bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation and Characterization of 3C-SiC Heteroepitaxial Layers on Si(111)
Authors: Yamanaka Mitsugu , Ikoma Keiko
Published: March 2011

3C-SiC layers were grown on Si(111) substrates by chemical vapor deposition (CVD) using SiH4-CH3CI-H2 gas mixture. 3C-SiC(111) heteroepitaxial layers were obtained with smooth surfaces and reduced warpage. All the epilayers were n- type, and the carrier density and Hall mobility were 2.1×1016∼2.8×1017 cm-3 and 120∼180 cm2/Vs at room temperature, respectively. Temperature dependences of the electrical properties of the self-supported 3C-SiC(111) epilayers were measured between 15 and 300 K for the first time. 3C-SiC(111) epilayers showed a similar temperature dependence of carrier density to 3C-SiC(001) heteroepitaxial layer. Hall mobility was maximum (∼360 cm2/Vs) around 100 K.
Hetero-Epitaxial Growth of SiC Films by CVD from Silane, Methane, Propane, and Hydrogen Mixtures
Authors: Bahavar B. , Chaudhiy M. I. , McCluskey R. J.
Published: March 2011

Epitaxial silicon carbide films have been produced on Si (100) substrates by CVD with 90% of the carbon supplied by methane and 10% by propane as compared to 100% by propane (or 100% by any carbon source more reactive than methane). This implies a methane to propane mole ratio of thirty. Among possible carbon gases, methane is the purest coimnercially available hydrocarbon source, But methane has not been commonly used for growth of silicon carbide due to its low chemical reactivity. Our process demonstrates the feasibility of achieving high SiC growth rates while using a carbon source that is predominantly methane. We have established that silicon carbide films grown at 1350 °C in a CVD reactor using the above carbon source ratio results in quality single crystalline films at similar growth rates and lower carrier concentrations than fikus grown from propane and silane.

The main tools used to characterize the grown films are X-ray and electron diffraction, optical microscopy, surface profilometry, Hall mobility measurements, and thickness measurements.
Electrical and Chemical Characterization of Contacts to Silicon Carbide
Authors: Petit Jeremy B. , Zeller Mary V.
Published: March 2011

Chemical and electrical studies were performed to determine the characteristics of contacts to 6H-SiC. Both elemental metals (Ni, Mo) and suicides (MoSi2, TaSi2, TiSi2) were studied. Chemical analysis by Auger Electron Spectroscopy (AES) was performed to examine interface reactions caused by heat treatment. Electrical measurements (current-voltage and capacitance-voltage) were made during annealing sequences to determine the rectifying or ohmic characteristics of the contacts. Where possible, barrier height and contact resistance values were calculated.
The CVD Diamond Nucleation Mechanism on Si Overlaid with sp2 Carbon
Authors: Pehrsson Pehr E. , Glesener John , Morrish Arthur A.
Published: March 2011

Rudder et al. [1] observed heavy (>109 cm-2) diamond nucleation on unscratched Si wafers overlaid with carbon fibers during CVD growth. We demonstrate that the nucleation occurs on the edges of etch pits and carbon-rich particles resulting from reaction between the fibers and the substrate. Both the etch pits and the particles satisfy what we consider to be two necessary conditions for ‘spontaneous’ nucleation; a carbon-saturated surface and high energy sites (unsatisfied valencies) at edges and steps.
The Effects of Substrate Bias and Si Doping on the Properties of Rf Sputtered Bn Films
Authors: Banerjee P.K. , Kim J.S. , Chatterjee B. , Platek M. , Mitra S.S.
Published: March 2011

The effect of substrate bias on the properties of rf sputtered boron nitride films on Si and GaAs substrate were investigated. IR transmission and reflectivity of films with different substrate bias were measured with Perkin Elmer 983 IR spectroscopy. From the IR reflectivity data, transverse optical mode(TO) and longitudinal optical mode(LO) frequencies were derived by fitting Kramer-Kronig model. Absorption coefficient was determined from IR transmission data. The resultant TO and LO modes showed that substrate bias caused broadening of reststrahlen band of rf sputtered boron nitride. We also tried to dope boron nitride films with silicon by alternate sputtering of BN and Si targets controlling sputtering time of each target followed by annealing. Electrical resistivity was measured over the temperature range between 175 K to 370 K for both intrinsic and Si-doped boron nitride films. Intrinsic rf sputtered boron nitride showed Little change in resistivity (109 Ω cm - 1011 Ω cm ) over the temperature range studied. While Si doped BN showed linear change in resistivity with increasing temperature and its activation energy was about 0.22 eV. The effect of substrate bias was also investigated by monitoring the XPS core level spectra of both Bis and N Is peaks, respectively. Substrate bias caused the shift of both B ls and N ls peak to higher binding energy. The effect of substrate bias on refractive index was also studied.
Electrical and Optical Properties of Oxygenated Microcrystalline Silicon (mc-Si:O:H)
Authors: Faraji M. , Gokhale Sunil , Chaudhari S. M. , Takwale M. G. , Ghaisas S. V.
Published: March 2011

Hydrogenated microcrystalline silicon with oxygen(mc-Si:O:H) is grown using radio frequency glow discharge method. Oxygen is introduced during growth by varying it's partial pressure in the growth chamber. The crystalline volume fraction ‘f’ and the crystallite size ‘δ’ are found to vary with the oxygen content. Results indicate that oxygen can etch the silicon surface when present in low amount while it forms a-SiO2-x with increasing contents. Optical absorption studies in the range of 2 to 3 eV suggest that the absorption coefficient ‘α’ lies in between the values of c-Si and a-Si:H.being closer to a-Si:H. The Hall mobility measurements for these samples indicate that for optimum oxygen contents the mobility as high as 35 cm2 V-1 sec-1 can be obtained. Results on I-V characteristics for p-i-n structure are presented.
Phase Mapping Sputter Deposited Wide Band-Gap Metal Oxides
Authors: Aita C.R. , Lee R.C. , Kwok C.-K. , Kolawa E.A.
Published: March 2011

Reactive sputter deposition is a widely-used process for growing films of high melting point materials near room temperature and desirable metastable structures not attainable in material grown under conditions of thermodynamic equilibrium. Both categories include wide band-gap metal oxides. A first step towards reproducible growth is to develop a “phase map” for the metal-oxygen system of interest. The map graphically relates independent sputter deposition process parameters, the growth environment, and the metallurgical phase(s) formed in the film. This paper shows how phase maps are constructed and used to observe general trends in oxide phase formation sequence, with examples from the Nb-O, Y-O, and Zr-O systems.
Influence of Substrate Temperature on Tin Oxide Thin Films Deposited by Electron Beam Evaporation Technique
Authors: Rozati S. M. , Mirzapour S. , Takwale M. G. , Marathe B. R. , Bhide V. G.
Published: March 2011

Transparent conducting tin oxide films were prepared by an electron beam evaporation technique. As-deposited films were amorphous or polycrystalline depending on the substrate temperature and the time of deposition. In order to get transparent and conducting thin films of SnO2, as-deposited films were subjected to further heat-treatment in air at 650°C for 2 hours. Physical properties of as-deposited and annealed films are discussed with reference to substrate temperature and deposition time.
Effects of Contact Materials on the Thermally Stimulated Current Spectra of Mercuric Iodide
Authors: Bao X. J. , Schlesinger T. E. , James R. B. , Cheng A. Y. , Ortale C. , Van Den Berg L.
Published: March 2011

Mercuric iodide (HgI2) single crystals deposited with transparent indium-tin-oxide (ITO), and semitransparent gold and nickel contacts were investigated by thermally stimulated current spectroscopy (TSC). The differences in the TSC spectra from these samples indicate that the defect structure in HgI2 may be modified by the contact material. These defects act as carrier traps and have strong implications in the application of HgI2 nuclear detectors. A method of numerical analysis was developed to extract information such as carrier trap activation energy, capture cross-section, and trap concentration-lifetime product from the TSC measurements.
Optical and Magnetic Resonance Investigations of Mercuric Iodide Crystals
Authors: Meyer B.K. , Hofmann D.M. , Eckstein J. , Benz K.W.
Published: March 2011

The optical properties of the red modification of mercuric iodide (HgJ2) were studied by optical absorption, magnetic circular dichroism, photoluminescence and optically detected magnetic resonance investigations. The experiments demonstrate the involvment of acceptors with energy levels at Ev + 0.14 ± 0.01 eV and 0.15 ± 0.01 eV in the absorption and recombination at 2.2 eV. The g - values are 0.85 and 0.74, respectively.
Pzt Interaction with Metal and Oxides Studied by Rutherford Backscattering Spectrometry
Authors: Revesz Peter , Li Jian , Szabo Nicholas , Mayer James W. , Caudillo David , Myers Edward R.
Published: March 2011

Annealing behavior in oxygen ambients of the of the ferroelectric PZT on Hf and Zr electrodes has been studied in the temperature range of 500-800°C using the 3.045MeV O16(∝,∝)O16 resonance in backscattering spectrometry. Internal oxidation of the buried metal electrode was observed. Oxygen concentration of the PZT film decreases with increasing temperature. Pb loss of the PZT film occurred above 700°C.
Polarity and Area Dependence of Reliability Characteristics of Sputitered and Sol-Gel Derived Thin Plzt Films for Dram Applications
Authors: Sudhama C. , Kim J. , Chikarmane V. , Lee J. C. , Tasch A. F. , Myers E. R. , Novak S.
Published: March 2011

The reliability properties of sputtered and sol-gel derived lanthanum doped lead-zirconatetitanate (Pb1-xLax(Zr,Ti)O3) have been studied for DRAM applications. A strong polarity dependence for times-to-breakdown (tbd) and significant space charge effects are observed under constant voltage stressing, and are understood to be related to the movement of oxygen vacancies in the d.c. field. The equilibrium current density attained during d.c. stressing appears to be Schottky emission limited. The endurance of lanthanum doped films to high voltage d.c. stressing improves with increasing lanthanum content and a linear extrapolation of log(tbd) with reciprocal electric field indicates a lifetime of ∼10 years. The low-voltage polarizability of fresh sputtered films depends strongly on the polarity; a.c. stressing leads to hysteresis relaxation. The asymmetry in the response to a.c. stressing is possibly due to the structural asymmetry of the device. Neither tbd nor the fatigue-rate seem to depend on the capacitor area for the areas studied.
PbTiO3 Films Deposited by an Alternating Dual-Target Ion Beam Sputtering Technique
Authors: Cole B.E. , Horning R.D. , Kruse P.W.
Published: March 2011

Thin films, 0.2 μm to 2 μm thick, of ferroelectric PbTiO3 have been deposit ed on Pt coated Si wafers using a novel dual target ion beam sputtering technique. The sputtering targets of PbO and Ti are shuttled back and forth into a Xe ion beam, depositing very thin (10 - 15 Å) alternating layers of PbO and TiO2. The substrate is heated in situ, allowing interdiffusion of the thin layers into a homogeneous PbTiO3 film. Film composition can be controlled accurately and repeatably by controlling the ratio of the sputtering times from each target. Structural characteristics were analyzed by x-ray diffraction, Rutherford backscattering as a function of the sputtering time ratio and the deposition temperature on Pt and Si3N4 coated Si substrates. The stoichiometric PbTiO3 films have a tetragonal perovskite structure with a slight c-axis preference. Capacitor structures show ferroelectric hysterisis loops, dielectric constants of 100-250, loss tangents between 0.002 and 0.04 and a pyroelectric coefficient greater than 5 x 10−8 C/cm2 °C.
Plasma Enhanced Mocvd of BaTiO3 Films
Authors: Buskirk Peter C. Van , Gardiner Robin , Kirlin Peter S. , Krupanidhi Salora , Nutt Steven
Published: March 2011

Bulk BaTiO3 has a large linear electro-optic coefficient and a very high dielectric constant. We report results obtained for two different MOCVD processes designed to deposit BaTiO3 films with properties suitable for nonlinear electro-optic or high charge storage applications. Epitaxial BaTiO3 films have been grown on NdGaO3 [100] substrates using a high temperature thermal process; the substrate temperature was 1000°C and the total pressure was 4 torr. Selected area electron diffraction (SAED) measurements indicate highly textured, single phase films on the NdGaO3 substrate which are predominantly [100] oriented. Fine grained polycrystalline films have been grown on Pt at 600°C by plasma-enhanced metalorganic chemical vapor deposition (PEMOCVD). Specular IR reflectance was used to determine the concentration of BaCO3 in the film, which was significantly reduced by the plasma. The polycrystalline films had dielectric constants as large as 300 and resistivities exceeding 5 x 108 Ω-cm at room temperature.
Synthetic Routes to Perovskite Phase Mixed Metal Oxides
Authors: Chandler Clive D. , Hampden-Smith Mark J. , Brinker Jeffrey
Published: March 2011

We are developing strategies to form single-component precursors to perovskite phase mixed metal oxides where the stoichiometry of the precursor is fixed at the molecular level to be that of the final desired phase. These strategies ean be applied to the formation of perovskite phase thin films. Two such methods are described herein, relying on ester elimination and alcohol elimination reactions. We have found the reaction between lead(II) acetate and titanium(IV) isopropoxide in ethanol results in ligand redistribution at room temperature. Reactions between (β-diketonate)2M(OR)2 where M = Ti, Zr and Sn and lead(II) acetate do not result in any detectable ester elimination under the reaction conditions employed, and this approach was not successful. Alcohol elimination experiments have been explored as an alternative strategy using a bifunctional glycolate ligand. Lead carbonate reacted with glycolic acid to form the corresponding lead glycolate complex Pb(O2CCH2OH)2. This compound reacted with (β-diketonate)2M(OR)2, M = Ti and Sn, to eliminate two equivalents of alcohol and form the corresponding single component (β-diketonate)2M(OCH2CO2)2Pb complexes. These complexes start to thermally decompose at 150°C and loss of weight is complete by 450°C to yield a product whose weight loss corresponds to the formation of PbTiO3 for M = Ti. Bulk thermolysis of a sample of (dpm)2Ti(OCH2CO2)2Pb at 400°C resulted in formation of crystalline perovskite phase lead titanate together with PbO, massicot and α-PbO phases.
Fabrication of Sol-Gel Derived Ferroelectric Plzt (9/65/35) Optical Waveguides
Authors: Baude P.F. , Ye C. , Tamagawa T. , Polla D.L.
Published: March 2011

Crack free transparent ferroelectric PLZT (9/65/35) thin films were deposited on silicon substrates using the sol-gel deposition technique. An intermediate layer of PLT was used to improve the PLZT's optical quality and to reduce the amount of film cracking. Wet chemical, plasma and reactive ion etching are investigated as means of realizing the necessary waveguide structures. Waveguiding is observed in 2-4mm long PLZT (9/65/35) fabricated by reactive ion beam etching.
Effects of Stoichiometry on Pzt Thin Film Capacitor Properties
Authors: Bernstein S.D. , Kisler Yanina , Wahl J. M. , Bernacki S. E. , Collins S. R.
Published: March 2011

The effects of excess Pb and Zr/Ti ratio on crystallization behavior and ferroelectric properties of sol-gel derived films were studied. Excess Pb was found to reduce the crystallization temperature. Films with good ferroelectric properties (remanent polarization greater than 8 μC/cm2 ) were achieved after 550 °C, 5 minute crystallization. The difference in the magnitude of the charge in response to switching and non-switching pulses was greater than 1 μC/cm2 after 1011 fatigue cycles for many of the films. The arnount of charge remaining after fatigue was found to be dependent on the initial charge. Reducing the partial pressure of oxygen during crystallization affected both the remanent polarization and fatigue behavior. The fatigue rate was relatively independent of composition and crystallization temperature.
Hydrothermal Synthesis of Barium Titanate Thin Films on Titanium Metal Substrates
Authors: Bacsa R. , Ravindranathan P. , Dougherty J.P.
Published: March 2011

Well crystallized polycrystalline films of cubic BaTiO3 have been synthesized on Ti metal substrates by the hydrothermal reaction of Ti metal with Ba(OH) 2 in the temperature range 80°C-200°C. The films have been synthesized on Ti foil and also on Ti sputtered Si and polymer substrates. The crystallinity, microstructure and electrical properties depend critically on the nature of the substrate.
Ferroelectric Switching in Lead Zirconatelead Zinc Niobate Thin Films
Authors: Udayakumar K. R. , Schuele P. J. , Chen J. , Brooks K. G. , Cross L. E.
Published: March 2011

Thin films of PbZrO3-Pb(Zn0.33Nb0.67)03, with PZN contents of 8- 12%, were fabricated through the sol-gel spin-on technique. The structural, low frequency capacitive, and polarization reversal characteristics were investigated as a function of composition in this solid solution system. The switching of ferroelectric polarization was tested by a sequence of square wave pulses consisting of two positive pulses followed by two negative pulses. Compositions with higher PZN contents are promising for switching applications; the films were typically characterized by a switched charge of 4-14 μC/cm2, coercive field of around 30 kV/cm, and relative permittivity of 400-800.
Epitaxial Growth of Ferroelectric Thin Films on GaAs with MgO Buffer Layers by Pulsed Laser Deposition
Authors: Nashimoto K. , Fork D. K. , Ponce F. A. , Geballe T. H.
Published: March 2011

Epitaxial growth of ferroelectric thin films on GaAs (100) by pulsed laser deposition was examined for integrated electro-optic device applications. To promote epitaxy of ferroelectrics and prevent interdiffusion, we have deposited several types of buffer layers. CeO2 reacted strongly with GaAs. Although Y203 9% stabilized-ZrO2 films showed epitaxial growth, YSZ reacted with GaAs at 780°C. MgO grew epitaxially and was stable even at 780°C. HRTEM observation showed a sharp interface between MgO and GaAs. BaTiO3 and SrTiO3 deposited on MgO/GaAs structures showed epitaxial growth. In-plane orientation was BaTiO3 [100
// MgO [100] // GaAs [100]. Epitaxial BaTiO3 films were c-axis oriented tetragonal phase and showed ferroelectric hysteresis.
Texturing and Dielectric Properties of Laser Deposited BaTiO3 Thin Films Grown on Heated Substrates
Authors: Vaudin M.D. , Cook L.P. , Wong-Ng W. , Schenck P.K. , Brody P.S. , Rod B.J. , Bennett K.W.
Published: March 2011

Thin films of BaTiO3 were deposited on platinum-coated silicon substrates using pulsed laser deposition and characterized using electron microscopy, powder x-ray diffraction and electrical measurements. The microstructure consisted of columnar BaTiO3 grains oriented normal to the substrate. Two preferred orientations were observed, with either the (001) or (111) planes of BaTiO3 being parallel to the substrate. The electrical properties of two films were measured and it was found that the (111) film was ferroelectric and the (001) film was not. Possible reasons for this are discussed.
The Control of Epitaxial Growth of LiNbO3 Thin Films on R-Cut Sapphire
Authors: Fujimura Norifumi , Kakinoki Masami , Ito Taichiro
Published: March 2011

It is argued that epitaxial films of ionically-bonded materials are more easily achieved than of covalently bonded materials. Good epitaxy can be achieved despite relatively large lattice mismatch with respect to the substrate. However, the strong influence of interfacial energy can result in difficulty in controlling the orientation of epitaxial films.

The crystallographic orientation of ionically-bonded LiNbO3 films was therefore studied. Growth orientation could be controlled by paying attention to the bonding between octahedra in the structure, and to the formation of the octahedra containing lithium and niobium ions. Lithium concentration could be increased by increasing the rf power, 02 partial pressure and total gas pressure, and decreasing the substrate temperature during deposition.

The orientation of the film changed from (012) to (100) via (110) by increasing the Li concentration in the film. The (012) and (100) films were epitaxial with respect to the substrate. In particular, the (100) films were of exce lent quality, being single crystalline with smooth surfaces.
Preparation of Ferroelectric Films of LiNbO3 and SbSI by Artificial Epitaxy.
Authors: Pankrashov A.I , Givargizov E.I.
Published: March 2011

Highly–ordered, up to nearly–single–crystalline films of SbSI and LiNbO3 on amorphous substrates (oxidized silicon, fused quartz) were prepared by laser zone–melting recrystallization basing on principles of artificial epitaxy, or graphoepitaxy. Some conclusions are made about tentative orientation mechanism(s) in these processes.
Gallogermanate Glasses As Near IR Optical Waveguides
Authors: Higby Paige L. , Merzbacher Celia I. , Aggarwal Ishwar D. , Friebele E. Joseph
Published: March 2011

Alkaline earth gallogermanate glasses are a possible low-loss oxide optical material which would be able to operate in the 1.6–2 μm wavelength range. Processing techniques investigated to date and pertinent optical property data are presented.
Materials Aspects of Optical Amplifiers
Authors: DiGiovanni D. J.
Published: March 2011

Optical amplifiers promise to revolutionize optical communication. Erbium-doped silica fiber amplifiers operating at 1.5 μm are now commercially available while the performance of devices using neodymium or praseodymium doped fiber in the 1.3 gtm telecommunications window are improving rapidly. This review discusses the importance of host material on amplifier characteristics.
Concentration Effect of Erbium-Doped Silica Based Multi-Component Glass Fibers
Authors: Morishita Y. , Muta K. , Sugiyama N.
Published: March 2011

Silica based multi-component glass fibers were fabricated using core glass doped with erbium concentration in the range of 650 to 34000wtppm. The highest gain of 18dB was achieved at the Er3+ concentraion of 7000wtppm under pump wavelength and power of 1.48μm and 40mW, respectively. The gain decreased at concentration over 7000wtppm due to clustering of Er3+ ions. The increases in the threshold value of the pump power caused by clustering of Er3+ ions was also recognized.
Erbium Doped Tellurite Glasses
Authors: Wang Jau-Sheng , Snitzer Elias , Sigel George H.
Published: March 2011

The results to be presented focus on the optimization of tellurite glass compositions which are suitable both for doping with erbium oxide as well as subsequent for fiber drawing. The laser related properties, such as fluorescence spectrum, lifetime, and optical transition cross sections will be presented. Judd-Ofelt parameters for erbium in the glasses have been exploited to predict fluorescence lifetime, excited state absorption(ESA), ground state absorption(GSA) and ground state fluorescence(GSF). For comparison, the absorption cross section, emission cross section, excited state absorption(ESA)/ground state absorption(GSA)(0.8μm pumping) and fluorescence terminating in the ground state(GSF)/excited state absorption(ESA) ratios are calculated for both Al2O3-SiO2 and tellurite glasses.
Nonlinear Optical Properties of Cds-SiO2 Glass Composite Thin Films Prepared by RF-Sputtering
Authors: Tanahashi I. , Yoshida M. , Manabe Y. , Mitsuyu T. , Tokizaki T. , Nakamura A.
Published: March 2011

CdS-microcrystallites-embedded films of SiO2 were successfully prepared by rf-sputtering. The optical absorption edge of the film with 18.5 at% CdS clearly exhibited a blue shift by 0.13 eV compared to bulk CdS, indicating the quantum size effect due to confinement of electrons and holes in CdS microcrystallites. The blue-shift decreased with increasing the CdS concentration. The photoluminescence spectra of the films also exhibited the blue shift in band-edge emission. From decay curves of the band-edge emission, the dominant decay time was estimated to be 100 ps, and longer components were weak. Optical nonlinear susceptibility of the films was measured by degenerated four-wave mixing experiments near band-edge. The third-order nonlinear susceptibility was estimated to be 5.0 × 10−7 esu at 77K for the film with 46.3 at% of CdS.
Anisotropic Metallic Island Films for Polarizers
Authors: Baba Kazutaka , Katsu Jun-Ichiro , Miyagi Mitsunobu
Published: March 2011

Ultra-thin gold island films with optical anisotropy have been fabricated by stretching ordinary isotropic island films in the high temperature. The origin of optical anisotropy seems to come from an elongated prolate island shape.
Waveguides Fabricated in LiNbO3 by Proton Implantation
Authors: Moretti P. , Thevenard P. , Wirl K. , Hertel P.
Published: March 2011

Optical planar waveguides, with a controllable thickness in a very wide range, typically from 3 to 20 μm, can be fabricated by thermally controlled proton implantation in LiNbO3. In the nuclear stopping region at the end of the ion's tracks a sufficient decrease in refractive index is obtained, thus forming an adequate optical barrier. The mode confinement was investigated by dark line mode spectroscopy, and the refractive index profiles were reconstructed. The effects of different ion fluences and ion energies in the Mev range on the refractive index profile at 300 K have been investigated.
Surface Chemistry of Fe Oxide Impregnated Porous Vycor Glass
Authors: Sunil D. , Rafailovich H. , Sokolov C. , Gafney H. D. , Schwarz S. A. , Wilkens B. J.
Published: March 2011

X-ray absorption and Mossbauer spectroscopy were used to study chemical and magnetic properties of photodeposited Fe in Porous Vycor Glass(PVG). Extended X-ray Absorption Fine Structure(EXAFS) measurements of Fe samples show that after photolyzation, the Fe atoms are surrounded by two shells of six oxygen atoms and eight Fe atoms. The Fe-O and Fe-Fe distances are 1.84 °A and 1.99 °A respectively. After heating to 650 °C and 1200 °C shortening of bond lengths are observed. The second shell of Fe in unheated and heated to 650 °C samples have Fe-Fe distances of 3.0 °A and 2.98 °A respectively. Samples consolidated at 1200 °C show the Fe atoms to be surrounded by two shells of Fe atoms at 2.86 and 3.03 °A. This data together with Mossbauer and XANES spectra suggest that Fe exists in two different configrations, one is an Fe-Fe compound and the other is an octahedral Fe oxide similar to Fe2O3.
Materials Effects on the Radiation Sensitivity of Single Mode Optical Fibers, II
Authors: Friebele E. J. , Askins C. G. , Putnam M. A. , Harrington C. C. , Gingerich M. E. , Schmidt W. H.
Published: March 2011

The effect of varying single mode fiber fabrication factors such as core and clad dopant concentrations, deposition conditions, and draw parameters on the recovery of the nuclear radiation-induced attenuation at 1.3 μm has been studied. Statistically significant correlations of core factors have been established with a 24 experimental design, and separate one-dimensional experiments revealed the effect of clad [Ge] and [F].
Pulse Energy Dependence of Defect Generation in Bragg Grating Optical Fiber Materials
Authors: Tsai T. E. , Askins C. G. , Friebele E. J.
Published: March 2011

Ge-associated defect centers induced by 5 eV (∼ 245 nm) photons of various intensities in Ge-doped silica were studied using electron spin resonance (ESR). We found that Ge E' centers observed in Bragg grating Ge-doped silica core fibers are induced and bleached by one- and two-photon absorption processes, respectively. The observation that Ge E's are the only paramagnetic centers induced by low intensity 5 eV photons supports the proposal that the Ge E' center is responsible for the photoinduced structures observed in both Bragg grating and second-harmonic-generation (SHG) fibers.
Characterization of Critical Properties of Optical Fiber Coatings
Authors: Shea John W. , Turnipseed John M. , Taylor Carl R. , Petisce James R. , Overton Bob J.
Published: March 2011

This paper describes four key measurements of critical coating performance attributes which can affect coated optical fiber performance. The four measurement methods to be described are: 1) primary coating adhesion, 2) coating toughness, 3) primary coating equilibrium modulus, and 4) primary coating glass transition temperature.
The Hydrothermal Stability of Cement Sealing Materials in the Potential Yucca Mountain High Level Nuclear Waste Repository
Authors: Krumhansl J. L. , Hinkebein T. E. , Myers J.
Published: March 2011

Cementitious materials, together with other materials, are being considered to seal a potential repository at Yucca Mountain. A concern with cementitious materials is the chemical and mineralogic changes that may occur as these materials age while in contact with local ground waters. A combined theoretical and experimental approach was taken to determine the ability to theoretically predict mineralogic changes. The cementitious material selected for study has a relatively low Ca:Si ratio approaching that of the mineral tobermorite. Samples were treated hydrothermally at 200°C with water similar to that obtained from the J-13 well on the Nevada Test Site. Post-test solutions were analyzed for pH as well as dissolved K, Na, Ca, Al, and Si. Solid phases formed during these experiments were characterized by scanning electron microscopy and X-ray diffraction. These findings were compared with predictions made by the geochemical modeling code EQ3NR/EQ6. It was generally found that there was good agreement between predicted and experimental results.
Interactions between Concrete and Brine at the Waste Isolation Pilot Plant (WIPP) Site, New Mexico
Authors: Lambert Steven J. , Nowak E. James , Wakeley Lillian D. , Poole Toy S.
Published: March 2011

A concrete liner emplaced in 1984 in a shaft at the Waste Isolation Pilot Plant has served as a natural laboratory for observing interactions among concrete, evaporite rocks, and brine. During a routine inspection of the liner in the spring of 1990, discoloration, deposition of secondary salts, wet areas with exposed aggregate grains, softening of paste, surficial spalling, and cracking were observed locally on the concrete surface of the liner. Some construction joints showed apparent leakage of brine from behind the liner, which was nominally 50 cm thick. Seepage brines were nearly saturated relative to CaCl2 and contained lesser amounts of MgCl2 and KCl, and minor NaCl. The liner surface was locally altered to a 1–2 cm friable hygroscopic layer containing little cement paste; concrete cores (7 or 10 cm diameter) through the liner at depths of 248, 254, 255, and 271 m showed similar degrees of alteration at the liner/rock interface. The most profound alteration of concrete was developed in a ˜7 cm zone sub-parallel to and straddling the construction joint cored at a depth of ˜254.5 m. This zone was extensively microfractured, transected aggregate grains, and contained brucite, gypsum, magnesium hydroxychloride hydrate, and locally calcium chloroaluminate instead of the usual phases of hydrated portland cement. Several mechanisms of chemical degradation have been proposed, the most likely being attack by magnesium ions.
Synthesis, Crystal Chemistry and Stability of Ettringite, A Material with Potential Applications in Hazardous Waste Immobilization
Authors: McCarthy Gregory J. , Hassett David J. , Bender Jason A.
Published: March 2011

Recent results on synthesis, crystal chemistry, structure and stability of ettringite*, with specific reference to use of this material in hazardous waste immobilization, are presented. Ettringites with selenate, chromate, borate, sulfite and carbonate replacing sulfate have been synthesized and characterized by XRD for phase purity and structure. In X-ray powder diffractograms, selenate and chromate etringites have the normal trigonal P31cettringite structure, whereas the borate, sulfite and carbonate ettringites can be indexed on a hexagonal unit cell with a halved c parameter. In excess of 95% of the Se and B in solutions spiked with various concentrations of these elements has been removed by precipitation of ettringite. Ettringites appear to be unstable in solutions outside of the approximate pH range 11.0-12.5, and there is a potential for some oxyanion exchange between ettringites and oxyanion-containing solutions. Buffering of pH, and dissolved Ca, Al and sulfate activities by other components of ettringite-based hazardous waste forms, combined with low-reactivity C-S-H matrices, could largely mitigate these concerns.
Cross-Linking Reactions in Macro-Defect Free Cement Composites
Authors: Desai P. G. , Young J. F. , Wool R. P.
Published: March 2011

The key to the processing and properties of Macro-Defect Free (MDF) cement composites is the interaction between the cement and the polymer. In calcium aluminate (CA) / polyvinyl alcohol (PVA) MDF composites, it has been hypothesized that aluminate (Al(OH)4−) ions released from the cement cross-link PVA in a manner similar to the well known interaction of the borate (B(OH)4−) ions with PVA. In this investigation, stable aluminate/PVA solutions at different concentrations have been studied. Results indicate that the nature of interaction of aluminate ions is not similar to that of borate ions in dilute and semidilute polymer solutions.
Self-Generating Zeolite-Cement Composites
Authors: Larosa Judith L. , Kwan Stephen , Grutzeck Michael W.
Published: March 2011

Zeolites can be synthesized in mixtures containing 80 wt% Class F fly ash and 20 wt% ordinary Portland cement if they are mixed with a concentrated NaOH solution and cured at temperatures of 60–90° C. Zeolite Y and NaP-type zeolite were grown in situ in a coexisting calcium silicate hydrate matrix. Those samples made with NaOH, which contained the zeolites, had higher compressive and flexural strengths than equivalent samples made with water.
The Use of Natural Fiber in Cementitious Composites
Authors: Chen Y. , Park C.K. , Silsbee M.R. , Roy D.M.
Published: March 2011

Variations in the mechanical properties of wood fiber reinforced cementitious (WRFC) materials containing treated fiber and water soluble polymers were investigated. Flexural strength is greatly improved by the addition of polymer. The interface bonding is enhanced by the fiber pre-treatment. The mechanism responsible for the strength increase in WRFC was studied by mercury intrusion porosimetry. Experimental results indicate that the increased strength results from an enhancement in the strength of the interface and reduced porosity.
Effects of Interfacial Zone Percolation on Cement-Based Composite Transport Properties
Authors: Snyder K.A. , Winslow D.N. , Bentz D.P. , Garboczi E.J.
Published: March 2011

In portland cement mortar and concrete, interfacial zones exist around the aggregate particles that have larger pore sizes and pore volumes than the bulk cement paste. If there are enough aggregate particles present, these zones may overlap so as to percolate. A computer simulation model has been developed that can predict this percolation point as a function of interfacial zone thickness, volume fraction of aggregates, and aggregate particle size distribution. The model was used to simulate 1cm3 of mortar, using approximately 10,000 aggregate particles. Results from this model are used to explain recent mercury porosimetry results on mortars having a variety of sand contents. The implications of interfacial zone percolation for the transport properties of mortar and concrete are discussed.
In Situ Transmission Electron Microscopy (TEM) Investigation of Fracture Mechanisms in a Calcium Aluminate MDF Cement.
Authors: Popoola O. O. , Kriven W. M. , Young J. F.
Published: March 2011

Fracture mechanisms in calcium aluminate macro-defect-free-cement were studied by in situ deformation in the TEM. Fracture occurred predominantly at the cement / polymer interface. The toughening mechanism involved crack bridging at the interphase / polymer interface. XPS studies of the chemistry of the interphase revealed it to be made up of an AlOC complex in addition to the amorphous hydration product phase.
Microstructural Development in Pore Reduced Cement (PRC)
Authors: Macphee D.E. , Lachowski E.E. , Taylor A.H. , Brown T.J.
Published: March 2011

Pore Reduced Cement (PRC) is a high density, high strength material which may have specialist use in the construction industry. It is produced by the high pressure processing of Ordinary Portland cement (OPC) pastes, or blends of OPC with certain supplementary cementing materials, such that effective water/cement ratios (w/c) are significantly reduced relative to those used for mixing. A previous paper [1] describes the mechanical properties of PRC (patent pending) during the early stages of product development and more recent data show that improved preparative techniques are leading to increasing densities and strengths. However, fundamental data on the microstructure, mineralogy and durability properties have not previously been reported. The present paper is directed towards the study of microstructural development in the closely compacted matrix using electron microscopy. Mineralogical and porosity data are also presented.
Setting and Strengthening Mechanisms of Cementitious Materials
Authors: Jiang W. , Roy D.M.
Published: March 2011

This paper highlights the physico-chemical characteristics of cementitious materials responsible for or involved in setting, and how these are related to the strengthening and mechanical properties. Five main mechanisms which can be used to increase cementitious materials strength were discussed. The substantially improved cement matrix materials can be obtained by deliberately using one or more above mechanisms. Experiments have been performed on ordinary portland cements and phosphate cements used as construction materials, whose setting time is several hours, and dental cement, whose setting time is several minutes.
Conversion of Red Muds into Pozzolans
Authors: Pera Jean
Published: March 2011

Red muds are waste materials obtained from the aluminium extraction industry. They consist mainly of clays, aluminium and iron hydrated oxides. Three muds were studied; they differed in chemical and mineralogical compositions. They were converted into reactive pozzolans by calcination in the temperature range 600–800°C for five hours. Pozzolanicity was investigated on calcined red mud-OPC mixes studying strength development and lime consumption as evaluated by DTA. The nature of hydrates formed during hardening was also identified.

The mineralogical composition of the mud is the most important factor affecting its pozzolanicity. Blended cements containing 30% calcined red mud develop significant strengths.
Ferroelasticity, Pseudoelasticity, and Shape Memory Effect in an Ionic Material Pb3(PO4)2
Authors: Yamada Y.
Published: March 2011

A theory of pseudoelasticity is developed within the framework of the phenomenological Ginzburg-Landau Scheme. The system with ℈stripe℉-type ferroelastic domain structure has been discussed using Transfer-Integral method, which directly gives the equillibrium density of domain boundaries and the response of domain pattern against the external stress. The results are applied to the case of Pb3(PO4)2, an ionic ferroelastic material which shows pseudoelasticity and shape memory effect. It is suggested that in this particular case, random stress field is mainly responsible for pseudoelastic behavior. The observed stressstrain curve has been analyzed quantitatively from this standpoint. The origin of the two-way shape memory effect has also been inferred qualitatively from the same stand point.
The Effect of Cyclic Transformation on the Shape Memory Characteristic in an Fe-Mn-Si-Cr-Ni alloy
Authors: Ohtsuka Hideyuki , Kajiwara S. , Ishihara T.
Published: March 2011

Evaluation of the shape memory characteristics under thermal and stress cycles is indispensable to ensure the reliability of shape memory alloys used in nuclear power reactors. Then the effect of γ↔E cyclic transformation on the shape memory characteristics was investigated in Fe-14Mn-6Si-9Cr-5Ni (wt%) alloy. ε martensites were stress-induced by pulling specimens at room temperature, and they were reverse transformed by heating under various stresses. The change of surface relief during reverse transformation was observed by a hightemperature optical microscope equipped with a tensile machine. The recovery stress was measured by this apparatus after the “yclic transformation” was repeated various times. The reverse-transformed microstructures were observed by transmission electron microscopy. As a result, the amount of residual ε martensite increased with increasing stress applied during reverse transformation. As the “cyclic transformation” was repeated, the recovery stress remarkably increased at first, and then gradually decreased. This rapid increase of recovery stress is attributed to not only the increase of elongation when specimen is deformed but also the increase of stacking faults which act as nucleation sites of martensite. The decrease of recovery stress is attributed to the decrease of elongation.
Characterization of NiTi Shape Memory Wires by Differential Scanning Calorimetry and Transmission X-ray Diffraction
Authors: Kao Ming-Yuan , Fariabi Sepehr , Thoma Paul E. , Ozkan Husnu , Cartz Louis
Published: March 2011

The reversible transformations between the Austenite (A) and Martensite (M) phases of NITI shape memory wires having a 78°C austenlte finish temperature (950°C annealed) were studied In the cold work and heat treatment ranges between 14 to 62% and 400 to 525°C respectively. The ranges of peak Transformation Temperatures (TI), determined by Differential Scanning Calorimetry (DSC) at a 10°C/min rate, were found to be 56 to 75°C, -28 to 33°C, and 38 to 52°C for the respective high temperature A, low temperature M, and the Intermediate Rhombohedral (R) phases. The degree of cold work and heat treatment had significant effects on the TT of NITI wires. The peak TT of A and M decreases with Increasing cold work. Except for the 14% cold worked wires, the peak TT Increases with Increasing heat treatment temperature for M, and Increases with Increasing heat treatment temperature for A for temperatures higher than 450°C. The peak IT of R Increases with Increasing cold work and decreasing heat treat temperature.

Using MoKα radiation, transmission x-ray diffraction analysis was utilized to determine the phases at room temperature on wires thinned down to 0.05 to 0.01 mm in diameter. The diffraction patterns of body-centered cubic austenite (132) and monodlinic martenslte (B19) for NITi were both Identified. In addition, extra diffraction lines observed for various samples were tentatively assigned to M and the Intermediate R-phase. Depending on the thermal history and the processing conditions, the NITI wires consist of either a pure M, a mixture of A and R, or a mixture of A, R, and M at room temperature.
Combustion Synthesis of Ni-Ti-X Shape Memory Alloys
Authors: Moore John J. , Yi Ru Chun
Published: March 2011

Combustion synthesis is an energetically favorable new method of producing Ni-Ti series shape memory alloys (SMA′s). The ΔH°f,,298/Cp298ratio plays a key role, especially if a liquid product is required. Solidified TiNi SMA's were hot rolled into plates exhibiting the shape memory effect. Ms transition temperatures can be controlled from -78 to 460°C by substituting Fe or Pd for Ni.
Residual Stress, Adhesion and Crystallization of Ion-Sputtered and Ibed Processed NiTi Films
Authors: Walles B. , Chang L. , Grummon D. S.
Published: March 2011

When conventional sputtering is used to deposit nickel-titanium thin films at temperatures below ∼623 - 723 Kelvins, the resultant structures are amorphous and the films must be annealed to form the requisite B2 parent ordering. This invites complications related to interface diffusion and chemical reaction with components of the substrate. For the present work, thin films of near-equiatomic NiTi were prepared on potassium chloride, (100) single-crystal silicon, and Si3N4 passivated silicon substrates by ion sputtering and by ion beam enhanced deposition (IBED). We have investigated residual stress levels produced by these processes, evaluated substrate adhesion levels, and explored the crystallization behavior of NiTi films grown under conditions of concurrent low-energy inert gas ion bombardment. Residual stresses of ionsputtered and IBED films were measured using profilometric techniques. Film crystallization behavior was studied by transmission electron microscopy of as-deposited films. Films produced by unassisted ion sputtering showed compressive residual stresses in the as-deposited amorphous state, which became highly tensile after annealing, leading to spontaneous cracking and delamination. Preliminary results from IBED experiments showed a reduction in the asdeposited stress, and improved adhesion. Under certain conditions, ion enhancement of the deposition process promoted film crystallization during deposition at moderate substrate temperature, producing a dispersion of extremely fine particles, indexed as Ni3Ti.
Structure and Properties of Rapidly Solidified Nitinol Materials
Authors: Wu K. H.
Published: March 2011

Ti50-(Pd(x)-Ni(50-x)) alloys were prepared with Pd ranging from 18 at% to 22%. Both hot-rolled strips and melt-spun ribbons were fabricated. Heat treatments from 400°C to 1000éC were evaluated. It was found that the meltspun ribbons demonstrated much higher transformation temperatures than those of as-cast materials. However, the hot-rolled strips failed to display a shape memory effect, as well as those ribbons with 18 at.% and 20% Pd.
Characterization of the Phase Transformations in the Shape Memory Alloy Ni-36 at.% Al
Authors: Horton J.A. , George E.P. , Sparks C.J. , Kao M.Y. , Cavin O.B. , Thoma P.
Published: March 2011

A survey by differential scanning calorimetry (DSC) and recovery during heating of indentations on a series of nickel-aluminum alloys showed that the Ni-36 at.% Al composition has the best potential for a recoverable shape memory effect at temperatures above 100°C. The phase transformations were studied by high temperature transmission electron microscopy (TEM) and by high temperature x-ray diffraction (HTXRD). Quenching from 1200°C resulted in a single phase, fully martensitic structure. The initial quenched-in martensites were found by both TEM and X-ray diffraction to consist of primarily a body centered tetragonal (bct) phase with some body centered orthorhombic (bco) phase present. On the first heating cycle, DSC showed an endothermic peak at 121°C and an exothermic peak at 289°C, and upon cooling a martensite exothermic peak at 115° C. Upon subsequent cycles the 289°C peak disappeared. High temperature X-ray diffraction, with a heating rate of 2°C/min, showed the expected transformation of bct phase to B2 between 100 and 200°C, however the bco phase remained intact. At 400 to 450°C the B2 phase transformed to Ni2Al and Ni5Al3. During TEM heating experiments a dislocation-free martensite transformed reversibly to B2 at temperatures less than 150°C. At higher temperatures (nearly 600°C) 1/3, 1/3, 1/3 reflections from an ω-like phase formed. Upon cooling, the 1/3, 1/3, 1/3 reflections disappeared and a more complicated martensite resulted. Boron additions suppressed intergranular fracture and, as expected, resulted in no ductility improvements. Boron additions and/or hot extrusion encouraged the formation of a superordered bct structure with 1/2, 1/2, 0 reflections.