What Is Uranium Oxide?
Also known as "uranyl oxide". Chemical formula UO3. The molecular weight is 286.03. Orange-red orthorhombic crystal. The relative density is 7.29. Insoluble in water, soluble in hydrochloric acid and nitric acid. Preparation method: ammonia water is slowly added to the uranyl nitrate aqueous solution, and the precipitate is precipitated. The precipitate is filtered by suction, washed, and heated in air at 500 ° C. Uses: used to make uranium dioxide, uranium tetrafluoride, etc. [1]
- UO 3 = 286.03. Due to different preparation methods and conditions, there are six types of heterogeneous crystals and one amorphous. The most stable variants are orthorhombic crystals, bright yellow, and the remaining variants are orange-red. Each variant was burned in high-pressure oxygen (40 × 101.325kPa) and turned into a yellow variant at 650 ° C; all crystals were decomposed into
- Uranium trioxide has six types of crystal structure, only the -type is more stable under normal pressure. The four crystal forms , , , and all decompose when heated under normal pressure to form uranium trioxide. By
- 1.Uranium trioxide is a
- Anhydrous uranium trioxide has many different phases due to different manufacturing methods, but no matter which phase is heated to high temperature, it will be decomposed into uranium trioxide U 3 O 8 .
- Production method 1 -UO 3 , -UO 3 , -UO 3 :
- Place the refined uranyl nitrate UO 2 (NO 3 ) 2 · 6H 2 O in a clean evaporating dish, heat it in the air, and slowly raise the temperature from room temperature to 500 ° C. After the nitrate melts, it will decompose into oxides. After sintering at 500 ° C for 12 hours and then rapidly cooling, -UO 3 can be obtained. If the temperature is gradually increased (3 to 5 ° C / min) to 500 ° C, and continuously heated for 2 to 3 weeks, and then naturally cooled to room temperature in a furnace, crystalline -UO 3 can be obtained. If the temperature is raised rapidly [(30 40) / min], -UO 3 will be generated, but if it is continuously heated at 500 for a long time (several weeks), it will gradually change to -UO 3. It is known that -UO 3 is the most stable form under an oxygen partial pressure of 1.01 × 103 kPa or less.
- -UO 3 : Anhydrous uranium trioxide (any phase is acceptable) and water are sealed in a reaction tube, and the reaction is performed when heated to 200-280 ° C. When the products (-UO 3 · H 2 O, etc.) obtained by the reaction are heated at 375 ° C. in the air for more than 24 hours, -UO 3 can be obtained.
- -UO 3 : -UO 3 can be obtained by heating U 3 O 8 to 250-375 ° C. in a stream of NO 2 .
- -UO 3 : -UO 3 can be prepared by dissolving metallic uranium in LiClO 4 .
- -UO 3 : -UO 3 can be obtained by heating UO 3 in 2961 atm oxygen to 1100 ° C.
- Preparation method 2-UO 3
- When ammonia water is added to the uranyl nitrate aqueous solution, a yellow ammonium diuranate precipitate is formed in the range of pH = 7-10, and this precipitate is heated to 500 ° C in the air to generate -UO 3 . In general, -UO 3 is easily converted to -UO 3 under such conditions, but -UO 3 generated by thermal decomposition using a salt containing ammonia is relatively stable.
- Method for producing amorphous UO 3 and -UO 3 .
- Hydrogen peroxide is added to an aqueous solution of uranyl nitrate to generate uranium peroxide UO 4 · 4H 2 O (at temperatures above 70 ° C, UO 4 · 2H 2 O is formed). Thoroughly wash uranium peroxide, completely remove nitrate ions, dry at 50 ° C or lower, put it into an evaporation dish after drying, and slowly heat to 400 ° C in air (decomposes into oxides at 200-225 ° C ), And maintained for 1 to 2 hours, the peroxide is completely decomposed, and an amorphous uranium trioxide is obtained.
- If uranium peroxide is not sufficiently washed, a considerable amount (about 5%) of nitrate ions will be present. After it is dried below 50 ° C, it is heated in air to form an amorphous uranium trioxide hydrate at 200 ° C. When the temperature rises to 400 ° C, -UO 3 is formed . If it is heated at 550 ° C for 1 to 2 hours, crystalline -UO 3 can be obtained. Uranium trioxide hydrate will not be completely decomposed even if it is heated below 550 for a long time, but when it is above 600 , it will slowly decompose into uranium octoxide, so the temperature must be kept at 525 575 In the range. [5]