Study on synthesizing Mg/Al layered double hydroxides at different pHs

Mg/Al layered double hydroxide (LDH) was successfully synthesized at different pHs values. The Mg/AL LDH was well characterized by X-Ray diffraction and Fourier transform infrared analysis. The morphology of the LDH was observed using Scanning electron microscopy with energy dispersive X-ray spectroscopy. The influence of pH values on the morphology of the Mg/Al LDHs were studied. The result showed that the well-synthesized Mg/Al LDHs could be obtained when the pH value was about 10.0 at room temperature.DOI: http://doi.dx.org/10.5564/mjc.v15i0.319 Mongolian Journal of Chemistry 15 (41), 2014, p36-3

The magnetic structures of double tungstates, NaM WO4 2, M Fe, Cr Examples for superexchange couplings mediated by [NaO6] octahedra

The crystal structures of the double tungstates NaM WO4 2 with M Fe, Cr and their solid solution are similar to the wolframite type structure in the space group P2 c, but with doubled a lattice parameter. Magnetization and neutron diffraction data reveal that NaFe WO4 2 orders antiferromagnetically below 5 K with a commensurate propagation vector k 1 2,1 2,1 2 and magnetic moments of Fe3 ions oriented along the a axis. NaCr WO4 2 is antiferromagnetic below 10 K. Its magnetic structure is based on the propagation vector k 1 2,1 2,0 , and the magnetic moments of Cr3 ions are aligned along the b axis. The magnetic structure in the bc plane is explained by a supersuperexchange mechanism. Long range magnetic superexchange interactions along paths including [NaO6] octahedra are necessary to explain the observed magnetic structures. Mixed NaFexCr1 x WO4 2 with x 0.25, 0.5, 0.75, do not indicate magnetic order, neither in magnetization nor neutron diffraction dat