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Author: Jeffrey D. Rimer Publisher: ISBN: Category : Languages : en Pages : 302
Book Description
In a broader scope, the techniques and findings derived in this thesis offer a general methodology that can be applied to other microporous, or silicate, materials to develop predictive models of growth, thereby serving as a framework toward rational syntheses of novel nanomaterials.
Author: Jeffrey D. Rimer Publisher: ISBN: Category : Languages : en Pages : 302
Book Description
In a broader scope, the techniques and findings derived in this thesis offer a general methodology that can be applied to other microporous, or silicate, materials to develop predictive models of growth, thereby serving as a framework toward rational syntheses of novel nanomaterials.
Author: Mohammad Navaid Khan Publisher: ISBN: Category : Languages : en Pages :
Book Description
Zeolites are an important class of materials in modern technology with applications in catalysis, separations, biosensing and microelectronics. There are over 200 different zeolite frameworks reported in literature, but only a handful have been used commercially. Understanding their self-assembly process would assist in the fabrication of new zeolites through the control of their pore size/shape, and surface area for advanced applications. With our research we aim to elucidate aspects of zeolite formation using molecular simulations. We have extended the lattice model of silica tetrahedra developed by Jin et al. [L. Jin, S. M. Auerbach and P. A. Monson J. Chem. Phys. 134(13), 2011: 134703] to study silica polymerization under various pH values and silica concentrations. We have investigated the transition from gels, at the iso-electric point of silica, to nanoparticles in the initial stages of the formation of silicalite-1. We focus on two systems: one with low silica concentration with composition comparable to the clear solution silicalite-1 zeolite synthesis, and a high silica concentration system that leads to gel states. In the dilute system, clusters have a core-shell structure with the core predominantly comprised of silica with some SDA+ cations, surrounded by a shell of only SDA+ cations. In the concentrated system there are larger number of smaller nanoparticles than those in dilute system. Next, we focused our attention to study the effects of two different type of structure directing agent (SDA) molecules -- quasi-spherical SDA and tetramethylammonium (TMA) -- on crystalline tetrahedral frameworks in the synthesis of microporous materials. We have implemented parallel tempering Monte Carlo algorithm to simulate the formation of ordered crystalline materials, and we have demonstrated that the presence of SDAs result in the formation of previously unobserved crystalline frameworks. In the case of quasi-spherical SDAs we have observed three-dimensional fully-connected materials as well as two-dimensional layered materials in our simulations, and observed that the interaction between SDAs and silica plays a significant role in directing the final micropore structure. For TMA we have developed two types of models based on silica-TMA interaction -- silica-nitrogen interaction vs silica-methyl interaction. In both of these models we have observed that the TMA molecule forms predominantly three dimensional materials, which suggests that the molecular structure directs the preferential formation of three dimensional frameworks as opposed to two dimensional layered materials. We have also studied the kinetics for formation of crystals using forward-flux sampling method. We have estimated the rate constant of transition from amorphous silica phase to crystalline silica phase. We have also predicted and characterized the transition state for this process. This is the first time when an enhanced sampling method is applied to understand the self-assembly process of microporous crystals. This research has been crucial in understanding the nature of silica polymerization and elucidating the role of structure directing agents in zeolite synthesis; it has taken us a step closer to answering the big question in zeolite science -- "How do all silica zeolites form ?"
Author: Khalid A. Askar Publisher: ISBN: Category : Languages : en Pages : 141
Book Description
Crystals. The newly developed coating methods have proven to be able to coat different substrates with a monolayer of silica particles and achieve less than 1% light reflection. These newly developed quarter wavelength based antireflection coatings are extremely cheap, easy and quick to fabricate, and can coat multiple substrates at the same time. Furthermore, due to the high quality of the ordered monolayer of silica particles, it is possible to use these particles as a mask for a chlorine reactive ion etching process to produce broadband moth-eye antireflection coatings on both single crystalline and multicrystalline silicon wafers.
Author: Szu-Chia Chien Publisher: ISBN: Category : Languages : en Pages :
Book Description
Porous materials are of great importance in many fields due to their wide applications. An ongoing theme in this area is the tailoring of materials for specific applications. With a better understanding of the formation mechanisms, tailoring and controlling the pore structure may be achieved. The objective of this research is acquiring further understanding of the fundamental physics that govern the formation of these materials using molecular simulations. We are aiming to unravel the assembly process of silica porous materials using a semi-rigid silica tetrahedral model. This model together with reaction ensemble Monte Carlo simulations allows us to study the formation of silica nanoparticles, the initial stages of microporous material formation. A two-step formation mechanism was found to be crucial for generating the nanoparticles. A replica-exchange reaction ensemble Monte Carlo sampling together with the silica tetrahedral model is developed and applied to cross the energy barrier between amorphous silica to crystalline silica materials for searching for the ground state structure of this model. The technique involves simulating several system copies with different equilibrium constants controlling silica condensation/hydrolysis reactions, which are essential for building higher-order network structures and eventually crystals, was preformed. Different silica polymorphs including all-silica zeolite frameworks were obtained. This model shows a great potential to study the crystallization of microporous materials. We also study the formation of mesoporous materials using molecular dynamics simulations. We investigate the interplay of silica molecules and surfactants, and different mesophases such as micellar rods, hexagonal, bicontinuous and lamellar phases were obtained. Multiple charges on silicate oligomers were found to play an important role in the formation of hexagonal phases. To study the later stages of MCM-41 formation, a hybrid molecular dynamics and Monte Carlo approach is proposed. The cooperation between the physical interaction and chemical reaction can be taken into account simultaneously. Preliminary study shows that the ratio of silicate to surfactant higher than 4 is essential to the growth of MCM-41. With a further enhancement on the model, this hybrid approach will be a powerful tool to simulate the formation of MCM-41 in a large system and at a long time scale.
Author: Teresa Yi Kao Publisher: ISBN: Category : Languages : en Pages : 338
Book Description
Silica chemistry provides a uniquely tunable platform for nanoparticle synthesis, where particle size, nanoscale morphology, and surface properties can be precisely controlled. Recent advances demonstrate that conveniently accessible parameters, including silica precursor chemistry, solvent, and reaction pH, can be used to tune particle size down to below 10 nm. By cooperative assembly of inorganic silica species and organic molecular structure directing agents, a diverse range of mesoporous silica nanoparticles with hexagonal, cubic, and multicompartment structures can be produced. This versatile chemistry provides pathways for answering fundamental questions about structure formation and developing novel functional nanomaterials for applications including separation, catalysis, and drug delivery. In this dissertation, two examples of such silica nanoparticle systems are discussed. As a first example, the development of an intensity-based fluorescent silica nanoparticle barcode is discussed. This work is motivated by a need for fluorescent tags that increase the number of molecular species that can be simultaneously labeled and reliably distinguished using commercially available fluorescence microscopes. In this study, the synthetic parameters that govern the incorporation of precisely controlled numbers of fluorescent dyes into silica nanoparticles in batch reactions are identified. Heterogeneities within particle batches are mapped using single particle fluorescence microscopy. Proof-of-concept experiments demonstrate that fluorescent silica nanoparticles with well-separated high and low fluorescence intensity distribution levels can be synthesized in batch reactions and used as an intensity barcode in fluorescence microscopy. In the second example, a mesoporous silica nanoparticle system, structure directed by surfactant-micelle self-assembly, is investigated. As a function of an added pore expander molecule or reaction stirring rate, a series of four distinct mesoporous silica nanoparticle structures is observed: hexagonal, cubic/hexagonal multicompartment, cubic, and dodecagonal quasicrystalline. The mechanism driving the structural transition between cubic crystalline and dodecagonal quasicrystalline mesoporous silica nanoparticles is investigated. Control of nanoparticle size down to a single tiling unit (
Author: Gregoire Nicolis Publisher: John Wiley & Sons ISBN: 1118309480 Category : Science Languages : en Pages : 352
Book Description
The Advances in Chemical Physics series—the cuttingedge of research in chemical physics The Advances in Chemical Physics series provides thechemical physics and physical chemistry fields with a forum forcritical, authoritative evaluations of advances in every area ofthe discipline. Filled with cutting-edge research reported in acohesive manner not found elsewhere in the literature, each volumeof the Advances in Chemical Physics series presents contributionsfrom internationally renowned chemists and serves as the perfectsupplement to any advanced graduate class devoted to the study ofchemical physics. This volume explores: Kinetics and thermodynamics of fluctuation-induced transitionsin multistable systems (G. Nicolis and C. Nicolis) Dynamical rare event simulation techniques for equilibrium andnonequilibrium systems (Titus S. van Erp) Confocal depolarized dynamic light scattering (M. Potenza, T.Sanvito, V. Degiorgio, and M. Giglio) The two-step mechanism and the solution-crystal spinodal fornucleation of crystals in solution (Peter G. Vekilov) Experimental studies of two-step nucleation duringtwo-dimensional crystallization of colloidal particles withshort-range attraction (John R. Savage, Liquan Pei, and Anthony D.Dinsmore) On the role of metastable intermediate states in the homogeneousnucleation of solids from solution (James F. Lutsko) Effects of protein size on thehigh-concentration/low-concentration phase transition (PatrickGrosfils) Geometric constraints in the self-assembly of mineral dendritesand platelets (John J. Kozak) What can mesoscopic level in situ observations teach us aboutkinetics and thermodynamics of protein crystallization? (MikeSleutel, Dominique Maes, and Alexander Van Driessche) The ability of silica to induce biomimetic crystallization ofcalcium carbonate (Matthias Kellermeier, Emilio Melero-GarcÍa,Werner Kunz, and Juan Manuel GarcÍa-Ruiz)
Author: Y.C. Ke Publisher: Elsevier ISBN: 0080457584 Category : Technology & Engineering Languages : en Pages : 405
Book Description
Polymer-Layered Silicate and Silica Nanocomposites includes advanced materials and nanocomposites based on silica and layered silicates obtained from resources in China. Using nanotechnology, these inorganic materials can be filled, in-situ polymerised and combined with polymers with nanoscale dispersions. In this book, many practical examples are presented to show how to prepare the nanocomposites. Several kinds of polymer (PET,PBT,PE,PP,etc.)-layered silicate and silica nanocomposites are prepared and investigated based on our research works, inventions and applications. They are prepared and modified aiming at their applications to such fields as, functional films, barrier materials, coatings, and engineering plastics. Their structure-property relationship, especially the nano effects from them are investigated under different techniques to show how the critical load of the inorganic phase has the effect on the final properties of the nanocomposite materials. Obviously, this new generation of materials has revolutionary effects on the traditional materials or industry as petroleum. Some of the prospects of them are thus included. Focus on the inorganic phase, which is of wide practical and industrial significance Dealing with many first report of the nanoeffect, nanostructure and its functional properties Especially, it covers the particle assembly and self-assemble by interaction with polymer matrix
Author: Ruren Xu Publisher: Elsevier ISBN: 0080548857 Category : Technology & Engineering Languages : en Pages : 2242
Book Description
The Proceedings of the 15th International Zeolite Conference contain 291 full papers, including the full papers of 5 plenary lecture, 12 keynote lectures, and 4 invited lectures at the R. M. Barrer Symposium. The topics of these full papers include synthesis, modifications, structures, characterization, adsorption, separation and diffusion, catalysis, host-guest chemistry and advanced materials, industrial applications, theory and modeling, mesostructured materials, MOF materials, and natural zeolites. The other 271 full papers were selected from the about 1000 contributions submitted to the 15th IZC. - Most recent research results in zeolite science- Full indexes- Wide coverage of zeolite science and technology
Author: Jeffrey D. Rimer
Author: Jeffrey D. Rimer
Author: Mohammad Navaid Khan
Author: 
Author: Khalid A. Askar
Author: Szu-Chia Chien
Author: Teresa Yi Kao
Author: Gregoire Nicolis
Author: Y.C. Ke
Author: Deying Xia
Author: Ruren Xu