The influences of P and rare earth （RE） complex modifier on the microstructure and mechanical properties of hypereutectic Al-21%Si alloy were studied. The ingots were made by metal mold casting and the proportion of...The influences of P and rare earth （RE） complex modifier on the microstructure and mechanical properties of hypereutectic Al-21%Si alloy were studied. The ingots were made by metal mold casting and the proportion of Ce＋P ingredient was different. The result showed that the size of grains could be refined obviously by the Ce＋P modifier and the effect of phosphorus was more intensive The primary silicon crystal was refined, while the needle-like eutectic silicon was turned fibrous or short. The alloy mechanical prop- erties had the best performance when 0.08% P and 0.6% Ce were added. The modification of primary silicon grains mainly depended on the heterogeneous nucleation mechanism, and the metamorphic mechanism of eutectic silicon was explained by adsorbing-twirming theory. The strengthening mechanism of experimental alloy was also discussed. The σb, 20 ℃ increases from 236.2 to 287.6 MPa and σb, 300 ℃ increases from 142.5 to 210 MPa.展开更多
Highly active MCM-41 supported nickel phosphide catalysts for hydrodesulfurization （HDS） were synthesized by two different phosphorus sources, in which the surface of Ni2P catalysts were modified by air instead of b...Highly active MCM-41 supported nickel phosphide catalysts for hydrodesulfurization （HDS） were synthesized by two different phosphorus sources, in which the surface of Ni2P catalysts were modified by air instead of being passivated by O2/N2 mixture. In addition, the catalysts need not be activated with flowing H2 （30 ml·min^-1） at 500℃ for 2 h prior to reaction as traditional method. X-ray diffraction （XRD）, X-ray photoelectro spectroscopy （XPS）, N2-adsorption specific surface area measurements and CO chemisorption were used to characterize the resulting catalysts. The effect of modification with air on the surface of the catalysts for HDS performance was investigated. Results showed that the surface modification with air can promote the formation of smaller Ni2P particles and more active Ni sites on surface of catalysts. At 3.0 MPa and 613 K, the dibenzothiophene （DBT） conversion of the catalysts modified with air was 98.7%, which was 7.1% higher than that of catalyst passivated by O2/N2 mixture. The higher activities of Ni2P（x）/M41-O catalysts can be attributed to the smaller Ni2P particles sizes and the increased hydrogen dissociation activity due to the surface modification.展开更多
基金supported by Advancing Front Science of Henan Province(092300410049)
文摘The influences of P and rare earth （RE） complex modifier on the microstructure and mechanical properties of hypereutectic Al-21%Si alloy were studied. The ingots were made by metal mold casting and the proportion of Ce＋P ingredient was different. The result showed that the size of grains could be refined obviously by the Ce＋P modifier and the effect of phosphorus was more intensive The primary silicon crystal was refined, while the needle-like eutectic silicon was turned fibrous or short. The alloy mechanical prop- erties had the best performance when 0.08% P and 0.6% Ce were added. The modification of primary silicon grains mainly depended on the heterogeneous nucleation mechanism, and the metamorphic mechanism of eutectic silicon was explained by adsorbing-twirming theory. The strengthening mechanism of experimental alloy was also discussed. The σb, 20 ℃ increases from 236.2 to 287.6 MPa and σb, 300 ℃ increases from 142.5 to 210 MPa.
基金Supported by the National Natural Science Foundation of China(21276048)the Project of Education Department of Heilongjiang Province,China(12541060)the Graduate Innovation Project of Northeast Petroleum University,China(YJSCX2016-019NEPU)
文摘Highly active MCM-41 supported nickel phosphide catalysts for hydrodesulfurization （HDS） were synthesized by two different phosphorus sources, in which the surface of Ni2P catalysts were modified by air instead of being passivated by O2/N2 mixture. In addition, the catalysts need not be activated with flowing H2 （30 ml·min^-1） at 500℃ for 2 h prior to reaction as traditional method. X-ray diffraction （XRD）, X-ray photoelectro spectroscopy （XPS）, N2-adsorption specific surface area measurements and CO chemisorption were used to characterize the resulting catalysts. The effect of modification with air on the surface of the catalysts for HDS performance was investigated. Results showed that the surface modification with air can promote the formation of smaller Ni2P particles and more active Ni sites on surface of catalysts. At 3.0 MPa and 613 K, the dibenzothiophene （DBT） conversion of the catalysts modified with air was 98.7%, which was 7.1% higher than that of catalyst passivated by O2/N2 mixture. The higher activities of Ni2P（x）/M41-O catalysts can be attributed to the smaller Ni2P particles sizes and the increased hydrogen dissociation activity due to the surface modification.
