Lub neej ntawm cov txhuam hniav feem ntau yog nyob nruab nrab ntawm 1000 thiab 3000 teev. Cov hauv qab no yog cov ncauj lus kom ntxaws txog carbon txhuam:
Lub luag haujlwm tseem ceeb ntawm cov txhuam hniav yog rub tawm cov hlau thiab ua hluav taws xob, uas txawv ntawm kev sib txhuam ntawm cov hlau. Kev sib txhuam ntawm cov hlau nce vim yog sintering ntawm qhov chaw sib cuag, tab sis qhov no tsis yog cov ntaub ntawv nrog cov txhuam hniav, vim tias cov pa roj carbon thiab hlau yog ob yam sib txawv uas tsis ua rau sintering ntawm qhov chaw sib cuag.
Thaum siv cov txhuam hniav, koj yuav tsum tau xyuam xim rau cov hauv qab no:
Cov txhuam hniav yuav tsum tau hloov thaum lawv hnav rau qee qhov, tab sis nws raug pom zoo kom hloov tag nrho cov txhuam hniav ib zaug. Yog tias cov txhuam hniav qub thiab cov pa roj carbon tshiab sib xyaw, qhov kev faib tawm tam sim no yuav tsis sib npaug.
Carbon txhuam, tseem hu ua hluav taws xob txhuam, yog siv dav hauv ntau yam khoom siv hluav taws xob raws li kev sib cuag. Cov txhuam hniav yog siv rau hauv cov khoom siv ntawm graphite, roj-impregnated graphite, hlau (xws li tooj liab, nyiaj) graphite.
