bluuebunny/crossref_metadata_2025_split huggingface dataset:
H-Diffusion in the H-Storage TiVMnCr Alloys as Deduced from Absorption and Mechanical Spectroscopy Experiments
Authors: Mazzolai Giovanni , Biscarini Andrea , Coluzzi Bruno , Mazzolai Fabio Massimo , Tuissi Ausonio 
Published: April 2011

ABSTRACTThe low H content portion of the PCT absorption curves of the 40Ti-xV-(50-x)Mn-10Cr alloys exhibits a plateau, whose pressure has been determined together with the solubility limit of H in the α–phase (solid solution). The chemical (Dc) and Einstein (DE) diffusion coefficients of H have been deduced from H absorption kinetics (273 K-1100 K) and from mechanical spectroscopy (150 K-200 K), which has revealed a Snoek-type of anelastic relaxation. The combined Arrhenius plot of DE and Dc gives the following parameters for H diffusion: W=0.318±0.005 eV, D0=(4±1)×10−7 m2/s (36 V alloy) and W=0.352±0.005 eV, D0=(5±1)10−7 m2/s (32 V alloy).
On the Thermoelectric Properties of Layered Cobaltates
Authors: Li Qiang 
Published: April 2011

ABSTRACTA study on the thermoelectric properties of layered cobaltates is presented, based on the dynamic mean field theory for strongly correlated electron systems. Electron correlation results in a crossover from coherent quasi-particle excitation at low temperature to incoherent excitation at high temperatures in cobaltates. With an extremely narrow quasi-particle bandwidth (hωc ∼ 50 meV), the thermal destruction of Fermi-liquid occurs at the moderate crossover temperature TM (∼ 200 K), and suggests a new scaling for thermoelectric power S of cobaltates (S ∼ kT/hωc ∼ T/TM) at low temperatures. At high temperatures, the dominating incoherent excitation leads to a weak temperature dependent S, and electric resistivity ρ approaches the Mott-limit ha/e2 ∼ a few mΩ·cm for cobaltates, where a is a lattice constant.
Effects of Antimony on the Thermoelectric Properties of the Cubic Pb9.6SbyTe10−xSexMaterials
Authors: Poudeu Pierre Ferdinand Poudeu , D'Angelo Jonathan , Downey Adam , Pcionek Robert , Sootsman Joseph , Zhou Zhenhua , Palchik Oleg , Hogan Timothy P. , Uher Ctirad , Kanatzidis Mercouri G. 
Published: April 2011

ABSTRACTThe thermoelectric properties of Pb9.6SbyTe10−xSexwere investigated in the intermediate temperature range of 300 – 700 K. The effect of the variation of Sb content (y) on the electronic properties of the materials is remarkable. Samples with compositions Pb9.6Sb0.2Te10−xSex(y = 0.2) show the best combination of low thermal conductivity with moderate electrical conductivity and thermopower. For Pb9.6Sb0.2Te8Se2(x = 2) a maximum figure of merit of ZT ∼ 1.1 was obtained around 700 K. This value is nearly 1.4 times higher than that of PbTe at 700 K. This enhancement of the figure of merit of Pb9.6Sb0.2Te8Se2derives from its extremely low thermal conductivity (∼0.7 at W/m.K at 700 K). High resolution transmission electron microscopy of Pb9.6Sb0.2Te10−xSexsamples shows broadly distributed Sb-rich nanocrystals, which may be the key feature responsible for the suppression of the thermal conductivity.
Fabrication of Grain-Aligned Bulks and Thick Films of Misfit Layered Cobalt Oxides by a Magneto-Scientific Process
Authors: Horii Shigeru , Okamoto Taichi , Kumagai Toshiaki , Uchikoshi Tetsuo , Suzuki Tohru S. , Sakka Yoshio , Shimoyama Jun-ichi , Kishio Kohji 
Published: April 2011

ABSTRACTWe report the preparation of grain-aligned [Ca2CoO3−δ]0.62CoO2 (Ca349) thick films and the conversion of the easy axis of magnetization from the a-axis to the c-axis. The thick films were fabricated by a simultaneous usage of electrophoretic deposition and magnetic alignment methods (MEPD) at high deposition rate with the order of 10 mm/min. Moreover, a multi-layered thick film of Al2O3/Ca349/Al2O3/Ca0.9La0.1MnO3/Al2O3 was also fabricated by the MEPD method by the optimization of condition of each suspension. The conversion of the easy axis was performed crystallochemically for a [Bi2Sr2O4]0.55CoO2 (BiSr222) compound with the easy axis parallel to the a-axis in order to fabricate c-axis grain-oriented bulks by the magnetic alignment method. The substitution of Ca for Sr in the [(Bi0.5Pb0.5)2Sr2O4] block layer induced the change of the easy axis into the c-axis direction, and the magnetic anisotropy was increased by the partial substitution of rare earth elements of Pr, Nd, Tb and Dy for Ca. Using a compound of [(Bi0.5Pb0.5)2(Ca0.8Pr0.2)2O4]0.55CoO2, we have successfully prepared the c-axis grain-aligned bulk by the magneto-scientific method. Our present results indicate that the magneto-scientific method is one of the useful and realistic processes for production of thermoelectric modules.
Thermal Conductivity and Thermoelectric Properties of Novel Rare Earth Boron-Rich Cluster Compounds; Discovery of first undoped n-type B12 icosahedral compound
Authors: Mori Takao 
Published: April 2011

ABSTRACTNovel rare earth boron icosahedral compounds are investigated as potential high temperature thermoelectric materials. REB50-type compounds and a homologous series of RE-B-C(N) compounds were synthesized and the thermal conductivity and thermoelectric properties measured. Seebeck coefficients in excess of 200 μV/K are observed at temperatures above 1000 K for the REB50-type compounds. Strikingly, n-type behavior was observed for REB22C2N and REB17CN. Up to now, non-doped B12 icosahedral compounds like boron carbide have all been p-type. The discovery of an n-type compound is extremely important in terms of the potential development of this class of compounds as viable thermoelectric materials. Low thermal conductivities of κ < 0.03 W/cm/K at room temperature was observed for these rare earth boron cluster compounds. In comparison among the homologous series in which there are rare earth and B6 octahedra layers separated by an increasing number of B12 icosahedra layers, we observe that the thermal conductivity actually increases as the number of boron cluster layers increases. We find that the rare earth B12 icosahedral cluster compounds in which RE atoms occupy voids among the clusters generally appear to have lower thermal conductivity than boron cluster compounds which do not contain RE atoms.
Selective laser melting of high aspect ratio 3D nickel – titanium structures for MEMS applications
Authors: Chalker Paul , Clare Adam , Davies Sean , Sutcliffe Christopher J. , Tsopanos Sozon 
Published: April 2011

ABSTRACTSelective laser melting has been used to build high aspect ratio, three-dimensional NiTi components for the first time. The influence of laser dwell time and raster pitch on the density of NiTi shape memory alloy parts and their resolvable feature sizes are reported. The properties of shape memory springs produced by this method are reported and the application of selective laser melted NiTi components in microelectromechanical devices is discussed.
Low-temperature Preparation of Crystallized Zirconia Films by ECR Plasma MOCVD
Authors: Masumoto Hiroshi , Goto Takashi 
Published: April 2011

ABSTRACTIt is known that zirconia has excellent thermal and chemical stability, and oxide ion conduction. Therefore, YSZ is expected to be used as oxide ion conducting materials, optical mirror materials, catalytic materials and heat-resistant materials. Zirconia films have been fabricated by PVD (ex. sputtering and laser-ablation), chemical vapor deposition (CVD) and sol-gel methods. CVD is capable to prepare high quality zirconia films with excellent conformal coverage; however, deposition temperature of conventional CVD was usually high than PVD. On the other hand, an electron cyclotron resonance (ECR) plasma is high-activity plasma and high quality crystalline films can be obtained at low temperature by using ECR plasma. In the present study, zirconia thin films were prepared at low temperatures on quartz, polycarbonate and polyimide substrates by ECR plasma MOCVD.Zr-hexafluoroacetylacetonato solution was used as a precursor. The source, which was placed in a glass bubbler, was carried into a reactor by Ar gas. A microwave (2.45 GHz, 500 W) was introduced into the ion chamber through a rectangular wave guide. A magnetic field (875 Gauss) was applied to the ion chamber to satisfy the ECR condition. A mirror-type magnetic field (450 Gauss at the substrate stage) was applied in order to raise a plasma density, which results in an increase of the deposition rates of films. Substrate temperature (Ts) was from 30 to 700 C by water-cooling holder and infrared lamp heater. Microwave power was changed from 0 to 900 W. The deposition time was from 30 to 120 minutes.Cubic, monoclinic and tetragonal zirconia films were obtained over Ts=400 C, and cubic and monoclinic zirconia films were obtained below Ts= C. Cubic and monoclinic zirconia films were also obtained at no heating. The deposition rate increased from 10 to 20 nm/min with increasing Ts from no heating to 600 C. Crystallized zirconia films were obtained on polycarbonate and polyimide substrates at no heating. The ECR plasma was significantly effective to prepare crystallized zirconia films at low temperatures.
High aspect ratio etching of GaSb/AlGaAsSb for photonic crystals
Authors: Nilsen Tron Arne , Martinez Anthony , Bugge Renato , Moscho Aaron , Lester Luke F , Fimland Bjørn-Ove 
Published: April 2011

ABSTRACTPhotonic crystal structures defined by interferometric lithography were etched into GaSb and AlGaAsSb with 90% Al content using Inductively Coupled Plasma (ICP) Reactive Ion Etching (RIE) with BCl3 and BCl3/Ar gas mixture. Effects of DC bias, hole diameter, etch time and gas composition, on the etch rate of GaSb were investigated. Hardened photoresist (PR) was used as an etch mask for the experiments.
Structural Defects in InSb Quantum Wells Grown on GaAs (001) Substrates via Al0.09In0.91Sb/GaSb-AlSb Strained Layer Superlattice/AlSb/GaSb Buffer Layers
Authors: Mishima Tetsuya D. , Edirisooriya Madhavie , Santos Michael B. 
Published: April 2011

ABSTRACTStructural defects in InSb quantum well (QW) samples have been investigated by transmission electron microscopy (TEM). Using molecular beam epitaxy, an InSb QW with remotely-doped Al0.09In0.91Sb barriers was grown on a GaAs (001) substrate with buffer layers consisting of, in order from the substrate: 1 μm of GaSb, 1 μm of AlSb, 50 nm of GaSb-AlSb strained layer superlattice (SLS), and 3 μm of Al0.09In0.91Sb. Cross-sectional TEM analysis indicates that high densities of threading dislocations (TDs) are created at the two highly lattice-mismatched interfaces, the Al0.09In0.91Sb/GaSb-AlSb SLS and the GaSb/GaAs interfaces. Pairs of stereo images taken from plan-view TEM (PV-TEM) specimens show that TDs propagate through the InSb QW layer. The densities of TDs and micro-twin (MT) defects measured by PV-TEM are 9×108/cm2 and 4×103/cm, respectively. These values are worse than those in an InSb QW layer grown with a different buffer layer by a factor of ∼4. The different buffer layer contains an InSb interlayer that effectively filters out both TDs and MTs. Adopting an interlayer structure and reducing the GaSb and AlSb layer thickness may make it possible to fabricate a lower-defect-density yet thinner InSb QW sample with the type of buffer layer examined in this study.
Epitaxial growth and characterization of BP on Si(100) substrate for use in c-GaN study
Authors: Takeuchi Tomohiko , Nishimura Suzuka , Sakuma Tomoyuki , Matumoto Satoru , Terashima Kazutaka 
Published: April 2011

ABSTRACTBoronmonophosphide(BP) is one of the suitable materials for a buffer layer between the c-GaN(100) and Si(100) substrates. The growth of BP layer was carried out by MOCVD on Si(100) substrate of 2 inch in diameter. The growth rate was over 2 μm/h without any troubles such as the bowing or cracking. In addition, the thickness of BP epitaxial layer was uniform over a wide area. A careful analysis of x-ray diffraction suggested that the growth of BP epitaxial layer inherited the crystal orientation from Si(100) substrate. Cross-sectional TEM images showed some defects like dislocations near the interface between BP layer and Si substrate. The Hall effect measurements indicated that the conduction type of BP films grown on the both n-Si and p-Si substrates was n-type without impurity doping, and that the mobility and carrier concentrations were typically 357cm2/Vs and 1.5×1020cm−3(on n-Si) and 63cm2/Vs and 1.9×1019cm−3(on p-Si), respectively. In addition, c-GaN was grown on the substrate of BP/Si(100) by RF-MBE.
Stabilization of mixed valencies in Cu, Zn-based oxides
Authors: Nestour Anne Le , Gaudon Manuel , Tréguer-Delapierre Mona , Andriessen Ronn , Demourgues Alain 
Published: April 2011

ABSTRACTCu and Zn-based oxides have been developed for the last decades because of their remarkable electronic properties and their relevant UV-Visible-NIR absorption properties. Cu in oxides can adopt various oxidation states (+I, +II, +III) stabilized in various environments (h, Td, D4h, C4v, D2h, Oh). Divalent copper cations can occupy Td or Oh sites in zinc aluminate spinel network. Solid state routes lead to homogeneous phases with Zn1−xCuxAl2O4 compositions. Depending on the inversion rate in the spinel matrix, various absorption bands have been identified in the UV-Visible-CNIR spectrum. The synthesis of the zinc-aluminate spinel solid solution Zn1−xCuxAl2O4 by an esterification route led to monocrystalline nanosized oxides. Two intense absorption bands at 300 and 500 nm can be attributed to charge transfer phenomena between oxygen and Cu2+ cations in tetrahedral and octahedral coordinations. Two other less intense absorption bands centred at 800 nm and 1500 nm are also appearing when the copper rate in the spinel increases but their relative intensity are not in good agreement with those observed in the case of the solid-state synthesis. In the case of the esterification route, the absorption band at 800 nm is much more intense than in the case of the solid-state synthesis. It can only be explained either by a deviation to the centrosymmetric character of octahedral sites or by the occurence of a non negligible amount of monovalent copper cations which give electronic transitions in this energy range. A magnetic study correlated to EPR measurements confirms the occurence of a mixed valence state for copper cations in the solid solution Zn1−xCuxAl2O4. EPR spectra at T=4K show for the small concentration of Cu2+ (x<0.10) a strong anisotropic signal due to the presence of Cu2+ ions in a distorted octahedral symmetry (gx=2.07, gy= 2.15 gz=2.23). Moreover the hyperfine structure, identified on EPR spectra tend to disappear as the compounds are annealed under air because the content of paramagnetic centers Cu2+ (3d9) as well as their interactions become significant. Furthermore, the color changes drastically with the Cu+ (3d10) content. Finally the structural features and UV-Visible-NIR absorption properties of copper-zinc aluminates will be discussed and compared to Cu-doped ZnO.
Characterization of a Dominant Electron Trap in GaNAs Using Deep-Level Transient Spectroscopy
Authors: Johnston Steven W. , Kurtz Sarah R. , Crandall Richard S. 
Published: April 2011

ABSTRACTDilute-nitrogen GaNAs epitaxial layers grown by metal-organic chemical vapor deposition were characterized by deep-level transient spectroscopy (DLTS). For all samples, the dominant DLTS signal corresponds to an electron trap having an activation energy of about 0.25 to 0.35 eV. The minority-carrier trap density in the p-type material is quantified based on computer simulation of the devices. The simulations show that only about 2% of the traps in the depleted layer are filled during the transient. The fraction of the traps that are filled depends strongly on the depth of the trap, but only weakly on the doping of the layers and on the conduction-band offset. The simulations provide a pathway to obtain semi-quantitative data for analysis of minority-carrier traps by DLTS.
Towards a Novel Broadband Spectrally Dynamic Solid State Light Source
Authors: Nicol David , Gupta Shalini , Li Nola , Asghar Ali , Graugnard Elton , Summers Christopher , Ferguson Ian 
Published: April 2011

AbstractThe developments of two major components of a three terminal dual wavelength LED for excitation of multiple phosphors are described. Such a configuration will be novel Broadband Spectrally Dynamic Light Emitting Diode (BSDLED). First, work towards a functional tunnel junction in the GaN system is discussed. The developments of p+ and n+ GaN layers are specifically discussed in relation to their use in a buried current spreading contact layer. Second, the analysis of several phosphors and their application in a spectrally dynamic source is explored. The response to multiple wavelengths of the phosphors is analyzed to create a light source that can be tuned in “real time” to a wide range of correlated color temperatures.
Cu Induced Optical Transitions in MOCVD Grown Cu Doped GaN
Authors: Senawiratne Jayantha , Strassburg Martin , Payne Adam , Asghar Ali , Fenwick William , Li Nola , Ferguson Ian , Dietz Nikolaus 
Published: April 2011

AbstractOptical and structural properties of in situ Cu doped GaN thin films grown on sapphire substrates were optically investigated by means of Raman, photoluminescence (PL), and absorption spectroscopy. Different Cu concentrations in the films were analyzed by secondary ion mass spectroscopy (SIMS) and found to vary from 2×1016cm-3to 5×1017cm-3. Raman studies confirmed high crystalline quality of GaN:Cu with no major structural damages due to Cu incorporation. PL investigation revealed that the origin of the emission around 2.4 eV is most likely due to Cu incorporation. The electrical conductivity of the samples was analyzed by Hall measurements and the found semi-insulating behavior was assigned to the compensation of intrinsic donors by the deep Cu acceptor states.
Preparation of Recycled Polycarbonate/Acrylonitrile-Butadiene-Styrene Composites
Authors: Jung Woo-Hyuk , Tortorella Nathan , Beatty Charles L. , McCarthy Stephen P. 
Published: April 2011

AbstractThe front cover of Motorola cellular phone housings were ground to the same size as original particles prior to use by a knife mill. The mixtures contained 15.2 wt% metals, 1.9 wt% foams, 1.4 wt% rubbers and 81.4 wt% thermoplastics where the major component was a polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) blend. The separation of the thermoplastic scraps was performed using the sink-float process in water and salt solution. The impact modification of all housing containing six thermoplastic parts was carried out by the addition of a polyolefin elastomer called as the functionalized polyethylene (PE). Unprinted glass fiber reinforced epoxy circuit boards were size reduced and pulverized using the knife mill and hammer mill. The ground epoxy circuit boards were then classified with a set of testing sieves using Gyro sifter, and their mean diameters were calculated by means of particle size distribution analysis. Izod impact strengths at two temperatures, tensile tests, scanning electron microscopy (SEM) on the fracture surfaces, and dynamic mechanical spectroscopy were performed to characterize the alloys and mixtures compounded by a batch mixer and a twin screw extruder.
The Ultrastructure of Brachiopod Shells - A Mechanically Optimized Material with Hierarchical Architecture
Authors: Griesshaber Erika , Kelm Klemens , Sehrbrock Angelika , Job Reinhart , Schmahl Wolfgang W. , Mader Werner 
Published: April 2011

AbstractBrachiopod shells consist of low-magnesium calcite and belong to one of the most intriguing species for studies of marine paleoenvironments, variations in oceanographic conditions and ocean chemistry [6, 7, 11 – 13]. We have investigated the ultrastructure together with nano- and microhardness properties of modern brachiopod shells with transmission electron microscopy (TEM), scanning electron microscopy (SEM), nanoindentation and Vickers microhardness analyses. Brachiopod shells are structured into several layers, a thin, outer, hard, protective primary layer composed of randomly oriented nanocrystalline calcite, which is followed inward towards the soft tissue of the animal by a much softer shell segment (secondary layer) built of long calcite fibres, stacked parallely into blocks. The hardness distribution pattern within the shells is non-uniform and varies on scales as small as a few tens of microns. Our results show that the hardness of this biomaterial is controlled by two predominant features: (1.) The morphological orientation of the calcite fibres (not by the crystallographic orientation of the fibres), and (2.) the amount and distribution pattern of organic material between and within the calcite crystals.
Assembly Design Concepts and Methods of Tailoring of CNT Orientation and Dispertion for Damping/Dynamic Properties of Nanoparticle-Reinforced Multifunctional Materials
Authors: Kireitseu Maksim , Tomlinson G.R. , Williams R.A. 
Published: April 2011

AbstractIn this paper, the concepts of nanotechnology-based fan blade have been introduced and CNT-reinforced hollow micro-balloon-based syntactic foams/composites and damping coatings have been applied so as to develop the next generation aerospace components. The focus in this paper is directed toward the development of the next generation of vibration damping systems, providing a road map to manufacturing technology and design solutions.
Complexes of conjugated polymer and carbon nanotubes: does blending with nanotubes influence the ordering of semi-crystalline polymers?
Authors: Goh Roland , Waclawik Eric Rolfe , Motta Nunzio , Bell John Marcus 
Published: April 2011

AbstractA detailed study of poly(alkylthiophene) self-assembly and organization on single-walled carbon nanotubes is presented. We show that ordered polymer domains are formed when a conjugated polymer is blended with small amounts of carbon nanotubes. By correlating the lowest energy feature in the absorption spectra of the polymer with ordering, we demonstrate that the degree of ordering in the polymer is enhanced when it is blended with carbon nanotubes. Furthermore, we elucidated the conformation of the polymer chain when it is absorbed onto the nanotube surface and imaged the high degree of ordering in the polymer/carbon nanotube complex by microscopy.
Static Microindentation and Displacement-Sensitive Indentation Tests on Undoped GaAs
Authors: Wang Shanling , Zhang Ming , Bradby Jodie , Pirouz Pirouz 
Published: April 2011

AbstractStatic microindentation as well as dynamic displacement-sensitive indentation (DSI) tests have been performed between RT and 450°C on the (001) surface of undoped GaAs. In the static tests, the 4-fold symmetry reduces to 2-fold symmetry in some studied range of temperatures. The temperature dependence of the indentation diagonal and the crack length has been measured and, from disappearance of indentation cracks, the indentation brittle-to-ductile transition (IBDT) temperature TIBDT has been estimated. It is found that the temperature at which a transition in the energy density in DSI tests occurs nearly coincides with TIBDT as measured by static indentation tests; for undoped GaAs, both these temperatures are in the range of 200-225°C. This is about 100°C lower than the true brittle-to-ductile temperature TBDT, as measured by 4-point bending tests. The difference between TIBDT and TBDT is explained in terms of the superimposed hydrostatic stress component in the indentation experiments, and the crack asymmetry around the indentations is interpreted in terms of the different mobilities of α and β dislocations in GaAs.