22831-39-6Relevant articles and documents
Alternative route for the preparation of CoSb3 and Mg 2Si derivatives
Godlewska,Mars,Zawadzka
, p. 109 - 113 (2012)
An alternative manufacturing route has been developed for cobalt triantimonide and magnesium disilicide derivatives. Elemental powders were mixed in stoichiometric proportions, cold pressed into cylindrical preforms and heated in oxygen-free environment to initiate the exothermic reaction. According to DTA/TG measurements and observations under high-temperature microscope, the onset of reaction occurred at a temperature not exceeding the melting point of the more volatile component, i.e. antimony in the case of CoSb3 and magnesium in the case of Mg2Si. The reaction products were additionally heat treated to secure homogenization. Dense sinters were obtained by hot uniaxial pressing of the obtained powders in moderate temperature-and-pressure conditions. Several advantages were identified in the proposed technology: absence of liquid phases, relatively short time of the synthesis, possibility of in-situ or ex-situ doping and grain size control.
Electrochemical characteristics of intermetallic phases in aluminum alloys : An experimental survey and discussion
Birbilis,Buchheit
, p. B140-B151 (2005)
This paper presents a survey of corrosion potentials, pitting potentials, and electrochemical characteristics for intermetallic particles commonly present in high-strength aluminum-based alloys. Results from relevant pure metals and solid solutions are also presented. It is seen that corrosion potentials and pitting potentials vary over a wide range for various intermetallics. Elaboration of the results reveals that the electrochemical behavior of intermetallics is more detailed than the simple noble or active classification based upon corrosion potential or estimated from the intermetallic composition. Intermetallics capable of sustaining the largest cathodic current densities are not necessarily those with the most noble Ecorr, similarly those with the least noble Ecorr will not necessarily sustain the largest anodic currents. The data herein was collected via the use of a microcapillary electrochemical cell facilitating electrode investigations upon intermetallic particles in the micrometer-squared range. This survey may be used as a tool for clarification of localized corrosion phenomena in Al alloys.
A metathesis reaction route to obtain fine Mg2Si particles
Itahara,Yamada,Oh,Asahi,Imagawa,Yamane
, p. 4315 - 4318 (2014)
We have developed a novel synthetic route for the production of fine Mg2Si particles (2, and Na. Mg2Si was suggested to be formed by a solid-state metathesis reaction, in which MgCl2 reacts with Na to form Mg and NaCl, and then Mg reacts with NaSi.
Mill setting and microstructural evolution during mechanical alloying of Mg2Si
Riffel,Schilz
, p. 3427 - 3431 (1998)
The mechanical alloying behaviour of magnesium and silicon to form the intermetallic compound Mg2Si and the optimum setting of a planetary ball mill for this task, were examined. For the ductile-brittle magnesium-silicon system it was found that the efficiency of the mill is mostly influenced by the ratio of the angular velocity of the planetary wheel to that of the system wheel and the amount of load. The examination of the kinetics inside the planetary ball mill for different mill settings showed that a ratio of angular velocities of at least 3 is necessary to compensate the reduction of efficiency due to slip. The optimum powder load for the 500 ml vial was found to be 10-20 g. The milling process starts with elemental magnesium and silicon bulk particles. During the milling, the silicon pieces are rapidly diminished and together with the constantly forming Mg2Si they act as an emery powder for the magnesium bulk pieces. Simultaneous to the diminution of the magnesium, alloying occurs.
Combined effect of high-intensity ultrasonic treatment and Ca addition on modification of primary Mg2Si and wear resistance in hypereutectic Mg-Si alloys
Moussa,Waly,El-Sheikh
, p. 576 - 581 (2014)
The combined effect of high-intensity ultrasonic treatment (HIUST) and 0.3 wt.%Ca addition on modification of primary Mg2Si and wear resistance in the hypereutectic Mg-5 wt.%Si alloy has been investigated. The results show that without treatmen
Thermoelectric properties of Al-doped Mg2Si1-xSnx (x ≦ 0.1)
Tani, Jun-ichi,Kido, Hiroyasu
, p. 335 - 340 (2008)
The thermoelectric properties of Al-doped Mg2Si1-xSnx (x = 0.0-0.1) [Mg2Si1-xSnx:Al = 1:y (0.00 ≦ y ≦ 0.02)] fabricated by spark plasma sintering have been characterized by Hall effect measurements at 300 K and by measurements of electrical resistivity (ρ), the Seebeck coefficient (S), and thermal conductivity (κ) between 300 and 900 K. Al-doped Mg2Si1-xSnx samples are n-type in the measured temperature range. By Al-doping, electron concentration is controlled up to 5.3 × 1019 cm-3 in the composition range 0.0 ≦ x ≦ 0.1. Al-doped Mg2Si0.9Sn0.1 shows a maximum value of the figure of merit ZT of 0.68 at 864 K, which is 6 times larger than that of nondoped Mg2Si0.9Sn0.1.
Altering hydrogen storage properties by hydride destabilization through alloy formation: LiH and MgH2 destabilized with Si
Vajo, John J.,Mertens, Florian,Ahn, Channing C.,Bowman Jr., Robert C.,Fultz, Brent
, p. 13977 - 13983 (2004)
Alloying with Si is shown to destabilize the strongly bound hydrides LiH and MgH2. For the LiH/Si system, a Li2.35Si alloy forms upon dehydrogenation, causing the equilibrium hydrogen pressure at 490?°C to increase from approximately 5 ?? 10-5 to 1 bar. For the MgH 2/Si system, Mg2Si forms upon dehydrogenation, causing the equilibrium pressure at 300?°C to increase from 1.8 to >7.5 bar. Thermodynamic calculations indicate equilibrium pressures of 1 bar at approximately 20?°C and 100 bar at approximately 150?°C. These conditions indicate that the MgH2/Si system, which has a hydrogen capacity of 5.0 wt %, could be practical for hydrogen storage at reduced temperatures. The LiH/Si system is reversible and can be cycled without degradation. Absorption/desorption isotherms, obtained at 400-500?°C, exhibited two distinct flat plateaus with little hysteresis. The plateaus correspond to formation and decomposition of various Li suicides. The MgH2/Si system was not readily reversible. Hydrogenation of Mg2Si appears to be kinetically limited because of the relatively low temperature, 150?°C, required for hydrogenation at 100 bar. These two alloy systems show how hydride destabilization through alloy formation upon dehydrogenation can be used to design and control equilibrium pressures of strongly bound hydrides.
Fast synthesis of nanocrystalline Mg2Si by microwave heating: A new route to nano-structured thermoelectric materials
Savary, Etienne,Gascoin, Franck,Marinel, Sylvain
, p. 11074 - 11080 (2010)
The ultra fast synthesis of nanocrystalline Mg2Si was carried out using microwave radiation. The elemental precursors were first milled together under dry conditions to get fine particles. The resulting mixture of powders of Mg and Si was cold pressed before being heated by microwave irradiation. Precursors and products were analyzed by X-ray diffraction and scanning electron microscopy. The high energy ball milling parameters utilized to prepare the reactive powders have quite an influence on the behavior of the mixture under irradiation. Moreover, SEM imaging demonstrates that the power and time of irradiation are crucial for the grain growth of the Mg2Si and must be adequately controlled in order to avoid the decomposition of the phase. Our results show that we successfully managed to easily and quickly synthesize homogeneous nanocrystalline Mg2Si with particle size smaller than 100 nm using a microwave power of only 175 W for two minutes on powders ball milled for two hours. The Royal Society of Chemistry 2010.
Metallurgical Synthesis of Mg2FexSi1- x Hydride: Destabilization of Mg2FeH6 Nanostructured in Templated Mg2Si
Asano, Kohta,Dam, Bernard,Doi, Masaaki,Fujita, Asaya,Isobe, Shigehito,Kim, Hyunjeong,MacHida, Akihiko,Maejima, Naoyuki,Nakamura, Yumiko,Sakaki, Kouji,Schreuders, Herman,Wang, Yongming,Watanuki, Tetsu,Westerwaal, Ruud J.
, p. 2758 - 2764 (2020)
Magnesium-based transition-metal hydrides are attractive hydrogen energy materials because of their relatively high gravimetric and volumetric hydrogen storage capacities combined with low material costs. However, most of them are too stable to release the hydrogen under moderate conditions. Here we synthesize the hydride of Mg2FexSi1-x, which consists of Mg2FeH6 and Mg2Si with the same cubic structure. For silicon-rich hydrides (x 2Si phase is observed by X-ray diffraction, and M?ssbauer spectroscopy indicates the formation of an octahedral FeH6 unit. Transmission electron microscopy measurements indicate that Mg2FeH6 domains are nanometer-sized and embedded in a Mg2Si matrix. This synthesized metallographic structure leads to distortion of the Mg2FeH6 lattice, resulting in thermal destabilization. Our results indicate that nanometer-sized magnesium-based transition-metal hydrides can be formed into a matrix-forced organization induced by the hydrogenation of nonequilibrium Mg-Fe-Si composites. In this way, the thermodynamics of hydrogen absorption and desorption can be tuned, which allows for the development of lightweight and inexpensive hydrogen storage materials.
Synthesis and crystal structure of RMgSi2 compounds (R=La, Ce, Pr, Nd), a particular example of linear intergrowth
Wrubl,Pani,Manfrinetti,Rogl
, p. 716 - 724 (2009)
A new series of rare earth compounds with stoichiometry RMgSi2 (R=La, Ce, Pr, Nd) is reported. The single crystal X-ray diffraction showed that CeMgSi2, which melts congruently at 1200 °C, crystallizes in a new tetragonal structure t
A magnesiothermic reaction process for the scalable production of mesoporous silicon for rechargeable lithium batteries
Xing, An,Zhang, Jing,Bao, Zhihao,Mei, Yongfeng,Gordin, Ari S.,Sandhage, Kenneth H.
, p. 6743 - 6745 (2013)
Mesoporous, 3-D, nanocrystalline Si has been synthesized via the magnesiothermic reduction of SiO particles at a peak temperature of only 500 °C in a scalable flow-through reactor setup. Such 3-D porous Si as an anode material exhibited high, reversible capacities (i.e., >900 mA h g -1 after 160 charge-discharge cycles at 1000 mA g-1).
Significant enhancement of flux pinning in MgB2 superconductor through nano-Si addition
Wang,Zhou,Qin,Munroe,Soltanian,Liu,Dou
, p. 461 - 465 (2003)
Polycrystalline MgB2 samples with 10 wt.% silicon powder addition were prepared by an in situ reaction process. Two different Si powders, one with coarse (44 μm) and the other with nano-size (a significantly improved field dependence of the critical current over a wide temperature range compared with both undoped samples and samples with coarse-Si added. Jc is as high as 3000 A/cm2 in 8 T at 5 K, one order of magnitude higher than for the undoped MgB2. X-ray diffraction results indicated that Si had reacted with Mg to form Mg2Si. Nano-particle inclusions and substitution, both observed by transmission electron microscopy, are proposed to be responsible for the enhancement of flux pinning in high fields. However, the samples made with the coarse-Si powders had a poorer pinning than the undoped MgB2.
Thermoelectric properties of Sc- and Y-doped Mg2Si prepared by field-activated and pressure-assisted reactive sintering
Meng,Fan,Chen,Munir
, p. 7922 - 7926 (2011)
Sc- and Y-doped-Mg2Si samples were reactively sintered by the field-activated and pressure-assisted synthesis (FAPAS) method. The incorporation of these rare-earth elements in this silicide resulted in an n-type semiconductor. The addition of Sc and Y had no discernable effect on the lattice constant of Mg2Si. The average grain size of the Y-doped Mg2Si was about 2 μm, which was smaller than that of the sintered pure Mg2Si. The power factor of samples doped with 2500 ppm Sc was consistently higher than that of pure Mg2Si in the temperature range of 300-550 K. Similarly, the power factor of 2000 ppm Y doped Mg2Si samples was higher than that of pure Mg2Si over the temperature range of 300-675 K; the highest value being about 2.2 × 10-3 W m-1 k-2 at 468 K. This value is about two times that of the undoped Mg2Si at the same temperature. The thermal conductivity of Mg2Si doped with 2000 ppm Y was 80% of that of pure Mg 2Si. The highest figure of merit (ZT) for the Y doped (2000 ppm) samples was 0.23 at 600 K which was higher by a factor of 1.6 than the corresponding value of pure Mg2Si at the same temperature. The results demonstrate the benefits of doping of Mg2Si with Sc and Y in enhancing its thermoelectric properties.
Selflating synthesis of silicon nanorods from natural sepiolite for high-performance lithium-ion battery anodes
Chen, Qingze,Zhu, Runliang,Liu, Shaohong,Wu, DIngcai,Fu, Haoyang,Zhu, Jianxi,He, Hongping
, p. 6356 - 6362 (2018)
Nanostructured silicon is an attractive anode material for next-generation lithium-ion batteries, but its commercialization remains a challenge owing to the energy-intensive, costly, and complex preparation of nanostructured silicon. Herein, one-dimensional (1D) silicon nanorods (SNRs) have been synthesized from natural sepiolite by a simple selflating synthesis method. The intrinsic crystal structure and chemical composition of sepiolite allow for the maintenance of 1D structures during magnesiothermic reduction without any additional templates and heat scavengers. The as-prepared SNRs showed a large specific surface area (～122 m2 g-1) and hierarchical porous structure (i.e., macro- A nd meso-pores). As anodes for lithium-ion batteries, SNRs exhibited a high reversible capacity of 1350 mA h g-1 at 1.0 A g-1 after 100 cycles, and 816 mA h g-1 at 5.0 A g-1 after 500 cycles (with a capacity retention of 98%). With a low-cost precursor and facile approach, this strategy for synthesizing 1D nanostructured Si would be promising in practical production of high-performance anode materials for lithium-ion batteries.
Thermoelectric performance of Mg2-xCaxSi compounds
Zhang,Zhao,Yin,Zhu
, p. 9 - 12 (2008)
Thermoelectric materials Mg2-xCaxSi (x = 0, 0.01, 0.03, 0.05, 0.07, 0.1) compounds have been prepared by vacuum melting followed by hot-pressing. Effects of the substitution of Ca for Mg on phase structures and the thermoelectric pro
Electrical, thermal, thermoelectric and related properties of magnesium silicide semiconductor prepared from rice husk
Bose, S.,Acharya, H. N.,Banerjee, H. D.
, (1993)
Polycrystalline, 10 μm size magnesium silicide was prepared by alloying 99.9% purity polycrystalline silicon obtained from rice husk ash and high purity magnesium powder. The material in sintered pellet form was characterized for its structural, electrical, thermal, thermoelectric and other properties. A typical sintered pellet exhibited at room-temperature (30°C) thermoelectric power of 565 μVK-1 and an electrical resistivity of 35 Ω cm. On the other hand, the material was found to be thermally quite stable up to 650°C with a room-temperature thermal conductivity of 6.3 × 10-3 cal s-1cm-1K-1 (2.6 Js-1m-1K-1. These properties of the material indicate that the material can find potential applications as a thermoelectric generator and in other semiconductor devices. Furthermore, an indigenous technology of large-scale production of silanes (SiH4) can be developed using this Mg2Si which could be prepared in large quantities by a simple and low-cost process.
Combustion synthesis of silicon by magnesiothermic reduction
Haouli, Saida,Boudebane, Said,Slipper, Ian J.,Lemboub, Samia,G?bara, Piotr,Mezrag, Samiha
, p. 280 - 287 (2018)
Magnesiothermic reduction of silica is a powerful method for producing silicon owing to its simplicity, low reduction temperature and low production cost. However, the inevitable formation of magnesium silicide (Mg2Si) limits the use of this method. A new approach was developed in this research to prevent the formation of Mg2Si by using alumina as a consumer of gaseous magnesium. Utilizing this approach, highly pure silicon was produced by firstly purifying the silica regent by acid-leaching. It was then subjected to magnesiothermic reduction regimes in order to optimize the power input and molar Mg/SiO2 ratio to minimize Mg2Si production. Silicon products were analyzed by X-ray powder diffraction (XRD) and quantitative Rietveld refinement. Optimum electrical power and molar ratio were found to be 3.75?kW and 2.25:1, respectively. The silicon product was examined by glow discharge mass spectrometry which indicated that its purity was 99.96%, with 0.10?ppm of B and 0.15?ppm of P, making it an attractive material for solar cell generation.
Effect of high-intensity ultrasonic treatment on modification of primary Mg2Si in the hypereutectic Mg-Si alloys
Moussa,Waly,El-Sheikh
, p. 693 - 700 (2013)
The effect of high intensity ultrasonic treatment (HIUST) on modification of primary Mg2Si in the hypereutectic Mg-5 wt.%Si alloy have been studied. Various resulted microstructures were produced in this alloy by employing ultrasonic vibrations during solidification process at different pouring temperatures and for different application times. The results showed clearly that in the absence of HIUST, the dendrites of primary Mg2Si were coarser and non-uniform in size. Upon HIUST of the alloy during solidification process, nearly uniform and polyhedral shape of primary Mg 2Si with a network of Mg phase segregated along the grain boundaries were obtained. Interestingly, the average size of primary Mg2Si decreased significantly with increasing the pouring temperature and the vibration time of HIUST reached a minimum at 800 °C and 90 s. After that the average size of primary Mg2Si increased slightly with further increasing the pouring temperature and the ultrasonic vibration time. Modification mechanism resulting in the development of microstructure is also investigated.
Enhancement of thermoelectric performance of Mg2Si via co-doping Sb and C by simultaneous tuning of electronic and thermal transport properties
Shiojiri, Daishi,Iida, Tsutomu,Kakio, Hiroki,Yamaguchi, Masato,Hirayama, Naomi,Imai, Yoji
, (2021/10/01)
Thermoelectric power generation using distributed waste heat energy has received attention as a long-life, environmentally friendly power supply. The intermetallic compound Mg2Si is a lightweight, mid-temperature thermoelectric material that contains no toxic elements, and its thermoelectric performance has been enhanced by various methods such as impurity doping, nanostructuring, and alloying. In this study, we examined the influence of the influence of co-doping with Sb and dilute amounts of the isoelectronic impurity C on the thermoelectric properties of Mg2Si. We fabricated dense polycrystalline specimens of Mg2CxSbySi using the melting process and subsequent plasma-activated sintering. Doping Mg2Si with Sb increased the electrical conductivity ~102 times. Further co-doping with isoelectronic C did not significantly change the electrical conductivity; however, it did reduce the thermal conductivity independently of the electrical properties. Consequently, the specimens co-doped with Sb and C achieved higher thermoelectric performance than specimens of Mg2Si single-doped with Sb. The dimensionless figure of merit ZT of the co-doped specimens reached 0.79 at 873 K over the temperature range 323–873 K.
