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Ionic liquids as recycling solvents for the synthesis of magnetic nanoparticles

Oliveira, Flavia C C; Effenberger, Fernando Bacci; Sousa, Marcelo H; Jardim, Renato de Figueiredo; Kiyohara, Pedro Kunihiko; Dupont, Jairton; Rubin, Joel C; Rossi, Liane Marcia
Fonte: ROYAL SOC CHEMISTRY Publicador: ROYAL SOC CHEMISTRY
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.90282%
This work describes an easy synthesis (one pot) of MFe(2)O(4) (M = Co, Fe, Mn, and Ni) magnetic nanoparticles MNPs by the thermal decomposition of Fe(Acac)(3)/M(Acac)(2) by using BMI center dot NTf(2) (1-n-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) or BMI center dot PF(6) (1-n-butyl-3-methylimidazolium hexafluorophosphate) ionic liquids (ILs) as recycling solvents and oleylamine as the reducing and surface modifier agent. The effects of reaction temperature and reaction time on the features of the magnetic nanomaterials (size and magnetic properties) were investigated. The growth of the MNPs is easily controlled in the IL by adjusting the reaction temperature and time, as inferred from Fe(3)O(4) MNPs obtained at 150 degrees C, 200 degrees C and 250 degrees C with mean diameters of 8, 10 and 15 nm, respectively. However, the thermal decomposition of Fe(Acac)(3) performed in a conventional high boiling point solvent (diphenyl ether, bp 259 degrees C), under a similar Fe to oleylamine molar ratio used in the IL synthesis, does not follow the same growth mechanism and rendered only smaller NPs of 5 nm mean diameter. All MNPs are covered by at least one monolayer of oleylamine making them readily dispersible in non-polar solvents. Besides the influence on the nanoparticles growth...

Optimal synthesis of anaerobic digester networks

PONTES, Ricardo F. F.; PINTO, Jose M.
Fonte: ELSEVIER SCIENCE SA Publicador: ELSEVIER SCIENCE SA
Tipo: Artigo de Revista Científica
ENG
Relevância na Pesquisa
46.9335%
The objective of this paper is to develop a mathematical model for the synthesis of anaerobic digester networks based on the optimization of a superstructure that relies on a non-linear programming formulation. The proposed model contains the kinetic and hydraulic equations developed by Pontes and Pinto [Chemical Engineering journal 122 (2006) 65-80] for two types of digesters, namely UASB (Upflow Anaerobic Sludge Blanket) and EGSB (Expanded Granular Sludge Bed) reactors. The objective function minimizes the overall sum of the reactor volumes. The optimization results show that a recycle stream is only effective in case of a reactor with short-circuit, such as the UASB reactor. Sensitivity analysis was performed in the one and two-digester network superstructures, for the following parameters: UASB reactor short-circuit fraction and the EGSB reactor maximum organic load, and the corresponding results vary considerably in terms of digester volumes. Scenarios for three and four-digester network superstructures were optimized and compared with the results from fewer digesters. (C) 2009 Elsevier B.V. All rights reserved.; CNPq; CAPES (Brazil)

Mechanochemical synthesis of CaTiO3 from CaCO3 - TiO2 mixture

Vukotić, Vesna M.; Srećković, T.; Marinkovic, Z. V.; Branković, G.; Cilense, M.; Arandjelović, D.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 429-434
ENG
Relevância na Pesquisa
46.867427%
The synthesis of calcium titanate, CaTiO3, was performed by mechanical activation and thermal treatment. Milling for up to 360 minutes in a planetary ball mill mechanically activated an equimolar mixture of CaCO 3 and TiO2 powders. A small amount of mechanically activated mixtures was pressed into briquettes and calcined at 850°C for two hours. The effect of mechanical activation on the solid-state reaction was studied using X-ray powder diffraction and differential thermal analysis. The change of morphology and size of powder particles due to milling, were determined by SEM, while BET analysis was used to determine the specific surface area of the powder. The sintering process was followed by a dilatometer during thermal treatment up to 1300°C. The main conclusion of the analysis of conducted investigations is that CaTiO3 ceramics can be obtained from an activated mixture at a much lower temperature than reported in the literature owing to acceleration of the chemical reaction and sintering.

Magnetoelectric coefficient in strontium ruthenate buffered lanthanum modified bismuth ferrite thin films grown by chemical method

Simões, Alexandre Zirpoli; Garcia, Filiberto Gonzalez; Moura, Francisco
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 94-99
ENG
Relevância na Pesquisa
46.923237%
This paper focuses on the magnetoelectric coupling (ME) at room temperature in lanthanum modified bismuth ferrite thin film (BLFO) deposited on SrRuO 3-buffered Pt/TiO 2/SiO 2/Si(100) substrates by the soft chemical method. BLFO film was coherently grown at a temperature of 500 °C. The magnetoelectric coefficient measurement was performed to evidence magnetoelectric coupling behavior. Room temperature magnetic coercive field indicates that the film is magnetically soft. The maximum magnetoelectric coefficient in the longitudinal direction was close to 12 V/cmOe. Dielectric permittivity and dielectric loss demonstrated only slight dispersion with frequency due the less two-dimensional stress in the plane of the film. Polarization reversal was investigated by applying dc voltage through a conductive tip during the area scanning. We observed that various types of domain behavior such as 71 ° and 180° domain switching, and pinned domain formation occurred. Copyright © 2009 American Scientific Publishers All rights reserved.

Synthesis of PTSH-modified CeO2 nanoparticles: Effect of the modifier on structure, optical properties, and dispersibility

Truffault, Laurianne; Andrezza, Caroline; Santilli, Celso Valentim; Pulcinelli, Sandra Helena
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 63-69
ENG
Relevância na Pesquisa
46.92958%
CeO2 nanoparticles were synthesized by the precipitation method and modified with para-toluene sulfonic acid (PTSH), either in situ or post-synthesis. The presence of PTSH in the samples was confirmed by FTIR. PXRD and FTIR analyses showed that the post-synthesis PTSH modification altered the CeO2 structure, whereas the in situ modification maintained intact the crystalline structure and UV-vis absorbance properties. For both in situ and post-synthesis modifications, TEM images revealed the presence of nanoparticles that were 5nm in size. The dispersibility of the in situ PTSH-modified material in a hydrophilic ureasil-poly(ethylene oxide) matrix was investigated using SAXS measurements, which indicated that CeO2 nanoparticles modified with PTSH in situ were less aggregated within the matrix, compared to unmodified CeO2 nanoparticles. © 2013 Elsevier B.V.

Clay and refractory materials slurries in inductively coupled plasma optical emission spectrometry: effects of mechanochemical synthesis on emission intensities of analytes

Santos,Mirian C.; Nogueira,Ana Rita A.; Nóbrega,Joaquim A.
Fonte: Sociedade Brasileira de Química Publicador: Sociedade Brasileira de Química
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/06/2005 EN
Relevância na Pesquisa
46.9335%
The developed work investigated the application of mechanochemical synthesis for promoting reactions in the samples and for synthesizing new compounds for increment of emission intensities of analytes in clays and refractory materials slurries in inductively coupled plasma optical emission spectrometry with axial viewing. The hypothesis is that it is possible to generate more volatile compounds during the grinding step and these new compounds will increase the intensities of emission signals for slurries introduced in the plasma. The action of two chemical modifiers, LiBO2 and Na2CO3, added during the grinding step was evaluated. The clays and refractory materials mixed with the chemical modifier were ground for 2 h using a high impact ball mill with a tungsten carbide grinding container and balls. Slurries were prepared by dispersing the modified clays and refractory materials in 10% v v-1 HNO3 solution and by shaking them in an ultrasonic bath to ensure good dispersion. The compounds produced during the grinding step were characterised by X-ray diffraction and thermogravimetric analysis. Both techniques indicated the formation of new compounds in clays and refractory materials by mechanochemical synthesis. Chemical modification effects were evaluated by changes of the emission intensities of Al...

Microchemical systems for rapid optimization of organic synthesis

Murphy, Edward R
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 129 leaves
ENG
Relevância na Pesquisa
46.9335%
In the chemistry laboratory, the desire to use smaller quantities of material to minimize both reagent cost and waste generation has driven chemists to develop new experimental techniques. The current approach to small scale experimentation has mostly been a simple reduction in the size of batch reaction apparatus. Working with these smaller volumes has increased the efficiency of experiments by accelerating the typically time consuming processes of heating, filtration, and drying. Furthermore, when working with hazardous materials, smaller scales minimize the exposure of a chemist to toxic materials and enable easier containment of potentially flammable or explosive systems. The use of microfluidic devices has shown several improvements when compared to traditional batch synthesis. The precise control of reaction conditions enabled within the microreactor format has proved advantageous for a wide range of single and multiphase reactions. Also, unlike conventional bench-top batch reactions, continuous microreactors are capable of producing both analytical and preparative quantities of material by simply changing the amount of reactor effluent collected.; (cont.) The aim of this work was to harness the microsystem advantages of improved safety and process intensification while demonstrating both improved quality and speed of data collection...

Continuous flow separation techniques for microchemical synthesis

Kralj, Jason G
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 153 leaves
ENG
Relevância na Pesquisa
47.184404%
Performing multistep microchemical synthesis requires many techniques from combining micromixers in series to the development of continuous microfluidic separation tools. Safety, high heat and mass transfer rates, and cost savings all continue to motivate microreactor development as a research tool, but many reactions generate a variety of (by)products including solid particles, immiscible fluids (gas and liquid), and miscible components requiring purification. We have endeavored to develop microfluidic systems which compliment existing microreactor technology, using forces that grow stronger with decreasing length scales such as electric fields and interfacial phenomena, and to use straightforward microfluidic mixers for kinetic studies of energetic material synthesis. Dielectrophoresis was used to study the continuous separation of polystyrene particles based on size. Essentially, a microfluidic particle "ratchet" was created using a soft-lithography microchannel and slanted interdigitated electrodes which provide a transverse force component on the particles. Experimental behavior agreed well with the model predictions, and 4 & 6 micron particles were continuously separated. Liquid-liquid extraction is another useful tool for microchemical synthesis and well-suited to small length scales because high mass transfer rates can be attained.; (cont.) However...

Design and operation of microchemical systems for multistep chemical syntheses

Sahoo, Hemantkumar
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 184 leaves
ENG
Relevância na Pesquisa
47.226636%
This thesis focused on advancing the microchemical field from single device based demonstrations to systems that can perform multi-step series and parallel synthesis. Few examples of micro-separators and micro-pumps suited for miniaturized lab-on-a-chip systems for organic syntheses exist, so the first half of this thesis developed systems for these micro-unit-operations, while the second half demonstrated multistep microchemical operations enabled by these systems. In-line continuous separation devices are developed that enabled removal of unreacted reagents/byproducts, making it possible to realize a series of reactions without leaving the microreactor environment. Differences in surface forces and preferential wettability characteristics of fluoropolymers are used for phase separation. Such microseparators are used to demonstrate 100% separation of two phase flows of hexane and water, toluene and water, dichloromethane and water, and hexane and methanol. Integrated liquid-liquid extraction devices are microfabricated that performed two -phase contacting by segmented flow, followed by separation - resulting in single stage extraction. Single stage extraction of N,N-dimethylformamide from dichloromethane to water, and from diethyl ether to water is demonstrated. The development of separators allows microreactors to be connected to microseparators to form microreactor networks enabling reactions and separations in succession. The starting reagents are loaded in syringes and syringe pumps push fluid through the train of microdevices. However...

Nanocompartmentalization of soft materials with three mutually immiscible solvents: synthesis and self-assembly of three-arm star-polyphiles

de Campo, Liliana; Moghaddam, Minoo J.; Varslot, Trond; Kirby, Nigel; Mittelbach, Rainer; Sawkins, Tim; Hyde, Stephen T.
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica Formato: 10 pages
Relevância na Pesquisa
57.00432%
We report synthesis, thermotropic, and lyotropic mesomorphism of a family of novel “star-polyphiles”: small star-shaped molecules bearing three mutually immiscible arms, hydrophilic (oligoethylene glycol), oleophilic (alkanes), and fluorophilic (perfluorinated alkanes), attached to a central 1,3,5-trihydroxybenzene core. A facile, flexible multistep synthesis giving high-purity yields of 14 distinct members of the family is described, with variable arm lengths, forming crystalline, or various mesostructured gel phases in their neat state at room temperature. Furthermore, we show that specific members of these star-polyphiles can be simultaneously loaded with up to three mutually immiscible solvents, dodecane, perfluoro-nonane, and water, to form liquid crystals and microemulsions with multiple chemically distinct mesoscale compartments. The mesoscale chemical polyfunctionality of these polyphiles, coupled with thermotropic and lyotropic polymorphism, make them promising potential soft materials for a variety of applications, including host matrices for multiple mutually immiscible chemicals and drug delivery; We acknowledge support from the Australian Research Council’s Discovery grant scheme.

Mechanochemical synthesis of CaTiO3 from CaCO3 - TiO2 mixture

Vukotić, Vesna M.; Srećković, T.; Marinkovic, Z. V.; Branković, G.; Cilense, M.; Arandjelović, D.
Fonte: Trans Tech Publications Ltd Publicador: Trans Tech Publications Ltd
Tipo: Artigo de Revista Científica Formato: 429-434
ENG
Relevância na Pesquisa
46.867427%
The synthesis of calcium titanate, CaTiO3, was performed by mechanical activation and thermal treatment. Milling for up to 360 minutes in a planetary ball mill mechanically activated an equimolar mixture of CaCO 3 and TiO2 powders. A small amount of mechanically activated mixtures was pressed into briquettes and calcined at 850°C for two hours. The effect of mechanical activation on the solid-state reaction was studied using X-ray powder diffraction and differential thermal analysis. The change of morphology and size of powder particles due to milling, were determined by SEM, while BET analysis was used to determine the specific surface area of the powder. The sintering process was followed by a dilatometer during thermal treatment up to 1300°C. The main conclusion of the analysis of conducted investigations is that CaTiO3 ceramics can be obtained from an activated mixture at a much lower temperature than reported in the literature owing to acceleration of the chemical reaction and sintering.

Microfluidic approaches to the synthesis of complex polymeric particles

Dendukuri, Dhananjay, 1978-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 128 p.
ENG
Relevância na Pesquisa
47.05333%
The synthesis of micron-sized polymeric particles with precise control over shape, monodispersity and chemistry is a technologically important objective. Varied applications including medical diagnostics. designer fabrics and optical devices could benefit from the availability of geometrically complex and chemically inhomogeneous particles. Microfluidics has recently emerged as an important alternative route to the synthesis of such complex particles. This thesis presents three new approaches to complex particle and structure synthesis in microfluidic devices. In the first approach. droplets formed by shearing a curable photopolymer. using a continuous water phase at a T-junction, were constrained to adopt non-spherical shapes by confining them using appropriate microchannel geometries. The non-spherical shapes formed were permanently preserved by photopolymerizing the constrained droplets in situ using focused ultraviolet (UV) light from an inverted microscope. The second and more general method called Continuous Flow Lithography (CFL) is a one-phase, projection photolithography based process to continuously synthesize polymeric microparticles in any 2-D extruded shape down to the colloidal length scale.; (cont.) Polymerization was also performed across laminar. co-flowing streams to generate Janus particles containing different chemistries...

Microfluidic synthesis of colloidal nanomaterials

Khan, Saif A
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 184 leaves
ENG
Relevância na Pesquisa
47.23589%
This thesis focuses on microfluidics based approaches for synthesis and surface-engineering of colloidal particles. Bottom-up assembly through colloidal nucleation and growth is a popular route to the controlled synthesis of nanomaterials. Standard bench-scale synthetic chemistry techniques often involve non-uniform spatial and temporal distributions of concentration and temperature, and are not readily scalable. Photolithography-based microfabrication enables the application of classical techniques of chemical reaction engineering to design chemical reactors that cannot be realized easily at the macroscale, and that closely approach theoretical 'idealized' reactor configurations. In addition, the microfluidic format allows precisely controlled reaction conditions such as rapid mixing, and concentration and temperature uniformity. The goal of this thesis was to design microfluidic reactors for synthesis of core-shell colloidal particles with tunable sizes. Microscale segmented gas-liquid flows overcome the large axial dispersion effects associated with single-phase laminar flows. Microchannel devices that yielded uniform, stable gas-liquid segmented flows over three orders of magnitude in flow velocity were first developed.; (cont.) Extensive experimental studies of the transport...

Flexible Synthesis of Enantiomerically Pure 2,8-Dialkyl-1,7-dioxaspiro[5.5]undecanes and 2,7-Dialkyl-1,6-dioxaspiro[4.5]decanes from Propargylic and Homopropargylic Alcohols

Schwartz, Brett; Hayes, Patricia Y; Kitching, William; De Voss, James Joseph
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.743594%
(Chemical Equation Presented) A new approach to enantiomerically pure 2,8-dialkyl-1,7-dioxaspiro[5.5]undecanes and 2,7-dialkyl-1,6-dioxaspiro[4.5] decanes is described and utilizes enantiomerically pure homopropargylic alcohols obtained from lithium acety

Studies toward the total synthesis of nominine

Hutt, Oliver; Mander, Lewis
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.86115%
(Chemical Equation Presented) The construction of the hetisane group of alkaloids, of which the extensively bridged nominine 17 is the simplest member, poses the ultimate challenge for those interested in the synthesis of the C 20 diterpene alkaloids. We

Nanoparticles of Mg(OH) 2 : Synthesis and Application to Paper Conservation

Giorgi, Rodorico; Bozzi, Claudio; Dei, Luigi; Gabbiani, Chiara; Ninham, Barry; Baglioni, Piero
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.743594%
We report an investigation on the effects of counterions of magnesium salts on the homogeneous phase precipitation reaction to yield nanoparticles. The results provide new parameters to guide the control of the size, monodispersity, crystallinity, and morphology of Mg(OH)2 nanoparticles. Evidence emerged that magnesium counterions affect the size of crystallites. The particle size increases from about 50 to 200 nm and follows the Hofmeister anion series: sulfate < chloride < nitrate < perchlorate. All of the results show that a proper choice of counterion and composition of reaction mixture allows one to modulate and set conditions that predetermine production of nanoparticles with desired size. The Mg(OH)2 nanoparticles have been applied to the successful conservation of paper. To demonstrate the efficacy of nanoparticles as deacidifying agent and as protection against cellulose aging, some samples of paper from the 18th century were treated with the nanoparticles and artificially aged by subjecting them to hydrothermal and photooxidative degradation. The treatment with nanoparticles preserved the mechanical features of paper, and the deterioration was consistently reduced. The comparison with the Wei t'O method (based on magnesium alkoxides)...

A Bimetallic Complex Spanned by the C 4 H Ligand: Synthesis of [Cl(CO) 2 L 2 RuC≡CCH=C=RuL 2 (η-C 5 H 5 )PF 6 (L = PPh 3 )

Bartlett, Michael; Hill, Anthony; Smith, Matthew
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.746074%
The synthesis of the first example of a bime-tallic complex spanned by the C4H alkynylvinylidene ligand, [Cl(CO)2L 2RuC≡CCH=C-RuL2(η-C5H 5]PF6 (L = PPh3), is reported: the reaction of [Ru(CO)2L3] with butadiyne provides [RuH(C≡CC≡ CH)(CO)2L2], whic

Total synthesis of sordaricin

Mander, Lewis; Thomson, Regan
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.86115%
(Chemical Equation Presented) An enantioconvergent total synthesis of sordaricin (3), the diterpene aglycon of an important class of antifungal compounds, is described. Two approaches were explored, the first of which utilized a possible biogenetic intramolecular [4 + 2] cycloaddition to form the complete carbon skeleton of the target molecule as a single regioisomer 30. A second approach employed a tandem cycloreversion/ intramolecular [4 + 2] cycloaddition process to afford not only the desired product 30 but also significant quantities of the undesired regioisomer iso-30. An investigation into the reasons for the difference in regioselectivity between these two reactions revealed the intervention of a cycloreversion/cycloaddition pathway at elevated temperatures leading to the formation of iso-30. Experimental evidence supports the hypothesis that iso-30 is the more thermodynamically stable of the two regioisomers.

Convergent Synthesis of Alkynylbis(bidentate phosphine)ruthenium Dendrimers

McDonagh, Andrew; Powell, Clem; Morrall, Joseph; Cifuentes, Marie; Humphrey, Mark
Fonte: American Chemical Society Publicador: American Chemical Society
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
56.746074%
The convergent synthesis of alkynylbis(bidentate phosphine)ruthenium dendrimers was discussed. The nonlinear optical (NLO) properties of alkynylmetal complexes were also examined. It was demonstrated that electron-rich organometallic dendrimers with metals dispersed through the dendritic structures were synthetically accessible.

Synthesis of chemically induced separation sequences using fuzzy heuristic based system

Cisternas,L. A.; Guerrero,Ch. J.; Melo,J. A.
Fonte: Latin American applied research Publicador: Latin American applied research
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/04/2002 EN
Relevância na Pesquisa
47.00432%
Chemical induced separation is used in a number of instances to accomplish difficult separations; however, there is a lack of information in the literature. In the present work, a fuzzy heuristic system for separation sequence synthesis using chemical induced separation is constructed. The construction of the present rule based system is based on the previous work of Huang and Fan (1990) in which knowledge-based system has been applied to physically induced separation sequence synthesis. Although the methodology proposed here, involves the use of declarative and procedural knowledge the emphasis is done on selection and sequence of chemical induced separation. A simple example is included to illustrate the procedure.