

View full text Add to dashboard Cite

show abstract

“…14 This technique, illustrated in Figure 1, produces nonequilibrium systems and novel materials, such as the oxide-dispersionstrengthened alloys initially developed for the aerospace industry. 15,16 With the subsequent discovery that mechanical alloying could yield amorphous metal alloys, 17 applications that employ mechanical alloying as a means of mixing inorganic materials have greatly increased and diversified. 14,18,19 The utility of mechanical alloying in obtaining unique multifunctional materials from commodity feedstock has not, however, extended to the organic materials arena until quite recently.…”

Section: Introductionmentioning

confidence: 99%

Cryogenic Mechanical Alloying of Poly(methyl methacrylate) with Polyisoprene and Poly(ethylene-alt-propylene)

et al. 2000

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Mechanical alloying is performed at cryogenic temperatures to incorporate polyisoprene (PI) or its hydrogenated analogue poly(ethylene-alt-propylene) (PEP) into poly(methyl methacrylate) (PMMA) as an example of high-energy solid-state blending. Morphological characterization of the blends by X-ray and electron microscopies confirms that the degree of dispersion of the constituent polymers improves with increasing milling time. Such dispersion in the PEP/PMMA blends is, however, ultimately compromised by phase coarsening when the materials are postprocessed above the PMMA glass transition temperature in the melt. Milling-induced PI cross-linking serves to suppress phase coarsening in PI/ PMMA blends, which remain relatively well-dispersed even after postprocessing. These blends are generally less fracture-resistant than the as-received PMMA due mainly to the accompanying reduction in PMMA molecular weight. Their optical transparency is observed to decrease dramatically with increasing PEP or PI concentration until they appear opaque. An overall improvement in blend properties by mechanical alloying is, however, anticipated upon judicious selection of more degradation-resistant polymers.

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“…HEBM has become a popular technique in recent years for the solid-state amorphization of binary metal systems, 6,7 metal-metalloid systems, [8][9][10] and even single-component systems. 11 Thermodynamic and kinetic models which explain these processes have been proposed.…”

Section: Introductionmentioning

confidence: 99%

Near-neighbor mixing and bond dilation in mechanically alloyed Cu-Fe

et al. 1996

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Extended x-ray-absorption fine-structure ͑EXAFS͒ measurements were used to obtain element-specific, structural, and chemical information of the local environments around Cu and Fe atoms in high-energy ballmilled Cu x Fe 1Ϫx samples ͑xϭ0.50 and 0.70͒. Analysis of the EXAFS data shows both Fe and Cu atoms reside in face-centered-cubic sites where the first coordination sphere consists of a mixture of Fe and Cu atoms in a ratio which reflects the as-prepared stoichiometry. The measured bond distances indicate a dilation in the bonds between unlike neighbors which accounts for the lattice expansion measured by x-ray diffraction. These results indicate that metastable alloys having a positive heat of mixing can be prepared via the high-energy ballmilling process. ͓S0163-1829͑96͒10033-3͔

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Preparation of ‘‘amorphous’’ Ni60Nb40 by mechanical alloying

Cited by 1,093 publications

References 5 publications

Onset of chaotic dynamics in a ball mill: Attractors merging and crisis induced intermittency

Onset of chaotic dynamics in a ball mill: Attractors merging and crisis induced intermittency

Cryogenic Mechanical Alloying of Poly(methyl methacrylate) with Polyisoprene and Poly(ethylene-alt-propylene)

Near-neighbor mixing and bond dilation in mechanically alloyed Cu-Fe

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