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Neutron Diffraction And Quasielastic Neutron Scattering Studies Of Films Of N Alkanes And A Branched Alkane Absorbed On Graphite
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Book Synopsis Neutron Diffraction and Quasielastic Neutron Scattering Studies of Films of N-alkanes and a Branched Alkane Absorbed on Graphite by : Leah Criswell
Download or read book Neutron Diffraction and Quasielastic Neutron Scattering Studies of Films of N-alkanes and a Branched Alkane Absorbed on Graphite written by Leah Criswell and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Alkane molecules are important as constituents of lubricants, fuels, and polymers. Often these applications, such as lubrication, involve molecularly thin films of alkanes. We have studied the structures of n-tetracosane (n-C24D50) and squalane (C30H62) adsorbed on graphite below room temperature using neutron diffraction. We find that both the n-tetracosane and the squalane monolayers undergo a phase transition from a more-ordered crystalline phase to a less-ordered "smectic" phase on heating. Quasielastic neutron scattering studies of multiple layers of n-heptane (n-C--D16) above a crystalline n-dotriacontane (n-C32D66) monolayer adsorbed on graphite reveal that two dynamical layers can be distinguished. The first is composed of the first heptane layer which exhibits slower motions. The second is composed of the additional layers above this monolayer, which exhibit faster diffusion comparable to that of bulk. We also studied a monolayer of n-tetracosane adsorbed on graphite by quasielastic neutron scattering. We found that a slower diffusion motion became activated at 330 K, where molecular dynamics simulations indicate most molecular motions become too fast for observation. Instead, these simulations indicate that intramolecular and rotational diffusion of more globularly shaped n-tetracosane molecules, which contain many gauche defects, is being observed at this temperature.
Book Synopsis Neutron Diffraction and Quasielastic Neutron Scattering Studies of Films of Intermediate-length Alkanes Adsorbed on a Graphite Surface by : Armand Diama
Download or read book Neutron Diffraction and Quasielastic Neutron Scattering Studies of Films of Intermediate-length Alkanes Adsorbed on a Graphite Surface written by Armand Diama and published by . This book was released on 2006 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past several years, we have conducted a variety of elastic neutron diffraction and quasielastic neutron scattering experiments to study the structure and the dynamics of films of two intermediate-length alkane molecules (C n H 2n+2), adsorbed on a graphite basal-plane surface. The two molecules are the normal alkane n -tetracosane [n-CH 3 (CH 2) 22 CH 3] and the branched alkane squalane (C 30 H 62 or 2, 6, 10, 15, 19, 23-hexamethyltetracosane) whose carbon backbone is the same length as teteracosane. The temperature dependence of the monolayer structure of tetracosane and squalane was investigated using elastic neutron diffraction and evidence of two phase transitions was observed. Both the low-coverage tetracosane (C 24 H 50) and squalane (C 30 H 62) monolayers have crystalline-to-"smectic" and "smectic"--To-isotropic fluid phase transitions upon heating. The diffusive motion in the tetracosane and squalane monolayers has been investigated by quasielastic neutron scattering. Two different quasielastic neutron scattering spectrometers at the Center for Neutron Research, National Institute of Standards and Technology (NIST) have been used. The spectrometers differ in both their dynamic range and energy resolution allowing molecular motions to be investigated on time scales in the range 10 -13 --10 -9 s. On these time scales, we observe evidence of translational, rotational, and intermolecular diffusive motions in the tetracosane and squalane monolayers. We conclude that the molecular diffusive motion in the two monolayers is qualitatively similar. Thus, despite the three methyl sidegroups at each end of the squalane molecule, its monolayer structure, phase transitions, and dynamics are qualitatively similar to that of a monolayer of the unbranched tetracosane molecules. With the higher resolution spectrometer at NIST, we have also investigated the molecular diffusive motion in multilayer tetracosane films. The analysis of our measurements indicates slower diffusive motion in the bottom layer of a bilayer tetracosane film compared to that in a monolayer, while the rate of diffusive motion in the bottom two layers of the trilayer film is comparable to that in a monolayer.
Book Synopsis Neutron and X-ray Scattering Study of Intermediate-length Alkane Films Adsorbed on Solid Surfaces by : Haiding Mo
Download or read book Neutron and X-ray Scattering Study of Intermediate-length Alkane Films Adsorbed on Solid Surfaces written by Haiding Mo and published by . This book was released on 2004 with total page 584 pages. Available in PDF, EPUB and Kindle. Book excerpt: Organic thin films grown on solid surfaces are of great importance in applications such as microelectronics, biosensors, lubrication, and coatings. Using neutron diffraction and synchrotron x-ray scattering, we have conducted experiments to study the growth and structure of alkane films on solid surfaces. Our neutron diffraction study of a high-coverage monolayer of tetracosane (an alkane-chain molecule containing 24 carbon atoms) adsorbed on a graphite substrate shows that, near room temperature, the monolayer has a different structure than in a lower coverage monolayer investigated previously. Upon heating, it transforms from a crystalline to a liquid-crystal-like phase. For dotriacontane (an alkane chain molecule containing 32 carbon atoms, denoted C32) films adsorbed on silicon wafers, our x-ray specular reflectivity measurements show a unique structure in that the first one or two layers of molecules are oriented with their long axis parallel to the surface and are followed by a layer of molecules oriented with their long axis perpendicular to the substrate. As more molecules are added onto the substrate, bulk particles having two different structures nucleate on top of the film. For C32 grown on a single-crystal silver surface, x-ray diffraction shows that monolayer and multilayer films have a different crystal structure near room temperature. Specular x-ray reflectivity measurements demonstrate that multilayer films exhibit a layered structure even when they are fluid at high temperatures. At higher coverage, bulk particles nucleate with three different orientations. The structure and growth behavior of alkane films discovered in this research may help design better methods to grow organic crystals for microelectronics devices and to develop better lubricants.
Book Synopsis On the Existence of a Resonance Absorption of Neutrons in Graphite by : Seymour Bernstein
Download or read book On the Existence of a Resonance Absorption of Neutrons in Graphite written by Seymour Bernstein and published by . This book was released on 1946 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis A Study of the Slowing Down Distribution of Sb124-Be Photo Neutrons in Graphite, and of the Use of Indium Foils by : L. D. Roberts
Download or read book A Study of the Slowing Down Distribution of Sb124-Be Photo Neutrons in Graphite, and of the Use of Indium Foils written by L. D. Roberts and published by . This book was released on 1950 with total page 24 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Neutron Scattering – Fundamentals by : Silvia C. Capelli
Download or read book Neutron Scattering – Fundamentals written by Silvia C. Capelli and published by Elsevier Inc. Chapters. This book was released on 2013-11-22 with total page 43 pages. Available in PDF, EPUB and Kindle. Book excerpt: Investigating the structure of a material is the first essential step in understanding its macroscopic properties. Getting insights of the interatomic and inter/intra-molecular interactions that influence the stability and the chemical behavior of a given compound allows its application in the best possible conditions and opens the way to design new materials with tailored properties. Neutron diffraction is a fundamental tool in structural characterization. Few examples concerning chemical crystallography, will be given to illustrate the properties that make neutrons the ideal probe for locating light atoms in the presence of heavy, electron-rich ones, and accurately determine atomic position and displacement parameters.
Book Synopsis Neutron Scattering in Earth Sciences by : Hans Rudolf Wenk
Download or read book Neutron Scattering in Earth Sciences written by Hans Rudolf Wenk and published by Walter de Gruyter GmbH & Co KG. This book was released on 2018-12-17 with total page 492 pages. Available in PDF, EPUB and Kindle. Book excerpt: Volume 63 of Reviews in Mineralogy and Geochemistry provides an introduction for those not yet familiar with neutrons by describing basic features of neutrons and their interaction with matter as well illustrating important applications. The volume is divided into 17 Chapters. The first two chapters introduce properties of neutrons and neutron facilities, setting the stage for applications. Some applications rely on single crystals (Chapter 3) but mostly powders (Chapters 4-5) and bulk polycrystals (Chapters 15-16) are analyzed, at ambient conditions as well as low and high temperature and high pressure (Chapters 7-9). Characterization of magnetic structures remains a core application of neutron scattering (Chapter 6). The analysis of neutron data is not trivial and crystallographic methods have been modified to take account of the complexities, such as the Rietveld technique (Chapter 4) and the pair distribution function (Chapter 11). Information is not only obtained about solids but about liquids, melts and aqueous solutions as well (Chapters 11-13). In fact this field, approached with inelastic scattering (Chapter 10) and small angle scattering (Chapter 13) is opening unprecedented opportunities for earth sciences. Small angle scattering also contributes information about microstructures (Chapter 14). Neutron diffraction has become a favorite method to quantify residual stresses in deformed materials (Chapter 16) as well as preferred orientation patterns (Chapter 15). The volume concludes with a short introduction into neutron tomography and radiography that may well emerge as a principal application of neutron scattering in the future (Chapter 17).
Book Synopsis Applications of Neutron Scattering to Soft Condensed Matter by : Barbara J Gabrys
Download or read book Applications of Neutron Scattering to Soft Condensed Matter written by Barbara J Gabrys and published by CRC Press. This book was released on 2000-12-21 with total page 377 pages. Available in PDF, EPUB and Kindle. Book excerpt: Neutrons, which are a penetrating yet non destructive probe, are ideally suited to studying the structure, organisation and motion of molecules responsible for the physical properties of materials under a variety of conditions. Applications are in fields as diverse as colloid and polymer science, earth sciences, pharmaceutics, biology and engineeri
Book Synopsis Some neutron scattering studies on magnetic and molecular phase... by : Leendert Bevaart
Download or read book Some neutron scattering studies on magnetic and molecular phase... written by Leendert Bevaart and published by . This book was released on 19?? with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Neutron Scattering Study of the Dynamics of Short-chain Hydrocarbon Films and the Structure and Phase Transitions of Iron Pentacarbonyl Films Adsorbed on Graphite by : Reynold W. Wang
Download or read book Neutron Scattering Study of the Dynamics of Short-chain Hydrocarbon Films and the Structure and Phase Transitions of Iron Pentacarbonyl Films Adsorbed on Graphite written by Reynold W. Wang and published by . This book was released on 1983 with total page 556 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Neutron Diffraction written by P. Chieux and published by Springer. This book was released on 1978 with total page 384 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Neutron Diffraction by : George Edward Bacon
Download or read book Neutron Diffraction written by George Edward Bacon and published by . This book was released on 1955 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Neutron Scattering in Chemistry by : George Edward Bacon
Download or read book Neutron Scattering in Chemistry written by George Edward Bacon and published by . This book was released on 1977 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Neutron Scattering Studies of Quantum Films by : Hans J. Lauter
Download or read book Neutron Scattering Studies of Quantum Films written by Hans J. Lauter and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Applications of Neutron Diffraction in Chemistry by : George Edward Bacon
Download or read book Applications of Neutron Diffraction in Chemistry written by George Edward Bacon and published by . This book was released on 1963 with total page 166 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Neutron Scattering written by and published by Forschungszentrum Jülich. This book was released on 2012 with total page 361 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Book Synopsis Quasielastic Neutron Scattering by : F. Fillaux
Download or read book Quasielastic Neutron Scattering written by F. Fillaux and published by . This book was released on 1996 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
