Author: Heock-Hoi KwonPublisher:
ISBN:
Category :
Languages : en
Pages : 284
Book Description
Synthesis and Characterization of Group V Metal Carbide and Nitride Catalysts
Author: Heock-Hoi KwonSynthesis and Characterization of Transition Metal Nitrides and Carbides for Catalysis and Electrochemistry Application
Author: Sarah MetzkePublisher:
ISBN:
Category :
Languages : en
Pages :
Book Description
It was the goal of this work to explore two different synthesis pathways using green chemistry. The first part of this thesis is focusing on the use of the urea-glass route towards single phase manganese nitride and manganese nitride/oxide nano-composites embedded in carbon, while the second part of the thesis is focusing on the use of the “saccharide route” (namely cellulose, sucrose, glucose and lignin) towards metal (Ni0), metal alloy (Pd0.9Ni0.1, Pd0.5Ni0.5, Fe0.5Ni0.5, Cu0.5Ni0.5 and W0.15Ni0.85) and ternary carbide (Mn0.75Fe2.25C) nanoparticles embedded in carbon. In the interest of battery application, MnN0.43 nanoparticles surrounded by a graphitic shell and embedded in carbon with a high surface area (79 m^2/g) were synthesized, following a previously set route.The comparison of the material characteristics before and after the discharge showed no remarkable difference in terms of composition and just slight differences in the morphological point of view, meaning the particles are stable but agglomerate. The graphitic shell ...
The Chemistry of Transition Metal Carbides and Nitrides
Author: S.T. OyamaPublisher: Springer Science & Business Media
ISBN: 9400915659
Category : Science
Languages : en
Pages : 565
Book Description
This book arose from a symposium titled 'Transition Metal Carbides and Nitrides: Preparation, Properties, and Reactivity' organized by Jae Sung Lee, Masatoshi Nagai and myself. The symposium was part of the 1995 Congress of Pacific Rim Chemical Societies, held in Honolulu, Hawaii between December 17-22, 1995. The meeting was the first major conference to exclusively address the theme of metal carbides and nitrides, and brought together many of the major researchers in the field. Over 50 scientists and engineers reported their latest findings in five sessions of presentations and discussions. The book closely follows the topics covered in the conference: Theory of bonding Structure and composition Catalytic properties Physical properties New methods of preparation Spectroscopy and microscopy The book is unique in its coverage. It provides a general introduction to the properties and nature of the materials, but also covers their latest applications in a wide variety of fields. It should thus be of interest to both experts and nonexperts in the fields of material science, solid-state chemistry, physics, ceramics engineering, and catalysis. The first chapter gives an overview, and many of the chapters provide summaries of advanced topics. All contributions were peer-reviewed.
New Catalysts for Coal Processing
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 5
Book Description
The subject of this research project was to investigate the catalytic properties of a new class of materials, transition metal carbides and nitrides, for treatment of coal liquid and petroleum feedstocks. The main objectives were: (1) preparation of catalysts in unsupported and supported form; (2) characterization of the materials; (3) evaluation of their catalytic properties in HDS and HDN; (4) measurement of the surface properties; and (5) observation of adsorbed species. All of the objectives were substantially carried out and the results will be described in detail below. The catalysts were transition metal carbides and nitrides spanning Groups 4--6 in the Periodic Table. They were chosen for study because initial work had shown they were promising materials for hydrotreating. The basic strategy was first to prepare the materials in unsupported form to identify the most promising catalyst, and then to synthesize a supported form of the material. Already work had been carried out on the synthesis of the Group VI compounds Mo2C, Mo2N, and WC, and new methods were developed for the Group V compounds VC and NbC. All the catalysts were then evaluated in a hydrotreating test at realistic conditions. It was found that the most active catalyst was Mo2C, and further investigations of the material were carried out in supported form. A new technique was employed for the study of the bulk and surface properties of the catalysts, near edge x-ray absorption spectroscopy (NEXAFS), that fingerprinted the electronic structure of the materials. Finally, two new research direction were explored. Bimetallic alloys formed between two transition metals were prepared, resulting in catalysts having even higher activity than Mo2C. The performance of the catalysts in hydrodechloration was also investigated.
Synthesis and transport properties of 2D transition metal carbides (MXenes)
Author: Joseph HalimPublisher: Linköping University Electronic Press
ISBN: 9176852199
Category :
Languages : en
Pages : 82
Book Description
Since the isolation and characterization of graphene, there has been a growing interest in 2D materials owing to their unique properties compared to their 3D counterparts. Recently, a family of 2D materials of early transition metal carbides and nitrides, labelled MXenes, has been discovered (Ti2CTz, Ti3C2Tz, Mo2TiC2Tz, Ti3CNTz, Ta4C3Tz, Ti4N3Tz among many others), where T stands for surface-terminating groups (O, OH, and F). MXenes are mostly produced by selectively etching A layers (where A stands for group A elements, mostly groups 13 and 14) from the MAX phases. The latter are a family of layered ternary carbides and/or nitrides and have a general formula of Mn+1AXn (n = 1-3), where M is a transition metal and X is carbon and/or nitrogen. The produced MXenes have a conductive carbide core and a non-conductive O-, OH- and/or F-terminated surface, which allows them to work as electrodes for energy storage applications, such as Li-ion batteries and supercapacitors. Prior to this work, MXenes were produced in the form of flakes of lateral dimension of about 1 to 2 microns; such dimensions and form are not suitable for electronic characterization and applications. I have synthesized various MXenes (Ti3C2Tz, Ti2CTz and Nb2CTz) as epitaxial thin films, a more suitable form for electronic and photonic applications. These films were produced by HF, NH4HF2 or LiF + HCl etching of magnetron sputtered epitaxial Ti3AlC2, Ti2AlC, and Nb2AlC thin films. For transport properties of the Ti-based MXenes, Ti2CTz and Ti3C2Tz, changing n from 1 to 2 resulted in an increase in conductivity but had no effect on the transport mechanism (i.e. both Ti3C2Tx and Ti2CTx were metallic). In order to examine whether the electronic properties of MXenes differ when going from a few layers to a single flake, similar to graphene, the electrical characterization of a single Ti3C2Tz flake with a lateral size of about 10 μm was performed. These measurements, the first for MXene, demonstrated its metallic nature, along with determining the nature of the charge carriers and their mobility. This indicates that Ti3C2Tz is inherently of 2D nature independent of the number of stacked layers, unlike graphene, where the electronic properties change based on the number of stacked layers. Changing the transition metal from Ti to Nb, viz. comparing Ti2CTz and Nb2CTz thin films, the electronic properties and electronic conduction mechanism differ. Ti2CTz showed metallic-like behavior (resistivity increases with increasing temperature) unlike Nb2CTz where the conduction occurs via variable range hopping mechanism (VRH) - where resistivity decreases with increasing temperature. Furthermore, these studies show the synthesis of pure Mo2CTz in the form of single flakes and freestanding films made by filtering Mo2CTz colloidal suspensions. Electronic characterization of free-standing films made from delaminated Mo2CTz flakes was investigated, showing that a VRH mechanism prevails at low temperatures (7 to ≈ 60 K). Upon vacuum annealing, the room temperature, RT, conductivity of Mo2CTx increased by two orders of magnitude. The conduction mechanism was concluded to be VRH most likely dominated by hopping within each flake. Other Mo-based MXenes, Mo2TiC2Tz and Mo2Ti2C3Tz, showed VRH mechanism at low temperature. However, at higher temperatures up to RT, the transport mechanism was not clearly understood. Therefore, a part of this thesis was dedicated to further investigating the transport properties of Mo-based MXenes. This includes Mo2CTz, out-of-plane ordered Mo2TiC2Tz and Mo2Ti2C3Tz, and vacancy ordered Mo1.33CTz. Magneto-transport of free-standing thin films of the Mo-based MXenes were studied, showing that all Mo-based MXenes have two transport regimes: a VRH mechanism at lower temperatures and a thermally activated process at higher temperatures. All Mo-based MXenes except Mo1.33CTz show that the electrical transport is dominated by inter-flake transfer. As for Mo1.33CTz, the primary electrical transport mechanism is more likely to be intra-flake. The synthesis of vacancy ordered MXenes (Mo1.33CTz and W1.33CTz) raised the question of possible introduction of vacancies in all MXenes. Vacancy ordered MXenes are produced by selective etching of Al and (Sc or Y) atoms from the parent 3D MAX phases, such as (Mo2/3Sc1/3)2AlC, with in-plane chemical ordering of Mo and Sc. However, not all quaternary parent MAX phases form the in-plane chemical ordering of the two M metals; thus the synthesis of the vacancy-ordered MXenes is restricted to a very limited number of MAX phases. I present a new method to obtain MXene flakes with disordered vacancies that may be generalized to all quaternary MAX phases. As proof of concept, I chose Nb-C MXene, as this 2D material has shown promise in several applications, including energy storage, photothermal cell ablation and photocatalysts for hydrogen evolution. Starting from synthetizing (Nb2/3Sc1/3)2AlC quaternary solid solution and etching both the Sc and Al atoms resulted in Nb1.33C material with a large number of vacancies and vacancy clusters. This method may be applicable to other quaternary or higher MAX phases wherein one of the transition metals is more reactive than the other, and it could be of vital importance in applications such as catalysis and energy storage.
Model Systems in Catalysis
Author: Robert RiouxPublisher: Springer Science & Business Media
ISBN: 0387980490
Category : Science
Languages : en
Pages : 531
Book Description
This book is an excellent compilation of cutting-edge research in heterogeneous catalysis and related disciplines – surface science, organometallic catalysis, and enzymatic catalysis. In 23 chapters by noted experts, the volume demonstrates varied approaches using model systems and their successes in understanding aspects of heterogeneous catalysis, both metal- and metal oxide-based catalysis in extended single crystal and nanostructured catalytic materials. To truly appreciate the astounding advances of modern heterogeneous catalysis, let us first consider the subject from a historical perspective. Heterogeneous catalysis had its beginnings in England and France with the work of scientists such as Humphrey Davy (1778–1829), Michael Faraday (1791–1867), and Paul Sabatier (1854–1941). Sabatier postulated that surface compounds, si- lar to those familiar in bulk to chemists, were the intermediate species leading to catalytic products. Sabatier proposed, for example, that NiH moieties on a Ni sur- 2 face were able to hydrogenate ethylene, whereas NiH was not. In the USA, Irving Langmuir concluded just the opposite, namely, that chemisorbed surface species are chemically bound to surfaces and are unlike known molecules. These chemisorbed species were the active participants in catalysis. The equilibrium between gas-phase molecules and adsorbed chemisorbed species (yielding an adsorption isotherm) produced a monolayer by simple site-filling kinetics.
2D Metal Carbides and Nitrides (MXenes)
Author: Babak AnasoriPublisher: Springer Nature
ISBN: 3030190269
Category : Technology & Engineering
Languages : en
Pages : 534
Book Description
This book describes the rapidly expanding field of two-dimensional (2D) transition metal carbides and nitrides (MXenes). It covers fundamental knowledge on synthesis, structure, and properties of these new materials, and a description of their processing, scale-up and emerging applications. The ways in which the quickly expanding family of MXenes can outperform other novel nanomaterials in a variety of applications, spanning from energy storage and conversion to electronics; from water science to transportation; and in defense and medical applications, are discussed in detail.
Transition Metal Carbides and Nitrides
Author: Louis TothPublisher: Elsevier
ISBN: 032315722X
Category : Technology & Engineering
Languages : en
Pages : 296
Book Description
Refractory Materials, Volume 7: Transition Metal Carbides and Nitrides discusses the developments in transition metal carbide and nitride research. This volume is organized into nine chapters that emphasize the mechanical and superconducting properties of these compounds. The introductory chapters deal with the general properties, preparation techniques, characterization, crystal chemistry, phase relationships, and thermodynamics of transition metal carbides and nitrides. The following chapter highlights the mechanical properties of these compounds, such as elastic and plastic deformation, fracture, strengthening mechanisms, and hardness. The discussion then shifts to specific electrical and magnetic properties, including electrical resistivity, Hall coefficient, and magnetic susceptibility. A separate chapter is devoted to carbides and nitrides as superconductors. The concluding chapters explore certain theories that explain the mechanisms of band structure and bonding in carbides and nitrides. This volume is of great value to research workers in metallurgy, ceramics, physics, chemistry, and related fields, as well as to advanced students investigating problems concerning high temperature materials or interstitial compounds.
Ammonia Synthesis Catalysts: Innovation And Practice
Author: Huazhang LiuPublisher: World Scientific
ISBN: 9814518808
Category : Science
Languages : en
Pages : 895
Book Description
This book provides a review of worldwide developments in ammonia synthesis catalysts over the last 30 years. It focuses on the new generation of Fe1-xO based catalysts and ruthenium catalysts — both are major breakthroughs for fused iron catalysts. The basic theory for ammonia synthesis is systematically explained, covering topics such as the chemical components, crystal structure, preparation, reduction, performance evaluation, characterization of the catalysts, the mechanism and kinetics of ammonia synthesis reaction. Both theory and practice are combined in this presentation, with emphasis on the research methods, application and exploitation of catalysts.The comprehensive volume includes an assessment of the economic and engineering aspects of ammonia plants based on the performance of catalysts. Recent developments in photo-catalysis, electro-catalysis, biocatalysis and new uses of ammonia are also introduced in this book.The author, Professor Huazhang Liu, has been engaged in research and practice for more than 50 years in this field and was the inventor of the first Fe1-xO based catalysts in the world. He has done a lot of research on Fe3O4 based- and ruthenium based-catalysts, and has published more than 300 papers and obtained 21 patents during his career.
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