La recherche s’appuie pour une grande part sur le développement de nanomatériaux. Ceux-ci constituent, en effet, les matières premières des nanosciences et ouvrent à l’industrie des perspectives extrêmement larges. Le développement des céramiques nécessite une grande maîtrise des procédés d'élaboration qui permettent d'obtenir des microstructures appropriées à l’élaboration de matériaux denses pour différentes applications par exemple biomédicales. Les évolutions récentes concernent les matériaux hybrides et bio-inspirés ; les problèmes de mise en forme et de structuration multi-échelles de ces derniers incitent au développement de nouveaux procédés telle que l’approche nouvelle dite ascendante (bottom-up) consistant à fabriquer un matériau à échelle microscopique voir macroscopique à partir de ses particules nanométriques.Dans ce contexte, les travaux de cette thèse ont pour objectif de faciliter, par l’intermédiaire d’une modification de surface, la mise au point d’une technique de mise en forme originale pour l’élaboration de céramiques issues d’un matériau nanométrique de type oxyde: la granulation par coagulation. Nous nous sommes intéressés au cas d’une nanopoudre de boehmite (AlO(OH)). Cependant, cette poudre nanométrique de boehmite présente de multiples instabilités en suspension. En effet, cette poudre est soumise à de fortes gélifications en fonction du pH et à basse concentration. Il est nécessaire dans ce cas pour obtenir une suspension stable de modifier les propriétés de surface. En conséquence, une partie de ces travaux est consacrée à la fonctionnalisation de surface par des organosilanes. Cette modification de surface n’est cependant qu’une étape à l’obtention d’une particule hybride constituée d’un cœur de boehmite et d’une couche polymérique. En réalité, le greffage d’organosilane à la surface permet de créer un pont entre la partie centrale inorganique et la partie externe organique constituée de latex pouvant se lier à l’organosilane utilisé (le MPS).Le matériau hybride boehmite-MPS-latex ainsi obtenu peut être utilisé dans une nouvelle technique de mise en forme colloïdale inspirée de la granulation par hétérocoagulation. En milieu aqueux, la polarité opposée des charges de surfaces de deux entités différentes conduit à l’hétérocoagulation en suspension. La coagulation observée dans cette thèse, met en relation deux particules identiques possédant chacune, les deux charges opposées à leur surface. Le principe de la granulation consiste à induire, sous l’effet d’un mouvement de rotation des échantillons, la coalescence des agglomérats en forçant leurs surfaces à interagir par contacts réciproques. En sélectionnant la formulation, la coalescence conduit à l'élaboration d'objets sphériques homogènes en taille et en forme. / Research in this field is multidisciplinary and relies largely on the development of nanomaterials. These are, in fact, the raw materials of nanoscience and open to industry extremely broad prospects. In the field of material sciences, nanostructured materials, among them nanostructured ceramics have grown considerably in recent years. Development of ceramic requires a mastery of production processes that achieve appropriate microstructures in the development of dense materials for various applications such biomédicals. Recent developments include hybrid and bio-inspired materials; the problems of shaping and multi-scale structure of these encourage the development of new processes such as the new so-called bottom-up approach of manufacturing and make macroscopic material from its nanoparticles. In this context, the work of this PhD aim to facilitate, through surface modification, the development of an original layout technique for the development of ceramics from a material nano-oxide type: granulation coagulation. We were interested in the case of a boehmite nanopowder (AlO(OH)). However, this nanoscale boehmite powder has many instabilities in suspension. Indeed, the powder is subjected to strong gelation as function of pH and at low concentrations. It is necessary in this case to obtain a stable suspension by modifying the surface properties. Accordingly, a part of this work is devoted to surface functionalization by organosilanes. This surface modification, however, is only one stage to obtain a hybrid particle comprised of a heart of boehmite and a polymeric layer. In reality, the grafting organosilane (MPS) at the surface permit to create a bridge between the inorganic core and organic outer part consists of latex. The boehmite-MPS-latex hybrid material thus obtained can be used in a new colloidal shaping technique inspired by heterocoagulation granulation. In aqueous medium, the opposite polarity of the charges of the surfaces of two different entities leads to heterocoagulation in suspension. Clotting observed in this thesis, connects two identical particles with each, the two charges opposite to the surface. The principle of the granulation is to induce, under the effect the rotational movement, the coalescence of the agglomerates by forcing their surfaces to interact by mutual contact. By selecting the formulation, coalescence leads to the development of homogeneous spherical objects in size and shape.

Abstract This thesis aims to increase our knowledge about the characteristics of chemical pulp process and wastewaters and how problematic substances, e.g. wood extractives, could be removed effectively and selectively by coagulation–flocculation with either internal or external water treatment. Characterization was performed by investigating kraft pulp bleaching filtrates, as well as wastewater, before (influent) and after (effluent) the activated sludge treatment by means of a range of chemical analyses and by carrying out size fractionation studies. Cationic polyelectrolytes were used to purify oxygen stage bleaching filtrate, and charge analyses (zeta potential, charge quantity) were carried out in order to understand the coagulation phenomenon. In activated sludge treatment, the enhancement of particle removal, either by filtration or using a chemical in the primary clarifier, would lead to savings in aeration costs and result in a more stable process. Microfiltration already with a large pore size (8 µm) removed 30–50% of the wood extractives from the influent. Separate treatment stages for certain wastewater fractions, e.g. debarking plant effluent, would ensure cost-efficiency. After the activated sludge process, the wood extractives were present as particles (18%) and < 3 kDa fraction (82%). β-sitosterol occurred only in particles in the effluent. The release of harmful components into the environment could be decreased by microfiltration (e.g. 0.45 µm) of the final effluent or using a chemical in the secondary clarifier. Interestingly a huge increase in BOD was realized in the 3 kDa fraction of both influent and effluent, which indicated the presence of toxic substances in the larger fractions. After passing the effluent into the water system, there might be a similar jump in the BOD because the effluent is diluted many-fold. This would contribute to the formation of areas with an oxygen deficit. In the coagulation–flocculation studies, effective and selective removal of wood extractives (92%) from the oxygen stage filtrate was obtained with a cationic polyelectrolyte of medium molecular weight and medium charge density at 72 °C and pH 5–6. The multimodal zeta potential distribution gave more information than the average zeta potential. Aggregation of colloidal particles occurred when only one zeta potential was observed. The number of different zeta potentials diminished with decreasing pH and after exceeding a certain polyelectrolyte dosage level.

The interfacial adsorption and bulk properties of a collagenous polypeptide derived from chicken eggshell membranes, the 40 KDa polypeptide, and its mixtures with common low molecular weight (LMW) surfactants, SDS, DTAB and C10E8, have been studied for the first time using surface tension, ζ-potential, foam observations and neutron scattering techniques. The biopolymer has been shown to act as an effective biosurfactant by lowering the surface tension of water below the values commonly achieved with conventional LMW surfactants, i.e. γ = 32 ± 1 mN/m. This capability is maximized at its isoelectric point, pH ~5, and addition of NaCl does not have a major impact upon adsorption. On its own, the 40 KDa polypeptide lacks the ability to foam. When mixed with cationic and anionic surfactants, a positive synergy is observed at low concentrations of both materials that exceeds the expectations from the individual components due to the formation of polypeptide/surfactant complexes with high surface activity and high ability to foam and foam stability. At these concentrations, maximum interfacial adsorption is achieved. The synergy is observed in spite of the type of charges present in the surfactant polar head. However, under the conditions studied, there is a difference in behaviour in regards to colloidal stability and surface film formation between the mixed solutions with the anionic SDS and the cationic DTAB. The non-existence of the synergy in the surface adsorption profile of the mixtures of the polypeptide with the non-ionic surfactant C10E8, as obtained via the plate method, suggests that electrostatic interactions are necessary for this strong synergy to act. ζ-potential has been used to prove the electrostatic nature of the synergy. Specular neutron reflection and SANS measurements offered an insight into the complex size and structure. The 40 KDa polypeptide thus offers a promising alternative to the use of high amounts of LMW surfactants in a range of products in which low surface tension and/or high and stable volumes of foams are needed, by combining small amounts of polypeptide and an ionic surfactant. This could be exploited by industries which have an interest in nanoparticle formation such as personal care or pharmaceutical companies. However, further work is needed to fully characterize these interactions.

The expected outcome of this project is to develop a general strategy to functionalize dispersions, by noncovalent adsorption of HMW surfactants, ultimately for applications such as hydrophobic coatings with high hiding power and hardness, improved mechanical properties via pigment-latex interactions, improved substrate adhesion or improved freeze-thaw stability. So far, we have produced poly (methyl methacrylate-co-butyl acrylate) latexes in the presence of HMW surfactants via emulsion polymerization and demonstrated stronger adsorption of HMW surfactants on particle surface than sodium dodecyl sulfate (SDS). In addition, we have developed surfactant-free latexes, poly (methyl methacrylate-co-butyl acrylate-co-methacrylic acid), as models for post functionalization with high molecular weight surfactants. The successful transfer of surfactants onto particle surface from liquid crystals was indicated by the increase in zeta potential and confirmed via chemical shifts variation in 1H NMR spectra. Additionally, the HMW surfactants were used for dispersing hydrophobic inorganic particles, such as hydrophobic carbon black, in aqueous phase, providing an indication of the general applicability and versatility of our approach.

The topic of this dissertation was the preparation of a high-quality sulphate binder based on secondary raw materials. For this purpose, the work was primarily focused on the laboratory preparation of beta gypsum from the selected industrial gypsum, the design of the technological process of production and its verification by pilot tests. In the next step, the thesis dealt with the modification of beta gypsum by a selected set of liquefiers. In addition to commercial dehumidifiers, the possible beta casting of beta gypsum was tested by increasing the zeta potential of the gypsum suspension. At the end, a complete complex of construction products was developed based on laboratory and semi-prepared beta plasters, consisting of gypsum plasters, mastics, gypsum premix and small plaster casts.

No description available.

No description available.

[pt] Nas últimas décadas a demanda por elementos terras raras (ETRs) cresceu consideravelmente devido a sua importância estratégica. Os ETRs são amplamente utilizados em diferentes setores, tais como, medicina, engenharia química, eletrônica e fabricação de computadores. Entre os ETRs, está o Neodímio, que é um dos metais mais valiosos utilizados em ligas, componentes eletrônicos e filtros ópticos. A necessidade da alta pureza dessas espécies requer a separação seletiva, e entre os métodos disponíveis, a adsorção ganhou maior atenção devido à sua simplicidade, alta eficiência e baixo custo. Neste trabalho foi avaliado o argilomineral palygorskita como potencial sorvente para remoção de Nd (III) de soluções aquosas através de ensaios em batelada. Para este propósito, a amostra proveniente da região de Guadalupe (Piauí) foi beneficiada e estudada a composição química e mineralógica com o intuito de utilizar no processo adsortivo a amostra com maior grau de pureza. A composição química apresenta teores de óxidos, sendo os principais, SiO2, Al2O3 e MgO corroborando a presença de palygorskita na amostra. Os estudos de potencial zeta apontam que o argilomineral apresenta carga superficial negativa em toda faixa de pH, além disso, a elevada área superficial de 118 metros quadrados por grama justificam a aplicação como adsorvedor de cátions. Diferentes tipos de isotermas de adsorção e modelos cinéticos foram utilizados para descrever o comportamento do Nd (III) na adsorção e os resultados experimentais que melhor se ajustaram são referentes ao modelo de Langmuir, e a capacidade máxima de captação foi de 15,39 mg/L avaliada em pH 5. A cinética de adsorção para o Nd (III) foi modelada pela equação de pseudo segunda ordem. A adsorção foi encontrada e sugere-se que o processo é endotérmico e espontâneo (delta H igual 17,12 KJ/mol; delta G igual -26,3 KJ/mol) em relação aos parâmetros termodinâmicos obtidos. Os resultados gerais sugerem que este adsorvente demonstrou ser um potencial sorvente para separação de Nd(III) a partir de soluções aquosas. / [en] In recent decades, the rare-earth elements (REEs) demand has considerably grown because of its strategic importance. REEs are widely used in different high-tech sectors such as nuclear power, metallurgy, medicine, chemical engineering, electronics and computer manufacturing. Among REEs, is Neodymium, which is one of the most valuable metals used in alloys, electronic components and optical filters. The need for the high purity of these species requires selective separation, between the available methods, adsorption has earned greater attention due to its simplicity, high efficiency and low cost. The removal of metal ions is a complex task due to the high cost of treatment methods. Contributed to the intensification of research for low-cost adsorbent materials, reusable alternatives were added to the adsorption process. In this work was evaluated the clay mineral palygorskite as a sorbent potential for Nd (III) removal from aqueous solutions by batch trials. For this purpose, the sample from Guadalupe (Piauí) was benefited and the composition of the chemical and mineralogical was studied in order to use the sample with the highest purity in the adsorptive process. The samples were found to be essentially composed of palygorskite, kaolinite, quartz and diaspore. The chemical composition presents oxide contents, the main ones being SiO2, Al2O3 and MgO, corroborating the presence of palygorskite in the sample. Zeta Potential studies point out that the clay mineral has a negative surface charge in the whole pH range, in addition, the high surface area of 118.43 square meter per gram justifies the cation adsorber application. Different types of adsorption isotherms and kinetics models were used to describe the behavior of Nd (III) in adsorption and the best experimental results set refer to the Langmuir model and pseudo second order model, respectively, with the maximum uptake capacity was 15.39 mg/L evaluated at pH 5. Adsorption was found as an endothermic and spontaneous process ( delta H equal 17.12 KJ/mol; delta G equal -26.3 KJ/mol) in relation to thermodynamic parameters obtained. Overall results suggest that this adsorbent has been shown to be a potential sorbent for enrichment and separation of Nd (III) from aqueous solutions.

<p>Microfluidic devices using electroosmotic flows (EOFs) in microchannels have been developed and widely applied in chemistry, biology and medicine. Advantages of using these devices include the reduction of reagent consumption and duration for analysis. Moreover the velocity profile of EOFs, in contrast to the parabolic profile found in pressure-driven flows, has a plug-like profile which contributes significantly less to solute dispersion. It also requires no valve to control the flow, which is done with the appropriate application of electrical potentials, thus becomes one of the favourite techniques for sample separation. However, high potentials of several hundred volts are usually required to generate sufficient EOF. These high potentials are not practical for general usage and could cause electrical hazard in some applications. One of the possible solutions is the introduction of zeta potential modulation. The EOF in a microchannel can be controlled by the zeta potential at the liquid/solid interface upon the application of external gate potentials across the channel walls. Combined with AC EOF, it can rectify the oscillating flows and generate pressure that can be used for microfluidic pumping applications. Since the flow induced by the alternating electric field is unsteady and periodic, it is critical to visualize the flow with high spatial and temporal resolutions in order to understand fluid dynamics. A novel method to obtain high temporal resolution for high frequency periodic electrokinetic flows using phase sampling technique in micro particle image velocimetry (PIV) measurements are first developed in order to characterize the AC electroosmotic flow. After that, the principle of zeta potential modulation is demonstrated to transport particles, cells, and other micro organisms using rectified AC EOF in open microchannels. The rectified flow is obtained by synchronous zeta-potential modulation with the driving potential in the microchannel. Subsequently, we found that PDMS might not be the best material for some pumping and biomedical applications as its hydrophobic surface property makes the priming process more difficult in small microchannels and also causes significant protein adsorption from biological samples. A more hydrophilic and biocompatible material, polyurethane (PU), was chosen to replace PDMS. A polyurethane-based soft-lithography microfabrication including its bonding, interconnect integration and in-situ surface modification was developed providing better biocompatibility and pumping performance. Finally, an electroosmotic pumping device driven by zeta potential modulation and fabricated by PU soft lithography was presented. The problem of channel priming is solved by the capillary force induced by the hydrophilic surface. Its flow rate and pressure output were found to be controllable through several parameters such as driving potential, gate potential, applied frequency, and phase lag between the driving and gate potentials.</p> / Doctor of Philosophy (PhD)

Although enormous potential benefits are envisioned with the application of nanotechnology in conjunction with biological systems, interactions of nano particulate materials with biological materials is not well understood. The focus of this dissertation is to determine the mathematical relationships of the forces between nanoparticles and biological agents. The systems under investigation are the alpha-SiC/H2O/LGG polar based systems. The mathematical analysis for the surface forces, based on the attractive van der Waals forces for the alpha-SiC/H2O/alpha-SiC and alpha-SiC/H2O/LGG polar solvent based systems are presented and discussed. The rheological parameters including pH, zeta potential, shear rate, shear stress and viscosity that alter the dispersion mechanisms are also presented and discussed. The concurrence of the experimental analysis with the mathematical modeling is also presented. The rheological analysis in these systems for determining of the optimum amounts of dispersant, binder, plasticizer and solids loading using the Krieger-Dougherty fit and Liu's model are presented and discussed. Alpha-SiC/H2O/alpha-SiC and alpha-SiC/H2O/LGG polar solvent based samples were also fabricated to test for an application area of nano-bio technology: A novel nano and micro porous materials fabrication process. Porous materials are used for a variety of applications including insulation, filtration, catalytic substrates, textiles and consumer goods and accounts for billions of dollars in sales annually. Results from the alpha-SiC/H2O/alpha-SiC and alpha-SiC/H2O/LGG polar solvent based slip and freeze cast samples and their characterization using digital and electron microscopy are presented and discussed. Finally, the green and sintered density, porosity and strength of the alpha-SiC/H2O/alpha-SiC and alpha-SiC/H2O/LGG polar solvent based dispersion samples are determined and discussed. / Ph. D.