This thesis is a collection of different application of silicon-based material. The phosphors of formula Ba5Si8O21:Eu2+,Dy3+ were synthesized and studied in order to improve their properties. Their synthesis conditions were evaluated as a function of precursors, crucible composition, flux agents, dopants and temperatures. The samples were characterised by means of a systematic investigation through elemental, kinetic, mineralogical (both qualitative and quantitative), and morphological analysis. A phosphor with improved long persistent phosphorescence (LPP) characteristics was obtained with Ba/Si = 0.7, Eu/Si = 2.8 × 10-3 and Dy/Si = 3.6 × 10-3 following a 6 h-synthesis in a quartz crucible at 1100°C. Si- based sol–gel graphite electrodes containing gold nanoparticles (AuNPs) have been prepared through a one-pot synthetic approach. At variance with the traditional synthesis AuNPs were here obtained directly inside the sol–gel, during its formation with two reduction methods (chemical and thermal). Different experimental parameters were tested: Si/Au molar ratio, graphite (g):silane precursor (mL) ratio, gold precursor and reductant, time and temperature of thermal treatment. Sol–gel was prepared trough sonication. Composition of the material and shape, size and distribution of AuNPs was evaluated. Electrochemical tests with respect to glucose and ascorbic acid oxidation allowed us to study the electrode behaviour. Another type of sol-gel electrodes are silica-based pellets containing copper nanoparticles (CuNPs), graphite and polystyrene. The chemical composition of the material was optimized on the basis of the current intensity due to glycerol oxidation, taking advantage of a proper experimental design. The composite showing best performance was fully characterized by spectroscopic and morphologic techniques trying to define the structure-property relationship. The last parts of the research are based on the use of KRY·AS, a secondary raw material obtained by the thermal transformation of cement-asbestos (CA). In the first of three application, KRY·AS was used to produce glass-ceramic frits used for the manufacturing of porcelain stoneware slabs. Two novel frits were with KRY·AS and minor amounts of natural raw materials as well as glass waste. The resulting frits were added in a ceramic body formulation (0, 1, 3, 5 wt.%). Phase composition, microstructure and technological properties of fired samples were evaluated, and the results were compared to those obtained when using a standard commercial frit. The second application of KRY·AS was the synthesis of blue and black ceramic pigments, with an amount of the thermally treated cement asbestos around 90 wt.%. Each pigment was synthesised considering the interaction of different variables: the type of raw materials, their ratio, the temperature and the time of the thermal treatment. All the samples have been characterised through UV-vis spectroscopy, colorimetry, mineralogical analysis and scanning electron microscopy. To evaluate the stability and performance of the pigments they have been tested as mass colorant for ceramic tiles. At last KRY·AS in addition to glass waste was used for the manufacture of foam glass. The research presents four phases. Firstly, the behaviour of different ratio of KRY.AS and RG at different temperature and soaking time has been studied. Secondly, a flux agent (Na2CO3 or Li2CO3) was added in order to decrease the working temperature. At the third step was studied the foaming agent SiC, at different grit and amount, which was added at the mixture prepared with 55 wt. % RG, 40 wt. % KRY·AS and 5 wt. % Li2CO3. The final products were 27 samples that differ for the amount of SiC 1500 (1, 2.5, 5 wt. %), peak temperature (1000, 1050, 1100°C) and soaking time (1, 6, 30 min) of the firing process.
Questa tesi è una raccolta di diverse applicazioni di materiali a base di silicio. Pigmenti fotoluminescenti di formula Ba5Si8O21:Eu2+,Dy3+ sono stati sintetizzati e studiati a partire da letteratura per migliorane le proprietà. Le variabili sintetiche studiate sono: precursori, la composizione del crogiolo, gli agenti fondenti, i dopanti e la temperatura di sintesi. I campioni sono stati caratterizzati tramite analisi elementare, cinetiche, mineralogiche (qualitative e quantitative) e morfologiche. In conclusione è stato ottenuto un pigmento fosforescente dopo una sintesi di 6h in un crogiolo di quarzo a 1100°C con rapporti Ba/Si = 0.7, Eu/Si = 2.8 × 10-3 e Dy/Si = 3.6 × 10-3. Elettrodi di sol-gel e grafite contenenti nanoparticelle di oro (AuNPs) sono stati ottenuti con una sintesi one-pot. In alternativa alla sintesi tradizionale le AuNPs sono state ottenute direttamente all’interno del sol-gel tramite due diversi metodi di riduzione (chimico e termico). Sono stati valutati diversi parametri sperimentali: durata e temperatura del trattamento termico, il rapporto molare Si/Au, il rapporto grafite (g):precursore del sinanolo (mL), natura chimica del precursore dell’oro e del riducente, durata e temperatura del trattamento termico. Il sol-gel è preparato tramite sonocatalisi. Caratterizzazioni spettroscopiche e microscopiche sono effettuate per valutare la composizione del materiale e la forma, dimensione e distribuzione delle AuNPs. I test elettrochimici hanno accertato la buona conduttività del materiale e l’attività elettrocatalitica delle AuNPs per l’ossidazione di glucosio e acido ascorbico. Sono stati preparati elettrodi sol-gel a pastiglia contenenti nanoparticelle di rame (CuNPs), grafite e polistirene. La composizione del materiale è stata ottimizzata sulla base dell’intensità di corrente del picco di ossidazione del glicerolo, utilizzando un appropriato disegno sperimentale. Il composto che ha mostrato la migliore performance è stato caratterizzato tramite spettroscopia e microscopia. Infine è stato studiato l’utilizzo del KRY·AS, una materia prima seconda ottenuta tramite trasformazione termica del cemento-amianto. Sono state preparate due fritte con KRY·AS, materie prime naturali e scarti di vetro. Le fritte sono state aggiunte ad un atomizzato in quantità di 0, 1, 3, 5 wt. %. I provini finali sono stati valutati secondo le loro proprietà tecnologiche, la composizione delle fasi e la microstruttura. I risultati ottenuti sono stati confrontati con quelli di provini preparati con una fritta commerciale. Nella seconda applicazione pigmenti blu e neri sono stati sintetizzati a partire dal KRY·AS (90 wt.%). Ciascun pigmento è stato sintetizzato considerando l’interazione di diverse variabili: la tipologia di materie prime, il loro rapporto, la temperatura e il tempo del trattamento termico. I campioni sono stati tutti analizzati tramite spettroscopia UV-vis, colorimetria, analisi mineralogia e microscopia elettronica scansione. Per valutare la stabilità e le performance dei pigmenti sono stati testati nella colorazione a tutta massa di provini ceramici. Per ultimo il KRY·AS e vetro di riciclo (RG) sono stati utilizzati nella preparazione di vetro schiuma. La ricerca presenta quattro fasi. Inizialmente, è stato studiato il comportamento a diverse temperature e tempi di miscele di KRY.AS e RG in diversi rapporti. Successivamente, è stato valutato l’effetto di un agente fondente (Na2CO3 or Li2CO3) in diverse quantità. Il terso step è stato lo studio della grana e quantità dell’agente schiumante, SiC, aggiunto a 55 wt. % RG, 40 wt. % KRY·AS e 5 wt. % Li2CO3. Per concludere sono stati preparati 27 campioni con variazione di SiC 1500 (1, 2.5, 5 wt. %), temperatura di lavoro (1000, 1050, 1100°C) and tempo alla massima T (1, 6, 30 min).
Sintesi, caratterizzazione e applicazione di materiali a base di silicio in diverse aree
LIGABUE, MARIA LAURA
2021
Abstract
This thesis is a collection of different application of silicon-based material. The phosphors of formula Ba5Si8O21:Eu2+,Dy3+ were synthesized and studied in order to improve their properties. Their synthesis conditions were evaluated as a function of precursors, crucible composition, flux agents, dopants and temperatures. The samples were characterised by means of a systematic investigation through elemental, kinetic, mineralogical (both qualitative and quantitative), and morphological analysis. A phosphor with improved long persistent phosphorescence (LPP) characteristics was obtained with Ba/Si = 0.7, Eu/Si = 2.8 × 10-3 and Dy/Si = 3.6 × 10-3 following a 6 h-synthesis in a quartz crucible at 1100°C. Si- based sol–gel graphite electrodes containing gold nanoparticles (AuNPs) have been prepared through a one-pot synthetic approach. At variance with the traditional synthesis AuNPs were here obtained directly inside the sol–gel, during its formation with two reduction methods (chemical and thermal). Different experimental parameters were tested: Si/Au molar ratio, graphite (g):silane precursor (mL) ratio, gold precursor and reductant, time and temperature of thermal treatment. Sol–gel was prepared trough sonication. Composition of the material and shape, size and distribution of AuNPs was evaluated. Electrochemical tests with respect to glucose and ascorbic acid oxidation allowed us to study the electrode behaviour. Another type of sol-gel electrodes are silica-based pellets containing copper nanoparticles (CuNPs), graphite and polystyrene. The chemical composition of the material was optimized on the basis of the current intensity due to glycerol oxidation, taking advantage of a proper experimental design. The composite showing best performance was fully characterized by spectroscopic and morphologic techniques trying to define the structure-property relationship. The last parts of the research are based on the use of KRY·AS, a secondary raw material obtained by the thermal transformation of cement-asbestos (CA). In the first of three application, KRY·AS was used to produce glass-ceramic frits used for the manufacturing of porcelain stoneware slabs. Two novel frits were with KRY·AS and minor amounts of natural raw materials as well as glass waste. The resulting frits were added in a ceramic body formulation (0, 1, 3, 5 wt.%). Phase composition, microstructure and technological properties of fired samples were evaluated, and the results were compared to those obtained when using a standard commercial frit. The second application of KRY·AS was the synthesis of blue and black ceramic pigments, with an amount of the thermally treated cement asbestos around 90 wt.%. Each pigment was synthesised considering the interaction of different variables: the type of raw materials, their ratio, the temperature and the time of the thermal treatment. All the samples have been characterised through UV-vis spectroscopy, colorimetry, mineralogical analysis and scanning electron microscopy. To evaluate the stability and performance of the pigments they have been tested as mass colorant for ceramic tiles. At last KRY·AS in addition to glass waste was used for the manufacture of foam glass. The research presents four phases. Firstly, the behaviour of different ratio of KRY.AS and RG at different temperature and soaking time has been studied. Secondly, a flux agent (Na2CO3 or Li2CO3) was added in order to decrease the working temperature. At the third step was studied the foaming agent SiC, at different grit and amount, which was added at the mixture prepared with 55 wt. % RG, 40 wt. % KRY·AS and 5 wt. % Li2CO3. The final products were 27 samples that differ for the amount of SiC 1500 (1, 2.5, 5 wt. %), peak temperature (1000, 1050, 1100°C) and soaking time (1, 6, 30 min) of the firing process.File | Dimensione | Formato | |
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https://hdl.handle.net/20.500.14242/80185
URN:NBN:IT:UNIMORE-80185