| The high performance solid buoyancy material that uses the hollow glassmicrospheres as filling-material combines the properties of low density and superstrength together organically and it has incomparable superiority in marineapplications. It has become a new type of special marine engineering material togradually replace the conventional buoyancy material. In order to reduce the densityof the solid buoyancy material, the hollow glass microspheres should be taken asmuch as possible only if the material can sustain a well-bonded status. So theperformance of the hollow glass microsphere is a dominant factor that determines theproperties of the buoyancy material.Although many kinds of hollow glass microspheres exist at the market and someof them are of good quality. However, the lack of uniformity in their density andparticle size distribution makes them difficult to fabricate the solid buoyancy materialwith ultra-low density. On this issue, we employed HGS8000x, VS5500and K20, thehollow glass microspheres existing in the lab, as raw material and the water asmedium to select the hollow glass microspheres with flotation method, on the otherhand to investigate the influences of the ratio of hollow glass microspheres/water, thefloating time and the times of flotation on the particle size and density. Researchresults demonstrate that the floatation method can effectively remove themicrospheres of small particle size small, which can decrease the density and elevatethe average particle size of the hollow microspheres. The ratio of water/glassmicrospheres is proportionate to the density of the microspheres selected by floatationand inversely proportional to the average particle size. The floating time also has asignificant impact on the density and the particle size of the glass microspheres. Asthe time increases, the density rises gradually due to the increment of the small microspheres. Correspondingly, it leads to a lower particle size. The density of theglass microspheres elevates with the increase of the floatation times and results in alarger average particles size. Via adjustment on water/glass microspheres ratio, thefloating time and the floatation times, the glass microspheres can be controllablyseparated by density and particle size.In this thesis, for the preparation of solid buoyancy material that can be used in4500m submarine circumstance, the floatation selected glass microspheres, theHGS8000x with average size of27.18μm and the VS5500with average size of46.52μm, were used as raw material. The buoyancy materials of the composite proportionranged from0%to100%(v%) were formed by molding method. Relatively, thedensity range is0.5809to0.6075g/cm3and the uniaxial compressive strength rangeis69~87MPa. The influence of the ratio of these two kinds of glass microspheres withdifferent particle size on the density, compressive strength, and percent of waterabsorption, hydrostatic resistance etc. were studied. The results indicate that the glassmicrospheres in bimodal distribution can effectively reduce the density of the solidbuoyancy material and does not damage its original performance. Furthermore, suchmethod increases the net buoyant force and strengthens the actual load of the material.The actual density of the composite displays a V-shape trend when altering thevolume fraction of VS5500. The critical volume fraction at the minimum density is60%and the related density is0.5809g/cm3.When the volume fraction of VS5500glass microspheres less than40%, the relevant composite can maintain the percent ofwater absorption that is lower than0.4%and endure the hydrostatic pressure that ismore than100MPa. However, as the volume fraction of VS5500exceeds40%, thehydrostatic resistance performance deteriorates with the increment of the volumefraction. Conclusively, through controlling the ratio of two kinds of glassmicrospheres with different particle sizes, the diverse excellent solid buoyancymaterials can be prepared and applied in different submarine depths from8000m to10000m respectively. |
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