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RISS 인기검색어
- 검색키워드
- 저자 : Arash Yazdani (검색결과 3 건)
- 무료
- 기관 내 무료
- 유료
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The effect of processing parameters on the hydrothermal synthesis of wollastonite at low pressure
Arash Yazdani 한양대학교 세라믹연구소 2013 Journal of Ceramic Processing Research Vol.14 No.1
In this research a hydrothermal method was applied to the synthesis of wollastonite. Silica, nano silica and calcium carbonate were used as the main raw materials and sodium chloride as a mineralizer. Six different slurries were prepared with SiO2/CaO molar ratios of 0.54, 0.8, 1 and a solid content of 50 wt%. Then the slurries were hydrothermally treated in an autoclave for 12 h at 130 ο C at a pressure of 1.5 atm. In the next step, the samples were dried at 150 ο C for 8 h and then calcined at 1000 ο C for 5 h. The microstructures and phases analyses were investigated using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Finally a three-stage mechanism was proposed for the hydrothermal synthesis of wollastonite. The results showed that by using nano silica, fine grain wollastonite was obtained.
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Study on the effects of processing parameters on the CVD alumina coating
Nasim Chenari,Mansour Soltanieh,Arash Yazdani 한양대학교 세라믹연구소 2013 Journal of Ceramic Processing Research Vol.14 No.6
The CVD alumina coatings were deposited on carbide cutting tools using gas mixtures of H2, CO2 and AlCl3 at the temperatures between 960-1000 o C, one atmosphere pressure and for different gas flows of H2, CO2. The AlCl3 gas is produced in a generator by passing the HCl gas through the mechanically worked aluminium granules. In a simulated laboratory setup it was found that the reactivity of aluminium granules with HCl was increased drastically. Thickness measurements showed that by using worked granules, the alumina thickness for the same conditions increases from 0.75 to 3 µm. Moreover, it was found that with increasing the coating temperature and flow of gases, deposition rate was increased. Calculations showed that the process is far from the equilibrium condition. It was found that the reaction is kinetically mass transfer controlled in the boundary layer. The activation energy of the process was equal to 207.02 Kj/mol.
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Hamid Reza Rezaie,Arash Yazdani,Hossein Ghassai 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.3
In this research a hydrothermal method was applied to synthesis of wollastonite. Silica, nano silica and calcium carbonate were used as raw materials. Different slurries were prepared with SiO2/CaO molar ratios of 0.54, 0.8, 1 and a solid content of 50 wt%. Then the slurries were hydrothermally treated in an autoclave for 2 h at 200 oC at pressures of 3, 5 and 7 atm. In the next step, the samples were dried at 150 oC for 8 h and then were calcined at 1000 oC for 5 h. The microstructure and phase analyses were investigated using SEM and XRD. The results showed that by using both silica and nano silica, with increasing pressure, the amount of wollastonite increased. At all pressures using silica, slurry with 50 wt% of solid content, SiO2/CaO molar ratio of 0.8 gave the optimum results while by using nano silica the optimum SiO2/CaO molar ratio was 1.
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