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Outline
The preparation of yttrium oxide (Y2O3) crystals suitable for industrial production of electronic ceramics by a two-step precipitation method using ammonia water and ammonium bicarbonate was studied. The effects of solution concentration, precipitant concentration, surfactant addition amount, reaction temperature, feeding rate, stirring speed, aging method and time, and calcination method and time of the precursor on the particle size of the prepared Y2O3 powder were investigated. The decomposition mechanism and kinetics of the precursor were also explored. The results show that the use of ammonium sulfide to purify 99.9% of yttrium oxide can effectively remove metal impurities. Under the optimal conditions of room temperature, Y(NO3)2 solution mass concentration of 100 g/L, NH4HCO3 solution mass concentration and addition rate of 200 g/L and 6 mL/min, respectively, stirring speed of 370 r/min, aging time of 1 h, surfactant addition amount of 2.5%, microwave drying for 10 min, calcination temperature of 800 ℃, and calcination time of 2 h, spherical cubic Y2O3 crystals with D50 = 1.018 μm and BET = 31.32 m2/g can be prepared, which meet the requirements of Y2 O3 powder for electronic ceramics. The analysis of the decomposition process and mechanism of the precursor Y2(CO3)3·2H2O to Y2O3 indicates that Y2(CO3)3·2H2O is converted to Y2 O3 through the intermediate state of Y2CO5. The decomposition of the precursor to Y2O3 occurs in three stages, with activation energies of 61.68, 564.22, and 590.103 kJ/mol, and corresponding reaction orders of 1.836 9, 0.896 4, and 0.972 2, respectively. The method can achieve industrial production of Y2O3 for electronic ceramics. The entire process is simple to operate, low-cost, environmentally friendly, and pollution-free, with significant economic and social benefits and broad application prospects.
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| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |
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