Dissertations / Theses: 'Supercritical Fluid Technology'

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Ahmed, Elizabeth Hannah. "Supercritical fluid technology for gastroretentive formulations." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/27853/.

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The oral route for drug administration offers an efficient and convenient method for drug delivery. However, there is an assortment of drugs which exhibit narrow absorption windows in the upper small intestine and as a result demonstrate limited bioavailabilities. One approach in the improvement of bioavailability in these cases is to retain the delivery system proximal to the absorption window for a prolonged period of time. Although controlled release products are widely available on the market, marketed gastroretentive systems remain elusive. This work explores the manufacture and characterisation of a multi-unit gastroretentive system utilising the biocompatible polymer poly (lactic-coglycolic acid). The novel PGSS technique enables the production of PLGA particles whilst omitting the use of volatile organic solvents. Morphological and microCT analyses of the particles revealed a highly porous matrix with porosity values in the order of 30-40%. The relationship between porosity, density and in vitro floating ability for particles with sizes between 100-2000 J.1m revealed that particle size plays an important role; larger microparticles possess decreased density, higher porosity and increased buoyancy. Encapsulation of two model drugs, riboflavin and furosemide, was carried out during the processing step with high encapsulation efficiencies (80-100%) being revealed. Release of the drugs in PBS (pH7.4) was found to be sustained over a period of 24 hours with a decrease in cumulative release in simulated gastric fluid (pHl.2). The introduction of the hydrophilic polymer poly(ethylene glycol) was found to modulate release rate; PEG with a molecular weight equal of more than 3 KDa increased the rate of release in PBS media up to 20% over hrs, however this was not observed for release in SGF. A comparison of morphology prior to and following exposure to the release media confirms that the emergence of intricate porous channels on exposure to the release medium is related to an increase in release rate. In order to augment the gastroretentive potential of the system the mucoadhesive polymer, chitosan was incorporated both as a post processing surface modification and as part of the initial formulation. ToF-SIMS surface analysis confirmed the presence of chitosan at the surface of the particles in both cases. Initially the potential for the particles to interact with mucus was evaluated utilising in vitro tests. The presence of chitosan significantly improved adsorption of mucin to particles, as well as enhancing adhesion of particles to a mucus producing epithelial cell layer. The thiolated chitosan derivative chitosan-N-acetyl-cysteine demonstrated an increase in adhesion of mucin solution; however the modified chitosan resulted in a decrease in adhesion to mucus producing cell line which was considered to be a result of the mucolytic actions it may exert on the mucus layer. Oral administration of buoyant particles to a rat model improved the pharmacokinetics of the anti-hypoglycaemia drug metformin, with addition of mucoadhesive properties providing further improvement. This study demonstrates that introduction of buoyancy and mucoadhesion functionalities to particles prepared by the PGSS method could improve delivery of drugs demonstrating narrow absorption windows in the upper small intestine.

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Silva, Mara Lília Soares da. "Development of molecularly imprinted polymers using supercritical fluid technology." Doctoral thesis, Faculdade de Ciências e Tecnologia, 2011. http://hdl.handle.net/10362/6697.

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Dissertação para obtenção do Grau de Doutor em Química Sustentável
Within the last decade, the interest in molecularly imprinted polymers (MIPs) has strongly increased because of their promising applications in separation processes, drug delivery, biomimetic sensing and catalysis. This thesis reports the development of MIPs using supercritical fluid technology as a viable and greener alternative to the synthesis and processing of these molecular recognition polymers. The affinity to the target molecule was introduced by means of non-covalent and semicovalent molecular imprinting and the performance of the materials was evaluated in specific applications of drug delivery, chiral chromatography and adsorption of environmental pollutants. The influence of experimental parameters, such as crosslinking degree, functional monomer nature and template: monomer ratio, on molecular recognition was investigated. The results show that it is possible to tune the affinity of the polymers by optimizing the imprinting reactional mixture. MIPs show higher loading capacities and affinity constants to the template molecule, both in supercritical and aqueous environments. Hybrid membranes were prepared by a scCO2-assisted phase inversion method, showing that imprinted particles can be immobilized into porous structures introducing affinity to the materials. Further, HPLC experiments attested that the synthesized MIPs have high selectivity towards the template, as an enantiomeric differentiation was achieved when the racemic mixture was loaded into the imprinted polymeric stationary phase. The work developed in this thesis contributes to the consolidation of scCO2 as alternative solvent and demonstrates the feasibility of synthesizing clean, easy-to-make and ready-to-use molecular recognition polymers using sustainable technologies.
Fundação Ciência e Tecnologia - grant SFRH/BD/31085/2006 and projects PTDC/QUI/66086/2006 and PTDC/QUI-QUI/102460/2008

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Meskar, Mahmoud. "Treatment of Petroleum Contaminated Soil using Supercritical Fluid Extraction (SFE) Technology." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/37393.

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In Canada, about 60% of contaminated sites involve petroleum hydrocarbon (PHC) contamination and most of these sites have been abandoned due to contamination. Among current technologies used for soil remediation, supercritical fluid extraction (SFE) is a relatively recent and potentially viable method. The main aim of this research was to investigate the application of SFE for removal of PHCs from contaminated soils. In the first phase, the effects of SFE operational parameters including fluid pressure, fluid temperature, time duration and mode of extraction on the removal efficiency of PHCs from a spiked sandy soil (with diesel fuel with a ratio of 5 wt%) were investigated. SFE experiments were performed at different pressures (15, 33 and 50 MPa) and temperatures (30, 75 and 120 °C). The combination of 10 min static mode followed by 10 min dynamic mode, repeated for 3 cycles (60 min in total) led to the highest PHC removal percentage. According to response surface methodology (RSM), the optimum pressure and temperature were found to be 50 MPa and 69.3 °C, respectively. According to experimental results, the optimum combination of pressure and temperature determined to be 33 MPa and 75 °C; which resulted in the extraction percentages of 99.2%, 91.7% and 86.1% for PHC F2, F3 and F4 fractions, respectively. In the second phase, the influence of several parameters including soil water content, soil pH and addition of modifier on PHCs removals from a field-contaminated sandy soil using SFE were experimentally investigated. SFE experiments were performed at 33 MPa pressure and temperatures of 45 and 75 °C. Three water content levels of 8%, 14% and 20% at two levels of pH 6.5 and 7.5 were investigated. The extraction of total petroleum hydrocarbon fractions (TPHF), the sum of F2, F3, and F4 fractions, decreased due to the increase in the water content from 8% to 20% at both pH 6.5 and 7.5. The difference of extractions of all PHC fractions at pH values of 6.5 and 7.5 were not statistically significant (at p < 0.05 confidence level) at all three water content levels and pH did not have a significant influence on the PHC removal efficiency. Addition of acetone as a modifier (33.7% TPHF removal) was more effective than hexanes (24.3% TPHF removal) to decrease the concentrations of PHCs for the field contaminated soil. In the third phase, the influence of soil texture and grain size on the extraction of PHC fractions was investigated. SFE experiments were performed at 33 MPa pressure and 75 °C temperature. Three types of soils (soil A, B and C) were spiked with diesel fuel with a ratio of 5 wt%. Soil A, B and C had different particle sizes and were categorized as sand, silt loam and clay, respectively. Soil A (sand) which had the largest particle size resulted in the highest TPHF removal percentage while soil C (clay) with the smallest particle size led to the lowest TPHF removal percentage. A higher clay content in soil C resulted in a lower extraction of PHCs. In the fourth phase, the effects of pressure and temperature on the extraction of PHC fractions from a clay soil spiked with diesel fuel with a ratio of 5 wt% were investigated. SFE experiments were performed at three pressures (15, 33 and 50 MPa) and temperatures (30, 75 and 120 °C). According to the statistical analysis including factorial design and RSM, the optimized combination of pressure and temperature was selected at 42.8 MPa and 120 °C; which resulted in the removal percentages of 74.9% and 65.6% for PHC F2 and F3 fractions, respectively. The optimum combination of pressure and temperature based on the experimental results was selected at 33 MPa and 120 °C that led to 70.3%, 58.4% and 32.6% removal of PHC F2, F3 and F4 fractions, respectively.

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Hafner, Kellye Padgett. "Design of solvent systems for supercritical fluid and high pressure applications." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/11211.

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Vandana, Vishnu. "Separation of taxol and related taxanes using supercritical fluids." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/10078.

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Collins, Niki Jane. "Construction of novel tissue engineering scaffolds using supercritical fluid gas foaming." Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/3184/.

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Three dimensional scaffolds were created from a biodegradable polymer (polylactide) and the mineral silica utilising supercritical fluid (SCF) gas foaming. The effect of silica on the scaffold pore architecture was investigated through X-ray computed microtomography (microCT); the scaffolds were shown to be up to 60% porous with pore diameters in the range of 0.088-0.924 mm (0% silica) to 0.044 – 0.342 mm (33.3% silica), demonstrating that silica controlled both pore size and overall scaffold porosity; Silica was found to enhance connectivity of the pores and pore wall thickness and pore connectivity were found have an inverse relationship. Differential scanning calorimetry (DSC) was used to investigate the effect of silica on the Tm, Tg and crystallinity of the PLA pre and post SCF processing; increases in ΔHf (4J/g) Tg (1oC) and crystallinity (3%) showed that silica had a beneficial effect pre-SCF but post-SCF the PLA reverted to an amorphous state; An isothermal conditioning process was found to restore the previous levels of crystallinity. Mechanical strength testing of the scaffolds showed that silica incorporation increased the load tolerated at yield by up to 60N and the strength by up to 1.5 mPa. The scaffolds were immersed in simulated body fluid (SBF), where the presence of silica was found to enhance mineral deposition by up to 10%; they were also subjected to degradation experiments in physiological saline solution and enzyme buffer solution, where degradation was found to occur most rapidly in the amorphous regions of the polymer (0% and 9.1% silica). The formation of degradation products (lactic acid, isopropanol and lactate) were monitored through HPLC. In conclusion, addition of silica up to a loading of 9.1-16.7% was found to have many beneficial effects on the PLA scaffolds but no observable benefit was found with additions higher than this.

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Zabot, Giovani Leone 1988. "Obtaining bioactive compounds from clove and rosemary using supercritical technology: influence of the bed geometry, process intensification and cost of manufacturing of extracts = Obtenção de compostos bioativos de cravo-da-índia e alecrim utilizando tecnologia supercrítica: influência da geometria do leito, intensificação de processos de extração e custo de manufatura dos extratos." [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/254901.

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Orientador: Maria Angela de Almeida Meireles
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
Made available in DSpace on 2018-08-26T17:00:04Z (GMT). No. of bitstreams: 1 Zabot_GiovaniLeone_D.pdf: 24740321 bytes, checksum: 93e515a410574c1037b0a53340db63d2 (MD5) Previous issue date: 2015
Resumo: Substâncias naturais extraídas de plantas têm propriedades funcionais que as tornam preferíveis em relação às substâncias sintéticas, havendo grande interesse para aplicação farmacológica e na elaboração de bioprodutos. Técnicas de extração, como a que utiliza fluidos supercríticos, vêm se destacando por proporcionarem a obtenção seletiva de compostos bioativos com elevada qualidade. No campo da tecnologia supercrítica, pesquisas são desenvolvidas para aumentar o rendimento de extração através da alteração de condições de processo, como pressão e temperatura. No entanto, há a necessidade de discriminar mais a influência tecno-econômica de outras variáveis, como a geometria do leito de extração. Em vista disso, realizou-se a avaliação técnica da extração com CO2 supercrítico de compostos bioativos de cravo-da-índia e alecrim em uma unidade de extração laboratorial constituída por dois extratores de 1 L com diferentes razões de altura do leito (HB) pelo diâmetro (DB), sendo para o extrator 1 (E-1) a razão de 7,1 e para o extrator 2 (E-2) a razão de 2,7. Dois critérios utilizados para mudança de geometria e aumento de escala foram aplicados, consistindo em: (1) manutenção da velocidade intersticial do solvente igual em ambas as geometrias; e (2) manutenção da razão de massa de solvente por massa de matéria-prima (S/F) igual em ambas as geometrias para um determinado tempo de processo. De acordo com os resultados cinéticos de rendimento de extrato e composição química, o critério (1) não se mostrou indicado para ser aplicado em processos de extração com fluidos supercríticos (SFE) de compostos de cravo-da-índia. O critério (2) mostrou-se apropriado para a obtenção de óleo volátil de cravo-da-índia, pois houve igualdade nos perfis das curvas de extração em E-1 e E-2, avaliados em termos de parâmetros cinéticos como taxa de transferência de massa, duração dos períodos de taxa constante de extração (CER) e taxa decrescente de extração (FER), rendimento de extrato e razão mássica de soluto no solvente. No entanto, o critério (2) não se mostrou adequado para a obtenção de compostos bioativos de alecrim, sendo que o leito de extração E-2 proporcionou rendimentos até 86 % maiores em relação ao E-1, sendo a diferença mais notória no final do período FER. Houve diferença também no custo de manufatura (COM) dos extratos de alecrim simulado pelo SuperPro Designer 8.5®, sendo 23 % menor em E-2 do que em E-1 para uma planta industrial com 2 extratores de 100 L. Com relação ao alecrim, terpenoides majoritários como 1,8-cineol e cânfora foram extraídos com CO2 supercrítico. No entanto, alguns compostos fenólicos foram extraídos em pequena quantidade (ácido carnósico) ou nem foram extraídos via SFE (ácido rosmarínico). Logo, o conceito de intensificação de processos foi utilizado para facilitar a extração das duas frações presentes em alecrim. O processo consistiu em extrair inicialmente a fração rica em terpenoides com CO2 supercrítico (SFE-CO2) e logo após, no mesmo equipamento e sem desempacotar o leito, a fração rica em terpenos fenólicos foi extraída com água líquida pressurizada (PWE). Com isso, aproximadamente 2,5 % (m/m, base seca) de óleo volátil contendo terpenoides e 18,6 % (m/m, base seca) de extrato não-volátil contendo terpenos fenólicos foram obtidos em frações separadas. Um método analítico para quantificação de terpenos fenólicos por cromatografia líquida de alta eficiência foi desenvolvido e validado, com tempo total de análise de apenas 10 min. O custo operacional anual de uma planta produtiva instalada no Brasil com 2 extratores de 100 L foi simulado para os processos SFE-CO2 + PWE para obtenção de compostos de alecrim. O aproveitamento maior da matriz vegetal para a obtenção diversificada de compostos bioativos permitiu a redução em 28 % dos custos anuais de produção em relação ao processo SFE-CO2
Abstract: Natural substances extracted from plants present functional properties which are preferable against the synthetic ones, being useful in formulating bioproducts and in the pharmaceutical area. Novel extraction techniques, as the use of supercritical fluids, are acquiring notoriety by providing the selective extraction of bioactive compounds with high quality. In the supercritical technology field, researches are performed to increase the extraction yield by changing process conditions (i.e., pressure, temperature). However, there is a need for further techno-economic discriminations about the influence of other variables, as the bed geometry. Thus, we performed the evaluation of the supercritical CO2 extraction of clove and rosemary bioactive compounds using a laboratory equipment containing two extractors of 1 L with different height (HB) to bed diameter (DB) ratios. Bed 1 (E-1) and 2 (E-2) present HB/DB ratios of 7.1 and 2.7, respectively. Two criteria used for geometry shift and scale up were applied: (1) maintaining the solvent interstitial velocity equal in both bed geometries; and (2) maintaining the solvent mass to feed mass (S/F) ratio equal in both bed geometries for a fixed processing time. According to the kinetic results of extraction yields and chemical composition, the criterion (1) is not indicated for supercritical fluid extraction (SFE) of rosemary compounds. Criterion (2) is suitable for obtaining clove extract, because the extraction curves profiles were similar in E-1 and E-2. We evaluated the extraction curves in relationship to kinetic parameters as mass transfer rate, duration of constant extraction rate (CER) and falling extraction rate (FER) periods, extraction yield and mass ratio of solute in the fluid phase. However, criterion (2) is inappropriate for obtaining rosemary bioactive compounds. E-2 provided extraction yields up to 86% higher than E-1. The difference was more pronounced in the end of FER period. We observed differences on the cost of manufacturing (COM) of rosemary extracts simulated by SuperPro Designer 8.5®. COM¿s were 23% lower in E-2 than in E-1 for an industrial plant of 2 extractors of 100 L. With respect to rosemary, major terpenoids as 1,8-cineole and camphor were extracted with supercritical CO2, while some phenolic compounds were low (carnosic acid) or no extracted (rosmarinic acid) using SFE. Thus, process intensification concept was used for becoming possible the extraction of two fractions of bioactive compounds found in rosemary. The procedure comprised the initial extraction of the terpenoids-rich fraction with supercritical CO2 (SFE-CO2) and, thereafter, in the same equipment without unloading the bed, performing the extraction of the polyphenols-rich fraction with pressurized water (PWE). Approximately 2.5 wt.% (dry basis) of volatile oil containing terpenoids and 18.6 wt.% (dry basis) of non-volatile extract containing phenolic terpenes were obtained in separated fractions. We developed and validated an analytical method for quantifying phenolic terpenes by high performance liquid chromatography, presenting a total time of analysis of 10 min. Also, we simulated the annual operating cost of a plant installed in Brazil containing 2 vessels of 100 L applying SFE-CO2 + PWE processes for obtaining rosemary compounds. The higher use of the vegetal matrix for diversifying the extraction of bioactive compounds enabled 28% reduction in the annual production costs whether compared to SFE-CO2 process alone
Doutorado
Engenharia de Alimentos
Doutor em Engenharia de Alimentos

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Sarup, Louise Santha. "Investigation of supercritical fluid technology to produce dry particulate formulations of antibody fragments." Thesis, University College London (University of London), 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406707.

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Anitescu, Gheorghe. "Supercritical fluid technology applied to the production and combustion of diesel and biodiesel fuels." Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2008. http://wwwlib.umi.com/cr/syr/main.

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Velaga, Sitaram P. "Preparation of Pharmaceutical Powders using Supercritical Fluid Technology : Pharmaceutical Applications and Physicochemical Characterisation of Powders." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-4006.

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Potter, Catherine. "Application of supercritical fluid technology to the pre-formulation and production of amorphous solid dispersions." Thesis, Queen's University Belfast, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.677955.

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García, González Carlos A. "Use of the supercritical fluid technology for the preparation of nanostructured hybrid materials and design of the interface." Doctoral thesis, Universitat Politècnica de Catalunya, 2009. http://hdl.handle.net/10803/42297.

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Los materiales compuestos nanoestructurados son considerados una opción prometedora para la concepción de materiales multifuncionales. Sin embargo, la falta habitual de interacción entre los componentes orgánicos e inorgánicos en los materiales híbridos nanoestructurados comporta unas propiedades macroscópicas anisotrópicas que limitan su uso. Por ello, se hace necesario el diseño de la interfase formada entre los componentes mencionados a fin de mejorar sus prestaciones. En esta Tesis Doctoral se ha optado por el uso de dióxido de carbono supercrítico (scCO2) para la modificación superficial de nanopartículas inorgánicas y para la preparación de materiales híbridos nanoestructurados. Estos procesos supercríticos, diseñados como sostenibles, se proponen como sustitutos de técnicas convencionales que empleen disolventes orgánicos. El tratamiento superficial de nanopartículas de dióxido de titanio (TiO2) con octiltrietoxisilano se ha empleado como sistema de estudio para evaluar el uso de recubrimientos de alcoxisilanos bifuncionales como promotores de adhesión de partículas inorgánicas nanométricas. El scCO2 se emplea como disolvente del alcoxisilano para la silanización del TiO2. También se han llevado a cabo estudios fundamentales de solubilidad de octiltrietoxisilano en CO2 y de la cinética del proceso de silanización del TiO2. La modulación de las propiedades fisicoquímicas del scCO2 con la presión y la temperatura permite el control de las características del recubrimiento con silano. El proceso de silanización supercrítico se ha extendido a diferentes sistemas alcoxisilano-nanopartículas inorgánicas. Asimismo, se ha evaluado la tecnología de scCO2 para la preparación de materiales híbridos nanoestructurados que contengan nanopartículas inorgánicas silanizadas. El tratamiento superficial de las nanopartículas favorece la distribución homogénea de éstas en el material híbrido y mejora la interacción relleno-matriz orgánica. Se han procesado matrices biopoliméricas de interés en ingeniería tisular, compuestas de ácido poliláctico o la mezcla iv polimetilmetacrilato/policaprolactona, con adiciones de nanopartículas de TiO2 o hidroxiapatita, respectivamente. Para su procesado, se ha empleado scCO2 como no-disolvente utilizando la técnica Particles from a Compressed Anti-Solvent (PCA). Además, se han preparado partículas híbridas formadas por una mezcla lipídica de aceite de ricino hidrogenado y glicerilmonoestearato con adiciones de TiO2 y cafeína, con posibles aplicaciones en cremas para uso tópico. Estas partículas sólidas lipídicas se han obtenido usando la técnica Particles from Gas Saturated Solutions (PGSS) que emplea scCO2 como soluto. Por último, el proceso de silanización supercrítico se ha ensayado para materiales híbridos complejos multiescalados. Se han procesado materiales de base cemento empleando un proceso supercrítico de carbonatación-silanización en dos etapas. Primero, el cemento se carbonata de manera acelerada usando scCO2 como agente de carbonatación. Este cemento, ya carbonatado, se somete, finalmente, a un tratamiento hidrofóbico mediante silanización supercrítica, para su posible aplicación en confinamiento de residuos peligrosos en ambientes húmedos o como material de construcción duradero.
Nowadays, society is asking for a global changing in the way of manufacturing goods in a more sustainable manner. Indeed, the weight of the classical factors (cost, quality, appearance) influencing the acceptance of a certain good in the market have currently changed. Manufacturing requirements and regulations concerning environment protection (e.g., resource consumption, sustainability, toxicity, CO2 footprint, recycling potential) and quality features (e.g., product guarantees, durability against aggressive environments, corporate vision) are aspects of increasing concern. The competitive position of a company is influenced by seizing the opportunities and challenges and by managing the risks that the changeable market has. As a consequence, the industry is continuously looking for smart and innovative solutions for the design and manufacturing of materials with novel properties and increased added value, and for the production of materials already existing in the market in a more efficient manner. Nanostructured hybrid composites have emerged as a promising class of innovative materials for many industrial sectors (e.g., energy, optoelectronics, biomedicine, cosmetics). The multicomponent composition of these materials provides them with unique properties arising from the synergistic combination of the characteristics of their individual components structured at the nanolevel. Nevertheless, in numerous hybrid materials, the lack of coupling or bonding between the components often leads to anisotropic macroscopic properties, limiting their use. Hence, the interaction at the interphase between hybrid components must be properly engineered to enhance materials properties. In this PhD Thesis, the quest for sustainable and environmentally friendly processes led to the use of supercritical carbon dioxide (scCO2) for both the surface modification of nanometric inorganic particles and the preparation of nanostructured hybrid materials. These processes are designed for the replacement of conventional methods using organic solvents. vi Bifunctional alkoxysilane molecules, acting as adhesion promoters, are, herein, investigated for the surface modification of nanometric inorganic particles. The surface treatment of titanium dioxide (TiO2) nanoparticles with octyltriethoxysilane is taken as the model system for study. In terms of processing, scCO2 is used as the solvent of choice for alkoxysilanes for the surface modification of TiO2. Fundamental studies on the solubility of the used silane in CO2 in the pressure range 8-18 MPa at two different temperatures (318 and 348 K) and on the kinetics of the TiO2 silanization process are performed. For the scCO2-aided silanization process, studies are conducted to ascertain the effects and interactions of the operating variables on the properties of the final material. Results show that the tunable physicochemical properties of scCO2 with pressure and temperature (e.g., density, solvation power) allows the engineering control of the characteristics of the silane coating. Examples of the extension of the application of the supercritical silanization process to other sets of alkoxysilanes and inorganic nanoparticles are also presented. The preparation of hybrid materials including silanized inorganic nanoparticles and organic matrices is further tested using scCO2 technology. Surface treated nanoparticles are used to facilitate the homogeneous distribution of the nanoparticles within the matix and to improve the inorganic filler-organic matrix interaction. Biopolymeric matrices of either poly(L-lactic acid) (L-PLA) or the blend poly(methylmethacrylate)/poly(ε-caprolactone) (PMMA/PCL) loaded with nanometric titanium dioxide or hydroxyapatite, respectively, are prepared. To obtain these hybrid materials, scCO2 is employed as an anti-solvent, using the Particles from a Compressed Anti-Solvent (PCA) technique. Studies are performed to pursue the effect of the processing conditions on the morphology of the precipitated hybrid materials. The resulting material, obtained in the form of fibers, has suitable properties for its potential application in tissue engineering. In a different system, hybrid particles composed of a lipidic matrix (hydrogenated castor oil/glyceryl monostearate) loaded with silanized titanium dioxide and caffeine are prepared. The Particles from Gas Saturated Solutions (PGSS) technique, assisted by the use of scCO2 as a solute, is employed for the production of these solid lipid particles. The obtained hybrid material is evaluated concerning the drug carrier and release ability and the UV-shielding capacity. The UV-light protection and photoaging prevention capacity of the lipid-based hybrid material provide excellent properties for the use of these particles in the formulation of sunscreens and pharmaceutical dermal products. vii Finally, the possibility of extending the supercritical silane treatment to multiscale complex hybrid materials is assessed. The technology based on the use of scCO2 is presented for the two-step carbonation-silanization process of cement-based materials. In the first step, the carbonation of cement is accelerated using scCO2 as the carbonation agent. The effects of the cement formulation and process operation conditions on the microstructure and physicochemical properties of carbonated samples are evaluated. The carbonation process is followed by the hydrophobic treatment of the carbonated samples using a supercritical silanization method. The surface modification of carbonated cement with octyltriethoxysilane confers water repellence to the material. The carbonation-silanization process is scheduled and integrated to mitigate the consumption of raw materials and the use of facilities.

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McCarney, Jonathan Paul. "Reactions and process separations in environmentally benign media." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/30362.

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Ramirez, Carmen Hernandez. "Enhancement of the rate of solution of relatively insoluble drugs from solid-solid systems prepared by supercritical fluid technology." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1179928429.

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Guardo, Zabaleta Alfredo. "Computational Fluid Dynamics Studies in Heat and Mass Transfer Phenomena in Packed Bed Extraction and Reaction Equipment: Special Attention to Supercritical Fluids Technology." Doctoral thesis, Universitat Politècnica de Catalunya, 2007. http://hdl.handle.net/10803/6455.

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El entendimiento de los fenómenos de transferencia de calor y de masa en medios porosos implica el estudio de modelos de transporte de fluidos en la fracción vacía del medio; este hecho es de fundamental importancia en muchos sistemas de Ingeniería Química, tal como en procesos de extracción o en reactores catalíticos. Los estudios de flujo realizados hasta ahora (teóricos y experimentales) usualmente tratan al medio poroso como un medio efectivo y homogéneo, y toman como válidas las propiedades medias del fluido. Este tipo de aproximación no tiene en cuenta la complejidad del flujo a través del espacio vacío del medio poroso, reduciendo la descripción del problema a promedios macroscópicos y propiedades efectivas. Sin embargo, estos detalles de los procesos locales de flujo pueden llegar a ser factores importantes que influencien el comportamiento de un proceso físico determinado que ocurre dentro del sistema, y son cruciales para entender el mecanismo detallado de, por ejemplo, fenómenos como la dispersión de calor, la dispersión de masa o el transporte entre interfaces.

La Dinámica de Fluidos Computacional (CFD) como herramienta de modelado numérico permite obtener una visión mas aproximada y realista de los fenómenos de flujo de fluidos y los mecanismos de transferencia de calor y masa en lechos empacados, a través de la resolución de las ecuaciones de Navier - Stokes acopladas con los balances de materia y energía y con un modelo de turbulencia si es necesario. De esta forma, esta herramienta permite obtener los valores medios y/o fluctuantes de variables como la velocidad del fluido, la temperatura o la concentración de una especie en cualquier punto de la geometría del lecho empacado.

El objetivo de este proyecto es el de utilizar programas comerciales de simulación CFD para resolver el flujo de fluidos y la transferencia de calor y de masa en modelos bi/tri dimensionales de lechos empacados, desarrollando una estrategia de modelado aplicable al diseño de equipos para procesos de extracción o de reacción catalítica. Como referencia se tomaran procesos de tecnología supercrítica debido a la complejidad de los fenómenos de transporte involucrados en estas condiciones, así como a la disponibilidad de datos experimentales obtenidos previamente en nuestro grupo de investigación. Estos datos experimentales se utilizan como herramienta de validación de los modelos numéricos generados, y de las estrategias de simulación adoptadas y realizadas durante el desarrollo de este proyecto.
An understanding of the heat and mass transfer phenomena in a porous media implies the study of the fluid transport model within the void space; this fact is of fundamental importance to many chemical engineering systems such as packed bed extraction or catalytic reaction equipment. Experimental and theoretical studies of flow through such systems often treat the porous medium as an effectively homogeneous system and concentrate on the bulk properties of the flow. Such an approach neglects completely the complexities of the flow within the void space of the porous medium, reducing the description of the problem to macroscopic average or effective quantities. The details of this local flow process may, however, be the most important factor influencing the behavior of a given physical process occurring within the system, and are crucial to understanding the detailed mechanisms of, for example, heat and mass dispersion and interface transport.

Computational Fluid Dynamics as a simulation tool allows obtaining a more approached view of the fluid flow and heat and mass transfer mechanisms in fixed bed equipment, through the resolution of 3D Reynolds averaged transport equations, together with a turbulence model when needed. In this way, this tool permit to obtain mean and fluctuating flow and temperature values in any point of the bed.

The goal of this project is to use commercial available CFD codes for solving fluid flow and heat and mass transfer phenomena in two and three dimensional models of packed beds, developing a modeling strategy applicable to the design of packed bed chemical reaction and extraction equipment. Supercritical extraction and supercritical catalytic reaction processes will be taken as reference processes due to the complexity of the transport phenomena involved within this processes, and to the availability of experimental data in this field, obtained in the supercritical fluids research group of this university. The experimental data priory obtained by our research group will be used as validation data for the numerical models and strategies dopted and followed during the developing of the project.

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Sih, Roderick Peng Tze Chemical Sciences &amp Engineering Faculty of Engineering UNSW. "New process development of dense gas technology for the processing of pharmaceuticals." Publisher:University of New South Wales. Chemical Sciences & Engineering, 2008. http://handle.unsw.edu.au/1959.4/41257.

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Drug re-engineering is an effective method for engineering existing products in alternative dosage forms and with enhanced pharmacokinetics. Insulin for the management of diabetic symptoms is an ideal candidate for re-engineering. Current subcutaneous therapy results in low patient compliance and is ineffective in meeting the physiological need for post-prandial insulin. Implementation of dose titration for more efficient blood-glucose management is also inconvenient and uncomfortable. Inhaled insulin is presented as a superior alternative to current therapy. The lungs offer excellent access to the circulatory system. Aerosols suspended in inspired air may deposit on lung epithelia and be available for systemic absorption. To evade the defense mechanism of the human respiratory tract, particle sizes have traditionally been minimized to achieve necessary aerosol performance. Recent developments indicate that more efficient performance augmentation may also be achieved by decreasing the bulk density of powders and modifying surface characteristics. Light and fluffy powders with rough surfaces experience much higher drag forces within an airstream. The Atomized Rapid Injection for Solvent Extraction (ARISE) process is a unique precipitation platform devised by incorporating a rapid injection technique for energetic solution delivery into supercritical fluid (SCF) media to effect recovery of previously dissolved pharmaceutical compounds. The quasi-instantaneous delivery of solutions alleviates the drawbacks of the use of capillary nozzles or micro-orifices, gradual elution and mixing controlled precipitation kinetics in existing SCF precipitation techniques. Most importantly, the energetic release of solution into SCF media effects supersaturation over a much larger spatial volume and promotes the homogeneous precipitation of low bulk density powders. ARISE processed insulin powders displayed characteristics that were highly influenced by anti-solvent conditions and powders of different qualities were obtained as a function of anti-solvent pressures. At lower anti-solvent pressures, powders of narrow particle size distribution were achieved, an indication of homogeneous supersaturation levels within processing. Span, the index of size distribution was as low as 0.991. At higher anti-solvent pressures, supersaturation rates were increased while mixing efficiencies decreased, resulting in powders of wider size distribution, and powder bulk densities as low as 0.01 g/ml. Low bulk density insulin displayed in-vitro respirable fractions as high as 78%.

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Grant, R. P. "Studies of supercritical fluid technology for benzodiazepine analysis, LC-MS for ecdysteroid screening and DCT spectroscopy of chloromethanes and bromomethanes." Thesis, Swansea University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.637087.

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The aim of the investigations was to evaluate the potential of a number of analytical techniques for studying various compound classes. The techniques employed in this study include supercritical fluid extraction (SFE), supercritical fluid chromatography (SFC), gas chromatography hyphenated to mass spectrometry (GC-MS), liquid chromatography hyphenated to mass spectrometry (LC-MS) and double-charge-transfer (DCT) spectroscopy. Chapter 1 reviews the properties of supercritical fluids and the historical developments of SFE and SFC. The fundamentals of chromatography, mass spectrometry and interfacing systems are also described, in particular, electrospray (ES) and atmospheric pressure chemical ionization (APCI) interfaces. Evaluation of qualitative SF for benzodiazepine screening and off-ine quantitative SFE-SFC-UV for the analysis of benzodiazepines in biological matrices is described in chapter 2. An improvement in the chromatographic efficiency and speed is shown for complex benzodiazepine mixture separation by SFC and a review of current analytical methodologies is reported. The use of GC-MS as a more sensitive detector for quantitative off-line SFE analysis is also shown, allowing comparison with the off-line SFE-SFC-UV assay described. In chapter 3, the utility of LC-MS is investigated in the screening of plant samples for ecdysteroids. Both ES and APCI interfaces are evaluated together with normal and reverse phase LC systems. The enhanced sensitivity and specificity of LC-MS-MS is also shown, along with a comparison with current state-of-the-art analytical methodologies described in the literature for analysis of ecdysteroids. Chapter 4 describes the use of DCT spectroscopy to gain information on ground and excited dication electronic states of chloromethanes and bromomethanes. Application of a semi-empirical computational method is also reported and consistently good agreement is obtained between measured and calculated double-ionization energies to singlet and triplet electronic states of the dications. Chapter 5 describes the instrumentation used in the investigations.

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Rodrigues, Liliana Andreia Amaro. "Development of a "green process" for the isolation of natural functional extracts with anti-cancer activity - Application of high-pressure technology." Master's thesis, Faculdade de Ciências e Tecnologia, 2014. http://hdl.handle.net/10362/12207.

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Dissertação para obtenção do Grau de Mestre em Engenharia Química e Bioquímica
The knowledge of the healing power of some species of plants is ancient. Nowadays, the preference for natural products has increased, and with it, the interest in recover and isolate bioactive phytochemicals with potential health benefits. The main goal of this thesis was to isolate anticancer bioactive compounds, namely terpenes and fatty acids, from Portuguese Lavandula (L. angustifolia and L. stoechas) and Mentha species (M. spicata, M. piperita var. citrata and M. pulegium), using supercritical fluid extraction (SFE). All extractions were performed at 50ºC and 250 bar in a two step methodology: a first step with supercritical CO2, during 60 minutes, followed by a second step, with a mixture of CO2 and ethanol (90:10 %v/v), for 180 minutes. Different fractions of the extracts were recovered every 30 minutes, and the resulting samples were characterized in terms of global yield (% g/g), screened for the presence of terpenes, by thin layer chromatography (TLC) and analyzed by gas chromatography coupled with mass spectrometry detection (GC-MS). Furthermore, ORAC, HORAC and HOSC assays were conducted for the determination of antioxidant activity. Cell-based assays in human HT-29 colorectal adenocarcinoma cells were also performed, in order to determine the potential of the extracts as cancer cell-growth inhibitors. The fractions of the extract of M. piperita var. citrata presented the highest antioxidant activity, whereas the fractions of L. angustifolia, L. stoechas and M. spicata extracts revealed to be the most promising colorectal cancer cell-growth inhibitors. The bioactive responses were correlated with the phytochemical composition of the extracts, and the main compounds, such as camphor, fenchone, carvone, linoleic acid, among others, were highlighted. However, it is possible that the bioactivities were due to synergistic effects between several compounds. Results of this thesis demonstrated that SFE is a reliable tool to extract anticancer bioactive components from some Lavandula and Mentha plants.

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Vahdatzaman, Maral. "Novel Catalytic Etherification Reaction of Glycerol to Short-Chain Polyglycerol." Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1491410157911627.

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Mohamed, Noha Nahedj Atia. "Pharmaceutical analysis and in-vitro aerodynamic characterisation of inhaled theophylline formulations containing drug particles prepared by supercritical fluid processing : chromatographic, spectroscopic, and thermal analysis of micron-sized theophylline particles prepared by supercritical fluid technology and in-vitro evaluation of their performance as inhaled dry powder formulations." Thesis, University of Bradford, 2009. http://hdl.handle.net/10454/4297.

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The aim of this work is to study the in-vitro aerodynamic performance of a new inhaled theophylline formulation prepared by supercritical fluids technique. For the analysis of the output from the in-vitro tests (and further in-vivo tests) a new, fast, sensitive high performance liquid chromatographic (HPLC) method was developed and validated for the determination of theophylline and other related derivatives in aqueous and urine samples using new packing materials (monolithic columns). These columns achieve efficient separation under lower backpressure and shorter time comparing to other traditionally or newly introduced C18 columns. Solution enhanced dispersion by supercritical fluid (SEDS) process has been applied for the production of anhydrous theophylline as pure crystals in the range 2-5 μm to be used as new inhaled dry powder formulation for asthma. Fifteen theophylline samples have been prepared under different experimental conditions. The drug produced by this method has been subject to a number of solid-phase analytical procedures designed to establish the crystal structure [X-ray powder diffraction (XRPD)], the structure and conformation [(FTIR), Fourier-transform Raman spectroscopy (FT-Raman)], and the morphology and particle size [scanning electron microscope (SEM)]. While, thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC) have been used to monitor any phase transition or polymorphic changes after processing. All these analytical techniques gave a satisfactory indication of the solid-state chemistry of the processed particles and assess the development of new inhalation product. The performance of inhaled SEDS theophylline with or without a carrier was evaluated using the developed HPLC method. Three samples having different particle sizes were selected out of the prepared powders by SEDS technique to be tested. The dose sampling unit and the Anderson Cascade Impactor were used to determine the in-vitro emitted dose and the deposition profiles of SEDS samples, respectively. The effect of different inhalation flows was studied using two different flows 28.3, and 60 L min-1 with 4 L inhalation volume. Different DPI devices were investigated in this study; Easyhaler® and Spinhaler®. The particle size has an important effect on the aerodynamic behaviour and deposition profile of inhaled drug, the smaller the particles the greater the total lung deposition. The presence of a carrier improves the respirable fraction for all the tested formulations.

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Mohamed, Noha N. A. "Pharmaceutical analysis and in-vitro aerodynamic characterisation of inhaled theophylline formulations containing drug particles prepared by supercritical fluid processing. Chromatographic, spectroscopic, and thermal analysis of micron-sized theophylline particles prepared by supercritical fluid technology and in-vitro evaluation of their performance as inhaled dry powder formulations." Thesis, University of Bradford, 2009. http://hdl.handle.net/10454/4297.

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The aim of this work is to study the in-vitro aerodynamic performance of a new inhaled theophylline formulation prepared by supercritical fluids technique. For the analysis of the output from the in-vitro tests (and further in-vivo tests) a new, fast, sensitive high performance liquid chromatographic (HPLC) method was developed and validated for the determination of theophylline and other related derivatives in aqueous and urine samples using new packing materials (monolithic columns). These columns achieve efficient separation under lower backpressure and shorter time comparing to other traditionally or newly introduced C18 columns. Solution enhanced dispersion by supercritical fluid (SEDS) process has been applied for the production of anhydrous theophylline as pure crystals in the range 2-5 ¿m to be used as new inhaled dry powder formulation for asthma. Fifteen theophylline samples have been prepared under different experimental conditions. The drug produced by this method has been subject to a number of solid-phase analytical procedures designed to establish the crystal structure [X-ray powder diffraction (XRPD)], the structure and conformation [(FTIR), Fourier-transform Raman spectroscopy (FT-Raman)], and the morphology and particle size [scanning electron microscope (SEM)]. While, thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC) have been used to monitor any phase transition or polymorphic changes after processing. All these analytical techniques gave a satisfactory indication of the solid-state chemistry of the processed particles and assess the development of new inhalation product. The performance of inhaled SEDS theophylline with or without a carrier was evaluated using the developed HPLC method. Three samples having different particle sizes were selected out of the prepared powders by SEDS technique to be tested. The dose sampling unit and the Anderson Cascade Impactor were used to determine the in-vitro emitted dose and the deposition profiles of SEDS samples, respectively. The effect of different inhalation flows was studied using two different flows 28.3, and 60 L min-1 with 4 L inhalation volume. Different DPI devices were investigated in this study; Easyhaler® and Spinhaler®. The particle size has an important effect on the aerodynamic behaviour and deposition profile of inhaled drug, the smaller the particles the greater the total lung deposition. The presence of a carrier improves the respirable fraction for all the tested formulations.
Egyptian Ministry of Higher Education

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Kosuri, Madhava Rao. "Polymeric membranes for super critical carbon dioxide (scCO2) separations." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/28242.

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Thesis (M. S.)--Chemical Engineering, Georgia Institute of Technology, 2009.
Committee Chair: William J. Koros; Committee Member: Amyn Teja; Committee Member: Carson Meredith; Committee Member: Sankar Nair; Committee Member: Wallace W. Carr.

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Sakellarios, Nikolaos Ioannis. "Combining ionic liquids and supercritical fluids for clean technology." Thesis, Imperial College London, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415500.

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Branch, Jack Anthony. "Electrochemical studies of diffusion in supercritical fluids." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/377597/.

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The challenges and specialised equipment associated with supercritical electrochemistry means standard reference electrodes (such as the saturated calomel electrode) cannot be used. The aim of the thesis is the investigation of a range of metallocenes as model redox systems against a Pt pseudo reference electrode in supercritical fluids. This work was then extended to the development of a new high pressure reactor. Initially, a range of metallocenes were investigated in liquid analogues of the supercritical fluids (acetonitrile and dichloromethane) to investigate their suitability. Cyclic voltammetry performed at both micro and macro electrodes were used to examine the behaviour of each individual redox couple. Electrochemistry of the metallocenes were then evaluated in supercritical fluids (supercritical carbon dioxide with acetonitrile and supercritical difluoromethane) for investigation as model redox systems. The diffusion coefficients have been determined at both micro and macro electrodes for both supercritical fluids. The implementation of baffled micro and macro electrodes has shown that the intrinsic convection (at the electrode surface) within supercritical fluids can be dampened. The diffusion of metallocenes in nanoporous aluminium oxide membranes (13 – 55 nm diameter cylindrical pores), in both supercritical fluids has also been investigated. This work was then extended to the development of a new high pressure plastic reactor leading to the first, successful, supercritical fluid electrodeposition of bismuth in the plastic reactor.

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Sacchetin, Priscila Soares Costa. "Produção de micropartículas poliméricas por tecnologia de fluidos supercríticos para aplicação como veículo na administração oral de 17'alfa'-metiltestosterona para tilápias do Nilo." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266610.

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Orientadores: Ângela Maria Moraes, Paulo de Tarso Vieira e Rosa
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: No presente trabalho propôs-se a formação de carreadores orais compostos pelos polímeros sintéticos PLA (poli(L-ácido lático)), PLGA (poli(50/50 DL-ácido lático-co-glicólico)) e PCL (policaprolactona) para a construção de sistemas de liberação controlada de 17a-metiltestosterona (MT) pelo método de precipitação das soluções pelo uso de CO2 supercrítico como antisolvente. A influência da pressão, da concentração hormonal, dos polímeros e da vazão da solução polimérica foi analisada. Partículas de PLA com diâmetros entre 5,4 a 20,5 mm foram eficientemente produzidas, observando-se que o aumento na concentração da solução polimérica foi capaz de produzir partículas menores e que o aumento da vazão de solução polimérica resultou em aumento no tamanho das partículas produzidas. Não foram observados efeitos sobre a morfologia e distribuição de tamanhos das partículas com a variação da pressão. Notaram-se também nas partículas de PLA mudanças nas características mecânicas e físicas do polímero, como a redução da temperatura de transição vítrea do polímero. A produção de partículas de PLA na presença de MT resultou em aumento no tamanho médio e alterações nas características morfológicas superficiais das partículas. Praticamente não se observaram alterações na temperatura de transição vítrea e de fusão das partículas quando estas foram produzidas na presença de MT. As análises de potencial zeta das partículas mostraram que estas possuem forte tendência à floculação. Obtiveram-se também partículas de PLA/PCL a partir da mistura destes polímeros a razões de 1/9 a 1/1 m/m. Altas concentrações de PCL provocaram aumento no diâmetro médio das partículas, que se mostraram mais agregadas e rugosas. A eficiência de incorporação de MT nestas partículas variou de 25,6 a 64%. Verificou-se a alteração do comportamento térmico das partículas quando altas concentrações de MT foram empregadas, notando-se a formação de estruturas mais amorfas. As partículas de PLA/PLC não se mostraram estáveis quando submetidas aos ensaios de potencial zeta. Partículas de PLA/PLGA foram também produzidas, apresentando diâmetros médios que variaram de 23 a 98 mm. A eficiência de incorporação de MT foi igualmente ampla, entre 41 a 90%. A cristalinidade das partículas foi afetada pelo processo, sendo que a presença de MT levou à formação de estruturas mais amorfas e porosas. A cinética de liberação da MT foi analisada in vitro pela exposição das partículas a soluções com diferentes valores de pH. As menores taxas de liberação foram obtidas para as partículas de PLA, enquanto as partículas de PLA/PCL e PLA/PLGA produziram comportamentos similares entre si. Observou-se que a quantidade de partículas teoricamente necessárias durante o tratamento de reversão sexual de tilápias do Nilo variou conforme a composição dos dispositivos, sendo estes valores entre 34 a 88 g de partículas/kg de ração
Abstract: In this work, the aim was to produce oral carriers consisting of the synthetic polymers PLA (poly(L-lactic acid)), PLGA (poly(50/50 DL-lactide-co-glycolide)) and PCL (polycaprolactone) by the precipitation of the polymer solutions using supercritical CO2 as an antisolvent for the controlled release of 17?-methyltestosterone (MT). The influence of pressure, hormone and polymers concentration, as well as of the flow rate of the polymer solution on the formation of these devices was analyzed. PLA particles with diameters between 5.4 to 20.5 mm were efficiently produced; increases in the concentration of the polymer solution resulted in smaller particles, while increasing the flow rate of polymer solution caused an increase in particle mean diameter. No significant effects on morphology and size distribution of the particles were observed with pressure variation. Changes in the mechanical and physical characteristics of the PLA particles were also noticed, as reduction in the glass transition temperature of the polymer. PLA particles prepared in the presence of MT showed larger average diameters and changes in surface morphology. The presence of MT did not result in changes of the glass transition and fusion temperatures of the particles. Zeta potential analyzes showed that the particles have a strong tendency to flocculate when exposed to aqueous solutions. PLA/PCL particles were obtained from the mixture of these polymers at ratios from 1/9 to 1/1 w/w. High concentrations of PCL caused increased formation of particles with greater mean diameters, which were rougher and had a higher tendency to aggregate. The incorporation efficiency of MT ranged from 25.6 to 64%, accompanied by an increase in mean diameter. Changes in the thermal behavior of the particles were observed when high concentrations of MT were used, which led to the formation of more amorphous structures. PLA/PLC particles were not stable when subjected to tests of zeta potential. PLA/PLGA particles were also produced, with mean diameters ranging from 23 to 98 mm. The incorporation efficiency of MT was also broad, varying from 41 to 90%. The process affected the crystallinity of the particles, and the presence of MT led to more amorphous and porous structures. The behavior of the PLA, PLA/PCL and PLA/PLGA particles regarding the in vitro release kinetics of MT was analyzed through exposure of the obtained systems to different pH conditions. The lowest release rates were observed for PLA particles, while the PLA/PCL and PLA/PLGA particles showed similar performances. It was observed that the theoretical amount of particles needed for the sex reversal treatment of tilapia varied according to the composition of the devices (polymer type and ratio, as well the quantity of MT). Depending on the device, the daily required amounts of particles can vary between 34-88 g particles/kg of fish feed
Doutorado
Desenvolvimento de Processos Biotecnologicos
Doutor em Engenharia Química

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Schaeffer, Steven T. "Extraction and isolation of monocrotaline from Crotalaria spectabilis using supercritical fluids." Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/10234.

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Hassan, Faiza. "Heterogeneous catalysis in supercritical fluids : the enhancement of catalytic stability to coking." Thesis, University of Birmingham, 2011. http://etheses.bham.ac.uk//id/eprint/3166/.

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Catalytic deactivation caused by coking was studied in ZSM5 and zeolite Y catalysts during the isomerisation of 1-hexene under sub and supercritical conditions. The effects of varying temperature and pressure, from 220–250 °C and 10-70 bar respectively, on conversion and coke deposition were studied in both zeolites. TGA, DRIFTS, nitrogen sorption isotherms for fresh and coked catalysts and catalyst acidity measurements were compared. In ZSM5 the catalyst was stable for 96 hours. TGA and DRIFTS results show coke deposits were mainly polyolefinic and the amount decreases considerably from 18.8 wt% in the subcritical region to 10 wt% in the supercritical region. In zeolite Y, decay in conversion was observed with the rate of deactivation being slower at supercritical conditions at 235 °C and 40 bar. Naphthalene hydrogenation on NiMo/γ-Al2O3 catalyst was also studied. The effect of temperature, pressure, varying naphthalene feed concentration and operating in sub and supercritical conditions were studied. Coke deposit decreased by 38 wt% in the supercritical region. SC CO2 (Tc 31.04 °C, Pc 73.8 bar) was also used to re-activate the coked catalysts. This resulted in recovering 93% of the catalytic activity and 37% of the coke was effectively extracted by SC CO2.

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Eason, Brandon Corey. "Benign processing with carbon dioxide." Thesis, Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/10939.

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Amaral, Gabriela Vieira do. "Whey drink de uva processado por di?xido de carbono supercr?tico: par?metros de qualidade e sensoriais." Universidade Federal Rural do Rio de Janeiro, 2017. https://tede.ufrrj.br/jspui/handle/jspui/2208.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior - CAPES
Emerging supercritical carbon dioxide (SCCD) technology has been studied as a cold pasteurizing agent, however, few studies are available on its efficiency in dairy products. In this study, the effects of SCCD processing by different pressures 14, 16 and 18 MPa (35 ? 2 ?C / 10 min) on whey drink, whey drink and grape juice were investigated in comparison To conventional pasteurization (heat treatment at 72 ?C / 15 s). Physicochemical analyzes of pH, titratable acidity, total soluble solids, phenolic compounds, anthocyanins, antioxidant activity, angiotensin converting enzyme (ACE) inhibitory activity and volatile compounds were performed. The color, particle size, rheology, physical stability, as well as microbiological quality and sensory analysis of beverages were also smoothed. The results of this study evidenced the absence of differences between treatments in pH, titratable acidity, soluble solids, total anthocyanins and DPPH activity (p> 0.05). A direct relationship between SCCD pressure and ACE inhibitory activity was observed, with 34.63, 38.75 and 44.31% (14, 16 and 18 MPa, respectively). Few differences were found in the volatile compounds profile. The beverage processing by SCCD resulted in a product with lower particle diameter, lower consistency index and a reduction in pseudoplastic character compared to the beverage treated by the conventional process. No effect of high pressure CO2 on the sensorial attributes of the drink was observed for the studied levels. Consumers found no difference between CO2 treated beverages and heat-treated beverages. The results confirm the processing of SCCD as a promising technology for the non-thermal treatment of grape whey drink made available a health and wellness promoter beverage. Background: Non-thermal food processing is configured as an interesting alternative for the food industry due to the increased nutrient retention and minimal sensory changes in processed products. Scope and approach: The aim of this review is to address the potential of supercritical carbon dioxide technology, emphasizing milk and dairy processing, including the historical aspects, main advantages, microbial inactivation mechanisms, as well as effects in some quality parameters of dairy products. Key findings and conclusions: The use of supercritical carbon dioxide technology (SC-CO2) presents great potential application in dairy processing, since it is effective to reduce microbial load when compared to the pasteurization process, thus obtaining a product with greater shelf life and better organoleptic properties with minimal and sometimes positive changes in the intrinsic quality parameters The effect of supercritical carbon dioxide technology (SCCD, 140, 160, and 180 bar at 35 ? 2 ?C for 10 min) on whey-grape juice drink characteristics was investigated. Physicochemical characterization (pH, titratable acidity, total soluble solids), bioactive compounds ( phenolic compunds, anthocyanins , DPPH and ACE activity) and the volatile compounds were performed. Absence of differences were found among treatments for pH, titratable acidity, soluble solids, total anthocyanins and DPPH activity (p>0.05). A direct relationship between SCCD pressure and ACE inhibitory activity was observed, with 34.63, 38.75, and 44.31% (140, 160, and 180 bar, respectively). Regards the volatile compounds, it was noted few differences except by the presence of ketones. The findings confirm the SCCD processing as a potential promising technology to the conventional thermal treatment. The use of supercritical technology as a non-thermal pasteurization process of the whey-grape juice drink was investigated in this study. The effects of supercritical carbon dioxide at 14, 16, and 18 MPa (35 ? 2?C/10 min) on the physical and sensory properties of the beverage, when compared to conventional pasteurization (heat treatment at 72?C/15 s) were evaluated. High-pressure CO2 processing of whey-grape juice drink resulted in a product with lower particle diameter, lower consistency index, and a reduction in pseudoplastic character when compared to the beverage treated by the conventional process. No effect of high-pressure CO2 was observed on the sensory attributes of the beverage for the levels studied. Consumers did not find differences between the CO2-treated and heat-treated beverages. Our findings suggest the use of supercritical technology with carbon dioxide as an effective alternative for the production and availability of a health and wellness promoting beverage
A tecnologia emergente de di?xido de carbono supercr?tico (DCSC) vem sendo estudada como agente pasteuriza??o a frio, no entanto, s?o poucos os estudos dispon?veis a cerca da sua efici?ncia em derivados l?cteos. Neste estudo, foram investigados os efeitos do processamento do DCSC por diferentes press?es 14, 16 e 18 MPa (35 ? 2 ?C / 10 min) no whey drink de uva, bebida a base de soro de leite e suco de uva, em compara??o ? pasteuriza??o convencional (tratamento t?rmico a 72 ?C / 15 s). Foram realizadas an?lises f?sico-quimicas de pH, acidez titul?vel, s?lidos sol?veis totais, compostos fen?licos, antocianinas, atividade antioxidante, atividade inibidora da enzima conversora de angiotensina (ECA) e compostos vol?teis. Tamb?m foramam alisados a cor, o tamanho de part?cula, reologia, estabilidade f?sica, assim como a qualidade microbiol?gica e analise sensorial das bebidas. Os resultados deste estudo evidenciaram a aus?ncia de diferen?as entre os tratamentos nas an?lises de pH, acidez titul?vel, s?lidos sol?veis, antocianinas totais e atividade de DPPH (p> 0,05). Foi observada uma rela??o direta entre press?o DCSC e atividade inibit?ria ACE, com 34,63, 38,75 e 44,31% (14, 16 e 18 MPa, respectivamente). Poucas diferen?as foram encontratdas no perfil dos compostos vol?teis. O processamento das bebidas por DCSC resultou em um produto com menor di?metro de part?cula, menor ?ndice de consist?ncia e uma redu??o no car?ter pseudopl?stico em compara??o com a bebida tratada pelo processo convencional. N?o foi observado efeito de CO2 de alta press?o nos atributos sensoriais da bebida para os n?veis estudados. Os consumidores n?o encontraram diferen?as entre as bebidas tratadas com CO2 e as bebidas tratadas termicamente. Os resultados confirmam o processamento do DCSC como uma tecnologia promissora para o tratamento n?o t?rmico de whey drink de uva disponibilizado uma bebida promotora de sa?de e bem-estar Antecedentes: Os processamentos de alimentos n?o t?rmicos s?o configurados como uma alternativa interessante para a ind?stria de alimentos devido ao aumento da reten??o de nutrientes e mudan?as sensoriais m?nimas nos produtos processados. ?mbito e abordagem: o objetivo desta revis?o ? abordar o potencial da tecnologia de di?xido de carbono supercr?tico, enfatizando o processamento de leite e l?cteos, incluindo os aspectos hist?ricos, as principais vantagens, os mecanismos de inativa??o microbiana, bem como os efeitos em alguns par?metros de qualidade dos produtos l?cteos. Principais conclus?es e conclus?es: o uso de tecnologia supercr?tica de di?xido de carbono (SC-CO2) apresenta grande potencial de aplica??o no processamento de l?cteos, uma vez que ? efetivo reduzir a carga microbiana quando comparado ao processo de pasteuriza??o, obtendo-se assim um produto com maior prateleira e melhores propriedades sensoriais com mudan?as m?nimas e ?s vezes positivas nos par?metros de qualidade intr?nseca. O efeito da tecnologia de di?xido de carbono supercr?tico (SCCD, 140, 160 e 180 bar a 35 ? 2 ?C durante 10 min) em caracter?sticas de bebidas de suco de uva foi investigado. Caracteriza??o f?sico-qu?mica (pH, acidez titul?vel, s?lidos sol?veis totais), compostos bioativos (compostos fen?licos, antocianinas, DPPH e atividade ACE) e os compostos vol?teis foram realizados. A aus?ncia de diferen?as foi encontrada entre tratamentos para pH, acidez titul?vel, s?lidos sol?veis, antocianinas totais e atividade de DPPH (p> 0,05). Foi observada uma rela??o direta entre press?o SCCD e atividade inibit?ria ACE, com 34,63, 38,75 e 44,31% (140, 160 e 180 bar, respectivamente). Atende aos compostos vol?teis, observou-se poucas diferen?as, exceto pela presen?a de cetonas. Os resultados confirmam o processamento do SCCD como uma potencial tecnologia promissora para o tratamento t?rmico convencional O uso da tecnologia supercr?tica como processo de pasteuriza??o a frio da bebida de suco de uva e soro de uva foi investigado neste estudo. Os efeitos do di?xido de carbono supercr?tico em 14, 16 e 18 MPa (35 ? 2 ?C / 10 min) nas propriedades f?sicas e sensoriais da bebida, quando comparados ? pasteuriza??o convencional (tratamento t?rmico a 72 ?C / 15 s) Foram avaliados. O processamento de CO2 de alta press?o da bebida de suco de soro de soro de leite resultou em um produto com menor di?metro de part?cula, menor ?ndice de consist?ncia e uma redu??o no car?ter pseudopl?stico em compara??o com a bebida tratada pelo processo convencional. N?o foi observado efeito de CO2 de alta press?o nos atributos sensoriais da bebida para os n?veis estudados. Os consumidores n?o encontraram diferen?as entre as bebidas tratadas com CO2 e as bebidas tratadas termicamente. Nossas descobertas sugerem o uso da tecnologia supercr?tica com di?xido de carbono como uma alternativa efetiva para a produ??o e disponibilidade de uma bebida promotora de sa?de e bem-estar

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30

Silva, Lígia Marina Clemente. "Development of Chitosan and Poly (Vinyl Alcohol) Blended scaffolds for cell culture using supercritical fluids technology." Master's thesis, FCT - UNL, 2008. http://hdl.handle.net/10362/1805.

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Dissertação apresentada na Faculdade de Ciências e Tecnologia da Universidade Nova de Lisboa para obtenção do grau de Mestre em Mestrado Integrado em Engenharia Química e Bioquímica
In this work new porous materials for biomedical applications were developed using supercritical fluids (SCF) technology. In this context, two types of porous structures constituted by blends of chitosan and poly (vinyl alcohol) (PVA) using different ratios were prepared: membranes and three dimensional (3D) scaffolds. Phase inversion method using supercritical carbon dioxide (scCO2) as non-solvent was used to prepare porous membranes. The characterization of these materials showed that the presence of PVA in the membranes composition causes a decrease in porosity values and contact angle and an increase on pores interconnectivity and swelling degree. The mechanical properties were also modified by the existence of PVA in the membranes composition, increasing the elongation capacity of these structures and decreasing the supported break stresses. The 3D-scaffolds were prepared using freeze-drying technique and were treated with glutaraldehyde using a CO2-assisted crosslinking process. The optimization of the crosslinking process comprised the study of different glutaraldehyde concentrations and operation time. Morphological characterization showed that the casting solution concentration was a parameter with no influence in the 3Dscaffolds porosity neither on the pores interconnectivity. However, the PVA content in these matrices and the temperature used in the freeze-drying process determined their morphology. These highly porous structures were also submitted to dynamic swelling tests proving to be pH-sensitive with the capacity of swelling and deswelling when submitted to pH variations. The best response was obtained for scaffolds crosslinked with 1% (v/v) of glutaraldehyde during 10 minutes. Membranes and 3D-scaffolds were also tested for in vitro biodegradation using lysozyme and for cytotoxicity, proving to have potential applications in tissue engineering and regenerative medicine.

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31

Dandy, Luke. "Supercritical fluids and their application to the recycling of high-performance carbon fibre reinforced composite materials." Thesis, University of Birmingham, 2015. http://etheses.bham.ac.uk//id/eprint/5896/.

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The decomposition of high-performance thermoplastic and thermoset polymers is carried out by using supercritical fluids, in conjunction with a caesium carbonate catalyst (Cs\(_2\)C0\(_3\)). Polyetheretherketone (PEEK) and its carbon fibre filled composite are used as the high-performance thermoplastic, owing to its strong chemical resistance and excellent thermal and chemical stability. 2,2-Bis[4-(glycidyloxy)phenyl]propane (BADGE) is cross-linked with 4,4' –diaminodiphenyl sulfone (DDS) to produce a high-performance thermoset resin used to investigate the decomposition of the polymer matrices used in the manufacture of carbon fibre reinforced polymers (CFRP’s). It is determined that the complete decomposition of the BADGE based thermoset resin is possible at 573 K when using a catalyst concentration ([Cs\(_2\)C0\(_3\)]) of 10 ml\(^-\)\(^1\) in 100% ethanol or propanol and a reaction time of 30 minutes, with a percentage degradation of 90 % being achieved after 45 minutes. The decomposition of PEEK at 623 K, 7 K above its melt temperature, is possible within 30 minutes when using a supercritical fluid mixture of ethanol and water ([EtOH] = 20 %v) and a Cs\(_2\)C0\(_3\) concentration of 10 mg ml\(^-\)\(^1\) decomposition of PEEK in 100 % ethanol was not observed, indicating that the decomposition reaction is hydrolysis. Conversely, the decomposition of the BADGE based thermoset resin was essentially impeded by the presence of water and is therefore one of solvolysis. Both decomposition reactions were found to be 1st order with respect to [Cs\(_2\)C0\(_3\)].

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32

Saint-Martin, Sabine. "Apport de la technologie fluide supercritique pour l'obtention de matériaux énergétiques de sensibilité réduite." Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14153.

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Le développement de nouvelles compositions propulsives, pour applications stratégique et spatiale par exemple, conduit à élaborer des charges énergétiques de plus en plus puissantes
The development of new compositions of propellants, for strategic and space applications for instance, leads to synthesis of more and more powerful energetic materials

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33

Yoganathan, Roshan Bertram Chemical Sciences &amp Engineering Faculty of Engineering UNSW. "Polymer processing using dense gas technology." Awarded By:University of New South Wales. Chemical Sciences & Engineering, 2009. http://handle.unsw.edu.au/1959.4/44499.

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The use of dense CO2 in polymer processing can provide a response to the need for more environmentally-friendly industrial processes. Products with high-purity, sterility, and porosity can be achieved using dense gas technology (DGT). Currently, DGT has been used in different aspects of polymer processing including polymerization, micronization, and impregnation. Due to its solubility in polymers, CO2 can penetrate and plasticize polymers, while impregnating them with low-molecular weight CO2 -soluble compounds. Biodegradable polymers and other medical-grade polymers have benefited from the application of DGT. Dense CO2 processing properties of inertness, non-toxicity, and affinity for various therapeutic compounds are specifically advantageous to the medical and biomedical industries. In this work, the different applications of DGT in polymer processing are revised, then implemented. The polymerization of polycarbonate (PC) and polycaprolactone (PCL) in dense CO2 are presented. The syntheses of both polymers were successful and were aided by the use of dense CO2 . A multi-stage approach using dense CO2 as a sweep fluid to extract the PC polymerization by-product phenol is reported. Polycaprolactone was synthesized with varying temperatures and dense CO pressures, then impregnated with a CO2 -soluble therapeutic agent. The impregnated PCL acted as a drug reservoir with a drug-loading of 27wt% and a sustained drug release profile was observed for all samples over several days. Polymer blends of PC/PCL have potential industrial and biomedical applications both in vivo and in vitro. The applicability of PCL can be extended by enhancing its mechanical properties by creating a bio-blend with a stronger polymer such as PC. In this work, PC/PCL nonporous and porous blends were produced. Three novel dense CO2 blending techniques were used. The macroporous PC/PCL blend was impregnated with a therapeutic agent using CO2 as the carrier. A drug loading of 20wt% was achieved and sustained drug release was observed over 3 days. The applicability of dense CO2 in polymer processing was further demonstrated by sterilizing macroporous PC/PCL blends and soft hydrogels with dense CO2 . The PC/PCL blends and hydrogels were inoculated with vegetative bacteria and bacterial endospores. Industrial standard sterilization levels were achieved.

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34

Jiang, Jian-Jhong, and 江建忠. "Preparation of Biodiesel Using Supercritical Fluid Technology." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/54763975721022412050.

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35

Du, Tz-Bang, and 杜子邦. "Separation of Petroleum Pitch Using Supercritical Fluid Technology." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/9x7sax.

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博士
國立臺灣大學
化學工程學研究所
107
Over million barrels of crude petroleum are refined in Taiwan every year. The light end products such as gasoline, C1~C3 and C4~C6 raw material, base oil and etc., are valuable in the chemical industry. However, the heavy end by-product petroleum pitch with amount of million ton per year exhibits much fewer values. Most of them are used to be road asphalt or petroleum coke for furnace. Artificial carbon material is one of high added value applications of mesophase pitch. These carbon materials are used in high technology processes and advanced equipment unit parts. It would be worth to study how to produce mesophase pitch from petroleum pitch in Taiwan. In the first part of the research, we acquired petroleum pitch samples of different petroleum refinery process, such as residue fluidized catalytic cracking (RFCC) process, pyrolysis fuel oil (PFO) process, vacuum distillation unit (VDU) process, asphalt product etc. and used for the analysis method research. The standard petroleum pitch sample A240 and coal tar pitch sample ST-CTP are examined and compared with the petroleum pitch samples. A novel dual detector gel permeation chromatography system is set up. A fast analysis method of the molecular weight, polydispersity index and characteristic structure of petroleum pitch is established. The UV-RI dual detector analysis method for petroleum pitch samples exhibit good stability and reliability. The analysis results are able to give a good reference for petroleum pitch starting material selection and mesophase pitch fabrication. In the second part of the research, the purification processes for PP6 petroleum pitch including: solvent dissolution separation method, solvent fraction method, supercritical carbon dioxide extraction method and subcritical anti-solvent method are investigated. The molecular weight distribution of the purified petroleum pitch is successfully narrowed down in all studied methods. In the solvent dissolution separation process, different solvent type results different dissolution extent of PP6 petroleum pitch, which will directly affect the molecular weight and molecular weight distribution of purified petroleum pitch. The most uniform petroleum pitch sample of solvent dissolution separation process is obtained in ethyl acetate solvent system, which equips molecular weight 3571 g/mole, PDI 1.6, but 8.6% recovery. Comparing with solvent dissolution method, supercritical carbon dioxide (scCO2) extraction method exhibits high selectivity to the small molecular component of PP6 petroleum pitch. At 80℃ and 4500 psi scCO2 extraction condition, a residual of 86.0% high recovery with molecular weight 1054 g/mole and PDI 3.6 is obtained. A large vessel of 500 ml of scCO2 extraction is established. Hundred gram purified petroleum pitch sample for thermal condensation polymerization is able to be produced in single batch scCO2 extraction operation. A novel subcritical anti-solvent (SAS) precipitation separation method for PP6 petroleum pitch is studied in the range of 1700 psi to 3700 psi at 25℃. The molecular weight distribution of precipitated is successfully narrowed down to 3.5 in advance. The molecular weight is found to be increasing with increasing pressure in the SAS process, a higher solvent power of carbon dioxide at higher pressure is proposed to be the dominated effect. As a result, the molecular weight of precipitated petroleum pitch can be manipulated via pressure in the SAS process. In the third part of the research, the thermal condensation polymerization process of petroleum pitch is investigated. Thermal condensation polymerization equipment size of 100 ml and 2000 ml are established to investigate the experimental factor of petroleum pitch thermal condensation polymerization. Soxhlet extraction apparatus is established to isolate mesophase carbon micro bead (MCMB) from petroleum pitch thermal condensation polymerization product. We found that the petroleum pitch purified with supercritical fluid extraction will lead to a higher mesphase pitch yield. The petroleum pitch MCMB product synthesized in this study is analyzed and compared with commercial MCMB product. The product is going on proceeding carbonization and graphitization process and composed into a Li-ion coin cell. The measurement electrical properties show that there are higher first time charge density, higher first time irreversible capacity and lower secondary charge density. The more defect is proposed and can be observed by Raman spectrum to response to the electrical result. The material of petroleum pitch MCMB is successfully synthesized in this study and the analysis result will helpful to further improvement of this material.

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36

Cunha, Andreia Raquel Simões. "Valorization of plant materials by Supercritical fluid technology." Master's thesis, 2018. http://hdl.handle.net/10362/37609.

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The aim of this work was to obtain extracts from two plants, namely Pterospartum tridentatum (Carqueja) and Waltheria indica, using supercritical carbon dioxide (scCO2), a green solvent. ScCO2 was used pure or with added co-solvent ethanol. The essential oils from these plants have economic value due to their content in compounds with medicinal properties. For comparison, extraction assays were performed using Soxhlet/ethanol and infusion/water. The highest yields of extraction were obtained when using infusion/water - 22,5% for Carqueja and 25,0% for W. indica – followed by Soxhlet/ethanol - 21,5% for Carqueja and 22,4% for W. indica. In the case of extractions with scCO2, higher yields of extraction were obtained at 500 bar than 350 bar at a temperature of 40 ºC – 1.28% and 0.64%, respectively. These values went up when at the same temperature and 300 bar, ethanol was added to CO2 as co-solvent – maximum of 4.36% for Carqueja and 14 wt.% ethanol, and maximum of 3.13% for Waltheria indica and 10 wt.% of ethanol. Extraction assays were also carried out by Soxhlet/ethanol and infusion/water from Carqueja and W. indica previously extracted with scCO2, with or without co-solvent ethanol. The trend observed was an increase in yields of extraction when Soxhlet/ethanol was used, suggesting that scCO2 was able to remove from both plants compounds that the Soxhlet/ethanol method cannot extract. In the case of infusion/water, the trend observed was a decrease in yields of extraction relative to the values obtained with the original plant material, suggesting that scCO2 was able to remove from both plants some compounds that are also extracted by the infusion/water method. Taking into consideration that polyphenols are the major class of compounds present in Carqueja and in W. indica, the extracts obtained were analyzed with a view to quantifying total phenolic compounds (TPC) and antioxidant capacity, the latter through values of EC50 (half maximum effective concentration). The best results for Carqueja were 64, 67 and 118 mg of gallic acid equivalents per g of plant and for extracts obtained with scCO2/ethanol, Soxhlet/ethanol and infusion/water, respectively, and for Waltheria indica 10, 77 and 91 mg of gallic acid equivalents per g of plant and for extracts obtained with scCO2/ethanol, Soxhlet/ethanol and infusion/water, respectively. The EC50 values were always very high (unfavorable) for extracts from both plants obtained by scCO2/ethanol extraction, and were of ca. 1 and 0.4 g of extract per g of DPPH (radical used in this assay) for Carqueja extracts obtained by Soxhlet/ethanol and infusion/water, respectively, and 2 and 0.3 g of extract per g of DPPH for Waltheria indica extracts obtained by Soxhlet/ethanol and infusion/water, respectively. A preliminary characterization of Carqueja extracts performed by thin layer chromatography (TLC) had already evidenced the presence of phenolic compounds in extracts obtained by Soxhlet/ethanol, as well as fatty acids, triglycerides and terpenes in extracts obtained by scCO2, Soxhlet/ethanol and Soxhlet/n-hexane extraction. This work can be considered a first approach to the use of supercritical technology to obtain extracts from Carqueja and W. indica.

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37

Burgos, Solórzano Gabriela Illiana. "Supercritical fluid technology computational and experimental equilibrium studies and design of supercritical extraction processes /." 2004. http://etd.nd.edu/ETD-db/theses/available/etd-04132004-113622/.

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Thesis (Ph. D.)--University of Notre Dame, 2004.
Thesis directed by Joan F. Brennecke and Mark A. Stadtherr for the Department of Chemical and Biomolecular Engineering. "April 2004." Includes bibliographical references (leaves 284-295).

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38

Lin, Yu-shuo, and 林郁碩. "Mechanism of Supercritical Fluid Repair Technology and Retention failure in RRAM." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/954q8w.

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碩士
國立中山大學
材料與光電科學學系研究所
106
Supercritical fluid (SCF) has solubility as a solvent-carrying substance, and high penetration force can penetrate the materials to eliminate defects and perform film modification. The semiconductor industry generally uses SCF to clean wafers, but this laboratory has uniquely applied this technology to device processing. In this article, we used SCF technology to treat failed resistive switching random access memory (RRAM) devices at 120 degrees Celsius for one hour, and successfully repaired the defect in the device’s switching layer and became operational again. On the basis of the current conduction mechanism fitting results, we propose a model to explain the phenomenon. According to papers and our laboratory’s researches, indium tin oxide (ITO) film used as the top electrode of the RRAM, the operating polarity is opposite to the platinum (Pt) top electrode of the RRAM, and the operating current and switching voltage are low, which means that the energy consumption is smaller. It is believed that ITO film has the opportunity to be practically used in commercial products. Therefore, supercritical fluid technology is also used to treat failed resistive switching ITO electrode RRAM to repair ITO oxygen vacancies, and the devices are also successfully restored. We hope to apply this low-temperature processing technology to batch processing in the future, and not just RRAM. Any electronic device can use this technology to improve or restore the performance of devices. Novel memory has been a hot research topic for the past 10 years. Because of fast read/write speed, low power consumption, high endurance and long-term retention, RRAM has the opportunity to apply in automotive electronics. For automotive products, high temperature stability of RRAM is the most important thing. Therefore, one of the issues to be clarified is retention failure mechanism of RRAM. This article uses TSMC 1T1R devices. We use the electrical properties of a single device to simulate the entire array. At 200°C, 3 hours’ retention test, it was found that the high resistance state (HRS) current was hardly decayed, whereas the low resistance state (LRS) current was decayed. And the lower the current is, the easier it decays. The decayed current value is located in the minor distribution region and corresponds to a small number of devices in the 1T1R array where retention isn’t good because the LRS current is too low. Analyzing the failure process by the current conduction mechanism, it is thought that the cause of the retention failure is that the filament in the LRS is too fine. Oxygen ions on the surface of the electrode diffuse and oxidize the filament at the high temperature, which cause the resistance state change. Finally, by increasing the compliance current during the forming process, the LRS current is increased. After the retention test, the retention failure is greatly improved.

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39

Tsai, Chih-Tsung, and 蔡志宗. "Study of Supercritical Fluid Technology for Low-Temperature Fabrication of Semiconductor Devices." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/37006742255072129328.

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博士
國立清華大學
電子工程研究所
96
Supercritical fluid owns the gas-like and liquid-like properties to extract matter from micro- and nano-structure without damage. In this paper, firstly, we apply the supercritical fluid technology to remove the moisture absorbed in carbon nanotube emitters. From experimental results, it is verified that the supercritical mixed with co-solvent could take moisture away operatively from carbon nanotubes at 50 °C, and the activated field carbon nanotubes have superior emission performance and electrical stability. Besides, the pressure of supercritical fluid would influence the efficiency of activating carbon nanotube emitters. Except extracting, it is allowed also for supercritical fluid to transport molecule into nano-structure. Therefore, we propose originally a low-temperature process for passivating traps by supercritical fluid. In our experiment, the supercritical fluid had delivered successfully the oxidants into sputter-deposited hafnium oxide layer to terminate traps at 150 °C. The material analyses report that the traps were passivated by oxidizing with oxidants. After the proposed treatment, the leakage current density of hafnium oxide is reduced significantly from 10-2 to 10-7 A/cm2, due to the conduction mechanism transformed from quantum tunneling to thermionic emission. The better capacitance-voltage curve and lower equivalent oxide thickness are achieved in addition. Next, the supercritical fluid technology is used to vary the traps density in band gap of electron-gun evaporation deposited silicon oxide films to produce the resistive switching memory material at 150 °C. The post-treated silicon oxide film exhibits superior dielectric characteristics and a resistive switching between high resistance state and low resistance state which is controlled by applied bias voltage. From experimental results, it is observed that the bistable resistance states are relative to the amount of traps. The silicon film with more traps would present lower voltages of switching resistance state and inferior retention property. Nevertheless, for the silicon film with fewer traps, the higher voltages of switching resistance state are required, and a longer retention property is achieved. Finally, the application of supercritical fluid technology on improving amorphous silicon thin film transistors is investigated. The transfer characteristics, such as off-current, density of states in middle gap of amorphous silicon, threshold voltage and subthreshold swing, have been enhanced by passivating Si dangling bonds.

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40

Nogueira, João Humberto Gonçalves Francisco. "Valorization of olive pomace through combination of biocatalysis with supercritical fluid technology." Master's thesis, 2015. http://hdl.handle.net/10362/16090.

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A supercritical carbon dioxide (scCO2) based oil extraction method was implemented on olive pomace (alperujo), and an oil yield of 25,5 +/- 0,8% (goil/gdry residue) was obtained. By Soxhlet extraction with hexane, an oil extraction yield of 28,9 +/- 0,8 % was obtained, which corresponds to an efficiency of 88,4 +/- 4,8 % for the supercritical method. The scCO2 extraction process was optimized for operating conditions of 50 MPa and 348,15 K, for which an oil loading of 32,60 g oil/kg CO2 was calculated. As a proof of concept, olive pomace was used as feedstock for biodiesel production, in a process combining the use of lipase as a catalyst with the use of scCO2 as a solvent, and integrating the steps of oil extraction, oil to biodiesel transesterification and subsequent separation of the latter. In the conducted experiments, FAME (fatty acid methyl ester) purities of 90% were obtained, with the following operating parameters: an oil:methanol molar ratio of 1:24; a residence time of 7,33 and 11,6 mins; a pressure of 40 MPa; a temperature of 313,15 K; and Lipozyme (Mucor miehei; Sigma-Aldritch) as an enzyme. However, oscillations of FAME purity were registered throughout the experiments, which could possibly be due to methanol accumulation in the enzymatic reactor. Finally, the phenolic content of olive pomace, and the effect of the drying process – oven or freeze-drying – and the extraction methods – hydro-alcoholic method and supercritical method – on the phenolic content were analysed. It was verified that the oven-drying process on the olive pomace preserved 90,1 +/- 3,6 % of the total phenolic content. About 62,3 +/- 5,53% of the oven-dried pomace phenolic content was extracted using scCO2 at 60 MPa and 323,15 K. Seven individual phenols – hydroxytyrosol, tyrosol, oleuropein, quercetin, caffeic acid, ferulic acid and p-coumaric acid – were identified and quantified by HPLC.

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41

Tzeng-Sheng, Wu, and 吳宗聲. "Study on stripping, purification and recrystallization of high explosives by supercritical fluid technology." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/xj52ve.

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博士
國防大學理工學院
國防科學研究所
103
Supercritical fluid technology is booming green technology in recent years. The low activity carbon dioxide as a solvent, has some advantages, such as less pollution, no toxicity, no flame, inexpensive, easy to obtain and low temperature operation; and applies to high thermal sensitive substances like explosives. Firstly, in this study, the Octol and Composition B were melting casted in sample bottle, and then the Octol and Composition B could be removed from sample bottle by supercritical carbon dioxide fluid. The removal rate of Octol is 97.2%, Composition B were 99.12% by the three steps. Secondly, the recovered Octol and Composition B are cleaned in acetone, and the HMX and RDX with a littie TNT were dissolved in acetone again, and then the purification process was conducted by supercritical CO2 fluid. The purities of the recovered HMX, RDX and TNT are about 100% which via HPLC analysis. Thirdly, the nano-reticular HMX, nano-particles of HMX and micron particles of RDX could be prepared by supercritical Precipitation with Compressed Fluid (PCA), and then the sensitivity of products prepared were measured by the impact, friction and electrostatic test. The results showed that the nano reticular HMX have good insensitive effect. Finally, the nano-reticular HMX was applied to the delay composition development. The result showed that the performance of the delay time 178.9μs in 25mm of insensitive nano-reticular HMX is good for replacing delay ignition of double type Armor Pierving.

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42

Moshashaee, S., M. Bisrat, Robert T. Forbes, Ellis A. Quinn, H. Nyqvist, and Peter York. "Supercritical fluid processing of proteins: lysozyme precipitation from aqueous solution." 2003. http://hdl.handle.net/10454/3486.

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No
Aqueous solutions of hen egg lysozyme (3% w/v) were dispersed and precipitated by a homogenous mixture of supercritical carbon dioxide-ethanol using the Solution Enhanced Dispersion by Supercritical fluid (SEDS) process. The effects of different working conditions, such as temperature, pressure and the flow rates of the solution and ethanol, on the particle-formation process were studied The morphology, particle size and size distribution and biological activity of the protein were determined The precipitates were examined with high-sensitivity differential scanning calorimetry (HSDSC) and high-performance cation-exchange chromatography Particle size measurements showed the precipitates to be aggregates with primary particles of size 1-5 ¿m. The similarity of HSDSC data for unprocessed and processed samples indicated that the different physical forces that stabilise the native form of lysozyme are unchanged after SEDS processing. From FT-Raman spectroscopic studies secondary structural changes were observed in certain SEDS-produced lysozyme, with most processed samples displaying a slightly more disordered secondary structure than the unprocessed sample However, SEDS samples produced at 200 bar and 40 C exhibited negligible disturbance Thus the SEDS process utilising aqueous solution was able to bring about size reduction of lysozyme with minimal loss of biological activity.

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43

Liao, Tai-Chun, and 廖泰鈞. "Development of silicon nanomembrane lift-off and transfer-maintain processes by supercritical fluid technology." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/62262216193532897334.

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碩士
國立高雄大學
電機工程學系碩士班
104
Nowadays, as the application fields for wearable electronic devices is getting extended, people in silicon industry therefore pay more attention on developing silicon thin-film processes and related flexible devices. In comparing to polycrystalline silicon (poly-Si), single-crystalline silicon (c-Si) has better conductive. However, c-Si can’t directly be grown on a flexible polyimide (PI) substrate because of high crystalline temperature (1200oC~1600oC). Currently, the main method for obtaining Si nanomembrane is selectively etching out the middle insulating layer of SOI (Silicon on Insulator) substrate as the sacrifice layer by using hydrofluoric (HF) acid to lift-off c-Si nano thin film – called epitaxial lift-off process (ELO). It exists many limitations when applying the traditional wet etching ELO method for large size wafer, such as ultra-low etching rate, thin-film is easy to wrinkle and crack, as well as difficult to maintain it well in liquid. In order to break those bottlenecks, we were inspired by those specific characteristics of supercritical fluid, including extremely low viscosity, ultra-high diffusion speed and zero surface tension. Hence, in this study, a corrosion-resistance supercritical fluid etching system was established and introduced into developing Si nanomembrane ELO process as well as the related thin-film transfer-maintain technology. In the beginning of this study, a size of 10mm x 10mm SOI sample was chosen for investigating its lateral etching rate (LER) by wet ELO process. It is found the LER will be getting slower as the etching tunnel is going deeper (i.e. 2m/min → 1.4m/min). On the other hand, we also found the spin-coated PI-layer on SOI wafer for keeping Si thin-film firmed during wet ELO process will provide an additional stress to make the etching tunnel gradually opening up from the side and the LER will be increased as well. In case of the thickness of PI-layer reaching to 3m, the LER can be enhanced to 3.6m/min and the Si nanomembrane can be maintained well without breaking and damage. As far the etching process under supercritical fluids (SCFs), the study was using aqueous-HF mixed in supercritical CO2 (scCO2) as the etchant for developing the ELO process under SCFs. First, how the temperature (T) and pressure (P) in the range of T = 40oC ~ 60oC and P = 2000psi ~ 3000psi, respectively, affecting the etching rate has been investigated. It is found the LER will be enhanced as either of T or P is increasing. Second, we also spent time on figuring out which one of co-solvent, including water, acetone and methanol, can interact well with scCO2 to make the lateral etching uniformly. We found although the acetone will make the overall LER drop; however, it benefits in producing a uniform etching edge and bringing a more stable average LER. Moreover, comparing to LER = 2m/min by wet etching in condition of [HF] = 49%, we can reach a 10 times of LER = 20m/min by using only 1/25 of 49% HF (i.e. [HF] = 2.4%) under scCO2 etching process. In this study, using HF mixed in scCO2 ([HF] = 0.7M) as etchant, a 150-nm Si thin-film without handle layer supported has been successfully lift-off and perfectly laid on the original Si substrate from a size of 10mm x 10mm SOI substrate in condition of T = 60oC and P = 3000psi. Finally, this 150nm-thick Si nanomembrane was also successfully transferred into a flexible PET substrate depending on the help of two kinds of polyimide, PDMS and NOA61. Also, the Si nano-film well attached on a PDMS cylinder surface (radius = 1cm) has been demonstrated. Overall, this study by introducing HF-etchant into scCO2 has demonstrated its excellent abilities in developing high-aspect-ratio SCFs ELO etching process. The LERs under different temperature and pressure were well-investigated. Furthermore, the co-solvent effect under scCO2 for ELO process was also evaluated. The results in this study should offer the foundation for developing SCFs etching technology in the future.

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44

Manrique, Yaidelin Josefina Alves. "Supercritical fluid extraction and fractionation of bioactive natural products from cork." Tese, 2017. https://repositorio-aberto.up.pt/handle/10216/103555.

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45

Manrique, Yaidelin Josefina Alves. "Supercritical fluid extraction and fractionation of bioactive natural products from cork." Doctoral thesis, 2017. https://repositorio-aberto.up.pt/handle/10216/103555.

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46

Abedin, Nowrin Raihan. "Micronization of Polyethylene Wax in an Extrusion Process using Supercritical Carbon Dioxide." Thesis, 2011. http://hdl.handle.net/10012/6326.

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Supercritical fluid technology is a well documented and emergent technology used in many industries today for the formation of micro- and nano- particles. The use of supercritical fluids allows synthesis of various types of particles since their properties can be varied with temperature or pressure, which sequentially can control the physical and chemical properties of the particles produced. Several different processes designed to generate powders and composites using supercritical fluids have been proposed in the past 20 years which can be used to synthesize materials with high performance specifications and unique functionality. In this research work, an extrusion micronization process using supercritical fluid has been proposed. This powder production technique could be a promising alternative to conventional techniques in terms of improvement in product quality as it provides a better control over particle size, morphology and particle size distribution, without degradation or contamination of the product. In addition, as extrusion is globally used for polymer production and processing, particle production by extrusion will allow production and processing in a single process step, eliminating the need for secondary particle production methods. The micronization process designed and described in this thesis involves a twin screw extruder equipped with a converging die and a high resistance spraying nozzle for particle production. A special CO2 injection device and polymer collection chamber was designed for CO2 supply and powder collection. To ensure complete dissolution of CO2 into the polymer matrix, stable injection of CO2, pressure generation and constant spray of micronized polymer particles, a special screw configuration was carefully designed for the extrusion process. The feasibility and the performance of this process have been demonstrated by experimental studies performed with low molecular weight polyethylene wax. Carbon dioxide at supercritical conditions was used as a solvent for processing the polymer. The generated polyethylene particles from the polyethylene wax/carbon dioxide solution system were analyzed and studied using an optical microscope, scanning electron microscope, capillary rheometer and differential scanning calorimeter. A detailed study on the effects of the processing parameters, such as temperature, pressure, flow rate and supercritical fluid on properties of polyethylene particle produced was carried out. The particle size data collected using an optical microscope indicate a significant impact of temperature and CO2 content on particle size. The obtained size data were utilized to generate particle size distribution plots and studied to analyze the effect of the processing variables. It was found that particle size distribution is affected by processing temperature and CO2 content. Studies of the SEM images reveal that the morphology of particles can be controlled by varying processing variables like temperature, polymer feed rate and CO2 content. The particles generated during this study indicate that particle production in an extrusion process using supercritical carbon dioxide is achievable and appears to be a promising alternative to conventional polymer particle production methods such as grinding, milling and other supercritical fluid-based precipitation methods. To validate and generalize the applicability of this process, micronization of other polymeric material should be performed. Commercialization of this technology will further require predictability and consistency of the characteristics of the product, for which a detailed understanding of the influence of all relevant process variables is necessary. In addition, development of theoretical models will further assist in the scale-up and commercialization of this supercritical fluid assisted micronization technology in the near future.

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47

Lin, Hua-Ching, and 林華經. "Preparation of Biodiesel and Improvement of RRAM (Resistant Random Access Memory) Performance by Supercritical Fluid Technology." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/49633111312303957744.

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博士
國立清華大學
化學工程學系
103
In this dissertation, both types of supercritical fluid reactions, “reaction with supercritical fluid” and “reaction in supercritical fluid”, were adopted for the study of preparation of biodiesel and improvement of resistant random access memory (RRAM) performance, respectively. In Chapter 1, a brief introduction to the development, properties, and applications of supercritical fluid was made. In the beginning of Chapter 2, the catalytic effect of metal reactor surface was investigated. Ever since Saka and Kusdiana proposed the method of preparation of biodiesel by supercritical fluid technology, “non-catalytic” has been recognized as one of the most advantages of this process. Nevertheless, our experimental results showed that, in the transesterification of vegetable oils with supercritical methanol, the reaction rate was indeed accelerated by the catalytic effect of stainless-steel reactor surface, resulting in a high conversion; after the deactivation of this catalytic ability, the biodiesel yield was decreased. Then we went on the screening of catalysts. Among various metal oxides tested in this study, MnO2 was found to be the most effective catalyst. The presence of MnO2 was essential for the complete conversion of vegetable oils to biodiesel under mild conditions; the conversion was relatively low during catalyst-free operation. Thereafter, transesterification of supercritical/subcritical methanol with coconut oil and jatropha oil were conducted in a continuous operation system. With or without the addition of catalyst and co-solvent, the effects of the operating variables, namely the temperature, pressure, residence time, methanol-to-oil molar ratio, on the yield of biodiesel were systematically examined. Our experimental results indicated that: regardless of the presence of catalyst, the effect of temperature on transesterification was more pronounced than that of pressure; the latter was apparent only at pressures far below the critical pressure of methanol and before the formation of a homogeneous liquid phase from the methanol/oil mixture. Through visual observation in a windowed-reactor, at 200 °C and 4.14 MPa, the methanol/coconut oil mixture formed a homogeneous liquid phase; the apparent activation energy decreased from 107.7 kJ/mol at temperatures below 180 °C to 35.3 kJ/mol at temperatures above 220 °C, more favorable for transesterification. The obtained results revealed that this transesterification does not necessarily have to be performed in supercritical methanol, nor in supercritical methanol/oil mixtures, but only at temperatures and pressures where a homogeneous liquid phase exists. The optimal residence time for the transesterification was dependent on the reaction temperature; higher temperatures required shorter residence times. The FAME yield and the apparent rate constant k both increased upon increasing the molar ratio, for example, when the molar ratio of methanol to coconut oil increased from 12/1 to 60/1 (fivefold), the apparent rate constant (k) also increased from 0.00476 to 0.02118 s–1 (4.45-fold); we did not, however, observe an optimal molar ratio within the range from 12 to 60. The effect of co-solvent in a continuous operation mode was investigated at the end of Chapter 2, and the experimental results showed that the effect of co-solvent on transesterification was negligible or even negative. The addition of co-solvent might enhance the miscibility between oils and methanol; on the other hand, it also increased the flux volume of transesterification , resulting in decreases in both the concentrations of reactants and residence time. Therefore, the overall effect of co-solvent in a continuous operation mode might be negligible or even negative. In Chapter 3, the operating current of silicon oxide-based RRAM was reduced by supercritical fluid processing (SFP) technology. At a temperature of 120 oC, with the facilities of low viscosity, low surface tension and high diffusivity of supercritical carbon dioxide, the water molecules could easily diffuse into the film and repair the dangling bonds of grain boundary; by SFP, the conduction path of RRAM film became discontinuous and its conduction resistance also increased due to the reduce of defects in the film, resulting in a significant decline in operating current. With the reduction of operation power consumption of RRAM, the degradation of IC caused by the Joule heat would therefore be improved. Thus, SFP techniques can improve the switching characteristics of RRAM and its operation performance, showing a great benefit on the development and applications of RRAM as next-generation non-volatile memory. In the experiment, the dangling bonds of Tin-doped Silica (Sn:SiO2) film were repaired by supercritical carbon dioxide (SCCO2). A discontinuous metal filament would be formed in Sn:SiO2 film through SCCO2 passivation process, causing the device current declined. In addition, we also use this technique to treat the RRAM with ITO transparent conductive electrode to effectively reduce the power consumption and operating voltage of device. At last, SCCO2 treatment technology was used to manipulate the temperature coefficient of resistance (TCR) of TaN thin-film resistors. After annealing process, the TCR value of TaN film resistor was changed from negative to positive; by SCCO2 treatment, the positive TCR value turned back to negative again. Through optimization of supercritical fluid technology combined with thermal annealing method, the TCR value of TaN thin-film resistor could be modulated to close to zero, making it conform the requirements of a stricter specification for car-used electronic applications or other harsh environments of high temperature. In Chapter 4, a summary of the content in this dissertation was made.

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48

Wang, Wei-Ya, and 王薇雅. "Study of Supercritical Fluid Technology on Novel Transparent Amorphous Aluminum Zinc Tin Oxide Thin Film Transistors." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/63930296102018721976.

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碩士
國立交通大學
顯示科技研究所
100
Quaternary compound semiconductors which had no indium and no gallium were chose as active layer of thin film transistors. In this study, a-AlZnSnO was chose. Due to supercritical fluid simultaneously possess gas-like high diffusivity and liquid-like high density; oxidant was carried into thin films which were deposited by supercritical fluid. It was used to successfully terminate the defect states in thin films at 150 °C, and the quality of thin films were improved. Furthermore, electrical stability and material analysis were used to verify that a-AZTO TFTs performances were improved. Frist, material components and surface structure of a-AZTO thin films were scarcely changed by thermal Annealing, supercritical fluid, and H2O vapor post-treatments. Next, basic electrical characteristics of a-AZTO TFTs were enhanced by supercritical fluid, and H2O vapor post-treatments. Effect of H2O and oxygen molecules were adsorbed on the backchannel of a-AZTO TFTs, which was decreased by a high temperature 450 °C thermal annealing. The a-AZTO TFTs were scarcely affected under negative gate bias stress. After supercritical fluid post-treatment, the migration of threshold voltage shifts was smaller under positive gate bias. Finally, treated a-AZTO TFTs were scarcely affected under illumination. Nevertheless, threshold voltage was shifted under negative bias illumination stress, and a-AZTO TFTs were treated by supercritical fluid post-treatment had the smallest threshold voltage shifts. At last, active layers, gate insulators, and both of layers of a-AZTO TFTs were treated by hydrogen plasma. That was successfully that decreased the post-annealing temperature from 450 °C to 300 °C.

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49

"Computational Fluid Dynamics Studies in Heat and Mass Transfer Phenomena in Packed Bed Extraction and Reaction Equipment: Special Attention to Supercritical Fluids Technology." Universitat Politècnica de Catalunya, 2007. http://www.tesisenxarxa.net/TDX-0515107-124052/.

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50

CHEN, WEI-JANG, and 陳偉徵. "Study on Resistive Switching Mechanism by Low Temperature Supercritical Fluid Nitridation Technology on ZnO-base Resistance Random Access Memory." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/58874757416023258744.

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碩士
國立高雄師範大學
化學系
104
In this study, supercritical CO2 fluid treatment technology at low temperature is used to prepare zinc oxide doping nitrogen (ZnO:N) thin film from zinc oxide (ZnO) successfully. Further, we analyze the ZnO:N thin film is zinc oxynitride (ZnON) which we use to fabricate resistance random access memory (RRAM) device of a resistance switching characteristic. We defined the device structure by mask aligner and deposited titanium nitride (TiN) as a bottom electrode. Then, we deposited the zinc oxide thin film by sputtering and treated by supercritical CO2 fluid with little. Finally, we deposited platinum (Pt) metal film upon the zinc oxide film as a top electrode to form Pt / ZnON / TiN RRAM device. We measured electrical properties on RRAM device by Agilent B1500A and analyzed current conduction mechanism to compare different between ZnO-based and ZnON-based RRAM. Through the reliability analysis, we knew that supercritical fluid nitridation treatment can enhance RRAM performance. Additionally, Pt/ ZnO (NH4OH SCCO2) / TiN RRAM ensured a better reliability. At 125oC, the Pt / ZnO (NH4OH SCCO2) / TiN RRAM kept resistance state feature ten thousand seconds and operated at least up to ten million times by AC pulse. Finally, we found a physical model to explain these phenomenons.

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