bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystal Growth of RuAl-base Alloys
Authors: Rosset Sebastien , Cefalu E. , Varner Louis W. , Johnson David R. 
Published: April 2011

ABSTRACTDifferent techniques to produce single crystals of RuAl were investigated. Processing from the melt is problematic due to the rapid loss of Al. However, very large grained RuAl specimens can be produced from the solid-state by arc-zone melting. Directional solidification of eutectic alloys is less problematic due to the lower melting temperature. Alloys of RuAl-Mo were found to be eutectic, and the eutectic composition was determined to be RuAl-51 wt% Mo.
Effect of surface defects on the fatigue behavior of a cast TiAl alloy.
Authors: Nazmy M. , Staubli M. , Onofrio G. , Lupinc V. 
Published: April 2011

ABSTRACTThe effect of surface defects on the performance of TiAl-base alloys is an issue of importance in contemplating their application into engine components. Due to the relatively low ductility and low impact resistance of gamma alloys the validation of models for estimating economic life and for safe-life approaches employed for components becomes of great importance. Surface defects can be attributed to various sources during the manufacturing or handling of the components. In fact, little is known about the detrimental effects of surface defects on gamma alloys. In the present study, the effect of artificially introduced surface defects, on the high cycle fatigue behavior of the Ti-47Al-2W-0.5Si, will be investigated and correlated with the crack growth behavior at 700°C. The results are reported in the form of the Kitagawa diagram in which the safe and unsafe zones for crack advance and fracture are defined.
Control of Lamellar Orientation in γ-TiAl Based PST Crystal by Using Seed Crystals
Authors: Yamamoto Y. , Morishima H. , Koike K. , Takeyama M. , Matsuo T. 
Published: April 2011

ABSTRACTUnidirectional solidification of Ti-48Al binary alloy using γ-TiAl single-phase seed crystals has been carried out by an optical floating zone method. The lamellar orientation of the grown PST crystal follows the orientation of the Ti-57Al seed crystal, while it fails to follow that in the case of the Ti-53Al seed. Microstructure analysis reveals that the seed crystal of Ti-57Al exhibits a flat liquid/solid interface in melting (γ→+L) even after making contact with 48Al to grow, whereas the seed of Ti-53Al shows a cellular interface due to the peritectic reaction in melting (γ→α+L). At the 57/48 interface, an abrupt change of Al concentration was detected from the seed to the grown crystal, indicating an occurrence of composition travel to skip the peritectic reaction, which is responsible for the control of lamellar orientation of the grown PST crystals. The same attempt has been made by using the 57Al single crystal seed with a different orientation, and the lamellar orientation of the grown PST crystal was confirmed to follow the orientation of the seed.
The Effect of Cu-Macroalloying Additions to Rapidly Solidified NiAl Intermetallic Compound
Authors: Colin J. , Campillo B. , Gonzalez C. , Alvarez-Fregoso O. , Juarez-Islas J. A. 
Published: April 2011

ABSTRACTThe effects of two variables on the NiAl intermetallic compound were studied: 1) copper macroalloying additions and 2) rapid solidification processing. For that purpose, several NiCuAl alloys were vacuum induction melted and rapidly solidified by using a copper wheel, rotating at 15 m/s, under an argon atmosphere. Chemical analysis of as-rapidly solidified ribbons indicated, that four alloy compositions lie in the β-(Ni, Cu)Al field, one alloy composition lie in the boundary of the β-(Ni, Cu)Al/(Ni, Cu)2Al3 fields, one alloy composition lies in the boundary of the β-(Ni, Cu)Al/β-(Ni, Cu)Al + (Ni, Cu)3Al fields and two alloy compositions lie in the β-(Ni, Cu)Al + (Ni, Cu)3Al field. Transmission electron microscopic observations carried out in as-rapidly solidified ribbons, revealed the presence of at least three main structures: i) β-(Ni, Cu)Al, ii) β-(Ni, Cu)Al + martensite (Ni, Cu)Al and iii) (Ni, Cu)3Al + martensite (Ni, Cu)Al. Microhardness Vickers and tensile test data indicated that alloys with a β-(Ni, Cu)Al + martensite (Ni, Cu)Al microstructure have improved room temperature ductility, reaching values of elongation up to 3.28 %.
Microstructure and Property Change of Ti-49Al Induced by Hydrogen Charging
Authors: Abe E. , Gao K.W. , Nakamura M. 
Published: April 2011

ABSTRACTWe have investigated an effect of hydrogen gas-charging on the microstructure and the mechanical property of a Ti-49at.%Al alloy. After hydrogen-charging performed under an atmospheric pressure of hydrogen gas at 1023K for 3 hours, the alloy with γ-single phase has become completely brittle, while this hydrogen-induced embrittlement is suppressed for that with (γ+α2) two-phase microstructure composed of lath-precipitates in the γ matrix. A significant microstructural change was found to occur for the two-phase alloy (approximately 340ppm hydrogen in the alloy); a thin amorphous layers with a few nm thickness appear at the preexisting γ/α2 interfaces in the lath-precipitates after hydrogen-charging. In-situ TEM observation confirmed that the amorphous region transforms to a nano-crystalline state after heating to 1000K at which the hydrogen could be removed (degassed), indicating that the amorphous phase is not a binary Ti-Al phase but a ternary Ti-Al-H one. This, in turn, suggests that the γ/α2 interface in the lath packets act as the most preferential sites for hydrogen storage. Therefore, the scavenging is expected to occur effectively for the microstructure composed of γ-α2 fine lamellae in which a large number of γ/α2 interfaces exist. It is worthwhile mentioning that the fine-scale of the lamellae makes it possible to have a large number of interfaces for a given volume of the α2 phase.
Mechanical Properties of γ-TiAl Based Alloys at Elevated Temperatures
Authors: Weller M. , Chatterjee A. , Haneczok G. , Appel F. , Clemens H. 
Published: April 2011

ABSTRACTMechanical loss (internal friction) and creep experiments were carried out on specimens of a Ti-46.5at.%Al-4at.%(Cr,Nb,Ta,B) alloy with differently spaced fully lamellar microstructures. The creep tests were performed in a temperature range of 970 K to 1070 K at 175 MPa. For the mechanical loss measurements a low frequency subresonance torsion apparatus was applied, operating in the frequency range of 0.01 Hz to 10 Hz. The mechanical spectra show two phenomena: (i) A loss peak of Debye-type at 900 K (0.01 Hz) which is controlled by an activation enthalpy of 3.0 eV. The loss peak is related to thermally activated (reversible) motion of dislocation segments which are pinned at the lamellae interface and within gamma lamellae. (ii) A viscoelastic high temperature background above 1000 K with an activation enthalpy of 3.8 eV. This value agrees well with the activation enthalpy of 3.6 eV from creep experiments. Both high temperature background as well as creep are assigned to diffusion controlled climb of dislocations.
Phase Stability and High Temperature Tensile Properties of W doped gamma-TiAl
Authors: Hashimoto Keizo , Hirata Hirohiko , Mizuhara Youji 
Published: April 2011

ABSTRACTTungsten (W) doped γ-TiAl is one of promising alloys among many other proposed TiAl base alloys, for the purpose of structural applications at elevated temperatures. Ingots of W doped γ-TiAl were produced by plasma arc melting, followed by homogenizing heat treatment and isothermal forging to control their microstructures. The phase stability of W doped γ-TiAl has been studied quantitatively, using the specimens quenched from 1273 K. Equilibrium compositions of consisting phases were analyzed by means of EDS analysis in a TEM. An isothermal cross section of the Ti-Al-W ternary phase diagram at 1273K has been proposed based on the experimental observations. Small amounts of W addition (< 1at%) to Ti-48at%Al cause a phase shift from α2+γ to α2+β+γ, which suggests that W is the strongest β stabilizer among transition metals, such as Cr and Mo. Mechanical property measurements of W doped γ-TiAl show that the high temperature tensile strength has been improved by the W addition. Relationships between the microstructures and the mechanical properties of W doped γ-TiAl have been discussed.
Lithium nanocluster formation in Li+ - ion implanted MgO
Authors: van Veen A. , van Huis M.A. , Fedorov A.V. , Schut H. , Falub C.V. , Eijt S.W.H. , Labohm F. , Kooi B.J. , Hosson J.Th.M. De 
Published: April 2011

AbstractPhoton absorption (PA), Positron Beam Analysis (PBA) and Neutron Depth Profiling (NDP) is applied to study the relation between photon absorption behavior and the precipitates formed by ion implantation and thermal annealing. Monocrystals of MgO(100) were implanted with 1.0×10166Li ions cm−2 at an energy of 30 keV. The samples were thermally annealed in air in steps up to 1200 K. After each step Doppler broadening Positron Beam Analysis (PBA) was applied to monitor the depth profile of the implantation defects. The evolution of the depth profile of lithium was followed with the aid of NDP. During the annealing there is hardly any change in the location of the lithium implantation peak at 150 nm (peak concentration 2 at. %). Only after annealing to 1200 K the majority of the lithium has left the crystal and optical absorption effects have disappeared. During annealing at 750 K an absorption band develops between 400 and 600 nm; at 950 K the maximum absorption is centered at 450 nm corresponding to Mie absorption and scattering by lithium nanoclusters. Positron beam analysis shows a considerable increase of annihilations with low momentum electrons in the implanted zone. A positron method for measuring electron momentum distributions (2D-ACAR) coupled to an intense positron beam gave evidence for the presence of semi-coherent metallic lithium inclusions.
Influence of carbon on erbium lattice location in Si:Er
Authors: Ren X. T. , Huang M. B. 
Published: April 2011

AbstractThe 1.5 µm luminescence from Si:Er is known to strongly depend on impurities (e.g. carbon) in silicon. In this work, we investigate the effect of carbon co-doping on the lattice location of Er atoms in Si by Rutherford backscattering(RBS)/channeling techniques. A float-zone (FZ) Si (100) wafer was first amorphized to a depth of ~ 0. 3 µm by Si ions implanted to a dose of ~ 1×1015cm2 at liquid nitrogen temperature. Carbon ions were then implanted into the amorphous silicon, which was recrystallized via solid phase epitaxial growth (SPEG) at 600°C following C implant. Finally Er ions were implanted into the C-doped and C-free Si crystals, with the substrate temperature at 25°C and 300°C respectively. The RBS/channeling results show that the Er redistribution and Si crystallinity are strongly affected by C co-doping. The incorporation of C into Si can significantly suppress Er surface segregation, and modify the lattice location of Er atoms in Si. We discuss these effects in terms of the formation of Er-C defect complexes.
tudies on Titanium Nitride Coatings - Effect of Ion Bombardment
Authors: Vargheese K. Deenamma , Rao G. Mohan 
Published: April 2011

AbstractIon bombardment during thin film growth is known to cause structural and morphological changes in the deposited films and thus affecting the film properties. These effects can be due to the variation in the bombarding ion flux or their energy. We have deposited titanium nitride films by two distinctly different methods, viz. Electron Cyclotron Resonance (ECR) plasma sputtering and bias assisted reactive magnetron sputtering. The former represents low energy (typically less than 30 eV) but high density plasma (1011cm−3), whereas, in the latter case the ion energy is controlled by varying the bias to the substrate (typically a few hundred volts) but the ion flux is low (109cm−3). The deposited titanium nitride films are characterized for their structure, grain size, surface roughness and electrical resistivity.
Investigation of Irradiation Damage in Silicon Dioxide Polymorphs using Cathodoluminescence Microanalysis.
Authors: Stevens-Kalceff Marion A. 
Published: April 2011

AbstractCathodoluminescence (CL) Microanalysis (spectroscopy and microscopy) provides unique high sensitivity, high spatial resolution information about the defect structure and distribution of defects in wide band gap materials and therefore is an ideal technique with which to investigate the microstructural processes induced by irradiation. CL microanalytical techniques allow the in situ monitoring and post irradiation assessment of electron irradiation induced damage. Changes in the defect structure and surface topography of electron irradiated silicon dioxide polymorphs and related silicates including pure crystal quartz, pure silica glasses, pure amorphous fused quartz and alkali-borosilicate glasses, have been investigated and compared using CL microanalysis and Scanning Probe Microscopy (SPM) techniques. CL and SPM evidence shows all specimens are sensitive to electron irradiation. CL evidence is consistent with the production and micro-segregation of irradiation induced defects. The observed damage is highly correlated with the electron irradiation induced changes in the surface topography of the investigated specimens.
Ion Implanted Er and Tb in SiO2 for Electroluminescence in MOS Diodes
Authors: Buchal Ch. , Coffa S. , Wang S. , Carius R. 
Published: April 2011

AbstractEfficient infra-red and visible electroluminescence(EL) has been obtained from implanted rare earth ions in the SiO2 of a silicon-metal-oxide-semiconductor (MOS) diode structure at room temperature. The rare earth ions are excited by the direct impact of hot electrons tunneling through the oxide at electric fields larger than 6 MV/cm. The internal quantum efficiencies of Er and Tb implanted MOS diodes are estimated to be 10 % and 3 %, respectively. The hgh quantum efficiency is due to the high impact excitation cross-section of more than 10− 15cm2. These observations on MOS structures are an experimental proof for efficient light generation by hot electron impact.
Enhancement of Porosity and Surface Roughness of Cured Phenolic Resin by Ion Implantation
Authors: Zimmerman R.L. , Ila D. , Smith C.C. , Evelyn A.L. , Poker D.B. , Hensley D.K. 
Published: April 2011

AbstractWe present recent results using ions such as C., O, Si, Fe, Zn, and Au at energies between 100 keV to 10 MeV to increase the roughness and porosity of the partially and fully cured precursor phenolic resins. The fully cured phenolic resin is called Glassy Polymeric Carbon (GPC). GPC is chemically inert, biocompatible and useful for medical applications, such as heart valves and other prosthetic devices. Ion implantation enhances biological cell/tissue growth on, and tissue adhesion to, prosthetic devices made from GPC. We have previously shown that increased porosity of GPC is also useful for drug delivery devices. The porosity of the ion implanted partially and fully cured precursor phenolic resins was measured by introducing lithium from a molten LiCl salt into each sample. By using Li(p,2α) nuclear reaction analysis (NRA) we measured the concentration of Li retention in the pre- and post-implanted samples. The surface roughness was measured using optical microscopy. The curing process was monitored using micro-Raman microscopy. We have correlated the NRA measurements of increased pore availability with the observations of increased surface roughness.
Post Implantation Treatment of Silicon Carbide-Based Sensors for Hydrogen Detection Properties Enhancement
Authors: Muntele I. C. , Muntele C. I. , Ila D. , Zimmerman R. L. , Poker D. B. , Hensley D. K. 
Published: April 2011

AbstractPalladium ion implantation was performed at energies of 35 keV, 50 keV and 100 keV, at both room temperature (RT) and 500 °C, on two identical sets of 6H, n-type silicon carbide samples. Then, one set of samples was subjected to a post-implantation sputtering process, in order to eliminate the substrate layer damaged by the palladium ions during implantation. Electrical and micro-Raman measurements have been performed on both sets of samples, aiming for a better understanding of the chemical processes that take place in the presence of hydrogen atmosphere in the chemical sensors prepared this way.
Modification of Carbon Related Films with Energy Beams
Authors: Naramoto Hiroshi , Xu Yonghua , Narumi Kazumasa , Zhu Xiaodong , Vacik Jiri , Yamamoto Shunya , Miyashita Kiyoshi 
Published: April 2011

AbstractWe report on typical examples of thin carbon films prepared employing energy beam techniques such as ion beam deposition, ion beam assisted deposition and Laser illumination. In an annealing study of ion beam deposited carbon films, small dots with sub-micron size are isolated through the selective oxidation of sp3-bonded amorphous carbon films, and they were confirmed to be diamond nano-particles by micro-Raman spectrometry. C60 deposition assisted with Ne ion beam results in two kinds of films: 1) The quality of C60 films is improved by the assist of 500eV Ne ion bombardment. 2) The increase of Ne ion Energy results in the decomposition of C60 and the films obtained at 700°C contain possible nano-diamond crystallites at the center of the intense beam spot. The Laser illumination decomposes C60 molecules in general, but the fine-tuning of Laser energy density makes it possible to prepare an array of high luminescent spots.
Properties of Gallium Disorder and Gold Implants in GaN
Authors: Jiang W. , Weber W.J. , Thevuthasan S. , Shutthanandan V. 
Published: April 2011

AbstractEpitaxial single-crystal GaN films on sapphire were implanted 60° off the <0001> surface normal with 1 MeV Au2+ or 3 MeV Au3+ over a fluence range from 0.88 to 86.2 ions/nm2 at 180 and 300 K. The implantation damage was studied in-situ using 2 MeV He+ Rutherford backscattering spectrometry in channeling geometry (RBS/C). The disordering rate in the near- surface region is faster than at the damage peak. In all cases, results show an intermediate stage of Ga disorder saturation at the damage peak. During the thermal annealing at 870 K for 20 min, some Au implants in GaN diffuse into the amorphized surface region, while the remaining Au atoms distribute around the mean ion-projected-range. These results suggest a high mobility of both Ga defects and Au implants in GaN. Deeper damage implantation by 3 MeV Au3+ indicates that GaN cannot be completely amorphized up to the highest ion fluence (86.2 ions/nm2) applied at 300 K.
Optimization of the Ion-Cut Process in Si and SiC
Authors: Holland O. W. , Thomas D. K. , Gregory R. B. 
Published: April 2011

AbstractH+-implantation is the basis for an ion-cut process, which combines hydrophilic wafer bonding, to produce heterostructures over a wide range of materials. This process has been successfully applied in Si to produce a commercial silicon-on-insulator material. The efficacy of implantation to produce thin-film separation was studied by investigation of H+-induced exfoliation in Si and SiC. Experiments were done to isolate the effects of the hydrogen chemistry from that of implant damage. Damage is manipulated independently of H+ dosage by a variety of techniques ranging from elevated temperature irradiation to a two-step implantation scheme in Si, and the use of channeled-ion implantation in SiC. The results will demonstrate that such schemes can significantly reduce the critical dose for exfoliation.
Ion Beam Slicing of Single Crystal Oxide Thin Films
Authors: Thevuthasan S. , Shutthanandan V. , Jiang W. , Weber W. J. 
Published: April 2011

AbstractEpitaxial thin film liftoff using the ion-slicing method has been applied to SrTiO3 single crystals. Rutherford backscattering spectrometry along with channeling (RBS/C) has been used to investigate the relative disorder as a function of temperature from the samples that were irradiated by 40 KeV hydrogen ions to a fluence of 5.0×1016 H+/cm2. Hydrogen profiles were also measured as a function of annealing temperature to understand the role of hydrogen in the ion slicing process. Film cleavage occurred during or after annealing at 570 K, and cleaved film has been successfully transferred to a silicon substrate using ceramic adhesive.
Ion Beam Assisted Texture Evolution during Thin Film Deposition of Metal Nitrides
Authors: Stritzker Bernd , Gerlach Jürgen W. , Six Stephan , Rauschenbach Bernd 
Published: April 2011

AbstractIon beam assisted deposition, i.e., the bombardment of thin films with a beam of energetic particles has become a highly developed tool for the preparation of thin films. This technique provides thin films and coatings with modified microstructure and properties. In this paper examples are presented for the modifying of the structure: in-situ modification of texture during ion beam assisted film growth and ion beam enhanced epitaxy.The biaxial alignment of titanium nitride films prepared on Si(111) by nitrogen ion beam assisted deposition at room temperature was studied. The bombardment perpendicular to the surface of the substrate causes an {001} alignment of crystallites. A 55° ion beam incidence angle produces both a {111} orientation relative to the surface and a {100} orientation relative to the ion beam. This results in a totally fixed orientation of the crystallites. The texture evolution is explained by the existence of open channeling directions.Epitaxial, hexagonal gallium nitride films were grown on c-plane sapphire by low-energy nitrogen ion beam assisted deposition (≤ 25 eV). The ion energy was chosen to be less than the corrected bulk displacement energy to avoid the formation of ion-induced point defects in the bulk. The results show that GaN films with a nearly perfect {0002} texture are formed which have superior crystalline quality than films grown without ion irradiation. The mosaicity and the defect density are reduced.By applying an assisting ion beam during pulsed laser deposition of aluminum nitride on the c-plane of sapphire, epitaxial, hexagonal films could be produced. The results prove the beneficial influence of the ion beam on the crystalline quality of the films. An optimum ion energy of 500 eV was found where the medium tilt as well as the medium twist of the crystallites was minimal.
A Scaling Approach to Modeling Indentation Measurements
Authors: Cheng Yang-Tse , Li Zhiyong , Cheng Che-Min 
Published: April 2011

ABSTRACTUsing dimensional analysis and finite element calculations, the relationships between hardness, elastic modulus, final contact depth, and the work of indentation are extended to conical indentation in elastic-plastic solids with various cone angles. These relationships provide new insights into indentation measurements. They may also be useful to the interpretation of results obtained from instrumented indentation experiments.
Determination of the Real Indenter Shape for Nanoindentation/Nanotribology Tests by Surface Metrological and Analytical Investigations
Authors: Enders S. , Grau P. , Hawthorne H. M. 
Published: April 2011

ABSTRACTIn this paper a critical comparison of different kinds of surface metrological methods like atomic force microscopy (AFM), scanning electron microscopy (SEM) and optical interferometric profilometry is made, as well as analytical investigations based on both Hertz and Sneddon theories of pure elastic contact, to qualify the real indenter shape function. The results obtained show the advantages and disadvantages of the respective methods by describing a rounded indenter tip.
Probing the Critical Stress Intensity Factor for Slip Transfer across Grain Boundaries by Subgranular Indentation Alfonso
Authors: Ngan H.W. , Chiu Y.L. 
Published: April 2011

ABSTRACTBy analysing the relevant results in the literature, we have found that, when indentation is made on a subgranular level, the hardness varies roughly inversely with the square root of the distance between the indent and the grain boundary. This effect is analogous to the Hall-Petch effect for macroscopic deformation.