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Membrane fouling limits the performance of membrane distillation (MD) and its application to seawater brine treatment. Silica fouling is considered one of the most complex type of fouling. In this study, we evaluated the flux decline and fouling ratio due to colloidal silica fouling in direct-contact MD and characterized the fouled membranes. We also tested the efficacy of high flow-rate water flushing for the restoration of flux after fouling. The formation and removal of silica scaling were monitored in real-time with optical coherence tomography (OCT). Our work demonstrated that fouling formation is influenced by silica particle size, feed temperature, salinity, and flow rate. Notably, silica formed cake-layer fouling on the MD membranes. Smaller silica particle size resulted in a higher flux decline and a denser cake layer. A higher feed temperature resulted in a higher flux, but more severe fouling. We also found that fouling was minimized at an optimal flow rate and salinity did not significantly affect fouling formation. OCT monitoring showed that silica fouling deposited on the membrane surface and evaluated the effect of each cleaning strategies on the cake layer. This comprehensive investigation provides valuable insights for the development of silica fouling control strategies in MD. © 2022 Elsevier B.V.

The impact of the use of sand treated with Colloidal Silica (CS) on a model 80 m high-earthfill dam was assessed through numerical modelling. The hydro-mechanical properties of the CS-Treated soil were taken from a previous laboratory study. Different strategies of treatment placement were studied, with increasing volumetric fractions of the dam being replaced by the treated material. Staged construction of the earthwork was simulated to evaluate the horizontal and vertical displacements at critical points within the dam. Different kinematics have been observed, depending on the quantities of CS-Treated material included in the soil structure. Moreover, the use of the treated soil was beneficial in terms of water outflow and upstream slope stability, in correspondence with different water reservoir levels. Different strategic patterns of CS-Treated sand placement are proposed herein to fully exploit the storage capacity of the dam, optimizing its stability. © 2022 American Society of Civil Engineers (ASCE). All rights reserved., Postprint (published version)

As society moves towards decarbonisation, it is important to assess the hydromechanical behaviour of binders that could offer a low-carbon alternative to Portland cement in ground improvement technologies. This work considers two such alternatives: one still largely unexplored (metakaolin-based geopolymers) and a better known one (colloidal silica). Results from unconfined compressive strength, permeability tests, undrained monotonic and cyclic triaxial tests on granular soils (sand and silty sand) treated with those two binders are presented and discussed, emphasizing similarities and differences with the response of similar soils treated with other conventional and unconventional binders. Effects of silt content, curing conditions and soil/binder ratios are examined. Both colloidal silica and metakaolin-based geopolymer significantly improve the mechanical properties of the treated soils, although the geopolymer results in a stronger and stiffer material. Both treatments reduce much the permeability of the treated soil, but the reduction achieved with colloidal silica is larger., Peer Reviewed, Postprint (author's final draft)

Nano-silica is an important admixture for ultra-high performance concrete (UHPC). However, complex production process and agglomeration problem of conventional nano-silica significantly limit its application in UHPC. In this study, a novel highly dispersed colloidal olivine nano-silica (C-OnS) is developed. The properties of C-OnS are characterized with laser light scattering, nuclear magnetic resonance and zeta-potential. The C-OnS is applied in UHPC to enhance the cement hydration and reduce the viscosity, while a commercial sol-gel colloidal nano-silica (C-nS) is used as a reference. The effects of C-OnS and C-nS on UHPC are investigated by calorimetry, thermal gravimetry, 29Si and 27Al nuclear magnetic resonance, nitrogen physisorption and mercury intrusion porosimeter. The results show that the performance of UHPC is enhanced by C-OnS at early ages thanks to its higher silanol content, surface area and dispersibility. The advantages of highly dispersive, strong pozzolanic reactivity and tailorable particle size provide new possibilities for application of C-OnS in cement-based materials.

Acid phosphatase (APase) was immobilized in discrete mesospaces of an assembly of silica nanoparticles (SiO_2NPA) to be used as a heterogeneous catalyst for the hydrolysis of organophosphates often found as pesticide residues in agricultural products. APase immobilized in ......

Acid phosphatase (APase) was immobilized in discrete mesospaces of an assembly of silica nanoparticles (SiO_2NPA) to be used as a heterogeneous catalyst for the hydrolysis of organophosphates often found as pesticide residues in agricultural products. APase immobilized in ......

Los depósitos de relaves presentan características geotécnicas que los hacen susceptibles de sufrir falla por licuefacción, por lo que las implicaciones de riesgo de este rasgo sólo se han apreciado en su totalidad recientemente. Por ello, es de interés actual estudiar las posibles técnicas de remediación de los depósitos existentes, centrándose en las posibilidades de tratamiento de los relaves mediante inyecciones por permeación. La tesis comienza presentando una visión general de los métodos de manejo de residuos y de las propiedades geotécnicas de los depósitos. Además, se presta especial atención a la permeabilidad mediante la ecuación propuesta por Chapuis y Aubertin (2003) y evaluada a partir de una base de datos de propiedades de relaves proporcionada por el Instituto Geológico y Minero de España. En consecuencia, se recalibra la ecuación original y se verifica utilizando los valores de permeabilidad de otros estudios publicados. A continuación, se revisan los posibles métodos de tratamiento del terreno adaptados a los relaves, divididos en tres grandes categorías: densificación, consolidación y tratamientos químicos. A continuación, se determina que el método de inyección por permeación es el más adecuado. A través de la evaluación de dos productos de sílice coloidal MP320 y MP325, aplicadas a un caso basado en la presa de Merriespruit, se obtienen los resultados de factor de seguridad, tiempos de ejecución y costo total de operación. A partir de los resultados obtenidos, se puede abrir la puerta a futuros estudios aplicados a la remediación de depósitos de relaves mediante tratamiento de inyección por permeación, Tailing deposits present geotechnical characteristics which make them susceptible to liquefaction flow failure, hence the risk implications of this trait have only been recently appreciated in full. It is therefore of current interest to study possible remediation techniques for existing deposits. This dissertation contributes to this end by focusing on the possibilities of tailing treatment by permeation of cementing agents. The thesis starts by presenting an overview of tailing disposal methods and geotechnical properties of tailing deposits. Furthermore, special attention is paid to permeability by examining the equations proposed by Chapuis and Aubertin (2003) and evaluated using a database of tailings properties provided by the Geology and Mine Institute of Spain. Consequently, the original equation is recalibrated and then verified using permeability values from other published studies. Possible ground treatment methods for tailings are then reviewed in three broad categories: densification, consolidation, and chemical treatments. It is then determined that permeation grouting method is the best adapted. Pre-design and evaluation of ground improvement treatment for a tailing dam are then carried on for two colloidal silica products (MP320 and MP325) in a case comparable to the Merriespruit tailing dam, which failed by overtopping-induced liquefaction. Through the evaluation of two colloidal silica products MP320 and MP325, applied to a case based on the Merriespruit dam, the safety factor results are then obtained and so the time and cost of operation. From these obtained results, a new door can be opened to future studies applied to the remediation of tailings deposits by permeation injection treatments., Els dipòsits de relaves presenten característiques geotècniques que els fan susceptibles de patir falla per liqüefacció, de manera que les implicacions de risc d'aquest tret només s'han apreciat en la seva totalitat recentment. Per això, és d'interès actual estudiar les possibles tècniques de remediació dels dipòsits existents, centrant-se en les possibilitats de tractament dels relaves mitjançant injeccions per permeació. La tesi comença presentant una visió general dels mètodes de maneig de residus i de les propietats geotècniques dels dipòsits. A més, es presta especial atenció a la permeabilitat mitjançant l'equació proposada per Chapuis i Aubertin (2003) i avaluada a partir d'una base de dades de propietats de relaves proporcionada per l'Institut Geològic i Miner d'Espanya. En conseqüència, es recalibra l'equació original i es verifica utilitzant els valors de permeabilitat d'altres estudis publicats. A continuació, es revisen els possibles mètodes de tractament del terreny adaptats als relaves, dividits en tres grans categories: densificació, consolidació i tractaments químics. A continuació, es determina que el mètode d'injecció per permeació és el més adequat. A través de l'avaluació de dos productes de sílice col·loïdal MP320 i MP325, aplicades a un cas basat en la presa de Merriespruit, s'obtenen els resultats de factor de seguretat, temps d'execució i cost total d'operació. A partir dels resultats obtinguts, es pot obrir la porta a futurs estudis aplicats a la remediació de dipòsits de relaves mitjançant tractament d'injecció per permeació.

There is a long-lasting uncertainty as to the structure of the metal oxide/water interface. Various structures have especially been invoked to rationalize the seemingly anomalous silica/water interface. But, none of them seems to be approved in a quantitative and systematic way. We show that the concentration ratio of monovalent counterions and coions around colloidal silica spheres, as detected by the cryo-XPS technique, follows fundamental theoretical predictions of either Boltzmann or Donnan distribution. It is suggested that the reason of the dual response is the formation of the swelling gel layer on the silica surface due to its longer contact with water.

There is a long-lasting uncertainty as to the structure of the metal oxide/water interface. Various structures have especially been invoked to rationalize the seemingly anomalous silica/water interface. But, none of them seems to be approved in a quantitative and systematic way. We show that the concentration ratio of monovalent counterions and coions around colloidal silica spheres, as detected by the cryo-XPS technique, follows fundamental theoretical predictions of either Boltzmann or Donnan distribution. It is suggested that the reason of the dual response is the formation of the swelling gel layer on the silica surface due to its longer contact with water.

The main challenge in scheelite flotation lies in the contamination of the concentrate by other calcium-bearing minerals, mainly calcite. To remedy this problem, sodium silicate is frequently used as a depressant. According to the literature, one hypothesis for the mechanism of water glass consists in its absorption onto calcite through colloidal silica formation, preventing hydrophobization by the collector. This short communication presents research conducted on the direct use of colloidal silica as a depressant in scheelite flotation. Colloidal silica is shown to have an impact on scheelite flotation, especially by depressing silicates.

type:Journal Article, Synthesis of fullerene (C60)-tethered polymer-grafted silica and colloidal crystallization of the particles was investigated. The particles were prepared by the reaction of C60 with 4-azidobenzoyl groups introduced in poly(methyl methacrylate-co-2-hydroxyethyl methacrylate), followed by esterification of 2-hydroxyethyl metharylate moieties with 4-azidobenzoyl chloride and grafting onto colloidal silica. The reaction afforded bindings of C60 in the range from 0.44 × 104 to 1.71 × 104 molecules/particle. The C60 amounts did not monotonously increase with 4-azidobenzoyl group on the particles, but decreased with mole fraction of methyl methacrylate in the copolymer. Colloidal crystallizations of the C60-tethered silica particles were observed in acetonitrile with critical volume fractions in the range from 0.018 to 0.024. Inter-sphere distances in the colloidal crystals were consistent with calculated values on assumption of face-centered cubic-closed packing, and then it was suggested that the crystallization took place due to electrostatic repulsion between the particles.

The influence of two different types of colloidal silica (CS) nanoparticles in a main pullulan coating on bi-oriented polypropylene (BOPP) was evaluated in this work with the goal of exploring new and more advantageous applications in the food packaging sector. It was observed that the addition of the nanoparticles did not affect the friction properties of the pristine pullulan coating, with the static and kinetic coefficient mean values being 0.35 and 0.22, respectively. An improvement in the barrier properties against O2 and CO2 was observed for all the tested nanocomposite coatings. The best performance was provided by the particles with the highest surface area (750 m2 g-1) (O2TR ~30 mL m-2 24 h-1 and CO2TR ~80 mL m-2 24 h-1 at 23 °C under dry conditions) compared to the pristine pullulan-coated BOPP (O2TR ~480 mL m-2 24 h-1 and CO2TR ~1245 mL m-2 24 h-1). Noteworthy, the change in the permeability properties ultimately yielded a decrease of the CO2/O2 selectivity towards 1. The addition of CS nanoparticles did not modify the optical attributes of the pullulan coating, with the final haze values being approximately 1.5% for all nanocomposite layers. The wettability of the final coatings was influenced by the addition of the CS nanoparticles, with a remarkable decrease of the water contact angle to ~19° for the formulation loaded with the lowest concentration of silica nanoparticles that have the smallest size and the highest surface area. The potential application of the pullulan-CS coatings for MAP-packaged fruit and vegetables is suggested.

The colloidal stability of a model paper coating dispersion consisting of silica particles, Pluronic F127, starch and glycerol was studied with respect to PF127 temperature responsiveness and its adsorption on the silica surface. Rheological characterization of this system in order to extract structural information for the wet suspension state was accomplished in terms of rotational tests. The analysis, done by Krieger-Dougherty model and the elastic floc model for all flow curves at three different temperatures, 20 degrees C, 25 degrees C and 30 degrees C, and at different particle volume fractions (phi between 0 and 0.31), revealed that the structure of the system changes. Two regions with different behaviour and a plateau region at particle volume fraction of phi similar to 0.16 were observed. At phi <= 0.16 temperature was affecting the suspension structure. By rising the temperature the well dispersed suspension at 20 degrees C transformed to flocculated one, where the higher the temperature was, more open floc structures were detected in terms of degree of flocculation parameter, C-fp, but at the same time with increasing the particle concentration the flocs got denser according to the calculated. At phi >= 0.16, there were not detected major structural differences by changing temperature or particle concentration. At phi similar to 0.16 a plateau in yield stress values was observed. The behaviour of the investigated model coating suspension was discussed in terms of shear stresses and C-fp.

Understanding of the interactions between particles and the substrate is important for successful sol-gel deposition of thin films. We have studied the deposition of silica nanoparticles on alumina coated surfaces in aqueous electrolytes by optical reflectometry (OR) and a quartz crystal microbalance with dissipation (QCM-D). The deposition of negatively charged silica nanoparticles on positively charged alumina was primarily controlled by the electric diffuse double layer interactions between the substrate and the deposited particles, modulated by the counter-ion release. The build-up of a negative charge on the positively charged substrate resulted in a decrease in the deposition rate with increasing surface coverage. Higher surface coverage of silica nanoparticles was obtained at low pH than at high pH conditions, due to reduced electric diffuse double layer repulsion between the silica nanoparticles. The deposition was enhanced at high pH by increasing the concentration of NaCl due to compression of the electric diffuse double layer. In particular, the repulsion between the silica nanoparticles was efficiently screened at a concentration of NaCl higher than 100 mM and thick silica layers could be deposited at pH = 6 and 8., AuthorCount:7

A set of four reference materials for the detection and quantification of silica nanoparticles (NPs) in food was produced as a proof of principle exercise. Neat silica suspensions were ampouled, tested for homogeneity and stability, and characterized for total silica content as well as particle diameter by dynamic light scattering (DLS), electron microscopy (EM), gas-phase electrophoretic molecular mobility analysis (GEMMA), and field-flow fractionation coupled with an inductively coupled mass spectrometer (FFF-ICPMS). Tomato soup was prepared from ingredients free of engineered nanoparticles and was spiked at two concentration levels with the silica NP suspension. Homogeneity of these materials was found sufficient to act as reference materials and the materials are sufficiently stable to allow long-term storage and distribution at ambient temperature, providing proof of principle of the feasibility of producing liquid food reference materials for the detection of nanoparticles. The spiked soups were characterized for particle diameter by EM and FFF-ICPMS (one material only), as well as for the total silica content. Although questions regarding the trueness of the results from EM and FFF-ICPMS procedures remain, the data obtained indicate that even assigning values should eventually be feasible. The materials can therefore be regarded as the first step towards certified reference materials for silica nanoparticles in a food matrix.

This thesis is about using nuclear magnetic resonance (NMR) spectroscopy for studying soft materials. Soft materials may be encountered everyday by most readers of this thesis, for example when taking a shower or watching TV. The usefulness of these materials originates from them being soft yet, at the same time, having some kind of a structure. The characteristic length scale of those structures is often on the order of nanometers (10-9 m) and the structure can respond to various external stimuli such as temperature, electric and magnetic fields, or the presence of interfaces. NMR spectroscopy excels when studying soft materials because it is a non-invasive technique with a large spectral resolution. Moreover, different NMR methods allow us to study local molecular dynamics or longer-range translational diffusion. Understanding those latter aspects is very important for the development of dynamic and responsive materials. Papers I-III present our work on assessing molecular adsorption on interfaces in colloidal dispersions. Here, carbon nanotubes (CNTs) or silica particles were the colloidal substrates to which proteins, polymers or surfactants adsorbed. Papers IV-VI concern ionic mobility in liquid crystals (LCs). The influence of material structure on, for example, the anisotropy of diffusion or on the association/dissociation of ions was studied in several LC phases., QC 20110225

This thesis is about using nuclear magnetic resonance (NMR) spectroscopy for studying soft materials. Soft materials may be encountered everyday by most readers of this thesis, for example when taking a shower or watching TV. The usefulness of these materials originates from them being soft yet, at the same time, having some kind of a structure. The characteristic length scale of those structures is often on the order of nanometers (10-9 m) and the structure can respond to various external stimuli such as temperature, electric and magnetic fields, or the presence of interfaces. NMR spectroscopy excels when studying soft materials because it is a non-invasive technique with a large spectral resolution. Moreover, different NMR methods allow us to study local molecular dynamics or longer-range translational diffusion. Understanding those latter aspects is very important for the development of dynamic and responsive materials. Papers I-III present our work on assessing molecular adsorption on interfaces in colloidal dispersions. Here, carbon nanotubes (CNTs) or silica particles were the colloidal substrates to which proteins, polymers or surfactants adsorbed. Papers IV-VI concern ionic mobility in liquid crystals (LCs). The influence of material structure on, for example, the anisotropy of diffusion or on the association/dissociation of ions was studied in several LC phases., QC 20110225

This thesis is about using nuclear magnetic resonance (NMR) spectroscopy for studying soft materials. Soft materials may be encountered everyday by most readers of this thesis, for example when taking a shower or watching TV. The usefulness of these materials originates from them being soft yet, at the same time, having some kind of a structure. The characteristic length scale of those structures is often on the order of nanometers (10-9 m) and the structure can respond to various external stimuli such as temperature, electric and magnetic fields, or the presence of interfaces. NMR spectroscopy excels when studying soft materials because it is a non-invasive technique with a large spectral resolution. Moreover, different NMR methods allow us to study local molecular dynamics or longer-range translational diffusion. Understanding those latter aspects is very important for the development of dynamic and responsive materials. Papers I-III present our work on assessing molecular adsorption on interfaces in colloidal dispersions. Here, carbon nanotubes (CNTs) or silica particles were the colloidal substrates to which proteins, polymers or surfactants adsorbed. Papers IV-VI concern ionic mobility in liquid crystals (LCs). The influence of material structure on, for example, the anisotropy of diffusion or on the association/dissociation of ions was studied in several LC phases., QC 20110225

This thesis is about using nuclear magnetic resonance (NMR) spectroscopy for studying soft materials. Soft materials may be encountered everyday by most readers of this thesis, for example when taking a shower or watching TV. The usefulness of these materials originates from them being soft yet, at the same time, having some kind of a structure. The characteristic length scale of those structures is often on the order of nanometers (10-9 m) and the structure can respond to various external stimuli such as temperature, electric and magnetic fields, or the presence of interfaces. NMR spectroscopy excels when studying soft materials because it is a non-invasive technique with a large spectral resolution. Moreover, different NMR methods allow us to study local molecular dynamics or longer-range translational diffusion. Understanding those latter aspects is very important for the development of dynamic and responsive materials. Papers I-III present our work on assessing molecular adsorption on interfaces in colloidal dispersions. Here, carbon nanotubes (CNTs) or silica particles were the colloidal substrates to which proteins, polymers or surfactants adsorbed. Papers IV-VI concern ionic mobility in liquid crystals (LCs). The influence of material structure on, for example, the anisotropy of diffusion or on the association/dissociation of ions was studied in several LC phases., QC 20110225

Projecte final de màster oficial fet en col.laboració amb Bauhaus's University., Català: L’estudi aquí presentat pretén millorar les qualitats dels àrids reciclats mitjançant un tractament superficial. La metodologia desenvolupada ha posat en pràctica diferents mètodes d’impregnació utilitzant àrids reciclats de diferent procedència i productes d’impregnació altament putzolànics. Avaluats cadascun dels mètodes d’impregnació estudiats, l’assaig dinàmic de doble impregnació ha estat el més efectiu, obtenint així resultats satisfactoris. Aquest assaig realitzat engloba dos tipus d’impregnacions, primer una impregnació amb hidròxid càlcic i després una impregnació amb la sílice col.loïdal, un material altament reactiu amb partícules entre 10 i 20 nm, totalment amorf. Aquesta tècnica d’impregnació prèviament citada, millora de forma clara les propietats mecàniques dels àrids reciclats de formigó. Aquest increment de resistència, mesurat mitjançant l’assaig crushing factor, ha sigut conseqüència directa del desenvolupament de la reacció putzolànica i de la funció de la sílice col.loïdal com a filler. A més, amb el fi de comparar la els resultat obtinguts, també s’han realitzat assajos paral.lels amb àrids naturals procedents de cantera., English: The study here presented aims to improve the recycled aggregates quality through surface treatment. The developed methodology has put into practice different impregnation methods using recycled aggregates of various origins and highly pozzolanic impregnation products. After evaluating each of the studied impregnation methods, the rotating double impregnation test has been the most effective, providing with the most successful results. This test included two types of impregnations: a calcium hydroxide impregnation first and afterwards,a colloidal silica impregnation. The colloidal silica is a highly reactive material with a particle size between 10 and 20 nm, totally amorphous. The impregnation technique aforementioned clearly improves the mechanical properties of the recycled concrete aggregates. This increase of resistance, evaluated through the crushing factor test, has been a direct consequence of the pozzolanic reaction developed, and the function of colloidal silica as filler. In addition, in order to compare the results obtained, parallel tests with natural aggregates from quarry were also carried out.

The complex nature of the structure of the anticoagulant warfarin is reflected in the diversity of binding modes observed in warfarin-protein recognition systems. A series of theoretical, H-1-NMR and steady state and time resolved fluorescence spectroscopic studies, have been used to establish correlations between the molecular environment provided by various solvent systems and the relative concentrations of the various members of warfarin's ensemble of isomers. A consequence of these observations is that the judicious choice of solvent system or molecular environment of warfarin allows for manipulation of the position of the equilibrium between isomeric structures such as the hemiacetal and open phenol-keto forms, the latter even possible in a deprotonated form, where in each case unique spectroscopic properties are exhibited by the respective structures. Collectively, warfarin's capacity to adapt its structure as a function of environment in conjunction with the fluorescence behaviours of the various isomers together provide an environment-dependent molecular switch with reporter properties, which allows for the simultaneous detection of warfarin in different states with lifetimes spanning the range <0.10-5.5 ns. These characteristics are here used to examine warfarin binding domains in a series of materials (solvents, protein, inorganic matrix and synthetic polymer). Moreover, these studies demonstrate the potential for using warfarin, or other switchable analogues thereof, as a tool for studying molecular level characteristics, for example local dielectricity.

The complex nature of the structure of the anticoagulant warfarin is reflected in the diversity of binding modes observed in warfarin–protein recognition systems. A series of theoretical, 1H-NMR and steady state and time resolved fluorescence spectroscopic studies, have been used to establish correlations between the molecular environment provided by various solvent systems and the relative concentrations of the various members of warfarin's ensemble of isomers. A consequence of these observations is that the judicious choice of solvent system or molecular environment of warfarin allows for manipulation of the position of the equilibrium between isomeric structures such as the hemiacetal and open phenol-keto forms, the latter even possible in a deprotonated form, where in each case unique spectroscopic properties are exhibited by the respective structures. Collectively, warfarin's capacity to adapt its structure as a function of environment in conjunction with the fluorescence behaviours of the various isomers together provide an environment-dependent molecular switch with reporter properties, which allows for the simultaneous detection of warfarin in different states with lifetimes spanning the range < 0.10–5.5 ns. These characteristics are here used to examine warfarin binding domains in a series of materials (solvents, protein, inorganic matrix and synthetic polymer). Moreover, these studies demonstrate the potential for using warfarin, or other switchable analogues thereof, as a tool for studying molecular level characteristics, for example local dielectricity. Copyright © 2010 John Wiley & Sons, Ltd.

Background The adsorption of bovine serum albumin (BSA) onto mesoporous silica spheres (MPS) synthesized from silica colloids was studied employing real time in situ measurements. The stabilities of the BSA at different pH values, their isoelectric points and zeta potentials were determined in order to probe the interactions between the protein and the mesoporous silica. Results The pore size of MPS was designed for protein, and this, coupled with an in depth understanding of the physico-chemical characteristics of the protein and MPS has yielded a better binding capacity and delivery profile. The adsorption isotherm at pH 4.2 fitted the Langmuir model and displayed the highest adsorption capacity (71.43 mg mL-1 MPS). Furthermore, the delivery rates of BSA from the MPS under physiological conditions were shown to be dependent on the ionic strength of the buffer and protein loading concentration. Conclusion Economics and scale-up considerations of mesoporous material synthesized via destabilization of colloids by electrolyte indicate the scaleability and commercial viability of this technology as a delivery platform for biopharmaceutical applications.

Surface characterization and foaming studies were carried out with nine industrially manufactured, colloidal silica dispersions with particles sizes from 5-40 nm. All the silica sols produced transient foams with short decay times and the dynamic foam generation (foamability) was found to vary according to the sol type with the greatest foamability occurring for the hydrophobically modified sol and the deionized hydrophilic sol. However, it was found that improved foamability of all the sols could be achieved by changing the pH to within the region of the pH(pzc) which corresponds to the region of lowest hydrophilicity. An increase in pH (and build-up of negative charge) enhances the surface hydrophilicity and caused a decrease in foamability. In addition, for selected hydrophilic sols, it was shown that the foamability (a) increased with decrease in particle size (within the 6-40 nm range) and (b) increased with particle concentration (within the range of 1-15 wt%). Overall, it was concluded that the foamability was primary controlled by hydrophobicity (and hence by pH) and also by the particle concentration, the particle size and the degree of agglomeration., QC 20110707

Thermal/hydrothermal stable silicalite-1 zeolite with high-porosity mesopores analogous to the crystal morphology has been synthesized by using large porous carbon (10-20 nm) as hard template originated from colloidal silica., authorCount :7

Nanotechnology offers the ability to create new material systems as well as dramatically improve the performance of existing systems through the introduction of new physical mechanisms not found in the original material. Nanomaterial modification of fibers and textiles has been used to increase fabric performance in areas ranging from biocidal capability to stain resistance and water repellency. In this study we use scalable methods to modify nanoscale features on organic materials to probe the potential for increased impact energy absorption and mechanical properties in composite applications. Specifically atmospheric plasma treatment and wetchemistry methods were utilized to create nanoscale chemical scaffolding and surface textures on model polyethylene films and fibers. This approach was successful at modifying the surfaces of these fibers and scaling to high speed web manufacturing is easily envisioned., See also ADM002075. Presented at the Army Science Conference (25th) held in Orlando, FL on 27-30 November 2006. The original document contains color images.

Denna avhandling presenterar experimentella studier av polyelektrolytadsorption på motsatt laddade ytor, där substrat av både kiseloxid och blekt barrsulfatmassa har använts. Ett huvudsakligt syfte med denna forskning var att karaktärisera konformationen hos adsorberade skikt av katjonisk polyakrylamid (CPAM) i jämförelse med katjonisk dextran (Cdextran) och relatera denna information till inbindningskapaciteten av kolloidal kiselsyra. Ett andra syfte i denna avhandling var att studera kinetiken för sekventiell adsorption av polyamidamin epiklorhydrin (PAE) och karboxymetyl cellulosa (CMC) på massafibrer och att bestämma adsorptionsisotermer för deponering av polyelektrolyter skikt för skikt på massafibrer. Adsorptionen av CPAM på kiseloxidytor studeras med stagnationspunkts-reflektometri och kvartskristalls-mikrogravimetri för att bestämma adsorptionskinetiken och mättnadsadsorptionens beroende av polyelektrolytens laddningstäthet, pH och NaCl koncentration. Konformationen hos adsorberade skikt av CPAM och Cdextran bestämdes både före och efter sekundär tillsats av kolloidal kiselsyra (CS) och adsorptionen av CS kvantifierades också som funktion av yttäckningen av polyelektrolyt. Resultaten indikerar att laddningstätheten hos CPAM kontrollerar den adsorberade mängden på kiseloxidytor vid låga NaCl koncentrationer. Både adsorptionen av CPAM och Cdextran på kiseloxid visades vara effektiv i NaCl koncentrationer upp till 1 M, vilket indikerar ett signifikant bidrag av icke-jonisk interaktion mellan polyelektrolyterna och kiseloxid. Adsorptionen av CS var högre på föradsorberad CPAM än Cdextran. Konformationen hos de adsorberade skikten efter tillsats av CS sågs expandera signifikant för skikt baserade på CPAM medan skikt av Cdextran vid låga salthalter verkade återta sin konformation efter en temporär expansion. I den andra delen av avhandlingen studerades sekventiell adsorption av PAE och CMC på massafibrer. Adsorptionsisotermer skikt för skikt på avkryllad massa vis, This thesis presents experimental studies of polyelectrolyte adsorption on oppositely charged surfaces, where substrates of both silica and bleached softwood kraft pulp were used. A major aim of this research was to characterise the conformation of adsorbed layers of cationic polyacrylamide (CPAM), in comparison to cationic dextran (Cdextran), and relate this information to the binding capacity of colloidal silica. A second aim in this thesis was to study the kinetics of the sequential adsorption of polyamide epichlorohydrine (PAE) and carboxymethyl cellulose (CMC) on pulp fibres, and to determine the adsorption isotherms for the layer-by-layer deposition of polyelectrolytes on pulp fibres. The adsorption of CPAM on silica surfaces was studied using stagnation point adsorption reflectometry and quartz crystal microgravimetry to determine its adsorption kinetics as well as the dependencies of polyelectrolyte charge densities, pH, and NaCl concentration on saturation adsorption. The conformation of adsorbed layers of CPAM and Cdextran, analysed in terms of amount of water and layer thickness, was determined both before and after the secondary adsorption of colloidal silica (CS), and the adsorption of CS was also quantified as a function of the surface coverage of the polyelectrolyte. Results indicate that the charge density of CPAM controlled the amount of the polyelectrolyte adsorbed on silica surfaces at low NaCl concentrations. The adsorption of both CPAM and Cdextran on silica was shown to be effective at up to 1 M NaCl concentrations, which indicates that non-ionic interactions between the polyelectrolytes and silica contribute significantly. CS adsorption was higher on pre-adsorbed CPAM than on Cdextran. The conformation of the adsorbed layer after CS addition was seen to expand significantly in CPAM-based layers, while the Cdextran layer appeared to restore its conformation after a temporary expansion at low salt concentrations. In the second part of the thesis, QC 20101112

Denna avhandling presenterar experimentella studier av polyelektrolytadsorption på motsatt laddade ytor, där substrat av både kiseloxid och blekt barrsulfatmassa har använts. Ett huvudsakligt syfte med denna forskning var att karaktärisera konformationen hos adsorberade skikt av katjonisk polyakrylamid (CPAM) i jämförelse med katjonisk dextran (Cdextran) och relatera denna information till inbindningskapaciteten av kolloidal kiselsyra. Ett andra syfte i denna avhandling var att studera kinetiken för sekventiell adsorption av polyamidamin epiklorhydrin (PAE) och karboxymetyl cellulosa (CMC) på massafibrer och att bestämma adsorptionsisotermer för deponering av polyelektrolyter skikt för skikt på massafibrer. Adsorptionen av CPAM på kiseloxidytor studeras med stagnationspunkts-reflektometri och kvartskristalls-mikrogravimetri för att bestämma adsorptionskinetiken och mättnadsadsorptionens beroende av polyelektrolytens laddningstäthet, pH och NaCl koncentration. Konformationen hos adsorberade skikt av CPAM och Cdextran bestämdes både före och efter sekundär tillsats av kolloidal kiselsyra (CS) och adsorptionen av CS kvantifierades också som funktion av yttäckningen av polyelektrolyt. Resultaten indikerar att laddningstätheten hos CPAM kontrollerar den adsorberade mängden på kiseloxidytor vid låga NaCl koncentrationer. Både adsorptionen av CPAM och Cdextran på kiseloxid visades vara effektiv i NaCl koncentrationer upp till 1 M, vilket indikerar ett signifikant bidrag av icke-jonisk interaktion mellan polyelektrolyterna och kiseloxid. Adsorptionen av CS var högre på föradsorberad CPAM än Cdextran. Konformationen hos de adsorberade skikten efter tillsats av CS sågs expandera signifikant för skikt baserade på CPAM medan skikt av Cdextran vid låga salthalter verkade återta sin konformation efter en temporär expansion. I den andra delen av avhandlingen studerades sekventiell adsorption av PAE och CMC på massafibrer. Adsorptionsisotermer skikt för skikt på avkryllad massa vis, This thesis presents experimental studies of polyelectrolyte adsorption on oppositely charged surfaces, where substrates of both silica and bleached softwood kraft pulp were used. A major aim of this research was to characterise the conformation of adsorbed layers of cationic polyacrylamide (CPAM), in comparison to cationic dextran (Cdextran), and relate this information to the binding capacity of colloidal silica. A second aim in this thesis was to study the kinetics of the sequential adsorption of polyamide epichlorohydrine (PAE) and carboxymethyl cellulose (CMC) on pulp fibres, and to determine the adsorption isotherms for the layer-by-layer deposition of polyelectrolytes on pulp fibres. The adsorption of CPAM on silica surfaces was studied using stagnation point adsorption reflectometry and quartz crystal microgravimetry to determine its adsorption kinetics as well as the dependencies of polyelectrolyte charge densities, pH, and NaCl concentration on saturation adsorption. The conformation of adsorbed layers of CPAM and Cdextran, analysed in terms of amount of water and layer thickness, was determined both before and after the secondary adsorption of colloidal silica (CS), and the adsorption of CS was also quantified as a function of the surface coverage of the polyelectrolyte. Results indicate that the charge density of CPAM controlled the amount of the polyelectrolyte adsorbed on silica surfaces at low NaCl concentrations. The adsorption of both CPAM and Cdextran on silica was shown to be effective at up to 1 M NaCl concentrations, which indicates that non-ionic interactions between the polyelectrolytes and silica contribute significantly. CS adsorption was higher on pre-adsorbed CPAM than on Cdextran. The conformation of the adsorbed layer after CS addition was seen to expand significantly in CPAM-based layers, while the Cdextran layer appeared to restore its conformation after a temporary expansion at low salt concentrations. In the second part of the thesis, QC 20101112

Denna avhandling presenterar experimentella studier av polyelektrolytadsorption på motsatt laddade ytor, där substrat av både kiseloxid och blekt barrsulfatmassa har använts. Ett huvudsakligt syfte med denna forskning var att karaktärisera konformationen hos adsorberade skikt av katjonisk polyakrylamid (CPAM) i jämförelse med katjonisk dextran (Cdextran) och relatera denna information till inbindningskapaciteten av kolloidal kiselsyra. Ett andra syfte i denna avhandling var att studera kinetiken för sekventiell adsorption av polyamidamin epiklorhydrin (PAE) och karboxymetyl cellulosa (CMC) på massafibrer och att bestämma adsorptionsisotermer för deponering av polyelektrolyter skikt för skikt på massafibrer. Adsorptionen av CPAM på kiseloxidytor studeras med stagnationspunkts-reflektometri och kvartskristalls-mikrogravimetri för att bestämma adsorptionskinetiken och mättnadsadsorptionens beroende av polyelektrolytens laddningstäthet, pH och NaCl koncentration. Konformationen hos adsorberade skikt av CPAM och Cdextran bestämdes både före och efter sekundär tillsats av kolloidal kiselsyra (CS) och adsorptionen av CS kvantifierades också som funktion av yttäckningen av polyelektrolyt. Resultaten indikerar att laddningstätheten hos CPAM kontrollerar den adsorberade mängden på kiseloxidytor vid låga NaCl koncentrationer. Både adsorptionen av CPAM och Cdextran på kiseloxid visades vara effektiv i NaCl koncentrationer upp till 1 M, vilket indikerar ett signifikant bidrag av icke-jonisk interaktion mellan polyelektrolyterna och kiseloxid. Adsorptionen av CS var högre på föradsorberad CPAM än Cdextran. Konformationen hos de adsorberade skikten efter tillsats av CS sågs expandera signifikant för skikt baserade på CPAM medan skikt av Cdextran vid låga salthalter verkade återta sin konformation efter en temporär expansion. I den andra delen av avhandlingen studerades sekventiell adsorption av PAE och CMC på massafibrer. Adsorptionsisotermer skikt för skikt på avkryllad massa vis, This thesis presents experimental studies of polyelectrolyte adsorption on oppositely charged surfaces, where substrates of both silica and bleached softwood kraft pulp were used. A major aim of this research was to characterise the conformation of adsorbed layers of cationic polyacrylamide (CPAM), in comparison to cationic dextran (Cdextran), and relate this information to the binding capacity of colloidal silica. A second aim in this thesis was to study the kinetics of the sequential adsorption of polyamide epichlorohydrine (PAE) and carboxymethyl cellulose (CMC) on pulp fibres, and to determine the adsorption isotherms for the layer-by-layer deposition of polyelectrolytes on pulp fibres. The adsorption of CPAM on silica surfaces was studied using stagnation point adsorption reflectometry and quartz crystal microgravimetry to determine its adsorption kinetics as well as the dependencies of polyelectrolyte charge densities, pH, and NaCl concentration on saturation adsorption. The conformation of adsorbed layers of CPAM and Cdextran, analysed in terms of amount of water and layer thickness, was determined both before and after the secondary adsorption of colloidal silica (CS), and the adsorption of CS was also quantified as a function of the surface coverage of the polyelectrolyte. Results indicate that the charge density of CPAM controlled the amount of the polyelectrolyte adsorbed on silica surfaces at low NaCl concentrations. The adsorption of both CPAM and Cdextran on silica was shown to be effective at up to 1 M NaCl concentrations, which indicates that non-ionic interactions between the polyelectrolytes and silica contribute significantly. CS adsorption was higher on pre-adsorbed CPAM than on Cdextran. The conformation of the adsorbed layer after CS addition was seen to expand significantly in CPAM-based layers, while the Cdextran layer appeared to restore its conformation after a temporary expansion at low salt concentrations. In the second part of the thesis, QC 20101112

Denna avhandling presenterar experimentella studier av polyelektrolytadsorption på motsatt laddade ytor, där substrat av både kiseloxid och blekt barrsulfatmassa har använts. Ett huvudsakligt syfte med denna forskning var att karaktärisera konformationen hos adsorberade skikt av katjonisk polyakrylamid (CPAM) i jämförelse med katjonisk dextran (Cdextran) och relatera denna information till inbindningskapaciteten av kolloidal kiselsyra. Ett andra syfte i denna avhandling var att studera kinetiken för sekventiell adsorption av polyamidamin epiklorhydrin (PAE) och karboxymetyl cellulosa (CMC) på massafibrer och att bestämma adsorptionsisotermer för deponering av polyelektrolyter skikt för skikt på massafibrer. Adsorptionen av CPAM på kiseloxidytor studeras med stagnationspunkts-reflektometri och kvartskristalls-mikrogravimetri för att bestämma adsorptionskinetiken och mättnadsadsorptionens beroende av polyelektrolytens laddningstäthet, pH och NaCl koncentration. Konformationen hos adsorberade skikt av CPAM och Cdextran bestämdes både före och efter sekundär tillsats av kolloidal kiselsyra (CS) och adsorptionen av CS kvantifierades också som funktion av yttäckningen av polyelektrolyt. Resultaten indikerar att laddningstätheten hos CPAM kontrollerar den adsorberade mängden på kiseloxidytor vid låga NaCl koncentrationer. Både adsorptionen av CPAM och Cdextran på kiseloxid visades vara effektiv i NaCl koncentrationer upp till 1 M, vilket indikerar ett signifikant bidrag av icke-jonisk interaktion mellan polyelektrolyterna och kiseloxid. Adsorptionen av CS var högre på föradsorberad CPAM än Cdextran. Konformationen hos de adsorberade skikten efter tillsats av CS sågs expandera signifikant för skikt baserade på CPAM medan skikt av Cdextran vid låga salthalter verkade återta sin konformation efter en temporär expansion. I den andra delen av avhandlingen studerades sekventiell adsorption av PAE och CMC på massafibrer. Adsorptionsisotermer skikt för skikt på avkryllad massa vis, This thesis presents experimental studies of polyelectrolyte adsorption on oppositely charged surfaces, where substrates of both silica and bleached softwood kraft pulp were used. A major aim of this research was to characterise the conformation of adsorbed layers of cationic polyacrylamide (CPAM), in comparison to cationic dextran (Cdextran), and relate this information to the binding capacity of colloidal silica. A second aim in this thesis was to study the kinetics of the sequential adsorption of polyamide epichlorohydrine (PAE) and carboxymethyl cellulose (CMC) on pulp fibres, and to determine the adsorption isotherms for the layer-by-layer deposition of polyelectrolytes on pulp fibres. The adsorption of CPAM on silica surfaces was studied using stagnation point adsorption reflectometry and quartz crystal microgravimetry to determine its adsorption kinetics as well as the dependencies of polyelectrolyte charge densities, pH, and NaCl concentration on saturation adsorption. The conformation of adsorbed layers of CPAM and Cdextran, analysed in terms of amount of water and layer thickness, was determined both before and after the secondary adsorption of colloidal silica (CS), and the adsorption of CS was also quantified as a function of the surface coverage of the polyelectrolyte. Results indicate that the charge density of CPAM controlled the amount of the polyelectrolyte adsorbed on silica surfaces at low NaCl concentrations. The adsorption of both CPAM and Cdextran on silica was shown to be effective at up to 1 M NaCl concentrations, which indicates that non-ionic interactions between the polyelectrolytes and silica contribute significantly. CS adsorption was higher on pre-adsorbed CPAM than on Cdextran. The conformation of the adsorbed layer after CS addition was seen to expand significantly in CPAM-based layers, while the Cdextran layer appeared to restore its conformation after a temporary expansion at low salt concentrations. In the second part of the thesis, QC 20101112

Denna avhandling presenterar experimentella studier av polyelektrolytadsorption på motsatt laddade ytor, där substrat av både kiseloxid och blekt barrsulfatmassa har använts. Ett huvudsakligt syfte med denna forskning var att karaktärisera konformationen hos adsorberade skikt av katjonisk polyakrylamid (CPAM) i jämförelse med katjonisk dextran (Cdextran) och relatera denna information till inbindningskapaciteten av kolloidal kiselsyra. Ett andra syfte i denna avhandling var att studera kinetiken för sekventiell adsorption av polyamidamin epiklorhydrin (PAE) och karboxymetyl cellulosa (CMC) på massafibrer och att bestämma adsorptionsisotermer för deponering av polyelektrolyter skikt för skikt på massafibrer. Adsorptionen av CPAM på kiseloxidytor studeras med stagnationspunkts-reflektometri och kvartskristalls-mikrogravimetri för att bestämma adsorptionskinetiken och mättnadsadsorptionens beroende av polyelektrolytens laddningstäthet, pH och NaCl koncentration. Konformationen hos adsorberade skikt av CPAM och Cdextran bestämdes både före och efter sekundär tillsats av kolloidal kiselsyra (CS) och adsorptionen av CS kvantifierades också som funktion av yttäckningen av polyelektrolyt. Resultaten indikerar att laddningstätheten hos CPAM kontrollerar den adsorberade mängden på kiseloxidytor vid låga NaCl koncentrationer. Både adsorptionen av CPAM och Cdextran på kiseloxid visades vara effektiv i NaCl koncentrationer upp till 1 M, vilket indikerar ett signifikant bidrag av icke-jonisk interaktion mellan polyelektrolyterna och kiseloxid. Adsorptionen av CS var högre på föradsorberad CPAM än Cdextran. Konformationen hos de adsorberade skikten efter tillsats av CS sågs expandera signifikant för skikt baserade på CPAM medan skikt av Cdextran vid låga salthalter verkade återta sin konformation efter en temporär expansion. I den andra delen av avhandlingen studerades sekventiell adsorption av PAE och CMC på massafibrer. Adsorptionsisotermer skikt för skikt på avkryllad massa vis, This thesis presents experimental studies of polyelectrolyte adsorption on oppositely charged surfaces, where substrates of both silica and bleached softwood kraft pulp were used. A major aim of this research was to characterise the conformation of adsorbed layers of cationic polyacrylamide (CPAM), in comparison to cationic dextran (Cdextran), and relate this information to the binding capacity of colloidal silica. A second aim in this thesis was to study the kinetics of the sequential adsorption of polyamide epichlorohydrine (PAE) and carboxymethyl cellulose (CMC) on pulp fibres, and to determine the adsorption isotherms for the layer-by-layer deposition of polyelectrolytes on pulp fibres. The adsorption of CPAM on silica surfaces was studied using stagnation point adsorption reflectometry and quartz crystal microgravimetry to determine its adsorption kinetics as well as the dependencies of polyelectrolyte charge densities, pH, and NaCl concentration on saturation adsorption. The conformation of adsorbed layers of CPAM and Cdextran, analysed in terms of amount of water and layer thickness, was determined both before and after the secondary adsorption of colloidal silica (CS), and the adsorption of CS was also quantified as a function of the surface coverage of the polyelectrolyte. Results indicate that the charge density of CPAM controlled the amount of the polyelectrolyte adsorbed on silica surfaces at low NaCl concentrations. The adsorption of both CPAM and Cdextran on silica was shown to be effective at up to 1 M NaCl concentrations, which indicates that non-ionic interactions between the polyelectrolytes and silica contribute significantly. CS adsorption was higher on pre-adsorbed CPAM than on Cdextran. The conformation of the adsorbed layer after CS addition was seen to expand significantly in CPAM-based layers, while the Cdextran layer appeared to restore its conformation after a temporary expansion at low salt concentrations. In the second part of the thesis, QC 20101112

Passive site remediation is a new concept proposed for non-disruptive mitigation of liquefaction risk at developed sites susceptible to liquefaction. It is based on the concept of slow injection of stabilizing materials at the edge of a site and delivery of the stabilizer to the target location using the natural groundwater flow. The purpose of this research was to establish the feasibility of passive site remediation through identification of stabilizing materials, a study of how to design or adapt groundwater flow patterns to deliver the stabilizers to the right place at the right time, and an evaluation of potential time requirements and costs. Stabilizer candidates need to have long, controllable gel times and low viscosities so they can flow into a liquefiable formation slowly over a long period of time. Colloidal silica is a potential stabilizer for passive site remediation because at low concentrations it has a low viscosity and a wide range of controllable gel times of up to about 100 days. Loose Monterey No. 0/30 sand samples (Dr = 22%) treated with colloidal silica grout were tested under cyclic triaxial loading to investigate the influence of colloidal silica grout on the deformation properties. Distinctly different deformation properties were observed between grouted and ungrouted samples. Untreated samples developed very little axial strain after only a few cycles and prior to the onset of liquefaction. Once liquefaction was triggered, large strains occurred rapidly and the samples collapsed within a few additional cycles. In contrast, grouted sand samples experienced very little strain during cyclic loading. What strain accumulated did so uniformly throughout loading and the samples remained intact after cyclic loading. In general, samples stabilized with 20 weight percent colloidal silica experienced very little (less than two percent) strain during cyclic loading. Sands stabilized with 10 weight percent colloidal silica tolerated cyclic loading well

Passive site remediation is a new concept proposed for non-disruptive mitigation of liquefaction risk at developed sites susceptible to liquefaction. It is based on the concept of slow injection of stabilizing materials at the edge of a site and delivery of the stabilizer to the target location using the natural groundwater flow. The purpose of this research was to establish the feasibility of passive site remediation through identification of stabilizing materials, a study of how to design or adapt groundwater flow patterns to deliver the stabilizers to the right place at the right time, and an evaluation of potential time requirements and costs. Stabilizer candidates need to have long, controllable gel times and low viscosities so they can flow into a liquefiable formation slowly over a long period of time. Colloidal silica is a potential stabilizer for passive site remediation because at low concentrations it has a low viscosity and a wide range of controllable gel times of up to about 100 days. Loose Monterey No. 0/30 sand samples (Dr = 22%) treated with colloidal silica grout were tested under cyclic triaxial loading to investigate the influence of colloidal silica grout on the deformation properties. Distinctly different deformation properties were observed between grouted and ungrouted samples. Untreated samples developed very little axial strain after only a few cycles and prior to the onset of liquefaction. Once liquefaction was triggered, large strains occurred rapidly and the samples collapsed within a few additional cycles. In contrast, grouted sand samples experienced very little strain during cyclic loading. What strain accumulated did so uniformly throughout loading and the samples remained intact after cyclic loading. In general, samples stabilized with 20 weight percent colloidal silica experienced very little (less than two percent) strain during cyclic loading. Sands stabilized with 10 weight percent colloidal silica tolerated cyclic loading well

The sol-gel synthesis of silicon nitride powders has been studied. The precursor gels were prepared from a colloidal dispersion of silicon dioxide and sucrose, with mole ratios of reactants, C/SiO2, ranging from 2 to 4. The carboreduction and nitridation processes were performed at temperatures between 1400-1550 degrees C under a dynamic nitrogen atmosphere, with a 4 h hold. The optimum C/SiO2 ratio and temperature for preparation of the Si3N4 powders were selected. For the SiO2-C-N-2 system examined, the boundary temperature between Si3N4 and SiC formation was established, in relation to the amount of carbon introduced.

The sol-gel synthesis of silicon nitride powders has been studied. The precursor gels were prepared from a colloidal dispersion of silicon dioxide and sucrose, with mole ratios of reactants, C/SiO2, ranging from 2 to 4. The carboreduction and nitridation processes were performed at temperatures between 1400-1550 degrees C under a dynamic nitrogen atmosphere, with a 4 h hold. The optimum C/SiO2 ratio and temperature for preparation of the Si3N4 powders were selected. For the SiO2-C-N-2 system examined, the boundary temperature between Si3N4 and SiC formation was established, in relation to the amount of carbon introduced.

Colloidal silica, the production of which has been patented all over the world, has a remarkable application in over a hundred different industrial branches. Laboratory process, which can serve as a basis for an industrial production of this important material, has been developed in this work, solely on the basis of available literature data and personal contacts. A complete characterization of initial, intermediate and final product has been made. Experimental data unambiguously suggest that the quality of the colloidal silica obtained, fully corresponds to the quality of the products commercially available from the leading world companies. This work is devoted to a better understanding of the sorption properties of colloidal silica and solids obtained from it. Accordingly, we intended to fulfill the following goals: to examine the sorption of alkali metals from aqueous solutions, sorption of a numerous organic compounds on the solid materials obtained by coagulation from the colloidal silica, to study the stability of the colloidal silica in the presence of alkali metal ions and, finally, to determine the heat of immersion of powders obtained from colloidal silica. The sorption of alkali metal ions from aqueous solutions on colloidal silica, has been studied at 298 K using the potentiometric titration method. Due to the considerable solubility of the colloidal silica, at the elevated pH values, the limit of the method used had to be determined. The application of the potentiometric titration method has been critically reconsidered with special regard to the literature data concerning the region in which dissolution process is a dominant one. The obtained hysteresis on the sorption-desorption curves, is explained in view of significant solubility of the colloidal silica at the particular pH region. Alkali metal ion selectivity sequence corresponds to the Hofmeister series, i.e. for the cations of the same charge the sorption affinity decreases with the increased hy

Colloidal silica, the production of which has been patented all over the world, has a remarkable application in over a hundred different industrial branches. Laboratory process, which can serve as a basis for an industrial production of this important material, has been developed in this work, solely on the basis of available literature data and personal contacts. A complete characterization of initial, intermediate and final product has been made. Experimental data unambiguously suggest that the quality of the colloidal silica obtained, fully corresponds to the quality of the products commercially available from the leading world companies. This work is devoted to a better understanding of the sorption properties of colloidal silica and solids obtained from it. Accordingly, we intended to fulfill the following goals: to examine the sorption of alkali metals from aqueous solutions, sorption of a numerous organic compounds on the solid materials obtained by coagulation from the colloidal silica, to study the stability of the colloidal silica in the presence of alkali metal ions and, finally, to determine the heat of immersion of powders obtained from colloidal silica. The sorption of alkali metal ions from aqueous solutions on colloidal silica, has been studied at 298 K using the potentiometric titration method. Due to the considerable solubility of the colloidal silica, at the elevated pH values, the limit of the method used had to be determined. The application of the potentiometric titration method has been critically reconsidered with special regard to the literature data concerning the region in which dissolution process is a dominant one. The obtained hysteresis on the sorption-desorption curves, is explained in view of significant solubility of the colloidal silica at the particular pH region. Alkali metal ion selectivity sequence corresponds to the Hofmeister series, i.e. for the cations of the same charge the sorption affinity decreases with the increased hy

Impregnace na bázi silikátů se široce používá k ochraně betonu před agresivním prostředím. Pochopení aspektů týkajících se tohoto typu impregnace však není zcela jasné. Tato práce představuje informaci o jednotlivých vlastnostech vybraných křemičitanů, přesněji draselného, sodného, lithného a koloidního oxidu křemičitého (koloidní silika), dále o účinnosti z hlediska nasákavosti, stupni účinku na hydrataci cementu, schopnosti těchto látek uzavřít póry a jejích vliv na mikrostrukturu cementového substrátu a na penetrační schopnost. Účinnost filmotvorných látek byla hodnocena jak na čerstvém cementovém tmelu, tak na vyzrálejším, aplikovaných po 1 a 24 hodinách od smíchání směsi. K dosažení kvalitativních výsledků byly použity instrumentální metody, jako je rtuťová porosimetrie, rheometrie, izotermální kalorimetrie, rentgenová difrakční analýza a skenovací elektronová mikroskopie. S ohledem na provedené testy byla prokázána určitá účinnost ošetřujících přísad. Výsledky všech testů ukázaly vyšší účinnost těchto látek v případě ošetření na vyzrálejším cementovém povrchu, což bylo pravděpodobně způsobeno vyšším stupněm hydratace, díky čemuž se vytvořily nové fáze, se kterými silikáty byly schopné zareagovat a jistým způsobem ovlivnit mikrostrukturu., Silicate-based impregnations are widely used for to protect concrete against the aggressive environment. Nevertheless, understanding of the several aspect concerning to this type of impregnation is not entirely clear. This thesis presents the information about individual properties of selected silicates, more precisely potassium, sodium, lithium silicates and colloidal silica, then effectiveness in terms of water absorption, degree the effect on cement hydration, the ability of these agents to close pores and the influence on the microstructure of the cement substrate as well as penetration capability. The effectiveness of film-forming substances was assessed both on fresh cement and on more hydrated ones, applied after 1 hour and 24 hours after mixing the mixture, respectively. Instrumental methods such as mercury porosimetry, rheometry, isothermal calorimetry, X-ray diffractometry and scanning electron microscopy were used to achieve quality results. Considering to the tests performed, a certain effectiveness of the care agents was proved. The results of all tests showed a higher efficiency of these substances in the case of treatment on a more hydrated cement surface, which was probably due to a higher degree of hydration resulting in the creation of new phases with which silicates were able to react and in some way affect the microstructure.

Diplomová sa zaoberá štúdiom spojivového systému solu oxidu kremičitého a jeho charakterizáciou predovšetkým pomocou metód termickej analýzy. V diplomovej práci je tiež využitá metóda reologie na stanovenie času gelatinácie, metóda TG/DTA na stanovenie exo a endotermických efektov pri zahrievaní, metóda FT-IR na rýchle stanovenie zloženia vzoriek, XRD na stanovenie fázového zloženia vzoriek a metóda SEM na pozorovanie topografie vzoriek. Ako gelatinačné činidlo je použitý MgO, ako plnivo reaktívna alumina., The master thesis deals with the study of the binder system of silica sol and its characterization mainly by methods of thermal analysis. The master thesis also uses method of rheology to determine the gelatinization time, method of TG/DTA do analyse the exo and endothermic effects during heating, the method of FT-IR to quickly determine the composition of samples, method of XRD to analyze phase composition of the samples and the method of SEM to observe the topography of the samples. MgO is used as a gelling agent, reactive alimina is used as a filler.

Diplomová sa zaoberá štúdiom spojivového systému solu oxidu kremičitého a jeho charakterizáciou predovšetkým pomocou metód termickej analýzy. V diplomovej práci je tiež využitá metóda reologie na stanovenie času gelatinácie, metóda TG/DTA na stanovenie exo a endotermických efektov pri zahrievaní, metóda FT-IR na rýchle stanovenie zloženia vzoriek, XRD na stanovenie fázového zloženia vzoriek a metóda SEM na pozorovanie topografie vzoriek. Ako gelatinačné činidlo je použitý MgO, ako plnivo reaktívna alumina., The master thesis deals with the study of the binder system of silica sol and its characterization mainly by methods of thermal analysis. The master thesis also uses method of rheology to determine the gelatinization time, method of TG/DTA do analyse the exo and endothermic effects during heating, the method of FT-IR to quickly determine the composition of samples, method of XRD to analyze phase composition of the samples and the method of SEM to observe the topography of the samples. MgO is used as a gelling agent, reactive alimina is used as a filler.

Impregnace na bázi silikátů se široce používá k ochraně betonu před agresivním prostředím. Pochopení aspektů týkajících se tohoto typu impregnace však není zcela jasné. Tato práce představuje informaci o jednotlivých vlastnostech vybraných křemičitanů, přesněji draselného, sodného, lithného a koloidního oxidu křemičitého (koloidní silika), dále o účinnosti z hlediska nasákavosti, stupni účinku na hydrataci cementu, schopnosti těchto látek uzavřít póry a jejích vliv na mikrostrukturu cementového substrátu a na penetrační schopnost. Účinnost filmotvorných látek byla hodnocena jak na čerstvém cementovém tmelu, tak na vyzrálejším, aplikovaných po 1 a 24 hodinách od smíchání směsi. K dosažení kvalitativních výsledků byly použity instrumentální metody, jako je rtuťová porosimetrie, rheometrie, izotermální kalorimetrie, rentgenová difrakční analýza a skenovací elektronová mikroskopie. S ohledem na provedené testy byla prokázána určitá účinnost ošetřujících přísad. Výsledky všech testů ukázaly vyšší účinnost těchto látek v případě ošetření na vyzrálejším cementovém povrchu, což bylo pravděpodobně způsobeno vyšším stupněm hydratace, díky čemuž se vytvořily nové fáze, se kterými silikáty byly schopné zareagovat a jistým způsobem ovlivnit mikrostrukturu., Silicate-based impregnations are widely used for to protect concrete against the aggressive environment. Nevertheless, understanding of the several aspect concerning to this type of impregnation is not entirely clear. This thesis presents the information about individual properties of selected silicates, more precisely potassium, sodium, lithium silicates and colloidal silica, then effectiveness in terms of water absorption, degree the effect on cement hydration, the ability of these agents to close pores and the influence on the microstructure of the cement substrate as well as penetration capability. The effectiveness of film-forming substances was assessed both on fresh cement and on more hydrated ones, applied after 1 hour and 24 hours after mixing the mixture, respectively. Instrumental methods such as mercury porosimetry, rheometry, isothermal calorimetry, X-ray diffractometry and scanning electron microscopy were used to achieve quality results. Considering to the tests performed, a certain effectiveness of the care agents was proved. The results of all tests showed a higher efficiency of these substances in the case of treatment on a more hydrated cement surface, which was probably due to a higher degree of hydration resulting in the creation of new phases with which silicates were able to react and in some way affect the microstructure.

Diplomová sa zaoberá štúdiom spojivového systému solu oxidu kremičitého a jeho charakterizáciou predovšetkým pomocou metód termickej analýzy. V diplomovej práci je tiež využitá metóda reologie na stanovenie času gelatinácie, metóda TG/DTA na stanovenie exo a endotermických efektov pri zahrievaní, metóda FT-IR na rýchle stanovenie zloženia vzoriek, XRD na stanovenie fázového zloženia vzoriek a metóda SEM na pozorovanie topografie vzoriek. Ako gelatinačné činidlo je použitý MgO, ako plnivo reaktívna alumina., The master thesis deals with the study of the binder system of silica sol and its characterization mainly by methods of thermal analysis. The master thesis also uses method of rheology to determine the gelatinization time, method of TG/DTA do analyse the exo and endothermic effects during heating, the method of FT-IR to quickly determine the composition of samples, method of XRD to analyze phase composition of the samples and the method of SEM to observe the topography of the samples. MgO is used as a gelling agent, reactive alimina is used as a filler.

Impregnace na bázi silikátů se široce používá k ochraně betonu před agresivním prostředím. Pochopení aspektů týkajících se tohoto typu impregnace však není zcela jasné. Tato práce představuje informaci o jednotlivých vlastnostech vybraných křemičitanů, přesněji draselného, sodného, lithného a koloidního oxidu křemičitého (koloidní silika), dále o účinnosti z hlediska nasákavosti, stupni účinku na hydrataci cementu, schopnosti těchto látek uzavřít póry a jejích vliv na mikrostrukturu cementového substrátu a na penetrační schopnost. Účinnost filmotvorných látek byla hodnocena jak na čerstvém cementovém tmelu, tak na vyzrálejším, aplikovaných po 1 a 24 hodinách od smíchání směsi. K dosažení kvalitativních výsledků byly použity instrumentální metody, jako je rtuťová porosimetrie, rheometrie, izotermální kalorimetrie, rentgenová difrakční analýza a skenovací elektronová mikroskopie. S ohledem na provedené testy byla prokázána určitá účinnost ošetřujících přísad. Výsledky všech testů ukázaly vyšší účinnost těchto látek v případě ošetření na vyzrálejším cementovém povrchu, což bylo pravděpodobně způsobeno vyšším stupněm hydratace, díky čemuž se vytvořily nové fáze, se kterými silikáty byly schopné zareagovat a jistým způsobem ovlivnit mikrostrukturu., Silicate-based impregnations are widely used for to protect concrete against the aggressive environment. Nevertheless, understanding of the several aspect concerning to this type of impregnation is not entirely clear. This thesis presents the information about individual properties of selected silicates, more precisely potassium, sodium, lithium silicates and colloidal silica, then effectiveness in terms of water absorption, degree the effect on cement hydration, the ability of these agents to close pores and the influence on the microstructure of the cement substrate as well as penetration capability. The effectiveness of film-forming substances was assessed both on fresh cement and on more hydrated ones, applied after 1 hour and 24 hours after mixing the mixture, respectively. Instrumental methods such as mercury porosimetry, rheometry, isothermal calorimetry, X-ray diffractometry and scanning electron microscopy were used to achieve quality results. Considering to the tests performed, a certain effectiveness of the care agents was proved. The results of all tests showed a higher efficiency of these substances in the case of treatment on a more hydrated cement surface, which was probably due to a higher degree of hydration resulting in the creation of new phases with which silicates were able to react and in some way affect the microstructure.

Impregnace na bázi silikátů se široce používá k ochraně betonu před agresivním prostředím. Pochopení aspektů týkajících se tohoto typu impregnace však není zcela jasné. Tato práce představuje informaci o jednotlivých vlastnostech vybraných křemičitanů, přesněji draselného, sodného, lithného a koloidního oxidu křemičitého (koloidní silika), dále o účinnosti z hlediska nasákavosti, stupni účinku na hydrataci cementu, schopnosti těchto látek uzavřít póry a jejích vliv na mikrostrukturu cementového substrátu a na penetrační schopnost. Účinnost filmotvorných látek byla hodnocena jak na čerstvém cementovém tmelu, tak na vyzrálejším, aplikovaných po 1 a 24 hodinách od smíchání směsi. K dosažení kvalitativních výsledků byly použity instrumentální metody, jako je rtuťová porosimetrie, rheometrie, izotermální kalorimetrie, rentgenová difrakční analýza a skenovací elektronová mikroskopie. S ohledem na provedené testy byla prokázána určitá účinnost ošetřujících přísad. Výsledky všech testů ukázaly vyšší účinnost těchto látek v případě ošetření na vyzrálejším cementovém povrchu, což bylo pravděpodobně způsobeno vyšším stupněm hydratace, díky čemuž se vytvořily nové fáze, se kterými silikáty byly schopné zareagovat a jistým způsobem ovlivnit mikrostrukturu., Silicate-based impregnations are widely used for to protect concrete against the aggressive environment. Nevertheless, understanding of the several aspect concerning to this type of impregnation is not entirely clear. This thesis presents the information about individual properties of selected silicates, more precisely potassium, sodium, lithium silicates and colloidal silica, then effectiveness in terms of water absorption, degree the effect on cement hydration, the ability of these agents to close pores and the influence on the microstructure of the cement substrate as well as penetration capability. The effectiveness of film-forming substances was assessed both on fresh cement and on more hydrated ones, applied after 1 hour and 24 hours after mixing the mixture, respectively. Instrumental methods such as mercury porosimetry, rheometry, isothermal calorimetry, X-ray diffractometry and scanning electron microscopy were used to achieve quality results. Considering to the tests performed, a certain effectiveness of the care agents was proved. The results of all tests showed a higher efficiency of these substances in the case of treatment on a more hydrated cement surface, which was probably due to a higher degree of hydration resulting in the creation of new phases with which silicates were able to react and in some way affect the microstructure.

Impregnace na bázi silikátů se široce používá k ochraně betonu před agresivním prostředím. Pochopení aspektů týkajících se tohoto typu impregnace však není zcela jasné. Tato práce představuje informaci o jednotlivých vlastnostech vybraných křemičitanů, přesněji draselného, sodného, lithného a koloidního oxidu křemičitého (koloidní silika), dále o účinnosti z hlediska nasákavosti, stupni účinku na hydrataci cementu, schopnosti těchto látek uzavřít póry a jejích vliv na mikrostrukturu cementového substrátu a na penetrační schopnost. Účinnost filmotvorných látek byla hodnocena jak na čerstvém cementovém tmelu, tak na vyzrálejším, aplikovaných po 1 a 24 hodinách od smíchání směsi. K dosažení kvalitativních výsledků byly použity instrumentální metody, jako je rtuťová porosimetrie, rheometrie, izotermální kalorimetrie, rentgenová difrakční analýza a skenovací elektronová mikroskopie. S ohledem na provedené testy byla prokázána určitá účinnost ošetřujících přísad. Výsledky všech testů ukázaly vyšší účinnost těchto látek v případě ošetření na vyzrálejším cementovém povrchu, což bylo pravděpodobně způsobeno vyšším stupněm hydratace, díky čemuž se vytvořily nové fáze, se kterými silikáty byly schopné zareagovat a jistým způsobem ovlivnit mikrostrukturu., Silicate-based impregnations are widely used for to protect concrete against the aggressive environment. Nevertheless, understanding of the several aspect concerning to this type of impregnation is not entirely clear. This thesis presents the information about individual properties of selected silicates, more precisely potassium, sodium, lithium silicates and colloidal silica, then effectiveness in terms of water absorption, degree the effect on cement hydration, the ability of these agents to close pores and the influence on the microstructure of the cement substrate as well as penetration capability. The effectiveness of film-forming substances was assessed both on fresh cement and on more hydrated ones, applied after 1 hour and 24 hours after mixing the mixture, respectively. Instrumental methods such as mercury porosimetry, rheometry, isothermal calorimetry, X-ray diffractometry and scanning electron microscopy were used to achieve quality results. Considering to the tests performed, a certain effectiveness of the care agents was proved. The results of all tests showed a higher efficiency of these substances in the case of treatment on a more hydrated cement surface, which was probably due to a higher degree of hydration resulting in the creation of new phases with which silicates were able to react and in some way affect the microstructure.

Diplomová sa zaoberá štúdiom spojivového systému solu oxidu kremičitého a jeho charakterizáciou predovšetkým pomocou metód termickej analýzy. V diplomovej práci je tiež využitá metóda reologie na stanovenie času gelatinácie, metóda TG/DTA na stanovenie exo a endotermických efektov pri zahrievaní, metóda FT-IR na rýchle stanovenie zloženia vzoriek, XRD na stanovenie fázového zloženia vzoriek a metóda SEM na pozorovanie topografie vzoriek. Ako gelatinačné činidlo je použitý MgO, ako plnivo reaktívna alumina., The master thesis deals with the study of the binder system of silica sol and its characterization mainly by methods of thermal analysis. The master thesis also uses method of rheology to determine the gelatinization time, method of TG/DTA do analyse the exo and endothermic effects during heating, the method of FT-IR to quickly determine the composition of samples, method of XRD to analyze phase composition of the samples and the method of SEM to observe the topography of the samples. MgO is used as a gelling agent, reactive alimina is used as a filler.