Molten salt fluxes, preparation

The preparation of some polychalcogenide solids can be achieved at 200-450 °C by molten salt (flux) methods. The reaction of tin with alkali metal sulfides in the presence of Ss at 200-450 °C gives a variety of alkali metal tin sulfides depending on the ratio of the starting materials, the reaction temperature, and the alkah metals (Scheme 30) [90]. These alkali metal tin sul-... 

This means that addition of elemental E to alkali metal polychalcogenide fluxes (200-600°C) will promote the formation of longer chains as potential ligands, when such molten salts are employed as reaction media for the preparation of polychalcogenide complexes. Speciation analysis for polychalcogenides in solution has been performed by a variety of physical methods including UV/vis absorption spectroscopy, Raman spectroscopy, Se, Te and Te NMR, electron spin resonance and electrospray mass spectrometry. 

The flux method is a well-known method used for single crystal growth. It has not been applied to the synthesis of fine powders because usually high temperature heating is necessary to obtain molten salts. However, the modified flux method has been reported for the preparation of fine panicles of Ce,. Pr Oj solid solutions.In the preparation of the powders by the flux method, molten salts of alkali metal hydroxides, nitrates, and chlorides are used as solvents. The use of molten salts. 

Molten salts are not only useful as solvents in chemical synthesis, electrolysis, soldering, enameling, de-enameling, metal recycling and preparation, coal gasification, and desulfuration, but they are also reactants, catalysts, and ambients for heat storage and heat transfer, as well as electrolytes in fuel cells (molten carbonates). The solvent can participate in the reaction that is carried out in fluxes. BaTiOa is made in molten TiO, as a solvent and Bio(AlClJ, can only be made in a very acidic cryolite (NaAlClJ. 

Molten salt synthesis based on the use of salts with low melting point has been reported to be one of the simplest techniques for preparing ceramic materials [57]. Well-faced LNM crystals were synthesized by molten salt technology using stoichiometric amount of LiOH, Ni(OH)2, and y-MnOOH (2 1 3) calcined at 700-1000 °C [57]. Micro-sized LNM crystals in plate and octahedral shapes were synthesized by molten-salt method in LiCl and LiCl-KCl fluxes the main surface facets on the plates were determined to be (112) crystal planes [58]. Recenfly, microscale LNM was synthesized using nanothom stmctured MnOa mixed with Li and Ni precursors [59]. 

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