Hlin\u00edk m\u00e1 slo\u017eit\u00e9 chemick\u00e9 slo\u017een\u00ed, v\u010detn\u011b r\u016fzn\u00fdch polymorf\u016f, kter\u00e9 lze tepelnou transformac\u00ed p\u0159em\u011bnit na formy s vysok\u00fdm povrchem, jako je tomu nap\u0159\u00edklad u boehmitu a bayeritu.<\/p>\n
Tepeln\u00fdm rozkladem vznikaj\u00ed lamel\u00e1rn\u00ed nebo vl\u00e1knit\u00e9 g-Al2O3, jejich\u017e morfologie z\u00e1vis\u00ed na v\u00fdchoz\u00edm materi\u00e1lu pou\u017eit\u00e9m k jejich vytvo\u0159en\u00ed.<\/p>\n
Hydr\u00e1t oxidu hlinit\u00e9ho (Al(OH)3) je b\u00edl\u00e1, jemn\u011b pr\u00e1\u0161kovit\u00e1 l\u00e1tka s chemick\u00fdm vzorcem Al(OH)3. Vyr\u00e1b\u00ed se Bayerov\u00fdm procesem z bauxitov\u00e9 rudy, je bez z\u00e1pachu a chuti a m\u00e1 n\u00edzkou rozpustnost a tepelnou stabilitu, co\u017e z n\u011bj \u010din\u00ed mimo\u0159\u00e1dn\u011b univerz\u00e1ln\u00ed surovinu s mnoha aplikacemi v mnoha pr\u016fmyslov\u00fdch odv\u011btv\u00edch jako zdroj Al2O3.<\/p>\n
Gibbsit (-Al(OH)3), bayerit (-Al(OH)3), doyleit a nordstrandit jsou \u010dty\u0159i polymorfy trihydroxidu hlinit\u00e9ho Al(OH)3, kter\u00e9 se obvykle vyskytuj\u00ed v p\u0159\u00edrod\u011b; v\u0161echny jsou si p\u0159\u00edbuzn\u00e9 a maj\u00ed podobnou strukturu; jejich morfologie se v\u0161ak v\u00fdrazn\u011b li\u0161\u00ed a ovliv\u0148uje jejich vlastnosti, p\u0159i\u010dem\u017e jejich viskozita se li\u0161\u00ed v z\u00e1vislosti na distribuci velikosti \u010d\u00e1stic; jejich morfologii v\u0161ak lze \u0159\u00eddit tepeln\u00fdm zpracov\u00e1n\u00edm, aby se dos\u00e1hlo specifick\u00e9 viskozity pro konkr\u00e9tn\u00ed aplikace.<\/p>\n
Schopnost hydr\u00e1tu oxidu hlinit\u00e9ho zpomalovat ho\u0159en\u00ed spo\u010d\u00edv\u00e1 v jeho schopnosti uvol\u0148ovat vodn\u00ed p\u00e1ru p\u0159i zv\u00fd\u0161en\u00fdch teplot\u00e1ch, \u010d\u00edm\u017e ochlazuje materi\u00e1ly, \u0159ed\u00ed ho\u0159lav\u00e9 plyny a zpomaluje \u0161\u00ed\u0159en\u00ed po\u017e\u00e1ru. Toho je dosa\u017eeno vytvo\u0159en\u00edm bari\u00e9ry zachycuj\u00edc\u00ed kysl\u00edk a dal\u0161\u00ed ho\u0159lav\u00e9 plyny, co\u017e t\u011bmto molekul\u00e1m zt\u011b\u017euje p\u0159\u00edstup k povrchu a jeho ho\u0159en\u00ed.<\/p>\n
Hydr\u00e1ty oxidu hlinit\u00e9ho maj\u00ed velmi n\u00edzkou absorpci kysl\u00edku a vysokou reaktivitu s r\u016fzn\u00fdmi plyny, jako je oxid si\u0159i\u010dit\u00fd, sirovod\u00edk, oxid uhelnat\u00fd a oxidy dus\u00edku. D\u00edky t\u011bmto vlastnostem mohou slou\u017eit jako ide\u00e1ln\u00ed n\u00e1hrada oxidu si\u0159i\u010dit\u00e9ho v mnoha aplikac\u00edch, jako je pyrotechnika a v\u00fdbojky.<\/p>\n
Hydr\u00e1ty oxidu hlinit\u00e9ho se pou\u017e\u00edvaj\u00ed jako prekurzory pro v\u00fdrobu aktivovan\u00e9ho oxidu hlinit\u00e9ho (AA). Aktivovan\u00fd oxid hlinit\u00fd je pr\u016fmyslov\u00fd v\u00fdrobek vyr\u00e1b\u011bn\u00fd tepeln\u00fdm rozkladem hydroxid\u016f a oxihydroxid\u016f oxidu hlinit\u00e9ho. Nach\u00e1z\u00ed uplatn\u011bn\u00ed v r\u016fzn\u00fdch pr\u016fmyslov\u00fdch odv\u011btv\u00edch, zejm\u00e9na v pap\u00edrensk\u00e9m pr\u016fmyslu jako plnidlo pigmentu nebo n\u00e1t\u011brov\u00e9ho pigmentu a ve farmaceutick\u00e9m pr\u016fmyslu jako pomocn\u00e1 l\u00e1tka; r\u016fzn\u00e9 techniky p\u0159\u00edpravy vedou k r\u016fzn\u00fdm druh\u016fm por\u00e9zn\u00edho oxidu hlinit\u00e9ho s jedine\u010dn\u00fdmi vlastnostmi a mo\u017enostmi vyu\u017eit\u00ed; nap\u0159. kalcinac\u00ed bayeritu vznikaj\u00ed spinelov\u00e9 roviny (111), zat\u00edmco kalcinac\u00ed Al(OH)3 vznikaj\u00ed \u0161estikoordinovan\u00e9 ionty Al3+.<\/p>\n
D\u00edky n\u00edzk\u00e9mu bodu t\u00e1n\u00ed m\u00e1 oxid hlinit\u00fd vynikaj\u00edc\u00ed vlastnosti zpomaluj\u00edc\u00ed ho\u0159en\u00ed. M\u016f\u017ee pomoci zabr\u00e1nit \u0161\u00ed\u0159en\u00ed plamene v plastov\u00fdch materi\u00e1lech nebo chr\u00e1nit m\u00edsta n\u00e1chyln\u00e1 k po\u0161kozen\u00ed ohn\u011bm p\u0159ed dal\u0161\u00edm \u0161\u00ed\u0159en\u00edm. Krom\u011b toho je oxid hlinit\u00fd d\u00edky sv\u00fdm schopnostem pohlcovat oleje vhodn\u00fd jako prost\u0159edek proti plamen\u016fm s uhlovod\u00edky; nav\u00edc se stal neoceniteln\u00fdm jako p\u0159\u00edsada do maziv, aby se zabr\u00e1nilo degradaci stroj\u016f.<\/p>\n
Hlin\u00edk je hojn\u00fd p\u0159\u00edrodn\u00ed miner\u00e1l, kter\u00fd se vyr\u00e1b\u00ed jako kone\u010dn\u00fd produkt Bayerova procesu z\u00edsk\u00e1v\u00e1n\u00ed hlin\u00edku z bauxitu, obvykle sr\u00e1\u017een\u00edm rozpustn\u00fdch hydroxid\u016f hlin\u00edku z vody nebo reakc\u00ed trihydr\u00e1tu hlin\u00edku s hydroxidy alkalick\u00fdch kov\u016f za vzniku boehmitu, extr\u00e9mn\u011b metastabiln\u00ed a \u0161patn\u011b krystalizuj\u00edc\u00ed l\u00e1tky s ionty Al3+ obklopuj\u00edc\u00edmi mikropor\u00e9zn\u00ed oxyhydroxidy v alkalick\u00e9m prost\u0159ed\u00ed (31). 27Al MAS NMR ukazuje v\u00edce koordina\u010dn\u00edch \u00farovn\u00ed mezi Al3 + a Al3 + s n\u011bkolika koordina\u010dn\u00edmi vzory (31); plocha BET g-Al2O3 je p\u0159ibli\u017en\u011b 275 m2g-1 (41).<\/p>\n
Tepeln\u011b rozlo\u017een\u00fd oxid hlinit\u00fd m\u016f\u017ee m\u00edt podobu r\u016fzn\u00fdch polymorf\u016f. B\u011b\u017en\u00fdmi p\u0159\u00edklady jsou gibbsit (tak\u00e9 hydrargilit) a bayerit, oba vyr\u00e1b\u011bn\u00e9 Bayerov\u00fdm procesem; nordstrandit se vyskytuje jako sou\u010d\u00e1st severoamerick\u00fdch lo\u017eisek bauxitu; gibbsit se \u010dasto pou\u017e\u00edv\u00e1 pro keramick\u00e9 glazury, zat\u00edmco nordstrandit lze nal\u00e9zt ve smaltech a kamenin\u011b.<\/p>\n
Sr\u00e1\u017een\u00ed spo\u010d\u00edv\u00e1 v p\u0159em\u011bn\u011b gel\u016f gibsitu a pseudoboehmitu na boehmit pomoc\u00ed \u0159\u00edzen\u00e9ho tlaku vodn\u00ed p\u00e1ry, kdy\u017e teplota klesne pod 80 stup\u0148\u016f C; pak se jejich forma vr\u00e1t\u00ed zp\u011bt do p\u016fvodn\u00ed formy hydroxid\u016f oxidu hlinit\u00e9ho, kter\u00e9 se snadn\u011bji rozpou\u0161t\u011bj\u00ed ve vod\u011b; t\u00edm se disociuj\u00ed na taveninu a vznik\u00e1 snadno rozpustn\u00fd oxid hlinit\u00fd, kter\u00fd se s \u010dasem nebo vy\u0161\u0161\u00ed teplotou rozpou\u0161t\u00ed snadn\u011bji (60). P\u0159i vy\u0161\u0161\u00edch teplot\u00e1ch nebo za p\u0159\u00edsn\u011bj\u0161\u00edch podm\u00ednek st\u00e1rnut\u00ed se tento oxid hlinit\u00fd m\u016f\u017ee nakonec p\u0159em\u011bnit na dob\u0159e krystalizovan\u00fd boehmit (60).<\/p>\n
Trihydr\u00e1t oxidu hlinit\u00e9ho, b\u011b\u017en\u011b ozna\u010dovan\u00fd jako kalcinovan\u00fd oxid hlinit\u00fd a hydroxid hlinit\u00fd, je mimo\u0159\u00e1dn\u011b univerz\u00e1ln\u00ed plnivo. V plastov\u00fdch aplikac\u00edch slou\u017e\u00ed ke zv\u00fd\u0161en\u00ed neho\u0159lavosti a mechanick\u00fdch a tepeln\u00fdch vlastnost\u00ed r\u016fzn\u00fdch polymer\u016f; jeho v\u0161estrannost se jako plnivo dob\u0159e uplat\u0148uje tak\u00e9 ve skle, keramice a pap\u00edru. V\u00fdrobci pap\u00edru jej d\u00e1le pou\u017e\u00edvaj\u00ed jako n\u00e1t\u011brov\u00fd pigment a ke zv\u00fd\u0161en\u00ed nepr\u016fhlednosti a jasu r\u016fzn\u00fdch pap\u00edr\u016f; jeho alkalick\u00e1 povaha mu tak\u00e9 pom\u00e1h\u00e1 v n\u011bkter\u00fdch aplikac\u00edch p\u0159i \u00faprav\u011b vody.<\/p>\n
Hydratovan\u00fd oxid hlinit\u00fd je d\u00edky sv\u00e9 vysok\u00e9 reaktivit\u011b vynikaj\u00edc\u00ed surovinou pro v\u00fdrobu keramick\u00fdch t\u011bles a glazur a \u010dasto slou\u017e\u00ed jako ekonomick\u00e1 n\u00e1hrada p\u0159\u00edrodn\u00edch surovin, jako je \u017eivec a k\u0159emen. Je k dispozici v such\u00e9 i mokr\u00e9 form\u011b a lze jej rozeml\u00edt na \u010d\u00e1stice s r\u016fznou distribuc\u00ed velikosti ve fluidn\u00edch energetick\u00fdch ml\u00fdnech nebo v kulov\u00fdch ml\u00fdnech s keramickou v\u00fdstelkou.<\/p>\n
Rozemlet\u00fd hydr\u00e1t oxidu hlinit\u00e9ho p\u0159idan\u00fd do glazury nebo sklen\u011bn\u00e9 taveniny se rychle rozkl\u00e1d\u00e1 na oxid hlinit\u00fd a molekuly vody prost\u0159ednictv\u00edm exotermick\u00e9 endotermick\u00e9 reakce, co\u017e tomuto materi\u00e1lu prop\u016fj\u010duje vlastn\u00ed neho\u0159lavost a b\u011bhem t\u00e9to reakce vznik\u00e1 nekorozivn\u00ed a nejedovat\u00fd kou\u0159.<\/p>\n
Aby trihydr\u00e1t oxidu hlinit\u00e9ho \u00fa\u010dinn\u011b fungoval jako zpomalova\u010d ho\u0159en\u00ed, mus\u00ed b\u00fdt vystaven teplot\u00e1m vy\u0161\u0161\u00edm ne\u017e 220 \u00b0C. P\u0159i zah\u0159\u00e1t\u00ed na tuto \u00farove\u0148 se 3 molekuly vody na molekulu oxidu hlinit\u00e9ho odpa\u0159\u00ed do taveniny glazury ve form\u011b p\u00e1ry. Tento rozklad hydr\u00e1tu oxidu hlinit\u00e9ho mu zaji\u0161\u0165uje charakteristickou \u00farove\u0148 zpomalen\u00ed ho\u0159en\u00ed, kter\u00e1 se u jin\u00fdch plniv nevyskytuje.<\/p>\n
P\u0159\u00eddavek hydr\u00e1tu oxidu hlinit\u00e9ho do glazur a skel m\u016f\u017ee zv\u00fd\u0161it nepr\u016fhlednost t\u00edm, \u017ee v tavenin\u011b glazury vytv\u00e1\u0159\u00ed plynov\u00e9 bubliny, kter\u00e9 pom\u00e1haj\u00ed sn\u00ed\u017eit smr\u0161\u0165ov\u00e1n\u00ed p\u0159i v\u00fdpalu a z\u00e1rove\u0148 vytv\u00e1\u0159ej\u00ed leskl\u00fd povrch a zaji\u0161\u0165uj\u00ed n\u00edzkou m\u00edru smr\u0161\u0165ov\u00e1n\u00ed p\u0159i v\u00fdpalu. Krom\u011b toho je ide\u00e1ln\u00ed volbou pro v\u00fdrobu glazur, kter\u00e9 vy\u017eaduj\u00ed n\u00edzkou m\u00edru smr\u0161t\u011bn\u00ed p\u0159i su\u0161en\u00ed.<\/p>\n
Hydr\u00e1t oxidu hlinit\u00e9ho je vynikaj\u00edc\u00ed katalyz\u00e1tor, kter\u00fd vytv\u00e1\u0159\u00ed plynov\u00e9 bubliny v glazur\u00e1ch a emailech a zvy\u0161uje tak jejich kryvost Bayerov\u00fdm procesem. Nejen\u017ee nen\u00ed toxick\u00fd a m\u00e1 n\u00edzkou smr\u0161\u0165ovac\u00ed schopnost p\u0159i v\u00fdpalu, ale je tak\u00e9 cenov\u011b v\u00fdhodn\u00fd, snadno se s n\u00edm manipuluje, je ekonomick\u00fd a m\u00e1 velk\u00fd povrch - co\u017e nejsou \u0161patn\u00e9 vlastnosti pro pr\u016fmyslov\u00fd materi\u00e1l, jeho\u017e ro\u010dn\u00ed produkce dosahuje p\u0159ibli\u017en\u011b 100 milion\u016f tun! Takto vyroben\u00fd trihydr\u00e1t oxidu hlinit\u00e9ho se rozem\u00edl\u00e1 bu\u010f na bezvodou, nebo kalcinovanou formu pro pou\u017eit\u00ed jako integr\u00e1ln\u00ed slo\u017eka.<\/p>\n
Existuj\u00ed r\u016fzn\u00e9 polymorfy oxidu hlinit\u00e9ho, z nich\u017e ka\u017ed\u00fd m\u00e1 odli\u0161n\u00e9 vlastnosti zp\u016fsoben\u00e9 r\u016fzn\u00fdm po\u0159ad\u00edm stohov\u00e1n\u00ed, geometri\u00ed mezivrstvov\u00fdch a vnitrovrstvov\u00fdch vod\u00edkov\u00fdch vazeb a substitu\u010dn\u00edmi vzorci hydroxylov\u00fdch skupin na okrajov\u00fdch oktaedrech Al(OH)6. P\u0159esto jejich termodynamick\u00e1 stabilita z\u016fst\u00e1v\u00e1 podobn\u00e1 - existence m\u016f\u017ee sp\u00ed\u0161e z\u00e1viset na kinetice ne\u017e na termodynamick\u00fdch vlastnostech tohoto materi\u00e1lu.<\/p>\n
Mikropor\u00e9zn\u00ed gibbsitov\u00e9 gely oxidu hlinit\u00e9ho (pseudoboehmit a boehmit) lze vytvo\u0159it pe\u010dliv\u00fdm \u0159\u00edzen\u00edm proces\u016f gelace\/flokulace, st\u00e1rnut\u00ed a su\u0161en\u00ed. Nam\u00e1\u010den\u00ed gel\u016f ve vod\u011b v\u0161ak vede k nenapraviteln\u00e9 ztr\u00e1t\u011b plochy BET a p\u0159em\u011bn\u011b na nepor\u00e9zn\u00ed bayerit.<\/p>\n
V\u00fdsledkem plamenov\u00e9 hydrol\u00fdzy chloridu hlinit\u00e9ho p\u0159i vysok\u00fdch teplot\u00e1ch je jemn\u00fd pr\u00e1\u0161ek g-Al2O3 o pr\u016fm\u011brn\u00e9 velikosti \u010d\u00e1stic 10 nm a povrchu 130 m2g-1. \u010c\u00e1stice oxidu hlinit\u00e9ho maj\u00ed obvykle spinelovou m\u0159\u00ed\u017eku, a\u010dkoli mohou b\u00fdt p\u0159\u00edtomny i hexagon\u00e1ln\u00ed nebo kubick\u00e9 krystaly s t\u011bsn\u00fdm uspo\u0159\u00e1d\u00e1n\u00edm.<\/p>\n
Hydr\u00e1t oxidu hlinit\u00e9ho je jedn\u00edm z nejstabiln\u011bj\u0161\u00edch a nejroz\u0161\u00ed\u0159en\u011bj\u0161\u00edch materi\u00e1l\u016f z oxidu hlinit\u00e9ho, kter\u00fd se vyzna\u010duje vysok\u00fdm povrchem a n\u00edzkou m\u00edrou smr\u0161t\u011bn\u00ed p\u0159i v\u00fdpalu, d\u00edky \u010demu\u017e je vhodn\u00fd pro celou \u0159adu aplikac\u00ed. Krom\u011b toho je d\u00edky sv\u00fdm antikorozn\u00edm vlastnostem a zpomalov\u00e1n\u00ed ho\u0159en\u00ed vhodn\u00fd jako zpomalova\u010d ho\u0159en\u00ed; prob\u00edh\u00e1 v\u00fdzkum antikorozn\u00edch vlastnost\u00ed a jeho \u010d\u00e1stice se tak\u00e9 osv\u011bd\u010dily jako autokatalyz\u00e1tory a sou\u010d\u00e1sti palivov\u00fdch \u010dl\u00e1nk\u016f d\u00edky objev\u016fm, kter\u00e9 odhalily, jak \u010d\u00e1stice oxidu hlinit\u00e9ho reaguj\u00ed s vodou a vytv\u00e1\u0159ej\u00ed proudy plynu bohat\u00e9 na vod\u00edk, kter\u00e9 lze n\u00e1sledn\u011b spalovat jako palivo pro automobily a tryskov\u00e1 letadla!<\/p>","protected":false},"excerpt":{"rendered":"
Alumina has a complex chemical makeup, including various polymorphs that can be converted to high surface area forms through thermal […]<\/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":[6],"tags":[],"class_list":["post-123","post","type-post","status-publish","format-standard","hentry","category-alumina-knowledge"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/aluminaceramics.net\/cs\/wp-json\/wp\/v2\/posts\/123","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/aluminaceramics.net\/cs\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/aluminaceramics.net\/cs\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/aluminaceramics.net\/cs\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/aluminaceramics.net\/cs\/wp-json\/wp\/v2\/comments?post=123"}],"version-history":[{"count":1,"href":"https:\/\/aluminaceramics.net\/cs\/wp-json\/wp\/v2\/posts\/123\/revisions"}],"predecessor-version":[{"id":124,"href":"https:\/\/aluminaceramics.net\/cs\/wp-json\/wp\/v2\/posts\/123\/revisions\/124"}],"wp:attachment":[{"href":"https:\/\/aluminaceramics.net\/cs\/wp-json\/wp\/v2\/media?parent=123"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/aluminaceramics.net\/cs\/wp-json\/wp\/v2\/categories?post=123"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/aluminaceramics.net\/cs\/wp-json\/wp\/v2\/tags?post=123"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}