Metal oxide Nanostructures from Electrospun Carbon Templates ab 79 € als Taschenbuch: Metal Oxide Nanofibers and Nanotubes. Aus dem Bereich: Bücher, Wissenschaft, Chemie,
Metal oxide Nanostructures from Electrospun Carbon Templates ab 79 EURO Metal Oxide Nanofibers and Nanotubes
Recently, porous ceramic materials are used as components in special and advanced engineering applications. These include filtering liquids and particles in gas streams, porous burners, biomedical devices, lightweight load-bearing structures, sandwich panels, core materials, heat insulation, fuel cell, as conductor as well as insulator, etc. Fabrications of open cell ceramic foams are of scientific and technological interest because of their ability to interact with atoms, ions and molecules not only at their surface, but throughout the bulk of the material. In present review, the three basic methods (i.e. replica, direct foaming and burn-out of fugitive route) for preparing ceramic foams are discussed. Highly-porous and interconnected carbon foams were manufactured via template route. The porous silica foams are obtained through a sintering of macro-casted PU foam templates with the hydrolyzed silica sol. Both the foams were highly interconnected having uniform porosity and pore size distribution.
This book puts forward a catalyst-free CVD approach for fabricating CNTs with totally controlled properties (e.g. geometry, shape, chemical composition, surface chemistry, etc.) by using nanoporous templates with well-defined chemistry and geometry from recycled plastic bags. As a result of its simplicity, versatility, scalability and cost-competitive fabrication process, this approach is envisaged for producing CNTs featuring standardized properties, which are required for a broad range of applications (e.g. separations, drug delivery, etc.). To develop this CVD approach, the optimal conditions for the fabrication of catalyst-free CNTs were determined by varying such parameters as temperature, reaction path length, absence or presence of catalyst, type of nanoporous template (i.e. nanoporous anodic alumina (NAA) or titania nanotubes (TNTs)) and type of carbon source.
The work covered herein discusses for the first time various techniques used in the fabrication of metal oxide nanofibers and nanotubes from eletrospun carbon fibers as templates. The nanofibers were prepared by electrospinning metal oxide precursor inside a polymer matrix. The metal oxide tubes were by tubes by fiber templating. This was followed by calcination to yield the nanofibers and nanotubes. Their morphological, structural, optoelectronic and catalytic properties are also discussed. Among key applications they have found utilization as catalyst supports. Palladium nanoparticles have been supported on Titanium dioxide nanofibers and applied in Heck-coupling reactions. Similarly, included is the effect of impurities on the metal oxide tubes properties done by doping with metal ions. In addition, photocatalytic behavior of metal oxides nanofibers have also been discussed.
Silicon carbide as a wide bandgap semiconductor material is by now widely introduced in the power device market. Its superior performance in terms of power density, high switching frequency and breakdown voltage leads to an advantage in efficiency and in the power to weight ratio of modules compared to silicon.All the devices on the market until now rely on the use of hexagonal polytypes. These show the highest bandgap and can be produced in high quality for the high-volume market by physical vapor transport technology.The only cubic polytype 3C cannot be used for high quality devices as the production is very difficult and the available material is still very defect rich. On the other hand this polytype has special properties concerning isotropic values (e.g. mobility) and the possibility to form a rather good interface to oxides as required for MOS devices.Nowadays, there are two main technologies used for the production of cubic silicon carbide. Both rely on the heteroepitaxial growth of 3C thin films on either hexagonal silicon carbide or on silicon substrates. The growth on hexagonal substrates provides a better quality but silicon substrates are more cost effective and by that more often used.To make the layers grown on silicon substrates by chemical vapor deposition more suitable for device applications a huge effort has to be raised to improve their crystalline quality regarding domain size and defect density as well as concerning stress in the layer.Within this work several steps during substrate preparation, seeding and the beginning of epitaxial growth and their influence on layer quality had been under research:In chapter 4.1 the substrate preparation was investigated. A particular interest was paid to the chemical cleaning and etching in hot hydrogen and their impact on the surface quality. Besides that, an influence of contamination inside the reactor was found and a new type of void defect was detected and described. In contrast to the typically applied carbonization step within the epitaxial process an ex-situ carbon deposition process was developed in chapter 4.2. It was combined with annealing steps in-situ or with the use of a rapid thermal annealing process.In chapter 4.3 detailed studies had been performed on the influence of the ramp design during in-situ carbonization for seed generation. An explanation of the effects by a theoretical model was found and confirmed.By utilization of high resolution TEM a focus was laid on the defect structures at and nearby to the silicon-carbide/silicon interface in chapter 4.4. The distribution of dislocations near the interface itself was studied.By comparison of the growth on polished and wet chemically textured substrates the beginning of epitaxial growth was investigated in chapter 4.5. A model for an overgrowth mechanism is proposed that can be observed for growth on flat silicon substrates.In chapter 5 as a supplement a possible application of CVD grown heteroepitaxial layers on silicon is shown. First promising experiments have been done showing the application as templates for the growth of thick freestanding cubic material by sublimation epitaxy.
The importance and actuality of nanotechnology is unabated and will be for years to come. A main challenge is to understand the various properties of certain nanostructures, and how to generate structures with specific properties for use in actual applications in Electrical Engineering and Medicine. One of the most important structures are nanowires, in particular superconducting ones. They are highly promising for future electronics, transporting current without resistance and at scales of a few nanometers. To fabricate wires to certain defined standards however, is a major challenge, and so is the investigation and understanding of these properties in the first place. A promising approach is to use carbon nanotubes as well as DNA structures as templates. Many fundamental theoretical questions are still unanswered, e.g. related to the role of quantum fluctuations. This work is tackling them and provides a detailed analysis of the transport properties of such ultrathin wires. It presents an account of theoretical models, charge transport experiments, and also conveys the latest experimental findings regarding fabrication, measurements, and theoretical analysis. In particular, it is the only available resource for the approach of using DNA and carbon nanotubes for nanowire fabrication. It is intended for graduate students and young researchers interested in nanoscale superconductivity. The readers are assumed to have knowledge of the basics of quantum mechanics and superconductivity.
Scanning electron microscopy (SEM) can be exploited not only for nanomaterials characterization but also integrated with new technologies for in-situ nanomaterials engineering and manipulation. Scanning Microscopy for Nanotechnology addresses the rapid development of these techniques for nanotechnology, in both technique and application chapters by leading practitioners. The book covers topics including nanomaterials imaging, X-ray microanalysis, high-resolution SEM, low kV SEM, cryo-SEM, as well as new techniques such as electron back scatter diffraction (EBSD) and scanning transmission electron microscopy (STEM). Fabrication techniques integrated with SEM, such as e-beam nanolithography, nanomanipulation, and focused ion beam nanofabrication, are major new dimensions for SEM application. Application areas include the study of nanoparticles, nanowires and nanotubes, three-dimensional nanostructures, quantum dots, magnetic nanomaterials, photonic structures, and bio-inspired nanomaterials. This book will appeal not only to a broad spectrum of nanomaterials researchers, but also to SEM development specialists. TOC:Techniques.- Fundamentals of Scanning Electron Microscopy (SEM).- Low Voltage and High-resolution SEM.- X-ray Microanalysis in Nanomaterials.- Backscattering Detector and EBSD in Nanomaterials Characterization.- Environmental Microscopy Application in Nanomaterials Research.- E-beam Nanolithography Integrated with SEM.- Focused Ion Beam Microscopy in Nanostructures Fabrication.- Scanning Transmission Electron Microscopy (STEM) in Nanostructure Characterization. Applications.- Quantum Nanowires and Carbon Nanotubes.- Photonic Crystals.- Nanoparticles and Colloidal Nanocrystal Self-assembly.- Nano-building Blocks Fabricated through Templates.- Oxide Nanostructures.- Biological and Bio-inspired Nanomaterials and Devices.- Nano-manipulators in-situ Nanomaterials Engineering.- Cryo- and High- Temperature Holder in Nanomaterials Research.
This volume continues the tradition formed in Nanotechnology in Catalysis 1 and 2. As with those books, this one is based upon an ACS symposium. Some of the most illustrious names in heterogeneous catalysis are among the contributors. The book covers:- Design, synthesis, and control of catalysts at nanoscale- Understanding of catalytic reaction at nanometer scale- Characterization of nanomaterials as catalysts- Nanoparticle metal or metal oxides catalysts- Nanomaterials as catalyst supports- New catalytic applications of nanomaterials TOC:Nanotechnology: Applications and Potentials for Heterogeneous Catalysts.- Oxide-Supported Metal Thin Film Catalysts: The How and Why.- Developing Catalytic Nanomotors.- Catalysis by Gold: Recent Advances in Oxidation Reactions.- Gold Catalysts Supported on Nanostructured Materials: Support Effects.- Highly Effective Nanocatalysts Prepared through Sol-gel Technique.- Dendrimer Templates for Supported Nanoparticle Catalysts.- Tungsten Oxide Nanorods: Synthesis, Cheracterization, and Applications.- Catalysis by Metal and Oxide Nano-Particles, Single Metal Atoms and Di-nuclear Oxo-Ions in Zeolites.- Dual Catalytic Role of Co nanoparticles in Bulk Synthesis of Si-Based Nanowires.- Influence of Particle Size and Interaction with the Support on Redox and Catalytic Properties of Metals, Metal Oxides and Metal Complexes.- Thermo-Catalytic Oxidation of Dihydroxybenzenes in the Presence of Nano-Particle Iron Oxide.- Synthesis of Palladium Based Supported Catalysts by Colloidal Oxide Chemistry.- Gold-Based Nanoparticle Catalysts for Fuel Cell Reactions.- Carbon Supported Core-Shell PtSnOx Nanoparticles: Synthesis, Characterization and Performance as Anode Catalysts for Direct Ethanol Fuel Cells.