Graphite yog cov ntxhia, qhov ruaj khov crystalline hloov pauv ntawm carbon. Nws khaws nws cov khoom qub raws li cov txheej txheem. Cov khoom yog refractory, txaus ntom thiab muaj hluav taws xob conductivity. Nws hloov tawm los ntawm cua sov anthracite yam tsis muaj cua nkag. Nws yog siv nyob rau hauv foundries, nyob rau hauv kev tsim cov hlau, raws li zoo raws li rau lubrication nyob rau hauv dov ntau lawm. Tab sis cov cheeb tsam no tsis suav nrog txhua qhov chaw siv.
Basic nta
Yog tias koj txaus siab rau lo lus nug ntawm dab tsi yog qhov ntom ntawm graphite, koj yuav tsum paub tias qhov ntsuas no yog 2230 kg / m3. Lwm daim ntawv allotropic ntawm carbon yog pob zeb diamond, uas yog vim li cas graphite qee zaum muab piv rau nws. Cov tom kawg muaj cov yam ntxwv ntawm hluav taws xob conductive thiab ua raws li semimetal. Cov cuab yeej no tau pom nws txoj hauv kev rau hauv cov txheej txheem tsim hluav taws xob.
Qhov ntom ntawm graphite tsis yog txhua yam koj xav paub yog tias koj txaus siab rau cov ntxhia no. Tseem muaj lwm yam khoom los xav txog thiab. Piv txwv li, qhov kev hloov pauv crystalline ntawm carbon tsis yaj, tab sis thaum twgraug rau qhov kub ntawm 3500 ° C ignites. Cov khoom dhau los ntawm cov kua theem, dhau mus rau hauv lub xeev gaseous.
Txawm li cas los xij, yog tias cov xwm txheej muab kev nce siab txog 90 MPa, nrog rau qhov kub thiab txias, ces melting tuaj yeem ua tiav. Qhov kev tshawb pom no tau ua thaum kawm txog cov khoom ntawm pob zeb diamond thaum lawv sim ua ke nws. Tab sis nws tsis tuaj yeem tau txais cov khoom no los ntawm molten graphite.
Crystal lattice
Cov siv lead ua lattice ntawm graphite muab rau muaj cov pa roj carbon atoms. Nws muaj txheej txheej txheej. Qhov kev ncua deb ntawm tus neeg txheej tuaj yeem ncav cuag 0.335 nm. Nyob rau hauv lub lattice, carbon atoms bond nrog peb lwm carbon atoms.
Cov lattice tuaj yeem yog hexagonal thiab rhombohedral. Nyob rau hauv txhua txheej, cov pa roj carbon atom nyob rau sab nraud ntawm lub hauv paus ntawm hexagons. Cov yav tas yog nyob rau hauv cov khaubncaws sab nraud povtseg, ces txoj hauj lwm ntawm cov khaubncaws sab nraud povtseg yog rov, uas tshwm sim tom qab ib tug.
Kev tsim cov graphite
Graphite thiab nws cov khoom tsis yog tib yam uas koj yuav tsum paub yog tias koj nyiam cov ntxhia no. Nws kuj tseem ceeb heev uas yuav tau nug txog kev tsim cov khoom siv dag zog. Nws txawv ntawm cov khoom siv ntuj tsim nyob rau hauv uas cov synthesis tsim ib yam khoom uas tau teev tseg.
Pov tseg roj av coke thiab thee xuab zeb yog siv hauv kev tsim khoom. Kev sib xyaw ntawm cov khoom nplua-grained raug rho tawm haujlwm, thiab tom qab ntawd txias rau li 5 lub lis piam. Qhov cuam tshuam ntawm qhov kub thiab txias ntawm thawj theem yog nrog rau nwsmus txog 1200 ° C.
Txhawm rau kom qhov theoretical ceev ntawm graphite, workpieces yog impregnated nrog xuab zeb. Nyob rau theem kawg, graphitization tshwm sim, nws suav nrog kev kho cua sov ntawm cov khoom siv hauv lub qhov cub tshwj xeeb, qhov twg qhov kub nce mus txog 3000 ° C. Nyob rau hauv cov ntaub ntawv no, nws muaj peev xwm tsim ib tug siv lead ua lattice.
Cov graphite no muaj cov thermal conductivity thiab hluav taws xob zoo heev. Lub anisotropy ntawm cov khoom yog muaj nyob rau hauv ib tug ntxhia tau los ntawm extrusion. Niaj hnub no, siv cov cuab yeej tshiab, uas yog hu ua isostatic nias. Qhov no ua rau nws muaj peev xwm tsim tau cov khoom siv uas tsis tshua muaj coefficient ntawm kev sib txhuam. Nws muaj cov khoom isotropic.
Qhov ceev ntawm graphite (g / cm3), uas tau txais thaum lub sij hawm extrusion txheej txheem, mus txog 2.23. Qhov taw qhia tib yam rau cov isostatic recrystallized ntau yam, nyob ntawm seb hom, tuaj yeem ncav cuag 5 g / cm 3. Cov khoom siv zoo li no yog siv rau kev tsim cov khoom loj loj, qhov ntev thiab txoj kab uas hla ntawm 1000 thiab 500 hli, feem, nrog rau kev tsim cov casting qhov chaw thiab pwm uas muaj cov khoom tiv thaiv kev sib txhuam.
Main Brands
Hnub no, qhov muaj peev xwm ntawm kev sib txuas nrog ntau qhov sib txawv yog siv. Yog li ntawd, graphite tuaj yeem muab faib ua:
- coarse;
- medium;
- fine-grain;
- fine-grain.
Cov ntsiab lus ntawm thawj zaug ncav cuag txoj kab uas hla ntawm 3,000 microns. Yog hais tias peb tham txog ib tug medium-grained ntau yam, ces lub grain loj yog 500µm. Fine-grained graphite qib MPG nrog cov nplej loj txog li 50 microns yog qhov txawv. Kuj tseem muaj cov ntxhia zoo-grained isotropic ntawm MIG-1 hom, cov khoom uas muaj qhov loj ntawm 30 txog 150 microns. Fine-grained graphite thiab isostatic graphite muaj nplej mus txog 30 microns loj, lawv txoj kab uas hla yam tsawg kawg nkaus yog 1 micron.
Siv dag graphite
Koj twb paub qhov ntom ntawm graphite. Txawm li cas los xij, nws tseem ceeb heev rau kev kawm txog thaj tsam ntawm kev siv cov khoom siv ntau yam. Nws yog siv nyob rau hauv tag nrho cov kev lag luam. Cov electrodes yog tsim los ntawm coarse-grained. Fine-grained structural mus rau kev tsim cov khoom zoo li cov khoom uas muaj cov duab complex.
Kev siv cov khoom siv dag zog ua rau nws ua tau kom ua tiav qhov siab tshaj plaws hauv kev tsim khoom. Niaj hnub no, cov cuab yeej tsim tawm uas ua tau raws li cov qauv ntawm lub xyoo pua no.
Cov ntaub ntawv ntxiv ntawm qhov ceev thiab thermal expansion
Nyob ntawm qhov ntxiv, qhov siab tshaj plaws ntawm graphite tuaj yeem yog 5g / cm3. Qhov tsawg kawg nkaus tus nqi yog 2. Nws muaj nyob rau hauv recrystallized graphite. Ib leeg siv lead ua muaj lub siab anisotropy, qhov no yog vim cov qauv siv lead ua lattice. Hauv cov dav hlau basal, thermal expansion yog qhov tsis zoo txog 427 ° C. Qhov no qhia tau hais tias cov ntxhia yog shrinking.
Nrog qhov kub thiab txias, nws tus nqi kiag li txo qis. Nyob rau theem saum toj no, thermal expansion yog qhov zoo. Nwsqhia perpendicular mus rau basal dav hlau. Qhov kub coefficient ntawm kev nthuav dav yog yuav luag tsis muaj kev ywj pheej ntawm qhov kub thiab siab tshaj tus nqi los ntawm ntau tshaj 20 npaug piv rau qhov nruab nrab qhov tseeb coefficient rau cov dav hlau basal.
Lwm yam koj yuav tsum paub txog kev ua haujlwm ntev
Lub zog thiab qhov ceev ntawm graphite hloov nrog nce kub. Rau feem ntau cov graphites dag zog, lub zog tensile nce los ntawm qhov tseem ceeb ntawm 2.5 nrog rau qhov kub thiab txias. Tus nqi siab tshaj plaws mus txog ntawm 2800 ° C.
Lub zog compressive nce 1.6 npaug thaum qhov kub siab tshaj 2,200 ° C. Lub shear thiab elasticity moduli nce 1.6 npaug thaum qhov kub siab tshaj 1,600 ° C.
In xaus
Cov duab txhais tau ntau yam ntawm graphite, uas tuaj yeem yog: lamellar, flaky thiab spherical. Flake tseem hu ua carbon annealing. Graphite kuj yog ib qho microstructural constituent ntawm malleable, grey ductile hlau thiab compacted graphite cam khwb cia hlau. Hauv qhov no, nws yog tsim los ntawm cov pa roj carbon thiab txiav txim siab cov khoom tshwj xeeb ntawm cov hlau cam.
Cov khoom no tau siv los tsim cov ntawv sau thiab kos duab txog 4,000 xyoo dhau los. Nws lub npe los ntawm lo lus "sau". Cov deposits yog nyob qhov twg deposits ntawm bitumen thiab hard thee tau raug mus rau kub kub.
