bluuebunny/crossref_metadata_2025_split huggingface dataset:
Critical Behaviour of the Fe3Nd Cluster Glass Phase in Bulk Glassy Nd60Fe30Al10 Hard Magnets
Authors: Ortega-Hertogs R. J. , Inoue A. , Rao K.V. 
Published: April 2011

AbstractThe magnetic properties of novel bulk glassy Nd60Fe30Al10 magnets around the transition to the paramagnetic state have been studied in order to understand the magnetic microstructure in these materials. Analyses of the critical behavior of the magnetic isotherms suggest a transition from a low field magnetic state to a ferromagnetic-like state upon the application of high enough magnetic fields. The ferromagnetic-like state is evidenced by a scaling of the magnetization curves with critical exponents λ=1.5(1), β=0.65(5), and TC=465 K. These results are consistent with the predictions for weak random magnetic anisotropy systems.
An Investigation of The Effects of Temperature on Fatigue Crack Growth Behavior of a Cast Nearly Lamellar Ti-47A1–2Cr-2Mn + 0.8 Vol. %TiB2 Gamma Titanium Alloy
Authors: Lou J. , Mercer C. , Soboyejo W.O. 
Published: April 2011

ABSTRACTThis paper presents the results of a study of the effects of temperature on fatigue crack growth in Ti-47A1–2Cr-2Mn + 0.8 Vol. %TiB2 gamma titanium aluminide intermetallics. Fatigue crack growth rate data are presented for the cast lamellar microstructure at 25,450 and 750°C. The trends in the fatigue crack growth rate data are explained by considering the combined effects of crack-tip deformation mechanisms and oxide-induced crack closure. Faster fatigue crack growth rates at 450°C are attributed to the high incidence of irreversible deformation-induced twinning, while slower crack growth rates at 700°C are due to increased deformation by slip and the effects of crack-tip shielding provided by oxide-induced wedging, which is analyzed using a modified Dugdale-Barenblatt model.
Experimental and Theoretical Investigations of the Phase Transformation in Al-rich TiAl Intermetallic Compounds
Authors: Koyama T. , Doi M. , Naito S. 
Published: April 2011

ABSTRACTThe phase decomposition of the Al-rich γ TiAl intermetallic compound in the TiAl(L10) and Ti3Al5(P4/mbm) two phases region is investigated experimentally. On the phase decomposition of the Ti-56at%Al alloy, the single precipitate(Ti3Al5) shape is an oblate spheroid at the early stage of precipitation and each particle is aligned along certain direction of the orientation about 20 degrees from [100]. During coarsening, the precipitates encounter each other, then, the shape of the particle becomes the slanted or bended plate. In the case of phase decomposition of the Ti-58at%Al alloy, the tweed-like structure is observed at the beginning of the aging. The precipitates are connected each other during coarsening, finally the microstructure becomes the large layered structure with a zigzag-shaped interface. These microstructure changes are simulated based on the phase field model. The morphology and the time development of the simulated microstructure are in good agreement with the experimental results.
Synthesis and Characterization of Mechanically Alloyed and HIP-Consolidated Fe-25Al-10Ti Intermetallic Alloy
Authors: Zhu Su-Ming , Tamura Makoto , Sakamoto Kazushi , Iwasaki Kunihiko 
Published: April 2011

ABSTRACTThe present study is concerned with the processing, microstructural characterization, mechanical and tribological properties of fine-grained Fe-25Al-10Ti intermetallic alloy. The alloy was synthesized from elemental powders by mechanical alloying in an attritor-type ball milling system for 100 h, followed by hot isostatic pressing (HIP). After HIP treatment at 1073 K under an ultra-high pressure of 980 MPa, fully dense compacts with a grain size of about 200 nm were produced. Mechanical properties were evaluated by compression tests from room temperature to 1073 K. At room temperature, the alloy exhibits yield strength as high as 2.4 GPa, together with considerable rupture strain of 0.16. The yield strength decreases monotonically with increasing test temperature with no positive temperature dependence observed. The grain growth after high temperature deformation is not severe, indicating that the alloy has a relatively high thermal stability. Finally, tribological properties of the alloy were evaluated by using a ball-on-disk type wear tester and compared with those for gray cast iron, a currently used material for automotive brake rotors.
Effects of ternary additions on the deformation behavior of single crystals of MoSi2
Authors: Inui Haruyuki , Ishikawa Koji , Yamaguchi Masaharu 
Published: April 2011

ABSTRACTEffects of ternary additions on the deformation behavior of single crystals of MoSi2 with the hard [001] and soft [0 15 1] orientations have been investigated in compression and compression creep. The alloying elements studied include V, Cr, Nb and Al that form a C40 disilicide with Si and W and Re that form a C11b disilicide with Si. The addition of Al is found to decrease the yield strength of MoSi2 at all temperatures while the additions of V, Cr and Nb are found to decrease the yield strength at low temperatures and to increase the yield strength at high temperatures. In contrast, the additions of W and Re are found to increase the yield strength at all temperatures. The creep strain rate for the [001] orientation is significantly lower than that for the [0 15 1] orientation. The creep strain rate for both orientations is significantly improved by alloying with ternary elements such as Re and Nb.
Processing and Properties of Gamma+Laves Phase in-situ Composite Coatings Deposited via Magnetron Sputtering
Authors: Huang Feng , Epling William S. , Barnard John A. , Weaver Mark L. 
Published: April 2011

ABSTRACTRecent research efforts have established that Laves phase reinforced gamma titanium aluminides (i.e. γ + Laves) offer significant potential as oxidation resistant coating in high-temperature structural applications and as wear-resistant coatings for cutting tools. In this study, TiAlCr coatings were magnetron sputtered from a Ti-51Al-Cr alloy target onto various substrates. The microstructure, hardness, and stress behavior of the as-deposited and annealed coatings have been investigated.
Tensile Properties of B2-Type CoTi Intermetallic Compound
Authors: Kaneno Y. , Takasugi T. 
Published: April 2011

ABSTRACTB2-type CoTi intermetallic compound that was hot-rolled and recrystallized was tensile-tested as functions of temperature and testing atmosphere. The tensile strength showed a peak at intermediate temperature (∼800K). The brittle-ductile transition (BDT) defined by tensile elongation took place at about 800K, above which large tensile elongation was observed. Corresponding to this transition, SEM fractography showed a change from cleavage-like pattern mixed with intergranular fracture pattern to large cross-sectional reduction, i.e. necking of the tensile specimen. Also, the observed mechanical properties were independent of heat-treatment procedures, indicating that retained vacancies did not affect the mechanical properties of CoTi intermetallic compound. However, the tensile elongation and UTS at room temperature were dependent on testing atmosphere, indicating that moisture-induced embrittlement occurred in CoTi intermetallic compound.
Incommensurate Structure in Al-rich TiAl Alloys
Authors: Wang S. , Fort D. , Jones I. P. , Abell J. S. 
Published: April 2011

ABSTRACTThe microstructures of Ti-Al alloys in the range 56–62 at.% Al have been studied. These compounds consist of a basic L10 structure on which is superimposed an irrational modulation (Ti3Al5 related). This is incommensurate by occupation. It has two-dimensional modulations in which the wave vectors are q1 = α(a* + b*) and q2 = α(-a* + b*) where a* and b* are the L10 reciprocal basis and α is an irrational fraction. α decreases from 0.282 to 0.26 as the Al concentration increases to 60 at.% Al, i.e., the positions of the satellites change continuously with varying Al concentration. A third phase, TiAl2, appears at a composition of 62 at.% Al which means that no Ti3Al5 (62.5 at.% Al) of stoichiometric composition can ever exist.
Improving the Understanding of Ion-Beam-Induced Defect Formation and Evolution by Atomistic Computer Simulations
Authors: Posselt Matthias 
Published: April 2011

AbstractThe morphology of the as-implanted damage in silicon is investigated using a recently developed combination of time-ordered computer simulations based on the binary collision approximation (BCA) with classical molecular dynamics (MD) calculations. The method is applied to determine the type and the amount of defects formed within the first nanosecond after ion impact. The depth profile and the total number of different defect species (vacancies, interstitials, disordered atoms, etc.) produced on average per incident ion are calculated for B+ (15 keV), P+ (5, 10, 20, 30 keV), and As+ (15 keV) implantations. It is shown that the as- implanted defect structure depends not only on the nuclear energy deposition per ion but also explicitly on the ion mass. Therefore for each ion species the damage morphology exhibits characteristic features. For heavy ions the percentage of extended defects is higher than for light ions. In all cases investigated the number of free or isolated interstitials exceeds the amount of free vacancies. The results obtained allow a microscopic interpretation of the phenomenological model for the as-implanted damage employed in conventional BCA simulations in order to describe the dose dependence of the shape of ion range profiles. They can be also applied to get more realistic initial conditions for the simulation of the defect kinetics during post-implantation annealing.
Film Fracture Phenomena During Indentation
Authors: Bahr D.F. , Pang M. , Rodriguez-Marek D. 
Published: April 2011

ABSTRACTDiscontinuities during both load and depth controlled continuous indentation tests have been ascribed to dislocation nucleation or multiplication and film fracture. In materials which exhibit permanent deformation prior to a discontinuity in loading, it is more likely that the phenomena is indeed controlled by film fracture, and not the rapid generation of dislocations. The current study has been undertaken to examine the properties of passivating films on engineering alloys. An electrochemical cell coupled with a scanning probe microscope and nanoindentation system allows growth and mechanical testing of passive films on an austenitic stainless steel as well as a titanium alloy. A complementary set of ex situ experiments shows the presence of deformation prior to film fracture with both load – depth sensing techniques as well as imaging the surface topography. The occurrence of excursions is shown in these materials to be linked directly with film fracture, rather than dislocation multiplication.
Molecular Dynamics simulations of displacement cascades: role of the interatomic potentials and of the potential hardening
Authors: Becquart C.S. , Domain C. , Legris A. , Duysen J.C. van 
Published: April 2011

ABSTRACTThe role of the interatomic potentials on the primary damage has been investigated by Molecular Dynamics (MD) simulations of displacement cascades with three different interatomic potentials dedicated to α-Fe. The primary damage, caused by the neutron interaction with the matter, has been found to be potential sensitive. We have investigated the equilibrium parts of the potential as well as the “short distance interactions” which appear to have a strong influence on the cascade morphology and defects distribution at the end of the cascade. The static properties as well as dynamical (thermal) characteristics of the potentials have been considered; the kinetic and potential energy transfers during the collisions have also been studied.
Crystallization of Isolated Amorphous Zones in Semiconductor Materials
Authors: Hollar Eric P. , Robertson Ian M. , Jenčič Igor 
Published: April 2011

ABSTRACTCrystallization of spatially isolated amorphous zones in Si, Ge, GaP, InP and GaAs was stimulated thermally and by irradiation with electrons and photons. The amorphous zones were created by a 50 keV Xe+ implantation. Significant thermal crystallization occurred at temperatures greater than 425 K, 375 K and 200 K in Si, Ge and GaAs, respectively. Electrons with energies between 25 and 300 keV stimulated crystallization in all materials at temperatures between 90 K and room temperature. For electron energies above the displacement threshold, the crystallization rate decreased as the electron energy decreased. As the electron energy was decreased below approximately 100 keV, the crystallization rate unexpectedly increased. The crystallization rate was independent of temperature for all electron irradiations. Irradiation with a 532 nm green laser (hv= 2.33 eV) caused crystallization in Si (Eg = 1.11 eV) and Ge (Eg = 0.67 eV) at a rate comparable to a thermal anneal at 425 K and 375 K, respectively, and caused minimal crystallization in GaP (Eg = 2.26 eV). The electron and photon irradiation results are consistent with the model that crystallization is controlled by defects (dangling bonds and kinks) created by electronic excitation at the amorphous-crystalline interface.
Inverse Ostwald Ripening and Self-Organization of Nanoclusters due to Ion Irradiation
Authors: Heinig K.-H. , Schmidt B. , Strobel M. , Bernas H. 
Published: April 2011

ABSTRACTUnder ion irradiation collisional mixing competes with phase separation if the irradiated solid consists of immiscible components. If a component is a chemical compound, there is another competition between the collisional forced chemical dissociation of the compound and its thermally activated re-formation. Especially at interfaces between immiscible components, irradiation processes far from thermodynamical equilibrium may lead to new phenomena. If the formation of nanoclusters (NCs) occurs during ion implantation, the phase separation caused by ion implantation induced supersaturation can be superimposed by phenomena caused by collisional mixing. In this contribution it will be studied how collisional mixing during high-fluence ion implantation affects NC synthesis and how ion irradiation through a layer of NCs modifies their size and size distribution. Inverse Ostwald ripening of NCs will be predicted theoretically and by kinetic lattice Monte-Carlo simulations. The mathematical treatment of the competition between irradiation-induced detachment of atoms from clusters and their thermally activated diffusion leads to a Gibbs-Thomson relation with modified parameters. The predictions have been confirmed by experimental studies of the evolution of Au NCs in SiO2 irradiated by MeV ions. The unusual behavior results from an effective negative capillary length, which will be shown to be the reason for inverse Ostwald ripening. Another new phenomenon to be addressed is self-organization of NCs in a δ-layer parallel to the Si/SiO2 interface. Such δ-layers were found when the damage level at the interface was of the order of 1-3 dpa. It will be discussed that the origin of the δ-layer of NCs can be assigned to two different mechanisms: (i) The negative interface energy due to collisional mixing gives rise to the formation of tiny clusters of substrate material in front of the interface, which promotes heteronucleation of the implanted impurities. (ii) Collisional mixing in the SiO2produces diffusing oxygen, which may be consumed by the Si/SiO2 interface. A thin layer parallel to the interface becomes denuded of diffusing oxygen, which results in a strong pile up of Si excess. This Si excess promotes heteronucleation too. Independent of the dominating mechanism of self-organization of a d-layer of NCs, its location in SiO2 close to the SiO2/Si interface makes it interesting for non-volatile memory application.
Grain Boundary Migration in Alumina
Authors: Farrer Jeffrey K. , Ravishankar N. , Michael Joseph R. , Carter C. Barry 
Published: April 2011

ABSTRACTThe sintering process of ceramics involves grain-boundary migration (GBM) that is accompanied by mass transport across an interface. In this study, electron backscatter diffraction (EBSD) has been used to examine grain-boundary migration in alumina bicrystals with liquid films at the interface. EBSD patterns, taken near the sintered interface, have been used to study the effects of crystallography on GBM and to study the orientation relationships within the migrated regions of the crystal. Results indicate that the direction of migration is not always the same as that predicted by the current theories on GBM. It was also found that there may be small-angle misorientations in the migrated regions.
The Effect Of Extended Superdislocation / Domain Boundary Interactions in Ordered Intermetallic Compounds
Authors: Rong Tie-Sheng , Aindow Mark , Jones Ian P. 
Published: April 2011

ABSTRACTIt has been known for many years that the presence of a distribution of domain boundaries in crystals with ordered superlattice structures can affect both the separation of glissile superpartial dislocations and the yield stress. Based on the details of the interactions between the domain boundaries and glissile extended superdislocations, we incorporate the effects of the thin band of perfect crystal that arises whencoupled superpartial dislocations straddle a domain boundary, and the additional domain boundary area createdonce the whole superdislocation has passed through. If these effects are included then, in an ordered phase containing many domains, we would expect the equilibrium separation of the coupled superpartial dislocations to vary more significantly with domain size than is predicted by previous models. These effects also change the way in which yield stress is predicted to vary with domain size. This variation gives a much better match to published experimental data than existing models.
Misfit Accommodation Mechanisms at Moving Reaction Fronts During the Initial Growth Stage of La2Zr2O7-based Pyrochlore on (001)YSZ
Authors: Lu C.J. , Senz S. , Hesse D. 
Published: April 2011

AbstractLa2Zr2O7-based pyrochlore (LZO) islands were grown on (001)-oriented Y2O3-stabilized ZrO2 (YSZ) single crystal surfaces by the reaction between the crystals and a La2O3 vapour. The islands are epitaxial with a small tilt. On a flat substrate surface each pyramidal island consists of four domains which are slightly tilted around different <110> axes with respect to the YSZ lattice. On a YSZ surface with pits of high density, more interestingly, each larger island formed at a pit has a central hole and contains two to four <100>-tilted stripe domains in addition to the four regular <110>-tilted domains. A square network of interfacial edge dislocations having Bur- gers vectors as/2 [101] (as being the lattice parameter of YSZ) was observed in the regular domains at the LZO/YSZ reaction front of positive lattice mismatch (+5%). In stripe domains two sets of orthogonal misfit dislocations are present with different Burgers vectors of type b = as/2 [101] andas/2 [010]. The perpendicular components of the Burgers vectors give rise to the observed tilts of the LZO lattices. Possible models are proposed to explain the generation of dislocation half-loops, the preferred nucleation of the islands near YSZ surface pits as well as their growth kinetics and the formation of stripe domains.
Atomic Force and Electron Microscopy Studies of Tin Dioxide Films Prepared from Solutions with High Fluorine Content
Authors: Acosta Dwight R. , Castanedo Rebeca , Estrada Walter , Avila-Godoy Rosario 
Published: April 2011

AbstractAtomic force microscopy and electron microscopy were used to study surface and structural properties in SnO2:F thin films deposited by spray pyrolysis on glass at a constant substrate temperature. The influence of high levels of fluorine in the starting solution on the surface topology and morphology of thin films and correlations with electrical properties are presented in this work.
Classical Interatomic Potential for Nb-Alumina Interfaces
Authors: Albe K. , Benedek R. , Seidman D. N. , Averback R.S. 
Published: April 2011

AbstractA modified-embedded-atom-method (MEAM) potential is derived for the ternary system Al-O-Nb in order to simulate the model oxide-metal interface sapphire-niobium. In the present work, MEAM parameters for Al and O given by Baskes were adopted, and the parameters for Nb are adjusted to match experimental data for pure Nb and calculated properties for Nb oxides and aluminides. The properties for niobium oxides and aluminides were obtained from local- density-functional-theory (LDFT) calculations. The resultant potential was tested in simulations for the Nb(111)/α -alumina(0001) interface. MEAM predictions of the work of separation and the interlayer relaxations for two interface terminations are in excellent agreement with LDFT calculations. The MEAM potential therefore appears suitable for large-scale computer simulation of oxide-metal interface properties.
MOCVD of Ir and IrO2 Thin Films for PZT Capacitors
Authors: Shimizu M. , Kita K. , Fujisawa H. , Niu H. 
Published: April 2011

AbstractIr films were prepared on SiO2/Si at 275-500°C by M°CVD (Metalorganic Chemical Vapor Deposition) using a new Ir precursor, Ir(EtCp)(cod) (iridium(ethylcyclopentadienyl) (1,5-cyclo°Ctadiene): Ir(C2H5C5H4)(1,5-C8H12). Ir films prepared at 275-300°C showed highly reflecting surfaces with Rrms roughness (root-mean-square roughness) of 1.4-10nm. At 500°C, Ir and IrO2 mixture-oriented films were grown. Ir films deposited at 300°C on patterned SiO2/Si substrates with aspect ratios of 0.3-2.0 showed good step coverage of 70-85%. Auger analysis revealed that Ir film had no incorporation of carbon and oxygen, and that Ir films performed well as a diffusion barrier in PZT/Ir/SiO2/Si structure.
A Dielectric Bolometer Behavior of BST Thin Film Prepared by Metal-Organic-Decomposition with Excellent Reproducibility in Thermal Cycling Test
Authors: Noda Minoru , Zhu Hong , Xu Huaping , Mukaigawa Tomonori , Hashimoto Kazuhiko , Okuyama Masanori 
Published: April 2011

AbstractWe have proposed a new type of simple detector pixel circuit and device structure for application of dielectric bolometer mode (DB) of infrared (IR) image sensor. The DB mode has merits such as uncooled room temperature operation, chopperless, low power dissipation, and high-sensitivity. A stable Ba1划xSrxTiO3 (BST) thin film has been successfully developed as a dielectric bolometer material for IR detector by Metal-Organic-Decomposition (MOD) method. The film was prepared on both Pt/Ti/SiO2/Si-bulk and Pt/Ti/NSG/Si3N4/SiO2 membrane structures, where an IR light is detected at the membrane as a change in dielectric constant (ε). So, the important issue for realizing a reliable IR sensor with high-sensitivity has been achieved to have a good thermal stability in ε against change in the detector temperature. XRD patterns and D-E hysteresis curves were measured and revealed that the BST film has a good perovskite structure and shows an adequate ferroelectric loops, especially for final annealing temperature higher than 700 °C. Temperature Coefficient of Dielectric constant (TCD), which decides the IR sensitivity, of the MOD made BST film is about 1 %/K. The reproducibility in ε, namely IR detector capacitance, was found to be very good in temperature ranging from about 10 to 80 °C within a relative change of 2 %. Finally, the stabilities in both the temperature dependence of ε and the output level have been obtained with a fairly large IR detectivity, where voltage sensitivity(Rv) and specific detectivity(D*) were about 1.2 kV/W and 2.9e8 cmHz 1/2/W, respectively.