bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ductile Phase Toughened Ceramics by Partial Reduction Reactions in the Ni-AI-O System: Mechanical Properties and Effect of Dopants
Authors: Üstündağ E. , Ret P. , Shapiro Y. , Subramanian R. , Dieckmann R. , Sassa S. L. 
Published: April 2011

ABSTRACTPartial reduction reactions in the Ni-Al-O system, starting with the spinel compound NiAl2O4, are used to form metal-ceramic microstructures in situ. Two different morphologies of nearly pure Ni particles, equiaxed and rod-like, form within a ceramic matrix depending on the choice of processing parameters. Electron microscopy studies were performed for microstructural characterization, phase identification and chemical analysis. The fracture toughness of the Ni-Al2O3 mixture was significantly improved with respect to that of the original spinel phase. It is shown that cracking at the original spinel grain boundaries, likely due to the large volume changes associated with the reduction reaction, can be avoided by the addition of small amounts of ZrO2. It is seen that ZrO2 also acts as a nucleation site for the precipitating metal and hence allows morphology control in microstructures obtained by partial reduction reactions.
Analytical Modeling in Support of the Development of Fiber Reinforced Ceramic Composite Materials for Re-Heater Burners
Authors: Kibler J.J. , DiPietro S.G. 
Published: April 2011

ABSTRACTDevelopment of Continuous Fiber reinforced Ceramic Composite (CFCC) materials is a process of identifying components which will benefit from CFCC properties, and defining appropriate composite constructions which will provide materials which will meet the structural and thermal requirements of the application. Materials Sciences Corporation (MSC) has been providing analytical support to Textron Specialty Materials in the development of re-heated tubes for metal reheating furnaces. As part of this support, a study has been made of the sensitivity of composite properties to fiber orientation as well as a number of matrix properties which control the stress-strain behavior of the composite.
An Experimental and Theoretical Investigation of Stick-Slip, Steady-State and Roughness Dominated Sliding in Fiber-Reinforced Composites
Authors: Mackin Thomas J. 
Published: April 2011

ABSTRACTThe mechanical properties of fiber reinforced composites depends strongly upon the properties of the fiber/matrix interface. Enhanced fracture resistance and strain to failure are synonymous with debonding and sliding of the reinforcement phase. Thus, the two key properties of the composite are the interfacial toughness and the post-debond sliding stress. After debonding a variety of interfacial sliding phenomena are noted, including: stick-slip, steady-state, and roughness dominated sliding. The interfacial properties, including the coefficient of friction, the radial clamping pressure, asperity amplitude, the elastic properties of the constituents, and the compliance of the test machine, each play a role in the operative sliding phenomenon. Experiments have been conducted to explore each of these phenomena. In addition, models have been developed that rationalize all of the observed behavior.
Fabrication of Advanced C/C Composites by a Hybrid Process of CVI/Liquid Precursor Impregnation
Authors: Ishizaki Masato , Shioda Muneyoshi , Miyahara Kaoru , Sasa Tadashi 
Published: April 2011

ABSTRACTFabrication process of advanced C/C composites was developed by combining the CVI and liquid impregnation-pyrolysis processes. Time-controlled temperature-gradient (TC-TG-) CVI process was developed to accelerate the carbon matrix deposition in the C-fiber preform within relatively short process-time. The temperature gradient in the preform was changed according to a controlled program. The present TC-TG-CVI process gave twice as much weight gain as that of the conventional steady TG-CVI process. The CVI process, however, showed limitation to fill up the large pores between the bundles. Liquid impregnation-pyrolysis was, therefore, carried out after the TC- TG-CVI process to improve the infiltration of these pores. Polycarbosilane (PCS) with the yield of about 50 wt% was used as the liquid precursor to form a SiC-rich matrix to improve the oxidation-resistance. SiC matrix was observed in the pores between bundles after pyrolysis of PCS. The weight gain after pyrolysis was found to be nearly saturated after 10 cycles of the impregnation-pyrolysis process.
Characterization of Pseudo-Porous SiC/C Coatings on Nextel™440 and Nicalon™ Fibers
Authors: Khasgiwale N.R. , Butler E.P. , Tsakalakos L. , Hensley D.A. , Cannon W.R. , Danforth S.C. , Gonczy S.T. 
Published: April 2011

ABSTRACTPseudo-porous SiC/C coatings were deposited on Nextel™440 and Nicalon™ fibers by CVD. The morphology and chemistry of the coatings was evaluated, both before and after oxidation, using Scanning Electron Microscopy (SEM), X-Ray Diffraction Analysis (XRD), X-Ray Photoelectron Spectroscopy (XPS) and Auger spectroscopy. Coated fibers were subjected to two different oxidation treatments to assess coating stability: a) oxidation at 600°C for 20 hours, and b) oxidation at 1000°C for 20 hours. Pseudo-porous SiC/C on Nicalon™ fibers appear to be more oxidation resistant than the same coatings on Nextel™440 fibers.
Neutron Diffraction Study of Highly Radioactive U3Si2 Reactor Fuel
Authors: Richardson J. W. , Birtcher R. C. , Mueller M. H. 
Published: April 2011

AbstractNeutron diffraction data were collected from a highly radioactive, low-enrichment uraniumU3Si2/A1 fuel mini-plate that had been irradiated to 42% uranium burnup. The experiment was performed using the General Purpose Powder Diffractometer at IPNS. Most prominent in the diffraction pattern were the Bragg reflections from crystalline Al (fuel plate) and V (sample container). Rietveld refinement revealed a broad oscillatory signal from the U3Si2 typical of amorphous material. This “amorphous” scattering pattern has peaks at the same positions as the amorphous scattering components observed following room temperature neutron irradiation of U3Si2 powder. The irradiated U3Si2 is amorphous with a remote possibility that it consists of recrystallized nanocrystalline particles subject to the requirements that the crystallites: (i) are no larger than 100-200 Å in size, and (ii) possess a crystalline lattice which is distorted relative to the unirradiated material.
Defect Configurations in Neutron-Irradiated U3Si2
Authors: Chan S.-K. , Birtcher R. C. , Mueller M. H. , Richardson J. W. 
Published: April 2011

AbstractInvestigations of the nature of defects in neutron-irradiated intermetallic U3Si2 as a function of dose have been carried out. Defect categories of vacancies and interstitials, their clusters and dislocation loops have been considered. The effects of the displacement field from each on the neutron scattering intensity profiles are presented. The theoretical predictions are compared with experimentally determined intensity profiles from time-of-flight data using the General Purpose Powder Diffractometer at the Intense Pulse Neutron Source of Argonne National Laboratory. The results are illustrated for a particular peak at various doses and the physical implications discussed.
Altering the Oxidation Resistance of Iron Via ion Beam Alloying
Authors: Murzin Ivan H. , Potter Donald I. 
Published: April 2011

AbstractFe-Cr, Fe-Y and Fe-Cr-Y surface alloys were produced by direct ion implantation, ion beam mixing, and combinations of implantation and vapor deposition. The influence of these treatments on the oxidation behavior of iron was investigated in 1 atm. of oxygen at 520°C. The oxidation rates were less in all the ion beam alloyed iron samples than in untreated iron. The oxidation follows parabolic kinetics in most cases, with the rate constants, Kp, in the range (3-8)×10−6 mg2cm−4 sec−l versus 2.2×10−5 mg2 cm−4 sec−1 for untreated iron. Yttrium fluences between 5×1014 and 5×lO15 cm−2 did not alter the microstructures of iron significantly. However, fluences of 1×1016, 3×1016, 5x1016 and 1x1017 cm−2 caused the crystalline structure of iron to be replaced by an amorphous phase. The presence of this phase was demonstrated with selected area channeling patterns and transmission electron microscopy.
Density Changes in Amorphous Pd80Si20 During Low Temperature ion Irradiation
Authors: Schumacher G. , Birtcher R.C. , Rehn L.E. 
Published: April 2011

AbstractDensity changes in amorphous Pd80Si20 during ion irradiation below 100K were detected by in situ HVEM measurements of the changes in specimen length as a function of ion fluence. A decrease in mass density as a function of the ion fluence was observed. The saturation value of the change in mass density was determined to be approximately -1.2 %.
Radiation Effects in Ceramic Insulators
Authors: Pells G P 
Published: April 2011

AbstractRadiation damage mechanisms in oxide ceramics are briefly discussed for irradiation by electrons, ions and neutrons. The effects of electron, ion and neutron irradiation on the evolution of the damage microstructure of MgO, A12O3 and MgAl2O4 are followed in detail. Particular attention is paid to differences in the microstructure produced by ions of varying mass and energy. The effects of damage microstructure on other properties are indicated.
Study of Neutron-Irradiated Quartz Upon Heat Treatment: A Relation Between Tunneling States and Microtwins?
Authors: Keppens V. , Laermans C. 
Published: April 2011

AbstractThis paper deals with the study of the tunneling states (TS) in neutron-irradiated quartz. Ultrasonic attenuation measurements are carried out for a dose of 1.2 x 1019 n/cm2, before and after heat treatment at 700°C and 840°C. The data give evidence for significant changes in the distributions of the tunneling parameters upon heat treatment. These modifications provide interesting information about the nature of the tunneling states and will be discussed in view of the possible relation between the TS and the twin domains: the influence of heat treatment on the distribution of the tunneling states can be related to changes in the twin formation upon annealing.
Temperature Effects on ion Irradiation Damage in MgAl2O4 Spinel Single Crystals
Authors: Yu Ning , Sickafus Kurt E. , Nastasi Michael 
Published: April 2011

AbstractSingle crystalline samples of magnesium aluminate spinel (MgAl2O4), <100> oriented, were irradiated at 100 K and 670 K with 370-400 keV Xe ions to doses of (1-2)x1016 Xe/cm2. The microstructures of irradiated samples were subsequently examined by cross-sectional transmission electron microscope. A uniform layer of amorphous phase was observed on the surface of spinel irradiated at 100 K. At the end of the damage range underlying the amorphous layer, a disordered transition layer resided on the undamaged substrate. Both high resolution electron microscopy and microdiffraction revealed that the transition layer retained single crystallinity with epitaxial relationship to the underlying substrate. However, the intensity of <220> reflections in the transition layer was significantly weaker than that of the undamaged spinel. No evidence of amorphization was found in the spinel sample irradiated at 670 K to a dose of 2x1016 Xe/cm2. The <220> reflections exhibit only limited diminution in the heavily damaged region. The observation of reduced intensity of <220> reflections or absent reflections suggests that spinel experiences a structural transition from its original cubic phase (a=0.808 nm) to a new cubic phase (a=0.404 nm). A transition sequence from the original phase to a metastable phase and then to an amorphous phase has been observed. The temperature dependence of metastable and amorphous phase formation has revealed that the accumulation efficiency of cation disorder decreases with increasing irradiation temperature due to the enhancement of interstitial-vacancy recombination.
Dissolution of Ordered Precipitates under ion Irradiation
Authors: Camus Eric , Bourdeau Françise , Abromeit Christian , Wanderka Nelja , Wollenberger Heinrich 
Published: April 2011

AbstractThe stability of the ordered γʹ precipitates under 300-keV Ni+ irradiation was investigated between room temperature and 623 K. The two competing mechanisms of destabilization by cascade producing irradiation, i. e. disordering and dissolution of the γʹ precipitates in Nimonic PE16 alloy, has been studied separately by electron microscopy and field-ion microscopy with atom probe. At high temperatures, the precipitates are stable. At intermediate temperatures, the precipitates dissolve by ballistic mixing into the matrix, but the interface is restored by the radiation-enhanced atomic jumps. The order in the precipitates remains stable. At low temperatures, the precipitates are dissolved by atomic mixing. The dissolution proceeds in a diffusional manner with a diffusion coefficient normalized by the displacement rate D/K = 0.75 nm2dpa−1. The precipitates become disordered by a fluence of 0.1 dpa, whereas precipitate dissolution needs much higher fluences.
Flowing Afterglow Synthesis of Polymer Films with Nonlinear Optical Properties
Authors: Haaland Peter , Jiang Hao 
Published: April 2011

AbstractExtensively conjugated polymer films with excellent morphology, homogeneity, robustness, and nonlinear optical coefficients have been synthesized in the flowing afterglow of a lowpressure argon plasma. Polymers of benzene, thiophene, furan, and napthalene are among the systems studied. The polymers, which grow by accretion of positive ions through a low-voltage sheath, have bulk and surface textures which scale systematically with film thickness. The hopes and perils of employing these new materials as active elements in gradient-index reflectors and optical switches will be described, as will the link between morphology and deposition mechanism.
New Self-Focusing Materials: Synthesis, Structures and Nonlinear Optical Properties of Butterfly Shaped Clusters
Authors: Shi S. , Xin X. Q. 
Published: April 2011

AbstractCompounds WCu2OS3(PPh3)4 (I) and MoCu2OS3(PPh3)3 (II) were synthesized by reactions of (NH4)2MO2S2 (M = W, Mo), Cu2S and PPh3 in solid state for nonlinear optical studies. A wide transparent window (λ = 400 - 1000 nm) was observed for both clusters, which makes them attractive for nonlinear optical (NLO) applications. NLO properties of the clusters were studied with a 7-ns pulsed laser at 532 nm. Cluster I exhibits mainly optical self-focusing (n2 = 8 × 10-18 m2 W-1, as measured with an 1.2 × 10-4 M acetonitrile solution) with negligibly small nonlinear absorption. Cluster II exhibits both optical self-focusing (n2 = 5 × 10-17 m2 W-1, as measured with a 7.4 × 10-5 M acetonitrile solution) and nonlinear absorption (α2 = 2.6 × 10-10 m W-1). The third-order NLO susceptibilities (χ(3)) of the two clusters at the above-mentioned concentrations are 2 × 10-11 esu for I and 1.2 × 10-10 esu for II respectively. These nonlinear optical properties of the clusters were compared with those of cubic cage shaped and nest shaped clusters to reveal a qualitative structure/NLO property correlation.
The Design of Candidate Optical Limiters
Authors: Pachter Ruth , Crane Robert L. , Adams W. Wade 
Published: April 2011

AbstractSeries of molecules and polymeric systems are being evaluated as optical limiters for the design of a high second molecular hyperpolarizability γ. For example, results for a series of tolanes are discussed, as well as those of semi-flexible, stiff-chain polymers, including substituted biphenyl (X, Y = H, CH3, NO2, or a halogen atom) and benzo-bisthiazole moieties. The non-linear optical response was calculated using a finite field approach and compared for various derivatives.
Modeling of Spiropyran: Calculation Of Absorption Spectra
Authors: Young J. A. , Farmer B. L. , Adams W. W. 
Published: April 2011

AbstractSemiempirical computational chemistry techniques were used to investigate the absorption spectra of 1′-isopropyl-3′,3′-dimethyl-indoline-spiro-6-nitro-8-methoxy-benzopyran. The spectra of both the closed (spiropyran) and open (merocyanine) forms were calculated using the INDO/CI method. Spectroscopic calculations showed the effects, both electronic and steric, that substituents such as hydrogen, methoxy and thiophene have on the absorption spectrum. Knowledge of the absorption spectra as a function of the choice and placement of substituents and molecular geometry will potentially allow optical properties to be optimized for specific applications.
Low Threshold ZnSe1−x Tex Optical Limiters
Authors: Ji W. , Tan H. S. , Feng Z. C. , Becla P. 
Published: April 2011

AbstractWe report an experimental investigation of optical limiting with bulk ZnSe1−xTex crystals at wavelengths just below the band edge, using nanosecond laser pulses. The limiting threshold as low as a few mJ/cm2 has been demonstrated. The generation of free charge carriers by singlephoton absorption, and subsequent free-carrier nonlinearities (nonlinear absorption and selfdefocusing) are responsible for the limiting behavior.
Effects of SiH2Cl2 Addition on the Growth Mechanism of Si Films Prepared by Photochemical Vapor Deposition
Authors: Oshima T. , Yamaguchi K. , Abe K. , Yamada A. , Konagai M. , Takahashi K. 
Published: April 2011

ABSTRACTEffects of SiH2Cl2 and H2 addition to SiH4 on photochemical vapor deposition (photo-CVD) of amorphous Si (a-Si) and epitaxial Si films were investigated, and roles of Cl and H in the growth mechanism were discussed. The surface morphology and the defect density of the obtained a-Si films were evaluated by atomic force microscope (AFM), and constant photocurrent method (CPM), respectively. It was found that the H2 dilution of SiH4 is effective to prepare the a-Si films with smooth surfaces and low defect density. Furthermore, nearly flat surface with the root mean square (RMS) of the roughness of 0.35nm was obtained by the SiH2Cl2 addition to H2-diluted SiH4. In the Si epitaxy, the SiH2Cl2 addition is also efficient to improve the film quality. It is suggested that the growing surface is terminated by both Cl and H, and the surface is more stable than that terminated by only H. Therefore, the diffusion on the growing surface of the film precursors such as SiH3 is enhanced, resulting in the improvement of the surface morphology and the film quality.
Microcrvstalline and Mixed Phase Si:H : Preparation. Potential and Properties for Devices
Authors: Dalai Vikram L. , Kaushal Sanjeev , Ping E. X. , Xu Jun , Rnox Ralph , Han K. 
Published: April 2011

ABSTRACTWe discuss the preparation, properties and device potential of microcrystalline Si:H (μc-Si:H) material deposited using plasma-CVD techniques. We have been able to deposit high quality μc-Si:H using both glow discharge and ECR plasma CVD techniques. In both cases, the critical parameter was the presence of a high flux of H, and high power. The quality of the material was measured using sub-gap photo-conductivity, in both films and devices. We find that the absorption coefficient in μc-Si:H films follows the c-Si curve very closely, with little excess absorption. We have also fabricated p-i-n devices in these materials. We find that the properties of the devices depend critically upon the p-i interface and on the deposition technique used to make the devices. We use quantum efficiency techniques to study the devices in detail. We find that often, a good device characteristic corresponds to a case where the undoped layer is a mixed phase (amorphous-microcrystalline) and not just microcrystalline. In contrast, using just the microcrystalline phase for i layers in devices leads to severe interface problems, which lead to inflexion points in I (V) curves. Using the mixed phase for i layer, we have made solar cells with 0.46 V open circuit voltage, and a fill factor of 0.58. In contrast, using a microcrystalline phase can lead to devices with high voltages (0.6), but poor fill factors. We also discuss the device potential of microcrystalline devices, and we find that it may be possible to fabricate devices with 8% solar conversion efficiency in this material once all the interface problems are solved. Such devices may have applications as low-gap cells in an a-Si:H/μc-Si:H cell structure.
Formation of a-Si:H Film by p-CVD Method with SiH4-He Mixture and its Opto-Electronic Properties
Authors: Nakamura Youichi , Yamaguchi Tsuyoshi , Okagawa Atsushi 
Published: April 2011

ABSTRACTFormation of hydrogenated amorphous silicon (a-Si:H) was carried out by rf glow discharge method in the reactive gas systems of silane. By preliminary experiments on a-Si:H for helium dilution, a relatively high deposition rate up to 2–3 μm/hr was obtained. In order to investigate the opto-electronic properties on a-Si:H films due to different dilution of helium or hydrogen, measurements on optical band gap Eop, electric conductivity and FT-IR were done. Optical emission spectra were also observed. Optical band gap value Eop on a-Si:H film for SiH4 (10%) -He (90%) was nearly constant about 1.73 eV, while that for SiH4 (10%) -H2 (90%) was increased from 1.75 eV to 1.78 eV with increase of residence time of silane molecule and it was relatively high. From the experimental results of FT-IR, ratio of bonding mode of SiH to (SiH+SiH2) for hydrogen dilution was about 90% and higher than that for helium dilution, while hydrogen concentration in the film for SiH4 (10%) -H2 (90%) was less than 10% and that for SiH4 (10%) -He (90%) was 20–30%.
Diffusion, Drift, and Recombination of Holes In a-Si:H
Authors: Schwarz R. , Wang F. , Grebner S. , Gu Q. , Schiff E. A. 
Published: April 2011

ABSTRACTWe compare measurements in a-Si:H of ambipolar diffusion length Lamb (from steady-state photocarrier gratings (SSPG)) and hole drift Χ (t) (from time-of-flight (TOF)). Using the response time tR from small-signal photocurrent decay measurements, we find that the equation L2amb = 2 (kT/e) Χ (tR) /E is consistent with the measurements, where E is the electric field inducing hole drift in TOF. Several samples under different temperature and light intensity levels have been studied. This equation has several implications. Under the usual SSPG illumination conditions, electron-hole recombination occurs while holes are still occupying valence bandtail states; hence SSPG is not sensitive to hole capture by deep levels. Furthermore, the experiments show that the Einstein relation is valid for holes in a-Si:H. We are unaware of prior direct tests of this relation in an amorphous semiconductor.
Flexible a-Si Solar Cells with Plastic Film Substrate
Authors: Fujikake S. , Tabuchi K. , Yoshida T. , Ichikawa Y. , Sakai H. 
Published: April 2011

ABSTRACTAn amorphous silicon solar cell deposited on plastic film substrate has been studied. The solar cell has a new monolithic series-connected structure called SCAF, and will be fabricated by a newly developed fabrication process based on “Stepping Roll” film deposition system.The process was compared with the conventional glass solar cell process. Preliminary results for small and large area SCAF solar cells were presented and discussed.
Relation of the Electroluminescence Measurements to A-Si.H Solar Cell Parameters
Authors: Wang Keda , Han Daxing 
Published: April 2011

ABSTRACTWe have measured the intensity of electroluminescence (EL) and its energy spectrum in a-Si:H solar cells having an initial energy conversion efficiency from 5.75 to 9.8 %, and open-circuit voltages (Voc) between 0.799 and 0.952 V. We found that (a) at room temperature, EL efficiency is proportional to the initial solar cell energy conversion efficiency; (b) the defect energy distribution in the i-layer can be detected by EL energy spectrum at room temperature; and (c) Voc is simply related to the quasi-Fermi level splitting obtainable in the i-layer and that the buffer layer serves to increase this splitting.