Karbid krem\u00edka alebo karborundum () je tvrd\u00e1 keramika, ktor\u00e1 sa prv\u00fdkr\u00e1t s\u00e9riovo vyrobila v roku 1893 na pou\u017eitie ako br\u00fasivo. Hoci existuj\u00fa pr\u00edrodn\u00e9 exempl\u00e1re (drahokamy moissanit a mal\u00e9 mno\u017estv\u00e1 ako vyvret\u00e1 hornina naz\u00fdvan\u00e1 korund), v\u00e4\u010d\u0161ina modern\u00e9ho pou\u017eitia sa uskuto\u010d\u0148uje synteticky.<\/p>\n
SiC sa vyzna\u010duje vysokou odolnos\u0165ou proti \u00fanave, vysokou tepelnou vodivos\u0165ou a n\u00edzkym koeficientom roz\u0165a\u017enosti, v\u010faka \u010domu je vhodn\u00fd na v\u00fdrobu, aby odolal vysok\u00fdm teplot\u00e1m a z\u00e1rove\u0148 zostal pevn\u00fd v koroz\u00edvnom prostred\u00ed.<\/p>\n
Karbid krem\u00edka je jedn\u00fdm z m\u00e1la materi\u00e1lov s vysokou tepelnou vodivos\u0165ou pri izbovej teplote. V\u010faka svojej tvrdej, tuhej a teplotne stabilnej povahe je karbid krem\u00edka vynikaj\u00facou vo\u013ebou materi\u00e1lu na pou\u017eitie v zrkadl\u00e1ch teleskopov pou\u017e\u00edvan\u00fdch astron\u00f3mami.<\/p>\n
Te\u00f3ria funkci\u00ed hustoty bola pou\u017eit\u00e1 na systematick\u00e9 teoretick\u00e9 sk\u00famanie \u0161truktur\u00e1lnych parametrov a tepelno-fyzik\u00e1lnych vlastnost\u00ed kubick\u00e9ho karbidu krem\u00edka (3C-SiC) pri kone\u010dnej teplote. Na\u0161e v\u00fdsledky t\u00fdkaj\u00face sa elastick\u00fdch kon\u0161t\u00e1nt a Knoopovej mikrotvrdosti uk\u00e1zali uspokojiv\u00fa zhodu s experiment\u00e1lnymi \u00fadajmi, ako aj s vypo\u010d\u00edtan\u00fdmi zisteniami publikovan\u00fdmi inde.<\/p>\n
Pou\u017eit\u00edm optimalizovan\u00fdch modelov \u0161trukt\u00fary sme z\u00edskali aj odhady energi\u00ed tvorby defektov na at\u00f3movej \u00farovni pre ZrC, TiC a SiC pomocou optimalizovan\u00fdch modelov \u0161trukt\u00fary. V\u00fdsledky odhalili, \u017ee Debyeho teplota kles\u00e1 s rast\u00facim po\u010dtom at\u00f3mov defektu, zatia\u013e \u010do CZr antisitov\u00e9 defekty a VC defekty vykazuj\u00fa ni\u017e\u0161ie energie vzniku ako ich n\u00e1protivky VSi a Sit defekty; zn\u00ed\u017eenie ich energie vzniku m\u00f4\u017ee ma\u0165 vplyv na odolnos\u0165 vo\u010di jednoosovej a \u0161mykovej deform\u00e1cii 3C-SiC \u0161trukt\u00far.<\/p>\n
Karbid krem\u00edka je jedn\u00fdm z najtvrd\u0161\u00edch a tepelne najvodivej\u0161\u00edch materi\u00e1lov v pr\u00edrode, odol\u00e1va \u00fatokom kysel\u00edn aj l\u00fahov a z\u00e1rove\u0148 je odoln\u00fd vo\u010di vysok\u00fdm teplot\u00e1m a\u017e do 1600 \u00b0C bez straty pevnosti. Okrem toho je karbid krem\u00edka vynikaj\u00facim elektrick\u00fdm vodi\u010dom.<\/p>\n
Karbid krem\u00edka je v\u010faka svojmu \u0161irok\u00e9mu p\u00e1smu vhodn\u00fd na pou\u017eitie v polovodi\u010dov\u00fdch zariadeniach, ako s\u00fa di\u00f3dy, tranzistory a tyristory, pri\u010dom jeho schopnos\u0165 odol\u00e1va\u0165 ve\u013ek\u00fdm nap\u00e4tiam a pr\u00fadom ho rob\u00ed u\u017eito\u010dn\u00fdm aj vo v\u00fdkonn\u00fdch zariadeniach.<\/p>\n
Por\u00e9zny SiC mo\u017eno upravi\u0165 pridan\u00edm graf\u00e9nov\u00fdch nanodr\u00f4tikov (GNP), \u010d\u00edm sa vytvor\u00ed materi\u00e1l so zlep\u0161en\u00fdmi tepeln\u00fdmi vlastnos\u0165ami. Tento materi\u00e1l sa d\u00e1 vyrobi\u0165 spekan\u00edm stechiometrick\u00e9ho alebo nestechiometrick\u00e9ho SiC pr\u00e1\u0161ku v kvapalnej f\u00e1ze v iskrovej plazme; testovali sa r\u00f4zne kombin\u00e1cie spekac\u00edch pomocn\u00fdch l\u00e1tok (Y2O3 a La2O3) s cie\u013eom vyhodnoti\u0165 ich vplyv na f\u00e1zov\u00e9 zlo\u017eenie, mikro\u0161trukt\u00faru a tepeln\u00fa vodivos\u0165 por\u00e9znych materi\u00e1lov s obsahom GNP a\u017e do 20 obj.%; pri kompozitoch s obsahom GNP a\u017e do 20% sa pozorovala nemonot\u00f3nna teplotn\u00e1 z\u00e1vislos\u0165.<\/p>\n
Jedine\u010dn\u00e9 zlo\u017eenie at\u00f3mov krem\u00edka a uhl\u00edka v kry\u0161t\u00e1lovej mrie\u017eke d\u00e1va SiC pozoruhodn\u00e9 mechanick\u00e9 vlastnosti, ktor\u00e9 z neho robia jeden z najtvrd\u0161\u00edch a najodolnej\u0161\u00edch keramick\u00fdch materi\u00e1lov. Je vysoko odoln\u00fd vo\u010di kor\u00f3zii sp\u00f4sobenej kyselinami, l\u00fahmi, roztaven\u00fdmi so\u013eami, ako aj vo\u010di abr\u00e1zii; tuhos\u0165 a pevnos\u0165 robia zo SiC atrakt\u00edvnu vo\u013ebu materi\u00e1lu pre s\u00fa\u010diastky odoln\u00e9 vo\u010di opotrebovaniu, ako s\u00fa br\u00fasne kot\u00fa\u010de alebo vrt\u00e1ky v mlynoch, expand\u00e9roch alebo extrud\u00e9roch.<\/p>\n
Okrem n\u00edzkej hmotnosti vykazuje keramick\u00fd materi\u00e1l aj vynikaj\u00facu odolnos\u0165 vo\u010di tepeln\u00fdm \u0161okom - vydr\u017e\u00ed teploty a\u017e do 1600 \u00b0C bez straty mechanick\u00fdch vlastnost\u00ed alebo tepelnej roz\u0165a\u017enosti, pri\u010dom n\u00edzka tepeln\u00e1 roz\u0165a\u017enos\u0165 a v\u00fdnimo\u010dne vysok\u00fd Youngov modul zabezpe\u010duj\u00fa rozmerov\u00fa stabilitu.<\/p>\n
P\u00f3rovitos\u0165 p\u00f3rovitej SiC keramiky sa l\u00ed\u0161i v z\u00e1vislosti od sp\u00f4sobu jej tvarovania (reak\u010dn\u00e9 lepenie alebo spekanie). \u0160t\u00fadie preuk\u00e1zali, \u017ee elektrick\u00e1 vodivos\u0165 aj pevnos\u0165 v ohybe sa zvy\u0161uj\u00fa so zvy\u0161uj\u00facim sa obsahom B4C v\u010faka jeho schopnosti adsorbova\u0165 kysl\u00edk z materi\u00e1lov s matricou Si-C, a t\u00fdm zni\u017eova\u0165 d\u013a\u017eku rozptylu fon\u00f3nov.<\/p>\n
Karbid krem\u00edka sa pou\u017e\u00edva ako abraz\u00edvum aj ako rezn\u00fd n\u00e1stroj vo v\u00fdrobe. V\u010faka svojmu tvrd\u00e9mu a tepelne odoln\u00e9mu povrchu sa karbid krem\u00edka nach\u00e1dza aj ako elektronick\u00fd polovodi\u010d v di\u00f3dach a tranzistoroch, preto\u017ee jeho nap\u00e4\u0165ov\u00e1 tolerancia m\u00f4\u017ee prekona\u0165 krem\u00edk.<\/p>\n
Tvrdos\u0165 karbidu krem\u00edka, jeho odolnos\u0165 vo\u010di kor\u00f3zii a vysok\u00e1 tepeln\u00e1 vodivos\u0165 z neho robia vynikaj\u00faci materi\u00e1l pre ochrann\u00e9 zariadenia, ako s\u00fa prilby a pancierov\u00e9 dosky. Okrem toho jeho chemick\u00e1 inertnos\u0165 znamen\u00e1, \u017ee nereaguje s vodou, tak\u017ee je ide\u00e1lny na pou\u017eitie v prostred\u00ed s vysokou vlhkos\u0165ou, ako s\u00fa vesm\u00edrne lode a morsk\u00e9 prostredie.<\/p>\n
Rekry\u0161talizovan\u00fd karbid krem\u00edka (RSiC) sa m\u00f4\u017ee pochv\u00e1li\u0165 bezkonkuren\u010dnou kombin\u00e1ciou mechanick\u00fdch, tepeln\u00fdch a elektrick\u00fdch vlastnost\u00ed ako v\u0161etky ostatn\u00e9 varianty SiC. V\u010faka hustej mikro\u0161trukt\u00fare m\u00e1 RSiC n\u00edzky koeficient roz\u0165a\u017enosti a z\u00e1rove\u0148 si zachov\u00e1va pevnos\u0165 a tuhos\u0165 pri vysok\u00fdch teplot\u00e1ch; navy\u0161e vykazuje relat\u00edvne vy\u0161\u0161ie hodnoty modulu pru\u017enosti ako \u0161truktur\u00e1lna zirk\u00f3nov\u00e1 keramika a m\u00e1 n\u00edzke hodnoty koeficientu tepelnej roz\u0165a\u017enosti v porovnan\u00ed so \u0161truktur\u00e1lnou zirk\u00f3novou 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\/sk\/wp-json\/wp\/v2\/posts\/190","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ceramicatijolart.com\/sk\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ceramicatijolart.com\/sk\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ceramicatijolart.com\/sk\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ceramicatijolart.com\/sk\/wp-json\/wp\/v2\/comments?post=190"}],"version-history":[{"count":1,"href":"https:\/\/ceramicatijolart.com\/sk\/wp-json\/wp\/v2\/posts\/190\/revisions"}],"predecessor-version":[{"id":191,"href":"https:\/\/ceramicatijolart.com\/sk\/wp-json\/wp\/v2\/posts\/190\/revisions\/191"}],"wp:attachment":[{"href":"https:\/\/ceramicatijolart.com\/sk\/wp-json\/wp\/v2\/media?parent=190"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ceramicatijolart.com\/sk\/wp-json\/wp\/v2\/categories?post=190"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ceramicatijolart.com\/sk\/wp-json\/wp\/v2\/tags?post=190"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}