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PECULIARITIES OF PHASE FORMATION IN REE-CONTAINING NITRATE PRECURSOR SYSTEMS IN PREPARATORY PROCESSES OF CONSTRUCTION OXIDE MATERIALS FORMATION

Journal: Academic Journal "Industrial Machine Building, Civil Engineering" (Vol.3, No. 45)

Publication Date:

Authors : ; ; ; ; ;

Page : 290-297

Keywords : rare earth elements (REE); sodium; nitrates; complex formation; water-salt systems; properties.;

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Abstract

Nowadays, search for new methods and integrated technologies for synthesizing REEcontaining construction oxide materials using multi-component water-salt systems is going on. The available information on the progress and possible trends of improving the technologies for such materials formation, the present requirements to their stability and their properties reproducibility and extension of their application scope initiated continuation of our studies on this subject. The purpose of the present research is fundamental study of the cooperative processes taking place at the preparatory stages of obtaining the above materials, using nitrates of elements possessing different electronic structure, and search for possible ways of effecting the liquid-phase and solid-phase systems based on the thermal activation of re-agents, with the purpose of their structure-sensitive properties reproduction. By means of physical and chemical methods, the chemical interaction and phase equilibriums in the model water-salt NaNO3 – Ln(NO3)3 – H2O (Ln – Y, La – Lu) systems have been studied. Within the interval of 25 – 100оС the exchange interactions between the structural components with formation of new anionic coordination lanthanide compounds, were detected. Concentration limits of the saturated solutions, where the coordination Ln nitrates are excreted from, correlate with the composition of nun variant points in the respective solubility isotherms. They all are synthesized in the mono-crystal form. Their identity is confirmed and the systemic study of a number of their properties is carried out. The mechanism of complexformation in the systems can be explained as the competitive water molecules substitution by the NO3 - -groups in the nearest Ln3+environment, the effect of the Ln3+-complex-forming central atom’s nature on these processes, disordering effect of the present single charged Na+ cations on the solution structure, concentration and thermal motion nature of structural elements. The following has been detected in the systems: differences in the complex-formation ability of the cerium- and yttrium-group elements and among REE within the first subgroup; considerable effect of the thermal factor on the above processes; presence of an energy barrier and the necessity of certain activation energy to perform such transformations, their phase nature; presence of a number of the intermediate phases. It has been determined that with heating the «water- NO3 - - anion» substitutions lability is rising in the Ln3+ environment, stability of new coordination forms and their new phase formation is growing.

Last modified: 2016-07-26 15:35:33