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Made available in DSpace on 2020-12-12T01:15:00Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-06-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) The challenge to obtain stable glasses containing monodisperse magnetic nanoparticles with controlled size and shape is an exciting and almost unexplored field of research. Such new materials can be used in magneto-photonics or ultra-sensitive magnetic sensors. In this work, for the first time, colorless and transparent bulk glasses containing monodisperse 20 nm Fe3−δO4 nanoparticles were prepared by a melt-quenching route. Magnetic nanoparticles were synthesized by thermal decomposition and covered with a stellate mesoporous silica shell in order to protect them against dissolution during the glass melting process. The incorporation of nanoparticles into glasses and the ideal parameters obtained for this system are discussed. The new nanocomposite materials were characterized in order to investigate the structure, thermal, and magnetic properties. Such an original approach is a very promising way to incorporate a wide panel of nanoparticles, including metallic, bimetallic and metal oxide nanoparticles, into a variety of glasses providing new properties to these materials. São Paulo State University - UNESP Institute of Chemistry, P. O. Box 355 Université de Strasbourg CNRS Institut de Physique et Chimie des Matériaux de Strasbourg UMR 7504 São Paulo State University - UNESP Institute of Chemistry, P. O. Box 355 CNPq: 153762/2018-7 FAPESP: 2013/07793-6 FAPESP: 2018/07727-7 FAPESP: 2019/19609-1 CAPES: 88881.134870/2016-01

Made available in DSpace on 2020-12-12T02:47:50Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-12-25 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Glasses are materials with highly flexible compositions and high chemical and physical durability. These characteristics make them suitable materials for hosting nanoparticles for different purposes. Hybrid glasses containing magnetic nanoparticles have been highlighted due to their potential for application as ultra-sensitive magnetic sensors and magnetic devices. In this work, phosphate bulk glasses containing 0.5%, 1.0%, and 2.0% in mass of metallic CoPt alloy nanoparticles were prepared by melt-quenching technique. The CoPt nanoparticles were synthesized by reducing metal precursors in a high temperature organic solvent and, in the second step, they were covered with a silica layer in order to protect the nanoparticles for the subsequent melting. The nanoparticles were treated at different temperatures. Heat treatment at 900 °C showed the highest values of saturation magnetization and coercivity, and for that reason these nanoparticles were chosen for incorporation into glass. In the transmission electron microscopy images of the glass containing 2.0% in mass of nanoparticles, the interplanar distance of 0.21 nm was identified and indexed to the 111 plane of CoPt, confirming that the nanoparticles were successfully embedded into the matrix. The UV–Vis spectra presented Co2+ characteristic bands at 528, 578, and 626 nm, indicating that these ions are tetrahedrally coordinated in the matrix. Themagnetic measurements presented behavior close to ferromagnetic, showing that it is possible to prepare a magnetic glass containing bimetallic nanoparticles. Institute of Chemistry - São Paulo State University - UNESP, P. O. Box 355 Federal University of Sao Carlos (UFSCar) Graduate Program in Materials Science and Engineering Department of Materials Engineering Instituto de Física Núcleo de Física Aplicada Universidade de Brasília Instituto Federal Goiano Institute of Chemistry - São Paulo State University - UNESP, P. O. Box 355 CAPES: 001 FAPESP: 2013/07793-6 FAPESP: 2018/07727-7 FAPESP: 2019/19609-1 CAPES: 88882.332718/2019-01

CdFe2O4 nanoparticles of around 3.9 nm were synthesized using the coprecipitation method and protected by a silica layer. The nanoparticles were mixed with a coacervate and transformed into phosphate glasses with 1, 4 and 8% in mass of nanoparticles by the melt-quenching method. TEM images confirm that the nanoparticles were successfully incorporated into the matrix without inducing crystallization. 31P NMR and Raman spectral analyses show that new P-O-Si bonds are formed in the glasses containing nanoparticles. The glass transition increases as a function of the nanoparticle content due to an increase in the connectivity of the phosphate glass chains. The UV-Vis spectra show bands at 415 and 520 nm assigned to Fe3+ ions and at 1025 nm, characteristic of Fe2+ ions, indicating that some of the nanoparticles dissolve during the melting process. The sample with 8% CdFe2O4 presents a paramagnetic behavior. The glasses obtained are transparent, non-hygroscopic and possess enormous thermal stability which is important for the production of optical devices.

Made available in DSpace on 2018-12-11T16:49:32Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-01-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) The emission properties of Ag nanoclusters (Ag NCs) dispersed in a transparent fluorophosphate glass host have been studied. The as-prepared glass shows that the Ag NCs emit a broad white emission band almost covering the entire visible region. By changing the excitation wavelength it is possible to tune the emission from blue to yellow. The spectral width of the white light is most likely due to the presence of a variety of Ag NCs with different sizes, particularly emitting in the blue, green and red regions. The possible interaction mechanism between the different Ag species was also elucidated. The observed results provide a new platform to acquire a broad band tunable light source. Institute of Chemistry São Paulo State University UNESP, P. O. Box 355 Institute of Chemistry São Paulo State University UNESP, P. O. Box 355 FAPESP: #2013/07793-6 FAPESP: #2016/16343-2

Oxidation stability is a parameter of great importance for biodiesel quality control to both producers and subsequent consumers. To maintain the quality of biodiesel, currently the most effective and economical method is the addition of antioxidants that prevent or retard the biofuel oxidation reaction. In this study, efficiency and cost of synthetic antioxidants added to B100 biodiesel from soybean oil and pork fat were evaluated, using butylhydroxyanisole (BHA), butylhydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ), in pure form or in mixtures, according to a simplex-centroid mixture experimental design. Results demonstrate an increased induction period (IP) in all trials when compared to the control sample, and TBHQ was the only antioxidant alone that met all the specification standards, while BHT and BHA alone met only the American standard specifications. The antioxidant mixture that presented the highest synergistic effect was that of TBHQ and BHA. Multi-response optimization indicated an optimum formulation containing 75 % TBHQ and 25 % BHA with an IP of 7.27 h at 110 °C and the antioxidant mixture cost of 31.31 USD, to be added for a ton of biodiesel. This simplex-centroid mixture experimental design shows an ability to be applied in the biodiesel, oils and fats industry to evaluate the oxidation stability and the occurrence of synergism between different mixtures of synthetic or natural antioxidants and their costs.

The temperature influence on the oxidation stability of biodiesel from ternary mixture of vegetable oil and animal fat (50% of soybean oil, 20% of beef tallow, and 30% of poultry fat) was evaluated at temperatures ranging from 110 to 130 °C applying the Arrhenius and Eyring equations. The kinetics and thermodynamics parameters determined, considering first-order reaction rate kinetics, were rate constant (k), varying from 0.5479 to 1.7110 h–1, activation energy (Ea) of 72.01 kJ mol–1, pre-exponential factor (A) of 3.84 × 109 h–1, enthalpy of activation (ΔH‡) of 68.75 kJ mol–1, entropy of activation (ΔS‡) of −72.05 J K–1 mol–1, and Gibb’s free energy of activation (ΔG‡) average of 97.08 kJ mol–1. Based on the activation complex theory (ACT), the thermodynamic activation parameters indicated a nonspontaneous, endergonic, and endothermic process: ΔG‡ > 0, ΔH‡ > 0, and ΔS‡ < 0, with estimated storage time of 149.82 d at 25 °C.

Made available in DSpace on 2022-04-28T19:45:59Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-01-01 Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The development of glasses containing nanoparticles dispersed homogeneously with controlled size and optimum parameters for functionality is a big challenge. In the present work, the ternary system 60SbPO4-30ZnO-10PbO containing CdFe2O4-SiO2 nanoparticles was studied. CdFe2O4 nanoparticles, with average size of 3.9 nm, were synthesized using the coprecipitation method and, in a second step, protected by a silica layer. Different mass percentages of nanoparticles were mixed to the glass precursors and then transformed into glasses by melt-quenching method. Thermal and structural properties were evaluated by differential scanning calorimetry, Raman spectroscopy, scanning electronic microscopy and transmission electron microscopy. While the optical properties were studied by M-Lines spectroscopy and UV-Vis spectroscopy. The glasses obtained were completely transparent, with yellow color and showed no sign of crystallization according to the techniques used. Scanning and transmission electron microscopy confirm that the methodology used for the incorporation of nanoparticles was efficient. The methodology used to protect the nanoparticles prior to incorporate them to glasses, strongly contributes towards the development of new functional glasses useful for magneto-optics devices. São Paulo State University (Unesp) Institute of Chemistry, 55 Prof. Francisco Degni St, São Paulo São Paulo State University (Unesp) Institute of Chemistry, 55 Prof. Francisco Degni St, São Paulo FAPESP: #2013/07793-6 CNPq: 141258/2014-4

Temperature's influence on biodiesel oxidation was evaluated by kinetic and thermodynamic data in biofuel from soybean oil and lard with synthetic antioxidants: butylatedhydroxyanisol (BHA), butylatedhydroxytoluene (BHT), tert-butylhydroquinone (TBHQ), and propylgallate (PG) by simplex centroid mixture design. The kinetic parameters ware obtained by Arrhenius equation and showed that addition of antioxidants in all tests increased activation energy (Ea) and that TBHQ and PG were more efficient and presented synergistic effect. BHT and BHA were the least efficient, as well as their mixtures. The thermodynamic activation parameters of the reactions, evaluated by the Eyring equation and based on the theory of the activated complex (ACT), indicated no spontaneous processes (∆G‡ > 0) with positive ∆H‡ values and positive and negative ∆S‡ values. The application of simplex centroid mixture design, using Ea as response, showed the optimised value of 174.46 kJ mol-1 for a mixture containing 33.33 and 66.67% of TBHQ and PG, respectively. A influência da temperatura sobre a oxidação de biodiesel foi avaliada pelos parâmetros cinéticos e termodinâmicos do biocombustível de óleo de soja e gordura suína com antioxidantes sintéticos: 3-terc-butil-4-hidroxianisol (BHA), 3,5-di-terc-butil-hidroxitolueno (BHT), 2-terc-butil-hidroquinona (TBHQ) e galato de propila (PG), de acordo com delineamento de mistura simplex-centróide. Os parâmetros cinéticos foram determinados considerando-se reação de primeira ordem e aplicando a equação de Arrhenius. A adição de antioxidantes promoveu o aumento da energia de ativação (Ea), sendo TBHQ e PG os mais eficientes, apresentando efeito sinérgico. BHT e BHA foram os menos eficientes, assim como suas misturas. Os parâmetros termodinâmicos de ativação, avaliados pela equação de Eyring, não indicaram processos espontâneos (∆G‡ > 0) com valores de ∆H‡ positivos, e ∆S‡ positivos e negativos. O delineamento simplex-centróide indicou valor otimizado de 174,46 kJ mol-1 para a mistura contendo 33,33 e 66,67% de TBHQ e PG, respectivamente.

The quality of biodiesel is extremely important for its commercialization and use; oxidation of biodiesel is a critical factor because it decreases the fuel storage time. A commercial biodiesel was mixed with synthetic antioxidants, according to a simplex-centroid experimental mixture design, and its stability was evaluated through induction period and activation energy. In all trials, addition of antioxidants increased activation energy in the mixtures containing tertiary butylhydroquinone (TBHQ). When a mixture containing 50% TBHQ and 50% butylated hydroxyanisole was used, synergistic effect was observed, and the major activation energy obtained was 104.43 kJ mol-1.

A qualidade do biodiesel é um fator determinante para sua comercialização e parâmetros como Ponto de Entupimento de Filtro a Frio (PEFF) e Período de Indução (PI), que determinam sua operabilidade no motor em dias frios e tempo de estocagem, respectivamente, são importantes para a caracterização do produto final. Um biodiesel B100 foi formulado através de uma otimização multirresposta, onde o PEFF e o custo foram minimizados e PI e rendimento maximizados, por meio do delineamento simplex-centroide utilizando uma mistura de óleo de soja, sebo bovino e gordura de ave. A formulação ótima obtida indicou 50% de óleo de soja, 20% de sebo bovino e 30% de gordura de ave, com valores de PEFF de 1,92°C, custo de matéria prima de U$903,87 ton-1, PI de 8,28 h e rendimento de 95,68%. A validação foi realizada em triplicata e o teste t mostrou que não houve diferença entre os valores estimados e a média dos resultados obtidos experimentalmente, para nenhuma das variáveis dependentes, mostrando que a otimização conjunta é uma ferramenta eficiente na obtenção de um biodiesel que atenda às normas especificadas no que diz respeito ao PEFF e PI com maior rendimento e menor custo. The quality of biodiesel is a determining factor in its commercialisation, and parameters such as the Cold Filter Plugging Point (CFPP) and Induction Period (IP) determine its operability in engines on cold days and storage time, respectively. These factors are important in characterization of the final product. A B100 biodiesel formulation was developed using a multiresponse optimisation, for which the CFPP and cost were minimized, and the IP and yield were maximized. The experiments were carried out according to a simplex-centroid mixture design using soybean oil, beef tallow, and poultry fat. The optimum formulation consisted of 50% soybean oil, 20% beef tallow, and 30% poultry fat and had CFPP values of 1.92 ºC, raw material costs of US$ 903.87 ton-1, an IP of 8.28 h, and a yield of 95.68%. Validation was performed in triplicate and the t-test indicated that there were no difference between the estimated and experimental values for none of the dependent variables, thus indicating efficiency of the joint optimization in the biodiesel production process that met the criteria for CFPP and IP, as well as high yield and low cost.