Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2017-09-27T11:09:10Z No. of bitstreams: 2 Dissertação - Ionara Pereira da Silva Sousa - 2017.pdf: 5120392 bytes, checksum: 786f15ae0e6cf83fa9560a114e84f6a2 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-09-27T11:09:36Z (GMT) No. of bitstreams: 2 Dissertação - Ionara Pereira da Silva Sousa - 2017.pdf: 5120392 bytes, checksum: 786f15ae0e6cf83fa9560a114e84f6a2 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-09-27T11:09:36Z (GMT). No. of bitstreams: 2 Dissertação - Ionara Pereira da Silva Sousa - 2017.pdf: 5120392 bytes, checksum: 786f15ae0e6cf83fa9560a114e84f6a2 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-09-15 / The basic science on cements and concretes has incorporated research related to the understanding of the effects of the addition of nanosilica, and more recently functionalized nanosilicas, on the properties of cement pastes, mortars and concretes. In this context, the aim of this work was to prepare amino-functionalized nanosilicas from a commercial nanosilica (NS), provided as an aqueous colloidal suspension, by employing 3-aminopropiltrietoxissilano (APTS) as reactant, and to evaluate the characteristics of the samples. The functionalization reactions were performed in a biphasic system composed of dichloromethane and water, and employing different APTS/NS molar ratios. The materials were obtained as aqueous suspensions and their characteristics were evaluated at pH 4, 7 e 10. The functionalization of NS was evidenced by the presence of infrared bands associated to the aminopropyl group. Bands associated to silanol (-SiOH) and alcoxide (Si-OCH2CH3) groups were observed indicating that the hydrolysis and condensation reactions were not complete. The 29Si NMR signals of Si-C bonds confirmed the functionalization. The thermogravimetric curves indicated an increase of the amount of aminopropyl groups incorporated on NS as the APTS/NS ratio increased. Transmission electron microscopy images showed an increase in the mean particle sizes after functionalization. The aqueous suspended nanoparticles showed a positive zeta potential at pH 4 (+23 to +27 mV) and at pH 7 (+14 to +29 mV), indicating the presence of protonated amine groups. The zeta potential at pH 10 was weakly negative (-0.10 to -7,6 mV) for the samples prepared from the lower APTS/NS molar ratios (7.1 and 14.2 x 10-2), and still positive (+11 and +15 mV) for those prepared from the higher molar ratios (28.5 and 42.7 x 10-2), suggesting the existence of a higher amount of superficial amino groups within the latter. The mean hydrodynamic radius of the functionalized particles were greater (22 a 281 nm) than that of the NS (12 nm) at all pH values, with superior values for suspended particles at pH 10, particularly for samples prepared from the lower APTS/NS ratios. The amount of aggregates of bigger size (~100 to 2000 nm) was greater for samples prepared from the lower APTS/NS ratios. These variable characteristics are interesting for comparative studies involving the effects of the addition of these suspensions in cement pastes over the microstructure and properties of the resulting materials. / A ciência básica na área de cimentos e concretos tem incorporado pesquisas relacionadas ao entendimento dos efeitos da adição de nanossílica e, mais recentemente, de nanossílica funcionalizada nas propriedades de pastas de cimento, argamassas e concretos. Neste contexto, o objetivo deste trabalho foi preparar nanossílicas funcionalizadas com grupos amina a partir de uma nanossílica comercial (NS), fornecida como uma suspensão coloidal aquosa, empregando-se o reagente 3-aminopropiltrietoxissilano (APTS) e avaliar as características das amostras obtidas. As reações de funcionalização foram realizadas em um sistema reacional bifásico constituído de diclorometano e água, empregando-se diferentes razões molares APTS/NS. Os materiais foram obtidos como suspensões aquosas, cujas características foram avaliadas em pH 4, 7 e 10. A funcionalização da NS foi evidenciada pela presença das bandas relativas ao grupo aminopropil nos espectros de infravermelho, onde também foram observadas bandas dos grupos silanol (-SiOH) e alcóxido (Si-OCH2CH3), indicando que as reações de hidrólise e condensação não foram completas. Os sinais nos espectros de RMN de 29Si característicos de ligações Si-C confirmaram a funcionalização. As curvas termogravimétricas indicaram que houve aumento no teor de grupos aminopropil incorporados à NS com o aumento da razão APTS/NS empregada. As imagens de microscopia eletrônica de transmissão mostraram um aumento do tamanho médio das partículas após a funcionalização. As nanopartículas funcionalizadas em suspensão aquosa apresentaram potencial zeta positivo em pH 4 (+23 a +27 mV) e em pH 7 (+14 a +29 mV), indicando a presença de grupos amina protonados. Já em pH 10, o potencial zeta foi fracamente negativo (-0,10 a -7,6 mV) para amostras preparadas com menor razão APTS/NS (7,1 e 14,2 x 10-2), e positivos (+11 e +15 mV) para aquelas preparadas com razão molar maior (28,5 e 42,7 x 10-2), sugerindo um maior teor de grupos amina superficiais nestas últimas. Os raios hidrodinâmicos médios das partículas funcionalizadas foram maiores (22 a 281 nm) do que o da NS (12 nm) para todos os valores de pH, com valores maiores para partículas suspensas em pH 10. O teor de agregados de maior tamanho (~100 a 2000 nm) foi maior para as amostras preparadas com menor razão APTS/NS. Essas características variadas são interessantes para estudos comparativos dos efeitos de adição dessas suspensões em pastas de cimento, sobre a microestrutura e propriedades dos materiais resultantes.

Shear thickening fluids have the potential to improve the effectiveness of fabric materials in body armor applications as they have shown to increase the puncture and ballistic resistance of Kevlar fabrics. However, the effect of using STFs with natural fabrics such as flax has never been studied. The rheology of STFs at varying concentrations of nanosilica dispersed in polyethylene glycol PEG was studied at different temperatures and it was found that the STFs behave as a non-Newtonian fluid in response to changes in shear rate. In this study the effectiveness on the puncture and ballistic resistance of impregnating flax fabric with STF of nanosilica in PEG were investigated. The effect of hybridization of flax and Kevlar was also investigated. The puncture and ballistic resistance of the samples treated with STFs was found to increase significantly and can be controlled by STF concentration.

This dissertation focuses on the versatility and integrity of a novel, ultrasoft polycarbonate polyurethane (PCPU) by the introduction of nanoparticles and lithium salts. Additionally, the research takes into account the use of electrospinning as a technique to create PCPU and polyimide (PI) fibers. These polymers are of interest as they offer a wide range of properties and uses within the medical and industrial fields. An industrial batch of an ultrasoft thermoplastic polyurethane (TPU) was synthesized using a two-step process. The first was to create an end capped pre-polymer from methylene bis (4-cyclohexylisocyanate), and a polycarbonate polyol made up of 1,6- hexanediol and 3-methyl-1,5-pentanediol. The second step was done by reacting the pre-polymer with an excess of the polycarbonate polyol with a chain extender, 1,4-butanediol. Biocompatibility testing such as USP Class VI, MEM Elution Cytotoxicity and Hemolysis toxicology reported that PCPU showed no toxicity. This novel type of polyurethane material targets growing markets of biocompatible polymers and has been used for peristaltic pump tubing, but also can be utilized as balloon catheters, enteral feeding tubes and medical equipment gaskets and seals. This material is ideal for replacing materials such as soft plastisols containing diethylhexyl phthalate for use in biomedical and industrial applications. After extensive characterization of this polymer system another dimension was added to this research. The addition of nanoparticles and nanofillers to polyurethane can express enhanced mechanical, thermal and adhesion properties. The incorporation of nanoparticles such as nanosilica, nanosilver and carbon black into polyurethane materials showed improved tensile strength, thermal performance and adhesion properties of the PCPU. Samples were characterized using contact angle measurements, Fourier transform spectroscopy (FTIR), differential scanning calorimetry (DSC), parallel plate rheology and tensile testing. The second chapter entails the fabrication and characterization of PCPU nanofibers and nanomembranes through a process known as electrospinning. The resulting PCPU nanomembranes showed a crystalline peak from the WAXS profile which is due to electrospun and solution strain induced crystallinity. The PCPU nanocomposite nanomembranes displayed increased thermal stability and an increase in tensile performance at higher weight percent. The nanomembranes were investigated using contact angle measurements, thermogravimetric analysis (TGA), DSC, WAXS, SAXS and tensile testing. The final chapter focuses on investigating the rheological properties of PCPU/lithium electrolytes as well as transforming an unprocessable polyimide powder into a nanomembrane. The PCPU/ lithium composite electrolyte showed an increase in the activation energy and conductivity, while the PI/lithium showed increased conductivity over time. Dynamic mechanical analysis and four-point probe was used to investigate the samples.

The presented diploma thesis deals with the potential use of colloidal silica in cement composites. Investigation is focused primarily on selected properties of cement pastes and mortars with colloidal silica content. Two selected types of colloidal silica (particles with average size of 14 nm) have been used as a cement addition and partial replacement of cement, respectively. The experimental program for cement pastes with colloidal silica included tests for isothermal calorimetry (the study of cement hydration) and thermal analysis (determining the portlandite content). Hardened cement pastes have been studied through measurements of compressive strength. The microstructure was examined by scanning electron microscopy. Hardened mortars with colloidal silica have been studied through measurements of compressive strength, flexural strength, modulus of elasticity and fracture mechanics parameters. Fracture mechanics tests show that 5 % and 20 % addition of colloidal silica can enhance after 28 days of curing fracture energy up to 18,4 % and 32,7 %, respectively. For the compressive strength enhancing effect of colloidal silica, it was found to be more pronounced in the early age, while rate of strength gain can be lower than the control in the later ages. Our investigations revealed that the silica sol will coagulate immediately when the cement is mixed into the water containing sol. The ionic composition of pore fluid significantly influences the stability of colloidal silica and lead to their aggregation. After additional tests it has been found that small addition of calcium hydroxide greatly improved the compressive strength of the resulting cement pastes with colloidal silica content. Addition of calcium hydroxide in conjunction with modified cement paste preparation can enhance compressive strength after 3 days of curing up to 64,4 % in comparison with the blank paste.

Polypropylene (PP) and ethylene-co-octene copolymer (EOC) blends were prepared at various component ratios and reinforced with silica nanoparticles (SiO2). Strategies to improve filler dispersion involved the grafting of a silane coupling agent on the PP matrix, the addition of a maleated PP (PP-g-MA) as a compatibilizer and the use of hydrophobic silica nanoparticles. These approaches resulted in a fine dispersion of the nanoparticles within the PP phase and induced a reduction of the size of the EOC domains, due to a barrier effect. Tensile and flexural properties were significantly increased, whereas ductility and impact properties were not affected. These enhancements are attributed to the favourable microstructure of the blends, featuring a segregated microstructure, and to the improved interfacial adhesion between the functionalized polymer matrix and the surface of the nanoparticles. The microstructure and rheology of model melt compounded EOC-based nanocomposites were investigated. Functionalization of the polyolefin matrix was accomplished through silane grafting, or addition of a maleated EOC (EOC-g-MA) compatibilizer. Various grades of unmodified SiO2 having different specific surface areas (SSA), as well as a surface-modified grade were added to the EOC matrix at various loadings. The formation of covalent and hydrogen bonds between the silanol groups and the functionalized polymer generated strong polymer/filler (P/F) interactions, resulting in improved filler dispersion. Bound polymer characterization revealed that in the compatibilized materials, the amount of polymer physically attached to the nanoparticles was higher than in the non-compatibilized samples. In the absence of a compatibilizer, larger SiO2 aggregates formed upon increasing SSA because of increased probability of hydrogen bonding between the particles. The increased propensity for aggregation was revealed by time sweeps as well as by the increased strain sensitivity in stress sweeps. On the contrary, the compatibilized composites exhibited a stable response and a higher critical strain for the onset of non-linearity, indicative of stronger adhesion between the fillers and the matrix. Superposition of oscillatory and creep/recovery experiments revealed that the viscoelastic properties in the terminal region were influenced substantially by the state of dispersion of the nanoparticles. In the absence of a compatibilizer, substantial enhancements in the linear viscoelastic (LVE) functions were noted and an increasing SSA resulted in more significant deviations from terminal flow. On the contrary, the SSA of the particles had no effect on the viscoelastic and mechanical properties of the compatibilized composites. / Thesis (Ph.D, Chemical Engineering) -- Queen's University, 2011-04-18 15:17:52.471

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2017-10-18T11:59:04Z No. of bitstreams: 2 Dissertação - Alex Mizael Martins - 2016.pdf: 6652239 bytes, checksum: 06fc65f07d3460875f7ecd163b128a49 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-10-18T12:00:09Z (GMT) No. of bitstreams: 2 Dissertação - Alex Mizael Martins - 2016.pdf: 6652239 bytes, checksum: 06fc65f07d3460875f7ecd163b128a49 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-10-18T12:00:09Z (GMT). No. of bitstreams: 2 Dissertação - Alex Mizael Martins - 2016.pdf: 6652239 bytes, checksum: 06fc65f07d3460875f7ecd163b128a49 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-12-16 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The introduction of wind energy into the brazilian energy matrix is of paramount importance for national energy policy. In this context, the viability of wind towers is a fundamental issue. In Brazil, these towers are built mainly in reinforced concrete, in regions of high aggressiveness (coastal regions, because of their greater wind potential) and, therefore, it is necessary to develop high performance concretes that are able to withstand environmental actions to which they are subjected, mainly the action of the chlorides, so that these structures reach the previously defined project life, thus guaranteeing the viability of the towers. In this sense, the present work evaluates the mechanical properties, the mechanisms of transport of chlorides and the performance in relation to the corrosion of the reinforcement, in concretes that contain high performance pozolanic mineral additions, in order to evaluate the influence of the presence of these additions in these properties. Three different study mixes were developed containing respectively, 9% of silica fume in composition with 1% of nanosilica, 5% of a high fineness metakaolin in composition with 5% of a slightly less fine metakaolin, both with high pozzolanic activity and a mix containing only 10% of the finest metakaolin, in addition to a reference mix. Analyzes related to the chloride transport are presented: penetrability and diffusion; analyzes related to the corrosion of reinforcement: induction of corrosion by aggressive solution wetting cycles and air drying, surface electrical resistivity of concrete and corrosion potential, besides the mechanical characterization. The concretes with incorporation of pozzolanic addition showed, in general, improvements in the mechanical properties. In the chloride transport properties and corrosion performance of the reinforcements, the improvements from the mineral additions were significant. Thus, it was concluded that the incorporation of the different mineral additions studied in the present work significantly altered the properties of the concrete, with a positive highlight for the properties associated with durability, in which the benefits of using mineral addition are more pronounced. / A introdução da energia eólica na matriz energética brasileira é de suma importância para a política energética nacional. Nesse contexto, a viabilidade das torres eólicas é questão fundamental. No Brasil essas torres são construídas, principalmente, em concreto armado em regiões de alta agressividade (regiões litorâneas, por terem maior potencial eólico) e, portanto, faz-se necessário o desenvolvimento de concretos de alto desempenho que sejam capazes de resistir às ações ambientais às quais são submetidos, principalmente à ação dos cloretos, de maneira que essasestruturas atinjam a vida útil de projeto previamente definida, garantindo assim a viabilidade das torres. Nesse sentido, o presente trabalho avalia as propriedades mecânicas, os mecanismos de transporte de cloretos e o desempenho em relação à corrosão das armaduras, de concretos que contêm adições minerais pozolânicas de alto desempenho, a fim de avaliar a influência dessas adições nessas propriedades. Foram elaborados três diferentes proporcionamentos de estudo contendo respectivamente, 9% de sílica ativa em composição com 1% de nanossílica, 5% de um metacaulim de elevada finura em composição com 5% de um metacaulim um pouco menos fino, ambos de elevada pozolanicidade e um proporcionamento contendo exclusivamente 10% do metacaulim de maior finura, além de um proporcionamento de referência. São apresentadas análises relacionadas ao transporte de cloretos: penetrabilidade e difusão; análises relacionadas à corrosão das armaduras: indução da corrosão por meio de ciclos de molhagem em solução agressiva contendo cloretos, medidas de resistividade elétrica superficial do concreto e potencial de corrosão, além da caracterização mecânica. Os concretos com incorporação de adição pozolânica apresentaram, em geral, melhorias em suas propriedades mecânicas. Já nas propriedades de transporte de cloretos, as melhorias advindas das adições minerais foram mais significativas, assim como no desempenho em relação à corrosão das armaduras. Desse modo, concluiu-se que a incorporação das diferentes adições minerais estudadas no presente trabalho alterou significativamente as propriedades do concreto, com destaque positivo para as propriedades associadas à durabilidade, nas quais os benefícios do uso da adição mineral são mais pronunciados.

Submitted by Erika Demachki (erikademachki@gmail.com) on 2017-05-04T19:01:17Z No. of bitstreams: 2 Dissertação - Marina Augusta Malagoni de Almeida - 2016.pdf: 12520522 bytes, checksum: 853486dc2fbdd4513ff1c2cf33d112b0 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-05-05T12:57:03Z (GMT) No. of bitstreams: 2 Dissertação - Marina Augusta Malagoni de Almeida - 2016.pdf: 12520522 bytes, checksum: 853486dc2fbdd4513ff1c2cf33d112b0 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-05-05T12:57:04Z (GMT). No. of bitstreams: 2 Dissertação - Marina Augusta Malagoni de Almeida - 2016.pdf: 12520522 bytes, checksum: 853486dc2fbdd4513ff1c2cf33d112b0 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-09-21 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Brazil's current water crisis, generated by the low level of reservoirs, has threatened the national energy production. Faced with this problem, the wind towers present themselves as a viable solution. It is known that these towers are constructed in regions of high aggressiveness and therefore, it is necessary to develop high performance concretes that are able to withstand environmental action to which they are submitted, so that these structures reach the lifespan previously defined in project, ensuring the viability of the towers. In this sense, the present study evaluates the mass transport mechanisms (permeability and absorption) that takes place inside the concrete containing mineral pozzolanic admixtures of high performance, in order to evaluate the influence of the presence of these additions in these properties. Three different study mixes were prepared containing, respectively, 9% of silica fume in composition with 1% of nanossílica, 5% of a metakaolin with high fineness in composition with 5% of a metakaolin slightly less fine, both with high pozzolanic activity, a mix containing only 10% of the metakaolin with higher fineness, and a reference proportioning. The analysis presented in this work involve the scanning electron microscope (SEM) to characterize the internal structure of the material, the trace reconstruction test to analyze the aggregate/binder ratio in the regions of the cover and the interior of concrete, and the analyzes related to the mass transport: water absorption by immersion and capillarity and the air permeability obtained by the Figg’s method, in addition to the mechanical characterization. The concrete with addition of pozzolanic admixtures showed significant improvements in compressive strength, in the modulus of elasticity, in the air permeability and in the refinement of pores. Furthermore, the evaluation of the microstructure by scanning electron microscope showed that the use of mineral admixtures may cause an improvement in the adhesion and in the densification of the transition zone between aggregate and cement paste. The trace reconstitution test showed that the concrete cover has lower ratio aggregate/binder, which corroborates the results of the capillary absorption test in which it was found that the cover of concrete presents a mean capillarity absorption lower than the interior region. Thus, it was concluded that the incorporation of the different mineral admixtures studied in this work significantly alter the properties of concrete, with positive emphasis on the properties related to the durability, in which the benefits of using mineral admixtures is more pronounced and, in addition, it was also concluded that the concrete cover presents itself more favorable to the durability than the interior region. / A atual crise hídrica brasileira, gerada pelo baixo nível dos reservatórios, tem ameaçado a produção energética nacional. Frente a esse problema, as torres eólicas se apresentam como uma solução viável. Sabe-se que essas torres são construídas em regiões de alta agressividade e, portanto, faz-se necessário o desenvolvimento de concretos de alto desempenho que sejam capazes de resistir às ações ambientais às quais são submetidos de maneira que essas estruturas atinjam a vida útil de projeto previamente definida, garantindo a viabilidade das torres. Nesse sentido, o presente trabalho avalia as propriedades mecânicas e os mecanismos de transporte de massa (permeabilidade e absorção) que ocorrem no interior dos concretos que contêm adições minerais pozolânicas de alto desempenho, com o intuito de avaliar a influência da presença dessas adições nessas propriedades. Foram elaborados três diferentes proporcionamentos de estudo contendo respectivamente, 9% de sílica ativa em composição com 1% de nanossílica, 5% de um metacaulim de elevada finura em composição com 5% de um metacaulim um pouco menos fino, ambos de elevada pozolanicidade e um proporcionamento contendo exclusivamente 10% do metacaulim de maior finura, além de um proporcionamento de referência. São apresentadas análises em microscópio eletrônico de varredura (MEV) visando à caracterização da estrutura interna do material, reconstituição de traço com vistas à análise do teor de agregado/ligante nas regiões do cobrimento e do interior do concreto, análises relacionadas ao transporte de massa: absorção de água por imersão e por capilaridade e permeabilidade ao ar pelo método de Figg, além da caracterização mecânica. Os concretos com incorporação de adição pozolânica apresentaram melhorias significativas na resistência à compressão, no módulo de elasticidade, na permeabilidade ao ar e no refinamento dos poros. Além disso, a avaliação da microestrutura por meio de microscopia eletrônica de varredura mostrou que o uso das adições minerais pode ter causado densificação e melhoria na aderência da zona de transição entre os agregados e a pasta de cimento. O ensaio de reconstituição de traço mostrou que a região do cobrimento apresenta menor relação agregado/ligante, o que corrobora o resultado do ensaio de absorção capilar, em que se constatou que a região do cobrimento apresentou absorção capilar média inferior à região do interior. Assim, se concluiu que a incorporação das diferentes adições minerais estudadas no presente trabalho alterou significativamente as propriedades do concreto, com destaque positivo para as propriedades associadas à durabilidade, nas quais os benefícios do uso da adição mineral são mais pronunciados e, além disso, também se concluiu que a região do cobrimento se apresenta mais favorável à durabilidade que a região interna.

The aim of this thesis is to summarize the knowledge regarding reduction of negative impact of high volumes of fly ash in HVFA concretes using nanotechnology and experimentally verify the findings. To compensate the inferior early-age properties, it is possible to use active nanoparticles, such as nanosilica or nanolimestone. The first step of the experiment was the production of stable nanoparticle’s dispersions using ultrasonic homogenization and UV/Vis spectroscopy. In subsequent steps the influence of nanoparticle’s presence on cementitious materials’ properties was verified on cement pastes and mortars with 40 a 60 % of fly ash. The best variant was then used to produce nano-modified HVFA concretes. Even at a minimum dose, the positive effect on early-age properties indicates the usefulness of nanoparticles in technology of concrete. An important contribution of this thesis is also the acquired knowledge related to the nanoparticle’s behavior and handling.

High surface area of used nanoparticles and their comparable size with polymer chains, are the most important characteristics of fillers in the preparation of non-Newtonian suspensions. Such structures at different concentrations have major influence on the rheological behavior of polymer solution in solvent. With increasing volume fraction of nanofiller, there is pseudoplastic or dilatant behavior present in the dissolved elastomers. Diploma thesis studies the influence of the concentration of different elastomers (SBR and SEBS copolymers) and nanofiller (hydrophobic nanosilica) in suspension, of rheological properties.

The current study aims towards a holistic utilization of agro-waste rice straw (RS) to synthesize nanosilica (SiNPs) employing the sol–gel method. The effect of ashing temperature was evaluated for the synthesis process. X-ray diffraction demonstrated a broad spectrum at 21.22° for SiNPs obtained using RSA-600, signifying its amorphous nature, whereas crystalline SiNPs were synthesized using RSA-900. The EDX and FTIR spectra confirmed the significant peaks of Si and O for amorphous SiNPs, confirming their purity over crystalline SiNPs. FE-SEM and TEM micrographs indicated the spheroid morphology of the SiNPs with an average size of 27.47 nm (amorphous SiNPs) and 52.79 nm (crystalline SiNPs). Amorphous SiNPs possessed a high surface area of 226.11 m2/g over crystalline SiNPs (84.45 m2/g). The results obtained attest that the amorphous SiNPs possessed better attributes than crystalline SiNPs, omitting the need to incorporate high temperature. Photocatalytic degradation of methylene blue using SiNPs reflected that 66.26% of the dye was degraded in the first 10 min. The degradation study showed first-order kinetics with a half-life of 6.79 min. The cost-effective and environmentally friendly process offers a sustainable route to meet the increasing demand for SiNPs in industrial sectors. The study proposes a sustainable solution to stubble burning, intending towards zero waste generation, bioeconomy, and achieving the Sustainable Development Goals (SDGs), namely SDG 13(Climate Action), SDG 3(Good health and well-being), SDG 7(use of crop residues in industrial sectors) and SDG 8 (employment generation).