bluuebunny/crossref_metadata_2025 huggingface dataset:
Laser Chemical Etching of Conducting and Semiconducting Materials
Authors: Chuang T. J.
Published: March 2011

The purpose of the paper is to examine the basic processes involved in the laser-enhanced chemical etching of solids. Specifically, the process of chemisorption, the reaction between the adsorbate and substrate atoms and the vaporization of product species affected by the laser radiation are discussed. It is shown that the laser method can provide important insight into the gas-surface reaction mechanisms. In addition, a number of examples are given to demonstrate the potential of the technique for applications to material processing. Some current studies on the laser-induced chemical etching of materials relevant to microelectronics are reviewed. Certain practical experimental approaches are also considered.
Molecular Composites of Rodlike/Flexible Polyimides
Authors: Rojstaczer S. R. , Yoon D.Y. , Volksen W. , Smith B.A.
Published: March 2011

Mixtures of a rodlike and a flexible polyimide were prepared by solution-blending of the respective poly(amic alkyl ester) and poly(amic acid), followed by solvent evaporation and thermal imidization. The size scale of the phase separation, as measured by light scattering, is primarily set during the demixing of the precursor polymers, with no significant coarsening observed due to the imidization performed at 400°C. The observed variation of the domain size with parameters such as composition, molecular weight and film thickness is discussed in terms of the miscibility of the precursor polymers as well as the thermal history to which these were exposed.
Miscibiuty in Blends of Polybenzimidazole and Fluorine Containing Polyimides
Authors: Yamaoka Hiroaki , Aubrey Norman E. , MAcknight William J. , Karasz Frank E.
Published: March 2011

Blends of polybenzimidazole (PBI) with either of two fluorine-containing polyimides were prepared by casting from solution and by precipitation. Dynamic mechanical thermal analysis (DMTA) and differential scanning calorimetry (DSC) were used to study miscibility in the two blend systems.

The blends of PBI with the first polyimide, the polysulfonimide Pl-1, consisted of a single phase when the blends contained less than 30 wt% Pl-1; above 50 wt% Pl-1, phase separation occurred even at room temperature. The PBI blends containing the second polyimide, Pl-2, were immiscible.
X-Ray Reflectivity and Fluorescence Measurements From Polystyrene-Co-Bromostyrene/Polystyrene Interfaces
Authors: Sokolov J. , Rafailovich M. , Zhao X. , Yun W.B. , Jones R.A.L. , Kramer E.J. , Composto R.J. , Stein R.S. , Bommannavar A. , Engbretson M.
Published: March 2011

X-ray fluorescence using synchrotron radiation at glancing angles of incidence was used to measure interface widths for the highly immiscible polymer blend system polystyrene/polybromostyrene (PS/PBrxS, with bromination level x = 0.8 bromine atoms per monomer). The interfacial widths are for bilayers annealed for 4 hours and 24 hours at 141±1C are found to be 100± 20Å and 110±20Å respectively.
A Mew Variable Angle Ft—ir Ellipsometer
Authors: Stehle J.L. , Thomas O.T. , Piel J.P. , Evrard P. , Lecat J.H. , Hammond L.C.
Published: March 2011

Use of a Fourier—transform interferometer integrated with a variable incidence angle ellipsometer extends the spectral range and the capabilities of spectroscopic ellipsometry into the infrared. With a spectral range of 600 to 6600 cm—1, thick layers, such as epitaxial doped layers and polymers can be analysed.

A full description of this novel instrument will be given. Incidence angle can be variedautomatically to enhance signal/noise and the ellipsometric data can be obtained together with vibrational absorption bands information to give a characteristic “fingerprint ” of the layers.

Examples of spectra of HCN polymer on nickel, DMHS on aluminium and PMMA on silicon willbe presented for various incidence angles and layer thickness.
Determination of Particle Size of a Dispersed Phase by Small-Angle X-ray Scattering
Authors: Wilson Frank C.
Published: March 2011

A method for determining particle diameters up to ca 500 rnm is described. X-ray data are obtained with an ultra-high resolution Bonse-Hart diffractometer and subsequently desmeared. The resultant data, viewed as the invariant argument h l(h), are interpreted as arising from a log-normal distribution of independent spherical particles. The distribution is characterized by its median value and breadth.
Synthetic Polymers in Water-in-Oil Microemulsions
Authors: Candau Francoise
Published: March 2011

High molecular weight water-soluble polymers are usually supplied in the form of water-in-oil emulsions which have advantages of low viscosity and easy storage and dissolution. Most uses in water treatment, flocculation, paper manufacture or mining fields require polymer latexes formed of finely dipersed particles. Polymerization in reverse micelles or microemulsions appears to be an attractive technique because it can lead, under appropriate formulations, to high molecular weight polymers entrapped within small-sized stable particles. The main characteristics and properties of the latexes and polymers formed by this process are described.
Stabilized Nanoparticles Obtained from Synthetic Polykerizable Micelles and Vesicles.
Authors: Paleos Constantinos M.
Published: March 2011

The structural characteristics and the formation of monomeric and stabilized polymeric micelles and vesicles are reviewed. Characterization of these nanoparticles involved stability studies, molecular weight determination, permeability and fluorescence investigations, as well as electron microscopy and DSC studies.
The Characterization of Infrared Transmitting Optical Fibers
Authors: Driver R. D. , Leskowitz G. M. , Curtiss L. E. , Moynihan D. E. , Vacha L. B.
Published: March 2011

The authors will review the methods used to characterize infrared transmitting optical fibers. The use of FTIR spectroscopic techniques for the measurement of fiber loss will be discussed. Fiber end preparation and fiber cleaving techniques will be reviewed. Data will be presented on silica fiber in the extended IR region, heavy metal fluoride, chalcogenide, silver halide fibers and sapphire crystalline fiber.
Preparation and Properties of Selenium-Tellurium Based Chalcogenide and Chalcohalide Glasses
Authors: Tuzzolo M. T. , Mcenroe D. J. , Drexhage M. G.
Published: March 2011

Chalcogenide and chalcohalide glasses were prepared and the resulting glass Tg's and spectra were investigated. Some chalcogenide glasses were prepared from thermally and chemically pretreated raw materials. Pretreatment steps produced a reduction in impurity absorptions caused by oxygen bonding to the constituent elements. Additions of small amounts of iodine improved attenuations by acting as a hydrogen getter material which eliminated H-Se absorptions. Due to low transition temperatures, chalcohalide glasses containing iodine may not meet commercial requirements.
31P Dipolar NMR Approaches Towards the Development of Structural Principles in Non-Oxidic Glasses.
Authors: Eckert Hellmut , Franke Deanna , Lathrop David , Maxwell Robert , Tullius Michael
Published: March 2011

While the utility of solid state NMR to provide structural information in amorphous systems is well established in silicate and borate glasses, the systematic application of modern NMR techniques to non-oxidic systems has just begun. One of the central issues in these types of glasses is the question of the chemical bond distribution and the existence of short range order. The present study utilizes the selective measurement of homonuclear 31p.31P dipole-dipole couplings via spin echo decay to address this issue in the glass systems P-Se, PSe- Ge and CdGeAs2-xPx. The results indicate that the first two systems are characterized by a high degree of chemical ordering. The chemical bond distribution in CdGeAs2-xPx glasses is found to deviate considerably from that in the stoichiometry-analog crystalline materials.
Advance of Plastic Optical Fibers
Authors: Ide Fumio , Yamamoto Takashi
Published: March 2011

Plastic optical fibers (so called POF) are already in wide use in a large number of fields. This paper gives an overview of the field including the advantages of plastic optical fibers, the various types of fibers and the materials in them.

Then, the properties of three types of fibers which have recently been developed, are discussed. The first is fibers with a poly-methyl-methacrylate (PMMA) core, which have a low transmission loss. Another is heat resistant fibers for use in automobiles. And the third is the multi-fiber type for image guides. And finally, the applications of these fibers and their future prospect are discussed.
Analysis of Thermal Variation of Length and Refractive Index of Lead Fluoride to Study its Optical Properties
Authors: Aurora T. S. , Pederson D. O. , Day S. M.
Published: March 2011

Linear thermal expansion and refractive index variation have been measured in lead fluoride with a laser interferometer as a function of temperature. Data has been analyzed using the Lorentz-Lorenz relation. Molecular polarizability, band gap, variation of refractive index with density, and strain-polarizability parameter have been studied as a function of temperature. They exhibit a small variation with temperature except near the superionic phase transition where the variation appears to be more pronounced. The results are in good agreement with the published data near room temperature.
Concentration and Distribution of ER, AL and P in Silica-Based Optical Fiber Preforms by Sims
Authors: Oblas D. W. , Wei T. , Miniscalco W. J. , Hall B. T.
Published: March 2011

Secondary ion mass spectrometry (SIMS) was used to measure the Er, Al and P distributions across (perpendicular to) and along (parallel to) the axis of Er3+-doped silica based preforms and fibers prepared by a solution doping technique. Specially prepared low-melting silicate glass standards containing known concentrations of Er were used to calibrate the spectrometer to obtain a semi-quantitative measurement of the Er concentration. It was found that the Er concentration can vary along a 4-cm section of the preform by as much as a factor of two. The Al concentration also changed along the length of the preform, but to a smaller degree. Finally, instrumental limitations for measuring the Er, Al and P distributions in the optical fiber samples were determined.
Excited State Absorption and Cross Sections for Er-Doped Glasses
Authors: Zemon S. , Lambert G. , Miniscalco W. J. , Andrews L. J. , Hall B. T.
Published: March 2011

Pump-excited-state-absorption (ESA) measurements on Er3+-doped phosphates, fluorophosphates, and silicate bulk glasses indicate that ESA cross sections are approximately equal to ground state absorption (GSA) cross sections in the 800-nm band. The oscillator strengths of the ESA and GSA bands are also approximately equal, in qualitative agreement with Judd-Ofelt calculations. Fluorozirconate samples were found to have substantial populations in the upper excited states for the measurement conditions used and ESA transitions originating from four excited states were identified. Fluorozirconate fiber amplifiers and lasers at 1.55 μm, therefore, would have decreased efficiency for 800-nm pumping.
Transfer Integrals and Band Structures in (Et)2X Salts
Authors: Leblanc Oliver H. , Blohm Margaret L. , Messmer Richard P.
Published: March 2011

Transfer integrals (tij) between pairs of nearest neighbor ET molecules were calculated by an ab initio method. Tight-binding one-electron energy bands constructed from thetijare similar to those previously calculated by Mori and by Whangbo and their coworkers by semi-empirical, extended Hückel methods, but quite different from those found by Kübler et al. in β-(ET)2I3using the augmented spherical wave (ASW) method. However, all these band models are suspect. The Hubbard on-site repulsion parameter U is estimated to be about twice the band widths, indicating that a full treatment of the Hubbard hamiltonian is needed. Also, polaron effects appear to control transport except at very low temperature.
Electron-Donating Radialenes. Potential Donors for Molecular Organic (Super) Conductors and Ferromagnets
Authors: Yoshida Z. , Sugimoto T. , Misaki Y.
Published: March 2011

The electron-donating [n]radialenes (n=3,4,5) were prepared with the aim of developing both new type of organic (super)conductors and unprecedented organic/molecular ferromagnets. The charge-transfer (CT) complexes of 1,3-dithiole[4]radialene with TCNQ and of 1,3-benzodithiole-[4]radialene with TCNQF4 and DDQ showed comparatively high electrical conductivities in compressed pellets. The single crystals of PF6 and CIO4 salts of 1,3-benzodithiole[4]radialene radical cation revealed temperature change of electrical conductivity characteristic of a semiconductor. The magnetic properties of the bis(trifluoroacetate)salt of thioxanthene[3]-radialene dication and of the CT complexes of 1,3-benzodithiole[5]-radialene with DDQ, TCNQF4, and hexacyanohexamethylenecyclopropane, were also investigated from the ESR and/or magnetic susceptibility measurements.
Aqueous Colloidal Dispersions of Polyaniline Particles
Authors: Armes Steven P. , Aldissi Mahmoud
Published: March 2011

Colloidal polyaniline has been prepared in acidic aqueous media by a modified chemical polymerization of aniline in the presence of a tailor-made polymeric surfactant. The surfactant which acts as a steric stabilizer used in this study is derivatized poly(vinyl alcohol-co-vinyl acetate). This surfactant contains pendant aniline units which participate in the aniline polymerization, resulting in the formation of sterically-stabilized polyaniline particles which have a non-spherical “rice-grain” morphology.

It is shown that this novel form of polyaniline is more processable than the bulk powder that is normally obtained from a conventional chemical synthesis. The solid-state conductivity of solution-cast films or compressed pellets of these dispersions is surprisingly high (⋍ 1 S/cm), despite the presence of the insulating outer layer of chemically-grafted stabilizer.
V2O5 Xerogels as Hosts For Conductive Polymers. Intercalative Polymerization of Aniline, Pyrrole and 2,2’-Bithiophene.
Authors: Wu Chun-Guey , Marcy Henry O. , DeGroot Donald C. , Kannewurf Carl R. , Kanatzidis Mercouri G.
Published: March 2011

Intercalative polymerization of aniline, pyrrole and 2,2’-bithiophene in vanadium oxide xerogels results in electrically conductive novel materials which are composed of alternating monolayers of metal-oxide and conductive polymers. The driving force for this intercalation is redox chemistry. The conductivity type in these materials is a function of the polymer/V2O5 xerogel ratio. Low ratios result in xerogel-based charge transport, while high ratios favor polymer-based charge transport properties. Chemical, spectroscopic and electrical data on the intercalative polymerization products of aniline, pyrrole and 2,2’-bithiophene with V2O5 xerogels are presented.
Resonant Raman Scattering of Poly-3-Alkylthiophenes
Authors: Botta C. , Luzzati S. , Bolognesi A. , Catellani M. , Destri S. , Tubino R.
Published: March 2011

We report Raman scattering measurements on poly-3-heptylthiophene and poly-3-undecylthiophenes both on resonance and preresonance conditions. We have studied different samples as solutions ,solution cast films and electrosynthetized as grown films. Our results indicate that the vibrational frequency of the mode which is strongly coupled to the π - π* electronic transition is sensible to “small” torsions between thiophenes rings , which do not necessarly interrupt completely the conjugation path.
Temperature Dependence of the Picosecond Photocurrent in Stretched Trans-Polyacetylene Films with Below Gap Excitation
Authors: Walser A. D. , Dorsinville R. , Tubino R. , Alfano R. R.
Published: March 2011

The temperature dependence of the picosecond photocurrent with below gap excitation (1.06 μm) has been measured for a highly oriented form of trans-polyacetylene. The 1-d picosecond photocurrent is independent of temperature. The 3-d picosecond photo-current is temperature dependent with an activation energy of 63 meV. These results demonstrate the photoproduction of nonlinear charged carriers ( solitons and polarons) at energies that are below the principal interband absorption edge.
Novel Photochromic Zwitterions For Multifrequency Data Storage
Authors: Ashwell G. J. , Dawnay E. J. C. , Kuczynski A. P. , Szablewski M.
Published: March 2011

Z-β-(N-alkyl-4-pyridinium)-α-cyano-4-styryldicyanomethanide (R-P3CNQ) and its quinolinium analogue (R-Q3CNQ) are photochromic. Their LB films show sharp charge transfer bands at 495 nm (C16H33-P3CNQ) , 565 nm (C16H33-Q3CNQ) and 614 nm (C8H17-Q3CNQ) with half widths at half maximum of 27, 22 and 37 nm respectively. They show interesting nonlinear optical properties and have the potential to store three bits per pixel when addressed at these wavelengths.
L.B. Films Exhibiting Cooperative Spin Transition, for 2D Molecular Memory Devices
Authors: Coronel P. , Ruaudel-Teixier A. , Barraud A. , Kahn O.
Published: March 2011

Molecular electronics requires materials of molecular size exhibiting switching or memory properties. The Langmuir-Blodgett method (L.B.) and its variants provide controlled fabrication of molecular films one molecule thick and their transfer onto solid supports. In these 2D monolayers, molecules are highly organized, so that complex organizates aimed at specific properties can be built. One of these, a semi-amphiphilic complex made of two NCS and two amphiphilic phenantrolines in a cis position, exhibits a spin transition around - 20 °C. It switches from high spin (S = 2) at room temperature to low spin (S = 0) at low temperature. The transition does not follow the expected thermal Boltzman statistics, but is rather steep, pointing out molecular cooperation. The L.B. film exhibits a hysteresis about 4 °C in width, while the parent 3D compound exhibits a hysteresis of less than 0.2 °C, but a much sharper transition. This apparently contradictory behaviour is ascribed to the high impurity content and the multicristallinity of the L.B. film in association with high intermolecular coupling. Because of its intrisic properties this new material is a breakthrough on the way to magnetic memories at the molecular scale for molecular electronics.
Optical and Magnetic Processes and the Side Chains of Diacetylenic Materials
Authors: Sandman Daniel J , Hamill Gregory P. , Levinson Mark , Rossoni Philip G. , Yost Elizabeth A , Papaefthymiou Georgia C.
Published: March 2011

Similarities in the molecular energy levels of alkylcarbazoles and aliphatic nitroxides motivate the detailed study of 4,4′-(butadiyne-l,4-diyl)-bis-(2,2,6,6-tetramethyl-4-hydroxypiperidin-l-oxyl) () as a precursor to a ferromagnetic polymer. A more convenient synthetic route to is reported, and an X-ray-induced transformation of the β-phase of to the α-phase has been observed. The magnetic properties of and derived polymers have been studied using a SQUID system. The observed level of ferromagnetism found in samples of polymerized is comparable to the amount of trace iron materials detected in these samples.
Synthesis and Second-Order Nonlinear Optical Properties of New Coumaromethacrylate-Methylmethacrylate Copolymers
Authors: Henry R. A. , Hoover J. M. , Knoesen A. , Kowel S. T. , Lindsay G. A. , Mortazavi M. A.
Published: March 2011

The synthesis and second-order nonlinear optical (NLO) properties of a new family of optically nonlinear coumarin dye-containing polymers is reported. Polymerizable coumaromethacrylate (CMA) monomers having various alkyl spacers (C2 to C5) between the polymerizable group and the chromophore were prepared and copolymerized with methylmethacrylate (MMA) and other vinyl monomers. The CMA copolymers had high chromophoric content (up to 18 × 1020) and glass transitions as high as 132°C. Spin cast films were prepared on BK7 substrates and oriented by corona-onset poling at elevated temperatures (COPET). The poled CMA copolymer films were characterized for spectroscopic absorption and second harmonic properties. A comparison of the nonlinear optical properties of poled CMA-MMA copolymers to poled guest-host systems is made. Relative to guest/host systems, CMA-MMA copolymer films exhibit larger and much more stable second-order nonlinear optical properties.
Electronic Structure of Long Polyenes: States and Transition Dipoles
Authors: Kohler Bryan E.
Published: March 2011

Electronic excitation energies and transition dipoles measured for symmetrically substituted linear polyenes (R-(CH=CH)N-R) with chain lengths n ranging from 2 to 8 are well fit by the functional form A+B/N. Extrapolation to the long chain limit correlates the band gap transition of polyacetylene with the polyene 11Ag to 11Bu transition. The amount by which the highly correlated polyene 21Ag state is lower than the 11Bu state increases with increasing chain length, extrapolating to roughly half of the 11Bu excitation energy. The 11Ag to 11Bu transition dipole magnitude per chain repeat unit attains a maximum value of 3.0 Debye at an effective conjugation length 5 double bonds.

Careful studies on linear polyenes provides insight into the electronic structure of polyacetylene.
Quantum Lattice Fluctuations and Nonlinear Optics of Conducting Polymers
Authors: Yu J. , Friedman B. , Su W. P.
Published: March 2011

Quantum lattice fluctuations of conjugated polymers in the form of virtual soliton-antisoliton pairs have important effects on the nonlinear optical properties. Quantitative calculations of nonlinear susceptibilities based on the solitonic molecular model are presented.
Effects of In-Plane π’ Bonding on Electronic Transition Energies for Inorganic Polymers
Authors: Ferris Kim F. , Risser Steven M. , Hanson Angela K.
Published: March 2011

The electronic structure of organic and inorganic polymeric systems are well described in terms of their molecular symmetry, even with the large bond polarity shown by such systems as polyphosphazenes. We have performed calculations using the semi-empirical CNDO/1 method to determine the valence electronic structure for a series of model phosphonitrilic and organic compounds. The optical transition energies for phosphonitrilic compounds are greater than their organic counterparts as a result of in-plane π’ bonding interactions. The extent of these interactions is modulated by the electronegativity of the substituent groups on the phosphorus atoms. We report values for the vertical ionization energy and electronic absorption wavelengths, and use molecular orbital contour analysis to show the effects of ligand electronegativity on the π’ network.
Thermal Stability of Magnetic Properties in Dehydrogenated Triarylmethane Resins
Authors: Otani Michiya , Otani Sugio
Published: March 2011

The stability of the magnetic properties of dehydrogenated triaryl-methane resins was investigated both at room temperature and at elevated temperatures. A magnetic property different from that reported in a previous paper was found in the course of studying the reproducibility of synthesis. This new property was examined through a mechanical response of the resins to a set of permanent magnets.
Polyphenoxy Radicals: Synthesis and Homo-Polymerization of 2-(3,5-Dl-t-Butyl-4-Hydroxyphenyl)Isobutyl Methacrylate
Authors: Upasani Ravindra B. , Chiang Long Y. , Goshorn D. P.
Published: March 2011

We evaluated the chemical stability of various polyphenoxy radicals prepared through the modified synthetic methods. The monomeric 3,5-di-t-butyl-4-hydroxyphenyl derivatized olefins and methacrylates were prepared in a multistep synthesis starting from 2,6-di-t-butylphenol. These monomers were polymerized in the presence of radical initiators at the refluxing temperature of aromatic solvents under an inert atmosphere. The most stable polyradicals were found to be highly hindered poly(DBPM) radicals.
Ferromagnetic Interactions in a Series of Schiff-Base Metal-Organic Polymers
Authors: Palacio F. , Lazaro F.J. , Garin J. , Reyes J. , Moron M.C.
Published: March 2011

Magnetization and frequency dependence a.c. magnetic susceptibility measurements of the metal-organic polymers of general formula {[M(C13H17N3)2]SO4 6H2O}n, where M = Fe(II) or Co(II), are indicative of superparamagnetic behavior as a consequence of the existence of strong ferromagnetic interactions in the materials. Scanning electron microscopy and X-ray dispersive spectrometry have been used to study the homogeneity in the composition of the iron polymer.
Biocatalytic Synthesis of Polyesters by Enzyme-Catalyzed Transesterification in Organic Media
Authors: Morrow Cary J. , Wallace J. Shield , Bybee Gregory M. , Reda Kristin B. , Williams Mark E.
Published: March 2011

Enzyme-catalyzed preparation of polymers offers several potentially valuable advantages over the usual polymerization procedures. This paper summarizes our successful use of lipase-catalyzed polycondensations to prepare both a series of achiral [AA-BBJx polyesters from simple bis(2,2,2- trichloroethyl) alkanedioates and diols and of an optically active, epoxy-substituted polyester having a stereochemical purity estimated to be greater than 96%, from racemic bis(2,2,2-trichloroethyl) trans- 3,4-epoxyhexanedioate and 1,4-butanediol. The somewhat less successful polycondensation of a series of A-B monomers is also described. All of the reactions were carried out at ambient temperature in anhydrous, low to intermediate polarity, organic solvents such as ether, THF, and methylene choride, using porcine pancreatic lipase (PPL) as the catalyst. Possible explanations for the difference between the A-B and AA + BB cases, based on NMR analysis of the reactions' progress are considered.
Synthesis of a Collagen Analog in Escherichia Coli Using Recombinant DNA Technology
Authors: Goldberg Ina , Salerno A. J.
Published: March 2011

A family of totally synthetic genes coding for multiple tandem repeats of the amino acid sequence (Gly-Pro-Pro) has been prepared and inserted into the Clal cloning site of the expression vector pJL6. A representative recombinant plasmid, pACI, with an insert of about 340 bp, was established in an Escherichia coli strain bearing a defective λ prophage, to study expression of the CII-collagen analog fusion protein produced from pACI upon heat induction. The in vivo levels of synthetic gene expression obtained showed that the fusion protein was synthesized in E. coli, but was labile compared to other cellular proteins. This degradation could be significantly reduced by the genetic inhibition of a bacterial protease system.
Ceramic Oxide Thin Film Formation Utilizing Biological Processes
Authors: Tarasevich B. J. , Rieke P. C.
Published: March 2011

Abstrac

Mineralization processes used by bioorganisms have been adapted for the nucleation and growth of ceramic oxide thin films onto surfaces from aqueous solutions. These strategies include the use of surfaces derivatized with specific functional groups that control the nucleation and growth and properties of materials deposited. Iron oxide materials were deposited onto functionalized polystyrene surfaces, resulting in the formation of thin films composed of densely packed, nanometer-sized crystallites. Evidence for the formation of oriented crystallites was found. This process may have advantages over conventional thin film processing methods due to the ability to systematically control properties of materials deposited.
Synthesis of Polyimide-Silicate Hybrids Via Sol-Gel Ultrastructure Processing
Authors: Spinu M. , Brennan A. , Rancourt J. , Wilkes G. L. , McGrath J. E.
Published: March 2011

New organic/inorganic hybrid materials were prepared by hydrolysis and co-condensation of tetramethylorthosilicate (TMOS) with trimethoxysilane functionalized polyimide oligomers via sol-gel ultrastructure processing. In the first reaction step, amine terminated, fully imidized, soluble, high Tg polyimides were prepared from appropriate diamines and dianhydrides by solution imidization techniques. The amine end-groups were then quantitativell derivatized to nadimide structures through reaction with cis-norbornene 2,3 dicarboxylic anhydride. Subsequently, the nadimides were quantitatively derivatized to trimethoxysilane functionalities via hydrosilylation reactions in the presence of chloroplatinic acid catalyst. The resulting hexamethoxy functionalized polyimide oligomers were hydrolyzed and co-condensed at elevated temperatures under mild pressure with TMOS via sol-gel processing to generate thermally stable polyimidesilicate hybrids. The synthesis and characterization of these materials is discussed.
Dielectric Relaxation Properties and Alignment Behaviour of Liquid-Crystalline Side-Chain Polymers
Authors: Williams Graham , Nazemi Ali , Karasz Frank E
Published: March 2011

We describe the alignment behaviour of different liquidcrystalline (LC) side-chain polymers when they are subjected to electrical/thermal treatments. It is shown that the alignment behaviour is determined by several variables for a given polymer, including the amplitude and frequency of the applied electric field and both the thermal and electrical history of the sample and its low-field dielectric relaxation properties. It is shown that the dielectric relaxation spectra vary systematically with the degree of macroscopic alignment of the sample and its temperature. The anisotropy of dielectric properties may be understood in terms of the anisotropic reorientational motions of the dipolar mesogenic groups. The permittivity data allow the degree of macroscopic alignment to be determined, via a director order parameter Sd for samples prepared in different ways and also for samples being realigned, as a function of time, by directing electric fields. We illustrate these principles through data we have obtained for a copolymer having the mesogenic groups attached longitudinally and transversely to the main chain.
Liquid Crystalline Materials for Polymers with Anisotropic Ultrastructures
Authors: Attard George S.
Published: March 2011

The in-situ polymerisation of reactive thermotropic and lyotropic liquid crystals affords a method of processing new polymers with anisotropic ultrastructures.
Dielectric Properties of Polymeric Liquid Crystals with Strong Lateral Dipole Groups
Authors: Haase Wolfgang , Pfeiffer Matthias
Published: March 2011

Using broad band dielectric spectroscopy on well oriented microdomains of mesogenic polymethacrylates the influence of strong lateral dipole groups on the dielectric parameters could be verified. The mesogenic groups investigated were phenylbenzoates with fluorine substituents at the phenyl ring. The orientation of the samples was maintained in a superconducting magnet with field strength of 7.2 T. The results are compared with those obtained for non-substituted compounds.
Thermotropic Chiral Nematic Polymers as Optical Materials
Authors: Chen S.H. , Tsai M.L. , Jacobs S.D.
Published: March 2011

Chiral nematic copolymers based on optically active cholesterol, dihydrocholesterol, (R)-(+)- and (S)-(−)-1-phenylethylamine, and (+)- and (−)- isopinocampheol were synthesized and characterized for the investigations of thermotropic and optical properties. Although helical sense does not appear to correlate with the sign of [α]D of the precursor chiral compound as suggested by the observations of cholesteryl and dihydrocholesteryl copolymers, the inversion of chirality in the pendant group, (R)-(+)- vs (S)-(−)-1-phenylethylamine, does lead to the opposite handedness in the resultant helical structure. To better understand the structure-property relationships involving helical sense and twisting power, systematic studies of the roles played by both nematogenic and chiral structures as well as other structural features of the comonomers should be conducted.
New Synthesis/Processing Routes to Materials Exhibiting Large Optical Nonlinearity
Authors: Dalton L. R. , Yu L. P.
Published: March 2011

Synthesis/processing schemes for the preparation of optical quality thin films of π-electron containing organic and organometallic materials are discussed. Fabrication approaches range from preparation of molecular/polymer composites, to preparation of copolymers containing pendant electroactive moieties, to preparation of copolymers with electroactive units incorporated into the polymer backbone, to the preparation of polymer/polymer composites. Such fabrication methodologies (particularly the latter three approaches) have the advantage of facilitating control over polymer solubility and of avoiding aggregation of electroactive units. The synthetic schemes discussed here yield materials with well-defined electroactive units; thus, diffuse bandedges associated with a distribution of π-electron conjugation lengths are avoided. Degenerate four wave mixing (DFWM) measurements at 532, 579–600, and 1064 nm are used to determine third order susceptibilities. Investigation of the frequency dependence of χ(3)/α established that resonance contributions dominate non-linear optical activity near the π-iπ* bandedge. A variety of electroactive moieties have been investigated with the largest values of χ(3)/α (= 10−12 esu cm) being observed for triphenodioxazine, metal phthalocyanine, metal tetraazaannulene, 6,6′-dimethoxy-quinolidine cyanine units.
Inorganic and Organometallic Principles in the Design of Multifunctional Materials
Authors: Michael D. , Mingos P.
Published: March 2011

The prospects of using the properties of inorganic solids with infinite structures in combination with the spectral, magnetic and chemical characteristics of co-ordination and organometallic compounds are reviewed with particular reference to their potential applications in the electronics, sensors and optoelectronic fields.

Solid state inorganic chemistry provides a great variety of thermally stable and optically transparent host materials which have sufficiently large cavities for the incorporation of small molecules. These include zeolites with either spherical or cylindrical three dimensional cavities, layered compounds with infinite two-dimensional spaces and a variable third dimension, and pillared materials with intersecting one-dimensional channels. These structures may be chosen on the basis of a particular function and a second introduced via the incorporation of molecules in the cavities. Alternatively, they may be viewed as neutral structural materials and the multifunctionality can be introduced via the incorporation of molecules with different spectral or chemical properties.

As guest materials co-ordination and organometallic compounds have the following properties which are important in the context of multifunctionality: the ability to co-ordinate small molecules such as O2, SO2, H2 reversibly, distinct reversible electrochemical properties, electronic transitions which show an enormous variation in extinction coefficients and oscillator strengths, polarised spectral transition and electrical conductivity properties.
Multifunctional Molecular and Polymeric Materials for Nonlinear Optics and Photonics
Authors: Prasad Paras N.
Published: March 2011

Molecular units in natural systems are multifunctional in that they exhibit more than one functionalities. This is nature's way of economizing and being efficient. For many technological applications, there is a need for synthetic multifunctional materials which simultaneously exhibit many necessary physical and chemical properties. By appropriate modification of structures both at the molecular and bulk levels, one can incorporate such multifunctionality in molecular and polymeric systems. Our research program focuses on investigations of multifunctional materials for applications in photonics. Photonics describes the emerging new technology in which a photon instead of an electron is used to acquire, process, store and transmit information.
A Theoretical Study of the Effect of the Leach Interval on a Semidynamic Leach Test (Ansi/Ans-16.1-1986)
Authors: Spence Roger D. , Cox Richard L.
Published: March 2011

Numerical solution of Fick's second law of diffusion demonstrated that the error introduced in the ANSI/ANS-16.1-1986 procedure, by assuming a zero surface concentration, varied from about 30% for a leachability index of 5 to about 0.1% for an index of 10. Waste forms typically have indexes of 7 or greater, implying errors of less than 5% with this assumption. The estimated leachability index differs from the actual value by less than 0.2 when the numerical solution is analyzed as input experimental data, except for a leachability index as low as 5 (essentially the value for water).
Porosity and Ion Diffusivity of Latex-Modified Cement
Authors: Nishi Takashi , Kuriyama Osamu , Matsuda Masami , Chino Koichi , Kikuchi Makoto
Published: March 2011

Latex-modified Portland cement, which would be expected to have low permeability and ion diffusivity, was studied for possible application as a solidification agent for radioactive wastes generated from nuclear power plants. In order to predict the leaching ratio of radionuclides from the cementitious waste forms, the effect of water and latex content in the fresh cement paste on total porosity and ion diffusivity of hardened paste was quantitatively estimated.

Total porosity of hardened cement paste decreased with the reduction of water content in the fresh paste and it was also reduced by latex addition. This latter effect could be attributed to the latex emulsion forming a water-proof film and filling the capillary pores. Also Cs ions diffusivity, which is the ratio of the diffusion coefficient in pore water to that in bulk water, showed an exponential correlation with total porosity for both cement materials. An empirical equation, expressing ion diffusivity as a function of total porosity, was derived from the consideration that the water constrictivity in this porous medium could cause an increase of the apparent viscosity of pore water. These results suggested a possibility that the transport behavior of radionuclides through the cementitious matrix could be estimated from the mixing parameters of the original cement pastes.
Durable Concrete for a Waste Repository - Measurement of Ionic Ingress
Authors: Feldman R.F. , Beaudoin J.J. , Philipose K.E.
Published: March 2011

A waste repository for the below ground disposal of low level radioactive waste is planned at Chalk River Nuclear Laboratories. It relies greatly on the durability of concrete for the required 500 year service life. A research program to design durable concrete and predict its service life is in progress.

The degradation of the concrete depends to a large extent on the rate of ingress of corrosive agents. Penetration of chloride and sulphate ions are particularly relevant. Twenty mix formulations were developed to create various types and qualities of concrete, and to study their behaviour in different site environmental conditions. A total of 1000 concrete specimens are being exposed at 20°C and 45°C to 25 different combinations of the corrosive agents including CO2. Procedures to measure the ionic profiles and to determine the factors controlling diffusion of the ions in the various concretes have been developed. Results of selected concrete systems exposed to chloride and sulphate solutions for 1 year are presented and discussed in terms of pore structure and permeability parameters of the concrete.
Mechanistic Model for the Durability of Concrete Barriers Exposed to Sulphate-Bearing Groundwaters
Authors: Atkinson Alan , Hearne John A.
Published: March 2011

The durability of concretes in radioactive waste repositories is likely to be limited by their reaction with sulphate-bearing groundwaters. In such a situation the concrete slowly degrades by sulphate penetrating into the concrete where it reacts with the cement to cause stress and eventual disruption. Experiments have been carried out to quantify these reactions and the resulting expansions. The data have been incorporated into an overall mechanistic model for sulphate degradation in which the criterion for disruption is the accumulation of a critical amount of stored elastic energy in the reaction zone. The results of this model are in good agreement with those of an earlier empirical model and enable extrapolations to be made to different concretes and groundwaters.
A Kinetic Model for Borosilicate Glass Dissolution Based on the Dissolution Affinity of a Surface Alteration Layer
Authors: Bourcier William L. , Peiffer Dennis W. , Knauss Kevin G. , McKeegan Kevin D. , Smith David K.
Published: March 2011

A kinetic model for the dissolution of borosilicate glass, incorporated into the EQ3/6 geochemical modeling code, is used to predict the dissolution rate of a nuclear waste glass. In the model, the glass dissolution rate is controlled by the rate of dissolution of an alkalidepleted amorphous surface (gel) layer. Assuming that the gel layer dissolution affinity controls glass dissolution rates is similar to the silica saturation concept of Grambow [1] except that our model predicts that all components concentrated in the surface layer, not just silica, affect glass dissolution rates. The good agreement between predicted and observed elemental dissolution rates suggests that the dissolution rate of the gel layer limits the overall rate of glass dissolution. The model predicts that the long-term rate of glass dissolution will depend mainly on ion concentrations in solution, and therefore on the secondary phases which precipitate and control ion concentrations.
Dissolution Mechanisms of the Perovskite and Hollandite Phases in the Synroc Assemblage
Authors: Nyhra S. , Pham D.K. , Smart R.St.C. , Turner P.S.
Published: March 2011

Perovskite (CaTiO3 )and hollandite ([BaxCsy,][(Ti,Al) 3+ Ti4 + ]016) 2x+y 8-2x-y are two of the three major phases of the Synroc titanate mineral assemblage. The chemical durabilities of these two phases have been investigated by solution analysis, surface analysis and electron microscopy. While a detailed model of the durability of perovskite has evolved from previous work, much less is known about the mechanisms which affect the durability of hollandite. The present investigations show that, for single-phase hollandite, selective extraction by ion exchange of Cs+ and Ba 2+ does not play a significant role. On the other hand, total dissolution of the network does seem to occur as a result of base-catalysed hydrolysis. Also, complexation and precipitation of Al and TI species in solution has the effect of driving the system to low pH. These results can be correlated with the more complete model for dissolution of perovskite in order to infer the overall effects of aqueous attack on the Synroc HLW solid.
A Comparison of the Behaviour of Vitrified HLW in Repositories in Salt, Clay and Granite: Part II: Results
Authors: Marples J.A.C. , Lutze W. , Kawanishi M. , van Iseghem P.
Published: March 2011

A ‘Round Robin’ test of the European Commission 's “Repository Systems Simulation Test” has been undertaken. This involved testing an inactive simulant of the French high-level waste glass SON68 (RTT7) in containers which also held backfill, geological materials and water. Ten laboratories undertook the granite option, six salt and three clay. The test procedure was closely specified and is given in detail in a companion paper [1]. Experiments with glass powder and (optionally) solid specimens in contact with aqueous solutions were run for periods of up to one year at 90 °C and the solutions were analysed for Si, B, Li and Mo (compulsory) and other constituents of the corroded glass (optional). The analytical results are used to compare the performance of the glass under conditions representing those that might occur in future repositories in the three media.
The Long-Term Corrosion and Modelling of Two Simulated Belgian Reference High-Level Waste Glasses - Part II
Authors: Patyn J. , Iseghem P. Van , Timmermans W.
Published: March 2011

The long term corrosion of two reference Belgian high-level waste glasses (SAN60 and SM58) were investigated in pure water. The corrosion was studied using powdered glass at a high surface area to volume ratio and temperatures of 90 and 120°C. The experimental data at 90°C reveal a “final” leach rate which decreases with time. At 120°C this “final” state is transient and followed by an enhanced dissolution, which was correlated with extensive surface crystallization. Modelling using the PHREEQE and GLASSOL computer codes described the initial corrosion, but was unable to account for the enhanced dissolution at 120°C.
Product Consistency Leach Tests of Savannah River Site Radioactive Waste Glasses
Authors: Bibler Ned E. , Bates John K.
Published: March 2011

The Product Consistency Test (PCT) is a glass leach test developed at the Savannah River Site (SRS) to confirm the durability of radioactive nuclear waste glasses that will be produced in the Defense Waste Processing Facility. The PCT is a seven day, crushed glass leach test in deionized water at 90°C. Final leachates are filtered and acidified prior to analysis. To demonstrate the reproducibility of the PCT when performed remotely, SRS and Argonne National Laboratory have performed the PCT on samples of two radioactive glasses. The tests were also performed to compare the releases of the radionuclides with the major nonradioactive glass components and to determine if radiation from the glass was affecting the results of the PCT.

The test was performed in triplicate at each laboratory. For the major soluble elements, B, Li, Na, and Si, in the glass, each investigator obtained relative precisions in the range 2–5% in the triplicate tests. This range indicates good precision for the PCT when performed remotely with master slave manipulators in a shielded cell environment. When the results of the two laboratories were compared to each other, the agreement was within 20%. Normalized concentrations for the nonradioactive and radioactive elements in the PCT leachates measured at both facilities indicated that the radionuclides were released from the glass slower than the major soluble elements in the glass. For both laboratories, the normalized releases for both glasses were in the general order Li∼B∼Na>Si>Cs-137>Sb-125>Sr-90. The normalized releases for the major soluble elements and the final pH values in the tests with radioactive glass are consistent with those for nonradioactive glasses with similar compositions. This indicates that there was no significant effect of radiation on the results of the PCT.
The Reaction of Synthetic Nuclear Waste Glass in Steam and Hydrothernal Solution
Authors: Ebert W. L. , Bates J. K.
Published: March 2011

Glass monoliths of the WVC4M4, WVCM50, SRL 165, and SRL 202 compositions were reacted in steam and in hydrothermal liquid at 200°C. The glass reaction resulted in the formation of leached surface layers in both environments. The reaction in steam proceeds at a very low rate until precipitates form, after which the glass reaction proceeds at a greater rate. Precipitates were formed on all glass types reacted in steam. The assemblage of phases formed was unique to each glass type, but several precipitates were common to all glasses, including analcime, gyrolite, and weeksite. Reaction in steam occurs in a thin layer of condensed water which becomes saturated with respect to the observed phases after only a few days of reaction. The reaction in steam is accelerated relative to reaction in hydrothermal liquid In the sense that secondary phases form after a shorter reaction time, that is, after less glass has reacted, because of the smaller effective leachant volume present in the steam environment. A knowledge of the secondary phases which form and their influence on the glass reaction rate is crucial to the modeling effort of the repository program.