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RISS 인기검색어
- 검색키워드
- 저자 : Dudi Adi Firmansyah (검색결과 3 건)
- 무료
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Exchange of Copper Nanoparticles Properties During Spray Pyrolysis
Dudi Adi Firmansyah,김태일(Tae Il Kim),이동근(Donggeun Lee) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
A continuous manufacturing process of copper nano particles by spray pyrolysis has been developed recently. Copper pure-phase nano particles were produced by spray pyrolysis of copper nitrates with ethanol as co-solvent over temperature of 450-600℃. The final products showed the properties exchanges as ethanol added as co-solvent. We found ethanol addition shifted the copper nanoparticles to smaller size that confirmed by DMA measurement results. Copper nanoparticles also experienced the morphological change from shell like to solid like as effect of ethanol addition, which was confirmed by TEM. The Energy Dispersive Spectroscopy (EDS) measurement showed that shell-like particles contained copper with high level of oxygen while the solid-like particle only consisted of copper. The XRD measurements revealed that ethanol addition induced the reduction of Cu₂O at isothermal spray pyrolysis of 600℃ and copper metallic phase were started to form at a 525℃ at a constant ethanol addition experiments. Thus, it can be assumed that copper nitrate involve the solid-state reaction to produce copper (Ⅰ) oxide and subsequently reduced to its metallic phase under reducing atmosphere result of ethanol decomposition.
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Firmansyah, Dudi Adi,Sullivan, Kyle,Lee, Kwang-Sung,Kim, Yong Ho,Zahaf, Riyan,Zachariah, Michael R.,Lee, Donggeun American Chemical Society 2012 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.116 No.1
<P>The oxidation mechanism of nanoaluminum particles, nominally employed as fuel component, is still an unsettled problem, because of the complex nature of thermomechanical properties of the oxide shell surrounding the elemental core. Although mechanical breakage of the alumina shell upon or after melting of aluminum core has been thought to play a key role in the combustion of aluminum nanoparticles, there has been little direct evidence. In this study, the microstructural behaviors of Al core and alumina shell lattices were investigated with increasing temperatures. Three in situ techniques, high-temperature X-ray diffraction analysis, hot-stage transmission electron microscopy, and high-resolution transmission electron microscopy for heat-treated samples, were employed to probe the thermal behaviors of aluminum and alumina lattices before and after melting of the aluminum core. High-temperature X-ray diffraction analysis revealed that nano aluminum lattice was initially expanded under tension at room temperature, and then when heated passed through a zero-strain state at ∼300 °C. Upon further heating above the bulk melting temperature of aluminum, the aluminum lattice expanded under almost no constraint. This interesting observation, which is contrary to almost all of the previous results and models, was ascribed to the inhomogeneous (localized) crystalline phase transformation of amorphous alumina. High-resolution transmission electron microscopy and in situ hot-stage transmission electron microscopy evidenced localized phase transformation accompanied by a significant shell thickening, presumably resulting from diffusion processes of Al cations and O anions, which is to absorb the pressure built in aluminum core, by creating a more ductile shell.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2012/jpccck.2012.116.issue-1/jp2095483/production/images/medium/jp-2011-095483_0009.gif'></P>
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Numerical simulations of supersonic gas atomization of liquid metal droplets
Firmansyah, Dudi Adi,Kaiser, Rashed,Zahaf, Riyan,Coker, Zach,Choi, Tae-Youl,Lee, Donggeun Institute of Pure and Applied Physics 2014 Japanese Journal of Applied Physics Vol. No.
<P>Computational fluid dynamics simulations incorporating supersonic turbulent gas flow models and a droplet breakup model are performed to study supersonic gas atomization for producing micron-sized metal powder particles. Generally such atomization occurs in two stages: a primary breakup and a secondary breakup. Since the final droplet size is primarily determined by the secondary breakup, parent droplets of certain sizes (1 to 5 mm) typically resulting from the primary breakup are released at the corner of the nozzle and undergo the secondary breakup. A comparison of flow patterns with and without the introduction of a liquid melt clearly indicates that the mass loading effect is quite significant as a result of the gas-droplet interactions. The flow pattern change reasonably explains why the final droplets have a bimodal mass size distribution. The transient size changes of the droplets are well described by the behavior of the Weber number. The present results based on the 1 mm parent droplets best fit previous experimental results. Moreover, the effects of inlet gas pressure and temperature are investigated in an attempt to further reduce droplet size. (C) 2014 The Japan Society of Applied Physics</P>
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