ASTM, silicon carbides

Insulated dye developers, 19 285-286 Insulated gate bipolar transistors (IGBTs), silicon carbide in, 22 539—540 Insulating brick, ASTM classifications and specifications for, 21 508, 509t Insulating castables, classification of, 21 510t... 

Silicon carbide has been described as a mild inhalation irritant (143). The threshold limit value for silicon carbide in the atmosphere is 5 mg/m3. Because of increased interest in SiC whiskers as a reinforcement for composites, the ASTM has established Subcommittee E34.70 on Single-Crystal Ceramic Whiskers to write standards for handling this form of SiC (144). 

Conclusive experimental studies on the effects of respirable fibrous SiC dusts (whiskers) are not yet available [255]. In the United States ASTM has published recommendations for safe handling procedures related to all ceramic fibers, including silicon carbide whiskers [256]. 

Standard Practice for Handling Silicon Carbide Whiskers, ASTM Designation E 1437-91 (Philadelphia ASTM 1991). 

New standards make manufacturing silicon carbide whiskers safer, a review, ASTM Standardization News, 23, p. 11 (1995). 

The Schramm-Zebrowski incandescent rod resistance method (ASTM D 757 ISO/R 181 DIN/VDE 0318 part 2) has been adopted internationally for solid electrical insulating materials. A glowing silicon carbide rod (950°C) is pressed against the specimen for three minutes. BHl indicates nonignition and less than 5 mm penetration by the rod. BH2 indicates > 5 mm penetration in three minutes. If the rod penetrates more than 95 mm in the test time, then BH3 gives the burning rate in mm/min. PP is BH3-20 mm/min. 

ASTM C-863 Evaluating oxidation resistance of silicon carbide refractories at elevated temperatures... 

The samples were cut into 25 x 25 x 3 mm coupons and mechanically polished using 400, 500 and 600 silicone carbide emery papers (ASTM G 1) and lubricated using distilled water. The polished samples were cleaned with acetone (Merck, 99.8% pnirity) washed using distilled water, dried in air and stored in moisture-free desiccators prior to use. 

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