Dispersing silicon nanoparticles in a stirred media mill – investigating the evolution of morphology, structure and oxide formation

Abstract

Silicon nanoparticles were dispersed for 24 hours in 1‐butanol using a stirred media mill. Via this process intrinsically stable suspensions (in regard to aggregation) of Si nanoparticles were produced after 6 hours of dispersing. The evolution of morphology, particle size and structure was investigated by dynamic light scattering, X‐ray diffraction, Raman spectroscopy and high resolution transmission electron microscopy as a function of dispersing time. The average crystallite size decreased from about 18 nm down to about 10 nm within 24 hours of milling as determined by X‐ray diffraction and Raman scattering measurements. In addition careful analysis of the Raman spectra revealed a decrease of the crystalline volume fraction from 75% down to 24% and a corresponding increase of the amorphous phase. The microstructural development with varying crystallite size and crystalline volume fraction was directly confirmed by transmission electron microscopy measurements. Elemental analysis showed an increase of oxygen content that was directly proportional to the increase in specific surface area of the silicon nanoparticles during the dispersing process. The surface chemistry of the Si nanoparticles was analyzed by diffuse reflectance infrared Fourier transform spectroscopy that indicated vibrational bands of HSi–Si3–x Ox , SiOx , and residual 1‐butanol. The final product of the dispersing process seems to be a two‐phase mixture of amorphous Si and Si nanocrystallites covered with SiOx on the surface. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Intrinsically stable dispersions of silicon nanoparticles

“…Suspensions of 20 wt% SiNP in 1-butanol and in ethanol (volume fraction 0.080 and 0.078, respectively) were dispersed for 6 h using a stirred media mill. A detailed description of the dispersing procedure is reported elsewhere [2,3].…”

“…A more detailed analysis of the structure and surface of the SiNP is reported elsewhere [2,3]. The DRIFT spectrum of SiNP dispersed for 6 h in 1-butanol ( [32].…”

“…As mentioned before stable suspensions (with regard to aggregation) of SiNP in 1-butanol and ethanol were obtained by dispersing in a stirred media mill [2,3] without the use of any additives. The high stability of SiNP in 1-butanol and ethanol has been predicted theoretically and confirmed experimentally by Bleier [9].…”

“…Equation [3] usually applies to what are normally referred to as dielectric or non-conducting materials [11] and was therefore used for calculating A 11 of 1-butanol and ethanol. The calculations of A 11 of silicon and amorphous silicon dioxide were based on the dielectric functions for a large energy range instead of the relative dielectric constants for more accurate approximation [14].…”

“…As reported recently [2,3], intrinsically stable suspensions of SiNP in 1-butanol were obtained by dispersing in a stirred media mill * Corresponding author. Fax: +49 9131 8529402.…”