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Author : Kuno Matzinger
Publisher :
ISBN 13 :
Total Pages : 196 pages
Book Rating : 4.:/5 (428 download)
Download or read book Evolution of Metal Catalyst During CVD Synthesis of Carbon Nanotubes written by Kuno Matzinger and published by . This book was released on 2006 with total page 196 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Evolution of Metal Catalyst During CVD Synthesis of Carbon Nanotubes written by and published by . This book was released on with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The revolutionary discovery of carbon nanotubes (CNT) in 1991 led to intense research activities in the domain of carbon science. The fascinating properties of these unique material has opened a great number of potential applications e.g. as electron field emitters, one-dimensional conductors, supercapacitors, reinforcing fibres or hydrogen storage. Despite these stunning technical progresses there is still much struggle in the development of a synthesis method suitable for commercial applications. A leading candidate is the chemical vapour deposition (CVD) technique. Nucleation and growth of CNTs are induced by the decomposition of carbon-containing gases (CO, CO2, C2H2, etc) over a metallic catalyst at temperatures between 600°C and 1200°. CVD is a widely used technique to generate CNTs in large quantities and much progress has been made from the point of view of the yield, the synthesis costs or the purity of the products. But the great conundrum of CVD process remains the growth mechanism. A key reaction step for nanotube growth seems to be diffusion of carbon through the metal catalyst and the most active metals are iron, cobalt and nickel but their catalytic action depends on the type of precursor, the type of substrate and of the reactive gases used. Highly controversial is the actual chemical nature of the active catalyst e.g. if it is present as metal, carbide or as mixed phase. So far few investigations of the chemical and morphological evolution of the catalyst during CVD process have been performed. This thesis focuses on the evolution of nickel-, cobalt-, chromium- and molybdenum-based catalysts under a nitrogen/acetylene and a nitrogen/acetylene/ hydrogen atmosphere at 600°C and 750°C. In order to elucidate the nature of the catalyst during synthesis runs an X-ray diffractometer equipped with a heating stage and an atmosphere controlling system was used to study in-situ the evolution of metal nitrate films. Samples quenched after different pyrolysis ti.
Author : Hosam El-Din Saleh
Publisher : BoD – Books on Demand
ISBN 13 : 1789844010
Total Pages : 250 pages
Book Rating : 4.7/5 (898 download)
Download or read book Perspective of Carbon Nanotubes written by Hosam El-Din Saleh and published by BoD – Books on Demand. This book was released on 2019-12-11 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon nanotubes belong to new nanomaterials and have been known for almost 20 years, but their history is somewhat lengthier. They have been identified as promising candidates for various applications.High-temperature preparation techniques are conventional techniques for the synthesis of carbon nanotubes using arc discharge or laser ablation, but today these methods are being replaced by low-temperature vapor deposition techniques, since orientation, alignment, nanotube length, diameter, purity, and density of carbon nanotubes can be precisely controlled. The synthesis of carbon nanotubes by chemical vapor deposition on catalyst arrays leads to nanotube models grown from specific sites on surfaces. The controlled synthesis of nanotubes opens up interesting possibilities in nanoscience and nanotechnologies, including electrical, mechanical and electromechanical properties and devices, chemical functionalization, surface chemistry and photochemistry, molecular sensors, and interfacing with moderate biological systems.Carbon nanotubes are used in many applications due to their unique electrical, mechanical, optical, thermal, and other properties. Conductive and high-strength composite materials, energy saving and energy conversion devices, sensors, visualization of field emissions and sources of radiation, means for storing hydrogen, and nanoscale semiconductor devices, probes, and interconnections are some of the many applications of carbon nanotubes.
Author : Haider H. Almkhelfe
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (12 download)
Download or read book Scalable Carbon Nanotube Growth and Design of Efficient Catalysts for Fischer-Tropsch Synthesis written by Haider H. Almkhelfe and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The continued depletion of fossil fuels and concomitant increase in greenhouse gases have encouraged worldwide research on alternative processes to produce clean fuel. Fischer-Tropsch synthesis (FTS) is a heterogeneous catalytic reaction that converts syngas (CO and H2) to liquid hydrocarbons. FTS is a well-established route for producing clean liquid fuels. However, the broad product distribution and limited catalytic activity are restricting the development of FTS. The strong interactions between the active metal catalyst (Fe or Co) and support (Al2O3, SiO2 and TiO2) during post-synthesis treatments of the catalyst (such as calcination at ~500°C and reduction ~550°C) lead to formation of inactive and unreducible inert material like Fe2SiO4, CoAl2O4, Co2SiO4. The activity of FTS catalyst is negatively impacted by the presence of these inactive compounds. In our study, we demonstrate the use of a modified photo-Fenton process for the preparation of carbon nanotube (CNT)-supported Co and Fe catalysts that are characterized by small and well-dispersed catalyst particles on CNTs that require no further treatments. The process is facile, highly scalable, and involves the use of green catalyst precursors and an oxidant. The reaction kinetic results show high CO conversion (85%), selectivity for liquid hydrocarbons and stability. Further, a gaseous product mixture from FTS (C1-C4) was utilized as an efficient feedstock for the growth of high-quality, well-aligned single-wall carbon nanotube (SWCNT) carpets of millimeter-scale heights on Fe and (sub) millimeter-scale heights on Co catalysts via chemical vapor deposition (CVD). Although SWCNT carpets were grown over a wide temperature range (between 650 and 850°C), growth conducted at optimal temperatures for Co (850°C) and Fe (750°C) yielded predominantly SWCNTs that are straight, clean, and with sidewalls that are largely free of amorphous carbon. Also, low-temperature CVD growth of CNT carpets from Fe and Fe-Cu catalysts using a gaseous product mixture from FTS as a superior carbon feedstock is demonstrated. The efficiency of the growth process is evidenced by the highly dense, vertically aligned CNT structures from both Fe and Fe-Cu catalysts even at temperatures as low as 400°C-a record low growth temperature for CNT carpets obtained via conventional thermal CVD. The use of FTS-GP facilitates low-temperature growth of CNT carpets on traditional (alumina film) and nontraditional substrates (aluminum foil) and has the potential of enhancing CNT quality, catalyst lifetime, and scalability. We demonstrate growth of SWCNT carpets with diameter distributions that are smaller than SWCNTs in conventional carpets using a CVD process that utilizes the product gaseous mixture from Fischer-Tropsch synthesis (FTS-GP). The high-resolution transmission electron microscopic (HR-TEM) and Raman spectroscopic results reveal that the use of a high melting point metal as a catalyst promoter in combination with either Co (1.5 nm ± 0.7) at 850oC or Fe (1.9 nm ± 0.8) at 750oC yields smaller-diameter SWCNT arrays with narrow diameter distributions. Scalable synthesis of carbon nanotubes (CNTs), carbon nanofibers (CNFs), and onion like carbon (OLC) in a batch reactor using supercritical fluids as a reaction media is demonstrated. The process utilizes toluene, ethanol, or butanol as a carbon precursor in combination with ferrocene that serves as a catalyst precursor and a secondary carbon source. The use of supercritical fluids for growth does not only provide a route for selective growth of a variety of carbon nanomaterials, but also provides a unique one-step approach that is free of aggressive acid treatment for synthesis of CNT-supported metallic nanoparticle composites for catalysis and energy storage applications.
Author : Jiji Abraham
Publisher : Springer Nature
ISBN 13 : 3030913465
Total Pages : 2099 pages
Book Rating : 4.0/5 (39 download)
Download or read book Handbook of Carbon Nanotubes written by Jiji Abraham and published by Springer Nature. This book was released on 2022-11-16 with total page 2099 pages. Available in PDF, EPUB and Kindle. Book excerpt: This Handbook covers the fundamentals of carbon nanotubes (CNT), their composites with different polymeric materials (both natural and synthetic) and their potential advanced applications. Three different parts dedicated to each of these aspects are provided, with chapters written by worldwide experts in the field. It provides in-depth information about this material serving as a reference book for a broad range of scientists, industrial practitioners, graduate and undergraduate students, and other professionals in the fields of polymer science and engineering, materials science, surface science, bioengineering and chemical engineering. Part 1 comprises 22 chapters covering early stages of the development of CNT, synthesis techniques, growth mechanism, the physics and chemistry of CNT, various innovative characterization techniques, the need of functionalization and different types of functionalization methods as well as the different properties of CNT. A full chapter is devoted to theory and simulation aspects. Moreover, it pursues a significant amount of work on life cycle analysis of CNT and toxicity aspects. Part 2 covers CNT-based polymer nanocomposites in approximately 23 chapters. It starts with a short introduction about polymer nanocomposites with special emphasis on CNT-based polymer nanocomposites, different manufacturing techniques as well as critical issues concerning CNT-based polymer nanocomposites. The text deeply reviews various classes of polymers like thermoset, elastomer, latex, amorphous thermoplastic, crystalline thermoplastic and polymer fibers used to prepare CNT based polymer composites. It provides detailed awareness about the characterization of polymer composites. The morphological, rheological, mechanical, viscoelastic, thermal, electrical, electromagnetic shielding properties are discussed in detail. A chapter dedicated to the simulation and multiscale modelling of polymer nanocomposites is an additional attraction of this part of the Handbook. Part 3 covers various potential applications of CNT in approximately 27 chapters. It focuses on individual applications of CNT including mechanical applications, energy conversion and storage applications, fuel cells and water splitting, solar cells and photovoltaics, sensing applications, nanofluidics, nanoelectronics and microelectronic devices, nano-optics, nanophotonics and nano-optoelectronics, non-linear optical applications, piezo electric applications, agriculture applications, biomedical applications, thermal materials, environmental remediation applications, anti-microbial and antibacterial properties and other miscellaneous applications and multi-functional applications of CNT based polymer nanocomposites. One chapter is fully focussed on carbon nanotube research developments: published papers and patents. Risks associated with carbon nanotubes and competitive analysis of carbon nanotubes with other carbon allotropes are also addressed in this Handbook.
Author : Mohammed Rahman
Publisher : BoD – Books on Demand
ISBN 13 : 1789230527
Total Pages : 366 pages
Book Rating : 4.7/5 (892 download)
Download or read book Carbon Nanotubes written by Mohammed Rahman and published by BoD – Books on Demand. This book was released on 2018-04-26 with total page 366 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book Carbon Nanotubes - Recent Progress contains a number of recent researches on synthesis, growth, characterization, development, and potential applications on carbon materials especially CNTs in nanoscale. It is a promising novel research from top to bottom that has received a lot of interest in the last few decades. It covers the advanced topics on the physical, chemical, and potential applications of CNTs. Here, the interesting reports on cutting-edge science and technology related to synthesis, morphology, control, hybridization, and prospective applications of CNTs are concluded. This potentially unique work offers various approaches on the R
Author : Ayako Nakagawa
Publisher :
ISBN 13 :
Total Pages : 184 pages
Book Rating : 4.:/5 (239 download)
Download or read book Catalytic Chemical Vapor Deposition Synthesis of Carbon Nanotubes from Methane on SiO Supported Fe and Fe-Ni Catalysts written by Ayako Nakagawa and published by . This book was released on 2009 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt: Influences of operating conditions on the production of carbon nanotubes (CNTs) were studied using Fe and Fe-Ni bimetallic catalysts supported on silicon monoxide (SiO). The catalysts were prepared in three steps: (1) impregnation of SiO powders with ferric nitride or combinations of ferric and nickel nitrides, (2) oxidation of nitrides in an air stream, and (3) grinding the powders obtained. CNTs were successfully synthesized by catalytic CVD using NH3/CH4 mixtures in a horizontal tubular flow reactor. The following process parameters were varied to investigate their effects on the growth rates of CNTs. The morphologies of catalysts and product CNTs were observed by scanning electron microscope (SEM). The particle size of SiO, metal composition, metal loading, temperature for catalyst oxidation, extent of grinding of catalysts, NH3 pretreatment time, reaction temperature for CNT growth, reaction time, and NH3/CH4 feed ratio. Two different average sizes of SiO particles, 8 [mu]m and 44 [mu]m, were compared based on the growth of CNTs in 5 min. Catalysts supported on 44 [mu]m average sized SiO particles demonstrated higher yields when they were not pretreated in an NH3 stream. When 1 wt% Fe was loaded, aligned CNTs were formed, and a highest growth rate per unit mass of catalyst was observed. The range of oxidation temperature to achieve highest catalyst activities depended on metals and metal contents: 600 - 750°C for 1 wt% Fe, 450 - 600°C for 3 wt% Fe, and 750 - 900°C for Fe-Ni. Grinding catalysts for at least 3 minutes increased the growth rate of CNTs by approximately 40 percent. The growth of CNTs was enhanced when no NH3 pretreatment of catalysts was carried out, regardless of metals and metal contents. However, CNTs did not grow appreciably from methane without ammonia. An NH3/CH4 feed ratio of 0.15 - 0.25 was observed to yield highest growth rates. The reaction temperature to achieve highest CNT growth rates was found to be in the range between 990 and 1000 °C. The growth of CNTs was not linear but decreased with reaction time.
Author : GuiPing Dai
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (139 download)
Download or read book Synthesis of Carbon Nanotubes by Catalytic Chemical Vapor Deposition written by GuiPing Dai and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: As a new carbon material in the twenty-first century, carbon nanotubes (CNTs) have excellent optical, electrical, magnetic, thermal, chemical, and mechanical properties. There are many synthesis methods to produce CNTs. Compared with other methods, chemical vapor deposition (CVD) is the most effective method that has broad prospects for large-scale control of CNTs in recent years due to its simple equipment, simple operation, and lower cost. In order to gain a comprehensive understanding of the controlling parameters about the formation of CNTs, this chapter reviews the latest progress in the preparation of CNTs by CVD from three of the most important influencing factors: carbon sources, catalysts, and substrates. Among them, the catalyst is the most influential factor for the morphology, structure, and properties of CNTs. It should be pointed out that many growth factors can control the particle size distribution, composition, and structure of the catalysts, such as catalyst substrate, metal transition components added, calcination temperature, etc.
Author : Amit Goyal
Publisher :
ISBN 13 :
Total Pages : 255 pages
Book Rating : 4.:/5 (935 download)
Download or read book New Approaches to Scaled-up Carbon Nanotube Synthesis and Nanotube-based Metal Composites and Sensors written by Amit Goyal and published by . This book was released on 2007 with total page 255 pages. Available in PDF, EPUB and Kindle. Book excerpt: The first phase of the work presented in this dissertation is the development of a scaleable process for the cost-effective synthesis of single walled carbon nanotubes (SWNTs) by thermally-induced catalytic chemical vapor deposition (CVD). With the goal of understanding the growth mechanism and optimize the synthesis process, the effect of CVD and catalyst parameters on nanotube formation was investigated in detail. It was found that nucleation and growth of SWNTs occurred within a few seconds of the introduction of the carbon source, carbon monoxide, at temperatures above 675°C over a Co-Mo/MgO catalyst/support system, resulting in the formation of high quality thinly bundled SWNTs with a narrow individual nanotube diameter distribution. A simple kinetic model is proposed to explain the observed growth and exit gas (CO2) concentration data. A scaled up run using fluidized bed reactor is performed to demonstrate large SWNTs production. In the second phase of the research performed some of the CVD parameters optimized for the synthesis of pure nanotubes were used to infiltrate SWNTs as well as multiwalled carbon nanotubes (MWNTs) into catalyst precursor filled iron and aluminum matrices, respectively, to directly fabricate metal-nanotube composites. Two carbon sources, carbon monoxide and acetylene were used for the synthesis of SWNTs and MWNTs, respectively. The yield strength of iron-carbon nanotube composites showed substantial enhancement of up to 45% and 36 % with 1 wt % of infiltrated SWNTs and MWNTs, respectively, relative to that of similarly treated pure iron samples of the same piece density without carbon nanotubes. Vickers hardness measurements showed an increase of 74% and 96% for iron composites filled with SWNTs and MWNTs, respectively. The use of a mixed feed of CO and acetylene resulted in carbide-free fabrication of the nanocomposites. A reaction mechanism supporting the observed carbide-free growth is also presented. In the third phase of the research performed, a SWNT fabrication protocol using CVD growth or electrophoretic deposition was employed for integrating nanotubes as biosensor and chemical gas sensor probes. For biosensor probes, vertically aligned SWNTs were grown or deposited on metal interconnects (Cr/Co), at precise locations, which were patterned on quartz substrates using photo- and e-beam Iithogrpahy to make electrical connections to each SWNT/bundle individually. Gas sensor probes were fabricated using individually suspended SWNTs contacted by Cr/Au pads as source and drain field effect transistor components for the monitoring of NO2 vapors. The adsorption of an electron donating gas such as NO2 on the SWNT sidewalls shifts the Fermi level of the p-type semiconducting nanotubes, consequently changing their electrical conductivity. Experimental results showed that sensor response to NO2 (at 10-300 ppm levels) was of the order of a few seconds at 100 ppm, and was reversible and reproducible. Recovery of the sensor response was achieved by heating the sensors at 120 °C for a period of 10-12 hours indicating physisorption of the NO2 molecules on the nanotube sidewalls.
Author : Michael J. O’Connell
Publisher : CRC Press
ISBN 13 : 1420004212
Total Pages : 339 pages
Book Rating : 4.4/5 (2 download)
Download or read book Carbon Nanotubes written by Michael J. O’Connell and published by CRC Press. This book was released on 2018-10-03 with total page 339 pages. Available in PDF, EPUB and Kindle. Book excerpt: Since their discovery more than a decade ago, carbon nanotubes (CNTs) have held scientists and engineers in captive fascination, seated on the verge of enormous breakthroughs in areas such as medicine, electronics, and materials science, to name but a few. Taking a broad look at CNTs and the tools used to study them, Carbon Nanotubes: Properties and Applications comprises the efforts of leading nanotube researchers led by Michael O’Connell, protégé of the late father of nanotechnology, Richard Smalley. Each chapter is a self-contained treatise on various aspects of CNT synthesis, characterization, modification, and applications. The book opens with a general introduction to the basic characteristics and the history of CNTs, followed by discussions on synthesis methods and the growth of “peapod” structures. Coverage then moves to electronic properties and band structures of single-wall nanotubes (SWNTs), magnetic properties, Raman spectroscopy of electronic and chemical behavior, and electromechanical properties and applications in NEMS (nanoelectromechanical systems). Turning to applications, the final sections of the book explore mechanical properties of SWNTs spun into fibers, sidewall functionalization in composites, and using SWNTs as tips for scanning probe microscopes. Taking a fresh look at this burgeoning field, Carbon Nanotubes: Properties and Applications points the way toward making CNTs commercially viable.
Author : Kamel Ahmed Abd-Elsalam
Publisher : Micro & Nano Technologies
ISBN 13 : 0128197862
Total Pages : 652 pages
Book Rating : 4.1/5 (281 download)
Download or read book Carbon Nanomaterials for Agri-Food and Environmental Applications written by Kamel Ahmed Abd-Elsalam and published by Micro & Nano Technologies. This book was released on 2019-11 with total page 652 pages. Available in PDF, EPUB and Kindle. Book excerpt: Carbon Nanomaterials for Agri-food and Environmental Applications discusses the characterization, processing and applications of carbon-based nanostructured materials in the agricultural and environmental sectors. Sections discuss the synthesis and characterization of carbon nanotubes, the technological developments in environmental applications of carbon-based nanomaterials, and agri-food applications. The book also covers the toxic effects of engineered carbon nanoparticles on the environment, and in plants and animals. Finally, quality control and risk management are addressed to assess health and environmental risks. This is an applicable book for graduate students, researchers and those in industrial sectors of science and technology who want to learn more about carbon nanomaterials. Compares a range of carbon-based nanomaterials, showing how they are used for a range of agricultural and environmental applications Discusses the challenges and toxicity of different types of carbon-based nanomaterials for environmental and agricultural applications Explores when different classes of nanomaterial should be used in different environments
Author :
Publisher :
ISBN 13 :
Total Pages : 8 pages
Book Rating : 4.:/5 (227 download)
Download or read book Preparation of Monodispersed Fe-Mo Nanoparticles as the Catalyst for CVD Synthesis of Carbon Nanotubes written by and published by . This book was released on 2001 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Uniform iron-molybdenum nanoparticles were prepared by thermal decomposition of metal carbonyl complexes using a mixture of long-chain carboxylic acid and long-chain amine as protective agents. The sizes of the nanoparticles can be systematically varied from 3 to 14 nm by changing the experimental conditions. High-resolution TEM images and EDX data show that the prepared nanoparticles are highly crystalline iron nanoparticles containing 4% molybdenum. The effects of the concentration, reaction time, the ratio of metal carbonyl complexes versus protective agents, and the ratio of acid/amine of the protective agents on the sizes of the produced nanoparticles were systematically studied. The prepared nanoparticles were used as catalysts for single-walled carbon nanotube growth and the results indicate that there is an upper limit for the size of the catalyst particles to nucleate singlewalled carbon nanotubes.
Author : Jing Kong
Publisher :
ISBN 13 :
Total Pages : 404 pages
Book Rating : 4.F/5 ( download)
Download or read book Carbon Nanotubes written by Jing Kong and published by . This book was released on 2002 with total page 404 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Jean-Charles Arnault
Publisher : John Wiley & Sons
ISBN 13 : 1119429382
Total Pages : 320 pages
Book Rating : 4.1/5 (194 download)
Download or read book Synthesis and Applications of Nanocarbons written by Jean-Charles Arnault and published by John Wiley & Sons. This book was released on 2020-09-21 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt: A crucial overview of the cutting-edge in nanocarbon research and applications In Synthesis and Applications of Nanocarbons, the distinguished authors have set out to discuss fundamental topics, synthetic approaches, materials challenges, and various applications of this rapidly developing technology. Nanocarbons have recently emerged as a promising material for chemical, energy, environmental, and medical applications because of their unique chemical properties and their rich surface chemistries. This book is the latest entry in the Wiley book series Nanocarbon Chemistry and Interfaces and seeks to comprehensively address many of the newly surfacing areas of controversy and development in the field. This book introduces foundational concepts in nanocarbon technology, hybrids, and applications, while also covering the most recent and cutting-edge developments in this area of study. Synthesis and Applications of Nanocarbons addresses new discoveries in the field, including: · Nanodiamonds · Onion-like carbons · Carbon nanotubes · Fullerenes · Carbon dots · Carbon fibers · Graphene · Aerographite This book provides a transversal view of the various nanocarbon materials and hybrids and helps to share knowledge between the communities of each material and hybrid type.
Author : Jean-Charles Arnault
Publisher : John Wiley & Sons
ISBN 13 : 1119429447
Total Pages : 320 pages
Book Rating : 4.1/5 (194 download)
Download or read book Synthesis and Applications of Nanocarbons written by Jean-Charles Arnault and published by John Wiley & Sons. This book was released on 2020-08-28 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt: A crucial overview of the cutting-edge in nanocarbon research and applications In Synthesis and Applications of Nanocarbons, the distinguished authors have set out to discuss fundamental topics, synthetic approaches, materials challenges, and various applications of this rapidly developing technology. Nanocarbons have recently emerged as a promising material for chemical, energy, environmental, and medical applications because of their unique chemical properties and their rich surface chemistries. This book is the latest entry in the Wiley book series Nanocarbon Chemistry and Interfaces and seeks to comprehensively address many of the newly surfacing areas of controversy and development in the field. This book introduces foundational concepts in nanocarbon technology, hybrids, and applications, while also covering the most recent and cutting-edge developments in this area of study. Synthesis and Applications of Nanocarbons addresses new discoveries in the field, including: · Nanodiamonds · Onion-like carbons · Carbon nanotubes · Fullerenes · Carbon dots · Carbon fibers · Graphene · Aerographite This book provides a transversal view of the various nanocarbon materials and hybrids and helps to share knowledge between the communities of each material and hybrid type.
Author : Robert William Atkinson (III)
Publisher :
ISBN 13 :
Total Pages : 223 pages
Book Rating : 4.:/5 (13 download)
Download or read book Vapor Synthesis and Thermal Evolution of Supportless, Metal Nanotubes and Application as Electrocatalysts written by Robert William Atkinson (III) and published by . This book was released on 2015 with total page 223 pages. Available in PDF, EPUB and Kindle. Book excerpt: One of the major limitations of proton exchange membrane fuel cells (PEMFCs) is the high cost and poor durability of the currently preferred catalyst design, small Pt nanoparticles supported on high surface area carbon (Pt/C). Unsupported, high-aspect ratio nanostructured catalysts, or extended surface catalysts, are a promising paradigm as electrocatalysts for a number of electrochemical reactions. These extended surface catalysts generally exhibit higher specific activities compared to carbon-supported nanoparticle counterparts that have been ascribed to the unique electronic, surface and structural properties of these materials. Extended surface catalysts frequently maintain enhanced durability over supported catalysts during fuel cell operation because these materials are not susceptible to the same modes of degradation inherent to small supported nanoparticles. Considering the promise of extended surfaces as catalysts, we have synthesized metallic, mixed-phase, and alloyed bimetallic nanotubes by a chemical vapor deposition (CVD) technique to catalyze a number of reactions relevant for fuel cells. In this CVD process, metalorganic precursors, namely metal-acetylacetonates, are decomposed by a mild thermal treatment and deposited as conformal nanoparticulate layers within a sacrificial anodic alumina template. Following vapor deposition, the nanotube samples may be annealed while still in the template to induce a series of changes with implications on electrocatalysis, including porosity, alloying, and increases in surface coordination. The metallic nanotubes prepared by this method are highly active catalysts for a host of electrochemical reactions that are promising for fuel cell applications. The effects of composition, heat treatment temperature and gas environment on the activity and durability of these materials have been studied for oxygen reduction, methanol oxidation, formic acid oxidation, and hydrogen oxidation.
Author : Boris S. Bokstein
Publisher :
ISBN 13 : 0198528043
Total Pages : 341 pages
Book Rating : 4.1/5 (985 download)
Download or read book Thermodynamics and Kinetics in Materials Science written by Boris S. Bokstein and published by . This book was released on 2005-06-30 with total page 341 pages. Available in PDF, EPUB and Kindle. Book excerpt: Accompanying CD-ROM contains ... "computer tests and laboratories."--CD-ROM label.
