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The quantitative distribution of different zirconium fluoride anions in molten LiF and FLiBe mixtures has been investigated by Raman and theoretical calculations. In molten LiF, zirconium fluorides are present in the forms of ZrF62− and ZrF73−. After correction, the Raman scattering cross sections corresponding to the symmetric stretching vibrational bands were obtained. The ZrF73− anion was a dominant species whatever the concentration of ZrF4 between 5 and 30 mol % in LiF melt, even though the content of which presents a decreasing trend from 92.3 to 73.2 mol % with the increase of ZrF4. Similar specification was identified in FLiBe‐ZrF4, and ZrF62−/ZrF73− anions were found in equilibrium with free F− ions and beryllium fluoride anions. Detailed deconvolution and calculation were performed on the Raman spectrum measured in the FLiBe melt containing 10 mol % ZrF4 giving a quantitative content of ZrF73− 78.1 mol % and ZrF62− 21.9 mol %. [ABSTRACT FROM AUTHOR]

In order to investigate the species in the FLiNaK–CeF3 and FLiNaK–CeF3–Li2O melts, in situ high temperature Raman spectroscopy was used with the aid of density functional theory (DFT) calculation. In molten FLiNaK, the CeF63− octahedra affected by alkali cations were identified to be the predominan species. Binuclear cerium oxyfluoride anions Ce2OF84− and Ce2OF106− were formed after adding O2− into the molten FLiNaK‐CeF3 (20 mol%) mixtures. Both of these two species were predicted to have Ce−O−Ce geometries with two CeF4/CeF5 moieties bridged by a single oxygen atom. [ABSTRACT FROM AUTHOR]

NaF is one of the most important sorption materials used in the UF6 purification, the stability of the complex formed after NaF absorbed UF6 was investigated by in situ Raman spectroscopy. The desorption behavior of UF6 from NaF adsorbent was examined by FT-IR, which show that UF6 did not desorb significantly from the NaF adsorbent until the temperature was above 200 °C, and the maximum desorption rate was reached at approximately 330 °C. Na2UF8 was hydrolyzed to form UO2F2·nH2O when it exposed to air containing moisture, there existed two desorption peaks for the air-exposed Na2UF8 complex in a fluorine atmosphere, one appeared at approximately 325 °C, attributed to the decomposition of UF6 from Na2UF8, and another was located at approximately 401 °C, attributed to the conversion of UO2F2 to UF6 by fluorine and the subsequent release of UF6. [ABSTRACT FROM AUTHOR]

The "one-pot" method to prepare cyclized m -CMP@SiO 2 fluorescence probe and fluorescence mechanism to detect Fe3+ and Cr3+ in aqueous solution. [Display omitted] • In situ cyclization was used to improve the stability of Sciff-base condensation products. • The "one-pot" method was successfully uesd to prepare CMP-coated silica nanospheres. • CMP-coated silica nanospheres were successfully applied to fluorescence detect Fe3+ and Cr3+. Schiff-base condensation reaction was often used to prepare conjugated microporous polymers (CMPs). However, due to the relatively unstable imine bond in the product, the application of CMPs in some strong acid-base environments was limited. Therefore, it was necessary to further strengthen the stability of CMPs by "bottom-up" strategy. For this purpose, three kinds of cyclized CMPs (x-CMP x = m, p, bi) were successfully prepared by Schiff-base reaction followed by an acid-catalyzed in situ cyclization with 1,5,9-triamine-triphenylene (TATP) and m -phthalaldehyde (m -PA), p -phthalaldehyde (p -PA) or 4,4'-biphenyldicarboxaldehyde (bi-PA) as precursors. The in situ cyclization at the imine bond was demonstrated by X-ray photoelectron spectroscopy and Raman spectroscopy. Because cyclized CMPs were amorphous powder, their dispersity were not ideal, which affects them further applications. Therefore, through a "one-pot" method, these CMPs were also coated onto silica nanospheres, assigned as x-CMP@SiO 2 (x = m, p, bi), exhibiting core–shell structure and excellent monodispersity. Due to the difference dispersity of three x-CMP@SiO 2 (x = m, p, bi) in aqueous solution, the fluorescence quantum yields were different, which were 15.3%, 14.4% and 11.2%, respectively. As fluorescent sensors, three cyclized x-CMP@SiO 2 (x = m, p, bi) could selectively generated fluorescence quenching response to Fe3+ and Cr3+ in aqueous solution. Compared with amorphous CMPs, the resulting CMP@SiO 2 nanomaterials not only improved the dispersity and mechanical strength, but also offered the convenience for subsequent applications. It is expected this feasible method would facilitate CMPs to be widely explored in fluorescence detection and other research fields. [ABSTRACT FROM AUTHOR]

• Zirconium and hafnium fluorides are present as MF 6 2– and MF 7 3– in the KF melts. • The influence of O2– on the speciation in melts has been studied by Raman and DFT. • Oxyfluorides exist in the form of MOF 5 3– with terminal oxygen structure. The influence of oxide ions on the speciation in molten KF containing ZrF 4 and HfF 4 has been studied by using Raman spectroscopy, and identification of the structures is carried out by density functional theory calculations within the polarization continuum model. Zirconium and hafnium fluorides are present as MF 6 2– and MF 7 3– (M = Zr, Hf) in the KF melts with low MF 4 concentrations, whereas MF 6 2– dominate at high MF 4 concentrations. With the addition of 3–5 mol% Li 2 O into the KF-MF 4 (10 mol%) melts, oxyfluorides in the form of MOF 5 3– were observed with characteristic terminal M O stretching bands at 775 (Zr) and 763 (Hf) cm−1. However, these oxyfluorides were not observed when 5 mol% Li 2 O was added into the KF melts with 30–40 mol% ZrF 4 and HfF 4. The formation of MOF 5 3– anion is consistent with the much lower average association energies of MF 7 3− than MF 6 2−. This makes it a lot more favourable to replace F− by O2− so as to generate MOF 5 3–, and the free F- ions released can further react with MF 6 2− to give MF 7 3−. As the Li 2 O concentration is increased to 15 mol%, the melts are no longer homogeneous and the Raman bands due to zirconium and hafnium oxides coming into exist. [ABSTRACT FROM AUTHOR]

• The structure of tantalum fluorides and oxyfluorides in molten FLiNaK was studied by Raman spectroscopy. • Density functional theory (DFT) calculations were employed to assist the assignment of the bands observed in molten salts. • The TaF 7 2− and TaF 8 3− octahedral was identified to be present in molten FLiNaK-K 2 TaF 7 mixtures. • The oxyfluorides of TaOF 5 2−, TaOF 6 3−, TaO 2 F 2 − and TaO 2 F 3 2− were formed with Li 2 O adding into the molten salts. Combined with Raman spectroscopy and theoretical calculations, the tantalum fluoride and oxyfluoride ions in molten FLiNaK were studied. Firstly, the Raman spectra of K 2 TaF 7 were recorded from 298 to 973 K and no structural evolution was observed. The coexistence of TaF 7 2– and TaF 8 3– anions was confirmed in K 2 TaF 7 and molten FLiNaK-K 2 TaF 7 mixtures. With the addition of Li 2 O (3 mol%), the terminal oxo ligands TaOF 5 2– and TaOF 6 3– were formed at the expense of TaF 7 2– and TaF 8 3– with the release of free F– ions, respectively. When the Li 2 O content increased to 13 mol%, two new oxyfluorides TaO 2 F 2 – and TaO 2 F 3 2– were observed that contained two non-bridging oxygens. As the content of Li 2 O further increased to 40 mol%, insoluble solid tantalum oxide species like β-Ta 2 O 5 was found, which indicates the transformation of intermediate oxyfluorides formed by the reaction of TaF 7 2– and TaF 8 3– fluorides with O2– in molten FLiNaK to oxides. [ABSTRACT FROM AUTHOR]

• The structure of cerium fluoride and oxyfluoride was studied by Raman and DFT. • Both LuF 5 2− and LuF 6 3− anions were identified in molten FLiNaK. • Lu 2 OF 8 4−, Lu 2 O 2 F 4 2− and Lu 2 O 2 F 6 4− anions were confirmed with the addition of Li 2 O. Combined with Raman spectroscopy and density functional theory (DFT) calculations, the micro-structures in molten FLiNaK-LuF 3 and FLiNaK-LuF 3 -Li 2 O systems were studied. Both LuF 5 2− (D 3h) and LuF 6 3− (O h) anions were identified in molten FLiNaK, and their relative content varied with the concentration of LuF 3. For regarding the affection of oxygen anion, Li 2 O was added into the molten FLiNaK-LuF 3 (20 mol%) sample. The lutecium oxyfluoride anion Lu 2 OF 8 4− was firstly formed which possesses a linear Lu O Lu geometry with two LuF 4 moieties bridged by one single oxygen atom. Further increasing the Li 2 O content to 10 mol% resulted in the formation of two species, which belonged to the Lu 2 O 2 F 4 2− and Lu 2 O 2 F 6 4− anions. When increased the concentration of Li 2 O to 20 mol%, a new species appeared which was approximate to the oxide structure. [ABSTRACT FROM AUTHOR]

The structural evolution of Li 2 BeF 4 from crystalline to molten states has been investigated by Raman spectroscopic technique with the assist of density functional theory (DFT). The experimental results of temperature-dependent Raman spectra of Li 2 BeF 4 showed that no solid-state phase transformation was taken place during heating process from 298 to 723 K. In the molten state, the structure of BeF 4 2− anion was affected by Li+ cation and environment. For the binary LiF-BeF 2 melts with varying LiF/BeF 2 ratio, the stretching bands of beryllium‑fluorine bonds in molten Raman spectra were deconvolved identified by Gaussian function. When the concentration of BeF 2 exceeding 33 mol%, the dimer Be 2 F 7 3− was formed and dominated the spectrum. It was characterized to have a linear Be–F–Be geometry with two BeF 4 moieties bridged by a single fluorine atom. A second anion Be 3 F 10 4− processing a triple chain structure formed when the content of BeF 2 increasing to 50 mol%. When the concentration of BeF 2 went beyond 60 mol%, the Raman intensity and band width gradually decreased. While the intensity and band width of Raman spectra gradually decreased with the concentration of BeF 2 exceeding to 60 mol%, which suggests that the band should be assigned to a hexatomic Be 6 F 18 6− ring which was similar to the situation in the pure BeF 2 network structure. • The structure of beryllium fluorides was studied by Raman and DFT calculations. • Different models and methods were established to simulate crystal and melt. • Fluoroberyllate species BeF 4 2−, Be 2 F 7 3−, Be 3 F 10 4−, and Be 6 F 18 6− were observed. [ABSTRACT FROM AUTHOR]

• Effect of Mg treatment on the corrosivity of molten chloride salt was studied. • Salt with Mg treatment exhibits lower corrosivity than salt without Mg treatment. • Mg treatment can remove the corrosive impurities MgOHCl and HCl. • The corrosivity of salt correlates with characteristic of Raman and IR spectra. • Raman and Infrared spectra can be used to monitor corrosivity of chloride salt. The effects of Mg treatment (i.e. adding Mg metal into the salt system) on the corrosion behavior of Ni-based alloys in molten NaCl-KCl-MgCl 2 salt at 800 °C were investigated using immersion tests and SEM/EDS analysis. The effects of Mg treatment on the salt chemistry were also characterized by ICP-OES, Raman and Infrared spectra. Results show that Mg treatment removes corrosive impurities HCl and MgOHCl which reduces the corrosivity of salt. The salt with different corrosivity shows the different characteristic peaks in its Raman and Infrared spectra. Raman and Infrared spectra may be used to monitor the corrosivity of Mg-based chloride salts. [ABSTRACT FROM AUTHOR]