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Author: Y. M. Sun Publisher: ISBN: Category : Languages : en Pages : 11
Book Description
Thin film models of catalysts known to show strong metal support interactions were investigated. These consist of vapor-deposited Pt or Rh on Ti02 films prepared in ultrahigh vacuum by oxidation of Ti(000 + or - ). TDS, AES and static SIMS were used to characterize the surfaces before and after thermal treatment in vacuum and with or without chemisorbed C0. The results indicate that heating in vacuum to near 750K leads to migration of a reduced form of titania to the metal film surface, accompanied by suppression of C0 and hydrogen chemisorption. In 1 to 2 ML metal films with no surface titania species, no significant suppression of hydrogen chemisorption is seen, indicating that surface segregation alone is not responsible for the changes in hydrogen chemisorption extent and energetics.
Author: Y. M. Sun Publisher: ISBN: Category : Languages : en Pages : 11
Book Description
Thin film models of catalysts known to show strong metal support interactions were investigated. These consist of vapor-deposited Pt or Rh on Ti02 films prepared in ultrahigh vacuum by oxidation of Ti(000 + or - ). TDS, AES and static SIMS were used to characterize the surfaces before and after thermal treatment in vacuum and with or without chemisorbed C0. The results indicate that heating in vacuum to near 750K leads to migration of a reduced form of titania to the metal film surface, accompanied by suppression of C0 and hydrogen chemisorption. In 1 to 2 ML metal films with no surface titania species, no significant suppression of hydrogen chemisorption is seen, indicating that surface segregation alone is not responsible for the changes in hydrogen chemisorption extent and energetics.
Author: Cameron Thurston Publisher: ISBN: Category : Languages : en Pages : 51
Book Description
Ab initio computer aided design drastically increases candidate population for highly specified material discovery and selection. These simulations, carried out through a first-principles computational approach, accurately extrapolate material properties and behavior. Titanium Dioxide (TiO2 ) is one such material that stands to gain a great deal from the use of these simulations. In its anatase form, titania (TiO2 ) has been found to exhibit a band gap nearing 3.2 eV. If titania is to become a viable alternative to other contemporary photoactive materials exhibiting band gaps better suited for the solar spectrum, then the band gap must be subsequently reduced. To lower the energy needed for electronic excitation, both transition metals and non-metals have been extensively researched and are currently viable candidates for the continued reduction of titania’s band gap. The introduction of multicomponent atomic doping introduces new energy bands which tend to both reduce the band gap and recombination loss. Ta-N, Nb-N, V-N, Cr-N, Mo-N, and W-N substitutions were studied in titania and subsequent energy and band gap calculations show a favorable band gap reduction in the case of passivated systems.
Author: Publisher: Newnes ISBN: 0080965296 Category : Science Languages : en Pages : 7694
Book Description
Comprehensive Inorganic Chemistry II, Nine Volume Set reviews and examines topics of relevance to today’s inorganic chemists. Covering more interdisciplinary and high impact areas, Comprehensive Inorganic Chemistry II includes biological inorganic chemistry, solid state chemistry, materials chemistry, and nanoscience. The work is designed to follow on, with a different viewpoint and format, from our 1973 work, Comprehensive Inorganic Chemistry, edited by Bailar, Emeléus, Nyholm, and Trotman-Dickenson, which has received over 2,000 citations. The new work will also complement other recent Elsevier works in this area, Comprehensive Coordination Chemistry and Comprehensive Organometallic Chemistry, to form a trio of works covering the whole of modern inorganic chemistry. Chapters are designed to provide a valuable, long-standing scientific resource for both advanced students new to an area and researchers who need further background or answers to a particular problem on the elements, their compounds, or applications. Chapters are written by teams of leading experts, under the guidance of the Volume Editors and the Editors-in-Chief. The articles are written at a level that allows undergraduate students to understand the material, while providing active researchers with a ready reference resource for information in the field. The chapters will not provide basic data on the elements, which is available from many sources (and the original work), but instead concentrate on applications of the elements and their compounds. Provides a comprehensive review which serves to put many advances in perspective and allows the reader to make connections to related fields, such as: biological inorganic chemistry, materials chemistry, solid state chemistry and nanoscience Inorganic chemistry is rapidly developing, which brings about the need for a reference resource such as this that summarise recent developments and simultaneously provide background information Forms the new definitive source for researchers interested in elements and their applications; completely replacing the highly cited first edition, which published in 1973
Author: Christoph Brabec Publisher: John Wiley & Sons ISBN: 3527623205 Category : Technology & Engineering Languages : en Pages : 597
Book Description
Providing complementary viewpoints from academia as well as technology companies, this book covers the three most important aspects of successful device design: materials, device physics, and manufacturing technologies. It also offers an insight into commercialization concerns, such as packaging technologies, system integration, reel-to-reel large scale manufacturing issues and production costs. With an introduction by Nobel Laureate Alan Heeger.
Author: Liam Howard-Fabretto Publisher: ISBN: Category : Languages : en Pages :
Book Description
Metal clusters are small groups of bound metal atoms which can have distinctly different electronic and catalytic properties, unique from those of a bulk sample of the same metal. The main motivation for research on clusters is their potential for use in catalysis and photocatalysis. The physical and chemical properties of metal clusters are dependent on size, as well as the cluster-substrate interaction. It is difficult to predict the properties of a cluster/substrate pair if studies have not been performed on that specific combination. Fundamental measurements into cluster properties have previously been performed on a range of cluster/substrate combinations, where Au clusters and TiO2(110) surfaces have received a large focus. However, there are many important cluster and substrate materials which have not had their surface properties measured, which is vital for the informed design of efficient catalytic materials. -- The original contribution to knowledge in this field is through the novel experimental measurements and analysis of the surface properties and electronic properties of 3-atom Ru3 clusters supported on radio frequency (RF)-sputter deposited titania substrates (RF-TiO2). Ru3 was chosen due to its potential catalytic and photocatalytic applications. RF-TiO2 is a cost-effective alternative to the commonly used TiO2(110) substrate and was chosen due to its ease of production and applicability to industrial applications. The aims were to determine details about the cluster-surface interaction and temperature stability of the clusters, in addition to measuring their electronic density of states (DOS). Additional cluster and substrate systems were analysed for comparison to Ru3/RF-TiO2. This study provides a strong basis for future work on the catalysis of RF-TiO2-supported Ru3. -- Ru3 clusters were deposited onto RF-TiO2 and analysed using temperature programmed desorption (TPD) to probe Ru-CO binding sites, and X-ray photoelectron spectroscopy (XPS) was used to provide chemical information. Differences in cluster-support interactions were compared for bare Ru3 deposited using an ultra-high vacuum (UHV) cluster source (CS), and the chemical vapor deposition (CVD) of ligated Ru3(CO)12 clusters. For CS-deposited Ru3, heating to 800 K caused partial oxidation of clusters on both non-sputtered and sputter-treated RF-TiO2. Furthermore, on sputter-treated RF-TiO2 all Ru-CO binding sites on the clusters were blocked immediately after deposition for CS-deposited Ru3, but for CVD-deposited Ru3(CO)12 the clusters were protected by their ligands and the Ru-CO binding sites were only blocked once the sample had been heated to 723 K. The mechanism for complete blocking of Ru-CO binding sites on sputtered RF-TiO2 could not be directly determined from this first study. -- To further probe the Ru3/RF-TiO2 system, additional temperature-dependent (TD) measurements were performed to analyse the effects of heat treatment. Samples were analysed with TD-XPS, angle-resolved (AR) XPS, and low energy ion scattering spectroscopy (LEIS). Ru3 was deposited onto RF-TiO2 using 3 methods: solution submersion of Ru3(CO)12, CVD-deposition of Ru3(CO)12, and CS-deposition of bare Ru3. TD-XPS showed that after heat treatment the Ru 3d BE was very similar between the methods suggesting the cluster oxidation state was the same. TD-LEIS showed the encapsulation of CVD Ru3(CO)12 on sputter-treated RF-TiO2 by a titania overlayer after heat treatment. The average overlayer thickness was calculated to be 0.35 nm ± 0.08 nm, which is thin enough that there is the potential for catalytic or photocatalytic reactions to occur. The encapsulation of the clusters help explain the mechanism behind the complete blocking of Ru-CO sites, suggesting CO is sterically hindered from accessing Ru by the overlayer. -- The electronic DOS for Ru3 on sputter-treated RF-TiO2 was measured using ultraviolet photoelectron spectroscopy (UPS) and metastable impact electron spectroscopy (MIES). Bare Pt3 clusters were CS-deposited for the purpose of comparison to a different cluster of the same size. Measurements both Ru3 and Pt3 were after sample heat treatment. UPS measures the top several layers while MIES has perfect surface sensitivity and measures only the top atomic layer. The electronic DOS of Ru3 was very similar for Ru3 deposited using solution submersion and CVD of Ru3(CO)12. UPS suggests that RF-TiO2-supported Ru3 clusters have metallic characteristics and Pt3 clusters have non-metallic characteristics. MIES suggests that the encapsulating layer above Ru3 clusters is composed of reduced titania with a bonding structure such as Ru-Ti-O, while Pt3 was not encapsulated. The mechanism for the encapsulation of Ru3, but not Pt3, is possibly an energetic benefit for Ru3 encapsulation in terms of the minimisation of surface energy. -- As an extension of previous studies, the effects of changing the supported Run cluster size by a single atom was studied by depositing size-selected Ru4 clusters onto sputter-treated RF-TiO2 and comparing results to previous experiments. Clusters were CVD-deposited with H4Ru4(CO)12 and analysed using TD-XPS, TPD, and UPS. Based on TD-XPS, H4Ru4(CO)12 begins to lose ligands at a slightly lower temperature than Ru3(CO)12, most likely related to the loss of H bridging ligands at low temperatures. Other results were very similar between the clusters. CO-TPD showed that after heat-treatment all Ru-CO binding sites were blocked, caused by encapsulation of the clusters. UPS provided evidence that the encapsulated Ru4 clusters have metallic properties, and the valence DOS was similar for both Ru3 and Ru4. This suggests that the resultant properties of CVD-deposited Ru4 after heat treatment are very similar to Ru3, and that both clusters have the same potential catalytic and photocatalytic benefits when supported on RF-TiO2.
Author: C. H. Bartholomew Publisher: John Wiley & Sons ISBN: 1118209737 Category : Technology & Engineering Languages : en Pages : 1224
Book Description
Catalysis is central to the chemical industry, as it is directly or involved in the production of almost all useful chemical products. In this book the authors, present the definitive account of industrial catalytic processes. Throughout Fundamentals of Industrial Catalytic Processes the information is illustrated with many case studies and problems. This book is valuable to anyone wanting a clear account of industrial catalytic processes, but is particularly useful to industrial and academic chemists and engineers and graduate working on catalysis. This book also: Covers fundamentals of catalytic processes, including chemistry, catalyst preparation, properties and reaction engineering. Addresses heterogeneous catalytic processes employed by industry. Provides detailed data on existing catalysts and catalytic reactions, process design and chemical engineering. Covers catalysts used in fuel cells.
Author: John J. Fitzgerald Publisher: ISBN: Category : Medical Languages : en Pages : 440
Book Description
This book strikes a balance between state-of-the-art solid-state NMR techniques and the applications of these techniques to problems in materials science. The applications focus on modern inorganic materials such as metal oxides, catalysts, zeolites, glasses, ceramics, semiconductors, ion conductors, superconductors, and composites. The book features chapters on multiple-quantum MAS NMR, dynamic-angle spinning NMR for quadrupolar nuclides, and two-dimensional NMR methods. It includes an introductory chapter that provides an a thorough and integrated overview of the field, complete with numerous references.
Author: Y. M. Sun
Author: Y. M. Sun
Author: Cameron Thurston
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Author: Christoph Brabec
Author: Liam Howard-Fabretto
Author: C. H. Bartholomew
Author: John J. Fitzgerald