bluuebunny/crossref_metadata_2025 huggingface dataset:
Structure Models of Massively Transformed High Niobium Containing TiAl Alloys
Authors: Scheu Christina , Cha Limei , Sturm Saso , Chladil Harald F. , Mayrhofer Paul H. , Clemens Helmut , Wolf Walter , Podloucky Raimund
Published: June 2019

Ab-initio calculations using the Vienna ab-initio simulation package (VASP) were performed for a high Nb bearing γ TiAl based alloy with a composition of Ti-46at.%Al-9at.%Nb in order to evaluate the effect of Nb on the crystal structure. The calculations revealed that upon doping with Nb the resulting structure can have Ti and Nb atoms on Al-sites, which leads to a reduction of the c/a ratio of the tetragonal γ TiAl cell to ~1.In contrast, the c/a ratio is increased, compared to the binary phase, if the Nb atoms occupy solely Ti sites and if Ti antisite defects (i.e. Ti on the Al sublattice) are formed. The relaxed structure models were used to perform high-resolution transmission electron microscopy (HRTEM) and high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) image simulations. The results showed that the positions of the Nb atoms should be detectable by these high spatial resolution methods, although it might be easier by HAADF-STEM investigations due to the stronger dependence of the signal on the atomic number Z.
Phase Transitions and Recrystallization in a Ti-46at%Al-9at%Nb Alloy as Observed by In-Situ High-Energy X-ray Diffraction
Authors: Liss Klaus-Dieter , Clemens Helmut , Bartels Arno , Stark Andreas , Buslaps Thomas
Published: June 2019

High-energy synchrotron X-ray diffraction is a powerful tool for bulk studies of materials. In this investigation, it is applied to the investigation of an intermetallic γ-TiAl based alloy with a composition of Ti-46Al-9Nb. The morphology of the reflections on the Debye-Scherrer rings is evaluated in order to approach grain sizes as well as crystallographic correlations. An in-situ heating cycle from room temperature to a temperature above the α-transus temperature has been conducted starting from a massively transformed sample. With increasing temperature the occurrence of strain relaxation, chemical and phase separation, domain orientations, phase transitions, recrystallization processes, and subsequent grain growth can be observed. During cooling to room temperature, crystallographic correlations between the re-appearing γ-phase and the host α-phase, known as the Blackburn correlation, are observed in the reciprocal lattice, which splits into different twinning and domain orientation relationships present in the fully lamellar microstructure.
Magnetron Sputtered Intermetallic Al2Au and Al-Zr-Y Coatings for the Oxidation Protection of γ-TiAl
Authors: Moser Martin , Mayrhofer Paul Heinz , Braun Reinhold
Published: June 2019

Al-based intermetallic coatings are widely used as bond coats and for oxidation protection of turbine blades and engine components. Here we present and discuss the structural and thermal properties of novel unbalanced-magnetron sputtered Al-based coatings (single-phase intermetallic Al2Au, binary Al-Zr, and nano-structured Al-Zr-Y) developed to protect gamma-TiAl from environmental attack at elevated temperatures. Al-Zr films exhibit a coarse-grained dual-phase Al3Zr2-Al2Zr structure and are nano-structured by alloying with ~5, 10, and 14 at% Y.

Combined dynamic differential-scanning calorimetry and thermogravimetric analyses up to a temperature of 1150 °C reveal that the Al2Au film is very stable with only marginal mass gain from oxidation found between 800 and 1000 °C. High temperature X-ray diffraction shows that this coating retains its (311) texture up to 900 °C where Al2O3 formation leads to the depletion of Al in Al2Au and subsequently the precipitation of intermetallic AlAu. When gamma-TiAl is coated with Al2Au and exposed to cyclic oxidation tests at 750 and 850 °C good oxidation resistance is obtained as a protective oxide layer is formed.

Dual-phase Al3Zr2-Al2Zr coatings form ZrO2 and Al2O3 in oxidizing atmosphere. However, the phase transition from monoclinic (m-)ZrO2 to tetragonal (t-)ZrO2 with the accompanying volume change causes flaking of the oxide. Yttrium addition to the Al-Zr films stabilizes the cubic (c-) and t-ZrO2 and hence avoids the fatal tetragonal-monocline transformation. The thermally grown c-ZrO2 based oxides allow good adhesion to thermal barrier coatings which are themselves based on c-ZrO2.
Evolution and Interaction of Dislocations in Intermetallics: Fully Anisotropic Discrete Dislocation Dynamics Simulations
Authors: Chen Qian , Biner Bulent
Published: June 2019

In this study, the origin of large ductility that is seen in recently discovered rare-earth intermetallic compounds: YCu, YAg and YZn is explored by using fully anisotropic 3D dislocation dynamics simulations. The stability of the glide dislocations, the behavior of the Frank-Read sources and the strength of junctions are evaluated and compared to those seen for the common intermetallics, NiAl and Fe-25Al.
Microstructural Evolution of Dual Multi-Phase Intermetallic Alloys Composed of GCP Ni3Al and Ni3V Phases Containing Ti
Authors: Takasugi Takayuki , Kaneno Yasuyuki , Tsuda Hiroshi
Published: June 2019

The microstructural evolution of intermetallic alloys, which have dual two-phase microstructure composed of Ni3Al (L12) and Ni3V (D022) phases, was investigated as a function of aging time at 1273K by TEM. At early aging time, the lower microstructure showed structurally decomposed clusters composed of L12 phase and three D022 variant structures. With proceeding aging time, the decomposed L12 and D022 phases coarsened and transformed to lamellar-like microstructures. At longer aging time, the L12 phase disappeared from the lamellar-like microstructure and alternatively the D022 phase composed of two different variant structures prevailed over the lamellar-like microstructures. Corresponding to this microstructural change, the direction of the lamellar and its interfacial plane rotated from <001> to <011> and from {001} to {011}, respectively.
Tensile Property of Cold-Rolled Foils of Ni-Based and Co-Based L12 Intermetallic Alloys
Authors: Kaneno Yasuyuki , Takasugi Takayuki , Myoki Tadamichi
Published: June 2019

Polycrystalline L12-type Ni3(Si,Ti), Co3Ti and Ni3Al alloys prepared through the thermomechanical process from arc-melted ingots were successfully cold-rolled to thin foils with a thickness of below 200μm. The cold-rolling with over 90% reduction in thickness was possible without providing intermediate annealing. The cold-rolled foils showed high tensile strength (~2GPa) at room temperature due to heavily cold rolling although no plastic elongation was observed. Room temperature tensile elongation increased with increasing annealing temperature, and reached to ~30-40% by high temperature annealing at 1173K. Among three kinds of intermetallic alloys, the Ni3(Si,Ti) foil annealed around at 900K exhibited an extremely high tensile strength and yield strength (over 2GPa) with a reasonable tensile elongation. The observed tensile properties, especially tensile strength at low temperature for the present intermetallic foils were found to be superior to those for the conventional alloys such as nickel based alloys and stainless steels.
Phase-Separations of Coherent Precipitates of Ordered Phases in Elastically Constrained Alloys
Authors: Doi Minoru , Kumagai Hiroshi , Nakashima Kanako , Kozakai Takao
Published: June 2019

Phase-separations of coherent precipitates of ordered phases were investigated by means of transmission electron microscopy (TEM) and the theoretical analysis from a thermodynamic point of view. When the two-phase microstructures of A1+L12 in elastically constrained Ni-Al-Ti and Ni-Si-Fe alloys are isothermally heated inside the two-phase region of A1+L12 , coherent L12 precipitate particles sometimes exhibit a phase-separation and A1 phase newly appears and grows in L12 particles. Phase-separations of the same type as the above are also observed in coherent two-phase microstructures of A2+D03 and A2+B2 in elastically constrained Fe-Si-V and Fe-Al-Ni alloys respectively: coherent D03 or B2 precipitates exhibit a phase-separation and A2 phase newly appears and grows in both precipitates. Such phase-separation is realized under the influence of chemical free energy and elastic energies.
Microstructure and Hydrogen Permeability of Duplex Phase M-ZrNi (M=V, Nb, Ta) Alloys
Authors: Ishikawa Kazuhiro , Kasagami Naoshi , Takano Tomoyuki , Aoki Kiyoshi
Published: June 2019

In order to develop non-Pd based high performance hydrogen permeation alloys, microstructure, crystal structure and hydrogen permeability of duplex phase M-ZrNi (M=V and Ta) alloys were investigated using a scanning electron microscope, an X-ray diffractometer and a gas flow meter. These results were compared with those of Nb-ZrNi ones which have been previously published. The hydrogen permeation was impossible in the V-ZrNi alloys, because they were brittle in the as-cast state. On the other hand, duplex phase alloys consisting of the bcc-(Ta, Zr) solid solution and the orthorhombic ZrNi (Cmcm) intermetallic compound were formed and hydrogen permeable in the Ta-ZrNi system. The Ta40Zr30Ni30 alloy shows the highest value of hydrogen permeability of 4.1×10-8 [molH2m-1s-1Pa-0.5] at 673 K, which is three times higher than that of pure Pd.
Effect of C11b-Stabilized Element on Deformation Mode in C40-Type (Nb1-xMox)Si2 (x=0-0.85) Single Crystals
Authors: Nakano Takayoshi , Hagihara Koji , Umakoshi Yukichi
Published: June 2019

Plastic deformation behavior and the dominant deformation mode in ternary (Nb1-xMox)Si2 (x=0-0.85) single crystals with the C40 structure were examined focusing on the phase stability between the C40 and C11b structures. Temperature dependence of CRSS for the (0001)<2-1-10] slip is strongly influenced by the Mo concentration accompanied by the change in the dissociation mode from the co-planar-type to the synchroshear-type. In the ternary crystals with x=0-0.30, anomalous strengthening clearly appeared, and the peak stress increased up to 1600¢ªC with an increase in the Mo content. Mo atoms may gather and form a dragging atmosphere around 1/3<2-1-10] dislocations containing a superlattice intrinsic stacking fault (SISF), resulting in anomalous strengthening. In contrast, in crystals with x=0.60-0.85, a high CRSS was obtained with fracture in a brittle manner at low temperatures, and the stress decreased remarkably with an increase in the test temperature. HRTEM observation showed that the synchroshear-type dissociation of each super-partial dislocation, 1/6<2-1-10], occurred on the neighboring slip planes, accompanied by a much wider separation distance of SF than that in the ternary crystals with a low Mo content. This change in plastic deformation behavior may be closely related to the decrease in phase stability of the C40 structure with the addition of the C11b-stabilized element, Mo. The phase stability can be represented by the ratio of (h/b), where h is the (0003) spacing and b is the amplitude of 1/3<2 0]. As the (h/b) ratio increases with the addition of Mo, the dissociation mode changes from the co-planar-type to the synchroshear-type at a ratio of 0.465.
Coercivity in nanostructured FeCo-based powders prepared by mechanical alloying
Authors: Zeng Qi , Baker Ian , McCreary Virginia , Yan Zhicheng
Published: June 2019

FeCo-based nanostructured powders were prepared by mechanical alloying and subsequently heat treated in an attempt to reduce their coercivity, HC. Although the powders had grain sizes smaller than the magnetic exchange length, a low HC, as expected from Herzer's model, did not occur. The results of magnetic measurements on dilute and concentrated samples of the powder, as well as measurements of the temperature dependence of the magnetic properties from 10-300 K, indicate that the degree of magnetic interaction between the individual powder particles determines the relatively high HC of 10-20Oe at room temperature.
Room Temperature Ductility of B2-Type CoZr Intermetallic Compounds
Authors: Kaneno Yasuyuki , Takasugi Takayuki , Yoshida Mitsuhiko , Tsuda Hiroshi
Published: June 2019

B2 (CsCl) CoZr intermetallic alloys with different chemical compositions were hot-rolled and subsequently recrystallized to evaluate tensile properties and rolling workability. Co-49.0Zr, -49.5Zr and -50.0Zr alloys showed the B2-matrixed microstructure containing C15 Co2Zr dispersions, while Co-50.5Zr and -51.0Zr alloys showed the B2-matrixed microstructure containing C16 CoZr2 dispersions. These homogenized ingots were successfully hot-rolled without edge cracks, except for the Co-51.0Zr alloy. The tensile tests revealed that the Co-49.5Zr, -50.0Zr and -50.5Zr alloys exhibited a notable tensile ductility at room temperature as well as at elevated temperatures. Moreover, the recrystallized CoZr alloys were cold-rolled up to 70% reduction without intermediate annealing. It was also found that tensile ductility was most prominent in the Co-50.0Zr alloy with the least volume fraction of second phase dispersions in the investigated alloys, suggesting that the B2 phase of CoZr was inherently ductile. Deformation microstructures were characterized by means of XRD and TEM observations. Mechanisms responsible for the observed large tensile ductility of the CoZr alloys were discussed, on the basis of the observed deformation microstructures.
On The Influence of Nb on the Transition Temperatures of Titanium Aluminides
Authors: Chladil Harald F. , Clemens Helmut , Takeyama Masao , Kozeschnik Ernst , Bartels Arno , Gerling Rainer , Kremmer Sascha
Published: June 2019

Phase transformations and phase transition temperatures in several Ti-45Al and Ti-45Al-(5-10)Nb (at%) alloys were investigated experimentally and compared to thermodynamic calculation. The present study combines scanning electron microscopy, high-energy and conventional X-ray diffraction as well as differential scanning calorimetry for the characterization of the prevailing phases and phase transformations. Thermodynamic simulation based on the CALPHAD method was used to predict phase stabilities. Modifications of a commercial available database, based on the thermo-physical measurements and long-term annealing treatments, were introduced in order to achieve better agreement between calculated and experimental results.
Catalytic Properties of Ni3Al Foils for Hydrogen Production
Authors: Hirano Toshiyuki
Published: June 2019

We have successfully developed thin foils of boron-free Ni3Al (below 100 μm in thickness) by cold rolling, and recently found that the foils exhibit high catalytic activity for methanol decomposition. A little has been known about catalytic activity in Ni3Al. Even more interestingly, the high catalytic activity appears on flat foils whose surface area is very low. This paper provides a review of the characteristic features of the catalytic properties investigated in my group. Methanol was effectively decomposed into H2 and CO over the foils above 713 K. The production rates of H2 and CO increased with an increase of time during the initial period of reaction, indicating that the Ni3Al foils were spontaneously activated under the reaction conditions. Surface analyses revealed that fine Ni particles dispersed on carbon nanofibers formed on the foils during the reaction. The high catalytic performance of the foils can be attributed to the spontaneous formation of this nanostructure during the reaction.
High Temperature Strength of Co-based γ/γ' Superalloys
Authors: Suzuki Akane , DeNolf Garret C , Pollock Tresa M
Published: June 2019

The high temperature strength of new Co-Al-W based alloys consisting of a ?-Co (fcc) matrix phase and a high volume fraction of ?'-Co3(Al, W) ternary L12 intermetallic compound has been examined in order to understand the strengthening mechanisms and to explore the possibility for high temperature applications. The flow stress exhibits a strong, positive dependence on temperature above 873 K. Additions of Ta improve the high temperature strength, and the strength of a Ta containing alloy is comparable to Ni-base superalloys at 1173 K. Transmission microscopy on the deformed Ta containing alloy revealed that the active slip modes within the ?' precipitates are <110>{111} and <112>{111} below and above the peak temperature, respectively. At the peak flow temperature, multiple slip modes including <110>{111}, <110>{001} and <112>{111} were observed.
Neutron Irradiation Resistance of RAFM Steels
Authors: Gaganidze Ermile , Dafferner Bernhard , Aktaa Jarir
Published: June 2019

The neutron irradiation resistance of the reduced-activation ferritic/martensitic (RAFM) steel EUROFER97 and international reference steels (F82H-mod, OPTIFER-Ia, GA3X and MANET-I) have been investigated after irradiation in the Petten High Flux Reactor up to 16.3 dpa at different irradiation temperatures (250-450 ¡ãC). The embrittlement behavior and hardening are investigated by instrumented Charpy-V tests with subsize specimens.

Neutron irradiation-induced embrittlement and hardening of EUROFER97 was studied under different heat treatment conditions. Embrittlement and hardening of as-delivered EUROFER97 steel are comparable to those of reference steels. Heat treatment of EUROFER97 at a higher austenitizing temperature substantially improves the embrittlement behaviour at low irradiation temperatures. Analysis of embrittlement vs. hardening behavior of RAFM steels within a proper model in terms of the parameter C=DDBTT/Ds indicates hardening-dominated embrittlement at irradiation temperatures below 350 ¡ãC with 0.17 ¡Ü C ¡Ü 0.53 ¡ãC/MPa. Scattering of C at irradiation temperatures above 400 ¡ãC indicates non hardening embrittlement. A role of He in a process of embrittlement is investigated in EUROFER97 based steels, that are doped with different contents of natural B and the separated 10B-isotope (0.008-0.112 wt.%).

Testing on small scale fracture mechanical specimens for determination of quasi-static fracture toughness will be also presented in a view of future irradiation campaigns.
Including the Effects of Electronic Excitations and Electron-Phonon Coupling in Cascade Simulations
Authors: Duffy Dorothy , Rutherford Alexis
Published: June 2019

Radiation damage has traditionally been modeled using cascade simulations however such simulations generally neglect the effects of electron-ion interactions, which may be significant in high energy cascades. A model has been developed which includes the effects of electronic stopping and electron-phonon coupling in Molecular Dynamics simulations by means of an inhomogeneous Langevin thermostat. The energy lost by the atoms to electronic excitations is gained by the electronic system and the energy evolution of the electronic system is modeled by the heat diffusion equation. Energy is exchanged between the electronic system and the atoms in the Molecular Dynamics simulation by means of a Langevin thermostat, the temperature of which is the local electronic temperature. The model is applied to a 10 keV cascade simulation for Fe.
Ion Beam Lithography And Resist Processing for Nanofabrication
Authors: Arshak Khalil , Gilmartin Stephen F. , Collins Damien , Korostynska Olga , Arshak Arousian , Mihov Miroslav
Published: June 2019

The International Technology Roadmap for Semiconductors (ITRS) identifies the shrinking of lithography critical dimensions (CDs) as one of biggest challenges facing the semiconductor industry as it progresses to smaller geometry nodes. Nanolithography, the patterning of masking CDs below 100nm, enables both nanoscale wafer processing and the exploration of novel nanotechnology applications and devices.

Focused Ion Beam (FIB) lithography has significant advantages over alternative nanolithography techniques, particularly when comparing resist sensitivity, topography effects, proximity effects and backscattering. FIB lithography uses the implantation of ions, such as Ga+, in its masking process. Ions implanted into resist in this manner typically have shallow penetration depths (<100nm for Ga+), and this would typically require the use of very thin resist layers during processing. This is often incompatible with subsequent fabrication steps such as plasma etching, where thicker resist layers are usually required to facilitate etch selectivity. Top surface imaging (TSI) is a solution to this problem.

When compared with conventional microelectronic lithography, nanolithography techniques such as EUV, electron beam and nanoimprint lithography require expensive process equipment and the use of non-standard process materials.

The 2-step negative resist image by dry etching (2-step NERIME) process is a FIB TSI scheme developed for DNQ/novolak based resists, and involves FIB exposure of resist with Ga+, followed by O2 plasma dry development using reactive ion etching. The 2-step NERIME process uses equipment sets and materials commonly found in microelectronic device fabrication (FIB tool, O2 plasma etcher, DNQ/novolak resists), and provides a low-cost and convenient nanolithography option for proof-of-concept nanoscale processing.

To be of practical use, a nanolithography scheme must be capable of patterning nanoscale resist features over substrate topography while retaining resist profile control. The nanolithography scheme must also integrate with subsequent plasma etch processing steps that etch various material films such as metals, Si, SiO2, SiN. The 2-step NERIME FIB TSI process has been used to successfully pattern nanoscale (40nm-90nm) resist features on planar and topography substrates. We have also demonstrated sub-100nm etched features on topography substrates using the 2-step NERIME process, reporting 80nm Polycide and TiN etched features, and 90nm Ti etched features, that exhibit excellent profiles and minimal line edge roughness (LER).

It is expected that the 2-step NERIME FIB TSI process will be further extended to etch sub-40nm features over topography substrates. The nanoscale etched features will be used to explore proof-of-concept geometry shrink & novel structures, with many possible applications, including NEMs and nanosensors research and development.
Effective Use of Focused Ion Beam (FIB) in Investigating Fundamental Mechanical Properties of Metals at the Sub-Micron Scale
Authors: Greer Julia R
Published: June 2019

Recent advances in the 2-beam focused ion beams technology has enabled researchers to not only perform high-precision nanolithography and micro-machining, but also to apply these novel fabrication techniques to investigating a broad range of materials' properties at the sub-micron and nano-scales. In our work, the FIB is utilized in manufacturing of sub-micron cylinders, or nano-pillars, as well as of TEM cross-sections to directly investigate plasticity of metals at these small length scales. Gold nano-pillars, ranging in diameter between 200 nm and several micrometers were fabricated from bulk gold and epitaxial gold films on MgO substrates and subsequently compressed using a Nanoindenter fitted with a custom-fabricated diamond flat punch. We show convincingly that fundamental mechanical properties like flow stress, yield strength, and stiffness strongly depend on the sample size, as some of our smaller specimens were found to plastically deform in uniaxial compression at stresses as high as 800 MPa, a value ~50 times higher than for bulk gold.

We believe that these high strengths are hardened by dislocation starvation. In this mechanism, once the sample is small enough, the mobile dislocations have a higher probability of annihilating at a nearby free surface than of multiplying and being pinned by other dislocations. Therefore, plasticity is accommodated by the nucleation and motion of new dislocations rather than by interactions of existing dislocations, as is the case for bulk crystals. To validate this mechanism, direct observation of dislocations was accomplished by utilizing the Omniprobe micromanipulator, coupled with FIB-milling and Pt deposition, for fabrication of site-specific TEM specimens. Preliminary TEM images show the lack of mobile dislocations in deformed pillars, which agrees with the proposed dislocation starvation mechanism, as discussed.
On the electronic configuration in Pu
Authors: Tobin J G , Soderlind P , Landa A , Moore K T , Schwartz A J , Chung B W , Wall M A , Wills J M , Haire R G , Kutepov A L
Published: June 2019

X-Ray Absorption Spectroscopy (XAS) and Photoelectron Spectroscopy (PES) have been performed upon highly radioactive samples, particularly Plutonium, at the Advanced Light Source in Berkeley, CA, USA. First results from alpha and delta Plutonium are reported as well as a detailed analysis of sample quality.
Facilities for the Performance of Fano Effect Measurements as a Probe of Electron Correlation
Authors: Tobin J. G. , Tobin S. W. , Komesu T , Chung B W , Morton S. A. , Waddill G. D.
Published: June 2019

Fano Effect measurements are the key to direct observation of the Kondo or spin shielding intrinsic to models of electron correlation. The Fano Effect is the observation of spin polarized photoelectron emission from NONMAGNETIC materials, under chirally selective excitation, such as circularly polarized photons. Below are described three spectrometers, with which Fano Effects measurements have been made.
Electronic Structure of AC-Clusters and High-Resolution Xray Spectra of Actinides in Solids
Authors: Kulagin Nicolay Alex
Published: June 2019

Ab initio calculations using SCF approach for and analysis of results of investigation of the electronic structure of the clusters RA+n:[L]k with rare earths or actinides were carried out for the clusters in solids and liquids. Theoretical results for the electronic structure, radial integrals and energy of X- ray lines are presented for AC ions with unoccupied 5f-shell in the clusters in oxides, chlorides and fluorides environment. Possibility of collaps of nf-shell for the separate clusters and identification of electronic state of ions with unstable nuclei, are discussed, too.
Systematic Investigation of the Superconducting Behavior in Aged PuCoGa5
Authors: Jutier Frédéric , Colineau Eric , Griveau Jean-Christophe , Rebizant Jean , Wastin Franck
Published: June 2019

In this work, we have undertaken to follow the evolution of the PuCoGa5superconducting behavior as a function of the damages created by self-radiation effects induced from the Pu-decay. It is shown that the critical temperature is particularly sensitive with ageing. Ageing effects on fundamental parameters such as the lattice parameters of the PuCoGa5and the electrical resistivity provide some new hints of the unconventional character of the superconductivity in this class of materials
Using Correlations to Understand Changes in Actinide Bonding
Authors: Haire Richard G. , Heathman Stephen
Published: June 2019

An important issue in actinide science is the changing role of the 5f electrons, both when progressing across the series, as well as how experimental variables affect these roles in a particular element's chemistries and physics. The function of these 5f electrons can be changed by experimental conditions: temperature and pressure being two of many such variables. The 5f electrons of several actinide metals, their alloys and compounds are affected greatly by pressure, due to the very large decreases in interatomic distances encountered under pressure. The latter bring about significant changes in the total energy of the system and in the electronic energy levels, which in turn affect the potential for overlap/hybridization) of their orbitals, promotion of electrons to other orbitals, etc. The physical state, temperature, pressure, specific structures, magnetic interactions and spin polarization effects are all critical parameters for bonding. Often correlations of behavior with these parameters can provide unique insights and understanding into the bonding and the changes that occur in it. With the advancement of modern computation approaches using FPMTO, or other approaches, theory has enlightened greatly the understanding of not only the bonding behavior of these elements but also the understanding of changes observed experimentally. But these computational efforts have some complications and limitations, and at times experimental findings and theory are not always in full agreement. In contrast to the behaviors of the elements, changes observed with compounds often are not be linked directly to the involvement of 5f electrons, due in part to the presence and bonding role of non-actinide atoms. The latter affect both the actinide interatomic distances and the type of electronic orbtals that interact. Presented here is an overview of the pressure behavior several actinide elements, some insights into the bonding behavior of compounds under pressure and selected correlations that help explain changes occurring in electronic configurations and bonding.
Observation of Radiolytic Field Alteration of the Uranyl Cation in Bicarbonate Solution
Authors: Snow Lanee , McNamara Bruce , Sinkov Sergei , Cho Herman , Friese Judah
Published: June 2019

Auto radiolysis of uranium (VI) carbonate solutions between pH 5.9 and 7.2 is shown to alter the uranium speciation over relatively short periods of time and was followed by 13C NMR and visible spectrophotometry, using dissolved [233(UO2)3(CO3)6]6- both as the radiolysis source (DÑ= 14.9 Gy/hr) and as a trap for the newly formed hydrogen peroxide. The speciation is different than the uranyl mixed peroxy carbonate species that have been reported for higher pH carbonate solutions.
Phase Formation and Dielectric Properties of Ln3NbO7 (Ln = Rare Earth Elements)
Authors: Cai Lu , Guzmán Julián , Pérez Louis A. , Nino Juan C.
Published: June 2019

The structure and dielectric properties of rare earth niobate compounds within the Ln3NbO7 (Ln = Nd, Gd, Dy, Er, Yb and Y) and Ln2(Ln',Nb)O7 (Ln = Nd, Sm and Ln' = Yb) series are investigated. The crystal structure of the all the studied materials is found to be fluorite-related including webertite-type, pyrochlore, and defect fluorite structures. It is observed that the relative permittivity of the defect fluorite Ln3NbO7 (Ln = Dy, Er, Yb and Y) increases with the increase in temperature and exhibits low dielectric loss up to approximately 350 K. Above 350 K, the dielectric loss increases rapidly with increasing temperature as the onset of electrical conductivity takes place. Of particular interests are Gd3NbO7 and Nd3NbO7, which exhibit a frequency and temperature dependent dielectric relaxation behavior. At 1 MHz Gd3NbO7 reaches its maximum relative permittivity of ∼34 at about 330K, while at the same frequency, the maximum relative permittivity of Nd3NbO7 is attained at about 500 K. By contrast, Nd2(Yb,Nb)O7 and Sm2(Yb,Nb)O7, which crystallize in a pyrochlore-type structure, do not show dielectric relaxation and, comparatively, exhibit a more temperature-stable dielectric permittivity response.
Interlayer Charge Conversion Through Intercalation of Polycations into a Synthetic Swelling Mica
Authors: Hata Hideo , Kobayashi Yoji , Mallouk Thomas E
Published: June 2019

A layered host material with the ability to encapsulate anionic substances was synthesized by intercalating polycations into a synthetic fluoromica. A cationic polyelectrolyte coiled in the interlayer galleries to overcompensate the negative charge on the silicate sheets, and bulky anionic dye molecules could site-selectively be intercalated into interlayer in which the polyelectorlyte coiled.
Bio-Inspired Hydrogel-Calcium Carbonate Core-Shell Particles
Authors: Kim Yi-Yeoun , Catino John W , Tomaino Gary P , Cox Sherman D
Published: June 2019

In this report, we present a bio-inspired encapsulation process to create nanocluster-assembled core-shell particles under aqueous, room temperature and non-toxic conditions. The approach to synthesize calcium carbonate core-shell particles is accomplished by employing a Polymer-Induced Liquid-Precursor (PILP) process. We demonstrate the amorphous mineral precursor is coated around a core of hydrogel nanoparticles, and subsequently solidified and crystallized. The synthesized core-shell particles are 300∼500nm diameter and ∼100 nm shell-thickness. We investigate the role of the hydrogel core of the particle using time-resolved XRD, thermal-XRD and thermal analysis. The organic hydrogel appears to influence the transformation of mineral phases, stabilizing the amorphous phase of calcium carbonate.
Magnetic Properties of Vanadium Oxide Nanotubes, Nanourchins, and Nanorods.
Authors: Jacobs Chris , Roppolo Megan , Butterworth Kristin , Ban Chunmei , Chernova Natasha A. , Whittingham M. Stanley
Published: June 2019

A better understanding of magnetic interactions, charge distribution, and redox properties of vanadium oxide nanotubes (VONTs) is necessary for accurate structure and mechanism of formation determination. Magnetic properties have been determined for pristine and lithiated VONTs and for the VONTs arranged in nanourchin morphology. Presence of paramagnetic V4+ ions and V4+ ions coupled in magnetic dimers is found, and their amounts are estimated. Both lithiation and change of morphology to nanourchin destroy the spin-gap behavior, which indicate changes in charge distribution. No ferromagnetic response is observed in lithiated VONTs. Magnetic properties of vanadium oxide nanorods with δ-V4O10 structure are also characterized.
A Scrolled Sheet Precursor Route to Niobium Oxide Nanotubes
Authors: Kobayashi Yoji , Hata Hideo , Mallouk Thomas E.
Published: June 2019

Potassium hexaniobate (K4Nb6O17) is one of the few relatively well-studied oxides which, upon exfoliation, rolls up into scrolls almost quantitatively with monodisperse length (∼300 nm) and diameter (30 nm). The tubes have high surface area (250-300 m2/g) and a wall thickness of 2-3 nm. These H4Nb6O17 scrolls were converted to Nb2O5 via a thermal dehydration process, yielding high surface area (150-200 m2/g) Nb2O5 nanotubes. Despite extensive atomic rearrangement during dehydration at 400-450 °C, little sintering is occurs, and so the tubular morphology is retained. Attempts to conduct further reactions to obtain LiNbO3 and KNbO3 nanotubes from reaction with molten alkali salts failed to yield the intended nanotubular oxides.
Microstructured Optical Fibers as New Nanotemplates for High Pressure CVD
Authors: Baril Neil , Badding John , Savio Pier , Gopalan Venkatraman , Won Dong-Jin , Scheidemantel Thomas , Finlayson Chris , Amezcua-Correa Adrian , Jackson Bryan
Published: June 2019

Solid state chemists have long been interested in templated growth of materials using many approaches. The resulting materials have been useful in areas as diverse as photonics and catalysis. Microstructured optical fibers (MOFs) form a new class of nanotemplates that can have sub 20 nm pores that are meters to kilometers long. We have developed a high-pressure microfluidic chemical process that allows for conformal deposition of materials within MOFs to form the most extreme aspect ratio semiconductor nanowires known. The wires can be spatially organized with respect to each other at dimensions down to the nanoscale because the MOF templates can be designed with almost any desired periodic or aperiodic pattern. Many if not most of the chemistries used for conventional chemical vapor deposition (CVD) can be adapted for this process. The resulting materials should enable a large range of scientific and technological applications.
Spontaneous Transformations in the Solid State: Towards Porous and Biphasic Materials
Authors: Toberer Eric S. , Seshadri Ram
Published: June 2019

Epitaxial thin films of Mn3O4 and ZnMn2O4 have been grown hydrothermally on (100) and (111) MgAl2O4 substrates. Film growth was characterized as a function of pH, concentration, and time and thin film X-ray diffraction revealed that the resulting films are an epitaxial continuation of the underlying spinel lattice. Reduction of these films to MnO occurred topotactically and in the case of ZnMn2O4, resulted in mesopores aligned along the <100> directions. As the films maintain an epitaxial relationship with the substrate, the mesopores are aligned macroscopically within a single crystal lattice.
Synthesis and Luminescent Property of Nanocrystalline Phosphors via Solvothermal Processes
Authors: Tung Chien-Yuen , Chang Shyue-Ming , Chen Teng-Ming
Published: June 2019

We have synthesized a series of nanocrysatlline (5±3 nm in diameter) and submicrom ZnS:Ag,Al phosphors with various dopant compositions via a newly developed emulsion method. The X-ray diffraction (XRD), EDS, SEM, and TEM were utilized in the characterization of phase purity and microstructure of phosphor particles. Photoluminescence (PL) and cathodoluminescence (CL) spectra were also utilized to characterize the optical properties of blue-emitting phosphor. The CL intensity of submicron ZnS:Ag,Al phosphor was found to be weaker than that of corresponding commercial product, which was attributed to the poor crystallinity and small grain size. In this article we described the synthesis of ZnS:Ag,Al nanophosphor with emphasis on the correlation between spectroscopic features and the microstructure.
Superconductivity in Clathrates Ba24IV100( IV = Si and Ge ) with Rattling Motions
Authors: Rachi Takeshi , Kumashiro Ryotaro , Fukuoka Hiroshi , Yamanaka Syoji , Tanigaki Katsumi
Published: June 2019

Both Ba24Si100and Ba24Ge100with crystallographically identical structure are the superconductors whose critical temperatures are 1.45 and 0.27 K, respectively. Intriguingly, physical properties of the both compounds are extremely different. The observed differences are considered to be associated with Ba rattling motions. We have exemplified such unique motions in terms of x-ray diffraction data using MEM/Rietveld analyses. We present these exotic systems especially focusing on the relation between superconductivity and the rattling phonons.
Probing Octahedral Tilting in Dion-Jacobson Layered Perovskites With Neutron Powder Diffraction and Raman Spectroscopy
Authors: Kurzman Joshu A. , Geselbracht Margret J.
Published: June 2019

Two new Dion-Jacobson type layered perovskite solid solutions, RbCa2-xSrxM3O10 (M = Nb, Ta; 0 ≤ x ≤ 2), were prepared and studied by X-ray powder diffraction, neutron powder diffraction, and Raman spectroscopy. X-ray powder diffraction confirmed single-phase solid solution formation with continuous expansion of the idealized primitive tetragonal unit cell with increasing strontium content. Neutron powder diffraction studies of selected samples revealed lower symmetries and larger unit cells, as necessitated by octahedral tilting within the perovskite slabs, compared to the idealized primitive cell. As the average size of the A-cation in the perovskite slab is varied from Sr2+ to Ca2+, more extensive octahedral tilting is introduced. Vibrational modes of the perovskite slab observed using Raman spectroscopy show subtle changes as a function of calcium/strontium content and more intriguing differences between the isostructural niobates and tantalates.
Electrochemical Insertion of Li into Sr2MO2Cu2S2 (M = Mn, Co, Ni)
Authors: Indris Sylvio , Zeng Dongli , Cabana Jordi , Smura Catherine F. , Rutt Oliver J. , Clarke Simon J. , Grey Clare P.
Published: June 2019

The layered oxysulfides Sr2MO2Cu2S2 (M = Mn, Co, Ni) consist of alternating perovskite-type Sr2MO2 layers and copper sulfide layers. We studied the electrochemical insertion of Li into these three samples. By this we were able to study the influence of the nature of the transition metal on the Li insertion process which appears to be at least partially reversible. While the Mn compound clearly shows a Cu-Li exchange reaction, the electrochemical process for the two other compounds is more complex. The lithiated materials were studied by 7Li MAS NMR.
Physical Properties of Oxygen Composition Controlled La1-xSrxMnOy Single Crystals
Authors: Yokota Yuui , Shimoyama Jun-ichi , Ogata Tetsuro , Horii Shigeru , Kishio Kohji
Published: June 2019

We have investigated the effect of high-temperature post-annealing and control of excess oxygen for La1-xSrxMnOy (0.05 ≤ x ≤ 0.2) single crystals. Thin plate-like single crystals prepared by careful cutting and polishing enabled the control of excess oxygen for the single crystals by post-annealing for relatively short times at various temperatures. Post-annealed crystals with y ∼ 3.00 exhibited higher TC than that of as-grown crystals due to homogenization of cation and oxygen compositions and reduction of local lattice strains. With an increase of y, TC systematically increased for all Sr compositions. Competition between an increase of mean valence of manganese and generation of cation vacancy determines the TC of La1-xSrxMnOy crystals.
Undergraduate Materials Research Initiative: Providing Active Research Experience
Authors: Stadler Bethanie J. H. , Omer Ingrid L. St.
Published: June 2019

The Materials Research Society's Undergraduate Materials Research Initiative (UMRI) is a program designed to introduce undergraduates to research and the excitement of discovery in materials science and engineering. Through an open competition process modeled after federal funding agencies, participants gain an understanding of the research process from proposal to final report. Each awardee receives a grant for the cost of a moderate research project (maximum $750). In addition, the student researcher receives an award of $250 upon completion of the project. The MRS awarded 20 grants for research performed during the inaugural 1998/99 academic year, and it has awarded 40 grants this academic year. In addition to financial assistance, the MRS also provides positive exposure for both the UMRI undergraduate researchers and their advisors in order to highlight the importance of an active research experience. Past and present UMRI awardees have been invited to present their work in a poster session during this meeting. The educational impact of the program will be explored in terms of applicant demographics and survey responses from awardees. The review process, international aspects, and suggested research timeframes will also be discussed. The basic operating principles of this program have potential application to any academic, industrial or governmental program designed to increase faculty and student interest in undergraduate research. Such programs address the need to attract and retain talented individuals to technical careers.
An Interdisciplinary Approach for Involving Undergraduates in the Materials Science and Engineering Program
Authors: Bruch Reinhard , Afanasyeva Natalia , Welser Leslie , Gummuluri Satya , Showers Stan , Kano Angelique
Published: June 2019

The University of Nevada, Reno (UNR) Physics Department has a successful history of involving undergraduate students in interdisciplinary research, including the fields of materials science and engineering. The group directed by Prof. Reinhard Bruch has given a number of undergraduates the opportunity to work on professional-level research projects early in their career development. In our Physics Department at UNR, it is common to have a high percentage of undergraduates involved in research projects. Therefore, we suggest that the Materials Science and Engineering Program could explore the potential opportunity for spawning inter-disciplinary research programs involving undergraduates.
Building Knowledge in Materials Science
Authors: Baillie Caroline , Emanuelsson Jonas , Marton Ference
Published: June 2019

The present paper discusses the outcomes of research exploring the formation of knowledge in one area of materials science, that of the ‘interface’ in composite materials. A series of interviews have been conducted with researchers from eight different countries, all involved in investigating a similar issue. Questions were aimed at exploring their understanding of certain key concepts. The interviews were transcribed and data analysed using a phenomenographic approach. Having a better understanding of the way in which the knowledge is understood by different researchers gives us a new way of helping students to approach their own understanding of the concepts. Students can see the concepts from many perspectives and realise that there is not one way to understand a scientific ‘fact’. This paper discusses the possibilities that this approach holds for Materials Science Education.
Everything you've always wanted to know about what your students think they know but were afraid to ask.
Authors: Werwa Eric
Published: June 2019

A review of the educational literature on naive concepts about principles of chemistry and physics and surveys of science museum visitors reveal that people of all ages have robust alternative notions about the nature of atoms, matter, and bonding that persist despite formal science education experiences. Some confusion arises from the profound differences in the way that scientists and the lay public use terms such as materials, metals, liquids, models, function, matter, and bonding. Many models that eloquently articulate arrangements of atoms and molecules to informed scientists are not widely understood by lay people and may promote naive notions among the public. Shifts from one type of atomic model to another and changes in size scales are particularly confusing to learners. People's abilities to describe and understand the properties of materials are largely based on tangible experiences, and much of what students learn in school does not help them interpret their encounters with materials and phenomena in everyday life. Identification of these challenges will help educators better convey the principles of materials science and engineering to students, and will be particularly beneficial in the design of the Materials MicroWorld traveling museum exhibit.
The Internet Microscope.
Authors: Marrow James , Derby Brian
Published: June 2019

The Internet Microscope is an image library, with a difference. Its web site (http://www.umist.ac.uk/~intmic/) is dedicated to the explanation and illustration of the relationship between microstructure, properties and processing in materials science. A growing selection of the samples is aimed directly at schools and colleges.

The microscope has been used with undergraduate teaching at the University in conjunction with computer presented multiple choice questions. It has replaced microscopy laboratories for a class of 100 engineering students, for whom materials science forms a small but important part of their syllabus. The microscope also allows students to test and revise their knowledge of phase diagrams.

The Internet Electron Microscope is an exciting development of the existing web site. It makes use of the concept of “Learning by Doing”. It will give schools and colleges on-line control of a free, simple and easy to use scanning electron microscope. Samples will range from sugar cubes to silicon chips, offering a real experience of microscopy.
A Home-Made Inch-Scale Scanning Force “Microscope”
Authors: Guerra-Vela Claudio , Zypman Fredy R.
Published: June 2019

We developed a foot-long aluminum “microscope” cantilever to use in our undergraduate laboratory. The detection mechanism is by means of a vibrating piezoelectric. The tip-sample interaction is obtained by means of springs attached at the end of the cantilever. The main objective is to provide students with a large cantilever from where they can build an intuitive feel of the instrument. Also, and perhaps more important, we teach the student how to extract forces from kinematics data. We let the cantilever move under the action of the interaction force, and record that motion as a voltage produced by the vibrating piezoelectric. That voltage is then processed to reproduce the F-d (Force-distance) curve. As opposed to what happens in the real microscope, in our case we have access to the sources of force and thus we can check the accuracy of our reconstruction algorithm by comparing our reconstructed Fd curve with the known one.