In order to obtain higher emission performance than that of a traditional M-type cathode, we have developed a new type impregnated dispenser cathode. The new cathode is impregnated with a new active substance with mol...In order to obtain higher emission performance than that of a traditional M-type cathode, we have developed a new type impregnated dispenser cathode. The new cathode is impregnated with a new active substance with molar ratio of 26BaO·29SrO·8Sc2O3 ·7CaO·Al2O3 . This paper introduces the emission performance, surface active material, and work function of the new cathode. At 1100℃B , the DC current density and pulse current density are 30.6±1.0 A/cm2 and 171.6±2.8 A/cm2 , respectively, 2.1 and 5.4 times of that of an M-type cathode. The work function of the new cathode is 1.668± 0.002 eV. High concentration O-Al-Sc-Sr-Ba and O-Al-Sc-Ba are found in the pores and at pore edges, respectively. By comparing the emission performances and surface characteristics of as-polished and as-cleaned cathodes, it is proposed that, the emission around pore ends forms the major part of the total emission for the new cathodes.展开更多
In this work FePt-Au heterostructured nanocrystals （HNCs） such as tadpole-, dumbbell-, bead-, and necklace-like nanostructures were synthesized by a facile heteroepitaxial growth of Au NCs onto FePt nanorods （NRs）...In this work FePt-Au heterostructured nanocrystals （HNCs） such as tadpole-, dumbbell-, bead-, and necklace-like nanostructures were synthesized by a facile heteroepitaxial growth of Au NCs onto FePt nanorods （NRs）. A study of the growth mechanism revealed that the morphology control of the final products can be correlated with the adsorption sites of hydrogen onto the FePt NRs, which can be manipulated by the amount of the forming gas （At/7% H2） added. Not only the optical characteristic and magnetic properties of the intrinsic materials were retained in the products, but also the FePt-Au HNCs showed the tunable multifunctional properties resulted from the interactions between Au and FePt. Moreover, for methanol oxidation, the FePt-Au HNCs exhibited enhanced catalytic activity and CO tolerance on the catalyst surface compared to commercial Pt catalysts. It is worth noting that as multifunctional units, the FePt-Au HNCs also possess a heterogeneous surface, which could potentially enable their site-specific functionalization for targeting or imaging purposes in biomedical applications. More interestingly, the catalytic properties of the FePt-Au HNCs also endow this material with application potentials in nanocatalysis.展开更多
基金Supported by the National Natural Science Foundation of China (No. 60871053)the Major State Basic Research Development Program of China (No. 2013CB328901)
文摘In order to obtain higher emission performance than that of a traditional M-type cathode, we have developed a new type impregnated dispenser cathode. The new cathode is impregnated with a new active substance with molar ratio of 26BaO·29SrO·8Sc2O3 ·7CaO·Al2O3 . This paper introduces the emission performance, surface active material, and work function of the new cathode. At 1100℃B , the DC current density and pulse current density are 30.6±1.0 A/cm2 and 171.6±2.8 A/cm2 , respectively, 2.1 and 5.4 times of that of an M-type cathode. The work function of the new cathode is 1.668± 0.002 eV. High concentration O-Al-Sc-Sr-Ba and O-Al-Sc-Ba are found in the pores and at pore edges, respectively. By comparing the emission performances and surface characteristics of as-polished and as-cleaned cathodes, it is proposed that, the emission around pore ends forms the major part of the total emission for the new cathodes.
基金This work was supported in part by National Natural Science Foundation of China （NSFC） （Nos. 90922033 and 20941003）, the National Basic Research Program of China （No. 2010CB934601）, the Doctoral Program （No. 20090001120010）, and New Century Talents of the Education Ministry of China （No. NCET-09-0177）, the Yok Ying Tung Foundation （No. 122043）, the Beijing Outstanding Talent Program （No. 2009D013001000013）, and New Star Program of Beijing Committee of Science and Technology （BCST） （No. 2008B02）.
文摘In this work FePt-Au heterostructured nanocrystals （HNCs） such as tadpole-, dumbbell-, bead-, and necklace-like nanostructures were synthesized by a facile heteroepitaxial growth of Au NCs onto FePt nanorods （NRs）. A study of the growth mechanism revealed that the morphology control of the final products can be correlated with the adsorption sites of hydrogen onto the FePt NRs, which can be manipulated by the amount of the forming gas （At/7% H2） added. Not only the optical characteristic and magnetic properties of the intrinsic materials were retained in the products, but also the FePt-Au HNCs showed the tunable multifunctional properties resulted from the interactions between Au and FePt. Moreover, for methanol oxidation, the FePt-Au HNCs exhibited enhanced catalytic activity and CO tolerance on the catalyst surface compared to commercial Pt catalysts. It is worth noting that as multifunctional units, the FePt-Au HNCs also possess a heterogeneous surface, which could potentially enable their site-specific functionalization for targeting or imaging purposes in biomedical applications. More interestingly, the catalytic properties of the FePt-Au HNCs also endow this material with application potentials in nanocatalysis.
