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用正电子湮没技术研究USY沸石的“二次孔”结构

马莉 陈志权 王少阶 彭治林 罗锡辉

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用正电子湮没技术研究USY沸石的“二次孔”结构

马莉, 陈志权, 王少阶, 彭治林, 罗锡辉

SECONDARY PORE STRUCTURE OF USY ZEOLITES STUDIED BY POSITRON ANNIHILATE TECHNIQUE

MA LI, CHEN ZHI-QUAN, WANG SHAO-JIE, PENG ZHI-LIN, LUO XI-HUI
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  • 测量了NaY及USY沸石的正电子寿命谱.得到NaY沸石有四个寿命分量:两个短寿命分量和两个长寿命分量.两个长寿命分量中,τ3,τ4分别是o-Ps在β笼和超笼中的湮没.USY沸石有五个寿命分量:两个短寿命分量和三个长寿命分量,三个长寿命分量中,τ3为o-Ps在笼中的湮没,τ4,τ5分别为o-Ps在“二次微孔”和“二次中孔”中的湮没.与NaY沸石相比,在真空中,USY的τ4增加到
    The structures of NaY and ultrastability Y-type (USY) zeolite were studied by positron lifetime spectroscopy.Four lifetimes could be obtained in NaY zeolite,the two larger components were assigned to be o-Ps annihilation in the β cage and supercage respectively.In USY zeolite,however,an additional lifetime component τ5 was observed,which was about 92ns in vacuum with continuous distribution from 39ns to 142ns by the Laplace inversion analysis of lifetime spectrum.The second larger lifetimes τ4 also increased to 14ns,compared to that in NaY zeolite.Existence of the longer lifetimes τ4 and τ5 is due to the porous structure of USY.The positron lifetime in USY zeolite was also measured as a function of air pressure ranging from 0 (vacuum) to 0.1MPa.The most interesting was the variation of the largest components τ5 and I5.They both decreased with increasing air pressure.The results can be explained as follows.First,the oxygen contained in the air could quench the Ps and reduce its lifetime and intensity.Second,the increasing density of air could also increase the probability of o-Ps pick-off annihilation and reduce its formation.These would lead to the decrease of its lifetime and intensity.
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出版历程
  • 收稿日期:  1996-11-05
  • 修回日期:  1997-03-04
  • 刊出日期:  1997-11-20

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