bluuebunny/crossref_metadata_2025_split huggingface dataset:
Low Temperature Growth of Silicon Dioxide Thin Films by UV Photo-oxidation
Authors: Fukano Atsuyuki , Oyanagi Hiroyuki 
Published: April 2011

AbstractThe low-temperature growth of thin SiO2 layers for gate insulators in very large-scale integrated (VLSI) circuits is becoming an urgent topic of silicon technology. In contrast, to conventional thermal oxidization processes (T>900°C), ultraviolet (UV) photo-oxidation of silicon technology is a promising approach for low-temperature growth of silicon dioxide thin films. We have grown silicon dioxide thin films at low temperature (T<500 °C) using an excimer lamp with various wavelengths and evaluated the quality of thin SiO2 layers as well as the SiO2–Si interface. We found that the SiO2 layers (t<5 nm) grown by UV photo-oxidation show significant differences in physical properties, such as density profile, from those of thermal oxidization, i.e., the higher average density 2.23 g/cm3 and more constant distribution, making the SiO2–Si interface region, so-called “transition layer” less eminent. Superior characteristics of ultra-thin SiO2 layer grown by UV photo-oxidation are demonstrated.
Analysis of Primary Crystallization in Amorphous Aluminum Alloys
Authors: Perepezko John H. , Tong William S. , Hamann Joe , Hebert Rainer J. , Rösner Harald R. , Wilde Gerhard 
Published: April 2011

ABSTRACTThe annealing response of amorphous Al based alloy samples were investigated to assess the role of the as-quenched state on primary crystallization of Al nanocrystals(nc). Continuous heating differential scanning calorimetry (DSC) traces of amorphous Al87Ni10Ce3powders were compared to those from melt spun ribbon (MSR) to examine the effect of sample subdivision on primary crystallization. While the powders exhibited the same onset temperature as MSR, thermal cycling experiments show fine powder sizes reacting at the onset temperature and coarse powder sizes with the lowest melt quench rate transforming at the highest primary reaction temperature. In Al92Sm8MSR, a kinetics analysis of Al nc distributions indicates a notable effect of the as-quenched state on primary crystallization during isothermal annealing. With Al88Y7Fe5MSR intense deformation can induce thedevelopment of an Al nc distribution without thermal annealing. In each case examined, the results support the inclusion of quenched in clusters in the analysis of primary crystallization reactions.
Structure, Annealing Characteristics and Mechanical Properties of Mg60Cu30-yY10Siy Bulk Amorphous Alloys
Authors: Wolff U. , Yang B. , Pryds N. , Wert J.A. 
Published: April 2011

ABSTRACTThe effect of different Si contents on the glass forming ability (GFA) and the amorphous-to-crystalline transformation has been investigated for the Mg-Cu-Y-Si system. Four Mg60Cu30-yY10Siy (y = 1–5 at.%) alloys were prepared using a relatively simple technique of rapid cooling of the melt in a copper mould. Crystallization was induced by heat treatment of the alloys and the samples were then characterized concerning their microstructure and thermal stability by X-ray diffraction (XRD), optical (OM) and scanning electron microscopy (SEM) and differential scanning calorimetry (DSC) at a constant heating rate. Partial substitution of Cu by Si leads to a transition of the as-cast structure at a constant cooling rate from amorphous to crystalline with increasing Si content. Furthermore, the glass transition temperature (Tg) of the Mg-Cu-Y-Si alloy is lower compared to the Mg-Cu-Y system. The mechanical properties of the bulk Mg-Cu-Y-Si alloys have been investigated and found to vary with the Si content.
Free Volume Evolution in Bulk Metallic Glass during High Temperature Creep
Authors: Sundar Daniel B. S. , Heilmaier Martin , Bartusch Birgit , Kanzow Jörn , Günther-Schade Katja , Rätzke Klaus , Eckert Jürgen , Faupel Franz 
Published: April 2011

ABSTRACTMetallic glasses lack long-range translational symmetry and have excess volume trapped within their amorphous structure, which has a direct bearing on their physical properties including deformation characteristics. Moreover, the trapped excess free volume is directly correlated to the defect concentration facilitating the possibility to model the temperature and time dependence of the free volume changes during creep as a trade off between defect generation and annihilation. Using differential scanning calorimetry (DSC) analysis the residual free volume of a metallic glass can be characterised based on the glass transition peak height (Δcp). In the present work constant strain rate tests were carried out at the ‘onset’ (Tgon = 685 K) and ‘point of inflection’ (Tgp = 705 K) of the calorimetric glass transition to study the time dependent flow behaviour in Zr55Cu30Al10Ni5 bulk metallic glass. Modelling based on DSC analysis and positron lifetime spectroscopy on samples creep deformed to different plastic strain values corroborate the stress decrease after the peak stress (‘stress overshoot’) occurring in bulk metallic glasses with increasing plastic strain to be associated with a small increase in free volume.
Elastic Properties and Microstructure of Metallic Glasses Pd39Ni10Cu30P21 Studied by Microacoustical Technique
Authors: Levin Vadim M. , Petronyuk Julia S. , Wang Limin , Hu Jiankai , Zhang Qianlin 
Published: April 2011

ABSTRACTThe elastic properties of Pd39Ni10Cu10P21 bulk metallic glass (BMG) have been analysed using measurements of sound velocities. Different states of the Pd39Ni10Cu10P21 system (glassy state, supercooled liquid (SCL) and polycrystalline state) were obtained by annealing the samples near the glass transition and crystallization onset temperature. The microacoustical technique has been applied to measure local values of longitudinal and transverse elastic wave velocities and their distribution over a specimen. Finally sound velocities VL and VT, density ρ, bulk K and shear G elastic moduli were measured for different states. The values of ρ, VL and K decrease as temperature increases and the transition from glass to SCL takes place. In the crystalline state ultrasonic measurements were performed by the standard pulse ultrasonic technique with low-frequency flat transducer because of high ultrasonic attenuation in this state. Acoustic images (C-scans) demonstrate coarse-grained microstructure in this state. This is assumed to be characteristic of the microstructure obtained by crystallizing BMG.
Mechanical Properties of La-based Bulk Amorphous Alloys and Composites
Authors: Lee M.L. , Li Y. , Carter W.C. 
Published: April 2011

ABSTRACTThe influence of different microstructures of La-based fully amorphous samples and its composites on the impact fracture energy were investigated and discussed. Results showed improvement in fracture energy of glassy metals with intermetallic phases, but deteriorated in the presence of dendrite phases and high volume % of crystalline phases.
On The Glass Forming Ability Criteria Of Bulk Metallic Glasses
Authors: Lu Z. P. , Liu C. T. 
Published: April 2011

ABSTRACTA new criterion γ, defined as Tx/(Tg+Tl) (where Tx is the onset crystallization temperature, Tg the glass transition temperature and Tl the liquidus temperature), has been proposed for glass formation in bulk metallic glasses (BMGs). The interrelationship between this new parameter and glass-forming ability (GFA) was elaborated and discussed in comparison with other established criteria. It was found that the new criterion γ had a much better correlation with GFA than other established parameters. An approximation of the critical cooling rate for glass formation was also formulated and evaluated in the light of this new parameter.
Measured and Calculated Electronic Structure of Ni0.40Pd0.400P0.20 and Cu0.400Pd0.400P0.20
Authors: Nicholson D. M. C. , Alamgir Faisal M. , Jain Himanshu , Williams David B. , Schwarz Ricardo B. 
Published: April 2011

ABSTRACTX-ray Photoemission spectra of Ni0.40Pd0.40P0.20 and Cu0.40Pd0.40P0.20 in the amorphous states are compared to each other and to first principles calculations of the electronic density of states. The electronic structure is calculated for a previously validated amorphous model of Ni0.40Pd0.40P0.20 and for the same amorphous structure but with Cu replacing Ni. The measured and calculated electronic structures of Ni0.40Pd0.40P0.20 agree and exhibit very little charge transfer to Pd. However, the measured and calculated electronic structures of Cu0.40Pd0.40P0.20 differ considerably. In Cu0.40Pd0.40P0.20 there is a large electron transfer to Pd. The local densities of states on Pd atoms in different CuPdP local environments that arise in the amorphous model shed light on this dramatic charge redistribution.
Effect of Compositional Short Range Order on Glass Formation in Binary Metallic System
Authors: Chen Hao , Khantha Mahadevan , Egami Takeshi 
Published: April 2011

ABSTRACTMolecular Dynamics simulation was carried out to study the glass transition and crystallization in the metal-metalloid binary system with pair-wise potentials. The results show that a repulsive potential between metalloid (small) atoms increases the glass forming ability. The observation is consistent with the recent theory of bulk metallic glass formation through local glass transition and nano-glass formation. The theory predicted that the compositional short-range order (CSRO) prevents the small atom pairing so as to increase the glass forming ability (GFA). The present results demonstrate the important role of CSRO in bulk metallic glass formation.
Theoretical scheme for the study of thermodynamic and transport properties of simple fluids at the liquid-glass transition line.
Authors: Robles M. , Uruchurtu L. I. , López de Haro M. 
Published: April 2011

ABSTRACTIn this work we present a theoretical scheme to study the thermodynamic and transport properties of simple fluids at the liquid-glass transition line. This scheme makes use of a recent reformulation of the classical perturbation theory of liquids [M. Robles and M. López de Haro, Phys. Chem. Chem. Phys. 3, 5528 (2001)]. Using the hard-sphere fluid as a reference system our approach requires the choice of an equation of state for the hard-sphere system and a criterion to determine an effective (density and temperature dependent) diameter. Selecting the diameter in the same way as in the Mansoori-Canfield /Rasaiah-Stell variational perturbation theory and two different equations of state for the hard-sphere system, the liquid-glass transition line in the density vs. temperature plane for a Lennard-Jones fluid derived with our approach is shown to be in very good agreement with recent numerical simulations. The transition line in the pressure vs density plane and the value of the transport coefficients in the vicinity of the liquid-glass transition for the Lennard-Jones fluid are also examined.
Neutron Scattering Experiments on the Short-Range Order in Undercooled Metallic Melts
Authors: Holland-Moritz Dirk , Schenk Thomas , Simonet Virginie , Bellissent Robert , Convert Pierre , Hansen Thomas , Herlach Dieter M. 
Published: April 2011

ABSTRACTThis work presents investigations on the short-range order of stable and deeply undercooled melts of the pure elements Fe, Zr and Ni. The liquids were undercooled by use of the electromagnetic levitation technique, which was combined with elastic neutron scattering in order to determine the structure factors of the liquids as a function of the temperature. The diffraction experiments provide evidence that a short-range order based on aggregates of icosahedral symmetry prevails in the melt. This short-range order is observed even at temperatures above the melting temperature and gets more pronounced if the liquids are undercooled.
Nonlinear Density Fluctuations and Spatial Heterogeneities near the Colloidal Glass Transition
Authors: Tokuyama Michio , Terada Yayoi , Oppenheima I. 
Published: April 2011

ABSTRACTHow the spatial heterogeneities play an important role in the dynamics of density fluctuations near the colloidal glass transition is discussed from a new viewpoint. A nonlinear stochastic diffusion equation for the density fluctuations recently proposed by one of the present authors (MT) is numerically solved in two different initial states, an equilibrium state and a nonequilibrium state. Depending on initial states, the dynamics of the spatial heterogeneities are shown to be quite different from each other. Such differences are thus shown to influence the slow relaxations of density fluctuations, leading to different types of two-step relaxations.
Accounting For Corrosion Of Hlw Glasses By Humid Air In TSPA
Authors: Ebert W. L. , Cunnane J. C. , Dietz N. L. 
Published: April 2011

ABSTRACTThis paper describes how the results of vapor hydration tests (VHTs) are used to model the corrosion of waste glasses exposed to humid air in the glass degradation model for total system performance assessment (TSPA) calculations for the proposed Yucca Mountain disposal system. Corrosion rates measured in VHTs conducted at 125, 150, 175, and 200°C are compared with the rate equation for aqueous dissolution to determine parameter values that are applicable to glass degradation in humid air. These will be used to determine the minimum for the range and distribution of parameter values in calculations for the Yucca Mountain disposal system license application (TSPA-LA). The rate equation for glass dissolution is rate = kE • 10 η • pH • exp(–Ea/RT). Uncertainties in the calculated rate due to the range of waste glass compositions and water exposure conditions are taken into account by using a range of values for the rate coefficient kE. The parameter values for the pH dependence (η) and temperature dependence (Ea) and the upper limit for kE are being determined with other tests. Using the values of η and Ea from the site recommendation model, the VHT results described in this paper provide a value of log kE = 5.1 as the minimum value for the rate expression. This value will change slightly if different pH-and temperature-dependencies are used for the TSPA-LA model.
Formation factor measurements in granite in the laboratory – Comparison of through diffusion and electromigration techniques.
Authors: Löfgren Martin , Neretnieks Ivars 
Published: April 2011

ABSTRACTTraditionally the effective diffusivity in and the formation factor of intrusive igneous rock have been measured in the laboratory by through diffusion (TD) experiments, which are very time consuming in larger samples with low porosity. In previous work alternating current (AC) has been used to measure the formation factor directly in large samples. In this paper direct current is used to actually transport the tracers through the rock sample in so called through electromigration (TEM) experiments. In these experiments electoosmosis has to be corrected for. The experimental time is reduced substantially when adding an electromigratory flux to the diffusive flux. TD, TEM and AC experiments were performed on a 15 mm thick unweathered granite sample from Laxemar, Sweden. The tracers uranin and iodide were used. The formation factor measured with the three methods varied between 1.2·10-4 - 2.87·10-4.
Fitting Element Profiles for Predicting Glass Dissolution Rates in Synthetic Interstitial Clay Water
Authors: Aertsens Marc , Lemmens Karel , Van Iseghem Pierre 
Published: April 2011

ABSTRACTAn analytical model is developed to derive diffusion coefficients from the element profiles of the most mobile glass elements. Congruent dissolution is considered as a transient phenomenon and neglected. In the model, altered glass consists of two sublayers: a gel layer at the solution side, and a diffusion layer at the pristine glass side. In both layers, mobile glass elements diffuse towards the solution, while hydrogen/water diffuses towards the pristine glass.Fitting the element profiles of boron, sodium and lithium leads to diffusion coefficients in the diffusion layer, which at 90°C are typically of the order of 10-22m2/s to 10-21m2/s. At 40°C, these diffusion coefficients are typically a factor ten lower. The diffusion coefficients in the gel are by less than a factor two hundred larger than those in the diffusion layer.The diffusion coefficients derived from the profiles in this way are used to predict the dissolution behavior. These predictions, for which a constant value (representing congruent dissolution) is added to the predicted diffusive release, agree reasonably well with the measured dissolution data. Those results support the idea that diffusion determines the long term release of glass matrix elements in synthetic interstitial clay water. Flux conservation at the interface between the gel and the diffusion layer is not consistent with a constant (as a function of time) width of the diffusion layer. Some experimental evidence supports that this width increases with time.
SON68 Glass Dissolution Kinetics at High Reaction Progress: Experimental Evidence of the Residual Rate
Authors: Gin S. , Frugier P. 
Published: April 2011

ABSTRACTSON68 borosilicate glass dissolution involves several parallel mechanisms: interdiffusion, hydrolysis of the silicate network, recondensation of dissolved species leading to the formation of an amorphous gel layer and precipitation of secondary crystalline phases. In a highly confined medium corresponding to geological disposal conditions, the gel formed during SON68 glass alteration quickly becomes protective and the hydrolysis rate drops by about 4 orders of magnitude compared with the initial dissolution rate. This study focuses on the state of reaction progress corresponding to apparent saturation of the solution. At 90°C in static mode, new experimental data show that the decreasing rate due to the protective gel formation is followed by a quasi-constant residual rate. Several hypotheses are discussed. We first demonstrate that silica dissociation related to a slowly rising pH is not a valid explanation. This hypothesis proposed 15 years ago was consistent with a rate controlled by affinity (equilibrium between the glass and solution). The hypothetical precipitation of secondary crystalline phases that consume elements from the protective gel layer is then considered in the light of data obtained with a simplified 8-oxide glass, but this mechanism is not sufficient to account for residual rate of the SON68 glass. Other hypotheses based on the gel evolution (dissolution, evolution of the porous texture) are also proposed. The proposed mechanisms imply the persistence of a protective gel with a constant thickness. Finally, this paper shows that the residual rate could be a decisive phenomenon affecting the long term behavior of glass in disposal conditions.
Layered Manufacturing: Challenges and Opportunities
Authors: Cooper Khershed P. 
Published: April 2011

ABSTRACTLayered Manufacturing (LM) refers to computer-aided manufacturing processes in which parts are made in sequential layers relatively quickly. Parts that are produced by LM can be formed from a wide range of materials such as photosensitive polymers, metals and ceramics in sizes from a centimeter to a few meters with sub-millimeter feature resolutions. LM has found use in diverse areas including biomedical engineering, pharmaceuticals, aerospace, defense, electronics and design engineering. The promise of LM is the capability to make customized complex-shaped functional parts without specialized tooling and without assembly. LM is still a few years away from fully realizing its promise but its potential for manufacturing remains high. A few of the fundamental challenges in materials processing confronting the community are improving the quality of the surface finish, eliminating residual stress, controlling local composition and microstructure, achieving fine feature size and dimensional tolerance and accelerating processing speed. Until these challenges are met, the applicability of LM and its commercialization will be restricted. Sustained scientific activity in LM has advanced over the past decade into many different areas of manufacturing and has enabled exploration of novel processes and development of hybrid processes. The research community of today has the opportunity to shape the future direction of science research to realize the full potential of LM.
Alumina-Doped Silica Gradient-Index (GRIN) Lenses by Slurry-Based Three-Dimensional Printing (S-3DP™)
Authors: Wang Hong-Ren , Cima Michael J. , Sachs Emanuel M. 
Published: April 2011

ABSTRACTThe traditional Slurry-based Three-dimensional Printing (S-3DP™) process has been used to fabricate complex structure materials by printing organic binders in selected positions on each printing layer. This process is modified to fabricate functional graded materials, such as gradient index (GRIN) lenses, by depositing different concentrations of dopant at different positions. The modified S-3DP™ process offers advantages over conventional GRIN lens processes, including reduced processing time, improved compositional flexibility, and increased index profile dimensionality. Two different approximately parabolic dopant concentration profiles, which have maximum alumina concentrations of 1.63 mol% and 2.50 mol%, are printed into silica powder beds using S-3DP™. The samples with maximum alumina concentration of 1.63 mol% have been sintered into optical transparency at 1650 0C for 30 minutes in a vacuum furnace (5×10-6 torr) while an additional dehydration process before sintering was required for the samples with maximum alumina concentration of 2.50 mol%. The magnifying effects of GRIN lenses with profiles of 1.63 mol% and 2.50 mol% alumina were observed, yielding effective focal lengths of 10 cm and 6.1 cm, respectively. Light diffraction, which results from the locally inhomogeneous dopant distribution and reduces the optical quality of GRIN lenses, was also observed.
Tunneling Current-Distance Characteristic of Scanning Vibrating Probe / 1-Alkanethiol Self-Assembled Monolayer (SAM) / Au (111) Structure
Authors: Yasutake Yuhsuke , Azuma Yasuo , Nagano Kouhei , Majima Yutaka 
Published: April 2011

ABSTRACTWe report measurements of the tunneling current – distance (I-d) dependence above alkanethiol self-assembled monolayers (SAMs) on Au (111) substrates with high probe voltage. From the semilogarithmic I-d plots of hexanethiol and octanethiol SAMs, a kink in the tunneling current slopes is clearly observed, which shows the point where the STM tip contacts the end of the SAMs. The conductance decay constants of the vacuum layer and the alkanethiol SAMs are estimated from the tunneling current slopes. We also discuss the contact conductance of alkanethiol SAMs.
Measurement of Work of Adhesion on Wafers for Direct Bonding
Authors: Turner Kevin T. , Mark Spearing S. 
Published: April 2011

ABSTRACTThe displacement loaded double cantilever beam (DCB), often referred to as the blade-insertion test or crack-opening method by the wafer bonding community, has become a common method for evaluating the work of adhesion of bonded wafer pairs. The test, while easy to perform, often yields results with large scatter and questionable accuracy. The mechanics of the specimen are investigated in detail in the current work. Expressions that demonstrate how wafer bow may lead to residual stresses that result in large errors in the calculated work of adhesion are developed. A three-dimensional finite element model is used to show that due to the circular wafer geometry and silicon anisotropy there is a large variation of the strain energy release rate across a straight crack front. The model is used to predict the actual crack front shape and shows good agreement with experiments. The results of the finite element simulations are compared to the traditional expression used for data reduction and implications of the model highlighted.