The surface behaviour of Pt/γ-Al_2O_3 and Pt-Ce/γ-Al_2O_3 catalysts was investigated by temperature-programmed desorption(TPD) and some other relevant methods.The results of high and low TPD experiments show that ce...The surface behaviour of Pt/γ-Al_2O_3 and Pt-Ce/γ-Al_2O_3 catalysts was investigated by temperature-programmed desorption(TPD) and some other relevant methods.The results of high and low TPD experiments show that cerium can increase the number of activated adsorption centres,and decrease the number of non-activated adsorption centres,but the total number of adsorption centres remains unchanged at high tem- peratures.The main model of Pt and Ce distribution on the γ-Al_2O_3 is proposed.展开更多
The surface tensions and contact angles of Fe_(78)Si_9B_(13) and Fe_(73.5)Cu_1Nb_3Si_(13.5)B_9 alloy melts were studied as a function of temperature in various atmospheres(vacuum, Ar and N_2 gas) and on different subs...The surface tensions and contact angles of Fe_(78)Si_9B_(13) and Fe_(73.5)Cu_1Nb_3Si_(13.5)B_9 alloy melts were studied as a function of temperature in various atmospheres(vacuum, Ar and N_2 gas) and on different substrates(Si C, Al_2O_3 and BN). It is indicated that Si_3N_4, NbN, Fe_2 Al B and B_(13)C_2 are generated as new phases at the interface between the melt and substrate, and reactive wetting behaviour exists during the heating process. The surface tensions of two alloy melts on BN substrate both firstly decrease and then increase along with increasing temperature, leading to V-shaped surface tension versus temperature, which results from atomic diffusion effects in the surface layer during the oxidation of BN and formation of C-rich layer. Comparably, the surface tensions on Al_2O_3 and Si C substrates decrease with increasing temperature throughout the entire temperature range. Among three substrates, BN exhibits the mildest wetting behaviour. The vacuum environment has the strongest protective effect on melt stability among the tested atmospheres. These findings enrich our knowledge about the effects of the substrate and atmosphere on Fe-based alloy melts at a high temperature, and provide theoretical reference for designing jet nozzles in melt-spinning techniques.展开更多
基金The Project supported by the National Natural Science Foundation of China
文摘The surface behaviour of Pt/γ-Al_2O_3 and Pt-Ce/γ-Al_2O_3 catalysts was investigated by temperature-programmed desorption(TPD) and some other relevant methods.The results of high and low TPD experiments show that cerium can increase the number of activated adsorption centres,and decrease the number of non-activated adsorption centres,but the total number of adsorption centres remains unchanged at high tem- peratures.The main model of Pt and Ce distribution on the γ-Al_2O_3 is proposed.
基金supported by the National Natural Science Foundation of China(Grant No.51501043)National Scientific and Technological Support Projects(Grant No.2013BAE08B00)+1 种基金National Key Scientific Instrument and Equiment Development Project(Grant No.2014YQ120351)Science and Technology Program of Beijing(Grant No.Z141100003814007)
文摘The surface tensions and contact angles of Fe_(78)Si_9B_(13) and Fe_(73.5)Cu_1Nb_3Si_(13.5)B_9 alloy melts were studied as a function of temperature in various atmospheres(vacuum, Ar and N_2 gas) and on different substrates(Si C, Al_2O_3 and BN). It is indicated that Si_3N_4, NbN, Fe_2 Al B and B_(13)C_2 are generated as new phases at the interface between the melt and substrate, and reactive wetting behaviour exists during the heating process. The surface tensions of two alloy melts on BN substrate both firstly decrease and then increase along with increasing temperature, leading to V-shaped surface tension versus temperature, which results from atomic diffusion effects in the surface layer during the oxidation of BN and formation of C-rich layer. Comparably, the surface tensions on Al_2O_3 and Si C substrates decrease with increasing temperature throughout the entire temperature range. Among three substrates, BN exhibits the mildest wetting behaviour. The vacuum environment has the strongest protective effect on melt stability among the tested atmospheres. These findings enrich our knowledge about the effects of the substrate and atmosphere on Fe-based alloy melts at a high temperature, and provide theoretical reference for designing jet nozzles in melt-spinning techniques.
