Štúdium nanokompozitov pre elektrické izolácie
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Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií
Abstract
Predkladaná práca sa zaoberá štúdiom dielektrických vlastností epoxidových nano-kompozitov s nanočasticami anorganických oxidov. Tieto nanokompozity majú sľubné technologické využitie pre elektrické izolácie vzhľadom k ich vyššej odolnosti voči čiastočným výbojom, avšak nie sú dostupné informácie o ich chovaní behom ich stárnutia. Pokiaľ by malo dôjsť k aspoň čiastočne hromadnej náhrade doterajších epoxidových izolácií izoláciami na základe nanokompozitov, znalosti zmien dielektrických vlastností v priebehu ich prevádzky sú nevyhnutné. V rámci DP boli vytvorené súbory epoxidov bez plniva a s plnivami Al2O3, WO3, TiO2 a SiO2 v podobe nanopráškov a v koncentráciách do 12 % hm. Tieto súbory boli jednak merané pred starnutím, jednak boli vystavené dlhodobému (až 5000 hodín) starnutiu pri zvýšených teplotách 200, 250 a 300 °C a v niektorých prípadoch i 330 a 360 °C a merané v priebehu starnutia zhruba v časovej logaritmickej rade 1, 2, 5, 10, 20, 50, 100, 200, 500, 1000, 2000 a 5000 hodín. Merané boli komplexná permitivita , vnútorná rezistivita i a stratový činiteľ tg pri teplotách od -153 °C do +167 °C a vo frekvenčnom rozsahu 10-2 do 106 Hz. Okrem dielektrických meraní boli ku skúmaniu zmien nanokompozitov použité aj ďalšie metódy, menovite: infračervená spektroskopia s Fourierovou transformáciou (FTIR), termogravimetrická analýza (TGA), diferenciálna skenovacia kalorimetria (DSC) a elektrónový mikroskop (SEM). Experimenty preukázali, že materiály s rôznymi plnivami reagujú pri rovnakých koncentráciách rôznymi spôsobmi. Pridanie iba nanočastíc, bez doplnku mikročastíc, v pomerne nízkej koncentrácii (max 12 % hmotnostných) nepostačovalo k dosiahnutiu zásadných zmien v dielektrickom spektru; dochádzalo iba k zmenám intenzity a k posunom relaxácií a v relaxačných mapách. Z výraznejších zmien je treba uviesť zmeny relaxácie vo vzorkách s plnivom SiO2, ktoré pri vzrastajúcej koncentrácii v epoxidovej matrice spôsobí pokles elektrickej vodivosti vo výslednom nanokompozite. Odlišne sa prejavilo plnivo TiO2. Rôzne koncentrácie TiO2 sa výrazne prejavujú v oblasti medzi relaxáciou a relaxáciou . U nanokompozitov plnených TiO2 sa neobjavuje jednoznačná závislosť elektrickej vodivosti na koncentrácii nanoplniva. Vážnym problémom všeobecne bola príprava nanokompozitu s rovnomerným rozdelením nanočastíc. Príprava takéhoto nanokompozitu nebola jednoduchá a v priemyslových aplikáciách bude treba venovať tejto problematike osobitú pozornosť tak, aby nedochádzalo k vytváraniu nežiaducich zhlukov. V rámci práce bola vypracovaná metodika výroby epoxidového nanokompozitu s čo možno najrovnomerrnejším rozdelením nanočastíc.
The dissertation thesis submitted deals with the study of dielectric properties of epoxy nanocomposites containing nanoparticles of inorganic oxides. These nanocomposites may have a promising technologic application for electric insulations in view of their higher resistance against partial discharges; yet information about their behavior in the course of ageing is not available. If at least a partial mass replacement of the currently used epoxy insulation with nanocomposite-based insulations is due to occur, the knowledge of the changes of their dielectric properties in the course of their operation will become indispensable. Within the framework of this dissertation, ensembles of samples of epoxy resins without fillers and with Al2O3, WO3, TiO2 and SiO2 fillers in the form of nanopowders, in concentrations up to 12 wt %, have been prepared. These ensembles have been measured prior to ageing and exposed to long-time (up to 5000 hours) ageing at increased temperatures 200, 250 and 300 °C and in a few cases also at 330 and 360 °C. Samples were measured in the course of ageing roughly in a logarithmic time series after 1, 2, 5, 10, 20, 50, 100, 200, 500, 1000, 2000 and 5000 hours. The measured quantities included complex permittivity , internal resistivity i and loss factor tan at temperatures ranging from -153 °C to +167 °C and in the frequency range 10-2 – 106 Hz. Changes in nanocomposites have been investigated using not just dielectric spectroscopy measurements, but other methods, too, namely Fourier-transformed infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The experiments have proved that materials with different fillers respond to the same concentrations of various fillers in different ways. The addition of nanoparticles, without the addition of microparticles, at a relatively low concentration (max 12 wt %), was not sufficient for reaching fundamental changes in dielectric spectrum; only smaller changes of dielectric strength and shifts of relaxations and in relaxation maps have occurred. Out of more pronounced changes, increase of concentration of the SiO2 filler in the epoxy matrix brings about a decrease of electrical conductivity in the resulting nanocomposite. The TiO2 filler had a different impact. Different TiO2 concentrations make their marked appearance in the region between the relaxation and relaxation. The TiO2-filled nanocomposites do not exhibit the unambiguous dependence of electrical conductivity on nanofiller concentration. It can be concluded that the mere addition of nanoparticles, without the addition of established microparticles, does not change the dielectric spectrum substantially. Generally, a serious problem was the production of the nanocomposite with a uniform distribution of nanoparticles. The preparation of such a nanocomposite was not trivial and, in industrial applications, this issue will require a specific focus, so as to avoid the formation of undesirable aggregates. Within the framework of this research, a methodology for the production of an epoxy nanocomposite has been developed with as high as possible uniformity of nanoparticle distribution.
The dissertation thesis submitted deals with the study of dielectric properties of epoxy nanocomposites containing nanoparticles of inorganic oxides. These nanocomposites may have a promising technologic application for electric insulations in view of their higher resistance against partial discharges; yet information about their behavior in the course of ageing is not available. If at least a partial mass replacement of the currently used epoxy insulation with nanocomposite-based insulations is due to occur, the knowledge of the changes of their dielectric properties in the course of their operation will become indispensable. Within the framework of this dissertation, ensembles of samples of epoxy resins without fillers and with Al2O3, WO3, TiO2 and SiO2 fillers in the form of nanopowders, in concentrations up to 12 wt %, have been prepared. These ensembles have been measured prior to ageing and exposed to long-time (up to 5000 hours) ageing at increased temperatures 200, 250 and 300 °C and in a few cases also at 330 and 360 °C. Samples were measured in the course of ageing roughly in a logarithmic time series after 1, 2, 5, 10, 20, 50, 100, 200, 500, 1000, 2000 and 5000 hours. The measured quantities included complex permittivity , internal resistivity i and loss factor tan at temperatures ranging from -153 °C to +167 °C and in the frequency range 10-2 – 106 Hz. Changes in nanocomposites have been investigated using not just dielectric spectroscopy measurements, but other methods, too, namely Fourier-transformed infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The experiments have proved that materials with different fillers respond to the same concentrations of various fillers in different ways. The addition of nanoparticles, without the addition of microparticles, at a relatively low concentration (max 12 wt %), was not sufficient for reaching fundamental changes in dielectric spectrum; only smaller changes of dielectric strength and shifts of relaxations and in relaxation maps have occurred. Out of more pronounced changes, increase of concentration of the SiO2 filler in the epoxy matrix brings about a decrease of electrical conductivity in the resulting nanocomposite. The TiO2 filler had a different impact. Different TiO2 concentrations make their marked appearance in the region between the relaxation and relaxation. The TiO2-filled nanocomposites do not exhibit the unambiguous dependence of electrical conductivity on nanofiller concentration. It can be concluded that the mere addition of nanoparticles, without the addition of established microparticles, does not change the dielectric spectrum substantially. Generally, a serious problem was the production of the nanocomposite with a uniform distribution of nanoparticles. The preparation of such a nanocomposite was not trivial and, in industrial applications, this issue will require a specific focus, so as to avoid the formation of undesirable aggregates. Within the framework of this research, a methodology for the production of an epoxy nanocomposite has been developed with as high as possible uniformity of nanoparticle distribution.
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Citation
KLAMPÁR, M. Štúdium nanokompozitov pre elektrické izolácie [online]. Brno: Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií. 2015.
Document type
Document version
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Language of document
sk
Study field
Fyzikální elektronika a nanotechnologie
Comittee
prof. RNDr. Pavel Tománek, CSc. (předseda)
prof. Ing. Jozef Kaiser, Ph.D. (člen)
doc. Ing. Pavel Trnka, Ph.D. (člen)
prof. Ing. Václav Mentlík, CSc. -oponent (člen)
dpc. Ing. Michal Váry, Ph.D. - oponent (člen)
doc. Ing. Ladislav Pína, DrSc. (člen)
RNDr. Emil Pinčík, CSc. (člen)
Date of acceptance
2015-11-19
Defence
Result of defence
práce byla úspěšně obhájena
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Standardní licenční smlouva - přístup k plnému textu bez omezení