Abstract: Microwave heating method was adopted to synthesize calcium borate (xCaO?yB₂O₃?nH₂O)so as to shorten reaction time and increase reaction efficiency when using boric acid and calcium hydroxide as raw materials.Effects of reaction factors,such as reaction temperature,microwave irradiation time,and mix ratio of raw materials,were investigated in the experiment.Suitable reaction conditions for synthesis of calcium borate (CaO?2B₂O₃?2H₂O) were determined as follows:reaction temperature was 95~105 ℃,time of microwave irradiation was 40 min,amount of substance ratio-of-calcium hydroxide to water was 1∶39.6, amount-of-substance ratio of calcium hydroxide to boric acid was 1∶4.5.Under those conditions,the product′s yield reached 88%,the composition analysis of product was up to the standard,its diameter was about 10 μm and its dehydration temperature was 190 ℃.Reaction was 4 times faster under microwave irradiation than that under conventional heating.

Key words: calcium hydroxide, calcium borate, microwave irradiation