Flammability is an important factor of safe practices for handling and storage of liquid mixtures and for the evaluation of the precise level of risk. Flash point is a major property used to determine the fire and explosion hazards of a liquid, and it is defined as the minimum temperature at which the vapor present over the liquid at equilibrium forms a flammable mixture when mixed with air. Experimental tests for the complete composition range of a mixture are time consuming, whereas a mixture flash point can be estimated using a computational method and available information. The information needed for mixture flash point predictions are flashpoints, vapor pressures, and activity coefficients as functions of temperature for each mixture component. Generally, sufficient experimental data are unavailable and other ways of determining the basic information are needed. A procedure to evaluate the flash point of binary mixtures is proposed, which provides techniques that can be used to estimate a parameter that is needed for binary mixture flash point evaluations. Minimum flash point behavior (MFPB) is exhibited when the flash point of the mixture is below the flash points of the individual components of the mixture. The identification of this behavior is critical, because a hazardous situation results from taking the lowest component flash point value as the mixture flash point. Flash point predictions were performed for 14 binary mixtures using various Gex models for the activity coefficients. Quantum chemical calculations and UNIFAC, a theoretical model that does not require experimental binary interaction parameters, are employed in the mixture flash point predictions, which are validated with experimental data. MFPB is successfully predicted using the UNIFAC model when there are insufficient vapor liquid data. The identification of inherent safety principles that can be applied to the flammability of binary liquid mixtures is also studied. The effect on the flash point values of three binary mixtures in which octane is the solute is investigated to apply the inherent safety concept.

No description available.

We study the formation of novel bicontinuous phases in binary mixtures of AB diblock copolymers (DBCP) using the polymeric self-consistent field theory. We predict that the bicontinuous double-diamond (DD) and plumber’s nightmare (P) phases, which are metastable phases of neat diblock copolymers, could be stablized in gyroid-forming A-minority DBCPs via the blending of specifically designed A-majority DBCPs. The mechanisms of stabilizing different bicontinuous phases are revealed by analyzing the spatial distribution of the different DBCPs. It is found that the A-majority DBCPs residing mainly in the nodes of the structure, thus alleviating the packing frustration of the A-blocks. Furthermore, a local segregation of the two DBCPs occurs at the AB interface, thus regulating the local curvature of the interfaces. A synergetic interplay of these two mechanisms results in a larger stable region of the DD and P phases via the addition of tailored A-majority DBCPs. The theoretical study provides an efficient route to obtain novel bicontinuous phases. / Thesis / Master of Science (MSc)

Molecular Dynamics (MD) simulation methods were used to perform simulations of the adsorption of multilayer films of three fluoromethane compounds -- nonpolar CF4 and its polar relatives, CF3Cl and CF3Br -- onto two chemically and structurally different substrates: graphite and hydroxylated α-quartz (a form of silica). The purpose of the simulations was to determine how differences in polarity and substrate type affect the structure of film layers at the adsorption surface, as well as to compare how these factors affect the mobility of molecules near the surface as they move along or away from the surface, to see how each of these factors affects the substrate affinity for the adsorbed compound. Simulations were performed for pure fluoromethane films as well as films created from binary mixtures of the above fluoromethanes adsorbed on each substrate over a range of temperatures from 80 K to 280 K. Analysis suggests a strong influence of substrate characteristics on both the structure and mobility of molecules in adsorbed layers, an effect that is partially temperature dependent but only weakly suggestive of effects due to the differences in polarity of the adsorbed molecules.

Orientador: Daniel Barrera-Arellano / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos / Made available in DSpace on 2018-08-15T08:05:38Z (GMT). No. of bitstreams: 1 Ribeiro_MarileneDeMoriMorselli_M.pdf: 5112345 bytes, checksum: 0515b869d93054892980d08c8bb30fd9 (MD5) Previous issue date: 2010 / Resumo: A facilidade de obtenção de micropartículas lipídicas e a possibilidade de produção em escala industrial aumentam o interesse do mercado alimentício de processar este tipo de material. Contudo, estas micropartículas apresentam desvantagens com relação à baixa encapsulação e à expulsão de material de recheio durante a estocagem. Assim, a finalidade deste trabalho foi estudar o comportamento das microcápsulas lipídicas produzidas pelo processo spray chilling utilizando as seguintes misturas em diferentes proporções: ácidos esteárico (AE) e oléico (AO), óleo de soja totalmente hidrogenado (STH) e ácido oléico (AO), álcool cetoestearílico (ACE) e ácido oléico (AO) como materiais de parede (matriz), lecitina de soja como tensoativo e solução de glicose como recheio. O objetivo foi aumentar a eficiência de encapsulação, verificando o efeito da composição e estrutura da matriz lipídica. Para este propósito, foram caracterizadas as matérias-primas lipídicas em composição de ácidos graxos e triacilgliceróis, bem como, as misturas lipídicas avaliadas por calorimetria diferencial de varredura (DSC), teor de gordura sólida (SFC) e curva de isosólidos. Nas micropartículas, foram avaliadas morfologia de superfície e microestrutura, tamanho e distribuição de partícula, quantidade de glicose superficial (não encapsulada), eficiência de encapsulação e perfil de liberação em solução aquosa. As micropartículas apresentaram formas esféricas e rugosas, com diâmetros médios entre 83 e 115 µm. Os resultados de eficiência de encapsulação nas misturas do AE e STH foram acima de 75% e nas misturas do ACE menor que 9%. A liberação do recheio foi avaliada a cada 30 minutos por 2 horas, obtendo-se valores de 28 a 89% ao término deste período para as misturas do AE e STH. Foi observado, nestas misturas, que a liberação de recheio é inversamente proporcional à quantidade de AO na mistura lipídica. Nas misturas do ACE, a liberação foi de 100% (efeito burst). A adição do lipídio líquido (AO) ao lipídio sólido (AE e STH) foi um fator determinante na modificação da cristalização da mistura lipídica, proporcionando uma alta eficiência de encapsulação / Abstract: The ease to obtain lipid microparticles and the possibility of their production in an industrial scale increase the interest of the food market to process this kind of particles. However, these microparticles present disadvantages with regard to low encapsulation and the expulsion of the core material core during storage. Thus, the purpose of this work was to study the behavior of lipid microcapsules produced by the spray chilling process, using the following mixtures in different proportions: stearic acid (SA) and oleic acid (OA), fully hydrogenated soybean oil (FHSO) and oleic acid (OA), cetostearyl alcohol (CEA) and oleic acid (OA) as the wall material (matrix), soy lecithin as surfactant and glucose solution as core. The objective was to increase the encapsulation efficiency, checking the composition effect and the lipid matrix structure. For this purpose, the lipid materials were characterized as to their fatty acids and triacylglycerol composition and the lipid mixtures were evaluated by differencial scanning calorimetry (DSC), solid fat content (SFC) and iso-solid curve. The surface morphology and microstructure were evaluated in the microparticles, as well as the particle size distribution, amount of core on the surface (not encapsulated), the encapsulation efficiency and controlled-release in an aqueous solution. The microparticles showed spherical and wrinkled shape with average diameters between 83 and 115 µm. The results of encapsulation efficiency of the mixtures with SA and FHSO were over 75% and lower than 9% in the mixtures with CEA. The core release was evaluated every 30 minutes for 2 hours obtaining values from 28 to 89% at the end of this period for the mixtures SA and FHSO. It was observed, in these mixtures, that the core release is inversely proportional to the quantity of AO in the lipid mixture. In the CEA mixtures, the core release was above 100% (burst effect). The addition of the liquid lipid (OA) to the solid lipid (SA and FHSO) was a determining factor in the modification of the crystallization of the lipid mixture providing high encapsulation efficiency / Mestrado / Mestre em Tecnologia de Alimentos

No description available.

Binary mixtures of polymers and soft nanocolloids, also called as polymer nanocomposites are well known and studied for their enormous potentials on various technological fronts. In this thesis blends of polystyrene grafted gold nanoparticles (PGNPs) and polystyrene (PS) are studied experimentally, both in bulk and in thin films. This thesis comprises three parts; 1) evolution of microscopic dynamics in the bulk(chapter-3),2) dispersion behavior of PGNPs in thin and ultra thin polymer matrices (chapter-4) 3) effect of dispersion on the glass transition behavior (chapter-5). In first part, the state of art technique, x-ray photon correlation spectroscopy is used to study the temperature and wave vector dependent microscopic dy¬namics of PGNPs and PGNP-PS mixtures. Structural similarities between PGNPs and star polymers (SPs) are shown using small angle x-ray scatter¬ing and scaling relations. We find unexpected (when compared with SPs) non-monotonic dependence of the structural relaxation time of the nanoparticles with functionality (number of arms attached to the surface). Role of core-core attractions in PGNPs is shown and discussed to be the cause of anomalous behavior in dynamics. In PGNP-PS mixtures, we find evidence of melting of the dynamically arrested state of the PGNPs with addition of PS followed by a reentrant slowing down of the dynamics with further increase in polymer frac¬tion, depending on the size ratio(δ)of PS and PGNPs. For higher δ the reen¬trant behavior is not observed with polymer densities explored here. Possible explanation of the observed dynamics in terms of the presence of double-glass phase is provided. The correlation between structure and reentrant vitrifica¬tion in both pristine PGNPs and blends are derived rather qualitatively. In the second part, the focus is shifted to miscibility between PGNPs and polymers under confinement i.e., in thin films. This chapter provide a compre¬hensive study on the different parameters affecting dispersion viz., annealing conditions, fraction of the added particles, polymer-particle interface and more importantly the thickness of the films. Changes in the dispersion behavior with annealing is shown and the need for annealing the films at temperatures higher than the glass transition temperature of the matrix polymers is clearly elucidated. Irrespective of the thickness of the films( 20 and 65 nm) studied, immiscible particle-polymer blends unequivocally prove the presence of gradi¬ent in dynamics along the depth of the films. To our knowledge for the first time, we report results on confinement induced enhancement in the dispersion of the nanoparticles in thin polymer films. The enhanced dispersion is argued to be facilitated by the increased free volume in the polymer due to confinement as shown by others. Based on these results we have proposed a phase diagram for dispersibility of the nanoparticles in polymer films. The phase diagram for ultra thin films highlights an important point: In ultra thin films the particles are dispersed even with grafting molecular weight less than matrix molecular weight. In the third part, we have studied the glass transition of the thin films whose structure has been studied earlier in the earlier part. Non-monotonic variation in glass transition with the fraction of particles in thin films has increased our belief on the gradient in the dynamics of thin polymer films. En¬hanced dispersion with confinement is captured with the enhanced deviation in glass transition temperature of ultra thin films. Effect of miscibility param¬eter on Tgis studied and the results are explained with the subtle interplay of polymer-particle interface and confinement.

Nesta tese utilizamos o Modelo de Bose-Hubbard (MBH) generalizado para duas espécies bosonicas para investigar a estabilidade dinâmica da fase superfluida de uma mistura binaria de átomos bosonicos ultra-frios confinados em uma rede optica periódica anelar com M sítios. Na primeira parte consideramos a Hamiltoniana do MBH sem a presença do tunelamento inter-especies. Deduzimos e resolvemos as equações de Gross-Pitaevskii para os estados de equilíbrio do MBH e mostramos que são misturas binarias de condensados nos quais os átomos de cada espécie ocupam um estado de quase-momento q bem definido. As excitações elementares foram determinadas resolvendo as equações de Bogoliubov-de Gennes o que foi possível graças a estrutura de acoplamento dos quase-momentos que reduziu a Hamiltoniana Efetiva a uma soma direta de um dubleto e quadrupletos. Através da analise do comportamento das energias de excitação como função dos parâmetros de controle do sistema, investigamos a estabilidade dinâmica de dois casos de misturas de condensados onde, em um caso, os átomos de cada espécie ocupam o mesmo estado de quase-momento, qA = qB e, no outro, quase-momentos opostos, qA = qB. Em ambos os casos as condições de estabilidade dependem do quase-momento q estar nos quartos centrais ou laterais da primeira zona de Brillouin. No caso qA = qB vemos que a forma do diagrama de estabilidade independe do quase-momento do condensado. Por outro lado, o mesmo não ocorre nos condensados contra-propagantes qA = qB. Esta diferença fica mais acentuada no limite termodinâmico onde os diagramas de estabilidade no centro e nas extremidades da primeira zona de Brillouin ficam idênticos nos dois casos. Já nas bordas que separam os quartos centrais e laterais o comportamento ´e diferente pois a presença de uma interação interespécies por menor que seja desestabiliza completamente a mistura com qA = qB. Em todos estes casos ficou evidente o papel desestabilizador da interação interespécies. Na segunda parte consideramos o efeito de um termo de tunelamento inter-especies. As soluções das equações de Gross-Pitaevskii revelam uma estrutura biestável de estados de equilíbrio essencial para a ocorrência de bifurcação no sistema e, portanto, a presença de catástrofe. Investigamos se a catástrofe e acessível a uma observação experimental. De acordo com nosso critério, esta observação e impossível se o plano de bifurcação for a fronteira de um domínio de instabilidade dinâmica. Através da analise da estabilidade dinâmica dos estados de equilíbrio vimos que para um sistema invariante por inversão de cor essa resposta depende apenas da razão entre as intensidades de tunelamento intra e inter-especies de modo que se JAB/J > 1 a observação e impossível e se JAB/J < 1 é possível, supondo existir uma rota adiabática ate a bifurcação. / In this thesis we used the two-component Bose-Hubbard Model (BHM) to investigate the dynamical stability of the superfluid phase of a binary mixture of ultra-cold bosonic atoms confined in a ring-shaped periodic optical lattice with M sites. In the first part we considered the BHM Hamiltonian without the presence of interspecies tunnelling. We deduced and solved the Gross-Pitaevskii equations for the equilibrium states of the BHM and showed that they are binary mixtures of condensates where the atoms of each species occupy a state of well defined quasi-momentum q. The elementary excitations were determined solving the Bogoliubov-de-Gennes equations which was possible thanks to the coupling structure of the quasi-momenta that reduced the Effective Hamiltonian to a direct sum of a doublet and quadriplets. Through the analysis of the behavior of the excitation energies as a function of the control parameters of the system, we investigated the dynamical stability of two cases of mixtures of condensates where, in one case, the atoms of each specie occupy the same state of quasi-momentum, qA = qB, and, in the other, opposite quasi-momentum, qA = qB. In both cases the stability conditions depend of the quasi-momentum q to be in the central or lateral quarters of the first Brillouin zone. In the case qA = qB, we see that the form of the stability diagram is not dependent of the quasi-momentum of the condensate. However, the same does not occur in the counter-propagating condensates qA = qB. This difference is accentuated in the thermodynamic limit where the stability diagrams in the center and in the extremities of the first Brillouin zone are identical in both cases. In the borders that separate the central and lateral quarters the behavior is different because the presence of a slightly non vanishing inter-species interaction completely destabilize the mixture with qA = qB. In all these cases it was evident the destabilizing role of the inter-species interaction. In the second part we considered the effect of a inter-species tunnelling term. The solutions of the Gross-Pitaevskii equations reveal a bi-stable structure of equilibrium states that is essential for the occurrence of the bifurcation in the system and, therefore, the presence of catastrophe. We investigated if the catastrophe is accessible to a experimental observation. According to our criteria, this observation is impossible if the bifurcation plane is the frontier of a dynamical instability domain. Through the analysis of the dynamical stability of the equilibrium states we saw that for a system invariant by color inversion this answer depends only on the ratio between the intra and inter-species tunnelling intensities in a way that if JAB/J > 1 the observation is impossible and if JAB/J < 1 it is possible, supposing that it exists an adiabatic route until the bifurcation.

The purpose of this work is to study the effects of boundaries on granular flows down vibrating inclines, on segregation in granular mixtures induced by boundary vibrations, and on flows of granular mixtures through vibrating sieves. In each case, we employ techniques borrowed from the kinetic theory to derive an appropriate set of boundary conditions, and combine them with existing flow theories to calculate the profiles of solid volume fraction, mean velocity, and granular temperature throughout the flows. The boundaries vibrate with full three-dimensional anisotropy in a manner that can be related to their amplitudes, frequencies, and phase angles in three independent directions. At impenetrable surfaces (such as those on the inclines), the conditions derived ensure that momentum and energy are each balanced at the boundary. At penetrable surfaces (such as sieves), the conditions also ensure that mass is balanced at the boundary. In these cases, the momentum and energy balances also are modified to account for particle transport through the boundary. Particular interest in all the applications considered here is in how the details of the boundary geometry and the nature of its vibratory motion affect the resulting flows. In one case, we derive conditions that apply to a monosized granular material that interacts with a bumpy, vibrating, impenetrable boundary, and predict how such boundaries affect steady, fully developed unconfined inclined flows. Results indicate that the flows can be significantly enhanced by increasing the total energy of vibration and are more effectively enhanced by normal vibration than by tangential vibration. Regardless of the direction of vibration, the bumpiness of the boundary has a profound effect on the flows. In a second case, we derive conditions that apply to a binary granular mixture that interacts with a flat, vibrating, penetrable sieve-like boundary, and predict how such boundaries affect the process in which the particles pass through the sieve. In the special case in which the particles are all the same size, the results make clear that energy is more effectively transmitted to the assemblies when either the total vibrational energy or the normal component of the vibrational energy is increased, but that an increase in the energy transferred to the material can sometimes actually decrease the flow rates through the sieve. Consequently, at any instant of time in the sieving process, there is an optimum level of vibrational energy that will maximize the flow rate. For the sieving of binary granular assemblies, the physics associated with the effects of energy transfer on the flow rates still applies. However, in these cases, the flows through the sieve are also profoundly affected by segregation that occurs while the particles reside on sieve before the pass through. For this reason, we also isolate the segregation process from the sieving process by considering the special case in which the holes in the vibrating sieve are too small to allow any particles to pass through. In this case, the results show that under most circumstances the region immediately adjacent to the vibrating surface will be populated almost entirely by the smaller particles or by the more dissipative particles if there is no size disparity, and that the reverse is true in a second region above the first.

Natural geomaterials exhibit a wide range in size, physical properties, chemical properties, and mechanical behaviors. Soils that are composed of mixtures of particles with different physical and chemical properties pose a challenge to characterization and quantification of the engineering properties. This study examined the behavior of particulate mixtures composed of differently sized silica particles, mixtures composed of aluminosilicate and organic carbon particles, and mixtures composed of particles with approximately three orders of magnitude difference in particle size. This experimental investigation used elastic, electromagnetic, and thermal waves to characterize and to quantify the small to intermediate strain behavior of the mixtures. The mechanical property of stiffness of mixed materials (e.g. binary mixtures of silica particles and fly ashes with various carbon and biomass contents) was evaluated through the stiffness of active grain contacts, and the stiffness of particles which carry applied load, using the physical concepts of intergranular void ratio and interfine void ratio. Additionally, the change in both contact mode/stiffness and electrical property due to the presence of nano-sized particles (i.e., iron oxides) on the surface of soil grains was evaluated according to applied stress, packing density, iron coating density, and substrate sand particle size. Finally, the biomass fraction and total organic carbon content of mixtures was used to quantify the electrical and thermal conductivities when particulate organic was mixed with aluminosilicate particles.