Karbid k\u0159em\u00edku neboli karborundum () je tvrd\u00e1 keramika, kter\u00e1 byla poprv\u00e9 s\u00e9riov\u011b vyrobena v roce 1893 jako brusivo. A\u010dkoli existuj\u00ed p\u0159\u00edrodn\u00ed exempl\u00e1\u0159e (drahokamy moissanit a mal\u00e9 mno\u017estv\u00ed jako vyv\u0159el\u00e1 hornina zvan\u00e1 korund), v\u011bt\u0161ina modern\u00edho pou\u017eit\u00ed se uskute\u010d\u0148uje synteticky.<\/p>\n
SiC vykazuje vysokou odolnost proti \u00fanav\u011b, vysokou tepelnou vodivost a n\u00edzk\u00fd koeficient rozta\u017enosti, tak\u017ee je vhodn\u00fd pro v\u00fdrobu, aby odol\u00e1val vysok\u00fdm teplot\u00e1m a z\u00e1rove\u0148 z\u016fstal pevn\u00fd v korozivn\u00edm prost\u0159ed\u00ed.<\/p>\n
Karbid k\u0159em\u00edku je jedn\u00edm z m\u00e1la materi\u00e1l\u016f s vysokou tepelnou vodivost\u00ed p\u0159i pokojov\u00e9 teplot\u011b. D\u00edky sv\u00e9 tvrdosti, tuhosti a teplotn\u00ed stabilit\u011b je karbid k\u0159em\u00edku vynikaj\u00edc\u00edm materi\u00e1lem pro pou\u017eit\u00ed v zrcadlech teleskop\u016f pou\u017e\u00edvan\u00fdch astronomy.<\/p>\n
Teorie funkce hustoty byla vyu\u017eita k systematick\u00e9mu teoretick\u00e9mu zkoum\u00e1n\u00ed strukturn\u00edch parametr\u016f a tepeln\u011b-fyzik\u00e1ln\u00edch vlastnost\u00ed kubick\u00e9ho karbidu k\u0159em\u00edku (3C-SiC) za kone\u010dn\u00e9 teploty. Na\u0161e v\u00fdsledky t\u00fdkaj\u00edc\u00ed se elastick\u00fdch konstant a Knoopovy mikrotvrdosti uk\u00e1zaly uspokojivou shodu s experiment\u00e1ln\u00edmi \u00fadaji i s vypo\u010dten\u00fdmi v\u00fdsledky publikovan\u00fdmi jinde.<\/p>\n
Pomoc\u00ed optimalizovan\u00fdch strukturn\u00edch model\u016f jsme tak\u00e9 z\u00edskali odhady energi\u00ed tvorby defekt\u016f na atom\u00e1rn\u00ed \u00farovni pro ZrC, TiC a SiC s vyu\u017eit\u00edm optimalizovan\u00fdch strukturn\u00edch model\u016f. V\u00fdsledky uk\u00e1zaly, \u017ee Debyeova teplota kles\u00e1 s rostouc\u00edm po\u010dtem atom\u016f defekt\u016f, zat\u00edmco CZr antisity a VC defekty vykazuj\u00ed ni\u017e\u0161\u00ed energie vzniku ne\u017e jejich prot\u011bj\u0161ky VSi a Sit defekty; sn\u00ed\u017een\u00ed jejich energie vzniku m\u016f\u017ee m\u00edt vliv na odolnost proti jednoos\u00e9 a smykov\u00e9 deformaci 3C-SiC struktur.<\/p>\n
Karbid k\u0159em\u00edku je jedn\u00edm z nejtvrd\u0161\u00edch a tepeln\u011b nejvodiv\u011bj\u0161\u00edch materi\u00e1l\u016f v p\u0159\u00edrod\u011b, odol\u00e1v\u00e1 p\u016fsoben\u00ed kyselin i louh\u016f a je tepeln\u011b odoln\u00fd a\u017e do 1600 \u00b0C bez ztr\u00e1ty pevnosti. Krom\u011b toho je karbid k\u0159em\u00edku vynikaj\u00edc\u00edm elektrick\u00fdm vodi\u010dem.<\/p>\n
Karbid k\u0159em\u00edku je d\u00edky sv\u00e9mu \u0161irok\u00e9mu p\u00e1smu vhodn\u00fd pro pou\u017eit\u00ed v polovodi\u010dov\u00fdch za\u0159\u00edzen\u00edch, jako jsou diody, tranzistory a tyristory, a d\u00edky sv\u00e9 schopnosti odol\u00e1vat velk\u00fdm nap\u011bt\u00edm a proud\u016fm je pou\u017eiteln\u00fd i ve v\u00fdkonn\u00fdch za\u0159\u00edzen\u00edch.<\/p>\n
Por\u00e9zn\u00ed SiC lze upravit p\u0159id\u00e1n\u00edm grafenov\u00fdch nanodesti\u010dek (GNP), \u010d\u00edm\u017e vznikne materi\u00e1l se zlep\u0161en\u00fdmi tepeln\u00fdmi vlastnostmi. Tento materi\u00e1l lze vyrobit pomoc\u00ed sp\u00e9k\u00e1n\u00ed stechiometrick\u00e9ho nebo nestechiometrick\u00e9ho SiC pr\u00e1\u0161ku v kapaln\u00e9 f\u00e1zi v jiskrov\u00e9m plazmatu; byly testov\u00e1ny r\u016fzn\u00e9 kombinace sp\u00e9kac\u00edch p\u0159\u00edsad (Y2O3 a La2O3), aby se vyhodnotil jejich vliv na f\u00e1zov\u00e9 slo\u017een\u00ed, mikrostrukturu a tepelnou vodivost por\u00e9zn\u00edch materi\u00e1l\u016f s obsahem GNPs a\u017e 20 obj.%; u kompozit\u016f obsahuj\u00edc\u00edch a\u017e 20% GNP byla pozorov\u00e1na nemonot\u00f3nn\u00ed teplotn\u00ed z\u00e1vislost.<\/p>\n
Jedine\u010dn\u00e9 slo\u017een\u00ed atom\u016f k\u0159em\u00edku a uhl\u00edku v krystalov\u00e9 m\u0159\u00ed\u017ece prop\u016fj\u010duje SiC pozoruhodn\u00e9 mechanick\u00e9 vlastnosti, kter\u00e9 z n\u011bj \u010din\u00ed jeden z nejtvrd\u0161\u00edch a nejodoln\u011bj\u0161\u00edch keramick\u00fdch materi\u00e1l\u016f. Je vysoce odoln\u00fd proti korozi zp\u016fsoben\u00e9 kyselinami, louhy, roztaven\u00fdmi solemi i proti ot\u011bru; tuhost a pevnost \u010din\u00ed z SiC atraktivn\u00ed materi\u00e1lovou volbu pro sou\u010d\u00e1stky odoln\u00e9 proti opot\u0159eben\u00ed, jako jsou brusn\u00e9 kotou\u010de nebo vrt\u00e1ky ve ml\u00fdnech, expand\u00e9rech nebo extrud\u00e9rech.<\/p>\n
Keramick\u00fd materi\u00e1l je nejen lehk\u00fd, ale vykazuje tak\u00e9 vynikaj\u00edc\u00ed odolnost proti tepeln\u00fdm \u0161ok\u016fm - vydr\u017e\u00ed teploty a\u017e 1600 \u00b0C, ani\u017e by ztratil sv\u00e9 mechanick\u00e9 vlastnosti nebo tepelnou rozta\u017enost, m\u00e1 n\u00edzkou tepelnou rozta\u017enost a mimo\u0159\u00e1dn\u011b vysok\u00fd Young\u016fv modul zaji\u0161\u0165uj\u00edc\u00ed rozm\u011brovou stabilitu.<\/p>\n
P\u00f3rovitost por\u00e9zn\u00ed keramiky SiC se li\u0161\u00ed v z\u00e1vislosti na zp\u016fsobu jej\u00edho tvarov\u00e1n\u00ed (reak\u010dn\u00ed lepen\u00ed nebo slinov\u00e1n\u00ed). Studie prok\u00e1zaly, \u017ee elektrick\u00e1 vodivost i pevnost v ohybu se zvy\u0161uj\u00ed se zvy\u0161uj\u00edc\u00edm se obsahem B4C d\u00edky jeho schopnosti adsorbovat kysl\u00edk z materi\u00e1l\u016f s matric\u00ed Si-C, a t\u00edm sni\u017eovat d\u00e9lku rozptylu fonon\u016f.<\/p>\n
Karbid k\u0159em\u00edku se ve v\u00fdrob\u011b pou\u017e\u00edv\u00e1 jako brusivo i jako \u0159ezn\u00fd n\u00e1stroj. D\u00edky sv\u00e9mu tvrd\u00e9mu a tepeln\u011b odoln\u00e9mu povrchu se karbid k\u0159em\u00edku vyskytuje tak\u00e9 jako elektronick\u00fd polovodi\u010d v diod\u00e1ch a tranzistorech, proto\u017ee jeho nap\u011b\u0165ov\u00e1 tolerance m\u016f\u017ee p\u0159ekonat k\u0159em\u00edk.<\/p>\n
Tvrdost karbidu k\u0159em\u00edku, jeho odolnost v\u016f\u010di korozi a vysok\u00e1 tepeln\u00e1 vodivost z n\u011bj \u010din\u00ed vynikaj\u00edc\u00ed materi\u00e1l pro ochrann\u00e9 vybaven\u00ed, jako jsou p\u0159ilby a panc\u00e9\u0159ov\u00e9 desky. Nav\u00edc d\u00edky sv\u00e9 chemick\u00e9 inertnosti nereaguje s vodou, tak\u017ee je ide\u00e1ln\u00ed pro pou\u017eit\u00ed v prost\u0159ed\u00ed s vysokou vlhkost\u00ed, jako jsou kosmick\u00e9 lod\u011b a mo\u0159sk\u00e9 prost\u0159ed\u00ed.<\/p>\n
Rekrystalizovan\u00fd karbid k\u0159em\u00edku (RSiC) se m\u016f\u017ee pochlubit bezkonkuren\u010dn\u00ed sm\u011bs\u00ed mechanick\u00fdch, tepeln\u00fdch a elektrick\u00fdch vlastnost\u00ed, kter\u00e1 je lep\u0161\u00ed ne\u017e u ostatn\u00edch variant SiC. D\u00edky sv\u00e9 hust\u00e9 mikrostruktu\u0159e m\u00e1 RSiC n\u00edzk\u00fd koeficient rozta\u017enosti a z\u00e1rove\u0148 si zachov\u00e1v\u00e1 pevnost a tuhost p\u0159i vysok\u00fdch teplot\u00e1ch; nav\u00edc vykazuje relativn\u011b vy\u0161\u0161\u00ed hodnoty modulu pru\u017enosti ne\u017e strukturn\u00ed zirkoniov\u00e1 keramika a m\u00e1 n\u00edzk\u00e9 hodnoty koeficientu tepeln\u00e9 rozta\u017enosti ve srovn\u00e1n\u00ed se strukturn\u00ed zirkoniovou keramikou.<\/p>","protected":false},"excerpt":{"rendered":"
Silicon carbide, or carborundum (), is a hard ceramic first mass-produced in 1893 for use as an abrasive. While natural instances exist (moissanite gems and small quantities as an igneous rock called corundum), most modern day usage occurs synthetically. SiC is known to exhibit high fatigue resistance, high thermal conductivity and a low coefficient of […]<\/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-190","post","type-post","status-publish","format-standard","hentry","category-knowledge"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/ceramicatijolart.com\/cs\/wp-json\/wp\/v2\/posts\/190","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=190"}],"version-history":[{"count":1,"href":"https:\/\/ceramicatijolart.com\/cs\/wp-json\/wp\/v2\/posts\/190\/revisions"}],"predecessor-version":[{"id":191,"href":"https:\/\/ceramicatijolart.com\/cs\/wp-json\/wp\/v2\/posts\/190\/revisions\/191"}],"wp:attachment":[{"href":"https:\/\/ceramicatijolart.com\/cs\/wp-json\/wp\/v2\/media?parent=190"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ceramicatijolart.com\/cs\/wp-json\/wp\/v2\/categories?post=190"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ceramicatijolart.com\/cs\/wp-json\/wp\/v2\/tags?post=190"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}