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Abstract The hydration of the two most reactive phases of ordinary Portland cement (OPC), tricalcium silicate (C3S), and tricalcium aluminate (C3A) is successfully halted when the activity of water () falls below critical thresholds of 0.70 and 0.45, respectively. It has been established that the reduction in relative humidity (RH) and suppresses the hydration of all anhydrous phases in OPC, including less explored phases like dicalcium silicate, that is, belite (β‐C2S). However, the degree of suppression, that is, the critical threshold, for β‐C2S, standalone has yet to be established. This study utilizes isothermal microcalorimetry and X‐ray diffraction techniques to elucidate the influence ofon the hydration of‐C2S suspensions via incremental replacements of water with isopropanol (IPA). Experimentally, this study shows that with increasing IPA replacements, hydration is increasingly suppressed until eventually brought to a halt at a critical threshold of approximately 27.7% IPA on a weight basis (wt.%IPA). From thermodynamic estimations, the exact criticalthreshold and solubility product constant of‐C2S () are established as 0.913 and 10−12.68, respectively. This study enables enhanced understanding of β‐C2S reactivity and provides thermodynamic parameters during the hydration of β‐C2S‐containing cementitious systems such as OPC‐based and calcium aluminate‐based systems.
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Enhanced spontaneous polarization in double perovskite Bi 2 FeCrO 6 films
Abstract We report the pulsed‐laser deposition of epitaxial double‐perovskite Bi2FeCrO6(BFCO) films on the (001)‐, (110), and (111)‐oriented single‐crystal SrTiO3substrates. All of the BFCO films with various orientations show theandsuperlattice‐diffraction peaks. The intensity ratios between the‐superlattice and the main 111‐diffraction peak can be tailored by simply adjusting the laser repetition rate and substrate temperature, reaching up to 4.4%. However, both optical absorption spectra and magnetic measurements evidence that the strong superlattice peaks are not correlated with theB‐site Fe3+/Cr3+cation ordering. Instead, the epitaxial (111)‐oriented Bi2FeCrO6films show an enhanced remanent polarization of 92 μC/cm2at 10 K, much larger than the predicted values by density‐functional theory calculations. Positive‐up‐negative‐down (PUND) measurements with a time interval of 10 μs further support these observations. Therefore, our experimental results reveal that the strong superlattice peaks may come fromA‐ orB‐site cation shifts along the pseudo‐cubic [111] direction, which further enhance the ferroelectric polarization of the BFCO thin films.
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- Award ID(s):
- 1708615
- PAR ID:
- 10371474
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of the American Ceramic Society
- Volume:
- 102
- Issue:
- 9
- ISSN:
- 0002-7820
- Format(s):
- Medium: X Size: p. 5234-5242
- Size(s):
- p. 5234-5242
- Sponsoring Org:
- National Science Foundation
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