An experimental investigation of gas-phase combustion synthesis of SiO2 nanoparticles using a multi-element diffusion flame burner

Abstract

The current work presents the results of an experimental investigation of gas-phase combustion synthesis of silica (SiO 2 ) particles using a multi-element diffusion flame burner (MEDB, a Hencken burner). Silane (SiH 4 ) was added to hydrogen/oxygen/argon (H 2 /O 2 /Ar) flames to produce SiO 2 nanoparticles at various burner operating conditions ( ϭ 0.47-2.16). To characterize the burner performance, temperature measurements were made using water absorption spectroscopy and uncoated, fine-wire thermocouples. The results demonstrated the non-premixed flow arrangement of the fuel tubes and oxidizer channels of the MEDB provided uniform, ϳ1D conditions above the surface of the burner, with temperature variations of less than Ϯ3% in the transverse direction (parallel to the surface of the burner) for elevations above the mixing region (z ϭ 0 -7 mm), extending to heights Ն 30 mm. At heights above the mixing region, approximately constant axial temperatures are also observed. Silica particle formation and growth were examined for comparison with current understanding of the physical mechanisms important in combustion synthesis of SiO 2 . The particle properties were determined using transmission electron microscope (TEM) imaging. Geometric mean diameters of the primary particles varied from d p ϭ 9 to 18 nm. The current study demonstrates the utility of the MEDB in providing a controlled environment for fundamental studies of gas-phase combustion synthesis phenomena, as well as offering broad flexibility in experimental design with control over process variables such as temperature field, particle residence time, scalable reactant loading, and particle precursor selection.

Comparison of line-peak and line-scanning excitation in two-color laser-induced-fluorescence thermometry of OH

“…1, which is similar to that used by Woolridge et al [17], Kulatilaka et al [18], Hancock et al [7], and Meyer et al [19]. The burner consists of a 24 mm square, Hastalloy honeycomb that supports hypodermic needles within a quarter of its cells.…”

Synthesis of TiO2 nanoparticles by premixed stagnation swirl flames

“…Moreover, flame-made catalysts (compared with wet-made catalysts), e.g., TiO 2 composites, can be fabricated with an open-pore structure that should facilitate mass-transfer limited reactions [9]. Reported flame synthesis configurations include co-flow diffusion flame [9,10], counterflow diffusion flame [11], multi-element diffusion flame [12], burner-stabilized premixed stagnation flat flame [13,14], and divergence-stabilized premixed stagnation flat flame (SFF) [3,15]. In the latter two SFF configurations [3,[13][14][15], the cooled stagnation substrate provides many advantages, such as: (i) steep temperature gradient for nanoparticle formation, (ii) controllable temperature histories based on burner-substrate distance, (iii) flame stabilization, (iv) collection source for TiO 2 nanoparticles deposition by thermophoresis, and (v) electric field application.…”

Image Analysis and Computer Simulation of Nanoparticle Clustering in Combustion Systems

“…The size of the primary particles depends on the relative rate of coalescence and collision. Initially, primary particles in combustion systems are on the order of 5-20 nm in diameter, and the primary particles are considered approximately spherical in shape (Nakaso et al 2001;Wooldridge et al 2002;Mueller et al 2009). The fractal structures are created by competition between the nucleation rate of the primary particles, the interparticle collision rate, and the coalescence or sintering rate.…”