SYSTEM (LiF)2 – (NaF)2 – (NaCl)2 – Na3FSO4

With the differential-thermal method of physico-chemical analysis the stable tetrahedron (LiF)2 – (NaF)2 – (NaCl)2 – Na3FSO4 of four-component mutual system Li, Na // F, Cl, SO4. It was established that the system is eutectic one.The eutectic crystallizes at 543 °C. The system Li, Na // F, Cl, SO4 is characterized by the presence of three compounds: one detectice (Na3FSO4) and two peritectically compounds Li2Na4(SO4)3, LiNaSO4. Four-component reciprocal systems, in the elements of faceting of which include irreversibly-reciprocal or singular three-component systems without compounds, are divided, as a rule, into three tetrahedra. In this case, the composition diagrams of the Li, Na / F, Cl, SO4 system are decomposed taking into account the incongruent and congruent melting compounds, resulting in the revealing the seven tetrahedra.: 1. (LiF)2 – (LiCl)2 – Li2SO4 – (NaCl)2; 2. (LiF)2 – Li2SO4 – (NaCl)2 – Na3FSO4; 3. Li2SO4 – Na2SO4 – (NaCl)2 – Na3FSO4; 4. (LiF)2 – (NaF)2 – (NaCl)2 – Na3FSO4; 5. Li2Na4(SO4)3 – LiNaSO4 – Na3FSO4 – (NaCl)2; 6. LiNaSO4 – Na3FSO4 – Li2SO4 – (NaCl)2; 7. Li2Na4(SO4)3 – Na3FSO4 – Na2SO4 – (NaCl)2. The theoretical analysis of the granular elements of these tetrahedra carried out by us, and later the investigation of the DTA of single compounds in each tetrahedron, shows that the nonvariant points from tetrahedra formed with the participation of incongruent melting compounds migrate to the tetrahedra bordering them with inversion into quaternary peritectics. The lack nonvariant points in the tetrahedra formed with the participation of the incongruent melting compounds: Li2Na4(SO4)3 – LiNaSO4 – Na3FSO4 – (NaCl)2; LiNaSO4 – Na3FSO4 – Li2SO4 – (NaCl)2; Li2Na4(SO4)3 – Na3FSO4 – Na2SO4 – (NaCl)2, confirmed by the absence in the thermograms of DTA unit composition of these tetrahedrons thermoeffect joint crystallization of four phases. In this study, a tetrahedron (LiF)2 - (NaF)2 - (NaCl)2 - Na3FSO4 was selected for experimental investigation, in a composition that does not include peritectic compounds and only one eutectic composition is localized in this system.The choice of this system for experimental research is also due to the fact that its composition includes lithium fluoride, which has a relatively large enthalpy of phase transition, which is one of the determining factors in the selection of heat accumulators, heat carriers for devices that store heat and solar energy.Also the system includes salts widely used in the pulp and paper, textile, food, construction industries. Investigation of phase equilibrium diagrams of such systems allows expanding the areas of application of low melting eutectic compounds.Forcitation:Verdiev N.N., Omarova S.M., Alkhasov A.B., Magomedbekov U.G., Gasangadzhieva U.G., Dvoryanchikov V.I. System(LiF)2 – (NaF)2 – (NaCl)2 – Na3FSO4. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 6. P. 77-82.

Preparation of RHA-Paraffin Phase Change Materials

In this paper, a kind of RHA-paraffin phase change material was prepared, and the SEM was used for observing its internal morphologies, DSC analysis was carried out for detecting its temperature and enthalpy of phase transition. The results showed that rice husk ash have a greater absorption rate for paraffin; a large number of pores of the RHA were filled by paraffin in the RHA-paraffin phase change material, and the absorption rate can reach 53.5%.

Comparison between Vanadium Dioxides Produced by Ammonium Metavanadate and Vanadium Pentoxide

The facile processes were developed for synthesizing vanadium dioxide (VO2) by pyrolyzing ammonium metavanadate (NH4VO3) in nitrogen (N2) flow and by thermal reduction of vanadium pentoxide (V2O5) in ammonia gas. X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) were applied to analyzing the product VO2. The experimental results indicated that VO2microcrystal particles were successfully synthesized from both NH4VO3and V2O5. From NH4VO3the product VO2presents two kinds of micro morphologies, torispherical and pentagonal prism. The phase transition mainly takes place at 337.8K and 341.8K. The average enthalpy of phase transition is 28.82 J/g. From V2O5the product VO2presents rhombohedral. The phase transition temperature is approximately 342.6K and the enthalpy of phase transition is 44.90 J/g.