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- 저자 : Naghi Parvini Ahmadi (검색결과 2 건)
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Maziyar Azadbeh,Naghi Parvini Ahmadi 한국물리학회 2009 Current Applied Physics Vol.9 No.4
Fe–Si alloys are of significant commercial and academic interests, due to the large diversity of their physical properties. In practice, alloy powders are unsuitable because of their hardness, poor compactibility and resulting excessive tool wear. Therefore the powder mixture route is suitable as alloying technique. The properties of the Fe–Si sintered materials depend strongly on the influence of the element Si and content of it, which influence mainly the compactibility and the sintering behaviour as well as sintering parameters such as the optimum temperature. In this study, Cr–Mo prealloyed steel powders with different Si contents were prepared by powder mixture route. Mixed powders compacted under pressing pressure of 600 MPa, and then sintered at 1120 and 1250 ℃. It was found out that in Si alloyed Cr–Mo steels sintered at higher temperatures such as 1250 ℃, an intermediate liquid phase appeared and caused extreme shrinkage and distortion, but strongly accelerated sintering and had a beneficial effect also on homogenization. Fe–Si alloys are of significant commercial and academic interests, due to the large diversity of their physical properties. In practice, alloy powders are unsuitable because of their hardness, poor compactibility and resulting excessive tool wear. Therefore the powder mixture route is suitable as alloying technique. The properties of the Fe–Si sintered materials depend strongly on the influence of the element Si and content of it, which influence mainly the compactibility and the sintering behaviour as well as sintering parameters such as the optimum temperature. In this study, Cr–Mo prealloyed steel powders with different Si contents were prepared by powder mixture route. Mixed powders compacted under pressing pressure of 600 MPa, and then sintered at 1120 and 1250 ℃. It was found out that in Si alloyed Cr–Mo steels sintered at higher temperatures such as 1250 ℃, an intermediate liquid phase appeared and caused extreme shrinkage and distortion, but strongly accelerated sintering and had a beneficial effect also on homogenization.
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Roohollah Azizi,Sousan Rasouli,Naghi Parvini Ahmadi,Amin Jafari jafar kolaei,Mohammad Azizi 한양대학교 세라믹연구소 2012 Journal of Ceramic Processing Research Vol.13 No.2
TiO2 nanoparticles were prepared by a sol-gel method using TiCl4 as a precursor. The effect of the TiCl4/H2O molar ratio and DBS/ethanol (two important parameters in this process) on the particle size and structure of the samples were studied. The structure and morphology of the nanoparticles were investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. A systematic study was made by using the results of Design-Expert software. The optimum ratio of TiCl4/H2O and DBS/ethanol, to achieve the smallest particle size and the highest rutile content, were studied. Results showed that a lower TiCl4/H2O molar ratio led to smaller nano particles and that this goal is achieved for the lowest TiCl4/H2O molar ratio and intermediate DBS/ethanol values.
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