Limits...
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.Our methodology is potentially competitive for a practical production of nanoporous Si-based materials.

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

Structural information of Si/Ge products via XRD and Raman, showing the sharp contrast between Bulk-SiGe and Nano-SiGe.XRD patterns of (a) Bulk-SiGe and (b) Nano-SiGe; (c) XRD of the (111) peaks for the Nano-SiGe. (d) Raman spectra of Bulk-SiGe and Nano-SiGe. XPS spectra of Nano-SiGe showing signals of (e) Si [2P] and (f) Ge [3d].
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3713525&req=5

f4: Structural information of Si/Ge products via XRD and Raman, showing the sharp contrast between Bulk-SiGe and Nano-SiGe.XRD patterns of (a) Bulk-SiGe and (b) Nano-SiGe; (c) XRD of the (111) peaks for the Nano-SiGe. (d) Raman spectra of Bulk-SiGe and Nano-SiGe. XPS spectra of Nano-SiGe showing signals of (e) Si [2P] and (f) Ge [3d].

Mentions: The crystalline phases of the Si/Ge composites were investigated by XRD. As Figure 4a shows, the XRD pattern of Bulk-SiGe displays the cubic phase similar to that of Bulk-Si. The Ge phase reflections are invisible in the XRD pattern, indicating the formation of a solid solution of Ge in the matrix of cubic silicon phase. In sharp contrast, the XRD pattern of Nano-SiGe clearly reveals both elemental phases of Si and Ge (Fig. 4b). Five pairs of peaks in the vicinity of 28°, 47°, 55°, 68°, and 75° are ascribed to the reflections of (111), (220), (311), (400), and (331) planes of Ge or Si, respectively. These peaks can be deconvoluted into the components from elemental Si and Ge cubic phases (Fig. 4c and Supplementary Fig. S7). The domain size is ~ 20 nm for Ge and ~ 6 nm for Si, estimated by the Scherrer Equation on the (111) peaks. A smaller silicon domain size in Nano-SiGe than that of Nano-Si can be attributed to a more efficient heat-scavenging effect due to the higher specific pore volume of SiGe oxides (0.41 cm3/g) than diatom (0.056 cm3/g) (Supplementary Fig. S8). In the Raman spectra of Nano-SiGe, the peaks at 509.8, 404.7, and 294.8 cm−1 from elemental Si, SiGe alloy, and elemental Ge, respectively, are observed while only a peak of Si at 513.0 cm−1 shows up in Bulk-SiGe (Fig. 4d). The surface oxidation states and the chemical composition of the Nano-SiGe were further examined by XPS. Similar to Nano-Si, the peak at 99.3 eV in the Nano-SiGe is contributed by elemental Si [2p] (Fig. 4e). Moreover, the peak at 29.4 eV can be ascribed to elemental Ge [3d] (Fig. 4f). Owing to slight surface oxidation, a weak peak around 32.0 eV is also detected. Judging from Raman spectra peak intensities and combining the XRD and XPS results, it can be concluded that the elemental phase is the primary phase for Ge element.


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 information of Si/Ge products via XRD and Raman, showing the sharp contrast between Bulk-SiGe and Nano-SiGe.XRD patterns of (a) Bulk-SiGe and (b) Nano-SiGe; (c) XRD of the (111) peaks for the Nano-SiGe. (d) Raman spectra of Bulk-SiGe and Nano-SiGe. XPS spectra of Nano-SiGe showing signals of (e) Si [2P] and (f) Ge [3d].
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: Structural information of Si/Ge products via XRD and Raman, showing the sharp contrast between Bulk-SiGe and Nano-SiGe.XRD patterns of (a) Bulk-SiGe and (b) Nano-SiGe; (c) XRD of the (111) peaks for the Nano-SiGe. (d) Raman spectra of Bulk-SiGe and Nano-SiGe. XPS spectra of Nano-SiGe showing signals of (e) Si [2P] and (f) Ge [3d].
Mentions: The crystalline phases of the Si/Ge composites were investigated by XRD. As Figure 4a shows, the XRD pattern of Bulk-SiGe displays the cubic phase similar to that of Bulk-Si. The Ge phase reflections are invisible in the XRD pattern, indicating the formation of a solid solution of Ge in the matrix of cubic silicon phase. In sharp contrast, the XRD pattern of Nano-SiGe clearly reveals both elemental phases of Si and Ge (Fig. 4b). Five pairs of peaks in the vicinity of 28°, 47°, 55°, 68°, and 75° are ascribed to the reflections of (111), (220), (311), (400), and (331) planes of Ge or Si, respectively. These peaks can be deconvoluted into the components from elemental Si and Ge cubic phases (Fig. 4c and Supplementary Fig. S7). The domain size is ~ 20 nm for Ge and ~ 6 nm for Si, estimated by the Scherrer Equation on the (111) peaks. A smaller silicon domain size in Nano-SiGe than that of Nano-Si can be attributed to a more efficient heat-scavenging effect due to the higher specific pore volume of SiGe oxides (0.41 cm3/g) than diatom (0.056 cm3/g) (Supplementary Fig. S8). In the Raman spectra of Nano-SiGe, the peaks at 509.8, 404.7, and 294.8 cm−1 from elemental Si, SiGe alloy, and elemental Ge, respectively, are observed while only a peak of Si at 513.0 cm−1 shows up in Bulk-SiGe (Fig. 4d). The surface oxidation states and the chemical composition of the Nano-SiGe were further examined by XPS. Similar to Nano-Si, the peak at 99.3 eV in the Nano-SiGe is contributed by elemental Si [2p] (Fig. 4e). Moreover, the peak at 29.4 eV can be ascribed to elemental Ge [3d] (Fig. 4f). Owing to slight surface oxidation, a weak peak around 32.0 eV is also detected. Judging from Raman spectra peak intensities and combining the XRD and XPS results, it can be concluded that the elemental phase is the primary phase for Ge element.

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.Our methodology is potentially competitive for a practical production of nanoporous Si-based materials.

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