Karbid krem\u00edka je mimoriadne tvrd\u00fd a pevn\u00fd materi\u00e1l s vysokou hustotou, v\u00fdnimo\u010dnou odolnos\u0165ou proti kor\u00f3zii a vynikaj\u00facimi tribologick\u00fdmi vlastnos\u0165ami. Dostupn\u00fd v spekanej aj reak\u010dne viazanej forme.<\/p>\n
Beztlakov\u00e9 spekanie zabezpe\u010duje vysok\u00fa hustotu v\u010faka zn\u00ed\u017eeniu povrchovej energie z\u0155n v d\u00f4sledku reakcie b\u00f3ru a uhl\u00edka1 , ale jeho vysok\u00e1 teplota vedie k nadmern\u00e9mu rastu z\u0155n, ktor\u00fd zhor\u0161uje mechanick\u00e9 vlastnosti.<\/p>\n
Karbid krem\u00edka, be\u017ene ozna\u010dovan\u00fd ako karborundum, je tvrd\u00e1 chemick\u00e1 zl\u00fa\u010denina zlo\u017een\u00e1 z krem\u00edka a uhl\u00edka, ktor\u00e1 sa prirodzene vyskytuje vo vz\u00e1cnych miner\u00e1loch, ako je moissanit; be\u017enej\u0161ie sa v\u0161ak vyr\u00e1ba vo forme pr\u00e1\u0161ku a gran\u00fal na pou\u017eitie ako br\u00fasivo a keramick\u00e9 dosky v nepriestreln\u00fdch vest\u00e1ch. Karborundum odol\u00e1va vysok\u00fdm teplot\u00e1m a z\u00e1rove\u0148 si zachov\u00e1va chemick\u00fa odolnos\u0165 - vr\u00e1tane odolnosti vo\u010di kyselin\u00e1m, ako s\u00fa kyselina fosfore\u010dn\u00e1, s\u00edrov\u00e1 a dusi\u010dn\u00e1.<\/p>\n
Spekan\u00fd karbid krem\u00edka na\u0161iel v\u010faka svojim pozoruhodn\u00fdm tepelnoizola\u010dn\u00fdm vlastnostiam \u0161irok\u00e9 uplatnenie v r\u00f4znych priemyseln\u00fdch odvetviach, od letectva a\u017e po astron\u00f3miu. \u017diaruvzdorn\u00fd materi\u00e1l zo spekan\u00e9ho karbidu krem\u00edka sa tie\u017e m\u00f4\u017ee pochv\u00e1li\u0165 p\u00f4sobivou odolnos\u0165ou a m\u00f4\u017ee by\u0165 presne opracovan\u00fd pomocou drah\u00e9ho zariadenia na dosiahnutie presn\u00fdch toleranci\u00ed.<\/p>\n
Keramika z karbidu krem\u00edka sa dod\u00e1va v dvoch variantoch, reak\u010dne sp\u00e1jan\u00e1 a spekan\u00e1. Reakt\u00edvne viazan\u00fd karbid krem\u00edka sa vyr\u00e1ba infiltr\u00e1ciou kompaktov zlo\u017een\u00fdch z SiC a uhl\u00edka tekut\u00fdm krem\u00edkom, \u010d\u00edm sa vytv\u00e1ra viac SiC, ktor\u00fd sa via\u017ee na p\u00f4vodn\u00e9 \u010dastice a vytv\u00e1ra viac reak\u010dne viazan\u00fdch \u010dast\u00edc karbidu krem\u00edka, ktor\u00e9 pri\u013en\u00fa \u013eah\u0161ie ako ich spekan\u00e9 n\u00e1protivky, ale zost\u00e1vaj\u00fa cenovo v\u00fdhodn\u00e9 v\u010faka zn\u00ed\u017eenej pevnosti a tvrdosti.<\/p>\n
Spekan\u00fd karbid krem\u00edka sa vyr\u00e1ba zahrievan\u00edm surov\u00edn na extr\u00e9mne vysok\u00e9 teploty v inertnej atmosf\u00e9re, \u010d\u00edm sa z nich st\u00e1va extr\u00e9mne pevn\u00fd materi\u00e1l, ktor\u00fd sa m\u00f4\u017ee pou\u017e\u00edva\u0165 v r\u00f4znych aplik\u00e1ci\u00e1ch, ako s\u00fa napr\u00edklad opotrebovate\u013en\u00e9 \u010dasti pieskov\u00fdch \u010derpadiel a bansk\u00fdch cykl\u00f3nov. Okrem toho sa vyzna\u010duje vynikaj\u00facou odolnos\u0165ou proti kor\u00f3zii, ako aj n\u00edzkou tepelnou roz\u0165a\u017enos\u0165ou.<\/p>\n
Reak\u010dne viazan\u00fd karbid krem\u00edka (RSiC) sa vyr\u00e1ba lisovan\u00edm a spekan\u00edm (zahrievan\u00edm) \u010dast\u00edc pr\u00e1\u0161ku, \u010d\u00edm sa vytvor\u00ed pevn\u00fd kus materi\u00e1lu s vysokou pevnos\u0165ou, tvrdos\u0165ou, odolnos\u0165ou proti kor\u00f3zii a oxid\u00e1cii - hoci nie tak tvrd\u00fd ako spekan\u00fd karbid krem\u00edka.<\/p>\n
Spekan\u00fd karbid krem\u00edka je technick\u00e1 keramika so siln\u00fdmi kovalentn\u00fdmi v\u00e4zbami, ktor\u00e1 poskytuje vynikaj\u00face mechanick\u00e9 vlastnosti pri vysok\u00fdch teplot\u00e1ch. Tento materi\u00e1l sa vyzna\u010duje ve\u013ekou tvrdos\u0165ou a odolnos\u0165ou proti opotrebovaniu, ako aj odolnos\u0165ou proti chemickej kor\u00f3zii, oxid\u00e1cii a tepeln\u00fdm \u0161okom spolu s ve\u013emi dobrou tepelnou vodivos\u0165ou, v\u010faka \u010domu je vhodn\u00fd na pou\u017eitie v n\u00e1ro\u010dn\u00fdch podmienkach.<\/p>\n
Spekan\u00edm v kvapalnej f\u00e1ze sa z\u00edskavaj\u00fa vysoko\u010dist\u00e9 materi\u00e1ly s rovnomernou mikro\u0161trukt\u00farou, ktor\u00e9 s\u00fa kompaktnej\u0161ie ako pri spekan\u00ed v tuhom stave. Zmeny ve\u013ekosti po\u010das zhut\u0148ovania s\u00fa minim\u00e1lne; mo\u017eno vyr\u00e1ba\u0165 presn\u00e9 diely so zlo\u017eit\u00fdmi tvarmi. Spek\u00e1rske pr\u00edsady b\u00f3ru a uhl\u00edka m\u00f4\u017eu modifikova\u0165 energie na hraniciach z\u0155n a povrchov\u00e9 energie, pri\u010dom zlep\u0161uj\u00fa r\u00fdchlos\u0165 objemovej dif\u00fazie a obmedzuj\u00fa tvorbu skla medzi zrnami.<\/p>\n
V\u00fdsledky spekania v pevnom stave maj\u00fa vy\u0161\u0161iu odolnos\u0165 proti te\u010deniu v tlaku ako ich konven\u010dn\u00e9 n\u00e1protivky v d\u00f4sledku zv\u00fd\u0161enia kinetickej energie kry\u0161talick\u00e9ho krem\u00edka a zr\u00fdchlenia pohybu dislok\u00e1ci\u00ed v zrnit\u00fdch oblastiach, ako aj zv\u00fd\u0161enia koncentr\u00e1cie kovov\u00e9ho krem\u00edka, \u010do pom\u00e1ha zn\u00ed\u017ei\u0165 r\u00fdchlos\u0165 te\u010denia spomalen\u00edm dif\u00fazie SiC cez hranice z\u0155n.<\/p>\n
Karbid krem\u00edka m\u00e1 vynikaj\u00facu odolnos\u0165 proti kor\u00f3zii, oxid\u00e1cii a opotrebovaniu - vlastnosti, ktor\u00e9 z neho robia vhodn\u00fd materi\u00e1l do n\u00e1ro\u010dn\u00fdch prostred\u00ed, kde by sa in\u00e9 materi\u00e1ly mohli \u010dasom rozbi\u0165. Okrem toho karbid krem\u00edka odol\u00e1va teplot\u00e1m a\u017e do 1 900 stup\u0148ov C, v\u010faka \u010domu je vhodn\u00fd na chemick\u00e9 spracovanie, kde m\u00f4\u017eu zariadenia prich\u00e1dza\u0165 do kontaktu s vysoko kysl\u00fdmi chemik\u00e1liami a plynmi, ktor\u00e9 koroduj\u00fa \u013eah\u0161ie, ne\u017e sa o\u010dak\u00e1va.<\/p>\n
Zistilo sa, \u017ee karbid krem\u00edka spekan\u00fd v pevnom stave (SSiC) aj karbid krem\u00edka s infiltr\u00e1ciou s\u00fa stabiln\u00e9 v r\u00f4znych chemick\u00fdch roztokoch, hoci karbid krem\u00edka s infiltr\u00e1ciou m\u00e1 ni\u017e\u0161iu kor\u00f3znu stabilitu kv\u00f4li vo\u013en\u00e9mu krem\u00edku. Na presk\u00famanie t\u00fdchto mechanizmov sme uskuto\u010dnili kr\u00e1tkodob\u00e9 aj dlhodob\u00e9 kor\u00f3zne experimenty na SiSiC v roztoku NaOH s vyu\u017eit\u00edm presn\u00fdch meran\u00ed h\u013abky kor\u00f3zie na le\u0161ten\u00fdch povrchoch, ako aj skenovacej elektr\u00f3novej mikroskopie na jej produktoch.<\/p>\n
Reak\u010dne viazan\u00fd karbid krem\u00edka (RBSiC) sa vyr\u00e1ba infiltr\u00e1ciou kvapaln\u00e9ho krem\u00edka do por\u00e9znych uhl\u00edkov\u00fdch alebo grafitov\u00fdch predliskov a jeho reakciou na SiC. RBSiC sa od svojho drah\u0161ieho n\u00e1protivku SSiC l\u00ed\u0161i v nieko\u013ek\u00fdch oh\u013eadoch; po prv\u00e9, m\u00e1 ni\u017e\u0161iu pevnos\u0165 a tvrdos\u0165, ale jeho v\u00fdroba stoj\u00ed podstatne menej a je priepustnej\u0161\u00ed pre plyny a kvapaliny; vyzna\u010duje sa tie\u017e dobrou odolnos\u0165ou proti oderu, kor\u00f3zii a tepeln\u00fdm \u0161okom, \u010do umo\u017e\u0148uje jeho pou\u017eitie v aplik\u00e1ci\u00e1ch, ako s\u00fa d\u00fdzy hor\u00e1kov alebo trysky a plame\u0148ov\u00e9 trubice; napokon sa vyzna\u010duje aj dobrou odolnos\u0165ou proti tepeln\u00fdm \u0161okom, \u010do umo\u017e\u0148uje r\u00fdchle zmeny teploty bez toho, aby boli ovplyvnen\u00e9.<\/p>\n
Spekan\u00fd karbid krem\u00edka sa m\u00f4\u017ee pochv\u00e1li\u0165 jednou z najvy\u0161\u0161\u00edch tepeln\u00fdch vodivost\u00ed spomedzi neoxidov\u00fdch keramick\u00fdch materi\u00e1lov, v\u010faka \u010domu je vhodn\u00fd pre aplik\u00e1cie s vysok\u00fdmi teplotami, ako je napr\u00edklad aplik\u00e1cia chemick\u00e9ho naparovania (CVD) SiC alebo reak\u010dne viazan\u00e9ho karbidu krem\u00edka.<\/p>\n
Jeho kry\u0161talick\u00e1 \u0161trukt\u00fara, ktor\u00e1 sa nach\u00e1dza v bl\u00edzkosti jadra, pom\u00e1ha zvy\u0161ova\u0165 tepeln\u00fa vodivos\u0165 keramiky s vysok\u00fdm tepeln\u00fdm v\u00fdkonom. Tento materi\u00e1l je schopn\u00fd odol\u00e1va\u0165 vysok\u00e9mu teplotn\u00e9mu za\u0165a\u017eeniu s mal\u00fdm po\u0161koden\u00edm a odolnos\u0165ou vo\u010di kor\u00f3zii, oxid\u00e1cii a \u00fanave - predstavuje vynikaj\u00facu vo\u013ebu materi\u00e1lu pre aplik\u00e1cie tesnenia \u010derpadiel, preto\u017ee si dok\u00e1\u017ee zachova\u0165 odolnos\u0165 vo\u010di tlaku a teplote po\u010das dlh\u0161ieho obdobia.<\/p>\n
Tento typ keramiky sa vyzna\u010duje aj vynikaj\u00facou h\u00fa\u017eevnatos\u0165ou, \u010do znamen\u00e1, \u017ee odol\u00e1va n\u00e1razom a vibr\u00e1ci\u00e1m lep\u0161ie ako in\u00e9 keramick\u00e9 materi\u00e1ly. Okrem toho patr\u00ed jej pevnos\u0165 a odolnos\u0165 vo\u010di oxid\u00e1cii k najvy\u0161\u0161\u00edm vo svojej kateg\u00f3rii.<\/p>\n
Spekanie v tekutej f\u00e1ze (LPS) je inovat\u00edvna technika zhut\u0148ovania karbidu krem\u00edka, ktor\u00e1 vyu\u017e\u00edva eutektick\u00e9 oxidov\u00e9 spekan\u00e9 pr\u00edsady na zhut\u0148ovanie pri ni\u017e\u0161\u00edch teplot\u00e1ch ako tradi\u010dne, \u010d\u00edm sa \u0161etria v\u00fdrobn\u00e9 n\u00e1klady a z\u00e1rove\u0148 sa zni\u017euje p\u00f3rovitos\u0165 hotov\u00e9ho v\u00fdrobku.<\/p>\n
Sn\u00edmky HRTEM vzoriek LPS-SiC s r\u00f4znymi spekan\u00fdmi pr\u00edsadami ukazuj\u00fa, ako zv\u00fd\u0161en\u00fd pr\u00eddavok pr\u00edsady vyrovn\u00e1va distrib\u00faciu kvapalnej f\u00e1zy medzi zrnami SiC, \u010do vedie k zhutneniu, vy\u0161\u0161ej relat\u00edvnej hustote a lep\u0161iemu elektrick\u00e9mu odporu, \u010do s\u00fa vlastnosti kritick\u00e9 pre aplik\u00e1cie vyu\u017e\u00edvaj\u00face mikrovlnn\u00e9 a milimetrov\u00e9 vlny.<\/p>","protected":false},"excerpt":{"rendered":"
Silicon carbide is an extremely hard and strong material with high density, exceptional corrosion resistance and outstanding tribological properties. Available both sintered and reaction bonded forms. Pressureless sintering provides high densification through reduction of surface energy of grains due to boron and carbon reaction1, but its high temperature leads to excessive grain growth that compromises […]<\/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-82","post","type-post","status-publish","format-standard","hentry","category-knowledge"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/ceramicatijolart.com\/sk\/wp-json\/wp\/v2\/posts\/82","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=82"}],"version-history":[{"count":1,"href":"https:\/\/ceramicatijolart.com\/sk\/wp-json\/wp\/v2\/posts\/82\/revisions"}],"predecessor-version":[{"id":83,"href":"https:\/\/ceramicatijolart.com\/sk\/wp-json\/wp\/v2\/posts\/82\/revisions\/83"}],"wp:attachment":[{"href":"https:\/\/ceramicatijolart.com\/sk\/wp-json\/wp\/v2\/media?parent=82"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ceramicatijolart.com\/sk\/wp-json\/wp\/v2\/categories?post=82"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ceramicatijolart.com\/sk\/wp-json\/wp\/v2\/tags?post=82"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}