Synthesis method:

1. Atmospheric pressure method

The boric acid is sent to the heating kettle, the temperature is raised, and the boric acid is slowly dehydrated. When the temperature rises to 107.5℃, it becomes metaboric acid (HBO2), and when the temperature rises to 150～160℃, it transforms into tetraboric acid (H2B4O7). If the temperature is above 650℃, the melt will produce a large amount of foam, and finally keep the temperature at 800～1000℃. Burn and dehydrate until the material is red and bubbling. The relative density of the melt is 1.52. At this time, the wire drawing machine is turned on for wire drawing, and the temperature is controlled at 700 to 900°C. Then the boron oxide wire on the wire drawing machine is cut with a stripper and packaged to obtain the boron oxide finished product. The reaction equation is as follows: Boron oxide

2. Vacuum method

Place the boric acid in a stainless steel pan, put it in an oven and bake it for 1.5 hours, then increase the temperature to 150°C and heat it for 4 hours. Frequent turning during the heating process to make the dehydration even. Then the material was removed, cooled, crushed, and then placed in a vacuum oven, kept sealed, heated at 220°C for 1.5 h, then heated to 260°C, and heated for 4 h. Then the material is cooled, crushed, put into a tube furnace, the heating temperature is controlled at 280°C, and dehydrated under vacuum for 4 hours to obtain a boron oxide product.

3. Put the crystalline boric acid in a small dish. Place it in a dry reactor containing phosphorus pentoxide and heat it to 200°C under vacuum to completely dehydrate it. The vacuum provided by the water vacuum pump is sufficient, but it is better to use a vacuum pump with a higher vacuum. It is important to slowly increase the temperature to 200°C, otherwise the boric acid will fuse and prevent the further escape of water vapor. The larger the amount used, the longer the heating time at 200°C. Sometimes the heat preservation reaches more than 4h before the dehydration can be completed. For 3g boric acid, heat for 1h. In addition, the dehydration of boric acid can be performed in a stream of dry air under the condition that the temperature is maintained at no more than 200°C. The dry air used is obtained by passing air and then drying it through phosphorus pentoxide or porous barium oxide.