The synthesis of precipitated calcium carbonate nanoparticles with the use of double water in oil emulsion has been developed. Restricting the mass of calcium ions present in the system makes it possible to predict particle size precipitated. A model was developed to calculate the concentration required to synthesize a desired particle size. This model took into account a coalescence factor. The coalescence factor is described at the probability of two emulsion droplets, with separate nucleation processes within them, colliding and forming one nucleation process. The Ca2+ ions diffused through the oil membrane into the emulsion droplets with (CaCO3)2- ions by concentration gradients and facilitated transport. The size and shape of precipitated calcium carbonate synthesized was confirmed using scanning electron microscope and light scattering. Particles ranging from 100 nm to 1200 nm have been synthesized using mass restriction. The effect of temperature on the crystalline structure of precipitated calcium carbonate was studied. This was done by x-ray diffraction, where it was found that calcite was the dominating crystalline structure.

Even minimal improvements in particle collection efficiency of electrostatic precipitators significantly reduce dust emission from fossil-fuelled power stations and reduce pollution. Yet current designs rely on the Deutsch collection theory, which was developed for tubular precipitators and has been applied to wire-plate precipitators on the assumption that the inter-electrode electric fields at the same discharge distance in both were similar. Differences in geometry and associated collector electric fields and current density non-uniformity have not been taken into account, although the collector electric field and current density of the wire-plate precipitator are not uniform. And observations show that precipitated dust patterns and the distribution of collector current density are interrelated. Investigations revealed a simple square law relationship between the collector electric field and the collector current density in the space charge dominated coronas. Applying this relationship to the Deutsch collection theory led to a current-density-based collection formula that takes into account the non-uniform collector current density distribution. The current-density-based collection formula is then used to assess the impact of collector current density on collection efficiency, the results closely following published measurements. Applying the current-density-based collection formula to estimate the dust accumulation shows that most of the dust accumulates at collector locations facing the corona wires. The effect of the non-uniform precipitated dust layer on collection performance is assessed using the distributed corona impedance - the ratio of the inter-electrode voltage and the non-uniform collector current. Re-distribution of the collector current profile as dust builds up is also compatible with published measurements. Finally this is applied to optimize the wire-plate precipitator collection performance. This shows that optimal collection performance is obtained with the wire-wire spacing less than the wire-plate distance, once again confirming published experimental results. This is the first analytical approach to show better collection performance can be achieved at the ratio of wire-wire spacing/wire-plate distance not equal to unity, which has been the standard industry practice since 1960.

The aim of this work is to develope fast-setting geopolymeric binders applicable in the chemical wall clamp. This clamping systems are big trend because of easy application, ability to transfer big forces and short setting time. Binders of this systems are based on polymeric resin. Their raw materials are expensive, toxic and flammable substances. Based on this consideration an anorganic fast-setting geopolymeric binder was developed. This binders consist of mixture of metakaolin and precipitated silica activated by potassium hydroxide. Binder were characterized by suitable analytic methods (XRD, SEM, DTA). The results of this metods were used for optimalization of binder properties.

Epidemiological data indicate that patients who experience a traumatic brain injury (TBI) have an elevated risk of developing a substance use disorder (SUD), but the underlying neurobiological connections remain unclear. To further understand the relationship between TBI and SUD, we investigated the effects of TBI on the abuse-related effects of oxycodone in preclinical models. Our evaluation utilized a lateral fluid percussion injury of moderate severity in adult male Sprague-Dawley rats. In the first aim, we tested the hypothesis that moderate TBI increases the risk for relapse to an opioid use disorder as measured by reinstatement of lever-pressing behavior following extinction in an intravenous oxycodone self-administration procedure. In the second aim, we tested the hypothesis that moderate TBI increases physiological dependence to oxycodone as measured by decreases in food-reinforced lever-pressing behavior and increases in other withdrawal behaviors in both precipitated withdrawal and spontaneous withdrawal. In tests for self-administration, brain-injured subjects, relative to non-injured subjects, showed no significant differences in the number of oxycodone-reinforced sessions required to meet stable maintenance criteria for lever-pressing behavior. Likewise, brain-injured subjects showed no significant differences in the number of non-reinforced sessions to meet extinction criteria for lever-pressing behavior relative to non-injured subjects. In tests for reinstatement, non-injured subjects reinstated responding under oxycodone-associated cue- and oxycodone prime-induced conditions, however, brain-injured subjects did not reinstate lever-pressing behavior under any conditions. In tests for physical dependence, brain-injured subjects showed no significant differences from non-injured subjects with regards to their mean withdrawal scores or food-reinforced lever-pressing behavior. Overall, these data suggest that brain-injured patients no significant pre-morbid history of opioid abuse are at a lesser risk of relapse to opioid use disorders. Moreover, the characteristic withdrawal syndrome in opioid-dependent patients may not contribute to continued opioid abuse to a greater degree in brain-injured patients than compared to non-injured patients.

L’impact environnemental est un paramètre prépondérant dans l’élaboration de nouveaux matériaux. Dans le secteur du transport, l’introduction de silice précipitée comme charge renforçante en remplacement d’une partie du noir de carbone a permis de mettre au point des pneus plus respectueux de l’environnement.L’objectif de notre projet consiste à déterminer l’effet des conditions d’élaboration et de traitement de la silice sur l’aptitude des granules de silice à se disperser dans l’élastomère, sans compromettre leur résistance à la fragmentation en milieu sec lors des opérations du procédé. Pour ce faire, différentes caractérisations ont été effectuées. Tout d’abord, une analyse de la texture des agglomérats de silice est réalisée dans le but d’obtenir une description morphologique de ces granules (surface spécifique, granulométrie, structure 3D). Une étude du comportement des granules sous contraintes mécaniques (ultra-sons, transport pneumatique) a permis de quantifier la cinétique de désagglomération des micro-granules de silice. Ces différentes mesures expérimentales nous permettent de mettre en évidence l’impact des étapes du procédé sur les propriétés des granules de silice. Ceci nous a permis de mettre en avant différents mécanismes de fragmentation des granules. Enfin, nous proposons une modélisation de la fragmentation au moyen d’un modèle matriciel. Ce modèle a permis, à partir de données expérimentales, de remonter aux mécanismes de fragmentation. / Silica is constantly gaining importance as a reinforcing filler for rubber compounds. It offers several advantages compared to carbon black. In tyres treads, silica can yield a lower rolling resistance at equal wear resistance and wet grip than carbon black. This work consists in the determination of the effects of processes and treatments of precipitated silica granules on their capacity to nicely disperse the silica in the elastomer, without impairing their breakage resistance during dry steps of the process.In this work, physico-chemical characterizations like laser granulometry, specific surface area, SEM, X-ray tomography have been given morphological and structural information on the granule properties. In a second step, the behaviour of silica granules under mechanical stress in various media (air, liquid) by ultrasound solicitation, fluidized bed, impact breakage, is investigated. Mechanisms are observed for the fragmentation of the granules (erosion, attrition, breakage, splitting) and a quantification of the breakage kinetics of granule is proposed. In the last step, a model of the fragmentation process in water is presented. All these experiments give us information about the impact of the process on the granule structures and mechanicals properties.

Excessive use of fossil fuels shall result in the significant energy problems in the coming century and causes global warming by CO2 emission. Use of petroleum in transportation constitutes the dominant part of total petroleum use. Researches on non-petroleum based, environmentally friendly alternative fuels have been ascended in last decades. Among the alternative fuels, DME has been considered as an attractive fuel alternate due to high cetane number, low PM (particulate matter) and low NOx emission. Synthesis of DME is possible with gasification of biowastes or coal and steam reforming of natural gas. DME is produced in two different methods. In the first method, methanol is formed from the synthesis gas, followed by methanol dehydration to DME. In the second method, called as direct synthesis of DME from synthesis gas, methanol formation and dehydration occurs simultaneously at the same location within the reactor. For the direct synthesis of DME, bi-functional catalysts must be used / one site is responsible for methanol synthesis and other site is responsible for methanol dehydration. Throughout this thesis work, several catalysts were prepared to be used as methanol synthesis component or methanol dehydration component of bi-functional direct DME synthesis catalyst and bi-functional catalysts were also prepared for the direct synthesis of DME from synthesis gas. Materials were characterized by XRD, EDS, SEM, N2 physisorption, and DRIFTS characterization techniques. Activity tests were conducted in a high pressure, fixed bed flow reactor at 50 bar and for the feed gas compositions of H2:CO=50:50 and H2:CO: CO2=50:40:10. Addition of zirconia and alumina promoters, long aging time, calcination temperature of 550 &deg / C and reduction at 250 &deg / C were found to be beneficial in methanol synthesis from the equimolar composition of CO and H2. Precipitated catalysts were usually active and selective to methanol. However, bi-functional co-precipitated catalyst was not successful in situ conversion of methanol into dimethyl ether. Furthermore, tungstosilisic acid impregnated SBA-15 was physically mixed with commercial methanol reforming catalyst and activity results revealed that high DME yield and selectivity were obtained. By physically mixing commercial methanol synthesis and reforming catalysts with &gamma / -Al2O3 and TRC-75(L) in appropriate proportions or by preparing the reactor bed in a sequential arrangement, very high DME yields were obtained and superiority of direct synthesis to conventional two step synthesis was proven. Presence of CO2 in the feed stream not only enhanced the catalytic activity but also utilization of the most important greenhouse gas was accomplished. It was seen that synthesized catalysts are very promising in the direct synthesis of dimethyl ether from synthesis gas.

No description available.

The impact of particle size, size distribution, and particle shape on the rheology of precipitated calcium carbonate (PCC) based coatings was studied. Evaluating the interactions between different particle sizes and shapes leads to a better understanding of the packing fraction of PCC. HIgh packing fraction is desirable because of the positive impact on the fluidity of suspensions. Suspension with higher levels of fluidity can potentially load larger amounts of solids while keeping low viscosities. High solids suspensions are key factors to improve the efficiency of coating processes. To address this issue, PCC of different sizes and shapes where mixed in different ratiosto find mixtures with higher packing fractions that could result in coatings with lower viscosities. When coatings containing 90% of large particles and 10% by weight of small particles of different shape, viscosity decreases by 50% for one combination. The effect is caused by the higher packing fraction achieved. Future research is also described here.

La modélisation du transport réactif du contaminant en milieu poreux est un problème complexe cumulant les difficultés de la modélisation du transport avec celles de la modélisation de la chimie et surtout du couplage entre les deux. Cette modélisation conduit à un système d'équations aux dérivées partielles et algébriques dont les inconnues sont les quantités d'espèces chimiques. Une approche possible, déjà utilisée par ailleurs, est de choisir la méthode globale DAE : l'utilisation d'une méthode de lignes, correspondant à la discrétisation en espace seulement, conduit à un système différentiel algébrique (DAE) qui doit être résolu par un solveur adapté. Dans notre cas, on utilise le solveur IDA de Sundials qui s'appuie sur une méthode implicite, à ordre et pas variables, et qui requiert à chaque pas de temps la résolution d'un grand système non linéaire associé à une matrice jacobienne. Cette méthode est implémentée dans un logiciel qui s'appelle GRT3D (Transport Réactif Global en 3D). Le présent travail présente une amélioration de la méthode GDAE, du point de vue de la performance, de la stabilité et de la robustesse. Nous avons ainsi enrichi les possibilités de GRT3D, par la prise en compte complète des équations de précipitation-dissolution permettant l'apparition ou la disparition d'une espèce précipitée. En complément de l'étude de la méthode GDAE, nous présentons aussi une méthode séquentielle non itérative (SNIA), qui est une méthode basée sur le schéma d'Euler explicite : à chaque pas de temps, on résout explicitement l'équation de transport et on utilise ces calculs comme données pour le système chimique, résolu dans chaque maille de façon indépendante. Nous présentons aussi une comparaison entre cette méthode et l'approche GDAE. Des résultats numériques pour deux cas tests, celui proposé par l'ANDRA (cas-test 2D) d'une part, celui proposé par le groupe MoMas (Benchmark "easy case") d'autre part, sont enfin présentés, commentés et analysés. / Modeling reactive transport of contaminants in porous media is a complex problem combining the difficulties of modeling the trasport with those of modeling the chemistry and especially the coupling between the two .This model leads to a system of partial differential equations and algebraic equations whose unknowns are the quantities of chemical species. One approach , already used elsewhere , is choosing the global DAE method : using the method of lines, discretization in space only, leads to a differential algebraic system (DAE ) to be solved by a suitable solver . In our case , the solver IDA Sundials relies on an implicit method, order is used but not variables, and requires at each time solving a large nonlinear system associated with a Jacobian matrix . This method is implemented in a software called GRT3D (Global Reactive Transport in 3D). This paper presents an improved GDAE method , from the standpoint of performance, the stability and robustness. We have enriched the possibilities of GRT3D , by taking full account of the equations of dissolution – precipitation for the appearance or disappearance of precipitated species. In addition to the study of the GDAE method, we also present a non-iterative sequential method ( SNIA ) which is a method based on the explicit Euler scheme : at each time step, we explicitly solve the transport equation and we use these calculations as data for the chemical system which is resolved in each cell independently. We also present a comparison between this method and GDAE approach . Numerical results for two test cases , one proposed by ANDRA ( 2D test case ) on one hand and one proposed by the group MOMAS ( Benchmark "easy case" ) on the other hand, are finally presented , discussed and analyzed.