Hollow glass microspheres can be used as thermal insulation materials owing to its hollow structure which brings excellent thermal insulation property and low density. At present, most researches on thermal conductivity of hollow glass microspheres are focused on polymer matrix/hollow glass microspheres composite materials. However, thermal conductivity of hollow glass microspheres at vacuum in room temperature has rarely been investigated.
In this work, thermal conductivity of six types of hollow glass microspheres (T17 (0.17g/cm3), T20 (0.20g/cm3), T22 (0.22g/cm3), T25 (0.25g/cm3), T32 (0.32g/cm3) and T40 (0.40g/cm3)) at vacuum in room temperature were calculated by heat transfer of solid conduction and radiation. The calculation results showed that thermal conductivity of hollow glass microspheres would be decreased by an order of magnitude compared with no vacuum.
In order to verify the calculation and study vacuum thermal insulation properties of hollow glass microspheres , thermal conductivity of above-mentioned hollow glass microspheres at no vacuum and high vacuum in room temperature were measured by a self-made thermal conductivity measuring apparatus which was based on the transient plane source (TPS) method.
The experimental results showed that thermal conductivity of hollow glass microspheres were in the range of 4.2030E-02 to 6.3300E-02 W/m.K (at no vacuum) and 3.8160E-03 to 4.9660E-03 W/m.K (at high vacuum). The results indicated that experimental thermal conductivity was consistent with the calculation results and both of them were all decreased by 8-13 times at vacuum compared with no vacuum. In addition, the relationship with physical properties and thermal conductivity of hollow glass microspheres has been discussed in detail. In conclusion, hollow glass microspheres possess excellent thermal insulation performance at high vacuum in room temperature and have potential to further reduce thermal conductivity at the same conditions.
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