Limits...
Complete magnesiothermic reduction reaction of vertically aligned mesoporous silica channels to form pure silicon nanoparticles.

Kim KH, Lee DJ, Cho KM, Kim SJ, Park JK, Jung HT - Sci Rep (2015)

Bottom Line: The procedure involves magnesium promoted reduction of vertically oriented mesoporous silica channels on reduced graphene oxides (rGO) sheets.The mesopores play a significant role in effectively enabling magnesium gas to interact with silica through a large number of reaction sites.The new method for complete magnesiothermic reduction of mesoporous silica approach provides a foundation for the rational design of silicon structures.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical and Biomolecular Engineering (BK21+Program), Korea Advance Institute of Science and Technology (KAIST), Daejeon 305-701 (Korea).

ABSTRACT
Owing to its simplicity and low temperature conditions, magnesiothermic reduction of silica is one of the most powerful methods for producing silicon nanostructures. However, incomplete reduction takes place in this process leaving unconverted silica under the silicon layer. This phenomenon limits the use of this method for the rational design of silicon structures. In this effort, a technique that enables complete magnesiothermic reduction of silica to form silicon has been developed. The procedure involves magnesium promoted reduction of vertically oriented mesoporous silica channels on reduced graphene oxides (rGO) sheets. The mesopores play a significant role in effectively enabling magnesium gas to interact with silica through a large number of reaction sites. Utilizing this approach, highly uniform, ca. 10 nm sized silicon nanoparticles are generated without contamination by unreacted silica. The new method for complete magnesiothermic reduction of mesoporous silica approach provides a foundation for the rational design of silicon structures.

No MeSH data available.


Related in: MedlinePlus

Schematic diagram of the fabrication process.(a) Mixing of silica source, block copolymer and graphene oxides (b) Synthesis of vertically oriented mesoporous silica channels on two-dimensional substrates. (c) Infiltration of gaseous magnesium into mesoporous silica. (d) Formation of magnesium oxide and silicon nanoparticles. (e) The formation of completely reduced silicon nanoparticles after removal of magnesium oxide by treatment with hydrochloric.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4355679&req=5

f1: Schematic diagram of the fabrication process.(a) Mixing of silica source, block copolymer and graphene oxides (b) Synthesis of vertically oriented mesoporous silica channels on two-dimensional substrates. (c) Infiltration of gaseous magnesium into mesoporous silica. (d) Formation of magnesium oxide and silicon nanoparticles. (e) The formation of completely reduced silicon nanoparticles after removal of magnesium oxide by treatment with hydrochloric.

Mentions: The new, mesoporous silica channel based strategy for magnesiothermic reduction of silica to produce silicon is illustrated in Figure 1. In this process, vertically aligned mesoporous silica channels are generated on a two dimensional GO substrate. While GO was used in this study, depending on target applications different types of substrates can be employed for this purpose. The mesoporous silica layer was then formed by simply mixing a solution of the GO substrate with a solution of cetyltrimethylammonium chloride (CTACl) in 1 M NaOH, followed by addition of tetraethyl orthosilicate (TEOS) (Figure 1a)13. By using this approach to control the pH precisely at 11.7, the mesoporous silica structure are produced via soft-templating of the block copolymer CTACl followed by hydrolytic condensation with TEOS (Figure 1b). The mesoporous silica formed in this manner was blended with the magnesium granules, placed within an alumina crucible, and heated in a tube furnace at 650°C under an atmosphere of argon (500 sccm) and hydrogen (50 sccm). In this process, magnesium infiltrates into the pores and covers the surface of the mesoporous silica template (Figure 1b), where it promotes the magnesiothermic reaction (equation 1) to produce silicon and magnesium oxide (Figure 1c). Loss of oxygen from silica enables the silicon atoms to arrange into a crystalline phase1. Finally, magnesium oxide generated in the reduction reaction is removed by using 1 M hydrochloric acid (Figure 1d). Vacuum filtration then leads to isolation of a dark brown silicon nanoparticle powder that does not contain any unreacted silica (Figure 1e).


Complete magnesiothermic reduction reaction of vertically aligned mesoporous silica channels to form pure silicon nanoparticles.

Kim KH, Lee DJ, Cho KM, Kim SJ, Park JK, Jung HT - Sci Rep (2015)

Schematic diagram of the fabrication process.(a) Mixing of silica source, block copolymer and graphene oxides (b) Synthesis of vertically oriented mesoporous silica channels on two-dimensional substrates. (c) Infiltration of gaseous magnesium into mesoporous silica. (d) Formation of magnesium oxide and silicon nanoparticles. (e) The formation of completely reduced silicon nanoparticles after removal of magnesium oxide by treatment with hydrochloric.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4355679&req=5

f1: Schematic diagram of the fabrication process.(a) Mixing of silica source, block copolymer and graphene oxides (b) Synthesis of vertically oriented mesoporous silica channels on two-dimensional substrates. (c) Infiltration of gaseous magnesium into mesoporous silica. (d) Formation of magnesium oxide and silicon nanoparticles. (e) The formation of completely reduced silicon nanoparticles after removal of magnesium oxide by treatment with hydrochloric.
Mentions: The new, mesoporous silica channel based strategy for magnesiothermic reduction of silica to produce silicon is illustrated in Figure 1. In this process, vertically aligned mesoporous silica channels are generated on a two dimensional GO substrate. While GO was used in this study, depending on target applications different types of substrates can be employed for this purpose. The mesoporous silica layer was then formed by simply mixing a solution of the GO substrate with a solution of cetyltrimethylammonium chloride (CTACl) in 1 M NaOH, followed by addition of tetraethyl orthosilicate (TEOS) (Figure 1a)13. By using this approach to control the pH precisely at 11.7, the mesoporous silica structure are produced via soft-templating of the block copolymer CTACl followed by hydrolytic condensation with TEOS (Figure 1b). The mesoporous silica formed in this manner was blended with the magnesium granules, placed within an alumina crucible, and heated in a tube furnace at 650°C under an atmosphere of argon (500 sccm) and hydrogen (50 sccm). In this process, magnesium infiltrates into the pores and covers the surface of the mesoporous silica template (Figure 1b), where it promotes the magnesiothermic reaction (equation 1) to produce silicon and magnesium oxide (Figure 1c). Loss of oxygen from silica enables the silicon atoms to arrange into a crystalline phase1. Finally, magnesium oxide generated in the reduction reaction is removed by using 1 M hydrochloric acid (Figure 1d). Vacuum filtration then leads to isolation of a dark brown silicon nanoparticle powder that does not contain any unreacted silica (Figure 1e).

Bottom Line: The procedure involves magnesium promoted reduction of vertically oriented mesoporous silica channels on reduced graphene oxides (rGO) sheets.The mesopores play a significant role in effectively enabling magnesium gas to interact with silica through a large number of reaction sites.The new method for complete magnesiothermic reduction of mesoporous silica approach provides a foundation for the rational design of silicon structures.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemical and Biomolecular Engineering (BK21+Program), Korea Advance Institute of Science and Technology (KAIST), Daejeon 305-701 (Korea).

ABSTRACT
Owing to its simplicity and low temperature conditions, magnesiothermic reduction of silica is one of the most powerful methods for producing silicon nanostructures. However, incomplete reduction takes place in this process leaving unconverted silica under the silicon layer. This phenomenon limits the use of this method for the rational design of silicon structures. In this effort, a technique that enables complete magnesiothermic reduction of silica to form silicon has been developed. The procedure involves magnesium promoted reduction of vertically oriented mesoporous silica channels on reduced graphene oxides (rGO) sheets. The mesopores play a significant role in effectively enabling magnesium gas to interact with silica through a large number of reaction sites. Utilizing this approach, highly uniform, ca. 10 nm sized silicon nanoparticles are generated without contamination by unreacted silica. The new method for complete magnesiothermic reduction of mesoporous silica approach provides a foundation for the rational design of silicon structures.

No MeSH data available.


Related in: MedlinePlus