Le développement d'un colorant naturel sensibilisateur pour les applications de cellules solaires a attiré beaucoup d'attention en raison de ses avantages inhérents, tels que son faible coût, la préparation simple, les ressources facilement disponibles et le respect de l'environnement. Toutefois, les principaux problèmes liés à la cellule solaire sensibilisée par colorant (CSSC) sont une faible photostabilité et une faible efficacité. Dans cette thèse, la bixine extrait de graines de rocou (Bixa orellana L.) a été utilisée comme sensibilisateur. Pour améliorer sa stabilité et la performance des CSSC, l’utilisation de la kaolinite activée a également été étudiée. Une CSSC à haute efficacité nécessite une photo-électrode avec une grande surface spécifique pour adsorber efficacement le colorant. Ainsi le couple TiO2/kaolinite a été préparé dans ce but. Il est considéré que la kaolinite peut confiner la lumière incidente à l'intérieur de l'électrode et peut aussi améliorer la conduction d'électrons. Dans ce système, la kaolinite a également un rôle important pour accroître la photostabilité de la bixine. Un autre facteur affectant les performances des CSSC est le rôle important de l’électrolyte. Dans ces travaux, les carbonates organiques cycliques qui ont une constante diélectrique élevée et aussi un point d’ébullition élevé (plus de 300oC) ont été évalués comme solvants de l’électrolyte. Ces travaux ont été réalisés en quatre étapes: (1) extraction, purification et caractérisation de la bixine, (2) préparation, activation et caractérisation de la kaolinite, (3) étude d’adsorption de la bixine sur la surface de la kaolinite et du TiO2, et (4) fabrication des cellules solaires sensibilisées par la bixine (CSSB). Les résultats montrent que l’extraction accélérée par solvant en utilisant un mélange de 60% de cyclohexane et 40% d’acétone peut être une méthode d’extraction efficace pour la bixine. Après purification par la chromatographie flash, la bixine est isolée avec un dégré de pureté de 99,86%. Elle est composée de 88,11% de cis-bixine et 11,75% de dicis- bixine. L’activation par l’ammoniaque de la kaolinite calcinée (la métakaolinite) est une bonne méthode pour produire la kaolinite avec une très grande surface spécifique et un rapport Si/Al élevé. L’étude d’absorption de la bixine a montré que le carbonate de diméthyle est un solvant approprié pour la bixine. Il permet à la bixine un coefficient d’absorption élevé et de bonnes caractéristiques d’adsorption sur la surface de la photo-électrode. L’adsorption de monocouche de la bixine sur la surface de TiO2 ou la surface de la kaolinite est plus favorable pour obtenir un rendement énergétique plus élevée. La présence de la métakaolinite activée dans la photo-électrode TiO2 a contribué à améliorer les performances et la stabilité de la CSSB par rapport à la CSSB fabriquée avec la photoélectrode de TiO2 pur. Ces performances sont reproductibles. L’électrolyte exerce un effet synergétique avec la métakaolinite activée en faveur de l’amélioration des paramètres électriques de la CSSB. Sous une intensité lumineuse de 200 W/m2, la CSSB comprenant une photo-électrode de TiO2 modifié par 5% de métakaolinite activée et un système électrolyte de KiI/I2 dans l’acétate de carbonate de glycérol produit un rendement énergétique de (0,050+0,006)%, ce qui est plus élevé que celui de la CSSB comprenant une photo-électrode de TiO2 pur (0,027+0,012)%. L’utilisation d’un couple redox de LiI/I2 dans l’acétate de carbonate de glycérol produit le rendement maximum (0,086+0,014)%. La fonction de stockage et de chargement d’énergie des CSSB fonctionnent bien jusqu’au troisième jour de l’analyse. A ce jour, la CSSB fabriquée en utilisant la photoélectrode de TiO2 modifiée par la métakaolinite activée est 16 fois plus stable que celle de la CSSB fabriquée en utilisant la photo-électrode de TiO2 pur. / The development of natural dye sensitizer for solar cell applications has attracted much attention because of its inherent advantages such as low cost, simple preparation, readily available resources, and low impact in the environment. However, the main problems related to dye-sensitized solar cell (DCCS) are low photostability and low efficiency. In this thesis, the bixin extracted from annatto (Bixa orellana L.) seeds was used as sensitizer. To improve its stability and the performance of the DSSC, the use of activated kaolinite was also studied. A high efficiency DSSC requires a photo-electrode with a high surface area to effectively adsorb the dye. So the couple of TiO2/kaolinite photo-electrode was prepared for this purpose. It is considered that kaolinite can confine the incident light within the electrode and can also improve the conduction of electrons. In this system, kaolinite also has an important role to increase the photostability of bixin. Another factor affecting the performance of DSSC is the important role of the electrolyte. In these studies, cyclic organic carbonates that have a high dielectric constant and also a high boiling point (above 300oC) were evaluated as solvents in the electrolyte. These works were carried out in four stages: (1) extraction, purification and characterization of bixin, (2) preparation, characterization and activation of kaolinite, (3) study of adsorption of bixin on the surface of kaolinite and TiO2, and (4) manufacturing of bixin sensitized solar cell (BSSC). The results show that the accelerated solvent extraction using a mixture of 60% cyclohexane and 40% acetone can be an effective method of extraction for bixin. After purification by flash chromatography, bixin with a degree of purity of 99.86% was isolated. It is composed of 88.11% cisbixin and 11.75% di-cis-bixin. The activation of calcined kaolinite (metakaolinite) by ammonia is a good method to produce kaolinite with very high specific surface area and a higher Si/Al ratio. The absorption study bixin has shown that the dimethyl carbonate is a suitable solvent for bixin. It allows bixin to have a high absorption coefficient and good adsorption characteristics onto the surface of the photo-electrode. The monolayer adsorption of bixin on the surface of TiO2 or kaolinite is more favorable to obtain higher energy efficiency. The presence of activated metakaolinite in the photo-electrode TiO2 has proven to improve the performance and stability of the BSSC compared to the BSSC manufactured with the pure TiO2 photo-electrode. These performances are reproducible. The electrolyte has a synergistic effect with the activated metakaolinite for improving the electrical parameters of the BSSC. Under a light intensity of 200 W/m2, the BSSC including a photo-electrode of TiO2 modified by 5% of the activated metakaolinite and KI/I2 electrolyte system in glycerol carbonate acetate produced an energy efficiency of (0.050+ 0.006)%, which is higher than that of the BSSC comprising a pure TiO2 photoelectrode (0.027+0.012)%. The use of LiI/I2 a redox couple in the glycerol carbonate acetate produces the maximum energy efficiency of (0.086+0.014)%. Its function of energy storage and loading worked well until the third day of analysis. To date, the BSSC manufactured using the photoelectrode TiO2 modified by activated metakaolinite is 16 times more stable than the BSSC manufactured using the pure TiO2 photo-electrode.

Submitted by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2018-04-20T13:07:11Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação Jucilene Lopes.pdf: 2211418 bytes, checksum: 953a473330915d500a4941021f07c45c (MD5) / Approved for entry into archive by Divisão de Documentação/BC Biblioteca Central (ddbc@ufam.edu.br) on 2018-04-20T13:08:40Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação Jucilene Lopes.pdf: 2211418 bytes, checksum: 953a473330915d500a4941021f07c45c (MD5) / Made available in DSpace on 2018-04-20T13:08:40Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertação Jucilene Lopes.pdf: 2211418 bytes, checksum: 953a473330915d500a4941021f07c45c (MD5) Previous issue date: 2017-10-30 / FAPEAM - Fundação de Amparo à Pesquisa do Estado do Amazonas / Metallic sulfates when used to modify acidic solids have conferred an increase in the acidity of the acidic sites of Lewis and Brønsted, presenting Hammett acidity constant superior to that of sulfuric acid, being called superacid materials. For this reason, superacid materials have been developed and used in many catalytic reactions. In this work the nickel sulfate (NiSO4) and metakaolinite obtained from the kaolinite soil of Manaus - AM were used to synthesize superacid materials varying NiSO4 concentration and calcination temperature. The materials were characterized by chemical analysis (FRX), thermogravimetry (TGA), Infrared Spectroscopy with Fourier Transform (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), adsorption-desorption of N2 (BET method) and still the acidity of the materials was studied by infrared spectroscopy technique of adsorbed pyridine. The catalytic activity was investigated by photodegradation of methylene blue. The characterization results showed that the addition of sulfate ions on the surface of metakaolinite did not alter the structure and morphology of the catalytic support. Bands relative to Lewis acid sites were observed at 1445 and 1607 cm -1 and Brønsted at approximately 1638 cm -1. The metakaolinite sample showed a 43.2% degradation of methylene blue, presenting better performance among all samples tested. Therefore, the characterization of the materials showed that there was interaction between the nickel sulfate and the catalytic support, resulting in the obtaining of the superacid materials and also the addition of nickel sulfate in the catalytic support caused some modification in the surface acidity of metakaolinite. However, the catalytic tests showed that the superacid materials had little catalytic activity for methylene blue photodegradation reactions. / Sulfatos metálicos quando utilizados para modificar sólidos ácidos tem conferido um aumento na acidez dos sítios ácidos de Lewis e Brønsted, apresentando constante de acidez de Hammett superior ao do ácido sulfúrico, sendo chamados de materiais superácidos. Por esse motivo, materiais superácidos têm sido desenvolvidos e utilizados em muitas reações catalíticas. Nesse trabalho o sulfato de níquel (NiSO4) e metacaulinita obtida de solo caulinitico de Manaus – AM, foram utilizados para sintetizar materiais superácidos variando concentração de NiSO4 e temperatura de calcinação. Os materiais obtidos foram caracterizados por meio de análise química (FRX), termogravimetria (TGA), infravermelho com transformada de Fourier (FTIR), difração de raios X (DRX), microscopia eletrônica de varredura (MEV), adsorção-desorção de N2 (método BET) e ainda a acidez dos materiais foram estudadas por meio da técnica de espectroscopia na região do infravermelho de piridina adsorvida. A atividade catalítica foi investigada por meio da fotodegradação do azul de metileno. Os resultados de caracterização mostraram que a adição de íons sulfatos na superfície da metacaulinita não alterar a estrutura e morfologia do suporte catalítico. As bandas referentes aos sítios ácidos de Lewis foram observadas em 1445 e 1607 cm-1 e de Brønsted em aproximadamente 1638 cm–1. A amostra de metacaulinita apresentou 43,2% de degradação do azul de metileno, apresentando melhor desempenho entre todas as amostras testadas. Portanto, a caracterização dos materiais demonstrou que houve interação entre o sulfato de níquel e o suporte catalítico, resultando na obtenção dos materiais superácidos e ainda a adição de sulfato de níquel no suporte catalítico causou alguma modificação na acidez superficial da metacaulinita. Porém, os testes fotocatalíticos demonstraram que os materiais superácidos apresentaram pouca atividade catalítica para reações de fotodegradação do azul de metileno.

Geopolymers are a relatively new class of materials that have many broad applications, including use as substitute for ordinary Portland cement (OPC), use in soil stabilisation, fire resistant panels, refractory cements, and inorganic adhesives. Geopolymers are an alternative binder to Portland cement in the manufacture of mortars and concrete, as its three-dimensional alumino silicate network develops excellent strength properties. Use of geopolymers in place of ordinary Portland cement is also favoured owing to the possible energy and carbon dioxide savings. Geopolymer is typically synthesized by alkali activation of pozzolanas at moderate temperatures (< 1000C). The focus of the thesis is synthesis and characterization of geopolymers as construction materials. In this context, the role of compositional factors, such as, pozzolana type (fly ash, kaolinite, metakaolinite, ground granulated blast furnace slag, red soil), alkali (sodium hydroxide is used in this study) activator concentration, Si/Al (Si= silicon, Al = aluminium) ratio of the pozzolana and environmental factors, namely, curing period and temperature are examined. Besides synthesizing geopolymers that could be an alternate to concrete as construction material, sand-sized aggregates were synthesized using geopolymer reactions. This was done as river sand is becoming scarcer commodity for use as construction material. Several compositional and environmental factors were varied in geopolymer synthesis in order to identify the optimum synthesis conditions that yield geopolymers with maximum compressive strength. Besides varying external (compositional and environmental) factors, the role of internal microstructure in influencing the compressive strength of the geopolymer was examined. Micro-structure examinations were made using X-ray diffraction (XRD), scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) studies. The studies on compositional and environmental factors in geopolymer synthesis brought out several interesting results. The results firstly brought out that amongst the pozzolanas studied, ASTM class F fly ash is most suited for maximum compressive strength mobilization upon geopolymer reactions. Moderate temperature (75-1000C) was adequate to mobilize large compressive strengths. Room temperature curing needed more than 7 days before the pozzolana-NaOH paste began to develop strength. Curing period of 56 days was needed for the geopolymer to develop significant strength (19.6MPa). A similar range of compressive strength could be developed by the pozzolana-NaOH paste upon curing for 3 days at 1000C. Likewise curing the pozzolana-NaOH paste at temperatures > 1000C led to reduction in compressive strength from shrinkage and breakage of bonds. A caustic soda (NaOH) concentration of 10 M was adequate to develop maximum compressive strength of the geopolymer. Caustic soda concentrations in excess of 10 M did not result in further improvement of strength. The Si/Al ratio also contributes to strength mobilization. The Si/Al ratio of the geopolymer was enhanced by mixing commercially obtained silica gel with the pozzolana. Maximum strength mobilization was observed at Si/Al ratio = 2.45 corresponding to 6.5 % silica gel addition to the pozzolana (on dry mass basis). Comparing compressive strengths of geopolymers with varying silica gel contents, geopolymer specimens with least water content and largest dry density did not exhibit maximum compressive strength indicating that the physico-chemical (bond strength, micro-structure) played a pivotal role than physical parameters (dry density, water content) in dictating the strength of the geopolymer. MIP results showed that bulk of the porosity in fly ash geopolymer specimens is contributed by macro pores and air voids. Geopolymerization leads to bulk consumption of cenospheres in fly ash and forms polymerized matrix with network of large pores. After geopolymerization, all the main characteristic peaks of Al–Si minerals observed in fly ash persisted, suggesting that no new major crystalline phases were formed. Presence of small amount of inorganic contaminants in fly ash can drastically reduce the strength of the fly ash geopolymer. For example, 5-20 % presence of red soil reduces the strength of fly ash geopolymer by 16 to 59 %. Presence of unreacted clay coupled with less porous structure is responsible for the reduction in compressive strength of fly ash geopolymer subjected to red soil addition. MIP studies with geopolymers also revealed that there is good bearing between compressive strengths and maximum intruded volume (from MIP test) of geopolymers. For example, fly ash geopolymer specimen exhibits highest total intruded volume (0.3908 cc/g) and largest compressive strength of 29.5 MPa, while red soil geopolymer specimen exhibit least intruded volume (0.0416 cc/g) and lowest compressive strength (5.4 MPa). Further, analysis showed that specimens with larger airvoids+macropores volume had larger compressive strength, suggesting that geopolymers with more porous microstructure develop larger compressive strength. All geopolymer specimens exhibited tri-modal nature of pores i.e. macro-pore mode (entrance pore radius: 25-5000 nm), mesopore mode (entrance pore radius: 1.25 to 25 nm) and air void mode (entrance pore radius >5000 nm). The micro pores (entrance pore radius < 1.25 nm) do not contribute to porosity of the geopolymer specimens. Sand particles prepared from geopolymer reactions (FAPS or fly ash geopolymer sand) predominated in medium sized (2mm to 0.425 mm) sand particles. Their particle size distribution characteristics (uniformity coefficient and coefficient of curvature) classified them as poorly graded sand (SP). Dissolution, followed by polymerization reactions led to dense packing of the Si–O–Al–O– units that imparted specific gravity of 2.59 to FAPS particles which is comparable to that of river sand (2.61). Dissolution in strongly alkaline medium imparted strongly alkaline pH (12.5) to the FAPS particles. The river sand is characterized by much lower pH (7.9). Despite being characterized by rounded grains, the FAPS particles mobilized relatively high friction angle of (35.5o) than river sand (∅ = 28.9o). The river sand-mortar (RS-M) and fly ash geopolymer sand-mortar (FAPS-M) specimens developed similar 28-day compressive strengths, 11.6 to 12.2 MPa. Despite its higher water content, FAPS-mortar specimens developed similar compressive strength and initial tangent modulus (ITM) as river sand-mortar specimens. The FAPS-M specimen is more porous (larger intruded volume) with presence of larger fraction of coarser pores. Total porosity is majorly contributed by macro-pores (67.92%) in FAPS-M specimen in comparison to RS-M specimen (macro-pores = 33.1%). Mortar specimens prepared from FAPS and river sand exhibit similar pH of 12.36 and 12.4 respectively. FAPS-mortar specimens have lower TDS (1545 mg/L) than river sand-mortar specimens (TDS = 1889 mg/L). The RS-M and FAPS-M specimens exhibit leachable sodium levels of 0.001 g Na/g RS-M and 0.007 g Na/g-FAPS-M respectively in the water leach tests. The larger leachable sodium of FAPS-M specimen is attributed to residual sodium hydroxide persisting in the FAPS even after washing. The ultra-accelerated mortar bar test (UAMBT) shows that the percentage expansion of FAPS-M and RS-M specimens are comparable and range between 0.07 to 0.08 %.