Search

Razvoj novih materijala koji služe u borbi protiv multirezistentnih sojeva je od velikog značaja. Titanijum-dioksid je u ove svrhe izučavan kao netoksični antimikrobni agens koji tu funkciju ispoljava zahvaljujući svojoj fotokatalitičkoj aktivnosti. Kako bi se unapredila svojstva ovog materijala, napravljen je kompozitni materijal sa srebrom. Dobijeni materijal pokazao je izrazitiju fotokatalitičku aktivnost u uslovima niske osvetljenosti. U ovom radu predstavljena je sinteza titanijum-dioksid/srebro nanokompozita dobijenog metodom ultrazvukom potpomognute fotoredukcije. Detaljno je opisana morfologija proizvoda, kao i ispitana antimikrobna svojsta.

Istraživanja u okviru teze imaju za cilj dobijanje polimernih mreža kod kojih se regulacijom sirovinskog sastava i uslova sinteze mogu menjati svojstva siloksanskih materijala u skladu sa krajnjom primenom. Osnovni cilj istraživanja ove teze je razvoj novih postupaka sinteze hibridnih siloksanskih nanokompozita na osnovu različitih prekursora mreža. Takođe, ispitan je i uticaj različitih tipova funkcionalizacije površina nanopunila silicijum(IV) oksida (sa hidrofobnom i hidrofilnom površinom) na svojstva kompozitnih materijala za specifične namene. Nanokompoziti na osnovu polimernih mreža se uglavnom koriste u onim primenama gde tradicionalne polimerne mreže ne mogu da zadovolje potrebe koje se pred njih stavljaju. Zato je potrebno razviti postupak koji bi omogućio dobijanje materijala na osnovu polimernih mreža sa poboljšanim mehaničkim, elastičnim i toplotnim svojstvima. Motivacija je vođena potrebom razvoja novih kompozitnih materijala koji imaju jedinstvena mehanička, toplotna, termomehanička svojstva sa mogućnošću da pomognu u rešavanju problema okoline, kao što su problem sa prostorom, sa automobilima, u elektronici i infrastrukturi, i naravno, oni će biti veliki izazov u nauci materijala i industriji. Siloksanske mreže su dobijene od α, ω-divinil poli(dimetilsiloksana) i poli(metil-hidrogen siloksana) u odnosu 60/40; 50/50 i 40/60. Nanokompoziti su sintetisani dodavanjem različitih sadržaja nanopunila silicijum(IV) oksida (1, 2, 5, 10 i 20 mas.%). Za potvrdu pretpostavljenog mehanizma reakcije umrežavanja siloksana korišćena je FTIR spektroskopija. TEM analiza je korišćena za procenu topologije i potvrdila je dobru disperziju punila u polimernom matriksu. Dodavanje nanopunila poboljšava mehanička svojstva dobijenih materijala i povećanje vrednosti prekidne jačine za kompozite sa hidrofobnim silicijum(IV)oksidom je veće u poređenju sa kompozitima sa hidrofilnim punilima, što je očekivano zbog bolje kompatibilnosti hidrofobne matrice i hidrofobnih punila. Termo, Research in the thesis aims to obtain polymeric networks in which the regulation of the raw material composition and the conditions of the synthesis can alter the properties of the silicone materials in accordance with the final application. The main goal of the research of this thesis is the development of new procedures for the synthesis of hybrid silicone nanocomposites based on different precursors. The influence of different types of surface functionalisation of nanofillers (with hydrophobic and hydrophilic functionalised surface) on the properties of composite materials for specific purposes was investigated. Nanocomposites based on polymer networks are mainly used in those applications where traditional polymer networks cannot meet the needs that are expected. It is therefore necessary to develop a process that would enable the production of materials based on polymeric networks with improved mechanical, elastic and thermal properties. Motivation is driven by the need to develop new composite materials that have unique mechanical, thermal, thermo-mechanical properties with the ability to help solve environmental problems, such as space problems, cars, electronics and infrastructure, and of course they will be a challenge in the material science and industry. Siloxane networks were prepared from α,ω- divinyl poly(dimethylsiloxane) and poli(methyl-hydrogen siloxane) with a ratio 60/40; 50/50 and 40/60. Nanocomposites were synthesised with the addition of different contents of silica nanofiller (1, 2 5, 10 and 20 wt%). For the confirmation of the presumed mechanism of siloxane crosslinking reaction FTIR spectroscopy was used. TEM analysis was used for topology evaluation and confirmed good dispersion of the fillers into the polymer matrix. Addition of nanofillers increased the mechanical properties of obtained materials and greater increase of the tensile strength for the composites based on hydrophobic silicon(IV)-oxide was assessed, compared with the hydrophil

Cilj ove doktorske disertacije je dobijanje srebro/polivinil-alkohol (Ag/PVA) i srebro/polivinil-alkohol/grafen (Ag/PVA/Gr) nanokompozita elektrohemijskom sintezom nanočestica srebra u PVA rastvoru, odnosno PVA/Gr koloidnoj disperziji. Elektrohemijska reakcija izvodi se pri galvanostatskim uslovima, pri čemu je količinu, oblik i veličinu nanočestica srebra (AgNPs) moguće kontrolisati izborom vrednosti gustine struje i vremena sinteze, te je međusobna zavisnost ovih parametara detaljno ispitana u ovom radu. Svojstva nanokompozita dobijenih u vidu koloidnih disperzija, filmova i hidrogelova ispitane su u cilju potencijalne biomedicinske primene..., The goal of this doctoral dissertation is to obtain silver/poly(vinyl alcohol) (Ag/PVA) and silver/poly(vinyl alcohol)/graphene (Ag/PVA/Gr) nanocomposites by electrochemical synthesis of silver nanoparticles (AgNPs) in the PVA solution, or PVA/Gr colloidal dispersion. The electrochemical reaction is performed under galvanostatic conditions, whereby the quantity, shape and size of the silver nanoparticles can be controlled by selecting the value of the current density and the time of the synthesis, and the relation between these parameters is thoroughly examined in this paper. The properties of the nanocomposites obtained in the form of colloidal dispersions, films and hydrogels were examined for potential biomedical application...

Doktorska disertacija je imala za cilj sintezu i karakterizaciju nanokompozita koji poseduju antimikrobna svojstva inovativnom metodom in situ fotoredukcije Ag+-jona na površini nanokristala TiO2 različitih oblika, prethodno deponovanih na tekstilnim materijalima. Ovakav pristup sintezi nanokompozitnih tekstilnih materijala je po prvi put realizovan u okviru ove teze..., This doctoral thesis relates to the synthesis and characterization of advanced nanocomposites which exhibit antimicrobial activity and UV protective properties. For the synthesis an innovative method based on in situ photoreduction of Ag+-ions onto the surface of differently shaped TiO2 nanocrystals, being in the form of either spherical nanoparticles or nanotubes, deposited on different textile materials was applied. Such synthesis route for the formation of textile nanocomposites has been realized for the first time in the context of this thesis...

U sredstvima lične balističke zaštite koriste se kompozitni materijali na bazi tkanina velike žilavosti i zatezne čvrstoće, poput aramidnih tkanina impregnisanih polimernim vezivom, uglavnom nekim termoplastičnim ili termoumrežavajućim polimerom. Kompoziti sa nanočestičnim puniocima su perspektivni materijali širokog spektra primene, koji objedinjuju svojstva i prednosti matrice (polimera) i punilaca. Tendencija je da se i u balističkim kompozitnim sistemima postigne maksimum ojačanja, i to uvođenjem nanočestica različitih svojstava i strukture..., In the means of personal ballistic protection, composite materials based on fabric of high toughness and tensile strength are used, such as aramid fabrics, impregnated with polymeric binder, mainly some thermoplastic or thermosetting polymer. Composites with nanoparticle fillers are promising materials for a wide range of applications, which combine the properties and benefits of matrix (polymer) and fillers. There is also a tendency in ballistic composite systems to achieve maximum reinforcement by introducing nanoparticles of different properties and structures...

U ovoj tezi je ispitana mogućnost sinteze novih, poboljšanih biomaterijala na bazi alginata, agara i cinka, primenom biomimetičkog principa dizajna – biomineralizacije. Cilj istraživanja je bio dizajn i karakterizacija novih nanokompozitnih biomaterijala, sa potencijalnom primenom u biomedicini i pakovanju hrane..., The aim of this study was to test the hypothesis whether biopolymer-based biomineralization, with essential metal salts, Zn-minerals, can be considered a good platform for designing nanocomposite biomaterials for potential biomedical and active food packaging applications...

Epoksidni nanokompoziti (NK) na bazi diglicidil-etra bisfenola A (DGEBA) pretpolimera i višefunkcionalnog poli(amidoamina) (PAA) kao umreživača su pripremljeni in situ polimerizacijom u prisustvu komercijalnih hemijski modifikovanih montmorijonita (Cloisite®30B; Cloisite®15A) i onih sintetisanih reakcijom jonske izmene sa protonovanim heksadecilaminom (HDA-Mt) i umreživačem (PA-Mt). Pri pripremi NK, 0,5–10 mas.% montmorijonita (Mt) je direktno umešavano sa rastvorom DGEBA, odnosno prethodno dispergovano u pogodnom sistemu rastvarača..., Epoxy nanocomposites (CPN) based on diglycidyl ether of bisphenol A (DGEBA) prepolymer and multifunctional poly(amidoamine) (PAA) curing agent were prepared by in situ polymerization in the presence of commercial chemically modified montmorillonites (Cloisite®30B; Cloisite®15A), as well as ones synthesized by ion exchange reaction with protonated hexadecylamine (HDA-Mt) and PAA (PA-Mt). The 0.5–10 wt.% of montmorillonite (Mt) was directly mixed with DGEBA solution or previously dispersed in a suitable solvent system...

Doktorska disertacija je imala za cilj sintezu i karakterizaciju nanokompozita koji poseduju antimikrobna svojstva inovativnom metodom in situ fotoredukcije Ag+-jona na površini nanokristala TiO2 različitih oblika, prethodno deponovanih na tekstilnim materijalima. Ovakav pristup sintezi nanokompozitnih tekstilnih materijala je po prvi put realizovan u okviru ove teze..., This doctoral thesis relates to the synthesis and characterization of advanced nanocomposites which exhibit antimicrobial activity and UV protective properties. For the synthesis an innovative method based on in situ photoreduction of Ag+-ions onto the surface of differently shaped TiO2 nanocrystals, being in the form of either spherical nanoparticles or nanotubes, deposited on different textile materials was applied. Such synthesis route for the formation of textile nanocomposites has been realized for the first time in the context of this thesis...

U ovoj tezi je ispitana mogućnost sinteze novih, poboljšanih biomaterijala na bazi alginata, agara i cinka, primenom biomimetičkog principa dizajna – biomineralizacije. Cilj istraživanja je bio dizajn i karakterizacija novih nanokompozitnih biomaterijala, sa potencijalnom primenom u biomedicini i pakovanju hrane..., The aim of this study was to test the hypothesis whether biopolymer-based biomineralization, with essential metal salts, Zn-minerals, can be considered a good platform for designing nanocomposite biomaterials for potential biomedical and active food packaging applications...

U okviru ove doktorske disertacije izvedena je radijaciono-hemijska sinteza i karakterizacija novih nanokompozita na bazi umreţenih polimernih matrica N-izopropilakrilamida (NiPAAm) i itakonske kiseline (IK) i nanočestica srebra (Ag/P(NiPAAm/IK)). Za sintezu nanokompozita je korišćena radiolitička metoda koja omogućava umreţavanje i fino podešavanje svojstava nosača tj. polimerne matrice, ali i formiranje nanočestica srebra ţeljenih svojstava unutar polimerne matrice (in situ sinteza). Radiolitička metoda sinteze je izvedena pod dejstvom gama zračenja na kobaltnom (60Co) izvoru. Sintetisani uzorci su podvrgnuti detaljnoj fizičko-hemijskoj karakterizaciji u cilju dobijanja informacija o polimernim matricama kao nosačima i nanočesticama srebra kao nanopuniocima, ali i u cilju ispitivanja njihovog sinergističkog dejstva u nanokompozitnim sistemima.Morfologija umreţenih sistema je ispitana primenom skenirajuće elektronske mikroskopije (SEM) i mikro kompjuterizovane topografije (mikro-CT), a studija bubrenja praćenjem kinetike bubrenja u medijumima različitih pH-vrednosti i temperature, pri čemu su simulirani fiziološki uslovi. Utvrđeno je da prisustvo itakonske kiseline i inkorporacija nanočestica srebra utiču na morfologiju nanokompozita, parametre polimerne mreţe, kao i na kapacitet bubrenja.Optička svojstva nanokompozita su ispitana metodom spektroskopije u ultraljubičastoj i vidljivoj oblasti spektra (UV-Vis) i teorijskim modelovanjem primenom MiePlot 3.4 programskog paketa čiji je algoritam zasnovan na Mie-ovoj teoriji. U apsorpcionim spektrima je zapaţena karakteristična plazmonska apsorpcija sa maksimumom u opsegu od 390 nm do 412 nm, dok jemodelovanjem određeno da se vrednost prečnika nanočestica srebra kreće između 6,8 nm i 16,2 nm..., In this study, radiation-chemical synthesis and characterization of the novel nanocomposite systems based on silver nanoparticles (AgNPs) and crosslinked copolymer matrix of N-isopropylacrylamide (NiPAAm) and itaconic acid (IA) (Ag/P(NiPAAm/IA)) were performed. Radiolytic method, which is used for synthesis, enables fine tuning of properties of polymer matrix as a carrier, as well as formation of the silver nanoparticles with desired properties within polymer matrix (in situ synthesis). The radiolytic synthesis method is carried out by gamma irradiation at a cobalt (60Co) radiation facility. Synthesized samples were undergo to detailed physico-chemical characterization in order to obtain information about polymer matrix as a carrier and silver nanoparticles as a nanofillers, but also to examine their synergistic effects in the nanocomposite systems.Morphology of the crosslinked systems was performed by scanning electron microscopy (SEM) and micro computerized topography (micro-CT), while swelling study was performed by monitoring the swelling kinetics in the swelling media with different pH and temperature, i.e. in simulated physiological conditions. It has been shown that the addition of itaconic acid and incorporation of AgNPs have influences on the morphology, network parameters as well as on the swelling capacity.The optical properties of the nanocomposites were investigated by ultraviolet–visible spectroscopy (UV-Vis) and theoretical modeling using MiePlot 3.4 software package, with algorithm based on Mie's theory. Obtained absorption spectra exhibit the characteristic plasmon peak with maximabetween 390 nm and 412 nm, while the modeling has shown that the mean size of the silver nanoparticles was in the range between 6.8 nm and 16.2 nm...

U okviru ove doktorske disertacije izvedena je radijaciono-hemijska sinteza i karakterizacija novih nanokompozita na bazi umreţenih polimernih matrica N-izopropilakrilamida (NiPAAm) i itakonske kiseline (IK) i nanočestica srebra (Ag/P(NiPAAm/IK)). Za sintezu nanokompozita je korišćena radiolitička metoda koja omogućava umreţavanje i fino podešavanje svojstava nosača tj. polimerne matrice, ali i formiranje nanočestica srebra ţeljenih svojstava unutar polimerne matrice (in situ sinteza). Radiolitička metoda sinteze je izvedena pod dejstvom gama zračenja na kobaltnom (60Co) izvoru. Sintetisani uzorci su podvrgnuti detaljnoj fizičko-hemijskoj karakterizaciji u cilju dobijanja informacija o polimernim matricama kao nosačima i nanočesticama srebra kao nanopuniocima, ali i u cilju ispitivanja njihovog sinergističkog dejstva u nanokompozitnim sistemima. Morfologija umreţenih sistema je ispitana primenom skenirajuće elektronske mikroskopije (SEM) i mikro kompjuterizovane topografije (mikro-CT), a studija bubrenja praćenjem kinetike bubrenja u medijumima različitih pH-vrednosti i temperature, pri čemu su simulirani fiziološki uslovi. Utvrđeno je da prisustvo itakonske kiseline i inkorporacija nanočestica srebra utiču na morfologiju nanokompozita, parametre polimerne mreţe, kao i na kapacitet bubrenja. Optička svojstva nanokompozita su ispitana metodom spektroskopije u ultraljubičastoj i vidljivoj oblasti spektra (UV-Vis) i teorijskim modelovanjem primenom MiePlot 3.4 programskog paketa čiji je algoritam zasnovan na Mie-ovoj teoriji. U apsorpcionim spektrima je zapaţena karakteristična plazmonska apsorpcija sa maksimumom u opsegu od 390 nm do 412 nm, dok je modelovanjem određeno da se vrednost prečnika nanočestica srebra kreće između 6,8 nm i 16,2 nm..., In this study, radiation-chemical synthesis and characterization of the novel nanocomposite systems based on silver nanoparticles (AgNPs) and crosslinked copolymer matrix of N-isopropylacrylamide (NiPAAm) and itaconic acid (IA) (Ag/P(NiPAAm/IA)) were performed. Radiolytic method, which is used for synthesis, enables fine tuning of properties of polymer matrix as a carrier, as well as formation of the silver nanoparticles with desired properties within polymer matrix (in situ synthesis). The radiolytic synthesis method is carried out by gamma irradiation at a cobalt (60Co) radiation facility. Synthesized samples were undergo to detailed physico-chemical characterization in order to obtain information about polymer matrix as a carrier and silver nanoparticles as a nanofillers, but also to examine their synergistic effects in the nanocomposite systems. Morphology of the crosslinked systems was performed by scanning electron microscopy (SEM) and micro computerized topography (micro-CT), while swelling study was performed by monitoring the swelling kinetics in the swelling media with different pH and temperature, i.e. in simulated physiological conditions. It has been shown that the addition of itaconic acid and incorporation of AgNPs have influences on the morphology, network parameters as well as on the swelling capacity. The optical properties of the nanocomposites were investigated by ultraviolet–visible spectroscopy (UV-Vis) and theoretical modeling using MiePlot 3.4 software package, with algorithm based on Mie's theory. Obtained absorption spectra exhibit the characteristic plasmon peak with maxima between 390 nm and 412 nm, while the modeling has shown that the mean size of the silver nanoparticles was in the range between 6.8 nm and 16.2 nm...

Unsaturated polyester resins (UPe) were synthesized from maleic anhydride and products of glycolysis, obtained by polyethylene terephthalate (PET) depolymerization with dipropylene glycol (DPG) in the presence of tetrabutyl titanate catalyst. Waste PET glycolyzed product and UPes were characterized by FTIR and NMR spectroscopy, elemental analysis, acid value (AV), hydroxyl value (HV) and iodine value. Nanocomposites, based on unsaturated polyester resins and hexamethyldisilazane modified silica nanoparticles, were prepared with intention to show one of valuable applicative commercialization of UPe resin. In order to determine potential of the possible implementation of developed new technology for UPe production some aspect of techno- economic analysis was analyzed. Economic potential/benefit and process profitability of the presented technology was based on the use of recycled raw input materials, i.e. waste PET, which is one of the most effective ways to save natural resources, protect the environment, and save money. Principles of green economy was incorporated in the results of developed UPe production technology which is related to both environmental protection and profitability achievement with no additional negative impact to environment, i.e. pollution decrease without negative effect of implemented technology., Nezasićene poliestarske smole (UPe) su sintetisane iz anhidrida maleinske kiseline i proizvoda glikolize, dobijenih depolimerizacijom poli(etilen tereftalata) (PET-a) sa dipropilen-glikolom (DPG) u prisustvu tetrabutil-titanata kao katalizatora. Proizvod glikolize otpadnog PET-a i UPe smole su okarakterisani pomoću FTIR i NMR spektroskopije, elementalne analize, kiselinskog (AV), hidroksilnog (HV) i jodnog broja. Nanokompoziti, bazirani na nezasićenim poliestarskim smolama i nanočesticama silicijum-dioksida modifikovanim heksametildisilazanom, pripremljene su sa namerom da se prikaže jedna od značajnih komercijalnih primena UPe smola. U cilju određivanja mogućnosti mogućih implementacija razvijenih novih tehnologija proizvodnje UPe smola, urađena je neki tehno-ekonomska analiza. Ekonomska korist i profitabilnost procesa prikazane tehnologije su zasnovani na primeni reciklaže sirovog materijala, otpadnog PET-a, što predstavlja jedan od najefektivnijih načina da se očuvaju prirodni resursi, zaštiti životna sredina i uštedi novac. Principi zelene ekonomije su ugrađeni u razvijenoj tehnologiji proizvodnje UPe smola, što se odnosi i na zaštitu životne sredine i dostizanje profitabilnosti bez dodatnih negativnih uticaja na životnu sredinu, odnosno na smanjenje zagađenja bez negativnog uticaja na implementiranu tehnologiju.

Unsaturated polyester resins (UPe) were synthesized from maleic anhydride and products of glycolysis, obtained by polyethylene terephthalate (PET) depolymerization with dipropylene glycol (DPG) in the presence of tetrabutyl titanate catalyst. Waste PET glycolyzed product and UPes were characterized by FTIR and NMR spectroscopy, elemental analysis, acid value (AV), hydroxyl value (HV) and iodine value. Nanocomposites, based on unsaturated polyester resins and hexamethyldisilazane modified silica nanoparticles, were prepared with intention to show one of valuable applicative commercialization of UPe resin. In order to determine potential of the possible implementation of developed new technology for UPe production some aspect of techno- economic analysis was analyzed. Economic potential/benefit and process profitability of the presented technology was based on the use of recycled raw input materials, i.e. waste PET, which is one of the most effective ways to save natural resources, protect the environment, and save money. Principles of green economy was incorporated in the results of developed UPe production technology which is related to both environmental protection and profitability achievement with no additional negative impact to environment, i.e. pollution decrease without negative effect of implemented technology., Nezasićene poliestarske smole (UPe) su sintetisane iz anhidrida maleinske kiseline i proizvoda glikolize, dobijenih depolimerizacijom poli(etilen tereftalata) (PET-a) sa dipropilen-glikolom (DPG) u prisustvu tetrabutil-titanata kao katalizatora. Proizvod glikolize otpadnog PET-a i UPe smole su okarakterisani pomoću FTIR i NMR spektroskopije, elementalne analize, kiselinskog (AV), hidroksilnog (HV) i jodnog broja. Nanokompoziti, bazirani na nezasićenim poliestarskim smolama i nanočesticama silicijum-dioksida modifikovanim heksametildisilazanom, pripremljene su sa namerom da se prikaže jedna od značajnih komercijalnih primena UPe smola. U cilju određivanja mogućnosti mogućih implementacija razvijenih novih tehnologija proizvodnje UPe smola, urađena je neki tehno-ekonomska analiza. Ekonomska korist i profitabilnost procesa prikazane tehnologije su zasnovani na primeni reciklaže sirovog materijala, otpadnog PET-a, što predstavlja jedan od najefektivnijih načina da se očuvaju prirodni resursi, zaštiti životna sredina i uštedi novac. Principi zelene ekonomije su ugrađeni u razvijenoj tehnologiji proizvodnje UPe smola, što se odnosi i na zaštitu životne sredine i dostizanje profitabilnosti bez dodatnih negativnih uticaja na životnu sredinu, odnosno na smanjenje zagađenja bez negativnog uticaja na implementiranu tehnologiju.

Uvođenje nanočestica u stomatološke kompozitne materijale predstavlja pokušaj da se odgovori univerzalnim zahtevima za kvalitetom direktnog zubnog ispuna, i da se stvori materijal koji kombinuje visoku mehaničku otpornost sa dobrim estetskim karakteristikama i zadovoljavajućim kvalitetom poliranja. Cilj sprovedene studije je bio da se ispita uticaj nanočestica, i soft-start metode svetlosne indukcije polimerizacije na mehanička i površinska svojstva savremenih stomatoloških nanokompozita, dostupnih na tržištu. Ispitana su četiri stomatološka nanostrukturisana kompozitna materijala na bazi smola i jedan univerzalni mikrohibridni kompozit, kao referentni materijal (Filtek Z250, 3M ESPE). Korišćena su po dva reprezentativna materijala iz dve podgrupe nanokompozita: nanopunjenih (Filtek Ultimate Body, 3M ESPE i Filtek Ultimate Translucent, 3M ESPE) i nanohibridnih kompozita (Filtek Z550, 3M ESPE i Tetric EvoCeram, Ivoclar Vivadent - TEC). Uzorci su polimerizovani nakon svetlosne aktivacije polimerizacije, uz korišćenje dva svetlosna režima: konvencionalnog i soft start režima. Pritisna i zatezna čvrstoća (dobijena poprečnim sabijanjem valjka, engl. diametral tensile strength) testirane su na Univerzalnoj mašini, kidalici. Tvrdoća uzoraka merena je testom za određivanje tvrdoće po Vickersu. Površinska tekstura i parametri hrapavosti određeni su skeniranjem površine mikroskopom atomskih sila. Uopšteno, TEC je pokazao najniže vrednosti pritisne i zatezne čvrstoće, i tvrdoće, i statistićki je značajno bio slabiji od drugih testiranih materijala kroz sve mehaničke testove. Suprotno, TEC je imao najniže vrednosti parametara hrapavosti među testiranim materijalima. Spoj prepolimerizovanog punioca i polimerne baze u ovom materijalu pokazao se kao njegova slaba tačka. Navedeni materijal je iz tog razloga pokazao značajno slabiju otpornost od ostalih na razvijene napone izazvane dejstvom mehaničkih sila. Čestice nanodimenzija u sastavu stomatoloških polimernih kompozita, samostal, The introduction of nanoparticles in dental composite materials was an attempt to respond to the universal quality requirements for a direct dental restoration, and to create a material that meets the needs of high mechanical resistance, good aesthetic characteristics and surface properties of tooth restoratives. The aim of this study was to investigate the effect of nanoparticles in materials composition, and the soft start photoactivation method on the mechanical and surface properties of contemporary dental nanocomposites, available in the market. Four dental resin based nanostructured composites were tested along with a universal microhybrid one, as reference material (Filtek Z250, 3M ESPE). Two representative materials from the two classification subgroups were tested, nanofilled (Filtek Ultimate Body, 3M ESPE and Filtek Ultimate Translucent, 3M ESPE) and nanohybrid composites (Filtek Z550, 3M ESPE and Tetric EvoCeram, Ivoclar Vivadent, TEC). Polymerization of the samples was light activated using two light modes: conventional and soft start. Compressive and diametral tensile strength were tested on the Universal testing machine. The Vickers hardness was also determined. Surface texture and roughness parameters were examined by atomic force microscopy. Generally, TEC showed the lowest values of compression, tensile strength and hardness, and was statistically different from the other tested materials throughout all mechanical tests. In contrast, TEC had the lowest values of roughness parameters among the tested materials. In this material, contact zone of prepolimeryzed filler and polymer matrix appeared to be a weak point. For this reason, this material showed significantly lower resistance than the others on mechanically developed stresses. Nanosized particles within the dental polymer composites, individually, did not have a significant influence on improving the mechanical and surface properties of tested composites. It is concluded that the inorganic volum

Cilj ove doktorske disertacije je elektrohemijsko dobijanje i karakterizacija nanokompozitnih sistema srebro/poli(N-vinil-2-pirolidon) (Ag/PVP), i srebro/alginat (Ag/alginat), u obliku koloidnih disperzija i hidrogelova, za biomedicinsku primenu. Elektrohemijska sinteza, u odnosu na hemijsku, pokazuje prednost u dobijanju malih čestica metala visoke čistoće, i to sa manjim brojem hemikalija, što je od izuzetnog značaja za primenu u biomedicini. Takođe, elektrohemijska sinteza daje mogućnost precizne kontrole veličine nanočestica, podešavanjem vrednosti gustine struje ili potencijala. Izvršena je optimizacija elektrohemijske sinteze nanočestica srebra u rastvorima PVP i alginata. Dobijene Ag/PVP i Ag/alginatne koloidne disperzije su karakterisane različitim fizičko-hemijskim metodama radi izbora najefikasnijeg režima i uslova sinteze. U cilju dobijanja što veće koncentracije nanočestica, sfernog oblika, ispitan je uticaj potencijala, gustine struje, vremena implementacije, sastava rastvora za sintezu. Sastav, morfologija i struktura nanokompozitnih sistema su ispitani UV-vidljivom spektroskopijom, optičkom, transmisionom i skenirajućom elektronskom mikroskopijom, cikličnom voltametrijom, spektroskopijom infracrvene svetlosti sa Furijeovom (Fourier) transformacijom (FT-IR). Elektrohemijska sinteza nanočestica srebra u rastvoru PVP je vršena u galvanostatskim i potenciostatskim uslovima, kao i primenom reversne struje. Utvrđeno je da galvanostatska sinteza obezbeđuje veću koncentraciju dobijenih nanočestica, koja raste sa povećanjem primenjene gustine struje. Najveća koncentracija nanočestica srebra dobijena je galvanostatskom sintezom, gustinom struje od 62 mA cm-2, tokom 10 min. Veličina dobijenih nanočestica je oko 75 nm. FT-IR spektroskopijom je utvrđeno da se interakcija između molekula PVP i nanočestica srebra dešava ili na atomu azota ili na atomu kiseonika u pirolidonskom prstenu (u zavisnosti od veličine nanočestica) koordinacionim vezama sa nanočesticama sreb, The objective of this doctoral dissertation is the electrochemical synthesis and characterization of silver/poly(N-vinyl-2-pyrrolidone) (Ag/PVP), and silver/alginate (Ag/alginate), nanocomposite systems, in forms of colloid dispersions and hydrogels, for biomedical purposes. The electrochemical synthesis, in comparison with the chemical, exhibits the advantages in obtaining of small metal nanoparticles of high purity, using smaller number of chemicals. This becomes of a great importance in biomedical applications. Electrochemical synthesis also gives a possibility of a precise particle size control, by the adjustment of the applied current density or potential. The optimization of the electrochemical synthesis of silver nanoparticles in PVP and alginate solutions was performed. As obtained Ag/PVP and Ag/alginate colloid dispersions were characterized by various physico-chemical methods in order to find the most efficacious regime and conditions of the synthesis. Aiming the highest possible nanopartcle concentration, the influence of the applied potential, current density, implementation time and the synthesis solution composition were examined. The composition, morphology and the structure of nanocomposite systems were investigated by UV-visible spectroscopy, optic, transmission and scanning electron microscopy, cyclic voltammetry and Fourier transform infrared spectroscopy (FT-IR). The electrochemical synthesis of silver nanoparticles inside PVP solution was performed in galvanostatic and potentiostatic conditions, as well as by using a reverse current. It is determined that the galvanostatic synthesis provides higher concentration of the obtained silver nanoparticles, increasing with the increase of the applied current density. So, the highest concentration of silver nanoparticles is obtained galvanostatically, at the applied current density of 62 mA cm-2, during 10 min. The size of the obtained silver nanoparticles was ~75 nm. FT-IR spectroscopy results showed th

The properties of polymer nanocomposites exceed the properties of common composite materials due to the nanoscale size and morphology of the fillers used. Particulate fillersare commonly used in polymers forimproved mechanical and thermal properties, as well as modified electrical properties and cost reduction. Organically modified layered clays, such asmontmorillonite, are among the most widely used fillers for the improvement of polymer matrices. Presented in this review are some of the most studied clay nanocomposites including clay-polyolefin, clay-polyester and clay-thermoplastic polyurethanenanocomposites. Additionally, the properties of clay-biopolymers nanocomposites will also be discussed., Svojstva polimernih nanokompozita prevazilaze svojstva uobičajenih kompozitnih materijala zbog nanodimenzija i morfologije upotrebljenih punioca. Čestični punioci se uglavnom koriste u cilju poboljšnja mehaničkih i toplotnih svojstava polimera, kao i za modifikovanje električnih svojstava polimerne matrice i smanjenja cene koštanja. Organski modifikovane slojevite gline, kao što je montmorilonit, su između ostalih, najzastupljeniji punioci u upotrebi za poboljšanje svojstava polimernih matrica. Ovim preglednim radom biće prikazani najznačajniji i najviše proučavani glina-polimerni nanokompoziti, kao što su glina-poliolefini, glina-poliestar i glina-termoplastični poliuretan nanokompoziti. Takođe, svojstva biopolimer-glina nanokompozita biće predstavljena i razmatrana u radu.

The properties of polymer nanocomposites exceed the properties of common composite materials due to the nanoscale size and morphology of the fillers used. Particulate fillersare commonly used in polymers forimproved mechanical and thermal properties, as well as modified electrical properties and cost reduction. Organically modified layered clays, such asmontmorillonite, are among the most widely used fillers for the improvement of polymer matrices. Presented in this review are some of the most studied clay nanocomposites including clay-polyolefin, clay-polyester and clay-thermoplastic polyurethanenanocomposites. Additionally, the properties of clay-biopolymers nanocomposites will also be discussed., Svojstva polimernih nanokompozita prevazilaze svojstva uobičajenih kompozitnih materijala zbog nanodimenzija i morfologije upotrebljenih punioca. Čestični punioci se uglavnom koriste u cilju poboljšnja mehaničkih i toplotnih svojstava polimera, kao i za modifikovanje električnih svojstava polimerne matrice i smanjenja cene koštanja. Organski modifikovane slojevite gline, kao što je montmorilonit, su između ostalih, najzastupljeniji punioci u upotrebi za poboljšanje svojstava polimernih matrica. Ovim preglednim radom biće prikazani najznačajniji i najviše proučavani glina-polimerni nanokompoziti, kao što su glina-poliolefini, glina-poliestar i glina-termoplastični poliuretan nanokompoziti. Takođe, svojstva biopolimer-glina nanokompozita biće predstavljena i razmatrana u radu.

Predmet istraživanja ove doktorske disertacije podrazumeva sintezu nanokompozita na bazi polianilina (PANI) i nanočestica titan (IV)‐oksida (TiO2) različitih oblika novom metodom, njihovu karakterizaciju većim brojem fizičkohemijskih metoda, kao i ispitivanje mogućnosti njihove primene u fotokatalizi. PANI/TiO2 nanokompoziti sintetisani su novim, ekonomičnim postupkom hemijske oksidativne polimerizacije anilina amonijum peroksidisulfatom u vodi, bez dodatka kiseline, kalupa i površinskih modifikatora, a u prisustvu nanočestica TiO2. Optimizacijom sinteze nanokompozita kroz variranje polaznog molskog odnosa anilina i TiO2 pronađeni su uslovi za dobijanje PANI/TiO2 nanokompozita u kojima su prisutne polianilinske nanostrukture. U disertaciji je ispitan uticaj nanočestica TiO2 na tok, brzinu i prinos reakcije polimerizacije anilina kao i na morfologiju, strukturu, provodljivost i magnetna svojstva polianilina. U cilju izučavanja potencijalne primene sintetisanih nanokompozita, ispitivana je sposobnost polianilina da senzitizira i pospeši fotokatalitičke procese na površini nanočestica TiO2. Rad se tematski može podeliti u tri celine i to: 1. Sinteza i karakterizacija nanokompozita na bazi polianilina i koloidnih nanočestica TiO2; 2. Sinteza i karakterizacija nanokompozita na bazi polianilina i nanotuba TiO2; 3. Ispitivanje fotokatalitičke aktivnosti nanokompozita na bazi polianilina i koloidnih nanočestica TiO2. Prvi deo teze odnosi se na ispitivanje svojstava nanokompozita sintetisanih hemijskom oksidativnom polimerizacijom anilina, uz pomoć amonijum peroksidisulfata, u prisustvu koloidnih nanočestica TiO2 (d = 4, 5 nm), bez dodatka..., The subject of this PhD thesis is the synthesis of nanocomposites based on polyaniline (PANI) and titanium (IV) oxide (TiO2) by a novel method, without added acids, templates and surfactants, their characterization by various physicochemical methods, as well as an investigation of their potential application in the field of photocatalysis. PANI/TiO2 nanocomposites were synthesized by a novel, economical method of oxidative polymerization of aniline with ammonium peroxydisulfate in water, without added acid, in the presence of shaped TiO2 nanoparticles. The optimization of polymerization process was done by varying initial mole ratio of aniline/TiO2. The aim was to find optimal conditions for the synthesis of PANI/TiO2 nanocomposites containing polyaniline nanostructures. Influence of TiO2 nanoparticles on the course, rate and yield of polymerization process of aniline, as well as their influence on the morphology, structure, electrical conductivity and magnetic properties of polyaniline is examined. Moreover, potential application of PANI/TiO2 nanocomposites in photocatalysis and ability of polyaniline to sensitize TiO2 nanoparticles are investigated. Topic of this work can be divided into three main units: 1. Synthesis and characterization of nanocomposites based on polyaniline and colloidal TiO2 nanoparticles; 2. Synthesis and characterization of nanocomposites based on polyaniline and TiO2 nanotubes; 3. The study of photocatalytic activity of nanocomposites based on polyaniline and colloidal TiO2 nanoparticles. The first part of the thesis refers to the investigation of properties of nanocomposites synthesized by the chemical oxidative polymerization of aniline with ammonium peroxydisulfate, in the presence of colloidal TiO2 nanoparticles (d=4, 5 nm), without added acid. As a reference sample, pure polyaniline...

Titan(IV)-oksid (TiO2) je zbog svoje fotokatalitičke aktivnosti, hemijske i biološke inertnosti, otpornosti na fotoindukovanu i hemijsku koroziju, netoksičnosti i relativno niske cene, jedan od najčešće proučavanih poluprovodničkih materijala za primenu u dekontaminaciji životne sredine, samo-čišćenju, uklanjanju mirisa, sterilizaciji i obnovljivim izvorima energije. Zbog široke zabranjene zone i velike brzine rekombinacije fotogenerisanih parova elektron-šupljina, efikasnost fotokatalizatora na bazi TiO2 je i dalje mala za potencijalnu praktičnu primenu. U poslednje četiri decenije veliki napor je uložen u istraživanja vezana za poboljšanje fotokatalitičke efikasnosti TiO2 i njegovu moguću praktičnu primenu. Generalno, fotokatalitička efikasnost TiO2 se može povećati: (1) smanjenjem energije zabranjene zone dopiranjem i/ili proširenjem apsorpcije (u vidljivu oblast) upotrebom fotosenzitizera, (2) poboljšanjem razdvajanja (smanjenjem brzine rekombinacije) fotogenerisanih nosilaca naelektrisanja (elektron/šupljina) i (3) povećanjem specifične površine i kvaliteta aktivnih mesta (za adsorpciju polutanata koje je potrebno fotokatalitički razgraditi). Cilj ove doktorske disertacije je proučavanje procesa formiranja nedopiranih i dopiranih nanostrukturnih prahova i tankih filmova titan(IV)-oksida znatno poboljšane fotokatalitičke efikasnosti. Da bi se postigla visoka fotokatalitička aktivnost u vidljivoj oblasti, neophodno je generisati aktivne apsorpcione centre za vidljivu svetlost. Pokazalo se da dopiranje anjonima nemetala predstavlja veliki potencijal u indukovanju takve apsorpcije i dosta napora se ulaže u razvijanje metoda za sintezu anjon-dopiranih TiO2 fotokatalizatora sa visokom aktivnošću u vidljivom delu spektra. Prema tome, u ovoj doktorskoj disertaciji prvo je predstavljeno dobijanje TiO2 filmova pulsnom laserskom depozicijom na staklenim supstratima u atmosferi kiseonika, metana, azota i mešavini kiseonika i azota. Inkorporacija azota u rešetku TiO2 je usp, Titania (TiO2) due to its photocatalytic activity, chemical and biological inertness, resistance to chemical- and photo-corrosion, non-toxicity, and relatively low cost, is one of the most studied semiconductors for environmental protection, selfcleaning, deodorizing, sterilizing and renewable energy sources. Owing to its wide band gap and high speed of electron/hole recombination, the efficiency of photocatalysts based on TiO2 is however small for potential practical applications. In the last four decades, much effort has been invested in research related to improving the photocatalytic efficiency of TiO2 and its possible practical applications. Generally, the photocatalytic efficiency of TiO2 can be increased by: (1) reducing the band gap energy by doping and/or enlargement of its absorption in the visible region using photosensitizes, (2) improving the separation (reducing the recombination rate) of photogenerated charge carriers (electron/hole) and (3) increasing the specific surface area and the quality of the active sites (for adsorption of pollutants to be photocatalytically degraded). The aim of this doctoral dissertation was the study of the process of the formation of undoped and doped nanostructured powders and thin films of titanium(IV) oxide with significantly enhanced photocatalytic efficiency. To this end, in order to obtain high photocatalytic activity in the visible light region, it was therefore mandatory to generate active visible light absorption centers. Anion doping proved itself to process great potential in inducing such absorption, and intensive efforts have been directed towards the development of methods for synthesizing anion-doped titania-based photocatalysts with a large visible light response. Therefore, in this doctoral thesis, first pulsed laser deposition of TiO2 films on glass substrates under oxygen, methane, nitrogen and mixture of oxygen and nitrogen atmospheres is presented. Nitrogen incorporation into the TiO2 lattice was succ

U uvodu istaknut je značaj istraživanja u oblasti nanokompozitnih materijali na bazi oksida aktiviranih jonima lantanida koji imaju veoma značajnu primenu za izradu lasera, laserskih i LED dioda, luminescentnih lampi, displeja, optičkih vlakana, biomedicinskih markera itd. Za primenu posebno su od interesa emisije uskog energetskog opsega, dugo vreme života pobuđenih elektronskih stanja (fosforescencija) i fotohemijska stabilnost. U zavisnosti od načina pobuđivanja, luminescencija se može podeliti na: a) fotoluminescenciju (PL) – posledica apsorpcije elektromagnetnog zračenja, b) elektroluminescencija – posledica apsorpcije električnog polja, c) radioluminescencija – posledica jonizujućeg zračenja, d) katodoluminescencija – posledica interakcije snopa elektrona velike brzine sa tankim slojem fluorescentne supstance, e) hemiluminescencija – posledica pretvaranja hemijske energije u svetlosnu, f) bioluminescencija. Predmet ove doktorske disertacije su luminiscentni materijali. Kada se fosforescentna čestica izloži dejstvu eksitacionog izvora, kao što je ultraljubičasta (UV) ili vacuum-UV (VUV) svetlost, ona prolazi kroz proces apsorpcije, relaksacije i emisije. Svetlost se apsorbuje od strane materijala domaćina i apsorbovana energija se prenosi sa materijala domaćina na aktivator (luminescentni centar). Aktivator na kraju emituje vidjivu svetlost preko mehanizma prenosa energije. Fotoekscitacija na određenoj talasnoj dužini u bliskoj infracrvenoj oblasti koja je praćena luminiscencijom na kraćim talasnim dužinama u vidljivoj svetlosti se naziva prelaz iz bliske infracrvene u vidljivu oblast. To je veoma neobična pojava jer se fotoni niže energije „pretvaraju“ u fotone sa višom energijom. Najmanje dva fotona u infracrvenoj oblasti su potrebna za generisanje jednog fotona u vidljivoj oblasti. Upkonverzija se uglavnom dešava u materijalima u kojima procesi relaksacije više fotona ne dominiraju, što omogućava više od jednog metastabilnog stanja. U jedinjenjima retkih zem, Dynamic Mechanical Analysis (DMA) is one of the most powerful tools to study the behavior of plastic and polymer composite materials and it is potentially very useful tool to simulate behavior of plastic optic fibers (POF) in real applications. Possibility of simultaneous measurements of some optical properties during DMA would significantly upgrade investigations of POF alone or embedded in some materials. In this work, single cantilever DMA of the POFs that was done simultaneously with measuring the transmitted optical signal intensity is described and discussed. In order to compare mechanical results of the same material for cylindrical and rectangular specimens, rectangular plates were prepared by melting POFs and the same kind of tests were performed. It is shown that changing the optical signal intensity corresponds to the changes of storage modulus of the POF during DMA, and the maximums in optical signals intensity indicate the beginning of glass transition processes in the POF material. The results of a study related to the processing and characterization of PMMA-Y2O3 (Eu3+) nanocomposites are presented herein. The nanocomposite samples were prepared using a laboratory mixing molder with different contents of Eu-ion doped Y2O3 nanophosphor powder. The influence of particle content on the optical and dynamic mechanical properties of the nanocomposites was investigated. The intensity of the luminescence emission spectra increased as the nanophosphor content in the composite increased. The results of dynamic mechanical analysis revealed that the storage modulus, loss modulus and glass transition temperature (Tg) of the polymer composites increased with increasing content of the nanophosphor powder. The microhardness data also confirmed that the hardness number increased with nanoparticles concentration in the PMMA nanocomposites. The obtained results revealed a relatively linear relationship between Tg and the Vickers hardness. This study reports research rela

Predmet istraživanja ove doktorske disertacije podrazumeva sintezunanokompozita na bazi polianilina (PANI) i nanočestica titan (IV)‐oksida (TiO2)različitih oblika novom metodom, njihovu karakterizaciju većim brojemfizičkohemijskih metoda, kao i ispitivanje mogućnosti njihove primene ufotokatalizi.PANI/TiO2 nanokompoziti sintetisani su novim, ekonomičnim postupkomhemijske oksidativne polimerizacije anilina amonijum peroksidisulfatom u vodi,bez dodatka kiseline, kalupa i površinskih modifikatora, a u prisustvu nanočesticaTiO2. Optimizacijom sinteze nanokompozita kroz variranje polaznog molskogodnosa anilina i TiO2 pronađeni su uslovi za dobijanje PANI/TiO2 nanokompozita ukojima su prisutne polianilinske nanostrukture. U disertaciji je ispitan uticajnanočestica TiO2 na tok, brzinu i prinos reakcije polimerizacije anilina kao i namorfologiju, strukturu, provodljivost i magnetna svojstva polianilina. U ciljuizučavanja potencijalne primene sintetisanih nanokompozita, ispitivana jesposobnost polianilina da senzitizira i pospeši fotokatalitičke procese na površininanočestica TiO2.Rad se tematski može podeliti u tri celine i to:1. Sinteza i karakterizacija nanokompozita na bazi polianilina i koloidnihnanočestica TiO2;2. Sinteza i karakterizacija nanokompozita na bazi polianilina i nanotubaTiO2;3. Ispitivanje fotokatalitičke aktivnosti nanokompozita na bazi polianilina ikoloidnih nanočestica TiO2.Prvi deo teze odnosi se na ispitivanje svojstava nanokompozita sintetisanihhemijskom oksidativnom polimerizacijom anilina, uz pomoć amonijumperoksidisulfata, u prisustvu koloidnih nanočestica TiO2 (d = 4, 5 nm), bez dodatka..., The subject of this PhD thesis is the synthesis of nanocomposites based onpolyaniline (PANI) and titanium (IV) oxide (TiO2) by a novel method, withoutadded acids, templates and surfactants, their characterization by variousphysicochemical methods, as well as an investigation of their potential applicationin the field of photocatalysis.PANI/TiO2 nanocomposites were synthesized by a novel, economicalmethod of oxidative polymerization of aniline with ammonium peroxydisulfate inwater, without added acid, in the presence of shaped TiO2 nanoparticles. Theoptimization of polymerization process was done by varying initial mole ratio ofaniline/TiO2. The aim was to find optimal conditions for the synthesis ofPANI/TiO2 nanocomposites containing polyaniline nanostructures. Influence ofTiO2 nanoparticles on the course, rate and yield of polymerization process ofaniline, as well as their influence on the morphology, structure, electricalconductivity and magnetic properties of polyaniline is examined. Moreover,potential application of PANI/TiO2 nanocomposites in photocatalysis and ability ofpolyaniline to sensitize TiO2 nanoparticles are investigated.Topic of this work can be divided into three main units:1. Synthesis and characterization of nanocomposites based on polyanilineand colloidal TiO2 nanoparticles;2. Synthesis and characterization of nanocomposites based on polyanilineand TiO2 nanotubes;3. The study of photocatalytic activity of nanocomposites based onpolyaniline and colloidal TiO2 nanoparticles.The first part of the thesis refers to the investigation of properties ofnanocomposites synthesized by the chemical oxidative polymerization of anilinewith ammonium peroxydisulfate, in the presence of colloidal TiO2 nanoparticles(d=4, 5 nm), without added acid. As a reference sample, pure polyaniline...

Titania (TiO2) due to its photocatalytic activity, chemical and biological inertness, resistance to chemical- and photo-corrosion, non-toxicity, and relatively low cost, is one of the most studied semiconductors for environmental protection, selfcleaning, deodorizing, sterilizing and renewable energy sources. Owing to its wide band gap and high speed of electron/hole recombination, the efficiency of photocatalysts based on TiO2 is however small for potential practical applications. In the last four decades, much effort has been invested in research related to improving the photocatalytic efficiency of TiO2 and its possible practical applications. Generally, the photocatalytic efficiency of TiO2 can be increased by: (1) reducing the band gap energy by doping and/or enlargement of its absorption in the visible region using photosensitizes, (2) improving the separation (reducing the recombination rate) of photogenerated charge carriers (electron/hole) and (3) increasing the specific surface area and the quality of the active sites (for adsorption of pollutants to be photocatalytically degraded). The aim of this doctoral dissertation was the study of the process of the formation of undoped and doped nanostructured powders and thin films of titanium(IV) oxide with significantly enhanced photocatalytic efficiency. To this end, in order to obtain high photocatalytic activity in the visible light region, it was therefore mandatory to generate active visible light absorption centers. Anion doping proved itself to process great potential in inducing such absorption, and intensive efforts have been directed towards the development of methods for synthesizing anion-doped titania-based photocatalysts with a large visible light response. Therefore, in this doctoral thesis, first pulsed laser deposition of TiO2 films on glass substrates under oxygen, methane, nitrogen and mixture of oxygen and nitrogen atmospheres is presented. Nitrogen incorporation into the TiO2 lattice was succ, Titan(IV)-oksid (TiO2) je zbog svoje fotokatalitičke aktivnosti, hemijske i biološke inertnosti, otpornosti na fotoindukovanu i hemijsku koroziju, netoksičnosti i relativno niske cene, jedan od najčešće proučavanih poluprovodničkih materijala za primenu u dekontaminaciji životne sredine, samo-čišćenju, uklanjanju mirisa, sterilizaciji i obnovljivim izvorima energije. Zbog široke zabranjene zone i velike brzine rekombinacije fotogenerisanih parova elektron-šupljina, efikasnost fotokatalizatora na bazi TiO2 je i dalje mala za potencijalnu praktičnu primenu. U poslednje četiri decenije veliki napor je uložen u istraživanja vezana za poboljšanje fotokatalitičke efikasnosti TiO2 i njegovu moguću praktičnu primenu. Generalno, fotokatalitička efikasnost TiO2 se može povećati: (1) smanjenjem energije zabranjene zone dopiranjem i/ili proširenjem apsorpcije (u vidljivu oblast) upotrebom fotosenzitizera, (2) poboljšanjem razdvajanja (smanjenjem brzine rekombinacije) fotogenerisanih nosilaca naelektrisanja (elektron/šupljina) i (3) povećanjem specifične površine i kvaliteta aktivnih mesta (za adsorpciju polutanata koje je potrebno fotokatalitički razgraditi). Cilj ove doktorske disertacije je proučavanje procesa formiranja nedopiranih i dopiranih nanostrukturnih prahova i tankih filmova titan(IV)-oksida znatno poboljšane fotokatalitičke efikasnosti. Da bi se postigla visoka fotokatalitička aktivnost u vidljivoj oblasti, neophodno je generisati aktivne apsorpcione centre za vidljivu svetlost. Pokazalo se da dopiranje anjonima nemetala predstavlja veliki potencijal u indukovanju takve apsorpcije i dosta napora se ulaže u razvijanje metoda za sintezu anjon-dopiranih TiO2 fotokatalizatora sa visokom aktivnošću u vidljivom delu spektra. Prema tome, u ovoj doktorskoj disertaciji prvo je predstavljeno dobijanje TiO2 filmova pulsnom laserskom depozicijom na staklenim supstratima u atmosferi kiseonika, metana, azota i mešavini kiseonika i azota. Inkorporacija azota u rešetku TiO2 je usp

Titania (TiO2) due to its photocatalytic activity, chemical and biological inertness, resistance to chemical- and photo-corrosion, non-toxicity, and relatively low cost, is one of the most studied semiconductors for environmental protection, selfcleaning, deodorizing, sterilizing and renewable energy sources. Owing to its wide band gap and high speed of electron/hole recombination, the efficiency of photocatalysts based on TiO2 is however small for potential practical applications. In the last four decades, much effort has been invested in research related to improving the photocatalytic efficiency of TiO2 and its possible practical applications. Generally, the photocatalytic efficiency of TiO2 can be increased by: (1) reducing the band gap energy by doping and/or enlargement of its absorption in the visible region using photosensitizes, (2) improving the separation (reducing the recombination rate) of photogenerated charge carriers (electron/hole) and (3) increasing the specific surface area and the quality of the active sites (for adsorption of pollutants to be photocatalytically degraded). The aim of this doctoral dissertation was the study of the process of the formation of undoped and doped nanostructured powders and thin films of titanium(IV) oxide with significantly enhanced photocatalytic efficiency. To this end, in order to obtain high photocatalytic activity in the visible light region, it was therefore mandatory to generate active visible light absorption centers. Anion doping proved itself to process great potential in inducing such absorption, and intensive efforts have been directed towards the development of methods for synthesizing anion-doped titania-based photocatalysts with a large visible light response. Therefore, in this doctoral thesis, first pulsed laser deposition of TiO2 films on glass substrates under oxygen, methane, nitrogen and mixture of oxygen and nitrogen atmospheres is presented. Nitrogen incorporation into the TiO2 lattice was succ, Titan(IV)-oksid (TiO2) je zbog svoje fotokatalitičke aktivnosti, hemijske i biološke inertnosti, otpornosti na fotoindukovanu i hemijsku koroziju, netoksičnosti i relativno niske cene, jedan od najčešće proučavanih poluprovodničkih materijala za primenu u dekontaminaciji životne sredine, samo-čišćenju, uklanjanju mirisa, sterilizaciji i obnovljivim izvorima energije. Zbog široke zabranjene zone i velike brzine rekombinacije fotogenerisanih parova elektron-šupljina, efikasnost fotokatalizatora na bazi TiO2 je i dalje mala za potencijalnu praktičnu primenu. U poslednje četiri decenije veliki napor je uložen u istraživanja vezana za poboljšanje fotokatalitičke efikasnosti TiO2 i njegovu moguću praktičnu primenu. Generalno, fotokatalitička efikasnost TiO2 se može povećati: (1) smanjenjem energije zabranjene zone dopiranjem i/ili proširenjem apsorpcije (u vidljivu oblast) upotrebom fotosenzitizera, (2) poboljšanjem razdvajanja (smanjenjem brzine rekombinacije) fotogenerisanih nosilaca naelektrisanja (elektron/šupljina) i (3) povećanjem specifične površine i kvaliteta aktivnih mesta (za adsorpciju polutanata koje je potrebno fotokatalitički razgraditi). Cilj ove doktorske disertacije je proučavanje procesa formiranja nedopiranih i dopiranih nanostrukturnih prahova i tankih filmova titan(IV)-oksida znatno poboljšane fotokatalitičke efikasnosti. Da bi se postigla visoka fotokatalitička aktivnost u vidljivoj oblasti, neophodno je generisati aktivne apsorpcione centre za vidljivu svetlost. Pokazalo se da dopiranje anjonima nemetala predstavlja veliki potencijal u indukovanju takve apsorpcije i dosta napora se ulaže u razvijanje metoda za sintezu anjon-dopiranih TiO2 fotokatalizatora sa visokom aktivnošću u vidljivom delu spektra. Prema tome, u ovoj doktorskoj disertaciji prvo je predstavljeno dobijanje TiO2 filmova pulsnom laserskom depozicijom na staklenim supstratima u atmosferi kiseonika, metana, azota i mešavini kiseonika i azota. Inkorporacija azota u rešetku TiO2 je usp

Predmet istraživanja ove doktorske disertacije pripada oblasti nanomateijala i nanotehnogija koja je u trendu savremenih istraživanja. Posebno su intenzivna istraživanja u oblasti polimernih nanokompozita gde tradicionalno slabe strane polimera (niske vrednosti parametara mehaničke čvrstoće i loša termostabilnost) se značajno poboljšavaju primenom malog udela nano punioca i ojačanja uz neznatan porast gustine. Razvijena je metoda dizajniranja strukture nanokompozitnih balističkih materijala sa gledišta poboljšanja njihovih svojstava otpornosti pri udarima visoke energije. Proučeni su uslovi dobijanja laminarnih kompozitnih materijala p-aramid/poli (vinil butiral). Poli (vinil butiralni) sloj nanošen je u obliku disperzije poli (vinil butirala) i nano čestica SiOR2R u etil-alkoholu, pri čemu su korišćene modifikovane i nemodifikovane čestice SiOR2 Rsa vezujućim agensom-AMEO silanom. Na taj nači je utvrđen veliki značaj modifikacije nano čestica SiOR2R sa silanima na mehanička, termička i antibalistička svojstva dobijenih hibridnih nanokompozitnih materijala. Savremena istraživanja u ovoj oblasti usmerena su u pronalaženju mehanizama zaustavljanja rasta prsline modifikovanjem strukture na nano nivou što je i predmet ove doktorske disertacije. Proučavanja u okviru ove disertacije bila su usmerena na istraživanja mehanizama apsorpcije energije u nanokompozitima pri udarnim opterećenjima visoke energije i ponašanje nano čestica kao konstituenata u strukturi hibridnih kompozitnih materijala. Sinteza ovih nanokompozitnih materijala izvršiće se primenom koloidnih suspenzija koje se karakterišu ekstremnim porastom viskoznosti pri velikim brzinama smicanja kojima su izloženi pri udarnim naprezanjima. Originalnost ideje se ogleda što je princip hibridizacije primenjen na izradu laminatnih balističkih ploča sa laminama koje su različito nanomodifikovane a samim tim i sa različitim svojstvima. Značaj ove ideje je što različito nanomodifikovane lamine omogućavaju izradu funkciona, The purpose of this dissertation is to investigate the effects of lamination and hybrid soft armor systems through ballistic impact. The investigation was carried out by using dynamic mechanical analysis and actual ballistic testing. The most important conclusions derived from this research are that lamination of the systems with very low resin content are superior to multiple non-laminated systems, and this advance could be improved further by hybrid systems using nanomodified fabric layers on the impact side and relatively tighter woven fabrics between the layers. This dissertation reports the preparation of SiOR2R and TiOR2R/poly (vinyl butyral) nanocomposites with enhanced dynamic mechanical properties. Silica and titania nanoparticles were introduced in the matrix as the neat powder and as colloidal sol using the melt mixing process. Composites reinforced with colloidal sol silica and titania showed higher mechanical properties than the ones reinforced with as-received particles. When sol TiOR2R particles are used, the highest increase of storage modulus of about 54% is obtained for 5 wt% loading, while for sol SiOR2R, the storage modulus increases with the addition of nanosilica with the largest increase of about 99% for 7 wt% loading. In addition, nanocomposites were introduced within Kevlar/PVB composites. The addition of 5 wt% silica and titania colloidal sol lead to the remarkable increase of the storage modulus for about 98 and 65%, respectively. Largest contribution of nanoreinforcements in lowering the glass transition temperature is observed for 7 wt% loading of TiOR2R and SiOR2R colloidal sol. This study reports the manufacture of new fabric forms from the preparation of hybrid laminated multi-axial composites with enhanced thermo-mechanical properties. Thermal and dynamic mechanical analysis of polymer matrix films and fabricated hybrid composites were employed in order to determine the optimal material composition and reinforcement content for compo

Ovaj rad je imao za cilj , razvoj postupka sinteze polimernih prekursora mreža na bazi obnovljivih sirovina. Razvijen je postupak sinteze poli laktida u rastvoru dihlor metana. Vreme trajanja postupka sinteze je 6 h, a uspešnost samog procesa je potvrđena metodama identifikacije i karakterizacije dobijenih polimera PLLA. U ovom radu, za ispitivanja dobijenih polimernih materijala, uzimajući u obzir ideju o krajnjoj nameni, korišćene su sledeće metode: GPC ( Gel Permeation Chromarography) za određivanje raspodele molekulske mase; IR spektrofotometrija, prikazuje vibraciju atomskih, molekulskih ili funkcionaknih grupa; i termička analiza TGA i DSC, za praćenje promena pri kontrolisanom zagrevanju i hlađenju. Jedan od ciljeva rada je bio i da se da pregled postojećih teorija ojačanja elastomera punilima sa nano česticama, i ispita ponašanje nano-kompozitnih materiajala pod dejstvom visoko energetskog zračenja ( gama zračenja). U eksperimentalnom delu ispitivani su elastomerni materijale na bazi butadienakrilonitrilnog kaučuka (NBR) i hlorsulfonovanog polietilenskog kaučuka (CSM) . Mešanjem CSM i NBR formiraju se umreženi sistemi, koji se koriste kao prekursori mreža za dobijanje nano-kompozitnih materijala ojačanaih česticama aktivnih punilačađi i silicijum (IV) oksida. Kod tako dobijenih materijala ispitivane su karakteristike pre i posle ozračivanja γ zracima. Dinamičko-mehaničkom analizom potvrđen je ojačavajući efekat punila., This work was aimed at the development procedure for the synthesis of polymer precursors network based on renewable raw materials. Developed a procedure for synthesis of poly lactide in solution, dichloro methane. The duration of the synthesis procedure was 6 h, and the success of the process was confirmed by the methods of identification and characterization of the obtained polymer PLLA. In this paper, the investigation obtained polymer materials, taking into account the idea of final destination, following methods were used: GPC (gel permeation Chromarography) to determine the distribution of molecular weight, IR spectrophotometry, showing the vibration of atomic, molecular or funkcionaknih group, and thermal analysis TGA and DSC, to track changes in a controlled heating and cooling. One of the aims of this study was to be given to review of existing theories of reinforcement fillers elastomer with nano particles, and examine the behavior of nano-composite materiajala under the influence of high energy radiation (gamma radiation). In the experimental part of elastomeric materials have been studied on the basis of butadienakrilonitrilnog rubber (NBR) and chlorosulphonated polyethylene rubber (CSM). CSM NBR mixing and forming the network system, which are used as precursors for a network of nano-composite particles ojačanaih active fillers-carbon black and silicon (IV) oxide. With so obtained materials were investigated characteristics before and after irradiation with γ rays. Dynamic-mechanical analysis confirmed the reinforcing effect of fillers.

Silver/poly(N-vinyl-2-pyrrolidone) (Ag/PVP) nanocomposites were obtained by electrochemical reduction of Ag+ at a constant voltage, by in situ synthesis of silver nanoparticles inside a poly(N-vinyl-2-pyrrolidone) matrix, previously cross-linked by g-irradiation. Optimal values of synthesis parameters were investigated: the composition of the solution for swelling of PVP hydrogel, implementation time and applied voltage. Ag/PVP nanocomposites were characterized by UV-Visible spectroscopy, and IR spectroscopy. UV-Visible spectroscopy results showed that the reduction of silver ions was more efficient when the more conductive solution for swelling of PVP hydrogel was used, i.e., the solution containing 3.9 mM AgNO3 with 0.1 M KNO3. It was also shown that the concentration of the reduced silver increases with the increase in implementation time and applied voltage, up to values of 4 min and 200 V, respectively. The Ag nanoparticle size was estimated to be 25 nm, by comparison of the experimental results of UV-Vis spectroscopy with the theoretical predictions obtained by the calculations in 'MiePlot v.3.4' software, having the algorithm based on Mie scattering from a sphere. The results of FTIR spectroscopy have shown that Ag nanoparticles were mainly bonded to PVP by coordination bondages between Ag nanoparticles and N from the pyrrolidone ring of PVP., Nanokompoziti srebra i poli(N-vinil-2-pirolidona), PVP, dobijeni su elektrohemijskom redukcijom Ag+ pri konstantnom naponu, in situ sintezom nanočestica srebra u umreženoj matrici PVP, prethodno dobijenoj radijaciono-hemijskim putem. Optimizacija elektrohemijske sinteze nanočestica srebra je vršena variranjem sledećih parametara: sastava rastvora za bubrenje PVP hidrogela, vremena implementacije i primenjenog napona. Prisustvo nanočestica srebra u Ag/PVP nanokompozitima potvrđeno je UV-vidljivom spektroskopijom, dok je postojanje interakcija između nanočestica srebra i molekula PVP potvrđeno FTIR spektroskopijom. Rezultati rada ukazuju na to da je redukcija srebra efikasnija kada se koristi rastvor za bubrenje veće provodljivosti, kao i da koncentracija dobijenih nanočestica srebra raste sa produžetkom vremena implementacije i povećanjem primenjenog napona.

Silver/poly(N-vinyl-2-pyrrolidone) (Ag/PVP) nanocomposites were obtained by electrochemical reduction of Ag+ at a constant voltage, by in situ synthesis of silver nanoparticles inside a poly(N-vinyl-2-pyrrolidone) matrix, previously cross-linked by g-irradiation. Optimal values of synthesis parameters were investigated: the composition of the solution for swelling of PVP hydrogel, implementation time and applied voltage. Ag/PVP nanocomposites were characterized by UV-Visible spectroscopy, and IR spectroscopy. UV-Visible spectroscopy results showed that the reduction of silver ions was more efficient when the more conductive solution for swelling of PVP hydrogel was used, i.e., the solution containing 3.9 mM AgNO3 with 0.1 M KNO3. It was also shown that the concentration of the reduced silver increases with the increase in implementation time and applied voltage, up to values of 4 min and 200 V, respectively. The Ag nanoparticle size was estimated to be 25 nm, by comparison of the experimental results of UV-Vis spectroscopy with the theoretical predictions obtained by the calculations in 'MiePlot v.3.4' software, having the algorithm based on Mie scattering from a sphere. The results of FTIR spectroscopy have shown that Ag nanoparticles were mainly bonded to PVP by coordination bondages between Ag nanoparticles and N from the pyrrolidone ring of PVP., Nanokompoziti srebra i poli(N-vinil-2-pirolidona), PVP, dobijeni su elektrohemijskom redukcijom Ag+ pri konstantnom naponu, in situ sintezom nanočestica srebra u umreženoj matrici PVP, prethodno dobijenoj radijaciono-hemijskim putem. Optimizacija elektrohemijske sinteze nanočestica srebra je vršena variranjem sledećih parametara: sastava rastvora za bubrenje PVP hidrogela, vremena implementacije i primenjenog napona. Prisustvo nanočestica srebra u Ag/PVP nanokompozitima potvrđeno je UV-vidljivom spektroskopijom, dok je postojanje interakcija između nanočestica srebra i molekula PVP potvrđeno FTIR spektroskopijom. Rezultati rada ukazuju na to da je redukcija srebra efikasnija kada se koristi rastvor za bubrenje veće provodljivosti, kao i da koncentracija dobijenih nanočestica srebra raste sa produžetkom vremena implementacije i povećanjem primenjenog napona.

Incorporation of inorganic nanoparticles can significantly affect the properties of the polymer matrix. The properties of polymer nanocomposites depend on the type of incorporated nanoparticles, their size and shape, their concentration, and interactions with the polymer matrix. Homogeneity of polymer nanocomposites is influenced very much by the preparation method. In this study, TiO2 nanoparticles surface modified with 6-palmitate ascorbic acid (6-PAA) were encapsulated in poly(methyl methacrylate) (PMMA) by in situ radical polymerization of methyl methacrylate initiated by 2,2'-azobisisobutyronitrile (AIBN). The surface modification of the TiO2 nanoparticles was achieved by the formation of a charge transfer complex between TiO2 nanoparticles and 6-palmitate ascorbic acid. The radical polymerization of MMA in the presence of TiO2-PAA nanoparticles was conducted in solution (PMMA/TiO2-PAA-R), in bulk (PMMA/TiO2-PAA-M) or in suspension (PMMA/TiO2-PAA-S). The main purpose of this study was to investigate the influence of the preparation method on the molar masses and thermal properties of PMMA/TiO2-PAA nanocomposite. It was obtained that molar masses of PMMA extracted from the composites had smaller values compared to molar masses of pure PMMA synthesized in the same manner, which indicated that TiO2-PAA nanoparticles affected the reaction of termination. Thermal properties were investigated by DSC and TGA. The values of glass transition temperature, Tg, were influenced by the way the radical polymerization was conducted, even in the case of the pure PMMA. The Tg of composite samples was always smaller than the value of the corresponding PMMA sample and the smallest value was obtained for PMMA/TiO2-PAA-M since they contained the largest amount of low molar mass residue. The TGA results showed that thermal and thermooxidative stability of polymer composites obtained in solution and in suspension was better than for the pure PMMA obtained in the same way., Predmet ovog rada je dobijanje i karakterizacija nanokompozita kod kojih polimernu matricu čini poli(metil metakrilat) (PMMA), a kao neorgansko punilo nanočestice titan-dioksida. Svi uzorci nanokompozita dobijeni su in situ polimerizacijom preko slobodnih radikala metil metakrilata (MMA) u prisustvu čestica punila. Površinska modifikacija korišćenih nanočestica titan-dioksida izvršena je palmitatom askorbinske kiseline. Uzorci nanokompozita su pripremljeni polimerizacijom metil metakrilata u rastvoru, u masi i suspenzionom polimerizacijom. Određene su vrednosti molarne mase PMMA ekstrahovanog iz kompozitnih uzoraka i dobijeno je da su one manje od vrednosti molarne mase čistog PMMA dobijenog na isti način, na osnovu čega se može zaključiti da nanočestice TiO2-PAA prisutne u toku polimerizacije u sva tri slučaja utiču na reakcije terminacije i dovode do smanjenja molarne mase PMMA matrice. Diferencijalnom skenirajućom kalorimetrijom i termogravimetrijskom analizom utvrđeno je i da način sinteze polimerne matrice i koncentracija čestica punila utiču na termička svojstva dobijenih polimernih nanokompozita.

Incorporation of inorganic nanoparticles can significantly affect the properties of the polymer matrix. The properties of polymer nanocomposites depend on the type of incorporated nanoparticles, their size and shape, their concentration, and interactions with the polymer matrix. Homogeneity of polymer nanocomposites is influenced very much by the preparation method. In this study, TiO2 nanoparticles surface modified with 6-palmitate ascorbic acid (6-PAA) were encapsulated in poly(methyl methacrylate) (PMMA) by in situ radical polymerization of methyl methacrylate initiated by 2,2'-azobisisobutyronitrile (AIBN). The surface modification of the TiO2 nanoparticles was achieved by the formation of a charge transfer complex between TiO2 nanoparticles and 6-palmitate ascorbic acid. The radical polymerization of MMA in the presence of TiO2-PAA nanoparticles was conducted in solution (PMMA/TiO2-PAA-R), in bulk (PMMA/TiO2-PAA-M) or in suspension (PMMA/TiO2-PAA-S). The main purpose of this study was to investigate the influence of the preparation method on the molar masses and thermal properties of PMMA/TiO2-PAA nanocomposite. It was obtained that molar masses of PMMA extracted from the composites had smaller values compared to molar masses of pure PMMA synthesized in the same manner, which indicated that TiO2-PAA nanoparticles affected the reaction of termination. Thermal properties were investigated by DSC and TGA. The values of glass transition temperature, Tg, were influenced by the way the radical polymerization was conducted, even in the case of the pure PMMA. The Tg of composite samples was always smaller than the value of the corresponding PMMA sample and the smallest value was obtained for PMMA/TiO2-PAA-M since they contained the largest amount of low molar mass residue. The TGA results showed that thermal and thermooxidative stability of polymer composites obtained in solution and in suspension was better than for the pure PMMA obtained in the same way., Predmet ovog rada je dobijanje i karakterizacija nanokompozita kod kojih polimernu matricu čini poli(metil metakrilat) (PMMA), a kao neorgansko punilo nanočestice titan-dioksida. Svi uzorci nanokompozita dobijeni su in situ polimerizacijom preko slobodnih radikala metil metakrilata (MMA) u prisustvu čestica punila. Površinska modifikacija korišćenih nanočestica titan-dioksida izvršena je palmitatom askorbinske kiseline. Uzorci nanokompozita su pripremljeni polimerizacijom metil metakrilata u rastvoru, u masi i suspenzionom polimerizacijom. Određene su vrednosti molarne mase PMMA ekstrahovanog iz kompozitnih uzoraka i dobijeno je da su one manje od vrednosti molarne mase čistog PMMA dobijenog na isti način, na osnovu čega se može zaključiti da nanočestice TiO2-PAA prisutne u toku polimerizacije u sva tri slučaja utiču na reakcije terminacije i dovode do smanjenja molarne mase PMMA matrice. Diferencijalnom skenirajućom kalorimetrijom i termogravimetrijskom analizom utvrđeno je i da način sinteze polimerne matrice i koncentracija čestica punila utiču na termička svojstva dobijenih polimernih nanokompozita.

Incorporation of inorganic nanoparticles can significantly affect the properties of the polymer matrix. The properties of polymer nanocomposites depend on the type of incorporated nanoparticles, their size and shape, their concentration, and interactions with the polymer matrix. Homogeneity of polymer nanocomposites is influenced very much by the preparation method. In this study, TiO2 nanoparticles surface modified with 6-palmitate ascorbic acid (6-PAA) were encapsulated in poly(methyl methacrylate) (PMMA) by in situ radical polymerization of methyl methacrylate initiated by 2,2'-azobisisobutyronitrile (AIBN). The surface modification of the TiO2 nanoparticles was achieved by the formation of a charge transfer complex between TiO2 nanoparticles and 6-palmitate ascorbic acid. The radical polymerization of MMA in the presence of TiO2-PAA nanoparticles was conducted in solution (PMMA/TiO2-PAA-R), in bulk (PMMA/TiO2-PAA-M) or in suspension (PMMA/TiO2-PAA-S). The main purpose of this study was to investigate the influence of the preparation method on the molar masses and thermal properties of PMMA/TiO2-PAA nanocomposite. It was obtained that molar masses of PMMA extracted from the composites had smaller values compared to molar masses of pure PMMA synthesized in the same manner, which indicated that TiO2-PAA nanoparticles affected the reaction of termination. Thermal properties were investigated by DSC and TGA. The values of glass transition temperature, Tg, were influenced by the way the radical polymerization was conducted, even in the case of the pure PMMA. The Tg of composite samples was always smaller than the value of the corresponding PMMA sample and the smallest value was obtained for PMMA/TiO2-PAA-M since they contained the largest amount of low molar mass residue. The TGA results showed that thermal and thermooxidative stability of polymer composites obtained in solution and in suspension was better than for the pure PMMA obtained in the same way., Predmet ovog rada je dobijanje i karakterizacija nanokompozita kod kojih polimernu matricu čini poli(metil metakrilat) (PMMA), a kao neorgansko punilo nanočestice titan-dioksida. Svi uzorci nanokompozita dobijeni su in situ polimerizacijom preko slobodnih radikala metil metakrilata (MMA) u prisustvu čestica punila. Površinska modifikacija korišćenih nanočestica titan-dioksida izvršena je palmitatom askorbinske kiseline. Uzorci nanokompozita su pripremljeni polimerizacijom metil metakrilata u rastvoru, u masi i suspenzionom polimerizacijom. Određene su vrednosti molarne mase PMMA ekstrahovanog iz kompozitnih uzoraka i dobijeno je da su one manje od vrednosti molarne mase čistog PMMA dobijenog na isti način, na osnovu čega se može zaključiti da nanočestice TiO2-PAA prisutne u toku polimerizacije u sva tri slučaja utiču na reakcije terminacije i dovode do smanjenja molarne mase PMMA matrice. Diferencijalnom skenirajućom kalorimetrijom i termogravimetrijskom analizom utvrđeno je i da način sinteze polimerne matrice i koncentracija čestica punila utiču na termička svojstva dobijenih polimernih nanokompozita.

Incorporation of inorganic nanoparticles can significantly affect the properties of the polymer matrix. The properties of polymer nanocomposites depend on the type of incorporated nanoparticles, their size and shape, their concentration, and interactions with the polymer matrix. Homogeneity of polymer nanocomposites is influenced very much by the preparation method. In this study, TiO2 nanoparticles surface modified with 6-palmitate ascorbic acid (6-PAA) were encapsulated in poly(methyl methacrylate) (PMMA) by in situ radical polymerization of methyl methacrylate initiated by 2,2'-azobisisobutyronitrile (AIBN). The surface modification of the TiO2 nanoparticles was achieved by the formation of a charge transfer complex between TiO2 nanoparticles and 6-palmitate ascorbic acid. The radical polymerization of MMA in the presence of TiO2-PAA nanoparticles was conducted in solution (PMMA/TiO2-PAA-R), in bulk (PMMA/TiO2-PAA-M) or in suspension (PMMA/TiO2-PAA-S). The main purpose of this study was to investigate the influence of the preparation method on the molar masses and thermal properties of PMMA/TiO2-PAA nanocomposite. It was obtained that molar masses of PMMA extracted from the composites had smaller values compared to molar masses of pure PMMA synthesized in the same manner, which indicated that TiO2-PAA nanoparticles affected the reaction of termination. Thermal properties were investigated by DSC and TGA. The values of glass transition temperature, Tg, were influenced by the way the radical polymerization was conducted, even in the case of the pure PMMA. The Tg of composite samples was always smaller than the value of the corresponding PMMA sample and the smallest value was obtained for PMMA/TiO2-PAA-M since they contained the largest amount of low molar mass residue. The TGA results showed that thermal and thermooxidative stability of polymer composites obtained in solution and in suspension was better than for the pure PMMA obtained in the same way., Predmet ovog rada je dobijanje i karakterizacija nanokompozita kod kojih polimernu matricu čini poli(metil metakrilat) (PMMA), a kao neorgansko punilo nanočestice titan-dioksida. Svi uzorci nanokompozita dobijeni su in situ polimerizacijom preko slobodnih radikala metil metakrilata (MMA) u prisustvu čestica punila. Površinska modifikacija korišćenih nanočestica titan-dioksida izvršena je palmitatom askorbinske kiseline. Uzorci nanokompozita su pripremljeni polimerizacijom metil metakrilata u rastvoru, u masi i suspenzionom polimerizacijom. Određene su vrednosti molarne mase PMMA ekstrahovanog iz kompozitnih uzoraka i dobijeno je da su one manje od vrednosti molarne mase čistog PMMA dobijenog na isti način, na osnovu čega se može zaključiti da nanočestice TiO2-PAA prisutne u toku polimerizacije u sva tri slučaja utiču na reakcije terminacije i dovode do smanjenja molarne mase PMMA matrice. Diferencijalnom skenirajućom kalorimetrijom i termogravimetrijskom analizom utvrđeno je i da način sinteze polimerne matrice i koncentracija čestica punila utiču na termička svojstva dobijenih polimernih nanokompozita.

Cilj rada je sinteza nanokompozitnih uzoraka hematita, maghemita i ε-Fe2O3 i proučavanje njihovih magnetnih osobina. Uzorci su dobijeni sol-gel metodom koristeći tetraetilortosilikat (TEOS) kao prekursor amorfnog silicijum dioksida i gvoţĎe nitrat (Fe(NO3)3·9H2O, Aldrich 98%) kao prekursor feri-oksida. Kontrolišući uslove sinteze dobijeni su nanokompoziti sa različitim strukturama i magnetnim karakteristikama. Karakterizacija uzoraka je izvršena difrakcijom X-zraka, transmisionim elektronskim mikroskopom i SQUID magnetometrom. Ispitivanja DC magnetizacije i AC susceptibilnosti pokazala su tipično ponašanje superparamagnetnih sistema, kao što je postojanje i frekventna zavisnost temperature blokiranja, ireverzibilnost zero-field-cooled (ZFC) i field- cooled (FC) krivih, pojava magnetne histerezisne petlje ispod temperature blokiranja i superparamagnetizam iznad temperature blokiranja. Ispitivani nanokompoziti su pokazali promene u vrednosti koercitativne sile od 0 Oe (hematit i maghemit) do 17000 Oe (ε-Fe2O3), i promene u saturacionoj magnetizaciji od 3,5 emu/g (hematit) do 67 emu/g (maghemit). Nanočestice ε- Fe2O3 faze su direktno dobijene od nanočestica hematita koje su ţarene do temperature od 1050˚C. Razmatrana je uloga meĎučestičnih interakcija na magnetne osobine. Ovi rezultati su vaţni za proučavanja magnetnih osobina nanočestičnih sistema, kao za mnoge industrijske i biomedicinske primene., The aim of this work was to synthesize hematite, maghemite and ε-Fe2O3 nanocomposites, and investigate their magnetic properties. The samples were obtained by sol-gel method using tetraethylorthosilicate (TEOS) as precursor of silica, and iron nitrate (Fe(NO3)3·9H2O, Aldrich 98%) as precursor of ferric oxides. By controlling the reaction conditions, it was possible to obtain the nanocomposites with different structural and magnetic properties. Samples were characterized by X-ray powder diffraction, transmission electron microscopy, and SQUID magnetometry. Investigation of the magnetic properties by DC magnetization and AC susceptibility measurements indicated behavior typical of a superparamagnetic systems, such as the existence and frequency dependence of a blocking temperature, irreversibility of the zero-field-cooled (ZFC) and field-cooled (FC) curves, emergence of magnetic hysteresis below the blocking temperature, and suprparamagnetism above the blocking temperature. The nanocomposites showed variation in the coercivity values from 0 Oe (hematite and maghemite) to 17000 Oe (ε-Fe2O3), and variation in the saturation magnetization from 3,5 emu/g (hematite) to 67 emu/g (maghemite). Nanoparticles of ε-Fe2O3 are directly acquired from nanoparticles of hematite by applying heat treatments at increasing temperatures up to 1050˚C. The role of magnetic interparticle interactions on the magnetic properties is discussed. These results are valuable for the study of the magnetic behavior of nanoparticle systems, as well as for use in many industrial and biomedical applications.

In order to achieve improved mechanical properties of dispersion strengthened nanocomposite, without influencing electrical and thermal conductivity it is necessary for dispersoide to be nano sized and uniformly distributed in base metal matrix. In this paper are presented the results concerning possibility of using UV spectrophotometry for determination of alumina particle size in Cu- AL2O3 system. Presented results show that this method is unefficient as method for determination of dispersoide particle size, due to the coalescence of particles false results are obtained, i.e. particle size significantly higher then one determined by image analysis., Izvod U cilju postizanja poboljšanih mehaničkih osobina disperzno ojačanih nanokompozita, bez uticaja na električnu i termičku provodljivost neophodno je da je dispergovana faza nano veličine i ravnomerno raspoređena u osnovnom metalu. U radu su prikazani rezultati vezani za mogućnost određivanja veličina čestica glinice u nanokompozitnim materijalima iz sistema Cu- AL2O3 primenom UV spektrofotometrije. Dobijeni rezultati pokazuju da je ova metoda nedovoljno pouzdana kao adekvatna metoda za određivanje veličine čestice diperzne faze, jer usled koalescencije čestica dolazi do pojave lažnih rezultata, tj. određena veličina čestica je višestruko veća od veličine određene analizom slike.

In order to achieve improved mechanical properties of dispersion strengthened nanocomposite, without influencing electrical and thermal conductivity it is necessary for dispersoide to be nano sized and uniformly distributed in base metal matrix. In this paper are presented the results concerning possibility of using UV spectrophotometry for determination of alumina particle size in Cu- AL2O3 system. Presented results show that this method is unefficient as method for determination of dispersoide particle size, due to the coalescence of particles false results are obtained, i.e. particle size significantly higher then one determined by image analysis., Izvod U cilju postizanja poboljšanih mehaničkih osobina disperzno ojačanih nanokompozita, bez uticaja na električnu i termičku provodljivost neophodno je da je dispergovana faza nano veličine i ravnomerno raspoređena u osnovnom metalu. U radu su prikazani rezultati vezani za mogućnost određivanja veličina čestica glinice u nanokompozitnim materijalima iz sistema Cu- AL2O3 primenom UV spektrofotometrije. Dobijeni rezultati pokazuju da je ova metoda nedovoljno pouzdana kao adekvatna metoda za određivanje veličine čestice diperzne faze, jer usled koalescencije čestica dolazi do pojave lažnih rezultata, tj. određena veličina čestica je višestruko veća od veličine određene analizom slike.