bluuebunny/crossref_metadata_2025_split huggingface dataset:
Metallurgical Control of the Ductile-Brittle Transition in High-Strength Structural Steels
Authors: Morris J.W. 
Published: April 2011

AbstractThe models that have been successfully used to control the ductile-brittle transition in high strength structural steels are qualitative in nature, and address the microstructural control of the mechanisms of brittle fracture. The basic idea is incorporated in the “Yoffee diagram”, which dates from the 1920's and attributes the ductile-brittle transition to the competition between deformation and fracture; the more difficult brittle fracture becomes, the lower the temperature at which ductile processes dominate. There are two important brittle fracture modes: intergranular separation and transgranular cleavage. The intergranular mode is usually due to chemical contamination, and is addressed by eliminating or gettering the contaminating species. There are also examples of brittle fracture that is due to inherent grain boundary weakness. In this case the failure mode is overcome by adding beneficial species (glue) to the grain boundary. Transgranular cleavage is made more difficult by refining the effective grain size. In high strength steel this is done by refining the prior austenite grain size, by interspersing islands of metastable austenite that transform martensitically under plastic strain, or by disrupting the crystallographic alignment of ferrite grains or martensite laths. The latter mechanism offers intriguing possibilities for future steels with exceptional toughness.
In Situ Examination of moving Crack Tips in Ordered Intermetallics
Authors: Heuer J.K. , Lam N.Q. , Okamoto P.R. , Stubbins J.F. 
Published: April 2011

AbstractRecent studies have shown that high stress concentrations at moving crack tips in the intermetallic compound NiTi can induce a crystalline-to-amorphous (C-A) transformation of the crack tip region. This stress-induced C-A transformation has a temperature dependence and crystallization behavior similar to those of ion irradiation-induced C-A transformation of NiTi. The present study examines if these similarities between stress- and irradiation-induced amorphization hold true for two other intermetallic compounds, CuTi and Ni3Ti. In situ straining was performed in an intermediate-voltage transmission electron microscope. The presence or absence of an amorphous phase was determined by dark field imaging and selected area diffraction of crack tip regions. Crack tips in both CuTi and Ni3Ti were found to remain crystalline upon fracture. The observed absence of stress-induced amorphization in Ni3Ti is consistent with its known absence during irradiation, but the absence in CuTi differs from its known irradiation-induced amorphization behavior. Reasons for the similarity and difference are discussed.
Mode-III Fracture Propagation in a Two-Dimensional Continuum Model with Frictional Dissipation
Authors: Ching Emily S.C. , Nakanishi Hiizu 
Published: April 2011

AbstractMode-III fracture propagation in a two-dimensional continuum model is studied the- oretically. The material is assumed to be isotropic and linearly elastic with a frictional dissipation, and the crack-tip r-gion is modeled by a cohesive zone. As the externally ap- plied load increases, the steady-state crack speed increases to a maximum value which can be substantially smaller than the sound speed when the dissipation is large. The fracture energy also becomes dependent on the velocity.
Making, Breaking and Sliding of Nanometer-Scale Contacts
Authors: Carpick R.W. , Enachescu M. , Ogletree D.F. , Salmeron M. 
Published: April 2011

AbstractThe contact between an atomic force microscope tip and a sample surface can form an ideal single asperity of nanometer dimensions, where the interaction forces can be measured with sub- nanoNewton force resolution. Studies of contact, adhesion and friction for these nano-asperities have been carried out for a variety of tips and single crystal sample surfaces. The major result is the observation of proportionality between friction and true contact area for a variety of systems, and an impressive agreement with continuum mechanics models for contact area even at the nanometer scale. The relevant continuum models can in fact be understood in the framework of fracture mechanics.
Chemical Solution Processing of Strontium Bismuth Tantalate Films
Authors: Lakeman C.D.E. , Boyle T. J. 
Published: April 2011

AbstractWe describe Chemical Solution Deposition (CSD) processes by which Strontium Bismuth Tantalate (SBT) thin films can be prepared at temperatures as low as 550°C. In this paper, we will present strategies used to optimize the properties of the films including solution chemistry, film composition, the nature of the substrate (or bottom electrode) used, and the thermal processing cycle. Under suitable conditions, ∼1700 Å films can be prepared which have a large switchable polarization (2Pr >10μC/cm2), and an operating voltage, defined as the voltage at which 0.80 × 2Prmax is switched, 2.OV. We also describe an all-alkoxide route to SBT films from which SBT can be crystallized at 550°C.
Effect of Characteristics of SrRuO3 Buffer Layer on the Ferroelectric Properties of (Pb0.97La0.30)(Zr0.66Ti0.34)O3 Thin Films
Authors: Chen Yu-Jen , Jamn Gwo , Liu Kuo-Shung , Lina I-Nan 
Published: April 2011

AbstractA two-step pulsed laser deposition (PLD) process, including PLD at a substrate temperature lower than 150°C and rapid-thermal-annealing (RTA) at around 550°C (30 s), has been successfully applied for growing (Pb0.97La0.03)(Zr0.66Ti0.034)0.9875O3, PLZT, thin films. Interdiffusion between layers is pronouncedly suppressed due to the presence of the SrRuO3 layer, which markedly improves the electrical properties of PLZT films. The PLZT films thus obtained exhibit large remanent polarization P,=19 µC/cm2 (with coercive force Ec=78 kV/cm), low leakage current density J11≤8 × 1O−6 A/cm2 (up to 400 kV/cm) and fatigue free characteristics.
The Role of Processing Parameters in Variation of Microstruture of Sol-Gel Derived Lead Zirconate Titanate Thin Films
Authors: Kim Chang Jung , Kim Tae-Young , Chung Ilsub , Yoo In Kyung 
Published: April 2011

AbstractThe PZT thin films were fabricated to investigate the effect of sol-gel processing parameters on the physical and the electrical properties. The films were made with different amount of excess Pb precursors and drying temperatures, and then annealed in various ambients. The physical properties of the films such as crystallinity and microstructure were evaluated using x-ray diffraction, scanning electron microscopy and atomic force microscopy. The ferroelectric properties and current density characteristics of the films were investigated using a standarized feiroelectric test system and pA meter, respectively. It is found that the drying temperature was playing a key role in the formation of the secondary phase on the PZT thin films. In addition, it turned out that the use of nitrogen as an annealing ambient promoted overall ferroelectric properties, when compared to oxygen ambients.
MBE Growth of Ferroelectric YMnO3 Thin Films on Si(111) Using Y2O3 Buffer Layers
Authors: Imada Shogo , Shouriki Shigeto , Tokumitsu Eisuke , Ishiwara Hiroshi 
Published: April 2011

AbstractA ferroelectric YMnO3 thin films are grown on Si (111) substrates using Y2O3 buffer layers by molecular beam epitaxy (MBE). In-situ reflection high-energy electron diffraction (RHEED) analyses show that both Y2O3 and YMnO3 films are epitaxially grown on Si substrates. X-ray rocking curve measurements also show that the best FWHM (full width at half maximum) values for Y2O3 and YMnO3 films are 0.40° and 0.8°, respectively. C-V characteristics of Al/YMnO3/Y2O3/Si structures indicate the ferroelectric properties of YMnO3 films with a memory window of 0.7V.
Dielectric Properties of Pulsed Laser Deposited SrTiO3 Thin Films
Authors: Clark A. M. , Hao Jianhua , Si Weidong , Xi X. X. 
Published: April 2011

AbstractLow frequency dielectric loss and nonlinearity in pulsed laser deposited SrTiO3 thin films were studied. A low loss tangent in the order of 10−4, close to the level found in SrTiO3 single crystals, was observed. Combined with a large tunability, this resulted in a figure of merit for frequency and phase agile materials that can rival that observed in single crystals. The SrTiO3 thin films with thickness ranging from 25 nm to 2.5μ1 were grown on SrRuO3 electrode layers. The loss depends strongly on the thickness, but differently above and below T ∼ 80 K. Our result suggests that, in the high temperature regime, the interfacial dead layer effect dominates while, in the low temperature regime, the losses related to the structural phase transition and quantum fluctuations are important. The effect of interfacial potential was studied by using different electrode materials that result in different Schottky barriers.
Modelling Intercalation Kinetics of Polymer Silicate Nanocomposites
Authors: Lee J. Y. , Baljon A. R. C. , Loring R. F. , Panagiotopoulos A. Z. 
Published: April 2011

AbstractPolymer layered silicates form an important class of nanocomposite materials. During their formation by melt intercalation, polymer molecules from a bulk fluid move into the galleries of layered silicates. An essential feature of this process is the flow of macromolecules from a bulk fluid to a confined environment. To model this phenomenon, we have performed molecular dynamics simulations of the flow of polymer molecules from a bulk melt into a rectangular slit. The simulations are consistent with a diffusive description of the transport, and show qualitative agreement with time-dependent x-ray diffraction measurements of intercalation kinetics in layered nanocomposites.
On the Glass Transition in Polymer Films: Recent Monte Carlo Results
Authors: Baschnagel J. , Binder K. 
Published: April 2011

AbstractThis paper reports results of a Monte Carlo simulation for a simplified lattice modelof a supercooled polymer film. The film geometry is realized by two opposite hard walls.The distance between the walls is varied. The chains exhibit a strong tendency to orientparallel to the walls and are flattened when being very close to them. This deviation of thepolymer structure with respect to the bulk is accompanied by an acceleration of local densityfluctuations. On the other hand, the diffusion coefficient of a chain remains unaffected.
Probing the Fractal Character of Pore Surfaces in Shale with Adsorption Technique
Authors: Ma Jian , Qi Hao , Wong Po-Zen 
Published: April 2011

AbstractWe report on an adsorption study on two shale samples that have previously been investigated by small-angle neutron scattering (SANS). The scattering data indicate that these samples can be characterized as surface fractals in length from 5 Å to 500 Å, with the fractal dimension D between 2.83 and 2.75. Using the existing models for adsorption on fractal surfaces, the values of D deduced from the adsorption data appear to be consistently lower than the SANS results. We discuss these findings.
Competing Elementary Reactions in a Capillary - Two Reaction Fronts Moving in Opposite Directions
Authors: Park Sung Hyun , Taitelbaum Haim , Kopelman Raoul 
Published: April 2011

AbstractThe behavior of two reaction fronts created in a system of two competing reactions has been investigated using the reaction between xylenol orange (XO) and chromium(III) ion in aqueous solution. Two reaction fronts have been shown to move in opposite directions, which is explained in terms of relative concentrations among three reactant species. This explanation was verified by the observation of only one reaction front for selected different relative concentrations, where both reaction fronts move in unison. As predicted by theory and confirmed by computer simulation, the position (xf) of each reaction front scales as t½, irrespective of the direction of motion.
Effect of Covalently Incorporated Azobenzenes on Dendrimers
Authors: McGrath D. V. , Junge D. M. , Cheng A. , D'Ambruoso G. 
Published: April 2011

AbstractSeveral new azobenzene-containing dendritic molecules have been prepared and characterized. The photoresponsive characterization of these dendrimers illustrates the insensitivity of the photochromic behavior of the azobenzene with respect to the nature of the attached dendritic fragment.
PE-CVD of Fluorocarbon/Silicon Oxide Composite thin Films from TFE and HMDSO
Authors: Shirafuji T. , Hayashi Y. , Nishino S. 
Published: April 2011

AbstractFluorocarbon/silicon oxide composite thin films were prepared, expecting higher thermal stability, by mixing hexamethyldisiloxane (HMDSO, (CH 3) 3-Si-O-Si-(CH 3)3) with tetrafluoroethylene (TFE, CF2=CF2) using an RF( 13.56 MHz) PE-CVD method for the purpose of application to low-k IMDs. Structure of the deposited films was investigated by XPS and FT-IR. Film composition can be changed gradually from fluorinated carbon to organic siloxane by changing the HMDSO mixing ratio. The films possessed dielectric constants less than 2.5 for HMDSO mixing ratios less than 10%. Thermal treatment of the films revealed that C-Fn, Si-O-Si, Si-(CH3)n and Si-(CH2)n-Si bonds were stable to 400°C, but C-Hn bonds were not. In situ gas-phase FT-IR spectroscopy was performed on the TFE/HMDSO plasma to help determine reaction mechanisms.
Magnetron Sputtered Ti-Basis Hard Material Coatings on Thermoplastic Polymers for Applications in Particle Sensitive Environments
Authors: Lugscheider E. , Barwulf S. , Barimani C. , Riester M. , Hilgers H. 
Published: April 2011

AbstractEven under demanding environments, like clean rooms, polymers are already used in different-ranges of applications. The wear and particle generation within a specific particle size even under-mechanical stress is a limiting factor. So it was the aim to develop an innovative material-concept, that enables to apply a thermoplastic polymer coated with a thin hard material (thickness-up to 2.5 gm), which also prevents for electrostatical discharges and is usable for complex-bodies. Therefore it was necessary to improve the wear resistance and the adherence between the-polymer and the coating. To take also economic aspects into consideration a two step production-process sequence was required, consisting of the injection moulding process and then the plasma-deposition process including a plasma pre-treatment. In this investigation, poly(butyleneterephthalate)-(PBT) and poly(amide) 6.6 (PA) and polycarbonate (PC) were chosen as substrate-material. The coating materials used, which were mainly deposited by Magnetron Sputter Ion-Plating (MSIP), were on titanium basis (Ti-N). To get detailed chemical information about the-coatings and the interfacial region they were analyzed by X-Ray Photoelectron Spectroscopy-(XPS), additionally Secondary Ion Mass Spectrometry (SIMS) experiments were carried out to-confirm the results. The process parameter's influence on the microstructure, which extend from-amorphous to columnar (crystalline), and the film thickness were analyzed by SEM. It will be-shown and discussed, that it is possible to improve the coating's adherence by plasmapretreatment-as well as to reduce the particle generation after a suitable etching and coating process.
Gas Phase and Particle Diagnostic of Hmdso Plasmas by Infrared Absorption Spectroscopy
Authors: Magni D. , Deschenaux C.H. , Courteille C. , Howling A. A. , Hollenstein C.H. , Fayet P. 
Published: April 2011

AbstractFTIR spectroscopy has been applied to a radio-frequency discharge in hexamethyldisiloxane (HMDSO) diluted with oxygen and helium, as typically used for industrial SiOx, deposition. By measuring the infrared absorption of the HMDSO molecule, the gas consumption during processing can be monitored, allowing process optimization. Additional information on various infrared active radicals formed within the plasma, such as CO, CO2 and aldehydes, helps to elucidate the plasma chemistry in HMDSO plasmas. Besides information on the formation of gaseous components in the plasma, infrared transmission spectra give at the same time important data on the nature of the particle contamination.
Grain Boundary Chemical Analysis Using Intense Electron Beams
Authors: Shang P. , Keyse R. , Jones I. P , Smallman R. E. 
Published: April 2011

ABSTRACTScanning Transmission Electron Microscope (STEM) Energy Dispersive X-Ray analysis (EDX) linescans and mapping have been used to examine the large angle grain boundary chemistry of Ni-rich Ni3AI both with and without boron. The results show that the Al content is reduced while the Ni content is unchanged at the grain boundaries in all these alloys, with the percentage of reduction of Al at the grain boundaries decreasing as boron concentration increases. This is ascribed to differential surface sputtering of the lighter Al atoms.
A Dislocation Constriction, Pinning Point Model for the Flow Stress Anomaly in Iron Aluminides
Authors: Morris David G. 
Published: April 2011

ABSTRACTIron aluminides with compositions from Fe3A1 to FeAl show an anomalous stress rise at temperatures about 600–800K. Many models have been suggested to explain this behaviour, with the suggestion of hardening by vacancies presently receiving much attention. An alternative model is suggested here, valid for those alloys where the simultaneous reduction of DO3order does not interfere, based on the density of constrictions produced on mobile <111> superdislocations and their subsequent pinning by decomposition or by their cross slip to produce jogs. The exponential increase in stress with temperature can be related to the pinning point density and the absolute values of strengthening correspond well with those predicted by this model. The orientation dependence of the stress anomaly and the tension-compression asymmetry can be related to the role of shear stresses in assisting constriction of the dislocation partials by modifying the core configuration and by assisting the expansion of the new, decomposed dislocations.
Atypical Defects in a B2 Fe-40A1–0.7C-0.5B Alloy
Authors: Pang L. , Kumar K. S. 
Published: April 2011

ABSTRACTThe nature of defects in a quaternary Fe-40A1–0.7C-0.5B alloy was examined by transmissionelectron microscopy (TEM) techniques including weak beam microscopy and z-contrast imaging.Complex {001} stacking faults were observed in certain conditions in these alloys that were not previouslynoted in a ternary Fe-40A1–0.6C alloy. These faults exhibit a 1/2<001> displacement vectorthat lies in the plane of the fault and structurally misses an aluminum layer. Six variants of this faulttype are present. These faults are absent in brine-quenched and furnace-cooled alloys, but are readilyobserved in the air-cooled condition. In addition to the usual <111> superdislocations that are APBdissociatedinto 1/2<111> superpartials, dissociated <100> dislocations (into two 1/2< 100> partials)are also observed under certain conditions. Quenched and aged alloys show dissociated <001> loops.The absence of such defects in the B-free alloy and following certain heat treatments in the B-containingalloy, suggests that boron may be segregating to the cube planes and lowering the interfacialenergy on these planes. The presence of dissociated <001> loops in the quenched and aged alloy alsosuggests the formation of B-vacancy complexes that coalesce during aging, forming such dissociatedloops.
Mechanical Anisotropy of a Gamma Titanium Aluminide Alloy After Hot Extrusion
Authors: Oehring M. , Lorenz U. , Niefanger R. , Appel F , Brokmeier H.-G. , Wagner R. , Clemens H. , Eberhardt N. 
Published: April 2011

ABSTRACTBy hot extrusion below and above the α transus temperature equiaxed and predominantly lamellar microstructures were obtained in a Ti aluminide alloy. In order to examine a possible orientation dependence of mechanical properties the flow stress, the activation parameters of plastic deformation and the fracture toughness were determined parallel and perpendicular to the extrusion direction at room temperature and 700 °C. The observed anisotropy in these properties may be mainly attributed to anisotropies in the microstructures, in particular to a preferential alignment of lamellae in lamellar microstructures.
Physical and Mechanical Properties of Two-Phase Zr-Cr-Mn Alloys
Authors: Goldberg A. , Luzzi D. E. 
Published: April 2011

ABSTRACTThe Zr-Cr-Mn system is used to explore the effect of a lowered SFE on the room temperature mechanical properties of a Laves phase using elements of similar atomic size. The ternary Zr-Cr-Mn diagram in the region from 0 to 12 at. % Mn is first determined and it is shown that Mn substitutes only for Cr in the Laves phase. TEM analysis of the density of stacking fault energy related defects such as annealing twins indicates that Mn substitution for Cr in ZrCr2 lowers the SFE of the cubic Laves phase. Mechanical testing of the two phase alloys is used to explore the effects of Mn content and the volume fraction of each phase on the ductility and fracture behavior in compression. It is found that the mechanical properties are well-described by a model incorporating solid solution strengthening in a ductile-brittle two phase alloy.
Annealing of Quenched Fe-Al Alloys With/Without B And Ti
Authors: Yang Y. , Baker I. 
Published: April 2011

ABSTRACTFe-40A1, Fe-40A1–0.12B and Fe-40A1–5Ti were annealed at a variety of temperatures, water quenched to obtain different vacancy concentrations, and heated at 10 K/min to 973K in a differential scanning calorimeter. Either one or two exothermic peaks were observed, at 533–613K and 743–933K, for all the alloys, while an additional exothermic peak was observed at 653K-693K for Fe-40A1–5Ti. All the peaks shifted to lower temperature with increasing quenching temperature. It is shown that the highest temperature exothermic peak is associated with the annihilation of thermal vacancies. Analysis of this peak as a function of temperature yields vacancy formation enthalpies of 102±15kJ/mol, 104±15 kJ/mol and 81±15 kJ/mol for Fe-40A1, Fe-40A1–0.12B and Fe-40A1–5Ti, respectively. The lower temperature exothermic peaks may arise from vacancy rearrangement.
Structure and Mechanical Properties of the Engine Valves with Intermetallic Disk
Authors: Kodess B. N. , Teterin G. P. , Kommel L. A. , Ovcharov V. K. 
Published: April 2011

ABSTRACTThe bimetallic valves were produced using a new technique, IFFM (Impact Fused-Forging Modeling). Distribution of the alloy components as well as phase composition across the valve section was obtained by means of energy-dispersive analysis and X-ray diffraction. Optic and electron microscopy research of macro- and microstructure was conducted. High quality of the joint between the sintermetallic (TiAl) head and the titanium (VT-9 and VT-6 alloys) stem was demonstrated. As a result of the contact of the stem with the semi-solid intermetallics at the temperature above Tc, a polymorphous transformation was obtained in the upper part of the Ti-based stem. The globular microstructure in the intermetallic head in the area near to the joint of the two alloys was achieved. The results proved that the process allows production of complex shaped parts based on advanced alloys of high quality, featuring extra wear-resistance and strength.
Observations of Orientation Dependent Creep of Ni3AI
Authors: Knobloch Carola , Glock Karin , Glatzel Uwe 
Published: April 2011

ABSTRACTThe influence of crystal orientation on the high temperature creep behavior of Ni3(Al Ti Ta) was investigated by tensile creep testing under a constant load at a temperature of 1123K. The single crystals were oriented close to [001], [011], [111], [557] and [012]. The results show an increasing stationary creep rate from [111] over [011] to [001]. The evolution of the microstructure during creep deformation was studied, using transmission electron microscopy (TEM). Only few systems are active in the primary regime, whereas several slip systems operate in the secondary stage. Habit planes of dislocation pairs separated by an antiphase boundary were examined and compared with anisotropic elastic calculations, explaining the good creep response of [111] oriented single crystals.