• Journal of Powder Materials
• /
• v.11 no.4
• /
• pp.308-313
• /
• 2004

An experimental study on the combustion of superfine aluminum powders (average particle diameter, a$_{s}$: ∼0.1 ${\mu}{\textrm}{m}$) in air is reported. The formation of aluminum nitride during the combustion of aluminum in air and the influence of the combustion scenario on the structures and compositions of the final products are in the focus of this study. The experiments were conducted in an air (pressure: 1 atm). Superfine aluminum powders were produced by the wire electrical explosion method. Such superfine aluminum powder is stable in air but once ignited it can burn in a self-sustaining way due to its low bulk: density (∼0.1 g/㎤) and a low thermal conductivity. During combustion, the temperature and radiation were measured and the actual burning process was recorded by a video camera. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and chemical analysis were performed on the both initial powders and final products. It was found that the powders, ignited by local heating, burned in a two-stage self-propagating regime. The products of the first stage consisted of unreacted aluminum (-70 mass %) and amorphous oxides with traces of AlN. After the second stage the AlN content exceeded 50 mass % and the residual Al content decreased to ∼10 mass %. A qualitative discussion is given on the kinetic limitation for AlN oxidation due to rapid condensation and encapsulation of gaseous AlN.N.

• Journal of the Korean Society of Propulsion Engineers
• /
• v.23 no.3
• /
• pp.88-95
• /
• 2019

The hydrogen torch ignition system has been widely used to ignite a pure aluminum for aluminum powder combustion system because of its simple ignition method. However, the conventional hydrogen torch ignition system has a disadvantage that requires a high-pressure tank to supply hydrogen, which leads to the increase of the weight. In order to solve this problem, a hydrogen ignition system using $NaBH_4$, a solid chemical hydride, was designed in this study. The thermal decomposition of $NaBH_4$ was initiated approximately at $500^{\circ}C$ and hydrogen was generated. The parameters affecting the thermal decomposition characteristics of $NaBH_4$ were analyzed and the aluminum combustion test was carried out using $NaBH_4$-based hydrogen ignition system to study the applicability to a practical aluminum-combustion propulsion system.

• 한국연소학회:학술대회논문집
• /
• 2012.04a
• /
• pp.241-243
• /
• 2012

Experiments were conducted to get the design concepts for the continuous aluminum particle feeding system. Two opposed cylinders were used. Aluminum particles in one cylinder were ejected to the air by the supplying gas and the pressure of the other cylinder. It was not possible to eject more aluminum mass flowrate than that of gas if particles were just thrust by the pressure difference between two cylinders. Aluminum particle/air mixture in the flow system was successfully ignited by the electric spark.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.27 no.5
• /
• pp.223-228
• /
• 2017

Aluminum nitride (AlN) powder was successfully synthesized at low temperature via carbothermal reduction and nitridation (CRN) assisted by microwave heating. The synthesis processes of AlN powder were investigated with X-ray diffraction, FE-SEM, FT-IR and TGA/DSC. Aluminum nitrate was used as an oxidizer and aluminum source, urea as fuel, and glucose as carbon source. These starting materials were mixed with D.I water and reacted in a flask at $100^{\circ}C$ for 20 minutes. After the reaction was finished, black foamy intermediate product was formed, which was considered to be an amorphous $Al_2O_3$ particles through intermediate product obtained by solution combustion synthesis (SCS) at the results of X-ray diffraction patterns and FT-IR. This intermediate product was nitridated at temperatures of $1300^{\circ}C$ and $1400^{\circ}C$ in $N_2$ atmosphere by a microwave heating furnace and then decarbonated at $600^{\circ}C$ for 2 hours in air. It should be noticed from FE-SEM images that as nitridated particles, identified as AlN from X-ray diffraction patterns, are covered with carbon residues. After decarbonating the nitridated powders, the spherical pure AlN powders were obtained without alumina and their particle sizes were dependent on the nitridating temperature with high temperature of $1400^{\circ}C$ giving large particles of around 70~100 nm.

• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2011.04a
• /
• pp.425-429
• /
• 2011

The development of metal plasma generated by high laser irradiance and its effect on the surrounding air using shadowgraph images after laser pulse termination are studied; hence the formation of laser supported detonation and combustion processes has been investigated. The core of the paper is in detecting chemical reaction using X-Ray Diffraction (XRD) between ablated aluminum plasma and oxygen from air by inducing high power laser pulse (>1000 mJ/pulse) and conduct a quantitative comparison of chemically reactive laser initiated waves with the classical detonation of exploding aluminum (dust) cloud in air. This study may suggest a new approach of initiating detonation from metal sample in its bulk form without the need of mixing nano-particles with oxygen for initiation.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.36 no.2
• /
• pp.197-204
• /
• 2012

We explore the evolution of metal plasma generated by high laser irradiances and its effect on the surrounding air by using shadowgraph images after laser pulse termination and X-ray diffraction (XRD) of aluminum plasma ablated by a high-power laser pulse (>1000 mJ/pulse) and oxygen from air. Hence, the formation of laser-supported detonation and combustion processes has been investigated. The essence of this paper is in observing the initiation of chemical reaction between the ablated aluminum plasma and oxygen from air by the high-power laser pulse (>1000 mJ/pulse) and in conducting a quantitative comparison of the chemically reactive laser-initiated waves with the classical detonation of an exploding aluminum (dust) cloud in air. The findings in this work may lead to a new method of initiating detonation from a metal sample in its bulk form without any need to mix nanoparticles with oxygen for initiation.