Effective adsorbents for polyfluorinated compounds (PFCs) were successfully prepared. And they were tested in the adsorption of perfluorooctanoic and perfluorooctanesulfonic acids. Bridged silsesquioxanes containing secondary and tertiary amino groups were synthesized by sol-gel condensation of bis[3-(trimethoxysilyl)propyl]amine and bis[3-(methylamino)propyl]-trimethoxysilane in acidic media with surfactants. Obtained materials are mesoporous with a high BET surface area. They combine high structural stability with a high concentration of surface amino groups serving as adsorption sites. Batch adsorption tests demonstrated their extremely high adsorption capacity on PFCs: in some experiments, it reached up to 88% of the adsorbent weight. Adsorption of PFCs changed the surfaces of the adsorbent nanoparticles from hydrophilic to hydrophobic thus providing their agglomeration and floatability. Column tests showed fast adsorption of PFCs even at high concentrations and high flow rates. Obtained results can be used in the development of an effective filtration device for clean-up of water contaminated by PFCs.

Metal alkoxides are easily available and versatile precursors for functional materials, such as solid catalysts. However, the poor solubility of metal alkoxides in organic solvents usually hinders their facile application in sol–gel processes and complicates access to complex carbonate or oxidic compounds after hydrolysis of the precursors. In our contribution we have therefore shown three different solubilization strategies for metal alkoxides, namely the derivatization, the hetero-metallization and CO2 insertion. The latter strategy leads to a stoichiometric insertion of CO2 into the metal–oxygen bond of the alkoxide and the subsequent formation of metal alkyl carbonates. These precursors can then be employed advantageously in sol–gel chemistry and, after controlled hydrolysis, result in chemically defined crystalline carbonates and hydroxycarbonates. Cu- and Zn-containing carbonates and hydroxycarbonates were used in an exemplary study for the synthesis of Cu/Zn-based bulk catalysts for methanol synthesis with a final comparable catalytic activity to commercial standard reference catalysts.

An investigation of electrochemical storage device materials has been undertaken in four parts. The bulk and interfacial resistance of Na+ beta-alumina tubes were separated using a galvanostatic charge-discharge method. Sodium silicide was characterized to better understand its synthesis. BiMn2O5 was produced using a sol-gel method and tested for pseudocapacity. Different lithium ion anode and cathode materials were deposited using a new electrophoretic deposition method. A novel galvanostatic charge-discharge method was developed for the determination of bulk and interface resistance in Na+ beta-alumina solid electrolytes [BASE]. Dense and duplex BASE tubes were tested by varying the exposed surface area. The results of dense BASE tube pairs were used to determine the bulk and interfacial resistance components, while duplex BASE tubes were tested to determine the reduction in interfacial resistance. It was found that duplex tubes had reduced the interfacial resistance by 75%, when compared to a uniformly dense electrolyte. Sodium silicide was characterized using various methods to better understand the phase and the Na-Si phase diagram. EMF experiments using Na+ BASE tubes was used to determine the activity in the silicon rich region of the phase diagram, which showed a sodium activity of 0.5 at 550°C. TGA/DSC was used to determine phase transformation temperatures, as well as the heat of formation for NaSi, which was recorded to be below 1 kJ mol-1. A sol-gel precipitation method was used to produce fine BiMn2O5 powders used for supercapacitors. The powders resulting from a consistent method were tested for pseudocapacitance using bulk and thin film electrodes. Bulk electrodes had a gravimetric capacitance of 10 F g-1, while thin film electrodes only reached 2.6 F g-1. Lithium ion battery anode (Li4Ti5O12) and cathode (LiFePO4, LiMn2O4, LiMn1.5Ni0.5O4) materials were electrophoretically deposited with the assistance of PAZO-Na and CMC-Na. Cathodes were successfully deposited on aluminium substrates, and were tested in the potential window 2 – 4.3 V. The LiFePO4 cathodes showed capacity of 146.7 mAh g-1 at C/10, while showing capacity retention of 103% after 50 cycles. / Thesis / Doctor of Philosophy (PhD) / The goal of this work is to examine materials used in different types of electrochemical storage devices. The modification of resistive properties of β-alumina electrolytes are examined for use in high temperature sodium batteries. Electrophoretic deposition methods are used to rapidly make thin electrodes for lithium ion batteries and supercapacitors. The stoichiometric compound NaSi, a potentially safer and greener method of producing hydrogen gas, is characterized for a better understanding of its properties, and therefore production.

Uma nova rota de síntese via metodo sol-gel para óxido de titânio (titânia) e óxido misto titânio/zircônio (zircônia) é proposta neste trabalho. As amostras foram submetidas ao tratamento hidrotérmico e obteve-se compostos mesoestruturados e de elevada área superficial. Algumas amostras foram submetidas à calcinação a 450°C para a verificação da estabilidade a altas temperaturas. As amostras foram analisadas por difratometria de raios-x (DRX), espalhamento de raios-x de baixo ângulo (SAXS), área superficial através do método BET, por microscopia eletrônica de varredura por emissão de campo (FE-SEM), além de serem testadas na fotodegradação de corantes. Foram testados diferentes alcóxidos precursores, isopropóxido de titânio e n-butóxido de titânio; ácidos, clorídrico e nítrico; e surfactantes, Pluronic® P123, Brij® 700 e Brij® 98; e também variadas as quantidades de surfactantes utilizadas, para que fosse possível analisar como estas variações afetam a síntese dos compostos e se estabelecer uma nova rota padronizada utilizando-se os melhores precursores em quantidades ideais. Para efeito de comparação, foi testada uma rota alcalina de síntese, que levou ao material com área superficial mais elevada. Como resultado deste trabalho, foi desenvolvida uma nova rota de síntese para óxidos mesoestruturados de titânio e titânio/zircônio corn elevada área superficial, na qual a etapa de calcinação para remoção do surfactante foi eliminada. Algunas dos materiais preparados mostraram excelente desempenho na degradação fotocatalítica de um corante comercial. / A new sol-gel based synthetic route for titania and mixed titania-zirconia ceramic powders is proposed in this contribution. This route combines a surfactant-template strategy with hydrothermal treatment, yielding mesostructured compoundes with a high surface area. Some samples were calcined at 450 °C in order to verify the stability of the structures at these temperatures. The materials were characterized by x-ray diffraction (XRD), small angle x-ray scattering (SAXS), surface area (BET method), field emission scanning electron microscopy (FE-SEM), and were also tested in the photocatalytic degradation of selected dyes. Different precursor alcóxidos were used: titanium isopropoxide and titanium n-butoxide. Two different acids were used to catalyze the hydrolysis reaction, HCl and HNO3. Three surfactants were used as templating agents: Pluronic P123®, Brij 700®, and Brij 98®. The amount of surfactant was also changed in order to verify how these variations affect the surface area and morphology of the resulting compounds. For comparison, an alkaline route was also tested, in which the highest surface area was observed. As a result of this work, a new synthetic route for mesostructured titania and titania-zirconia mixed oxides was developed, in which the surfactant is removed without a calcinations step, resulting in compounds with high surface areas and, in some cases, excellent photocatalytic properties for the degradation of a dye.

Uma nova rota de síntese via metodo sol-gel para óxido de titânio (titânia) e óxido misto titânio/zircônio (zircônia) é proposta neste trabalho. As amostras foram submetidas ao tratamento hidrotérmico e obteve-se compostos mesoestruturados e de elevada área superficial. Algumas amostras foram submetidas à calcinação a 450°C para a verificação da estabilidade a altas temperaturas. As amostras foram analisadas por difratometria de raios-x (DRX), espalhamento de raios-x de baixo ângulo (SAXS), área superficial através do método BET, por microscopia eletrônica de varredura por emissão de campo (FE-SEM), além de serem testadas na fotodegradação de corantes. Foram testados diferentes alcóxidos precursores, isopropóxido de titânio e n-butóxido de titânio; ácidos, clorídrico e nítrico; e surfactantes, Pluronic® P123, Brij® 700 e Brij® 98; e também variadas as quantidades de surfactantes utilizadas, para que fosse possível analisar como estas variações afetam a síntese dos compostos e se estabelecer uma nova rota padronizada utilizando-se os melhores precursores em quantidades ideais. Para efeito de comparação, foi testada uma rota alcalina de síntese, que levou ao material com área superficial mais elevada. Como resultado deste trabalho, foi desenvolvida uma nova rota de síntese para óxidos mesoestruturados de titânio e titânio/zircônio corn elevada área superficial, na qual a etapa de calcinação para remoção do surfactante foi eliminada. Algunas dos materiais preparados mostraram excelente desempenho na degradação fotocatalítica de um corante comercial. / A new sol-gel based synthetic route for titania and mixed titania-zirconia ceramic powders is proposed in this contribution. This route combines a surfactant-template strategy with hydrothermal treatment, yielding mesostructured compoundes with a high surface area. Some samples were calcined at 450 °C in order to verify the stability of the structures at these temperatures. The materials were characterized by x-ray diffraction (XRD), small angle x-ray scattering (SAXS), surface area (BET method), field emission scanning electron microscopy (FE-SEM), and were also tested in the photocatalytic degradation of selected dyes. Different precursor alcóxidos were used: titanium isopropoxide and titanium n-butoxide. Two different acids were used to catalyze the hydrolysis reaction, HCl and HNO3. Three surfactants were used as templating agents: Pluronic P123®, Brij 700®, and Brij 98®. The amount of surfactant was also changed in order to verify how these variations affect the surface area and morphology of the resulting compounds. For comparison, an alkaline route was also tested, in which the highest surface area was observed. As a result of this work, a new synthetic route for mesostructured titania and titania-zirconia mixed oxides was developed, in which the surfactant is removed without a calcinations step, resulting in compounds with high surface areas and, in some cases, excellent photocatalytic properties for the degradation of a dye.

<p style="text-align: justify;">Kroz istoriju, otkrivanje novih materijala i njihovog dizajna dovodilo je do tehnolo&scaron;kih revolucija. U pro&scaron;lom veku, novi materijali naprednih svojstava uveli su elektronske uređaje u svakodnevni život čoveka. Industrija mikročipova predstavlja ogroman deo svetskog trži&scaron;ta, i traži neprestan razvoj da bi pružila bolje proizvode potro&scaron;ačima. Početkom ovog veka, nova grupa materijala, pod nazivom multiferoici, privukla je pažnju naučno-istraživačkog dru&scaron;tva u svetu. Ovi materijali poseduju jedinstvenu karakteristiku da istovremeno ispoljavaju vi&scaron;e od jedne feroične osobine (feroelektričnost, feromagnetizam, feroelastičnost), a &scaron;to je jo&scaron; važnije, mogu da ostvare interakciju među njima. Naime, magnetizacija multiferoika se može postići primenom spolja&scaron;njeg električnog polja, a takođe se mogu i polarisati primenom spolja&scaron;njeg magnetnog polja. Ovo vrlo interesantno svojstvo otvara potencijlanu primenu u oblasti hibridne računarske memorije, senzora, aktuatora, i dr. Sredinom pro&scaron;log veka, jednofazni multiferoici su prvi privukli pažnju, ali poseldnjih godina, kompozitni multiferoici su pokazali bolje rezultate u pogledu funkcionalnih karakteristika. Trend minijaturizacije je takođe prisutan u ovoj oblasti, stoga su multiferoični tanki filmovi vrlo atraktivni u istraživačkih krugovima ne samo zbog niske potro&scaron;nje električne energije, malog utro&scaron;ka meterijala i malih dimenzija, već i zbog dobre magnetoelektrične interakcije.&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Glavni cilj ove doktorske disertacije je bio određivanje optimalnog procesa sinteze/depozicije, i vr&scaron;enje strukturne i funkcionalne karakterizacije multiferoičnih vi&scaron;eslojnih tankih filmova, sačinjenih od naizmenično deponovanih feroelektričnih BaTiO₃ i fero/ferimagnetnih NiFe₂O₄ slojeva (uglavnom na silicijumskim supstratima sa slojem platine). Različite strukture slojeva dizajnirane su u cilju određivanja optimalne, koja bi dala najvi&scaron;e vrednosti magnetoelektričnog efekta.&nbsp;&nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp; &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; U prvom koraku, sintetisani su stabilni solovi/rastvori prekursora, veličine čestica od nekoliko nanometara, reolo&scaron;kih karakteristika pogodnih za depoziciju tehnikama iz tečne faze. Vi&scaron;eslojni filmovi su dobijeni &quot;spin&quot; procesom nano&scaron;enja, pri čemu je termički tretman svakog sloja na 500 &deg;C bio neophodan radi potpunog otparavanja zaostalog rastvarača. Filmovi bez pukotina, ukupne debljine ispod 1 &mu;m, uniformne debljine sloja (60 nm sloj BaTiO₃ i 40 nm sloj NiFe₂O₄) i ravne povr&scaron;ine mogu biti dobijeni sinterovanjem u temperaturnom opsegu od 750 do 900 &deg;C. Strukturna karakterizacija je potvrdila sistem bez prisustva sekundarnih faza, sačinjen od perovskitnog BaTiO₃ i spinelnog NiFe₂O₄. Dielektrična merenja su bila u saglasnosti sa mikrostrukturnom analizom, i vrednostima dielektrične konstante tipične za nanostrukturni sistem, niske vrednosti dielektričnih gubitaka i male provodljivosti. Uticaj međuslojne polarizacije, koja nalikuje Debajeovoj relaksaciji, izražena kroz povećanje dielektrične konstante uspod 100 kHz, bio je jači u nižoj frekventnoj regiji na povi&scaron;enim temperaturama usled termičke aktivacije nosilaca naelektrisanja u feritnoj fazi. Samo čist BaTiO₃ film je pokazao slab feroelektrični histerezis nepotpune saturacije, malo vi&scaron;e polarizacije filma sinterovanog na 900 &deg;C usled ogrubljivanja strukture. Meuđuslojni efekti su takođe primećeni kod feroelektričnih merenja na sobnoj temperaturi, sa izraženijim prisustvom kada se primeni jače električno polje. Na osnovu dielektričnih i feroelektričnih merenja, zaključeno je da film sa debljim titanatnim i tanjim feritnim slojevima ima najverovatnije najbolji dizajn slojeva. Magnetne histerezisne petlje su snimljene na sobnoj temperaturi za čiste NiFe₂O₄ filmove i vi&scaron;eslojne filmove. Analizom vi&scaron;eslojnih filmova različitog dizajna slojeva, pretpostavljeno je da zatezanje nastalo mehaničkom interakcijom između titanatnih i feritnih slojeva jeste prisutno, i da raste sa povećanjem broja kontaktnih povr&scaron;ina, stoga film sa tanjim titanatnim i feritnim slojevima verovatno predstavlja najbolji izbor sa aspekta megnetnih osobina.</p> / <p>Through history, discovery of new materials and material design have led to technological revolutions. In the last century, new materials with advanced properties have introduced electronic devices in our everyday lives. Microchip industry represents one huge part of world market, and needs constant development to provide better products to consumers. In the beginning of this century, a novel group of materials, called multiferroics, have attracted close attention of research society around the world. These materials have a unique property to express more than one ferroic property simultaneously (feroelectricity, ferromagneticity, ferroelasticity), and more important, to achieve coupling between them. Namely, magnetization of multieferroic may be changed with application of external electric field, and they can be polarized with application of the external magnetic field. This is a very interesting property that opens the potential applications in fields of hybrid computer memory, sensors, actuators, etc. In the middle of last century, single phase multiferroics were the first to trigger interest in this special property, but in recent years, composite multiferroics have shown more promising results in terms of functional properties. The trend of miniaturization is also present in this field, so multiferroic thin films are very attractive for research not only because of low power and material consumption or small size, but also because of strong magnetoelectric coupling.<br />The main goal of this thesis was to determine optimal synthesis/deposition process, and perform structural and functional characterization of multiferroic multilayer thin films, composed of ferroelectric BaTiO3 and ferro/ferrimagnetic NiFe2O4 layers in alternating order (mostly on platinum coated silicon substrates). Different layer structures were designed in order to find optimal one which could show the strongest magnetoelectric effect.<br />In the first step, stable precursor sols/solutions were synthesized, with particle size of a few nanometes, and rheological properties suitable for solution deposition. The multilayered thin films were obtained by spin coating and thermal treatment of each layer on 500 &deg;C was necessary in order to completely evaporate traces of residual solvents. Crack free films with overall thickness below 1 &mu;m, uniform single layer thickness (60 nm of BaTiO3 layer and 40 nm of NiFe2O4) and flat surface can be obtained by sintering in temperature range from 750 to 900 &deg;C. Structural characterization confirmed that secondary phase free system with microstructure on nanometer scale was obtained, composed of perovskite BaTiO3 and spinel NiFe2O4. Dielectric measurements were in agreement with microstructural characterization, showing the values of dielectric constant typical for nanostructured system, low values of dielectric losses and low conductivity. The influence of interfacial polarization, resembling Debye behavior, expressed as a rise of dielectric constant below 100 kHz, was stronger in lower frequency range on higher temperatures due to thermal activation of mobile charge carriers in ferrite phase. Only the pure BaTiO3 films showed weak unsaturated ferroelectric hysteresis loops, with slightly higher polarization of films sintered on 900 &deg;C due to coarsening of the structure. The interface effects were also detected in ferroelectric measurements on room temperatures, showing increased presence when higher field is applied. Regarding dielectric and ferroelectric characterization, it was concluded that the multilayered films with thick titanate and thin ferrite layers may probably have the most promising layer design. Magnetic hysteresis loops were recorded on room temperatures for the pure NiFe2O4 and multilayers films. By analysis of different layer design of multilayers, it was assumed that mechanical straining between the ferrite and titanate layers may be present, and increases with the number of contact surfaces, thus the films with thinner titanate and ferrite layers may probably have the best layer design from aspect of magnetic properties.</p>

This doctoral thesis is focused on the study of reactions in the CaO–SiO2–H2O complex system, primarily to the synthesis of crystalline tobermorite. Hydrothermal conditions are necessary for the formation of crystalline tobermorite, whereas the course of the reaction is influenced by several factors. The main studied factor was the choice of the silica sources differing in means of solubility, crystallinity, particle size distribution, specific surface area, and purity. The water-to-solid ratio turned to be also an important factor as the length of the hydrothermal reaction. The influence of the mechanochemical pretreatment of starting materials to the final phase composition of samples was studied as well. The obtained results show that the crystallinity of the silica source is the main factor influencing the reaction rate and the purity of the synthesized tobermorite. While using the crystalline silica source the shorter silicate chains are formed and the formation of tobermorite structure is easier. Using the amorphous silica sources and the mechanochemical pretreatement of starting materials prolong the hydrothermal reaction. The prepared samples are always the mixture of crystalline or semicrystalline calcium hydrosilicates instead of the phase pure tobermorite.

The aim of the work was a processing of ceramic material based on BST for ferroelectric application. Wet chemical techniques based on precipitations and sol-gel methods with ultrasound, hydrothermal or mechanochemical treatment supporting deaglomeration and reducing particle growth were used for BST ceramic powder synthesis. Suitable powders were selected by the evaluation of particle morphology, size and agglomeration, from these powders BST bulk ceramic with defined phase composition and morphology applicable for ferroelectric applications was prepared. It was found, that the most suitable method for preparation of phase pure and nanosized BST powder was sol-gel synthesis with solvothermal treatment (200 °C/48 h). Ceramic with relative density of 85 % TD and with the average grain size of about 1, 22 µm was prepared by pressing and sintering of the powder synthesized by the sol-gel method.

No description available.

Ce travail concerne la synthèse et la caractérisation structurale de nanocristaux de faible taille (~1-3 nm) d’oxydes métalliques simples, à savoir le dioxyde de titane (TiO2), le dioxyde d’étain (SnO2) et le monoxyde de zinc (ZnO). Les synthèses ont été réalisées au moyen de méthodes sol-gel non-aqueuses voire strictement non-hydrolytiques sous contrôle cinétique. La caractérisation structurale s’est principalement appuyée sur la diffraction des rayons X, la microscopie électronique en transmission et la méthode des fonctions de distribution de paires atomiques, obtenues grâce à la diffusion totale des rayons X, couplées à des méthodes de modélisation à l’échelle atomique. Dans le cas de TiO2, des nanoparticules d’anatase bien cristallisées de 4 nm à 8 nm ont été synthétisées. Le ratio molaire de donneur d’oxygène par rapport au titane s’est avéré être un paramètre influençant fortement la taille des particules. Nous avons également mis en évidence la formation d’une phase intermédiaire caractérisée par des nanoparticules faiblement cristallisées de très faible taille dont la structure pourrait s’apparenter à une structure brookite désordonnée. Pour SnO2, des nanocristaux présentant une structure rutile ont été obtenus avec des tailles comprises entre 2 nm et 4 nm. Dans le cas de l’utilisation d’un éther, nous avons mis en évidence la formation concomitante d’une phase organique polymérisée et de nanoparticules primaires dont la structure intermédiaire présente de fortes similitudes avec la structure rutile. L’utilisation de solvants possédant une fonction benzyle en présence de tétrachlorure d’étain a conduit à la formation d’eau dans le système. Dans le cas de ZnO, nous avons montré que l’utilisation d’une base organique pour initier la formation du réseau oxyde dans une solution méthanolique d’acétate de zinc en présence d’un agent complexant du zinc permettait d’obtenir des nanoparticules de l’ordre de 1 nm. Même pour les faibles valeurs de taille, les nanoparticules présentent une structure très proche de la wurtzite avec un désordre croissant au niveau du réseau cationique. / The aim of this work was to synthesize small size (~1-3 nm) metal oxide nanocrystals namely titanium dioxide (TiO2), tin dioxide (SnO2) and zinc oxide (ZnO), and to study their structure. Syntheses were conducted via non-aqueous or even strictly non-hydrolytic sol-gel methods under kinetic control. The structural characterization was mainly carried out by X-Ray diffraction methods, transmission electronic microscopy and the study of pair distribution functions, obtained by X Ray total scattering, coupled with atomic scale modelling methods. In the case of TiO2, anatase nanocrystals were obtained with sizes ranging between 4 nm and 8 nm. The molar ratio of the oxygen donor with respect to titanium was shown to be an important parameter to control the nanoparticle size. In peculiar conditions we have been able to isolate an intermediate phase characterized by very small sized and poorly crystallized nanoparticles which the structure can be assimilated to a disordered brookite structure. Concerning SnO2, rutile-type nanocrystals were synthesized with sizes ranging between 2 nm and 4 nm. The use of an ether as oxygen donor led to the simultaneous formation of an organic polymeric phase and of primary nanoparticles characterized by an intermediate structure close but still different from the rutile-type structure. Moreover, the use of benzyl-type solvents in the presence of tin tetrachloride led to the formation of water in the system. Lastly, for ZnO, we have shown that using an organic base to induce the formation of the metal oxide network in a methanolic solution of zinc acetate in the presence of a strong complexing agent of the zinc allowed us to obtain wurtzite nanocrystals of ultrasmall sizes around 1 nm. Even for the smallest sizes, the nanoparticles exhibit a structure very close to that of wurtzite with an increasing disorder of the cationic network.