Fabrication of nanocrystalline Mg2Si via ball milling process: Structural studies

Ιωάννου, Μαρία; Hatzikraniotis, Euripides; Lioutas, Ch. B.; Hassapis, Th.; Altantzis, Th.; Paraskevopoulos, K. M.; Kyratsi, Theodora

doi:10.1016/j.powtec.2011.11.014

Cited by 49 publications

(22 citation statements)

References 26 publications

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“…The milling of the Mg- and Si- powder mixture was performed not only for reducing and homogenizing the grain size, aiming at enhancing the extrusion of pastes by 3D printing, spray and electrospinning, but also for verifying if any amount of the Mg 2 Si phase had formed as a result of the relatively short duration of the ball milling. Usually, much longer durations are required [11, 12]. XRD measurements on pristine Mg and Si powders, and mixtures of both, followed by 2 h, 5 h and 10 h milling are shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of thermoelectric magnesium-silicide pastes for 3D printing, electrospinning and low-pressure spray

Marques

Miglietta

Gaspar

et al. 2019

Mater Renew Sustain Energy

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In this work, eco-friendly magnesium-silicide (Mg2Si) semiconducting (n-type) thermoelectric pastes for building components concerning energy-harvesting devices through 3D printing, spray and electrospinning were synthetized and tested for the first time. The Mg2Si fine powders were obtained through the combination of ball milling and thermal annealing under Ar atmosphere. While the latter process was crucial for obtaining the desired Mg2Si phase, the ball milling was indispensable for homogenizing and reducing the grain size of the powders. The synthetized Mg2Si powders exhibited a large Seebeck coefficient of ~ 487 µV/K and were blended with a polymeric solution in different mass ratios to adjust the paste viscosity to the different requirements of 3D printing, electrospinning and low-pressure spray. The materials produced in every single stage of the paste synthesis were characterized by a variety of techniques that unequivocally prove their viability for producing thermoelectric parts and components. These can certainly trigger further research and development in green thermoelectric generators (TEGs) capable of adopting any form or shape with enhanced thermoelectric properties. These green TEGs are meant to compete with common toxic materials such as Bi2Te3, PbTe and CoSb that have Seebeck coefficients in the range of ~ 290–700 μV/K, similar to that of the produced Mg2Si powders and lower than that of 3D printed bulk Mg2Si pieces, measured to be ~ 4866 μV/K. Also, their measured thermal conductivities proved to be significantly lower (~ 0.2 W/mK) than that reported for Mg2Si (≥ 4 W/mK). However, it is herein demonstrated that such thermoelectric properties are not stable over time. Pressureless sintering proved to be indispensable, but difficultly achievable by long thermal annealing (even above 32 h) in inert atmosphere at 400 °C, at least for bulk Mg2Si pieces constituted by a mean grain size of 2–3 μm. Hence, for overcoming this sintering challenge and become the silicide’s extrusion viable in the production of bulk thermoelectric parts, alternative pressureless sintering methods will have to be further explored.

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Section: Resultsmentioning

confidence: 99%

Synthesis of thermoelectric magnesium-silicide pastes for 3D printing, electrospinning and low-pressure spray

Marques

Miglietta

Gaspar

et al. 2019

Mater Renew Sustain Energy

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“…, ϵ ∞ is the high frequency dielectric constant, the second summing term, corresponds to the lattice contribution, with f j being the oscillator strength of each mode, ω TO, j the transverse phonon frequency and γ TO, j the damping constant, and the third term expresses the effect of the free carriers effect (plasmon), with ω PL the plasmon frequency and γ PL the plasmon damping factor. For the present study is considered j = 2, corresponding to the two phonon modes assigned to the fundamental IR active modes of the crystalline magnesium silicide . Surface roughness is modeled by

R_{SR} = R_{0} exp (- \frac{16 π^{2} σ^{2} n_{0}^{2}}{λ^{2}}),

assuming a Gaussian distribution of surface roughness, where the reflectivity of the rough surface ( R SR ) is related to the one of the same smooth surface ( R 0 ), σ is the RMS value of surface roughness, n 0 the (complex) refractive index, and λ the vacuum wavelength of the radiation.…”

Section: Resultsmentioning

confidence: 99%

“…(2), e 1 is the high frequency dielectric constant, the second summing term, corresponds to the lattice contribution, with f j being the oscillator strength of each mode, v TO,j the transverse phonon frequency and g TO,j the damping constant, and the third term expresses the effect of the free carriers effect (plasmon), with v PL the plasmon frequency and g PL the plasmon damping factor. For the present study is considered j ¼ 2, corresponding to the two phonon modes assigned to the fundamental IR active modes of the crystalline magnesium silicide [17][18][19]. Surface roughness is modeled by [20,21] …”

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confidence: 99%

Thermoelectric properties of Mg₂Si coatings deposited by pack cementation assisted process on heavily doped Si substrates

Stathokostopoulos

Stefanaki

Ιωάννου

et al. 2014

Physica Status Solidi (a)

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This work presents a study of structural and thermoelectric properties of Mg 2 Si coatings deposited on heavily doped p-and n-type Si substrates, at 650 8C. The as-grown layers were smooth and uniform in thickness without any texture, voids, or large density of cracks. The sign of Seebeck coefficient in deposited layers follows the one of the corresponding substrate, indicating effective doping of the grown layers with the dopant already present in Si substrate (B for p-type and As for n-type). Doping levels of $9 Â 10 18 cm À3 for p-type and $5 Â 10 18 cm À3 for n-type, were obtained. IR reflectivity analysis revealed a strong mode at 272 cm À1 and a shoulder at 316 cm À1 . Thermoelectric properties were successfully modeled by a multiple-band model, with optical phonon scattering. Temperature dependence of electrical conductivity for the deposition layers. The lines represent the theoretical fitting.

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“…Mechanical milling on various Mg/Mg alloys or composites, such as pure Mg, Mg–Y–Cu, Mg2Si, Mg–3Al–Zn, Mg–C, Mg–graphene nanoplates, AZ61–10 at% Ti, and Mg–alumina, has been carried out to achieve specific characteristics and structures. Homogeneous biodegradable Mg–Zn alloy was fabricated through mechanical milling for 10 h. The hardness of this alloy is enhanced as a result of strain‐hardened or cold‐worked alloy particles obtained through milling .…”

Section: Introductionmentioning

confidence: 99%

Effect of High‐Energy Ball Milling on Mechanical Properties of the Mg–Nb Composites Fabricated through Powder Metallurgy Process

Vahid

Hodgson

2017

Adv Eng Mater

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New biocompatible and biodegradable Mg-Nb composites used as bone implant materials are fabricated through powder metallurgy process. Mg-Nb mixture powders are prepared through mechanical milling and manual mixing. Then, the Mg-Nb composites are fabricated through cold press and sintering processes. The effect of mechanical milling and Nb particles as reinforcements on the microstructures and mechanical properties of Mg-Nb composites are investigated. The mechanical milling process is found to be effective in reducing the size of Mg and Nb particles, distributing the Nb particles uniformly in the Mg matrix and obtaining Mg-Nb composite particles. The Mg-Nb composite particles can be bound together firmly during the sintering process, result in Mg-Nb composite structures with no intermetallic formation, lower porosity, and higher mechanical properties compared to composites prepared through manual mixing. Interestingly, the mechanical properties of manually mixed Mg-Nb composites appear to be even lower than that of pure Mg.

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Fabrication of nanocrystalline Mg2Si via ball milling process: Structural studies

Cited by 49 publications

References 26 publications

Synthesis of thermoelectric magnesium-silicide pastes for 3D printing, electrospinning and low-pressure spray

Synthesis of thermoelectric magnesium-silicide pastes for 3D printing, electrospinning and low-pressure spray

Thermoelectric properties of Mg₂Si coatings deposited by pack cementation assisted process on heavily doped Si substrates

Effect of High‐Energy Ball Milling on Mechanical Properties of the Mg–Nb Composites Fabricated through Powder Metallurgy Process

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Fabrication of nanocrystalline Mg2Si via ball milling process: Structural studies

Cited by 49 publications

References 26 publications

Synthesis of thermoelectric magnesium-silicide pastes for 3D printing, electrospinning and low-pressure spray

Synthesis of thermoelectric magnesium-silicide pastes for 3D printing, electrospinning and low-pressure spray

Thermoelectric properties of Mg2Si coatings deposited by pack cementation assisted process on heavily doped Si substrates

Effect of High‐Energy Ball Milling on Mechanical Properties of the Mg–Nb Composites Fabricated through Powder Metallurgy Process

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Thermoelectric properties of Mg₂Si coatings deposited by pack cementation assisted process on heavily doped Si substrates