on ▁market . ▁ ▁Bor os il icate ▁glass ▁ ▁Bor os il icate ▁glass , ▁which ▁is ▁typically ▁ 1 2 – 1 5 % ▁B 2 O 3 , ▁ 8 0 % ▁Si O 2 , ▁and ▁ 2 % ▁Al 2 O 3 , ▁has ▁a ▁low ▁coefficient ▁of ▁thermal ▁expansion , ▁giving ▁it ▁a ▁good ▁resistance ▁to ▁thermal ▁shock . ▁Sch ott ▁AG ' s ▁" D ur an " ▁and ▁O w ens - Cor ning ' s ▁tra dem ark ed ▁Py re x ▁are ▁two ▁major ▁brand ▁names ▁for ▁this ▁glass , ▁used ▁both ▁in ▁labor atory ▁glass ware ▁and ▁in ▁consumer ▁cook ware ▁and ▁b ake ware , ▁chief ly ▁for ▁this ▁resistance . ▁ ▁Bor on ▁car b ide ▁cer am ic ▁ ▁Several ▁bor on ▁comp ounds ▁are ▁known ▁for ▁their ▁extreme ▁hard ness ▁and ▁t ough ness . ▁Bor on ▁car b ide ▁is ▁a ▁cer am ic ▁material ▁which ▁is ▁obtained ▁by ▁decom pos ing ▁B 2 O 3 ▁with ▁carbon ▁in ▁an ▁electric ▁furn ace : ▁ 2 ▁B 2 O 3 ▁+ ▁ 7 ▁C ▁→ ▁B 4 C ▁+ ▁ 6 ▁CO ▁ ▁Bor on ▁car b ide ' s ▁structure ▁is ▁only ▁approximately ▁B 4 C , ▁and ▁it ▁shows ▁a ▁clear ▁de ple tion ▁of ▁carbon ▁from ▁this ▁suggested ▁sto ichi ometric ▁ratio . ▁This ▁is ▁due ▁to ▁its ▁very ▁complex ▁structure . ▁The ▁subst ance ▁can ▁be ▁seen ▁with ▁empir ical ▁formula ▁B 1