Preparing And Research On Solid Buoyancy Materials Of Low-aluminum Borosilicate

This paper prepared buoyancy materials with relatively high strength and temperature resistant from aluminum borosilicate glass and hollow microspheres. The inorganic buoyancy materials could withstand high temperature of 750?,to meet the requirements of new marine weapon. The samples were prepared by gel-casting process. Several sets of control experiments were designed to analyze the effect of sintering temperature, content of glass powders and the addition of B2O3 or B4 C on the sample's strength, density, thermal conductivity and water absorption.Results showed that the stability of the slurry was a prerequisite for success in gel-casting process. A slurry with pH=3-4 had a good stability, which was beneficial to prepare samples with uniform structure. Sintering temperature had a great influence on the performance of samples. With the increase of temperature, the density and strength increased before 750?, then decreased after 750?. The samples sintered at 750 ? processed a strength of 14.6 MPa, a density of 0.88 g/cm3, a thermal conductivity of 0.1564 W/(m·K) and a water absorption of 3%. Though the strength of samples increased with the increase of the content of glass powders, the density increased, too. Therefore, the content of glass powders shouldn't too high, which could be set as 60%. Besides, the addition of B2O3 could reduce the softening temperature of glass powders to realize low temperature sintering, but B2O3 was easy to combine with water to form boric acid, which locked the water in the binder phase. After sintering, a large number of irregular holes were left in the sample, which reduced the strength of samples. What's more, the addition of B4 C could increase the strength of samples. Because of the decomposition reaction at about 500? and the volume expansion effect, the melt glass could fully fill into the gaps between the microspheres, realizing a dense bonding phase. This ensured that the internal structure of the composite materials was uniform and the samples process high strength. For example, the sample with 6% B4 C sintered at 700? processed a strength of 18.6 MPa, a density of 0.81 g/cm3, a thermal conductivity of 0.156 W/(m·K) and a water absorption of 1.9%.