bluuebunny/crossref_metadata_2025_split huggingface dataset:
Deformation Behavior of Bulk Amorphous Zr-Base Alloys
Authors: Leonhard A. , Heilmaier M. , Eckert J. , Schultz L. 
Published: April 2011

AbstractBulk Zr-Al-Cu-Ni alloys were produced by die casting into a copper mold under Aratmosphere. The microstructure of fully amorphous as well as partially crystalline samples was analyzed by X-ray diffraction (XRD), scanning (SEM) and transmission electron microscopy (TEM), and chemical analysis with special emphasis on the size and composition of the crystallites. The mechanical behavior of the different samples was investigated by constant compression rate tests. At room temperature the samples show inhomogeneous deformation and, independent of the chosen composition, relatively low Young's moduli of about 70 GPa, flow stresses around 2 GPa and elastic strains of up to 3 %. Fully amorphous samples show microplasticity of up to 2 % strain without significant work hardening while specimens with a fairly high volume fraction of crystalline phases are extremely brittle. In contrast, at high temperatures around the glass transition temperature T8 both amorphous and partially crystalline specimens exhibit at low strain rates homogeneous deformation with an initial stress overshoot followed by an extended region of plastic flow. As compared to room temperature, the peak stresses are much lower and are hardly influenced by the presence of small volume fractions of crystalline phases. The observed thermal stability against crystallization provides a promising possibility for easy shaping of complex parts at temperatures around Tg.
High-Strength Bulk Nanostructure Alloys Consisting of Compound and Amorphous Phases
Authors: Inoue Akihisa , Fan Cang 
Published: April 2011

AbstractBulk nanocrystalline alloys with good ductility and high tensile strength (σ f) in Zr-Al-Cu- Pd and Zr-Al-Cu-Ni-Ti systems were formed by partial crystallization of cast bulk amorphous alloys. The nanostructure alloys consist of Zr2(Cu, Pd) or (Zr, Ti)2Al surrounded by the remaining amorphous phase. The particle size and interparticle spacing of their compounds are less than 10 and 2 nm, respectively. The crystallization of a Zr60Al10Cu30 amorphous alloy occurs by the simultaneous precipitation of Zr2Al and Zr2Cu with a large particle size of 500 nm and hence the addition of Pd or Ti is effective for formation of the nanostructure. The Pd or Ti has much larger negative heats of mixing against Zr or Al, respectively, and the Zr-Pd or Ti-Al atomic pair seems to act as preferential nucleation sites leading to the primary precipitation of Zr2(Cu, Pd) or (Zr, Ti) 2Al. The nanostructure alloy cylinders of 2 to 3 mm in diameter keep good ductility in the volume fraction (Vf) range of the compounds below 40 %. The σ f and Young's modulus (E) increase from 1760 MPa and 81.5 GPa, respectively, at Vf=40 % to 1880 MPa and 89.5 Gpa, respectively, at Vf =40 % for the Zr60Al10Cu20Pd10 alloy and from 1830 MPa and 89.0 GPa, respectively, at Vf =0 % to 1940 MPa and 95.2 GPa, respectively, at Vf =28 % for the Zr53Al12Cu20Ni10Ti5 alloy. The formation of the bulk nanostructure alloys with high σ f is presumably due to the reentrance of free volumes into the remaining amorphous phase caused by quenching from the supercooled liquid region.
A Local Probe into the Atomic Structure of Metallic Glasses Using EELS
Authors: Alamgir F. M. , Ito Y. , Jain H. , Williams D. B. , Schwarz R. B. 
Published: April 2011

AbstractElectron energy loss spectroscopy (EELS) is used to extract information on the topological arrangement of atoms around Pd in the bulk-glass-forming Pd60Ni20P20. It is found that the environment around Pd in the glass is only a slight modification of the Pd crystalline structure. However, the modification is enough to allow this alloy to form a glass in bulk. In examining the differences between the structure of crystalline Pd and glassy Pd60Ni20P20 it is concluded that incorporation of Ni and P into the structure frustrates the structure enough that glass formation becomes easy.
Oxide Formation on the Bulk Metallic Glass Zr46.75Ti8.25Cu7.5Ni10Be27.5
Authors: Kiene M. , Strunskus T. , Hasse G. , Faupel F. 
Published: April 2011

AbstractIn this investigation depth profiling by Ar+ ion sputtering in combination with x-ray photoelectron spectroscopy was used to determine the thickness and the chemical composition of the oxide layers formed on the bulk metallic glass Zr46.75Tig8.25Cu7.5Ni10Be27.5 (V4) under different preparation conditions. The thickness of the oxide layer was in the range between 4 nm and 30 nm for samples oxidized in air at room temperature and annealed in air at 573 K for 15 hours, respectively. The oxide layers showed an enrichment of Be at the outermost surface followed by a Be, Zr and Ti rich phase. Cu and Ni are depleted within the whole oxide layer. BeO, ZrO2 and various Ti oxides were detected in the oxide layer, whereas Cu and Ni occurred only in a non-oxidized zerovalent state. Our data indicate that the oxidation is controlled by the inward and outward diffusion of the metallic components.
Critical Cooling Rate Vs. Reduced Glass Transition: Scaling Factors and Master Curves
Authors: Clavaguera N. , Clavaguera-Mora M. T. 
Published: April 2011

AbstractThe aim of the present paper is to analyse the glass formation and stability of bulk metallic glasses. Attention is focused to metallic alloys as systems which may develop a large glassforming ability. Glass formation when quenching from the liquid state is discussed in terms of the thermodynamics and kinetics of the stable/metastable competing phases. Thermodynamics is required to relate glass transition temperature, Tg, to the energetics of the supercooled liquid. Kinetic destabilisation of equilibrium solidification and, consequently, glass forming ability are favoured by the high viscosity values achieved under continuous cooling. The relative thermal stability of the supercooled liquid depends on the thermodynamic driving force and interfacial energy between each competing nucleating phase and the molten alloy. It is shown that the quantities representative of the process, once scaled, have a temperature dependence that is mostly fixed by the reduced glass transition temperature, Tgr= Tg/Tm, Tm being the melting temperature. Based on the classical models of nucleation and crystal growth, the reduced critical cooling rate is shown to follow master curves when plotted against Tgr. Experimental trends for specific systems are compared to predicted values from these master curves.
Hydrogenation and Crystallization of Zr-Cu-Ni-Al Glasses
Authors: Köoster U. , Zander D. , Leptien H. , Eliaz N. , Eliezer D. 
Published: April 2011

AbstractZr-Cu-Ni-Al belongs to the best glass forming systems known. Hydrogen charging was performed electrochemically in a 2:1 glycerin-phosphoric acid electrolyte. In comparison to binary Zr-Ni glasses the absorption kinetics in amorphous Zr-Cu-Ni-Al were found to be slower, but the storage capacity is similar. Desorption is hindered by the formation of thin ZrO2 layers. Partial replacement of Ni by Pd in an amorphous Zr68 5Cu13Ni11Al7.5 alloy was found to change the absorption behavior to a faster kinetic and to improve the desorption. The influence of hydrogen on the thermal stability was studied by DSC as well as by xray diffraction and TEM. Hydrogen was observed to play an important role. With increasing H/M ratio amorphous Zr69.5Cu12Ni11Al7.5 was found to transform during annealing above the glass transition temperature into a quasicrystalline structure with decreasing grain size until a nanocrystalline microstructure is achieved. Above a hydrogen content of H/M = 0.05 instead of quasicrystals a tetragonal phase with lattice parameters close to those of Zr2Ni is formed. At very high hydrogen contents phase separation is assumed to take place followed by the formation of nanocrystalline ZrH2 and other phases with reduced Zr content.
Elastic and Dissipative Properties of Amorphous and Nanocrystalline Mg-Ni-Y Alloy
Authors: Soifer Y. M. , Kobelev N. P. , Brodova I. G. , Manukhin A. N. , Korin E. , Soifer L. 
Published: April 2011

AbstractThe internal friction and Young's modulus of amorphous Mg84Ni12.5Y3.5 alloy obtained by the melt spinning technique have been measured by a vibrating reed method at frequency of 250 Hz at heating and cooling runs in the temperature range from 300K to 625K.. The crystallization kinetics of the alloy was studied by the calorimetric methods (DSC and DTA). The structure of the samples was determined by the x-ray diffraction technique. The Young modulus measurements have revealed the irreversible multi-step changes (up to 50%) accompanied by the irreversible internal friction peaks. These changes were observed in the same temperature intervals where the anomalies of thermal properties were found out. The results obtained are explained by the structural rearrangement from amorphous to nanocrystalline state during the annealing.
Deformation Behavior of FCC Crystalline Metallic Nanowires Under High Strain Rates
Authors: Qi Yue , Ikeda Hideyuki , Cagin Tahir , Samwer Konrad , Johnson William L. , Goddard William A. 
Published: April 2011

AbstractWe used molecular dynamics (MD) methods to study the deformation behavior of metallic alloy crystal nanowires of pure Cu, NiCu alloy and NiAu alloy, under high rates of uniaxial tensile strain, ranging from 5* 108/s to 5* 10/s. These nanowires are just about 2 nm thick and hence cannot sustain dislocations, instead we find that deformation proceeds through twinning and coherent slipping mechanisms. NiAu has a 13% size mismatch whereas NiCu only 2.5%. As a result the critical strain rate at which the “nanowire crystals” flow like a “liquid” is 100 times smaller for NiAu. We also calculated the elastic constants at each strain state for all strain rates to identify the relation between mechanical “shear” instability and deformation process.
Amorphous and Disordered Materials - the Basis of New Industries
Authors: Ovshinsky S. R. 
Published: April 2011

AbstractAs in the past, materials will shape the new century. Dramatic changes are taking place in the fields of energy and information based on new synthetic materials. In energy, the generation of electricity by amorphous silicon alloy thin film photovoltaics; the storage of electricity in nickel metal hydride batteries which are the batteries of choice for electric and hybrid vehicles. In the information field, phase change memories based on a reversible amorphous to crystalline transformation are widely used as optical memories and are the choice for the new rewritable CDs and DVDs. The scientific and technological bases for these three fields that have become the enabling technologies are amorphous and disordered materials. We will discuss how disordered, multielemental, multiphase materials can throw new light upon metallic conductivity in both bulk and thin film materials. We will demonstrate new types of amorphous devices that have the ability to learn and adapt, making possible new concepts for computers.
Heat Treatment of Molten Rapidly Quenched Precursor as a Method to Improve the Glass Forming Ability of Alloys
Authors: Manov V , Brook-Levinson E , Molokanov V. V. , Petrzhik M. I , Mikhailova T. N. 
Published: April 2011

AbstractImprovement of glass forming ability (GFA) of two soft magnetic amorphous alloys (Fe75.5Ni1 3Si8.6B13.5 and Co69.6Fe1.3Mn4.5Si14.3B9 3Mo1) by heat treatment of melts prepared from different precursors (bulk ingot, rapidly quenched ribbons and granules) was studied. An assumption that the maximum undercooling ability corresponds to the maximum GFA was used to optimize the heat treatment mode. A temperature range was found by DTA for each alloy melt, favoring its undercooling (so called “undercoolable melt”). Usage of rapidly quenched precursor expands the range towards lower temperatures. GFA of the alloys was estimated by several melt quench techniques (casting, spinning and INROWASP). Fully amorphous samples with the thickness of 0.06–0.5 mm were prepared.
NMR Investigations of the Bulk Metallic Glass Zr55Cu30Al10Ni5
Authors: Hoffmann W. , Baenitz M. , Lüders K. , Gebert A. , Eckert J. , Schultz L. 
Published: April 2011

AbstractNuclear magnetic resonance (NMR) was applied for structural investigations of the bulk metallic glass system Zr55Cu30A110Ni5. The 63Cu as well as 27Al resonance was used. For both nuclei, two different spin-lattice relaxation rates were found which can be explained by different local environments of the nuclei.
Deposition of Epitaxial Carbide Films and Superlattices by Co-Evaporation of C60 and Transition Metals
Authors: Högberg H. , Norin L. , Lu J , Malm J. O. , Jansson U 
Published: April 2011

ABSTRACTThin films of TiC, VC and NbC have been deposited on MgO(001) by co-evaporation of C 60 and the metal. The metal induced a decomposition of the C60 cage and a subsequent carbide formation at 100 °C. Epitaxial TiC films were easily obtained at 250 °C, while higher deposition temperatures were required for epitaxial growth of VC(400 °C) and NbC(500 °C). The films grew with the relation MeC(001)//MgO(00 1) and MeC[ 100]//MgO[ 100]. It was also possible to deposit TiC/NbC/MgO polycrystalline multilayers and TiC/VC/MgO superlattices structures by a sequential evaporation of the metals.
Properties of Catalytic CVD SiNx For Antireflection Coatings
Authors: Izumi A. , Matsumura H. 
Published: April 2011

AbstractWe propose a novel preparation of high quality silicon nitride (SiNx) films by catalytic chemical vapor deposition (Cat-CVD) method for the application of antireflection coatings. It is found that the refractive index (n) of the Cat-CVD SiNx films are controlled from 2.0 to 2.5 by varying the flow ratio of SiH4 and NH3. The properties of the SiNx (n = 2.0) are investigated, and it is found that, 1) the 16-BHF etching rate of the Cat-CVD SiNx film is only 23 A/min, and the film shows excellent moisture resistance, 2) the Cat-CVD SiNx film shows good insulating properties, and the breakdown electric field is higher than 9 MV/cm and the interface state density is 5.6x 1011 cm2eV-1, 3) the step coverage of the film is very conformal.
Growth and Stress Characterization of LPCVD SiC Films Deposited on Bare, Carbonized and Oxidized Si(001) Substrates
Authors: Hurtós E , Rodríguez-Viejo J , Zekentess K , Clavaguera-Mora M. T 
Published: April 2011

AbstractA simple LPCVD reactor has been used to deposit 3C-SiC on oxidized, bare and MBE carbonized Si (001) wafers. The deposition experiments were conducted at different temperatures, times and gas flows pyrolizing tetramehylsilane (TMS). Voids at the interface and hillock formation were observed preferentially on the bare Si substrates due to Si outdiffusion. The best LPCVD films were obtained at temperatures around 1170°C on smooth single-crystalline carbonized substrates. The nucleation and growth of 3C-SiC on Si02/Si substrates proceeds at a slower rate with the formation of 3D island with a high aspect ratio.
The Chemical Vapor Deposition of Zirconium Carbide onto Ceramic Substrates
Authors: Glass John A. , Palmisiano Nick , Welsh R. Edward 
Published: April 2011

AbstractZirconium carbide is an attractive ceramic material due to its unique properties such as high melting point, good thermal conductivity, and chemical resistance. The controlled preparation of zirconium carbide films of superstoichiometric, stoichiometric, and substoichiometric compositions has been achieved utilizing zirconium tetrachloride and methane precursor gases in an atmospheric pressure high temperature chemical vapor deposition system. Laminar and equiaxial microcrystalline morphologies were obtained for superstoichiometric and substoichiometric zirconium carbide; respectively, allowing cursory metallographic identification of composition. Observed reductions in film density associated with zirconium carbide films that contain additional free carbon or excess zirconium are reported. These changes in film density were found to be consistent with compositional changes. An apparently linear relationship (correlation of 0.99) between methane flow in this chemical vapor deposition system and zirconium carbide stoichiometry in the substoichiometric range deposited above ZrC0.61 has been observed.
Chemical Vapor Deposition of Diamond from Alcohol Precursors at 1.0 Torr
Authors: Gilbert Donald R. , Singh Rajiv K. , Huang Ming 
Published: April 2011

AbstractTypically, diamond chemical vapor deposition (CVD) is conducted at pressures of 10 to 100 Torr and temperatures of 700 - 1000 °C. Both thermally activated (hot-filament) and plasma enhanced (DC, microwave) systems are used to deposit diamond from mixtures of hydrogen and some carbon-containing monomer, most typically methane. These systems may produce films of high phase purity which typically exhibit tensile intrinsic (non-thermal) growth stresses. We have used an electron cyclotron resonance (ECR) enhanced plasma system to deposit diamond films at a pressure of 1 Torr over a temperature range of 550 - 700 °C using methyl alcohol as the carbon source. Optical emission spectroscopy (OES) was used to analyze the plasma discharge for the determination of active species present during diamond growth. Correlations of emission variations with film characteristics were made to evaluate their importance in the diamond formation process. Particular emphasis was placed on the nature of the intrinsic growth stresses developed in this process, which appeared to be consistently compressive in nature based on Raman analysis.
Gas Phase and Surface Kinetics of Diamond-Like Carbon Films Growth in Pecvd Reactors
Authors: Masi Maurizio , Cavallotti Carlo , Carrà Sergio 
Published: April 2011

AbstractThe surface and gas-phase kinetic of deposition of diamond-like carbon films (DLC) obtained in plasma reactors using methane as precursor was here investigated. Kinetic constants of electronic reactions were evaluated using experimental ionization and neutral dissociation cross sections and the Druyvestein electron distribution function. Kinetic constants for ionic and neutral reactions were found in the literature. Surface reactions were divided into processes involving the impingement of gas-phase radicals or ions from the plasma and desorption or recombination reactions of adsorbed surface species. The kinetic constants of the former processes were evaluated.from the ambipolar theory or from the kinetic theory of gases, while the other kinetic constants were determined from analogy with hydrocarbon chemistry. The exception is the desorption of adsorbed methyl radicals, whose kinetic constant was fitted over experimental data. The predictivity of the model was tested through the simulation of three reactors described in the literature widely differing for operating conditions.
Epitaxial Growth of Diamond on an Iridium (100) Substrate by Microwave Plasma-Assisted Chemical Vapor Deposition
Authors: Tsubota Toshiki , Tsuruga Shigenori , Saito Takeyasu , Kusakabe Katsuki , Morooka Shigeharu , Maeda Hideaki 
Published: April 2011

AbstractDiamond films were grown heteroepitaxially on iridium (100) substrates by microwave plasma-assisted chemical vapor deposition (MPCVD) using methane gas as the carbon source. The iridium substrate, which was formed on a MgO (100) substrate by means of sputtering at 850 °C, was treated by imposing a negative bias between -150 and -200 V for 15 min. Methane concentration and substrate temperature were maintained at 3° and 650–740 °c, respectively. At a substrate temperature of 740 °C, diamond particles were formed at a population density of (0.15- 1.5)x108 cm-2, and most of them were oriented to MgO (100). After a further reaction for 1 h under conditions which were optimized for diamond growth, the oriented diamond particles were coalesced, and islands of (100) diamond were formed.
Growth and Erosive Wear Properties of MPCVD Diamond Coatings on Sintered Tungsten Carbide Substrates
Authors: Amirhaghi S. , Reehal H. S. , Wood R. J. K. , Wheeler D. W. 
Published: April 2011

AbstractAdherent diamond coatings up to ∼35 um thick have been grown by microwave plasma CVD (MPCVD) on sintered tungsten carbide (WC) substrates and their erosive wear properties investigated under high velocity air-sand erosion testing. Two different sintered tungsten carbide (WC) substrates have been investigated and compared, the binder being either 6%Co or 5%Ni by weight. Coating properties are sensitive functions of surface pre-treatment and deposition procedures. Adherent coatings offer significantly better erosion resistance compared to uncoated substrates, with the erosion rate being lower by up to a factor between ∼5 and 20 for particle test velocities of 148 ms-1 and 63 ms-1 respectively. Films with low residual stress appear to exhibit longer times to failure which tends to occur catastrophically along the coating-substrate interface.
Process Windows and Properties of Tungstenand Vanadium-Oxides Deposited by MSIP-PVD-Process
Authors: Knotek O. , Lugscheider E. , Bäarwulf S. , Barimani C. 
Published: April 2011

AbstractThe tungsten and vanadium oxides are well known to be usable as solid lubricants at elevated temperatures. Such metal-oxides are interesting for tribological insets at atmospheric conditions because of their “oxidation stability”. This paper reports about investigations made to find stable process windows for the deposition of tungsten and vanadium oxides in a reactive d.c. mode by the MSIP-PVD-process. One focus of the study is on the metal oxide-phases generated in the MSIP-process under various conditions and their mechanical and metallographic properties. Coatings were deposited, developed and analyzed by standard testing methods such as SEM, microhardness (nanoindentation), XRD and scratch testing to characterize the mechanical and structural properties. Stable process windows will be presented for the reactive mode as well as the influence of different process parameters to the microstructure and the material properties. It will be shown that it is possible to deposit vanadium-oxides despite contamination effects in wide ranges by adapting the gas-flow. Process failure was determined at 15 - 18 % oxygen partial pressure for reactively deposited tungsten oxides.
Hafnium Hydroxide Complexation and Solubility: the Impact of Hydrolysis Reactions on the Disposition of Weapons-Grade Plutonium
Authors: Cerefice G. , Draye M. , Noyes K. , Czerwinski K. 
Published: April 2011

AbstractThe stability constants for the complexation of hafnium by hydroxide ions is investigated by potentiometric titration over a range of ionic strengths (1m = 0.1 to 6.6 molal). The stability constants are determined from the titration data using the HYPERQUAD suite of programs. The stability constants at infinite dilution are determined using the Specific Ion Interaction Theory from the stability constants determined by titration. The results are shown with the error given as 2 standard deviations.log β11 (Hf(OH)3+) = 13.84 ± 0.54
log β12 (Hf(OH)22+) = 25.71 ± 0.39
log β13 (Hf(OH)3+) = 36.24 ± 0.88
log β14 (Hf(OH)40) = 45.52 ± 0.80The solubility product of Hf(OH)4 (s) is determined in 0.1 M NaC1O4 by measuring the total hafnium in solution that is in equilibrium with an excess of hafnium hydroxide solid under an argon atmosphere. The total Hf concentration is determined by ICP-AES. The solubility product is determined using the stability constants measured for the H f hydrolysis products in 0.1 M NaClO4. The precipitate examined is confirmed to be a hydroxide by IR spectroscopy. For Hf(OH)4 (s) in 0.1 M NaC1O4, the solubility product is log Ksp (Hf(OH)4 (s)) = −51.8 ± 0.5The solubility and stability constants determined are used, along with literature values for plutonium solubility and complexation constants, to examine the behavior of hafnium and plutonium under the conditions expected at Yucca Mountain.