This specification covers carbon in the form of hollow microspheres. This product has been used typically as a filler material in syntactic foam shapes, but usage is not limited to such applications.
SAE AMS3753B-2009 Referenced Document
ASTM D1895-96 Standard Test Methods for Apparent Density, Bulk Factor, and Pourability of Plastic Materials
ASTM D280-01 Standard Test Methods for Hygroscopic Moisture (and Other Matter Volatile Under the Test Conditions) in Pigments