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Author: Vladimir N. Popok Publisher: ISBN: 9783036527291 Category : Languages : en Pages : 112
Book Description
The book represents a collection of papers from Special Issue “Formation of Advanced Nanomaterials by Gas-Phase Aggregation” published in journal Applied Nano. It contains review and original articles covering a range of topics on the growth of clusters/nanoparticles using gas-phase aggregation approaches, the application of cluster beams for the formation of nanomaterials with advanced properties and specific nanostructures as well as providing new fundamental insights on nanoscale properties of materials.
Author: Vladimir N Popok Publisher: Mdpi AG ISBN: 9783036527284 Category : Science Languages : en Pages : 112
Book Description
The book represents a collection of papers from Special Issue "Formation of Advanced Nanomaterials by Gas-Phase Aggregation" published in journal Applied Nano. It contains review and original articles covering a range of topics on the growth of clusters/nanoparticles using gas-phase aggregation approaches, the application of cluster beams for the formation of nanomaterials with advanced properties and specific nanostructures as well as providing new fundamental insights on nanoscale properties of materials.
Author: Yves Huttel Publisher: John Wiley & Sons ISBN: 3527340602 Category : Technology & Engineering Languages : en Pages : 416
Book Description
The first overview of this topic begins with some historical aspects and a survey of the principles of the gas aggregation method. The second part covers modifications of this method resulting in different specialized techniques, while the third discusses the post-growth treatment that can be applied to the nanoparticles. The whole is rounded off by a review of future perspectives and the challenges facing the scientific and industrial communities. An excellent resource for anyone working with the synthesis of nanoparticles, both in academia and industry.
Author: Axel Lorke Publisher: Springer Science & Business Media ISBN: 3642285465 Category : Science Languages : en Pages : 425
Book Description
Gasphase synthesis of nanoparticles and nanostructured materials offers high chemical purity and crystalline quality as well as scalability up to industrial quantities. It is therefore highly attractive for both basic and applied science. This book gives a broad and coherent overview of the complete production and value chain from nanoparticle formation to integration into products and devices. Written by experts in the field – with backgrounds in electrical engineering, experimental and theoretical physics, materials science, and chemical engineering – the book offers a deep insight into the fabrication, characterization and application of nanoparticles from the gasphase. The first part of the book, “Formation”, covers chemical and growth kinetics, in-situ diagnostics, numerical simulation, process development and material deposition. In the second section, the reader is introduced to the structure and dynamics that lead to functional nanoscale systems and materials. The third section, “Properties and Applications”, provides a detailed discussion of the optical, electronic, magnetic and chemical characteristics of nanostructures and demonstrates how these can be used in tailored materials and devices.
Author: Rickard Gunnarsson Publisher: Linköping University Electronic Press ISBN: 9176854663 Category : Languages : en Pages : 69
Book Description
Nanotechnology can profoundly benefit our health, environment and everyday life. In order to make this a reality, both technological and theoretical advancements of the nanomaterial synthesis methods are needed. A nanoparticle is one of the fundamental building blocks in nanotechnology and this thesis describes the control of the nucleation, growth and oxidation of titanium particles produced in a pulsed plasma. It will be shown that by controlling the process conditions both the composition (oxidationstate) and size of the particles can be varied. The experimental results are supported by theoretical modeling. If processing conditions are chosen which give a high temperature in the nanoparticle growth environment, oxygen was found to be necessary in order to nucleate the nanoparticles. The two reasons for this are 1: the lower vapor pressure of a titanium oxide cluster compared to a titanium cluster, meaning a lower probability of evaporation, and 2: the ability of a cluster to cool down by ejecting an oxygen atom when an oxygen molecule condenses on its surface. When the oxygen gas flow was slightly increased, the nanoparticle yield and oxidation state increased. A further increase caused a decrease in particle yield which is attributed to a slight oxidation ofthe cathode. By varying the oxygen flow, it was possible to control the oxidation state of the nanoparticles without fully oxidizing the cathode. Pure titanium nanoparticles could not be produced in a high vacuum system because oxygen containing gases such as residual water vapour have a profound influence on nanoparticle yield and composition. In an ultrahigh vacuum system titanium nanoparticles without significantoxygen contamination were produced by reducing the temperature of the growth environment and increasing the pressure of an argon-helium gas mixture within whichthe nanoparticles grew. The dimer formation rate necessary for this is only achievable at higher pressures. After a dimer has formed, it needs to grow by colliding with a titanium atom followed by cooling by collisions with multiple buffer gas atoms. The condensation event heats up the cluster to a temperature much higher than the gas temperature, where it is during a short time susceptible to evaporation. When the clusters’ internal energy has decreased by collisions with the gas to less than the energy required to evaporate a titanium atom, it is temporarily stable until the next condensation event occurs. The temperature difference by which the cluster has to cool down before it is temporarily stable is exactly as many kelvins as the gas temperature.The addition of helium was found to decrease the temperature of the gas, making it possible for nanoparticles of pure titanium to grow. The process window where this is possible was determined and the results presented opens up new possibilities to synthesize particles with a controlled contamination level and deposition rate.The size of the nanoparticles has been controlled by three means. The first is to change the electrical potential around the growth zone, which allows for size (diameter) control in the order of 25 to 75 nm without influencing the oxygen content of the particles. The second means is by increasing the pressure which decreases the ambipolar diffusion rate of the ions resulting in a higher growth material density. By doing this, the particle size can be increased from 50 to 250 nm, however the oxygen content also increases with increasing pressure when this is done in a high vacuum system. The last means of size control was by adding a helium flow to the process where higher flows resulted in smaller nanoparticle sizes. When changing the pressure in high vacuum, the morphology of the nanoparticles could be controlled. At low pressures, highly faceted near spherical particles were produced. Increasing the pressure caused the formation of cubic particles which appear to ‘fracture’ at higher pressures. At the highest pressure investigated, the particles became poly-crystalline with a cauliflower shape and this morphology was attributed to a lowad atom mobility. The ability to control the size, morphology and composition of the nanoparticles determines the success of applying the process to manufacture devices. In related work presented in this thesis it is shown that 150-200 nm molybdenum particles with cauliflower morphology were found to scatter light in which made them useful in photovoltaic applications, and the size of titanium dioxide nanoparticles were found to influence the selectivity of graphene based gas sensors.
Author: Karine Philippot Publisher: John Wiley & Sons ISBN: 3527821759 Category : Technology & Engineering Languages : en Pages : 384
Book Description
Nanoparticles in Catalysis Discover an essential overview of recent advances and trends in nanoparticle catalysis Catalysis in the presence of metal nanoparticles is an important and rapidly developing research field at the frontier of homogeneous and heterogeneous catalysis. In Nanoparticles in Catalysis, accomplished chemists and authors Karine Philippot and Alain Roucoux deliver a comprehensive guide to the key aspects of nanoparticle catalysis, ranging from synthesis, activation methodology, characterization, and theoretical modeling, to application in important catalytic reactions, like hydrogen production and biomass conversion. The book offers readers a review of modern and efficient tools for the synthesis of nanoparticles in solution or onto supports. It emphasizes the application of metal nanoparticles in important catalytic reactions and includes chapters on activation methodology and supported nanoclusters. Written by an international team of leading voices in the field, Nanoparticles in Catalysis is an indispensable resource for researchers and professionals in academia and industry alike. Readers will also benefit from the inclusion of: A thorough introduction to New Trends in the Design of Metal Nanoparticles and Derived Nanomaterials for Catalysis An exploration of Dynamic Catalysis and the Interface Between Molecular and Heterogeneous Catalysts A practical discussion of Metal Nanoparticles in Water: A Relevant Toolbox for Green Catalysis Organometallic Metal Nanoparticles for Catalysis A concise treatment of the opportunities and challenges of CO2 Hydrogenation to Oxygenated Chemicals Over Supported Nanoparticle Catalysts Perfect for catalytic, organic, inorganic, and physical chemists, Nanoparticles in Catalysis will also earn a place in the libraries of chemists working with organometallics and materials scientists seeking a one-stop resource with expert knowledge on the synthesis and characterization of nanoparticle catalysis.
Author: Benjamin Adam Legg Publisher: ISBN: Category : Languages : en Pages : 117
Book Description
Nucleation, growth, and aggregation are interconnected processes which control the formation nanoparticles within aqueous environments and the development of nanoparticle structures. These processes are of fundamental engineering importance for the development of new nanoparticle synthesis methodologies and the creation of hierarchical self-assembled structures. They are also fundamentally important concepts for describing how nanoparticles and minerals are formed and distributed throughout the natural environment. The development of more sophisticated models for nucleation, growth, and aggregation within the aqueous environment has become a pressing scientific need, because nanoparticle size, shape, and aggregate structure are known to impact particle reactivity, bioavailability, transport and fate within the environment. In recent years, it has become apparent that complex interactions may exist between the processes of nucleation, growth, and aggregation, and these interactions are especially important during the formation of nanometer scale particles. For example, aggregation has been shown to serve as a mechanism for the growth of nanocrystals, and as a potential driver for phase transformations. However, the details of these interactions are not fully understood. In this work, a combination of advanced in situ characterization techniques, including cryogenic transmission electron microscopy (cryo-TEM) and small angle x-ray scattering (SAXS), have been combined to better understand the development of nanoscale structures in aqueous systems. These techniques are complementary. Cryo-TEM provides new capabilities for nanoscale imaging of particles in aqua. It is especially useful for imaging fragile aggregate structures, which cannot be dried without damage, and for obtaining snapshots of reactive solutions that are evolving over time. Furthermore, cryo-TEM can be used to produce three-dimensional tomographic reconstructions (cryo-ET), providing structural models for particles and nanoparticles. However, TEM methodologies are limited by sampling statistics and are not ideal for determining the kinetics of structural change. SAXS is a complementary method that allows suspension properties such as particle size and aggregate structure to be characterized in a time-resolved fashion. SAXS has the potential to provide more statistically robust measurements, and to provide detailed reaction kinetics. However, SAXS data interpretation requires some level of a priori knowledge of the structure being characterized. Thus, by combining SAXS with cryo-TEM, a structurally accurate and statistically robust description of nanoparticle aggregate structure can be obtained. This dissertation consists of four studies, which seek explain how iron oxyhydroxide nanoparticles nucleate and develop new structures via aggregation, within the aqueous environment. The aim of the first study is to determine the structure of ferrihydrite nanoparticle aggregates in aqua. This is achieved using complimentary cryo-TEM and SAXS methodologies. Ferrihydrite nanoparticles are known to form complex aggregate structures. Interpretation of SAXS data is difficult due to suspension polydispersity. Cryo-ET is used to obtain three-dimensional images of the nanoparticle suspensions. A variety of aggregate structures are observed, with branched networks of linear chains of particles being prevalent in most suspensions. The tomographic structural models are processed to determine aggregate fractal dimensions, using an autocorrelation function based approach. These results are combined with SAXS data to obtain a more comprehensive understanding of the suspension complexity. The networks of linear chains are shown to possess low fractal dimensions, between 1.0 and 1.4; significantly lower than would be expected from traditional models for aggregation. This has important consequences for the aggregate's physical behavior, and allows very large aggregates to exist in stable colloidal suspension without flocculation. The second study addresses how the ferrihydrite aggregate structure responds to changes in the ionic strength of the suspension, and how low-dimensional aggregate structures may influence nanoparticle transport through subsurface environments. Introducing ferrihydrite particle aggregates into solutions of 2 mM to 50 mM NaNO3 is shown to induce aggregate collapse, with more salt leading to the formation of denser aggregate structures and eventual flocculation. Complementary experiments show that millimolar quantities of NaNO3 induce a fundamental change in nanoparticle transport through a saturated quartz sand column. In deionized water, where low fractal dimension aggregates are stable, nanoparticles deposit evenly throughout the column, which soon saturates with particles so that subsequent injections are transported freely. When conditions favor aggregate collapse, dense localized accumulations occur and more nanoparticles can be deposited within the column. These deposits may be mechanically unstable, leading to irregular transport behavior. In the third study, the relationship between aggregation and iron oxyhydroxide phase transformations is explored. Previous researchers have found that akaganeite ([beta]-FeOOH) nanoparticles transform to create hematite ([alpha]-Fe2O3) nano-spindles in response to hydrothermal aging, but the mechanism of transformation is unknown. Some researchers have proposed a process based on the aggregation of hematite precursors, while others advocated for dissolution and re-precipitation mechanisms. In this study, the kinetics of the phase transformation from akaganeite to hematite is studied, and cryo-TEM is used to characterize the aggregate structures in the transforming suspension. The hematite spindles are shown to be nanoporous, while akaganeite nanoparticles display a tendency for oriented aggregation. Hematite spindles are frequently found in intimate contact with akaganeite nanoparticle aggregates during the process of phase transformation, suggesting a model for phase transformation in which the dehydration of akaganeite to form hematite is enhanced by aggregation. In the final study, the nucleation and growth of akaganeite nanoparticles from acidic (pH 1.5-3) FeCl3 solutions is tracked with in situ small angle x-ray scattering (SAXS). The hydrothermal precipitation process studied can generate highly monodisperse particles, whose size, shape, and nucleation rate can be tuned by varying solution saturation and temperature. Classical nucleation modeling is applied to determine new values for the interfacial energy of ferric oxyhydroxide clusters. The interfacial energy (interfacial tension) of the nucleus is shown to be pH dependent and ranges from 0.06 to 0.12 J/m2 within the range of experimental conditions. The interfacial tension decreases with decreasing pH. At the onset of nucleation, this corresponds to very small critical nuclei, containing just 4 to 30 iron atoms. The free energy of the early critical nuclei (40-70 kJ/mol) is found to be small relative to the effective activation energy for particle growth (140-200 kJ/mol). This suggests a situation where differences in growth kinetics may be as important for determining the first formed phase as differences in precipitate solubility or interfacial energy. A thermodynamic construction for the free energy of an embryonic cluster is presented that can be extended to clusters of arbitrarily small size, including iron monomers. This construction can be used to define the interfacial tension of dissolved species, and determine this interfacial tension from readily available solubility data. The interfacial tension of the monomer is shown to closely track the experimentally determined interfacial tension of the critical nucleation clusters, suggesting a new method for estimating oxyhydroxide interfacial tensions when direct experimental measurements are unavailable. In combination, these studies reveal the wide array of structures and behaviors that can occur in aqueous suspensions of ferric oxyhydroxide nanoparticles. In aqua methodologies with nanoscale resolution have allowed novel nanoparticle structures to be observed (e.g. linear particle chains and nanoporous hematite), and have been used to show the impact of nanoparticle aggregation on a variety of important physical processes (e.g. nanoparticle transport and phase transformation). These in aqua methods are also powerful tools for quantitative characterization of fundamental processes such as nanoparticle nucleation and growth; allowing important material properties (i.e. interfacial energy) that were previously unknown to be obtained. This type of information will allow for the refinement of existing iron oxyhydroxide synthesis approaches, to provide better control over particle size, shape, and phase, and will allow scientists to predict where nanoparticles may form within the environment.
Author: Oliver Diwald Publisher: John Wiley & Sons ISBN: 1119436745 Category : Technology & Engineering Languages : de Pages : 903
Book Description
Metal Oxide Nanoparticles A complete nanoparticle resource for chemists and industry professionals Metal oxide nanoparticles are integral to a wide range of natural and technological processes—from mineral transformation to electronics. Additionally, the fields of engineering, electronics, energy technology, and electronics all utilize metal oxide nanoparticle powders. Metal Oxide Nanoparticles: Formation, Functional Properties, and Interfaces presents readers with the most relevant synthesis and formulation approaches for using metal oxide nanoparticles as functional materials. It covers common processing routes and the assessment of physical and chemical particle properties through comprehensive and complementary characterization methods. This book will serve as an introduction to nanoparticle formulation, their interface chemistry and functional properties at the nanoscale. It will also act as an in-depth resource, sharing detailed information on advanced approaches to the physical, chemical, surface, and interface characterization of metal oxide nanoparticle powders and dispersions. Addresses the application of metal oxide nanoparticles and its economic impact Examines particle synthesis, including the principles of selected bottom-up strategies Explores nanoparticle formulation—a selection of processing and application routes Discusses the significance of particle surfaces and interfaces on structure formation, stability and functional materials properties Covers metal oxide nanoparticle characterization at different length scales With this valuable resource, academic researchers, industrial chemists, and PhD students can all gain insight into the synthesis, properties, and applications of metal oxide nanoparticles.
Author: Vladimir N. Popok
Author: Vladimir N Popok
Author: Claes Granqvist
Author: Yves Huttel
Author: Axel Lorke
Author: Rickard Gunnarsson
Author: Karine Philippot
Author: Benjamin Adam Legg
Author: Frank Einar Kruis
Author: Oliver Diwald
Author: Yangchuan Xing