Жарияланымдар / Публикации

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    Acid Modification of Diatomite-Based Sorbents
    (2020-09-30)
    Araylim Nurgain
    ;
    Meruyert Nazhipkyzy
    ;
    Aizhan A. Zhaparova
    ;
    Almagul Issanbekova
    ;
    Michela Alfè
    In this work, the effect of acid pre-treatment (hydrochloric acid, HCl) and calcination of diatomite, a silicon dioxide-material from natural sources, was studied with the aim to obtain diatomite-based sorbents with specific physicochemical properties. For this, acid pre-treatments with HCl at different calcination conditions, namely HCl concentration (0.5, 1 M) and calcination temperatures (from 600 to 900 °C) were studied. Morphological features different from those of natural diatomite were obtained. It has been found that treatment of diatomite with 0.5 M HCl at 800 °C showed a specific pore volume of 0.008 cm3/g, and a specific surface area of 19.26 m2/g, while the treatment of diatomite with 1.0 M HCl showed a specific pore volume of 0.011cm3/g, and a specific surface area of 25.57 m2/g. The performance of the acid pretreatment of diatomite for adsorption of Pb ions from water was also studied.
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    Combined-Method Synthesis of CaTiO3 and SrTiO3 Perovskites with n-Hexane: Impact on Structure and Microstructure
    (2026-07-17)
    Zh.A. Abdimomyn
    ;
    M.M. Mataev
    ;
    Zh.I. Tursyn
    ;
    A.N. Torgaeva
    ;
    K. Ramachandran
    This study reports the synthesis of CaTiO3 and SrTiO3 with a perovskite structure by a combined route involving preliminary wet mixing of CaCO3/SrCO3 carbonates and TiO2 in n-hexane, followed by a solid – state reaction during high-temperature calcination. The phase composition and crystal structure of the obtained materials were examined by X-ray diffraction with Rietveld refinement, while the microstructure and elemental distribution were studied using SEM\EDX, and local structure and surface groups were probed by ATR– FTIR spectroscopy. It is shown that the presence of the organic solvent and the applied thermal treatment lead to the formation of single-phase CaTiO3 and SrTiO3 with orthorhombic and cubic modifications, respectively, and with crystallographic parameters with reference PDF cards. The average crystallite size calculated using the Sherrer equation confirmed the nanocrystalline nature of the powders, whereas SEM/EDX analysis reveals a highly porous microstructure and a homogeneous elemental distribution without noticeable metallic impurities. It is established that A-site cation substitution Ca2+/Sr2+ in combination with n-hexane wet mixing induces systematic changes in lattice symmetry, IR band positions and agglomerate morphology, enabling targeted tuning of the texture and potential functional properties of perovskite titanates. The proposed combined approach is a technologically simple and scalable method for producing nanostructured oxide perovskites that are promising as supports and active phases in catalytic systems for combustion processes, plasma-chemical oxidation and functional ceramics.