The Effect of Water Vapor on the Particle Structure and Size of Silica Nanoparticles During Sintering

Figures & data

FIG. 1 Experimental setup to study the influence of the water concentration of the carrier gas on the sintering process of SiO₂ nanoparticles.

FIG. 2 Size distribution and TEM image of SiO₂ nanoparticle aggregates synthesized at 900°C.

FIG. 3 FTIR absorbance spectra of the particle filtered gas streams entering the sintering furnace before mixing. The lower black line presents the spectra resulting from TEOS decomposition at 900°C. The middle and upper black lines represent the spectra of added nitrogen loaded with water at a bubbler temperature of 20°C and 60°C, respectively.

FIG. 4 Primary particle diameter d _P, mobility diameter d _M, and particle number concentration c _N downstream of the sintering furnace as a function of sintering temperature. No additional water vapor was added.

FIG. 5 TEM images of SiO₂ nanoparticles downstream of the sintering furnace as a function of the sintering temperature T _S and the water concentration of the carrier gas in the sintering furnace.

TABLE 1 Impact of the water concentration of the carrier gas on the aggregate structure when adding water vapor upstream of the sintering furnace

Temperature	1100°C	1200°C	1300°C	1400°C	1500°C
Water concentration
0 vol.%
1.9 vol.%
17.2 vol.%
Note: aggregates, spherical particles.

FIG. 6 Influence of the water concentration of the carrier gas on the primary particle size distributions measured downstream of the sintering furnace at T _S = 1400°C, determined by TEM image analysis.

TABLE 2 Median and geometric standard deviation of primary particle size distributions (lognormal fit) of silica agglomerates, sintered at 1400°C with different water concentrations in the carrier gas

Water concentration	Median (nm)	Geometric standard deviation
0 vol.%	9.8	1.14
1.9 vol.%	15.3	1.20
17.2 vol.%	21.1	1.37

FIG. 7 Influence of the water concentration of the carrier gas on the SMPS mobility size distributions downstream of the sintering furnace at T _S = 1400°C.

FIG. 8 Influence of the water concentration of the carrier gas on the primary particle size distributions downstream of the sintering furnace at T _S = 1500°C, determined by TEM image analysis.

TABLE 3 Median and geometric standard deviation of primary particle size distributions (lognormal fit) of silica agglomerates, sintered at 1500°C with different water concentrations in the carrier gas

Water concentration	Median (nm)	Geometric standard deviation
0 vol.%	20.5	1.24
1.9 vol.%	20.6	1.17
17.2 vol.%	14.3  and  27.8	1.16  and  1.52

FIG. 9 Influence of the water concentration of the carrier gas on the SMPS mobility size distributions downstream of the sintering furnace at T _S = 1500°C.