bluuebunny/crossref_metadata_2025_split huggingface dataset:
Fabrication and Characterization of Electrically Functional Lanthanum Hexaboride Thin Films on Ultrasmooth Sapphire Substrates
Authors: Kato Yushi , Ono Yusaburo , Akita Yasuyuki , Hosaka Makoto , Shiraishi Naoki , Tsuchimine Nobuo , Kobayashi Susumu , Yoshimoto Mamoru 
Published: February 2009

AbstractThe crystal growth of lanthanum hexaboride (LaB6) thin films was examined by applying the laser molecular beam epitaxy (laser MBE) process. C-axis (100) highly-oriented LaB6 thin films could be fabricated on ultrasmooth sapphire (α-Al2O3 single crystal) (0001) substrates with atomic steps of 0.2 nm in height and atomically flat terraces. The obtained film exhibited a smooth surface with root mean square roughness of 0.15 nm. The lattice parameter of the LaB6 thin film was close to the bulk value reported previously. In the case of deposition on commercial mirror-polished sapphire substrates, the grown film was amorphous. The resistivity of the prepared crystalline LaB6 thin films was as low as 2.2 × 10−4 Ω cm and almost constant in the temperature range of 10–300 K.
Inducing Grain Alignment in Metals, Compounds and Multicomponent Thin Films
Authors: Harper James M.E. 
Published: February 2009

AbstractSeveral methods to induce grain alignment in polycrystalline thin films are discussed, in which directional effects can dominate over the normal evolution of fiber texture during thin film growth. Early experiments with ion beam assisted deposition showed the importance of channeling directions in selecting grain orientations with low sputtering yield or low ion damage energy density. Examples of this approach include the formation of biaxial fiber textures in Nb, Al and AlN. Grain orientations may also be selected by the release of stored energy during abnormal grain growth initiated by solute precipitation (Cu-Co) or phase transformation (TiSi2). Other energy sources such as mechanical deformation, crystallization or compound formation may also contribute to producing desired grain alignments. In multicomponent thin films, combinations of these mechanisms provide opportunities for more specific control of grain orientations.
Investigation of Early Nucleation Events in Magnesium Oxide During Ion Beam Assisted Deposition
Authors: Groves James , Hammond Robert , DePaula Raymond F. , Clemens Bruce M. 
Published: February 2009

AbstractIon beam assisted deposition (IBAD) is used to biaxially texture magnesium oxide (MgO), which is useful as a template for the heteroepitaxial growth of various thin film devices and most notably as a template layer for high temperature superconductors. Improvements in the quality of IBAD MgO films have been largely empirical and there is uncertainty as to the exact mechanism by which this biaxial texture is developed. Using a specially built quartz crystal microbalance (QCM) as both a substrate and monitor in conjunction with reflected high-energy electron diffraction (RHEED) acting on the same surface, we have probed the initial stages of IBAD MgO growth in-situ. We have correlated corresponding RHEED images with real-time mass accumulation QCM data during the film growth. During IBAD growth, the mass accumulation exhibits a sharp change in slope corresponding to a sudden decrease in growth rate. Corresponding RHEED images show an abrupt onset of crystallographic texture at this point. A simple model incorporating differential etch rates of the MgO film and silicon nitride substrate can be used to fit the data but is inconsistent with the behavior during ion etching with no growth. It is, therefore, postulated that a more complex mechanism is responsible for the observed behavior.
Ion-beam assisted pulsed laser deposition of textured transition-metal nitride films
Authors: Hühne Ruben , Kidszun Martin , Güth Konrad , Thoss Franziska , Rellinghaus Bernd , Schultz Ludwig , Holzapfel Bernhard 
Published: February 2009

AbstractIon-beam assisted deposition (IBAD) offers the possibility to prepare thin textured films on amorphous or non-textured substrates. It was shown within the last decade that the ion beam influences the nucleation in material with a rocksalt structure leading to a strong cube texture already within the first 10 nanometres. Among these materials, transition metal nitrides exhibit interesting physical properties as superconductivity, metallic behaviour or superior hardness. Therefore, a reactive IBAD process was applied for the preparation of highly textured transition metal nitride layers using pulsed laser deposition of pure metals in combination with a nitrogen-containing ion beam. The results on the in-plane textured growth of TiN are promising for the development of conducting buffer layer architectures for YBCO coated conductors based on the IBAD approach. Furthermore, this approach was used to prepare other highly textured transition metal nitride thin films like NbN and ZrN.
Low-Temperature Selective Growth of Heteroepitaxial α-Al2O3 Thin Films on a NiO Layer by the Electron-Beam Assisted PLD Process
Authors: Hosaka Makoto , Akita Yasuyuki , Sugimoto Yuki , Kato Yushi , Ono Yusaburo , Matsuda Akifumi , Koyama Koji , Yoshimoto Mamoru 
Published: February 2009

AbstractSelective heteroepitaxial growth of α-Al2O3 thin films on a NiO layer was investigated using an electron-beam assisted pulsed laser deposition process. The epitaxial NiO layer was grown on an ultrasmooth sapphire (α-Al2O3 single crystal) (0001) substrate. The α-Al2O3 thin film could be grown epitaxially only in the electron-beam irradiated region of the epitaxial NiO layer at 300°C, while the amorphous Al2O3 film was grown in the non-irradiated region. The homoepitaxial growth of α-Al2O3 thin films could not be attained on the sapphire (0001) substrate at 300°C. This indicates that the electron-beam irradiation enhances heteroepitaxial growth of the α-Al2O3 thin films on the NiO layer at 300°C. When we annealed the epitaxial Al2O3/NiO bilayer film at 350°C in a hydrogen atmosphere, we could reduce only the NiO layer to an epitaxial Ni metal layer, allowing the fabrication of epitaxial Al2O3/Ni (insulator/metal structure) films. The fabricated Al2O3/Ni bilayer films exhibited a very smooth surface.
Carbon Nanotube-Induced Changes of Crystal Growth In Polymer Films
Authors: Georgiev Georgi Yordanov , Cabrera Yaniel , Wielgus Lauren , Iftikhar Zarnab , Mattera Michael , Gati Peter , Potter Austin , Cebe Peggy 
Published: February 2009

AbstractIsotactic Polypropylene (iPP) nanocomposites with low concentrations of multiwall carbon nanotubes (CNTs) 0-1% were studied, using differential scanning calorimetry and Avrami analysis. The nanocomposites were isothermally crystallized at 135°C, in order to measure the effect of nanotubes on the kinetics of crystallization. In our study there is a great effect of the CNTs on the iPP crystallization kinetics. The Avrami analysis shows increase in the crystallization rate constant and constancy the Avrami exponent with increase of the CNTs concentration. The full width at half maximum (FWHM) of the heat flow exotherm and the peak time for crystallization (tp) change dramatically. For iPP, the carbon nanotubes serve as nucleation agents to speed up the crystallization process.
Artificial Grain Alignment of Organic Crystalline Thin Films
Authors: Shimada Toshihiro 
Published: February 2009

AbstractIt is important to obtain single crystalline organic thin films for electronics and optics applications. Due to the mismatching in the crystal symmetry, it is difficult to align the crystalline grains of organic molecular films even on single crystalline surfaces. We have developed several techniques for the artificial grain alignment in organic epitaxial growth. (1) Use of nanoscale-textured surfaces prepared by step bunching of vicinally-cut single crystalline surfaces, in which the height of the steps is critically important. (2) Application of external electric field. (3) Optical excitation of the molecules which can be applied to the polar semiconducting molecules. These techniques might be applicable to other materials including ionic materials and ferroelectrics.
Liquid-Liquid Phase Transition in Undercooled Silicon: Structural, Electronic and Dynamical Aspects
Authors: Jakse Noel , Pasturel Alain 
Published: February 2009

ABSTRACTWe have proposed a new mixed approach by combining efficiently classical and first-principles molecular dynamics to study undercooling of liquid silicon, regardless of a specific empirical interaction model. Our results show an enhancement of the local tetrahedral ordering in the deep undercooled region associated to the appearance of propagating shear waves and give a strong support to the existence of a transition between a high density liquid to a low density liquid near 1050 K. An analysis of the structural, dynamics and electronic properties is proposed to elucidate these features.
Improved bond valence models for ion transport pathways in glasses
Authors: Adams Stefan N. 
Published: February 2009

ABSTRACTStructure property function relationships provide valuable guidelines for a systematic development of functional materials. It is demonstrated how an augmented bond valence (BV) approach helps to establish such relationships in solid electrolytes. In principle it permits to identify mobile species, transport pathways and provides estimates for ion mobilities. In this work we discuss ion conduction pathways in glassy Lithium metasilicate as an illustrative example. The required representative local structure model is derived from Molecular Dynamics simulations, which provides the opportunity to compare the bond-valence-based predictions from a static structure model with a comprehensive analysis of a complete simulation trajectory. It is shown that understanding the bond valence mismatch as an effective Morse-type interaction opens up a way for systematically analyzing ion transport pathways and for a generally applicable method with improved reliability to predict ion transport characteristics in solid electrolytes from the structure model.
Long‐term effects of plant diversity and composition on soil nematode communities in model grasslands
Authors: Viketoft Maria , Bengtsson Janne , Sohlenius Björn , Berg Matty P. , Petchey Owen , Palmborg Cecilia , Huss-Danell Kerstin 
Published: February 2009

An important component of plant–soil feedbacks is how plant species identity and diversity influence soil organism communities. We examine the effects of grassland plant species growing alone and together up to a richness of 12 species on nematode diversity and feeding group composition, eight years after the establishment of experimental grassland plots at the BIODEPTH site in northern Sweden. This is a substantially longer time than most other experimental studies of plant effects on soil fauna. We address the hypotheses that (1a) higher species or functional diversity of plants increases nematode diversity, as well as influences nematode community composition. Alternatively, (1b) individual plant species traits are most important for nematode diversity and community composition. (2) Plant effects on soil organisms will decrease with increasing number of trophic links between plants and soil fauna.Plant species identity was often more important than plant diversity for nematode community composition, supporting hypothesis 1b. There was a weak positive relation between plant and nematode richness, which could be attributed to the presence of the legume Trifolium pratense, but also to some other plant species, suggesting a selection or sampling effect. Several plant species in different functional groups affected nematode community composition. For example, we found that legumes increased bacterial‐feeding nematodes, most notably r‐selected Rhabditida, while fungal‐feeding nematodes were enhanced by forbs. Other bacterial feeders and obligate root feeders were positively related to grasses. Plant effects were usually stronger on plant‐, bacterial‐ and fungal‐feeding nematodes than on omnivores/predators, which supports hypothesis 2.Our study suggests that plant identity has stronger effects than plant diversity on nematode community composition, but when comparing our results with similar previous studies the effects of particular plant species appear to vary. We also found that more productive plant species affected bacterial‐feeding nematodes more than fungal feeders. Moreover, we observed stronger effects the fewer the number of trophic links there were between a nematode feeding group and plants. Although we found clear effects of plants on soil nematodes, these were probably not large enough to result in strong and persistent plant–soil‐organism–plant feedback loops.
A model for the intrinsic kinetic parameters of the direct reduction of MoS2 with hydrogen
Authors: Mehdi Afsahi Mohammad , Sohrabi Morteza , Ale Ebrahim Habib 
Published: February 2009

AbstractThis study was carried out in order to obtain intrinsic kinetic parameters for the reaction between molybdenum disulfide and hydrogen. The experiments were performed using thermogravimetry within the temperature range of 1073 – 1223 K and at atmospheric pressure. The reaction was conducted by applying thin pellets and the data obtained were analyzed using a nucleation and growth kinetic model. The reaction was first order with respect to the gas phase reactant. The activation energy for the reduction process was determined to be 135.4 kJ mol− 1.
Thermodynamic consideration and experimental study on the preparation of heat-treated hollow nickel fibres
Authors: Li Fan , Sichen Du 
Published: February 2009

AbstractIn the present work, heat-treated hollow nickel fibres were prepared by thermal decomposition from nickel viscose composite. The thermodynamic properties of viscose fibre, namely standard enthalpy of formation, heat capacity, absolute entropy, and standard Gibbs free energy of formation were estimated by bond enthalpy. Thermodynamic analysis showed that viscose fibres could decompose at any reachable temperature, when the kinetic conditions were favourable. The results of thermogravimetric analysis experiments indicated that viscose filling could be removed by heat treatment in air. The thermogravimetric analysis results along with X-ray diffraction, scanning electron microscopy and X-ray energy dispersive spectrum analysis showed that hollow nickel fibre could be prepared by direct thermal decomposition in air flow at low temperatures, e. g. 573 K. Decomposition of the viscose filling could also be carried out at higher temperatures. However, serious oxidation of nickel would also take place during the decomposition. To remove nickel oxide, reduction by hydrogen gas could be applied.
Are data correctly fitted by the sin2 ψ and similar methods?
Authors: Ortner Balder 
Published: February 2009

AbstractThe sin2 ψ method is a frequently used, very successful method for data evaluation in X-ray or neutron stress measurements, but besides all its merits it also has a number of disadvantages and shortcomings. One of the shortcomings is the fact that in the general case of an in-plane stress measurement the method is not a correct least-squares fit. This results in an unnecessary loss of accuracy of the calculated stress tensor. The same must be said about some other methods which are similar to the sin2 ψ method, inasmuch as they also rely on a linear dependence of measured data on sin2 ψ or some other function of ψ. This is proved by analyzing the mathematical basis of these methods.
The effect of thermal exposure on the microstructure and hardness of as-cast Mg–Zn–Al alloys with Sn addition
Authors: Jihua Chen , Zhenhua Chen , Hongge Yan , Suqiong Li , Peiyun Xia 
Published: February 2009

AbstractMicrostructural evolution and hardness changes of as-cast Mg-6Zn-2Al alloys with Sn addition during prolonged thermal exposure to 150 °C and 200 °C were studied using optical microscopy, X-ray diffraction, scanning electron microscopy and hardness tests. Neither obvious grain growth nor new phases were detected in these alloys during thermal exposure. There were initial precipitation hardening peaks followed by long-term hardness stability during thermal exposure to 150 °C, indicating that all the alloys exhibited excellent microstructural stability. There were two peaks in the hardness vs. annealing time curves of these alloys during thermal exposure to 200 °C, which corresponded to the precipitation of MgZn and Mg2Sn. The overall hardness of these alloys decreased with prolonged time, resulting from the aggregation and coarsening of Mg2Sn.
Suitability of maraging steel weld cladding for repair of die casting tooling
Authors: Klobčar Damjan , Tušek Janez , Taljat Boštjan , Kosec Ladislav , Muhič Mitja 
Published: February 2009

Abstract
This study was done to evaluate precipitation annealing of 18 % Ni maraging steel repair welds during aluminium alloy die casting and to predict the prolonged in-service tool life. The emphasis of this study was the influence of post-weld precipitation annealing heat treatment and aluminium die casting thermal cycling on metallurgical and mechanical properties. A series of specimens of 1.2344 tool steel was prepared to which 1.6356 maraging steel was gas tungsten arc weld clad. Analysis of weld microstructure and hardness was made in order to understand the metallurgical processes during heat treatment at elevated temperatures and at prolonged time. The Response Surface model for prediction of hardness after heat treatment was developed. The edges of immersion test specimens are gas tungsten arc weld clad with 1.6356 maraging steel and machined to the final edge geometry. Two specimens were tested in as-welded condition and two in optimally aged condition. Testing was performed on specially developed immersion test apparatus, which enables the simulation of thermal fatigue during aluminium alloy die casting. After completion of a particular number of thermal fatigue cycles the weld microstructure and hardness were evaluated. A hypothetical model for prediction of precipitation annealing time during aluminium alloy die casting was proposed. The results showed that tool heating lasts 30 % of molten metal injection time, preparing conditions for precipitation annealing at 10 % of injection time, and precipitation annealing at 60 % of injection time. These results, together with a finite element model for prediction of tool temperature and response surface model for prediction of hardness after precipitation annealing, enable accurate prediction of maraging steel tool hardness after any particular number of die casting cycles and consequently in-service tool life. The thermal fatigue resistance of maraging steel welds was compared to AISI H13 tool steel. The results showed superior thermal fatique resistance for AISI H13.
STAU – a review of the Karlsruhe weakest link finite element postprocessor with extensive capabilities
Authors: Riesch-Oppermann Heinz , Härtelt Martin , Kraft Oliver 
Published: February 2009

Abstract
The inherent brittleness of ceramics led to a probabilistic approach for designing with ceramic materials. For tackling this issue, numerous research projects led to the generation and continuous development of the weakest link postprocessor STAU over the last twenty years. Compared to other similar tools, STAU is unique in its comprehensive capabilities addressing spontaneous fracture, sub-critical crack propagation under transient loading, including a temperature-dependent fracture stress, and crack propagation parameters and analysis of strong stress gradients allowing for solving general thermo-mechanical problems including thermal shock and contact loading. Remarkably, the stress analysis, using commercial finite element codes, does not require a separate meshing with respect to the subsequent probabilistic analysis. Within the framework of a collaborative research effort (SFB 483) ceramics are qualified with respect to friction and wear for highly demanding applications. Here, uncertainty analysis methods for STAU were developed and led to an important extension of STAU for several technological applications. In this paper, the main features of STAU as well as the physical background are revisited and some application cases are shown.
Effect of phase stability and composition on hydrogen diffusion in the binary systems Ti–Mo and Ti–V and related Ti-base alloys
Authors: Schmidt Peter , Christ Hans-Jürgen 
Published: February 2009

Abstract
Hydrogen diffusion coefficients DH were determined in various commercial β titanium alloys and binary titanium alloys of the Ti – Mo and Ti – V systems, since molybdenum and vanadium are the most important β-stabilizing alloying elements. For this purpose, hydrogen concentration step profiles were established in long thin titanium rod samples via electrochemical hydrogenation. Subsequent diffusion annealing at various temperatures led to hydrogen diffusion inside the samples. The hydrogen concentration profiles established were evaluated either numerically by means of a finite-difference application or analytically by applying the Matano technique and the hydrogen diffusion coefficients were calculated. The results show that the DH-values increase with increasing β stability, obey an Arrhenius-type temperature dependence and are not affected by hydrogen concentration.
A transmission electron microscopy procedure for in-situ straining of miniature pseudoelastic NiTi specimens
Authors: Olbricht J. , Wagner M. F.-X. , Condó A. , Dlouhy A. , Großmann Ch. , Kröger A. , Somsen Ch. , Eggeler G. 
Published: February 2009

Abstract
The in-situ transmission electron microscopy technique allows direct observations of formation and growth of stress-induced martensite in pseudoelastic NiTi shape memory alloys. The present paper reports on the development of a miniature test procedure for in-situ straining experiments with specimens taken from small components. The deformation of an ultra-fine grained NiTi specimen is characterised by transmission electron microscopy (at early loading stages) and by optical microscopy (at larger strains). A complementary finite element analysis of the complex strain state in the specimen rationalises why the stress-induced martensitic transformation first occurs in the thin foil region of the specimen before spreading towards the outer rim of the specimen.
Development of multifunctional thin films using high-throughput experimentation methods
Authors: Ludwig Alfred , Zarnetta Robert , Hamann Sven , Savan Alan , Thienhaus Sigurd 
Published: February 2009

Abstract
This paper describes the use of thin film high-throughput experimentation methods for the efficient development of multifunctional materials, using Ni – Ti – X and ferromagnetic shape memory alloys as examples. The thin films were fabricated in the form of binary, ternary, and quaternary materials libraries by special magnetron sputter deposition processes. These materials libraries were subsequently processed and characterized by high-throughput experimentation methods in order to relate compositional information with structural and functional properties. For this, appropriate visualization of the data is necessary. Results show that the martensitically transforming regions in ternary thin films are generally larger than was known from literature. Within these regions, the variation of the functional properties can be mapped with respect to the composition and microstructure, and thus the most suitable materials for applications can be effectively selected.
“Evolution” of microstructure in materials
Authors: Hornbogen Erhard 
Published: February 2009

Abstract
The term “evolution” is used in both biology and materials science. There are however large differences in what is meant by it. It will be shown that one difference is the probability of single or multi step nucleation. Biological structures are too complex to be recreatable by nucleation. They originate by a very rare event. Consequently they are prone to extinction, if they had no chance to multiply and modify in particular environments (populations, generations).
Formation of various dispersoid microstructures in Al – Cu alloy is shown as an example of nucleation controlled evolution in materials science.