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本文分别用X-射线光电子能谱(ESCA)、X-射线衍射仪(XRD)、正电子湮没谱(PASCA)及Faraday式磁天平等测试技术对WO_3在γ-Al_2O_3表面上的分散进行了研究.实验结果发现,用ESCA和XRD测定WO_3在γ-Al_2O_3表面上的最大单层分散量为27m%,相当于0.185g WO_3/100m~2.此结果与按WO_3在γ-Al_2O_3表面上作密置单层排布模型计算值极为吻合.而用PASCA和磁天平测定WO_3在γ-Al_2O_3表面上的最大单层分散量约为20m%,相当于64%的表面覆盖率,该值低于ESCA和文献[4,8]所测定的值.PASCA和磁天平的灵敏度比XRD和ESCA要高得多.因为PASCA可以在分子或原子水平上反映出物质结构的细微变化.从理论上讲Al_2O_3表面也不可能100%为WO_3所覆盖,因为Al_2O_3表面上不可避免会有一些“隐蔽”的角落和一部分WO_3进不去的微孔结构.XRD和ESCA测得的值可能是偏高的,而PASCA和磁天平测得的WO_3在γ-Al_2O_3表面上覆盖率为64%较为可信.
In this paper, the dispersion of WO_3 on γ-Al_2O_3 surface has been studied by X-ray photoelectron spectroscopy (ESCA), X-ray diffraction (XRD), positron annihilation spectroscopy (PASCA) and Faraday magnetometer The experimental results showed that the maximum monolayer dispersion of WO 3 on γ-Al 2 O 3 surface was 27m% by ESCA and XRD, which was equivalent to 0.185g WO_3 / 100m ~ 2.This result was consistent with that of WO_3 on the surface of γ-Al_2O_3 Calculated by PASCA and magnetic balance, the maximum monolayer dispersion of WO_3 on γ-Al_2O_3 surface is about 20m%, which is equivalent to 64% surface coverage, which is lower than that of ESCA And literature [4,8] .The sensitivity of PASCA and magnetic balance is much higher than that of XRD and ESCA because PASCA can reflect the subtle changes in the structure of matter at the molecular or atomic level.In theory, the surface of Al 2 O 3 It is also impossible to cover 100% WO_3 because some “hidden” corners and some porous structures that WO_3 can not penetrate are inevitable on the surface of Al_2O_3.The values measured by XRD and ESCA may be high, The PASCA and magnetic balance measured WO_3 γ-Al 2 O 3 surface coverage of 64% is more credible.