Controlled synthesis of alumina in a spray flame aerosol reactor

Abstract

In this study, a spray flame aerosol reactor (S‐FLAR) is used to synthesize alumina nanoparticles. The as‐produced powders are then characterized by X‐ray diffraction, N2 physisorption, and transmission electron microscopy to determine the crystal phase, surface area, particle size distribution, and morphology. The effects of the precursor, dispersion oxygen, and sheath oxygen rates on the characteristics of synthesized alumina were investigated. On increasing the precursor rate, decreasing the dispersion oxygen rate or sheath oxygen rate; the alumina powder surface area decreased. With increasing precursor rates and decreasing dispersion oxygen rates, the proportion of theta alumina increased and that of eta alumina decreased. When using an S‐FLAR to synthesize alumina, the dispersion oxygen rate offers the best control of the surface area, while the precursor rate controls the crystal phase proportions. This result is useful for the design and operation of spray flame aerosol reactors to produce alumina‐based catalysts.

Flame Synthesis of Carbon and Metal-Oxide Nanoparticles: Flame Types, Effects of Combustion Parameters on Properties and Measurement Methods

“…Tungsten-oxide nanoparticles are promising for the fabrication of photoelectrodes because they present high electron mobility and a bandgap satisfactory for this purpose [ 17 ]. Aluminum-based nanoparticles (Al 2 O 3 ) have also been studied, and relevant features discovered, such as their crystal structure, phase transformations, and useful properties, such as thermodynamic stability [ 18 ]. These features are excellent for application in optics and electronics, in catalysis, and as adsorbent, coating, and abrasive materials [ 18 ].…”

“…Aluminum-based nanoparticles (Al 2 O 3 ) have also been studied, and relevant features discovered, such as their crystal structure, phase transformations, and useful properties, such as thermodynamic stability [ 18 ]. These features are excellent for application in optics and electronics, in catalysis, and as adsorbent, coating, and abrasive materials [ 18 ]. Synthesized Al 2 O 3 , with thermodynamic stability, is known as the corundum (α-Al 2 O 3 ) [ 18 ]; however, metastable transition phases have been found in the production of these NPs, some of them are named γ-, η-, ρ-, θ-, δ-, χ-, and κ-Al 2 O 3 [ 18 ].…”

“…These features are excellent for application in optics and electronics, in catalysis, and as adsorbent, coating, and abrasive materials [ 18 ]. Synthesized Al 2 O 3 , with thermodynamic stability, is known as the corundum (α-Al 2 O 3 ) [ 18 ]; however, metastable transition phases have been found in the production of these NPs, some of them are named γ-, η-, ρ-, θ-, δ-, χ-, and κ-Al 2 O 3 [ 18 ].…”

“…CVD’s are commonly used in the production of iron-oxide nanoparticles [ 11 ]. Shortcomings of the chemical methods include the difficulty in disposing of the residuals, and the impurity in the materials obtained, observed for Al 2 O 3 production through precipitation (i.e., the Bayer process) [ 18 ]. Consequently, the particles produced by these techniques require high temperature calcination treatment to increase their purity [ 27 ], and improve the crystallinity of the NPs obtained [ 17 ].…”

“…In certain metal-oxides and carbon NPs, combustion operating parameters significantly influence their properties (e.g., structural phase) [ 11 , 12 , 18 ], as shown in alumina NPs [ 18 ], and iron-oxide nanoparticles [ 13 ], with special consideration for the hematite phase [ 12 ] and the CNTs, where an analysis of the effects on their features from the sampling substrate [ 3 ], and the fuel structure [ 4 , 25 ] were conducted. Turbulent flames also improved the production of NPs at a large scale.…”