bluuebunny/crossref_metadata_2025 huggingface dataset:
Atmospheric pressure chemical vapor deposition of TiN from tetrakis(dimethylamido)titanium and ammonia
Authors: Musher Joshua N. , Gordon Roy G.
Published: March 2008

Near stoichiometric titanium nitride (TiN) was deposited from tetrakis(dimethylamido)titanium (TDMAT) and ammonia using atmospheric pressure chemical vapor deposition. Experiments were conducted in a belt furnace; static experiments provided kinetic data and continuous operation uniformly coated 150-mm substrates. Growth rate, stoichiometry, and resistivity are examined as functions of deposition temperature (190−420 °C), ammonia flow relative to TDMAT (0−30), and total gas-flow rate (residence time 0.3−0.6 s). Films were characterized by sheet resistance measurements, Rutherford Backscattering Spectrometry, and X-Ray Photoelectron Spectrometry. Films deposited without ammonia were substoichiometric (N/Ti, 0.6−0.75), contained high levels of carbon (C/Ti = 0.25−0.40) and oxygen (O/Ti = 0.6−0.9), and grew slowly. Small amounts of ammonia (NH3/TDMAT ≥ 1) brought impurity levels down to C/Ti, 0.1 and O/Ti = 0.3−0.5. Ammonia increased the growth rates by a factor of 4−12 at temperatures below 400 °C. Films 500 Å thick had resistivities as low as 1600 μΩ-cm when deposited at 280 °C and 1500 μΩ-cm when deposited at 370 °C. Scanning electron micrographs indicate a smooth surface and poor step coverage for films deposited with high ammonia concentrations.
Effect of substrate orientation on the crystal quality and surface roughness of Nb-doped TiO2 epitaxial films on TiO2
Authors: Gao Y. , Chambers S. A.
Published: March 2008

We have grown Nb-doped TiO2 epitaxial films on (100) and (110)-oriented TiO2 rutile substrates by molecular beam epitaxy. Nb substitutionally incorporates at cation sites in the rutile lattice, forming NbxTi1−xO2 solid solutions. However, the crystal quality and surface roughness of the films depend strongly on the substrate orientation. Surface roughening and defect formation occur at lower values of x on (100) than on (110). This result is due to anisotropic changes in the metal-oxygen bond lengths within the rutile structure in going from TiO2 to NbO2; there are 1% and 12% changes in the metal atom to octahedron-base oxygen and metal atom to octahedron-vertex oxygen bond lengths, respectively. Every metal atom in the (100) growth surface has in-plane components of the 12% mismatch. However, only half of the metal atoms in the (110) growth plane have such components. Thus, there is substantially larger in-plane lattice mismatch when the growth surface is (100) compared to (110), resulting in surface roughening and formation of defects at a lower doping level for (100)-oriented NbxTi1−xO2 epitaxial films.
The mechanism of spontaneous infiltration of Al–Si alloy into SiC preform in air
Authors: Xi X. M. , Xiao L. M. , Yang X. F.
Published: March 2008

Rapid, spontaneous infiltration can be achieved by dipping a SiC preform that contains pyrolyzed carbon into an Al–Si alloy bath in an open air environment. The mechanism for infiltration is investigated in the present work by studying the effects of several relevant parameters on the infiltration process. Experimental results have shown that the requirements for rapid spontaneous infiltration are an infiltration temperature higher than 1400 °C, the presence of a pyrolyzed carbon, and the presence of SiC particle in the preforms. The concentration of Si in the alloy does not have significant influence on the infiltration rate, but it strongly affects the resulting microstructures in the infiltrated composites.
Bisethylacetoacetato Cu(II) as a novel metal-organic precursor for Cu film production by plasma-enhanced chemical vapor deposition toward ultra-large-scale integration metallization
Authors: Hwang Soon T. , Shim Ilwun , Lee Kyung O. , Kim Kyeong S. , Kim Ju H. , Choi Guang J. , Cho Young S. , Choi Hyungsoo
Published: March 2008

Bisethylacetoacetato Cu(II), referred to as Cu(etac)2, was synthesized and used as a novel metal-organic precursor to produce Cu films by PECVD processing. Cu(etac)2 is a nonfluoride compound that is solid at room temperature with reasonable volatility at 120–150 °C of 0.8 Torr. Effects of selected process variables on the characteristics of Cu film deposition were studied. Considered variables were plasma power, hydrogen flow rate, deposition time, substrate temperature, and precursor temperature. The process conditions to give Cu films of a high quality were determined. The electrical resistivity approached 2 μΩ · cm as the Cu film thickness became greater than 2500 Å. The conformality of the Cu film deposition by PECVD was sufficient to result in complete via-hole fillings of wafers patterned for 256 Mb DRAM.
Analysis of the NdBa2Cu3Ox thin film growth mechanism by time of flight mass spectrometry of the laser plume
Authors: Badaye M. , Fukushima K. , Morishita T.
Published: March 2008

Time of flight (TOF) spectroscopic measurements are used to diagnose the laser-generated plume of ceramic NdBa2Cu3Ox targets. We have been able to directly correlate the laser-deposited films' properties such as superconductivity, crystallinity, and orientation with plasma properties. Study of the TOF spectra shows that at laser fluences greater than 3 J/cm2 the plume become Nd-rich, and this leads to a low Tc in the deposited film. We have also shown the effect of target density on the energy of the plume species, and through energy considerations we have explained the observed change in the crystalline orientation of films from c- to a-orientation with increasing the target density. Finally, we have examined the oxidation mechanism of NdBa2Cu3Ox thin films, and have shown that highly energetic atomic oxygens have a prevailing role in oxidizing our laser-deposited thin films.
Low temperature magnetic transition and high temperature oxidation in INCONEL alloy 718
Authors: Seehra Mohindar S. , Suresh Babu V.
Published: March 2008

X-ray diffraction and temperature dependent (5 K–380 K) magnetic measurements have been carried out in INCONEL 718 superalloy before and after high temperature aging treatments. (INCONEL is a trademark of the INCO family of companies.) The nominal composition of this alloy is Ni (52.5%), Cr (19.0%), Fe (18.5%), Nb (5.1%), Mo (3.0%), Ti (0.9%), Al (0.5%), Cu (0.15%), and C (0.08%), and it yields an x-ray diffraction pattern consisting of a fcc phase with α = 3.5987 (3) Å and an orthorhombic phase associated with δ-Ni3Nb. It is concluded that the fcc pattern is due to both the γ austenitic phase and γ′ Ni3(Al, Ti) phase of alloy 718. The standard annealing and aging treatment carried out in air at temperatures between 621 and 982 °C produces surface oxides (Cr, Fe)2O3 and FeNbO4 (which are easily removed by etching and polishing) and contracts the lattice. Magnetic measurements show a distinct phase transition at Tc = 14 K, which has been attributed to the γ′-Ni3(Al, Ti) phase by the process of elimination and by observing that it has most of the characteristics of the weak itinerant ferromagnet Ni74.5Al25.5. This transition may have some effects on the cryogenic applications of this alloy.
The positive roles of metallic droplets in deposition of alloy films by cathodic arc plasma deposition
Authors: Wang She-Guan , Bai Xin-De , Wang Bao-Chu , Fan Yu-Dian
Published: March 2008

The roles of metallic droplets, which generated from the cathodic arc spot holes in the technology of Cathodic Arc Plasma Deposition (CAPD), are investigated by SEM, TEM, image analysis apparatus, and electronic probe energy spectrum analysis. The results show that though many papers in recent years are devoted to eliminate them, the metallic droplets, including the macrodroplets, have many important positive roles in the preparation of alloy films: they are the main factor to transfer the original composition of alloy cathodic target to the alloy thick films; they preserve the high deposition rate of CAPD to form the basic characteristics of the microstructure and to affect the pore ratios of the films; they also preserve the high melting point elements in the alloy films, and therefore preserve the corrosion resistance of the alloy in the films. The macrodroplets can be eliminated by raising the substrate temperature properly, which is permitted in some cases, such as depositing alloy films onto middle carbon steel as an anticorrosion system, etc.
Effect of TiO2 doping on rapid densification of alumina by plasma activated sintering
Authors: Mishra R. S. , Mukherjee A. K. , Yamazaki K. , Shoda K.
Published: March 2008

The effects of plasma cycle and TiO2 doping on sintering kinetics during plasma activated sintering (PAS) of γ−Al2O3 have been studied in the temperature range of 1473–1823 K. Multiple plasma cycle leads to higher densification. Also, TiO2 doping enhances the sintering kinetics during PAS. In TiO2 doped specimens, near full density was obtained at 1673 K in less than 6 min using multiple plasma cycle. It is suggested that the dielectric properties of a material are critical for the success of the PAS process.
Effect of substrate bias voltage on the properties of arc ion-plated TiN films onto high speed steels
Authors: Yamamoto Syuji , Ichimura Hiroshi
Published: March 2008

The effect of substrate bias voltage on the properties of arc ion-plated TiN films onto high speed steels has been investigated. The high density structure with a large crystallite size grew at the high bias voltage. TiN films deposited by higher bias exhibited strong preferential (111) orientation from XRD. The internal stress of TiN films increased at first with increasing substrate bias voltage; however, it decreased as the bias voltage increased over 100 V. The coating adhesion measured by the scratch tester increased with increasing bias voltage, and this is coupled with a cohesion of films. Cutting performance of TiN coated drills, which increased markedly with increasing substrate bias, has been studied in relation to the physical and chemical properties of deposited films.
Evidence for hydrothermal growth of diamond in the C–H–O and C–H–O halogen system
Authors: Roy Rustum , Ravichandran D. , Ravindranathan P. , Badzian A.
Published: March 2008

Powder x-ray diffraction (XRD) and Raman evidence are presented for the formation of crystalline diamond in the “hydrothermal” pressure-temperature regime 1–5 kbars, <1000 °C. Two different methods appear to enable diamond to nucleate and grow. One—a Low Pressure Solid-State Source (LPSSS) route—utilizes special solid precursors, especially low temperature glassy carbon (GC-500), with very fine diamond seeds in sealed gold capsules with H2O at, say, 800 °C and 1 kbar. The other includes pyrolysis of highly selected organic solid/liquid precursors (halogenated aliphatics such as iodoform) onto similar diamond seeds. In all the cases, powder x-ray diffraction evidence shows a marked increase of the diamond XRD peaks, likewise the Raman spectrum shows a strong increase of the 1331 cm−1 line. However, the crystals apparently are too small to be seen in the SEM. TEM diffraction data, on the other hand, seem to lend support to the possibility of all the grown diamonds being very small.
Nanocrystalline BaTiO3 from freeze-dried nitrate solutions
Authors: McHale J. M. , McIntyre P. C. , Sickafus K. E. , Coppa N. V.
Published: March 2008

An aqueous, all nitrate, solution-based preparation of BaTiO3 is reported here. Rapid freezing of a barium and titanyl nitrate solution, followed by low temperature sublimitation of the solvent, yielded a freeze-dried nitrate precursor which was thermally processed to produce BaTiO3. XRD revealed that 10 min at temperatures ≧600 °C resulted in the formation of phase pure nanocrystalline BaTiO3. TEM revealed that the material was uniform and nanocrystalline (10–15 nm). The high surface to volume ratio inherent in these small particles stabilized the cubic phase of BaTiO3 at room temperature. It was also found that the average particle size of the BaTiO3 produced was highly dependent upon calcination temperature and only slightly dependent upon annealing time. This result suggests a means of selection of particle size of the product through judicious choice of calcination temperature. The experimental details of the freeze-dried precursor preparation, thermal processing of the precursor, product formation, and product morphology are discussed.
Investigation of low- and high-resistance Ni–Ge–Au ohmic contacts to n+ GaAs using electron microbeam and surface analytical techniques
Authors: Lumpkin Nancy E. , Lumpkin Gregory R. , Butcher K. S. A.
Published: March 2008

A process for the formation of low-resistance Ni–Ge–Au ohmic contacts to n+ GaAs has been refined using multivariable screening and response surface experiments. Samples from the refined, low-resistance process (which measure 0.05 ± 0.02 Ω · mm) and the unrefined, higher resistance process (0.17 ± 0.02 Ω · mm) were characterized using analytical electron microscopy (AEM), transmission electron microscopy (TEM), scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS), and x-ray photoemission spectroscopy (XPS) depth profiling methods. This approach was used to identify microstructural differences and compare them with electrical resistance measurements. Analytical results of the unrefined ohmic process sample reveal a heterogeneous, multiphase microstructure with a rough alloy-GaAs interface. The sample from the refined ohmic process exhibits an alloy which is homogeneous, smooth, and has a fine-grained microstructure with two uniformly distributed phases. XPS analysis for the refined ohmic process sample indicates that the Ge content is relatively depleted in the alloy (relative to the deposited Ge amount) and enriched in the GaAs. This is not evidenced in the unrefined ohmic process sample. Our data lead us to conclude that a smooth, uniform, two-phase microstructure, coupled with a shift in Ge content from the post-alloy metal to the GaAs, is important in forming low-resistance ohmic contacts.
Ion beam mixing, diffusion, and phase stability in Cu/Al2O3 interfaces
Authors: Neubeck K. , Hahn H. , Balogh A. G. , Baumann H. , Bethge K. , Rück D. M. , Angert N.
Published: March 2008

Ion beam mixing, diffusion properties, and phase stability have been investigated in Cu/Al2O3 bilayer samples. Specimens were prepared by vapor deposition and irradiated with 150 keV Ar+ ions up to a fluence of 1.5 · 1017 Ar+/cm2. Sample temperature under irradiation was varied between 77 K and 673 K. The mixing behavior was studied by analyzing the concentration depth profiles, determined by Rutherford Backscattering Spectroscopy. It was found that mixing efficiencies of Cu, Al, and O scale with Ar+ fluence. Radiation enhanced diffusion (RED), observed above room temperature, is separated from ballistic mixing and high temperature diffusion. The migration enthalpy for interdiffusion in the RED region (between RT and 300 °C) was estimated to be approximately 0.3 eV. Sputtering yields depending on temperature gradient near to sample and phase stability versus ion dose and temperature are also discussed.
Microstructural development of BaTiO3powders synthesized by aqueous methods
Authors: Zhao L. , Chien A. T. , Lange F. F. , Speck J. S.
Published: March 2008

The hydrothermal growth of perovskite BaTiO3powders has been studied by transmission electron microscopy. The growth is carried out under high alkaline conditions (pH — 14) achieved with Ba(OH)2. Anatase (TiO2) is used as a titanium source. The perovskite BaTiO3nucleates heterogeneously on anatase TiO2 particles with an epitaxial relationship of (001)TiO2‖ (001)BaTiO3and [010]TiO2‖ [010]BaTiO3. This epitaxial relationship preserves the parallel alignment of the oxygen octahedra between the structures. A mosaic misorientation between (001)TiO2and (001)BaTiO3along 〈110〉 is seen in this relationship due to the lattice mismatch between TiO2and BaTiO3. After complete conversion of the anatase to BaTiO3, the BaTiO3particles develop into {111} octahedrons with ∼10 nm {001} and {110} microfacets on the {111} faces. This evolution suggests that {111} becomes the stable crystallographic facet for BaTiO3under highly alkaline conditions.
Waveguide formation of KTiOPO4 by multienergy MeV He+ implantation
Authors: Wang Ke-Ming , Shi Bo-Rong , Ding Pei-Jun , Wang Wei , Lanford W. A. , Zhuo Zhuang , Liu Yao-Gang
Published: March 2008

X-cut potassium titanyl phosphate (KTiOPO4 or KTP) was implanted by multienergy MeV He+ implantation with a total dose of 2 × 1016 ions/cm2 at liquid nitrogen temperature. The energy and dose used are as follows: 3.3 MeV and 2 × 1015 ions/cm2, 3.2 MeV and 4 × 1015 ions/cm2, 3.1 MeV and 4 × 1015 ions/cm2, and 3.0 MeV and 1.0 × 1016 ions/cm2 to reduce tunneling effect. The 22 dark modes were measured by the isosceles prism coupling method. The 15 bright modes were observed after 250 °C, 60 min annealing. The result shows that the waveguide formation of KTiOPO4 implanted by MeV He+ is not strongly dependent on the cut direction, which is different from the waveguide formation of KTiOPO4 by ion exchange process.
Cation sublattice stacking faults in Cu-rich chalcopyrite CuInSe2
Authors: Hellman Olof , Tanaka Shun-ichiro , Niki Shigeru , Fons Paul
Published: March 2008

Using transmission electron microscopy, we have found stacking faults on the cation sublattice in the chalcopyrite structure of CuInSe2. These films are grown by molecular beam epitaxy under Cu-rich conditions. These stacking faults are found to extend large distances in the plane of the film, and are not found to be present in samples not grown in Cu-rich conditions. We suggest that this defect is triggered by a Cu-induced transformation of the surface structure of the growing film.
Glass-ceramic sealants for solid oxide fuel cells: Part I. Physical properties
Authors: Ley K. L. , Krumpelt M. , Kumar R. , Meiser J. H. , Bloom I.
Published: March 2008

A family of sealant materials has been developed for use in the solid oxide fuel cell (SOFC) and in other applications in the temperature range of 800–1000 °C. These materials are based on glasses and glass-ceramics in the SrO–La2O3–Al2O3–B2O3–SiO2 system. The coefficients of thermal expansion (CTE) for these materials are in the range of 8–13 × 10−6/°C, a good match with those of the SOFC components. These sealant materials bond well with the ceramics of the SOFC and, more importantly, form bonds that can be thermally cycled without failure. At the fuel cell operating temperature, the sealants have viscosities in the range of 104–106 Pa-s, which allow them to tolerate a CTE mismatch of about 20% among the bonded substrates. The gas tightness of a sample seal was demonstrated in a simple zirconia-based oxygen concentration cell.
Pulsed laser ablation-deposition of La0.5Sr0.5CoO3 for use as electrodes in nonvolatile ferroelectric memories
Authors: Dat R. , Auciello O. , Lichtenwalner D. J. , Kingon A. I.
Published: March 2008

La0.5Sr0.5CoO3 (LSCO) thin films have been deposited on (100) MgO substrates using pulsed laser ablation-deposition (PLAD). The crystallographic orientation of LSCO was found to be dependent on the surface treatment of (100) MgO prior to deposition. PLAD deposition parameters were optimized to yield LSCO films with an RMS surface roughness of 40–50 Å. A smooth surface morphology was reproduced as long as the oxygen content of the LSCO target was preserved. Otherwise, “splashing” occurred which resulted in the transfer of condensed particles from molten spherical globules of LSCO from the target to the substrate. Splashing was subsequently eliminated and smooth surface quality was restored after annealing the LSCO target at 550 °C in oxygen for 3 h. Optical emission spectroscopy (OES) of the LSCO's plume identified excited atomic cobalt neutrals, excited singly ionized strontium and lanthanum, and excited molecular LaO species. Oxygen interaction with the plume produced no new species. Furthermore, the OES data suggest that the observed LaO molecules were not created by the chemical reaction between La and O2 during ablation, but were ejected directly from the target during the PLAD process.
Stick-slip in the scratching of styrene-acrylonitrile copolymer
Authors: Li Kangjie , Ni Beta Yuhong , Li J.C.M.
Published: March 2008

Stick-slip process occurred during the scratch test of styrene-acrylonitrile copolymer. For the first time, a bamboo-like morphology of the scratch track corresponding to the stick-slip phenomenon was observed. A “joint” was formed during the stick stage and during slip a uniform “stem” was made. The period and amplitude of the stick-slip both increase with the vertical load and decrease with the driving speed. A theoretical model is constructed based on the stiffness of the system and the plastic deformation of polymer both in the vertical and horizontal directions. The model assumes no distinction between the coefficients of static and kinetic friction and gives quantitatively consistent results with experiments.
Electrically active organic and polymeric materials for thin-film-transistor technologies
Authors: Lovinger Andrew J. , Rothberg Lewis J.
Published: March 2008

Organic and polymeric materzials have seen a tremendous growth in research in the last five years as potential electroactive elements in thin-film-transistor (TFT) applications. These are driven by the increasing interest in flat-panel-display applications, for which organic and polymeric materials offer strong promise in terms of properties, processability, cost, and compatibility with eventual lightweight, flexible plastic displays. In this review we summarize the current status of our knowledge on the science of these organic and polymeric semiconducting materials. Most of these are based on linear thiophenes, especially a-hexathienyl, which has elicited by far the most attention. Mobility values in the 10−2–10−1 cm2/Vs and especially source-drain current on/off ratios of up to 106 make this a highly promising potential alternative to amorphous silicon. Other thienyl compounds are also discussed, as are polymeric analogues. A brief discussion of technological potential, limitations, and problems that need to be overcome is given at the end.
Mechanical behavior of MgO-whisker reinforced (Bi, Pb)2Sr2Ca2Cu3Oy high-temperature superconducting composite
Authors: Yuan Y. S. , Wong M. S. , Wang S. S.
Published: March 2008

The inherently weak mechanical properties of bulk monolithic high-temperature superconductors (HTS) have been a concern. Properly selected reinforcements in fiber and whisker forms have been introduced to the HTS ceramics to improve their mechanical properties. In this paper, mechanical behavior of a MgO-whisker reinforced Pb-doped Bi-2223 (BPSCCO) HTS composite fabricated by a solid-state processing method is studied. The (MgO)w/BPSCCO HTS composite has been shown to exhibit excellent superconducting properties. Elastic properties, strengths, and notched fracture toughnesses of both the monolithic BPSCCO and the (MgO)w/BPSCCO HTS composite are investigated. Detailed mechanical properties are reported for the first time for the (MgO)w/BPSCCO HTS composite. Mechanisms of strengthening and toughening in the MgO-whisker-reinforced HTS composite are also discussed.
Highly conducting transparent thin films based on zinc oxide
Authors: Wang Ruiping , King Laura L. H. , Sleight Arthur W.
Published: March 2008

Doped zinc oxide thin films were prepared by rf magnetron sputtering using the dopants Al, Ga, In, and Ge. The best results were obtained with Al and Ga doping where room temperature conductivities were as high as 1600 and 1800 ohm-1cm-1, respectively. Hall measurements were performed at 77 K and 298 K. The Hall mobility as in the range of 9 to 22 cm2/Vs, and there was generally very little temperature dependence of the mobility or conductivity. Cation doping levels were as high as 10 at. %, but the conductivities did not increase beyond 3 at. % doping level. For films with high conductivity, electron carrier concentrations from Hall measurements were significantly lower than the concentrations of dopants. Optical measurements on the films showed that the average transmittance though the visible range is higher than 85%. The measurements also indicated a blueshift of the absorption edge with doping.
Thermally induced solute migration in 2011 Al alloy implanted with Ti, Cr, or Al ions
Authors: Chu J. W. , Evans P. J. , Sood D. K.
Published: March 2008

A systematic experimental study of solute migration during thermal annealing and oxidation of type 2011 aluminum alloy is described. Specimens of this alloy were implanted with Ti, Cr, or Al ions to doses in the range 2 × 1015–2 × 1017ions cm-2. The implanted substrates were annealed at 500 °C in vacuum or an oxygen atmosphere and analyzed with Rutherford backscattering and scanning electron microscopy. Changes to the alloy composition resulting from segregation of constituents in the near surface region occurred for both implanted and unimplanted specimens, though the effect was substantially more pronounced following implantation. In addition, segregation was affected by the type and dose of the implanted ion. For the Ti implants under oxidizing conditions, the Ti ions were found to diffuse toward the surface and form a thick oxide layer. Segregation of Cu and Pb/Bi then occurred below this oxide layer. In contrast, implanted Cr ions under similar conditions were observed to diffuse into the substrate with only a thin oxide layer being formed at the surface. Consequently, Cu and Pb/Bi segregated close to the surface.
Electron microscopic interfacial analysis of diamond film grown on silicon substrate
Authors: Jiang N. , Hatta A. , Ito T. , Zhang Z. , Sasaki T. , Hiraki A.
Published: March 2008

We have investigated the near-interface characterization of diamond films grown on Si(100) substrates by means of a hot-filament chemical-vapor-deposition (HFCVD) method using high-resolution-electron microscopy (HREM). Atomic scale study of the diamond/Si interface reveals that on the top of the amorphous intermediate layer, there exists a precursor phase which seems to be a diamond-like structure, which provides a suitable site for subsequent diamond nucleation. High density crystal defects directly originate from the precursor phase. HREM images also reveal that during the deposition Si recrystallizes in some damaged areas left by pretreatment, such as scratching grooves. In the recrystallization process twins and microtwins can be formed, and amorphous solid is left in the Si crystals.
Spontaneous ferromagnetism at room temperature in oxygen-rich dicalcium cuprate Ca2CuO3+δ
Authors: Abdelgadir Mahjoub A. , Burrows Richard S. , McDaniel Darl H.
Published: March 2008

Stoichiometric Ca2CuO3, having square-planar Cu-chains [C. L. Teske and H. Müller-Buschbaum, Z. Anorg. Allg. Chem. 379, 234 (1970); M. Hjorth and J. Hyldtoft, Acta Chem. Scand. 44, 516 (1990)], is expectedly antiferromagnetic due to 1D intrachain superexchange [K. Okuda, S. Noguchi, K. Konishi, H. Deguchi, and K. Takeda, J. Magn. Magn. Mater. 104–107, 817 (1992)]. Nonetheless, we report remarkable spontaneous ferromagnetism at 293 K after sintering, prominently in oxygen. This apparently introduced excess oxygen at vacant quasioctahedral sites, promoting spin-flip and ferromagnetic interchain coupling. Thermogravimetry (TGA) revealed excess oxygen, ≈0.17 O/Cu. X-ray diffraction (XRD) yielded a comparatively smaller unit cell. Ferromagnetism disappeared by oxygen depletion, mimicking reported nonmagnetism of Ca2CuO3−δ [Okuda et al. (1992)]. Elemental analysis showed insignificant magnetic impurity traces. Tc ranged between 680 K and 723 K, depending on freshness and purity. Saturation magnetization varied with processing, optimally 0.30 A · m2/kg at 1.0 T applied field. Coercivity and remanence varied with purity.
Structure and physical properties of sodium antimony germanate glasses
Authors: Pal M.
Published: March 2008

The structure and physical properties of sodium antimony germanate glasses with compositions 10Na2O − xSb2O3 − (90 − x)GeO2, x = 10−30 mol%, prepared by the melt-quenched route have been studied. It is observed from x-ray diffraction, SEM, density and oxygen molar volume, infrared (IR), differential thermal analysis (DTA), and optical absorption that single phase homogeneous glasses with a random network structure can be obtained in this system. The strength and connectivity of the glass network increase with GeO2 content. The main Ge−O stretching vibration also shifts to higher wavelength side. Two oxidation states of antimony, Sb3+ and Sb5+, are present, while the so-called “germanate anomaly” is absent in these glasses. This study discusses the probable structural reasons behind this type of behavior of these glasses.
Thermal expansion of bulk amorphous Zr41.2Ti13.8Cu12.5Ni10Be22.5 alloy
Authors: He Y. , Schwarz R. B. , Mandrus D. G.
Published: March 2008

The linear thermal expansion of the bulk amorphous Zr4.12Ti13.8Cu12 5Ni10Be22.5 (atomic percent) alloy has been measured from 80 K to 773 K. The data for T, Tg were fitted by a model based on the Grüneisen relation and a Debye expression for the heat capacity. From the fit, we deduced the Grüneisen parameter, g = 1.25, and the Debye temperature, QD = 400 K. Annealing the amorphous alloy at 663 K, which is between the glass transition temperature Tg = 623 K and the crystallization temperature Tx = 693 K, causes viscous flow in the sample. This is due to the small viscosity in the undercooled liquid.
A new method for fabricating high performance polymeric thin films by chemical vapor polymerization
Authors: Gaynor Justin F. , Jay Senkevich J. , Desu Seshu B.
Published: March 2008

A vacuum deposition method is presented in which copolymer films are grown from a vinylic monomer chosen for desirable properties and paraxylylene. The concentration of paraxylylene in the final copolymer can be negligibly small if proper deposition conditions, presented here for the first time, are employed. Films of paraxylylene with N-phenyl maleimide deposited at 40 °C, for example, showed thermal stability and FTIR spectra nearly identical with homopolymers of poly(N-phenyl maleimide). Different rate-limiting steps are proposed to explain film composition; paraxylylene is under surface reaction control, while the comonomer obeys mass flow control. This results in a deposition environment extremely rich in comonomer. Growth rates and compositions were consistent with predictions. The initiation reaction did not appear different from homopolymerization of paraxylylene. The general method presented here allows fabrication of vapor-deposited thin films with properties limited primarily by the comonomer employed.
Synthesis of oxide perovskite solid solutions using the molten salt method
Authors: Gopalan Srikanth , Mehta Karun , Virkar Anil V.
Published: March 2008

The molten salt method has in the past been employed to synthesize a large number of compounds at low temperatures. In this work we report the formation of solid solutions of BaTiO3–SrTiO3 and BaZrO3–SrZrO3 using a molten salt eutectic of NaOH–KOH as a solvent. Alkaline earth carbonates and titanium oxide were used as precursors for the titanate system, and alkaline earth carbonates and zirconium oxide were used as precursors for the zirconate system. It was found that both systems form solid solutions throughout the composition range. The implications of these results with regards to the applicability of the molten salt method as a tool to investigate low temperature phase equilibria are discussed.
Microwave-hydrothermal processing of layered anion exchangers
Authors: Komarneni Sridhar , Li Q. H. , Roy Rustum
Published: March 2008

We have compared the microwave-hydrothermal (M-H) processing with conventional hydrothermal (C-H) processing in the preparation of two layered anion exchangers, i.e., Mg3Al(OH)8NO3 · nH2O and Ni1-xZn2x(OH)2(CH3COO)2x · nH2O. Both these phases can be crystallized more rapidly (an order of magnitude) under M-H processing compared to C-H processing. The above layered mixed basic salt of Ni and Zn was found to exhibit very high selectivity for PO4= (Kd = 15,000). Its order of selectivity for various anions in the presence of 0.1 N̲ NaC1 (ratio of C1- to anion in question is 100) increases as follows: PO4= ≫ SO4= > NO3-.
In-depth and ion image analysis of minor and trace constituents in V–Cr–Ti alloy welds
Authors: Odom Robert W. , Grossbeck Martin L.
Published: March 2008

This paper describes the application of dynamic secondary ion mass spectrometry (SIMS) to the study of the chemistry of welds in V–Cr–Ti alloys and presents preliminary data on the distribution of minor and trace elements (H, C, N, O, P, S, and C1) in welds produced by gas tungsten arc (GTA) and electron beam techniques. The motivation for this research is to develop techniques that determine correlations between the concentration and distribution of trace elements in alloy metal welds and the physical properties of the weld. To this end, quantitative SIMS techniques were developed for N, O, and S analysis in vanadium alloy welds using an ion implantation/relative sensitivity factor methodology. The data presented in this paper demonstrate that trace compositions and distributions of selected welds correlate, at least qualitatively, with such properties as microhardness and tensile elongation. These data support continuing these investigations to develop microanalysis methods that quantitatively correlate weld composition with mechanical properties.
Ferroelasticity of the displacive tetragonal phase in Y2O3 partially stabilized ZrO2 (Y-PSZ) single crystals
Authors: Martínez-Fernández J. , Jiménez-Melendo M. , Domínguez-Rodríguez A.
Published: March 2008

Ferroelasticity of the tetragonal displacive (t′) phase was studied on 4.7 mol% Y2O3 partially stabilized zirconia single crystals. Samples were deformed at 1400 °C at constant strain rate to induce the ferroelastic behavior. Domain reorientation due to the applied stress has been studied as a function of the compression axis and aging time at 1600 °C. Domain switching was found in the as-received and 2-h-aged crystals deformed along the 〈100〉 direction, in which an exceptional high flow stress was reached (>700 MPa). Transmission electron microscopy observations were performed on deformed and undeformed crystals to study the microstructural changes associated with the domain switching. Incremental strain steps on the stress-strain curves and surface texture on the lateral faces of the deformed samples were correlated with the microstructural evidence.
Fabrication and structural analysis of ZnO coated fiber optic phase modulators
Authors: Fox G. R. , Setter N. , Limberger H. G.
Published: March 2008

Fiber optic modulators were fabricated by coating optical fibers with electrode and piezoelectric ZnO layers. The techniques of piezoelectric fiber optic modulator (PFOM) fabrication are presented, and the microstructure and crystallographic texture of the coatings are analyzed. In order to produce thick (approximately 5 μm) ZnO coatings, it was necessary to study the reactive dc magnetron sputtering process in O2/Ar gas mixtures under conditions close to the transition between an oxidized and nonoxidized Zn target surface. In situ quartz crystal microbalance measurements of the deposition rate revealed thee distinct regions in the deposition rate (R) vs oxygen partial pressure behavior, at constant total pressure, for sputtering under conditions that provided an oxidized Zn target surface. Additionally, a transition between oxygen and argon dominated sputtering as observed by varying the sputtering pressure while maintaining a constant The transition between oxygen and argon dominated sputtering influences R to varying extents within the three R vs regions for an oxidized target surface. Correlations among the cathode current and voltage, deposition rate, and gas flow rate are presented to give a better understanding of the reactive sputtering processes occurring at the oxidized Zn target surface. Sputtering conditions optimized for a high ZnO deposition rate were used to produce 〈001〉 radially oriented ZnO fiber coatings for PFOM devices that can produce optical phase shifts as large as 0.38 rad/V.
Effect of nickel addition on the combustion reaction of the Ti–C system during mechanical alloying
Authors: Ye L.L. , Huang J.Y. , Liu Z.G. , Quan M.X. , Hu Z.Q.
Published: March 2008

The explosive reactions or self-propagating high temperature synthesis (SHS) take place during milling Ni20Ti50C30 and Ni50Ti30C20 elemental powder mixtures. The coexistence of agglomerates and powders in products indicates the occurrence of melting and solidification. TiC phase and NiTi compound were obtained during millingNi20Ti50C30, while no compound of nickel and titanium was observed when milling Ni50Ti30C20, the final product of which is TiC and Ni. It is suggested that the explosive reaction is ignited by the heat releasing from initial formation of TiC through heavy collisions of milling balls, and the reaction between Ni and Ti, as well as the existence of Ni–Ti liquid, make the following reaction self-sustained. The variation of the addition of nickel did not affect the reaction time in both compositions, but made the reaction temperature different due to the difference of composition of Ni and Ti. It is estimated that the temperature during the reaction in Ni20Ti50C30 rises above 1112 °C, while in Ni50Ti30C20, it might rise above 1349 °C. However, no phenomenon suggests the melting of pure elemental Ti; the formation of TiC is mainly controlled by the diffusion mechanism in SHS.
Comments on “A new procedure for measuring the decohesion energy for thin ductile films on substrates,” by A. Bagchi, G. E. Lucas, Z. Suo, and A. G. Evans [J. Mater. Res. 9, 1734 (1994)]
Authors: Jørgensen O. , Horsewell A. , Sørensen B. F.
Published: March 2008

A recently proposed method for measuring decohesion energy of ductile films on substrates is discussed. The loading mechanism that causes the decohesion of the ductile film is that of gradually depositing an additional layer, with large residual tensile stresses, on top of the film. Hence, the method involves the decohesion of a bilayer film on a substrate. The suggested method assumes that the unloading of the film is controlled entirely by elasticity. This assumption is a prerequisite for the suggested linear elastic analysis, from which the interfacial debond energy is derived in closed form. However, as is shown in the present comment, large scale yielding can occur in the wake of the crack tip and is prohibitive to the suggested linear elastic analysis. A sufficient condition for the occurrence of said large scale yielding is outlined in the present comment. Indeed it is shown that large scale plasticity must have occurred in the experiments described by Bagchi et al.1
Subglossopalatal Synechia in Association with Cardiac and Digital Anomalies
Authors: Oh Albert K. , Thakuria Joseph , Kimonis Virginia , Mulliken John B.
Published: March 2008

A 1-day-old boy in respiratory distress had a midline soft tissue band between the floor of the mouth and the posterior edge of the hard palate. There was also a soft palatal cleft, cardiac anomalies, and a hypoplastic right fifth finger and toe. Although his airway initially improved following urgent excision of the subglossopalatal band, he continued to have episodic desaturations. A tongue–lip adhesion opened his airway, and he subsequently underwent resection of juxtaductal aortic coarctation and ligation of patent ductus arteriosus and left superior vena cava. Congenital oral synechiae are uncommon. Affected infants often require prompt intervention secondary to respiratory distress and feeding difficulty. Review of the literature indicates that midline subglossopalatal synechia with cardiac and digital anomalies may be in the oromandibular–limb hypogenesis spectrum.
Improving Divergence Time Estimation in Phylogenetics: More Taxa vs. Longer Sequences
Authors: Svennblad Bodil , Britton Tom
Published: March 2008

Maximum Likelihood (ML) is used as a standard method for estimating divergence times in phylogenetic trees. The method is consistent and hence the precision can be improved by analyzing longer sequences. In this paper we show that the precision can be improved also by including more taxa to the existing tree. It is a theoretical study, complemented with simulations, showing that the gain in precision is faster with increasing sequence length than with increasing number of taxa.We further compare the results of estimating divergence times using Maximum Likelihood with the much faster and less complex estimation method of Mean Path Length (MPL), which works with the evolution model of Jukes-Cantor (1969). It is shown that MPL is as good as ML in estimating divergence times of nodes that are located near the root in the tree, but ML is better in estimating the divergence times of nodes lower down.
Financial Hypocrisy
Authors: Stiglitz Joseph E.
Published: March 2008

Ten years after the East Asian crisis, Joseph E. Stiglitz reviews what we have learned and asks how those lessons apply to the current sub-prime credit debacle.
Intergenerational Earnings Mobility in Italy
Authors: Mocetti Sauro
Published: March 2008

This paper contributes to the growing number of studies on intergenerational mobility by providing a measure of earnings elasticity for Italy. The absence of an appropriate data set is overcome by adopting the two-sample two-stage least squares method. The analysis, based on the Survey of Household Income and Wealth, shows that intergenerational mobility is lower in Italy than it is in other developed countries. We also examine the reasons why the long-term labor market success of children is related to that of their fathers.
Common Variants in Maturity-Onset Diabetes of the Young Genes and Future Risk of Type 2 Diabetes
Authors: Holmkvist Johan , Almgren Peter , Lyssenko Valeriya , Lindgren Cecilia M. , Eriksson Karl-Fredrik , Isomaa Bo , Tuomi Tiinamaija , Nilsson Peter , Groop Leif
Published: March 2008

OBJECTIVE—Mutations in the hepatocyte nuclear factor (HNF)-1α, HNF-4α, glucokinase (GCK), and HNF-1β genes cause maturity-onset diabetes of the young (MODY), but it is not known whether common variants in these genes predict future type 2 diabetes.

RESEARCH DESIGN AND METHODS—We tested 14 previously associated polymorphisms in HNF-1α, HNF-4α, GCK, and HNF-1β for association with type 2 diabetes–related traits and future risk of type 2 diabetes in 2,293 individuals from the Botnia study (Finland) and in 15,538 individuals from the Malmö Preventive Project (Sweden) with a total follow-up >360,000 years.

RESULTS—The polymorphism rs1169288 in HNF-1α strongly predicted future type 2 diabetes (hazard ratio [HR] 1.2, P = 0.0002). Also, SNPs rs4810424 and rs3212198 in HNF-4α nominally predicted future type 2 diabetes (HR 1.3 [95% CI 1.0–1.6], P = 0.03; and 1.1 [1.0–1.2], P = 0.04). The rs2144908 polymorphism in HNF-4α was associated with elevated rate of hepatic glucose production during a hyperinsulinemic-euglycemic clamp (P = 0.03) but not with deterioration of insulin secretion over time. The SNP rs1799884 in the GCK promoter was associated with elevated fasting plasma glucose (fPG) concentrations that remained unchanged during the follow-up period (P = 0.4; SE 0.004 [−0.003–0.007]) but did not predict future type 2 diabetes (HR 0.9 [0.8–1.0], P = 0.1). Polymorphisms in HNF-1β (transcription factor 2 [TCF2]) did not significantly influence insulin or glucose values nor did they predict future type 2 diabetes.

CONCLUSIONS—In conclusion, genetic variation in both HNF-1α and HNF-4α predict future type 2 diabetes, whereas variation in the GCK promoter results in a sustained but subtle elevation of fPG that is not sufficient to increase risk for future type 2 diabetes.
Central Nervous System Neuropeptide Y Signaling Modulates VLDL Triglyceride Secretion
Authors: Stafford John M. , Yu Fang , Printz Richard , Hasty Alyssa H. , Swift Larry L. , Niswender Kevin D.
Published: March 2008

OBJECTIVE—Elevated triglyceride (TG) is the major plasma lipid abnormality in obese and diabetic patients and contributes to cardiovascular morbidity in these disorders. We sought to identify novel mechanisms leading to hypertriglyceridemia. Resistance to negative feedback signals from adipose tissue in key central nervous system (CNS) energy homeostatic circuits contributes to the development of obesity. Because triglycerides both represent the largest energy depot in the body and are elevated in both the plasma and adipose in obesity and diabetes, we hypothesized that the same neural circuits that regulate energy balance also regulate the secretion of TGs into plasma.

RESEARCH DESIGN AND METHODS—In normal fasting rats, the TG secretion rate was estimated by serial blood sampling after intravascular tyloxapol pretreatment. Neuropeptide Y (NPY) signaling in the CNS was modulated by intracerebroventricular injection of NPY, receptor antagonist, and receptor agonist.

RESULTS—A single intracerebroventricular injection of NPY increased TG secretion by 2.5-fold in the absence of food intake, and this was determined to be VLDL by fast performance liquid chromatography (FPLC). This effect was recapitulated by activating NPY signaling in downstream neurons with an NPY-Y5 receptor agonist. An NPY-Y1 receptor antagonist decreased the elevated TGs in the form of VLDL secretion rate by 50% compared with vehicle. Increased TG secretion was due to increased secretion of VLDL particles, rather than secretion of larger particles, because apolipoprotein B100 was elevated in FPLC fractions corresponding to VLDL.

CONCLUSIONS—We find that a key neuropeptide system involved in energy homeostasis in the CNS exerts control over VLDL-TG secretion into the bloodstream.
Haptoglobin Genotype
Authors: Costacou Tina , Ferrell Robert E. , Orchard Trevor J.
Published: March 2008

OBJECTIVE—Haptoglobin is a plasma protein that binds free hemoglobin, thereby inhibiting hemoglobin-induced oxidative damage. We investigated the association between the haptoglobin genotype and the incidence of coronary artery disease (CAD) in a cohort of individuals with childhood-onset type 1 diabetes.

RESEARCH DESIGN AND METHODS—Participants from the Epidemiology of Diabetes Complications Study who were free of CAD at study entry and had DNA available were selected (n = 453, mean age 27.1 years, and diabetes duration 18.8 years). CAD was defined as angina, ischemic electrocardiogram, myocardial infarction confirmed by Q-waves on electrocardiogram or hospital records, angiographic stenosis >50%, or revascularization.

RESULTS—The proportions of the cohort with the haptoglobin 1/1, 2/1, and 2/2 genotypes were 11.5, 41.3, and 47.2%, respectively. During 18 years of follow-up, there were 135 (29.8%) incident CAD events. Univariately, the proportion of CAD events increased from 15.4 to 28.3 and 34.6% for haptoglobin 1/1, 2/1, and 2/2, respectively (P = 0.02, P-trend = 0.007). Cumulative incidence (including 33 baseline prevalent cases) also increased from 24.1 to 32.3 and 39.1%, respectively (P = 0.07, P-trend = 0.02). In Cox proportional hazards models adjusting for traditional CAD risk factors, the haptoglobin 2/2 genotype was associated with increased CAD incidence compared with the haptoglobin 1/1 genotype (hazard ratio [HR] 2.21, 95% CI 1.05–4.65, P = 0.04). Although the risk associated with the haptoglobin 2/1 genotype did not reach significance (1.78, 0.84–3.79, P = 0.13), there remained a significant trend across the three groups (P = 0.03).

CONCLUSIONS—These data support the hypothesis that the haptoglobin genotype influences cardiovascular risk in type 1 diabetes.