Synthesis of Nanocrystalline α‐Alumina Powder Using Triethanolamine

Abstract

Nanocrystalline ␣-Al 2 O 3 powders have been prepared by pyrolysis of a complex compound of aluminum with triethanolamine (TEA). The soluble metal-ion-TEA complex forms the precursor material on complete dehydration of the complex of aluminum-TEA. The single-phase ␣-Al 2 O 3 powder has resulted after heat treatment at 1025°C. The precursors and the heat-treated final powders have been characterized by X-ray diffractometry, thermogravimetric and differential thermal analysis, and transmission electron microscopy (TEM). The average particle sizes as measured from X-ray line broadening and TEM are ϳ25 nm. The powder has crystallite sizes of the same order indicates the poor agglomeration of crystallites.

Synthesis of Cu/Cu2O core/multi-shelled microcrystal via shape and structure transformation of pre-grown crystals

“…Compared above two products, it suggests that TEA is essential for the formation of the assynthesized core/multi-shelled truncated octahedron. Recently TEA has been used to prepare nanosized oxide powders [33][34][35]. After aging for 5 h, few particles in the mixture are octahedron, but most of them agglomerate together and become irregular particles ( Fig.…”

Synthesis and sintering of pure nanocrystalline α-Al2O3 powder

“…This effect explains that the size of α Al 2 O 3 particles does not depend on the amount of injected seed at low temperatures, at which the speed of diffusion mass transfer is too small to facilitate a sig nificant increase in the detached alpha phase particles during the experiment. In this case, if particles with the original size of 50 nm managed to grow up to 100-400 nm under the conditions taken in [4], i.e., 1025°C, this growth stops at 930°C or below.…”

“…Thus, if only the artificially injected seed particles grow, the final size of the α phase crystallites cannot be less than 100 nm, which contradicts the experiment. Note that, even with the injected seed size of 100 nm, the size of the majority of grains of the resulting α Al 2 O 3 was about 50 nm at 1025°C and 95% degree of transformation and increased to 0.1-0.4 μm only at a later time [4].…”

“…The numerous efforts to prevent the formation of coarse fine powder by injecting organic components which separate the forming the α Al 2 O 3 particles ster ically have been made [4][5][6][7][8]. However, this leads to contamination of the product with carbon and makes the process considerably more expensive.…”

An important role of temperature dependent scattering time in understanding the high temperature thermoelectric behavior of strongly correlated system: La0.75Ba0.25CoO3

“…33 The step-by-step synthesis details of barium doped LaCoO 3 compounds are provided in the earlier work by Devendra et al 26,27 For Seebeck coefficient measurement, the synthesized powder sample was pelletized under the pressure of ∼35 Kg/cm 2 . Further, it was sintered at 1100 0 C for 12 hours.…”