Solid-State Synthesis of Mg&lt;SUB&gt;2&lt;/SUB&gt;Si from Mg-Si Mixture Powder

Kondoh, Katsuyoshi; Oginuma, Hideki; Yuasa, Eiji; Aizawa, Tatsuhiko

doi:10.2320/matertrans.42.1293

Cited by 44 publications

(20 citation statements)

References 3 publications

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“…The silicon content was 2.5 and 5 mass%. Silicon particles were employed to form Mg 2 Si intermetallics by the solid-state reaction 15) with magnesium during the pre-heating of the green compact after the BMA or RPW process. Therefore, when using the latter raw material, magnesium composite alloys reinforced with fine Mg 2 Si dispersoids were fabricated by this reaction process.…”

Section: Methodsmentioning

confidence: 99%

Environmentally Benign Fabricating Process of Magnesium Alloy by Cyclical Plastic Working in Solid-State

Kondoh

Aizawa

2003

Mater. Trans.

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Solid-state processing via cyclically plastic working to output the green compact has been developed to fabricate magnesium alloys with fine microstructures. The relationship between the energy consumption during the plastic working and the characteristics of hot extruded magnesium alloys was evaluated from the viewpoint of the environmentally benign process. The cyclical plastic working marks a significant advance in refining microstructures, such as matrix grain and silicon particles added to synthesize Mg 2 Si via solid-state reaction with magnesium. For example, the grain size of hot extruded AZ31 alloy is 3-15 mm, which is remarkably smaller than that with 20-80 mm in employing the cold compact without using such a plastic working. As a result of the grain refinement, AZ31 alloys reveal higher UTS of 330-355 MPa than the conventional alloys of 270 MPa. The energy consumption of the cyclical plastic working with 200 cycles is 10 kJg À1 to fabricate the billet consolidated by hot extrusion, when using a high-speed screw-driven press machine. This is less than 10% of the energy consumed by the conventional recycling process in re-melting wasted magnesium alloys (126 kJg À1 ). This process is highly capable of producing high performance magnesium alloys with a small energy consumption and is environment-friendly.

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Section: Methodsmentioning

confidence: 99%

Environmentally Benign Fabricating Process of Magnesium Alloy by Cyclical Plastic Working in Solid-State

Kondoh

Aizawa

2003

Mater. Trans.

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“…Mg 2 Si bulky material, fabricated via the solid-state reaction with an exothermic heat, 7) showed high micro-hardness of 600 $ 700 Hv and high Young's modulus of 120 GPa, in employing the elemental powder mixture of magnesium and silicon. In the result of the spray salt test (JIS Z 2731), no corrosion phenomenon of Mg 2 Si intermetallic bulk occurred after spraying 5% salt water over 1000 hrs at 308 K. On the other hand, the corrosion started at 300 $ 600 h in using the conventional 304 stainless steel, that is, Mg 2 Si has superior corrosion resistance.…”

Section: New Recycling Process Design Of Glass Wastesmentioning

confidence: 99%

New Process to Fabricate Magnesium Composites Using SiO<SUB>2</SUB> Glass Scraps

Kondoh

Luangvaranunt

2003

Mater. Trans.

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To realize the lightweight effects by materials technology, a new process for fabricating high-performance magnesium composites via a solid-state reaction by using high purity SiO 2 glass scraps has been established. From a viewpoint of the microstructures control of the composites, the core technologies to improve the physical and mechanical properties are; a solid-state synthesis of Mg 2 Si and MgO particles by the deoxidization of SiO 2 glass by magnesium, and a refinement of both their dispersoids and the magnesium matrix grains by the RPW process. For example, when using the elemental AZ31 magnesium alloy and 2 mass% SiO 2 glass powder mixture as starting raw materials, the hot extruded composite including Mg 2 Si and MgO shows 363 MPa of the ultimate tensile strength. The addition of only 2 mass% SiO 2 powder also causes the remarkable improvement of the corrosion resistance because of the uniform distribution of refined Mg 2 Si not only at the particle boundary but also inside the grains. This process is quite safety and environmentally benign compared to the conventional re-melting process, because of utilizing course magnesium raw powder and no use of SF 6 toxic gas. It also shows a possibility to employ SiO 2 glass scraps as starting raw materials to fabricate magnesium alloys.

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“…1(a) (diffractogram 1) is in good agreement with literature data. 34,35 Normalization was performed by giving the main diffraction peak an intensity of 1000. Trace amounts of silicon and MgO could be identified in the powder as a result of incomplete synthesis.…”

Section: Structural Characterization Of Prepared Materialsmentioning

confidence: 99%

Enhanced thermoelectric properties of Mg2Si by addition of TiO2 nanoparticles

Cederkrantz

Farahi

Borup

et al. 2012

Journal of Applied Physics

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The effects on the thermoelectric properties of Mg 2 Si when adding TiO 2 nanoparticles have been evaluated experimentally. A batch of Mg 2 Si was prepared through direct solid state reaction and divided into portions which were mechanically mixed with different amounts of TiO 2 nanoparticles ranging from 0.5 to 3 vol% and subsequently sintered to disks. All materials showed n-type conduction and the absolute value of the Seebeck coefficient was reduced with increasing amount of TiO 2 added, while the electrical resistivity was greatly reduced. The thermal conductivity was surprisingly little affected by the addition of the nanoparticles. An optimum value of the thermoelectric figure-of-merit ZT ¼ TS 2 r/k was found for the addition of 1 vol% TiO 2 , showing almost three times higher ZT value than that of the pure Mg 2 Si. Larger TiO 2 additions resulted in lower ZT values and with 3 vol% added TiO 2 the ZT was comparable to the pure Mg 2 Si. The sintering process resulted in reduction or chemical reaction of all TiO 2 to TiSi 2 and possibly elemental titanium as well as reduced TiO x . The increased electrical conductivity and the decreased Seebeck coefficient were found due to an increased charge carrier concentration, likely caused by the included compounds or titanium-doping of the Mg 2 Si matrix. The low observed effect on the thermal conductivity of the composites may be explained by the relatively higher thermal conductivity of the included compounds, counter-balancing the expected increased grain boundary scattering. Alternatively, the introduction of compounds does not significantly increase the concentration of scattering grain boundaries.

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Solid-State Synthesis of Mg<SUB>2</SUB>Si from Mg-Si Mixture Powder

Cited by 44 publications

References 3 publications

Environmentally Benign Fabricating Process of Magnesium Alloy by Cyclical Plastic Working in Solid-State

Environmentally Benign Fabricating Process of Magnesium Alloy by Cyclical Plastic Working in Solid-State

New Process to Fabricate Magnesium Composites Using SiO<SUB>2</SUB> Glass Scraps

Enhanced thermoelectric properties of Mg2Si by addition of TiO2 nanoparticles

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