Cump\u0103r\u0103torii ne trimit \u00een continuare cereri de ofert\u0103 \u00een care scrie doar \u201cpulbere de alumin\u0103, 99%\u201d. Acest num\u0103r indic\u0103 faptul c\u0103 este vorba de Al\u2082O\u2083. Nu v\u0103 spune \u00eens\u0103 dac\u0103 pulberea se va sinteriza la 1550 \u00b0C, dac\u0103 va lustrui o suprafa\u021b\u0103 de etan\u0219are sau dac\u0103 va r\u0103m\u00e2ne \u00eentr-o matrice turnabil\u0103 f\u0103r\u0103 a se densifica. O discu\u021bie constructiv\u0103 \u00eencepe cu patru elemente: sod\u0103, suprafa\u021ba specific\u0103, dimensiunea particulelor \u0219i gradul de calcinare \u00een direc\u021bia alfa.<\/p>\n
Majoritatea pulberilor industriale au la origine hidratul Bayer. Le calcinin\u0103m, de obicei la temperaturi cuprinse \u00eentre 1100 \u0219i 1500 \u00b0C, pentru a elimina apa \u0219i a le transforma \u00een \u03b1-Al\u2082O\u2083. Intensitatea calcin\u0103rii determin\u0103 dimensiunea cristalelor \u0219i suprafa\u021ba specific\u0103 BET. O pulbere u\u0219or calcinat\u0103 poate prezenta o suprafa\u021b\u0103 specific\u0103 de c\u00e2\u021biva metri p\u0103tra\u021bi pe gram \u0219i poate con\u021bine \u00eenc\u0103 faze de tranzi\u021bie reziduale. O pulbere calcinat\u0103 intens scade la valori cuprinse \u00eentre 0,3 \u0219i 2 m\u00b2\/g, formeaz\u0103 cristale primare mai grosiere \u0219i prezint\u0103 \u00een principal alfa. Alumina reactiv\u0103 este versiunea m\u0103cinat\u0103 a acestei idei: D50 adesea \u00een jur de 1\u20132 \u03bcm, BET \u00een intervalul 1\u20135 m\u00b2\/g, con\u021binut ridicat de alfa, conceput\u0103 pentru compactare \u0219i sinterizare. Acesta este un material diferit de o alumin\u0103 calcinat\u0103 nem\u0103cinat\u0103, cu un D50 de 60\u201380 \u03bcm.<\/p>\n
Soda este impuritatea pe care oamenii o subestimeaz\u0103. Calcinatele normale de sod\u0103 au un con\u021binut de Na\u2082O cuprins \u00eentre 0,3 \u0219i 0,5%. Cele cu con\u021binut redus de sod\u0103 se situeaz\u0103 mai aproape de 0,05\u20130,15%. Cele cu con\u021binut extrem de redus coboar\u0103 sub 0,03%. Sodiul ac\u021bioneaz\u0103 ca un flux. \u00centr-o c\u0103r\u0103mid\u0103 refractar\u0103, acest lucru poate fi acceptabil. \u00cen cazul unei piese de uzur\u0103 cu con\u021binut ridicat de alumin\u0103, al unui substrat sau al unui izolator de bujie, sodiul rezidual determin\u0103 cre\u0219terea granula\u021biei, scade rezisten\u021ba \u0219i afecteaz\u0103 performan\u021ba electric\u0103. Dac\u0103 piesa trebuie s\u0103 fie alb\u0103, dens\u0103 \u0219i f\u0103r\u0103 interferen\u021be electrice, nu pornim de la un grad de sodiu de baz\u0103 \u0219i nu ne baz\u0103m pe faptul c\u0103 cuptorul va remedia problema.<\/p>\n
Distribu\u021bia granulometric\u0103 reprezint\u0103 cealalt\u0103 jum\u0103tate a procesului de compactare. O pulbere reactiv\u0103 fin\u0103, monomodal\u0103, umple matricea. O granula\u021bie mai larg\u0103 poate reduce necesarul de ap\u0103 \u00eentr-un material turnabil dac\u0103 este plasat\u0103 \u00eentre agregatul tabular \u0219i cea mai fin\u0103 frac\u021bie reactiv\u0103. Dac\u0103 introduce\u021bi o valoare D90 incorect\u0103 \u00eentr-o past\u0103, ve\u021bi ob\u021bine fie o roc\u0103 care nu se dezareaz\u0103, fie o suspensie care se depune \u00eenainte de turnare. Pulberile de lustruire acord\u0103 o importan\u021b\u0103 mai mare durit\u0103\u021bii \u0219i dimensiunii cristalelor dec\u00e2t sinterabilit\u0103\u021bii. Cristalele grosiere, calcinate la temperaturi ridicate, taie. Materialul fin, calcinat la temperaturi sc\u0103zute, finiseaz\u0103. Aceea\u0219i compozi\u021bie chimic\u0103 pe sac. Roluri opuse.<\/p>\n
De asemenea, ni se cere s\u0103 trat\u0103m granulele fuzionate \u0219i cele tabulare ca \u0219i cum ar fi pulbere. Dar nu sunt. Alumina fuzionat\u0103 este topit\u0103 \u0219i m\u0103cinat\u0103. Alumina tabular\u0103 este sinterizat\u0103 la temperaturi cuprinse \u00eentre 1800 \u0219i 1900 \u00b0C, form\u00e2nd pl\u0103ci dense, apoi este m\u0103cinat\u0103 pentru a ob\u021bine agregat. Acestea constituie scheletul unui amestec. Pulberile calcinate \u0219i reactive sunt particulele fine care trebuie s\u0103 se lege \u00eentre ele.<\/p>\n
Dac\u0103 specifica\u021bi pulbere de alumin\u0103, men\u021biona\u021bi pe fi\u0219\u0103 con\u021binutul de Na\u2082O, BET, D50\/D90, con\u021binutul de alfa \u0219i LOI \u00eenainte de a negocia pre\u021bul. Un Al\u2082O\u2083 de 99,5% cu 0,4% sod\u0103 \u0219i o dimensiune median\u0103 de 70 \u03bcm nu se va comporta ca un material reactiv cu con\u021binut redus de sod\u0103 la 1,5 \u03bcm, indiferent c\u00e2t de asem\u0103n\u0103toare ar p\u0103rea compozi\u021bia. Cuptorul nu remediaz\u0103 o alegere gre\u0219it\u0103 a pulberii. Pur \u0219i simplu face ca gre\u0219eala s\u0103 devin\u0103 definitiv\u0103.<\/p>","protected":false},"excerpt":{"rendered":"
Alumina Powder Is Not One Spec. Soda and Surface Area Decide What It Does. Buyers still send us RFQs that […]<\/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":"default","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":"default","adv-header-id-meta":"","stick-header-meta":"","header-above-stick-meta":"","header-main-stick-meta":"","header-below-stick-meta":"","astra-migrate-meta-layouts":"set","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":[13],"tags":[],"class_list":["post-116","post","type-post","status-publish","format-standard","hentry","category-knowledge"],"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/aluminapowder.net\/ro\/wp-json\/wp\/v2\/posts\/116","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/aluminapowder.net\/ro\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/aluminapowder.net\/ro\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/aluminapowder.net\/ro\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/aluminapowder.net\/ro\/wp-json\/wp\/v2\/comments?post=116"}],"version-history":[{"count":1,"href":"https:\/\/aluminapowder.net\/ro\/wp-json\/wp\/v2\/posts\/116\/revisions"}],"predecessor-version":[{"id":117,"href":"https:\/\/aluminapowder.net\/ro\/wp-json\/wp\/v2\/posts\/116\/revisions\/117"}],"wp:attachment":[{"href":"https:\/\/aluminapowder.net\/ro\/wp-json\/wp\/v2\/media?parent=116"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/aluminapowder.net\/ro\/wp-json\/wp\/v2\/categories?post=116"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/aluminapowder.net\/ro\/wp-json\/wp\/v2\/tags?post=116"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}