bluuebunny/crossref_metadata_2025_split huggingface dataset:
Direct observation of an ordered arrangement of vacancies and large local thermal vibration in rhenium silicide by Cs-corrected STEM
Authors: Harada Shunta , Tanaka Katsushi , Kishida Kyosuke , Okamoto Norihiko L , Endo Noriaki , Okunishi Eiji , Inui Haruyuki 
Published: April 2011

ABSTRACTThe crystal structure of thermoelectric rhenium silicide with an ordered arrangement of vacancies is investigated by utilizing spherical aberration (Cs) corrected scanning transmission electron microscopy (STEM) combined with synchrotron X-ray diffraction and conventional transmission electron microscopy. By STEM Cs corrected imaging, we can clearly observe Si vacancies in rhenium silicide, which is impossible without Cs correction. In addition, significantly reduced contrast levels are noted in STEM images for particular Si sites near vacancies. From the STEM image simulation, the reduced contrast levels are concluded to be due to anomalously large local thermal vibration of these Si atoms. The crystal structure of rhenium silicide can be successfully refined by the synchrotron X-ray diffraction starting with the deduced structure model from the STEM images and the occurrence of large local thermal vibration can be qualitatively confirmed. Furthermore, we confirm the validity of the refined crystal structure of rhenium silicide by comparing experimental images with simulated image generating with the refined crystal structure parameters.
Mo Fiber Reinforced NiAl Composites Produced by Directional Solidification – Process, Microstructure and Mechanical Properties
Authors: Hu L. , Bogner S. , Hu W. , Bührig-Polaczek A. , Gottstein G. 
Published: April 2011

ABSTRACTComposites with a eutectic composition NiAl-9at.%Mo were produced by controlled directional solidification (DS) so that refractory metallic Mo fibers were precipitated and aligned in the NiAl matrix parallel to the solidification direction through the eutectic reaction. Such NiAl composites can be used for structural applications at high temperatures (> 1000 °C), for example as blade material for modern gas turbines. The microstructure of the composites was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The interface fine structure between Mo fiber and NiAl matrix was studied by high resolution TEM (HRTEM). Mechanical properties were measured by tensile tests at 700 °C and 1100 °C. Accordingly, a correlation of the DS parameters, microstructure and mechanical properties was established.
Local Stress-strain Structure in CVD Diamond Observed by Raman Peak-shift Mapping
Authors: Kato Yukako , Umezawa Hitoshi , Teraji Tokuyuki , Shikata Shin-ichi 
Published: April 2011

ABSTRACTSemiconductor epitaxial CVD single crystal diamond is considered a potential material for power devices because of its unique characteristics. In the discussion on the relationship between crystal quality and device performance, the atomic purity and defect concentration have been considered; however, the information on the local stress-strain distribution in a single crystal is not sufficient. In this paper, the local stress-strain distribution of the epitaxial CVD single crystal diamond is quantitatively examined using the birefringence and cathodoluminescence images and the Raman peak-shift map. From the Raman peak-shift map, the local stress-strain is estimated and the stress is found to range from -67 MPa to +160 MPa in the observed area.
The Li-adsorbed C(100)-(1x1):O Diamond Surface
Authors: O’Donnell Kane M. , Martin Tomas L. , Fox Neil A. , Cherns David 
Published: April 2011

ABSTRACTThis paper presents density functional theory results for the Li-adsorbed C(100)-(1x1):O system. Previously it has been shown that at a single monolayer coverage, the binding energy for Li on oxygenated C(100) diamond is substantially higher than that of heavier alkali metals, while at the same time, the presence of the lithium generates a large shift in the diamond workfunction. The system is therefore promising for electronics applications involving diamond. Here, further calculations are presented showing that additional Li atoms above 1ML coverage are far less strongly bound, suggesting the 1ML surface is the most useful for vacuum microelectronic applications.
Determination of Boron Concentration in Doped Diamond Films
Authors: Demlow S.N. , Grotjohn T.A. , Hogan T. , Becker M. , Asmussen J. 
Published: April 2011

ABSTRACTThe electrical characteristics of high quality single crystal boron-doped diamond are studied. Samples are synthesized in a high power-density microwave plasma-assisted chemical vapor deposition (CVD) reactor at a pressure of 160 Torr. The boron-doped diamond films are grown using diborane in the feedgas at concentrations of 0-0.25 ppm, and are compared to those grown previously with 1-10 ppm. The boron acceptor concentration is investigated using infrared absorption, and compared to the boron concentration obtained by SIMS. A four point probe is used to study the conductivity. The temperature dependent conductivity is analyzed to determine the boron dopant activation energy.
Homoepitaxial growth of high quality thick diamond film with microwave plasma CVD technique
Authors: Wang Hong-Xing , Ishigaki Noritaka , Ohkawa Toshiki , Kokami Shinichi , Inoue Hideo , Terajima Ryuuichi , Mutoh Katsuhiko , Kotaki Toshiro 
Published: April 2011

AbstractA growth of high quality thick diamond film has been carried out on high pressure and high temperature diamond substrate by microwave plasma chemical vapor deposition system. First, the effect of growth parameters on the growth film morphologies was investigated, indicating that the diamond film is very sensitive to the growth temperature and input microwave power. Then, sample holders with different geometries were used in our experiment, illustrating that high quality diamond film can be grown by using the sample holder with flat surface. Finally, the characterization of the as grown samples has been carried out.
The Effect of Silanisation on Microstructural Stability and Magnetic Properties of the Intermetallic Sm2(Co, Fe, Cu, Zr)17·
Authors: Qadeer M. I. , Azdhar Bruska , Savage S. J. 
Published: April 2011

ABSTRACTThe effects of silanising using the coupling agent γ-glycidoxpropyltrimethoxysilane on microstructural stability and magnetic properties of Sm-Co powder particles have been investigated. The silanisation provides structural stability by improving the oxidation resistance at 400oC for 10 hours. The untreated particles undergo microchemical changes by redistribution of alloying elements which mainly accumulate in parallel black and grey streaks in the interior of the particles. The silanised particles after heat treatment show coercivity of 836 Oe and the untreated particles show a much lower coercivity of 376 Oe. The difference in magnetic properties of uncoated particles is caused by diffusion of oxygen and microstructural instability.
Fabrication and Characterization of Single-crystal CVD Diamond Current Amplifier
Authors: Yater Joan E. , Shaw Jonathan L. , Jensen Kevin L. , Feygelson Tatyana , Myers Robert E. , Pate Bradford B. , Butler James E. 
Published: April 2011

ABSTRACTHigh-current-density cathodes are required for the development of high-power mm-wave and upper mm-wave devices, as well as for other electron beam applications. To address this need, a current amplifier stage is being developed that will multiply a primary electron-beam current (via the secondary-electron multiplication process) and then emit the amplified beam so as to achieve a current gain of 50-100. Diamond is a particularly promising current amplification source due to the negative electron affinity present at stable hydrogenated surfaces. As such, we are fabricating current amplifiers using single-crystal CVD diamond grown at NRL, with our growth effort focused on reducing the impurity concentration in the epitaxial diamond and on fabricating microns-thick freestanding films. The current amplification characteristics of the diamond films are examined using secondary-electron-emission measurements in both reflection and transmission configurations. In our initial study of an 8.3-µm-thick CVD diamond film, the single-crystal diamond is shown to have superior transport and emission properties compared to similar polycrystalline material. While transmission gains have been obtained under field-free conditions from the unbiased diamond film, we are striving to increase the gain by increasing the transport efficiency in a biased amplifier structure. Towards this end, recent efforts have focused on optimizing the bonding and metallization processes as needed to establish and control the internal electric field. In addition, Monte Carlo simulations are being used to predict the optimal material and device parameters needed to achieve high amplifier gain and low energy spread.
Investigations of microwave and THz radiation losses in CVD diamond and chemically modified diamond
Authors: Scherer T. A. , Strauss D. , Meier A. , Mathis Y.-L. , Judin V. , Müller-Sebert W. , Smirnov W. , Nebel C. 
Published: April 2011

ABSTRACTTo counteract plasma instabilities like Neoclassical Tearing Modes (NTM-modes) in nuclear fusion reactors (JET, ITER, DEMO) high power microwaves are used for the Electron Cyclotron Resonance Heating (ECRH) and for the plasma current drive (CD). The foreseen power level for ITER (Cadarache, France) is Ptot = 24 MW at f = 170 GHz. Each transmission line is designed for a maximum of 2 MW power. The vacuum and tritium barrier to the ITER vacuum vessel is realized by a CVD diamond disk window assembly. Diamond has an extremely high thermal conductivity of about k = 2100 W/Km and a very low loss tangent of tan δ < 10-5 for this frequency and shows therefore a very small microwave absorption. The normalized absorbed power A=Pabs/P0 can be calculated as A = (f/c) • π • (1+εr‘) • tan δ • t (with the rule of thumb estimate: (f/c)=0.5 mm-1; π • (1+εr‘) = 20; tan δ =10-5; A=10-4 • t [mm]); i.e. each t = 1 mm thickness of diamond absorbs Pabs = 100 W of Po = 1 MW microwave power transmitted through the CVD diamond window with an effective tanδ of 10-5.
Influence of methane concentration on the electric transport properties in heavily boron-doped nanocrystalline CVD diamond films
Authors: Janssens Stoffel D. , Pobedinskas Paulius , Petráková Vladimíra , Nesládek Miloš , Haenen Ken , Wagner Patrick 
Published: April 2011

ABSTRACTA study is presented on the morphology and electric properties of heavily boron-doped nanocrystalline diamond (B:NCD) thin films (≈150snm) grown with two different C/H-ratios (1% and 5%) and a fixed 5000sppm B/C-ratio in gas phase on fused silica substrates. AFM measurements confirm that a higher C/H-ratio leads to smaller grains and more grain boundaries. Electric transport measurements reveal a higher resistivity and a lower mobility as function of the C/H-ratio for all temperatures measured. The resistivity of the 1% sample is almost not temperature dependent while the 5% sample is much more temperature dependent. The electric transport properties of the grain boundaries, more present in the 5% sample, can be responsible for the difference in transport properties of both samples. The active boron concentration, calculated from the electric transport measurements, is remarkably higher for the 5% sample which indicates there is more boron incorporation for higher C/H-ratios. Although both samples are disordered metals, the 1% sample with the least grain boundaries tends more to the behavior of a highly doped single crystalline diamond film, which behaves like a real metal when heavily boron-doped.
50nm Gate-Length Hydrogen Terminated Diamond Field Effect Transistors – Characterization and Inspection of Operation.
Authors: Moran David A. J. , MacLaren Donald A. , Porro Samuele , Hill Richard , McLelland Helen , John Phillip , Wilson John 
Published: April 2011

ABSTRACTHydrogen terminated diamond field effect transistors (FET) of 50nm gate length have been fabricated, their DC operation characterised and their physical and chemical structure inspected by Transmission Electron Microscopy (TEM) and Electron Energy Loss Spectroscopy (EELS). DC characterisation of devices demonstrated pinch-off of the source-drain current can be maintained by the 50nm gate under low bias conditions. At larger bias, off-state output conductance increases, demonstrating most likely the onset of short-channel effects at this reduced gate length.
Temperature Dependence of Yield Stress and Dislocation Dissociation in L12-Ordered Intermetallic Compounds
Authors: Inui Haruyuki , Okamoto Norihiko L. 
Published: April 2011

ABSTRACTThe temperature dependence of yield stress and the associated dislocation dissociation in L12 intermetallic compounds are investigated in order to check the feasibility of the classification of L12 intermetallic compounds so far reported in terms of the planarity of core structures of partial dislocations with b = 1/2<110> and 1/3<112> on {111} and {001} glide planes. In contrast to what is believed from the reported classification, the motion of APB-coupled dislocations is proved to give rise to the rapid decrease in yield stress at low temperatures for Co3Ti and Co3 (Al,W). The temperature dependence of yield stress at low temperatures is newly interpreted in terms of a thermal component of solid-solution hardening, at least, for these two L12 compounds. We have proposed a new way to describe the yield stress–temperature curves of L12 compounds with three parameters (the athermal and thermal components of solid-solution hardening and the anomalous strengthening component) when the dislocation dissociation scheme is of the APB-type.
A Phase-Field – Finite Element Model for Instabilities in Multilayer Thin Films
Authors: Zaeem Mohsen Asle , Mesarovic Sinisa Dj. , El Kadiri Haitham , Wang Paul T. 
Published: April 2011

ABSTRACTCahn-Hilliard type of phase-field (PF) model coupled with elasticity equations is used to study the instabilities in multilayer thin films. The governing equations of the solid state phase transformation include a 4th order partial differential equation representing the evolution of the conserved PF variable (concentration) coupled to 2nd order partial differential equations representing the mechanical equilibrium. A mixed order Galerkin finite element (FE) model is used including C0 interpolation functions for the displacement, and C1 interpolation functions for the concentration. It is shown that quadratic convergence, expected for conforming elements, is achieved from this coupled mixed-order FE model.Using the PF – FE model, first, we studied the effect of compositional strain on the PF interface thickness and the results of simulations are compared with the analytical solutions of an infinite thin film diffusion couple with a flat interface.Morphological instabilities in binary multilayer thin films are investigated. The alloys with and without intermediate phase are considered, as well as the cases with stable and metastable intermediate phase. Maps of transformations in multilayer systems are carried out considering the effects of initial thickness of layers, compositional strain, and growth of a stable/unstable intermediate phase on the instability of the multilayer thin films. It is shown that at some cases phase transformation, intermediate phase nucleation and growth, or deformation of layers due to high compositional strain can lead to the coarsening of the layers which can result in different mechanical and materials behaviors of the original designed multilayer.
Nanoindentation Induced Deformation Near Grain Boundaries of Corrosion Resistant Nickel Alloys
Authors: Herbert F. William , Yildiz Bilge , Van Vliet Krystyn J. 
Published: April 2011

ABSTRACTThe damage accumulation behavior of different grain boundary structures in Inconel 690 (Ni-29wt%Cr-9wt%Fe) was investigated in the presence of large, localized plastic strains induced by nanoindentation. Spatially-resolved hardness was measured as a function of lateral distance from ‘random’ high-angle grain boundaries and twin boundaries. The confinement of induced defects between the indenter tip and grain boundaries did not lead to significant differences in measured hardness between high angle and twin boundaries. Critical “pop-in” loads indicating the onset of incipient plasticity were lower within 1μm of grain boundaries, but were statistically equivalent for random and twin boundaries. These results suggest a comparable extent of dislocation mobility and absorption at the different grain boundary types in Inconel 690 under ambient conditions.
Effects of chemical composition on the structural relaxation in ternary Zr-Cu-Al bulk glassy alloys studied by EXAFS and positron annihilation techniques.
Authors: Ishii A , Mineno S , Iwase A , Yokoyama Y , Konno T J. , Hori F 
Published: April 2011

ABSTRACTMechanical properties and thermal stability of bulk glassy alloys depend on their chemical composition ratios, although their detailed local structures especially around free volume have not been clarified yet. In order to know the origin of property dependence on alloy composition in Zr-Cu-Al ternary bulk glassy alloys in a view point of atomic scale, positron annihilation lifetime, coincidence Doppler broadening (CDB) and EXAFS (extended X-ray absorption fine structure) measurements have been employed for eutectic Zr50Cu40Al10 and hypoeutectic Zr60Cu30Al10 bulk glassy alloys before and after structural relaxation by annealing below glass transition temperature Tg.The result of CDB experiment, which represents the electron momentum distribution around free volume, shows that significant atomic reordering around free volume does not take place by the annealing in each alloy. Besides, CDB ratio profiles for each alloy suggest that the fraction of Zr atom around free volume does not match the chemical composition of each alloy system. Change in positron lifetime, which is proportional to the size of free volume, during annealing for hypoeutectic alloy almost remains unchanged.
Use of clays using ursolic acid with anti-inflammatory
activity
Authors: Domínguez-Patiño M.L. , Chávez-Castillo M. , Rodríguez-Martínez A. 
Published: April 2011

ABSTRACTToday the company seeks alternative natural medicine that are compatible
with the body, which does not produce side effects and hang time are easily
accessible and cost of those who currently have. The concern of researchers
and specialists in the development of new materials is to seek, to
experiment and create products that can be useful and compatible with human
beings so as to obtain a curative effect without a side effect
originates.The development of pharmacologically active materials has increased in
recent years. People lack access to most drugs and is therefore a need for
more rapid and less expensive than current, which can be applied to cellular
systems in vitro, in order to evaluate the biocompatibility of new
materials. The current study seeks to experiment in a new line of research
that helps health care and have a better quality of life.The excipients in the drug are auxiliary substances that help the active
ingredient is the one with the therapeutic action, can be formulated in an
effective and pleasant for the patient. It is one or more substances that
are incorporated into the product to facilitate its preparation, maintenance
or administration. We therefore tested clay known as bentonite to serve as a
vehicle for transport of an active substance (ursolic acid) [1] and some
scientific studies have shown that it possesses anti-inflammatory,
antibacterial, antifungal and highly cytotoxic capacity. Both materials were
mixed to generate a new biomaterial that has anti-inflammatory activity.
Evaluation of this model was under the inhibition of edema produced by
13-acetate-12-ortho-tetradecanoylphorbol (TPA) in mouse ear.
Nanocomposite Scaffolds for Bone Tissue Engineering: Design,
Fabrication, Surface Modification and Sustained Release of Growth
Factor
Authors: Wang Min , Duan Bin 
Published: April 2011

ABSTRACTFrom the material point of view, the extracellular matrix (ECM) of bone is a
natural nanocomposite consisting of an organic matrix (mainly collagen) and
inorganic nanofillers (bone apatite) which are inserted in a parallel way
into the collagen fibrils. For human bone tissue repair or regeneration,
nanocomposites consisting of a biodegradable polymer matrix and nano-sized
fillers such as bioactive ceramics or glasses, which mimic the hierarchical
structure of bone, are considered a promising strategy. Combining living
cells with biodegradable materials and/or bioactive component(s), the
concept of tissue engineering first elucidated in the early 1990s
represented a paradigm shift from tissue grafting, with autografts being the
gold standard, or even completely from prosthesis implantation. In
scaffold-based tissue engineering, scaffolds play an important role for
tissue regeneration. Currently, acellular scaffolds with or without
biomolecules such as growth factors are considered as an effective strategy
for certain tissue repair due to their relatively low costs and easier
process to gain surgeons’ acceptance and regulatory approval. In the current
study, integrating an advanced manufacturing technique, nanocomposite
material and controlled delivery of growth factor to form multifunctional
tissue engineering scaffolds was investigated. Three-dimensional,
osteoconductive and totally biodegradable calcium phosphate
(Ca-P)/poly(hydroxybutyrate-co-hydroxyvalerate) (PHBV) nanocomposite
scaffolds with customized architecture, controlled porosity and
interconnecting pores were designed and fabricated using selective laser
sintering (SLS). The surface of nanocomposite scaffolds was modified with
gelatin and then heparin, which facilitated the incorporation of a growth
factor, recombinant human bone morphogenetic protein-2 (rhBMP-2).
Experimental results demonstrated the effectiveness of this strategy in
guiding the osteogenic differentiation of mesenchymal stem cells. Together
with osteoconductive nanocomposite material and controlled growth factor
delivery, the use of SLS technique to form complex scaffolds provides a
promising route towards individualized bone tissue regeneration.
Bioinspired Artificial Protein Materials: Self-Assembly and
Order from Nano to Macroscale
Authors: Dai Min , Haghpanah Jennifer S. , Yuvienco Carlo , Montclare Jin Kim 
Published: April 2011

ABSTRACTWe describe the biosynthesis and characterization of protein materials
comprised of two distinct self-assembling domains (SADs): elastin (E) found
in tissue for its elastic properties and cartilage oligomeric matrix protein
coiled-coil (COMPcc, C) predominantly locatedin joint and in bones. Based on
earlier studies on protein block polymers comprised these two SADs,
orientation and number of blocks play a crucial role in the overall
stimuli-responsive supramolecular assembly behavior. Here we fabricate a
range of EnC and CEn block polymers in which the E
domain is systematically truncated to explore the effects of the E domain on
the overall physicochemical behavior.