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240219s2024 xx |||||o 00| ||eng c |
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|a 10.1021/acs.chemmater.3c02039
|2 doi
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|a pubmed24n1300.xml
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|a (NLM)38370277
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|a DE-627
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|a eng
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| 100 |
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|a Konar, Sumit
|e verfasserin
|4 aut
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|a Revisiting Solid-Solid Phase Transitions in Sodium and Potassium Tetrafluoroborate for Thermal Energy Storage
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|c 2024
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|a Text
|b txt
|2 rdacontent
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|a ƒaComputermedien
|b c
|2 rdamedia
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|a ƒa Online-Ressource
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|2 rdacarrier
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|a Date Revised 20.02.2024
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|a published: Electronic-eCollection
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|a Citation Status PubMed-not-MEDLINE
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|a © 2024 The Authors. Published by American Chemical Society.
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|a In situ synchrotron powder X-ray diffraction (PXRD) study was conducted on sodium and potassium tetrafluoroborate (NaBF4 and KBF4) to elucidate structural changes across solid-solid phase transitions over multiple heating-cooling cycles. The phase transition temperatures from diffraction measurements are consistent with the differential scanning calorimetry data (∼240 °C for NaBF4 and ∼290 °C for KBF4). The crystal structure of the high-temperature (HT) NaBF4 phase was determined from synchrotron PXRD data. The HT disordered phase of NaBF4 crystallizes in the hexagonal, space group P63/mmc (no. 194) with a = 4.98936(2) Å, c = 7.73464(4) Å, V = 166.748(2) Å3, and Z = 2 at 250 °C. Density functional theory molecular dynamics (MD) calculations imply that the P63/mmc is indeed a stable structure for rotational NaBF4. MD simulations reproduce the experimental phase sequence upon heating and indicate that F atoms are markedly more mobile than K and B atoms in the disordered state. Thermal expansion coefficients for both phases were determined from high-precision lattice parameters at elevated temperatures, as obtained from Rietveld refinement of the PXRD data. Interestingly, for the HT-phase of NaBF4, the structure (upon heating) contracts slightly in the a-b plane but expands in the c direction such that overall thermal expansion is positive. Thermal conductivities at room temperature were measured, and the values are 0.8-1.0 W m-1 K-1 for NaBF4 and 0.55-0.65 W m-1 K-1 for KBF4. The thermal conductivity and diffusivity showed a gradual decrease up to the transition temperature and then rose slightly. Both materials show good thermal and structural stabilities over multiple heating/cooling cycles
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|a Journal Article
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|a Zieniute, Gertruda
|e verfasserin
|4 aut
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|a Lascelles, Elliot
|e verfasserin
|4 aut
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|a Wild, Beth
|e verfasserin
|4 aut
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| 700 |
1 |
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|a Hermann, Andreas
|e verfasserin
|4 aut
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| 700 |
1 |
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|a Wang, Yi
|e verfasserin
|4 aut
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| 700 |
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|a Quinn, Robert J
|e verfasserin
|4 aut
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| 700 |
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|a Bos, Jan-Willem G
|e verfasserin
|4 aut
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| 700 |
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|a Fitch, Andrew
|e verfasserin
|4 aut
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| 773 |
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|i Enthalten in
|t Chemistry of materials : a publication of the American Chemical Society
|d 1998
|g 36(2024), 3 vom: 13. Feb., Seite 1238-1248
|w (DE-627)NLM098194763
|x 0897-4756
|7 nnns
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| 773 |
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|g volume:36
|g year:2024
|g number:3
|g day:13
|g month:02
|g pages:1238-1248
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|u http://dx.doi.org/10.1021/acs.chemmater.3c02039
|3 Volltext
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