Nanofabrication and STM/XPS Studies of Automotive Model Catalysts PDF Download
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Author: Masaru Ishii
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author: Masaru Ishii
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Author: Masaru Ishii
Publisher:
ISBN:
Category : Automobiles
Languages : en
Pages :
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Book Description
"The work in this thesis is a study of the study of the structure and NOx storage reactivities of precious metal and oxide support model catalysts by using surface science techniques. The introduction details the current situation of automobile catalysts and NOx storage reduction (NSR) catalysts. The experimental gives details of surface microscopy techniques, the preparation of clean TiO2 (110) and Pt (111) surface and the construction of a barium source. The main body of data presented here uses scanning tunnelling microscopy (STM) technique" - introduction.
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Category : Dissertations, Academic
Languages : en
Pages : 308
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Author:
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ISBN:
Category :
Languages : en
Pages :
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High Pressure Scanning Tunneling Microscopy (HP-STM) and Ambient Pressure X-ray Photoelectron Spectroscopy were used to study the structural properties and catalytic behavior of noble metal surfaces at high pressure. HP-STM was used to study the structural rearrangement of the top most atomic surface layer of the metal surfaces in response to changes in gas pressure and reactive conditions. AP-XPS was applied to single crystal and nanoparticle systems to monitor changes in the chemical composition of the surface layer in response to changing gas conditions. STM studies on the Pt(100) crystal face showed the lifting of the Pt(100)-hex surface reconstruction in the presence of CO, H2, and Benzene. The gas adsorption and subsequent charge transfer relieves the surface strain caused by the low coordination number of the (100) surface atoms allowing the formation of a (1 x 1) surface structure commensurate with the bulk terminated crystal structure. The surface phase change causes a transformation of the surface layer from hexagonal packing geometry to a four-fold symmetric surface which is rich in atomic defects. Lifting the hex reconstruction at room temperature resulted in a surface structure decorated with 2-3 nm Pt adatom islands with a high density of step edge sites. Annealing the surface at a modest temperature (150 C) in the presence of a high pressure of CO or H2 increased the surface diffusion of the Pt atoms causing the adatom islands to aggregate reducing the surface concentration of low coordination defect sites. Ethylene hydrogenation was studied on the Pt(100) surface using HP-STM. At low pressure, the lifting of the hex reconstruction was observed in the STM images. Increasing the ethylene pressure to 1 Torr, was found to regenerate the hexagonally symmetric reconstructed phase. At room temperature ethylene undergoes a structural rearrangement to form ethylidyne. Ethylidyne preferentially binds at the three-fold hollow sites, which are present on the Pt(100) hex reconstructed phase, but not the (100)-(1x1) surface. The increase in ethylene pressure caused the adsorbate interactions to dominate the crystal morphology and imposed a surface layer structure that matched the ethylidyne binding geometry. The STM results also showed that the surface was reversibly deformed during imaging due to increases in Pt mobility at high pressure. The size dependence on the activity and surface chemistry of Rh nanoparticles was studied using AP-XPS. The activity was found to increase with particle size. The XPS spectra show that in reaction conditions the particle surface has an oxide layer which is chemically distinct from the surface structure formed by heating in oxygen alone. This surface oxide which is stabilized in the catalytically active CO oxidation conditions was found to be more prevalent on the smaller nanoparticles. The reaction-induced surface segregation behavior of bimetallic noble metal nanoparticles was observed with APXPS. Monodisperse 15 nm RhPd and PdPt nanoparticles were synthesized with well controlled Rh/Pd and Pd/Pt compositions. In-situ XPS studies showed that at 300 C in the presence of an oxidizing environment (100 mTorr NO or O2) the surface concentration of the more easily oxidized element (Rh in RhPd and Pd in PdPt) was increased. Switching the gas environment to more reducing conditions (100 mTorr NO and 100 mTorr CO) caused the surface enrichment of the element with the lowest surface energy in its metallic state. Using in-situ characterization, the redox chemistry and the surface composition of bimetallic nanoparticle samples were monitored in reactive conditions. The particle surfaces were shown to reversibly restructure in response to the gas environment at high temperature. The oxidation behavior of the Pt(110) surface was studied using surface sensitive in-situ characterization by APXPS and STM. In the presence of 500 mTorr O2 and temperatures between 25 and 200 C, subsurface oxygen was detected in the surface layer. STM images show that these conditions were found to cause a roughened surface decorated with 1 nm islands. The formation of this surface oxide is a high pressure phenomenon and was not detected in 50 mTorr O2. After forming the surface oxide at high pressure, its chemical activity was measured through the reaction with CO at low pressure while continuously monitoring the oxygen species with XPS. The subsurface oxygen was removed by CO oxidation at a comparable rate to the chemisorbed oxygen at 2 C. Repeating the experiment at -3 C reduced the reaction rate, but not the relative activity of the two chemical species suggesting that neither species is significantly more active for the CO oxidation reaction. These studies use molecular level surface characterization in the presence of gases to show the structural changes induced by gas adsorption at high pressure.
Author: Bing Zhou
Publisher: Springer Science & Business Media
ISBN: 0387346880
Category : Technology & Engineering
Languages : en
Pages : 342
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Book Description
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.
Author:
Publisher: Elsevier
ISBN: 0080538312
Category : Science
Languages : en
Pages : 677
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Book Description
The book is a multi-author survey (in 15 chapters) of the current state of knowledge and recent developments in our understanding of oxide surfaces. The author list includes most of the acknowledged world experts in this field. The material covered includes fundamental theory and experimental studies of the geometrical, vibrational and electronic structure of such surfaces, but with a special emphasis on the chemical properties and associated reactivity. The main focus is on metal oxides but coverage extends from 'simple' rocksalt materials such as MgO through to complex transition metal oxides with different valencies.
Author: Ampere A. Tseng
Publisher: World Scientific
ISBN: 9812790896
Category : Technology & Engineering
Languages : en
Pages : 583
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Book Description
Many of the devices and systems used in modern industry are becoming progressively smaller and have reached the nanoscale domain. Nanofabrication aims at building nanoscale structures, which can act as components, devices, or systems, in large quantities at potentially low cost. Nanofabrication is vital to all nanotechnology fields, especially for the realization of nanotechnology that involves the traditional areas across engineering and science. This is the first book solely dedicated to the manufacturing technology in nanoscale structures, devices, and systems and is designed to satisfy the growing demands of researchers, professionals, and graduate students. Both conventional and non-conventional fabrication technologies are introduced with emphasis on multidisciplinary principles, methodologies, and practical applications. While conventional technologies consider the emerging techniques developed for next generation lithography, non-conventional techniques include scanning probe microscopy lithography, self-assembly, and imprint lithography, as well as techniques specifically developed for making carbon tubes and molecular circuits and devices. Sample Chapter(s). Chapter 1: Atom, Molecule, and Nanocluster Manipulations for Nanostructure Fabrication Using Scanning Probe Microscopy (3,320 KB). Contents: Atomic Force Microscope Lithography (N Kawasegi et al.); Nanowire Assembly and Integration (Z Gu & D H Gracias); Extreme Ultraviolet Lithography (H Kinoshita); Electron Projection Lithography (T Miura et al.); Electron Beam Direct Writing (K Yamazaki); Electron Beam Induced Deposition (K Mitsuishi); Focused Ion Beams and Interaction with Solids (T Ishitani et al.); Nanofabrication of Nanoelectromechanical Systems (NEMS): Emerging Techniques (K L Ekinci & J Brugger); and other papers. Readership: Researchers, professionals, and graduate students in the fields of nanoengineering and nanoscience.
Author: Ronald M. Heck
Publisher: John Wiley & Sons
ISBN: 0470275030
Category : Science
Languages : en
Pages : 548
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Book Description
Catalytic Air Pollution Control: Commercial Technology is the primary source for commercial catalytic air pollution control technology, offering engineers a comprehensive account of all modern catalytic technology. This Third Edition covers all the new advances in technology in automotive catalyst control technology, diesel engine catalyst control technology, small engine catalyst control technology, and alternate sustainable fuels for auto and diesel.
Author: R.S. Williams
Publisher: Springer Science & Business Media
ISBN: 9401595763
Category : Technology & Engineering
Languages : en
Pages : 367
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Book Description
energy production, environmental management, transportation, communication, computation, and education. As the twenty-first century unfolds, nanotechnology's impact on the health, wealth, and security of the world's people is expected to be at least as significant as the combined influences in this century of antibiotics, the integrated circuit, and human-made polymers. Dr. Neal Lane, Advisor to the President for Science and Technology and former National Science Foundation (NSF) director, stated at a Congressional hearing in April 1998, "If I were asked for an area of science and engineering that will most likely produce the breakthroughs of tomorrow, I would point to nanoscale science and engineering. " Recognizing this potential, the White House Office of Science and Technology Policy (OSTP) and the Office of Management and Budget (OMB) have issued a joint memorandum to Federal agency heads that identifies nanotechnology as a research priority area for Federal investment in fiscal year 2001. This report charts "Nanotechnology Research Directions," as developed by the Interagency W orking Group on Nano Science, Engineering, and Technology (IWGN) of the National Science and Technology Council (NSTC). The report incorporates the views of leading experts from government, academia, and the private sector. It reflects the consensus reached at an IWGN-sponsored workshop held on January 27-29, 1999, and detailed in contributions submitted thereafter by members of the V. S. science and engineering community. (See Appendix A for a list of contributors.
Author: Richard W. Siegel
Publisher: Springer Science & Business Media
ISBN: 9780792358541
Category : Technology & Engineering
Languages : en
Pages : 378
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Book Description
Timely information on scientific and engineering developments occurring in laboratories around the world provides critical input to maintaining the economic and technological strength of the United States. Moreover, sharing this information quickly with other countries can greatly enhance the productivity of scientists and engineers. These are some of the reasons why the National Science Foundation (NSF) has been involved in funding science and technology assessments comparing the United States and foreign countries since the early 1980s. A substantial number of these studies have been conducted by the World Technology Evaluation Center (WTEC) managed by Loyola College through a cooperative agreement with NSF. The National Science and Technology Council (NSTC), Committee on Technology's Interagency Working Group on NanoScience, Engineering and Technology (CT/IWGN) worked with WTEC to develop the scope of this Nanostucture Science and Technology report in an effort to develop a baseline of understanding for how to strategically make Federal nanoscale R&D investments in the coming years. The purpose of the NSTC/WTEC activity is to assess R&D efforts in other countries in specific areas of technology, to compare these efforts and their results to U. S. research in the same areas, and to identify opportunities for international collaboration in precompetitive research. Many U. S. organizations support substantial data gathering and analysis efforts focusing on nations such as Japan. But often the results of these studies are not widely available. At the same time, government and privately sponsored studies that are in the public domain tend to be "input" studies.
