Ethanol‐Water‐Derived Sucrose‐Coated‐Al₂O₃ for Submicrometer AlON Powder Synthesis

Abstract

Fluffy and homogenous sucrose‐coated‐γ‐Al2O3 structured precursor was prepared by drying ethanol‐water sucrose/Al2O3 suspension, in which the ethanol content of 85 vol% was optimized. Using the C/Al2O3 mixture pyrolyzed from such precursor with 23.2 wt% sucrose, single‐phase AlON powder was synthesized by two‐step carbothermal reduction and nitridation method at 1550°C for 2 h and 1700°C for another 1.5 h. The particle size of the AlON powder was around 0.6–1.0 μm. Compared with those synthesized by the traditional approaches with mechanical C/Al2O3, Al/Al2O3, or AlN/Al2O3 mixtures, the synthesis temperature was reduced about 50°C, and the AlON powder was fine and exhibited good dispersity. Such superiority of this method was attributed to that the pyrolyzed carbon film on Al2O3 particle greatly restrained Al2O3 coalescence during the thermal treatment.

Preparation of γ‐aluminum oxynitride phosphor with Eu doping by direct nitridation in ammonia and postannealing

“…After calcination at 1750°C, the as‐prepared AlN and Al 2 O 3 reacted to form AlON, exhibiting a multifaceted grain morphology with micron particle size (Figure B). The particle size of agglomerated AlON product fell in the range of 1‐5 μm, comparable that of carbothermal reduction nitridation method, but much finer than AlON prepared by other methods such as solid‐state reaction method, combustion method, or direct nitridation of Al/Al 2 O3 mixtures . It was believed that N/O atom diffusion was accelerated shortened due to the homogenous and fine particle of Al 2 O 3 /AlN intermediate formed in the first‐step nitridation, consequently, the synthesis temperature and time was reduced in the calcination step, resulting in the fine AlON powder.…”

“…Various routes can be used to synthesize AlON powders, among them, solid‐state reaction (SSR) of Al 2 O 3 and AlN, carbothermal reduction and nitridation (CRN) of Al 2 O 3 , and combustion synthesis of Al and Al 2 O 3 are mostly used. Usually, high temperature (as high as above 1800°C) is required for the SSR method.…”

“…The CRN method is attractive for its cheap raw materials, alumina, and carbon, but it is difficult to control the stoichiometry of Al:O:N due to the complicated experimental factors such as the type of precursors, atmosphere, temperature, etc . Especially, the carbon content and the mixing uniformity of Al 2 O 3 /C mixture are key factors that influence the phase compositions of reaction product . For example, Loghman‐Estarki reported that single AlON phase can be formed with no residual Al 2 O 3 or AlN only when the carbon content reaches 7.1%, with higher carbon content, Al 2 O 3 , AlN, and AlON coexisted in the powders, whereas Liu obtained single phase AlON by adding 5.8% carbon into Al 2 O 3 /C mixture, and Xie claimed 5.1 wt% carbon was proper for single‐phase AlON.…”

“…Especially, the carbon content and the mixing uniformity of Al 2 O 3 /C mixture are key factors that influence the phase compositions of reaction product . For example, Loghman‐Estarki reported that single AlON phase can be formed with no residual Al 2 O 3 or AlN only when the carbon content reaches 7.1%, with higher carbon content, Al 2 O 3 , AlN, and AlON coexisted in the powders, whereas Liu obtained single phase AlON by adding 5.8% carbon into Al 2 O 3 /C mixture, and Xie claimed 5.1 wt% carbon was proper for single‐phase AlON. Moreover, residual carbon contamination is detrimental to the luminescence properties of phosphors, thus postcalcination in air is necessary for CRN method to remove the excessive carbon.…”

Properties of Nano-Aluminum Powder Composite Phase Change Energy Storage Materials

“…In addition, the carbon layer can burn quickly under high heat conditions, and the core aluminum is exposed to the high heat environment for combustion. The combustion of the carbon layer provides additional energy, which indirectly increases the enthalpy of combustion of nano-aluminum powder [11][12]. However, the preparation of carbon-coated nano-aluminum particles is difficult.…”