Beztlakov\u00e9 spekanie karbidu krem\u00edka sa pova\u017euje za najs\u013eubnej\u0161\u00ed spekan\u00fd karbid krem\u00edka a beztlakov\u00fdm spekan\u00edm mo\u017eno pripravi\u0165 zlo\u017eit\u00e9 tvary a ve\u013ek\u00e9 rozmery keramiky z karbidu krem\u00edka. V z\u00e1vislosti od mechanizmu spekania mo\u017eno tento druh spekan\u00e9ho karbidu krem\u00edka \u010falej rozdeli\u0165 na spekanie v pevnej f\u00e1ze a spekanie v kvapalnej f\u00e1ze. \u03b2-SiC obsahuj\u00faci stopov\u00e9 mno\u017estv\u00e1 SiO sa m\u00f4\u017ee spiec\u0165 pri atmosf\u00e9rickom tlaku pridan\u00edm B a C. T\u00e1to met\u00f3da v\u00fdrazne zlep\u0161uje kinetiku spekania karbidu krem\u00edka. Po pridan\u00ed vhodn\u00e9ho mno\u017estva B sa B po\u010das spekania nach\u00e1dza na hraniciach z\u0155n SiC a \u010diasto\u010dne tvor\u00ed pevn\u00fd roztok s SiC, \u010d\u00edm sa zni\u017euje energia na hraniciach z\u0155n SiC. Dopovanie mierneho mno\u017estva vo\u013en\u00e9ho C je v\u00fdhodn\u00e9 pre spekanie v pevnej f\u00e1ze, preto\u017ee povrch SiC je zvy\u010dajne oxidovan\u00fd s mal\u00fdm mno\u017estvom tvorby SiO a pr\u00eddavok mierneho mno\u017estva C pom\u00e1ha, aby sa film SiO na povrchu SiC zredukoval a odstr\u00e1nil, \u010d\u00edm sa zvy\u0161uje povrchov\u00e1 energia. Spekanie v kvapalnej f\u00e1ze v\u0161ak bude ma\u0165 negat\u00edvny \u00fa\u010dinok, preto\u017ee C bude reagova\u0165 s oxidov\u00fdmi pr\u00edsadami za vzniku plynu, vzniku ve\u013ek\u00e9ho po\u010dtu otvorov v keramickom spekanom telese, \u010do ovplyvn\u00ed proces zhut\u0148ovania. \u010cistota, jemnos\u0165 a f\u00e1zov\u00e9 zlo\u017eenie suroviny s\u00fa ve\u013emi d\u00f4le\u017eit\u00e9 v procese spekania karbidu krem\u00edka. s. Proehazka spekal spekan\u00fd karbid krem\u00edka s hustotou vy\u0161\u0161ou ako 98% pri teplote 2020 \u00b0C za atmosf\u00e9rick\u00e9ho tlaku s\u00fa\u010dasn\u00fdm pridan\u00edm vhodn\u00fdch mno\u017estiev B a C do ultrajemn\u00fdch pr\u00e1\u0161kov \u03b2-SiC (obsahuj\u00facich menej ako 2% kysl\u00edka). Syst\u00e9m SiC-B-C v\u0161ak patr\u00ed do kateg\u00f3rie spekania v pevnej f\u00e1ze, ktor\u00e9 si vy\u017eaduje vysok\u00fa teplotu spekania a n\u00edzku lomov\u00fa h\u00fa\u017eevnatos\u0165, lomov\u00fd re\u017eim je typick\u00fd lom cez kry\u0161t\u00e1l, hrub\u00e9 zrn\u00e1 a slab\u00e1 rovnomernos\u0165. Zahrani\u010dn\u00fd v\u00fdskum SiC sa s\u00fastre\u010fuje najm\u00e4 na spekanie v kvapalnej f\u00e1ze, t. j. ur\u010dit\u00fd po\u010det spekac\u00edch pr\u00edsad, pri ni\u017e\u0161ej teplote, aby sa dosiahlo zhutnenie SiC. Spekanie SiC v kvapalnej f\u00e1ze nielen zni\u017euje teplotu spekania v porovnan\u00ed so spekan\u00edm v pevnej f\u00e1ze, ale zlep\u0161uje aj mikro\u0161trukt\u00faru, a t\u00fdm sa zlep\u0161uj\u00fa vlastnosti spekan\u00e9ho telesa v porovnan\u00ed s vlastnos\u0165ami spekan\u00e9ho telesa v pevnej f\u00e1ze.
\nM. Omori a kol. pou\u017eili na hust\u00e9 spekanie SiC oxidy vz\u00e1cnych zem\u00edn v zmesi s AlO alebo boridmi. Na druhej strane Suzuki spekal SiC len s AlO ako pr\u00edsadou pri teplote pribli\u017ene 2 000 \u00b0C. A. Mulla a kol. spekali 0,5 \u03bcm \u03b2-SiC (s mal\u00fdm mno\u017estvom SiO na povrchu \u010dast\u00edc) s AlO a YO ako pr\u00edsadami pri ,1850-1950 \u00b0C a z\u00edskali relat\u00edvnu hustotu keramiky SiC, ktor\u00e1 bola v\u00e4\u010d\u0161ia ako 95% teoretickej hustoty, a zrn\u00e1 boli jemn\u00e9, s priemernou ve\u013ekos\u0165ou 1,5 \u03bcm.
\nZistilo sa, \u017ee mikro\u0161trukt\u00fara keramiky z karbidu krem\u00edka m\u00e1 hrub\u00e9 zrn\u00e1 a ty\u010dinkovit\u00fa \u0161trukt\u00faru s dobrou lomovou h\u00fa\u017eevnatos\u0165ou. Ty\u010dinkovit\u00e9 zrn\u00e1 zvy\u0161uj\u00fa lomov\u00fa h\u00fa\u017eevnatos\u0165 a z\u00e1rove\u0148 zni\u017euj\u00fa pevnos\u0165 keramiky z karbidu krem\u00edka. S cie\u013eom dosiahnu\u0165 lep\u0161iu pevnos\u0165 a h\u00fa\u017eevnatos\u0165 pri s\u00fa\u010dasnom zn\u00ed\u017een\u00ed teploty spekania sa uskuto\u010dnilo mnoho pokusov o zlep\u0161enie vlastnost\u00ed tohto spekan\u00e9ho karbidu krem\u00edka \u00fapravou zlo\u017eenia sklenej f\u00e1zy pomocou r\u00f4znych pr\u00edsad. Po\u010das procesu spekania viedlo zavedenie kvapalnej f\u00e1zy na hranici z\u0155n a jedine\u010dn\u00e1 medzif\u00e1zov\u00e1 \u0161trukt\u00fara k oslabeniu medzif\u00e1zovej \u0161trukt\u00fary a lom materi\u00e1lu sa zmenil na \u00fapln\u00fd pozd\u013a\u017eny lom, \u010do viedlo k v\u00fdrazn\u00e9mu zv\u00fd\u0161eniu pevnosti a h\u00fa\u017eevnatosti materi\u00e1lu. Av\u0161ak vzh\u013eadom na to, \u017ee pri pou\u017eit\u00ed pr\u00edsady AlO vznik\u00e1 sklovit\u00e1 f\u00e1za s n\u00edzkym bodom topenia a vysokou prchavos\u0165ou, ktor\u00e1 pri vy\u0161\u0161\u00edch teplot\u00e1ch podlieha siln\u00e9mu vyparovaniu, \u010do sp\u00f4sobuje \u00fabytok hmotnosti materi\u00e1lu a nepriaznivo ovplyv\u0148uje zhutnenie materi\u00e1lu, hmotnostn\u00fd podiel AlO v pr\u00edsade by sa mal primerane zv\u00fd\u0161i\u0165.<\/p>","protected":false},"excerpt":{"rendered":"
Pressureless sintered silicon carbide is considered to be the most promising sintered silicon carbide, and complex shapes and large sizes of silicon carbide ceramics can be prepared by the pressureless sintering process. Depending on the sintering mechanism, this kind of sintered silicon carbide can be further divided into solid-phase sintering and liquid-phase sintering. \u03b2-SiC containing […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"ngg_post_thumbnail":0,"footnotes":""},"categories":[30],"tags":[],"class_list":["post-578","post","type-post","status-publish","format-standard","hentry","category-sic-knowledge"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/siliconcarbide.net\/sk\/wp-json\/wp\/v2\/posts\/578","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/siliconcarbide.net\/sk\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/siliconcarbide.net\/sk\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/siliconcarbide.net\/sk\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/siliconcarbide.net\/sk\/wp-json\/wp\/v2\/comments?post=578"}],"version-history":[{"count":1,"href":"https:\/\/siliconcarbide.net\/sk\/wp-json\/wp\/v2\/posts\/578\/revisions"}],"predecessor-version":[{"id":579,"href":"https:\/\/siliconcarbide.net\/sk\/wp-json\/wp\/v2\/posts\/578\/revisions\/579"}],"wp:attachment":[{"href":"https:\/\/siliconcarbide.net\/sk\/wp-json\/wp\/v2\/media?parent=578"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/siliconcarbide.net\/sk\/wp-json\/wp\/v2\/categories?post=578"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/siliconcarbide.net\/sk\/wp-json\/wp\/v2\/tags?post=578"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}