... Cenospheres (microspheres) are silica-alumina fly ash lightweight fractions obtained from burning pulverized coal. These fractions are characterized by spherical particle shapes of 40 to 400 μm diameter (apparent bulk density 400 kg/m 3 ). The thermal-insulation properties of microspheres...

... Bureau of Standards (NBS) particle-sizing standard microspheres, deposited on polished silicon substrates, as an alternative working standard until such time as a true national calibration artifact is developed. To this end, several techniques for depositing the microspheres on semiconductor surfaces...