Abstract
The synthesis of a novel Li+ /Mg2+ /Al3+ containing layered double hydroxide (LDH) by using a hydrothermal synthesis route is represented in this work. The autoclaves were heated up to 100oC, 120oC, 140oC and 160oC for 10 h and 48 h with a water to solid ratio (W/S) of 15:1. The physicochemical properties of the synthesized LDHs were investigated by X-ray powder diffraction (PXRD), fourier transform infrared spectroscopy (FTIR), thermo gravimetric and differential thermal analysis (TG-DTA), inductively coupled plasma optical emission spectroscopy (ICP-OES) and scanning electron microscopy (SEM). The formation of a solid solution phase depends strongly on the composition of the reactants and the synthesis temperature. Using an exact stoichiometric ratio of Li+/Mg2+/Al3+ resulted in the synthesis of amorphous phases without producing plenty of crystalline amounts of the expected solid solutions while using higher temperatures than 140oC resulted in a formation of AlO(OH). To avoid the formation of an Al containing amorphous phase or an AlO(OH) crystalline phase, the stoichiometric ratio of Li+ was changed. The results show solid solutions with the formula [Li0+xMg2-2xAl1+x(OH)6][Cl.mH2O] with X ≥ 0.9. The lattice parameters and chemical compositions for solid solutions with different compositions were determined and the pure solid solution with the highest amount of Mg (x = 0.9) is [Li0.9Mg0.2Al1.9(OH)6] [Cl.0.50H2O] with the lattice parameters a = 5.1004(4) Å, c = 15.3512(1) Å, V = 345.844(9) Å3. For X 2+ and a Li+ dominated solid solution, are coexistent.
Highlights
Layered double hydroxides (LDHs) consist of alternate positively charged mixed metal hydroxide layers and negative charged interlayer anions
The synthesis of a novel Li+ /Mg2+ /Al3+ containing layered double hydroxide (LDH) by using a hydrothermal synthesis route is represented in this work
The physicochemical properties of the synthesized LDHs were investigated by X-ray powder diffraction (PXRD), fourier transform infrared spectroscopy (FTIR), thermo gravimetric and differential thermal analysis (TG-DTA), inductively coupled plasma optical emission spectroscopy (ICP-OES) and scanning electron microscopy (SEM)
Summary
Layered double hydroxides (LDHs) consist of alternate positively charged mixed metal hydroxide layers and negative charged interlayer anions The stoichiometry of these materials can be formulated as [Mz+1−xM3+x(OH)2]p+[(An−)p/n·mH2O] with z = 2, M = bi- and trivalent metallic elements, A = organic or inorganic anions and m = amount of interlayer H2O depending on the temperature, relative humidity and hydration level [1]. The ratio between Li and Al is always 1:2 [2] while the ratio between Mz+ and M3+ (z = 2) can vary strongly [3] depending on which M2+ ion or synthesis parameters are used These layered materials are able to intercalate negatively charged and neutral molecules or exchange the interlayer anion with organic [4] [5] [6] [7] [8] or inorganic [3] [9] anions of different sizes or charges. The [Mz+1−xM3+x(OH)2]p+ main layer remains stable and is not capable of ion exchange once it is formed
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