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Efficient fabrication of nanoporous si and Si/Ge enabled by a heat scavenger in magnesiothermic reactions.

Luo W, Wang X, Meyers C, Wannenmacher N, Sirisaksoontorn W, Lerner MM, Ji X - Sci Rep (2013)

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA.

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.

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Related in: MedlinePlus

Structural properties of Nano-Si and Bulk-Si, and morphologies of diatom, Bulk-Si, and Nano-Si, demonstrating the effect of a heat scavenger.(a) XRD patterns and (b) Raman spectra of Nano-Si and Bulk-Si. For an ease of comparison, the XRD and Raman results are normalized to the intensity of the strongest peak. FESEM images of (c) diatom, (d) Bulk-Si and (e) Nano-Si. Inset of (d) is the enlarged FESEM image of Bulk-Si corresponding to the red-square marked area in (d). (f) the enlarged FESEM image of Nano-Si corresponding to the red-square marked area in (e).
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f1: Structural properties of Nano-Si and Bulk-Si, and morphologies of diatom, Bulk-Si, and Nano-Si, demonstrating the effect of a heat scavenger.(a) XRD patterns and (b) Raman spectra of Nano-Si and Bulk-Si. For an ease of comparison, the XRD and Raman results are normalized to the intensity of the strongest peak. FESEM images of (c) diatom, (d) Bulk-Si and (e) Nano-Si. Inset of (d) is the enlarged FESEM image of Bulk-Si corresponding to the red-square marked area in (d). (f) the enlarged FESEM image of Nano-Si corresponding to the red-square marked area in (e).

Mentions: The synthesized Nano-Si and Bulk-Si were firstly characterized by X-ray diffraction measurements (XRD). As shown in Figure 1a, the XRD peaks exhibited by the two samples can be readily indexed to a cubic phase of silicon (JCPDS No. 27-1402). Compared with the XRD pattern of Nano-Si, the diffraction peaks from Bulk-Si are much narrower, indicative of a much higher degree of crystallinity. The domain size of the Nano-Si is estimated to be 12 nm by the Scherrer Equation based on the (111) peak at 2θ of 28.4°. The domain size of Bulk-Si is clearly much larger than that of Nano-Si, indicated by the sharp XRD peaks. The smaller domain size of Nano-Si can only be attributed to the heat-scavenging effect of NaCl in a MRR. In order to further examine the characteristics of the obtained Si materials, Raman spectra were recorded. Compared with the Bulk-Si, the Raman peak of Nano-Si is slightly broader and shifts towards a lower wavenumber (Fig. 1b). According to the previously reported theoretical fit on porous silicon products, this confirms smaller domain size2728.


Efficient fabrication of nanoporous si and Si/Ge enabled by a heat scavenger in magnesiothermic reactions.

Luo W, Wang X, Meyers C, Wannenmacher N, Sirisaksoontorn W, Lerner MM, Ji X - Sci Rep (2013)

Structural properties of Nano-Si and Bulk-Si, and morphologies of diatom, Bulk-Si, and Nano-Si, demonstrating the effect of a heat scavenger.(a) XRD patterns and (b) Raman spectra of Nano-Si and Bulk-Si. For an ease of comparison, the XRD and Raman results are normalized to the intensity of the strongest peak. FESEM images of (c) diatom, (d) Bulk-Si and (e) Nano-Si. Inset of (d) is the enlarged FESEM image of Bulk-Si corresponding to the red-square marked area in (d). (f) the enlarged FESEM image of Nano-Si corresponding to the red-square marked area in (e).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3713525&req=5

f1: Structural properties of Nano-Si and Bulk-Si, and morphologies of diatom, Bulk-Si, and Nano-Si, demonstrating the effect of a heat scavenger.(a) XRD patterns and (b) Raman spectra of Nano-Si and Bulk-Si. For an ease of comparison, the XRD and Raman results are normalized to the intensity of the strongest peak. FESEM images of (c) diatom, (d) Bulk-Si and (e) Nano-Si. Inset of (d) is the enlarged FESEM image of Bulk-Si corresponding to the red-square marked area in (d). (f) the enlarged FESEM image of Nano-Si corresponding to the red-square marked area in (e).
Mentions: The synthesized Nano-Si and Bulk-Si were firstly characterized by X-ray diffraction measurements (XRD). As shown in Figure 1a, the XRD peaks exhibited by the two samples can be readily indexed to a cubic phase of silicon (JCPDS No. 27-1402). Compared with the XRD pattern of Nano-Si, the diffraction peaks from Bulk-Si are much narrower, indicative of a much higher degree of crystallinity. The domain size of the Nano-Si is estimated to be 12 nm by the Scherrer Equation based on the (111) peak at 2θ of 28.4°. The domain size of Bulk-Si is clearly much larger than that of Nano-Si, indicated by the sharp XRD peaks. The smaller domain size of Nano-Si can only be attributed to the heat-scavenging effect of NaCl in a MRR. In order to further examine the characteristics of the obtained Si materials, Raman spectra were recorded. Compared with the Bulk-Si, the Raman peak of Nano-Si is slightly broader and shifts towards a lower wavenumber (Fig. 1b). According to the previously reported theoretical fit on porous silicon products, this confirms smaller domain size2728.

Bottom Line: 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.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Oregon State University, Corvallis, Oregon 97331, USA.

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.

Show MeSH
Related in: MedlinePlus