Download or read book Positron Annihilation Spectroscopy A Nondestructive Submicroscopic Characterization Technique for Structural Polymers written by and published by . This book was released on 1989 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: Positron annihilation lifetime spectroscopy (PALS) has been used to characterize as extruded and aged LEXAN polycarbonate. The long-lived component of the PALS analysis is attributed to orthoPositronium (oPs) pick off annihilations. The oPs pickoff component lifetime and intensity decrease as the result of the aging heat treatment, and this decrease is associated with a decrease in the free volume site size and concentration in glassy polycarbonate due to aging. Isothermal relaxation experiments performed over the range 12 C to 30 C performed on as-extruded and aged polycarbonate indicate that the relaxation kinetics are significantly different, and are consistent with a decrease in molecular mobility as the result of aging. An activation energy for structural relaxation of 8.2 kcal/mole for aged polycarbonate versus 3.0 kcal/ mole for unaged polycarbonate was determined. The relaxation kinetics observed using PALS is related to the structural state and molecular mobility of the polymer.

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1990 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Characterization of Radiation Induced Lattice Defects by Means of Positron Annihilation Spectroscopy written by Riley Craig Ferguson and published by . This book was released on 2023 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Positrons provide a non-destructive technique for probing the nature and size of defects in materials with atomic-scale sensitivity. This work will focus on the powerful capabilities of positron annihilation spectroscopy (PAS) to study the evolution of defects and defect structures. This invaluable tool can aid in developing and characterizing advanced materials, with diverse applications such as nuclear reactors, optoelectronics, nanotechnology, polymers, medical sciences, and more. The work presented in this thesis aims to gain a fundamental understanding of the formation and evolution of defect structures of various metals and alloys under irradiation by applying the techniques and concepts of PAS. Various other characterization techniques are also utilized simultaneously to interpret the positron data better and further enhance our understanding of these materials. Depth-resolved PAS was used to identify vacancy clusters and measure their density as a function of depth in three samples (HfMoTiVZr, HfNbTiZr, and HfNbTaTiZr bulk alloys), performed at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR) in Dresden, Germany. The samples were studied before and after irradiation from 10 MeV Si ions. The behavior of these alloys under irradiation is discussed and quantified in this work. A single branch of samples from the multi-principal element alloy (MPEA) HfNbTaTiZr (Nb, HfNb, HfNbZr, HfNbTiZr, HfNbTaTiZr) was synthesized into thin films on MgO substrate at the Center of Integrated Nanotechnologies (CINT) at the Los Alamos National Laboratory (LANL), to study the role of chemical complexity in an alloy's response to irradiation. There are four sets of these MPEA-based thin film samples, where one will be kept as a reference, and one will be studied with in situ PAS (iPAS), and two sets will be studied with ex situ PAS. The synthesis of these MPEA-based thin films and the design of the PAS experiment for each set is described in this work, along with other characterization techniques used together with this work. This work was made possible through the support of the National Science Foundation (NSF) under grant number DMR-2005064 and by the Fundamental Understanding of Transport Under Reactor Extremes (FUTURE), an Energy Frontier Research Center funded by the DOE, Office of Science, Basic Energy Sciences.

Download or read book Characterization of Free volume Properties in Polymers by Positron Annihilation Spectroscopy written by Qin Deng and published by . This book was released on 1993 with total page 320 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Positron Lifetime Spectroscopy for Investigation of Thin Polymer Coatings written by Jag J. Singh and published by . This book was released on 1993 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Spectroscopic Techniques for Polymer Characterization written by Yukihiro Ozaki and published by John Wiley & Sons. This book was released on 2022-03-14 with total page 500 pages. Available in PDF, EPUB and Kindle. Book excerpt: An insightful exploration of cutting-edge spectroscopic techniques in polymer characterization In Spectroscopic Techniques for Polymer Characterization: Methods, Instrumentation, Applications, a team of distinguished chemists delivers a comprehensive exploration of the vast potential of spectroscopic characterization techniques in polymer research. The book offers a concise outline of the principles, advantages, instrumentation, experimental techniques, and noteworthy applications of cutting-edge spectroscopy. Covering a wide range of polymers, from nylon to complex polymeric nanocomposites, the author presents recent developments in polymer science to polymer, analytical, and material chemists, assisting them in keeping track of the progress in modern spectroscopy. Spectroscopic Techniques for Polymer Characterization contains contributions from pioneers in modern spectroscopic techniques from around the world. The included materials bridge the gap between spectroscopists, polymer scientists, and engineers in academia and industry. The book also offers: A thorough introduction to the progress in spectroscopic techniques, including polymer spectroscopy and near-infrared spectroscopy Comprehensive explorations of topical polymers studied by spectroscopy, including polymer thin films, fluoropolymers, polymer solutions, conductive polymers Practical discussions of infrared imaging, near-infrared imaging, two-dimensional correlation spectroscopy, and far-ultraviolet spectroscopy In-depth examinations of spectroscopic studies of weak hydrogen bonding in polymers Spectroscopic Techniques for Polymer Characterization: Methods, Instrumentation, Applications is a must-read reference for polymer, analytical, and physical chemists, as well as materials scientists and spectroscopists seeking a one-stop resource for polymer characterization using spectroscopic analyses.

Download or read book Polymer Characterization Interdisciplinary Approaches written by Clara D. Craver and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 278 pages. Available in PDF, EPUB and Kindle. Book excerpt: Physical and spectroscopic methods have been used jointly for characterization of polymers for at least four decades. Yet, new techniques permit increasingly refined determination of polymer chemistry and morphol ogy_ The correlation of this knowledge with physical properties of polymers is helpful to planned synthesis of new products. The most prominent spectroscopic techniques through the forties and fifties were infrared and ultraviolet spectroscopy. Nuclear magnetic resonance, electron spin resonance and MOssbauer spectroscopy started making sig nificant contributions to polymer chemistry in the early sixties. Still more recently fluorescence spectroscopy and laser Raman spectroscopy have become readily appli cable to polymers and are contributing significantly to the understanding of the relationship between polymer structure and properties. Determination of the distribution of monomer se quences by molecular size has become possible through combined gel permeation chromatography and spectroscopic analysis. Fragments of polymers from chemical break down or from pyrolysis are further fractionated and structurally analyzed. The relationship between the chemistry of polymers and performance can be determined from changes in chemical structure and orientation after curing, degradation, or physical or thermal manipulation of the polymers.

Download or read book Positron Annihilation in Semiconductors written by Reinhard Krause-Rehberg and published by Springer. This book was released on 1999-01-15 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This comprehensive book reports on recent investigations of lattice imperfections in semiconductors by means of positron annihilation. It reviews positron techniques, and describes the application of these techniques to various kinds of defects, such as vacancies, impurity vacancy complexes and dislocations.

Download or read book Characterization of Thermotropic Liquid Crystalline Polymer Blends by Positron Annihilation Lifetime Spectroscopy written by Naslund Robert Alec and published by . This book was released on 1992 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Positron Annihilation Spectroscopy as a Probe of Microscopic Structure and Physical Aging in Polymer written by Minzi Yu and published by . This book was released on 1992 with total page 276 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Microstructural Characterization of Semi Interpenetrating Polymer Networks by Positron Lifetime Spectroscopy written by National Aeronautics and Space Adm Nasa and published by Independently Published. This book was released on 2019 with total page 38 pages. Available in PDF, EPUB and Kindle. Book excerpt: Thermoset and thermoplastic polyimides have complementary physical and mechanical properties. Whereas thermoset polyimides are brittle and generally easier to process, thermoplastic polyimides are tough but harder to process. A combination of these two types of polyimides may help produce polymers more suitable for aerospace applications. Semi-Interpenetrating Polymer Networks (S-IPN) of thermoset LaRC(TM)-RP46 and thermoplastic LaRC(TM)-IA polyimides were prepared in weight percent ratios ranging from 100:0 to 0:100. Positron lifetime measurements were made in these samples to correlate their free volume features with physical and mechanical properties. As expected, positronium atoms are not formed in these samples. The second lifetime component has been used to infer the positron trap dimensions. The 'free volume' goes through a minimum at a ratio of about 50:50, and this suggests that S-IPN samples are not merely solid solutions of the two polymers. These data and related structural properties of the S-IPN samples are discussed. Singh, Jag J. and Pater, Ruth H. and Eftekhari, Abe NASA-TP-3617, NAS 1.60:3617, L-17576 RTOP 505-63-50-01...

Download or read book Application of Positron Annihilation Lifetime Spectroscopy PALS to the Characterization of Nanostructure in Ordered Self assembled Systems written by Aurelia Wenjing Dong and published by . This book was released on 2012 with total page 522 pages. Available in PDF, EPUB and Kindle. Book excerpt: Positron annihilation lifetime spectroscopy (PALS) has long been used to characterize porosity in polymers and ceramics, and has been shown in past studies to be sensitive to conformational changes in self-assembled amphiphile systems. However, due to inconsistencies in experimental setup, sample configuration and data analysis, direct comparison between studies was often not possible. This has resulted in a limited knowledge of the response of the PALS parameters (oPs lifetime and intensity) to structure in these systems, and hence the full potential of PALS as a characterization technique in mesophase systems remains unrealised. The research undertaken in this thesis utilizes a systematic approach to gain more understanding of the potential of using PALS to characterize self-assembled amphiphile systems.This thesis addresses a number of classes of nanostructures in soft self-assembled materials including micelles, lamellar phases, non-lamellar liquid crystals and microemulsions. The micellar to hexagonal phase transition of four different micellar systems prepared using cationic, anionic and non-ionic surfactants were investigated using both PALS and small angle x-ray scattering (SAXS). It was found that in all four systems the hexagonal (H1) phase had a lower oPs lifetime than the micellar (L1) phase, suggesting restricted chain packing and reduced chain mobility in the H1 phase. A characteristic oPs lifetime of 3.5 ns was also obtained for the H1 phase for systems with C12 surfactants. Past PALS studies often investigated either bulk or dispersed lamellar phases without putting emphasis on stating the sample composition. However it was not known whether there is a difference in the behaviour of the oPs parameters between the dispersed and bulk forms. In this study both bulk and dispersed lamellar systems were investigated and it was found that the dispersed lamellar phases (liposomes) resulted in an overall larger oPs lifetime than the bulk systems. It was also found that PALS was able to indicate the temperature of the main phase transition (Tm) from the rigid lamellar phases to the fluid lamellar phase (L[alpha]). In the bulk systems a characteristic oPs lifetime of 3.4 ns was determined for the fluid lamellar phase, which was independent of lipid chain length.PALS was also used to probe the phase transitions of more complex nanostructures found in the phytantriol/water system. PALS was able to differentiate between these structures in both the bulk and dispersed systems. This thesis is the first to use PALS to characterise dispersed hexagonal (hexosomes) and bicontinuous cubic (cubosomes) phases. The most significant change in the oPs lifetime occurred at the Q2Pn3m to H2 phase transition. Addition of increasing concentrations of vitamin E acetate resulted in a more gradual change in lifetime at this phase transition. PALS was used to characterize the w/o to bicontinuous to o/w phase transitions in two microemulsion systems. Phase boundaries were confirmed using electrical conductivity and viscosity measurements. A difference of 0.4 ns was observed across the three phase transitions.The research described in the thesis highlights the potential of using PALS to characterize nanostructured self-assembled amphiphile systems.

Download or read book Microstructural Characterization of Polymers by Positron Lifetime Spectroscopy written by Jag J. Singh and published by . This book was released on 1996 with total page 6 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Principles and Applications of Positron Positronium Chemistry written by Y. C. Jean and published by World Scientific. This book was released on 2003 with total page 426 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book provides a comprehensive description of the principles and applications of positron and positronium chemistry. Pedagogical and tutorial in nature, it will be ideal for graduate students and researchers in the area of positron annihilation spectroscopy. The contributing authors are authoritative scientists prominent in the frontiers of research, actively pursuing positron annihilation research on chemical and applied systems. Contents: Introduction to Positron and Positronium Chemistry (Y C Jean et al.); Compounds of Positrons and Positronium (D M Schrader); Experimental Techniques in Positron Spectroscopy (P G Coleman); Organic and Inorganic Chemistry of the Positron and Positronium (G Duplotre & I Billard); Physical and Radiation Chemistry of the Positron and Positronium (S V Stepanov & V M Byakov); Positrons and Positronium in the Gas Phase (D M Schrader); Positron Porosimetry (M H Weber & K G Lynn); Positron Annihilation Studies on Superconducting Materials (C S Sundar); Positronium in Si and SiO 2 Thin Films (R Suzuki); Applications to Polymers (P E Mallon); Applications of Slow Positrons to Polymeric Surfaces and Coatings (Y C Jean et al.); Positron Annihilation Induced Auger Spectroscopy (S Amdani et al.); Characterization of Nanoparticle and Nanopore Materials (J Xu); AMOC in Positron and Positronium Chemistry (H Stoll et al.). Readership: Materials science researchers; physical chemists; polymer scientists and engineers; chemical and mechanical engineers; solid state physicists; graduate students in chemistry, physics, engineering and polymer science; coating industry researchers."

Download or read book Positron Annihilation Spectroscopy for Chemical Analysis PASCA written by Krishnan Venkateswaran and published by . This book was released on 1985 with total page 482 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Positron Annihilation Spectroscopy and Small Angle Neutron Scattering Characterization of Nanostructural Features in Irradiated Fe Cu Mn Alloys written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Radiation embrittlement of nuclear reactor pressure vessel steels results from a high number density of nanometer sized Cu-Mn-Ni rich precipitates (CRPs) and sub-nanometer matrix features, thought to be vacancy-solute cluster complexes (VSC). However, questions exist regarding both the composition of the precipitates and the defect character and composition of the matrix features. We present results of positron annihilation spectroscopy (PAS) and small angle neutron scattering (SANS) characterization of irradiated and thermally aged Fe-Cu and Fe-Cu-Mn alloys. These complementary techniques provide insight into the composition and character of both types of nanoscale features. The SANS measurements indicate populations of CRPs and VSCs in both alloys. The CRPs are coarser in the Fe-Cu alloy and the number densities of CRP and VSC increase with the addition of Mn. The PAS involved measuring both the positron lifetimes and the Doppler broadened annihilation spectra in the high momentum region to provide elemental sensitivity at the annihilation site. The spectra in Fe-Cu-Mn specimens thermally aged to peak hardness at 450 C and irradiated at 288 C are nearly identical to elemental Cu. Positron lifetime and spectrum measurements in Fe-Cu specimens irradiated at 288 C clearly show the existence of long lifetime ((almost equal to)500 ps) open volume defects, which also contain Cu. Thus the SANS and PAS provide a self-consistent picture of nanostructures composed of CRPs and VSCs and tend to discount high Fe concentrations in the CRPs.

Download or read book Third International Workshop on Positron and Positronium Chemistry written by Jerry Y. C. Jean and published by . This book was released on 1990 with total page 648 pages. Available in PDF, EPUB and Kindle. Book excerpt: