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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >High-pressure and high-temperature transformation of Pb(II)-natrolite to Pb(II)-lawsonite
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High-pressure and high-temperature transformation of Pb(II)-natrolite to Pb(II)-lawsonite

机译:Pb(II)-钠沸石向Pb(II)-钠钠钙石的高温高压转变

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摘要

We report on high-pressure and high-temperature chemical transformations of Pb2+-exchanged natrolite (Pb-NAT, Pb8Al16Si24O80.16H(2)O) using a combination of in situ synchrotron X-ray powder diffraction and ex situ HAADF-STEM real space imaging. Three high-pressure polymorphs of natrolites (Pb-NAT-I, II, III) are observed via step-wise pressure-induced hydrations (PIH) up to 4.5 GPa, during which the number of H2O molecules located inside the natrolite channel increases from 16 to 40 H2O per unit-cell. At 4.5 GPa after heating the high-pressure Pb-NAT-III phase at 200 degrees C a reconstructive phase transits into a lawsonite phase (Pb-LAW, Pb4Al8Si8O28(OH)8.4H(2)O) with an orthorhombic space group Pbnm and a = 5.8216(9), b = 9.114(1) and c = 13.320(1) angstrom is obseed. The structure of the recovered Pb-LAW phase was characterized using Rietveld refinement of the in situ synchrotron X-ray powder diffraction data and HAADF-STEM real space imaging. In the recovered Pb-LAW phase the Pb2+ content is close to 42 wt% and as bond valence approximations reveal the Pb2+ cations are more tightly coordinated to the framework oxygen atoms than originally in the natrolite phase.
机译:我们使用原位同步加速器X射线粉末衍射和非原位HAADF-STEM实空间相结合的报告,对Pb2 +交换的钠沸石(Pb-NAT,Pb8Al16Si24O80.16H(2)O)进行高压和高温化学转化成像。通过逐步的压力诱导水合作用(PIH)观察到高达4.5 GPa的三种钠沸石的高压多晶型物(Pb-NAT-I,II,III),在此期间位于钠沸石通道内的H2O分子数量从每单位电池16至40 H2O。在将高压Pb-NAT-III相加热到200摄氏度后,在4.5 GPa下,重构相转变为具有正交晶空间群Pbnm和Pbnm的钙钛矿相(Pb-LAW,Pb4Al8Si8O28(OH)8.4H(2)O)。 a = 5.8216(9),b = 9.114(1),c = 13.320(1)埃。使用Rietveld精制原位同步加速器X射线粉末衍射数据和HAADF-STEM真实空间成像来表征回收的Pb-LAW相的结构。在回收的Pb-LAW相中,Pb2 +含量接近42 wt%,并且随着键合价的近似显示,Pb2 +阳离子与骨架氧原子的配位比最初在钠铝石相中的配位更紧密。

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