Application of sol-gel technology for production of ceramic nanocomposites and functional coatings
Date
2015-04-20
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Abstract
Kosmose-, lennuki- ja energiatehnoloogia tormiline areng on tekitanud vajaduse uudsete nano-komposiitmaterjalide ning funktsionaalsete pinnakatete järele, mida kasutatakse kaasaegsete seadmete ja konstruktsioonide väljatöötamisel. Materjalid peavad vastu pidama ekstreemsetele oludele kaotamata seejuures oma funktsionaalsust. Selleks otstarbeks sobivad metallkarbiidide ja -oksiidide komposiidid ning pinnakatted, millel on äärmuslik kulumiskindlus ning mis kannatavad kõrgeid töötemperatuure, samas vastu pidades temperatuurikõikumistele. Sarnased nõuded materjalidele on järjest enam ka meie igapäevaellu jõudnud.
Käesoleva töö eesmärgiks oli kõvade keraamiliste nano-komposiitmaterjalide ja funktsionaalsete katete väljatöötamine lähtudes sool-geel tehnoloogiast. Eesmärgi saavutamiseks läheneti probleemile mitmest aspektist: töö hõlmas sool-geel tehnoloogia kasutamist, materjalide töötlust ja katsetamist kõrgetel temperatuuridel, tulemi täppis-karakteriseerimist ja nano-osiste mehaaniliste omaduste selgitamist.
Sool-geel meetodi kasutamise üheks peamiseks eeliseks alternatiivide ees on, et lähteained segatakse kokku vedelas faasis ehk molekulaarsel tasandil, mille tulemusena saadakse ühtlaselt jaotunud komposiitmaterjalid. Töös näidati, et väljatöötatud meetodiga valmistatud lähteainete kasutamisel on võimalik oluliselt vähendada karbiidsete komposiitmaterjalide karbotermilise taandamise temperatuuri. Erilist tähelepanu pöörati titaan-tsirkooniumkarbiidi segu (TiC-ZrC), titaankarbiidi/ süsiniknanotorude komposiidi (TiC/MWCNT) ja titaanoksiidiga kaetud hõbeda nanotraatide (TiO2/AgNW) sünteesile ning karakteriseerimisele. Ühedimensionaalsete nanoosakeste täpsemaks tundmaõppimiseks konstrueeriti kõrglahutusega elektronmikroskoobi sisse spetsiaalne seade osakeste mehaaniliste omaduste väljaselgitamiseks. Nanostruktuuride mehaaniliste omaduste määramine aitab mõista seoseid nende suuruse, geomeetria ja koostise vahel. Saadud teave aitab komposiitmaterjalidesse funktsionaalseks täitematerjaliks või tugevdavaks armatuuriks sobivaid nanostruktuure valida. Töös selgitati välja näiteks, kas üksikuid alumiiniumoksiid(Al2O3)fiibreid ja hõbeda nanotraate on võimalik painutada elastselt miljon tsüklit.
The conventional industry is undergoing a dramatic change towards an innovative, high-technology, knowledge-based grounds. Increasing competition on the global market constantly demands for materials with advanced properties and producing technology. During recent decades researchers have paid great attention to new materials that are stable at extreme environmental conditions as candidates for technological applications like supersonic flights and rockets. Metal carbides and oxides are promising candidates for extreme environmental conditions due to their excellent and unique combination of high melting point, good thermal-shock resistance and high hardness. The development of nanocomposites and nanostructured coatings are more relevant and preferable research directions in modern material science. The particular aim of this thesis is related to elaboration of ceramic nanocomposites and functional coatings with desired properties by sol-gel method. It is chosen since in contrast to conventional ceramic materials synthesis methods, in sol-gel process reactants are mixed together in liquid state at molecular level, the synthesis conditions enable to decrease synthesis temperatures and prepare homogeneous and pure multi component systems. In particular, the thesis describes the synthesis of titanium / zirconium carbide blend (TiC-ZrC), titanium carbide / carbonnanotube composites (TiC/CNT) and titanium oxide / silver nanowires (AgNW/TiO2) nano-composites precursors. The problems of dispersion and thermal stability of filler material are treated. Moreover, the thesis reports mechanical characterisation of individual nanofillers like Al2O3 nanofibers and AgNW using advanced experimental set-up installed inside a scanning electron microscope. Development and construction of experimental equipment are also involved. As a part of the study, the thesis also includes development of experimental set-up, which was used for in situ SEM mechanical characterisation of individual one-dimensional nanostructures (1DNS) served as reinforcing phase or functional filler in the considered nanocomposites.
The conventional industry is undergoing a dramatic change towards an innovative, high-technology, knowledge-based grounds. Increasing competition on the global market constantly demands for materials with advanced properties and producing technology. During recent decades researchers have paid great attention to new materials that are stable at extreme environmental conditions as candidates for technological applications like supersonic flights and rockets. Metal carbides and oxides are promising candidates for extreme environmental conditions due to their excellent and unique combination of high melting point, good thermal-shock resistance and high hardness. The development of nanocomposites and nanostructured coatings are more relevant and preferable research directions in modern material science. The particular aim of this thesis is related to elaboration of ceramic nanocomposites and functional coatings with desired properties by sol-gel method. It is chosen since in contrast to conventional ceramic materials synthesis methods, in sol-gel process reactants are mixed together in liquid state at molecular level, the synthesis conditions enable to decrease synthesis temperatures and prepare homogeneous and pure multi component systems. In particular, the thesis describes the synthesis of titanium / zirconium carbide blend (TiC-ZrC), titanium carbide / carbonnanotube composites (TiC/CNT) and titanium oxide / silver nanowires (AgNW/TiO2) nano-composites precursors. The problems of dispersion and thermal stability of filler material are treated. Moreover, the thesis reports mechanical characterisation of individual nanofillers like Al2O3 nanofibers and AgNW using advanced experimental set-up installed inside a scanning electron microscope. Development and construction of experimental equipment are also involved. As a part of the study, the thesis also includes development of experimental set-up, which was used for in situ SEM mechanical characterisation of individual one-dimensional nanostructures (1DNS) served as reinforcing phase or functional filler in the considered nanocomposites.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone.
Keywords
sool-geel protsessid, nanomaterjalid, komposiitmaterjalid, keraamilised materjalid, kattematerjalid, sol-gel processes, nanomaterials, composite materials, ceramic materials, coating materials