Karbid k\u0159em\u00edku (SiC) je velmi tvrd\u00fd syntetick\u00fd materi\u00e1l, kter\u00fd poprv\u00e9 syntetizoval Edward Acheson v roce 1891 v peci zah\u0159\u00e1t\u00e9 uhl\u00edkem a oxidem hlinit\u00fdm. Od sv\u00e9ho uveden\u00ed do pr\u016fmyslu jako pr\u016fmyslov\u00e9ho brusiva ve 20. letech 20. stolet\u00ed se SiC rychle stal jedn\u00edm z nejvyhled\u00e1van\u011bj\u0161\u00edch materi\u00e1l\u016f ve velk\u00e9m m\u011b\u0159\u00edtku.<\/p>\n
SiC se vyr\u00e1b\u00ed v r\u016fzn\u00fdch krystalov\u00fdch struktur\u00e1ch zn\u00e1m\u00fdch jako polytypy; pro aplikace s vysok\u00fdm v\u00fdkonem je nejvhodn\u011bj\u0161\u00ed polytyp s hexagon\u00e1ln\u00ed atomovou strukturou 4H-SiC.<\/p>\n
Karbid k\u0159em\u00edku je jemn\u00e1 keramika s rozmanit\u00fdmi fyzik\u00e1ln\u00edmi vlastnostmi, kter\u00e9 z n\u00ed \u010din\u00ed jeden z nejuniverz\u00e1ln\u011bj\u0161\u00edch \u017e\u00e1ruvzdorn\u00fdch materi\u00e1l\u016f na trhu. Od jeho pevnosti, tvrdosti, odolnosti proti korozi a vysok\u00e9ho bodu t\u00e1n\u00ed a\u017e po jeho v\u0161estrannost v extr\u00e9mn\u00edch technick\u00fdch aplikac\u00edch - jako jsou lo\u017eiska \u010derpadel, ventily, p\u00edskovac\u00ed vst\u0159ikova\u010de a vytla\u010dovac\u00ed formy - karbid k\u0159em\u00edku se osv\u011bd\u010dil jako d\u016fle\u017eit\u00fd prvek pro modern\u00ed elektronick\u00e1 za\u0159\u00edzen\u00ed. Krom\u011b t\u011bchto p\u016fsobiv\u00fdch mechanick\u00fdch vlastnost\u00ed nab\u00edz\u00ed karbid k\u0159em\u00edku jako nepostradateln\u00e1 slo\u017eka v\u00fdznamn\u00e9 polovodi\u010dov\u00e9 schopnosti.<\/p>\n
\u010cist\u00fd karbid k\u0159em\u00edku je bezbarv\u00e1 krystalick\u00e1 l\u00e1tka s hustotou 3,21 g\/ml a teplotou t\u00e1n\u00ed vy\u0161\u0161\u00ed ne\u017e 2700 \u00b0C. \u010casto se vyr\u00e1b\u00ed Achesonov\u00fdm procesem, kdy se k\u0159emi\u010dit\u00fd p\u00edsek a koks kombinuj\u00ed a zah\u0159\u00edvaj\u00ed na vysok\u00e9 teploty v elektrick\u00e9 peci, dokud se k\u0159emi\u010dit\u00fd p\u00edsek nezkarbonizuje a nevytvo\u0159\u00ed hrubozrnn\u00e9 krystalick\u00e9 struktury, jako je a-SiC, zat\u00edmco u ingot\u016f b-SiC se vytv\u00e1\u0159ej\u00ed diamantov\u00e9 krychlov\u00e9 struktury.<\/p>\n
Alfa-SiC je nej\u010dast\u011bji se vyskytuj\u00edc\u00ed polymorf karbidu k\u0159em\u00edku, kter\u00fd m\u00e1 hexagon\u00e1ln\u00ed krystalovou strukturu podobnou wurtzitu. Formy beta-SiC s diamantovou krystalovou strukturou se nej\u010dast\u011bji vyskytuj\u00ed v meteoritech; krom\u011b toho se tato forma \u010dasto pou\u017e\u00edv\u00e1 v pr\u016fmyslov\u00e9 v\u00fdrob\u011b p\u0159i tavic\u00edch a lic\u00edch procesech k v\u00fdrob\u011b r\u016fzn\u00fdch v\u00fdrobk\u016f.<\/p>\n
Karbid k\u0159em\u00edku je hou\u017eevnat\u00e1 neoxidov\u00e1 keramika s pozoruhodn\u00fdmi fyzik\u00e1ln\u00edmi a chemick\u00fdmi vlastnostmi: vysokou tvrdost\u00ed a tuhost\u00ed, n\u00edzkou tepelnou rozta\u017enost\u00ed a v\u00fdjime\u010dnou odolnost\u00ed proti korozi. Krom\u011b toho je d\u00edky sv\u00e9mu \u0161irok\u00e9mu p\u00e1smu vhodn\u00fd pro aplikace ve vysoce v\u00fdkonn\u00e9 elektronice.<\/p>\n
Voda, alkohol a v\u011bt\u0161ina kyselin s v\u00fdjimkou kyseliny fluorovod\u00edkov\u00e9 a kysel\u00fdch fluorid\u016f ji nerozpou\u0161t\u00ed, co\u017e j\u00ed zaji\u0161\u0165uje vy\u0161\u0161\u00ed chemickou stabilitu ne\u017e v\u011bt\u0161in\u011b ostatn\u00edch \u017e\u00e1ruvzdorn\u00fdch keramik.<\/p>\n
Karbid k\u0159em\u00edku byl poprv\u00e9 um\u011ble syntetizov\u00e1n Edwardem Achesonem v roce 1891 jako n\u00e1hodn\u00fd vedlej\u0161\u00ed produkt jeho elektricky zah\u0159\u00edvan\u00e9 taveniny uhl\u00edku a oxidu hlinit\u00e9ho a stal se jednou z nejd\u016fle\u017eit\u011bj\u0161\u00edch pr\u016fmyslov\u00fdch keramik na sv\u011bt\u011b, kter\u00e1 se pou\u017e\u00edv\u00e1 jako brusn\u00fd materi\u00e1l pro ocelov\u00e9 slitiny i jako konstruk\u010dn\u00ed keramika.<\/p>\n
Karbid k\u0159em\u00edku m\u00e1 t\u011bsn\u00e9 tetraedrick\u00e9 uspo\u0159\u00e1d\u00e1n\u00ed kovalentn\u011b v\u00e1zan\u00e9. R\u016fzn\u00e1 po\u0159ad\u00ed uspo\u0159\u00e1d\u00e1n\u00ed d\u00e1vaj\u00ed vzniknout r\u016fzn\u00fdm polytyp\u016fm - ka\u017ed\u00fd z nich se vyzna\u010duje odli\u0161n\u00fdmi fyzik\u00e1ln\u00edmi a chemick\u00fdmi vlastnostmi.<\/p>\n
Alfa forma (a-SiC) m\u00e1 hexagon\u00e1ln\u00ed krystalovou strukturu podobnou wurtzitu, zat\u00edmco jej\u00ed beta verze (b-SiC) vykazuje krystalovou strukturu zinkov\u00e9ho blende podobnou diamantu. Ob\u011b odr\u016fdy SiC lze snadno opracov\u00e1vat s pouze omezen\u00fdmi omezen\u00edmi tvrdosti a brousit do r\u016fzn\u00fdch tvar\u016f pro pou\u017eit\u00ed jako brusn\u00e9 v\u00fdrobky nebo zrcadla v dalekohledech, co\u017e jsou obl\u00edben\u00e9 aplikace t\u011bchto materi\u00e1l\u016f.<\/p>\n
Karbid k\u0159em\u00edku je polovodi\u010dov\u00fd materi\u00e1l, co\u017e znamen\u00e1, \u017ee vykazuje n\u011bkter\u00e9 vlastnosti, kter\u00e9 se vyskytuj\u00ed jak u kov\u016f (kter\u00e9 vedou elektrick\u00fd proud), tak u nekov\u016f, jako jsou izolanty (kter\u00e9 se br\u00e1n\u00ed toku elekt\u0159iny). P\u0159esn\u00e1 povaha jeho elektrick\u00fdch vlastnost\u00ed z\u00e1vis\u00ed na teplot\u011b a p\u0159\u00edpadn\u00fdch ne\u010distot\u00e1ch p\u0159\u00edtomn\u00fdch v jeho krystalov\u00e9 struktu\u0159e - p\u0159i ni\u017e\u0161\u00edch teplot\u00e1ch se chov\u00e1 sp\u00ed\u0161e jako izolant, kter\u00fd se br\u00e1n\u00ed pr\u016ftoku elekt\u0159iny, zat\u00edmco p\u0159i vy\u0161\u0161\u00edch teplot\u00e1ch se st\u00e1v\u00e1 sp\u00ed\u0161e vodi\u010dem a umo\u017e\u0148uje pr\u016fchod elekt\u0159iny.<\/p>\n
Krystalov\u00e1 struktura SiC se skl\u00e1d\u00e1 z vrstev slo\u017een\u00fdch z atom\u016f k\u0159em\u00edku a uhl\u00edku v\u00e1zan\u00fdch v tetraedrick\u00e9 konfiguraci. Tyto t\u011bsn\u011b zabalen\u00e9 vrstvy vytv\u00e1\u0159ej\u00ed t\u011bsnou strukturu, kter\u00e1 d\u00e1v\u00e1 vzniknout r\u016fzn\u00fdm krystalov\u00fdm struktur\u00e1m naz\u00fdvan\u00fdm polytypy; ka\u017ed\u00fd polytyp m\u00e1 stejn\u00e9 chemick\u00e9 slo\u017een\u00ed, ale odli\u0161nou krystalovou strukturu, kter\u00e1 ovliv\u0148uje jeho elektrick\u00e9 vlastnosti. Po\u0159ad\u00ed vrstven\u00ed jednotliv\u00fdch polytyp\u016f m\u016f\u017ee vytv\u00e1\u0159et krystalov\u00e9 struktury kubick\u00e9, hexagon\u00e1ln\u00ed nebo romboedrick\u00e9.<\/p>\n
SiC je atraktivn\u00edm materi\u00e1lem pro vysokonap\u011b\u0165ov\u00e1 v\u00fdkonov\u00e1 za\u0159\u00edzen\u00ed d\u00edky sv\u00e9 tetraedrick\u00e9 krystalov\u00e9 struktu\u0159e a \u0161irok\u00e9 meze\u0159e v elektronick\u00e9m p\u00e1smu, co\u017e jej \u010din\u00ed zvl\u00e1\u0161t\u011b vhodn\u00fdm pro diody a tranzistory. \u0160ir\u0161\u00ed elektronick\u00e1 p\u00e1smov\u00e1 mezera SiC mu umo\u017e\u0148uje odol\u00e1vat vy\u0161\u0161\u00edm pr\u016frazn\u00fdm elektrick\u00fdm pol\u00edm ne\u017e k\u0159em\u00edk a z\u00e1rove\u0148 m\u00e1 ni\u017e\u0161\u00ed sp\u00ednac\u00ed ztr\u00e1ty, kter\u00e9 pom\u00e1haj\u00ed zlep\u0161it energetickou \u00fa\u010dinnost. Krom\u011b toho lze vodivost por\u00e9zn\u00edho karbidu k\u0159em\u00edku modifikovat jeho dopov\u00e1n\u00edm ne\u010distotami, aby se dos\u00e1hlo vy\u0161\u0161\u00ed vodivosti i nap\u011b\u0165ov\u00e9 schopnosti pro pou\u017eit\u00ed v \u00fa\u010dinn\u00fdch m\u011bni\u010d\u00edch energie pro m\u011bni\u010de energie v elektrick\u00fdch vozidlech.<\/p>\n
Karbid k\u0159em\u00edku je extr\u00e9mn\u011b tvrd\u00fd, chemicky inertn\u00ed materi\u00e1l, kter\u00fd se v p\u0159\u00edrod\u011b vyskytuje v podob\u011b \u010dern\u00fdch diamant\u016f s tvrdost\u00ed podle Mohse 9. M\u00e1 mnoho v\u00fdhodn\u00fdch vlastnost\u00ed, v\u010detn\u011b teplotn\u00ed stability, n\u00edzk\u00e9 tepeln\u00e9 rozta\u017enosti a odolnosti v\u016f\u010di chemick\u00fdm vliv\u016fm, tak\u017ee je ide\u00e1ln\u00ed jako polovodi\u010dov\u00fd materi\u00e1l.<\/p>\n
Oxid lithn\u00fd je v\u00fdjime\u010dn\u00fd elektrick\u00fd izolant s v\u00fdjime\u010dn\u00fdm faktorem nap\u011b\u0165ov\u00e9 odolnosti, kter\u00fd je desetkr\u00e1t vy\u0161\u0161\u00ed ne\u017e u k\u0159em\u00edku, co\u017e z n\u011bj \u010din\u00ed st\u00e1le atraktivn\u011bj\u0161\u00ed mo\u017enost n\u00e1hrady k\u0159em\u00edku pro v\u00fdkonovou elektroniku a dal\u0161\u00ed vysoce v\u00fdkonn\u00e9 aplikace.<\/p>\n
SiC se vyr\u00e1b\u00ed pomoc\u00ed r\u016fzn\u00fdch polymorfn\u00edch krystalov\u00fdch struktur, z nich\u017e ka\u017ed\u00e1 m\u00e1 sv\u00e9 specifick\u00e9 uspo\u0159\u00e1d\u00e1n\u00ed atom\u016f. T\u0159i b\u011b\u017en\u00e9 polytypy SiC, kter\u00e9 se vyr\u00e1b\u011bj\u00ed, jsou 3C-SiC, 4H-SiC a 6H-SiC; li\u0161\u00ed se po\u0159ad\u00edm vrstven\u00ed, co\u017e vede k odli\u0161n\u00fdm fyzik\u00e1ln\u00edm a mechanick\u00fdm vlastnostem.<\/p>\n
Ned\u00e1vn\u00fd v\u00fdzkum proveden\u00fd na jednotliv\u00fdch SiC nanodr\u00e1tc\u00edch s r\u016fzn\u00fdmi strukturn\u00edmi pom\u011bry obsazen\u00ed ODD byl testov\u00e1n in-situ v tahu pomoc\u00ed SEM, aby se posoudila jejich pevnost a pru\u017enost, modul pru\u017enosti ve smyku, v\u00fdpo\u010dty Poissonova pom\u011bru jednotliv\u00fdch f\u00e1z\u00ed a anal\u00fdza mechanick\u00e9 anizotropie odhalily, \u017ee Pm-SiC m\u00e1 siln\u011bj\u0161\u00ed chov\u00e1n\u00ed ve smyku ve srovn\u00e1n\u00ed s b-SiC a Pnnm-SiC NWs; nav\u00edc pevnost rostla s rostouc\u00edm pom\u011brem obsazen\u00ed ODD a\u017e do dosa\u017een\u00ed 32,6%, kdy pevnost za\u010dala exponenci\u00e1ln\u011b klesat.<\/p>","protected":false},"excerpt":{"rendered":"
Silicon carbide (SiC) is an ultrahard synthetic material first synthesized in 1891 by Edward Acheson in a furnace heated with carbon and alumina. Since its release into industry as an industrial abrasive in the 1920s, SiC has quickly become one of the most sought-after materials on a large scale. SiC comes in various crystal structures […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"site-sidebar-layout":"default","site-content-layout":"","ast-site-content-layout":"","site-content-style":"default","site-sidebar-style":"default","ast-global-header-display":"","ast-banner-title-visibility":"","ast-main-header-display":"","ast-hfb-above-header-display":"","ast-hfb-below-header-display":"","ast-hfb-mobile-header-display":"","site-post-title":"","ast-breadcrumbs-content":"","ast-featured-img":"","footer-sml-layout":"","theme-transparent-header-meta":"","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"default","ast-page-background-enabled":"default","ast-page-background-meta":{"desktop":{"background-color":"var(--ast-global-color-4)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"tablet":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"mobile":{"background-color":"","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""}},"ast-content-background-meta":{"desktop":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"tablet":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""},"mobile":{"background-color":"var(--ast-global-color-5)","background-image":"","background-repeat":"repeat","background-position":"center center","background-size":"auto","background-attachment":"scroll","background-type":"","background-media":"","overlay-type":"","overlay-color":"","overlay-gradient":""}},"footnotes":""},"categories":[64],"tags":[],"class_list":["post-335","post","type-post","status-publish","format-standard","hentry","category-knowledge"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/ceramicatijolart.com\/cs\/wp-json\/wp\/v2\/posts\/335","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ceramicatijolart.com\/cs\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ceramicatijolart.com\/cs\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ceramicatijolart.com\/cs\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ceramicatijolart.com\/cs\/wp-json\/wp\/v2\/comments?post=335"}],"version-history":[{"count":1,"href":"https:\/\/ceramicatijolart.com\/cs\/wp-json\/wp\/v2\/posts\/335\/revisions"}],"predecessor-version":[{"id":336,"href":"https:\/\/ceramicatijolart.com\/cs\/wp-json\/wp\/v2\/posts\/335\/revisions\/336"}],"wp:attachment":[{"href":"https:\/\/ceramicatijolart.com\/cs\/wp-json\/wp\/v2\/media?parent=335"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ceramicatijolart.com\/cs\/wp-json\/wp\/v2\/categories?post=335"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ceramicatijolart.com\/cs\/wp-json\/wp\/v2\/tags?post=335"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}