Efficient Fabrication of Nanoporous Si and Si/Ge Enabled by a Heat Scavenger in Magnesiothermic Reactions

Abstract

Magnesiothermic reduction can directly convert SiO2 into Si nanostructures. Despite intense efforts, efficient fabrication of highly nanoporous silicon by Mg still remains a significant challenge due to the exothermic reaction nature. By employing table salt (NaCl) as a heat scavenger for the magnesiothermic reduction, we demonstrate an effective route to convert diatom (SiO2) and SiO2/GeO2 into nanoporous Si and Si/Ge composite, respectively. Fusion of NaCl during the reaction consumes a large amount of heat that otherwise collapses the nano-porosity of products and agglomerates silicon domains into large crystals. Our methodology is potentially competitive for a practical production of nanoporous Si-based materials.

All-in-one synthesis of mesoporous silicon nanosheets from natural clay and their applicability to hydrogen evolution

“…Metal salts (for example, NaCl, KCl, and MgCl 2 ) with a high melting point can be used as heat scavengers to reduce the exothermic heat. 19,20 NaCl was used as the metal salt in this system on the basis of the following criteria: (i) the melting point of NaCl (801°C) is much higher than the melting temperature of the metal reductant used (Mg = 650°C), and (ii) MMT clay contains Na + cations and a small amount of alkylamines, which are exchangeable with NaCl. If the metal salt used has a lower melting point than the metal reductant used, the salt will not be able to function as a heat scavenger.…”

Porous Silicon Formation by Porous Silica Reduction

“…Examination of the literature (Bao et al 2007;Richman et al 2008;Hai et al 2009;Ibisate et al 2009;Won et al 2009Won et al , 2011Yu et al 2010;Zhu et al 2010Yermekova et al 2010;Chen et al 2011aChen et al , b, 2012aChen et al , b, 2013a Gallego-Gomez et al 2011;Gao et al 2011;Guo et al 2011;Jia et al 2011;Lu et al 2011;Pallavidino et al 2011;Zhang and Huang 2011;Batchelor et al 2012;Fang et al 2012;Shen et al 2012Shen et al , 2013Tao et al 2012a, b;Wang et al 2012;Yoo et al 2012;Huachao et al 2013;Jung et al 2013;Du et al 2013;Hong et al 2013;Jiang et al 2013;Lee et al 2013;Liu et al 2013;Luo et al 2013;Ma et al 2013;Meekins et al 2013;Wen et al 2013;Xing et al 2013a, b;Yoo et al 2013;Yu et al 2013;Yue et al 2013;Xia et al 2014) reveals that all three classes of porosity (see handbook chapters on ▶ Macroporous Silicon, ▶ Mesoporous Silicon, and ▶ Microporous Silicon) are achievable with magnesiothermic reduction, as are extremely high surface area structur...…”

Formation mechanism and optical characterization of polymorphic silicon nanostructures by DC arc-discharge

“…The arc current Fig. 7 (a) UV-visible absorption spectra; the plots of (b) (ahn) 2 (n ¼ 1/2), and (c) (ahv) 1/2 (n ¼ 2) versus photon energy for Si NPs, NSs, and NRs at room-temperature, respectively. was set at 90 A and the voltage was maintained at about 20 V. The atmosphere was the key factor in control of the morphologies of Si nanomaterials.…”

“…It has been studied intensively in the elds of condense matter physics, material science and engineering, and industrial semiconductors. 1,2 In recent decades, silicon nanomaterials (like silicon nanoparticles and nanosheets) have attracted interest because of their quantum connement effects, non-toxicity, high surface activity, biocompatibility, photostability, etc. They can be used, for example, in biosensors, cell imaging, lasers, or optical mixers.…”