Must\u0103\u021bile de carbur\u0103 de siliciu, particule monocristaline de dimensiuni de ordinul micronilor cu propriet\u0103\u021bi fizice \u0219i chimice remarcabile, au st\u00e2rnit un interes semnificativ \u00een cercetare datorit\u0103 aplica\u021biilor lor extinse \u00een numeroase domenii, inclusiv materiale structurale la temperaturi ridicate \u0219i ceramic\u0103 pentru scule.<\/p>\n
Ceramica Mullite este un material refractar foarte stabil din punct de vedere chimic, cu propriet\u0103\u021bi mecanice \u0219i fizice superioare, cum ar fi duritatea ridicat\u0103 \u0219i rezisten\u021ba la fluaj la temperatur\u0103, \u00eens\u0103 rezisten\u021ba la rupere r\u0103m\u00e2ne relativ sc\u0103zut\u0103. Must\u0103\u021bile de SiC \u00eembun\u0103t\u0103\u021besc semnificativ aceast\u0103 proprietate.<\/p>\n
Must\u0103\u021bile de carbur\u0103 de siliciu sunt fibre monocristaline de dimensiuni de ordinul micronilor, cu o structur\u0103 asem\u0103n\u0103toare cu cea a diamantului, care au calit\u0103\u021bi unice de rezisten\u021b\u0103 ridicat\u0103, rigiditate, rezisten\u021b\u0103 chimic\u0103 \u0219i stabilitate la temperatur\u0103, ceea ce le face un excelent material de \u00eent\u0103rire pentru ceramic\u0103, metale \u0219i compozite polimerice.<\/p>\n
Umpluturile minerale pot fi utilizate pentru a consolida ceramica, cresc\u00e2nd \u00een acela\u0219i timp ductilitatea \u0219i duritatea, rezisten\u021ba la oxidare, rata de expansiune termic\u0103 \u0219i rezisten\u021ba la rupere. \u00cen plus, acestea pot fi ad\u0103ugate la compozitele cu matrice polimeric\u0103 pentru a reduce necesarul de materiale de umplutur\u0103, f\u0103c\u00e2ndu-le \u00een acela\u0219i timp mai rezistente la fisurare, la deformare \u0219i la deteriorarea prin oboseal\u0103.<\/p>\n
Must\u0103\u021bile pot fi fabricate prin diferite tehnici, inclusiv reducerea carbotermic\u0103 a siliciului, reac\u021bia chimic\u0103 dintre halogenurile de siliciu \u0219i CCl4 sau CVD cu catalizatori metalici. Din nefericire, calitatea \u0219i dimensiunea lor este adesea limitat\u0103 de aglomerare \u0219i anizotropie (Wright, 2006). Un proces mai avansat implic\u0103 cre\u0219terea vapori-lichid-solid care permite plasarea must\u0103\u021bilor \u00een profunzimea porilor din substraturile poroase \u0219i ofer\u0103 propriet\u0103\u021bi dezirabile.<\/p>\n
Must\u0103\u021bile au fost studiate \u0219i comparate cu fibrele de subproduse industriale \u00een suspensie \u00een aer pentru a stabili orice risc pentru lucr\u0103torii care le manipuleaz\u0103, f\u0103r\u0103 a se constata c\u0103 must\u0103\u021bile de SiC prezint\u0103 riscuri respiratorii semnificative. Rezultatele cercet\u0103rii au concluzionat c\u0103 \u0219uvi\u021bele de SiC nu prezint\u0103 niciun pericol major atunci c\u00e2nd sunt manipulate.<\/p>\n
Carbura de siliciu a fost sintetizat\u0103 pentru prima dat\u0103 \u00een mod artificial de Edward Acheson \u00een 1891 ca material abraziv cunoscut sub numele de carborundum (Encyclopedia Britannica, 2014). De atunci, a fost produs\u0103 \u00een mas\u0103 folosind nisip de cuar\u021b \u0219i carbon \u00eenc\u0103lzit la temperaturi ridicate pentru a forma loturi de carbur\u0103 de siliciu pe scar\u0103 larg\u0103, care \u00ee\u0219i g\u0103se\u0219te utilizarea \u00een mai multe domenii industriale datorit\u0103 rezisten\u021bei sale excep\u021bionale, avantajului de greutate \u0219i stabilit\u0103\u021bii la temperaturi ridicate, precum \u0219i datorit\u0103 faptului c\u0103 este foarte rezistent\u0103 la expunerea la radia\u021bii; garniturile ceramice \u0219i duzele de sablare utilizeaz\u0103 carbur\u0103 de silicon, \u00een timp ce \u00eenlocuirea durabil\u0103 a substan\u021belor din azbest, printre altele.<\/p>\n
Carbura de siliciu (SiC) este un compus semimetalic alc\u0103tuit din siliciu \u0219i carbon, cu un punct de topire de 2260 grade Celsius \u0219i o presiune sc\u0103zut\u0103 a vaporilor care \u00eel face insolubil \u00een ap\u0103, dar solubil \u00een alcool \u0219i eter; cu toate acestea, datorit\u0103 expunerii la aer la temperatura camerei, se degradeaz\u0103 rapid, ceea ce duce la o degradare rapid\u0103 \u00een timp. SiC poate fi g\u0103sit ca abraziv \u00een h\u00e2rtia abraziv\u0103, precum \u0219i \u00een uneltele de acoperire, cum ar fi uneltele de sablare, precum \u0219i \u00een discurile de rectificat sau alte echipamente de prelucrare.<\/p>\n
Must\u0103\u021bile de SiC pot fi periculos de toxice pentru celule, distrug\u00e2nd membranele celulare \u0219i duc\u00e2nd la moartea celulelor. Studiile efectuate pe celule fibroblaste de \u0219oarece au demonstrat citotoxicitatea acestora prin inducerea de muta\u021bii ale ADN-ului, cre\u0219terea con\u021binutului total de ADN celular \u0219i ducerea la transformare malign\u0103 - aceste efecte fiind diminuate atunci c\u00e2nd sunt acoperite cu agen\u021bi tensioactivi netoxici. Atunci c\u00e2nd au fost testate \u00eempotriva celulelor epiteliale traheale ciliate umane, acestea s-au dovedit a fi mai toxice dec\u00e2t fibrele de subproduse industriale, cum ar fi azbestul \u0219i sulfura de nichel, fiind \u00een acela\u0219i timp mai pu\u021bin d\u0103un\u0103toare dec\u00e2t talcul \u0219i dioxidul de titan.<\/p>\n
Must\u0103\u021bile de carbur\u0103 de siliciu sunt un material de armare ideal pentru \u00eent\u0103rirea ceramicii, a metalelor \u0219i a compozitelor polimerice. Propriet\u0103\u021bile lor includ rezisten\u021b\u0103 ridicat\u0103, duritate, iner\u021bie chimic\u0103 \u0219i rezisten\u021b\u0103 la temperatur\u0103, precum \u0219i o rezisten\u021b\u0103 \u00eembun\u0103t\u0103\u021bit\u0103 la oxidare a materialelor, cum ar fi materialele ceramice din oxi-carbur\u0103 de siliciu, care au fost studiate pe scar\u0103 larg\u0103 ca unelte, componente pentru motoare \u0219i ceramic\u0103 rezistent\u0103 la uzur\u0103 - \u00een func\u021bie de chimia, structura \u0219i dimensiunea cristalelor sintetizate prin reducere carbotermic\u0103, CVD sau combustie de produse reziduale, cum ar fi coaja de orez.<\/p>\n
Cu toate acestea, propriet\u0103\u021bile mecanice ale acestora sunt cu mult inferioare celor ale siliciului cristalin monolit (c-Si). Pentru a \u00eembun\u0103t\u0103\u021bi rezisten\u021ba la trac\u021biune \u0219i la oboseal\u0103 a acestor materiale, cercet\u0103torii le-au modificat cu materiale organice sau cu fibre anorganice cunoscute sub numele de must\u0103\u021bi SiC pentru a \u00eembun\u0103t\u0103\u021bi rezisten\u021ba la compresiune \u0219i la trac\u021biune, precum \u0219i pentru a reduce concentra\u021bia de tensiuni \u00een jurul acestora \u00een timpul ruperii. Aceast\u0103 modificare a crescut \u00een mod semnificativ rezisten\u021ba la compresiune, reduc\u00e2nd \u00een acela\u0219i timp concentra\u021bia de tensiuni \u00een timpul ruperii.<\/p>\n
Ad\u0103ugarea de must\u0103\u021bi de SiC la o matrice vitroceramic\u0103 \u00eembun\u0103t\u0103\u021be\u0219te semnificativ rezisten\u021ba \u0219i tenacitatea acesteia, men\u021bin\u00e2nd \u00een acela\u0219i timp u\u0219urin\u021ba form\u0103rii sticlei \u0219i \u00eembun\u0103t\u0103\u021bind performan\u021ba tribologic\u0103. \u00cen plus, poate cre\u0219te ductilitatea, precum \u0219i limita elastic\u0103 Hugoniot cu c\u00e2teva ordine de m\u0103rime; \u00een plus, morfologia fracturii sale demonstreaz\u0103 acest lucru prin prezen\u021ba multor gropi\u021be \u0219i muchii de rupere, ceea ce indic\u0103 comportamentul s\u0103u ductil.<\/p>\n
Carbura de siliciu (SiC) este un compus chimic extrem de dur, format din siliciu \u0219i carbon, care se g\u0103se\u0219te \u00een mod natural sub form\u0103 de piatr\u0103 pre\u021bioas\u0103 moissanit, dar versiunile de serie au fost produse \u00eenc\u0103 din 1893 sub form\u0103 de pulbere \u0219i cristale pentru a fi utilizate ca abraziv. Carbura de siliciu este utilizat\u0103, de asemenea, \u00een aplica\u021bii care necesit\u0103 o rezisten\u021b\u0103 ridicat\u0103, cum ar fi discurile de fr\u00e2n\u0103 ceramice pentru automobile \u0219i vestele antiglon\u021b, precum \u0219i garniturile de etan\u0219are a arborelui de pomp\u0103; punctul s\u0103u de topire \u00eei permite s\u0103 reziste la temperaturi extreme f\u0103r\u0103 a se fisura sau deforma \u00een timp.<\/p>\n
Propriet\u0103\u021bile termice ale must\u0103\u021bilor de SiC depind \u00een mare m\u0103sur\u0103 de microstructura, chimia de suprafa\u021b\u0103 \u0219i dimensiunea acestora. Cu o presiune sc\u0103zut\u0103 a vaporilor \u0219i o stabilitate de p\u00e2n\u0103 la 1650 grade Celsius, aceste \u0219uvi\u021be pot fi utilizate ca \u00eent\u0103rituri \u00een diverse materiale, cum ar fi metalele \u0219i polimerii, \u00eembun\u0103t\u0103\u021bind rezisten\u021ba, tenacitatea, iner\u021bia chimic\u0103 \u0219i rezisten\u021ba la oxidare, prelungind \u00een acela\u0219i timp durata de via\u021b\u0103.<\/p>\n
Analiza microstructurii must\u0103\u021bilor de SiC poate fi efectuat\u0103 cu ajutorul microscopiei electronice de scanare \u0219i al difrac\u021biei de raze X. Acestea constau \u00een structuri policristaline alc\u0103tuite din poliprotipuri 3C beta-SiC \u0219i 6H-SiC; o examinare suplimentar\u0103 a ar\u0103tat c\u0103 regiunile cristaline posed\u0103 densit\u0103\u021bi de defecte plane mai mari dec\u00e2t regiunile amorfe, datorit\u0103 micro\u021besuturilor formate pe planurile 1 1 1 1 care exercit\u0103 efecte semnificative at\u00e2t asupra suprafe\u021belor de rupere la trac\u021biune, c\u00e2t \u0219i la \u00eencovoiere ale nanocompozitelor 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\/ro\/wp-json\/wp\/v2\/posts\/363","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ceramicatijolart.com\/ro\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ceramicatijolart.com\/ro\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ceramicatijolart.com\/ro\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ceramicatijolart.com\/ro\/wp-json\/wp\/v2\/comments?post=363"}],"version-history":[{"count":1,"href":"https:\/\/ceramicatijolart.com\/ro\/wp-json\/wp\/v2\/posts\/363\/revisions"}],"predecessor-version":[{"id":364,"href":"https:\/\/ceramicatijolart.com\/ro\/wp-json\/wp\/v2\/posts\/363\/revisions\/364"}],"wp:attachment":[{"href":"https:\/\/ceramicatijolart.com\/ro\/wp-json\/wp\/v2\/media?parent=363"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ceramicatijolart.com\/ro\/wp-json\/wp\/v2\/categories?post=363"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ceramicatijolart.com\/ro\/wp-json\/wp\/v2\/tags?post=363"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}