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Klemkaite K.,Vilnius University | Prosycevas I.,Kaunas University of Technology | Taraskevicius R.,Institute of Geology and Geography | Khinsky A.,Amiagus | Kareiva A.,Vilnius University
Central European Journal of Chemistry | Year: 2011

Three layered double hydroxides (LDH) [Mg 1-xAl x(OH) 2] x+(A m-) x/m] •nH 2O and [M II 1-xM III x (OH) 2] x+(A m-) x/m] •nH 2O (M II - Mg, Co, Ni; M III - Al; A - CO 3 2-) were successfully synthesized by the low supersaturation method. The as-synthesized LDH samples were thermally decomposed and the derived mixed metal oxides reformed back to layered structures in water and magnesium nitrate media at different temperatures. All synthesized samples were characterized by X-ray diffraction (XRD) analysis, thermogravimetric (TG) analysis, X-ray fluorescence (XRF) analysis and scanning electron microscopy (SEM). The results of XRD and XRF analyses showed that single-phase layered double hydroxides were formed during synthesis and reformation. It was demonstrated, that a partially substituted by cobalt and nickel LDH samples also show memory effect. The crystallite size of regenerated LDH depends on the regeneration media, temperature and chemical composition. The LDH samples after regeneration consist of large particles with sharp edges along with a large amount of smaller particles. © Versita Sp. z o.o.

Klemkaite-Ramanauske K.,Amiagus | Zilinskas A.,Vilnius University | Taraskevicius R.,Institute of Geology and Geography | Khinsky A.,Amiagus | Kareiva A.,Vilnius University
Polyhedron | Year: 2014

Preparation of MoO4 2--containing Mg/Al layered double hydroxide (LDH) using co-precipitation method has been suggested. The possibility of introduction of molybdate ions from solutions with different concentrations of molybdate to the structure of LDH has been investigated. For this purpose, the mixture of magnesium and aluminium nitrates was added to the solution of molybdate or vice versa. The XRD patterns of obtained specimens showed formation of layered double hydroxide phases without any impurities. The basal spacing of formed LDH was not affected when concentration of molybdate used in the synthesis process was low. However, at higher concentration of molybdate an increase of cell parameter c was observed. The determined Mg/Al ratio and the amount of Mo in LDH were found to be dependent on the preparation conditions. Molybdate-containing LDH was tested as a catalyst in solvent free synthesis of 2-adamantylidene(phenyl)amine. It was demonstrated, that the addition of molybdenum in LDH improved the yield of Schiff base. © 2013 Elsevier Ltd. All rights reserved.

Klemkaite K.,Vilnius University | Khinsky A.,Amiagus | Kareiva A.,Vilnius University
Materials Letters | Year: 2011

Layered double hydroxide (LDH) having a different cation (Mg, Ni, Al) composition was successfully synthesized by the low supersaturation method. The sample was thermally decomposed and reconstituted in water and nitrate media at different temperatures. X-ray powder diffraction and X-ray fluorescence were used to investigate the differences between the obtained layered materials and those after the reconstitution process. To the best of our knowledge, there are only few studies where the influence of the third metal cation on the reconstitution process was analyzed. © 2010 Elsevier B.V. All rights reserved.

Ivanov M.,Vilnius University | Klemkaite K.,Vilnius University | Khinsky A.,Amiagus | Kareiva A.,Vilnius University | Banys J.,Vilnius University
Ferroelectrics | Year: 2011

Hydrotalcite-type materials are made of positively charged two-dimensional sheets of mixed hydroxides with water and exchangeable charge-compensating anions. The crystal structure of hydrotalcite consists of octahedral brucite-like layers. The interlayer space between each brucite sheets is filled with water and anions that compensate the positively charged layers. This region is highly disordered and the amount of water, which influences heavily physical properties of the material, is a function of temperature, of water vapour pressure and of nature of the anions present. We present an initial study of dielectric and conductive properties of synthetic hydrotalcite in this contribution. Copyright © Taylor & Francis Group, LLC.

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