Sil\u012bcija karb\u012bds, ko bie\u017e\u0101k d\u0113v\u0113 par karborundu, dab\u0101 sastopams k\u0101 retais miner\u0101ls moizan\u012bts un meteor\u012btos, tom\u0113r liel\u0101k\u0101 da\u013ca m\u016bsdien\u0101s p\u0101rdot\u0101 SiC ir sint\u0113tiski ra\u017eots.<\/p>\n
Ar oglek\u013ca \u0161\u0137iedru stiegrota plastmasa (CFRP) ir \u0101rk\u0101rt\u012bgi ciets kovalent\u0101s saites materi\u0101ls, ko ra\u017eo, karbotermiski reduc\u0113jot sil\u012bcija smiltis un naftas koksu elektrisk\u0101 pretest\u012bbas kr\u0101sn\u012b, padarot to iztur\u012bgu pret koroziju un abraziju.<\/p>\n
Sil\u012bcija karb\u012bds (SiC) ir antimona keramika, kas paz\u012bstama ar savu ciet\u012bbu, augstu siltumvad\u012btsp\u0113ju un iztur\u012bbu pret \u0137\u012bmisk\u0101m reakcij\u0101m. Turkl\u0101t SiC ir zems termisk\u0101s izple\u0161an\u0101s koeficients, kas to padara piem\u0113rotu lietojumiem, kuros nepiecie\u0161ama karstuma vai termisk\u0101 trieciena iztur\u012bba.<\/p>\n
SiC ir \u0101rk\u0101rt\u012bgi t\u012brs materi\u0101ls, kura ciet\u012bba p\u0113c Mosa skalas ir 9. To var izveidot, kars\u0113jot smil\u0161u un oglek\u013ca mais\u012bjumu elektrisk\u0101s pretest\u012bbas tipa kr\u0101sn\u012b; t\u0101l\u0101ka pilnveido\u0161ana var ietvert alum\u012bnija piedevu pievieno\u0161anu, lai ieg\u016btu n vai p tipa pusvad\u012bt\u0101ju ier\u012bci.<\/p>\n
SiC ku\u0161anas temperat\u016bra var at\u0161\u0137irties atkar\u012bb\u0101 no t\u0101 polimorf\u0101s krist\u0101lisk\u0101s strukt\u016bras. Pieejams vair\u0101k nek\u0101 70 da\u017e\u0101d\u0101s form\u0101s, tostarp visizplat\u012bt\u0101k\u0101 ir alfa sil\u012bcija karb\u012bda (4H-SiC) ar se\u0161st\u016brainu krist\u0101lisko strukt\u016bru, kas atg\u0101dina vurc\u012btu. Past\u0101v ar\u012b beta sil\u012bcija karb\u012bds ar sejas centr\u0113tas kubiskas krist\u0101liskas strukt\u016bras krist\u0101lisko strukt\u016bru, kas l\u012bdzin\u0101s cinkblendam vai sfaler\u012btam, un ir pla\u0161i izplat\u012bts.<\/p>\n
Sil\u012bcija karb\u012bds ir krist\u0101lisks materi\u0101ls ar vair\u0101k\u0101m \u0161\u0137irn\u0113m jeb politipiem, un katram no tiem ir savs \u012bpa\u0161s sl\u0101\u0146u izk\u0101rtojums, ko sil\u012bcija un oglek\u013ca atomi saista kop\u0101 tetraedru form\u0101cij\u0101s. Katra politipa sak\u0101rtojuma sec\u012bba pie\u0161\u0137ir tam unik\u0101lu krist\u0101lisko strukt\u016bru.<\/p>\n
Sil\u012bcija karb\u012bds ir divu veidu - alfa sil\u012bcija karb\u012bds (a-SiC) un beta sil\u012bcija karb\u012bds (b-SiC). No \u0161\u012bm div\u0101m form\u0101m beta SiC ir ar sejas centr\u0113tu kubisku krist\u0101lisko strukt\u016bru, kas atg\u0101dina dimantu, cinkblendi vai sfeller\u012btu.<\/p>\n
SiC ugunsiztur\u012bgajai keramikai ir lieliska siltumvad\u012btsp\u0113ja, jo a-SiC un b-SiC atomu r\u0101diusi ir gandr\u012bz vien\u0101di, nodro\u0161inot labu siltumvad\u012btsp\u0113ju. Turkl\u0101t \u0161\u012b \u012bpa\u0161\u012bba \u013cauj fononiem br\u012bvi izplat\u012bties t\u0101s sast\u0101v\u0101. Visas \u0161\u012bs \u012bpa\u0161\u012bbas apvienojum\u0101 ar augstu ku\u0161anas temperat\u016bru un zemu termisk\u0101s izple\u0161an\u0101s koeficientu padara sil\u012bcija karb\u012bdu par pievilc\u012bgu materi\u0101lu augstas temperat\u016bras kr\u0101sn\u012bm, k\u0101 ar\u012b nodro\u0161ina iztur\u012bbu pret koroziju un stingr\u012bbas \u012bpa\u0161\u012bbas, kas padara \u0161o materi\u0101lu par pievilc\u012bgu izv\u0113li.<\/p>\n
Sil\u012bcija karb\u012bds ir keramikas materi\u0101ls, kas nav oks\u012bds, ar \u0137\u012bmisku inertumu un lielisk\u0101m meh\u0101nisk\u0101m un fizik\u0101l\u0101m \u012bpa\u0161\u012bb\u0101m, tostarp augstu iztur\u012bbu, Mosa ciet\u012bbu 9, zemu termisk\u0101s izple\u0161an\u0101s \u0101trumu, iztur\u012bbu pret \u0137\u012bmisk\u0101m reakcij\u0101m, lielisku iztur\u012bbu pret sl\u012bd\u0113\u0161anu un temperat\u016bru l\u012bdz 1600 gr\u0101diem p\u0113c C, nes\u0101kot oksid\u0113ties.<\/p>\n
Cietin\u0101\u0161anas rezult\u0101t\u0101 oglek\u013ca un sil\u012bcija atomi veido tr\u012bsk\u0101r\u0161as koordin\u0101cijas strukt\u016bras, k\u0101 to atkl\u0101j to formas koeficienta sadal\u012bjums, kur\u0101 redzams skaidrs maksimums pie 109 gr\u0101diem (tetraedriskais le\u0146\u0137is), k\u0101 ar\u012b pla\u0161i apgabali ap \u0161o maksimumu, kas liecina par da\u017e\u0101du lok\u0101lu strukt\u016bru esam\u012bbu.<\/p>\n
SiC var ieg\u016bt, kaus\u0113jot kop\u0101 m\u0101lu un pulverveida ogles vai tie\u0161i reduc\u0113jot elektrisk\u0101s kr\u0101sn\u012bs ar oglekli vai \u016bde\u0146radi. Edvards Goodrich Acheson 1891. gad\u0101, izmantojot elektrotermisko procesu, pirmo reizi izgatavoja SiC lielos apjomos; kop\u0161 t\u0101 laika \u0161is iztur\u012bgais materi\u0101ls ir pla\u0161i izmantots abraz\u012bvai apstr\u0101dei un oder\u0113jumam, k\u0101 ar\u012b citos pielietojumos, piem\u0113ram, ugunsiztur\u012bgajos materi\u0101los un elektroniskajos komponentos.<\/p>\n
Sil\u012bcija karb\u012bdu var izmantot vair\u0101kos lietder\u012bgos veidos. Tas ir popul\u0101rs abraz\u012bvs, ko izmanto met\u0101lu, piem\u0113ram, misi\u0146a, bronzas, t\u0113rauda un marmora, sl\u012bp\u0113\u0161anai un pul\u0113\u0161anai, k\u0101 ar\u012b keramikas grie\u0161anai. Turkl\u0101t Mosa skalas 9. pak\u0101pe noz\u012bm\u0113, ka t\u0101 ciet\u012bba ir \u013coti l\u012bdz\u012bga dimanta ciet\u012bbai, k\u0101 ar\u012b tas ir \u013coti iztur\u012bgs un notur\u012bgs pret \u0137\u012bmisk\u0101m reakcij\u0101m.<\/p>\n
Alum\u012bnija nitr\u012bda lielisk\u0101s \u012bpa\u0161\u012bbas ir siltumvad\u012btsp\u0113ja un termisk\u0101 izple\u0161an\u0101s, t\u0101p\u0113c tas ir ide\u0101li piem\u0113rots ballistisko bru\u0146u izmanto\u0161anai. Turkl\u0101t t\u0101 stipr\u0101s un stingr\u0101s \u012bpa\u0161\u012bbas padara to piem\u0113rotu ballistisko iero\u010du sist\u0113m\u0101m, k\u0101 ar\u012b ra\u0137e\u0161u un ra\u0137e\u0161u dzin\u0113jiem.<\/p>\n
Akme\u0146u sl\u0101\u0146a reaktors (PBR). Turkl\u0101t \u0161\u012b materi\u0101la rakstur\u012bg\u0101 iztur\u012bba pret oksid\u0113\u0161anos padara to piem\u0113rotu ugunsiztur\u012bgo \u0137ie\u0123e\u013cu ra\u017eo\u0161anai un kodolreaktoru, piem\u0113ram, Pebble Bed Reactors, oder\u0113jumam. Turkl\u0101t ar\u012b alum\u012bnijkeramik\u0101 un cirkonija keramik\u0101, kas ra\u017eota no \u0161\u012b materi\u0101la, izmanto Pebble Bed Reactor; turkl\u0101t t\u0101 ciet\u012bba, stingr\u012bba un zem\u0101 termisk\u0101 izple\u0161an\u0101s padara to par pievilc\u012bgu spogu\u013cu materi\u0101lu izmanto\u0161anai astronomiskajos teleskopos.<\/p>","protected":false},"excerpt":{"rendered":"
Sil\u012bcija karb\u012bds, ko bie\u017e\u0101k d\u0113v\u0113 par karborundu, dab\u0101 sastopams k\u0101 retais miner\u0101ls moizan\u012bts un meteor\u012btos, tom\u0113r liel\u0101k\u0101 da\u013ca m\u016bsdien\u0101s p\u0101rdot\u0101 SiC ir sint\u0113tiski ra\u017eots. Ar oglek\u013ca \u0161\u0137iedru stiegrota plastmasa (CFRP) ir \u0101rk\u0101rt\u012bgi ciets kovalenti saist\u012bts materi\u0101ls, ko ra\u017eo, karbotermiski reduc\u0113jot sil\u012bcija smiltis un naftas koksu elektrisk\u0101 pretest\u012bbas kr\u0101sn\u012b, t\u0101d\u0113j\u0101di ...<\/p>\n