Study On Preparation Of Borate Whiskers And Neutron Shielding Performance Of Its Polymer Composites

Because of its superior performance,borate whisker, led by magnesium borate whisker and aluminum borate whisker, was widely used in high-tech fields such as aviation, aerospace and defense.Its low price also shows a great application prospect. However,the preparation processes of borate whisker now have many deficiencies, it has not been industrialized yet. Therefore,the development of new borate whisker preparation methods, and the promotion of its wide applications appear imminent.Firstly, the preparation of magnesium borate whisker by high temperature molten salt method was studied. The effects of singtering temperature, singtering time, n(B)/n(Mg) and flux were investigated by XRD and SEM. The growth mechanism for magnesium borate whisker was also proposed. The results show that the best preparation conditions are determined as follows:singtering temperature is900℃, singtering time is8.0h, n(B)/n(Mg)=1.2, n(NaCl)/{n(Mg)+n(B)}=3.0. Under the conditions, magnesium borate whisker is obtained, the length of which is about100～250μm, the diameter is about5～10μm, and length-diameter ratio is above10.For high singtering temperature, long time and corrosive gases of high temperature molten salt method, oxalate precursor method was studied. The effects of singtering temperature, singtering time, n(B)/n(Mg) and n(H2C2O4)/n(Mg) were investigated by XRD, SEM, TG-DTA and FT-IR. The growth mechanism for magnesium borate whisker was also proposed. The results show that the best preparation conditions are determined as follows:singtering temperature is800℃, singtering time is4.Oh, n(B)/n(Mg)=1.2,n(H2C2O4)/n(Mg)=1.2. Under the conditions, magnesium borate whisker is obtained, the length of which is about4～8μm, the diameter is about0.6～1.5μm, and length-diameter ratio is about10. The singtering temperature of this method is reduced to100℃, singering time is reduced to4.Oh, and corrosive gases are effectly resolved.The preparation of aluminum borate whisker by oxalate precursor method was also studied. The effects of singtering temperature, singtering time, n(B)/n(Al) and n(H2C2O4)/n(Al) were investigated by XRD, SEM, TG-DTA and FT-IR. The growth mechanism for aluminum borate whisker was also proposed. The results show that the best preparation conditions are determined as follows:singtering temperature is850℃, singtering time is4.0h, n(B)/n(Al)=0.75, n(H2C2O4)/n(Al)=2.0. Under the conditions, aluminum borate whisker is obtained, the length of which is about200-400nm, the diameter is about50-80nm, and length-diameter ratio is about6.Using magnesium borate whisker and aluminum borate whisker prapared as fillers, PF and PE as matrix materials, borate whisker/polymer composites were prepared, and the effects of whisker content, matrix material, and thickness on neutron shielding performance were investigated. The results show that magnesium borate whisker and aluminum borate whisker can enhance neutron shielding performance of composite materials, and magnesium borate whisker is superior to aluminum borate whisker. When content of magnesium borate whisker and aluminum borate whisker is60shares, the neutron shielding ratio of composite materials can reach72.7%and68.9%respectively.