Page 117 - Synthesis of Functional Nanoparticles Using an Atmospheric Pressure Microplasma Process - LiangLiang Lin

Yttrium Oxide Nanoparticles Synthesis - a Model Study on the Plasma-Liquid Interaction and Opener to Nanophosphors
water or linked water that forms physical bounds with Y(OH)3 powders. The second endothermic peak appears at ~290 °C, originated by the removal of structural water from Y(OH)3 to form yttrium oxyhydroxides as intermediates. Combined with the TG curve, the weight loss at this stage (up to 350 °C) is estimated to be 11% (from 97% to 86%), implying that Y(OH)3 powders are mostly decomposed to YOOH. The last endothermic peak is observed at ~480 °C, with a weight loss of 10% derived from the TG curve (from 84% to 72%). Meanwhile, the TG curve is almost stable at temperatures above 550 °C. It is inferred that at this stage yttrium oxyhydroxides are furtherly decomposed to form Y2O3,22 but no significant changes happen beyond this temperature. The whole process can be expressed stoichiometrically as follows:
100 95 90
3,4 3,2 3,0 2,8
85 2,6
80 75 70
Figure 6.2 DSC/TG analysis of the prepared Y(OH)3 powder
SEM is applied to characterize surface morphology of the synthesized Y(OH)3 and Y2O3 products. Representative examples are shown in Figure 6.3. As indicated by the low magnification image, Y(OH)3 forms flakes composed from loosely stacked lamellar-like structures. Their surface appears to be smooth and uniform, with the absence of any sharp grains. However, the high magnification image reveals their porous and uneven morphology. Compared with Y(OH)3, Y2O3 products, derived by annealing, are smaller and have relatively
0 100 200 300 400 500 600 700 800 Temperature (°C)
105
2,4 2,2 2,0 1,8
TG (%)
Heat Flow (W/g)