Preparation Of Amorphous Boron Powder Using Boron Trifluoride Etherate

The preparation of amorphous boron powder using boron trifluoride etherate included three processes.The first process was about preparation of boric acid,in which the hydrolytic reaction of boron trifluoride etherate in defluorinate agent A solution and the esterification reaction with alcohol then the hydrolytic reaction of trimethyl borate were studied.Then the boric acid was dehydrated to boron oxide by heating.Lastly the amorphous boron powder was formed by heating reduction with Magnesium and boron oxide.1.Prepare the boric acidTwo methods of preparing boric acid were studied,that the boron trifluoride etherate was hydrolyzed in defluorinate agent A solution and the boron trifluoride etherate was esterified into trimethyl borate and then trimethyl borate was hydrolyzed into boric acid.In the first method,the influence of mole rate of defluorinate agent A and boron trifluoride etherate,reaction temperature and reaction time on the yield and purity of boron acid were studied.The conditions were comfirmed by experiments:the mole proportion of defluorinate agent A and boron trifluoride etherate was 5:3;Reaction temperature was 100℃;Reaction time was 6h.The yield and purity of boric acid in the first method were 78.14%and 97.67%.In the second method,the influence of the amount of defluorinate agent B and reaction temperature on the yield and purity of boron acid were studied.The conditions were comfirmed by experiments:the amount of defluorinate agent B was 30g;Reaction temperature was 55,C.The yield and purity of boric acid in the second method were 67.78%and 98.72%.The color change of curcumin paper and XRD indicated both two methods can prepare boric acid successfully.SEM indicated the particle diameter of boric acid was about 100μm,and the particle diameter of boric acid using the first method was more large and regular than one using the second method.2.Prepare the boron oxideThe DTA-TG curve of boric acid being dehydrated gave 45.31%weight loss between 50 and 350℃,which was consistent with the theoretical weight loss of 43.67%.It was surface structure water removed that at around 80℃,and the major peak at around 160℃ was due to the first dehydration of boric acid,and the second peak at around 200℃ was due to the second dehydration.The paper studied the influence of the pressure and temperature change on the dehydration of boron acid.The result indicated the size of boron oxide prepared in vacuum was regular,and the vitreous boron oxide was prepared in atmospheric conditions.The purity of boron oxide in series heating was higher than one in the constant temperature.The conditions were comfirmed by experiments:the boric acid was dried in drying oven for 1.5h at around 85℃,then dried for 4h at 150,C,and stirred per 10min,then at 220℃ the sample was dried for 1.5h in vaccum,for 2.5h at 260℃ and for 4h at 280℃.3.Prepare the amorphous boron powderThe paper studied the influence of the mass rate of Mg and boron oxide,reaction temperature and time of eternal temperature on purity of boron powder.The conditions are comfirmed by experiments:the mass rate of Mgnesium and boron oxide was 1:3;Reaction temperature was 850oC;The time of eternal temperature was 30min.The yield and purity of boron powder which was gained the reduction product washed twice by acid,alkali and water were 74.82%and 85.73%.The XRD indicated boron powder was amorphous crystalline and its impurity was mainly MgxB2O(x+3)which can’t dissolve in acid.