Properties of heat resistant hollow glass microsphere/phosphate buoyancy materials with different coatings

The heat resistant buoyancy materials were fabricated by the molding method using the aluminum dihydric phosphate as the matrix and hollow glass microspheres as the filler, respectively. In order to improve the waterproof performance of the buoyancy, two strategies, adding the B₄C additives and introducing the silica-based coatings, were adopted. The study showed that the samples with the B₄C content of 10 wt% possessed the optimal comprehensive performance, such as low density (0.540 g/cm³) and low water absorption (29.6%). The effect of the coating types and coating times on the density, water absorption, compressive strength and specific strength of the buoyancy materials were also studied. After 4 times of coating, the density and the compressive strength of the sample increased to 0.62 g/cm³ and 6.0 MPa, respectively; the water absorption of the samples greatly decreased to 10%. Besides, all samples exhibited significant pseudoductility. The buoyancy materials with the above superior properties can be potentially used in the deep see fields.