1997 Volume 105 Issue 1217 Pages 79-84
Hollow glass microspheres named Shirasuballoons have been produced from glassy volcanic fragment named as Shirasu or Hakudo. Finer Shirasuballoons are required to increase in physical and chemical properties of conventional Shirasuballoons and glass balloons. Fine Shirasuballoons of mean particle sizes under 20μm and bulk densities under 0.5 (103kg/m3) were successfully prepared by rapid heating of milled powders using a fluidized bed furnace. Strengths, thermal stabilities and chemical durabilities of fine Shirasuballoons, conventional Shirasuballoons and glass balloons were measured under the same conditions. Strengths and chemical durabilities of fine and conventional Shirasuballoons were obviously superier to these of conventional glass balloons. Higher the particle density of fine Shirasuballoons tended to increase in the strength. Fine and conventional Shirasuballoons held their structure up to 800°C, approximately 200°C higher than the conventional glass balloons.
