Sp\u00e9k\u00e1n\u00ed keramiky z karbidu k\u0159em\u00edku obsahuj\u00edc\u00ed prvky C a B4C jako sp\u00e9kac\u00ed prost\u0159edky prob\u00edh\u00e1 v pevn\u00e9 f\u00e1zi a proces sp\u00e9k\u00e1n\u00ed je \u0159\u00edzen p\u0159edev\u0161\u00edm difuzn\u00edm mechanismem, p\u0159i\u010dem\u017e optim\u00e1ln\u00ed teplota sp\u00e9k\u00e1n\u00ed je 2150 \u00b0C. Proces sp\u00e9k\u00e1n\u00ed je jednoduch\u00fd a snadno kontrolovateln\u00fd. P\u0159id\u00e1n\u00ed vhodn\u00e9ho obsahu C + B4C sp\u00e9kac\u00edch p\u0159\u00edsad sp\u00e9k\u00e1n\u00ed karbidu k\u0159em\u00edku proces sp\u00e9k\u00e1n\u00ed je jednoduch\u00fd a snadno kontrolovateln\u00fd, keramick\u00e9 sp\u00e9k\u00e1n\u00ed ve srovn\u00e1n\u00ed s polotovarem m\u00e1 asi 30% objemov\u00e9ho smr\u0161t\u011bn\u00ed, m\u016f\u017eete z\u00edskat vy\u0161\u0161\u00ed hustotu, mechanick\u00e9 vlastnosti karbidu k\u0159em\u00edku speci\u00e1ln\u00ed keramiky. V sou\u010dasn\u00e9 dob\u011b se b\u011b\u017en\u011b pou\u017e\u00edvaj\u00ed sp\u00e9kac\u00ed p\u0159\u00edsady B4C + C, BN + C, BP (fosfid boru) + C, AI + C, AIN + C atd. P\u0159id\u00e1n\u00edm vhodn\u00e9ho obsahu C + B4C SiC beztlakov\u00fdm sp\u00e9k\u00e1n\u00edm je proces pro tento druh sp\u00e9kan\u00e9ho siku jednoduch\u00fd, snadno kontrolovateln\u00fd, hustota materi\u00e1lu je vy\u0161\u0161\u00ed, maxim\u00e1ln\u00ed hustota 3,169\/cm3 (relativn\u00ed hustota 98,75%); mechanick\u00e9 vlastnosti jsou lep\u0161\u00ed, maxim\u00e1ln\u00ed pevnost v tlaku 550MPa.
\n Surovina karbidu k\u0159em\u00edku m\u00e1 p\u0159ednostn\u011b hodnotu D50 0,5 - 0,8 mikrometru jednoduch\u00e9ho mikropr\u00e1\u0161ku. Obvykle se jedn\u00e1 o chemicky upraven\u00fd zelen\u00fd karbid k\u0159em\u00edku o specifick\u00e9m povrchu 20 m3\/g. A obsah kysl\u00edku by m\u011bl b\u00fdt co nejni\u017e\u0161\u00ed; d\u00e1le by m\u011blo b\u00fdt zvoleno mno\u017estv\u00ed p\u0159idan\u00e9ho B, kter\u00e9 se pohybuje kolem 0,5% - 1,5%, zat\u00edmco mno\u017estv\u00ed p\u0159idan\u00e9ho C z\u00e1vis\u00ed na \u00farovni obsahu kysl\u00edku v pr\u00e1\u0161ku SiC. Chemick\u00e9 slo\u017een\u00ed SIC>99%, F-C<0,1, Si+SiO2<0,1, Fe2O3<0,08. Tvar a velikostn\u00ed slo\u017een\u00ed \u010d\u00e1stic, tvar \u010d\u00e1stic je t\u00e9m\u011b\u0159 kulovit\u00fd, aby se dos\u00e1hlo co nejkompaktn\u011bj\u0161\u00edho stohov\u00e1n\u00ed.
\n P\u0159\u00eddavek B4C a C pat\u0159\u00ed do kategorie slinov\u00e1n\u00ed v pevn\u00e9 f\u00e1zi, kter\u00e9 vy\u017eaduje vy\u0161\u0161\u00ed teplotu slinov\u00e1n\u00ed.Hnac\u00ed silou slinov\u00e1n\u00ed SiC je: rozd\u00edl mezi povrchovou energi\u00ed \u010d\u00e1stic pr\u00e1\u0161ku (Eb) a kmitav\u00fdm povrchem zrn polykrystalick\u00e9ho slinovan\u00e9ho t\u011blesa (Es), co\u017e vede ke sn\u00ed\u017een\u00ed voln\u00e9 energie syst\u00e9mu. B4C dopovan\u00fd vhodn\u00fdm mno\u017estv\u00edm B4C se b\u011bhem sp\u00e9k\u00e1n\u00ed nach\u00e1z\u00ed na hranici zrn SiC a \u010d\u00e1ste\u010dn\u011b tvo\u0159\u00ed s SiC pevn\u00fd roztok, \u010d\u00edm\u017e se sni\u017euje kapacita hranice zrn SiC. Dopov\u00e1n\u00ed m\u00edrn\u00e9ho mno\u017estv\u00ed voln\u00e9ho C je pro slinov\u00e1n\u00ed v pevn\u00e9 f\u00e1zi v\u00fdhodn\u00e9, proto\u017ee povrch SiC je obvykle oxidov\u00e1n, co\u017e vede ke vzniku mal\u00e9ho mno\u017estv\u00ed Si02, a p\u0159\u00eddavek m\u00edrn\u00e9ho mno\u017estv\u00ed C pom\u00e1h\u00e1, aby se redukce filmu Si02 na povrchu SiC odstranila, \u010d\u00edm\u017e se zvy\u0161uje povrchov\u00e1 energie Eb.
\n Syst\u00e9m SiC podl\u00e9h\u00e1 rozkladu a sublimaci p\u0159i tlaku 1,013x105Pa a teplot\u011b vy\u0161\u0161\u00ed ne\u017e 1880 \u00b0C. Syst\u00e9m SiC obsahuje plynn\u00e9 f\u00e1ze, jako jsou Si, Si2, Si3, C, C2, C3, C4, C5, SiC, Si2C, SiC2 atd., a teplotn\u00ed rozd\u00edl je z\u00e1kladn\u00edm faktorem sublima\u010dn\u00edho procesu b\u011bhem r\u016fstu krystal\u016f SiC a cel\u00e9mu procesu dominuje transport hmoty. Tyto r\u016fzn\u00e9 plynn\u00e9 f\u00e1ze v syst\u00e9mu SiC se difuz\u00ed sr\u00e1\u017eej\u00ed na matrici krystalu SiC, co\u017e vede k r\u016fstu \u010d\u00e1stic krystalu SiC. U vzork\u016f syst\u00e9mu C+B4C s pomocn\u00fdm sp\u00e9k\u00e1n\u00edm je po\u017eadovan\u00e1 teplota sp\u00e9k\u00e1n\u00ed vy\u0161\u0161\u00ed z d\u016fvodu p\u0159ev\u00e1\u017en\u011b pevnof\u00e1zov\u00e9ho sp\u00e9k\u00e1n\u00ed a argon se p\u0159iv\u00e1d\u00ed jako ochrann\u00e1 atmosf\u00e9ra p\u0159i teplot\u011b p\u0159ibli\u017en\u011b 1300 \u00b0C, proto\u017ee argon je p\u0159\u00edzniv\u00fd pro sn\u00ed\u017een\u00ed rozkladu SiC p\u0159i vysok\u00fdch teplot\u00e1ch nad 1300 \u00b0C. M\u011b\u0159en\u00ed kvality slinut\u00e9ho t\u011blesa SiC m\u00e1 dv\u011b nezbytn\u00e9 podm\u00ednky: n\u00edzk\u00e1 p\u00f3rovitost, co nejhust\u0161\u00ed; co nejmen\u0161\u00ed zrna.<\/p>","protected":false},"excerpt":{"rendered":"
The sintering of silicon carbide ceramic containing C and B4C elements as sintering aids is solid-phase sintering, and the sintering process is mainly controlled by the diffusion mechanism, with an optimum sintering temperature of 2150\u00b0C. The sintering process is simple and easy to control. Add the appropriate content of C + B4C sintering additives […]<\/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-574","post","type-post","status-publish","format-standard","hentry","category-sic-knowledge"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/siliconcarbide.net\/cs\/wp-json\/wp\/v2\/posts\/574","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/siliconcarbide.net\/cs\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/siliconcarbide.net\/cs\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/siliconcarbide.net\/cs\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/siliconcarbide.net\/cs\/wp-json\/wp\/v2\/comments?post=574"}],"version-history":[{"count":3,"href":"https:\/\/siliconcarbide.net\/cs\/wp-json\/wp\/v2\/posts\/574\/revisions"}],"predecessor-version":[{"id":577,"href":"https:\/\/siliconcarbide.net\/cs\/wp-json\/wp\/v2\/posts\/574\/revisions\/577"}],"wp:attachment":[{"href":"https:\/\/siliconcarbide.net\/cs\/wp-json\/wp\/v2\/media?parent=574"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/siliconcarbide.net\/cs\/wp-json\/wp\/v2\/categories?post=574"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/siliconcarbide.net\/cs\/wp-json\/wp\/v2\/tags?post=574"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}