Whiskery karbidu krem\u00edka, mikrometrov\u00e9 \u010dastice s v\u00fdnimo\u010dn\u00fdmi fyzik\u00e1lnymi a chemick\u00fdmi vlastnos\u0165ami, si z\u00edskali zna\u010dn\u00fd v\u00fdskumn\u00fd z\u00e1ujem v\u010faka ich \u0161irok\u00e9mu vyu\u017eitiu v mnoh\u00fdch oblastiach vr\u00e1tane vysokoteplotn\u00fdch kon\u0161truk\u010dn\u00fdch materi\u00e1lov a n\u00e1strojovej keramiky.<\/p>\n
Mullitov\u00e1 keramika je vysoko chemicky stabiln\u00fd \u017eiaruvzdorn\u00fd materi\u00e1l s vynikaj\u00facimi mechanick\u00fdmi a fyzik\u00e1lnymi vlastnos\u0165ami, ako je vysok\u00e1 tvrdos\u0165 a odolnos\u0165 vo\u010di teplotn\u00e9mu te\u010deniu, av\u0161ak jej lomov\u00e1 h\u00fa\u017eevnatos\u0165 zost\u00e1va relat\u00edvne n\u00edzka. SiC whiskery t\u00fato vlastnos\u0165 v\u00fdrazne zlep\u0161uj\u00fa.<\/p>\n
Vl\u00e1kna karbidu krem\u00edka s\u00fa mikr\u00f3nov\u00e9 monokry\u0161talick\u00e9 vl\u00e1kna, ktor\u00e9 svojou \u0161trukt\u00farou pripom\u00ednaj\u00fa diamant a maj\u00fa jedine\u010dn\u00e9 vlastnosti, ako je vysok\u00e1 pevnos\u0165, tuhos\u0165, chemick\u00e1 odolnos\u0165 a teplotn\u00e1 stabilita, ktor\u00e9 z nich robia vynikaj\u00faci v\u00fdstu\u017en\u00fd materi\u00e1l pre keramiku, kovy a polym\u00e9rne kompozity.<\/p>\n
Miner\u00e1lne plniv\u00e1 sa m\u00f4\u017eu pou\u017ei\u0165 na spevnenie keramiky a z\u00e1rove\u0148 zvy\u0161uj\u00fa jej \u0165a\u017enos\u0165 a tvrdos\u0165, odolnos\u0165 vo\u010di oxid\u00e1cii, tepeln\u00fa roz\u0165a\u017enos\u0165 a lomov\u00fa h\u00fa\u017eevnatos\u0165. Okrem toho sa m\u00f4\u017eu prid\u00e1va\u0165 do kompozitov s polym\u00e9rnou matricou, aby sa zn\u00ed\u017eili po\u017eiadavky na plniv\u00e1 a z\u00e1rove\u0148 sa zv\u00fd\u0161ila ich odolnos\u0165 vo\u010di praskaniu, zm\u00e1\u010daniu a \u00fanavov\u00e9mu po\u0161kodeniu.<\/p>\n
Whiskery mo\u017eno vyr\u00e1ba\u0165 r\u00f4znymi technikami vr\u00e1tane karbotermickej redukcie oxidu kremi\u010dit\u00e9ho, chemickej reakcie medzi halogenidmi krem\u00edka a CCl4 alebo CVD s kovov\u00fdmi katalyz\u00e1tormi. Nane\u0161\u0165astie, ich kvalita a rozmery s\u00fa \u010dasto obmedzen\u00e9 aglomer\u00e1ciou a anizotropiou (Wright, 2006). Pokro\u010dilej\u0161\u00ed proces zah\u0155\u0148a rast para-kvapalina-pevn\u00e1 l\u00e1tka, ktor\u00fd umo\u017e\u0148uje umiestni\u0165 whiskery hlboko do p\u00f3rov v por\u00e9znych substr\u00e1toch a poskytuje \u017eiaduce vlastnosti.<\/p>\n
Whiskery sa sk\u00famali a porovn\u00e1vali s vl\u00e1knami ved\u013eaj\u0161\u00edch priemyseln\u00fdch produktov pren\u00e1\u0161an\u00fdch vzduchom s cie\u013eom zisti\u0165 ak\u00e9ko\u013evek rizik\u00e1 pre pracovn\u00edkov, ktor\u00ed s nimi manipuluj\u00fa, pri\u010dom sa nezistilo \u017eiadne v\u00fdznamn\u00e9 respira\u010dn\u00e9 riziko v pr\u00edpade whiskerov SiC. V\u00fdsledky v\u00fdskumu viedli k z\u00e1veru, \u017ee SiC whiskery nepredstavuj\u00fa pri manipul\u00e1cii s nimi \u017eiadne z\u00e1va\u017en\u00e9 nebezpe\u010denstvo.<\/p>\n
Karbid krem\u00edka prv\u00fdkr\u00e1t umelo syntetizoval Edward Acheson v roku 1891 ako br\u00fasny materi\u00e1l zn\u00e1my ako karborundum (Encyclopedia Britannica, 2014). Odvtedy sa masovo vyr\u00e1ba s pou\u017eit\u00edm kremenn\u00e9ho piesku a uhl\u00edka zahrievan\u00e9ho pri vysok\u00fdch teplot\u00e1ch, aby sa vytvorili ve\u013ek\u00e9 d\u00e1vky karbidu krem\u00edka, ktor\u00fd nach\u00e1dza vyu\u017eitie vo viacer\u00fdch priemyseln\u00fdch oblastiach v\u010faka svojej v\u00fdnimo\u010dnej pevnosti, hmotnostnej v\u00fdhode a stabilite pri vysok\u00fdch teplot\u00e1ch, ako aj vysokej odolnosti vo\u010di p\u00f4sobeniu \u017eiarenia; keramick\u00e9 tesnenia a trysky na pieskovanie vyu\u017e\u00edvaj\u00fa karbid krem\u00edka, pri\u010dom trvanlivos\u0165 okrem in\u00e9ho nahr\u00e1dza azbestov\u00e9 l\u00e1tky.<\/p>\n
Karbid krem\u00edka (SiC) je polokovov\u00e1 zl\u00fa\u010denina pozost\u00e1vaj\u00faca z krem\u00edka a uhl\u00edka s teplotou topenia 2260 \u00b0C a n\u00edzkym tlakom p\u00e1r, v\u010faka \u010domu je nerozpustn\u00fd vo vode, ale rozpustn\u00fd v alkohole a \u00e9teri; v d\u00f4sledku vystavenia vzduchu pri izbovej teplote v\u0161ak r\u00fdchlo degraduje, \u010do vedie k r\u00fdchlej degrad\u00e1cii v priebehu \u010dasu. SiC mo\u017eno n\u00e1js\u0165 ako abraz\u00edvum v br\u00fasnom papieri, ako aj v n\u00e1strojoch na povrchov\u00fa \u00fapravu, napr\u00edklad v n\u00e1strojoch na pieskovanie, ako aj v br\u00fasnych kot\u00fa\u010doch alebo in\u00fdch obr\u00e1bac\u00edch zariadeniach.<\/p>\n
Vl\u00e1kna SiC m\u00f4\u017eu by\u0165 pre bunky nebezpe\u010dne toxick\u00e9, nar\u00fa\u0161a\u0165 bunkov\u00e9 membr\u00e1ny a vies\u0165 k ich smrti. \u0160t\u00fadie vykonan\u00e9 na bunk\u00e1ch my\u0161\u00edch fibroblastov preuk\u00e1zali ich cytotoxicitu t\u00fdm, \u017ee vyvolali mut\u00e1cie DNA, zv\u00fd\u0161ili celkov\u00fd obsah bunkovej DNA a viedli k mal\u00edgnej transform\u00e1cii - tieto \u00fa\u010dinky sa zn\u00ed\u017eili, ke\u010f boli potiahnut\u00e9 netoxickou povrchovo akt\u00edvnou l\u00e1tkou. Pri testovan\u00ed na bunk\u00e1ch \u013eudsk\u00e9ho riasinkov\u00e9ho epitelu priedu\u0161nice sa uk\u00e1zalo, \u017ee s\u00fa toxickej\u0161ie ako vl\u00e1kna ved\u013eaj\u0161\u00edch priemyseln\u00fdch produktov, ako je azbest a sulfid nikelnat\u00fd, pri\u010dom s\u00fa menej \u0161kodliv\u00e9 ako mastenec a oxid titani\u010dit\u00fd.<\/p>\n
Whiskery karbidu krem\u00edka s\u00fa ide\u00e1lnym v\u00fdstu\u017en\u00fdm materi\u00e1lom, ktor\u00fd je ide\u00e1lny na spev\u0148ovanie keramiky, kovov a polym\u00e9rnych kompozitov. Medzi ich vlastnosti patr\u00ed vysok\u00e1 pevnos\u0165, tvrdos\u0165, chemick\u00e1 inertnos\u0165 a teplotn\u00e1 odolnos\u0165, ako aj zv\u00fd\u0161en\u00e1 odolnos\u0165 materi\u00e1lov vo\u010di oxid\u00e1cii, napr\u00edklad keramick\u00fdch materi\u00e1lov z oxykarbidu krem\u00edka, ktor\u00e9 sa vo ve\u013ekej miere sk\u00famaj\u00fa ako n\u00e1stroje, s\u00fa\u010dasti motorov a keramika odoln\u00e1 vo\u010di opotrebovaniu - v z\u00e1vislosti od chemizmu, \u0161trukt\u00fary a ve\u013ekosti kry\u0161t\u00e1lov syntetizovan\u00fdch karbotermickou redukciou, CVD alebo spa\u013eovan\u00edm odpadov\u00fdch produktov, napr\u00edklad ry\u017eov\u00fdch \u0161upiek.<\/p>\n
Ich mechanick\u00e9 vlastnosti v\u0161ak z\u010faleka nedosahuj\u00fa vlastnosti monolitick\u00e9ho kry\u0161talick\u00e9ho krem\u00edka (c-Si). Na zlep\u0161enie pevnosti v \u0165ahu a \u00fanavy t\u00fdchto materi\u00e1lov ich v\u00fdskumn\u00edci modifikovali organick\u00fdmi materi\u00e1lmi alebo anorganick\u00fdmi vl\u00e1knami zn\u00e1mymi ako SiC whiskers, aby sa zlep\u0161ila pevnos\u0165 v tlaku a \u0165ahu, ako aj zn\u00ed\u017eila koncentr\u00e1cia nap\u00e4tia v ich okol\u00ed po\u010das lomu. T\u00e1to modifik\u00e1cia v\u00fdrazne zv\u00fd\u0161ila pevnos\u0165 v tlaku a z\u00e1rove\u0148 zn\u00ed\u017eila koncentr\u00e1ciu nap\u00e4tia po\u010das lomu.<\/p>\n
Pridanie SiC whiskerov do sklokeramickej matrice v\u00fdrazne zvy\u0161uje jej pevnos\u0165 a h\u00fa\u017eevnatos\u0165 pri zachovan\u00ed jednoduchej tvorby skla a zlep\u0161uje tribologick\u00e9 vlastnosti. Okrem toho dok\u00e1\u017ee zv\u00fd\u0161i\u0165 \u0165a\u017enos\u0165, ako aj Hugoniotovu medzu pru\u017enosti o nieko\u013eko r\u00e1dov; morfol\u00f3gia lomu o tom navy\u0161e sved\u010d\u00ed t\u00fdm, \u017ee vykazuje mno\u017estvo jamiek a trhac\u00edch hr\u00e1n, \u010do sved\u010d\u00ed o jej \u0165a\u017enosti.<\/p>\n
Karbid krem\u00edka (SiC) je extr\u00e9mne tvrd\u00e1 chemick\u00e1 zl\u00fa\u010denina pozost\u00e1vaj\u00faca z krem\u00edka a uhl\u00edka, ktor\u00e1 sa prirodzene vyskytuje ako drahokam moissanit, ale od roku 1893 sa s\u00e9riovo vyr\u00e1ba vo forme pr\u00e1\u0161ku a kry\u0161t\u00e1lov na pou\u017eitie ako br\u00fasivo. Karbid krem\u00edka sa pou\u017e\u00edva aj v aplik\u00e1ci\u00e1ch vy\u017eaduj\u00facich vysok\u00fa odolnos\u0165, ako s\u00fa keramick\u00e9 brzdov\u00e9 kot\u00fa\u010de pre automobily a nepriestreln\u00e9 vesty, ako aj tesnenia hriade\u013eov \u010derpadiel; jeho bod topenia mu umo\u017e\u0148uje odol\u00e1va\u0165 extr\u00e9mnym teplot\u00e1m bez toho, aby \u010dasom praskol alebo sa deformoval.<\/p>\n
Tepeln\u00e9 vlastnosti SiC whiskerov z\u00e1visia vo ve\u013ekej miere od ich mikro\u0161trukt\u00fary, chemick\u00e9ho zlo\u017eenia povrchu a ve\u013ekosti. V\u010faka n\u00edzkemu tlaku p\u00e1r a stabilite a\u017e do 1650 \u00b0C sa tieto whiskery m\u00f4\u017eu pou\u017e\u00edva\u0165 ako v\u00fdstu\u017ee v r\u00f4znych materi\u00e1loch, ako s\u00fa kovy a polym\u00e9ry; zlep\u0161uj\u00fa pevnos\u0165, h\u00fa\u017eevnatos\u0165, chemick\u00fa inertnos\u0165 a odolnos\u0165 vo\u010di oxid\u00e1cii a z\u00e1rove\u0148 predl\u017euj\u00fa \u017eivotnos\u0165.<\/p>\n
Anal\u00fdzu mikro\u0161trukt\u00fary SiC whiskerov mo\u017eno vykona\u0165 pomocou skenovacej elektr\u00f3novej mikroskopie a r\u00f6ntgenovej difrakcie. Pozost\u00e1vaj\u00fa z polykry\u0161talick\u00fdch \u0161trukt\u00far pozost\u00e1vaj\u00facich z polytypov 3C beta-SiC a 6H-SiC; \u010fal\u0161ie sk\u00famanie odhalilo, \u017ee kry\u0161talick\u00e9 oblasti maj\u00fa vy\u0161\u0161iu plo\u0161n\u00fa hustotu defektov ako amorfn\u00e9 oblasti v d\u00f4sledku mikrotkan\u00edn vytvoren\u00fdch na rovin\u00e1ch 1 1 1, ktor\u00e9 maj\u00fa v\u00fdznamn\u00fd vplyv na \u0165ahov\u00e9 aj ohybov\u00e9 lomov\u00e9 plochy nanokompozitov PI-SiCw.<\/p>","protected":false},"excerpt":{"rendered":"
Silicon carbide whiskers, single-crystal micron-sized particles with outstanding physical and chemical properties, have garnered significant research interest due to their wide-ranging applications across many fields including high temperature structural materials and tool ceramics. Mullite ceramic is a highly chemically stable refractory material with superior mechanical and physical properties such as high hardness and temperature creep […]<\/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-363","post","type-post","status-publish","format-standard","hentry","category-knowledge"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/ceramicatijolart.com\/sk\/wp-json\/wp\/v2\/posts\/363","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=363"}],"version-history":[{"count":1,"href":"https:\/\/ceramicatijolart.com\/sk\/wp-json\/wp\/v2\/posts\/363\/revisions"}],"predecessor-version":[{"id":364,"href":"https:\/\/ceramicatijolart.com\/sk\/wp-json\/wp\/v2\/posts\/363\/revisions\/364"}],"wp:attachment":[{"href":"https:\/\/ceramicatijolart.com\/sk\/wp-json\/wp\/v2\/media?parent=363"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ceramicatijolart.com\/sk\/wp-json\/wp\/v2\/categories?post=363"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ceramicatijolart.com\/sk\/wp-json\/wp\/v2\/tags?post=363"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}