bluuebunny/crossref_metadata_2025_split huggingface dataset:
Extended Tomlinson Model for Rheological Response
Authors: Zaloj V. , Urbakh M. , Klafter J. 
Published: April 2011

AbstractWe investigate the response of a confined harmonic chain to an external harmonic driving force. A model is introduced which extends the one-dimensional Tomlinson model to include motion in the normal direction. This model with lateral-normal coupling mimics recent measurements on friction, using surface forces apparatus (SFA). The model predicts a critical driving amplitude below which the response is linear. For higher amplitudes the system exhibits a nonlinear behavior and an apparent shear thinning. We discuss the effects of shear induced dilatancy, which results from the lateral-normal coupling, on the energy dissipation, and therefore on the frictional properties. It is demonstrated that measurements of response in the normal direction provide additional information on the mechanisms of friction.
Anomalous Surface Diffusion of Water in Nanopores
Authors: Korb J.-P. , Bryant R. G. 
Published: April 2011

AbstractProton nuclear magnetic relaxation dispersion experiments show remarkable differences between water and aprotic liquids in contact with microporous glass surfaces containing trace paramagnetic impurities. Proton surface diffusion permits long range effectively 1-dimensional exploration along the pores for water. This gives a direct measurement of the translational diffusion coefficient at the pore surface.
Vacuum Ultraviolet Irradiation of Polymers
Authors: Fozza A. C. , Bergeron A. , Klemberg-Sapieha J. E. , Wertheimer M. R. 
Published: April 2011

AbstractThe interest in incoherent sources for wavelength selective photochemistry has increased lately, but little is still known about the behavior of polymers when exposed to far UV and vacuum UV (VUV) radiation, for example that emitted from low-pressure plasmas. In order to study VUV-UV effects on several polymers (polyethylene - PE, polystyrene - PS, hexatriacontane - HTC, polymethylmethacrylate - PMMA and polycarbonate - PC), we used the wellcharacterized emissions from hydrogen and hydrogen/argon mixture plasmas as light sources. Mass changes were measured in-situ using a quartz crystal microbalance (QCM); irradiated samples were analyzed ex-situ by XPS, spectroscopic ellipsometry, and AFM.
Preparation of SiC Thin Film Using Organosilicon by Remote Plasma CVD Method
Authors: Xu Ying-Yu , Muramatsu Takahiro , Aoki Toru , Nakanishi Yoichiro , Hatanaka Yoshinori 
Published: April 2011

AbstractAn organosilicon compound, hexamethyldisilane (HMDS) was incorporated for SiC thin film preparation by remote plasma enhanced CVD method. We investigated how plasma excited radicals react with source monomers using two kinds of gas mixtures. It was found that film component and formation mechanism depends on stronger on plasma gases. Using a mixture of nitrogen and hydrogen gases as plasma gas source, deposited films contained large amounts of nitrogen. When uing an argon and hydrogen mixture, deposited film was a SiC with large hydrogen contents. In this research, we found that hydrogen radicals are very active for decomposition of monomer source gas and this can be related to precursors for film deposition. When using a mixture of argon and hydrogen as plasma gas, the film deposition speed was influenced by substrate temperature. The estimated activation energy was larger than the case of using nitrogen and hydrogen gases. Different reaction mechanisms were observed for different plasma gas source
Precise and Smooth Removal from Polymer Surfaces by VUV Excimer Laser Ablation at 157 nm: PMMA.
Authors: Padeletti G. , Lapczyna M. , Stuke M. 
Published: April 2011

AbstractSmooth polymer surfaces can be generated by VUV laser ablation at 157 nm. This has been demonstrated for poly-methyl-metacrylate (PMMA) by atomic force microscopy (AFM) analysis of laser-exposed surfaces. At excimer laser fluences below 30 mJ/cm2 the mean roughness (Ra) remains below 10 nm for both single and 10 shot exposures.A detailed characterization of the surface nano-morphology distribution carried out by the “power spectral density” (PSD) analysis, shows that the surface is smoothened by the VUV laser for lateral scales smaller than 20 μm.
Conjugation of DNA to Plasma-Treated Polymer Surfaces and Their Application to Multiplex DNA Sequencing
Authors: Lambert Stephen M. , Chen Jer-Kang , Chiesa Claudia , Fry George A. , Furniss Vergine C. , Mehrpouyan Majid A. , O'Neill Roger A. 
Published: April 2011

AbstractPlasma treatment and deposition techniques have been used to facilitate the covalent attachment of DNA to polymer surfaces. The variety of surface functional groups that can be created by plasma techniques enables different chemical conjugation routes to be explored. For example, a phosphodiester linkage can be used for surfaces with hydroxyl groups. Likewise, a carboxyamide linkage can be used for surfaces with carboxyl or amine groups. The primary application of the engineered materials has been the hybridization-based separation of multiplexed DNA sequencing products. Traditionally, sequencing reactions are performed individually on single templates. Multiplex sequencing offers reagent and time savings by permitting multiple sequencing reactions on single or multiple templates. The method developed uses recoverable DNA sequencing primers with additional “capture sequences” attached to the 5' end. The capture sequences are designed to be complementary to “binding sequences” covalently attached to the plasma-treated polymer supports. When a solution of the extended recoverable primers is exposed to a polymer support, primers with complementary capture sequences hybridize to the immobilized binding sequences. Contacting a multiplexed sample with a series of solid supports (each having a different binding sequence) selectively removes each set of sequencing products from the mixture. Washing each solid support, followed by releasing the hybridized DNA, results in isolated and purified sequencing products that are amenable to analysis by gel or capillary electrophoresis.
Silicon Quantum Dots in Silica
Authors: Henderson D. O. , Wu M. H. , Mu R. , Ueda A. , White C. W. , Meldrum A. 
Published: April 2011

AbstractSilicon ions were implanted into fused silica substrates at doses of 1×1021, 2×1021, 5×1021, and 1×1022 ions/cm3. The implanted substrates were annealed at 1100°C for one hour in a reducing atmosphere (95% Ar+5% H2). Optical absorption spectra recorded after the annealing treatment showed absorption onsets at 3.86, 3.73, 2.86 and 2.52 eV for substrates implanted with 1×1021, 2×1021, 5×1021, and 1×1022 ions/cm3, respectively. Static photoluminescence (PL) measurements indicated red emission between 1.72 and 1.61 nm with a slightly increasing red shift with ion dose. Time resolved PL at room temperature revealed slow (∼50 μs) and fast (×20 μs) lifetimes which increased with decreasing temperature. TEM studies showed that the particle size increased with increasing ion dose. Typical particle sizes ranged between 2 and 5 nm indicating quantum confinement of the exciton, which can account for the blue shift in the absorption edge with decreasing ion dose. However, the maxima in the PL spectra for all ion doses are relatively independent of the ion dose and are strongly shifted from the absorption spectra. This suggests that radiative recombination occurs from a common luminescent center, possibly a surface or interfacial state in thexs SiOx, layer surrounding the nanocrystal.
Development of Metallic Closed Cellular Materials Containing Polymers
Authors: Kishimoto S. , Shinya N. 
Published: April 2011

AbstractA new material for structures in space, which have a high energy absorbability has been developed using a powder particle assembling technique. Powder particles of polystyrene coated with nickel-phosphorus alloy layers using electroless plating were sintered at high temperature. A metallic closed cellular material containing polystyrene was then constructed.The mechanical and ultrasonic properties of this material were measured at both room and high temperatures. The compressive tests of this material show a low Young's modulus and high energy absorption. Ultrasonic measurement shows that the attenuation coefficient of this cellular material is very large and would change due to increasing temperature. These results indicate that this metallic closed cellular material can be used for the space applications.
The Dependence of Tensile Ductility on Investment Casting Parameters in Gamma Titanium Aluminides
Authors: Raban R. , L. L. , M. T. 
Published: April 2011

ABSTRACTPlates of three gamma titanium aluminide alloys have been investment cast with a wide variety of casting conditions designed to influence cooling rates. These alloys include Ti-48Al-2Cr-2Nb, Ti- 47Al-2Cr-2Nb+0.5at%B and Ti-45Al-2Cr-2Nb+0.9at%B. Cooling rates have been estimated with the use of thermal data from casting experiments, along with the UES ProCAST simulation package. Variations in cooling rate significantly influenced the microstructure and tensile properties of all three alloys.
Effect of Thermal Residual Stress on the Mechanical Properties of NiAl-Based Composites
Authors: Choo Hahn , Bourke Mark , Nash Philip 
Published: April 2011

ABSTRACTNiAl-based hybrid composites containing 5, 15 and 30 volume percent of A12O3 fibers in addition to AIN dispersion particles were fabricated via a powder metallurgy route. The strengthening mechanisms associated with the short A12O3 fiber in NiAl-(A1N)dispersion,-(A12O3)fiber, composite were studied with an emphasis on the effect of thermal residual stress on the compressive strength at room temperature and 1300K. At 300K, the yield strength of the composites was predicted using a linear superposition of the monolithic yield strength, direct fiber strengthening and tensile matrix residual stresses. The prediction shows good agreement with the measured data. The majority of the room temperature strengthening is attributable to the residual stress. At 1300K, the strengthening was achieved only by the load sharing of the fibers and there is no direct influence from the process-induced thermal residual stresses since they were completely relaxed at this temperature.
Creep Mechanisms in Niobium-Silicide Based In-Situ Composites
Authors: Bewlay B. P. , Whiting P. W. , Davis A. W. , Briant C. L. 
Published: April 2011

ABSTRACTThis paper will discuss the relationship between microstructure and creep behavior in hightemperature niobium-silicide based in-situ composites. The creep behavior of composites generated from binary Nb-Si alloys, and higher order alloys containing Mo, Hf and Ti additions, will be described. In-situ composites were tested in compression at temperatures up to 1200°C and stress levels in the range 70 to 280MPa. It was found that the Hf concentration can be increased to 7.5 with little increase in creep rate, over that for the binary Nb3Si-Nb composite, but at higher concentrations the creep rate is increased at stress levels higher than 21OMPa. At stresses less than 21OMPa the Ti concentration can be increased to 21 without a detrimental effect on creep performance, but at higher concentrations there is a substantial increase in the creep rate.
Microstructures and Mechanical Properties of Two-Phase Alloys Based on NbCr2
Authors: Chen Katherine C. , Kotula Paul G. , Cady Carl M. , Mauro Michael E. , Thoma Dan J. 
Published: April 2011

ABSTRACTA two-phase, NbCrTi alloy (bce + C15 Laves phase) has been developed using several alloy design methodologies. In efforts to understand processing-microstructure-property relationships, different processing routes were employed. The resulting microstructures and mechanical properties are discussed and compared. Plasma arc melted (PAM) samples served to establish baseline, as-cast properties. In addition, a novel processing technique, involving decomposition of a supersaturated and metastable precursor phase during hot isostatic pressing (HIP), was used to produce a refined, equilibrium two-phase microstructure. Quasi-static compression tests as a function of temperature were performed on both alloy types. Different deformation mechanisms were encountered based upon temperature and microstructure.
Microstructural Evolution during Superplastic Deformation in Large-grained Iron Aluminides
Authors: Lin Dongliang , Liu Yi 
Published: April 2011

ABSTRACTSuperplastic behavior has been found in Fe3A1 and FeAl alloys with grain sizes of 100–600μm. The large-grained Fe3Al and FeAl alloys exhibit all deformation characteristics of conventional fine size superplastic alloys. However, superplastic behavior was found in large-grained iron aluminides without the usual pre-requisites for superplasticity of a fine grain size and grain boundary sliding. The metallographic examinations have shown that the average grain size of large-grained iron aluminides decreased during superplastic deformation. Transmission electron microscopy (TEM) observations have shown that there were a great number of subgrain boundaries which formed a network and among which the proportion of low and high angle boundaries increased with increased strain. The observed superplastic phenomenon is explained by continuous recovery and recrystallization. During superplastic deformation, an unstable subgrain network forms and these subboundaries absorb gliding dislocations and transform into low and high angle grain boundaries. A dislocation glide and climb process accommodated by subboundary sliding, migration and rotation, allows the superplastic flow to proceed
Plasticity Of Quasicrystals
Authors: Feuerbacher M. , Klein H. , Schall P. , Bartsch M. , Messerschmidt U. , Urban K. 
Published: April 2011

AbstractResults of plastic deformation experiments on two quasicrystalline phases of different structure, icosahedral Al-Pd-Mn and decagonal Al-Ni-Co, and of an approximant phase, ξ'-Al-Pd-Mn, are described. They are interpreted on the basis of a model for the deformation process, the clusterfriction model, which is discussed in a number of modifications.
Modulated Photocurrent Measurements On Icosahedral Quasicrystals Of AI-Pd-Re System
Authors: Sakairi Yoshiko , Takeda Masatoshi , Tamura Ryuji , Edagawa Keiichi , Kimura Kaoru 
Published: April 2011

AbstractModulated photocurrent method originally developed for analyzing the electronic states of semiconductor has been applied to an Al-Pd-Re quasicrystal having high electrical resistivity. The measured DC component of the photocurrent has indicated that the mobility of the photocarrier is approximately the same as that of the dark carrier at the Fermi level. The data of the amplitude and phase shift of the AC component can be explained well by a simple model in which only the two processes, carrier generation and recombination, are involved. The recombination time obtained by fitting is by about six orders larger than those reported for semiconductors. The long recombination time as well as the energy independent mobility of carriers are discussed in view of a spiky structure in electron density of states expected for the quasicrystals.
Polymer Ultrathin Films Via Alternate Self-Assembly Adsorption of Polyelectrolyte and Azo-Dye Molecules: Photo-Induced Alignment and Lc Display Properties
Authors: Advincula R.C. , Baba A. , Kaneko F. 
Published: April 2011

ABSTRACTIn this report, we describe the fabrication and photo-induced alignment of ultrathin films of small molecular azobenzene dyes and polyelectrolytes using the alternate polyelectrolyte deposition (APD) technique. The molecular self-assembly process were investigated by QCM, ellipsometry, UV-vis spectroscopy, X-ray reflectometry, and other surface sensitive spectroscopic and microscopic methods to correlate with film formation parameters. The importance of layer ordering and dye aggregation phenomena is emphasized. We then utilized polarized UV-light to induce photo-alignment of these ultrathin films and observed high anisotropies dependent on the dye, layer preparation and thickness. Fabrication of hybrid LC cells using a nematic LC reveal that in-plane homogeneous alignment is influenced by the anisotropy of the dye aggregates.
Electrical Properties of Liquid-Crystal Materials for Display Applications
Authors: Naemura S. 
Published: April 2011

ABSTRACTBoth dielectric permittivity and AC conductivity are important properties of LC materials for use in displays. By taking typical LC substances as examples, quantitative data are presented on these properties. From microscopic point of view, permanent dipole of LC molecules and ions contained in LC materials play important roles in these electric properties. Quantitative discussions are also presented on these microscopic characteristics. Theoretical understandings of these properties are reviewed, providing good explanations of the relation between these microscopic and macroscopic properties.
Effect of Side Chain Substitution on the Field-Dependent Birefringence in a Series Of Chiral Smectic a Liquid Crystals
Authors: Lindle J. R. , Bartoli F. J. , Flom S. R. , Selinger J. V. , Shashidhar R. , Ratna B. R. 
Published: April 2011

ABSTRACTThe field dependent birefringence and the tilt angle are measured for a series of four electroclinic liquid crystals. The zero-field birefringence decreased significantly and monotonically with the length of the siloxane side chain. For all four samples, the birefringence and the electroclinic tilt angle increased substantially with the application of a field. At 10 V/µm, the electroclinic tilt angle in DSiKN65 and TSiKN105 exceeded 22.5 degrees and the phase retardation due to the change in the birefringence exceeded a quarter wave. In all four liquid crystals, the electroclinic tilt angle and the field-dependent birefringence were shown to be strongly correlated, suggesting a common origin. Moreover, this correlation persists even at high fields where both processes undergo saturation. A simple orientational model, based on a distribution in the molecular optical axis, was developed to explain the large change in birefringence in the substituted compounds as well as the dependence of δn on electric field.
An Analysis of the Photo-Polymerization Induced Phase Separation Process in Liquid Crystal/Polymer Composite Films
Authors: Fujisawa Toru , Hayasi Masanao , Nakada Hidetoshi , Matumoto Sigeru , Tani Yuitiro , Yada Makoto , Aizawa Masao 
Published: April 2011

ABSTRACTWe have analyzed the micro-phase separation during photo-polymerization in the liquid crystal/polymer composite films for a variety of light-control applications. The photo-polymerization induced phase separation process is remarkably affected by the reactivity in diacrylates and the fraction volume in liquid crystals. It is presumed that the nematic transition in a liquid crystal-rich phase and the reactivity play an important role to determine the morphology.
Deposition Kinetics and Microstructural Evolution in Sputtered TA Films: a Real-Time/In-Situ Study
Authors: Whitacre J. F. , Yalisove S. M. , Bilello J. C. 
Published: April 2011

ABSTRACTTa films were grown using sputter gas (Ar) pressures ranging from 1.7 to 20 mTorr. This produced growth environments where incoming adatom kinetic energies ranged from over 100 eV to less than 1 eV. Film development was monitored in-situ using a x-ray diffraction set-up that allowed complete diffraction patterns to be rapidly collected without interrupting the growth process. Traditional x-ray diffraction methods, transmission electron microscopy (TEM), and transmission electron diffraction (TED) were used to examine film microstructure after growth. It was found that lower Ar pressures, which allow higher adatom kinetic energies, produced films that displayed significant grain growth, texturing, and a smooth surface morphology. Those films grown at increasingly higher Ar pressures displayed smaller grain sizes, less texturing, and increasingly porous microstructures. To further explore this effect, the Ar pressure was varied during deposition for several films. The in-situ probe allowed the effects of each pressure increment to be analyzed and compared with previous x-ray and microscopy results. It was found that the microstructure of any particular film layer depended more on the deposition conditions during its formation rather than the structure or crystallography of previous layers.
Stress Development in Mo/Si and Ru/Si Multilayers
Authors: Freitag J. M. , Clemens B. M. 
Published: April 2011

ABSTRACTThe stress evolution of Mo/Si and Ru/Si multilayers sputtered under the same processing conditions has been investigated. A series of Mo/Si multilayers was also prepared with varying sputtering pressures. The stress evolution of each multilayer displays a well-defined modulation concurrent with the deposition of Mo (Ru) and Si. Large stress develops during the early stages of deposition of each successive layer with Mo (Ru) exhibiting apparent tension and Si exhibiting apparent compression. In the Mo/Si multilayers, these initial transients cause curvature changes of, ∼ 2.5 to 4.5 N/m depending on the sputtering pressure. For Ru/Si the transients exceed 8 N/m and extend across a larger fraction of the total layer thickness. Intermixing and reaction at the interfaces of Mo/Si and Ru/Si multilayers lead to a volume contraction and consequently a contraction of the bilayer period. Moreover, volume contraction due to intermixing is a stress generating mechanism that may explain the initial transients in the stress evolution. The volume of the interdiffused regions of Mo/Si and Ru/Si multilayers was estimated by measuring the contraction of the bilayer period using x-ray diffraction. The results show a strong correlation with the size of the initial stress transients suggesting that intermixing may cause them.
Highly Oriented Co Soft Magnetic Films on Si Substrates
Authors: Gong Heng , Yang Wei , Rao Maithri , Laughlin David E. , Lambeth David N. 
Published: April 2011

ABSTRACTThin Co and Co based alloy films with the face centered cubic (FCC) structure have been epitaxially grown on single crystal Si wafers by sputter deposition. Epitaxial orientation relationships have been determined by x-ray diffraction, x-ray pole figure scans and TEM. Magnetic properties have been characterized using vibrating sampling magnetometer (VSM), torque magnetometer and BH loop tracer. Soft magnetic properties have been observed for the pure Co films.
Permanent Magnetism In Exchange-Coupled Nanocomposites
Authors: Skomski R. , Liu J. P. , Sellmyer D. J. 
Published: April 2011

ABSTRACTThe magnetic properties of permanent magnetic nanocomposites are investigated both experimentally and by model calculations. Rare-earth transition-metal films and nanocomposite thin films containing a L10hard phase (PtFe) have been prepared by plasma sputtering and heat treatment. By choosing suitable heat-treatment processes a nearly ideal nanostructure and high energy products of up to about 50 MGOe have been achieved for the Fe-Pt system. The behavior of the nanocomposites is discussed in terms of a model applicable to nearly ideal magnets, where there are no pronounced shoulders in the hysteresis loops. Analytic expressions for M(H) are obtained for a number of cases, and it is discussed how the loops depend on the micromagnetic parameters of the involved phases. A novel aspect of magnetic nanostructures is that very small magnetic grains exhibit very large energy products, even if they are intrinsically soft-magnetic.