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Dizajniranje mikrostrukture alumina-cirkonia kompozita dobijenog sol-gel metodom / Designing of the Sol-Gel Derived Alumina-Zirkonia Composite Microstructures

<p><strong>Apstrakt je obrađen tehnologijama za optičko prepoznavanje teksta (OCR).</strong></p><p>Dobro je poznato da se žilavost keramičkih matrica znatno može povećati sa cirkonia česticama iz razloga &scaron;to se transformacijom tetragonalne u monokliničnu fazu cirkonie znatna količina energije može apsorbovati, a koja bi inače bila pukotini na raspolaganju za njeno napredovanje.<br />U ovom radu je primenom različitih varijanti sol-gel procesiranja menjana priroda i skala veličine polaznih alumina i cirkonia čestica u cilju dizajniranja mikrostrukture alumina-cirkonia kompozita. Ukazano je na postojanje interakcije između cirkonie i alumine, &scaron;to je i pored &scaron;irokog proučavanja alumina-cirkonia kompozita skoro nepoznata pojava. Pokazano je takođe da stepen interakcije zavisi od prirode i veličine polaznih čestica, pri čemu je najveći kod alkoksidnih matričnih kompozita sa cirkoniom dodanom u obliku veoma finih sol čestica ili cirkonjjumovih soli (na primer cirkoniju oksihlorid), a najmanji kod čestičnih matričnih kompozita kod kojih su kori&scaron;čene guste čestice (alumine-cirkonie).<br />Potvrđeno je da stepe interakcije određuje mikrostrukturni razvoj kompozita u toku zagrevanja. Uticaj interakcije na mikrostrukturni razvoj alumina-cirkonia kompozita je praćen različitim metodama karakterizacije (merenje gustine, IR spektroskopija, rentgenska difrakcija, diferencijalno termijska analiza i skening elektronska mikroskopija). Posle finalnog sinterovanja i bez toplog presovanja su dostignute gustine bliske teorijskim, a postignute mehaničke osobine merene su tvrdoća i žilavost) su razmatrane u funkciji mikorstrukturnih parametara. Utvrđeno je da je dominantan mehanizam povećanja žilavosti naponom indukovano povećanje žilavosti, a maksimalno postignuta vrednost odnosa povećanja žilavosti prema žilavosti matrice iznosi K<sub>s</sub>/K<sub>o</sub> = 0.69 (&scaron;to odgovara vrednosti kritičnog faktora intenziteta napona od K<sub>c</sub>=5.4 MPa m<sup>1/2</sup>). Na kraju treba jo&scaron; istaći da eksperimentalno dobijene vrednosti žilavosti dobro fituju izvedenu zavisnost doprinosa transformacionog povećanja žilavosti od veličine tetragonalni cirkonia čestica.</p> / <p><strong>Abstract was processed by technology for Optical character recognition (OCR).</strong></p><p>It is already known that fracture toughness of the ceramic matrices could be increased by dispersing of zirconia particles. The role of zirconia is in the absorption of a substantial amount of energy, which could be consumed by crack advansing, with the transformation from tetragonal to monoclinic simetry.<br />In the presented study the microstructure of the alumina-zirconia composites were designed by changing the nature and the size of original alumina and zirconia panicles, by using a different types of the sol-gel processing methods. It is pointed out on the mutual interaction between zirconia and alumina, which is almost unknown phenomena inspite of very intensive investigation of the alumina-zirconia composite system. The mutual interaction depends on the nature and size of the original particles. The largest interaction exists in alkoxide matrix composites with zirconia added in a form of very fine so! particles or zirconijum-salts (zirconium-oxychloride), and the smallest in the particulate matrix composites with dense panicles (alumina or zirconia). It is confirmed that interaction between zirconia and alumina determine the microstructure development of the heat treated composite samples. The influence of the interaction on the microstructure development was characterised by different method: density measurement, IR spectroscopy. X-ray diffraction, differential thermal analysis and scanning electron microscopy. After final sintering without hot pressing the density reach very high values (in some case &gt;99 % theoretical density). Mechanical properties (hardnes and fracture toughness) were studied in the function of the microstructural parameters. It was shown that the stress induced transformation toughening is a dominant mechanism in the sol-gel processed composites (with zirconia partcles less than critical size)., and the maximal value of the AKc/Ko = 0.69 corresponds to the fracture toughness of Kc = 5.4 MPa m1/2. Experimental fracture toughness data fit the analytically derived functional dependent between fracture toughness and zirconia particle sizes.</p>

Identiferoai:union.ndltd.org:uns.ac.rs/oai:CRISUNS:(BISIS)71430
Date31 August 1995
CreatorsSrdić Vladimir
ContributorsRadonjić Ljiljana, Isakovski Slobodan, Ranogajec Jonjaua
PublisherUniverzitet u Novom Sadu, Tehnološki fakultet Novi Sad, University of Novi Sad, Faculty of Technology at Novi Sad
Source SetsUniversity of Novi Sad
LanguageSerbian
Detected LanguageEnglish
TypePhD thesis

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