bluuebunny/crossref_metadata_2025 huggingface dataset:
Friction Between Polymer Brushes
Authors: Sokoloff Jeffrey B.
Published: June 2019

A type of static friction between two polymer brush coated surfaces, resulting from fluctuations from mean field theory is found, but with creep-like motion for forces below the force of static friction, which is much more rapid than the usual creep between solid surfaces in contact.
Equilibrium and Dynamic Properties of Dislocation Dipoles
Authors: Veyssiere Patrick
Published: June 2019

This paper embraces several aspects related to dislocation self-organization in single slip. The formation of prismatic loops, seminal to the nucleation and growth of dislocation braids, is a dynamical process involving elastic dipolar interactions. Preliminary simulations of the concerted process of loop generation are presented. Elastic properties of dislocation dipoles are analysed as a function of dipole character. Equilibrium properties are investigated under the isotropic and anisotropic elastic approximations. The orientation dependence of the so-called dipole passing stress is examined, and its implication in the elementary mechanisms that take place under constrained deformation conditions, such as fatigue cycling, are discussed.
Effects of Sample Size on the Fracture Behavior in Fe-3%Si Alloy Single Crystals
Authors: Takashima Kazuki , Taki Eiji , Kawakami Yuji , Otsu Masaaki
Published: June 2019

Fracture tests have been performed for both macro- and micro-sized specimens prepared from an Fe-3%Si alloy single crystal, and the effects of length scale on fracture behavior have been investigated. Micro-sized cantilever beam specimens with dimensions of 10 × 10 × 50 μm3 were prepared by focused ion beam machining. Notches with a depth of 5 μm were introduced into the micro-sized specimens and fatigue pre-crack was also introduced ahead of the notch. Macro-sized three-point bending specimens with dimensions of 2 × 2 × 10 mm3 were also cut from the same Fe-3%Si alloy single crystal. Notches with a depth of 1mm were introduced into the macro-sized specimens, and fatigue pre-crack was also introduced. Notch plane was set to be (100), which is a cleavage plane of this material, and notch direction was set to be [010] for both size of specimens. For macro-sized specimens, cleavage fracture occurred during introducing fatigue pre-crack. In contrast, the micro-sized specimens were fractured by ductile manner. A plastic zone was clearly observed on the specimen surface near the crack tip and dimples were found on the fracture surface. The plastic zone size of this material is calculated to be 90 μm. This size is small enough to satisfy small scale yielding for macro-sized specimens, although this size corresponds to large scale yielding in micro-sized specimens. This may cause the size effect on the fracture behavior of this material.
Study of the Effects of Si Addition on the Properties of Hard Nanocomposite Thin Films
Authors: Endrino Jose Luis , Palacin Sergio , Gutierrez Alejandro , Aguirre Myriam , Schäfers Franz
Published: June 2019

In the present study, hard TiSiN coating compounds with different Si content have been deposited by the magnetron sputtering technique. X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) have been employed to investigate the effects of Si addition on the composition, structure and phase development of the cubic NaCl-type structure. To get some insight on these changes, X-ray absorption spectra have been measured at the Ti and Si K-edges in fluorescence yield mode. The collected data showed that the interaction between Ti and Si was weak and the formation of a-Si3N4 can be assumed. Hardness measurements were also consistent with the formation of hard nanocomposite films. A maximum hardness of about 36 GPa was obtained for the sample with 11 at. % Si.
The Identation Size Effect and Hall-Petch Behaviour of Annealed Polycrystalline Copper
Authors: Hou XiaoDong , Zhu T.T. , Jennett N. M. , Bushby A. J.
Published: June 2019

Methods to obtain tensile stress-strain properties of materials from a practically non-destructive indentation test are of great industrial interest. However, to do this successfully, indentation size effects must be accounted for. Many indentation size effects, such as strain gradient plasticity and micro-pillar experiments [1], show a size dependence proportional to the inverse square root of a length scale, in common with Hall-Petch behavior. Recently, however, the indentation size effect from small radius spherical indenters has been shown, for a range of fcc metals, not to follow a Hall-Petch-like relationship but to be proportional to the inverse cube root of indenter radius [2]. Here, we investigate these differences further and present results for the indentation size effect with spherical indenters on Cu samples that have been engineered to have different grain sizes. The important experimental control parameter of the relative size of the indentation compared to the grain size is also explored since the cross over from grains significantly smaller than the contact radius to grains significantly larger than the contact radius occurs at different length scales in each sample. A thorough understanding of the various length-scale effects in the different test methods (e.g. the indentation size effect and grain size effect in indentation), is essential if a relationship, robust enough for industrial application, is to be defined to obtain tensile properties from an essentially non-destructive indentation test.
Two-way Shape Memory Surfaces
Authors: Zhang Yijun , Cheng Yang-Tse , Grummon David S
Published: June 2019

Recently, we discovered that a two-way shape memory effect can be realized on NiTi shape memory alloy surfaces by spherical indentation. Either thermomechanical cycling or slip-plastic deformation under contact loading conditions is effective in inducing reversible indent depth changes: deeper indents in the low temperature martensitic phase and shallower indents in the high temperature austenitic phase [1, 2]. By planarization of these spherical indents to restore a flat surface, circular reversible surface protrusions appear upon heating and disappear upon cooling. Nano-protrusions are also realized in sputter deposited NiTi thin films. Furthermore, two-way reversible line protrusions are made by planarizing scratch tracks on a NiTi shape memory alloy. Shape memory surfaces can be exploited for a wide range of potential applications, including information storage, optical devices, and smart tribological surfaces.
Phase Transformations in Non-stoichiometric GaAs with Sb and P Doping
Authors: Chaldyshev Vladimir , Bert Nikolay A. , Boitsov Anton V. , Musikhin Yurii G. , Yagovkina Maria A. , Preobrazhenskii Valerii V. , Putyato Mikhail A. , Semyagin Boris R.
Published: June 2019

We investigate the phase transformation in non-stoichiometric GaAs films, which are doped with group V isovalent impurities, namely Sb and P. In contrast to Al and In atoms of group III, group V atoms may not only form substitutional alloys with the GaAs matrix, but also can be dissolved in As precipitates. Our experimental study based on transmission electron microscopy, x-ray diffraction and optical characterizations revealed an opposite impact of the P and Sb alloying on the nucleation, growth and coarsening of the second phase. While Sb enhances the precipitation rate, P retards it. Delta-doping with Sb causes two-dimensional precipitation, whereas such doping with P does not result in heterogeneous nucleation. The microstructure and strains have been found to be different around nanoinclusions in the Sb-doped and P-doped materials, indicating different thermodynamics and kinetics of segregation of the two isovalent impurities in As nanoclusters. We analyze the observed phenomena in terms of thermodynamic and kinetic models taking into account the underlying phase equilibriums and diffusion mechanisms.
Analysis of Split Patterns in ?-?' Ni Alloys
Authors: Calderon Hector A. , Kisielowski Christian , Mori Tsutomu
Published: June 2019

Pairs of ?' particles in different Ni base alloys are investigated in order to determine the mechanism responsible for the formation of several particle arrays. Special attention is given to symmetrically arranged particles or the split patterns i.e., they have been believed to result from the splitting of large particles. High resolution electron microscopy is used to determine the translation domains of coherent ?' particles. The [001] zone axis allows determination of all possible translations due to differently nucleated domains. About 72 % of particle pairs forming splitting configurations are in the out-of-phase relationship (different translation order domains), indicating that most adjacent pairs are not formed by the splitting of a large particle. On the other hand, particles in symmetrical array (quartets) always have at least one particle with a different translation order domain. Additionally, the frequency of out-of-phase pairs is 78 % in quartet configurations. Calculation of probabilities shows that the quartet split patterns are not formed by splitting but most likely by means of migration due to diffusion.
Phase Stability of Carbides and Nitrides in Steel
Authors: Sluiter Marcel
Published: June 2019

Carbides, nitrides, and carbonitrides have great influence on the properties of steel but are relatively little studied at a fundamental level: experimentally because of small dimensions of the precipitates and other difficulties, theoretically because of complex structures and poorly defined compositions. Modern density functional calculations reveal significant trends that can be partially summarized in terms of atomic size, carbon affinity, and hybridization de-magnetization concepts. Phase stability and order-disorder phenomena in widely occurring Cr-based M23C6 carbides and Mo-based M6C carbides are used to illustrate predictions relevant to low alloyed steel.
Microstructure Control Using Precipitate Phases for the Development of Heat Resistant Fe3Al-based Alloys
Authors: Kobayashi Satoru , Zaefferer Stefan
Published: June 2019

A thermomechanical process (TMP) was performed to create a fine grained and recovered structure with densely formed fine particles in Fe3Al-Cr-Mo-C alloys. The TMP consists of two parts; the first part is to obtain fine recrystallised grains using coarse particles and the second to produce deformed/recovered structure using fine particles. It was found that k-Fe3AlC (E21) carbide phase tends to precipitate coarsely, which is effective to refine grain size in the first process. In a special composition range, the k carbide phase is thermo- dynamically stable in the Fe3Al matrix only at higher temperatures and fine M(Mo,Cr,Fe)2C (B81) carbide phase precipitates at lower temperatures. This fine M2C particles stabilize recovered structure by inhibiting the migration of subboundaries in the second process. This result suggests that if the fine particle density remains high, recovered structure can be maintained at 700°C.
Precipitation-Induced Nano-Twinning
Authors: Fischer Franz Dieter , Appel Fritz , Clemens Helmut
Published: June 2019

γ(TiAl) alloys containing Ti3AlC perovskite precipitates show overlapping planar faults, which can apparently rearrange into embryonic twins and subsequently grow into large twins. An electron-microscopical study is introduced and followed by a micromechanical modelling of the fault and twin development process. The thickness and length of the embryonic twins can be predicted with the developed model.
L10 Ordered Intermetallics for Ultrahigh Density Magnetic Recording Media: Phase Formation and the Role of Alloy Chemistry and Composition
Authors: Berry David C. , Barmak Katayun
Published: June 2019

In this paper we provide a summary review of our research regarding the effect of composition on the A1 to L10 transformation in binary FePt with compositions in the range of 39.3 to 55.3 at.% Pt and ternary FeCuPt alloys with Cu additions in the range of 1.0 to 19.4 at.%. These binary and ternary alloy films have been studied using non-isothermal differential scanning calorimetry (DSC) combined with the calculation of TTT diagrams generated via experimentally validated Johnson-Mehl-Avrami-Kolmogorov (JMAK) analysis. Composition is found to play a significant role in the transformation kinetics in both FePt and FeCuPt. However, when comparing equivalent FePt and FeCuPt alloys, the addition of Cu has no significant effect. TTT diagrams show that as little as a 90 °C increase in peak temperature from the DSC measurements can result in a >300× increase in the time required for full transformation using isothermal anneals. Our results on the effect of Cu additions are compared with those reported in the literature.
Defect Control and Defect Engineering of Transition-metal Silicides
Authors: Inui Haruyuki , Tanaka Katsushi , Kishida Kyosuke
Published: June 2019

The microstructure, defect structure and thermoelectric properties of two different semiconducting transition-metal silicides, ReSi1.75 and Ru2Si3 upon alloying with a substitutional element with a valence electron number different from that of the constituent metal have been investigated in order to see if the crystal and defect structures of these silicides and thereby their physical properties can be controlled through defect engineering according to the valence electron counting rule. The Si vacancy concentration and its arrangement can be successfully controlled in ReSi1.75 while the relative magnitude of the metal and silicon subcell dimensions in the chimney-ladder structures can be successfully controlled in Ru2Si3. As a result, the improvement in the thermoelectric properties and the p- to n-type conduction transition are successfully achieved respectively for these semiconducting transition-metal silicides.
Solid-State Synthesis of Magnesium Base Thermoelectric Alloys via Bulk Mechanical Alloying
Authors: Aizawa Tatsuhiko , Song Renbo
Published: June 2019

Magnesium binary and ternary alloy systems have been popular as a thermoelectric light-weight alloy to be working in the medium temperature range. The solid-state reactivity via the bulk mechanical alloying is applied to yield these types of alloys. The diffusion-controlled solid-state synthesis is first stated as a process to yield a binary compound, Mg2X (X = Ge, Sn and Pb). This processing is further applied to directly synthesize several ternary thermoelectric alloys Mg2Si1-xGex, Mg2Si1-ySny and Mg2Sn1-zPbz for 0.0 < x, y, z < 1.0 and to evaluate their thermoelectric properties. Hot pressing is used to make full-dense billets and samples for thermoelectric measurement. The effect of germanium and tin contents on their Seebeck coefficient and band-gap is investigated to describe the p-n transition behavior and to understand the change of electric structure with solid solution formation.
The Evolution of Prior-BCC Grain Boundary Cracking During In-situ Creep Deformation of a Ti-15Al-33Nb(at%) Alloy
Authors: Cowen Christopher J. , Boehlert Carl J.
Published: June 2019

In-situ tensile-creep experiments were performed on a Ti-15Al-33Nb(at%) alloy using a specialized tensile stage placed within the vacuum chamber of a Camscan 44 FE scanning electron microscope (SEM). The creep damage evolution on the sample surface was chronicled through backscattered electron (BSE) imaging as a function of stress, time, and creep displacement at 650°C. The experiments revealed that the prior-BCC grain boundaries were the locus of damage accumulation during creep and significant grain boundary cracking was observed. The grain boundary cracking was verified to occur within the bulk of the material through post-mortem analysis.
Phase Equilibria among γ-Fe, γ-Fe and Fe2Mo Phases and Stability of the Laves Phase in Fe-Mo-Ni Ternary System at Elevated Temperatures
Authors: Ishikawa Shigehiro , Matsuo Takashi , Takeyama Masao
Published: June 2019

Phase equilibria among the bcc Fe(α), fcc Fe(γ) and Fe2Mo(λ)_phases in Fe-Mo-Ni ternary system, particularly paying attention to the existence of the γ+λ two-phase region, have been examined at elevated temperatures below Tc (1200 K), the peritectoid reaction temperature in Fe-Mo binary system: λ?α+Fe7Mo6 (μ). At 1173 K the α+γ+μ three-phase coexisting region exists near the Fe-Mo binary edge and no λ phase region was identified. At 1073 K the λ phase in equilibrium with α and γ phases exists, although the composition homogeneity region of the ternary λ phase was limited to its binary edge toward the equi-nickel concentration direction up to about 3at % Ni. Instead, large two-phase region of γ+μ was extended along the same direction up to 20 at% Ni. The γ+λ two-phase region appears below Tc through a transition peritectoid reaction: α+μ¨γ+λ. The γ phase in equilibrium with λ phase is stable only at elevated temperatures, and it transforms martensitically to α phase during cooling. The addition of Ni stabilizes γ and μ phases against α and λ phases, thereby decreasing the relative stability of the λ phase.
UFG to NC FePd by Combined Reaction Transformation Mode of Severely Plastically Deformed Disordered FePd
Authors: Sokalski Vincent , Kulovits Andreas , Wiezorek Jorg
Published: June 2019

Numerous studies have shown that equiaxed ultra fine grained FePd alloys can be produced by phase transformation of heavily deformed austenitic FePd via the combined reaction mode. As the magnetic properties can be improved by suppression of the polytwinned micro-constituent formed by the conventional ordering mode it appears reasonable to speculate that further grain refinement might lead to further enhancement. In order to reduce the grain size in bulk intermetallic alloys severely plastically deformed austenitic FePd has been phase transformed in this study. Equal channel angular pressing (ECAP) has been used to deform disordered FePd. The microstructure and property evolution during the deformation process and post-deformation annealing have been studied using SEM, TEM and hardness and magnetization curve measurements. The observations are compared to known results from use of other deformation processing routes, such as cold rolling.
Microstructure and Mechanical Properties of Dual Two-Phase Intermetallic Alloys Composed of GCP Ni3Al and Ni3V Phases containing Nb
Authors: Soga Wataru , Kaneno Yasuyuki , Takasugi Takayuki
Published: June 2019

Dual multi-phase intermetallic alloys composed of Ni3X (X: Al and V) containing Nb were developed, on the basis of the Ni3Al-Ni3Nb-Ni3V pseudo-ternary alloy system. The dual multi-phase intermetallic alloys were characterized by scanning electron and transmission electron microscopies. High-temperature compression and tension tests, and compression creep test were conducted. It was found that the dual multi-phase intermetallic alloys show high yield and tensile strength with good temperature retention, accompanied with reasonable tensile ductility. The compression creep test conducted at high temperature showed lower creep rate in the dual multi-phase intermetallic alloys than in conventional Ni-base superalloys. The obtained results are superior to the dual multi-phase intermetallic alloys containing Ti.
The Broadening of Crystallographic Orientation Distribution in Crept Ni-base Superalloys
Authors: Inoue Toru , Tanaka Katsushi , Adachi Hiroki , Kishida Kyosuke , Inui Haruyuki
Published: June 2019

The crystallographic orientation distribution, and its change accompanied with tilting γ/γ boundaries in Ni-based single crystal superalloys have been investigated by a theoretical elastic-plastic calculation, X-ray diffractometry and SEM-EBSD analysis. The distribution of the crystallographic orientation has significantly broadened by creep deformations. The broadening can be explained by an unbalance of the amount of creep dislocations of each slip system, which agrees with the result of elastic-plastic calculations. Creep strain of superalloys crept at a condition forming the raft structure can be estimated by the measurement of the width of rocking curve of a diffraction peak.
Effect of Heat Treatment on the Ductility of Ni(γ)/Ni3Al(γ') Two-phase Alloy Foils
Authors: Nakamura Motonori , Demura Masahiko , Xu Ya , Hirano Toshiyuki
Published: June 2019

The microstructures and room-temperature tensile properties were examined in the 95% cold-rolled and subsequently heat-treated foils of the boron-free Ni(γ)/Ni3Al(γ') two-phase (Ni-18at.%Al) alloys. The electron backscatter diffraction measurements revealed that the recrystallization started at 873 K/0.5 h and that it completed at 1273 K/0.5 h. While the foils showed no tensile elongation in the cold-rolled state, they became ductile after the heat-treatments at 873 K and above. The tensile elongation increased with the increasing heat-treatment temperature: it reached to 14% at 1273 K/0.5 h. The tensile elongation and the fracture strength were high, compared to those in the γ' single-phase foils. The fracture mode was intergranular, and it changed to a mix of intergranular and transgranular in the foils heat-treated at 1273 K/0.5 h, where the area fraction of crack resistant boundaries such as °1, °3 and °9 was high, 0.63. The high ductility was ascribed to the existence of the ductile γ matrix and to the high fraction of crack-resistant boundaries.
Dynamics of Ultrafast Laser Induced Damage in Single Crystal Ni-based Superalloy During Machining
Authors: McDonald Joel P. , Ma Shuwei , Nees John A. , Pollock Tresa M. , Yalisove Steven M.
Published: June 2019

Pump-probe imaging of femtosecond pulsed laser ablation was performed to investigate the mechanical shock induced on an intermetallic superalloy CMSX-4 during femtosecond laser machining. Time resolved shadowgraphic images were collected of the shock wave produced in the air above the target following laser exposure (0-10.3 nanoseconds). The dimensions of the shock wave were measured as a function of delay time and laser fluence (1.27 J/cm2 - 62.8 J/cm2). Time-resolved shadowgraphic images of the ablation event will be presented, and the corresponding damage morphology as a function of incident laser fluence will be discussed.
Microstructure and Mechanical Properties of Multi-Phase Intermetallic Alloys Composed of GCP Ni3X (X:Si, Ti and Nb) Phases
Authors: Fujita Masayoshi , Kaneno Yasuyuki , Takasugi Takayuki
Published: June 2019

Using alloys whose initial microstructures are composed of Ni3Si(L12), Ni3Si(L12)+Ni3Ti(D024) and Ni3Si(L12)+Ni3Nb(D0a), aging phenomenon and the associated high-temperature tensile property were investigated. It was shown by micro hardness measurement that age hardening behavior due to the precipitation of the Ni3Ti(D024) phase occurs in all alloys at temperatures above 823K. It was however shown by tensile test that the precipitated Ni3Ti(D024) phase is not so much effective in improving the mechanical properties of alloys whose initial microstructures are composed of Ni3Si(L12)+Ni3Nb(D0a) or Ni3Si(L12)+Ni3Ti (D024). In alloys whose initial microstructures are composed of Ni3Si(L12)+Ni3Nb (D0a), a good combination of tensile strength and tensile elongation was found over a wide of test temperature whether or not they contain the precipitated Ni3Ti(D024) phase.
Effect of processing and Microalloying Elements on the Thermal Stability of Cr-Cr3Si and NiAl-Mo eutectic alloys
Authors: Gali A. , Bei H. , George E. P.
Published: June 2019

The thermal stability of multiphase intermetallics at temperatures to 1400°C was investigated by studying two model eutectic systems: Cr-Cr3Si having a lamellar microstructure and NiAl-Mo having a fibrous microstructure. In drop cast Cr-Cr3Si, coarsening was found to be interface controlled. The coarsening rate could be reduced by microalloying with Ce and Re, two elements which were chosen because they were expected to segregate to the Cr-Cr3Si interfaces and decrease their energies. Similarly, directional solidification, which is also expected to lower the Cr-Cr3Si interfacial energy, was found to dramatically decrease the coarsening rate. In the case of NiAl-Mo, coarsening was found to occur by fault migration and annihilation. Microalloying with B was found to significantly decrease the coarsening rate. The fiber density in the B-doped alloy was smaller than in the undoped alloy, suggesting that B affects the coarsening rate by lowering the fault density.
Crystal Structures and Thermoelectric Properties of Ru1-xRexSiy Chimney-Ladder Compounds
Authors: Ishida Akira , Okamoto Norihiko L. , Kishida Kyosuke , Tanaka Katsushi , Inui Haruyuki
Published: June 2019

The phase relationship of Re-alloyed Ru2Si3 and the variations of the crystal structures and thermoelectric properties of the Ru1-xRexSiy chimney-ladder phases have been studied as a function of the Re concentration. The Ru1-xRexSiy chimney-ladder phases are formed in a wide compositional range. Compositional formula of the chimney-ladder phases are determined to be Ru1-xRexSi1.5386+0.1783x (0.14 ≤ x ≤ 0.76), which are systematically deviated from the idealized composition conforming the valence electron counting rule: VEC=14. Measurements of thermoelectric properties of single crystals with different compositions reveals that the chimney-ladder phases exhibit n-type semiconducting behavior at low Re concentrations and p-type semiconducting behavior at high Re concentrations. These results suggests that the VEC=14 rule can be used for predicting the semiconducting behavior of the chimney-ladder phases through the adjustment of VEC values by substituting elements, producing p-type semiconductors for VEC<14 and n-type for VEC>14, with the carrier concentration related to the deviation from VEC=14.
Thermoelectric and Electrical Properties of InSb Thin Films Prepared by Metalorganic Chemical Vapor Deposition
Authors: Matsumoto Masashi , Yamazaki Jun , Yamaguchi Shigeo
Published: June 2019

We studied the thermoelectric and electrical properties of InSb thin films prepared by metalorganic chemical vapor deposition. The thermoelectric properties were evaluated using power factor (Pf =α2/Ï), which is an important criterion, and a value of 10-3 W/mK2 is a standard for practical use. Maximum value of Pf was 2.4×10-3W/mK2 at 600K for 1-μm-thick InSb, 3.4×10-3W/mK2 at 600K for 3-μm-thick InSb, and 5.8×10-3W/mK2 at 600K for 5-μm-thick InSb. On the other hand, the maximum Pf of bulk-InSb was 5.4×10-3W/mK2 at 600K.
Lanthanide Based Ternary Intermetallics as Advanced Thermoelectric Materials
Authors: Kurosaki Ken , Sekimoto Takeyuki , Kawano Kenta , Muta Hiroaki , Yamanaka Shinsuke
Published: June 2019

Polycrystalline ingots of the lanthanide based ternary intermetallics: LaNiSb, GdNiSb, ErNiSb and ErPdSb were prepared and characterized. The thermoelectric properties of ErNiSb and ErPdSb were measured at high temperatures. We succeeded in preparing the single phase ingots of ErNiSb and ErPdSb, while the ingots of LaNiSb and GdNiSb contain appreciable quantities of the impurity phases. ErNiSb and ErPdSb crystallize the MgAgAs-type structure (half-Heusler structure). ErNiSb and ErPdSb indicate positive values of the Seebeck coefficient. The values at room temperature are 36 and 240 micro VK-1 for ErNiSb and ErPdSb, respectively. The electrical resistivity of ErNiSb and ErPdSb decreases with temperature, indicating semiconductor-like behavior. ErPdSb exhibits a relatively large power factor 1.5x10-3 Wm-1K-2 at around 700 K, which is approximately two times larger than that of ErNiSb.
Investigation of AuNi5 Films Deposited by Pulsed Laser Deposition for RF MEMS Switch Contacts
Authors: Farghal Noha , Ghannam Moustafa Yehia , Shaarawi Amr M. , El Samman Hussein , Soussan Philippe , Baert Kris
Published: June 2019

In this work, the material properties of AuNi5 films prepared by Pulsed Laser Deposition (PLD) to be used as contact materials in RF MEMS switches are investigated. PLD is used because it provides good wide range thickness control (few nanometers to tens of microns) while preserving ablation target stoichiometry. Films with thickness in the range 50 - 450 nm were deposited at Laser energy density (fluence) in the range 0.55 - 1.38 J.cm-2 on silicon substrates at room temperature. An aperture was placed between the plume and the substrate to filter out large particulates. The presence of the aperture reduced surface roughness from 8.5 nm to 4.3 nm as determined by optical profilometry. In addition, the presence of the aperture during deposition has been found to affect film stoichiometry. The latter was evaluated using X-ray Fluorescence and the Nickel content has been found to vary in the range 1.1 - 9.5%. Only films deposited with the aperture removed maintain target stoichiometry (5.2% Ni). Hence, it is believed that the presence of the aperture causes non-congruent transfer. The Nickel content within the range under investigation has practically no effect on film morphology or hardness. Laser fluence, however, has been found to be the dominant factor determining film properties. Finally, 100 µm wide AuNi5 strips 290 nm and 130 nm thick deposited at room temperature have been successfully formed on silicon wafers by lift-off photolithography.
Crystal Growth of β-FeSi2 Thin Film on (100), (110) and (111) Plane of Si and Yittria-stabilized Zirconia Substrates
Authors: Akiyama Kensuke , Kaneko Satoru , Kiguchi Takanori , Suemasu Takashi , Kimura Takeshi , Funakubo Hiroshi
Published: June 2019

Iron silicide thin films were prepared on silicon (Si) and yittria-stabilized zirconia (YSZ) substrates using RF magnetron sputtering and evaporation methods. Epitaxial b-FeSi2 thin films were grown on (100) and (111) planes of Si and YSZ substrates, while noncrystallized films were deposited on (110) plane of both Si and YSZ substrates. The epitaxial relationships between the b-FeSi2 and YSZ were the same as those between b-FeSi2 and Si, in the case of (100) and (111) planes. It is possible that epitaxial b-FeSi2 film can be grown when substrates and b-FeSi2 surfaces consist of either a single element or only cations, while the crystalline film was not shown when either substrate or b-FeSi2 surface consists of a mixture of anions and cations or iron and silicon.
Evolution of Antiphase Domains and γ Lamellae in Ti-39at%Al Single Crystals
Authors: Koizumi Yuichiro , Iwamoto Kazuki , Tanaka Takayuki , Minamino Yoritoshi , Tsuji Nobuhiro
Published: June 2019

We studied antiphase domain (APD) growth and lamellar structure formation during isothermal annealing of Ti-39at%Al single crystals at α2+γ dual phase temperature after quenching from α single phase state, intending to obtain a APD/lamellae mixed microstructure and to examine whether such a microstructure provides a strength higher than that obtained only by refining lamellar structure. The effect of plastic deformation prior to the annealing was also examined expecting a acceleration of γ lamellae formation through a preferential nucleation of γ-plates at dislocations. The lower was the annealing temperature, the smaller both the APD size and the lamellar spacing at the moment of a homogeneous lamellar structure formation tended to be, although naturally both the APD growth and the γ lamellae formation were slower. However, the APD size in the homogeneous lamellar structure was no smaller than 400 nm. A structure with finer APDs and finer lamellar structure was obtained by deforming the crystal before annealing since the lamellar structure formation was accelerated and the time for APD growth before the lamellar structure formation was shortened. For instance, a structure with an average lamellar spacing of 88 nm and an average APD size of 214 nm was obtained by deforming the crystals to 10 % plastic strain and subsequently annealing at 1073 K for 1×104 s, while no γ plate was obtained only by such an annealing without deformation.
Nano-Scale Design of TiAl Alloys Based on beta-Phase Decomposition
Authors: Appel Fritz , Oehring Michael , Paul Jonathan
Published: June 2019

Phase decomposition and ordering reactions in beta-phase containing TiAl alloys were utilized to establish a novel, previously unreported, type of laminate microstructure. The characteristic constituent of this microstructure are laths with a nanometer-scale substructure that are comprised of several stable and metastable phases. The constitution and microstructure of this novel type of alloy has been assessed by high-resolution transmission electron microscopy. Finally brief mention is made of the mechanical properties of the material.
Mechanical Properties of E21 Ti3AlC-base Alloy
Authors: Hosoda Hideki , Inamura Tomonari , Wakashima Kenji
Published: June 2019

Mechanical properties and phase constitution of an E21-type Ti3AlC-base alloy were investigated by compression tests in a temperature range from room temperature (RT) to 1273K, scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). The unit cell of E21 Ti3AlC is constructed by ¡§L12 Ti3Al¡¨ and a carbon atom occupying the body-center octahedral-interstitial-site surrounded by the Ti atoms. The nominal composition of the alloy was chosen to be the stoichiometric composition of 60mol%Ti-20mol%Al-20mol%C. The alloy was synthesized by mechanical alloying using high purity elemental powders followed by hot pressing at 1473K for 3hrs. It was found by XRD and SEM that the alloy was mainly composed of E21 Ti3AlC in addition to Cr2AlC-type Ti2AlC precipitates as a second phase. The density of Ti3AlC is calculated to be 4.29g/cm3 based on the lattice parameter of 0.4134nm of E21. The average grain size was 2μm by SEM. By the compression tests, the 0.2% flow stress at the temperature range from RT to 1073K exceeded 1GPa. The yield stress is comparably higher than those of other E21 intermetallic carbides: at 1073K, 1084MPa for Ti3AlC, 50MPa for Mn3AlC and 135MPa for Fe3AlC. Besides, a weak positive temperature dependence of strength was observed where the peak temperature was around 900K. This suggests that a Kear-Wilsdorf type dislocation pinning mechanism may be activated. It is concluded that E21 Ti3AlC-base alloy shows promise for a new high-temperature light-weight structural material.
Orientation Relationship Between the bcc and σ Phases in Cr-Co Alloys
Authors: Doi Toshihiro , Tanimura Makoto , Koyama Yasumasa
Published: June 2019

To obtain deeper understanding of the Ð structure, the formation of the Ð structure in the (bcc¨bcc+Ð) reaction at 873K and 1173K have been investigated by transmission electron microscopy. As for the orientation relationship between the bcc and Ð structures, as a results, both the common first relation of [110]bcc//[110]Ð and three second relations given by α=0°, 33°, and 64° were found in the 1173K annealing, where α is an angle between the [_110]bcc and [001]Ð directions. In the 873K annealing, on the other hand, there was only one second relation with α=0°. Based on the α=0° relation found in both annealing temperatures, the features of atomic shifts in the Ð-structure formation were also discussed.
Evaluation of the Stability of Raft Structure in Nickel Base Superalloys Throughout their Lifetime
Authors: Tanaka Katsushi , Inoue Toru , Ichitsubo Tetsu , Kishida Kyosuke , Inui Haruyuki
Published: June 2019

Stability of raft structure in nickel base superalloys has been examined by using elastic energy calculations based on a microelasticity theory. The numerical calculation method for a structurally heterogeneous system is applied. The results indicate that the raft structure is significantly stabilized by introductions of creep deformations till the critical creep deformation at which the lattice misfit between gamma and gamma-prime phases is completely compensated by creep dislocations. When the magnitude of creep deformations exceed the critical value, the (001) lamellar interfaces become elastically unstable and a tilted lamellar interface become the most stable one. This instability of the 001 raft structure leads a tilted or wavy lamellar interfaces for reducing the internal strain energy, that is a precursor to collapse the raft structure.
Irradiation Assisted Grain Boundary Segregation in Steels
Authors: Lu Zheng , Faulkner Roy G
Published: June 2019

The understanding of radiation-induced grain boundary segregation (RIS) has considerably improved over the past decade. New models have been introduced and much effort has been devoted to obtaining comprehensive information on segregation from the literature. Analytical techniques have also improved so that chemical analysis of layers 1 nm thick is almost routine. This invited paper will review the major methods used currently for RIS prediction: namely, Rate Theory, Inverse Kirkendall, and Solute Drag approaches. A summary is made of the available data on phosphorus RIS in reactor pressure vessel (RPV) steels. This will be discussed in the light of the predictions of the various models in an effort to show which models are the most reliable and easy to use for forecasting P segregation behaviour in steels. A consequence of RIS in RPV steels is a radiation induced shift in the ductile to brittle transition temperature (DBTT). It will be shown how it is possible to relate radiation-induced P segregation levels to DBTT shift. Examples of this exercise will be given for RPV steels and for ferritic steels being considered for first wall fusion applications. Cr RIS in high alloy stainless steels and associated irradiation-assisted stress corrosion cracking (IASCC) will be briefly discussed.
The All Boron Carbide Diode Neutron Detector: Experiment and Modeling Approach
Authors: Sabirianov Ildar , Fairchild Robert W , Brand Jennifer I
Published: June 2019

Boron carbide diode detectors, fabricated from two different polytypes of semiconducting boron carbide, will detect neutrons in reasonable agreement with theoretical expectations. The performance of the all boron carbide neutron detector differs, as expected, from devices where a boron rich neutron capture layer is distinct from the diode charge collection region (i.e. a conversion layer solid state detector).

Diodes were fabricated from natural abundance boron (20% 10B and 80% 11B.) directly on the metal substrates and metal contacts applied to the films as grown. The total boron depth was on the order of 2 microns. This is clearly not a conversion-layer configuration. The diodes were exposed to thermal neutrons generated from a paraffin moderated plutonium-beryllium source in moderated and unmoderated, as well as shielded and unshielded experimental configurations, where the expected energy peaks at at 2.31 MeV and 2.8 MeV were clearly observed, albeit with some incomplete charge collection typical of thinner diode structures. The results are compared with other boron based thin film detectors and literature models.
A Mechanical Study of T91 Embrittlement by Liquid Lead-bismuth Eutectic
Authors: Hamouche Zehoua , AUGER Thierry , GUILLOT Ivan
Published: June 2019

The susceptibility of liquid metal embrittlement of the T91 martensitic steel is investigated from slow deformation rate (6.67x10-8 m.s-1) to high deformation rate (6.67x10-3 m.s-1), using a Center Cracked in Tension geometry. Brittle fracture, characterized by elongated river cracks on all the fracture surfaces, indicates that T91 is sensitive to the Embrittlement by LBE. This embrittlement effect is very marked at the low deformation rate (~10-5 mm.s-1). A ductile-brittle transition is observed in the high strain rate range investigated. In this transition regime, there is a competition between the growth of dimples and the cracking induced by the liquid metal. Ductility recovery is complete at the highest investigated displacement rate. This dependence of T91/LBE susceptibility to LME on the displacement rate and the brittle to ductile transition at high strain rate is confirmed by a fracture mechanics analysis.
Bubble Density Dependent Functionals to Describe Deformation and Stress Equilibrium Evolution for In-Reactor Nuclear Fuel Materials
Authors: Stout Ray B.
Published: June 2019

Future designs of nuclear fuels require an increased understanding of fission gas bubble density evolution. Derivations will be provided for a generic Boltzmann bubble density evolution equation, a bubble density deformation field equation, and a Cauchy stress/bubble-pressure equilibrium equation.
Ordered Arrays of Colloidal Gold Nanoparticles Fabricated by Focused Ion Beam Techniques
Authors: Simpson Todd , Mitchell Ian V
Published: June 2019

Through-holes of diameter 35nm and larger were milled in 100nm thick silicon nitride windows by focused ion beam milling. The holes were sized to optimize capture of gold nanoparticles from a liquid suspension. The colloidal suspensions of gold particles were deposited onto the membrane and drawn through the holes by capillary forces. Efficient, single particle filling is demonstrated for both 100nm and 250nm diameter particles indicating that once a hole is filled, flow can be effectively blocked. We show that lithographically defined arrays of colloidal gold can be achieved with >98% filling.
Direct Focused Ion Beam Drilling of Nanopores
Authors: Patterson Nick , Hodges V. Carter , Vasile Michael J. , Adams David P. , Chen Zhu , Brinker C. Jeff
Published: June 2019

Focused 30keV gallium ion beam, single-pixel drilling combined with backside particle detection is used to fabricate pores having exit diameters as small as ~11 nm in 200 nm-thick silicon nitride membranes. The backside channelplate detector response obtained about the onset of breakthrough is interpreted by plan-view transmission electron microscopy investigations of hole morphology. Immediately prior to breakthrough, there is a rise in detector signal as the local membrane thickness is reduced. This likely occurs as a result of ion transmission and, possibly, forward sputtering. At the dose required for breakthrough a maximum detector signal is obtained thus providing a potential method for end point detection. The focused ion drilling technique avoids broad area beam exposure methods that are often used to reduce hole diameter to nanometer dimension. In addition, the current approach overcomes difficulties in determining a required dose for breakthrough such as those that arise from an inhomogeneous membrane thickness, redeposition, or ion channeling.
Fabrication of Sub-250nm High Aspect Ratio Apertures by Focused Ion Beam Lithography
Authors: Simpson Todd , Mitchell Ian V
Published: June 2019

Aperture arrays were fabricated in 1.0µm thick gold films supported on 20nm thick silicon nitride membranes. Lithographic milling strategies in gold were evaluated through the use of in-situ sectioning and high resolution SEM imaging with the UWO CrossBeam FIB/SEM. A successful strategy for producing a 250nm diameter hole with sidewalls approaching vertical is summarized.
Probe Tip Replacement System Inside the FIB
Authors: Amador Gonzalo , Zaykova-Feldman Lyudmila , Moore Thomas M
Published: June 2019

The in-situ lift-out method for TEM sample preparation, based on the use of a chamber-mounted nanomanipulator and FIB induced material deposition, has proven its effectiveness over the last several years. The time-efficiency introduced by this method is one reason for its success and rapid adoption within the semiconductor industry. Improvements to in-situ TEM lift-out preparation have been pursued to further improve sample processing time. One area targeted has involved methods to enable rapid in-situ probe tip replacement without having to remove the probe shaft from the vacuum chamber. This paper describes an in-situ probe tip replacement system that successfully solves this problem.
Micro-Fracture testing of Ni-W Microbeams Produced by Electrodeposition and FIB Machining
Authors: Armstrong David , Haseeb Abdul , Wilkinson Angus , Roberts Steve
Published: June 2019

Electrodeposited nickel-tungsten alloys are being considered as a candidate material for components for microelectromechanical systems (MEMS) fabricated by the LIGA (German acronym for lithography, electrodeposition, and forming) technology. In spite of having a useful range of properties including; hardness and strength, better tribological and chemical resistance and improved high temperature resistance as compared with the conventionally used electrodeposited Ni, these alloys possess certain brittleness. In this study, the fracture toughness of Ni-17.5 at%W alloy microcantilever beams (dimension: 60µm × 20µm x 14µm) fabricated by UV lithography and electrodeposition and notched by focused ion beam machining is investigated. Load was applied to the beams using a nanoindenter, which also allowed accurate positioning of the sample. Fracture toughness was calculated from the fracture load assuming a linear elastic behaviour. The Ni-W alloy beams were found to possess a mean fracture toughness of 2.97 MPa √m. The fracture toughness of Ni-W alloy is found to be higher than that of Si - another important MEMS material, but considerably lower than that of electrodeposited nickel and nickel base alloys.
3D Structure Fabrication by FIB Milling and Deposition
Authors: Fujii Toshiaki , Iwasaki Koji , Munekane Masanao , Yamamoto Yo , Takeuchi Toshitada , Hasuda Masakatsu , Ikku Yutaka , Tashiro Hiromi , Asahata Tatsuya , Kiyohara Masahiro , Kaito Takashi
Published: June 2019

Focused Ion Beam (FIB) system is equipment used to make a wide variety of micro and Nano structures. Structures can be created using various materials by irradiating focused gallium ion beam on to the surface of specimens and by sputtering, etching and ion beam induced deposition. In order to realize greater diversity for nano construction by using the FIB system, we have developed technologies incorporating:

- Built-in pattern signal generator

- Multiple Gas Unit for gas assisted etching and beam induced deposition

- A precision wheel for the stage.

This latest FIB system has a narrow Ion beam with a diameter of better than 4nm. Beam current is controlled from 0.15pA to 20nA. These performances contribute significantly to the study 3D structures fabrication and modification.
Comparative Photoemission Study of Actinide (Am, Pu, Np and U) Metals, Nitrides, and Hydrides
Authors: Gouder Thomas , Seibert Alice , Rebizant Jean , Huber Frank , Havela Ladislav
Published: June 2019

Core-level and valence-band spectra of Pu and the other early actinide compounds show remarkable systematics, which can be understood in the framework of final state screening. We compare the early actinide (U, Np, Pu and Am) metals, nitrides and hydrides and a few other specific compounds (PuSe, PuS, PuCx, PuSix) prepared as thin films by sputter deposition. In choosing these systems, we combine inherent 5f band narrowing, due to 5f orbital contraction throughout the actinide series, with variations of the chemical environment in the compounds. Goal of this work was to learn more on the electronic structure of the early actinide systems and to achieve the correct interpretation of their photoemission spectra. The highly correlated nature of the 5f states in systems, which are on the verge to localization, makes this a challenging task, because of the peculiar interplay between ground state DOS and final-state effects. Their influence can be estimated by doing systematic studies on systems with different (5f) bandwidths. We conclude on the basis of such systematic experiments that final-state effects due to strong e-e correlations in narrow 5f-band systems lead to multiplet like structures, analogous to those observed in the case of systems with localized electron states. Such observations in essentially band-like 5f-systems was first surprising, but the astonishing similarity of photoemission spectra of very different chemical systems (e.g. PuSe, Pu2C3 and δ-Pu) points to a common origin, relating them to atomic features rather than material dependent density of states (DOS) features.