کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
1333311 | 979072 | 2007 | 7 صفحه PDF | دانلود رایگان |
![عکس صفحه اول مقاله: Anisotropic thermal expansion and hydrogen bonding behavior of portlandite: A high-temperature neutron diffraction study Anisotropic thermal expansion and hydrogen bonding behavior of portlandite: A high-temperature neutron diffraction study](/preview/png/1333311.png)
The structure of deuterated portlandite, Ca(OD)2, was investigated using time-of-flight neutron diffraction in the temperature range 308–643 K. Rietveld analysis reveals that with increasing temperature, the c dimension expands at a rate ∼4.5 times larger than that for a. This anisotropy of thermal expansion is due to rapid increase in the interlayer thickness along c with increasing temperature. Fitting of the measured cell volumes yields a coefficient of thermal expansion, α=α0+α1T, where α0=5.966×10−5 K−1 and α1=3.333×10−8 K−2. On heating, hydrogen-mediated interatomic interactions within the interlayer become weakened, as reflected by increases in the interlayer D⋯O and D⋯D distances with increasing temperature. Correspondingly, the three equivalent sites over which D is disordered become further apart, suggesting a more delocalized configuration of D at high temperatures.
With increasing temperature, the Ca(OD)2 structure expands ∼4.5 times larger between the [CaO6] octahedral layers than within the layers. Correspondingly, the D-mediated interatomic interactions become significantly weakened, and the three equivalent sites over which D is disordered become further apart, suggesting a more delocalized configuration of D at elevated temperatures.Figure optionsDownload as PowerPoint slide
Journal: Journal of Solid State Chemistry - Volume 180, Issue 4, April 2007, Pages 1519–1525