bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Seeding Effect of Lanthanum Nickel Oxide Ceramic/Ceramic Nanocomposite Thin Films Prepared by the MOD Method
Authors: Zhang Yu , Zhou Qifa , Chan Helen Lai-wa , Choy Chung-Loong 
Published: April 2011

AbstractLanthanum nickel oxide (LNO) is a conducting ceramic which has potential to be used as electrodes in multilayer ceramic actuators. Thick LNO films have been formed by incorporating nanosized LNO powder (annealed at 700°C, with diameter around 100 nm) into a LNO solution prepared by a metal-organic decomposed ( MOD ) method. Three different weight percents, 2%, 4%, and 10% of LNO powder have been added. The structural variation of the ceramic/ceramic composite film with annealing temperature was studied by X-ray diffraction and differential thermal analysis. The crystallization temperature of the film is found to decrease from ∼590°C to ∼510°C due to the seeding effect introduced by the nano-powder.
Thermal Stability and Semiconducting Properties of Epitaxial La0.7Sr0.3MnO3 Films
Authors: So K. S. , Wong K. H. , Wu W. B. 
Published: April 2011

AbstractLa0.7Src.3MnO3 (LSMO) perovskite oxide films have been grown on (001) LaAlO3 (LAO) by pulsed laser deposition. The films were deposited in an ambient oxygen pressure of 0.1 m Torr to 200 mTorr and under different substrate temperatures. Their structural properties were examined by X-ray diffractometry. Heteroepitaxial growth was confirmed for films deposited at 650°C or above. Electrical measurements suggest that the charge carrier concentraticn of the films varies with their oxygen content and shows high stability against further thermal treatment. Semiconducting LSMO films at room temperature were obtained for deposition at oxygen pressure ≤ 60 m Torr. The epitaxial LSMO films have been used as the semiconducting channel of a ferroelectric field effect transistor. Heteroepitaxial Pb(Zr0.52Ti0.48)O3/LSMO/LAO structures have been fabricated and characterized.
Transport Anisotropy in PLD-Made La0.75Sr0.25MnO3 Films
Authors: Johnsson P. , Khartsev S.I. , Grishin A.M. 
Published: April 2011

AbstractA sequence of epitaxial La0.75Sr0.25MnO3 (LSMO) films with thickness ranging from 2400 to 50 Å have been prepared by pulsed laser deposition onto (110) SrTiO3 (STO) substrates. Compared with oar previous results on LSMO/STO(100) films [1], films on STO(110) substrates exhibit strong, anisotropy of electrical resistivity p. p measured in [110] direction is comparable with the resistivity of LSMO/STO(100) films while p in [001] direction is 25 times higher than in STO(100) case. The maximum value of anisotropy parameter p[001]/p[110] = 25 is reached for thick films at the low temperature of 90 K. Distinct crossover from 3D to 2D case has been observed. For thick films anisotropy monotonously decreases with the temperature increase. Films thinner than 200 Å exhibit a maximum of anisotropy parameter, which shifts to lower temperatures with the thickness decrease. The maximum temperature coefficient of resistivity (TCR) was found to be around 2% if measured along [001] direction and about 50 % higher in [11O] inplane direction. We explain the observed effects in terms of the crystalline properties of fabricated films.
Junction Properties of Metal/SrTiO3 Systems
Authors: Shimizu Takashi , Okushi Hideyo 
Published: April 2011

AbstractElectrical properties of Nb-doped SrTiO3 (STO:Nb) Schottky barrier (SB) junctions have been investigated in detail for a comprehensive understanding of metal/oxide interfaces. Using a high-purity ozone surface treatment, rectification ratio over 9th order of magnitude has been successfully obtained, while without the surface treatment, anomalous large reverse bias leak currents were observed in the current-voltage characteristic of the junctions. The X-ray photoelectron spectroscopy (XPS) shows that carbon contamination which adsorbed the STO:Nb surface in air, induces surface states in the band gap of the STO:Nb, which probably originate the large reverse bias leak currents of the metal/STO:Nb junctions. Thus we present importance, of surface treatment for oxides to obtain controllability and reproducibility of the electrical properties of the oxide devices. Photocapacitance spectroscopy has been performed to investigate deep levels due to bulk defects and impurities in the Au/STO:Nb junctions. The photocapacitance spectra clearly indicate existence of the deep levels in the Au/STO:Nb and the concentration of the deep levels were of the order of 1013∼1015 cm−3. These values are too low to affect the Fermi level pinning at the interface if the deep levels exist in the near surface region of the bulk STO:Nb. We have shown some interesting electrical properties, characteristic of the SB junction of the dielectric oxide compared with that of the conventional semiconductor's. The schematic band diagram of the Au/STO:Nb junction with the intrinsic low permittivity layer at the interface has been proposed, which explains all the characteristic electrical properties. Considering the chemical trend of the SB height (SBH) estimated from the J-V results, we have pointed out the importance of the metal reactivity for understanding the formation mechanism of the SBH.
High Resolution Copper Lines by direct Imprinting
Authors: Hong C.M. , Sun X. , Wagner S. , Chou S.Y. 
Published: April 2011

ABSTRACTOne-micrometer wide copper lines are patterned by direct imprinting and thermolysis. First, a layer of plastic copper hexanoate is spun on a substrate and patterned by direct imprint. Then the copper hexanoate line pattern is converted to copper metal lines by thermal and hydrogen anneals. The converted copper film resistivity is ∼8 μωcm. The direct imprinting of a fine metal pattern points the way to the direct patterning of device materials at high resolution
All-Printed Inorganic Logic Elements Fabricated by Liquid Embossing
Authors: Bulthaup Colin , Wilhelm Eric , Hubert Brian , Ridley Brent , Jacobson Joe 
Published: April 2011

ABSTRACTThe liquid embossing process, devices made by this process, and their characteristics are presented. Structures fabricated and discussed here include: conductive lines with cross line resistance greater than 100 Gω and resistivities 4 times that of the bulk material, multilayer structures with etched sacrificial materials, vias that conduct through an embossed insulating layer, photodetectors made with nanocrystal solutions of CdSe, and all printed inorganic field effect transistors
Thermal Stability and Analysis of Laser Deposited Platinum Films
Authors: Berry G.J. , Cairns J.A. , Davidson M.R. , Fan Y.C. , Fitzgerald A.G. , Fzea A.H. , Lobban J. , McGivernt P. , Thomson J. , Shaikh W. 
Published: April 2011

ABSTRACTAs the trend towards device miniaturisation continues, surface effects and the thermal stability of metal deposits becomes increasingly important. We present here a study of the morphology and composition of platinum films, produced by the UV-induced decomposition of organometallic materials, under various annealing conditions. The surface composition of the metal deposits was studied by X-ray photoelectron spectroscopy, both as-deposited and following thermal treatment. In addition, the morphology of the surface was studied by atomic force microscopy which enabled the investigation of film restructuring. These studies were performed over a range of temperatures up to 1000°C in air and up to 600°C in reducing environments. Complementary information regarding the film morphology has been obtained from transmission electron microscopy. The data has been used to provide an insight into the effects of elevated temperatures on metal films deposited by a direct write method
Real-World Applications of Laser Direct Writing
Authors: Ehrlich D. J. , Aucoin Richard , Burns M. J. , Nill Kenneth , Silverman Scott 
Published: April 2011

ABSTRACTLaser microchemical direct write deposition and etching methods have found an essential niche in debug and design for yield of wire-bonded and flip-chip integrated circuits. Future applications should develop in package-level system modification.
µ-Mold Shape Deposition Manufacturing of Ceramic Parts
Authors: Nam S.W. , Stampfl J. , Liu H.C. , Kang S. , Prinz F. B. 
Published: April 2011

AbstractRapid Prototyping is a versatile method to build complex-shaped ceramic or metallic parts on a mesoscopic scale. In this work the fabrication of ceramic gas turbine engine parts with Mold Shape Deposition Manufacturing (Mold SDM) is described. Mold SDM exists of two steps: The pattern generation in wax using deposition and machining of wax layers and the pattern transfer process with gel-casting. For parts with feature sizes that are too small for machining, microfabrication methods are used to fabricate the mold. By combining micro- and macro-fabrication, complex parts in a wide variety of sizes can be manufactured.The surface quality of the mold significantly influences the mechanical properties of the final ceramic part. The contribution of the mold quality to the final mechanical properties is studied in this work.
Freeform Fabrication of Functional Silicon Nitride Components by Direct Photo Shaping
Authors: Ventura S. , Narang S. , Guerit P. , Liu S. , Twait D. , Khandelwal P. , Cohen E. , Fish R. 
Published: April 2011

AbstractThis paper describes a new multilayer solid freeform fabrication process, “Direct Photo Shaping” (DPS), where visible digital light projection is used as a maskless tool to build images on photocurable ceramic dispersions (ceramic powders in photopolymerizable liquid monomers) by flood exposure. For each layer, the projected image is changed according to the CAD data describing the object being built and solidification takes place by photocuring the exposed areas. Multiple layers are dispensed and photocured to fabricate the object of interest. A final rinse with a suitable solvent allows the removal of any uncured ceramic dispersion. The porous free formed “green” ceramic object can then be fired and sintered into a highly dense ceramic part. Digital Light Processing™ technology (developed by Texas Instruments) enables SRI International to project digital, high resolution, high brightness, high contrast visible light to photocure and form components with a good degree of accuracy. This paper describes the Direct Photo Shaping process and its advantages, and how DPS is being applied to the fabrication of ceramic (Honeywell AS800) gas turbine components for military and commercial applications. ASS00 test specimens with flexural strength in excess of 800MPa were fabricated by DPS. A first-stage AS800 turbine vane for the Rolls-Royce Allison Model 501-K industrial gas turbine was fabricated by DPS and tested in a gas-burner test rig at 1204°C. Initial tests show that ceramic samples with optimized surface finish (comparable to that achieved by ceramic bisque machining) can be fabricated by applying a pixel anti-aliasing filter along the boundaries of the sample projected slice images.
TEM Observation of Nanocrystalline Copper During Deformation
Authors: Youngdahl Carl J. , Hugo Richard C. , Kung Harriet , Weertman Julia R. 
Published: April 2011

ABSTRACTNanocrystalline samples of copper were prepared using inert gas condensation and an optimized sequence of powder outgassing and compaction. TEM specimens were cut, electropolished, and mounted in a straining stage. In situ TEM observations including real-time video were captured during straining in the microscope. Areas of presumed increased stress concentration were identified near small cracks around the perimeter of the electropolished hole. Such locations were observed in the TEM while the specimen was pulled in tension. Several microstructural changes were captured during deformation including numerous sudden shifts in contrast of grains and parts of grains, occasional dislocation motion, opening and propagation of the crack. Relationships between grain size and deformation are described.
Superplasticity in Nanocrystalline Ni3Al and Ti Alloys
Authors: Mcfadden Sam X. , Sergueeva Alla V. , Kruml Tomas , Martin Jean-Luc , Mukherjee Amiya K. 
Published: April 2011

ABSTRACTThe advent of nanocrystalline materials has provided new opportunities to explore grain size dependent phenomenon. Superplasticity is such a grain size dependent phenomenon defined by the ability to attain tensile elongation of 200% or more. Superplasticity in microcrystalline materials has been well characterized. The constitutive equations that describe microcrystalline superplasticity predict enhanced properties for nanocrystalline materials. Enhanced properties in such nanocrystalline material include lower superplastic temperature at constant strain rate, higher superplastic strain rate at constant temperature, and lower flow stresses. Investigations with nanocrystalline Ni3Al and ultra-fine grained Ti-6Al-4V alloy have shown a reduction in the superplastic temperature. However, the flow stresses in these materials are significantly higher than expected. The high flow stresses are accompanied by strong strain hardening.Transmission electron microscopy in situ straining of nanocrystalline Ni3Al has shown that grain boundary sliding and grain rotation occurred during straining. The sliding and rotation decreased with strain. Dislocation activity was observed but was not extensive. There was no observable dislocation storage. The parameters of the generalized constitutive equation for superplasticity for nanocrystalline Ni3Al and Ti-6Al-4V are in reasonable agreement with the parameters for microcrystalline material. The rate parameters suggest that nanocrystalline superplasticity shares common features with microcrystalline superplasticity. In contrast, the observed flow stresses and strong strain hardening indicate that nanocrystalline superplasticity is not a simple extension of microcrystalline behavior scaled to finer grain size.
The Role Played By Two Parallel Free Surfaces In The Deformation Mechanism Of Nano-crystalline Metals: A Molecular Dynamics Simulation
Authors: Derlet P. M. , Swygenhoven H. Van 
Published: April 2011

ABSTRACTFormer molecular dynamics computer simulations of polycrystalline Ni and Cu metals with mean grain sizes ranging between 3 and 12 nm demonstrated a change in deformation mechanism as a function of grain size: at the smallest grain sizes all deformation is accommodated in the grain boundaries. In this paper we report on the influence of the presence of two free surfaces on the deformation behaviour. The purpose of this simulation is to study which phenomena observed in in-situ tensile experiments performed in the electron microscope can be expected to be intrinsic properties of the deformation process and which phenomena are due to the presence of two free surfaces separated by a very small distance.
Molecular Dynamics Simulation of Nano-Sized Crystallization During Plastic Deformation in an Amorphous Metal
Authors: Tarumi R. , Ogura A. , Shimojo M. , Takashima K. , Higo Y. 
Published: April 2011

ABSTRACTAn NTP ensemble molecular dynamics simulation was carried out to investigate the mechanism of nano-sized crystallization during plastic deformation in an amorphous metal. The atomic system used in this study was Ni single component. The total number of Ni atoms was 1372. The Morse type inter-atomic potential was employed. An amorphous model was prepared by a quenching process from the liquid state. Pure shear stresses were applied to the amorphous model at a temperature of 50 K. At applied stresses of less than 2.4GPa, a linear relation between shear stress and shear strain was observed. However, at an applied shear stress of 2.8 GPa, the amorphous model started to deform significantly until shear strain reached to 0.78. During this deformation process, phase transformation from amorphous into crystalline structure (fcc) was observed. Furthermore, an orientation relationship between shear directions and crystalline phase was obtained, that is, two shear directions are parallel to a (111) of the fcc structure. This crystallographic orientation relationship agreed well with our experimental result of Ni-P amorphous alloy. Mechanisms of phase transformation from amorphous into crystalline structure were discussed.
Computer Simulation of Misfit Dislocation Mobility in Cu/Ni and Cu/Ag Interfaces
Authors: Kurtz Richard J , Hoagland Richard G. , Heinisch Howard L. 
Published: April 2011

ABSTRACTThe mobility of misfit dislocations in semicoherent Cu/Ni and Cu/Ag interfaces is determined by molecular dynamics and elastic band simulation methods. Cube-on-cube oriented Cu/Ni and Cu/Ag systems were studied with the interfaces parallel to (010). Core structures of misfit dislocations in semicoherent interfaces are found to be quite different in these systems. In Cu/Ni the misfits have very narrow cores in the plane of the interface. Consequently, the shear stress to move these dislocations is large, ∼1.1 GPa. The core width and hence the misfit mobility can be changed by placing the misfit away from the chemical interface. Placement of the misfit oneatom layer into the Cu increased the core width a factor of 1.6 and lowered the threshold shear stress to 0.4 GPa. The misfit dislocations in Cu/Ag interfaces, on the other hand, are wide and therefore are much more mobile. The threshold shear stress for misfit movement in Cu/Ag is very low, ∼0.03 GPa.
Biased Deposition of Nanocrystalline Be1−xCux Coatings
Authors: Jankowski A. 
Published: April 2011

ABSTRACTCoatings of Be1−xCux are prepared by magnetron sputter deposition onto spherical polymer mandrels. The application of an applied bias during deposition refines the columnar morphology of the coating and surface finish to the nanoscale. A mechanical testing technique is developed to load the thin-walled spherical capsules under uniaxial tension at constant strain to fracture. The bias-deposited material exhibits an increase in strength by a factor of three or more following a Hall-Petch type relationship with surface roughness.
Dislocation Models for Strengthening in Nanostructured Metallic Multilayers
Authors: Misra A. , Hirth J. P. , Kung H. , Hoagland R. G. , Embury J. D. 
Published: April 2011

ABSTRACTUltra-high strength metallic multilayers are ideal for investigating the effects of length scales in plastic deformation of metallic materials. Experiments on model systems show that the strengths of these materials increase with decreasing bilayer period following the Hall-Petch model. However, as the layer thickness is reduced to the nm-scale, the number of dislocations in the pile-up approaches one and the pile-up based Hall-Petch model ceases to apply. For nm-scale semi-coherent multilayers, we hypothesize that plastic flow occurs by the motion of single dislocation loops, initially in the softer layer, that deposit misfit type dislocation arrays at the interface and transfer load to the harder phase. The stress concentration eventually leads to slip in the harder phase, overcoming the resistance from the misfit arrays at the interface. A model is developed within the framework of classical dislocation theory to estimate the strengthening from this mechanism. The model predictions are compared with experimentally measured strengths.
Atomistic Simulations of Steps in Bimetallic Interfaces as Barriers to Interface Slip Transmission
Authors: Henager Charles H. , Heinisch Howard L. , Kurtz Richard J. , Hoagland Richard G. 
Published: April 2011

ABSTRACTAtomistic models of coherent interfaces in the CuNi system with and without (111)-steps were used to study slip transmission across interfaces in CuNi metallic bilayers. The lattice mismatch of the CuNi system results in large coherency stresses at the interface. The (111)-steps afford a larger barrier to slip than the flat, coherent interface. The coherent flat interface dislocation barrier is largely due to the large compressive stresses in the Cu layer that must be overcome by applied tensile stresses. Additional Koehler forces are present as the dislocation in the elastically softer Cu approaches the stiffer Ni layer. The step, however, possesses a small residual edge dislocation with a Burgers vector equal to the difference of bCu and bNi times the height of the (111)-step in (111)-layers. We find that these steps are potent slip barriers, which suggests that homogeneous slip is preferred in such systems.
Sol-gel synthesis and characterization of mesoporous organosilicas by using block copolymer templates
Authors: Cho Eun-Bum , Kwon Kwan-Wook , Char Kookheon 
Published: April 2011

ABSTRACTMesoporous organosilicas based on a bridged organosilicate have been synthesized using a triblock PEO-PLGA-PEO copolymer containing more hydrophobic poly(DL-lactic acid-coglycolic acid) block and the structural difference between mesoporous organosilicas prepared from PEO-PLGA-PEO and PEO-PPO-PEO block templates is discussed.
Millimeter-Wave Driven Polyol Processing of Nanocrystalline Metals
Authors: Kurihara L. K. , Lewis D. , Jung A. M. , Fliflet A. W. , Bruce R. W. 
Published: April 2011

ABSTRACTNanocrystalline metallic powders and coatings have been synthesized using a millimeter wave driven polyol process. We have been able to prepare powders of single elements, alloys, metastable alloys, composites and coatings. Examples of a few of the metals processed in this study include Fe, Co, Ni, Cu, Ru, Rh, Pt, Au, FePt, FexCo100−x, NiAg and Cu-Ni. The polyol experiment was set up in the millimeter wave processing chamber, the beam was directed into the center of the solution and it was brought to reflux, using the millimeter wave beam as a heat source. Varying the power input easily controlled the rate of reflux.
Atomic Scale Characterization of Supported and Assembled Nanoparticles
Authors: Pauwels B. , Yandouzi M. , Schryvers D. , Tendeloo G. Van , Verschoren G. , Lievens P. , Hou M. , Swygenhoven H. Van 
Published: April 2011

ABSTRACTDifferent structural configurations of nanoparticles have been investigated by advanced transmission electron microscopy (TEM) techniques. The cluster-surface interaction of Au clusters, produced in a laser vaporization source and deposited with low energy on MgO cubes, is investigated by high-resolution transmission electron microscopy (HRTEM). A dilation of the Au lattice that perfectly accommodates the misfit with the MgO lattice is measured and modeled with Molecular Dynamics (MD). To study the chemical ordering in bimetallic clusters, Au-Cu alloy clusters with different stoichiometries are produced and deposited in the same way as the Au clusters. Electron diffraction (ED) ring patterns obtained from these alloy clusters lying on amorphous carbon, are indexed as face-centered cubic, which is confirmed by HRTEM. This indicates that clusters of Au-Cu alloys are solid solutions, i.e. no ordering takes place in these clusters. Assembled nanoclusters of Ni3Al, produced by the inert gas condensation (IGC) technique and pressed under high pressure (2 GPa), are investigated by HRTEM. These studies indicate that nanocrystalline Ni3Al consists of small crystallites of random crystallographic orientations separated by grain boundaries, with the presence of several nanoscaled voids. From the selected area electron diffraction (SAED) ring pattern, an incomplete L12 ordering is concluded.
Nanoparticles and Polymers. Bricks and Mortar Self-Assembly of Nanostructures
Authors: Boal Andrew , Ilhan Faysal , Rotello Vincent , Russell Thomas 
Published: April 2011

AbstractPolymers provide a useful tool for the controlled assembly of colloidal nanoparticles. We have developed a bricks and mortar strategy in which colloidal gold particles functionalized with recognition elements serve as the bricks and polymers bearing complementary functionality serve as mortar to hold together the nanoparticles. In this methodology, the conformational flexibility of the polymer compensates for irregularities in the size and shape of the aggregate structure. We have used this method to create discrete micrometer-scale spherical assemblies based on 2 nm gold nanoparticles. Both the size and shape of these assemblies can be controlled, providing spherical assemblies ranging from 50 nm to 1500 nm, as well as network structures.