The Effects of Sulfate Artlon Exchange on Structural Feature and Thermal Behavior of Y_2(OH)_5NO_3-nH_2O Layered Hydroxide Nanosheets

摘要

Layered rare-earth hydroxide nanosheets (3-8 nm thick) of (NCV-LYH) were successfully synthesized in one step via chemical precipitation at -4°C and pH -8, using yttrium nitrate and ammonium hydroxide as reagents. The interlayer NO3" was found to be free ions and can be completely replaced with SO_4~(2-) to yield Y_2(OH)_5(SO_4)_(0.5)-nH_2O (SO_4~(2-)-LYH). Thermal decomposition behavior of the SO_4~(2-)-LYH was studied in detail, and the phase and morphology evolutions upon calcination in the temperature range 500-1100°C were also investigated. Characterizations via XRD, FE-SEM, TEM, and FT-IR found that anion exchange did not bring about any appreciable change to the 2-dimensional crystallite morphology but the basal spacing of the crystal structure shrank from -0.884 to 0.840 nm owing to the indirect coordination of SO_4~(2-) to the Y~(3+) ions. DTA/TG and XRD analysis found that the NO_4~--LYH converts to Y_2O_3 at -600°C, but the SO_4~(2-)-LYH decomposes to oxide at a higher temperature of-1000°C via monoclinic Y_2O_2SO_4 in the range of 800-900°C. The resultant Y_2O_3 particles have an average size of-60 nm.