bluuebunny/crossref_metadata_2025 huggingface dataset:
1200 to 1400 K Slow Strain Rate Compressive Properties of NiAl/Ni2AlTi-Base Materials
Authors: Whittenberger J. Daniel , Viswanadham R. K. , Mannan S. K. , Kumar K. S.
Published: March 2011

Owing to their superior strength in comparison to other single phase intermetallics, NiAl-Ni2AlTi alloys have potential for the matrix material in high temperature composites. An investigation of two compositions, Ni-40Al-10Ti and Ni-45Al-5Ti with and without 20 vol. pct. TiB2 in the form of −1μm diameter particles, was initiated with materials produced by the Martin Marietta XDTM process and compacted by hot pressing. The as fabricated materials were fully dense and polycrystalline where the grain sizes measured −8μm for Ti-poor and about 15μm for the Ti-rich unreinforced materials but could not be determined for ei her TiB2-containing composite. Elevated temperature compression testing was conducted to approximately 8 percent deformation between 1200 and 1400 K with strain rates varying from −10−4 to −10−7 s−1. While the majority of the tests exhibited diffuse yielding over approximately one percent strain followed by negative strain hardening, a few experiments resulted in steady state behavior where deformation continued under a constant stress. The flow strengths on yielding of both forms of Ni-40Al-1OTi were higher than those for the Ni-45Al-5Ti versions. Although for each matrix composition the addition of 20 vol. pct. TiB2 decreased the strength at the higher strain rates in comparison to the TiB2-free forms, the particles do provide reinforcement during slow deformation conditions. Optical microscopy of tested specimens revealed that these materials are generally quite brittle as numerous longitudinal and transverse cracks were found irrespective of the type of stress-strain behavior.
Continuous Ordering Reactions in NiAl/Ni2, AlTi Dual Phase Alloys
Authors: Tso N. C. , Sanchez J. M.
Published: March 2011

The Cluster Variation Method is used to study metastable phase equilibrium and possible ordering reactions in the Ni2AlTi⇆;NiAl dual phase alloy system. The Cluster Variation Method was also used to model the corresponding binary alloys and the results were extrapolated to the ternary system. The occurrence of a continuous ordering reaction in the Ni-Al-Ti system is proposed and possible decomposition reactions are discussed.
The Effect of Boron on the Microstructure of Ni2 AITi.
Authors: Schuon S. R. , Rehzets V.
Published: March 2011

Ingots with a nominal composition of Ni–34a/o Al–15a/o Ti + O.Ow/o B, 0.05w/o B, 0.1w/o B or 0.3w/o B were prepared and compression tested at a strain rate of 1.7 x 10–7/s at room temperature, 650°C, 870°C, and 1000°C in air. Alloys were single-phase Ni2 AITi and borides were contained in all compositions containing boron. The compressive yield strength and the ultimate compressive strength of NA2AITi containing boron is strongly affected by the type and distribution of borides. The formation of TiB2 at 0.3w/o B increased the strength at room teperature, 650°C, 870°C, ang 1000°C, while formation of a TiB-Ni2 AITi eutectic at 0.05w/o and 0.lw/o B decreased strength at all temperatures. Crack deflection by TiB2 is an important strengthening mechanism at room temperature and 650°C. However, at 1000°C, dispersion strengthening may be an important strengthening factor.
The Alloying of Titanium Aluminides with Carbon
Authors: Cam G. , Flower H. M. , West D. R. F.
Published: March 2011

An investigation has been made on the constitution of the Ti-Al-C system in the range of 15–55 at% Al and of 0.1–1.0 at% C and the temperature range of 1250–450 °C. Equilibria including three compounds TiC, Ti3AlC, and Ti2AlC have been studied and transmission electron microscopy (t.e.m.) observations of ordering reactions in az have been made.
The Effect of Microalloying B on the High Temperature Mechanical Properties of Ti3Al
Authors: Newkirk Joseph W. , Feldewerth Gerald B.
Published: March 2011

The effect of adding boron to Ti3Al on the microstructure and high temperature tensile properties has been studied. Boron caused a large grain refinement that dominated the tensile properties at all temperatures. Particles of Ti2B were found in all of the boron containing alloys. TiB was found only at concentrations of 0.1% B or more.
Microstructural Studies of the Deformation of TiAl Alloys
Authors: Hall Ernest L. , Huang Shyh-Chin
Published: March 2011

The mechanical behavior and microstructures of TiAl alloys after tensile and bend tests at room temperature and elevated temperatures were studied. The results for two-phase Ti52Al48 alloys are compared with those of single phase Ti48Al52, and the effect of adding 3 at. pct. vanadium as a substitute for Ti in these two alloys is considered. It is shown that Ti52Al48 has greater strength and ductility than Ti48Al52 at room temperature and elevated temperatures up to 871°C (1600°F). Adding vanadium increases the ductility of both binary alloys. The microstructure of the Ti52Al48 alloy deformed at room temperature contains primarily twins and 1/2<110> easy slip dislocations, whereas the similar Ti48Al52 sample exhibits superdislocations and associated pinned faulted dipoles. If these samples are deformed at 540°C (1000°F) or above, the Ti52Al48 exhibits extensive twinning, and the pinned faulted dipoles in the Ti48Al52 sample disappear. The vanadium additions do not noticeably change the deformation microstructure at room temperature. It is suggested that the strength and ductility of these alloys may be controlled by tetragonality, bonding, interstitial element, and grain size effects, which in turn are affected by the presence of second phases and by the alloy composition.
Preparation of Ti2CuAl5 by Reactive Sintering
Authors: Maeland Arnulf J , Narasimhan Dave
Published: March 2011

The exothermic formation of intermetallic compounds from the constituent powders through reactive sintering at relatively low temperatures is a promising new process being explored for the preparation of nickel aluminides. The process is useful for synthesis of other intermetallics as well.

We describe here the preparation of Ti2CuAl5 using the technique of reactive sintering. This intermetallic compound has a L12 structure which is also the structure of the very interesting Ni3Al intermetallic. Characterization of the Ti2CuAl5 phase is done by x-ray diffraction, microhardness, and microstructure.
Influence of Stoichiometry on the Strength of Nickel Beryllide
Authors: Nieh T. G. , Wadsworth J. , Liu C. T.
Published: March 2011

It is demonstrated that the hardness of NiBe is dependant upon its stoichiometry; a minimum hardness is observed at the equiatomic composition. This behavior is similar to intermetallics that have the same crystallographic structure, e.g., NiAI and CoAl. The hardness increase for the off-stoichiometric compositions is a result of defect and anti-site defect structures, but may also, in part, be caused by interstitial oxygen. Nickel beryllides appear to have some intrinsic room temperature ductility, as evidenced by the absence of cracking near hardness indentations.
Twinning in A-15 Compounds
Authors: Khantha M. , Vitek V. , Pope D. P.
Published: March 2011

Twinning modes in topologically close-packed A-15 compounds are examined from a geometrical viewpoint. The crystallographically possible twinning modes with a shear less than a certain maximum are tabulated along with the percentage of shuffles involved for each of the modes. Based on some simple criteria, two of the most likely modes for deformation twinning are discussed in detail. The shuffle parameters usually employed to determine the percentage of lattice shuffles for a given mode have not been found to be useful in these structures because the primitive unit cell typically contains more than one formula unit. One has to examine the distribution of atoms in detail in order to determine the percentage of shuffles involved.
Articulated Rigid-Rod Polymers Containing Benzobisoxazole and Benzobisthiazole Moieties
Authors: Evers Robert C. , Dotrong My
Published: March 2011

Articulated rigid-rod polymers with 2,6-benzobisoxazole and 2,6-benzobisthiazole units in the backbone were synthesized by copolycondensation in polyphosphoric acid of 4,6-diamino-l,3-benzenediol dihydrochloride and 2,5-diamino-l,4-benzenedithiol dihydrochloride, respectively, with terephthalic acid and suitably-structured difunctional monomers. Early efforts centered on the incorporation of flexible diphenoxybenzene tructures into the polymer backbone while subsequent efforts involved the more thermooxidatively stable 3,3'-biphenyl- or 4,4'-(2,2'-bipyridyl)-structures. Under dilute reaction conditions, the copolycondensation reactions proceeded in the isotropic phase to yield polymers with inherent viscosities of less than 13dL/g (CH3 SO3 H, 25°C, 0.2g/dL). Later efforts carried out under higher concentration in the nematic state led to intrinsic viscosities as high as 20dL/g. Films which exhibited optical birefringence under crossed polars could be cast from methanesulfonic acid solutions of the polymers. Thermooxidative stability of the articulated polymers was evaluated by isothermal aging in air at 316°C and/or 371°C. Stability of the polymers was found to decrease with increased content of the flexible structures, with the loss of thermooxidative stability being more pronounced with the diphenoxybenzene structures.
The Synthesis and Characterization of Polybenzamides Containing Siloxanes.
Authors: Kumpf Robert J. , Gordon Bernard
Published: March 2011

Three different kinds of siloxane-containing polybenzamide copolymers have been prepared: a series of siloxane-containing segmented copolymers; a siloxane-poly(benzamide) random copolymer; and a poly(benzamide) - poly(dimethylsiloxane) block copolymer. The structures of these copolymers were confirmed using diffuse reflectance FTIR spectroscopy. Dilute solution viscometery showed them to be high polymers. The thermal stabilities of these copolymers were studied using thermal gravimetric analysis. Incorporation of siloxane units via a phenyl link was found to not affect the inherent thermal stability of the poly(benzamide) chain. The solution phase behavior of these copolymers in DMAC/LiCl was studied using an optical microscope fitted with cross-polars. The segmented copolymers and the block copolymer exhibited lyotropic behavior, which was influenced by the amount of siloxane and the overall molecular architecture. Solutions of the random copolymer were isotropic at all concentrations studied.
Conformational Rearrangement in the Nematic Phase of a Polymer Comprising Rigid and Flexible Sequences in Alternating Succession. Orientation-Dependent Interactions Included
Authors: Flory P. J.
Published: March 2011

Consider a homopolymer consisting of rigid and flexible sequences in alternating succession. The prototype is

The degree of polymerization DP is very large. The oxyethylene units may occur in various disordered conformations or in the ordered one, ttt, with a statistical weight s* compared with unity for the disordered forms, collectively. Let γζ be the number of rigid sequences containing ζ rigid units, i.e., consisting of ζ rigid members joined by ζ-1 oxyethylene units in extended (ordered, ttt) conformations, the oxyethylene units flanking this sequence being otherwise conformed.
Nonlinear Elasticity of Poly (P-Phenylene Benzobisthiazole) (PBZT) Fibers
Authors: Jiang H. , Eby R.K. , Adams W. W. , Lenhert Galen
Published: March 2011

We have developed a method which uses laser-generated ultrasound to measure the Young's modulus of fibers as a function of temperature and static tensile stress. For fibers of PBZT, measurements have been made to 580°C and 1.7 GPa. The fibers are shown to exhibit nonlinear elasticity which changes systematically with temperature, tensile stress and fiber processing conditions. They exhibit a relaxation associated with a structure change at about 300–400°C.

We have also used x-ray diffraction to measure both the crystal modulus and aspects of the ultrastructure such as crystal orientation as a function of static tensile stress, crystal size and unit cell. It is shown that improved crystal orientation with increased tensile stress is one of the most important mechanisms of the nonlinear elasticity. The measurements of orientation distribution are combined with other measurements to make calculations of the crystal modulus for the assumptions of uniform stress and uniform strain. These apparent crystal moduli are considerably greater than the measured ultrasonic ones and both are less than the theoretical values. The assumptions of uniform stress and uniform strain have also been used together with the orientation distribution and other parameters to calculate the macroscopic modulus. Both results exhibit less nonlinear elasticity than that observed experimentally, indicating that there is another mechanism in addition to the crystal reorientation which contributes to the nonlinear elasticity. The x-ray measurements of unit cell as a function of temperature to 450°C show a structure change at about 300-400°C. It is consistant with an oscillation of the phenyl and bisthiazole moities around the connecting single bonds.
Direct Imaging of Compressive Failure Zones in Rigid-Rod Polymer Fibers
Authors: Martin David C. , Thomas Edwin L.
Published: March 2011

Fibers of rigid-rod polymers are comparatively weak in compression with deformation occurring by strain localization into kink bands. Here, we present an ultrastructural study of the deformation processes accompanying kink formation in fibers of poly(paraphenylene benzobisthiazole) (PBZT) and poly(paraphenylene benzobisoxazole) (PBZO). Lateral packing between chains is maintained after shear deformation. The local strain is heterogeneous and has been analyzed in detail. Observation of sharp, high angle tilt boundaries confirms a deformation mechanism which involves kinking of individual polymer chains. A model of the micromechanisms involved in kinking is proposed.
Structural Transformations in Crystalline Oligomers of Polyparaphenylene
Authors: Baker Kenneth N. , Knachel Howard C. , Fratini Albert V. , Adams W. Wade
Published: March 2011

We report the room and low temperature crystal structures of the unsubstituted pquinquephenyl (PQP) and p-sexiphenyl (PSP), and substituted 22,45 -diphenyl-pquinquephenyl (DPQP), 22,65-diphenyl-p-septiphenyl (DPSP), and 1,2,4-triphenylbenzene (TPB) polyparaphenylene oligomers. The unsubstituted oligomers exhibit a solid state transition when cooled from room temperature to 110K, as indicated by a change in crystallographic space group. No transition is observed for the substituted oligomers other than the usual thermal contraction of the unit cell. The transition observed for the unsubstituted oligomers is interpreted in terms of a conformational change from an “averaged” planar structure to a static non-planar one. Comparisons of room temperature and low temperature crystal data are presented.
Nonlinear Optical Properties of Rigid Rod Polymers and Model Compounds
Authors: Prasad Paras N.
Published: March 2011

Picosecond and femtosecond degenerate four-wave mixing have been used to measure third-order nonlinear optical susceptibility of several rigid-rod polymers and model compounds. A significant X(3) with femtosecond response was observed. The effects of processing conditions and structural variations on X(3) were studied. Four-wave mixing studies can also be conveniently used to generate ultrasonic phonons of well defined wave length and propagation direction. From this result one can investigate mechanical properties of polymers. Using this technique both the longitudinal and shear components of the elastic moduli for a uniaxially oriented rigid-rod polymer, poly-p-phenylene bis benzooxazole (PBO), were determined.
Rigid Rod Polymers for Nlo Applications: An Overview and Evaluation
Authors: Druy Mark A. , Domash Lawrence H.
Published: March 2011

Nonlinear optics (NLO) is increasingly important for a variety of military and commercial needs ranging from new types of laser weapons to fiber optic communications networks, to optical computing applications. Rapid advances in optical phase conjugation, optical switching, and logic have demonstrated the enormous potential for practical applications with concurrent fast-paced materials development. A new class of organic materials called rigid rod (also known as ordered polymers) have the excellent intrinsic properties and tailorability to meet the requirements of a wide range of nonlinear optical devices. This manuscript provides a multidisciplinary effort to target key applications and material and processing requirements for ordered polymers. This manuscript provides the framework for the applications development required for the rapidly growing field of NLO devices from ordered polymeric materials.
Electrically Conductive Molecular Composites Based Upon Ppbt and Metallophthalocyanines: Processing, Microstructure, and Electrochemistry
Authors: Depra P. A. , Giesler J. M. , Marks T. J. , Carr S. H.
Published: March 2011

Mechanically strong, environmentally stable, and electrically conductive polymeric films and fibers can be fabricated by processing (dry-jet, wet-spinning) solutions of PPBT and metallophthalocyanine molecular metal precursors, followed by chemical or electrochemical oxidation. X-ray diffraction, and resonance Raman measurements on (PPBT)-[Ni(Pc)I]x fibers indicate a microstructure consisting of small Ni(Pc)I crystallites imbedded in a PPBT matrix. Cyclic voltammetry and controlled potential coulometry indicate that PPBT/NiPc films can be reversibly doped.
New Approaches to the Synthesis of Ladder Polymers: Copolymers of Aniline and Thiophene
Authors: Polis David W. , Dalton Larry R. , Vachon David J.
Published: March 2011

We would like to report the synthesis of new third order nonlinear optical materials formed from reaction of dibromothiophenes with p-phenylenediamines under Ullmann condensation conditions. Initial measurements of the third harmonic NLO susceptibilities (X3~= 4 × 10−10 esu ), high laser damage thresholds ( 4 GW/cm2 ), and low absorptions have provided promising materials for device applications. Composite films in poly(vinylalcohol), poly(methylmethacrylate). or poly(carbonate) also gave significant X3 values in less than 10 percent w/w concentrations.
Polymeric Electrolytes and Polyelectrolytes: Salt Concentration and Domain Effects on Conductivity
Authors: Ratner Mark A. , Druger Stephen D. , Nitzan A.
Published: March 2011

Solvent-free polymer electrolytes and polyelectrolytes are usually studied at quite high ionic concentrations, (into the range above 1M). Under these conditions, correlation effects arising from ion-polymer and ion-ion interactions are expected to be important in the mechanism of conductivity. We sketch some specific ionic effects, separating those actittg on the mobility from those effecting carrier concentration. Mobility effects include reduction of the fluidity due to the effective cross-linking by cations, screening of applied fields due to high ionic concentrations, frictional drag due to counterion motion, and in some polymer hosts, lowered local availability of cation solvation sites due to reduction of the number of coordinating basic oxygens. Reduction of the carrier density from its stoichipmetric value can be discussed in terms of a generalized ion-pairing model. Though the concentrations usually studied are so high that Debye-Huckel theory is invalid and the stoichiometric average cation-anion separation is smaller than the Bjerrum length (a situation in which ordinary electrolyte theory considers all ions paired), nevertheless consideration in terms of contact ion pairs, solvent separated ion pairs and mean stoichiometric separation can be used to compute the effective concentration of carriers. Estimates based on an electrostatic continuum, cavity model for the binding energy of a pair describe the reduction of effective carrier number observed in poly (propylene oxide) materials.
Properties of Electrolyte and Electrode Films Prepared by RF and DC Magnetron Sputtering
Authors: Bates J. B. , Dudney N. J. , Chu Y. T. , Mazumdar P.
Published: March 2011

Increased interest in ion conducting thin films and thin-film devices is evidenced by the number of papers on this topic presented at the recent Garmisch conference [1[. Magnetically enhanced (magnetron) sputtering [2,3] is an important technique for depositing these as well as other kinds of ceramic thin films. Two advantages of magnetron over conventional diode sputtering are the increased sputtering rate, which is important in the deposition of ceramic materials, and the reduction in electron bombardment of the substrate and growing film. In this paper, we describe our high-vacuum film growth chamber and present the results of tests of this system in fabricating films of lithium ion conducting glass electrolytes, TiS2, and vanadium oxide by reactive dc and rf magnetron sputtering. The results of combining these films into a thin film lithium battery also are discussed.
Intrinsic Fast Oxygen Ionic Conductivity in the Gd2(ZrxTil−.)2O7, and Y2 (ZrxTil−x,)2O7, Pyrochlore Systems
Authors: Moon P.K. , Tuller H.L.
Published: March 2011

The pyrochlore solid solution Gd2(Zrx Til−x)2O7, was found to be an attractive system for investigating the relationship between composition, structural disorder and ionic conductivity. Both cation and anion order parameters were found to decrease systematically with increasing substitution of Zr for Ti leading ultimately to intrinsic fast oxygen ion conductivity in the solid solution. The degree of intrinsic disorder was determined quantitatively from doping experiments and was found to be equal to l.0×lO39 exp(-O.24±0.03eV/kT)cm−6sfor x = 0.3 and substantially larger for higher values of x. Oxygen vacancy mobilities, on the other hand, were found to be relatively independent of x with values of μv, = 0.15exp(-0.78 ± 0.02 eV/kT)cm2V−1s−1. These, and more recent results, on Y2 (ZrxTil−x)2O7, are discussed in the context of the similarities between the pyrochlore and fluorite phases.
Hydrogen - Transporting Mixed Conductors
Authors: Schreiber Martha , Huggins Robert A.
Published: March 2011

Hydrogen has been found to exhibit high mobility in several classes of solids, which also have appreciable electronic conduction.

The structure and properties of such mixed -conductor materials will be dicussed. In addition, several types of applications, based upon their special properties, will be described.
Composite Polyphase Electrochemical Cell Components
Authors: Crouch-Baker S. , Huggins R. A.
Published: March 2011

A number of composite polyphase electrode systems employing the mixed-conducting matrix principle have been proposed in this laboratory as alternatives to single lithium alloy systems for use as negative electrodes in both room and intermediate temperature lithium-based cells. Further, a composite hydroxide ion conducting electrolyte has been considered for use at intermediate temperatures which utilises liquid lithium hydroxide formed in situ and contained within a lithium aluminium oxide ceramic matrix.

Both these, and other, composite electrochemical cell component systems serve to overcome certain disadvantages found in simpler, non-composite designs. In order to operate effectively, the electrode and electrolyte systems described here must satisfy certain thermodynamic, kinetic and mechanical criteria. In this work, these criteria are discussed, using, among others, the examples given above, with particular emphasis on the thermodynamic phase stability conditions which must be satisfied by a viable composite electrode or electrolyte system.
Spectroscopic Studies of Fast Ionic Conducting Halogenoborate Glasses
Authors: Massot M. , Haro E. , Oueslati M. , Balkanski M.
Published: March 2011

Lithium borate glasses B2O3-Li2O-LinX with n=l, X=F, Cl or I are fast ionic conductors. In the perspective of their use as an electrolyte in solid state micro-batteries, spectroscopic investigations of their structure were performed by using experimental techniques sensitive to the local ordering as Raman scattering and F.T.I.R. spectroscopy. In the light of these results, we find that binary and ternary systems (“doped glasses”) with same O/B ratio do not exhibit identical boron-oxygen network. The observed modifications are attributed to interactions between the network and the anions of the doping salt. In addition, the type of the anion plays an important role in the observed effects. We propose here a possible interpretation for the variation of conductivity reported on halide glasses.
Determination of Transport Properties for Solid Ionic Conductors
Authors: Pollard Richard , Comte Thierry
Published: March 2011

A mathematical model has been developed that describes multicomponent transport in solid electrolytes that contain either three or four independent species. The treatment includes homogeneous reactions, short-time transients, and the effects of a co-continuous inert phase. Application of the model to low-frequency AC impedance experiments shows that accurate information on reaction stoichiometries and the nature of the mobile species is needed for proper interpretation of transference numbers and diffusion coefficients. A set of consistency checks for the impedance data is identified that helps distinguish between dilute and concentrated solid ionic conductors and between systems that should be regarded as four-species electrolytes rather than binary electrolytes.
The Electrical Conductivity Measurements of Solid Electrolyte, CuZr2(PO4)3
Authors: Lee T.J. , Yao P.C. , Hsu S.E. , Fray D.J.
Published: March 2011

This study reports measurements of electrical properties of the solid state copper ion conductor CuZr2(PO4)3.
Single-Ion Conducting Polymer Electrolytes: Synthesis and Characterization
Authors: Doan Kate E. , Ganapathiappan S. , Chen Kaimin , Ratner M.A. , Shriver D.F.
Published: March 2011

Two classes of alkali metal single-ion conducting polymer electrolytes have been characterized and their conductivities examined. Both polymers are sodium ion conductors. The first class is based upon a tetra(alkoxy)-aluminate counterion incorporated into a polyether network, and the second has a sulfonate counterion covalently bonded to a phosphazene backbone. The temperature dependent and concentration dependent conductivities of these polymers are contrasted. Phosphazene polymers that are anion conductors are also discussed.
Intercalation Compounds: Covalent and Ionic Approach
Authors: Hagenmuller Paul
Published: March 2011

In contrast with amphoteric graphite layer type oxides or chalcogenides play generally the role of acceptors in intercalation reactions. Due to the more ionic character of the M-0 bonds the structural evolution of the oxides may usually be explained on hand of electrostatic considerations, or in terms of cation oxido-reduction. On contrary for the more covalent chalcogenides occupancy of energy levels in the band structure by the transferred electrons constitute a determining factor, influencing strongly not only the structural changes but also the physical properties. Similar bonding considerations account for the strong tendency of the oxides to undergo 2D → 3D transformations.
Characterization of Ionically Conductive Chalcogenide Glasses
Authors: Kennedy John H.
Published: March 2011

The synthesis methods and chemical properties of conducting chalcogenide glasses are reviewed with special emphasis on SiS2 -based glasses. Structural information obtained from DSC, FT-IR, and solid state NMR is discussed, as well as electrochemical properties, and the use of ionically conductive glasses in battery applications.
Raman Scatteringl And Infrared Absorption in Lithium Intercalated MoS2
Authors: Sekine T. , Julien C. , Jouanne M. , Weber M. , Balkanski M.
Published: March 2011

Raman scattering and IR absorption were studied in Li-intercalated MoS2 at room temperature. After intercalation, new Raman peaks were observed at low-frequency sides of the high-frequency original Raman peaks and around a rigid-layer mode. This fact indicates the formation of superlattice structure along the c-axis. An intercalation mode in which Li atoms vibrate strongly against the host lattice was observed at about 205 cm−1. Two new broad bands grow in the high-frequency region as the concentration of Li increases. The corresponding peaks were observed by IR absorption. They appears to be caused by vibrations of substitutional defects, in which the Li atoms have substituted for Mo atoms in the host lattice.
Structure and Stability of βAlumina Type Phases
Authors: Petric Anthony , Kirchnerova Jitka , Bale Christopher W. , Pelton Arthur D.
Published: March 2011

Polycrystalline β“alumina isomorphs have been produced by ion exchange of Na β“alumina in various molten salts or salt vapors. The exchanged samples were heated to determine their stable structure after thermal decomposition. The stable structures are classified according to the cation on the conduction plane. Cation size and charge are believed to be the critical factors determining the stable structure.
Sodium Sulfur Battery Accomplishments and Remaining Problems
Authors: Fischer Wilfried
Published: March 2011

NaS batteries are at a state of development at which the principal problems are resolved and prototype batteries have been tested for major applications such as electric vehicle propulsion and off-peak electric energy storage in electric networks. An overview will be presented on the state of development and on application tests performed so far.

Nevertheless, cell and battery ccmponents need to be further optimized. Major areas for potential improvements are the beta alumina solid electrolyte with regard to conductivity, mechanical strength and life, the metal ceramic joint, the cell casing with regard to corrosion resistance, and the vacuum thermal enclosure with regard to a lower thermal conductivity. Possible solutions will be discussed.
A Gamma-Ray Spectrometer For Measurement Of The Water Diffusivity Of Cementitious Materials
Authors: Quenard D. , Sallee H.
Published: March 2011

A gamma ray spectrometer using an Americium source has been built. The source and the detector are mounted on two separate towers and can move vertically. The studied sample is mounted on a platform that can move horizontally. The movements of the towers and the platform are controlled and synchronized by a computer which is also used to define the parameters of each test, to run the test, and to collect the data. This equipment has been used to analyze the capillary moisture transfer through two cement pastes.
Relationships Between Permeability, Porosity, Diffusion And Microstructure Of Cement Pastes, Mortar, And Concrete At Different Temperatures
Authors: Roy Della M.
Published: March 2011

Permeabilities to water and diffusion of ionic species in cementitious grouts, pastes and mortars are important keys to concrete durability. Investigations have been made of numerous materials containing portland and blended cements, and those with fine-grained filler, at room temperature and after prolonged curing at several elevated temperatures up to 90°C. These constitute part of studies of fundamental material relationships performed in order to address the question of long-term durability. In general, the permeabilities of the materials have been found to be low [many <10−8 Darcy (10−13 m·s−1)] after curing for 28 days or longer at temperatures up to 60°C. The results obtained at 90°C are somewhat more complex. In some sets of studies of blended cement pastes with w/c varying from 0.30 to 0.60 and cured at temperatures up to 90°C the more open-pore structure (at the elevated temperature and higher w/c) as evident from SEM microstructural studies as well as mercury porosimetry are generally correlated also with a higher permeability to liquid. The degree of bonding and permeability evident in paste or mortar/rock interfacial studies present somewhat more conflicting results. The bond strength (tensile mode) has been shown to be improved in some materials with increased temperature. The results of permeability studies of paste/rock couples show examples with similar low permeabilities, and some with increased permeability with temperature.

Ionic diffusion studies also bring important bearing to understanding the effect of pore structure. The best interrelationships between chloride diffusion and pore structure appear to relate diffusion rate to median pore size. Similar results were found with “chloride permeability” test.
The Divided Flow Permeameter
Authors: Jefferis Stephan A. , Mangabhai Raman J.
Published: March 2011

In permeameters for rigid materials such as concrete, cement paste, or rock the sample is generally sealed into the test cell with a resin or with a pressurised membrane and the permeability is calculated from the total flow through the apparatus. Clearly any leakage around the edge of the sample or other inhomogeneity in the peripheral region will lead to inaccuracy in the measured permeability. This problem is particularly severe with low permeability materials such as concrete and is further exacerbated by the fact that the true permeability of concrete can vary by many orders of magnitude and there may be little information with which to assess whether particular test results are reasonable.

The divided flow permeameter offers a technique by which edge leakage and other edge effects can be assessed and several permeability results obtained from different areas of a single sample. The basic principle of this permeameter is that either the inflow or the outflow surface, or both, of the sample are divided into separate flow regions. Provided that there is no difference in pressure between the regions there should be no tendency for flow between them and the flow through each should be proportional to its area.

As the technique gives several permeability results for a single sample information about permeability variation within the sample can be obtained; for example data on microcracking, moisture distribution etc. The technique can be used with gas or liquid permeants. The divided flow permeameter system developed at King's College is inexpensive and with a simple system of ‘0’ rings a flow division head can be fitted to many conventional permeameters.
Numerical Modeling Of The Freezing Process In A Cementitious Matrix
Authors: El-Korchi Tahar , Alexandrou Andreas N. , Sullivan John M.
Published: March 2011

A numerical model has been developed that predicts the freezing process in a cementitious matrix. Freezing point depression due to pore size characteristics is incorporated into the numerical model. An idealized pore size distribution based on a mature paste with a water-cement ratio of 0.6 was adopted. The pore size range was randomly distributed over the test domain. Results are shown for the advancement of the freezing fronts and the progression of the isotherms.
Chlorides In Concrete
Authors: Hansson Carolyn M. , Berke Neal S.
Published: March 2011

Chlorides are currently the main culprit in the deterioration of concrete structures in most parts of North America and Europe. During the last few years the authors have investigated the following properties: (i) the steady state diffusion of chlorides through cement pastes; (ii) penetration of chlorides into mortar and concrete; (iii) the binding of chlorides in the paste phase; (iv) the threshold value of chlorides below which corrosion of reinforcement is unlikely to occur; and (v)the relationship between the electrical resistivity and diffusivity of paste, mortar, and concrete. The variables investigated include water/cement ratio, cement type, curing conditions, effects of admixtures, and pozzolanic additions and the cover depth.
Microstructures Of Modified Hardened Cement Pastes
Authors: Kurdowski W. , Petri M. , Trybalska B.
Published: March 2011

The influence of different admixtures: gypsum, tartaric acid, silica fume and C4A3S upon the HCP developing microstructures has been studied. Investigations of flexural strength, E-modulus, porosity, DT-analysis, X-ray analysis and SEM observations were carried out. The obtained results showed that these samples differ in microstructure and porosity.
Effect of Curing on Some Pore Structure-Dependent Properties of Concrete
Authors: Gebauer J. , Torrent R. J.
Published: March 2011

The effect of the curing conditions on two properties of concrete, strongly dependent upon the pore structure, namely the strength development and the carbonation rate, was studied in the laboratory. The influence of the cement type, mix proportions and specimen size on the measured properties is also discussed. The importance of the quality of the “covercrete” for good durability is emphasized.
Dielectric Response Of Polymer-Modified Cements With Controlled Porosity.
Authors: Polo G. Vazquez , Martina E. , Castaño V. M.
Published: March 2011

Polymer-modified cements were prepared macro-defect free by adding poly(vinyl acetate) to the normal water/cement mixture. The resulting samples, that corresponded to different volume porosity, were subjected to capacitance measurements in the range 5 Hz to 13 Mhz.
The Effect Of W/C Ratio And Cement Type On The Longevity Of Grouts For Use In A Nuclear Fuel Waste Disposal Vault
Authors: Onofrei Maria , Gray Malcolm
Published: March 2011

Cement-based grouts are being considered for use as sealing materials in the Canadian concept for nuclear fuel waste disposal. This paper describes laboratory studies of the longevity of these materials, with special emphasis on the effect of hardened grout porosity and cement type. The longevity properties determined for reference grout (90% Type 50 cement, 10% silica fume and superplasticizer) are compared with those of a slag cement grout.

The fractional factorial statistical method of Box-Behnken was used to design a series of leach tests, which covered a wide range of conditions that could occur in a nuclear waste disposal vault. The leach tests have been carried out to determine the effect of temperature, ionic strength of groundwater, and cation exchange capacity (CEC) of clay (which may be in contact with the grout) on the leach resistance of the cement. The temperature ranged from 25 to 150°C and the ionic strength of the groundwaters from 0.0015 to 1.37 mol. Leach rates of Ca and Si were taken as the major indicators of the long-term chemical stability of the grouts.

Preliminary analysis suggests that the reference grout would be more stable than slag cement in the high-temperature environment of a nuclear fuel waste disposal vault. Within the ranges investigated, decreasing the porosity appears not to significantly decrease leach rates.
Factors Affecting The Ability Of A Fly Ash To Contribute To The Sulfate Resistance Of Fly Ash Concrete
Authors: Mccarthy G. J. , Tikalsky P. J. , Carrasquillo R. L. , Manz O. E. , Thedchanamoorthy A.
Published: March 2011

The objective of this summary is to report on work in progress that is examining parameters, measurable through chemical and XRD analyses, that could indicate whether a fly ash will enhance, degrade or have no effect on the sulfate resistance of fly ash concrete.
The Influence of Pore Structure on the Properties of Cement Paste: Initial Observations about Research-in-progress
Authors: Lange D. A. , Jennings H. M. , Shah S. P.
Published: March 2011

Initial observations of the influence of pore structure on material properties of cement paste are described. The total porosity is held constant and pore structure is altered by use of a superplasticizer. Corresponding changes in strength and fracture energy are observed. Changes in the cement paste pore structure are evaluated by analysis of images obtained by optical microscopy. The technique is a direct method of measurement that avoids assumptions about pore geometry.
Microdefects and Impurities in Dislocation-Free Silicon Crystals
Authors: Abe Takao , Harada Hirofumi , Chikawa Jun-Ichi
Published: March 2011

Microdefects in striated (swirl defects) and nonstriated distribution (D-defects) have been observed in float-zoned crystals doped with various impurities by x-ray topography following copper decoration. A new type of defects were found to be present in swirl-free and D-defect-free regions and to become invisible by doping gallium. This gallium effect led to the conclusion that they are microprecipitates produced from residual oxygen impurity in FZ crystals. Effects of various impurities on defect formation indicate that D-defects are of vacancy agglomerates. It was observed that swirl defects are formed when the temperature gradient near the interface is high, and that their formation is suppressed by doping nitrogen. Formation processes of microprecipitates, swirls, and D-defects are discussed on the basis of observation of their mutual interaction and the impurity effects.
Thermal Donor Formation by the Agglomeration of Oxygen in Silicon
Authors: GÖsele U. , Tan T. Y.
Published: March 2011

We suggest that thermal donor formation in silicon involves fast-diffusing, gas-like molecular oxygen in dynamical equilibrium with atomic oxygen in interstitial position. We will discuss still remaining difficulties in understanding thermal donor formation in the light of recent experimental observations by Stavola, Patel, Kimerling and Treeland, indicating that the diffusivity of interstitial oxygen apparently depends on the thermal history of the silicon sample.
Complex Defects in GaAs and GaP
Authors: Lin-Chung P. J.
Published: March 2011

A study of the electronic states associated with divacancy defects and with the defect complexes involving an anion antisite with a group IV atom (Ac-IV) in GaAs and GaP is reported. The local densities of states have been determined using the large cluster recursion approach. The properties as well as the position of the gap states of the divacancy defect in GaAs are found to be consistent with the experimental results for the EL2 level. The change of the position of the defect levels of (Ac-IV) as a result of the change of bonding is analyzed. The effect of GaAs-A&As interface on the (Ac-IV) defect level is also examined.
Enhanced Inp Substrate Protection for Lpe Growth of Ingaasp DH Lasers
Authors: Besomi P. , Wilson R. B. , Wagner W. R. , Nelson R. J.
Published: March 2011

Thermal degradation of InP single crystal substrates prior to LPE growth has been virtually eliminated by using an improved protection technique. The phosphorus partial pressure provided by a Sn-In-P solution localized inside an external chamber surrounding the InP substrate prior to growth prevents thermal damage to the surface. Nomarski contrast photomicrographs,photoluminescence and X-ray diffractometric measurements indicate that InP substrates protected by this method suffer negligible deterioration, in contrast to the results of the more commonly used cover wafer method.
The Electrical Behavior of Grain Boundaries in Silicon
Authors: Seager C. H.
Published: March 2011

Despite the fact that lattice imaging studies have shown that grain boundaries in group IV semiconductors often have structures which are complicated and inhomogeneous on the scale of tens-tohundreds of angstroms, simple theories assuming uniform double depletion layers have recently been shown to successfully predict many of the majority carrier transport properties of these defects. On the other hand our knowledge of the interaction of grain boundaries with minority carriers is in a considerably more primitive state. I will describe recent attempts to understand the effects of illumination on grain boundary potential barrier heights and the influence of these defects on the optically generated minority carrier population. Quantifying this latter interaction is particularly important in estimating the performance of polycrystalline solar cells. Simple but elegant scanned excitation measurements for measuring s, the minority carrier recombination velocity at grain boundaries, will be reviewed. I will discuss recent measurements of s as a function of temperature and illumination intensity and show how these data can be correlated with zero-bias impedance measurements.
The Interface Structure of Grain Boundaries in Polysilicont
Authors: Johnson S. M. , Yoo K. C. , Rosemeier R.G. , Soltani P. , Lin H. C.
Published: March 2011

Normal grain growth in polysilicon material proceeds by a twinning mechanism such that the individual grain orientations are related by single or multiple twinning steps. The twinning relationship between adjacent grains can result in the alignment of their boundary interfaces along certain planar segments which have a very low electrical activity. The varying degree of electrical activity of these boundaries, and boundary positions, is attributed to the smaller dislocation portion of the larger change in orientation across the grains.
Enhanced Diffusion of Phosphorus at Grain Boundaries in Silicon
Authors: Cheng L.J. , Shyu C.M. , Stika K.M.
Published: March 2011

It is found that the grain boundaries in cast polycrystalline silicon material capable of enhancing diffusion always have strong recombination activities. Both phenomena could be related to the existence of dangling bonds at boundaries. Because the enhanced diffusion is an atomic transport phenomenon and the recombination is an electronic process, the relationship between the two phenomena is still not clear at this moment. The present study gives the first evidence that incoherent second order twins of {111/115} type are phosphorus diffusion-active.
Degradation Behavior of Optoelectronic Devices
Authors: Matsui Junji
Published: March 2011

Various degradation modes and features of crystalline defects associated with the degradation observed both in GaA1As/GaAs and InGaAsP/InP double heterostructure light emitting sources (LED's and Lasers) are reviewed, noticing similarities and differencies between those two material systems. Non-existence of rapid degradation in the quaternary caused by DLD formation (dislocation motion) will be discussed in terms of atomic rearrangements arouna the dislocation core.
Measurements of Ion-Implantation Damage in GaP
Authors: Myers D. R. , Peercy P. S. , Gourley P. L.
Published: March 2011

We have applied stress measurements using the cantilever beam technique and Raman spectroscopy to characterize the dose dependence of damage production for He+, C+, or Ar+ implants into GaP. Stress increases monotonically with dose until a speciesdependent critical dose is reached. Above that dose, the material yields at an integrated lateral stress of ∼2×105 dynes/cm2 corresponding to an expansion of ∼1% in the implanted volume. The dose dependence of stress scales well with the volume density of ion energy deposited into atomic collisions. Raman measurements indicate that the material is still crystalline when the yield stress is reached.
Non Destructive Optical Analysis of Implanted Layers in GaAs by Raman Scattering and Spectroscopic Ellipsometry
Authors: Biellmann Joseph , Prevot Bernard , Schwab Claude , Theeten Jean-Bernard , Erman Marko
Published: March 2011

Non destructive analysis by Raman Scattering (RS) and Spectroscopic Ellipsometry (SE) is demonstrated on B+- and Se+ shallow implanted GaAs. Qualitative informations are obtained from 1st and 2nd order RS spectra. The former are analysed using the intensity ratio of the T0 and L0 modes, which defines a lattice potential perfection scale. The SE analysis of the E1, E1 +Δ1 structure in the imaginary part of the dielectric function confirms the RS results and its multilayer analysis yields the depth profile of the implanted ions.